A~C MIEn4X Rvt3ENGR'!~Qual If

N. Mvid Kirrcrcry >~q.ratrment of Mtcrbals Rierce and Encline~~ing viassachu~mtts Inst ' tute af Tiecharrlociy Caribxll+Ae p %3ssachusc~tts

iltudiea of the charao terlSt iCS Of ice and rnacrOSCoplc computatians are useful. Ni ver- de to tnaat iori properties were f irst ca r r ied theless, a lot of progress has beer. n.aoe th' to tal.ucidate the behavior of glaciers, and it last several years, and Dr. pr.rtchard w 1' nas only been in the last few decades that inform us atoi.t. the oresent start Of affairs. i.hs properties of sea r.r e have been seri rnusly Sea ic behavior can also be approached studied. During the c:arly yearS oe yrorld 4'ar f'rom the poirit of view of rcateriril s - ropcr- the rani;e of British airCraft was inac'ne- tiis in which the characte.istics rrf the c- gus'te for protection of the North Atlarrtlc are related to its crystallirie structure, itS saa lanes and several Suggeetl'ons were made cor!paa l. t' ron, l ts rrll.cl Ostl uct!ir'p. ar.'d f:l uaing natural lce aS t.ernparary landing ir:fluence Of vari ous impurit leS whi.ch n ay be f'e 'da, lrowever, icebergs are notoriously present. This l: a'so a complex subject unstable and the prospect of. a landrng fie]d SlnCe iCe fsrma ln VariOuS WayS. ri'e -ar. flipping Over during an apprOach was nat very expect that the prof>ert.ic:s of sea cr whi cli =omfortablo. sea ice platforms are al.so COritain;." a gOOd deal Of entr apperl brine Will inadequate. Aa a result a. substantial er fOrt be Similar ta the higher purity, l,irger gr in va 8 Q ev o 'te di 'to d ev e 1 opI rl g a n ic c e s 'tr uc 'tii x t- size giLacier ice carved from the shc re ~ of would be mare useful. A new ice alloy Green'and and Ellesmers Island. E'nce its .'=s devciloped called "pykretr. "! and prel 'm- mcchanica' properties ara of interest ir. r-arl desi ion iS Still mOSt. dlf lcult, Similarly, .lie react;ion of sea ice to the oppased f ' cs rs a complex otic and depends ori the sour e of the: ice and time, teni era+ are, ar:d ta -"- al can sideratior.s that are riios' if i" lt to Simpllfv ir. a fo m for whi h

223

LrtODELINGOF ARCTIC SEA ICE FIELOS Robert S. Pritchard Flow Industries, Inc . Research and Technology Oivision Kent, 'Hashington 98031 USA

The capability to model sea ice dynamics behavior ily through the formation of open water, which in- has increased substantially during the last decade, creases heat transfer fram the ocean to the atmos- TTse literature deSCribing maCrOSCale and meSOSCale phere. The ice stress is not of direct physical ~cling in the Arctic Basin, especially the Beaufort concern . On mesoscales of tens to hundreds of ki lo- Sea. the Chukchi Sea and Bering Strait region, and meters, both ice motions and stresses are important. tile Bal tiC, Bering and Greenland Seas is reviewed. Ice motions would influence an oil spill by trans- Basic contributions to model development are ident- porting it. Also' the large-scale ice stress could. sf led with the intent of determining the essential be transmitted shoreward to generate forces on off- s i ~ i larities in approach. Features needed to des- shore drilling structures. The geophysical scale cribe ice behavior in a physically acceptable way are forces from winds and currents over wide areas of the discussed. Although models have come into more con- ice pack cause its motion . These effects can be «n use, many of these models have not incorporated realized at large distances vrhen internal tee 'the results of recent studies of small-scale pro- stresses are high . These large-scale forces and ceSSeS. The Sea ice madeling cOmmunity is Challenged stresses rannot be measured dirertly. To compare to take this better understanding of individual phy- with observed behavior, our attention must be focused sical processes and to incorporate it into the models, on the motions, the only directly observable vari- able, On small scales of a hundred meters and less, these forces affect the design and use of offshore 1 . INTROoUCTIOaL drilling structures. Artifici al i sl ands, docks, breakwaters, and conical platforms must be designed poring the 'last decade, the unders,tanding «sea to withstand the forces that sea ice ran apply. For ice behavior has increased substantially. As in scales between a hundred meters and ten kilon ters, other engineering and scientific fields, modeling of sea ice behavior i s difficult to categorize. There this behavior has been able to keep pace because of is not a c.lear separation of scales ano several the great advances in computer hardware and soft~are problems fal 1 within the mesoscale and small -scale end. to a lesser extent, because of advances i n nu- bounds. mricaI solution techniques for solving complicated In current sea iCe mOdelS, the phySical behavicr prcrblems. The techniques needed to simulate sea ice of sea ice is described by accounting for mass, mo- tarehavior are some of the most sophisticated in use mentum and energy balance and the constitutive laws anywhere today. relating deformation to stres,s and thickness redis- The purpose af this revie~ is to survey the mod- tribution and thermal growth. In this review, the ~ 1s currently in use and to examine and compare the i r numeri cal schemes used to sol ve the mathemati ca 1 basic components. In this way, the differences and, model s are discussed brief ly. Computational consid- even more, the similarities in the var ious approaches erations include the choice of a tagrangian or Euler- Can be 'Identified. It is hoped that this analysis ian descr iption, a finite element or finite dif- mi 11 encourage and help other investigators to focus ference approximation. and an implicit or explicit ran improving our understanding and description of sea time integration. tce processes and thereby adapt and extend present This review is not complete in the sense that not acrcle'I s . all ice modeling publications are discussed. Atten- Models are used in a diverse r ange of applica- tionn is focused on mesoscale and smaller modeli ng in tions. extending from the need for more fundaraental whirh stress, velocity and ice conditions are equally scientific knowledge to a variety of specific opera- important- past reviews by Rothrock [1,2j and Hibler t i trna I needs. These app1i cat tons include under- [3,4] on macroscale modeling are updated, but models standing climate dynamics, determining oil spill tra- developed primarily for studying climate dynarrics are jectories, estimating loads that might be applied to only included as they apply to mesoscale problems. a f ixed structure operating within the ice cover, Also, small-s cele engineering studies are ignored. estimating noise generated by the ice cover, or warn- These engineering studies will, in the future, provide ing of possible future ice invasions dur ing petroleum input to modeling individuaL processes, but, at tnrs dr i I I ing operations in open-water con di ti ons . Time tirae, have not been included in larger scale models. and space scales in each of these problems differ ftany valuable engineering studies are to be found irr s 1g ni f i cant I y. proceedings of the POACand OTC confer ences as well On macroscales of hundreds of kilometers, sea ice as the numerous recent ASrtEand ASCE conferenc s with bractav i Or af fects climate dynamic s. The ef f ec ts o f Arctic sessions The RTLS has also prepared a pub- sea ice motions and deformations are realized primar- lished search on sea ice. The works ref renced in this paper can provide detailed information on speci- variance in ice velocity in winter and about 95 per- fic topics and references to further relevant studies. cent in summer. Velocity vector errors between The remainder of this paper is divided into four observed and modeled velocities have a standard sections. A lengthy review of literature on sea ice deviation of about 4 .0 cm/s . Nearer to shore where models appears in Section 2. Then, computati ona1 ice is often in contact with the coast, about 50 per- Conaiderat IOnS needed tO SO1Ve problems with theSe cent of the variance is described. Mean vector errors models are presented in Section 3. In Section 4, an over monthly periods are nearly constant and may be overv iew of the fundanenta I compo~ants of a mode 1 attributed to long-term ocean currents . This may be needed ta Cmnpletely deSCribe ICe dynamiCS behaviOr the best available estimate of the ocean currents is given. Reconmendatlons for future a~tensions are because of the sparcity of direct measurements. also made. Finally, in Section 5, a brief conclusion Thomasand Pritchard [ 18] and Pritchard I 19] have evaluates the current status of ice dynmnics modeling. used a free-drift model with quadratic drag lavvs to analyze AIOJEXdata for the Beaufort Sea in 1975-76. They found that modeledvelocity vectors have montlily 2. LITERATijtEREviEM mean errors less than 1.0 cm/s and standard deviations af about 3.6 cm/s in sunmer and up to 10 cm/s in The 92I terature re v Iewed in thi s sec t i on is ex- winter. This model is also used with 25 years of tensive. It includes macroscale and mesoscale models barometric pr essure data for the Beaufort Sea to esti- of almost all arctic and subarctic ice-covered oceans. mate the range of ice motions that may be expected for Since different length and time scales, geographic this region. The study updates a similar estimate by regions and specific applications are involved, it is Sater et al. [2O]. difficult to separate the presentation into logical DimensI onless var i ab les have been introduced by subsections. In general, the disc~ssion I s broken Pritchard and Thoma~L21] and Lepphranta [8]. The down by geographic region. Separate subsections are choice of reference variables differs and dlmensian- presented on models developed for use in the Arctic less parameters appear in different combinations. but Basin and Beaufort Sea region. the Chukchi Sea and similar results are obtained. Bering Strait area, the Baltic Sea, and the Bering McPheeI 22] has used free drift to study inertial and Greenland Seas. The first subsection is an oscillations in the Beaufort Sea. when ice stress is exception, ho~ever. In that it is a general discus- negligible, incr tial and Curio lis forces respoavdto sion of free drift. This seems reasonable because wind drag and produce inertial oscillations. ln the free-drift models, in neglecting ice stress, do not subarctic water s of the llal tie and Bering Seas the show strong regional differences. thinner ice means that inertial a.nd Coriolis accelera- tions are smaller and, therefore, produce sealler 2.1 Free Grift inertial osci 1 let ions Leppdranta [8] ! . Pease e t al. [13] have shown that air and water drag are nearly in Free drift of sea ice is defined as the condition balance in the Bering Sea because the ice is thinner. where all forces act on the Ice cover except ice stress divergence. In most present models these 2.2 Arctic Basin and Beaufort Sea other forces include inertial and Coriolis accelera- tionn, air and water drag, sea surface tilt and, at an The strain that may occur in an ice floe before ICe edge, waVe radiat,ion drag. alany authOrS have failure is small compared to the deformation due to discussed free drift. with early references to Ilansen failure by opening, rafting and ridging. A model may [5] and Zubov [6]. Recent articles typically trace describe behavior on a scale small enough to resolve the mome~turnbalance in free drift to Campbell [7]. variations from floe to floe or may average aver a RathrOCkI.I,2] and Leppairanta[8] have preSented re- number of floes and describe a set of average prop- cent reviews. erties. This set of properties must be complete McPhee [9] has used AIDJEX data from the sumner enoughso that the desired output variables, such as of 1975 to analyze the relationship bet~can blinds and velocity and stress, are determined in an average ice motions. This time period was chosen because it sense at this length scale. Then, even though there appears that ice motions then were unaffected by in- are known variations on smaller scales. it is not ternal ice stress. The study had as a primary goal necessary to resolve them explicitly. the determination of an oceantc drag law. This work The velocities of individual partirles of ice on has continued, and a comprehensive report has been a floe differ, especially when floes are large com- published comparingvarious drag laws [ 10]. Overland pared to the scale of reso lot ian. These velocity and Pease [ IT ] and McPhee I 1 2] have developed similar variations cannot be described well as a continuum models of the oceanic mixed layer for shallow seas. velocity field because deformations are localized at Pease et al. $13] have used a free-drift model with floe boundaries rather than being distributed as con- quadratic drag laws to determine drag coefficients tinuous straining of the floes Nye and ThomasI 23] near the ire edge in the Beri ~g Sea. Another ocean have shown how ice velocities vary over an area model that is useful to note is the multilevel ocean several hundred kilometers long by using satellite model of Liu and Leendertse I14], which treats ice as images. On smaller scales, Hibler et al. [24] hsve a linear viscous layer but includes most acean trans- presented s imi 1 ar res ul ts. Thi s work h as been re- port processes in great detail. viewed by Rothrock I'2]. More recently, Thorndike and All of these water drag models may be incorpor- Colony [25] and Colony and Tharndlke L16] have ana- ated into more complex and complete ice dynamics lyted iCe mOtion data from the Beaufort Sea and the mOdelS, but have been exerCISed to date Only in free- central Arctic Basin to determine the portion of ob- drift models except Thomas [ 15] has used McPhee's served motion that can be explained by a continuum shallow ocean model in his nearshore Beaufort Sea velocity field and the portion that appears as s*- studies!. grid-scale velocity inhomogeneities. Their weri; COlOny and Thorndike [ 16] and ThOrndike and Calany focuses on large-scale behavior, 100 km and lar ger in [ 17] have analyzed ice motion data and geostropbic resalution. Velocity variations as large as 0.4 ce/s wind data from Arctic Basin buoy deployments in 1975- in winter and 1.1 cm/s in sunvser cannot be describe'- 76, 1979-80, lgBO-Bl and !981-82 to determine how by a continuum velocity field . Strains calculate' well a linear model relates daily average motions. from buoys about, 1/0 km apart have an uncertainty of They found that at distanres further than 4OOkm from 0.4 to 1.1 x 10 z s-1. An uncertainty of th's shore, free dr~ft describes about 85 percent of the magnitude makes it difficult to determine whether a area is d1verging or converging. An uncertainty in all other forces in the momentum balance using ice shear and rotation is less severe because these quan- motion, wind and current observations directly. They tities are larger than dilatation . The impact of thi s concluded that an ideal plastic model with a teardrop uncertainty is that the stress can be in substantial yield surface did not satisfy momentumbalance for the error because it 1s determined from the strain through three times it was tested during the AIDJEX experi- a constitutive law and limits the accuracy of a con- ment. Kolle and Pritchard I42] have determined tinuum model for a selected length scale. velocity vector errors for a series of simulations of Sea ice dynamics modeling in the Beaufort Sea ad- Beaufort Sea ice dynamics, Errors in da11y average vanced at a rapid pace with the concentrated efforts ice velocities are shown to have a mean of less than during AILIEX, as discussed by llntersteiner [ 26]. 1.0 cm/s and a standard deviation of 3 6 cm/s, includ- Coon [27] has sunmarized the model developed during ing both nearshore and far offshore s1tes. These that prograra. One of the major contributions of the errors appear to hold for simulations througnout the AIL3EX model is the attempt to describe large-scale AIOJEX field experiment in 1975-76. ice behavior by describing individual processes such Hibler [ 3,43] has developed a viscous-plastic con- as lead formation, rafting and ridging. st1tutive law to describe the mechanical response. Ice conditions, which are expected to control the Th1s change from elastic ta viscous behavior at low relative 1mportance of individual processes, are stress levels is a valuable extension because it descr1bed in terms of the thickness distribution by allows different numerical techniques ta be used to Thorndike et al. L28]. The large-scale heat flux solve the model. No definitive study has yet been between ocean and atmosphere that affects climate made to determine the range of conditions for which dynmnics thr oughout the world is also affected viscous or elastic behavior is superior in numerical directly by ice conditions [29,30]. Thermal growth simulations. However, the U.S. Navy has adapted the and ablation of sea ice has been descr1bed by the viscous mode'l for simulations and predictions of ice c limatological average rates for each thickness behavior over the whole Arctic Basin and the elastic throughout the year. This approach was used for model for regional ice behavior analysis, rhett-term simulations [31]. Thermal growth has also Both the elastic-plastic and the v1scous-plastic been accounted for by simulating the heat budget constitutive laws were developed to describe sea ice d lrec'tly. This approach was used by Hibler I 32] to that is nearly rigi d at low stress levels but that simulate year-long behavior, and it is the approach succumbs to large deformation s at a limit stress . needed for climate dynmn1cs simulations. These proper ties are consistent with t.he ridging Large-scale ice stress is related to deformations raechanism model of parmerter and Coon [363, who found by an elastic-plastic canstitutive law [ 33,34]. Ice that deformations are rate independent and that as a strength has been determined by Rothrock 5! by limit height is r eached the ridge extends horizontal- equating the energy d1ssipated in plastic ly. This behavior could be described reasonably well deformations to two sraall-scale energy sinks . These by a rigid-plastic constitutive law in a model seeking two sinks, which have been identified by parmerter to describe sea ice motions' but such a constituti ve and Coon [36] in their study of the mechanisms pre- law poses serious numerical difficulties and the valent in ridgi ng, are increases in gravitatianal assumption of rigidity prohibits determination of potential energy as 1ce conditions change and fr ic- stress 1n the ice cover. The viscous-plastic madel timnal diSSipat1an aS iCe blOCkS Slide through the of Hi hler [ 3, 43] also has difficulties in determ i ni ng rubble of a ridge. This AIOJEX model provides the stress because of the presence of a static pressure framework within which all recent modifications and term that treats pr essure 1n the ice similarly to 'lmproverrmnts are discussed. pressure in a gas . This term induces a pressure in Simulations of sea ice behavior using the AIDJEX the ice equal to half the isotropic yield strength model hyve indicated that strength ~aloes less than whenever deformations are zero, a result that is not l. x 104 N/m are unrealistically low [37]. Bugden acceptable near an ice edge, for example. McKenna [38] modified the redistribution function to allow [44j has circumvented this shortcoming by eliminating thin ice to be ridged into a range of thi cker ice the static pressure term. categories, 1nstead of assuming that all 1ce r1dges NcKenna has studied the effects of constitutive into ice 5 times its original thickness as a.ssumed by law on ice behavior for short time periods I 44]. A Coon et al. [31] and Thorndike et al. [28]. Rothrock f1n1te element formulatian was used, and both elastic- f 2! reviews this aspect of the model development . plastic and viscous -plastic laws were studied. He Hibler j32] has introduced an alternative formulation found little difference in the resultant ice behavior. of the redistribution function in a simulation af Although the finite element formulation 1s limited ta Arctic Basin ice drift for 1962-63. This redistribu- allow only triangular elements, the consideration of tionn also accounts for ice being ridged into a range arbitrary yield surface shapes and bath elastic anc Of thicker categories, and it more accurately reflerts viscous behavior is a valuable step ioward developirg the morphology of the ridged ice cover and the square- one computer program that can solve problems using any root thickness scaling found by Parmerter and Coon of the models already developed [ 36]. This assumption increases the strength to more In addition to mass and momentum balance, which acceptable levels for accurately simulating ice tra- have been included in the ice models previously des- jectories. Pritchard I 39! summarized the framework Cribed, the meChaniCal ener gy balance has been deS- of the AIOJEX model and gener a11zed the const1tutive cr ibed by Coon and Pr itchar d [45] . The mechanical law by adding an energy sink to account for shearing energy budget has been evaluated by Pritchard et al. deformations. He assumed that shearing occur s along I 46] for the Beaufort Sea in 1 975-76. During two narrow bands rather than over wide areas and, as a si.rong storm events, the ice dynamics model represen- result, does not redistribute ice. These assumptions ted each term in this mechanical energy budget accura- have allowed more accurate simulations to be made, tely. Further work has snown that one of tne terms while still retaining the physically realistic model in the budget, the energy dissipated by ridging, ex- developed initially during AIOJEX. Accurate simula- plains about half of the variance in low-frequency tions of nearshore ice dynamics have been performed background noise observed during the winter of 1975-76 w 1th this model and with an ideal plastic mode'I I 40j. Lgy]- Itothrock [2! has called for a more tharough vali- ln the Canadian Beaufort 5ea, drilling activities dation of the performance of these models. Rothrock offshore of the NacKenzie River delta have led to the et al. 1! presented a method for evaluating model need for a smaller scale model to pr edict ice moti ois . performanre by calculating the stress divergence and l eavitt et al. [48] have adapted the visroris-plastic rnOdel by introduCing a faur-COnesenent CharaCteriZatiOn use results of a soil model adapted for sea ice, which of the ice thickness distribution, first presen'ted in prov i ded consistent results. Studies by R. T. Hall [49j, to characterize this primarily first-year ice. personal communication! have attempted a similar ap- ln the Alaskan Beaufort Sea, offshore tracts in proach using large-scale lead patterns observed in 'the the Dsapir f 1eld from Oemarcati on point to Barrow have Beaufort Sea, but poor correlations between character- been leased, The enviromnental impact statement re- istic directions and lead directions were found. quires that the probab11ity of impact in case of an oil Spill be determined for the Alaakan ShOreline. TO 2.4 Baltic Sea determine ice motions that affect this probability, Thomas [ 15] has adapted the ATDJEKmodel presented by Year-round shipping in the Baltic Sea has led to pritchard [39] to estimate the range of ice trajector- an active effort to develop a model to predict the ies that can be expected. Daily ice mot1ons were effect of an ice cover on icebreaker performance- simulated. The computational grid sIze was typically Field experiments carried out by both Finnish amd about 40 km, but was as small as 5 km in some cases, Swedish Investigators as early as 1974 have provided This small-scale resolution allowed the effects of the a COmprehenSive Set Of data On ice cOnditionS, iCe shoreline to be lgcluded. Even at moderate ice motions, ~inds and currer ts see, for example, Blma- s trengths of 5. x 10~ H/m, the smallest resolution was quist et al. [59j; Udin and Omstedt, [60]; Omstedt and found to be unnecessary for determining the range of Sahlberg [61]!. Mathematical models of ice motion ice tra!ectorles. Most simulations were performed the Bay of Bothnia have been developed and used with the larger grid. Some 2250 ice tra]ectories were Finland Valli and Lepparanta [62]; l.epparanta [ B!! calculated for 30 starting sites. The range of mo- and in Sweden Udin and Ullerstig [63]; Udln and ti Ona ShOwShOw I Ce behaVeS under different ice, wind Omstedt [60]; Omstedt [64j!. Research to develop the and current conditions. models has continued. An outstanding description of' ice mechanics and modeling of sea ice behavior in tbe 2.3 Chukchi Sea and Bering Strait Bay of Bothnia is given by Lepparanta [B]. This ccaa- prehensivestudy discusses both observed ice behavior ifhen a shorter fetch is available for winds and and models used to predict short-term Ice motions end Currenta tO att On the ICe, the internal stress di- conditions. vergence becomes raore important than the other driv- Leppgranta [B] uses the thir.kness di stri butiom ing forces. ln the Chukchi Sea, the smaller scales concept to characterize ice conditions. He separates are caused by surrounding land masses. Thus, the the thickness distribution into flat ice and a distri- Chukchi Sea differs from the Beaufort Sea because it bution of ridged ice. This allows the shape of is bounded by land on all sides but its northern edge. ridge sail and keel to be introduced simply and ridg- Moreover, at its southern edge the funneling effect ing intensIty to be used as a means of observing the near the Bering Strait reduces the ice cover to a result of ridging. Nondimensional variables are de- mere 80 km in width. The behavior of sea ice here is fined to estima'te the importance of each term in domInated by the internal ice stress. The dimension- momentumbalance, inertial and Coriolis acceleration, less parameter that reflects the ratio of ice stress air and water drag, sea surface tilt and ice stress dIVergenCe tO water drag prOVideS a meaaure Of the divergence. The important dimensionless groups are relative Importance of the ice stress [21]. expressed as ratios of each force to the inertial The mot1on of the Chukchi Sea ice cover is gen- force, a common technique in flu1d mechanics. The erallyy toward the northwest. However, along the stress-deformation law is assumed as a viscous law. an Alaskan shore the ice is extremely mobile, often unfortunate shortcom ing in light of recent success moving alongshore in one direction or the other see with plasticIty models. The mechanical energy budget Shapiro and Burns, [50]!. Sodhi [51], Pritchard et in the Bay of Bothnia has also been derived and com- al. [52] and Kovacs et al. [53] have used plasticity pared with observed valueS. However, no attenert models of the ice to describe the formation of the appears to have been made to use this relationship to structural arch that forms across the Bering Strait. estimate mesoscale ice strength or other properties. They also studied breakouts of ice from the Chukchi Hibler et al. [65,66] have presented a similar model 1 nto the Bering Sea when the arch collapses . Re leer that is under development for use by the Swedish et al. [54! have related breakouts to the intensity Meteorological and Hydrological !nstitute for short- of winds and curr ents and have shown that currents term ice forecast,s. This is an application of the provide the primary driving force that controls break- macroscale model of H1bler that uses the viscous- outs. Reimer et a l. [ 55] give accurate simulations plastic constitutive law [3,4,32.43]. of ice motions in this region, including the h igh- Leppgranta [67] has questi oned captains of the Speed ICe mOtiOnS near ShOre. icebreakers that operate in the Balt1c dur1ng ~i~ter The strong influence of internal stress in the to evaluate the accuracy and usefu 1 ness of a model for vicinity of the Bering Strait has allowed some study predIcting icebreaker performance in this area. These of ice strength values. Rei mer et al . [54j have individuals gave a somewhat mixed response, but agreed estimated the unconfined compressive strength to be that the model was useful. Mhile this evaluation of on the order of 1.5 x lO5 II/m, Kovacs et al. [53] model performance is only qualitative, it is neverthe- have pursued the determination of yield strength and less a critical test of model performance, i.e., estImated the ice cover on this scale to have an whether or not it helps those who must operate in the internal friction of 30 degrees by considering the sea ice cover. wedge-shaped protrusions of Ice around Fairway Rock, which is southeast of the Oiomede islands in the 2.5 Bering and Greenland Seas Bering Strait. This. approach is attractive because it allo~s a direct evaluation of one parameter. the Discussions of modeling efforts for these two angle of internal friction. in terms of a directly regions are combined because the ice dynamics proces- measurable guantity, the location of a slip line in ses are relatively similar. The essential sImilari- the plasticity solution. Pritchard and Reimer [56] ties are that an ice edge is present, tracking its have determined the mathematical characteristics as- position is necessary in most applications, and ice sociated with the two-dimensional plasticity models; is usually thin enough that Internal ice stress these give a means for i nterpreting lead directions divergence is not the dominant force 1n the momentuv in terras of slip lines as suggested by Marco and balance. However, ice stress raust be included in any Thomson [ 5!, 58]. Sodhi [ 51] and Kovacset al. [53] model used to predict ice edge motion because onshore ice motions compact the ice and, thus, make ice 3. COMPUTATIOMALCONSIDERATIOKS stress an important factor. The set of processes that affects ice motion and deformation differs under Either a Lagrangian or an Euler i an descript1or is the compact and d i spers ed i ce condi t i ons th at used in sea 1ce dynamics modeling, depending upon the aCCOmpanyOnShore and offShOre motionS. The application. Both approachesprovide the ability to plastic1ty models developed for Beaufort and Chukchi describe ice velocity and stress fields. Sea ice behavior are appl1cable for describing The Lagrangian description refers each grrd loca- coaqract ice behavior here. The plasticity raodels tion to aninit1el parti cl e position. It i s most automatically produce zero stress levels in dispersed frequently used to describe the behav1 or of s o11d Ice if a thickness distribution is included to materials that are strained up to perhaps 50 to descr1be the ice conditions. Therefore, they are 100 percent ~ but no more. An advantage is that indi- Irmaediately adaptable to the thinner ice conditions vidual ice floes may be tracked simply. 4 disadvan- occurr1ng in these subarct1c ~aters, and they provide tage is that grids can becometoo distorted over long the best available simulations of ice behavior. periods of time. The Lagrangian approach is most However, these models lack a tuning of the useful for simulations of fairly short duration, say constitutive laws and a description of the more 5 to 'lO days, where total strains do not exceed the complex oceanographic features and the1r effects on usual 60 to 100 percent. lichen observed 1ce motions the ice. are prescr ibed as boundarycondit ions, the Lagrangian The essential processes controlling ice behavior description directly accepts these data as boundary in the Bering Sea have been categorized by Pease [68] conditions e.g., Pritchard [ 39]!. free data taken in March 1979. During that time, ice The Eulerian descr iption refers each grid location advected south~ard in a "conveyer belt," melting at. to a fixed point in space. It is most frequently used the southern edge and growing in polynyas adjacent to to describe the behavior of fluids, An advantage with northern land masses by freezing . Thomas and this approach is that, since the grid does not dis- pritchard [ 69] deployed buoys on the ice during the tort, arbitrar 11y large strains may be s1mulated. A winter of 1980-81 and found that, while the "conveyer disadvantage is that numerical dispersion occurs as belt" is active at times, nor thward mations also the ice cover moves through the grid. The Eulerian occur frequently. The northward motions persisted description is most useful when long-term s1mulations during this winter so that ice was advected northward are needed . An example is the Arctic Basin sinu 1ation through the Bering Strait into the northern Chukch1 of Hibler [32] in which yearlong ice motions are Sea. calculated . 4 comprehensive field prograrx is sheduled for the S ince mathematical relationships relate t1me deri- 1982-83 1ce season as part of MIZEX [10j, The data vat1ves in either description, the two approaches are will include ice motions and deformations, winds, essentially the same. The advection through the fixed currents, and ice conditions, as well as other Eulerian grid adds terms to each of the equations for metearalagical and oceanogr aphiC ObServations near conservation of mass, momentum, and energy. However, the ice edge. Some ice motion abservat1ons are for ice dynamics, the magnitude of these advective planned within the ice pack to allow comparison with terms is negligible in almost all cases Hibler et al, motions observed near the ice edge. A conceptual [66j; Leppgranta [Bj!. Therefore' they may be neg- mOClel Of fOrCeS applied tO the ice has been preSented lected for determining instantaneous solutions and by Muench et al. [71! to describe forces applied by only need to be considered when veloc1ties are w1nd and current drag, wave radiation and internal accumulated to determine long-term d isplacements. wav» drag. However, little effort has been focused finite difference schemes were developed for early on modeling the physical processes governing ice ice dynamics modeling efforts Pri tchar d and Colony behav1or or developing the constitutive laws r elating [77] I Hrbler [78j !. More recently, finite element deformations to ice stres.s and 1ce conditions. schemes have been developed Leavitt et al. [48]; Several different mechanisms have been offered to McKenna [44!!. Both methods have potential benefits. exp'lain the bands, streaks and patches of ice that The most valuable feature of the f inite elanent fo mu- OCCurduring Off-1 Ce windS. iaadhams [ 72] and Martin lation is its flexib11ity. This method allows arbi- et al. [73! have shown how forces due to wave trary connectivity of elements, simple specification radiation separate ice floes that air eady are of boundary tractions, and a variety of t1me integra- Isolated from the pack and cause them to accelerate tors. The use of finite element formulations does, away from the pack. McPhee [10j describes how the hOWeVer, inCreaSe Cumputer COStS, whi Ch SOmetime S melti»g of ice at the ice edge reduces the ocean drag makes finite difference formulations more des1rable. coef f1 cient and al laws higher f'loe velocities. Implicit or exp11cit t1me-stepping procedures may Together these two mechanismscould explain how bands be used with e1ther finite element or f1nite differ- and streaks occur. ence schemes. The time step is restricted for expli- Tucker and Hibler [74j and Tucker [75] have simu- cit schemes, w1th the size depending on either th lated ice behavior east of Greenland for October and elastic modul i or viscosities. Reasonable estimates IIovember1979 using the viscous-plastic model discus- of the time step limits are: sed earlier [32,76j. The thickness distribution Elastic alt < included two categories of ice, open water and thick 2 M/ch!' ice; therefore, compactness and average ice thickness were simulated. Data provided by two buoys that had fx Yi s tous rent, drifted through this region during the simulation period allowed simulated ice velocities to be com- where pared with actual velocities. The average velocity at 1s time step sj, error vector was about lg cm/s and the standard ex is roughly the smallest grid spacing m! deviat1on of daily velocity errors was 18 cm/s. oh is mass dens1ty times thickness xg/mZ!, Correlation coefficients for each velocity romponent M is elast1c modulus, whicn must exceed for the two buoys ranged from 0.48 to 0.57. The ice 200 times the ice strength if elastic strair thickness and ice edge motion were reasonable, but is limited to O.B percent, and excessive. Inaccurate thermal growth rates were felt i s ki ~amatic v i scosity,wh icn mustexceeo to be at fault. Since this was a first, rough 10 s times the ice st.rength if viscous calculation to determine which processes are most strain 1s limited to 0.5 x 10-7 s-I about important, results were judged acceptable. 0.5 percent per day!. The explicit numer1cal schmaeof Pr1tchard and Eolony counting for thermal growth and ablation. iiechanicel [77] requires time steps as small as a few minutes for red1stributlon is assumed to depend linearly on the winter simulat1ons in the Beaufort Sea. This scheme magnitudeof plastic stretching so that the evolut1on is cost-effective, though, because each t1me step re- of the thickness di st r1buti on is rate i ndependent. quires little computer time. Solutions at each node The fraction of open water i s specified for all are found 1ndependently of surrounding nodes at each stretching states, including both dilatation and step, so no large systems of nonlinear equations must shear. The ridging function that describes the di s- be solved. Under similar cond1ti ons, the expl 1 cit tribution of categories into which ice is rafted and viscous law requires time steps of only a few seconds, ridged is assumed. The effects of thermal growth and and 1n Just about a 11 real istic situat1ons, the ablat1on appear in the thermal growth rates for each viscous time step is smaller than the elastic time 1ce category. Thermal growth and ablation also re- step . Therefore, explicit numerical schemes, while distribute ice as its thickness changes . Either a effective for elastic-plastic models, do not appear fixed grewth rate table or an active model of the to be useful for viscous-plastic models. heat budget may be used, For useful implicit schemes, the time step is not Although the thickness distribution provides an restricted, except that it must be small enough to excellent framework for describing ice conditions, resolve the physical processes. This is often about our knowledge of ice redistribution is inadequate. 1 day. However, since solutions at all nodes are Data are needed to estimate the fraction of open water determined simultaneously, large systems of siraultan- forraed in shearing, the fract1on of ice participating eous nonl1near equations must be solved. The number in redistr1butlon and the range of thicknesses into of computer operations needed to determine the solu- which ice is ridged. These, in fact, are all of the tiOn at One time Step, therefore, iS far greater far constitutive relationships defining redistribution, an 1mpliCit SChemethan fOr an eXpliCit SCheme. The and all are inadequately understood. viscous-plastic constitutive lar of Hiblar I 7B] is The effects of veiocity inhomogeneities should attractive because it allo~s the easy use of an im- also be included in the equation descr1bing the evolu- plicit finite difference scheme. The treatment of tion of the thickness distribution. A relationship advection requires that the time step be limited by a that determines part of the thickness distribution in Courant cohdition terms of a statistical measure of the velocity inhomo- geneity should be reasonable,and it, should describe ht < dxf12vl better the effects Of this Subgrid-scale proCesS than do present models. Although these velocity inhomo- whe~ey 1s the maximumice velocity. Tine-steplimi- geneities cannot be resolved in a deterministic way, tations are about 0.25 day for the same parmaeters their effects can be taken into account statistically. used to estimate time-step lim1tations for explicit They generate leads, the leads freeze and thin ice schemes. results. This process alters the thickness distribu- In applying the finite element method, most codes tion as do the rafting and ridging processes. Pri- use matrix notation and store all solutions in arrays. marilyy, it 1s the thin ice category in the thi ckness lt is natural, then, to formulate a set of simul- distribution that is a'ltered. Any change in the taneous equations whether an explicit or implicit fraction of thin ice affects the ice strength, ~hich time integrator Is used. Therefore, most finite in turn affects the large-scale stresses . element codes offer both expl1cit and implicit time Therraal growth rates are fairly well understood, integrators. but only because thermal growth is less important in the short-term problems usually addressed in meso- scale eodeling, However, at an ice edge, where 4. MODELC01NPOltfNTS AiiD FUTUREEKTEIISTONS freezing can cause the ice cover to extend hundreds of kilometers in a few days' better models are re- The physical behavior of sea ice is described by quired. Here, the heat budget of the upper ocean accounti~g for mass. momentumand energy balance. tn will likely be necessary. additi on, the consti tot i ve 1aws def1ning thermal The forces exerted on the ice ~over are from growth and relating stress to deformation and to the rinds, currents, waves, sea surface tilt, and inter- redistribution of ice must be g1ven. The equations nal ice stress. Acceleration must account for both describing a specific model are not given here; inertial and Coriolis components. The r elative im- general formulations can be found in Rothrock [2], portanceof each force and the accelerations differ Hibler I 3,a]. teppdranta B] and Pritchard [3g]. with time scale and location. The conservation of Different levels of detai 1 are presented in these hor izontal momentumprovides the equation relating wOrkSfar the vari Oua COmpOnentSOf the models. HOw- forces and accelerations. The force from wind is ever, in total they provide a rather comprehensive described as a quadratic law. The force from cur- view of conservation laws and constitutive laws, as rents is also included as a quadratic function of the well as descriptions of the important physical proces- Currenti relative to the ice, thOugh it can be a mOre ses described by the models. ln this paper, brief complicated function of this relative velocity, verbal descriptions are given for each componentof a especially in shallow waters where bottomeffects are hypothetical model that reflects the bas1c physical important. Nave radiation forces and internal wave processesthat occur in sea ice . The model is generic drag also influence ice floe motions at an ice edge in the sense that the different levels of importance and the motion of the edge itself. Incoming raves of various parameters in different regions are break the ice floes in addition to adding to the ~ster ignored. drag. Furthermore,rhen off-ice winds form bands, Ice conditions can be described by the thickness streaks and patches, wave radiation in the leads ac- distribution or by a simpler functio~ that describes celerates the ice floes and disperses the ice. Sea only a few of the thickness categories. lt is neces- Surface tilt may be preScribed fr om the knowndynamic sary, ho~ever, to include open wate~ and thin ice in topographyor from the geostrophic current 1f appro- this function because these fractions strongly influ- prlate. Tidal currents can in somelocations add to ence ice strength and vertical heat flux . liass con- the short-term motions. They can be added to the servation is satisfied by describing the evolution of currents or can be included in an active dynamical the thickness distribution, 1.e.. by accounting for ocean model. The inert1a of the ice i s negligible mechan1cal redistribution of ice between categories whenaveraged over a day. However,on shorter time as the ice cover opens, r afts and ridges and by ac- scales ~ si gni f i cant inert i el osci 1 1ati ons can be generatedby the ba1 anceof inertial and Cor1oli s What ~ould be ideal is a set of cases that al laws 4meierations. On these shorter time scales, however, 1 solation of 1ndiv i dual parameters rather than com- tha inertia of the water column becomes just as impor- pl1cateds imul ations. Hathematica1 characteri st i cs tant and should be i~eluded along with the inertia of of the mode'Ioffer somepotential here. the ic.e, Althaugh the forces acting on sea ice have been described, we are not yet able to estimate them ac- 5. COHCLUSION curately. For example~ our knowledgeof current drag is improving, but there remains a need for extending The past decadehas seenmajor advancesin sea the model to treat large-scale currents 1n a shallow iCe dynamiCSmodeling CapabilitieS, largely because Saa. A1SO,even theugh wave radiation forCeS Can be of the concentrated efforts of the government- estimated, the e ff eCt On i Ce diSpersion muSt be sponsoredAIOBEK program. However,the past few determined. It is likely that this effect rill be yearshave shown far lesscoordination in fundingof described as a subgrid-scale process and not calcula- sea ice modelingresearch by the U.S. government. On ted dlreotly from the divergence Of the ice velOcity the other hand, Canadian, F inni s h and Swedish field. The problem Of sea 1Ce behavier near an edge governmentsand the U.S. petroleumindustry have wilt rightly receive extensive study soon. increased their interest and funding. During this Wechanical energy is typically 1nput by the wind time several neet groups have developed computer and transferred into the ocean by the current drag programsto solve a rangeof specific problems. acc~anied by ice motion. In addition, energy is While our understandingof the basic physics involved 1nput by wave radiation and sea surface tilt. The in individual i ce processeShas increaSed, this kinetic energy of the ice cover is modified as ice information has not yet found its way inta the ice velocity changes under the influence of these dynamicsmodels. A few attemptshave been made to farces. The internal ice stress dissipates part of validate the models by quantitative comparisonw1th this energy through deformation. In addition, the observations, but. manymore quantitative comparisons streSS flux divergencetranSferS energyhori zantally are needed. It is good that more knowledgeable through the ice, Effects of ice stress divergence scientists and engineers have becomeinvol ved in are therefore felt long distances awayfrom locations arctic research, and there is an increasing needfor at which energy is input by other forces acting on bath basic scientific knowledge and practiral the ice. app1i cat.ion of this knowledge. Hopefully, then, i f In ice dynamics models, the strength of the ice these past few years are to prove fruitful, we are cover may be determined by assumingthat the work done poised for some new ideas and somebasic progress. hy the ice stress during deformations is equal to the If this paper helps to give perspect1ve to our energy dissipated by small-scale processes. Hut only present capabilities and identifi es some of the twO Small SCale SinkS haVe been included in the mech- effort needed to make this progress, then it will amiCa'Ienergy budget tO date: gravitational potential have served its purpose energy and frictional sliding. 4 shear sink has been shown to improve model performance, but the mechanism has not yet beenanalyzed. Also~ s1nceenergy dissi- REFERENCES pated by ridging correlates well with observed back- groundnoise ~ other energysinks suchas fracture of 1. Rothrock~ 0. A., The mechanicalBehavior of Pack the ice sheet should be reexam1ned. While too small Ice, in Annual Reviewof Earth and Planetar to affect ice motion, energy released dur1ng fracture Sciences, vo . 3. pp. 3 7-342, 1975. might expl sin more of the noi se. Fi naily, other 2. %oOtrock, D. 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N., nterna ona ac i o og1ca1 Soc i ety, Cambridge, Bering Strait Sea Ice and the F'airway Rock Ice- Eng 1and, 1983. foot, Cold Regions Research and Engineering Lab- 67. Lepparanta, M., An Ice Drift Model for the Baltic oratory Report No. 82-31, Hanover, NH, 1982. Sea, Tellus, vol. 33, no. 6, pp. 583-596, 1981. 54. Reimer, R. M., Pritchard, R. S., and Coon, M. D., 68. Pease, C. H., Eastern Bering Sea Processes, Mori. Beaufort and Chukchi Sea Ice Motion, Part 2. Mea, Reva9 vol. 108, no. 12, 1980. Onset of Large Scale Chukchi Sea Ice Breakout, 69. ~homas, . Rit and pritchard, R. i., norto saond Report No. 1 33, Flow Industries, Inc ., Kent, and Bering Sea Ice Motion: 1981, Report No. 209, Mash., Iglg. Flow Industries, Inc., Kent, Mash., 1981. 55. Reimer, R. W., Schedvin, J. C., and Pritchard, R 70. Wadhams, P., Martin, S., Johannesen, O, M., Sam Chukchi Sea Ice Motion, in PDACBI. vol. II, Hibler, M. D. III, and Campbell, W. J. eds.! pp. 1038-1046, Oniversitd Laval, I ueTuec,1981. MIZEX. A Pro ram for Mesoscale Air-Ice Ocean 56. Pritchard. R. S., and Reimer, R. M,, Mathemati- rlteract ion x erlmerlts in rctlc Mar ina Ice cal Characteristics of a Plastic Model of Sea Ice Zones, Government Print ing Of fi ce, 701-831/144, Dynamics, AIDJEX Bulletin No. 40, pp. 109-151, Tel . University a as ng an, ea e, 1978. 71. Huench, R. D., Stegen, G. R., Hachmeister, L. E,, 57. Marco, J. R. and Thomson, R. E., Spatially Perio- and Martin, S., Predict1on of Ice Distribution dic Lead Patterns in the Canada Basin Sea Ice: A and Movement in the Outer Marginal ice Zone, to Possible Relationship to Planetary lfaves, Geo h s. appear in PDACB3, Technical Research Ce~tre of Res. Letters, vol. 2, no. 10, pp. 4392-434, 9 S. Finland, He~svn v, 1983. 66. Rraarco, . t., and Thomson. R. E., Rectiiinea 12. Madhams, P., A Mechanism for the Formation of Ice Leads and Internal Motions in the Pack Ice of the Western Arctic Ocean, J. Geo h s. Resam vol. 82 ~ 1983. no. 6, pp. 979-987, 19 73. Martin, S., Kauffman, P., and Parkinson, C., The 59. Blomquist, A., Pilo, C. and Thompson, T., Sea Movement and Decay of Ice Edge Bands in the Winter Ice-75 Surmnary Report, Research Report No. 16.9, Minter Navigation Research Board, Swedish Admin- 1983, istration of Shipping and Navigation and Finnish 74. Tucker, 'M. B. III, and Hibler, M. D. III, Prelimi- Board of Navigation, Stockholm/Norrkoping, 1976. nary Results of Ice Model1ng in the Greenland 60 Udin, I. and Dnstedt, A., Sea Ice-75 Dynamica 1 Area, 1n POACB1, vol. III, pp. 867-878, Universitcs Report, Research Report No. 16.8, Minter Naviga- Laval, Oueeeec,1981. tion Research Board, Swedish Admini strati on of 75. Tucker, W. B. I II, Application of a Numerical Sea Shipping and Navigation, Finnish Board of Navi- Ice Model to the East Greenland Area, Cold gati on, S tockho 1 m/Nor rkop in g, 1976. Regions Research and Engineering Labor atory 61. Ihastedt, A., and Sahlberg, J., SomeResults from Report No. 82-16, Hanover, NH, 1982. a Joint Swedish-Finnish Sea Ice Exper1ment, March 76. Hibler, W. D. III, A Dynamic Thermodynamic Sea Ice 1917, Swedish Meteorolog i cal and Hydro 1og1cal Model. J. Ph s. Oceano ., vol. 9, pp. B15-846, Institute, Report No. 10, Norrkoping, 1978. 'I 919. 62. Val li, A., and Lepparanta ~ M., Calculation of Ice 71. Pritchard, R. S., and Colony, Rhm A Difference Drift in the Bothnian Bay and the iluark, Report Scheme for the AIDJEX Sea Ice Model, in Numer- No. 13, Winter Navigation Research Board, ical Methods in Geomechanics, vol. Il, ed. C. Y. Ne3sinki, 1975. Desai, pp. 1194-1209, Amer1can Sac1ety of iv11 63. Udin, I., and Ullerstig, A., A Numerical hlodel for Engineers, New York, 1976. Forecasting the Ice Motion in the Bay and Sea of 78 . H1bler, W . D . I I I, Documentation for a Two-Level Bothni a, Swedish Admin1str at1 on of Sh1pping and Dynamic Therrnodynam1c Sea Ice Model, Special Navigation and F1nnish Board of Navigation, Report Report No. 80-8, Cold Regions Research and Eng1- ilo . 18, Norrko ping, 1916. neer1ng Laboratory, Hanover, NH, 1980.

HECHABICALPROPERTIES OF ICE IM THE ARCT1CSEAS

M.y. ifeeks and K. Hellor U.s. Army Cold Regions Research and gagineeri.ng Laboratory Hanover' Hev Hampshire 03755 USA

SUGARY snd s listiog of some of the more useful references. Ia doiag this we draw heavily on mors exhaustive reviews that have already been published [1-7]. The cm:chemical properties are reviewed for the Current interest fn the pt'opert.ies of ice in the main typps of ice ia arctic seas [glacial <,icebergs!, Sea is neither the result of such ice bei.ng an ideal shelf fce islands!, eea feei and representative material far study, nor of the desire of materials values sre given. Each ice type possesses a charac- eagineets to speacl their spare moments vtsit.lng the terlstgc range of structures aad compositions that arctic iee pack, with its nubile scenery and delight- differentiate it from other varieties of i.ce and to s ful climate. Ice in the sea is the primary obstacle considerable extent, these produce large var iatioas tn sffeotive and Safe reaOval ot the presumed large in mechanical praperties. Factors affecting mechani- oil aod gas reserves of the continental shelves ot cal properties temperature, brine and gas voluzss, the Arctic, ss well as s barrier to development of crystal orientation and siss, strain rate! sre new ees routes across the Pol.e that wo~ld result in discussed. as are gapa, contradictions, aad inadequa- great changes in current patterns of marine com- cies in available date. merce. 'To overcome this barrier, it is essential that sagineers understand both the behavior of ice ln the sea as well as its pertinent properties. I. IllTRODVCTIOB

Even pure ice displays complicated mechanical 1 ~ STRVCTUitgAHD COHPOSITIDHOF ICE IM TILE SEA peopertise, largely because it exists in esture at high homologoustemperatures, commonly above 0.95 and To understand the mechanical behavior of the calmant alvays above 0.90. @hendeformed at high varieties of ice that occur in arctic sess, ooe mcraia rates or loaded for brief periods, it behaves should first understand something about the structure elastically. By contrast, when strained slowly or and compositian of these materials and also of pure ashen mubjactecl to suetai.ned loadings ice is ductile, ice. 9e now bt'iefly review this subject, stetting ~ md it caa creep to large strains vithout breslting. vi.th pure ice, thea glacier iceberg! ice, then sea At aay gives stage in such a creep process . the ice, aod finally shelf ice isLand! ice thereby relation betweu strain-rate snd stress is strongly moving from simple to coaplex strucc.ures and composi.- aonlinaar. i.a. ice is vince-plastic rather chas tions. Neat atteation will be given to ses ice, in liammrly viscous. Because ice propertdes are highly that it is the most important ice type in the majori- sensitive to strain rats and temperature, streagth ty of arctic marine areas. River and lake ice vill can vary greatly Furthermore, the general effects not be discussed as they are not of csajor importance of maitiaxial stress states, as represented by in most marine areas. failure criteria, also change drastically with changes in temperature and strain-rate. 2.l lce lh It ia aot aur purpose to discuss the idealired properties af bubble-f ree, f lac-grained, randomly Although there are several polymorphs of ice oriented, pure ica ia this paper. Iastead «e shall [g!, ice Ilc so-called ordinary ice! is the only one discuss the mre complicated ics that occurs natural- of these that exists in significant quanti.ties undec ly in tbs sea. The sources of these aaterisle are the physical conditions eacouutered at the earth' s highly varied, raaging from ice sheets and valley surface. In fact, ice Ih which vill be referred to glaciers fcebergs!, ice shelves ice islaacls!, simply as ice! is the stable polymorph even at the rivers and lakes freshwater ice!, and from the hot tens af the world's thickest ice sheets. Ice is frecxing of the sea itself sea ice!. This last unusual ia ccasparisna to most materials in that the ~ aterial is the predomiaaut ice type ia the sess of sol.id phase is less dense than rhe liquid phase. tbe Arctic and it comes in a variety of types, each Therefore, ice floats, forming a cover over the seas, saith its cm characteristic assoclatioa of grain lakes, and rivers of rhe Arc.tic., causing a variety oz mince, crystal orieatatioas ~ snd gas aad brine engiaeeriag and operational problems that have f nclueions. Ve shall discuss briefly how each type largely iuspirsd this meeting. develops, its iateraal structure and i.ts assaci.ate.d The geaeral atomic st.ructure of ice is well mechanical praperties. To do this fully is a task understood aa ica lh vas one ot the first substances far beyond the present limitatioas of time and to have its structure determined [9j ~ Each oxygen mpaCe. Bere We Simply attempt ta pravide a bal.anced, ar.oe is located at the ceoter ot a tetrahedton vir.h general feel for the current state of this subject four other oxygen atoms located at each of che apices 235 uso! j' 1 [

le1 o[ Inzo] [ ao] Figure l. Structure of ice I.

Figure 1!. The tetrahedral coordination of the 'the Greenland Ice Sheerwhich contains 2.4 x 10 lrmg oxygen atoms produces an open, lov density crystal of water, has s maximus rhickness oi 3300 m, and ~ tructure with hexagonal ~ try. Dns important annually calves about 240 km3 of ice into the sur feature of this structure i ~ that the oxygenatoms rounding sees. If all the other permanent ice fialdm are concentrated close to s series of parallel. located in the Canadian and Soviet arctic and in planes, referred to ss the basal planes. The Svalbsrd are taken together, they contain eight tinea direction petpendicular tn these planes is the prin- times lees ice then Greenland. The iceberg produc- cipal hexagonalaxis, or c-axi ~ . The arrangementi ~ tion from these latter regions, although not wall such that, in any unit cell which contains four known, is certainly small and primarily of local oxygen atoms, fracture along the basal or 001! iaportance good examples are the small icebe rgs plane invol.ves the rupture of only two bonds, while produced by the glaciers on Svalbard snd the Soviet fracture along any plane normal to this plane arctic islands [1 0[!. gecause of the distribution. nf requires the rupture of at least four bonds. iceberg sources, icebe rgs are not much of s problem Therefore ths observation that ice glides snd cleaves in the North Pacific, the gering Sea or nost parte of readily oa tha basal plane can easily be explained in the arctic Ocean. terms of its atomic arrangement~ When the positions Estimates of the total number of iceberge of the oxygen atoms are pro!ected parallel to the spavned annually by the Greenland Ice Sheet vary from c-axis. the resulti,ng hexagonalarray Figure la! can 20 to 34 thousand, with most being produced by wast be seen to be composedof three close-packed rows of coast glaciers. The iceberg drift pattern is such atoms with each row paralleling the <1]20! or a-axis that iceberga formed along the east coast usually directions. Thesedirections, whichsre all equiva- drift around the coot'bern tip of Greenland and then lent, correspondto the dit'actions of the armsof a! move north, Joining the drift of the icebergs pro- ~ nowflakee groving from tha vapor, b! dendritic eea duced by the large outlet glaciers located along tbe ice crystals growing from the melt and c! internal west coast. This northern drift continues up to melt features Tyndall figures! ther form in ~ ide ice gaffin Say, where the iceberge swing around end start crystals as ths result of absorbed solar radiation. moving south along the coasts of gaf fin Island, Al I ere macroscopic manifeetatione of the atomic Labrador and Newfoundland. They finally reach the Grand structure. Ranks and ultimately melt in the Not'th atlantic. The structure of ice provides reasons for its Although the southern liait. of iceberg drift is in characteristically low impurity content. For sn general defined by the northern edge of the ware impurity atom to occupy lattice sites in the atoaic >12'C! North atlantic Current, iceberga have been structure of an ice crystal, the impurity arors must knOWntO tranait rhie Current in COld Water eddies be of ~ ~imilar size and charge, and arnot form a and have been sighted as fsr south as Berauda and as similar type of chemical borul ae the atma it ie far east as the Azores [ll [. ht present, concern replacing. Impurf ties meeting these requirmsents for about the drift and properties of icebergs is focused substitution into ice sre rare. Possibilities are on the regionsoff the Naffin and labrador coasts, on F, HE, NN> and %II ~ NBvOH,NN>F and the hydra- the Grand Nanks, and to a lesser extenr. off the coast halogen acids aad, in fart, sll of these substances of WestGreenland' especially in stean where do substitute in the ice structure in very small exploration for offshore oil and gss is currently saounts uoie fractions of I in 5000 or lees!. undervay. Kowsver ~ such aateriala are not present in signifi- Few studies have been made of the chatacter- cant amounts in natural water bodies. The amountof istice of the ice in actual icebetgs [ll]. In the other more comson eolutee that go into solid-solution Antarctic this is not a eurjor probiera as the proper in ice crystals is so small. that ice formed by ties of mostof the icebergs can, with someconfi- f reesi.ng even concentrated solutions can be con- dence, be inferred frets the properties of the parent sidered pure. Therefore, the phase diagrams thar. ice shelves which have beenwell studied [4 }. govern the freesing of aqueous solutions ate invari- Siailar inferences cannot be madeas readily in the ably of the si.mple eutectic type where the pure ice case of. Greenlandicebergs, even though the Greenland thar. forms initially is at equilibrium with Ice Sheet itself hae been reasonably wall studied. increasingly concentrated solutions of brine aa the The reason for this dif Eerence is that in Greenland r.empetstore decreases. the inlandice invariablypasses through the coastal 2.2 Ice bergs mountains in outlet glaciers before forming ice- bergs~ This usually produces strong defornatioo with resulting rerrystalli.zation changingboth the crystal In the Arctic, the pri.mary source of icebergs is ot'lent'ation and the grain sire. The ice is then r

I

LX-ATION2 ~ LOCATION1 2nosRAIRA snosea Isa

t.OCATION y anaesaIRS

Ftgure 2. Four fabric diagrams of c-axis orienta- tions in glscter tce fram sttes along the eargin of the Greenland Ice Sheet [12]. comparable to a metamarphic rock. Figure 2 shows bubbles present in the icebergs. Ice with random four fabric diagrams for ice from the margins of the c-axis orientations generally has tounded bubbles up Greealeud Ice Sheet [12], Two diagrams locations 7 to about 2 sm in diameter. In anisotropic ice, air aad 8! show a random pattern, 1ndicsttng the absence bubbles tend to bv tubular ~ wirh diameters between af recrystalliration io s attangly anisotropic stress 0.02 and 0.18 ssa and lengths up to 4 ms [15]. As gas fteld. Such fabrics sre coemonly observed in ice pressures in bubbles in glacier ice are commonly from. the upper porti.ons of large ice sheets, where equal to the hydrostatic pressure at a specific representative crystal cross-sectional areas are 2 to depth, the gas pressures in bubbles in icebe.rgs would 3 ma . The third disgtsm location 1! shove an be eXpeCted to vary frora 20 bare rOughly equal to eXtremely StrOng C-aXia aligrsaent normal to the the maximumtensile strength of rce! to some lower f oliatioo i.e. aormal to the plane of implied value, depending upon ice relaxation and gas shear!. Such strong single-pole allgneents are leakage. In fact, gas pressures ranging from 2 to 20 usually tound tn fine-grained ice thar. is undergoiog bars 1nIve been observed [11] . raptd sheer deformatton in either temperate or polar Aa the firn limit snowline! in Greealand is at glaciers. The tourth diagrsa location 2! is of cbe roughly 1400 m, Ii.ttle or no snow or permeable ice is ~ltimaximum type, in which the indi. vidual maxima sre found fn Greealand icebergs, and the ice density is iavariably wtthin 45 of the center of fabric sym- presumably reasonably uniform in the range of 880-910 metry. Such aultiaaximna fabrics sre believed to Mg/m [16]. This scans that between 88 and 89X of develop by recrystallisation in strongiy deformed ice these icebergs are suhserged as compared to about that is at or near the pressure melting point [13]. 83X subaergence for Anrarctic she lf icebergs vhich Such fabrics would be axpecr.ed to be commonin contain snow in their upper levels!. Creealand iceberge, as the majority of Greenland Outlet glaCi.era are believed tO be teeperste. fror iastamre, fabrics tram the Naltke Glacier, a sajor 2.3 Sea Ice iceberg producer in 1% Greenland, sre of this type [12] i Associated with this recrystal1izarion there Sea ice, formed by the frecsing of sea vater, is charactet'ietically a pronounced ].ncreaae in grain different from glaci.er ice in both structure and stre with ct'oss-sectional areas ranging between 100 compositio~. In contrast to glacier ice ~ where and 1000 sss . Ia contrast to the roughly equi- chemical impurities are cosmonly at concentrations ot dtmeaeional crystals commonly associated with the parts per million or lover, sea ice salt concenrra- ftrst rvo fabric types, the crystals shoving the tions saltnities! are invariably in the parts per Tmilttmaximumfabric type are not only large, but show thousand range. The ice structure is also quite extremely complex interlocking shapes that makes different, exhibiting a characteristic defect struc- their charscterixation by simple thin section ture within each sea tce crystal associated with the analysis both difficult and time-consuming [14] . entrapment of impurities, snd also strong, dis- Changes in crystal alignment are usually associ- tinctive crysral alignments caused by directional ated with chaages i.n characteristics of the air growth. In the Arctic, there are pronounced changes 237 Site 78.9 s

62 crn

figure 3. Sspresentattvefabric disgracefor seaice collectedaloag the coastline of arctic ALaska:a! raadomc-axle distributioa in Chehorisoatal plane, CapeThompsoa, b! preferredc-axis alignmentia the horisontal plane, KocrebueSound [20J ~

in the propertiesof the sea i,ce that hassurvived oneor moreeusenar melt seasons eo-called multi-year ice!. tfe thereforediscuss Che structure end compo- ~ itionof severaldifferent types of first yearice, of multi-yearice andof tha highlydeformed ice chat FigureA. photomicrographof a thin section of ssa composespressure ridges. ice showingita characteristic substructure. Grid spacing equ~ ls l as. Structurally, first-yesr sea ice is similar to ~ cast ingoC. There is aa Initial skim, then a transi- tion COaewhere rapid changesla Crystal orientstiOn occur, anda columnarsons formed of longcrystals suggest that sr.roag alignments can develop in the orientedvertically parallel to ths directionof the pack [lg, 23J if there is little rotation of the heaCflow!. Althoughthe structureof the iaitial floes relative to Checurrent direction. Suchcondi- skin aad Chetransition sonsare iaCeteetiagfrom t'he tions do exist vali off shote in the Arctic Ocean. point of viav of crystal grovch,these layer ~ are Seaice withsuch slignznents ie orthotropic,shoving tluite thin the haseof the Craasitioalayer is property differences along three orthogonal axes usually lass than 30 cmbelov the uppersurface of Associated vith selective grain grovth in the the ice sheet!. For preseatpurposes vs onLy upper potCioa of Che columnar anne is a marked coasider the properties of ice in. ths columnarsoae. iacresse ia grain site with depth [l, 24J. Limited daCasuggest Chat mesa grain diameteris proportional As s matter of fact, there have beenno specific Co depth in eea ice lees than 60 as thick. lfesn studies made of the mechanical nroeertiss of the ice above the columnar none. diametersraage from 0.5 to over 2 ca [. In The sCructure of ice in the colusnar noae is thickerice the linear increasein grain diameter fairly uniform,with eeseatially all Chscrystals with depthbecoeses Lees clear, and somedecreases having pronouncedelongation in the directioa of vith depthhave beenobserved [25J. In ice that has growth. Thacrystal orienCarionia iavariablyc-axi ~ developeda strong c-axis sligrunent, it becomes horlsoataL, se crystals in this orieatation havea difficult to di.stinguiehone crystal from another when grovth advantage over ctyetale oreinted ia oCher orientationdifferences are less than 5 degrees directioss their directioa of maximumthermal con- The en~ t distinctive feature of sea ice ~ in ductivity is orieaCed parallel to tbs di.recCioe of addiCioato its high salt content, is rhe suhetruc- heat flow [l, LTJ!~ for years it sss believed that tete viChln the ice crystals. In the colusnar xoae Che c-sais orientations in tbn colueer noae were each sea ice crystal is composedof a ousber of ice always rsadomia the horisoaCalpleas [6J as a number plaCeletsthat are joined together to producee of such fabri.cs had baca observed~ gucb a materiaL quaei~aagcnaLnetVOrk in the horisOntal plane- vould be transversely leotropic; it would showpro- This substructure,shown in Figure 4, results from perty vsriatioas in the vertical directioa associated crystal grovthwiCh a non-planarsolid-Liquid inter- with changesin grain nice, crystal substructure,and face. Similar substructuresare coamonlyproduced salt coateat, but st any given level sll directioas du«ag tha solidif tear.ionof impuremelts, Io fact Q in the horisontal pleaswould be identicaL. govever, i.s Cheeatraptsent of brine betweenthe ice plates recent ~ tudies [!8-ZL[ have shown thaC most of the eC the aon"planar interface that causes sea ice to be faut LCe OCCurring Over tba COntlnentel ShelVea Of ~sl.ty. Thespacing measuredparallel to rhe c-eats! the Arctic showa strong c-axis aligaaenta vithin the betveeathe brimspocket arrays so! is ~aly horisootal plane. Theory, field obeervatioae aad referredto eitherss the brine Layerspacing or as experiment[19, 22J suggestthat these altgmant the plate spacing,and it varies inversely«th directions are controlled by the directioa of che grovth veLocity [I, 26J. Typical a variations curreat at the ice-sea water i.ntetf ace. Figure 3 range from 0.4 ma near the upper surface nf the ice showstvo representative fabric diagramsfor sea ica, sheet to [.0 rmnat the base of the 2 s ice sheet The beet available study of Chessvarlatlons [27J the f irst showiag a tendons c-axle orientation ia the madetecently aC gclipae Soundin the horthvest horiaoatal pleas. ths secoada strong c-axis align- Territories. The results ere shownin Figure ment. La s tacent study of c-axis oriaatatioas eloag inverserelaCion between a aodgrowth velocity is the Alaskan coast, over 95I of the' sitse sampled clear. In thick ~lti-year sea ice, whichpresumably shoved strong crystal alignments [20J. At first grove very slowly, so values of i.5 nn have eight ir. mighr. appear that such alignaeate would only observed,In the seaice formingon the develop in fast ice areas. However, observations the RosSICe Shelf at S location Vhere the s"elf -I CROWNRAZE IO ml4 0 004 0 10 0 II OZO 0

OZ

04 04

0.4 I 0

IF 0 OI 10 14 ZO~ I, I IZOZ 40 OO OI 10 12 10 GROWIHRA1Z Rm'SIV SllI'Ill'4, aiiu APERICKORIIIE Ll'I'ER IPI inc iii i Figure S. Profiles of growthrate, salinity and brine layer spacing. Curve b repraseste the scan of the calculated grovth rate, curve 8, for an interval of t $0 aa for every 25 m [27] ~

Alen uePI Fac IIOEC44 mr IIIIR zzIIR 44404Iws IPakRiaMIR IRAPR aIPR

40

m As ss m so 104 144 I04 140 100 Figure 6. salinity profiles of ice of Eclipse gonad usda at tWOweek intervals during the IPinter Of f977 78. Scale for salinity is shown in insert. Vertical solid lines represent a value of 6 o/oo and are given as reference [3L [.

016 a Chich and the ice only growsabout 2 cn/year, an Valuea Of S 004have been nnt ed [2BJ . Brine layer spacing is believed to affect the strength of sca ice [29!. ds ~attuned earlier, the salt in the sea ice is aot Cheresult of solid solution, but ia causedby Cheentrspaant of brine betweenthe platelete of pure ice that cospose individual crysCals of sea ice. The aaoust of salt entrapped is not constant, but varies eysteaatically with the salinity of the water being frosen and with the ice growthvelocity. Very ~ 1OWgrOIptb reaulta in near-total rc]cCtinn of Salt fr~ the ica, while very rapid freering causes near total entrapnent [I, 30j ~ The effect of changes in growth rata on ice salinity can also bc seen clearly ln Figure 5. h series of representative salinity profiles for first year sea ice ia shownin Figure 6 [311- OZotethat the upperand lower porticos of the ice characteristically have higher salE.nitice theo the ice in between, and there is a gradual decrease in the aeon salinity of tha ice IrLth tine. The drainage of brine f ron saline icc appears to be a conplicated process and several different ~chanisna are believed to be involved [I[. ln the present context, the aost inportant results of brine drainage are changes in the porosity and the develop- of brise drainage channels These structural features' ons of which ia shown schesatically in 'Figure 7, can be considered as tubular " river" Figurc 7. gchesatlc drawingot a cut througha bri.ne drai.nage channel [32[. Pl.gure 8. Shapes of brine pockets: a! horirontal vi.ew brine layer spacing is approximately0.5 mz!, b! vertical view. Ice is from Thule, Greenland ~

ehepea of a seriee of bri.ne pockete; they cczmnonly are rather complex. The dark circles sre gas bubbles. Ac Lower temperatures there also are several different eolad salts that precipitate in tbe Lce -8.7, NafSO~10820, -22.9, MsCL2820; -3fa.g ÃCL; etc!. Pigure 9 ie a scanning electron micrograph of a vertical section of a brine pocket at -30'C showing the solid salt cayetals 5'. The effect of these solid salts on the mechanical properties of saa Lce has been studied surprisingly Li.ttle. ln addition to columnar sea Lce ~ there Ls one other type of first-year undeformed ses ice that should be cmntioned. This is frazil ice, produced by accumulation of individual discs and spicules of ice Chat fora in the water. lt hss commonly been thought thaC, although frazil ice is frequently observed during the formation of the initial ice cover, once this cover stsbi.lixed frazil ice generation would greatly decrease. Exceptions tu this would be areas near the Lce edge or i.n large polynyas where substan- tial regions of open water are found. However, recent work in the 'Weddell Ses to the east of the AACaactic Penisula has indicated that, at least in that region, frazil ics generation is a very important ice producing mechanism [L ~ 36]. Por instance, of the ice smspled, over 502 was frazil sad Pigure 9. Scanning electron micrograph of ~ vertical the thicker the floe, the higher the percentage of ~ ection of ~ brine pocket at -30'C 5j. frazil ice it contained. Whether such large amounts of frazil also occur in the Arctic is not known but Chere is no strong evidence against such a possi- systems in which the tributaries are arranged with bility. Lf ma!or quantities of frazil Lce form in cvlindrical aysmutry atound each main channel the ArcCic, there are interesting implications. [32-33} . A represent.ac ave channel diameter at the Pirst, because frazil ice fores by s completely bot.tora of ~ L,55-u-thick Lce sheet is 0.4 cu and different mechanism than columnar ice, present esti- chere is, on the average, one channel every 180 cm mates of Che amount of ice being generated Ln the Channel diameters ae large as 30 cm have been noted, Arctic night have to be revised. Secondly, f razi 1 though mast diameters range between 0.1 and 1 cm. Lce hss a completely different crystal structure than Although Chase Large flaws" presumably have an does COluunar LCe. Strutturally, fraxil LCe ie COm- effect oo the mechanical properties of sea ice, oo moaly fine"grained, with crystal sixes of 1 ms or studies have been made of the matter. lees, it has a crystaL orientation which is presumed Given a sample of sea f.ce with a specified salt to be random, and there are brine pockets Located content, the aeouot oi LLaluid brine the briae mainly between Che ice crystals, as opposed to within volume! present io the ice is a function of tempera- crystala. Although there have not yet been sny ture only, because st each temperature tba composi- systematic studies of the physical properties of tion of brine Ln equilibrium with rhe Lce Le speci- frazil icc, they clearly would be expected to be fied by the phase diagrsa 4!. ChangesLn the different from those of columnar sea ice. volume of brine in the sea Lce are mast pronouncecl Whenees ice goes through a suaaaer melt period near the melting point, where small. changes in it undergoes a pronounced change io salinity produced Cemperature Canes Large Changea Ln brine velum.. AS the percolation of relatively fresh surface malt- most first-year eea ice bas ealinities i.n the range wsCer down through the Lce. The result is an. ice of 4 to 12 o/oo and temperatures between -2 and sheet with very low salinities CL /on! in the -30'C, the brine voluse u csn be expected co vary portion above water level and sslioities af between. 2 between 30 and 300 Joo. Ptgure 8 shows detailed and 3.5 t'oo in the portion below water level. Figure 11. Thin section of ice f rom a multi-year ridge in ths Beaufort Sea showing a block of columnar Figure 10. Gross-aectioa of a fce "cemented" by fine grained granular ice. Core is multi-yesr floe [37!. l 0. 9 cm in di arnet er [ 43! .

Omos tfse brine has drained from the upper portion., first-year ridges, multi-year tidges are comnonly fes is quite porous and it may recrystallize. composedof massive ice, in that all the voids Icm that has survived several summers ultimately preseat in aewly formed ridges have aow bees filled a layercake of the annual layers formed with ice. Figure 11 shows thin sections of ice from ~ mrgng successive sister periods of growth [37-3gl ~ a multi-year ridge. The ics is quite complex, cross-sectioa of such a floe ls shown la Figure showing fragments of the initial ice cover that wes lO In. fact, much asilti-year ice was probably crushed to form the riclge, plus a large amount of ~ mfrsrmedac som time in its pest aad would show a fine grained ice presumably similar to frazil! that ~ sch msre complex cross-section. Confident srate- fortaed in the voids between the blocks [43!. ~re ennCerai.ng the relatiVe perCSntagee of multi- year ice that are undeformed, deformed, coluisnar or 2.4 Ice Islands fcmmil vill have to await more adequate smapliag, In gmmmral~ usdefotmsd tmrltf-year ice in the Arctic So called ice islands are, in fact, tabular ~tsmgm is believed to reach a steady-state thickness icebergs froa a relfct Pleistocene ice shelf that. sf 3 tn 5 m, at which time the thickness ablated still exists along t' he north coast of Ellesmere dmrgmg ths eaamer equals the thickness grown during Island, the northern-most island in the Canadian tfsm minter t39l ~ Although deformed sea ice can grow Archipelago. Sttictly speakiag, ice islarids are guet tm greater thicknesses ~ rather atypical coaditi,ons a specific type ot stieli iceberg, but we will discuss ~ rm required Snd SuCh iCe, althOugh knave, would them iti a separate category as chey are uriique to the sgsfsmarto be rare [40]. Arctic Ocean and are composed of a rather complex aix Ice thicker then 5 m is, ho~ever, rather commas of ice types. They are a particular hazard along th» im rlas ArctiC. Basin. For instance, ia a recent study coasts of Northern Greenland, the Canadian Archi- of mubaarfne sonar prof iles of the underside of sea pelago, aad off the North Slope of ALaska. Ice ime over 40Z was thicker than 5 m [4L j. This islaads can have long lifetiaes. For instance, the thicker ice is generally believed to be pressure best kaama ice islaad T-3 hss been drl.f r.ing around ridges aad rubble fields that are produced by the the Beaufort Gyre the large clockwise circulation in dmformstfon af thinner ice. Pressure ridges and the Beaufort. Bea! for over 30 years. If current dmfmxmmdice in general are commonin all areas of predictions of i.ts tra!ectory are correct, T-3 may peck fce, arul are particularly cormnonin the land- "die" wichln the next year by leaving the Arctic LtsclamdArctic Ocean. Although data are Lisiited, it Ocean via the East Greenland Drift Streets arel meLttng currently appears that the most highly deformed, aod in the Storth Arlantt,C. ICe islands also have been ajmrs the thickest, ice in the Arctic occurs in a known to leave the A.tctic Ocean via Robeson channel broad bend starting off the NB corner of Greenland between Greenlaad and Ellesmere Island! aad also arel stretching to the Nest, north of Ellesmere Land through the Canadian Archipelago into Viscount assg thea veering toward the SM down the coast of the ttelvil Ie Sound. It is only after they leave the Arcfsfpelago to the coast of Northern Alaska. The A.rctic Oceao that they drift through regions where Lmrgeet free-floating ridges that have beeri observed oi dinary i.cebergs produced by glaciers art common. hmvvasails up to l3 m high and keels up to 50 m As their origin i.s an i.ce shelt, ice islatids are dmetls. Ia near-coastal areas where pressure ridge tabular with t'hicknesses of several tens of metets keels caa ground, ridge sails can be particularly T-3 had an initiaL thf ckness of approxiraately 70 kgtght heights in excess of 30 m have been aoted. m! ~ Lateral dimensions are highly variable ranging from snore than 10 kilometers to a tew tens of sieters Considering the importance of ridges, there has fot ice island iragmsnts There is no adequate ~ eeis smrprisl.ngly little vork done on thea ss census of the number of ice is lands currently Eirmt~ear ridges ate composed of blocks, it would be drifting in the Arctic Ocean. The numbers "sighted" intmres tlag to have quantitative information on at specific locations are highly variable. For blxsck

Vacanfermlr e Sl ~ cb n I u n

ApprexlrsOie Slr~ lf BOSS Interface D vowlzostat seats cent

Pigure 12. Iaterpretstion oE stratigraphy of patC of itard gust Ics Shelf, based on drill-core and labora- tory studies [501. that grouaded aorth of Barter Island. The curreat layers that formed from the freezing of a layer of interest in ice islands res~its from Che threaC they brackish melt water that. Ie known to be preseor, pose Co offshore structuree ia ths deeper vaters of be~eath the ice shalt at some locetioas I50]. This tbe Beaufort Shelf. Tbe ice island problem is explanation can account for both the complex inter- similar to that posed by large hurricanes in the Gulf etratif icatioa of this ice wl.th normal eea ice ~ and of Mexico ia that although tha probability of a given for the measured oxygen isotope ratios. structure being iwpncCed by an ice ialsad is smell, Che probability of Che structure sustaining damage if ~ colliei,on does occur is high. 3. KECHASICALPIIOPERTIKS Although the ice la ice islands has aot bees extensively studied, eaough ia kaoua to be able Co 3.1 General bsheviout give ~ general descriptioa of the several dif ferent ice types involved [44-50 I . The complex a tructures Systematic kaovledge of the mechanical proper- aacouatered ia soma ice islands caa best bs appre- ties of ice derives mainly from studies ot norr-saline ciated by referrl.ag tO Pigure 10 in Swithre study of polycrystalline ice which ie aot etroagly eaten Arlis XI [4'7I asd to Figure 12 which is presented tropic. The principal motivations for study have here aad which swmarixes the lyons et al. [50! baca glaciology, vhere the chief cancers is vith f Lov picture of Chs structure of Cha ice in part of Che uader waall deviatoric streeeee < 0.2 Hpa!, and lfard lhint lce Shelf. There sre at least four dif- engineeriag, vhere the emphasis is on strength at fereat types of ice present, These are as follows: relatively high scrais rates > LO s !. It ia aov lake ice - Tha Lake ice is tha result of the possible to uaity the findings f rom these areas of fremring of elongated bodies of vater that form on rhe Study [51 I, eepecially sInCe it has been demnaatrated surface of ice islands during the melt season. The that the favoured teat ot glacioLogy, the constant ice cam be easily recognised by i.ts medium to very load creep Cest, caa give essentially the ease infor- coatee grained texture, the LOng col,ulenarcrystals mation as the favoured test of ice engineeriug, the with straight grain boundaries and the long, linear, constant scrain rate ecrength test [$2,33] vol 1 orisaced bubbles. Typical graf.n diameters are In simple terms, l.ce has the followiag charac- 1st get 'Chan3 cws teristics. Snowice - This ice Cype, whiCh Coeposeetarch of l. Uader moderate hydrostatic pressure and the upper part of the glleemsre Shelf, is produced by moderately low temperature, ice compresses elastical- the densificatioa aad recrysCalliaation of eaov. The ly vl.th s bulk nodulus of about 9 GPa. Any bubbles crystals are equsat and suhedral showing~ typical ia the ice compress so as to equilrbrate in accord- mosaic texture. Crystal orieatatioas are randomaad aaCe slith the gae laws, and they may eVentually die- grata sisse characteristically range frow 0.$ to 1.5 appear to form a clathrats. Under sufficiently high pressure, ice Ih transforms into high density poly- Sea ice - Sea ice usually occuts in ths lower morphs including water!. as described by the phase portion of the ics shelf ~ This material has the diagram far taethermal conpreesiOn. Under intenee characteristics of muLti-year see ice, although the adiabatic compression e.g. explosive loading!, eelinitiee are somewhatLover 2 o/oo!. The discrete phase transitioas are not detected, but the crystals show the characteristic elongacion of colum- gaakiae-ItugnaiOr. CharaCterietiC giVee a preeaure- nar xone sea ice aad the substructure vithin each volume relation that ie not such dif ferent frow a crystal ie still evident. Somefine grained tracll "smeared~st" version of the Bridgman isothers. ice bae also bees reported. Iu t.vo cases 7, 49I 2. Under deViatOriC Streee, ice daturea aa a strong preferred c-axis all.gtuaente have been noted. aon-liaear viscous solid, changi.ng its fabric aad Brackish ice - This ice shows a well developed structure ia Che process. Under constant stress, e stratificatioa, vhich is a ref lectioa of cyclic complete creep curve shove deceleration toliowed by variatioae ia the amount of entrapped gas and the acceleratioa to a iioal rate in the usual way, average grain eisa ~ Typical layer Chickaesses are alChough there sre possible complications. Under betveen 20 aad 25 cw, and the strata nay locally be constant strain rate, a complete stress/strain curve varped into a series of folds. Very large crystals showsstress rfsirut to a peak before telling and are Cameos with some.ae large as 120 cm. C-axis tending asymptotically to a limit, again vith a orieatatioae aly are vertical and aali.nities pOssible COmpliCatioa ia the form Of an initial yield are usually very low. Although several differeat point. Fnr aay gives eCage of detarnatiOn, the explanatioas have been advanced to account for such stress/strain-rate relation is non-linear. Lt is unusual inca the most Likely sxplaoation is that this usually gives as a simple power relation, alrhough material developed as a series of annual grovth the expoaeat changesover the complete range of 2i2 stresses and strain rates. Below about -IOvC the Another f act or Co be considered is the s i se of effect ef temperature can be described by an the stressed volume, since non-aetalllc brittle dttkssmius telation with an activation energy of about SOlida tepiCally get. veaker aa values inCreaeee 70 hd/aele. Hovever, closer to the melting point., increasing the probability of encounterrng bigger ~ratmre sensitivity ia greaCer than SuCh an flame!. Publiabed data fOr iCe on this topic cover «Lmetfsn would predict. oaly a narrow range of voluaes, but it is to be 3. High sensitivity to strain rate end tempera- ekpettad that fracture Strength wf.ll deCiueee with tata causes ice to display a broad range of theo- increasing volume st high strain rates where cracks leggcal properties. 'Hfth hi.gh rates and low teapera- aad similar flaws control the failure!. The deforma- tete, a lae tie behaviour dominates ~ and dev Catoric tioo teaietanCe im nOC eapeoted tO be SsuChaffected ~ training culminsces in brittle fracture. 'Ifith lov by Site at very low strain rates where the control- rates and high temperatures, ductili.ty is predoai- ling flaws are thought to be dislocations!. ramC, and large creep deformatfone can occur. Very perhaps the most dif ticult variables to deal sf Ceo bOth elaatieity Snd nOn-linear viacosity make with are aniaotropy and iohoaogeneity. Studies of ~ ggrsiftoast contributions to deformatfan and rupture ~ nisotropy are not very far advaaced, so it is prmcmasas I dangerous to venture general lcations. However, Chere i. In mrltisxisl ett'ess staCes, compressive is not larch doubC that ice with preterred crystal Mt aCress Lsotropic component of stress tensor! orientation flows most easily when the resolved litcle effect on the devistoric stress/scrain- stress ia parallel to tbe basal planes of the rate telstf.on whee stress deviators ars very low and cryscals. Qfth high strain rates end multfaxfel teegserature is well below 0 G. By coatrest, moderate stress, the "strength" of columnar ice varies depend- preeeute suppreasea internal aicrocracks at high ing on vhether the stress field ls tending to push ~ tteih ratea, end it ineressea defnraatinn resistaace the columns together or apart, sed "strength." Extreae pressure at Cypical tempera- ice testln and ex rimental data. Under the tmtas peahen ice tovarda the phase transformation to best of circuae lances, most sachanica 1 tests sre smch amtat, and coassquently deforaatioa resistance and anre complicated than their textbook ideelizetions. ~ Ctmngth decrease with increasing pressute, almost ifhen typical tests are applied to ice, the problems irrespective of Che magnitude of devi.atoric eCrems or are magnified by thermal instability of the material ~ train race. melting, eVapOratina, brine drainage, vapour and gtrengCh and deformation resistance are inf lu- surface diffusion! and by high sensitivity co rate smnmdby strain rate, Camperature, porosity snd grain and teaperature changing the balance of clast.icity ~ imm ie the following way. and plasticity! . Strain rate. Deformation assistance and An international grOup hee been trying far the "strength intrease with increase ot imposed strain last decade to bring some order to ice cestrng, but rate. Conversely, strain tate r. Lncteases with the standards of experimental work are still highly imctmame of imposed stress n. In either case~ variable. For the present we have to use results where n eight range f tom'2 at very low froa noae test progress thet are obviously flawed, scteee < 0.0l ffpa! to 4 st high strain rates and lt is necessary to be aware of cossaon sources of > LO"gs I!. error and ndeunderatandfng. The fOllOwing poinra Tmapetature. ifhen ice is Cruly "solid" below might be kept in miod when considering the data given -l0 G for mon-salina ice, or below the eutectics of in the remainder of this paper. dimmolved impurities!, strain rate c ror a given l. Fot tests neer O'C, lax temperature control stress o can be described by a relation of the form can introduce large errors. t ~ exp

and the sheer modulus C is

C 8/2+v! ~ G.38K

In ice engineering it is f requently necessary to appLy elastic analysee in situations where the ice 3 deforaecion isnot purely elastic. In such cases, it aay be apptopriate to uee "ef factive" sxydulf derived from relatively slow quasi-static teats. because these sftective moduli 8'! represent the combined sf f ects ot e les tie it y, re cove rs ble "delayed e last ic ity, and irrecoverable creep, they are appreciably aors sensitive to teaperature, strain rate aod vi bra- tional frequency than is Young's modulus B. At temperatures and/or high strain rates, LL' ~ 8, but at low strain rates ~ LO s ! or relatively high temperatures » -LG C!, 8' may be as low as 258 to 30X of E. When low strain rates are coabined with temperatures approaching O'C, 8' can have very low values ~ and the elastic approximation may cease to hm useful. In coaparison with the eitects oi tempera- ture snd strain rate on 8', porosicy variations over the typical range sre not very significant, but there is e slight decrease of 8' with increase of n de- crease ot p!. "Bt rect iva" values of Young' s modulus 8' should 10 OO OZ o.s O.a O.e be paired with effective values of Poisson's ratio, p. DsyuuyLs/csy, Mermr! Although v' does not receive explicit treatment in the literature, soae deductione can be made I2I. Figure 13. Suamaryof Young'~ modulus date for non- As ductility increases it is reasonable to expect ~ elise ice and snow for data sources sse 163 I. s 1/2, representing incmspressible flow, with 8'/Lc O.Forice whichhas lowporosity or walter-filled anical properties of ice that has been collected from puree! the bulk aodulue 1 should not vaty mruchwith icebsrge ~ but there ie pLanty of inforaation about porosity, temperature, or strain rate, aod for a glacier ica, which is what icebergs consist of. Over firet apprOXiaatiOn ir. Csn be aeeumed equal to the the interior areas of Creenlarul and Antarctica, true Young's modulus for sero porosity, E . Thus glacier ica forms by a sedimentation process involv- v' can be expressed ae ing vieco-plastic compaction of dry snow. The re- sulting material is fine-grained and almost ieotrop- 1 8' v 2 f98 ic, withincluded mir whichforms close! bubbles when o che bulk density reaches about G.B Hg/m . Only the layers very close to the glacier bed is there which gives a systeaatic variation between the limits. signif leant shearing, with consequent devalopaent of I/3 and L/2. preferred crystal orientation, bnt when ice from che interior le funneled out to the eea through ica Stean th and detoraation rsei.stance. Strength streams and va!ley glaciers there is more general for any specified state of stress can be defined as shearing, and come inclusion of rock debris. There- the aaximua stress, or detormst ion resistance, for a fore, in lieu of data on ice froa actual icebergs we given strain race. For ductile yielding of fine- have to be content with ~ suaaary of the properties grained ice, constant strain rate strength tests gtve of glacier iCe, of artitiCial ice which eiaulatee essentially the ease information as consrant sr.ress ieotropic polar glacier ice, and of noae other cypea creep teste, so that "strength can be obtained from ot mon-salina ice. either the peak of a conventional stress/strain curve glasticmoduli. For polycrqstaLLLne ice of low or the inflection point of s conventional creep curve 9 lty~deyty 9 + O.yly NEI !. high 9 9 yyy [52, 53]. dynamic measurementsof Young'a modulus8 give values The most coamon test is uniaxial compression. ot approximately 9.0 to 9.5 CPs in the temperature V t xi 1 stretch oc for non-saline ice range -5 to -LO'C. Careful measuremeots of the at -5 to -10 C varies by three orders of aagnir.ude initial tangent modulus for quasi-static uniaxial G.OL to 1D Spa! as strain race varies trna about compression teste give quite similar values 4-57!. 10 to 10 e . At high strain rates, ck re not as temperature decreamesyB inrreases nonlimearly highly sensitive to temperature, and at very high Fig. 13!. but the ett'ect is small for "true" Young'~ rates the temperature et teer. is expected co bc ~ odulus se opposed to aif ective values of 8 whfeh comparable to that for Young's modulus Fig, 14!. At include creep etfecte!. Porosity n ~ which can be very low strain rates, the variation ot oc vith expressed alternatively es bulk density p, hss temperature Fig. 14! can be deduced from the depend- signit leant influence on 8 Fig. 13!, amd it is ence of miniaua creep rate on temperature Fig. 15!. interesting to note that 8 drops sharply beLow the Because the stressistrsin rats reiat too rs tne same density vhicb represents close-packing or equant for constant strain rate and constant stress Ftg. grains p 0 55 LLg/a3 !. Lfy! 9 the ctrees/strain-rate relations developed hy ao

10

-lo -so P I'CI Figure . Oompilatios of temperature relationships [2[ ~ All stress values are normelfxed with respect to the value for - C. !! Verietfon of Young'4 eodulus with teaperature. 2a! Un!axial tensile strength - data from [58]. 2h! Un!axis! tensile strength - data from [59], 3a! Un!axial compressive strength data from [58]. 4! Ductile yield stress data from [60]. 5! pressure for phase transition from ice !h ta water under isothermal hydrostatic rompre salon.

102 «!'] -184410 CT 10 Ido o! 5<2 i2,r IO y 14tes!s deleted! I IO

a o IK

er 10

IO

J Stress rdJs Nl 40 4.2 ~ 4 ss 44 sorrr Iro n 8O e rx I' 0 M -20 -do -40 -do -So IO Ol IO IO I 00 «sessor mrs '4! CT,Slrrss !tlPo! pdgmzs ~ gap!tidal relation !etween minimum strafes Figure . Date f res testa ender Ccnateot Load Sod Cate aad temperature LOr high-atrees creep [6O[. constant displacement rate. Lines A aod 8 are regression L!nee, as indicated on the figure [53]. Ion

bio~ IQ

~ 10l o P. I IQ I-

[f IQ

a s «u I 'o lo IQ' OCTAHEDRALSHEAR STRESS rj,bere IQ' IQ 10 IQ 10 IQ I, StrataRote s '! Figure 17. Stress/~ Crainrate relations far creep of glacier ice [6 j, Broken linea indicate relations derived from earliet studies [62!. IO' glaciologists [61I for minimum creep tete Pig. 17! can be interpreted ae ecrength/strain-rate relations for Losr rate ductile yield. It sight be noted that gleciologiets cosmonly represeat axial stress ot io terms of octahedral shear stress r r 4 o 3! oct and axiaL strain rate ti in terms oi octahedral IO etraia rate toct e oct e>/A!. It is sometimes useful to knosr the "time-to- 0 failure" Cf, def ised as the time taken Co reach the lL peak of e stress/ ~ train curve or the inf Lection poinr. ft of a creep curve. Figure LB shosrshov tf tar fine- grained ice is iaversely proportionaL to both strain tate and a paver ot stress. AC high strain rates, a decreasee as porosity increasee p decreaeee!, as ehosrnin Figure 19. Par Lou.strain rates, the ~ ftect oi porosity on the «rc-c telatlon hss to be deducedladirectly Pig. 20!. Grain siss d does not eppeat to effect q systematically st Lost strain rates < 10 ~ !. At high strain rates, oc ie expects«[ to decrease ss d incr'esses,perhaps vith ec ~ d 1», bot adequate data are not yst available. IQ In cases where ice undergoes durtile yield eith- 0.! I.Q oa.t fracture or rupture, it ie sometiaee useful to knov the "residual strength" st relatively large fT, Stress MPo! strains. The relation bets«eon residual strength and F'igure 18. Time-to-failure tf for fine grained St.rei«l raCe ie much the Salsa sa the relati.on betveen non-saline ice. tf ie gives as a function of creep tate aad applied stress for lstge etrsi.ns, aad straia tate Pig. 18e!, and as a funct.ion oi stress relevant deCa for both coastent strain rate aod coa- Pig. 18b!. etant Sttees are gives in Figure 21. 0fti $«*l «c i~it* th«1th SameWay that Ocvae defined, there ie li.r.tie dsf- ferencebetsreen OT and I[c tor ieotroPiC I.ce at rate Limit of oT ie about 2 ! pa, vith a around lov strain rates < 10 ~ ! Ln both cases the ice I ! Hpa. This gives a ratio of oc/of welL belov yields by shearing, and the dif ference ot aormel the theotaticel values of 8 or mtre that are Sr.rene does nOC seem ta have larch eifect. Abase SOme prediCted by Gritf ith theOry and its derlvarivee critical e'tt'eia tare 0 e et -7'C sea Fig. another reason vhy dlateetraL compress.ion of a disc 22! there is s bifurcatian in the stress/strain-rate at cyliader can«lot be used to measure oT in ice!, curves for teasion and compression, presumably be- The et tact of temperature an oT is the same ss cause internal edcroctacks can for«s snd inf Lueace the ite effect oa oc at Lov strain rates. By contrast, -5 f at lure at high rates. At high rates 10 s !, the lack of sensitivity to strain rate at very bifh OTtenda tO a limiting value, Srhfle «kCOntitules rates leads to the expectation that there vill be a to increase. Par f ine-Brained l.Ce at -7 C, the high corresponditlg insensitivity to temperature tn that ioe

Io

r 92 e,I z oP~ N

g er

0

1o o oz oa o.s o.s t lo Oeeanr pew~, Uene~r OI Wo~ ecu&0Wt h wsWarl

Figure 19. Bu~ry of data on the strength of non- Figure 20. Deviatoric stress/strain-rate relations sallns ice and snow for details oo data sour'ces see deduced in4irectly froa various data sources 3]. [63] !. h! Snow, ~ -10'C. B! Boov, ~ 0' to 7 'C. C! Ice, ~ 0.9 !fg/n, -2 C to -10'C. fr! Snow, 0.49 Ng/n, -1 C co -10'C.

range. ine iiaited expel'inestal date supportthis idea Figs. 14 and 23!. ht high strain rates, rrf decreases with in- creasing porosity decreasing density!, es indicated in Figure 19. Ac lov strain rates, the trend is expected to follow that for oc Fig. 20!. The grain sine 4 hae a considerable influence on oTat aoderatestrain rates i0 4 s 1!. Thecrt act can be described by the !bill-Petch relation

-1/2 n a+bd

where a an4 b are constsots 164]. This type of be. haviour is expecte4 to prevail at strain rates higher 10' than 10" s . but at very low sr.rain rates d aay not have such etfect. For practical purposes the value 2 %'a for fi.ne-grai.ned ice cao be regarded as an upper linit.. Zsore COarae-grained nOn-Saline ma- terial that is encountered in glacier ice, fake ice, and old sea ice will usually have tensile strength IO such lower than 2 Hpa typically l Hpa or less!. Failut'e strains an4 ielrl strains. Traditionall- yy there has been rather little interest in ebeolu'te value of the strains at which fracture and ductile yielding occur in ice, and yield criteria have always been foraulated in terna of stress. Ho~ever, while 10 yield stressee for ice vary by orders ot nagoitude, 04 10 10 100 the strains fot fracture and ductile yield stay with- 0; Stress Vpo! in auch aors liaited ranges. Rheo fine-g.rained ice is strained in uniaxiel Pfgure 21 Stress/strain-rate data for 102 axial conpression et rates less then shout 10 s 1, under ~trains obtained frow extrapolation of constant loa4 either constant strain-rate or coostant stress Pig. and constant: displaceaeot rate tests at -5 C. The 24!, there is a well.-defined ductile yield at axial regression U.ne represents the coabined data set strains of approxinately 12 2]. This shows up f53]. either as a peak stress on a stress/strain curve, or 247 i' gvo

i6u ina id% 1o inr Mamavl ssi ~ CE !

1 i~ i ~ 92~u s ~i ~ I~ v

Pigura 22. Kft'ect oE ~ Crain rate on u and for non-saline ice. Figure 22a indicates oc values Eros various eourres and for various ice types. Pigure 22b cospares uc and oT for fine-grained non-saline ice [55 j.

cracking is followed ilsmediately by free'cure of the entire specimen. Comparabledata for coarse-grained ice ara not yet aval.labia, but current work on coarse-grained oL4 Ses ice Of luv Sal.inity Suggeets thar. there Smy be only one identifiable yield point, with strains ~t that point always well below L%. Nultiaxisl stress states. Por auitissial stress staten, strengrh is beet specified by a formal fail- ure CriCeri.On ~ SuCh as an equatiOn Or graph deSCtlb- ing the failure envelope tn principal screen space. A.general criterion is hard to formulate even f or isotropic ice none of the classical criteria are broadly appLicable!, and for auisotropic ice there are very great dif f iculties. Consequently, engineers often have to get by with the most. primitive of assusptious, e.g. failure occurring when the medor prinCipal Stress reeChae oT Or n , dependingOn t.he nature of the problsa. There have been speculations about the quaLits- tive fores of failure criteria for isotropic ice l66I, drawing on the observed facts that. i! hydro- St.atiC preeaure hae li.ttle effeCt Ou Shestl.ng at Very Low creep rates, li! moderare pressure increases msvsraivrv tl strength and deformation resistance at high strain rates, iii! high pressure lovers the deformation Pigure 23 Variatfnn Of OEvith teaperature fOr resistance at all rates, iv! rhe envelope intersects non-saline ice. Dare tron 8 ~ 59. yl j. the principal stress axes at oT and s, and inrersects the hydrostat at the pressure tor the phase transition from Tce Ih to water. In addition to data Eor oT and g, snd lor as a strain-rate minimum on s creep curve. Evan when phase Craosition pressures, there are a fev dar.a seta l.he c.cmpressive stress is cycled sc varying frequen- Eros triaxial tests d2 ~ oI! in the compression- cies Fig. 25!, the sean Creep Curve still ShOWS compressionquadrants 71, and in the tension- aininum creep rate st about it axial strain 5j. tension quadrants [68 j. There are also some data with strain rates in the range l0 to l0 s, the from biaxial Ccats 3M! [69j. However, when the Sa~ ice haa an initial yield point which OCCure ~ C number and range of potentiei variables are con- smaller strains .03 to 0.5%! ~ This isi.tial yield sidered, these results are too fragsentary ts provide is associated with thi= onseC ot internal cracking. a clear picture t or this review. At very high strain rates s ! the initial yieid becomes the sole yield, i.e. onset ot internal 4

31CD I', X E ~514xlp s'! lo

~ 20 x IP s'1 O2 xIP s'! 2 34xlp s'! ps I! -43 52 15 x IO s i! IO s!

o" O I 2 3 4 5 6 7 OI IO Axial Slroin 6! ST:T:IIIII asi Sl T

Figure 24. Exemple of s! stress/st.rain curves and b! creep curves for fine-grained non-saline ice at -5 C [52J.

by the nucleation and propsgar.ion ot cracks. The f lexutal tests t.ypically used to seasure Klc, the critical stress intensity factor for "Node I" crack extension, can be I,nterpreted by elastic theory at high rates aod lov temperarure, but the elastic assvmptions became progressively vorse as rates and temperstvres produce greater ductility. Ifhere ice is elastic aod brirtle, glc should be prediCtable free Yvung TS mOdulue 6 ~ lp GPa! and the specif ic surface energy y O.l J/m 2 !. For plane st ress,

1/2 -3/2 g + gy! 45 kN-m lc

Neasured values of Itic do aPPear to have a lover limit cLose to this valve. Nore typical xeasured values are around lOO kSI-m5/, implying that yp, the specif ic energy for plastic. vorking of proven/l.rvio theory, is about 5 y. 'lfxth this Jirims iscie evidence that sitaple I;riftith theory might be applicable ror the elastic/brittle condition, one is 2 4 teepted to calculate oT from 2, y and t.he AcoumulsiadCxasp SIToI n IZI controlliog crack length 2c.. For plane st.ress, Figut'e 25, Examplesof msaocreep curves tor tests oxx f toe~rained ioe io vhich compressive stress ! 1/2 ~E! 2.52x 10' Cycles bstveen 0 and 2 Kpa at the frequenci.es ii c v'c isssfteated 5 J. vhere c is in imt res. If »e make a guess that. 2c ts T t T~l. Th I t t* gh equal to the grain size of the ice, calculated vaiues tc» hmmattracted considerable interest in recent of of are as sheen in 1 igure 26, vhich also gives years, bmt published data have to be approached vir.h measured values ot camtiora The generaL concept is clearly spplica ble ashen Cnndit iona are Such that ice has sOme duc- to icm uncter elastic/btittle conditions, but it is tl lit.y, it might be expected that "toughness" vou~d irrelevant. vhen rates aod temperature> are such that i acre ass vi tb in cress i ng temperatu re and de creas tng lcm yields by flov and recrystallizatioo rather than strain rate. IJtth che exception ot one data set, th» e xper i meac el ev i dence aupp or ts thi s exp ect aCion f or lo rate eflects Fig. 27!. However, test. data show that Klc tncreases as temperature decreases Eig. 28!, coatradicting the simple expectar.ton. Lookiag at thtags another wsy, Klc can be expressed aa

K ~ a v ,I /2

end c.his suggescs thar. K«might vary with rate aad temperature in the same wsy as of. The expectation would thea be for Klc to be iasens itive to race, and for Klc to increase slowly with decreasing temperature ~ The latter appears to be borne our when test tag raCes are high Etg. 28!. However, another posstbility ts that the existence of Liquid tileis or liquid-like layers in the grata boundaries aighc 'lead to a Rehbtnder, or Boffo, effect J. Since the liquid/solid value of y is about 302 of tne vspout /solid value, Klc could be halved by ev,res Sivv Ivvv I intrusion of s liquid file into a growiag crack. Such intrusLon ~ould probably not occur where rates Figure 26. Comparison of CheoreCical teamt le ere very high, irrespective of temperature, but it stceagth with measured values, asaumi.ngthat f law could occur with a combinat.ion oi hig'h teaperature ~ tse equals grata sine 0 J. and low test cate. A more complete discussl.on oi the lracture toughaees of ice, end the underlying theory, is given el.sevhere !.

3. 3 Sea ice

precise emesurements of the basic mechanical properties of sea ice aro not plentiful. partly because the material ls difficult to work with brl.ne mobility, complex structure!, aad pertly because of practical desuinds for relatively crude f ield date. Coasequeatly we have to draw upon experimental results tor noa-saline ice for a bsclcground pictuce of how sea ice eight behave ia a geaeral sense. In assessing the eea i.ce data, i.t msy be helptul to regard saltnity as a major new variable, with freshwater tce of rero salinity repreecatiag a reference state. galtntty has a direct tnt luence on porosity, ~o-< mP ~oI mr ~na since salts rejected by the ice crystals during 0 Ivs-vr>"-a'I I freexing fora concentrated brine, which Ls dts- figure 21. gf fact of Loading rate oa Klc for aon- tribured through the tce sass io poree. At eny give~ teaperature, the volume of brine-filled pores "brine saline ice 0, 72 . porosity"! increases with increase ot overall salini" ty. However, the bri ne-filled pores are not. rhe only pores Ln sea ice; there are also gdis bubbies, and the total porostty ts the "gas pornsi ry" plus the "brine porosity." In the paar., the "gae porosity" waa usually unknowa, aad brine pocoslt.y was substituted ior total porosity. There is aow a simple method iot overcoming this problem 0], As temperat.ure decreases ta ice of a given salinity, brine volume decreases, since equilibrium concentration hes ro be mainCataed. This meaas that temperature haa a dual ef tact on the mechanical properties of saline ice ic sf recce the tce marrix, much as ic does in noa- saliae ice, but tt also changes the porosity. gecause increasing temperature and increasing s X porosity both tend to lower the stl.t t aces, the deforaation reetstance sad the strength of Lce, it might be expected that temperature ef f sets in eea ice iiouid be stronger than those ia non saline ice. Hechantcal properties of sea Lce are often plotted egal.nsr. pores tty and against Cempcrature. Vhen exaaintag such plots, it should be understood that these two variables are not aormally independent of each other. Tetaperature is usually aa implicit eo -no 4 variable in porosity eff ects porosity is varied by TevvvmsweIXI changiag Che temperature ia ice ot given salinity!. Figure 28. Variation of Klc with teeperature aad Siailarly, porostty is often an imp li cit variable in loading rate 3 }. reaperarure ettects . s

ga 1J

o oi O2 oi OZ aavvcdr Oca Fermccr FLgtsre 29. Young's modulus as a function of porosity Figure 30. Summary of data for effective modulus F.' ]2 63 75 76F 77F 78~ 79 ~ 80[ ~ plotted against porosity [2, 81, 82, 83, 84J.

ia g s

f s ki a ,-2

o -co -ao XI so 02 os os ra~acv aCCI Cf.Sc mu sac~ c usam I Figure 31. Summaryof values for ef factive tsodul« Figure 32. Varfatfon of effective modulus E' with E' plotted against temperature [2, 83, 85[ ~ stress rate and temperatore ]8$].

Elastic moduli.. Measurements oi Young'4 moduaus value of salinity. At very [ow temperature snd high 8 have been made hy methods dependi.og oo high fre- stress or strain! rate, 8' approaches E queacy waves, pulses or vibratians. Ettect ve moduif Etfective values ot Poisson's ratio v' tor sea E' [save beeo measured by quasi-static tests typicai- ice were measured .n beam flexure experiments by Iy bema flexure!, both in the laboratory end in the Morat end tainey ]66] . For very Iow stress raCes, f ieLd. tended to the expected limit value ot 0.5 see page Figure 29 gives a geoeral impression ot E values 244!,For the highesttest rates II-6Mpa/s, and up for mmaice over a range ot parosity. It also pro- to I.. 6 x 10 " e !, v' had values between 0.36 and vides 4 c~arfson with non-saline ice. The results 0,4. The tacan value for high rate decreased wit'h for small-scale sacsplee c}ata bands 1, 3, 5! show decreasing temperature, from about 0.40 at -5'E, to good agreement with non saline ice data bend 2! . 0.37 at -30' and 40'C. This observed temperature The Valuem Obtained t'rom eeiemiC teate and t lexural trend supports a speculation made much earlier by waves over wid» areas are mostly much lower than E tseeks snd Assur [6] on the basis of Soviet sei sexic'. fot non-saline ice, but this is oot too surprising data. Such e trend is opposite to what would be rhea alj of the compLicatioos ot the ica sheet are expected with air-f illecl poree, but it cao bc. commAdored. explained by expressing u in rerrss of E aod the bulk Values Of Z' are inciiCared in Figure 30, and are modulus K [2 ] c Cemgcaredwith 8' valuee fOr non-saline iCe. There is K 8!/6K -E/K!/e close agreement between sea ice and non-saline tce at Since K is about the same ror ice and water, a seall l~ parnaity, Snd the lov valuea tOr Sea iCe at inCreaee in the volume Of warer-rilied porous should ftfgbmr poroaities can prabably be attributed ro the have littl~ effect on the overall value ot K. Thus comgrined effects of porosity and temperature. Data the var at on ot v with porosity will be cont tollea bmmd3 for E' in Figure 30 agre~a vali virh data largeiy by variariOna in E, WhiCh decreases as hands fc and 7 far E in Figure 29. porosiCy increases. The equation therefore predi.cts The eftett of temperature an 8' is indicated in an increase oi u vith increase of porosity. Because Figure 31. The slightly sreeper trend in data band porosity increases with increasing Cemperature i:I Ls probably due to the fact that all tests vere made saline ice, v should i.ncrease with increasing at a single value ot salinity. Figure 32 shows how temperature. 8' varies with sCress rate aod temperature at a fixed In columnar sea ice, anisoc.ropy may have a greater influence on v than do temperature or FOrOSity. Wang [88! found that Sea iCe vaa IsuCh ruprure or "flexural strength" from uniaxial tensile stiffer in a direction parallel to the long axes ot Strength Sf, Weuae the Symbol 8T. 'Hehave columns vertical! than in the perpendicular completely disregarded results from once-popular direCriOn hOrirOntal!, giving v' Sn the range 0 CO Braril. tests and ring tests diaeetral compression of 0.2 vertically and 0.8 to !.Z horixontally. discs and annuli!, since these test have proved Bulk modulus K and shear modulus G sre not unsuitable for ice [89!. COmmOnlymeaaured ae SuCh in Sea iCe, bur given paire in C*CX o r l ~u* of values for 8 and u they are easily calculated see expect.edto vary with strain rate, temperatureand page 244! ~ porosity in a mannerqualitatively similar to non- Stre th and defer sation resistance. Uniaxial ssline ice. Figure 33 represencs sosmdata by '4tang stress tests provide clear and unambiguous data if [90! which conform to a power relation between scraia they are dona well. Uniaxial compression tests have rate and stree ~, With an eXpOnent Of abnut 4. S nm been applied to sea ice by many investigators, but other data, selected Eros results hy Schwmrs[9 [ !, mniaxial tension has rarely been atteepted. The mset are shownagainst strain rate in Figure 34. lo cosmnnstrength teste hawe inVO1Ved fleXure Of beast Figure 35, the effeCt Of temperature On O ie Shinrn or centi levers ~ For laboratory experiments small for eea ice and for sense roughly comparable fresh- beams are cut fr'om an ice sheet, or saline ice is ~ster ice lake encl river ice!. produced artificially. For large scale field tests, The effect of porosity on qc and other beams or cantilevers are sawn in the ice sheet, with mechanical properties has traditionally been dis- the "fixed* endo still attaChed to the Sheet liisited played by plotting the property against the square flexure at the beam root is still possible!. For the root of brine volume. F'or reasons discussed reasons mentioned earlier paga243!, bass tests can elsewhere [2!, this practice is not followed here; give misleading results, acd beam data for non-saline brine volume ie represented simply as brine ice have been ignored in this review. However, in porosity.Variation of ~cwith brine porosity at the absence of adequate uniaxial data for sea ica, we high strainrates » l0 s l! is shownin Figure36, have to make use of beam data. which do have speci.al which also brings out the well established fact that value when bass tests are regarded as analogue tests oc ie strongly dependenton the direction of for plate flexure. To distinguish the "aodulue of loading in columnar ice. Further evidencels given

92so

ID io S IO-2 F.seee ~i ~ ri Su»»nai ~ s'I Figure 34. Variation Of oC With strain C'ate, Figure 33. Vniaxial coapressivestrength of sea ice temperaturear dgrain orientatiOn data SeleCtedfrOm aa a funCtiOn Of strain rate data Seletted from [88!!. [91! ! ~

IS

lo oos 0 rsswei»I Al ~ II»I R»osl S Figure 35. Variation of oc with temPerature for Figure 36. Summaryof data for o as a function ol three ice types data from [9l j!. brine porosity [83, 92!, bp Ff4gere 3y, which shows the ice to be weakest shen direCtiOOS. aa Ssfght be expect.ed, «q increasea ~er principal stress is at 4$ to the direction Of vith decreasing teaperature aod decreasing salinity. Cbse axes f ie., at 45' to the horixontal plane!. Zt ia greater fOr Vertical epetiaae V! Ot COluanar ice Figure 38 prOvidea Confitvsatioo that Fig. 39a! than for horixootal specieens Fig. 39b! . ~ acreasesvith increase of grain sire at fairly high The te aperatura effect tepliea a porosity effect, strata rates > 10 s !. which is illustrated by a re-plot of sean values Eros !oiaxial tensile teats on sea ice have been t'are Figure 39 in Figure 40. i!scauae ot the difficulty in eaintaining perfect Fleaural Stree th OFf haa been Ia enured in vpeegaenaxiality and in avoiding perturbstions of enny teat prpgralssinvOlving bOth labOratory wprk and kbe stress fle!.d. These difficulties ere now being field work. The variability of results is eoeewhat eesreoaer but nev data have not yet appeared. The daunting, aa can ha seen froe the sue sary in Figure eely usable published data see s to be those repre- 41, vhere uFT is shown against brine porosity. ~ sated in Figure 39, where of is plotted against Figure 42 sus!nsrixea ance data on the variation o Casperature for two salinities aod two loading oFTwith te!spersture, but the resul.ts should be

100O

I DOP LF

~ I Vl

100 I P-2 lo. 2 1O-l 1O-s IC S IO-I IO-2 10-2 I O-1 10-1 IO-l 1O+ S rein A ~lc SCOI ! S r~ rnRCIC Scn !

Fig Ore 3!. VariatiOn Of 1!c with Strain rate in Figure 38 ~ Variat.ion of oc with strain rate in col~oar sea ice at -10'C. The three data eats show granular sea tce at -10' :. The effect ot grain siss the effect of crystal orientation [93[. is also indicated [93}.

If Z os 17 F e F os ci 7 I- oc

C 0 02

Oc O -I0 -2O - le Zo lnmvnraiir~ Y! TCrive c I i ~I CI

Figure 39. Variation or uniaxial tens ale strength wir.h teeperature and Salinity for Sea iCe! a! Vertical Speciuens, b! horizootal S!ratio!eOS [94 J. enseVS vsiIV pigure40. OTas a functionof brine porosity [94]

.IO n15 S

treatedwith cautionbecause of probabledeparture froa ideal elasticity at high tesperaturee.h discussionof rate effects, tesoeratureeffects and other conplicationsia givenelsewhere [2], but it sight be worth eentioning here that in Situ baaaaare sub!actto 1.argevaristiona in grainstructure, steep teaperatura gradients, beaIs-rontstress Concentra- t'iona,acaL» effects and, at high rates, inertial effects in the underlying water. Practure tou hnese seesuremnt ~ on aee ice have beenreported frns severalstudies [72 ~ 83, 99, 100~ 102!. Theeffect of loadingrate onKIC ia shown in Figures 43 and 44, and it can be seenthat ~ for s io high loading rates, Klc tends to values that are a uP CLOse to the theOretical "Criffith Value for W non-saline ice see page249!. In Figure 43, teeperature senna co have very little effect on Klc, in contract to the trend shownearlier in Figure 28 for cosperable deflection rates. One study lo [102] hesgiven none evidence of a decreasein Klc with increase of brine porosity; anotherstudy [83] purporta to showthe saIeetrend. but the data points haVe nOSignificant Cart'elati.on. In bOth Figure 43 end Figure 44, it aeeas that Klc increases with an increase in train sine, ICP SomconventionaL triaxial teats a1S uf ~ o3! nsIIvIIIOIIsvl~ 4Fle IIIIIII I have beensade on aea ice at eoderate].y high rates. SOVietteste 03] na artificial andnatural Sea ice Pigure43, Variation of Klc with loadingrate, grain Site end teeperature [109] for coluenar ftneb ShOVthe unior prinCipalStress O1inCreaa ing with water ice. O2. O3,and the uaxisuashear Streea, a1 a2! J2, increasing nonlinearly with the noraal stress on the planeof uaxiuussheet. Thefailure value of ol vas an Orderof aagnitudehigher than nt Irlth O2arOund 4 Hpa. Under conf ining pressure, the faiLure stress decreasedarith increasingeaLiuity andinctessing teeperature, guet aa it does in the uniaaiaL streSS 0

lOOO

f4. o .s n 2 L oo' o' C ~ I =' 2 cll Vl

fp ~ ~ O-a t nu-son-rb 51roinRe fe r~!

figure 44 ~ Effect of loadiog rate oa Xlc for sea Pigure 45. lfnfaxial coapressive strength of ice data from 21!. aultiysar sea ice at -5'G aad strain rates of lO and l0 3 a [43j. arete lsotropic fisc-grained ice behaveddiff er- 3 4 Ice Ielaad Ice esaly from aoisotropic i.ce, snd strength varied with issedtmgdiractioa in aaisotropic ice, Values of The earlier notes oo ice islsads indicate a fssr the Nohr-Coulomb criterioa vere farstly ia the rather catsplicated structure, vittt four different rmags30 to 50', with extreme values of l4' aad 53 types of ice distinguishable. Since nechanrcaL test.s "True" triaxial tests of s of s og! hevs been have aot been made on ica islands to aay significant ~ mdsoa anisatropic saline ice 04!, but so far the extent, ft is useful to simplify the earliet picture rsssalts ars too coapl.icated to be summarised coa- so ss to draw som conclusions about probable cgaeLp. mechanical behaviour. Dna poteat.ial problem in triaxlal test.ing is Of the listed constituents tor ice islands, two clast failure. could be iafluenced by differssces of are aon-salise ice: lake ice, and saow ice which is lauding rates for the principal stresses, or by lust glacier Lce!. The properries of lake ice as variations in the ratio ar/ of. because s complex such have aot been reviewed here, but they can be stress field in naturaL ice is likely to fluctuate inferred from the geaeral properties oi granular and trgth Cbe ratio of principal stresses staying f ai rly col.uaaar aon-saline ice. h more speci tie review of constant, s sew triaxiaL test device haa been lake ice properties caa be iousd elsewhere [7 I. Saov daeslogtedto keep the rat.io ar/o> constast throughou't ice is the material that makes up glaciers, ice ceps a test f051. aad ice shelves. Unless it hss been meramorphosed by %try little vork hss been doae an the aechasical strong sheariag, it is typicsl.ly isot ropic, with properties of tarlti- ear sea ics, aad it is still graia cise aad porosity varying. Por polar glacier hard to germrsli!e about diff ereaces between "new" ice, grain sine varies tron. around l tas in "snow," old' ice. Somestudies suggest that uul tiyear where the burt density is less then 0.8 ffg/m, to fee ia weaker thea first year ics [L06], but recent Srauad 5 tae in very denSe iCe paraeity + O! from the dmtatged studies [43! do aot support this idea. deep layers. The properties ot porous glacier ice it is aot easy ta make coaparisons becaiise have already been suamarised, aad the properties oi of the great varisbili.ty af etreagth in xultiyear snow" aad "snov ice" for lo~er ranges ot bulk les, which contains many differeat types of ice. density are dealt vith elsewhere 3, 107J. pggsre 4S gives some values of n at strsia rates The renaintag two coastitueats of ice islaads and LO s ~ with a temperature ot -5 C. Lf are salina ice types aea ice, brackish ice!, but pdgure 43 fa comparedwith Figures 31 and 38, it caa salioity is likely to be very low. The sea ice bs seen that the strength range for uultiyear ice is componeat is very old sea ice, and therefore perhaps similar te that for gt'anular first-ysar ice at comparable to some of the multiyear ice that hss lust At LO s, the ~lti.year ice is about the been discussed. Not ruach is knows about ice formed strength as columnar ff.rst-year ice, but at lp fram btackish ester, but a first guess might be that the- colueaar ice is weaker than mlttyeer ice it. would be similar t.o lake ice. ~ txcsptmben testsxf in the "hard fail" directioa. Actually, the small. ice island f ragscnts that thsiaxial teasioa tests on aultiyear ice are drif t iato shallov coastal ~stets have sut tered bateg madeas part of a curtest prograta at Okftp->, aad ablatioa rrom both top aad bottom surfaces, and they tbe indications so far are that oT is always less say not include all the ice types that have been l Nps. listed. Prom impressions gained during visits to u number of small ice islands, and tram drl.l ling snd methods, and the data generated by them, have hsd blasting work on ice islands, one ot ua is Inc lined be discarded, s process that h.as f oread both ot the to regard theta simply se small ice bergs. present euthors to !unk some of their older work. Current activity is based on test techaiques that «e sore refined and more carefully selected, and there 3. 5 Fragmented Ice are mOveetOWards standardization Ot test teChmiquea vorldvide. Teste can be designed, coaducted snd Ttlete is a tendency to assume that the problems Intvrprered wtth bettct appreciation for the relevant created by floattng ice are solved once the ice ie constitutive relations and tat lure critert.a, and with brakes. ln faCt, accumuletiOne ot fragmented ice less slavish conformance to methodologies borrowed can, in noae cit'cumstances, resist ship sovement and from other technical fields. Soae experimental areas load structures such more severely than sn uabraken are stilL deficieat, and more emphasis needs to be ic» sheet. given to malt iaxial stress states and to losdings Fragmented tce covers a br'osd spectrum, fram long duration. fine-graf.ned a>ah ice, through blocky brash ice ~ up The things we call basic mechanical properttes to floe ice, ref ted tce, and ~rid ed tce. As far aa are, ot course, ooly meaningful wtthtn the framevorh ~ hips aad sttucturee are concerned, the accumulations ot underlying theory, and they have to be applied to ot fragmented. ice that are of most cancers are mush, engineering design through the appropriate theory. brash, end first-year pressure ridges . ht present there is only loose coordination of ice ltush tcs ie something Like vsterlogged enov, engi*eeriag research in the areas of theoretical with fluid properties while it is fl.oating freely, mechanics, experiaental determination of properties, aad high cohesioa when it is coepacted or drained. snd soLution ot practical boundary value prable Although lt cen cause real probleas for ships end Consequently, there is a danger thar. efforts in these marine structures, systematic ~ tudy ot mushice is various areas aight be mismatched. For example, only ]ust startiag and, apart froa a small saount of theoreticians might be calling tor highly complex tnforaatioa in ttsn saow mechanics Literature, data data from polyaxial teats oa rare-dependent aniso- are not yet available. tropic material at a time vhen design engineers st'e ttrash tce has aors or less equsnt part tclea in ~truggling ta progresa beyOndSimple clear.ir. analyst the sire tangs 0,02 to 2.0 a, the tendency has been and sax imua prtnci pal stress teilure criteria. Some to treat it analyttcally sa a granular 'c-g" eaterisl aeaeure of coordination is needed io ordet to satisfy thea coat' oras to a Itohr-Cou Lombt ai lure critecion, the legitimate deaande of both lmeic research and but for hortsontal penetration at a unit'arm layer the p tact i eel e ngi neeri n a. acreea-free upper arui lower boundarnes appear to ln sptte of all these difficulties, tbe general petmit yielding in conformance to a criterion of the situation is encout'aging. Ice mechanics has made voa lttses type j l08J. Itowevvr, aeasureeents ot considerable progress in recent years snd mny, in have been made in ~ number of studtes. f SCt be asking same nev Cnni'Yibutians to applied Large tca blocks pushed together into pressure mechanics and marerials science. There is a good ridges also fora a "grsouler" asterial vhich collect ton of basic data, snd many practical problems initially haa Cohesion c and iateraal friction shear csn be tackled with conf idence. Perhaps the greatest reetstance! $. The scale of thL ~ aatertal is tso big problem at the present tine ts ther the accelerated fot conveatioaaL aeasureaants of tts bulk properties, leering schedule for the Beaufort, Chukchi snd gering but some deducttoas can be aade from ensLysts of Seas vill create a heavy demand for high quality natural processes. data, while the nutabvr ot experienced research 'Ihe properttea ot fragmented ice are euaaartxed peopLe~ the physical factlities for ice research> and snd discussed elsevhere 121' the level ~ of tunding support sre all severely limited. TO OVerCOaethis prOblem, the very least that ta needed ts an expansion aad intensification of 4, COftCLVSLON collaboration betveen academia, i.ndustry snd govvro- aent . Froa thie brief SurVsy Of the difterent varle- t.ies. of ice eacount.crud in arctic vaters, it ia evident that there are large gape in the available gEFERKNCKS date. There are vtrtually no data dertved f roe direct studies on icebergs end ice islands. Although weeks, 1I.Y. and Acklcy, S.F., The grovr.h ma!or studies on these ice masses ate perhaps structure and properti es oi sea ice, UShCRREi. unnecessary, aoae exploratory studies would be useful ttono~rsyh 82-i, l30 pp., 1982. tn order to conf trm that tceberge snd ice islands Bailor, It., itechanrcai behavior ot aes ice. are, in face, similar to their parent lce bodies. USAtgRE1ltono~rayh 83-l, 92 pp., 1983. qtudtes an first-year ees ice have been cede almost Coon, It.Iy., Brown, C.B., Cox, G.F.N., Ralston, entirely on ice whtch has formed near the coast. T.D., Shapiro, L. and Meeks, tI.F-, Research is Thts kind of sea tce ie belteved to have strong Sea ice Nechmnice, ttarine BOard, Aasemb y OI. c-axis alignments tn the horirontal plane. but Eagineertng, tfatiosat Res. Council, Itet tonaL only ta a fev casus hae the or tentation of the sr.rese Aced. Press, 80 pp., l 9g I ~ f ieLd relattve to c-axis orientation hvea taken into tfeeks, W.p. and Bettor, N., Some elements ot coaaideratioo. The aost significaat shortcoming at iceberg techaology, in lceb~er Techno~la, ed. the present time ts lack of inforaation aa multiyear A.h. Iiueseiny, pp. 45 98, Pargamon Presa, l97d. ice, which ie the moat cmmnonaaterial is the cenr,ral Schwarz, J. and Weeks, H.F,, Rngineerrng arctic peck, and probabLy the ~st threatening properties of sea ice. J t Glaciolo~, vc L ~ L9, aatvrial for ottehoru structures. I'tnally, Little no. gl, pr. 499-530, L977. known abOut the ptopertiea at aarine frsxil Lte, lr. Reeks, If. F. and Assur, A., The mechanical may bc sore conmon than vas ptevtouely thaught to be properties of sea ice. USACRLIELMonograph ll the case, snd the fine-gratned coherent ice formed C3, 80 pp., L967 tram fregtl msy be arranger than ttrst year cangela- tracks, II.F. and Assur, A, Fracture ot lake and tnon ice. sos ice. IISAGMKL Research RePort 269, 77 pp., far ea rhe acquisition and tntsrpretstton of I 969 test date Ls concerned. the tield of ssa ice research Itobbs, P., Ice Physics, Oxtord Vnnv. Press, tt3l is moving into a nev phase. Someor the oLder test pp.. I974. Bragg, W.tf., The crystal structure of ice. 30 Weeks, W.F and Lofgren, G., The effective Proc. Ph s. Soc., vol. 34, pp. 98-103, 1922. solute distrtbution toe ff tcient during the lO Leppsranta ~ M., Observations of icebergs in the f *IV f tl Cl I I, I ~ph I f Barents Sea in July 1980. Iceber Research, and Ice, ed. N. Ours, Ins t. I.ow Temp. Sci., No. 2, pp. 3-4, 1982. Nokkaido, vol. I, no. 1, pp, 579-597, 1967. ll. Robe, R.Q., Iceberg drift and deteriorar.ion, ln 31 Naksvo, M and Sinha, N.K., Growth rate and mica of Snow snd Ice ltasses, ed. S.C. salinity profile of ftrst-year sea ice jn the Colback, pp. 211-59, Academic Press, Naw Yor'k, hlRhd CI,.I.GI IIIC, l. 27, . 96, f980. pp. 315-330, 1981. l2. Rigsby, G.P., Study of tce fabrics, Thule ares, 32 l,ake ~ R.A and Lewis, R.L., Salt refection by G 1*d, S I** dP* f tg 4th sea ioe during growth, J. Geo h s. Res., vol 0 t bltel t lie t 26, 6 pp., 1955. 75, no. 3, pp. 583-597, 1970. 13. Gow, A.J. and Williamson, T., Rhaol.ogica1 Niedrauer, T.M. snd Hartin, S., An expertmental implications of the internal structure and study of brine drainage and convection in young crystal fabrics of the 'ffest Antarctic ice sheet Ie, J G~h. R ., oI. 84, . 03, pp. as revealed by deep core drilling at Byrd 1176-1186, 1979. Station. Geol. Soc. Amer. Bull., vol. 87, pp. Aeaur, A., CompoaitiOn Of Sea tCe Srgdit,s 1665-77, 1976. tensile strength, in Arctic Sea Ice, U.S. Nat, 14. Rigsby, G.P., The complexities of the three- Aced. Sciertces blat. Res. Council Pub. 598, dimensional shape of individual. crystals of pp. 106-138, t958- Riel I . ~J.GI il, 1.7, .50, 3'$. Sinha, N.K., Technique I or studying structure of pp, 233-52, 1968. 92, ~J. Gl 92 I, l. Ilt, . 79, pp. Scholander, P.P. and Nutt, U.C., Bubble pressure 315-323, 1977. t 0 I df bg,~3.0111,1.3, 36 cow, A.J., Ackley, S.P., weeks, N.1'. and rpovoni, no. 28, pp. 671-678, 1960. J.W., Physical end structural ch*racterisr.ics of Smith, E.R., Arctic ice, with special reference Antarcttc eea ica. Annals of Glee~telo , vol. to its distribution in the North Atlantic. Ocean, 3, pp. 11.3-117, 1982. U.S. Coast Guard Bull. No. 19: I-X, 221 pp., Cherepsnov, N.V. ~ Using t' he ret.hods of crystal 1931. opttcs for determining the age of drift' ice, 17. Weeks, W.F., The structure of aea teer a pro- Probl hrkt tki, vol. 2, pp 179-184, 1957. gress report, tn Arctic Ses Ice, U.S. Nat. 38. Schwaraacher, W., Pack-ice studies in the Arctic Aced. Sciences - Nat. Res. Council Pub. 598, Ocean., J. Geo h s. Res., vol. 64, pp. 2357-2367, pp. 96-98, 1958. 1959. tg. Charepanov, N.V., Spat i.al arrangemenr. of sea ice 39 Kaykut, G. and Untersteiner, N., Some results crystal structure. Prob. Ar kt. i Ants t'kt., from a time-dependent thertsodynamic model of sea vol. 38 ' pp. 176-181, 1971. ice. J. Geo h s. Res., vol. 67, pp. 155O 1567, l9. Veskss W.P. and Gow, A.J., Preferred crystal 1971. ortentations along the margi.ns of the Arctic 4O. Walker', 8 ~R. and Wadhass, PP0 Thick ses ice Ocean. J. Geo h s. Res., vol. 84, no. C10, pp, floes, Atcti.c, vol. '32, no. 2, pp. 14f3-147, 5105-51219 1978. 1979 20. Weeks~ W.P. and Cow, A,.J., Crystal alignrsenta in 41 Wadhams,P., Sea iCe topography Of t15eAre tiC the fast ice of arctic Alaska, J. Geo h s. Res. ~ Ocean in the region 70' W to 25'E. Phil. vol. 85, no. C2, pp. 1137-1146. Trans. Ro . Soc. london, vol. A302, no. 1464. 21. Rovacs, A. and Horsy, R., Radar anf.sotropy of pp. 45-85. ees ice due to preferred sr imuthal ortentation 42 Tucker, W.B., Sodhi, D. and Govoni, J., of the bortsontal c-axes of ice crystals, J. Strrlcture. of f irat-year' pressure ridge sails in ~00 . R ., I. 83, . Ct2, pp. 6037-6046, the Prud'hoe Bay region, in The Beaufort Sea- 1978. Ph steal and Biolo ical Environment, eds P, 22. tarnghurne9 P., 1Wboratnry expetiaenta On Cryatal B ames, O. Schel1 and B. Reimn.it s, Acaderatc orientation fn NaC1 ice. Annals of Glactolo Press, 1983. vol. 4, 1983. 43 Cox, r,.P.N., Richter, J., Weeks, W.F., Mailer, 23. Rovacs, A. and Morey, R.M., Investigations of and Bosworth, N., The mechanical proper ties pcs ice arrisotropy, electromagnetic properttes, of multi.-yeat sea ice, Phase I 2 Test results. strength, and under-ice current orientation, VSACIIRSh~gt 83-, 191!3. CRRELRa ort 80-20, 18 pp., 1980. 44 Crary, A.P., Arctic ice island and ice shelf 24. Tsbats, T. and Ono, hl., On the crystallographic studies, in Scientific Studies at Fletcher's Icc tdy f Ibid ft,~tt .S I I* d 2-3 1952-1955 V l. 111, d. v. vol. A20, pp. 199-214, 1962. I! I 11, PP. 1-37, Ai P * C 4 'df lt .«h 25. Cow, A.-l. and Weeks, W.F., Tbe internal Center ipeophysicsl Research Paper No. 63 structure of fast ice near Narwhal Island, AFCRC TR-232! !, 1960. Beaufort Sea, Alaska, CRRL?1.Re ort 77 29, 8 pp., btarahatl, W.P., StruCture and strarigraphy of ,1977. T-3 and tha Rllesaere Ide Shelt, in Scientific 2e. Lofgren, G. and Weeks, W.F., Bffect of growth Studies at Fletcher's Ice Island T-3 parsmetets on the substructure spacing in NaC1 1952-1955 vol. IIT., ed. Ir. Bushnell, pp. 45-57, t I,~JG1 I I I I, . 52 Alr Force Catsbridge Research Center Geophysical pp. 153-164, 1969. Research Paper ho. 63 APCRC-TR-232! !, 1960~ 27. Nakswo, H. and Sinhs, N.K., Brine layer spacing Regle, R.N-, rtlair, R.G. and Persson, 1..F., Ice of f t rat-year ssa f ce. D reft manuscript, 1982. core studies of 'WardHunt I ce Shelf, 196fr. J ~ 28 Zotikov, '! A., Zagorodnov, V.S. and Raikovski, ~01 I I, I, 92, . 'l7, pp, 39-59, 1964. J.V., Core drilling through the Ross Ice Shelf 47. Srsith, D.U., lce li.thologies and structure of Antarctica! conf trrsed basal freesing. Science, I I d 4 ll It. ~J. Gl f I, ' l. 5, vol 207, no 4438, pp. 1463-1465, 1980. no 37, pp. 1738, 1964, 29. Weeks, W.F. and Assur, A., Sr,ructural control of Nakaya, U., Hugururss, J. and Eiiguch 1, K., the vertical variation of the strength of sea Glsciological sr udice on Fletc her 's Ice Island d lt t, I. I* dS P I-3!. Arctic. I~stitute of North America P tl d A li tt d. V.II. 2' 2 ~yh 9 0 . 21. '962. pp 258-276, MIT Press, 1963. Cherepancv, N.V., Structure of Sea ice of great thickness. ~Trod Arkt. I Antes'kt~ 8 Id 74 Cox, C.P.N. and Reeks, R.F., Equations for Institut, vol. 367, pp. 13-18, 1964. determining the gas and brinte volurae in se* ice 50. Lyane, J.B., Savin, S.M. and Tamburi, A.J ~, samples. CRRELRe ort 82-30, 7 pp., 1982~ Basement ice, Ward Hunt Ire Shel.f, El learners Lsngleben, M.P snd Pottnder, F..R., Elastic 11 d.Cd.~J.G11o1,1.10,.18, parameters af sea ice, in Ice and Snow- pp. 93-100, 1971. Pro rties Processes and A lications, ed. R.D. 51. Mailer. M., Glacier mechanics, IARR Internet. Kingery, MIT Prese, pp. 69-78, 1963. ~84. I, 0 I, 0 8, I l. Il, Rp. Tubate, T., Studies nf the vista elastic proper- 455-473, 1981. ties of sea ice, in Arctic Sea Ice, 17.8. Itrst. 52. Mellor, M. end Cole, D,, Defarmation and failure Aced Sci. - fist. Res. Council Pub. 598, pp of ice under constant stress or consteat 139-147, 19$8. strain-rate, Cold Re lone Bci. Tech., vol. 5, 77, Kahnen, H,, Seismic and ultrasonic measurements pp. 201-219, 1982. on rhe eea ice of Eclipse Sound near PoradInlet, $3. Keller, M, and Cole, D.M., Stress/strain/rfme N.R.T. in northern Baffin Island. Polar- relations far ice under unisxial compression, ~fh, J h 8 I, . 2, pp. 66-74, 1972. Cold Re iona Sci, Tech,, 1983. Abele, G. and Frankenstein, G., Snow and ice 54, Gold, L.R., Some observations of the dependence properties as related to runways in Antarctica. f t I t f te,~cd.J.yh ~ .. USACRREl,Technical~Re ort 176, 37 pp., 1967. vol. 36~ no. 113, pp. 1265-1275, ! 958. 79 BrOwn, J.H., FlaeticiCy and Strengttr Of Sea fee, '55. Hawkes, I. and Mellor, M., Defarmstian snd in Ice and Snow: Pro erties Processes and fracture of ice under uniaxial stress. J. i~it I, 4, II,D. K928 y, pp. 79-1116, ttly ~GI I I, l. Il, *. 61, pp. 103-131, 1972. Press, 1963. 56. Sinhe, N.K., Short-term rheology of AndereOn. D.l.. ~ Preliminary reaulta and reviev ply y till I,J.~GIIII, 1. 21, of sea ice elasticity and relaced studies, no. 85, pp. 4 57"4 7'3, 1978, Trans. En ineerin Inst. Canada, vol. 2, no. 3, 57. Sinha, R.K., Rheology of columnar grained fcs, pp. 116-122, 1958. gx rimental Mechanics, vol. 18, no. 12, pp. 81 Traetteberg, A. ~ Gold, L.W. snd R. Frederking, 464-4713, !978. The strain tete and temperature dependence on 58. Carter. D., Brittle fractute of snow ice, 'Young's modulus of ice, International S osiua Proceed. IAkR S os. Re ka vik, Iceland, Paper on Ice Problem~s IAHR. Hanover, NH, USA, pp. 5.2, 1970. r 79-486, 1975. 59. Haynes, F.D., Effect af temperature on the 82 Kovace, A., Weeks, R.P. and F. Michitti, Varia- strength of snow-ice, DSACRRELRe rt 78-27, 18 tion of some mechanical properties of polar pp., 1978. snow, CampCentury, Greenland, CRRRLResearch 60. Mellar, M. and Testa, R.. Eft'ect of temperature ~84 yt 27633 pp,., 1969. Ih p f I,J~GI 11, oI. 8, 83. Ilaudrey, K.D., Ice engineering arudy of 52, pp. 1-145, 19li9. related properties of floating sea ice sheets 61. Paterson, R.S.B. snd Budd, R.P., Plow parameters and summary of elastic and viscnelaa tie far ice sheet model.ing, Cold Ra lans Bci. Tech., analyses' U.S. Naval Civil E ineerin Lab. vol 6, na. 2, pp. 175-177, 1982~ Tech. Re t. R860, 1977. 62 Budd, Q.P. I The dynamiCe Of ice Seaaee. 84. Morat, J-R. and R. Tinewi, Sea ice testing in Austrailian Mat. Antarctic Research Ex ditian flexure, Proceedin e of PrJAC77, St. John' s, S i tiff R rt lDR. 1969. Rewfoundland, vol. 2, pp. 638-653, 1977. 63. Mellor, M., A review of basic snow mechanics. Lainey, L. snd Tinawi., R., Parametric studies of Snow Mechanics S oe. Crindelwald, IARS Pub. eee ice beams under shore and long terra loading, Na. 114, pp. 251-291, 1974. IARR Internet. 8 m os. on Ice,

CLOSBlG REMidtKS PROLOGUEand EPILOGUE Red A. Ost ens o liat lanai Oceanic and Atmospheric Administ at ion iiatfonal Sea Grant College Program

The opportunity to provide the closing remarks a single oceanic depression varying little in detail for this series of distinguished lectures and the from that constructed by Nansen in 1904 based upon seminar on Arctic Technology and Policy is a triple sounding data from the 1893-96 drift of the FRAN. treat for me. One is because of my long, albeit In 1962, I published what I believe to be the first late. association with Arctic research. Another is. bathymetric map of the Arctic Orean that, indicated to be identified «ith the Sea Grant program at the presence of three trans-basin ridges, In IIIT. And finally to be here among old friends. preparing this chart, I had available, either But having said that I am faced with capping published or by reconstruction from over 1ayi ng off an intense session of presentations and Soviet drift and high latitude airli fted expedition discussions spanning the intellectual gamut frcm stations 1ocat ions over their bathymetric charts, a "Legal Regime of' the Arctic" to "Concrete Structures scant few thousand soundings in the entire ice- for the Arctic" to "Tectonics of the Arct ic covered Arctic other than my own data. Ocean.' [n ranging over this seemingly disparate Second, is the awareness that the waters of the spectrum for a focus to concluding remarks, I am ocean have a certain ordered mot ion, or dynamics. struck by a common thread other than the obvious The fi rat des cri bed i n pub1 ication was that of the Arctic connection! and that is the pioneering nature Gulf Stream by 6enjamin Franklin in 177O. The of all of these fields of endeavor. This, indeed is C rcxnwel1 Current which i s 3, SOO mil es long, almost the nature of oceanography itself. as swift and carrying nearly half the flow vo1ume of Most disciplines of human endeavor can be the Gulf Stream was not discovered until 1952. measured by milestones of significant new Third, is the realization that the ocean basins understandi ng. Irr virtually every case, these are not featurel ess depressions but, r ather, ruat milestones stretch back in hi story for centuries, if they are geologically complex like their terrestrial not nil leni a; f'rom Aristarchus to Copernicus to counterparts. The ffrst clue to structure" in an Kepler' to Herschel in Astronomy; fran Hero of ocean basin came in 1873 when a rise in the miridle Alexandria to Galileo to Newton to Maxwell to of the Atlantic was discovered by the 6ri tish Einstein in Physics; from Hippocrates to Harvey to research ship CHALLENGER.However, it was rot until Hooke to Pasteur to Crick and Watson in Medicine; 1956 that Maurice Ewing and Bruce Heeze predicted an from Mamnurabi to Justinian to Marshall In Law. interconnected global-encirc1 ing oceani c ridge Oceanographyhas no such long history, which is system. It requi red another decade to describe thi s it,s thrill and cha'llenge. To make my point, I will largest structural feature on the surface of tl.e argue that there are seven salient milestones in our Earth being over 40,OOO miles in length! understanding of the oceans; sufficient detail to show its major features of FIrst, is that the oceans in fact exist--that black faulting, central grabens, systematic af f sets, is as deep terrestrial basins versus relative thin etc. laminae of water over an otherwise homogeneous The fourth and fifth intellectual milestones in [excepting surficia'1 geology! Earth. Geologists ocea nography were near1y cont ervporaneous in t hei r refer to these as the fi rst order features-- inceptiors in the mid-1960's. Ore was the continents and ocean basi ns . Even thi s most realization that not only did the ocea~ contain primitfve understanding is relatively recent . In structural geologic features but that the 1854' Matthew Fontaine Murray published the first controlling tectonic proces ses were going on at bat hyraetric map of any ocean based upon accumulated rates many orders of magnitude faster than the recOrdS af deep sea saundi ngs in the North "Uni formitarianism" of geologic orthodoxy could Atlantir., Acoustic ranging of the seafloor was readily comprehend. This grand discovery of developed between the World Wars and the recorriing seaf1oor spreading and global tecto ism showed the bathymeter did not come into common usage until Earth to be constructed of some two-dozer after World War I[. l.eadtrme soundingswere tedious structurally competent plates that are driver. by and imprecise. Few were made beyond depths to forces, stil 1 poorly understood, in di f ferent i a' assure safety of navigation. Illustrative of this motion relative to each across the surface of the paucity of data is the first moder~ chart of the Earth. Plate tectonics, as this proces s is na» Arctic Ocean Basirr published by K. 0, Emery in c ommonly refe r r ed to, i s a sc i ent i f i c concept o. 1949, This chart vras based upon only 152 soundings power and beauty ri vali no those of Hut ton, Oarwi r deeper than 915m, or an average of one for each and Kepler; vet the sin.pie descripr.ive phase of thi s 12,OGOsquare miles. His bathymetric map portrayed discovery is barely completed and the processes car only be Imagined . The assimilative capacity of the oceansto digest The other was the realization that oceanic raan's waste products in the seafloor, water coluam currents are but a small fraction of the internal dynamicsof the ocean, indeed only about and even the atmosphere must be completely percent, In addition, there are great eddies and reassessed. To date, our uses of the ocean has been gyres In the ocean that are analogousto the high 1 arge 'ly 1 imited to waging war, a medium of and low pressurecells of the atmosphere. Put transportation, and a source of food and fiber frgxa somewhatpoetically, we learned that the ocean like a primitive hunting and gather1ng process, On this the atmospherehas both c11maticand metearological intellectually bankrupt foundation, we have tried scales Of mass,energy and momentumtransfer. The repeatedly and fai led successive ly to develop description of thesemesoscale eddys in the oceanis national ocean policy. Incomplete and the>r physics poorly understood Haw, with these new discoveries and the today, application of other scientific advances,such as Sixth is the effort to achieve a new sense of genetic engineering, microbiology and salt water legal orderand internationalorder liness through fermentation the possibiliry is real that the acean the powerfulconcept of the oceansbeing a global can be a virtually unlimited cornucopiaof metals, coamens. The ocean has been the subject of energy, protein, phargnaceuticals, industrial codificat Ion sinca a 1493 Papal SulI di vided the feedstocks and other resources. Atlantic betweenSpain and Portugal. This tidy The point of thI s ef fort to suavnarize your arrangement waS upset in 1588 when England and the semInar i s to emphasize the intel 1 actual lietherlandadefeated the SpaniSharmada and "rights" adolescence,if not youth, of the oceanphysical, basedupon the powerto exercisetham were replaced biol oglea 1 and soci al scIence s and engineering. In by the conceptof freedcvaof the seasas articulated our nascent field, we must not be lulled into the by HugoQrotius in his t609 tract IlareLiberum, A mental t id Iness of an A Ir stot1 e but rather, 1 ike aeateemaetlarge aoey of eaollclt e~ecottmeeryla» Ga11'leo,to look with wonderand openmimdednessfor has developedto defI ne and protect Indi viduals what we see that is new. The diversity of topics rl ghtS On, in, and under the OCean, In 1973, discussedhere wi1 1 surely be exceededby the seriesof conferenc.esonthe Lawof the Seebegan un antI cI pated and excI t i ng pathways t hese basic with the express purposeof codifying not an research, app1 I ed technof ogies a nd pol 1cy indi Vidual' S but rather the WOrid'S rightS to the considerations wil 1 lead mankind, 1 am honored to ocean under t he concept of I t being t he ccmuoon be a part of this collegium and am grateful for yctur heritage of mankind. This is at once one of the participation . most noble and di f f'I cult ef fort s at international legislationsince the AntarcticTreaty. Although the camplexityof the issuesaird the d'iversity and numbersof the participantsaugers ill for success, the veryprOCeSS Of the cOnventiOn~has Set a new tone for humanrelations. Surely the prospectsaf nswinternatIonal accords must be viewedas a major resource derived fran the ocean, Seventh,and finally, the recentlydiscovered biological, geochem1cal,geo'logical, and physIcal processes at seafloor spreading loci is one of the sa'Iient discoveries of this decade, if not the century. A whole new fore of life has been dIscovered that is completelydecoup'led fr aa the photosynthetic process. The only ctveparable life hitherto knownto exist on Earth rely on a photosynthetic substrate for their existence. Thesepurely chemosynthetic anImals are a biological marvel as alien to our prior understanding as creatures frox another world. klhatpraoISe might they hold fOr exotIC new drugs and pharmaceutIcalST Temps-ratore differentials as great as 400 C occurover a spanof just a few meters. Thr ough our Ocean Theneal Conversionprogram, we are spendingtens of milliens of dollars to capturethe energy of a temperature di f ferent1 at 1 on of only a few degrees over a kilometer! A megawatt of energy is produced fran a sma11 fumera le not much larger than thi s podium. Polymetallie sulfides are being deposited at rates that may exceed humanconsumption. Are metals renewable resource I I The oceans have been viewed as a passive catchbasin accumulating all the wastes, natural and anthropogenic, that wash of f the continents. Other than depositionaland somebIoalteration processes, the ocean's accumulation of such 'contaminants" was ever increasing. ge nowcomprehend that alongthe locus of seaf'loor spreading massivequantities of materi el, probably every element in the periodic table, are being injected into the ocean's waters. ue must learn to underitand the oCeanSaS the gleet chemiral processing plan that It surely must be. ABOUT THE AUTHORS

Archer B. Ra eroer is an KIT professor with a operations. Currently, Ur. Chryssostoeidis is joint appointment in the Departesent of Ocean studying the dynamics of marine risers end is Engineering and Deparcment of Electrics I pursuing reseat'ch in computer aided design snd Engineering and Coeqmter Science. Be is also s executive systems that have tsvltidisciplinsry Guest InvesCigator at Quads Bole Oceanographic applications. Be received s B.Sc. in naval Institution. Professor baggeroer hes undertaken architect.ure f rossthe University af Durham st the research in adaptive array processing studies, Voiversity of Bewcastle upon Tyne, England. Be multichannel seismic array design and Cesting an received from MIT an S.M. in navel architecture and Georgesbank and dereverberation of deep~ster marine engineering, the engineers degree in naval miltiple ~ in the East Atlantic Continental Margin architecture, and a Ph.D. in ship systems Program. He has been part of PRAMII. and PRAMIV, ana lysi ~ ~ two Arctic programs sponsored by the U. 8 ~ Office of Naval Research. Hc hes also conducted studies of Gre o I.. Duckvorth is a Ph.D. candidate in a lang-range, Iov- frequency reverberation in the joint BIT and Woods Hole Oceanographic Institution CanadaBasin. At present he xs else working on an program expected campletion March 1983!. His MIT Sea Grant project investigating acoustic thesis ia on the use of dsts adaptive signal telemetry for untethered, underwater vehicles and prncessisxg~ Igorithms for the analysis of Arctic sensors. Professor Baggeroer completed his refraction aad Iongmange propagation data. As e undergradvate studies aC Purdue University and staff member and consultant st HIT' s Lincoln received hi ~ 8 ~H. and Sc~ D. from MIT. Laboratory in 1979 and 19SD, he helped to develop and evaluate hardware end prograasning for passive p. Dos las bruchet is Assistant project Manager for acoustic location systems~ In 1980 snd 1982 he Petro-Canada's Arctic Pilot Project. Be directe undertook experimental vnrk in ocean and seismic the development of policies, programs and acoustics in Che Arctic Ocean as a participant in ~ tretegies for selecting pipeline and terminal the East Arctic programs. Mr. Duckvorth vas siCes for liquid natural gas LNG! snd for graduated summacurn laude frais Rice University in assessing the environmental, socioeconomic and Houston and received his S,M. from MIT. ~ efety effects. Be is also responsible for direcCiag the project throughout the vax'iove F. P. Dunn joined Shell Oil in 1961 snd vss assigned federal and provincial regulatory processes ~ Ne vithi.n the year as a Project Engineer in an ~ erves on the Environmental Advisary Cosssitree an of f shore product ion division vot'king on f scil i t ir s Areti» Marine Transportation which reports tn and small platforms. He has been Manager of the Canada's Ministry of Environment; the coesnittee is Of fshore Construction snd Design Group for over 13 currently formulating guidelines far marine years. The group des igas sll Shell Dil platforms transportation throughout the Northwest Passage. and consults on many problems related to offshore and Arctic constrvctian. Mr. Dorm spent f xve years Billion J. Cam ll completed his undergraduate as an elect.ronic countermeasures officer and vork ia physics at the University of Alaska and navigator in the U. S. Air Force after being received his M.S. and Ph.D. in atmospheric physics graduated from Ohio State University vith a B.S. and oceanography fram the University of and H.g. in civi.l engineex'ing,. Washington. Be vaa ~ Fulbright Scholar at cambridge University, England where he vorked with I 0D, L f ' Mlf' D P t I 0 the Scott Polar Institute. During the psst Engineering, is weLl knows for his underwater twenty-five years he has done extensive field work acoustics t'esearch. Most recently, be hes been in the Arctic and Antareti». In 1964 Dr. Campbell stvdying the acoustic propert iee of the Arctic joined the U.S. Geological Survey and in 1969 Ocean, including ssebient noise and continental became the Chief of its Ice Dynamics Project st the margin backscattering. Be leads the Acoustics Sub University of Puget Sound, vhexe he also serves ae Panel of the Science Group far the Marginal Ice a Research Professot in the Physics Department. Zone Experiment MISER!. With Professor Arthvr Beggexoer of MIT, he hss led acousti~ studies on asostomseCh ssostomidis is a Professor in the FRAMsnd CANBARXprojects. Before joining the MIT s Department of Ocean Engineering and the MIT faculty in 1971, Dr. Dyer vas Vice President Director of the MIT Sea Creat College Program. Be fax' Bolt Berenek snd Newman,Inc. A graduate of is recognised internationally for his research and the Institute with his S.B., S.M., snd Ph.D. teaching of ship design and of fshore marine physics, he served from 1973-1975 as Dixector of tbeleLT gea Grant Program and Eros l 971-1981as Beadof theOcean Engineering DeparCeent. Heis e slip faultsin Alaska.Dr. Grants,Geologist with ~emberofthe National Academy of Engineering, and USUS,has had extensive experience in geoLogic haarecei.ved awards from the Acoustical Society of mappingand in stt'atigraphic,eeronagnetic and America,theLy.g. Cease Guard, and the LEEK Oceanic petroleumresource studies in Alaska.Since 1969 BngineeringSociety. hehas been involved in geologicand petroleum resourceinvestigations of the continental shelf BenCD Gerwitk Jr. baabeen ~ PrpfessarOfCivil and slope in the Chukchiand Beaufort seas. Bngrnseringat the Vnivera icy of California, flerhelay~ ines 1911, focusing onconstruction engineeringsndassnagenant ~ prom1974-1978, he NieCOnein,Bilraukee Gengraphy Department and rice servedes PteeidenC of Paderat ion internationale de Presidentof Cornice'Arctique International ~ le Precontrainte FXP! snd from 1979-1960 ve~ organizationof Arcticspecialists which sponsors Chafrmanof tbe llarine Board of theNational conferenceson polar subjectsand coordinates BteeearchCouncil Professor Gervick has been ~ inCarnaCionalAtctic expeditions and research consultantonoffshore platforms including gkofiek, projects~ Bia researchhas primarily focusedon getylA., Binien Central, Stat Ejord platforms A,B, the cultural andeconomic geography of the Arctic endC, andthe TareiuCCaieeion-Ltetained 1 land.~ sndaub-arctic regions, vith his field experience Hebes vorkad on corsceptual designs for concrete takinghia to thoseareas almost every year since offshore~ true torse in the Beaufort andBering seas 1956. ProfessorBaglund teaches the onlv andoffshore eastern Canada. Be i ~a graduateof university-basedArctic winter field coursein the theUniversity of California,Berkeley with a veeternvot'ld. An active part icipant in a number degreein civil engineering. Of PrOfeasiOtialaOCietiea, he haechaired the CODWitteeOnPoint RasOurceDevelopastnt Of the U.S. NatinnalAzademy Of SCienCea and recenCly caapfeCed ~ three~ear term ea ChairmanOf the Boardof AttorneyGeneral' ~ Office since 1916. Be taught ~ t Governorsof the Arctic lnsCitute of North thsUnivsraicy of Singapore in 1972 and ras in America.He received hi~ B.A.in geographyand priratepraCtice in AnchorageandTnkyo before romancelanguages Eros Drake Univetsity, and hi e joiningthe Alaska Department of Lav. A gt'aduate N.A andph D. in geographyand economics from the of thaCollege of Pisheriea at the University of University of Pennsylvania. 'Baehington B.gc ~ ~19651 ~ he alen has degrees from theUniversity of lfichigan J.D., 1970;Ph.D. in JohnLawrence Bar rove i ~ theDirector of Studies fisheries,19!. Boreend raised in Juneau,Dr. of the AmericanSocieCy of internationalLav. Be Gieshergie ~ fourchgeneration Alaskan resident. i ~ elanthe current Director of theDepattment of LegalStudies of theJohns Bopkine University DMtCiwD D'%dD' M 8 4 DlD ' phy Schoolof Advancedinternational Studies. I DD DDMMM DMDMD D ' D DDD,D iii, M ~DDi graduateof BaylorUniver ~ ity,Dr. Hergroveholds afterdoing undergraduaC ~ vorkthere. Hi ~ theai~ ~ nL.L.B. frOS Ber Yerk Univeraity and e Ph.n- fran amddissertation wrm oa production andanalysis of Narvatd~ Be ie novserving as a memberof the U.B~ Lsafratmdapecta'a of hydrogen bromide aed the governmentAdvisory Corsair tee on Antarctic molecnleaof hydrogen aed ic ~ isotopes.From Resources. 1956-19he carried ouc research. in pL~ ernephysic ~ ~ ttha General Bl~ cttie Spacegctences Laboratory ~ ltil liamD. Hibler 111haa been a Research llheahs joined the NASA Goddard Space plight Center Physici ~C wtthChe Cold RegionsResearch and in 1970be directed hie research tovard obt~ ining gtlgineeringleboratnry in BanOVer,Hev Hampshire andinterpretimg microvaw spectre of tiesearth and ~inca 19y0with two intarruptiona when he vas a it ~ atmospbar~ fra»sensors located onaircraft end VL~iting Fellovin theGeophysical Fluid Dynamics spacecraft.This vork haa contributed to an Programat PrincetonUniversity. At the Cold improwdmicrovave instrument, the Scsaning RegionsLabor ~ toryhis priaaryresearch intereaC s Hultiehannellticrereva Radiometer BLBQ! D uhich i ~ havebeen in large-scalenumerical modelling of sea currentlyoperating on boardche Nimbus 7 ice andice coveredoceans and lakes ', ~ atellito. At presenthe i.~ currentlya Senior applicaCion of modal~ to ice forecastingand gcientieCat the GoddardLaboratory ~ nearehoreice characteristics,'and the relationship of eeaice to clisaaticchange. A 1965graduate of ChrisA. Grahamrec ~ ivmdhi ~ Bachelorof Science the Universityof Hi~ eouri in physics,Dr. Bibler receivedhi ~ Ph.D.from Cornell University. engineeringand has practiced geocechnicel engineeringfor canyears. Prior Co joining OlaK. Johannesaeni ~an Associate professor st Gulf-CanadaResources, lnc ~ in 9tay1972, he vorkad CeopbyeacalXnatttute Untveretty of Bergen, vith geotb~trna 1 andgeotachnical induscry Norvay,the school from vhich he vas graduated " consultant~ and ~ idedin theevaluation and da ~ign 1965.Pme 1966 to 1970he vaa on thefaculty at of pipelinseand structuresoe permafrost~ tttGi11 Universityin Boncrealvorking with ice areifiCi ~ 1i ~lande in the BeaufOrtgea, end drifCproblems in the Cult of St. Lawrence.After CnnVentional geOCeChniCal Saudi~ sin nsngermafrest fouryears at SAC ANTASif Research Center in regions lli~ meinreeponsibiLitiea ~ tGulf are for Lagpeais,italy, hareturned to the Universityof geotechnical evaLueCioe for well cosplstiona Bergentovork on marginal ice zone problems. throughpermaf root, of f shoredrilling structurea, 19BL-1982heheld the Office of ttavalResearch and Subeea and onalsore pipe linea or ArcticChair et cheNaval Post Graduate School in pre+evelopment ~ tudi~ e. nteamy,CeliEornia where he coordinatedthe fnrsatinnOf the lnteraatiOnal Barginal 1Ce gene ArChurGrantz joined the U.S. GeologicalSurvey Program Hfggg!. At presentDr. Johannessenie ~ DDDDi DDDD f M 4 '~ i D M il ~ erring~ sthe ChiefScientist or HIRE>. University vith an A.B. in geology. Bothbis sl,g. and Ph.D. vere taken at Stanford University vhere +onardJohnson hae been the Di.rectorof the his doctot~ 1 dissertation wasvritten on strike Arctc Programia che U.S. Office of NavalLtesearch ~ inca1980. Pot five yearsprior to that ~seignmsnt he had been the Physical Science Before coming to NIT in 19BGas a Research Administrator for the Arctic Program end had served Associate, he was a geophysicist with the USGSin ia the D.S. Havel Oceanographic Office as Deputy their Geothermal Studies project for two years. At Director of Ocean Floor Analysis Division and pt'eeeatDr. Lsmver'sresearch interests are in heat Oceanographer. He has been a Lecturer at the flow and tectonics of the South Atlantic and Scotia University of South Carolina in Columbia end See, ae well as the CanadaBasin. Be is a member Catholic University in Hashington D.C. Dr. Johnson of the American Geophysical Union and the Royal rec~ ived s B.A. from 4lilliame College and a N.S. Astronomical Society. Dr. Lawver is currently from Hev York University in geology. His drPhil suparvising the Tectonics of Sovthem Dceans vsa coepleted in marine geology at the University Programfor Dr. JohnG. Sclater at KlT. of Gopenhag,en,Denmark. Samsel Vi Haxwell i ~ the Hanager of Front ter Zan J ~ Jordaen as Head of Research and Development Davelopment Bnganeering for Gulf CanadaResources inc. His responeiblitias touch upon all the for Dot norske veritsa Canada! Ltd. overseas the development~ 1 projects in the frontier reg,iona organisation'e research in cold climate technology, north aod east of Canada. h managementexpert ~ Dr. offshore structuree and risk analysis. Before Hexwel1 has helped plan large- and small-scale joinieg this organigaCion in 19HZ, he vas a Professor of civil engineering at the University of proj ects in areas aroundthe world f romthe Gvlf of Sees to China. As Vice President of Parsons Calgary> Alberta. He managed numerous research Brincksrhoff, Inc ~, he had major responsibilities projects and delivered lectures et the university on statics, dynamics, omchanics, probability theory in raenaginga coerplete program ro design the U.S. ~ ndmaterials. As a Research Assiscant ~ Kings Departmentof Energy Strategic Petroleum Reserve. He hc lds a B.S. in petroleum engineering from the College and consultant at Ove Arup h Partners, London, Dr. Jordaan specialised in the design of University of Oklahoma,an K.S. in engineering from concrete ~ tructures. He received his B. S, and H.S. the University of Hsrecaibo, Venezuela, end a Ph.D. in ertgineering from the University of in engineering f roe the University of Salvador. Hitwatersrand ~ Johannesburg, South Africa snd his Ph.D. from the University of London, Kings College, Engineeringdegree in mechanical engineering in England. 1975. During six years with Gulf Canada'sFrontier Banc J. Kellnet' is a Research Associate and Development Division, he has been responsible for Assi ~ tant to the Director of Studies of the f isld and an.~ lyt ical research projects in the American Society nf international Law. She wss Beaufort Sea on ice characteristics, scour, graduated from Amherst College and holds sn H.A. ice/structure interaction, ice management, and from the Johns Hopkins School of Advanced oceanography,end for the applicaCionof this International Studies ~ information to the design end operation of offshore systems for oil exploration snd production. Judith Te er Kildov, Associate Professor of Ocean Policy at HIT, has specie lixed in anslysing the Linda R. Heinke is a Research Specialist in HXT's responses of complex political systems to DepertmenCof Earth snd Planetary Sciences. Ks. technological change; her work, vhich etaphaeises Heinke received a B.h. in mathematics from the the asltidiaciplinary aspects of marine management, University of California, San Diego and focused her haa focused on Law of the Sea, coastal r.ene snd graduate studies on computer science et the ocean resource management issues, and on the University of 4Iashington, Seattle. problems of international technology transfer. Professor Kildow, who received her H.A., M.A..I..D. Kelcelm Keller ie an Engineer and Scientist at the and Fh.D~ from The Fletcher School, Tufts Cold Regions Research and Engineering Laboratory University, Boston, joined the NlT faculty in CRREL! in Hanover, Hev Hampshire,' he is also a 1973i Prom 1976-197S she vas a Visiting hssociate private engineering research consultant. At CRREL Professor at the University of California at San he serves as a technical advisor for enpineering Diego in the Departmentof Political Science and a research on snow, ice and f roxen ground, His ~eeearcher at the Scrippe institution of personal research covers material properties, Oceanography. machine design for drilling, excavating, cutting,, trenching, and tunneling, eaplosione technology, H. David Ki e joined the NIT faculty in 1951 and avalanche protection, and iceberg technology. Dr. became a full Professor in the Department of Keller'a field work has taken him to Antarctica, Haterials Science snd Engineering in 1962. The Greenland, Alas'ks, the Canadian src tie, Siberi a, graduate education program he established at the Korea, and the Yukon. He received hie B.Sc. in lusts tute hae had sn influence on ceramic currtcula civil engineering f rom Hottingham University, throughout the vorld. His ceramic science England and hie K Sc and D.Sc ~ in applied science contributions ere considered to be seminal in the frere Kelbeurne llniversity in Australia, His Pb.D. fields of diffusion, thermal stresses, thermal in engineering is from Shef field Un.iversity, conductivity, microetructure effects, sintering and England. liquid~see eintering, refractory corrosion and graimMvndary phenomenain ceramics. Professor Ned A. Osteneo ie the ArCing Assistant gingery is the recipient of the RoseCoffin purdy Administrator for Research and Development viCh the Award of the American Ceramic Society, the John National Oceanic. and Atmospheric Administration JeppsoeAward, and the Robert SeamanHemorial HQAA! and the Director of the National Sea Grant Lecture Award. He vas elected to the National College Program vhich is under tbe aegis of NOAA. Acadmmyof Engineering in 1975. An alumnus of the Vnivereity of Qisconsin, Dr. Ostenso completed his B.S. and K.S. in geology and Lawrence h. Lawvet after receiving a B ~S. frosn his Pb-D. in geology and geophysics. He helped to SCanfordUniversity and s Ph.D. from the University found the Geophysical and polar Research Center at nf California, San Diego completed his the University. Dr. Ostenso's extensive research poat~radustevorlt as a ltesearchGeophysicist at experience in solid-earth and marine geophysics has Scripps institution of Oceanographyin 1977. been honored with his name designer.ing s maIor Antarctica mountain snd sn Arctic Ocean seamount. iavolved in several major Alaskan projects and Be hae led the U.g. delegations to the United studies including the Cook Inlet Developaent, Nations and Buesoa Aires and ves the Chief U.g. Prudhoe Bsy and Kuparuk Fields, Trans-Alaska delegate far the Bilateral Agreementbetveea tbe Pipeline and the Alaska Natural Gas Transmission U.S. and the People's Republic of China in the System. field of cooperation in asrine and fishery scientific technology and with the Soviet Unios Ge P V i ~ the Arct ic Technology Bilateral Agreement on World Ocean Studies. Dewlopment Group Leader for Mobil Research end Development Corparstion in Parmers Branch, Texas. Robert S. Pritchard i ~ aa Associate of Plow Be joined lfobil in l980 following three years ss a industrtes, Inc ~ in Kent, Washington. Porasrly ~ he Research Engineer at the U ~S ~ Army Gold Regions ~ erved the firm as Senior Research Scienti ~ t and Research and Engineering laboratory in Hanover, Bev Director of the Geo/Solid RechsnLcaDepartment. Hampshireand twenty years «itb the U.S. Coast Prior Co that, he had been ~ PrinCipal gcienCi ~ C in Guard, ten sa a Professor of Marine and Ocean ths Arctic LCS Dynamics Joint Experiment at Che Engineering at the U.S. Coast Guard Academy!~ Dr, University of Washiagton Snd ResearChEngineer at Vance i ~ an expert in modeling systems far vessel ~ the Eric R. WangCivil Engineering Research in ice and has published numerous papers on the Facility in Albuguerque, Bev Bsxico. Rs subject. h graduat ~ of the Coast Guard hcademy, he ~ pecialises in solid mechanics, applied received a R.S. in naval architecture and marine mathematics, plasticity, numerical analysi ~ and the engineering and nuclear engineering from the transfer of technology froa amchanics to applied University of Ltichigan. Bis Ph.D. in ocean probleae in gsaaechanic ~ . For the past Lit years he engineering i ~ from the University of Rhade haa focused on modeLLing sea ice dynaaic~ . Dr. Is Land. Pritchard hss suthored or co-authored over 60 publications and report ~, primarily in the areas of 'Narbert Unterateiner, PrafeSSOr of htmOSphsriC ice, soil and rack mschaaics. Re received his B,g, Sciences and Geophy~ ics, Directar af tbs Poler from Lehigh University and his H.S. and Ph.D. from Science Center, Applied Physic ~ laboratory st the ths UaiversiCy of Nev Naxico. Uniwrsity of Washington, Seattle ~ ia a participant in aaay national and internatiansl cold region NiChaeL R. Rabertaan i ~ Che Reneger af RegulaCOry efforts. In 19gl he organired end directed ~ BAZO and Enviromsental Af fai.rs vith Petro Canada'~ hdvsncedStudy Institute on Air-Sea-Ice Arctic Pilot Project APP! and hae bees cLosely InCeract'ion. Prior to Chat, he developed and involved with the Rational Energy Board and other direcCed s larg,e interdisciplinary project. AINEX, hearings that have been held in cnajunctios vith in the Arctic Ocean. Dr. Untersteiner hss served this project. Before joining APP, he vss Director an numerousaatioaal and international cossnitrees. of the Canadian WildLife Service, responsible for AC present he i ~ on the Rational Academyof Scieocs ventura Canada and the llorthvssC Territories. Be Casaittee on tha Polar Regions and Climate Changes aLso hss considerable experience i,n Che and serves as Chairman of the Science Working Croup governmental side of t'ha regulatory proces~ . Hie on Passive Ricravave Data for Sea Ice Research for graduate studies vere dane ~ t the University of RASh. Dr. Uncezsteinsr vas graduated from the hl.bsrta, Canada in limnology snd be is ~ memberof Reslgyaaasius q ga1 sburg, hue tria and complated hi s several professional biologicsl eocietiee. Ph.D. at the University af Innsbruck, Austria.

R T k S Ll i ~ the Director of the Office of Peter wsdhaaei ~ Assistant Utrector of Research, Oceans and Polar Affair ~ in the U.S. Depsrtaent of Scott Polar Research Institute, University of State. Be joined tbe Departmeat of State is 1965 Cambridge, England Educated at Churchill College, and served abroad both in Lebanon end Greece. Cambridge B.A. in physics, f969!, he vs~ an Since returning I rom Greece, eight years ago, he assistant to the Senior Scientist in "godson-70n has been involved in acesns policy matters. Be has expedition of Bedford Institute first ~erved an U.g. delegations Co the Lav at the Sea circutmlvigation of Americas! froa 1969-l970. Confereoce and represented the U.S. in a variety of During 1970-L974 he undertook grsduat'e research on oCher nsgotiaCi.ona rsLatisg to ocean snd poler wave-ice interaction at SPRI Ph.D. L9y4!. Be matters. Rest recently he haa acted as U.S. vorked with the Prossn Ssa Research Group, Victoria spokesmanin negotiations relating to Antarctica B.C., working on the Beaufort Sea Project, s study and Antarctic resources. Be aCCendedthe of geaufott Sea ice morphology in L974 and 1975. Univac~ ity of Virgini ~, graduaCing in 1962 vi.th ~ And in 1976 he becameleader of Saa Ics Group, B.A. in foreign affairs. Bs i ~ a membero! Che SPRI, cartying out research on Arctic sea ice Raven Society and Phi Beta Kappa. Be umiertook thickness profiling, wave-ice interactioa, ice edge graduate work at the University of Virginia in dynaaics and ~imilar sea ice problems. Prom polit ical acieace and ~ C the Uaiversity of Rhode 1980-19gl he vas Visiting Professor of Arctic Is land from which hs received a Rasters of Marine Rarine Sciesce at the Naval Postgraduate School. Af fairs Degree in L975~ Nonte ray, Calif ami ~ .

Robert E. Saith completed his Ph.D. sc the Wilford 'P. Basks 'oined the U.S. Army Cold Regions University of Texas with a concentration os Research and Engineering laboratory in Rsaover, Bev structures and sail mechanics. Dr. Saith joined Hampshireia L962 after two years vith the sir Atlantic Richfield in L964 ia the Research sad Farce Cambridge Research Center and five years with Development Department vhere he worked on the Department of Earth Sciences at Washiogton horizontal fracturing ~ underwater technology, and University. Be ie currently s Research offshore technology In L966 hs aoved to ths GLaciologist in the Snav end Ice Branch vhere his General Engineering staff in Dallas as a structural field experieace has extended geographically from and soi.l engineer. Since Chat time he hss been the Arctic Ocean to AnCarctica. He ie also an active in offehare design, soil mechanics, and Adjunct Professor at Dartmouth College. Dr. Weeks Arctic engineering and enviroaaentsl studies. Dr. hs~ been aa active participant on many scientific Smith ~ curreatly the Director of Civil Enginesriag and engineering c~ittses iocluding the Steering for ARCOOil and Gas Company-Dallas, has been Caasittee os RASAInitiatives Concerning Long-Term ChangesAffecting the Habitability of the Globe, Grande Ecole, E.B.S.T.A., Paris and a H,g. 915! the Betionai Academyof Science Task Force on and Ph.D, 97B! from HIT. Arctic Science Policy and the National Petroleum Council' ~ Production Engineering Task Group on ~H,J,i li 'sd itl» I Sv,0d Arctic Oil and Gas Resources. Be received his B.S. lce Branch in BABA's Goddsrd Laboratory for and B. S. st the University of Illinois , amd Ph.D. Atmospheric Sciermes Be received his Ph.D~ is frOm the University of Chicago in geoChemistry. physics vith a minor in mathematics from the University of Hery land. Dr. Zvally has been Paul C. Xirouchaki ~, an Assistant Professor of extensively involved in the application of rseote Ocean Engineering at NIT, has focused hi ~ research ~ ensing to ssov and ice research. Be has been the oo the noo-linear response of structoree under Program !inager for RemoteSensing and Glaciology load. including buckling, creep, and viscowlaatic for the Bational Science foundation's Division of deformationa. At present he is vorking on a gaa Poler Programs and a BABAStudy Scientist directing Oraot project on rational eslectioo of ~ definition study for aa advanced satellite ~trengthsning criteria for navigation in ice. Ln mission for ice, ocean, and climate research. 19BI, Professor Xirouchakis vas a guest researcher Currently be managesand conducts research rn polar at Dat norake Veri tao in Oslo, Borvay. Be i ~ an oceanography and glaciology including variability associate ammberof the Society of Bevel Architects of polar ice, ice/ocean/atmosphereinteractions, aod ffmrina Engineers and a member of the Panel aaa ice dynamics, ice sheet and shelf dynamics, BS 9, "Ocean Engineering in Frigid Knvironm.nts.u associated physical processes asd remote sensing of Be received ~ Diploma in mechanical eoginaerisg, ice and ocean parameters. B.l'.U.A. ~ Athena, Greece, a Diploma D'Iogenieut'

AUTHOR INDEX

Aagaard, K., 133, 160 Clarke, A. J., 136 Gammelsrtid, T.. 136 Ackley, S. F., 136, 185, 192 Clayton, R., 167 Gavin, J., 134 Aki, K13, 15, 167 Coachman. L. K133, 160 Gerwick, B. C., Jr., 113, 115-125, 129 Andersen, B., 133 Coiony, R., 204, 226, 229, 230 Gilman, J, J., 14 Assur, A., 199, 251 Comiso, J. C., 198 Gissberg, J., 42, 61-68 Atwater, T., 151 Coon, M. D., '133. 136, 161,227 Gloersen,P., 138, 197-222 Avery, D. E., 159, 160 Cooper, A, K151 G old smith, W., 114 Cramer, H., 15 Goodman, D. J., 136 Crane.R., 197, 200-201, 204, 205 Graham, C., 97-111 Backrnan, M. E., 114 Crary, A, P., 13, 173 Grantz, A., 147 160, 174 Baggeroer,A. B., 153, 159-176 Croasdale. K. R,. 101, 125, 128 Griffiths, R. W., 136 Baker. M,J86 Grotius, H., 262 Barath, F. T205 Grow, J. A., 151 Dawes, R. R., 155 Baal, M. A., 152, 159 Gutmanas, E. Y., 14 Demenitskaya, R. M., 149 Beloussov,V, V149 Bessonova,E. N., 167 Detrick, R, S., 167 Diebold. J. B., 167 Bjerknes, V., 131 Hall, J. K., 160 Drury, C. M.. 71 Blenkarn, K. A., 82 Hall, R. T., 228 Duckworth, G. L., 159-176 Bloomquist, A., 228 Hargrove, J. L., 41, 47-60 Dunbar, M. J., 138 Boucher, G., 174 Harrison, C. H., 181 Brosge, 'Ihf,P., 153 Dorm, F. P89 Dyer. I., 11-38, 133-146, 160, 163, Hasselmann, K, 133-146 Brown, R. A., 136 Heezen, B, C149, 152, 154, 261 166 Bruchet, P. D69, 71-78 Helland-Hansen, B., 131, 133 Brtsne, J, N14 Herron. E. M., 152-154, 160 Bryan, K., 134 Edgerton,A. T201. 205 Hibler, W. D., Ili, 84, 133-146, 187. Buckley, J. R., 135 Edwards, R. Y125, 126, 128 188, 191, 225 230 Budgen, G, L., 227 Eittreim. S., 159 Hnatiuk, J., 97 Burns, J. J228 Ekrnan, V. W., 131, 133 Horne, R. J., 187, 188 Eldholm, D., 150, 159 Hudson, R., 184 Emery, K. 0261 Hunkins, K., 13-14, 133, 135, 160, Cammaert, A. B., 125, 129 Enkvist, E125 163, 166 Campbell, W. J., 133-146, 177, 197- Ewing, W. M., 13. 149, 173, 261 222, 226 Car ay, S. W., 153, 154 Carsey, F, D., 197 Falconer, R, K. H., 131, 160, 166, 167 Jackson, H, R159, 165-167 Cavalieri, L. S., 205 Feden. R. H., 159 Johannessen, D. M., 131, 133-146 Chang, D. C., 185 Fitzgerald, E. R., 14 Johnson, C. M. 134 Chang. T. C199, 201 Fleldstand, J. E., 131 Johnson, G L.. 16, 131, 151, 152, Chen, Y,-M13 Flint, A. R.. 86 159, 160 Churkin, M., Jr., 151 Forsyth, D. A., 149, 154, 160, 166 Johnston, W. G., 14 Clark, D. L., 160 Franklin, B., 131 Jones. P. R.. 154 Jordaan,I, J.. 69, BE-88 Manabe, S., 134 Jordan,T. H., 147, 149 Prada, K., 165. 167 Manley, T. O., 163 Pritchard, R. S133, 161, 221-230 Marcellus,R, W., 101 Prodanovic, A., 125 Marco, J. R., 228 Karasik,A, M., 147-150,154 Purdy, G. M., 187 Marshall,B. V161 Pushcharovskiy,Y. M., 147, 152 Kari, A., 125 Marshall,W, F., 165 Kashteljan, V. I., 125,126 Martin, S., 137, 229 Keen.C, E., 131 Marsh,H. W., 12 Keenan,R, E,1S Rabinowitz, P. D., 155 Maxwell,S, V., 97-1E1 Ralston, T. D., 126, 128 Kellner,N., 41, 47-60 May, S. D., 153 Kennett,B. L, N., 167 Rarnseier,R. 0197 Maykut,G, A., 136, 187 Readey D W 14 Kerr, A. D., 114 Medwin, H., 139 Kerr, J. W., 155 Reimer R W 228 Meeks,D, C196, 202-203 Rey, L., 133 Kildow,J. T.,41-46 Meinke, L. 147-168 Kingery,W. D., 14,223 Rice, J. R., 13, 15 Mellen,R. H., 12 Richards,P, G., 13, 15, 167 Knajcinovic,D114 Mellor,M14, 85, 235-259 Knapp,A. E.,82 Rickwood, F. K., 163, 164 Mertz,R. W., 172 Robertson, M., 69, 71-78 Knudsen,M., 131 Michel, B., 125, 128 Kolle,J. J., 227 Rttled, L, P., 136 Milano, V. R., 'l25, 126 Roethlisberger, H., '162 Kovacs,A., 22B Milne,A. R., 13, 'IS,168 Kovacs,L. C., 159 Rogers, J. C., 'l73 Minster,J. B., 147, 149 Rossby, C. G131 Kozo, T, L185 Mock,S. J., 187 Kristoffersen,Y., 159, 161, 163, 165, Rothrock D A 187 191 226-227 Moe, J,. 113 230 167 Mohn,H131 Kry, P. R., 101 Runeburg, R125 Morlson,J. H.. 135 Ryvlin, A., 126 Kukla, G134 Mosby, H., 131 Kutschale,H., 1BE,163, 171 Muench,R. D229 Munk,W., 138 Murat, J. R., 261 Sahlberg, J., 228 Labelle,J. B., 12 Murray, M. F., 26'I La Brecque, J., 1 55 Sander, G. W., 166 Lachenruch,A. H161 Sandstrom,J. W131 Sater, J. E., 226 Lainey, I.. M., 25'I Naegle,J. N., 125, 126 Langseth,lb', G.. 151 Savostin,L, A., 149, 150, 154 Nansen,F., 131,133, 226, 261 Schwarz J 262 Larabee. 198 Nye, J. F., 226 Lawver,L. A., 131,147-1 SB, 160 Sclater,J. G149, 152, 154 Leavitt, E., 227, 229 Shapiro, L. H., 228 Shepard G W. 13 Leendertse.J, J., 228 O'Brien, J. J., 136 Lepparanta,M., 187, 226, 22&-230 Shimansky, J. A., 125 Oliver,J., 13 Simonson,D. R., 126 LeSchack,L. A185, 191 0mstadt, A., 228 Lewellen, R. I173 Smith, D. C., 136 Ostenso,N.A., 147, 149, 152, 160, Smith, D. D., 242 Lewis, J. W,. 125, 126 161, 163, 18S, 166, 261-262 Smith, J. D126 Lilwall, R. C15, 16 Ottolini, R., 167 Linden, P. F., 136 Smith, R. E91-96 Overland,J, E., 226 Smith, S. D., 134 I ui, S. K., 226 Overton,A166 I iu, T., 136 Sodhi, D, S., 228 Lowry, R. T187 Sorensen,Jens, 43-45 Spiesberger,J136 Lyons, J, A., 166, 157 Parmerter,R. R., 227 Spindel, R., 138 Lyons, J. B., 242 Parsons,B., 149,152, 154 Squire, V. A., 136 Peary, R.,4 Srivastava,S. P., 154 Pease,C. H., 226, 229 Starr, C., 81 McGonigal. I7., 97-111 Perdue,W. F., 13S Stefannson,V., 6 McKenna. R. F., 227, 229 Peyton,H, R., 125 Stewart, I. F. C., 171 McLaren. A, S., 187 Pharand,D.. 53 Stiles, W. H,, 205 McMechan, G. A., 167 Pitman.W. C, III, 147.149. 153, 154 Stoffa, P. L., 167 McPhee, M. G., 135, 226, 229 Pogrebrtskiy,Y. Y., 147 Stouffer, R.. 134 Mair, J. A., 149, 154, '160, 166, 157 Poznjak,I. I126 Sundvor, E., 159 ~. E., 205 Tveit, O., 81 Wallace, H. A5 Sesrdrup,U131 Udin, I., 228 Wal sh, J. E 134, 136 Sweeney,J. F., 131, 152, 160, 163 Ulaby, F, T.,205 Wang,Y, $, 252 Srrift, C. T, 205 Ullerstig, A., 228 Week~. W. F, 14, 187, 231-255 Untersteiner,N., 137, 177, 187, 227 Wheeler, J. D., 85 Urick, R, J12 White, R. M.. 125 Tailleur, I. L., 153 Wilheit, T. T., 197, 200 Taiwani,M., 147, 149, 150, 153, 154 Williams, E186, 187 Taylor, P. T.. 147, 152, 153 Valii, A., 228 Wilson, J. T.. 149 Tharp, M., 154 Vance, G, P., 114, 125-130 Whipple, C., 81 Thomar,D. R., 226, 228, 229 Vent, M. R.,'l97 Wold,R, J., 149, 16 'I, 163, 165 Thompson,R. E., 228 Vaudry, K., 129 Wunsch, C., 138 Thorndike,A. S., 186, 187, 191, 204, V inje, T. E., 135 226, 227 Vinnikov, K. Y., 134 Xirouchakis, P. C., 113-114 Toussaint,N., 125, 128 Vinogradov,I. V., 125 Toynbee,A., 47 Vogt, P. R., 147, '149, 150, 152, 153, Yakolev, G. N., 203 Trexhr, J. H., Jr., 151 159-16'I, 166 Tahe, lyl64 Trovrbridge,R., 163 Zubov, N, N., 226 Tucker,W. B. I II, 136, 185, 1B7, 191, Wadhams,P., 133-146, 161, 173, 177, Zwaily, H. J., 197-222 229 179-195, 229

SUBJECT INDEX

A{s{atiors,227, 230, 241, 255 American Society of MechanicalEngineers ASM'!. 225 Acoustic tomography, 138-139 Anchors structures!. 117 Acoustics, 1 '1-38, 134, 138-139, 165, 261 Anisotropic ice, 237, 243, 255 aarthborne vs. waterborne, 15 Antarctic Treaty of 1959, 5, 6, 47, 48, 56 Wee Hao Ice acoustics;Sonar; Underwater acoustics! Antarctica, 3, 6, 48, 57. 131, 134,'l37, 1 77, 199, 236, 244 Adviaction, 134, 229 Applied mechanics, 256 Ace el photography, 138, 139, 193, 226 Arco Oil and Gas Company Dallas!, 91 {Btaeralm Satellite data! Arctec, 125-126 Aesosrtagneticdata, 147-155, 159, 161 Arctic see individual topics! Aerosols, 135 Arctic, definitions, 3-4 A!t}JKX Arctic Ice Dynamics Joint Experiment!. 133, 136, Arctic Basin, 201-205, 225-233, 241, 261 138, 163, 1 &6, 197, 201-203, 226-228, 231 Arctic Mid OceanR idge,15, 147-154.159 Air lett-Clceanographyinteraction, 131, 133-146, 185 Arctic Ocean,11-38, 147-158, 197-222, 236, 241 Atr-Sea-IceResearch Programs ASI!, 137-'138 Arctic OceanBuoy Deployments AOBD!, 203-205, 226, 229 Airborne r ader, 192, 200 Arctic policy, 3-7, 41-45, 61-66, 69, 71-78, 81-68, 262 Aarcraft, 162-163, 168, 167, 191, 193 Seealso individual countriesand subjects! Aircraft landing areas see lce runways! Arctic Research and Policy Act U.S.!, 6, 7, 61 Airtpsns, 163, 172 Arctic Waters Pollution Prevention Act AWPPAI 54, 72-74 tssudguns,172 76-77 Asassta.44, 16, 42, 48, 72, 132, 153, 160, 204, 228 Arlis Program U,S.!, 149, 162, 242 Arctic policy and laws, 61-68 Artificial/Caisson islands, 97-111, 225 fisheries policies,63, 65-67 designand construction, 99-104 foreign fishing competition, 65, 67 geotechnics,104-105, 110 non-resident businessmen, 61, 66 legal status, 51, 52 state-federal relations, 61, 64-67 slope protection, 103 urban vs, rural residents, 62-63 Atinosph eric circulation, 133-146, 262 Alaata Lands Act of 198'I, 6 Alaska National Interest Lands Conservation Act of 1980 {AN ILCA!. 62-63 Backscattering, 16, 166 A!as%a Native Claims Settlement Act of 197 l ANCSA!, 58, Baffin Bay, 75, 150, 236 82, 85 Ballast, 108 A!bedo. 134-135 Baltic Sea, 228-229 Akesttian Islands, 4 Barcelona Convention, 7 A!pisa Cordillera, 152 Barents Sea, 115, 160, 200 A!pha-ISende!eevRidge, 147, 151-153, 160 shelf, 149, 150, 171 AtsseraaianBasin, 147-155, 159-161, 171 Barges, 106 AssseaicastBureau of Shipping ABS!, 118 Barrier ice see Ice islands and Ice shelves! AssseiricanConcrete Institute ACI!, 118 Barrier islands, legal status, 64, 65 Arrteaican Petroleum Institute IAPI!, 118 Barter Islands, 183, 242 AmeescanSociety of Civil Engineers ASCE!, 225 Bathymetry, 16, I35, 137, 147, 154, 159, 161, 166, 261 ArnevicasnSociety of international Law, 47 Bay of Bothnia, 228 273 Beaufort Sea. 16. 73, 77, 89, 115, 'I 19, 200, 201, 204 Carbon dioxide, 134, 135 environmental conditions, 11, 89, 97, 99 Cartography, 16, 261 floor conditions, 99, 103-'105 Catalina Island,jurisdiction dispute, 64-65 ice modeling, 225-233 CESAR, 132 ice morphology, 182-186, 188 Chukchi continental borderland, 151-152, 160 jurisdiction and boundary disputes, 63%5 Chukchi Sea,54, 89, 1'l5, 199, 200, 204 offshore structures, 97-111, 118-119 ice modeling, 225-233 resources, 1'I Circulation seaAtmospheric circulation and Ocean underwater features, 16 csrcul at ion! Beaufort SeaContinental Shelf, 99, 132, 171, 190, 191, 241, Circumpoilar current, 160 242 Circumpolar states,4, 41 Beaufort Sea Gyre, 160, 203-204, 241 Clay soils see Soil mechanics! Beaufort SeaSeismicity Cluster, 99, 1'IO Climatology, 5, 131, 134, 225, 227 Bering Sea, 4, 11, 137, 200, 236 Clouds, 135, 198, 204, 205 environment, 11, 89 Seea/so hJIeteorology! fisheries, 65-67 Coastalstates rights and responsibilities.51, 52, 54, 56 ice modeling, 225-233 Seee/so Coastalzone management! resources, 11 Coastalzone m anagement, 50-57, 63 Bering Strait, 229 CoastalZone ManagementAct of 1972 CZMA!. 63 ice mode ing, 225-233 Codes aee Building codes and standards! Berms,subsea, 101, 102-105, 108, 110 Cognac structure, 89 BESEX US/USSRj Bering SeaExperiment, 138, 197 Columnar ice, 238, 251-253, 255 Biot boundary wave, 139 Comit4 Arctique, 1, 69, 138 Bird colonies, 62, 75 Commissionon the Limits of the Continental Shelf, 52 Bottom production systems, 12 Computerizedsimulation aeeModels, numerative and Boundaries aeeJurisdiction and sovereignty! predictive! Bowheadwhale harvest,61-62 Concrete: Bridgeman isotherm, 242 adrnixtures for arctic marine structures, 116-117 Brines, 199, 235, 236, 238-240, 250, 252. 254 air entrainment. 116-117 Bubbles. 237, 242. 250 coatings, 115, 119 Buckfing, 101, 116 construction, 113, 115-124 Building codesand standards,gg, 117-118 ductility, 1'15, 116, '116, 119 Building technology eee Construction! durability, 113, 115-'117 failure mode, 118 freezingand thawing, 113, 115-118 Cables: lightweight, 115, 118 cable fairing, 163 precast, 118-119 policy issues, 52 prestressed and reinforced, 113, 115-124 strum, 13, 163, 165 steel-concrete composites, 115-119 Caissons, 115, 118 shells and slabs, 115, 117, 118, 119 drilling, 119 ships, 1', 116 flotable, 106-106 structures, 113, 115-124 reusable, '108 design, 113 See also Artificial/Caisson islands! Condeep structures, 118-119 Canada, 4. 44, 49, 53, '160, 204, 231 Construction, 97- 111, '113, 115-124 Arctic policy and laws, 54, 56, 71-78 costs, 101, 113, 119 jurisdiction and boundary disputes,49, 53, 54, 57, 65, 69 equipment, 105-106, 110 Ministry of Transport Control Authority, 73 facilities, 101, 105-106 Oil ard Gas Lands Administration, 73, 77 materials, 103-104, 105, 106 transportation regulation. 71-78 Seealso Concrete; Steel concretecomposites! treaties, 48. 56-57, 72 standards sea Building codes and standards! See a/eo Labrador, Northwest Territories; Quebec; Yukon Continental drift, 147-158, 160 Territory 1 Continental shelf, 48, 52, 53, 64, '159-'163 Canada Basin. 131, 147, 153-155, 160, 165, 184 boundaries, 52, 64 Canadian Archipelago, 16, 71-72, 159, 171, 204, 241 exploration and technoiogy, 171-174 jurisdiction disputes, 48%9 jurisdiction, 52 CAfeBARX, 163, 114 Seea/so Jurisdiction and sovereignty! 271 OaattilrNntalah atf Cont, !: Emissivity, 197-222 palissyand regulation, 50-57, 63 Scca/so Microwavedetec.tion! resources,11-12 Endangered species,62 QktaAN specific areas,e.g., Beaufort Sea! Enterprise International Seabed Authority!, 53 eetsvantieri on the Conservation of Antarctic Mar ne Living Environmentalimpact statement, 63, 73 Resources980!, 47, 57 Environmentalmanagement and law, 5, 41-42, 54, 56. 71-78 eaemntioe on the Continental Shelf 958!, 52, 53 Seea/ao Coastalzone rnanagernent;Oil spills! Crack kslet Alaska!, 89, 125 Environmentalprotection zone, S4 Corkatisforce, 226, 228, 230, 23'I Environmentalreview process, 41-42, 7 I-78 Cktst4ertefit analysis, 81-82 Equtdistanceprinciple, 53 tatsrgrstcondition, 230 Erlang, pdf, 15 I Mrrant, 261 Erlang distribution, 84 ~ o aeeOil, gas,and minerals! Erosion,by waves,103, 104, 106, 110 Otrssalstnscture, 132, 147-155 ESMR-5 Electrically Scanning MicrowaveRadiometer!, 177, INaa tataoTectonics! 19/-222 Ctsflrrst Qaa festive interests and self determination! ESSO CaissonIsland. 103, 10& Eulerian modeling, 229 EurasianBasin, 147-161. 171, 1&2-185 Exclusive Economic Zone EEZ!, 50-53, 55 Dating. 147-158 Experiment stations sae ice stations;Drift stations! ~a/ao Ice dating! Exploration seeOil, gas.and minerals,explorationi Omit Strait, 84 Explosives,16. 163. 165-168, f 72 Oaapseabed, 62-53, 56 Exxon floating caissonspar, 119 Astra/aoMining, deepsea! OtaapSaa Drilling Project,147 Qaap aaa seismic exploration, 162-171 Oartdrst}c ice. 236 Fairway Rock, 228 Oaratsark: Fault/plane solutions, 147 ttaatlas, 48, 72 Federation Internationale de la Prricontrainte F IP!, 118 ~ry disputes,48 Finite difference method, 229-230 ClarttrsarkStrait, 1&5 Finland, 4, 44, 231 Ofssperfield, 228 First-year ice, 177, 186-187, f 97-222,226, 238, 240, 255- OrrrslksrmSands, jurisdiction dispute,64 256 Okg&P DefenseMeteorological Satellite Program!, 204 Fishery ConservationZone, 65-66 OIW Get NorskeVeritas!, 81, 84 Fishery policy and laws,49, 52, 65-67 OortvaPetroleum, 72, 108, 119, 125 Bering Seaherring, 66-67 Orattipterprocessing, 139 king crab, 66 Orat 134. 136. 226, 228, 229 Tanner crab, 66 Orakia froint, 73 Fishing industry, 61, 65-67 Saedgfng,105-106, 108, 110 Fletcher Ice island T-3!. 162-163, 241 Oslft atatkxts, 1S9-176, 201, 203 Flow Industries. inc. Kent, Wash,!, 225 Qae a/ao ica stations! Forecasting seeClimatology; Ice forecasting;Models, 43rlftirrgbuoys, 1 60,203-205, 226, 229 numerical and predictive; Weather forecasting! OrgI cora analysis, 132, 'l47, 16'I, 177, 179, 192, 242 Foundations, soil conditions, 103-105 Ovfl strips, 89 Fracture zones, 147, 150 8afwing. 108, 119,227 Fragmentedice, 129, 256 Fram I-IV Series, 163, 165. 167, 174 Fram Basin, 147 Syrih fills. 103-105, 108 Fram Strait, 135, 137-138, 160, 184, 189 SarCssftrakes,13, 15-16, 99, 9204-105, 147, 150, 171 France. 44 Easeltareesrland Polar Front, 134-136 treaties, 56-58 645pae Sound, 238 Franz Josef Land Archipelago, jurisdiction disputes, 48, 53 Hcaaeaspiral, 131, 133 58 Haa5cptastic constitutive law, 227 Frazil ice. 240-242, 256 Ataliaolmcic model, 229-232 Freedom of the seas,6, 262 &eeoc waves accost.ical,13 See a/so High seasconcept; Transit passage! ESaaelere Island, 183, 199, 241, 242 Fronts meteorology l, 134-135, 137, 204-205 Gakkai Ridge, 147 Ice bearing capacity, 114 See a/so Arctic Mid Ocean Ridge! See e/ao Ice strength! Gas tace Oil. gas, and ininerals} Ice bottom surface, 179, 192-193 Gas liquefaction see Liquified natural gas; Liquified ice breakers,11, 69, 72, 74-75, 116, 119, 125, 228. 24 petroleum gas1 steel, 119 Gaussiandistribution, 84-BS tankers, 119 Gaussiantime function, 14 lce breaking, 1'l, 110, 113, 114, 125-130 Geol ogy, 12, 99, 131, 132 ice breakup, 75, 99, 136-137, 193, 228 Geophysics, 12, 16, 159-176 ice composition, 235-259 Geotech nical engineering. 103-105 ice concentration, 133, 197-222 Glacier ice, 244-251 ice core analysis see Drill core analysis! Gl aciers, 236-237 Ice cover, 3, 13'l, 1S9, 160-162, 166, 167, 166-187, 193, Glaciology, 242 197-222. 225, 226, 230, 231 Goddard Space Flight Center Laboratory for Atmosph eric ice covered waters: Sciences, 197 legai status, 3, 4, 50, 51, 54, 56 Gravel islands, 89. 114 steel structural engineering, 91-96 Gravity measurement, 161 See e/so Sector theory! Great Britain, 44, 71 Ice cracking, 248-250 treaties, 66-58 Ice creep, 235, 242, 244-246, 248 Greenland Oenm ark l, 4, 44, 49, 72, I 36, '150, 159-1 60, 199, ice crystals, 223, 235-238, 244 200, 236, 241 Ice dating, 177, 197-222 jurisdiction and boundary disputes, 48, 49, 69 Ice deformation, 114, 136, 223, 225-229, 236, 237, 242-243. Greenland ice sheet, 236-237 246, 250-252 Greenland Sea, 11, 131, 133-139, 150, 204, 24'I Ice draft, 177, 179-195 environment. 11 distribution, 1BS-186 ice modeling, 225-233 mean, 182-1 85, 187-188, 191-192 ice morphology, 182-185 ice drift, 136, 160-161, 163-16S, 226-229 resources,11 ice ductility, 235, 243. 249 Griffith theory, 246, 249 ice dynamics, 133-137, 185, l93, 225-233 Griffith value. 254 ice edge, 131, 133-146, 161, 197, 199-200, 204-205, 2 Ground truth measurements,136, l97, 201 226, 230, 231 Guif Canada Resources, Inc., 97, 'l06, 108, 119 ice edge map, 200 Gulf Mobile Arctic Caisson. 'l01, 103-105, 108 Ice elasticity, 235, 242-244, 249, 251-252, 254 Gulf Stream, 261 Ice floes, 'l2, 89, 97, 104, 'l93, 229-230 ice fog, 163 Ice forecasting, 190, 225-233 Hall-Petch relation, 247 See e/so ice modeling! Hans Island, 125 Ice formation, 240 Heat flow, 152, 161, 185 Ice fracture, 193, 231, 236, 243, 247, 249-250, 254 Heat flux, 137, 227, 230 lce fragments, 129, 256 Heat transfer, 131, 225 ice free reaches isee Polynyasl Helicopters, 108, 163, 166, 193 ice grain size, 235-238. 242-248, 254 H.M.S, Soirereigncruise, 179, 181-187, 189, 192 Ice Ih, 235-236 High seasconcept, 47, 52, 53 Ice impurities, 236 Hovercraft, 172 Ice islands,241-242 Human rights law,49-50, 53 ice, 2SS-256 Huinmocks, 184, 200 legal status, 50, 54, 55, 57, 162, 235 Hunting rights, 50, 52, 75-76 Ice loading, 11, 89, 101-104, 106, 110. 113, 114, '118, 119, Hydrodynamics see Ship resistancel 120, 125-130, 225, 256 Hydrophones, 13. 161. 163. 165-167 loading on ice, 253-255 vs. design levels 106 Ice mapping, 139, 197-222 Ice isea ice!, 97, 115, 138, 177, 223, 235-236, 250-251 ice mechanical tests, 253-255 Ice acoustics, I 1-15 lce mechanics,11, 125-130, 136, 177, 169, 223, 235- 259 Ice-Air-Oceanography interaction Isee Air-ice-Oceanography ice modeling, 84, 133-146, 225-233 interaction I Ice morphology, 12, 177, 179-195, 227 Ice Atlas IArcticl, 12 ice m overnent, 226-230

276 ke noise, 13, 16, 139, 231 international law, 47-60 loe openings see Leads; Open water! future trends, 55-57 ke physics, 13, 225-233 See also Jurisdiction; Law of the sea; Treatiesl ke plasticity, 227-229, 231, 235 International Maritime OrganizationI IIVIOI,54-55 ke: Poisson's ratio, 244, 251 International polar years, 5 ke porosity.239, 243-244, 246-247, 250-254 International Seabed Authority, 53 ke rafting, 230 International Seismological Center, 16 ke relaxation, 237 International Ship Structures Congress, '! 13 ke research problems,177. 243, 253, 255 international Whaling Commission, 61-62 ke roughness, 12, 139, 172, 192 lnuit Circumpolar Conference, 5, 49, 72 Ice runways. 162, 189, 223 lssungnak, 97, 106 ke salinity, 237, 239, 240, 242, 247, 250-255 fce sampling seerDrill core analysis! Ice sheets.236-237 Japan, 44, 55, 61, 65 fce shelves,241, 255 treaties. 56-58 4%e afao Ice islands! Joffe effect, 250 ke stations, 159-176 July isotherm, 4, 41 Isegafstatus. 50, 54, 55, 57 Jurisdiction and sovereignty, 3-7, 48-60 See afhS Drift stations! disputes, 48, 52-54, 57, 63-65 ke strength. 11, 12, 227, 228, 230, 235. 239, 242-255 history of, 4-7, 4S Ice stress, 13-15, 136, 225-230, 235, 242-247, 251, 254 future of, 55-57 ke structure, 13, 191-193, 235-259 boundary criteria, 4-5, 47-49, 53, 60, 64 Seeafso Ice morphology! zones kewtructure interaction, 11, 101-105, 108, 110, 114-130 3 mile territorial sea, 51, 64 See also ice breaking! 3-200 mile Fishery Conservation Zone. 65-66 ke surface, 191-193 12 mile terntorial sea, 51, 54 Ice temperature, 198, 199, 240, 243-254 100 mile environmental protection zone, 54 ke thermal growth, 135, 187, 225, 227, 229, 230, 238 200 mile exclusive economic zone EEZ!, 50-53, 55 ke thickness, 12, 137, 177, 179, 185, 200, 225, 227-230, 200-350 mile continenta! shelf, 52, 64 238, 241 detection, 197 Kadluk, '108 di stribution, 137 Kaltag Fauit, 154 mean. 185 Kara Sea. 54, 149, 160, 200 Ice velocity, 203, 225-227, 229-230 Knipovich Ridge, 150 ke viscosity, 235. 243 Kugrnallet channel, 103 Ice volume. 243 Kula plate, 151 ke waifs, 115, 11S, 119 Ice- Young's inodulus, 243-244, 249, 251 Seeal'so Anisotropic ice; Columnar ice; Dentri tie ice; First- Labrador, 4. 115 year ice: Fragmented ice; Frazil ice; Glacier ice; Lake Labrador Sea, 152-154, 236 ice; Level ice; Multi-year ice; Pack ice; Pure ice'I Lagrangian modeling, 229 kebergs. 84. 115, 223, 235-237, 243, 244, 256 Lake ice, 242, 243, 247, 255 Iceland, 4, 44, 159 Lancaster Sound, 74-75 kceciuakes,13, 15 Laptev Sea. 54, 160, 200 ICE REM, 125-126 Laser profiling, 179, 188, 191-193 ICEX, 160 Laurasia, 147 Imrrserk, 106 Law of the sea,47, 50-51, 54, 56, 262 Impact force, 125, 129 fu tore trends, 55-57 Indentation force, 128 See e/so Interne:ional law, Jurisdiction, Treaties,' Inertial force, 226, 228, 230, 231 Laws and legislation, 6, 47 6D,61-68 Infrtsred detection, 193, 200 ISee also indi vidual states! InteragencyArctic Policy Group lU.S.!, 6, 7 Leads iice!, 97, 139, 179, 188-1 90. 193, 197, 201, 227-228, InterfacesI~ Air-ice-Qceartography Interactiort! 230 gnternalwaters" legalstatus, 51, 54 Level ice, 185-187 International Convention for the Prevention of Pollution front Liability, 50, 55, 55, 58-59 Ships MARPOL!. 55 Limit stress/'imit fo"ce calculat ons, 101 international GeophysicalYear 1957-58, 5 Liauified natural gas ILNG I, 69, 73. 74, 76. 113, 116

277 Liquified petroleum gas LPG!, 113 lylodels,numerical and predictive, 136-137, 147-148, 192 Living resources,12, 'l3, 47, 52, S7, 134, 136. 262 223, 225-233 Seealso Endangeredspecies; Environmental management; Seea/so Ice models; Simulatiori! Fishery policy; Marine mammals! Mohr-Coulomb failure criterion, 256 Lloyd's mirror reflection, 165 Monitors, 105. 106 Loading farce!, 84. 103-105, 117 Morris Jessup Rise, 'l6, 159 cyclic, 103 Multiaxial prestressingconcrete, 113. 115 on ice, 235, 253-255 Multiaxial stress states, 243, 248, 256 See also Ice loading! Multi-year ice, 97, 108, 'l77, 184, 186-'l87, 197-222. 238, Lomonosov Ridge,58, 132, 147, 149-151, 154, 159-16D 241, 242, 247, 255-256 LOREX, 163 Muskapi-MontagnaisBand Association Canada!,58

IVI.I.T.Department of Earth and Planetary Science,147 Nansen Ridge, 147 M,I.T. Departmentof Ocean Engineering,41, 113 See a/so Arctic Mid Ocean Ridge! McClure Islands,jurisdiction dispute, 64 Nares Strait, 131, 154 McClure Strait, 183, 164, 188, 190 National Building Code U.S.!, 99 MacKenzie River Delta. 89, 99, 147, 153, 204, 227 National Environmental Protection Act of 1969 U.S,!, 63 MacKenzie Trough, 103 National Security Decision Memorandum144, 971! U.S.!, MacKenzie Valley, 77, 99 5-6 Magneticanomalies, 147, 149-151, 152, 161 Nationalization of resources, 51-53 Magneticmeasurement seeAeromagnetic data! Native interestsand self-determination,4, 58, 61-63, 65, 69, MagnusonFishery Conservationand ManagementAct of 1977 71, 73-75 IVIF CMA!, 65-67 culture, 49 Makarov Basin, 147, 152-153, 165 fishing, 49 Mapping,geographic seeCartography! hunting, 49, 161, 172 Marginalice zone, 11-12, 97, 99, 133-146,184, 189, 193 land, 49-50 5ee a/so M IZ EX! Naval architecture, 113, 114, 116, 1'l9, 125-130 Marine biology seeLiving resources! Navarin Basin, 89 Marine Mammal Protection Act of 1972, 62 hlavigability,62, 84. 133-146. 1B9 Iylarine mammals, 74-76, 172 Nerlerk, 108 !Vlateriel science, 223, 256 Newfoundland, 115, 236 Mathematical models see Models! Nimbus-5, 177, 191-222 Mediterraneanregion comparedto Arctic region,6-7, 56-S7 Nimbus-7, 205-206 Melt ponds, 200-205 Ninian Central Platform, 119 Melting, 198-199, 201, 205, 223 Noise interference! 163, 165, 173 Melville Island, 73 See a/so Ice noise! Ntetals, 262 Noise pollution!, 76 Meteorology, 131. 134, 135, 137, 205 NORSEX NorwegianRemote Sensing Experiments!, 135, 13B Microwave detection, 138, 177, 'l92 Norske Veritas see DNV! ice concentration, 199 North Cape Basin, 150 ice edge, 199-200, 204 North Pacific Fishery ManagementCouncil, 66-67 ice signatures,198-2DO, 201-208 North Pole, 179, 183. 2D2 low radiance areas and interpretation, 200-204 North Sea,structures, 89, 115, 117, 118, 119 seasonalvariation, 199, 204-205 North Slope, 64, 147, 153, 241 maps, 201 Northeast Passage,54 Mid-Atlantic Ridge, 16, 147, 150, 159 Northlands Compact, 5-7 Midway Islands,jurisdiction dispute, 64 hlorthwest Passage,4, 54-56, 74 MigratoryBird Treaty Act of 1972,62 Northwest Territories, 4, 238 Military operations,4. 12, 42, 47, 54, 57, 223 Arctic policy and laws, 71 Minerals see Oil, gas, and minerals! Northwind Escarpment, 16, 160 IV!ining,deep sea, 50-53, 72 Norway, 4, 44. 49 Nlitsui, 125-126 boundary disputes,48, 53, 58 MIZEX fvlartinal Ice Zone Experiment!, 131, 133, 137-139 treaties, 48 229 Norwegian Sea, 131, 137-139, 150 Mobil Research and Development Corp., 125 Numerical analysis, 225-233 278 ~ion settlement!,6, 48-49, 56 Poissons ratio, 244, 251 0oaancirculation, 131, 133-146, 203, 204, 205, 262 Pole of rotation, 149, 152-154 currents,99.'l37, 160, 225, 226-231. 236, 236 Policy, 3-7, 4 146 current meter, 131 Seee/so individual statesand issues! dumping seseWaste disposal I Political geographylsee Jurisdiction and sovereignty! thermalenergy conversion, 262 Pollution seeEnvironmental management and law; Noise, OoeancRidge System, 147-158, 261 Oil spills; Waste disposal! Oceanography,15-16, 131, 133-135, 137, 162,261 Polynyas, 139, 185. 188-190, 197, 201-204, 229 Offshoreoperations, 82-84 Portand ocean engineering under Arctic conditions IPOAC!, Offshorestructures, 84-85, 89, 97-111, 114, 'I 15, 225, 242, 119, 225 256 Pressureridges, 75, 84, 89, 97, 125,129, 172, 179,18l, 183- buildingcodes, 117-11S 1 91, 221, 228, 238, 241, 256 concrete, 11 5-124 Prince Patrick Island, 184 designconsiderations, 99-106 Prudhoe Bay, 5, 62, 115 drilling structures, 119 Punching shear, 115, 1 I 7 floatingplat forms, 119, 125 Pure ice, 235 lca breaking. 125-130 Pykrete lice alloy!, 223 legalstatus, 51, 52 ntulti4eg, 125 productionstructures, 108 Quebec, 4, 76 risk assessment.81-8S Queen Elizabeth Islands, 132. 147, 205 shape, 103, 'IOS, 118-119, 125 single-leg,125 steel. 91-96 Radar, 135, 13S, 179, 192, 204 ~urfisce piercing platforms, 11-12 See also Airborne radar l Oar a/so Artific ial/Caisson isl ands! Radiance see Temperature brightness! 0ffshore Technology Conference, 225 Rankine-Hugoniot characteristics,242 0il. gas,and minerals: Rehbinder ef feet, 250 devefopmantpolicy, 50, 52, 53, 57, 73-74 Remote sensing. 12, 138, 166 exploration. 50, 63, 71, 160- '162, 171-174. 236 See a/so Aerial photography, Aeromagnetic data; Laser leasing,83-65, 256 profiling; Microwavedetection; Radar;Seismic markets,5, I1,41, 73 surveys; Sonar! resources,11, 13, 57, 63, 72, 73, 97 Research,need for coordination of, 5-6, 41-42, 231, 256 0T spills,SS, 56, 82, 85, 225, 228 Researchpolicy and regulations,6, 50-53, 63 Openwater, 97, 99, 139, 161, 166, 171, 200-203, 225, 230 Researchprojects and suggestedfuture directions, 76-77, 108, acoustics, 12 110, 113-115, 119, 132, 137, 193, 231, 240, 256 Drown/Irwin Theory, 249 benefits, 12-13 OuterContinental Shelf Lands Act of 1953, 64 Revanchesharing, 52, 53 Outer sp~ concept lawj, 47 Riprap, 103, 105 Risk assessment, 81-88, 10S, 242 Ross Ice Shelf, 238 Packice, 13,85, 136, 161, 238 Rossbyinternal radiusof deformation, 135 Pafeoceanography,99, 'l31, 147-158 Rubblefields and rubble, 11. 104, 106, 108 Pafeocfimatol ogy, 131 Rupert's Land, 71 PanarcticOi/s, Ltd., 72 Permafrost,3, 99, 104, 110, 161, 172, 173 PermwsentCourt of International Justice, 48, 49 Safety, 13, SS, S I. 86. 105, 106, 108, 113, 'I 90, 241, 242 PersianGulf resources. 11 See a/so Monitors; R isk assessmentl PetroCanadaArctic Pilot Project, 69, 71-74, 76-77 Salinity, 134, 135, 203 Petroseum saic Oil, gas,and mineralsf See a/so ice salinity l Plpeiines,42, 49, 89, 72, 73, 77, SS, 191 Sand and gravel, 103-105 Planetaryboundary layer, 135, 136, 138 Satellite data, 177. 192, 193, 197-222, 226 Plasticitymodel, 228-229 Satellites for microwave detection, 138, 177, 197-222 Plates tectonics!, 147, 149-151, 'f53, 154 ScanningMultichannel MicrowaveRadiometers ISIVIMRl, 205 PointBarrow, 183 206 distribution, 84 Scott Polar Research Institute U. of Cambridge, England I, process,84-SS 179

279 Scouring, 85, 103. 108, 173, 190 Stirrups shear steel!, 118 Sea floor spreading, 147-159, 261 Storms, 103, I06, 108 Sea ice see ice! Strain rate, 135, 243-248 Sea surface tilt, 226, 230, 231 Straits, legal status,51, 54, 75, 193, 231 Sea water, 197, 198 See also Transit passage! constants, l31 Submarines,12, 47, 51, 114, 119, 159, 166, 177, 179, 181, Seasat, 205-206 182, 189, 190, 192, 241 Seasonalconditions, 5 1, 97, 99, 104, 106, 135, 138-139, 159. cruises under ice, '!80 161, 171, 172, 183-185, 189, 190, 199, 204-205, 226, Seea/so Subrnersibles;Unmanned underwater vehic esf 240 Submerged lands, 16 Seasonal ice zones see Marginal ice zone! SubmergedLands Act of 1953, 64, 65 Sector theory, 4, 47-49, 52, 53 Submersibles, 179 Seismicsurveys, 147, 149. 152, 159-176 Subsistence uses, 61-63 analogand digital recording, 165, 167 Surface truth, 136, 197, 201 earthquake seismology, 14-16 SvalbardArchipelago, 4, 48, 55, 137-138,159-160, 17 I, 200, reflection data. 163-166, 171 204 ref raction data, 149, 152, l61, 166-171 jurisdiction and boundary disputes,48, 56 single and multi-channel systems,165-166 treaties, 48, 55 Settlement structural!, 104-105, 110 Svalbard Treaty, 48, 53, 55, 56 Shear, 227, 244-246, 248 Sweden, 4, 44, 231 stress and strain, 254 treaties, 58 wave displacement, 13-14 SwedishIVleteorolog ical and Hydrological Institute, 228 zone, 11,85, 183, 185 Shelf ice see ice islands! Shell Oil Company, 89 Tanker ships, 17, 113, 119 Ship resistance,114, 125-$26, 256 Tarsiut,97, 103-106, 108, 115, 117, 118, 125 Shipping, 12, 54-55, 72, 76, 82, 84-85 IV44 well, 103 See a/so Transportation! Tectonics, 16, 131-132, 147-176, 261 Siberia. 4, 159, 204 modeling, 154 Siberian Sea, 54, l60, 200, 205 Temperature,84, 198, 200, 201, 205, 235 Signalprocessing, 138, 165, 167, 172-174 See a/so Ice temperature! Silica fumes, 115, 119 Temperaturebrightness, 177, 197-222 Simul ation, 225 See also Microwave detection! See a/so Models, numerical and predictive! Territorial seas, 51-52, 54, 64 Slope protection, 103, 104, 106. 110 Thermodynamics.134-137, 177, 185, 189, 229 Snow cover, 199, 201, 205 Time series analysis, 13-15 Snow ice, 244, 255 Topography, 12, 16, 136 Snow mechanics, 256 Traditional usages,49, 54 Soil mechanics, 99, 103-105, 110 Trans Polar Drift Stream, 83, 193, 203-205 See a/so Foundations! Transit passage,51, 52, 54, 72 Sonar, l 2. 177, 179-9295, 24 I Transportation: beamwidth correction. 181-182 cost, 89 side scan, 18'I regulationand rights, 55, 58, 69, 71-78 wide beam, 188-189 regulatory process, 72-74 Son o buoy s, 163, 165- 167, 171 technology, 11, 69, 89, 235 Sovereignty see Jurisciiction and sovereignty! See a/so Shipping; individua I modes! Spelling, 101, 118. 119 Treat lsl and, 11 7 Spitzbergen, 150 Treaties and international agreements, 4-7, 47-60 treaties, 4, 58 future trends in, 55-57 See a/so Svai lbard Archipelago! Sees/so individual treaties; International law; Law of the Spitzbergenplate, 149, 150 sea! S.S. IÃanhartarr, 11, 54, 71 Treaty on the Status of Spitzbergen 920!, 4 Standards see Building codes and standards! Tyndall Process, 232 Statistical methods, 177, 192-193 Steel-concretecomposites, 115, 119 Steel ships. 113, 116 Underwater acoustics. 12-17 SteeI structures. 91-96 Uniaxial compression, 244-247, 252 NationsConvention on th» Law of the Sea982!, 50- U.S.S.Gvrnard cruise, 182-184, 186-'!87, 189, 191 51,54, 56 U,S.S. Nautilus, 159, 179 v'SS.R., 4. 42, 44, 49, 53-54, 65, 1 15, 1 59,160, 162, 203 Universityof California,Berkeley, Dept. of Civil Engineering, Arcticpolicy and laws, 54 115, 118 ictionand boundary disputes,48, 49, 51, 54, 57, 58 Unmanned underwater vehicles, 132, 179 treaties.48 Upwelling, 134-137, 204 lSaaafats Siberia! Utility theory, BE,85-86 IIX. 12. 4'I. 44, 54, 231 Uviluk, 97, 108 Arcticpolicy laws, 3-7, 49, 262 Arcticp-rograms, 45 1aridctiorsand boundary disputes, 51, 53, 54,64-65 Viscous-plasticconstitutive law, 227-230 ~rces, 5 V iscou s plast ic model, 229-232 treaties,6. 48, 50, 53, 58 Von Mises criterion, 256 Q.S.Alaska relations, 61, 64-67 VS,~ifornia jurisdiction dispute, 64-65 fSeeaAe Alaska; Aleutian islands, Bering Sea! Ward Hunt Ice Shelf, 242 U.KAnny Cold Regions Research and Engineering Lab, 235, Wastedisposal. 54-55, 262 256 Water depth in designof OSS,99-101 'J S Artny Corps of Engineers. 117 Waves water!, 12, 99, 103,104, 106, 108, 110, 13!, 136- 05. CentralIntelligence Agency, 160-161 137, 193, 229 JX GaologicafSurvey, Alaskan and Pacific Arctic Marine Weather, 41, 134 Branches,155 Weather forecasting, l3, 131 GS Maritime Administration, 12 ISeea/so Models, numerical and predictive I 0 S. National Academy of Sciences, 6. 7 Weddell Sea, 136, 240 u S. NationalAeronautics and SpaceAdministration, 201- Weibul, pdf, 15, 191 202, 204-205 West Germany. 44 uk National Oceanic and Atmospheric Administration, West Spitzbergencurrent, 137 I93 Wind 131 136 225-231 'JS National Sciencefoundation, Division of Polar Programs, Wind-current theory, 131 156 Wind stress, 135-136 05. National Technical Information Service NTIS!, 225 J.S NavalResearch Lab, 147 J S Navy, 12, 227 Yermak Plateau, 159 0 S 0fficeof NavalResearch, Arctic ProgramOffice, 92 74,193 Yukon Territory, 4, 71

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