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Ing Cor!Paa L. T' Ron, L Ts Rrll.Cl Ostl Uct!Ir'p. Ar.'D Present. This L: A'so 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<lns carried out, Howe.er, by the temperature ra~ge quite close to its melting ' ir. e it gct that: f.ar the exigencies of. thr point, terrpe rats,re ard strain rate are al so Wirlr Situaticn harl ichanq -'il a!!d t he pin Jeot impar:tant variablCs. SinCe sc rersl ..rlabl=s "=is not carried to ..orir.let.lon. This story inf1 uence the resulting properties. a cer .a iri semess to be sympt.orna t ic o f our up-arid-down camp lexi ty rouse be adrlressed and this . s tire ai pros- h t.i arr.tic: endr.avors. That w'as task which Dr. tiecks and Dr. Keller ha; e cer a inl'; the case when i n 196 ' we carr '' ecl u"ide r taken. succeaaf ul experlmer,t.al landings crf the crit ir e Air Force i nventory of aircraft. T.ia 1 O, Cr'eenlanrl, lne l ucl i ng Caria truC t ed '-,arking area suitable for the heaviest airs- a f r. Boon the reaf ter t hs Air Force lest l;trar'eSt. Let us hopr,. that our preach a-cti.c policy wil 1 incl.udge a sus ainr-.d ef fort ar understanding the propr'rtles and beha. iors arctrc 'Ce, The papers presented this ter nsan will make it. clear that their'e l.s still mcuch to learn. fn this session we shall look to the behaVisr rrf arCtie Sea lCe f rOm tWO cluite dif fe erst points of view, First, .' c tchard will take- a r..acroscopic view of sea 'ce behavior on the scale of hundrecls and t =.ris of kilometers, modeirng its behavior an terms of the imposed f'orc es and character- istic ice properties, The problem is a rifficult one since the forces actinc ice are complex a.,d cove f rom dif ferent ori.giins.which can be evaluated and descr ibed .=- ai'ltatlve'y, but their quanti atlve es'tl. :.a> 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.
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