OS78 2002 Ocean Sciences Meeting

2 the pycnocline south of the front. These subsurface Applied Physics Lab University of Washington, 1013 OS12O HC: 323 A Monday 1330h features had T-S characteristics and optical properties NE 40th St., Seattle, WA 98195, United States typical of north-side mixed layers and were found be- 3Naval Research Laboratory, Ocean Sciences Branch Western Pacific Marginal Seas II tween the 27.0 kg/m3 and 26.7 kg/m3 isopycnals (a CODE 7333, Stennis, MS 39529, United States , layer that outcrops on the northern edge of the front) at 4Woods Hole Oceanographic Institution, MS #21, 360 Presiding: SRamp Dept. of distances as far as 50 km south of the frontal interface. Woods Hole Road, Woods Hole, MS 02543, United ; , Moreover, these features often exhibit anticyclonic cir- States Oceanography CLee Applied Physics culation and negative potential vorticity, a result of the 5Kwangju University, Div. Civil & Environmental En- anticyclonic flow and large, negative contributions from Laboratory gineering, Kwangju 503-703, Korea, Republic of the tilting term. These properties are consistent with recent theories of frontogenesis and enhanced subduc- The subpolar front of the Japan/East Sea is present tion rates driven by symmetric and baroclinic instabil- throughout the year and is characterized by strong hor- OS12O-01 1330h INVITED ities under strong wind and buoyancy forcing. izontal temperature and salinity gradients in the upper 200 meters of the water column. The front is also char- URL: http://sahale.apl.washington.edu/jes acterized by higher phytoplankton abundances as in- The formation and Circulation of the dicated by both chlorophyll fluorescence and inherent Intermediate water in the Japan/East optical properties (IOPs, such as beam attenuation and Sea OS12O-03 1405h absorption coefficient). During spring and early sum- mer, seasonal heating of the upper layer results in a 1 northward propagating spring bloom. Seasoar mapping Jong-Hwan Yoon (81-92-583-7910; Ekman Frontogenesis: Generation of of the frontal region shows that subduction processes [email protected]) Negative Potential Vorticity, along the frontal boundary can transport nearsurface 2 Subsequent Instability, and water characteristics (low salinity, high oxygen, high Hideyuki Kawamura (81-92-583-7997; chlorophyll fluorescence and IOPs) from north of the [email protected]) Application to the Subpolar Front of front to depths of at least 250 m. During winter, ele- 1RIAM, Kyushu University, 6-1 Kasuga-koen, Kasuga, the Japan/East Sea. vated fluorescence and optical absorption at the front Fuk 816-8580, Japan result from increased stratification and convergence at the frontal boundary. As in summer, subduction of Leif N Thomas1 (206-543-0769; 2ESST, Kyushu University, 6-1 Kasuga-koen, Kasuga, water transports IOPs downward in the water column. [email protected]) Fuk 816-8580, Japan North of the front the IOPs were uniformly mixed to a 2 > In order to clarify the formation and circulation Craig M Lee (206-685-7656; depth of 120 m and within the front IOPs were high- of the Japan/East Sea Intermediate Water (JESIW) [email protected]) est in the upper 50 m. South of the front, absorption and the Upper portion of the Japan Sea ProperWater 1 and attenuation spectra show a uniform upper layer Peter B Rhines (206-543-0593; from the surface to ∼75 m. A subsurface absorption (UJSPW), numerical experiments have been carried out [email protected]) using a 3-D ocean circulation model. The UJSPW is and attenuation maximum from 80 to 110 m is charac- 1 formed in the region southeast off Vladivostok between School of Oceanography, University of Washington, terized by decreased absorption in the red wavelengths, 41oN and 42oN west of 136oE. Taking the coastal orog- Box 355351, Seattle, WA 98195-5351, United States indicative of the subducted water from north of the raphy near Vladivostok into account, the formation of front. During winter elevated bio-optical signals were 2Applied Physics Laboratory and School of Oceanog- the UJSPW results from the deep water convection in not detected as deeply in subducted water as in sum- raphy, University of Washington, 1013 NE 40th St., winter which is generated by the orchestration of fresh mer, but they demonstrated specific spectral changes Seattle, WA 98105-6698, United States water supplied from the Amur River and saline water that would be expected in a subducted phytoplankton from the Tsushima Warm Current under very cold con- North-south sections of density and upper ocean ve- population. These results indicate that frontal pro- ditions. The UJSPW formed is advected by the current locity made while crossing the subpolar front of the cesses provide a mechanism for significant downward at depth near the bottom of the convection and pene- Japan/East Sea during January 2000 were used to cal- transport of the products of primary production from trates into the layer below the JESIW. The origin of the culate the two dimensional Ertel potential vorticity the upper layer. JESIW is the low salinity coastal water along the Rus- (PV). In some sections, during cold air outbreaks, the sian coast originated by the fresh water from the Amur PV in the core of the front above 60 m was negative yet River. The coastal low salinity water is advected by the the stratification was stable and the absolute vorticity OS12O-05 1435h current system in the northwestern Japan Sea and pen- was positive. The negative PV was attributable to the etrates into the subsurface below the Tsushima Warm strong north-south density gradient and vertical shear Apparent Removal of Carbon Current region forming a subsurface salinity minimum of the zonal velocity associated with the front. We sug- Tetrachloride in the Thermocline layer. gest that the process of Ekman frontogenesis is respon- sible for generating negative PV of this type. Indeed, Waters of the East Sea (Sea of Japan) as revealed by QuikSCAT scatterometer winds, the lo- OS12O-02 1350h cation of the subpolar front during cold air outbreaks in Dong-Ha Min1 (206-221-6741; this period was in a region of Ekman convergence where [email protected]) conditions are favorable for Ekman frontogenesis. Evidence of Wintertime Subduction at Using a weakly nonlinear analytic theory and nu- Mark J Warner1 ([email protected]) the Subpolar Front of the Japan/East merical simulations we have shown that convergent Ek- 1 man transport can generate fronts with negative PV by School of Oceanography, University of Washington, Sea intensifying lateral density gradients, steepening isopy- box 355351, Seattle, WA 98195-5351, United States cnals, and reducing the absolute vorticity. The numer- Dissolved carbon tetrachloride (CCl4) was mea- 1 Craig M Lee ((206) 685-7656; ical simulations demonstrate how fronts with negative sured for the first time in the East Sea (Sea of Japan) PV, formed by the process of Ekman frontogenesis, are throughout the water column in summer 1999 during [email protected]); Burton H Jones2 unstable to symmetric instability, a two dimensional in- the HNRO-7 and KH36 expeditions. Seawater sam- ((213) 740-5765; [email protected]); Kenneth H ples were collected and stored in flame-sealed glass am- 3 stability characterized by an overturning cell which di- Brink ((508) 289-2535; [email protected]); Leif N verts the down the dense side of the poules for later analysis in the laboratory. The dis- Thomas4 ((206) 525-7944; front. The along-front vorticity associated with this solved chlorofluorocarbons (CFCs) CFC-11 and CFC- [email protected]); Robert Arnone5 overturning cell is driven by the dominance of buoyancy 12 were measured onboard the R/V Roger Revelle ((228) 688-5268; [email protected]); Richard twisting over the tilting of planetary vorticity by the (HNRO-7). CCl4, a man-made compound, has been 5 6 vertical shear of the along-front velocity. For symmet- released to the atmosphere since the early 20th cen- Gould ((228) 688-5587); Clive Dorman ((619) tury, several decades earlier than CFC-11 and CFC- 3 ric instability to grow, this imbalance must increase. 534-7863; [email protected]); Robert Beardsley This is accomplished by the convergent surface flow 12. CCl4 has been used in several recent studies as ((508) 289-2536; [email protected]) of the overturning cell, which, through horizontal ad- a time-dependent ocean tracer for water mass dating vection of density, strengthens buoyancy twisting and and delineating pathways of newly ventilated deep wa- 1Applied Physics Laboratory, University of Washing- intensifies the front. Underneath the surface expres- ters. However, CCl4 has been observed to be removed, ton, 1013 NE 40th St, Seattle, WA 98105-6698, sion of the front, the divergent flow at the base of the presumably by biological activity, in warm upper ocean United States overturning cell spreads apart isopycnals and generates waters and in anoxic waters. CCl4, CFC-11 and CFC- 2Department of Biological Sciences, University of anticyclonic vorticity. These signatures of symmetric 12 levels were close to equilibrium in surface waters of Southern California, Los Angeles, CA 90089-0371, instability, i.e. thick isopycnal layers and anticyclonic the East Sea, however CCl4 in the upper 1000 m of the United States vorticity, were evident in the observations of the sub- water column had lower saturation levels than those polar front of the Japan/East Sea for sections where of the other CFCs, especially south of the subpolar 3Department of Physical Oceanography, Woods Hole the PV was negative, and suggests that frontal inten- front. Evidence of CCl4 removal in thermocline waters Oceanographic Institution , MS-21, Woods Hole, sification through Ekman convergence and symmetric is indicated by comparing the profiles of the predicted MA 02543, United States instability is active in this region. CFC-11 and CCl4 levels to the measurements,using the 4 pCFC-12 ages and atmospheric source functions and as- School of Oceanography, University of Washington, URL: http://www.ocean.washington.edu/research/ suming ideal mixing conditions. The observed CFC-11 Box 355351, Seattle, WA 98195-5351, United States gfd/jfm101701.pdf matches fairly well with the predicted CFC-11, while 5Naval Research Laboratory, Code 7343, Stennis the observed CCl4 is significantly lower than the pre- Space, MS 39529, United States dicted CCl4. CCl4 removal rates, calculated by divid- OS12O-04 1420h ing the predicted-observed CCl4 levels by the pCFC ap- 6 Center for Coastal Studies, Scripps Institution of parent age are estimated to be 2-10 % yr-1 in the upper Oceanography , University of California at San 1000 m waters. Potential biases in estimating the CCl4 Diego, La Jolla, CA 92093-0209, United States A Comparison of Bio-Optical removal due to mixing effects and the nonlinear input Strong wintertime outbreaks of cold, dry Siberian Characteristics of the Subpolar Front function of CCl4 will be discussed using a simple box air produce intense cooling, convective overturning in the Japan/East Sea in Spring and model. and mechanical mixing at the subpolar front of the Winter Japan/East Sea. These events may also drive insta- OS12O-06 1450h bilities which serve both to sharpen the front and to 1 generate strong downdrafts which sweep cold, north- Burton H Jones (213-740-5765; [email protected]); side mixed layer waters into the south-side pycnocline. Craig M Lee2 (206-685-7656; Diagnoses of Water Mass Subduc- Four high-resolution towed profiler (SeaSoar) surveys [email protected]); Robert tion/Formation/Transformation in the made at the front in January 2000 document the re- Arnone3 (228-688-5268; [email protected]); sponse to three strong atmospheric events. Measure- 3 Japan/East Sea (JES): Impact of ments of upper ocean velocities, temperature, salinity Richard Gould ([email protected]); Kenneth 4 Atmospheric Forcing With Different and bio-optical parameters, combined with extensive Brink (508-289-2535; [email protected]); Sung R. meteorological observations and remote sensing track Yang5 (82-62-670-2618; Time-Space Scales the temporal and spatial evolution of the front. The [email protected]) , surveys provide evidence of active overturning and sub- HeeSook Kang1 2 (228-688-2881; 1University of Southern California, Dept. of Biolog- duction. Sections reveal small scale (O(20 km) hori- [email protected]) zontal, O(20 m) vertical) pycnostads embedded within ical Sciences USC, Los Angeles, CA 90089-0371, United States Cite abstracts as: Eos. Trans. AGU, 83(4), Ocean Sciences Meet. Suppl., Abstract #####-##, 2002. 2002 Ocean Sciences Meeting OS79

1 Christopher N.K. Mooers (305-361-4088; 1Scripps Institution of Oceanography, 9500 Gilman OS12O-10 1610h [email protected]) Dr., La Jolla, CA 92093-0230, United States 1RSMAS/University of Miami, 4600 Rickenbacker 2 Formation and Propagation of Bottom Causeway, Miami, FL 33149, United States Pacific Oceanological Institute, Russian Academy of Sciences, 44 Baltiskaya St., Vladivostok, Russian Water Anomaly in the Japan/East 2Department of Marine Science/University of South- Federation ern Mississippi, 1020 Balch Boulevard, Stennis Sea Space Center, MS 39529, United States The Japan/East Sea (JES) is well-ventilated to the 1 The deep/intermediate waters in the Japan/East bottom (3500 m depth), and is much better ventilated Anatoly Salyuk ([email protected]); Vyacheslav Sea (JES) are formed by local winter convec- than the adjacent North Pacific at the same depth and Lobanov1 ([email protected]); Lynne Talley2 tion/ventilation since all the straits connecting JES to density. Winter data from 1999 and 2000 show that 1 the adjacent oceans are not deep enough (< 200 m) for the JES is one of the few sites in the world with deep ([email protected],edu); Vladimir Ponomarev those dense waters to flow in or out. The area west winter convection, and that convection in the JES has ([email protected]); Alexander ◦ ◦ 1 of 138 E between 40 and 43 N has been proposed as many similarities to convection in the Mediterranean. Nedaskovskiy ([email protected]); Anatoly a potential location of water mass formation by Sudo It has been shown previously that deep oxygen in the Obzhirov1 ([email protected]); Sergey (1986) and Senjyu and Sudo (1996), which has been JES has been declining over many decades, suggesting Sagalayev1 ([email protected]); Svetlana substantiated by examining the atmospheric conditions that ventilation was more vigorous early in the 20th 1 (Kawamura and Wu, 1998) and historical hydrographic century than in recent decades. Nevertheless, the pres- Ladychenko ([email protected]) data (Seung and Yoon, 1995). ence of significant oxygen and chlorofluorocarbons to 1V.I.Il’ichev Pacific Oceanological Institute, Far East- The Princeton Ocean Model was implemented for the JES bottom suggests ongoing ventilation. In win- ern Branch, Rassian Academy of Sciences, 43, JES (JES-POM) to simulate interannual, seasonal, and ter, 1999, a first late-winter survey of the northern Baltiyskaya Str., Vladivostok 690041, Russian Fed- mesoscale variations in velocity and hydrographic fields JES included one hydrographic station with evidence eration for five year from 1993 to 1997. It reproduced the gen- of open-ocean convection to about 1100 meters in the 2 M eral features of the JES circulation. cold air outbreak region south of Vladivostok, and weak Scripps Institution of Oceanography, University of From simulations, there are three areas (Area V: 41- California, San Diego, 9500 Gilman Drive, La Jolla, ◦ ◦ ◦ ◦ evidence of brine rejection under ice formation in Pe- 43 N west of 137 E, Area K: 36-38 N west of 132 E, ter the Great Bay (shelf near Vladivostok). Topogra- CA 92093-0230, United States O and Area KB: near Korea Bay) with a local maxi- phy and the presence of a semi-permanent anticyclonic Appearance of new bottom water (NBW) was ob- mum subduction rate (> 500 m/yr). The “flux center” eddy and the subpolar front delineate the convection served in the Northwestern Japan/East Sea in winter, N off Vladivostok is identified as the primary subduction region, which is in the path of strong northerly winter 2001. Process of formation and distribution of this wa- area, though the positions and values of the localized winds. ter of lower temperature and higher density over the maximum subduction rate are different year-to-year. Because of persistent cold conditions at the begin- deep Japan Basin during February-June period is an- ning of the next winter, including Vladivostok air tem- alyzed using hydrographic and chemical observations peratures colder than any other year since 1976 and implemented in 3 successive cruises and satellite data. OS12O-07 1525h SST -2C below normal in the northern Japan Sea, a Two modifications NBW were observed in February: second winter survey was conducted in late February NBW1 found at the slope of Peter the Great Bay had 2000. Evidence of convection deeper than 1200 m was Studies of Deep Convection Processes negative salinity anomaly of 0.003 psu, while NBW2 much more widespread than in the previous, warmer observed to the east had positive salinity anomaly of Using a Numerical Ocean Model: The winter. Shelf water subjected to brine rejection in Pe- 0.004-0.005 psu. This suggests different areas or con- ter the Great Bay had also created significant amounts Japan (East) Sea ditions of this water formation. of bottom water along the base of the continental slope Oxygen concentration in anomalous waters as well just south of Vladivostok. Carol Anne Clayson1 (765-496-2866; as concentrations of nutrients, pH, methane are in good [email protected]) correlation with potential density. Correlation fields for depths below 2800 m corresponding to NBW are Maria Luneva1 ([email protected]) straight lines. This can be interpreted as a mixing line of two water masses: cold surface one characterized by 1Department of Earth and Atmospheric Sciences, high oxygen, low nutrient and surface concentrations Purdue University, 1397 CIVL Building, West OS12O-09 1555h of other parameters like methane, and deep saline one Lafayette, IN 47907-1397, United States with normal potential temperature, and rich in nutri- The Japan (East) Sea is an area of intense inter- ents, which is typical for Japan Sea proper water. Good action between the atmosphere and the ocean during Japan/East Sea Bottom Water Renewal approximation by the straight line proves the fact of winter. Cold Siberian airmasses are advected past a in Winter 2001 mixing of only two source waters and permits to con- relatively warm ocean by prevailing westerlies, a situa- strain and estimate preform nutrient concentrations for tion analogous to winter-time cold air outbreaks off the second mode water as well as end member concentra- east coast of the US. In addition, the cold air masses are Vyacheslav B Lobanov1 ([email protected]); tions of methane and all other properties of both mix- funneled through gaps in the coastal range, for exam- 1 ing water sources. ple off Vladivostok. The subpolar front that separates Anatoly N Salyuk ([email protected]); Vladimir I Spatial distribution of NBW thickness, depth of lo- 1 the East Korea Warm Current masses from the rela- Ponomarev ([email protected]); Lynne D cation and anomalies of water characteristics is very tively cold ambient water masses of the Japan Basin Talley2 ([email protected]); Kuh Kim3 inhomogeneous. Most of NBW thickness observed was is home to one of the most intense mesoscale activity 3 about 150 - 300 m. The strongest anomaly of about 700 observed in the global oceans; the region abounds in ed- ([email protected]); Kyung-Ryul Kim 1 m was found at only one station and was not caught in dies and meanders that span a wide spectrum of scales. ([email protected]); Sergei G Sagalaev vicinity of 10 miles around. This can be interpreted 3 Off Vladivostok, during winter, strong very cold winds ([email protected]); Guebuem Kim as a center of lens like anticyclonic eddy. Following get channeled through gaps in the mountain range onto ([email protected]) Nof, 1982 one can expect its propagation alone fixed JES and this may cause deep mixing and at least In- 1 isobaths. If we assume the NBW formation by slope termediate Water (if not Deep Water) formation. Most V.I.Il’ichev Pacific Oceanological Institute, Far East- convection off Primorye and westward translation by often, some preconditioning of the underlying ocean is ern Branch, Russian Academy of Sciences, 43, Bal- the eddies, this would explain apparent patchiness of essential for deep convection and Deep Water forma- tyiskaya Str., Vladivostok 690041, Russian Federa- NBW characteristics observed over Japan Basin. Satel- tion. In this study we focus on the deep convection pro- tion lite infrared data for April demonstrate existence of cesses in the JES through the use of a three-dimensional 2 mesoscale eddy situated over the location of maximal ocean model. The three-dimensional ocean model used Scripps Institution of Oceanography, University of pronounced anomaly which possibly can be associated for this research is the University of Colorado version California, San Diego, 9500 Gilman Drive, La Jolla, with propagation of NBW. of the Princeton sigma-coordinate model, which con- CA 92093-0230, United States tains a second moment closure turbulence mixed layer model. The 3-D circulation model is run at a fine ver- 3School of Earth and Environmental Sciences, Seoul tical resolution (10 m in the upper layer, less than 1 National University, San 56-1 Sillim-dong, Kwanak- OS12O-11 1625h m near the surface) to resolve the mixed layer, a nec- gu, Seoul 151-747, Korea, Republic of essary step for the intricate surface layer of the JES. CFCs Indicating Renewal of the Bottom Horizontal resolution is 1/24 degree. Surface fluxes are To study process of the Japan/East Sea ventilation provided by ECMWF model analyses. in winter the ship CTD and chemical observations were Water in the Winter of 2001 in the The focus of this research is on wintertime intense implemented in 3 consecutive cruises in the western Japan Sea and Providing Evidence on wind forcing, deep convection events and the forma- part of deep Japan Basin by r/v Professor Khromov in the Continental Shelf Pump tion of intermediate water/deep water and its variabil- February-March and r/v Professor Gagarinskiy in April ity during the June 1999 May 2000 time period. During and May-June of 2001. As a result of extremely se- 1 this time a comprehensive observational program was vere winter new bottom water (NBW) formation was Shizuo Tsunogai (81-11-706-2368; initiated by the ONR. The in situ data is used for ini- observed in February at a few stations located close [email protected]) tializing the model and for determination of locations to continental slope. It was a layer of 200-800 m thick 1 where deep convection is occurring. Regions off the overlaying the bottom (2700-3200 m) with water of high Kentaro Kawada (81-11-706-2246; Siberian coast are examined for deep mixing episodes oxygen content (235-247 uM/kg) and negative potential [email protected]) during strong cold-air outbreaks. The simulations of temperature anomaly of 0.02-0.18 C. Other 30 stations Shuichi Watanabe1 the model show the sensitivity of the ocean in these taken in February cruise down south to 40 N did not cases to the surface forcing. The influence of the 3- show NBW signal. Surprisingly, the April and May- 2 D processes, such as the circulation patterns and their Takafumi Aramaki June cruises revealed spreading of NBW over the whole 1 mesoscale variability on the deep convection events and central and southern part of the deep Japan Basin down Graduate School of Environmental Earth Science, subsequent formation of Intermediate/Deep Water in to 40-15 N. Estimation of this bottom water flow from Hokkaido University, Kiata-10, Nishi-5, Sapporo JES will be shown. the continental slope zone suggests a flow speed of 4-6 060-0810, Sapporo, Hk 060-0810, Japan cm/s which is quite realistic. 2Japan Atomic Research Institute, Mutsu, Minato 4- Comparison with our observations of April 1999 and 24, Mutsu, Aomori, Mutsu, Ao 035-0064, Japan OS12O-08 1540h March 2000 shows that such intense ventilation of bot- tom water was never observed in previous years. Pe- Based on the results obtained in the East China Sea, Winter Convection and Brine Rejection culiarity of winter 2001 conditions was not only more Tsunogai et al. (1999) have proposed a concept, conti- frequent cold air outbreaks with lower air temperature nental shelf pump (CSP), for the transport of C from in the Japan/East Sea resulted in SST anomaly up to 2.0-2.5 C but also higher the shelf zone to the pelagic ocean. salinity in the area off Peter the Great Bay. Integra- The CSP starts with more cooling of the shelf sur- Lynne D. Talley1 (1-858-534-6610; [email protected]); tion of these factors caused intense dense water forma- face water than that of the open sea surface water, tion at the shelf area of Primorye and ventilation of which forms the denser shelf water and accelerates Vyacheslav Lobanov2 ([email protected]); Pavel bottom layer of the entire Japan Basin. It seems that the absorption of atmospheric CO2 in the shelf zone. 2 Tishchenko ([email protected]); Vladimir such process was never observed since the 50-th. How- Rivers flowing into the zone bring fresh water and nu- Ponomarev2 ([email protected]); Anatoly ever an evidence of bottom water anomalies observed trients. The fresh water reduces the fugacity of CO2, Salyuk2; Sergey Sagalaev2; Igor Zhabin2 off the slope of Peter the Great Bay in April 1999 sug- f(CO2), of the mixed water, and the nutrients and those ([email protected]) gests that weak ventilation process might took place in supplied from other sources also lower the f(CO2) mak- other years. ing organic C. The organic C is decomposed largely at

Cite abstracts as: Eos. Trans. AGU, 83(4), Ocean Sciences Meet. Suppl., Abstract #####-##, 2002. OS80 2002 Ocean Sciences Meeting

2Graduate School of Oceanography, University of the shallow bottom and the water containing regener- In recent decades, a notable infusion of fresh wa- Rhode Island, Narragansett, RI 02882, United ated CO2 as well as directly dissolved CO2 is mixed ter in the Northern North Atlantic and an extreme States into the deeper subsurface layer of the open sea by fluctuation of surface wind patterns together precipi- 129 isopycnal diffusion and advection. The isopycnal mix- tated major shifts in the character and production of I (half-life = 16 million y) discharged from nu- ing still continue under the pycnocline, even in the deep waters in the Nordic Seas and Labrador Basin – clear facilities in France and the UK is transported warming season. In the high latitudes, the formation the headwaters of the global through the North Sea into the Norwegian/Greenland of sea ice amplifies the pump activity. In the low lat- (THC). The consequences of this high latitude THC Seas in 1-2 years. Deep mixing and convection in the itudes, the evaporation of water from the surface also variability are now recognizable downstream in the Greenland Sea injects tracer 129Iintointermediatewa- performs as a starter. subtropical and tropical deep circulation as conspic- ters that overflow the sills between Greenland, Iceland The CSP is functioning more strongly in Funka Bay uous shifts in temperature-salinity characteristics, at- and Scotland and ventilate the deep North Atlantic. in the northern Japan (Nakayama et al. 2000) and mospheric tracer gas concentrations, and vertical den- 129I is well suited to determining ventilation ages for in the Okhotsk Sea (Tsunogai et al., 2001). Here we sity structure in the deep western North Atlantic Deep Water (NADW), because it has present the results obtained in the Japan Sea. (DWBC). Hydrographic changes are quite prominent a direct pathway for injection into NADW source re- In the last 50 years, dissolved oxygen contents de- near the two principle cores of DWBC flow– the Up- gions and provides an excellent comparison with venti- creased year by year and it is considered that its deep per and Lower North Atlantic Deep Water – directly lation tracers such as CFCs. An 129I section measured water was not formed. The Japan Sea is connected to reflecting recent freshening and ventilation history at across the Labrador Sea in 1997 showed decreasing lev- the Pacific and the Okhotsk Sea through 4 straits, but their respective sources. The DWBC velocity struc- els with increasing water depth in Labrador Sea Water, their sill depths are shallower than 140 m. Thus, its ture is exhibiting attendant modifications: a weaken- 7 deep and bottom waters are produced within the sea. ing of the deeper core of Overflow Waters and an ap- with the lowest values (3-4 x 10 atoms/l) measured at We studied their formation process using CFCs. The parent strengthening of the upper core of Labrador Sea 1800 m, close to the deepest historical extent of convec- 129 7 observations were carried out twice in 2000 and 2001 Water (LSW). In the 1990’s, these signals moved pro- tion. The highest I levels (> 15 x 10 atoms/l) were and obtained interesting results. gressively through the subtropical circulation and have measured in Denmark Strait Overflow Water (DSOW), In 2000, the CFC-11 concentrations decreased al- now entered the tropics enroute to the equator. By below 3000 m. From a comparison of 129I/CFC ra- most exponentially with depth from 6 pmol/kg at 500 year 2000, just 10-12 years following dramatic events tios measured in DSOW with the Greenland Sea input m depth to 0.3 pmol/kg or less at the bottom, 3500 m in the Labrador Sea, a plume of anomalously cold, function, a ventilation age of 2-3 y was estimated for depth at 3 stations (40 – 41 E

Could China’s Development Lead to OS12P-02 1345h Raymond T Pollard1 (44-2380-596433; Bottom Water Formation in the [email protected]) Japan/East Sea? Rapid Freshening of the Deep North N Penny Holliday1 Atlantic Over the Past Four Decades. Doron Nof ([email protected]) John T Allen1 Florida State University, Department of Oceanogra- Robert R. Dickson1 ((44) 1502-524282; phy 4320, Tallahassee, FL 323064320, United States Harry Leach2 [email protected]); Igor Yashayaev2 Using hydrographic data and box models and a com- (902-426-9963; [email protected]); 1Southampton Oceanography Centre, Empress Dock, parison between the cooling of the Mediterranean and Jens Meincke3 ((49) 40-42838-5985; Southampton SO14 3ZH, United Kingdom the Japan/East Sea, it is shown that the presently dis- 4 cussed diversion of rivers such as the Yellow or the [email protected]); William R. Turrell 2University of Liverpool, Liverpool L69 3BX, United Yangtze for agricultural use is likely to cause the re- ((44) 1224-295429; [email protected]); Kingdom newal of Bottom Water formation in the Sea of Japan. Stephen R. Dye1 ((44) 1502-524508; Many detailed surveys have been made in the sub- Such formation was common (near the Siberian coast) 3 [email protected]); Jurgen Holfort ((49) polar North Atlantic during the past decade. However, in the 1930s, 40s and 50s but subsided since that time 40-42838-5756; [email protected]) descriptions of the circulation vary in their pattern and due to a warming trend (accompanied by a decreased magnitude. Satellite studies and eddy resolving ocean salinity due to the melting of ice). Since a diversion of 1CEFAS, The Laboratory Pakefield Road, Lowestoft, models indicate that eddies may dominate mean cur- fresh water is analogous to evaporation, a (diversion- Suf NR33 OHT, United Kingdom rents in some regions, effectively aliasing traditional induced) increase of salinity is expected and the in- 2 basin scale ocean observations. However the region is crease is large enough to allow Bottom Water formation BIO, Dept. of Fisheries and Oceans PO Box 1006, important climatically and biologically. It is an area even at the present-day cooling rates. Even a mod- Dartmouth, NS B2Y 4A2, Canada of cooling and deep winter mixing. Zooplankton distri- est diversion of merely 3000 cubic meters per second 3IFMH, University of Hamburg Troplowitzstrasse 7, butions (specifically Calanus finmarchicus) are heavily (which is 10 percent of the total fresh water flux) will D-22529 Hamburg, Germany constrained by the circulation. Thus it is an important probably cause Bottom Water formation at a rate of area to understand dynamically. roughly 750,000 cubic meters per second. This is the 4 FRS Marine Lab., PO Box 101 Victoria Road, Ab- Surveys made in the subpolar North Atlantic in first known case where anthropogenic effects can easily erdeen, Sco AB11 9DB, United Kingdom 1996 and 2001 were designed to investigate the path- reverse an existing vertical structure. The overflow and descent of cold dense water from ways of the and distinguish the sills of the Denmark Strait and Faroe-Shetland areas of eddy activity, particularly in the region be- Channel is the principal means by which the deep ocean tween Iceland and Scotland. An upper ocean SeaSoar is ventilated and so is a key element of the global ther- survey (0-400 m) with scattered full depth CTD casts OS12P HC: 316 B Monday 1330h mohaline circulation (THC). Most projections of green- was made in Oct - Nov 1996 (Vivaldi’96). Extending house gas induced climate change anticipate a weaken- from west of Ireland and Scotland to East Greenland The North and Its ing of the THC in the North Atlantic in response to it showed clear current paths of warm stratified water increased freshening and warming in the subpolar seas flowing into the region and deep winter mixed subpo- Changing Climate II and the supposition is that this climate signal will be lar mode water to the east and in the north Iceland transferred to the deep ocean via the two overflows. Basin. However the vertical extent of mode water was Presiding: B Dickson, CFEAS, The Nevertheless, these simulations do not yet deal ade- greater than the SeaSoar could survey. Thus a second quately with many of the mechanisms believed to con- survey using full depth CTD casts was made in May- Laboratory; TMJoyce, Woods Hole trol the THC, and our observations cannot yet detect June 2001 to investigate the end of winter distribution whether the rate of the oceans overturning circulation of mode water. FISHES 2001 (Faroe - Iceland - Scot- Oceanographic Institution is changing. Here, complementing recent evidence that land Hydrographic and Environmental Survey) concen- overflow transport may be slackening, we show that the trated on the region between Iceland, the Faroes and entire system of overflow and entrainment that venti- Scotland. Results showed a large area of weakly strat- OS12P-01 1330h INVITED lates the deep Atlantic has steadily changed in charac- ified water extending 500-600 m vertically and spread- ter over the past four decades, resulting in a sustained ing westwards from the Scottish shelf edge between the freshening of the deep and abyssal waters of the North- Rockall - Hatton and Faroe Plateaux out into the Ice- Tracking Hydrographic Change Through ern North Atlantic — the headwaters of the global ther- land Basin. Circulation was weak and no clear current the Deep Western Boundary Current mohaline circulation. paths were apparent, but topography clearly influenced System the distribution of mode water. Here we will discuss the circulation observed in the two surveys five years apart, contrast the distribution of mode water and investigate 1 OS12P-03 1400h Ruth G. Curry (508-289-2799; [email protected]) the factors affecting them. 129 William M. Smethie2 (845-365-8566; I Ventilation Ages for Denmark Strait [email protected]) Overflow Water in the Labrador Sea OS12P-05 1430h Bob Dickson3 (44-1502-524282; [email protected]) John Norton Smith1 (902 426-3865; First Direct Thickness Observations of 1Woods Hole Oceanographic Institution, MS #21 [email protected]) the Denmark Strait Overflow Clark Laboratory, Woods Hole, MA 02543, United Peter Jones1 (902 426-3869; States [email protected]) Stephen R Dye1 (+44 (0) 1502 524508; 2 2 Lamont-Doherty Earth Observatory, Columbia Uni- Bradley Moran (401 874-6530; [email protected]) versity, Palisades, NY 10964, United States [email protected]) Robert R Dickson1 ([email protected]) 3CEFAS, The Laboratory, Pakefield Road, Lowestoft, 1Bedford Institute of Oceanography, Fisheries and Suf NR33 OHT, United Kingdom Oceans Canada, Dartmouth, NS B2Y 4A2, Canada Cite abstracts as: Eos. Trans. AGU, 83(4), Ocean Sciences Meet. Suppl., Abstract #####-##, 2002.