Abstract.A

ObjectiveSatellite telemetry was used to investigate the migratory behaviour of southern elephant seals (Mirounga leonina). The seal studies were part of the German-Argentinean cooperation project and carried out at Stranger Point on King George Island between September 1996 and February 1997. Stranger Point (62°14'S; 58°40'W) is the southernmost breeding site of elephant seals. Elephant seals are able to dive to depths in excess of 1500 m and feed on squid and fish. The objective of this study was to identify the wintering areas and feeding grounds of elephant seals of this true Antarctic breeding colony. The results can potentially be compared between years or sites, in order to monitor differences in migratory and foraging behaviour that can be attributed to environmental changes in physical parameters (e.g. sea ice distribution) or to human impact on prey resources of these top predators. Field methodsAdult female elephant seal with satellitelinked dive recorder (SDR). SDRs were glued to the hair on the backs of 7 two month-old juveniles and on the heads of 13 moulted cows. To attach the instruments, seals were sedated with a combination of ketamine, xylazin, and diazepam. The initial doses of the drugs were either administered by hand (juveniles) or by a dart gun (adults) with automatically evacuating syringes. To maintain an immobilization of 1.5 to 3 h, small additional doses of ketamine and/or diazepam were administered by hand while the transmitters were being attached and the epoxy resin allowed to set.Satellite-linked dive recorder. Two types of ARGOS (CLS/Service Argos, Toulouse, France) transmitters were used in this study: 1) Satellite transmitters (ST-10 Telonics, Mesa, AZ, USA) are designed to provide the seals' at-sea locations. 2) In addition to transmissions of locations, satellite-linked dive recorders (SDR T-6 Wildlife Computers, Redmond, WA, USA) also process data on dive depths in the form of histograms. The histograms are encoded into messages and transmitted to a polar-orbiting satellite. The accessed data provide the horizontal extent of the seals' migrations and the distribution of their dive depths. Results and DiscussionComputer animation: To obtain a comprehensive picture of the seal's foraging activity in its three-dimensional marine environment the data need to be interpreted in the context of both biological and physical parameters. In our first attempt, a computer animation was developed to relate the animals behaviour to sea ice cover. A QuickTime (Apple Computer, Inc.) animation shows the tracks of the satellite tagged elephant seals in conjunction with seasonal changes in sea ice cover in the Antarctic Peninsula region from

Abstract. Sea ice circulation in the Laptev

ABSTRACT. Experiments with d yna mic th erm od yna mic sea-ice m odel s indicate a stro ng dep e nde nce of t he net rreez ing ra te, sea-ice tra nspo rt a nd \'a ri a bilit )" o n dy na mic m odel pa ra me ters. Altho ug h c urrent d yna mi c-t hcrm od yna mic sea-ice m odels show relati\'ely good agree m ent with o bse rvations, a n o ptimi zati o n see m s to be necessa r y, es pecia ll y for th e pa ra m e teri zati o ns of d yn a mic processes.Presentl y, o nl y a few co upl ed clima te m odel s use d yna mic-th er m od yna mi c sea-ice m odels. In o rder to prom o te, by mea ns of coordina ted num er ica l ex perime nts, th e de\'elop ment or a n optim a l sea-ice model fo r elim a te resea rch, the Sea Ice O cca n l\fodelling Pane l o f th e Arc ti c C lim a te Sys tem S tud y ( ACSYS, a p roj ec t of th e \\'o rld C lim a te R esea rch Prog ram me) has initi a ted the Sea Ice l\lodel Inte rco mpa riso n Projec t (SIl\IIP). Th e first res ults from thi s m odel hi era rchy a pproach a re prese nted.

ABSTRACT. Th e Sea-Ice M odel Int erco mpa riso n Proj cct (SIM1P) is pa rt oCthc ac tiviti es o r-the Sea Ice O cca n M odeling Panel (SIOM ) orthc Arctic C lim ate System Study (\Vr-.[O ) (ACSYS) th at a ims to detcrmin e th e optimal sea-ice m odel [or clim ate simula ti ons. This im"C'stigation is foc used on the d yna mics of sea ice. A hi erarchy o f four seaice rheologies is app lied, incl uding a vi scous-pl as tic rheo logy, a cavitating-Ouid model, a compressible New tonian Ouid, a nd a simpl e scheme with a step-functi on stoppage for ice drift.For co mparison, th e samc g rid, la nd bo und ari es a nd forcing fi eld s are a pplied to a ll models. Atm os ph eric fo rcing [or a 7 yea r peri od is obta in ed from th e Europea n C entre for !vIed i um-Ra nge Weather Forecas ts ( U K ) (EC MWF) a nal yses, whil e oceanic forcing consists of a nnu a l mea n geostro phi c currents a nd h ea t Ou xes into a fixed mixed layer. D a ily buoy-drift data monitorcd by th e Intern a ti onal Arctic Buoy Progra m (IABP) a nd ice thickn esses at th e North Pole fr om subm a rin e upwa rd-l ooking sonar a re avail a ble as \'erificati on data. Th e da il y drift sta tisti cs fo r sepa rate regions a nd seasons co ntribute to a n error functi on showing sig nifica nt d ifferences betwee n the m odcl s. Additi ona ll y, Fra m Stra it ice expo rts predictcd by th e d iflcrent models a re im·estigated. The ice export of the viscous -plas ti c model a mounts to 0. 11 Sv. w hen it is optimi zed to the m ea n daily bu oy ve locities a nd th e observed North Pole ice thi ckn esses. Th e cav ita ting-fluid model yield s a ve r y simil a r Fra m Stra it o utOow, but underestim ates th e :\fo rth Pole ice thickn ess. The two oth er dyn amic schemes predict unreali stica ll y la rge ice thicknesses in the ce ntra l Arctic region, whil e Fram Strait ice exp orts ar c too low.