HR: 0800h
AN: PP51A-0196    [Abstracts]
TI: Water Masses and Brine Formation on the Southwestern Svalbard Margin During the Last 20,000 Years
AU: * Rasmussen, T L
EM: tine.rasmussen@ig.uit.no
AF: Tine L. Rasmussen, Simon P. Jessen, Department of Geology, University of Tromsø, Tromsø, N-9037, Norway
AU: Thomsen, E
EM: erik.thomsen@geo.au.dk
AF: Erik Thomsen, Department of Geology, University of Aarhus, Aarhus C, DK-8000, Denmark
AU: Slubowska-Woldengen, M
EM: marta.woldengen@npd.no
AF: Marta Slubowska-Woldengen, Norwegian Petroleum Directorate, N-9488, Harstad, Norway
AU: Jessen, S P
EM: simon.jessen@ig.uit.no
AF: Tine L. Rasmussen, Simon P. Jessen, Department of Geology, University of Tromsø, Tromsø, N-9037, Norway
AU: Solheim, A
EM: anders.solheim@ngi.no
AF: Anders Solheim, Norwegian Geotechnical Institute, Oslo, N-0806, Norway
AU: Koc, N
EM: nalan@npolar.no
AF: Nalan Koc, Norwegian Polar Institute, Tromsø, N-9296, Norway
AB: The western Svalbard shelf and slope area is situated at the northernmost reach of the Atlantic Water before it enters the Arctic Ocean and continues as the Atlantic layer below polar surface waters. On the shelf, the relatively warm water Atlantic water meets with the cold, icy, low saline polar water derived from the polar East Spitsbergen Current, which enters the Barents Sea from the Arctic Ocean. In Storfjorden southwestern Svalbard, wind driven, brine formation takes place during the winter in the innermost, shallow part of the fjord. We have studied two cores from the Storfjorden area on the southwestern shelf taken at 389 m and 1485 m water depth, respectively. The study area is situated close to the boundary between the warm and cold surface water in an area where even small changes in their distributional pattern should be recorded. In addition, the flow of brine exiting the fjord at the bottom of the Storfjorden Trough passes the shelf core site on its way to deeper waters on the slope. In the present study we reconstruct the distribution of the Atlantic Water and polar water and the flow of brine on the southwestern margin of Svalbard during the last ca 20 14C kyr B.P. The purpose of the study is to assess the behavior and interplay of the two water masses under widely different climatic conditions. Furthermore, our purpose is to reconstruct the extent of brine overflow in relation to the shifting surface ocean and climatic conditions. The study period comprises 1) the last glacial maximum (LGM) ca 20-15.5 14C kyr B.P., 2) Heinrich event H1, ca 15.5-13 14C kyr B.P., when numerous icebergs were delivered to the North Atlantic, 3) the warmer Bølling and Allerød Interstades 13-11 14C kyr B.P., 4) the cold Younger Dryas Stade ca 11-10 14C kyr B.P., and 5) the Holocene, including the early Holocene climate optimum, when the climate was warmer than today. The cores were analyzed for benthic and planktic foraminifera, oxygen isotopes, and IRD. The results show that over the last 20 14C kyr B.P., Atlantic Water has been continuously present on the southwestern Svalbard shelf. However, from 15 to 9 14C kyr B.P., comprising Heinrich event H1, the Bølling-Allerød Interstades and the Younger Dryas Stade, it flowed as a subsurface water mass below a layer of polar surface water, which apparently had expanded >1000 km to the south as compared to it present distribution. In the benthic environment, the shift to interglacial conditions occurred at 10 14C kyr B.P. However, due to the continuing presence of a thin upper layer of polar water, surface conditions remained cold until ca 9 14C kyr B.P., when the warm Atlantic Water finally appeared at the surface. A general cooling of the Atlantic surface water took place during the late Holocene from ca 4000 14C years BP. Brine formation and the overflow of brine over the shelf apparently increased during this period.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4944 Micropaleontology (0459, 3030)
DE: 4954 Sea surface temperature
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting