HR: 0830h
AN: PP51C-0940    [PDF]
TI: Climate Controlled Changes in Deep Ocean Flow: Examples From the Riiser Larsen Sea (Antarctica) and the Fram Strait (Arctic Ocean)
AU: * Hass, H
EM: chass@awi-bremerhaven.de
AF: Alfred Wegener Institute, Wadden Sea Research Station, Hafenstrasse 43, List/Sylt, 25992 Germany
AU: Hegner, E
EM: hegner@petro1.min.uni-muenchen.de
AF: Munich University, Dept. Earth Environ. Sci., Theresienstr. 41/IIIe, Munich, 80333 Germany
AU: Fuetterer, D K
AF: Alfred Wegener Institute, Columbusstrasse, Bremerhaven, 27568 Germany
AU: Schmitt, W M
AF: Munich University, Dept. Earth Environ. Sci., Theresienstr. 41/IIIe, Munich, 80333 Germany
AB: Sediment cores from the northeastern Fram Strait (Arctic Ocean) and the western Riiser Larsen Sea (Antarctica) were investigated to reconstruct climate forced fluctuations of bottom currents. In terms of global water-mass circulation, the Arct ic Ocean plays a rather passive role with only very limited deep-water exchange through the Fram Strait. The cores investigated here are primarily influenced by the Yermak Slope Current (YSC), a water mass that is mainly composed of NSDW. Since NSDW is fo rmed in the Greenland Sea as a result of deep-water production, it is suggested that fluctuations in the speed of the YSC are linked to fluctuations in thermohaline overturn which in turn is strongly related to climate development. It turns out that cold events s uch as the Younger Dryas (12.7-11.5 kaBP) were periods of lower bottom-current speed whereas warmer periods suggest increased bottom-current activity. Holocene climate phases such as the cold "8,200 year Event" left clear traces in the record. In the Ri iser Larsen Sea that forms the easternmost part of the Weddell Gyre, deep-current controls are different. A large system of channels on the continental slope suggests that the channels are active pathways of either dense shelf waters or turbidity current s. Long sediment cores recovered from levees that flank the channels reveal carbonate-rich sediments with few IRD during the interglacials and carbonate-depleted sediments during the glacials in the sand f raction. High resolution granulometric data suggest that the channels were more active during interglacials than during glacials. In glacial climates surface-water bio-production in the RLS was low. Presumably a quasi-permanent ice cover prevailed that al so prevented the deposition of IRD. During interglacials conditions were like those of today with a very large sea-ice cover in winter and open water conditions in the austral summer. It can be assumed that dense water formation on the upper continental slope is reduced during the glacials and somewhat higher during interglacials.
DE: 1600 GLOBAL CHANGE (New category)
DE: 3022 Marine sediments--processes and transport
DE: 9310 Antarctica
DE: 9315 Arctic region
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting