HR: 13:40h
AN: PP43C-01    [Abstracts]
TI: Evidence for a Progressive Change of Interglacial Climate Conditions Forced by Different Ocean-Atmosphere Circulation Regimes
AU: * Bauch, H A
EM: hbauch@ifm-geomar.de
AF: Mainz Academy of Sciences, Humanities and Literature c/o IFM-GEOMAR, Leibniz Institute of Marine Sciences, Wischhofstrasse 1-3, Kiel, D-24148 Germany
AU: Kandiano, E S
EM: ekandiano@ifm-geomar.de
AF: IFM-GEOMAR, Leibniz Institute of Marine Sciences, Wischhofstrasse 1-3, Kiel, D-24148 Germany
AU: Helmke, J P
EM: jhelmke@ifm-geomar.de
AF: IFM-GEOMAR, Leibniz Institute of Marine Sciences, Wischhofstrasse 1-3, Kiel, D-24148 Germany
AB: Most paleoclimatic interpretations directly hinge on observations drawn from studying present day processes. Although considerable progress has been made in understanding the overall glacial-interglacial climate system, still little is known in detail about climate forcing and feedback mechanisms of the interglacial past. In order to better estimate the 'natural range' of climatically important mechanisms, it seems crucial to make detailed comparison of the present interglaciation (Holocene) with previous warm periods of the late Quaternary. As the impact of climate change is usually strongest in more extreme environments, the temperature-sensitive northern high latitudes are a suitable region for such comparative studies. There is ample evidence from terrestrial and marine archives that the major warm periods of the Quaternary differed significantly from each other. For instance, the last interglacial period (Eemian/125 ka) had climatic conditions indicating slightly higher temperatures at mid-northern latitudes than during the Holocene hypsithermal. Comparing Holocene with Eemian records using marine sediment cores from the polar-subpolar North Atlantic suggests two different circulation styles. During most of the Holocene surface water circulation was dominated by a polar-directed transport of relatively warm surface water from the Atlantic which entered the eastern Arctic Ocean through Fram Strait and across the western Eurasian shelf seas. This type of circulation forced oceanographic fronts into a meridional alignment, a situation which still exists today. For Eemian times, however, paleoproxies indicate a much steeper north-to-south temperature gradient than for the Holocene, suggesting a zonal configuration of the main water mass fronts. This situation led to a reduced water mass exchange between the Arctic Ocean and the Nordic seas. Reconstructions of surface conditions during stage 11 (Holsteinian/405 ka) indicate, despite overall boundary conditions were quite comparable to the two younger periods, the weakest penetration of warm surface water into the northern high latitudes. In summary, a stepwise, northward expansion of polar-directed heat transfer from one interglaciation to the next youngest is proposed, marking the Holocene a time with the strongest impact on north-polar warming. A fundamental difference in ocean-atmosphere circulation with consequences on high-latitude precipitation-runoff rates and seas-ice drift patterns seems to be the likely forcing behind the unprecedented situation found for the Holocene.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4904 Atmospheric transport and circulation
DE: 4936 Interglacial
DE: 4944 Micropaleontology (0459, 3030)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005