The Seasonal Cycle In North Pacific Sea Surface Temperature And The Glaciation Of North America 2.7 Million Years Ago

HR: 16:00h
AN: PP24A-01 INVITED [Abstracts]
TI: The Seasonal Cycle In North Pacific Sea Surface Temperature And The Glaciation Of North America 2.7 Million Years Ago
AU: * Haug, G H
EM: haug@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AU: Ganopolski, A
AF: PIK, Telegrafenberg, Potsdam, 14473 Germany
AU: Sigman, D M
AF: Department of Geosciences, Princeton University, Guyot Hall, Princeton, NJ 08544 United States
AU: Rosell-Mele, A
AF: ICTA, Autonomous University of Barcelona, Bellaterra, 08193 Spain
AU: Swann, G E
AF: University College London, Environmental Change Research Centre, Department of Geography, London, WC1H 0AP United Kingdom
AU: Tiedemann, R
AF: Geomar, Wischhofstr. 1-3, Kiel, 24148 Germany
AU: Jaccard, S L
AF: ETH Z〉ich, Department of Earth Sciences, Z〉ich, 8092 Switzerland
AU: Bollmann, J
AF: ETH Z〉ich, Department of Earth Sciences, Z〉ich, 8092 Switzerland
AU: Maslin, M A
AF: University College London, Environmental Change Research Centre, Department of Geography, London, WC1H 0AP United Kingdom
AU: Leng, M J
AF: British Geological Survey, NERC Isotope Geosciences Laboratory, Keyworth, Nottingham, NG12 5GG United Kingdom
AU: Eglinton, G
AF: Bristol University, Biogeochemistry Centre, Bristol, BS8 1TH United Kingdom
AB: The causes for major intensification of Northern Hemisphere Glaciation 2.7 Million years ago, one of the most dramatic climate shifts in the Cenozoic, are not yet resolved. In particular, the onset of Northern Hemisphere Glaciation has proven to be inconsistent with early ideas regarding the water vapor requirement. It has been suggested that glaciation began in response to increased North Atlantic Deep Water formation and the flow of warm Gulf Stream waters into the high-latitude North Atlantic, associated with the closure of the Panama seaway. However, recent studies show that this closure and associated changes in North Atlantic circulation occurred 4.6 Ma ago, well before the onset of intense NHG. Thus, the Atlantic Ocean is unlikey to be a key factor in this climate change enigma. The role of the North Pacific has so far been overlooked, despite the fact that it is the major water vapor source upstream (in an atmospheric sense) of the North American continent. We report two independent data sets from a sediment core in the western subarctic Pacific indicating that summertime/autumn sea surface temperature in this ocean region rose in response to a freshwater-driven stratification 2.7 million years ago2, even as the wintertime surface ocean cooled, wintertime floating ice became abundant, and global climate descended into glacial conditions. This increase in the seasonal temperature variation of the subarctic Pacific reflected a reduction in the buffering of surface temperature by the ocean interior. The late summer/autumn warming 2.7 million years ago would have extended into the autumn, providing water vapor to northern North America when it could be precipitated and accumulated as snow. Thus, stratification of the subarctic Pacific at 2.7 Myr allowed for the initiation of major Northern Hemisphere Glaciation by maintaining the water vapor source to the continents even as climate cooling favored the preservation of snow and ice.
DE: 4805 Biogeochemical cycles (1615)
DE: 4267 Paleoceanography
DE: 1620 Climate dynamics (3309)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting