Palynological tracers of ocean and climate changes

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The present program has two major components. One addresses a critical element of the climate-ocean system: the linkage between the Arctic and North Atlantic oceans and its impact on large-scale oceanic circulation changes. The other is methodological and concerns the use of fossil algae (dinoflagellate cysts = dinocysts) from marine sediments to reconstruct changes in hydrographic conditions at high latitudes. The ultimate goal of the research is to produce the best possible reconstructions of past climate and ocean synopses during the last two million years, with special attention paid to warm episodes, to support predictive climate-ocean modeling efforts. Long sedimentary records will thus be examined to identify intervals that have been free of perennial Arctic sea-ice and evaluate the impact of reduced sea-ice and Greenland ice volume on the climate and oceanic circulation in the NW North Atlantic. Detailed analyses of sediment cores spanning the present interglacial (the last 11,000 yrs) will be made to examine natural variability of the Arctic sea-ice and NW North Atlantic hydrography, and to explore the millennial pacing and linkages between Arctic sea-ice production and freshwater-meltwater export into the North Atlantic. Finally, some attention will be given to records spanning the last centuries in order to improve the accuracy of dinocysts as tracers of sea-ice and hydrographic conditions and to evaluate the impact of human activities, particularly in estuarine and coastal areas that are affected by eutrophication. Sedimentary records to be used include cores collected during the international expeditions of the Integrated Ocean Drilling Program (IODP) in the North Atlantic (2004), the HOTRAX expedition in the Arctic Ocean (2005), and the International Polar Year "WarmPast" project in Fram Strait, which is the main sill between the Arctic and Atlantic oceans. This research is conducted through collaboration for the setting of chronologies, the reconstruction of climate and ocean parameters, and climate-ocean model assessment. From a methodological point of view, my contribution mostly concerns dinocysts and their use as tracers of sea-surface conditions (sea-ice, temperature, salinity, productivity).