APPLICATION OF MODERN ANALOG TECHNIQUE TO MARINE ANTARCTIC DIATOMS - RECONSTRUCTION OF MAXIMUM SEA-ICE EXTENT AT THE LAST-GLACIAL-MAXIMUM

Modem analog technique (MAT) applied to Antarctic diatoms is a new app roach for quantitative sea-ice paleoreconstructions in the Southern Oc ean. Tn a first step we show that MAT is a better approach than the Im brie and Kipp Method to reconstruct the modern sea-ice pattern. We the n use this approach to reconstruct sea-ice presence in number of month s per year during the last glacial maximum (LGM). At this time, sea-ic e presence was greater than today, leading to a shorter diatom growing season. The maximum sea-ice extent, inferred from quantitative values of sea-ice presence, was located 5-8 degrees north of its actual posi tion, leading to double the surface of modern winter sea ice. This gre ater sea-ice extent may have played a significant role on atmospheric and surface oceanic circulations and therefore on southern mid-latitud e and high-latitude climates. It may also have reduced the amount of h eat, moisture, and CO2 from the ocean to the atmosphere, thus particip ating in the lowering of atmospheric CO2 during the LGM.