Late-Holocene initiation of ice-free ecosystems in the southern Ross Sea, Antarctica

New data on marine sediments, seawater paleotemperatures, and the occupation history of Adelie penguins indicate that modern ice-free conditions in the southern Ross Sea developed only within the last 1000 yr. Here we show that penguins permanently abandoned the southern Victoria Land Coast 2000 yr ago when extensive sea-ice cover blocked access to ice-free terrain for breeding. The first colonization of Ross Island in East McMurdo Sound, where over 300000 penguins breed today, did not commence until after 1170 yr BP when coastal areas became exposed from under the Ross Ice Shelf. Our results demonstrate that investigations of abandoned penguin colonies can provide increased resolution to Holocene paleoclimatic records and paleoceanographic conditions in Antarctica.