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Time lags between sea surface and air temperatures at the time of the Younger Dryas in palynological records from the Northwest Atlantic
  • Elisabeth Levac,
  • Gail Chmura
Elisabeth Levac
Bishop's University

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Gail Chmura
McGill University
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The Younger Dryas (YD) in Bay of Islands, Newfoundland is characterized by major changes in both pollen and dinocyst assemblages, which translate into large drops in air and sea surface temperatures and sea surface salinity. Changes in vegetation are similar with those observed in Newfoundland lakes. Reconstructed air temperature shows a 7ºC drop at the time of the YD, an amplitude comparable to changes recorded in northeastern North America. Changes observed in dinoflagellate cyst assemblages are also like those at nearby sites from the Gulf of St. Lawrence and Laurentian Channel. Sea surface dropped by 7ºC, salinity by 4 psu and sea ice cover duration increased by 7 months. The YD period in eastern North America was traditionally defined by changes in sediments and pollen records. Our records show that the cooling in sea surface and air temperatures started 250 and 110 years before the start of the YD as defined by radiocarbon dates and pollen zones. By having exceptionally high resolution records for both terrestrial and marine conditions in the same core, we can show that there is a 140 years delay between ocean and atmosphere. We speculate that the major lithological and vegetation changes observed in lakes around the time of the YD period in eastern North America might actually represent the full impacts of the cooling, since the cooling trend actually started before the start of the YD period.