Time lags between sea surface and air temperatures at the time of the
Younger Dryas in palynological records from the Northwest Atlantic
Abstract
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.