Elizabeth Levec

During the Holocene, the interaction of various forcings (shrinking ice sheet, meltwater, insolation) along the Eastern Canadian Margin caused climate changes which are reflected in the pollen records from Nova Scotia lakes. In contrast, earlier paleoceanographic studies based on low resolution records, did not show major changes in the past 8000 years.

A high resolution palynological study was undertaken to establish the Holocene history of paleoceanographic changes in the region. Cores from La Have and St. Anne's Basins (Scotian Shelf) and Bay of Islands (Newfoundland) provided dinoflagellate cyst data used to reconstruct sea surface conditions (temperature, salinity and sea ice cover), based on transfer functions. Oceanatmosphere interactions are determined by onshoreoffshore correlation of pollen records.

In the early Holocene, the three cores record sea surface temperature (SST) 3 to 5ºC warmer than today's average and higher salinity, followed by cooler SST than present. The last 7000 years are characterized by frequent oscillations of SST and salinity.

Comparison with sites from the Labrador Shelf and Northern Baffin Bay shows that paleoceanographic events are progressively younger toward the north and depend on the location relative to the Laurentide ice sheet and meltwater sources. Overall, these records reveal a complex Holocene paleoceanography and the importance of high resolution records as SST can change by a few degrees in less than 100 years.

Timing of paleoclimatic events relative to paleoceanographic events is variable. The midHolocene warm interval (hypsithermal) is apparently delayed relative to optimum SST. While migration delay cannot be totally excluded, other factors might be involved. The lateHolocene Neoglacial cooling trend started earlier on land at southern locations (Scotian Shelf and Bay of Islands) but earlier in the sea surface at northern sites (Labrador Shelf and Baffin Bay). Paleoclimatic reconstructions independent from pollen are necessary to determine which of the land or the ocean leads the changes.

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Pages: 445
Supervisor: David Scott