High resolution palynological records from Atlantic Canada: Regional Holocene paleoceanographic and paleoclimatic history.

• Main Author: Levac, Elisabeth.
• Other Authors: Ph.D.
• Format: Text
• Language: English
• Published: Dalhousie University 2014
• Subjects: Paleoecology; Palynology; Baffin Bay; Canada; Labrador Shelf; Newfoundland; Baffin; Ice Sheet; Sea ice
• Online Access: http://hdl.handle.net/10222/55918

During the Holocene, the interaction of various forcings (shrinking ice sheet, meltwater, insolation) along the Eastern Canadian Margin caused changes in atmospheric circulation and climate 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 (western Newfoundland) provided dinoflagellate cyst data that was used to reconstruct sea surface conditions (temperature, salinity and sea ice cover duration), using transfer functions. Ocean-atmosphere interactions are determined by onshore-offshore correlation of pollen records from Nova Scotia and Newfoundland. In the early Holocene, the three cores record sea surface temperature (SST) 3 to 5°C 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 around the present day average. Comparison with other sites from the Labrador Shelf and Northern Baffin Bay show that paleoceanographic events are progressively younger toward the north and suggests that difference in paleoceanography are most likely due to the location relative to Laurentide ice sheet and meltwater sources. Overall, these records reveal a complex Holocene paleoceanography and illustrate the importance of obtaining high resolution records as SST can change by a few degrees (as much as 4--5°C) in less than 100 years. Timing of paleoclimatic events relative to paleoceanographic events is variable. The mid-Holocene warm climatic event (hypsithermal) is apparently delayed relative to optimum SST. While forest migration delay cannot be totally excluded, other factors might be involved (competition). The late Holocene Neoglacial cooling trend started earlier on land at the southern location (Scotian Shelf and Bay of Islands) but earlier in the sea surface at the 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. Thesis (Ph.D.)--Dalhousie University (Canada), 2002.