High resolution Holocene palynological record from the Scotian Shelf

Because of their location at the confluence of polar and subtropical airmas ses and near a transition zone between the cold Labrador Current and the Gu lf Stream, the Atlantic Provinces experience some of the most dynamic clima te conditions in Canada. Major climate changes occurred during the Holocene , as shown by pollen records from takes, but previous paleoceanographic stu dies. based on low-resolution proxy-data records do not show major changes during the past 8000 years. Therefore, the Holocene history of Canada's Atl antic region was examined using a high-resolution palynological record from the Scotian Shelf (La Have Basin). Sea surface conditions were reconstruct ed using proxy-data from dinoflagellate cysts and paleobioclimatic transfer functions. Ocean-atmosphere interactions are determined by onshore-offshor e correlation of marine and pollen records from Nova Scotia. Results show a succession of major paleoceanographic events. Sea surface te mperatures (SST) (February and August) up to 5 degreesC higher than today's average and slightly higher salinity are reconstructed between 10.5 and 8. 5 ka. The last pulse of meltwater from the residual ice sheet affected the shelf waters between 8.5 and 6.5 ka by lowering the SST (in February) and t he salinity. Most previous studies failed to record this event. Since 6.5 k a, August temperature generally remained around today's value. while Februa ry temperature was generally 2 degreesC above it. except for recurring cold er and lower salinity intervals. These cold intervals have a recurrence of about 1000 years. A slight cooling of summer SST is recorded in the last 50 0 years. Comparison with climatic reconstructions from Nova Scotia pollen records sh ows a difference in timing between ocean and atmosphere. The onset of the c limatic optimum (hypsithermal) in Nova Scotia lags by about 2000 years (unt il 8 ka) relative to the ocean but it lasted longer. The Neoglacial cooling in Atlantic Canada however, started earlier (2 ka) than the late Holocene ocean cooling. La Have Basin's Holocene paleoceanography presents some differences from mo st other studies from the region: (1) the hypsithermal started earlier; (2) the last pulse of meltwater is recorded; (3) the last 6500 years are punct uated by colder intervals. Increased productivity and blooms of toxic algae in the early Holocene are probably due to a combination of factors: increased nutrients and a greater stability of the water column because of meltwaters, higher SST and increa sed upwelling or storm activity. (C) 2001 Elsevier Science B.V. All rights reserved.