DINOFLAGELLATE CYST DISTRIBUTION IN HIGH-LATITUDE MARINE ENVIRONMENTSAND QUANTITATIVE RECONSTRUCTION OF SEA-SURFACE SALINITY, TEMPERATURE,AND SEASONALITY

A data base of 179 reference sites documents the relations between the assemblages of organic-walled dinoflagellate cysts and sea-surface te mperature, salinity, and seasonality throughout the North Atlantic, ad jacent subpolar basins (Labrador Sea, Baffin Bay, Irminger and Iceland basins) and epicontinental environments off eastern Canada (estuary a nd Gulf of St. Lawrence, Hudson Bay). Principal-component analyses sho w close relationships between dinoflagellate cyst data and sea-surface conditions: the first component (71.1 % of the variance) correlates w ith the winter temperature, salinity, and seasonal duration of sea-ice cover, whereas the second component (11.3 % of the variance) appears mainly related to summer temperature. Transfer functions using the bes t analogue method were tested by reconstructing modern sea-surface con ditions on the basis of the reference dinoflagellate cyst assemblages. The correlation coefficient between instrumental averages and reconst ructed values ranges from 0.87 (August temperature) to 0.97 (annual du ration of sea-ice cover). These transfer functions appear most accurat e for the reconstruction of sea-surface conditions in marginal marine environments of high-latitude basins. The only reservation concerns th e validity of reconstruction in offshore regions characterized by low productivity where sparse cyst fluxes may result from long-distance tr ansport through currents. The transfer functions that were applied in, as an example, a late Quaternary sequence of the Davis Strait in the northern Labrador Sea, notably suggest seasonal sea-ice cover extent o f 6 - 10 months/year and August temperature and salinity of 1-4-degree s-C and 31 - 33 parts per thousand, respectively, during the last glac ial optimum (isotopic stage 2).