Diachronous Evolution of Sea Surface Conditions from the Labrador Sea to Baffin Bay since the Last Glaciation
Diachronous Evolution of Sea Surface Conditions from the Labrador Sea to Baffin Bay since the Last Glaciation
Previously Published Material: These findings are currently under review by the scientific journal The Holocene. A portion of these findings were presented at the Arctic Change 2014 meeting in December in Ottawa, ON.
Abstract ID#: 35900
English Abstract:
An increased understanding of the dynamics and variability in Labrador Sea Water (LSW) formation requires assessing past regional hydrographic responses driven by changes in climate and ocean circulation, specifically freshwater outflow through Baffin Bay. The shift from the most recent glacial to postglacial interval with deglacial meltwater influx from surrounding ice sheets provides examples of the breadth of conditions. Here, we reconstruct sea surface conditions based on dinoflagellate cyst (dinocyst) assemblages from four cores collected from Baffin Bay, Davis Strait, and the northwest Labrador Sea. All exhibit a major shift from a polar-subpolar heterotrophic species assemblage tolerating cold and extensive sea ice cover, to assemblages characterized by a higher diversity and the presence of phototrophic taxa associated with North Atlantic waters. Sea surface reconstructions using transfer functions display an abrupt shift from harsh, quasi-perennial ice cover to warmer summer sea surface temperatures and seasonal sea ice cover. This shift occurred at ca. 11.9 cal ka BP south of the Davis Strait sill under the influence of warm North Atlantic waters, while Baffin Bay remained densely sea ice covered. These warmer waters penetrated into Baffin Bay and mixed with the West Greenland Current (WGC) by ca. 7.4 cal ka BP. A major change in Labrador Sea surface conditions occurred at about the same time, when the strong stratification of surface waters weakened, due to the reduction in meltwater supplies from the Laurentide Ice Sheet. This change finally allowed winter convection and the inception of LSW formation. Therefore, these shifts were facilitated by the advection of North Atlantic water and retreat of the Greenland and Laurentide Ice Sheet margins. Since deglaciation, however, these records demonstrate large fluctuations in sea surface conditions possibly controlled by the relative strengths and shifts of the warmer WGC and colder Baffin Island Current.