Labrador Coastal Current Variability During the Holocene

Abstract The Labrador Coastal Current (LCC) is a buoyancy driven current comprised of outflows from Baffin Bay and Hudson Bay that transports freshwater and nutrients to the Scotian Shelf and Gulf of Maine in the NW Atlantic. This study reconstructs Holocene flow speeds over the Labrador Shelf, using the sortable silt index at two core sites off northern and central Labrador. Reconstructions of current speeds at these two sites are similar through time and suggest that the LCC is controlled by Hudson Bay outflow, and experiences a 1,500 cyclicity consistent with the Arctic Oscillation and flow patterns from the NE Atlantic. Surface sediments suggest an increase in LCC velocity in recent decades, consistent with increased freshwater export from the Arctic, and possible recent weakening of the Atlantic meridional overturning circulation. Our new flow speed reconstructions differ from other major North Atlantic Holocene current speed records, but correspond to changes in salinity and bottom water temperature on the Labrador Shelf. This likely reflects the influence of cold and fresh Arctic waters versus warm, saline Atlantic waters. Results indicate recirculating Atlantic waters were likely the main LCC driver during an establishment period from 9 to 6 ka B.P whereas Hudson Bay outflow became the dominant control 6 ka B.P.—present, during a stabilization period once postglacial conditions were established.