A Wind-Driven Nonseasonal Barotropic Fluctuation of the Canadian Inland Seas

Abstract:

We identify a wind-driven, spatially coherent mode of nonseasonal, depth-independent variability in the Canadian Inland Seas (i.e., the collective of Hudson Bay, James Bay, and Foxe Basin) on the basis of GRACE retrievals, a tide-gauge record, and a barotropic ocean model over 2003-2012. This dominant mode of nonseasonal variability is partly related to the North Atlantic Oscillation and is associated with net flows into and out of the Canadian Inland Seas; the anomalous inflows and outflows, which are reflected in mean sea surface height and ocean bottom pressure changes, are driven by wind stress anomalies over Hudson Strait, probably by means of a wind setup, and over the northern North Atlantic, possibly mediated by continental shelf waves. The mode is also associated with mass redistribution within the Canadian Inland Seas; the anomalous internal mass redistribution, which relates to changes in the depth-mean ocean circulation, reflects linear ocean response to local wind stress variations under the combined influences of rotation, gravity, and variable bottom topography. Results have implications for interpreting the multidecadal tide-gauge record as well as inferring ocean circulation and climate changes from the GRACE retrievals.