Abstract
Abstract. 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) is identified based on Gravity Recovery and Climate Experiment (GRACE) retrievals, a tide-gauge record, and a barotropic model over 2003–2013. This dominant mode of nonseasonal variability is correlated with 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 level and bottom pressure changes, are driven by wind stress anomalies over Hudson Strait, probably related to wind setup, as well as over the northern North Atlantic Ocean, possibly mediated by various wave mechanisms. The mode is also associated with mass redistribution within the Canadian inland seas, reflecting linear response to local wind stress variations under the combined influences of rotation, gravity, and variable bottom topography. Results exemplify the usefulness of GRACE for studying regional ocean circulation and climate.
Highlights
To determine more rigorously whether there is such a wind-driven nonseasonal barotropic fluctuation of the Canadian inland seas (CIS), we perform an empirical orthogonal function (EOF) analysis, which boils down to solving for the eigenvalues and eigenvectors of the covariance matrix of a scalar that varies in space and time
A tide gauge, and a barotropic model, we identified a wind-driven nonseasonal barotropic fluctuation of the Canadian inland seas (CIS) that is correlated with the North Atlantic Oscillation (NAO) (Figs. 2–6)
Anomalous inflows and outflows, which are reflected in spatially averaged changes in sea level and bottom pressure over the CIS, are driven by wind stress over Hudson Strait (Fig. 7), probably through a wind setup, and the northern North Atlantic Ocean (Fig. 8), possibly communicated by means of wave mechanisms
Summary
Direct measurements of the baroclinic boundary current by a moored current array deployed in Hudson Strait reveal that the outflow through Hudson Strait is responsible for a substantial portion of the fresh water supplied to the Labrador Current and the North Atlantic Ocean (Straneo and Saucier, 2008a) This region is of interest in the context of changes ongoing in the Arctic system (White et al, 2007). Drometric data indicate strong interannual changes in Hudson Bay streamflow along with a marked shift in the seasonality of river discharge (Déry and Wood, 2004; Déry et al, 2011) It remains unclear whether the subsurface waters of the CIS have undergone change. The remainder of this paper is organized as follows: in Sect. 2, we describe and contrast the observational data; in Sect. 3, we describe the ocean model, comparing it to the available observations as well as output from a higher-resolution ocean/sea-ice model, and use it to understand the leading mode of nonseasonal behavior of the CIS; in Sect. 4, we summarize and discuss our results
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