Seasonal and Interannual Variability of the West Greenland Current System in the Labrador Sea

摘要

Using various types of in situ data combined with air-sea flux and satellite altimetry data products, I studied the variability of both the boundary current system and the eddies of the Labrador Sea, and their influence on the restratification of the interior on seasonal to interannual time scales. The analysis presented here supports previous theoretical studies that argue that lateral fluxes, driven by the boundary current/interior exchange, play an important role in setting the properties of the interior. I found that both components of the boundary current, the surface West Greenland Current and the subsurface Irminger Current, exhibit considerable seasonal and interannual variability. My analysis suggests that the seasonal changes in velocity are primarily due to changes in the boundary current/interior properties (i.e. in the baroclinic geostrophic flow) while the interannual variability, and especially the observed slowdown of the subpolar gyre, is due to changes in the velocity of the entire water column (the barotropic flow). The interior heat content variability is set by both the surface and lateral fluxes, and, indeed, the latter dominate in some years - when anomalies in the boundary current flow and properties, propagating in from upstream, result in an anomalous convergence of heat into the Labrador Sea.