Is there a north‐south phase shift in the surface Labrador Current transport on the interannual‐to‐decadal scale?

Abstract

The transport of the Labrador Current has substantial interannual‐to‐decadal variability that may significantly impact the ocean climate and marine ecosystem off Atlantic Canada and Northeast United States. Nevertheless the alongshore coherence of the Labrador Current on the interannual‐to‐decadal scales has been a long standing question. Here we have used satellite altimetry data to study interannual‐to‐decadal variability of the unit‐depth surface Labrador Current in the past two decades, in the context of the subpolar gyre of the North Atlantic. The study for the first time reveals that the transport over the Labrador and northeastern Newfoundland Slope is out of phase with that over the Scotian Slope. The surface Labrador Current transport is positively and negatively correlated with the winter North Atlantic Oscillation (NAO) index (with the transport lagging by about 1 year) in the north (the Labrador and northeastern Newfoundland Slope) and in the south (the Scotian Slope), respectively. In addition, the surface Labrador Current transport declines over the Labrador Slope and northeastern Newfoundland Slope and increases over the Scotian Slope. The north‐south phase shift suggests two distinct regimes, which warrants further studies of underlying dynamic mechanisms and may have important implications for regional ecosystems and climate.