Sea ice drift and its relationship to altimetry-derived ocean currents in the Labrador Sea

Abstract

Low frequency sea ice drift variability and its oceanic and atmospheric forcing are investigated for the Labrador Sea over the period 1979-2002. Our objective is to separate the ocean forced component of ice drift in order to corroborate the changes in the subpolar gyre circulation found by Häkkinen and Rhines (2004). The atmospheric and oceanic forcing components can be approximately separated by comparing the time series resulting from an Empirical Orthogonal Function (EOF) analysis of sea ice motion with local sea level pressure gradients and altimetry-derived oceanic velocities. The first ice motion EOF is found to be associated with wind driven ice drift. The second mode is associated with oceanic forcing, because its time series is similar in its fluctuations to the oceanic velocities derived from altimetry. These two data sets confirm a major weakening of the subpolar ocean circulation between the early 1990s and the latter 1990s.