Eddies in the Labrador Sea as Observed by Profiling RAFOS Floats and Remote Sensing

Abstract

Data from profiling RAFOS floats, TOPEX/Poseidon altimetry, and the alongtrack scanning radiometer (ATSR) aboard ERS-1 have been used to describe the spatial and seasonal patterns of eddy variability in the Labrador Sea. Peaks in sea surface height (SSH) variability appear in two regions: off the west Greenland shelf near 61.5°N, 52°W where the 3000-m isobath separates from the shelf, and in the center of the basin at 58°N, 52°W. Both locations show seasonal ranges in SSH variability of up to 40 mm, with the Greenland site, having largest variability in January–March, leading the central site by 50 days. A sea surface temperature image from the ATSR at the Greenland site shows numerous eddies, both cyclonic and anticyclonic, being formed by injection of West Greenland Current water into the Labrador Sea interior. Data from profiling RAFOS floats launched in 1997 as part of the Labrador Sea Deep Convection Experiment are used to describe three of the West Greenland Current eddies in detail. One of the sampled eddies was anticyclonic, while the other two were cyclonic. The eddies contained various mixtures of Irminger Sea Water. Peak azimuthal velocities ranged from 22 to 42 cm s⁻¹, and diameters from 20 to 50 km. Although the floats were at a depth of 375 m, the surface elevations derived from cyclogeostrophy agreed with those obtained from TOPEX/Poseidon. The temporal and spatial patterns in SSH variability are thought to be caused primarily by seasonal variations in the strength and stability of the West Greenland Current and, less likely, by eddy formation following deep convection in the basin interior.