Interannual and Decadal Sea Surface Height Variability Over the Northwest Atlantic Slope

Abstract

The Northwest Atlantic continental slope features strong interactions among the western boundary currents of the subpolar and subtropical gyres, and, thus, the sea-level variability over the slope may be an indicator for the large-scale ocean circulation. In this study, temporal and spatial sea-level variability in the Northwest Atlantic continental slope has been investigated based on a satellite altimetry dataset and a temperature and salinity dataset. The altimetric results from 1993 to 2012 are compared with steric height anomalies relative to 1500 m, calculated from the temperature and salinity dataset. This study shows significant interannual and decadal sea-level variability, with prominent regional differences and varying linkages to large-scale atmospheric and oceanic variability in the North Atlantic. Both the altimeric and steric height anomalies in the western Labrador Sea are negatively correlated with the winter North Atlantic Oscillation (NAO) index primarily via wintertime deep convection. The altimetric height anomalies in the Laurentian Fan have a weak (insignificant at the 95% confidence level) positive correlation with those in the Labrador Sea, while the steric height anomalies have a negative correlation. The thermosteric (halosteric) height anomalies in the Labrador Sea are negatively (positively) correlated with the winter NAO index, while those in the Laurentian Fan are not correlated with the winter NAO index. The along-slope differences in the interannual and decadal variations of the sea surface height anomalies imply that there is an interior pathway of the southward-flowing Labrador Sea intermediate water toward the central North Atlantic basin before reaching 55 ˆN.