The mean surface circulation of the North Atlantic subpolar gyre: A comparison of estimates derived from new gravity and oceanographic measurements

Abstract

A new mean sea surface topography (MSST) is used to estimate the surface circulation of the subpolar gyre of the northwest Atlantic. The MSST is produced using a new geoid model derived from a blend of gravity data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission, satellite altimeters, and terrestrial measurements. The MSST is compared with a topography produced by an ocean model which is spectrally nudged to a new Argo period temperature and salinity climatology. The mean surface circulation associated with the geodetic MSST is compared with estimates of the circulation from surface drifters, moorings, and other in situ measurements. The geodetic MSST and circulation estimate are found to be in good agreement with the other estimates, both qualitatively and quantitatively. The topography is found to be an improvement over an earlier geodetic estimate with better resolution of the coastal currents. Deficiencies are identified in the ocean model's estimate of flow over shelf regions.