A high resolution salinity time series 1993–2012 in the North Atlantic from Argo and Altimeter data

Abstract

AbstractThe study of salinity changes has been hampered by the lack of temporal and spatial resolution of the observations. In order to improve the spatial and temporal distribution of salinity observations, we used the Gravest Empirical Mode (GEM) technique to calculate high‐resolution salinity distributions as a function of dynamic height for the period 1993–2012. This technique combined Argo and altimeter data to exploit the relationship between T/S profiles and dynamic height in the North Atlantic. The method was valid in the upper 700 m mainly at and near the pathways of the North Atlantic Current (NAC), but failed in regions with weak stratification or with ambiguities in the T/S relationships. Coherent, multiannual large‐scale variability was observed, with many features present in all regions, albeit with weaker amplitudes in the eastern basins. Some of the interannual features in the northeastern Atlantic basins were unrelated to the variability further south and west, pointing to an occasional advection of subtropical water in the eastern Atlantic. Origin and advection of salinity anomalies with the NAC from the North American Basin into the western subpolar North Atlantic are correlated with the state of the North Atlantic Oscillation (NAO) and dampened by the surface freshwater fluxes. Other mechanisms influencing the salinity pattern are the changing location of the subpolar front, also related to the NAO. The large multiyear variability in the 20 year time series obscured any potential trends caused by global warming. Only the Rockall Trough showed a salinity increase of 0.03 per decade.