Variability of Salinity in the North Atlantic Using High Resolution Data Set that Combines Argo and Satellite Altimetry Data

Up to recent years, the study of salinity and freshwater distribution changes was hampered by the lack of temporal and spatial resolution of the observations, so that salinity anomalies could up to now only be studied by averaging over 5 years. With the onset of the Argo program, the temporal and spatial resolution of salinity and temperature profiles since early 2000 have significantly improved. The subpolar North Atlantic is one of the most densest sampled regions in order to cope with the large seasonal to internannual variability and strong mesoscale features (eddies, meanders). Despite this effort, the spatial and temporal coverage is not sufficient to identify salinity variations in detail. By combining Argo profiles with altimetry data a “Transfer function”, the Gravest Empirical Mode (GEM), can be calculated. The GEM technique exploits the relationship between T/S profiles and dynamic height in order to parameterize temporal and spatial high-resolution salinity data as a function of dynamic height from the satellite altimetry. This technique gives us the opportunity to extend the investigation of the salinity variability, with extremely high temporal (daily) and spatial (1/4°) resolution, back to 1993, the beginning of the altimetry data. This method was tested on several regions of the North Atlantic and it works particularly well for those regions where the North Atlantic Current plays an important role. Within these regions, salinity variability over the first 700 m is analyzed. The salinity fields are used together with the freshwater fluxes of the updated HOAPS 3.3 climatology to study short- and long-term changes. Results from this analysis will help us to better understand the role of freshwater fluxes and shift of the subpolar front on the interannual variability of salinity.