Abstract Sea Surface Salinity (SSS) is investigated south of Greenland using products derived from satellite radiometric data at pixel resolution: the weekly CCI SSS+ V4.4 dataset from the Climate Change Initiative (CCI) for 2010–2022 and a higher temporal resolution dataset, CATDS-HR, for 2015–2022. These are compared to quality assured in situ measurements. Both satellite data products reveal large positive biases on the shelves. The CCI product removes more data on the Greenland shelves and underestimates variability in this region by almost twice as much as CATDS-HR. In contrast, in regions with low SSS variability in the central North Atlantic subpolar gyre, satellite salinity products overestimate variability by 40% (0.17 instead of 0.12 pss, Practical Salinity Scale), due to uncertainties of about 0.14 pss in SSS retrievals. Nevertheless, there, CATDS-HR is 10% closer to in situ data than CCI-V4. In regions with high SSS variance, farther than 100 km from the Greenland coast, the two products capture significant seasonal and interannual SSS variability of salinity, resolving variability at 50 km length scales. Both satellite products and in situ data from 2010–2022 indicate that the freshest water in the eastern Labrador Sea occurred in September-October 2021. Then, the satellite products show a larger than 2 pss drop in SSS over the slope, and still over 1 pss 300 km further offshore, lagging behind the variability near the shelf break. This suggests that satellite SSS products contribute to resolve freshwater exchange from the shelves to the ocean interior, albeit adjustments are needed on the shelves closer to Greenland to adequately correct for systematic biases.
Reverdin et al. (Tue,) studied this question.