Thermosalinograph devices aboard research vessels and ships of opportunity have been measuring sea surface salinity (SSS) and sea surface temperature (SST) with spatial resolutions much finer than those of satellites. In some regions of the global ocean, the substantial number of observations allows the elaboration of a seasonal climatology of mesoscale and subsmesoscale density gradients. This climatology also provides an estimate of the Available Potential Energy for mixed-layer instabilities and frontogenesis that feed submesoscale motions.

Because submesoscale-permitting ocean models lack observational assessments of their capacity to simulate correctly mesoscale and submesoscale density gradients, this climatology is compared to NEMO outputs ran at 1/60° resolution over the North Atlantic basin. Seasonal variations in temperature and salinity gradients are highlighted, without a seasonality marked on density gradients. As more and more high-resolution observations will become available in the future, we believe that this climatology will become more accurate, while gaining popularity amongst the modelling and observational communities.