Satellite altimetry has provided a unique contribution to the global observation of mesoscale variability, one of the dominant signals in the ocean circulation. In this context, we will briefly review past studies showing the impact of merging up to four altimeter missions which can be critical for a proper recovery of the mesoscale. We will also show that the agreement between altimetry and independent in situ data is significantly improved when four satellites are merged. However, satellite altimetry alone only provides surface information. Thus, in the second part of the talk, we will focus on the combination of several satellite remote-sensors with in-situ observations with the aim of analyzing the 3-D variability. Particular attention will be devoted to the estimation of vertical motion associated with mesoscale oceanic features, which is of fundamental importance for the exchanges of heat, fresh water and biogeochemical tracers between the surface and the ocean interior. Unfortunately, direct measurements of the vertical velocity are difficult to obtain for usual values (order 10's m/day). Instead, it can be inferred from a 3D snapshot of the density field by assuming a few simplifications in the quasi-geostrophic (QG) formulation. We investigate the feasibility of diagnosing vertical velocity combining glider profiles of temperature and salinity with satellite altimetry data. We will conclude the presentation by showing the first results of SINOCOP, a multiparametric experiment carried out along the north-western coast of Mallorca Island (Western Mediter-ranean). The general goal of this experiment was to develop new methodologies to estimate the 3-dimensional state of the ocean using a multi-sensor observational approach combined with numerical modelling. Observations included coastal and deep gliders, drifters, standard CTDs and remote sensing (altimetry, sea surface temperature and ocean colour). Preliminary results show that the multi-sensor sampling strategy allowed investigating small scale filaments and eddies associated with the Balearic Current, the main oceanographic feature of the area. Moreover, comparisons reveal that altimeter gridded products do not have sufficient resolution for the detection of small mesoscale (20-100 km) and submesoscale (< 20 km) features present both in the glider fields as well as in the drifter data. This highlights the need of synergetic approaches through the combined use of observing systems at several spatial/temporal scales, with the aim of better understanding (sub)mesoscale signals.

Peer Reviewed