Ocean CIRculation from ocean COLour observations (CIRCOL)

The monitoring of the oceanic surface currents is a major scientific and socio-economic challenge. Ocean currents represent one of the fundamental elements that modulate natural and anthropogenic processes at several different space and time scales, from global climate change to local dispersal of tracers and pollutants, with relevant impacts on marine ecosystem services and maritime activities (e.g. optimization of the ship routes, maritime safety, coastal protection). An appropriate monitoring of the oceanic currents must rely on high frequency and high resolution observations of the global ocean, which are achieved using satellite measurements. At present, no satellite sensor is able to provide a direct measurement of the ocean currents – The indirect and synoptic retrieval of the large-scale geostrophic component of the sea-surface motion is given by satellite altimetry at a spatial (~100km) and temporal (~one week) resolution which is not sufficient for many applications, even more in semi-enclosed basins as the Mediterranean Sea where the most energetic variable signals are found at relatively small scales. In this context, the objective of the CIRCOL (Ocean Circulation from Ocean Colour Observations) project is to improve the retrieval of altimeter-derived currents in the Mediterranean Basin combining the largescale, altimeter-derived geostrophic currents with the high-resolution dynamical information contained in sequences of satellite-derived surface Chlorophyll (Chl) observations. The project will be implemented in two phases.

During Phase 1, an Observing System Simulation Experiment (OSSE) based on CMEMS (Copernicus Marine Environment Monitoring Service) physical and biogeochemical models will be implemented to investigate the potentialities of the proposed approach for the improvement of the altimeter derived currents.

During Phase 2, the optimal Chl-based reconstruction of the sea-surface currents will be implemented using the satellite-derived multi-sensor, L4 (gap-free) altimeter and sea-surface Chl for the Mediterranean Sea distributed by CMEMS. The resulting products will be validated against in-situ velocity measurements (drifting buoys, HF radar).