Atlas of currents and their variability in the mediterranean and canary-iberian-biscay waters

VI Expanding Ocean Frontiers Conference (EOF 2021), 5-7 July 2021
The Canary-Iberian-Biscay and Mediterranean basins are of particular interest for the high anthropic pressure regarding the use of the marine space for navigation, fisheries, aquaculture, and tourism. Just a few numbers, approximately 16% of the global marine trade and 33% of the global oil transportation cross through the Mediterranean. Their neighbour ountries are the destination for 33% of all international tourism. Such accumulation of population is a challenging situation for managing the maritime space from many aspects that go from marine safety issues to ecosystems threats associated with eutrophication, fisheries exploitation, pollutants, and plastics discharges. In facing all these aspects, the information about the surface currents and their variability is of primary importance. The climatological atlases of ocean currents are of great interest to have a first approach on how the flow organization may affect the aforementioned issues as a complementary tool despite the most recent advances in operational oceanography. Still, the well-known pilot charts often used by sailors include currents atlas for routing and navigation. One may see climatology value as the most representative field value for a given location in a given season or month. The determination of the velocity fields from measurements is still a challenging topic of the Earth observation system [Isern-Fontanet et al. 2017]. Nevertheless, operational centres are able today to provide reanalyses of the ocean circulation over the last three decades. We present here an Atlas of monthly climatological currents for the waters in the Canary-Iberian-Biscay and Mediterranean basins built from the latest up-to-date reanalysis for such region [Martínez et al. 2021]. The advances in terms of data collection and time span facilitate the derivation of statistically robust but also representative high-resolution climatological atlas that may be used for operational purposes. The monthly climatological atlas includes surface and subsurfacecurrents and variance matrix at each grid point to provide quantitative information on the variability of currents. The climatological fields are computed using two different current velocity products for the Mediterranean (from altimetry measurements and MEDSEA reanalysis) and one product for the Atlantic domain only based on data (GLOBCURRENT project). Results unveiled important differences between surface (0-1 m.) and subsurface (15-16 m.) currents patterns in both the Atlantic and Mediterranean basin, a fact never discussed in dealing with typical ocean circulation schemes. The differences are significant in summer, in both the Mediterranean and Atlantic waters, showing the non-negligible role of winds [Gerin et al. 2009] even in the climatological value of the ocean currents. Figure 1 illustrates some qualitative examples with true independent data using drifters trajectories extracted from the COSMO database (http//cosmo.icm.csic.es/drifters/). Northern winds mould the east Mediterranean superficial currents in summer (see atlas currents and 4-meters CMOD drifters¿ trajectories in the left upper side of fig. 1). Left lower side of fig.1 shows the winter Atlas currents at the north east of the Iberian Peninsula together with the trajectories of drifters deployed in November 2006 the Cape of Finisterre [García-Ladona et al. 2015] and those deployed in December 2002 [García-Ladona et al. 2005]. Drifters from [Sotillo et al. 2008] also reflect the current towards the south in summer (right hand side of the figure)