Regional circulation patterns of Mediterranean Outflow Water nearthe Iberian and African continental slopes

Abstract. The Mediterranean Outflow Water (MOW) is a dense water mass originated in the Gibraltar Straight. After exiting the Gulf of Cadiz, the MOW forms a reservoir region west of the Iberian continental slopes with a buoyant depth of approximately 1000 m depth. This region is a key role as the main centre where the MOW is mixed and distributed into the North Atlantic. The seafloor in this area is characterised by the presence of a complex bathymetry with three abyssal plains separated by mountain chains. Despite of this topographic features does not reach the surface, they influence ocean flows at intermediate and deep ocean layers conditioning the distribution and circulation of MOW. The CMEMS IBI ocean reanalysis is used to provide a detailed view of the circulation and mixing processes of MOW near the Iberian and African Continental slopes. This work emphasizes the relevance of the complex bathymetric features defining the circulation processes of MOW in this region. The high resolution of the IBI reanalysis allows to make a description of the meso-scale features forced by the topography. The temperature, salinity, velocity, transport, and vorticity fields are analysed to understand the circulation patterns of MOW. The high-resolution circulation patterns found reveals that Horseshoe Basin and the continental slope near Cape Ghir are key areas controlling the mixing processes of MOW with the surrounding waters mases, mainly North Atlantic Central Water (NACW), and Antarctic Intermediate Water (AAIW). The water masses variability is also analysed by means of composite analysis, results indicate the existence of a variability of the MOW tongue which retracts and expands westwards in opposition to the movement of the underlying North Atlantic Deep Water.