Overview of Fine-scale Multiplatform Experiments in the Southwest Mediterranean Sea: Lessons Learnt in the Last Five Years

This study is a review of recent high-resolution multiplatform experiments performed in the SouthWest Mediterranean Sea with the goals of (1) improving our understanding of submesoscale dynamics and interactions at the mesoscale and (2) identifying advances and limitations of present and future altimetry constellations. After a brief overview of AlborEx, a multi-disciplinary process study conducted in the eastern Alboran Sea in 2014, we will present an evaluation of Sentinel-3A. An experiment was undertaken in the Algerian Basin in May 2016, employing an ocean glider and a ship mission with ADCP, along the same track and synchronous with an overpass of the Sentinel-3A mission. This provided three independent views of the ocean velocity field, along a section that encompassed three different oceanographic regimes. The results demonstrate the capacity of Sentinel-3A to retrieve fine-scale oceanographic features (~20 km). The intercomparison with in situ platforms showed a significant improvement, order 30% in resolution and 42% in velocity accuracy using a synthetic aperture radar mode with respect to lower-resolution mode of conventional altimetry. In addition, the three-platform view provided valuable insight into the variability of evolving oceanographic features, in an area of the Mediterranean that remains chronically under sampled. A summary of the results of IRENE, carried out in July 2017 in the Almeria-Oran front, will be also presented. IRENE is a pilot experiment of CALYPSO, a new Office of Naval Research (ONR) Departamental Research Iniative that aims to advance the state of science for theoretical, observational and numerical understanding of vertical transport on a range of scales. In the second part of the presentation, we will focus on the PRE-SWOT cruise, which will take place in May 2018 in the southern region of the Balearic Islands onboard R/V García del Cid. PRE-SWOT aims at anticipating the daily high-resolution 2D SSH fields that SWOT will provide during the fast sampling phase after launch in selected areas of the global ocean; one of them being the region around the Balearic Islands. Special attention will be devoted to separate the scales typically resolved by the present altimeter gridded products compared to the scales that will be observed by SWOT and lead the observations of vertical transports associated with finescale features. In situ systems, including gliders, drifters, CTD, ADCP, and water samples, will be used in synergy with satellite data and modeling simulations to determine physical and biochemical ocean variability. This experiment will contribute to the preparatory SWOT cal/val activities and will be coordinated with the French BIOSWOT cruise. We will conclude with the lessons learnt during the last 5 years in terms of advantages and limitations of synergetic approaches combining satellite altimetry with other cutting-edge and well established observational techniques and numerial modeling. Future directions of research will be also addressed.