Study of fine-scale dynamics in the Balearic Sea through high-resolution observations and SWOT satellite data

Abstract

The Surface Water and Ocean Topography (SWOT) satellite mission was launched in December 2022 by NASA/CNES and is considered a major breakthrough in ocean observation from space. It is expected to measure the elevation of the Earth’s surface water with a spatial resolution one order of magnitude higher than present altimeters (between 15 and 30 km), providing an unprecedented view of mesoscale dynamics [1, 2, 3]. The FaSt-SWOT project is the Spanish contribution to the validation of SWOT data. The main goal of FaSt-SWOT is to integrate SWOT measurements with in-situ observations from two high-resolution multi-platform experiments and advanced data-assimilative models to characterize fine-scale (10-100 km) dynamics and quantify the associated horizontal and vertical transports [4]. During the initial fast-sampling phase from January to July 2023, the Balearic Islands region in the Western Mediterranean Sea was chosen for SWOT validation. SWOT gathered high-resolution sea surface height (SSH) measurements on a daily basis as part of this validation effort [3]. The two FaSt-SWOT experiments were specifically designed to collect multi-platform in-situ observations within the swath of the SWOT satellite, focusing on the area around the Balearic Sea during the validation phase. Both campaigns (Figure 1) took place in April and May 2023 and involved the simultaneous use of various ship-based instruments (CTD, Moving Vessel Profiler (MVP), thermosalinograph, Acoustic Doppler Current Profiler (ADCP), GoPros), autonomous platforms (surface drifters and gliders), and satellite observations (SST, ocean color, altimetry). These campaigns brought together a unique multidisciplinary expertise in physical oceanography, satellite remote sensing, in-situ monitoring, numerical modelling and deep learning methods. Satellite observations were used to identify the structures of interest to be sampled during the FaSt-SWOT experiments [5]. Within the domain of the swaths of the SWOT, the location of the sampling was defined based on the presence of a remarkable smallscale eddy detected in SST imagery just before the start of the first campaign (Figure 2). Therefore, the context was ideal to analyze SWOT capability to detect such small structures. This presentation will provide an analysis of the multi-platform data collected during the FaSt-SWOT experiments, including shipbased observations, and measurements from autonomous platforms such as the drifters and gliders. Moreover, a first glance at SWOT data in the region of the Balearic Sea, as well as a preliminary analysis of the dynamics of the area of study and of the eddy, will be provided.