Surface ocean currents on the Southwestern Atlantic Continental Shelf from Altimetry datasets

Surface ocean currents inferred from satellite altimetry are a key tool for observing large-scale ocean circulation; however, their performance over continental shelves remains challenging due to issues associated with conventional altimetry and global processing strategies. Several recent developments in gridding methods, combined with the increased spatial resolution enabled by the Surface Water Ocean Topography (SWOT) mission, present new opportunities for enhancing current estimates in coastal and continental shelf regions.

In our study, we investigated the mean and seasonal circulation over a 10-year period on the Southwestern Atlantic Continental Shelf using several altimetry-based datasets, including the freely available Copernicus Marine Environment Service (CMEMS) gridded product and newly generated regional datasets specifically adapted to shelf dynamics, as well as output from the GLORYS12v1 numerical model. The resulting circulation patterns are evaluated in the context of previous studies to identify common features and discrepancies among datasets, as well as the influence of recent methodological advances. Differences in the structure and seasonality of the dominant along-shore currents emerge clearly when analyzing cross-shelf transects, partly supplemented by in-situ data from Acoustic Doppler Current Profiler (ADCP) data.

Despite their limited availability to date, we also investigated experimental gridded products that incorporate SWOT observations. Considering the study's findings, the SWOT-induced gridded dataset demonstrates an enhanced ability to resolve small-scale circulation, resulting in higher variability in the ocean currents, and underscores the importance of high-resolution altimetry in representing surface currents over the study region.