Wide-swath satellite altimetry and novel subsurface temperature observations improve predictions in a dynamic western boundary current: System optimization and performance

Abstract. Understanding and predicting regional and coastal ocean dynamics requires the effective combination of numerical models and observations that resolve key processes at suitable time and space scales. Fine-scale oceanic features and the ocean's complex subsurface structure remain a significant source of uncertainty in coastal and regional models due to lack of observations at necessary scales. Recently available observation platforms provide an unprecedented view of the ocean's fine-scale structure both at the surface (the Surface Water and Ocean Topography satellite mission, SWOT) and below the surface (using data from the Fishing Vessel Observation Network, FVON). Here we use advanced data assimilation to demonstrate the impact of these novel observation types on dynamic ocean state estimates in an eddy-dominated western boundary current region, the East Australian Current. First we show that these newly available observations benefit from an updated data assimilation configuration. Using this improved configuration, we show that the inclusion of SWOT data improves model representation of both the ocean surface across scales and of subsurface temperature (as observed by FVON). Assimilating FVON data, which drastically increases subsurface information in the coastal and shelf region, significantly improves subsurface temperature representation. Using novel observations from SWOT and FVON in a realistic ocean model, we show enhanced representation of ocean structure, particularly below the surface, essential for improved ocean forecasts and projections.