Ole baltazar Andersen (DTU Space, Denmark); Bjarke Nilsson (DTU Space, Denmark)

The recently launched Surface Water Ocean and Water Topography (SWOT) mission provides Sea Surface Height (SSH) observations over a 120 km wide swath at 2 km resolution. This presents a unique opportunity to map the mesoscale and submesoscale ocean dynamics that are not currently resolved by conventional altimetry. The aim of this project is to produce high resolution maps of the SSH field that are consistent in time and space along the East Greenland coast. From the SSH field, geostrophic currents and relative vorticity can be derived and used to study the mesoscale (20km-200km) and submesoscale (200m-20km) dynamics developing in the East Greenland Current (EGC) and along the Polar Front. The submesoscale is associated with vertical exchanges of nutrients, heat, and carbon, and is thus particularly important for understanding the effects of the warming and freshening the region is experiencing due to climate change. Because of its location at high latitudes, the study area benefits from small Rossby number and short satellite revisit time. However, in the period between November and June a large part of the East Greenland shelf is covered by Arctic sea ice that has been transported south by the EGC. To overcome the problem of limited altimetry observations in these months, SWOT data in the marginal ice zone will be exploited by masking individual ice floes. The linear Optimal Interpolation (OI) methods traditionally used on conventional altimetry is not able to fully exploit the high-resolution content of the SWOT observations because the decorrelation time of the small-scale dynamics are much smaller than the satellite revisit time. Thus, a Dynamical Optimal Interpolation (DOI) method based upon conservation of potential vorticity in a quasi-geostrophic framework is applied to assimilate SWOT and conventional altimetry data. The spatial resolution is significantly increased compared to the DUACS products which are based on OI of conventional altimetry data. Moreover, the coverage is significantly increased in coastal and sea-ice covered areas. The capability of the DOI method of capturing mesoscale and submesoscale features will be validated with Sea Surface Temperature (SST) data. This project illustrates how combining high resolution SWOT data with a dynamic model can increase both the accuracy and the spatial and temporal resolution of SSH mapping.