New insight into the ocean mesoscale field at the Nordic high latitudes

The Norwegian Atlantic Current contributes fundamentally to the temperate climate of northwestern Europe and maintains an ice-free ocean well into the Barents Sea even in winter. The interaction between the two branches of the Norwegian Atlantic Current is not known in detail but is generally understood to be mediated by mesoscale eddies. In particular, the Lofoten Basin appears as a hot-spot of mesoscale activity in several studies in the literature, based on conventional altimetry. While satellite altimetry has made a fundamental contribution to our understanding of ocean circulation, the current constellation of nadir altimeters does not allow for resolving the spatial and temporal scales characterizing the intensification and dissipation of the mesoscale features. The Surface Water and Ocean Topography (SWOT) mission, based on Ka-band Radar Interferometry (KaRIn), extends the capability of existing nadir altimeters to two-dimensional mapping of the ocean surface at an unprecedented spatial resolution. The fast-sampling phase (1-day repeat) of the mission also allowed for resolving the temporal evolution of mesoscale eddies. The Lofoten Basin is located in an area where the SWOT tracks cross, which was sampled twice a day over 90 days in 2023. Building on this unique opportunity, the results presented in this work rely on both the fast-sampling and science (21-day repeat) phases of the SWOT mission to show a comparison of KaRIn retrievals with conventional altimeters and characterize the representation of the mesoscale field emerging from the different altimetry concepts.