High Spatial Resolution Mesoscale Oceanic Variability from Non-repeat Satellite Altimetry

Satellite altimetry has revolutionized our understanding of ocean processes, yet the spatial resolution of sea surface height maps is generally limited by the wide spacing between repeat tracks (e.g., 300 km for the Topex/Jason series and 80 km for the ERS/Envisat/SARAL series). Here we supplement these standard measurements with non-repeat altimeter data from Geosat, Jason-1/2, Cryosat-2, and SARAL/Altika to improve the spatial resolution of ocean surface variability maps. We focus on the 12-600 km wavelength band. Two-pass waveform retracking is performed on all the data to reduce the noise due to ocean waves in the 15-45 km wavelength band. Each profile is then differentiated along-track to form sea surface slope (SSS), and the best mean SSS model is removed to reveal SSS anomalies. The profiles are then filtered over several bands (15 – 25 km, 25 – 50 km, 50 – 100 km, 100 – 200 km, 200 – 300 km and > 300 km). Slope variability maps constructed from the longer-wavelength bands (200 – 300 km and > 300 km) show the usual mesoscale variability signals associated with the western boundary currents and the Antarctic Circumpolar Current. The most interesting results come from the maps constructed from the shorter wavelength (< 100 km) components of SSS. In many cases, the SSS variability is correlated with the bathymetry of continental margins, seafloor spreading ridges, and transform fault valleys. We find several examples where short-wavelength SSS anomalies emerge at sharp continental margins and dissipate over the rugged bathymetry of the slower spreading ridges. Our findings provide insight into the detection of balanced mesoscale and sub-mesoscale signals from the forthcoming Surface Water and Ocean Topography (SWOT) mission, which is expected to resolve the sea surface height at 15 km wavelengths.