Since the early 1990s, satellite altimeters have been used to measure sea surface height (SSH) from space. The SSH maps generated have widespread use among the scientific and operational oceanography and climate science community including monitoring the global mean sea level and El Niño Southern Oscillation, predicting hurricane intensification, tracking large scale eddies and oceanic fronts, and estimating ocean circulation, among others.

Up until now, these altimeters have been monitoring SSH at mesoscale. The spatial resolution of the SSH maps has been evolving from ~300 km in the 1990s to ~100 km at present. However, SSH measurements at even higher resolution are necessary for effectively monitoring the vertical transport of heat and carbon within the ocean, which is of utmost importance to study global climate change and readily realized by the newly launched Surface Water Ocean Topography (SWOT) satellite.

The animation shows first the total sea surface height (SSH) using the ECCO 1/24th deg simulation daily SSH maps. It shows that the surface of the ocean is not perfectly flat. The height of the sea surface has highs (red) and lows (blue) like the Earth landscape as it reacts to the atmospheric pressure on the surface at large scales. It is also affected by ocean internal tides. The ripples shown in the animation above reveal internal gravity waves happening below the ocean surface. The hills and valleys are associated with the ocean circulation and eddies transporting heat, nutrients, tracers, and marine debris. These features are not captured at resolutions higher than 1 degree (current altimeters) become visible in the 15-km resolution maps (that are captured by SWOT).

These small-scale ocean features become more visible from the anomaly field (deviation from time mean) that the animation shows as a ‘bump’ on the surface. These small scale features (eddies and internal waves) are associated with strong vertical velocity in the ocean interior below the surface (seen in the animation in the section of the ocean: blue for downward and red for upward).

Dataset NameProcessing
Level
Start/StopFormatSpatial ResolutionTemporal
Resolution
MEaSUREs Gridded Sea Surface Height Anomalies Version 22054 to PresentNETCDF-40.17 Decimal Degrees x 0.17 Decimal DegreesDaily - < Weekly
SWOT Simulated Level-2 KaRIn SSH from MITgcm ECCO LLC4320 for Science Version 12 to PresentNETCDF-42000 Meters x 2000 Meters