CoAuthors

David Sandwell (UCSD, USA); Sarah Gille (UCSD, USA); Ana Beatriz Villas Bôas (UCSD, USA)

The Ice, Cloud, and land Elevation Satellite 2 (ICESat-2) laser altimetry mission, launched in September 2018, uses 6 parallel lidar tracks with very fine along-track resolution (15 m) to measure the topography of ice, land, and ocean surfaces. Here we assess the ability of ICESat-2 ocean data to recover oceanographic signals ranging from surface gravity waves (wavelengths from 30 m to 1000 m) to the marine geoid (wavelengths > 16 km). We focus on a region in the tropical Pacific and study photon height data in both the wavenumber and space domain. Results show that ICESat-2 can recover the marine geoid at wavelengths > 16 km which is similar to the best radar altimeter data. At some times, the amplitude, wavelength, and propagation direction of surface gravity waves is well resolved by using a combination of the strong and weak beams, which are separated by 90 m. We find higher than expected power in the 3 km to 20 km wavelength band where geoid and ocean signals should be small. This artificial power is caused by the projection of large amplitude, 2-D surface waves from ~300 m wavelengths into longer wavelengths (5-10 km) because of the 1-D sampling along the narrow ICESat-2 profile. Thus ICESat-2 will not provide major improvements to the geoid in the open ocean, although it may be valuable in small bodies of water where ocean swell has low amplitude.