1. Scripps Institution of Oceanography, La Jolla, CA 92093, USA.
2. EarthByte Group, School of Geosciences, University of Sydney, New South Wales, Australia.
3. Laboratory for Satellite Altimetry, National Oceanic and Atmospheric Administration (NOAA), College Park, MD 20740, USA.
4. European Space Agency/European Space Research and Technology Centre, Keplerlaan 1, 2201AZ Noordwijk, Netherlands.