A Method of Stacking AltiKa Repeat Cycle Data that May Reveal 75,000+ Possible Small Seamounts

Abstract

AbstractThe SARAL AltiKa radar altimeter measured sea surface height along ground tracks that were regularly revisited by repeating cycles. We devised an automated method of “stacking” the repeat cycles that aligns them to common positions along a model track, selects segments that pass quality criteria, removes the non‐geoidal height and height error from each repeat profile, and calculates the median height profile. This procedure reinforces geoid signals while reducing measurement noise and height signals produced by ocean dynamics. A seamount detection filter applied to the median profiles reveals 75,208 possible small seamounts along AltiKa ground tracks globally. Of these, 4824 are located over multibeam surveys. Seamount heights estimated by subtracting regional depths from the multibeam depths follow a Poisson statistical distribution that suggests at least 84% are less than 2 km tall. A 1 km along‐track sampling of the stacked repeat cycles is available from the National Centers for Environmental Information (NCEI) data repository.