Search

Sentinel‐3 A&B radar altimeters yield sea surface height measurements in both a high‐precision Synthetic Aperture Radar Mode (SARM), and a Pseudo‐Low Resolution Mode (PLRM). We stacked repeat cycles from both missions and in both modes to compare their resolution of small seamounts. Stacking entailed removing non‐geoidal heights and height errors, testing for consecutive measurements over ocean, aligning to common locations at 1 km intervals along a synthetic track, and forming a median height profile. These profiles are available from the National Centers for Environmental Information (NCEI) data repository. Global maps show that, over the oceans, the median height is usually derived from more than 49 cycles, and the typical error in an individual PLRM measurement is approximately 1.9 times greater than an individual SARM measurement. We applied a seamount detection bandpass filter to the median profiles and compared their spectral resolution to that of the Satellite for ARgos and AltiKa (SARAL) AltiKa mission. Small seamounts are similarly resolved by Sentinel‐3 A&B SARM data and by the SARAL/AltiKa data. Key Points: An automated method of stacking Sentinel‐3 sea surface height data is documentedSentinel‐3 A&B Pseudo‐Low Rate Mode (PLRM) non‐geoidal noise and stacked height noise is 1.9 times that of Synthetic Aperture Radar Mode (SARM)Sentinel‐3 A&B SARM and PLRM median sea surface height profiles are available from the National Centers for Environmental Information [ABSTRACT FROM AUTHOR]

The 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. Plain Language Summary: Our automated method of combining and processing sea surface height data collected by the AltiKa satellite that revisited the same ground tracks over time may reveal more than 75,000 possible small seamounts globally, and resolves seamounts down to 720 m tall. These detections may be useful for seamount census studies and for attempting to identify seamounts that may pose hazards to submarine navigation. The combined satellite profile data are available for download from the National Centers for Environmental Data (NCEI) data repository. Key Points: Automated method of stacking altimeter sea surface height data reinforces signal from small seamounts while reducing noiseSeamount detection filter applied to stacked data profiles may reveal 75,208 possible small seamounts along AltiKa ground tracks globallyUnfiltered stacked sea surface height profiles are available from the National Centers for Environmental Information data repository [ABSTRACT FROM AUTHOR]