Abstract
Seamounts can be habitats and hazards to submarine navigation, and their
distribution reveals the volcanic history of the oceans. As only a few
percent of ocean floor has been sounded, seamount distribution must be
mapped by satellite altimetry. Wessel (doi:10.1029/2000JB000083) looked
at data from an earlier generation of altimeter technology and suggested
that all seamounts 2 km and taller had been found, but there might be as
many as 50,000 seamounts between 1–2 km tall that were not yet found.
The AltiKa altimeter delivers more precise sea level measurements at a
higher along-track sampling rate than previous altimeters. These data
resolve small seamounts not previously resolvable (Smith,
doi:10.1080/01490419.2015.1014950), particularly if repeat-track
profiles are “stacked” and band-pass filtered (Marks and Smith,
doi:10.1007/s11001-016-9293-0). These two studies looked at only a few
isolated locations where multibeam acoustic depth sounding surveys were
available for “ground truth” for tuning a band-pass filter to detect
the small seamount geoid signal. In the new work we present here we have
stacked 32 repeat cycles of SARAL AltiKa data world-wide, and band-pass
filtered the stacks, to yield 75,208 potential seamount locations
distributed between +/- 81.5 latitude throughout the global ocean. These
locations are detected as local maxima in the filtered geoid at least 2
cm above background and with a full-width at half-maximum (FWHM) at
least 4 km wide. Of these, 4824 detections were over multibeam surveys.
We assign a proxy seamount height to each by subtracting the regional
SRTM30 depths from the multibeam depths. These proxy heights follow a
Poisson statistical distribution similar to that which fits acoustic
bathymetry profiles over seamounts (Jordan et al.,
doi:10.1029/JB088iB12p10508). We are currently investigating how to
derive proxy heights from anomaly amplitude and FWHM, optimizing the
trade-off between false negative and false positive detections, and
whether it is possible to identify potential seamounts that may pose
hazards to submarine navigation.