Abstract
Seamounts are isolated elevations in the seafloor with circular or
elliptical plan, comparatively steep slopes, and relatively small summit
area (Menard, 1964). The vertical gravity gradient (VGG), which is the
curvature of the ocean surface topography derived from satellite
altimeter measurements, has been used to map the global distribution of
seamounts (Kim & Wessel, 2011). We used the latest grid of VGG to
update and refine the global seamount catalog; we identified 10,796 new
seamounts, expanding the catalog by 1/3. 739 well-surveyed seamounts,
having heights ranging from 421 m to 2500 m, were then used to estimate
the typical radially-symmetric seamount morphology. First, an Empirical
Orthogonal Function (EOF) analysis was used to demonstrate that these
small seamounts have a basal radius that is linearly related to their
height – their shapes are scale invariant. Two methods were then used
to compute this characteristic base to height ratio: an average Gaussian
fit to the stack of all profiles and an individual Gaussian fit for each
seamount in the sample. The first method combined the radial normalized
height data from all 739 seamounts to form median and median-absolute
deviation. These data were fit by a 3-parameter Gaussian model that
explained 99.82% of the variance. The second method used the Gaussian
function to individually model each seamount in the sample and further
establish the Gaussian model. Using this characteristic Gaussian shape
we show that VGG can be used to estimate the height of small seamounts
to an accuracy of ~270 m.