Abstract
Sparse distribution of depth soundings in the ocean make it necessary to
infer depth in the gaps using alternate information such as
satellite-derived gravity and a mapping from gravity to depth. We design
and train a neural network on a collection of 50 million depth soundings
to predict bathymetry globally using gravity anomalies. We find the best
result is achieved by pre-filtering depth and gravity in accordance with
isostatic admittance theory described in previous predicted depth
studies. When training the model, if the training and testing split is a
random partition at the same resolution as the data, the training and
testing sets will not be independent, and model misfit results will be
too optimistic. We solve this problem by partitioning the training and
testing set with geographic bins. Our final predicted depth model
improves on old predicted depth model rms by 16%, from 165 m to 138 m.
Among constrained grid cells, 80% of the predicted values are within
128 m of the true value. Improvements to this model will continue with
additional depth measurements, but higher resolution predictions, being
limited by upward continuation of gravity, shouldn’t be attempted with
this method.