GLOBAL SEAFLOOR TOPOGRAPHY FROM A LEAST-SQUARES INVERSION OF ALTIMETRY-BASED HIGH-RESOLUTION MEAN SEA SURFACE AND SHIPBOARD SOUNDINGS

Abstract

We present a new worldwide $1/16°× 1/16°$ map of seafloor topography computed from an iterative inversion combining altimetry measurements of the marine geoid and shipboard echo soundings from the global National Geophysical Data Center (NGDC) database. The input geoid data for this computation are derived from altimetry measurements of the sea-surface height from the ERS-1 Geodetic Mission, and the Geosat, ERS-1 and Topex-Poseidon Exact Repeat Missions. To calculate the seafloor topography from sea surface height measurements, it is necessary to take the regional isostatic compensation of the topographic load into account. For that purpose, we consider a model of elastic flexure of the oceanic lithosphere in which the elastic plate thickness increases with crustal age. With the solution, we provide an uncertainty map that reflects the uneven distribution of and errors in the data, and uncertainties in the model parameters, as well as the increase of the geopotential error with the deepening of the seafloor. The bathymetric solution is compared with the Smith & Sandwell's (1997, Science, 227, 1956-1962) solution. The root mean square difference between the two amounts to 350 m. However the two maps agree within 150 m over 65 per cent of the ocean surface.