Inversion of GEOHALO aerogravimetry to infer ocean bottom topography: application to the Tyrrhenian, Ionian and Adriatic seas

Abstract

A detailed and precise knowledge of ocean bottom topography is essential in many geoscientific and oceanographic applications. Shipborne echo sounding provides the only direct bathymetric method. However, even after decades of applying this technique only a fraction of the global ocean could be covered. Alternatively, gravity data inversion is a feasible method to infer ocean bottom topography since the gravity field correlates with topography at short to medium wavelengths. Gravity field observables are globally provided by dedicated satellite missions like GOCE, GRACE and GRACE-FO and, over the oceans, by satellite altimetry. Regional and local measurements are realised by means of ground-based, shipborne and airborne gravimetry. For the first time in Europe a jet aircraft was used for airborne gravimetry. During the GEOHALO flight campaign over Italy and the Tyrrhenian, Ionian and Adriatic seas in June 2012, the German research aircraft HALO carried an entire suite of geodetic-geophysical instrumentation, including gravity metres. The careful processing of the gravity data acquired by the CHEKAN-AM instrument of the German Research Centre for Geosciences allowed to achieve an accuracy at the mGal level. Subsequently, the Parker-Oldenburg inversion was applied to predict ocean bottom topography along the GEOHALO profiles flown over the ocean. To constrain the parameter space in the inversion we used the Crust1.0 model. Finally, the obtained results were compared to the General Bathymetric Chart of the Oceans in order to estimate the performance of the method. Our study demonstrates that airborne gravimetry aboard a jet aircraft is capable to provide valuable data for regional geoscientific studies.