Gravity field signatures of ocean dynamics

Henryk Dobslaw, Robert Dill, Maik Thomas
GeoForschungsZentrum Potsdam, Section 1.5: Earth System Modelling, Potsdam, Germany

The vastness of the world's ocean together with the water's opacity for large fractions of the electromagnetic spectrum renders the open seas one of the most undersampled parts of the Earth's system. In analogy to satellite altimetry, continuous observation of the ocean's time-variable gravity field are providing a globally homogeneous picture of ocean bottom pressure, that in principle can be used as a proxy to transfer information to areas and times not properly covered by in-situ measurements.

However, instantaneous observations of ocean mass anomalies are primarily affected by ocean tides and barotropic currents caused by atmospheric wind and pressure forcing. The spatial and temporal variability of these non-periodic variations will be reviewed by means of data from a recent version of the Ocean Model for Circulation and Tides (OMCT), which currently provides the marine part of the GRACE atmosphere-ocean de-aliasing product.

Assuming a sufficiently accurate reduction of these barotropic signals from the satellite observations, gravity observations can be used to infer more subtle dynamic quantities. By means of simulated data, it will be discussed how oceanic mass signals connected to changes in thermocline depth on shallow continental shelfes are generated. The spatial and temporal extent of the associated gravity signals will be assessed and related to potential contaminations due to leakage effects from near-by continental sources as simulated by a global hydrological model.