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Abstract

Global ocean circulation generates large-scale secondary electromagnetic signals, which provide a potentially interesting source of information about the oceanographic system. Radial magnetic fields caused by the movement of conductive seawater through Earth's magnetic field are, in principle, observable in geomagnetic satellite observations such as magnetometer data from the current Swarm mission. However, contrary to magnetic signals induced by tides, the signals resulting from ocean circulation have not been identified yet. Recently, the detectability of these ocean circulation-induced signals was investigated within an observing system simulation experiment using a Kalman filter-based approach. In this approach, the crucial separation from other magnetic contributions is achieved by predefining the temporal behavior of the oceanic component using presumed estimates. We applied this approach to real Swarm magnetometer observations and determined a scale factor for various a priori assumed ocean circulation-induced magnetic fields through the assimilation. Furthermore, we evaluated the outcomes in terms of identifying magnetic signals caused by ocean circulation for the first time in geomagnetic satellite observations. We present and discuss the evaluation of these results and report on the detectability of magnetic fields induced by ocean circulation in Swarm satellite observations.