On the Use of Satellite Altimetry to Detect Ocean Circulation's Magnetic Signals

Oceanic magnetic signals are sensitive to ocean velocity, salinity, and heat content. The detection of respective signals with global satellite magnetometers would pose a very valuable source of information. While tidal magnetic fields are already detected, electromagnetic signals of the ocean circulation still remain unobserved from space. We propose to use satellite altimetry to construct proxy magnetic signals of the ocean circulation. These proxy time series could subsequently be fitted to satellite magnetometer data. The fitted data could be removed from the observations or the fitting constants could be analyzed for physical properties of the ocean, e.g., the heat budget. To test and evaluate this approach, synthetic true and proxy magnetic signals are derived from a global circulation model of the ocean. Both data sets are compared in dependence of location and time scale. We study and report when and where the proxy data describe the true signal sufficiently well. Correlations above 0.6 and explained variances of above 80% can be reported for large parts of the Antarctic ocean, thus explaining the major part of the global, subseasonal magnetic signal. Plain Language Summary Oceans are a crucial part of Earth's climate system. Satellite magnetometers could pose as a unique and valuable source of oceanic information. Unfortunately, magnetic signals of ocean circulation are not jet detected from space. This manuscript proposes to use satellite altimetry as a by-pass to generate characteristic magnetic time series of the ocean circulation. These characteristic time series can subsequently be searched for with satellite magnetometers. If successful, this would allow to observe, for example, changes in the ocean heat budget.