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The tides play a crucial role in global oceanic mixing, but our understanding of global tidal transports is limited. However, for the past twenty years, magnetic signals produced by ocean tides have been detectable in satellite magnetometer data from satellites like Swarm or CHAMP. In this study, researchers demonstrate how satellite magnetometer observations can be used to directly determine global ocean tidal transports. Unlike other methods, this approach relies on minimal constraints from numerical models.

The movement of electrically conducting materials within the Earth’s magnetic field generates an electromagnetic field through induction. This applies to oceanic currents and tidal motions as they occur within the geomagnetic field. By extracting tidal magnetic (TM) signatures from direct measurements of the Earth’s magnetic field, researchers can detect and analyze the magnetic signals associated with tidal currents. These signals are crucial for geomagnetic modeling and can also provide information about the spatial distribution of conducting materials, such as in the deeper mantle.

Using electromagnetic signals from the ocean to derive information about ocean properties and transports is highly desirable. Previous studies have heavily relied on numerical ocean models or limited local measurements, resulting in high uncertainties. However, recent advancements in global satellite electromagnetic fields have enabled the estimation of oceanic heat content variations using tidal magnetic variations.

Understanding tidal currents from satellite magnetometer observations has broader implications beyond Earth. The possibility of liquid salty oceans on icy moons around Jupiter and Saturn has led to discussions on detecting these oceans and estimating their properties through electromagnetic induction processes. This involves observing the electromagnetic response of the oceans as they move through the ambient magnetosphere of their respective planets.

To derive tidal transports from satellite magnetometer observations, the researchers combined the Kalman Filter algorithm, used in the Kalmag geomagnetic field model, with x3dg, a 3D electromagnetic induction solver. The Kalman Filter algorithm allows for sequential assimilation of data, while x3dg provides an accurate estimation of the magnetic response to the inducing field. With this approach, tidal transports can be estimated directly from satellite magnetometer data without relying on specific oceanographic forward models.

By expanding the Kalmag data assimilation, the researchers were able to constrain tidal oceanic transports using major tidal constituents such as M2, N2, and O1. This approach has the potential to improve our understanding of global tidal transports and their impact on oceanic processes.

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