The magnetic sea

Seawater is a conductor and therefore its motion in the Earth’s magnetic field leads to the induction of weak currents and low intensity magnetic fields. The magnitude of the fields induced is of the order of a few nanotesla. The fields are larger near the surface of the ocean than at greater depths due to the higher velocity of water near to the surface.

Violent magnetic storms can amplify the effect, inducing oceanic magnetic fields of around 100 nT that concentrate near coasts. Satellite observation of the magnetic fields created by the motion of seawater can be used to study the movement of tides at different depths and to understand the flow of energy through the oceans, which can provide information on climate change.