Absolute geostrophic current from merged altimetry data (year 2016)

The Gulf Stream is one of the most famous, and most studied ocean currents. B. Franklin did the first scientific map of it in 1769, and from then on the interest has never faltered.
However, contrary to what the B. Franklin’s map (and the very name of it) could led to believe, the Gulf Stream is not a steady and straight “stream”. It is a turbulent, moving, flow with meanders, eddies detaching (and attaching) quite rapidly.

Altimetry provides with the ocean surface topography, with gridded Duacs maps produced for every day. Knowing the topography in two dimensions in turn enable to compute the surface “geostrophic” currents, i.e., the ocean circulation generated by the balance between the horizontal pressure gradient forces exerted by water masses and the effect of acceleration due to the Earth’s rotation. Geostrophic currents are computed from the gradient of the surface slopes, at least outside an Equatorial band (see Duacs derived products ), and provided in the Duacs files.

The animation shows the absolute geostrophic current modulus over the year 2016 for the Gulf of Mexico-Gulf Stream area. Eddies are frequently detaching from the main current.