Journal club

are normally used to measure the amount of water that sinks and how fast it does so, but generating such data from satellite readings would provide more complete coverage. Marine Herrmann of the CNRS in Toulouse, France, and her colleagues have gone some way towards this by comparing satellite measurements of sea-surface elevation for the years 1994–2007 to a simulation of the Western Mediterranean Deep Water convection. Sea level is always lower where convection takes place. Herrmann’s study shows that it is sufficiently so off the southern coast of France (and by implication, many other sites around the world) for altimetry measurements to determine year-on-year convection changes.