A Mediterranean tour

Image of the month - March 2002

This month, Aviso is bringing you several images in one with a guided tour of some of the oceanographic "curiosities" of the Mediterranean Sea.

Variability in the Mediterranean between 1993 and 1999. Zones that experienced noticeable variations are in green; the largest variations are in yellow and red. Such variability can be cyclic-essentially seasonal-or more isolated. (Credits CLS/Legos).

Our tour starts in the Strait of Gibraltar, the "mouth" of the Mediterranean. The two eddies in the Alborán Sea appear in the wake of the Strait. These marked seasonal variations occur from year to year.

Eddies in the Alborán Sea intensify in summer and tail off in winter (here in 1993), varying 10 centimeters on average over the year. (Credits CLS/Legos).

Moving further east, we see a zone of intense activity along the Algerian coast. Eddies and meanders in the Algerian Current are among the most turbulent features of the Mediterranean-but some are more stable. Combining measurements from Topex/Poseidon and ERS (or Jason-1 and Envisat) proves particularly valuable in zones like this, making it possible to track eddies for weeks or even months.

South of Italy, in the Ionian Basin, circulation seems to have varied between 1997 and 1999 (see also Mean rise in sea level is only part of the story, Image for March 2001).

Mean sea level anomalies for January 1997 to December 1999. We can see a clear drop in the Ionian Basin, possibly reflecting a change in ocean circulation, which is more cyclonic than during the previous period (January 1993 to December 1996). (Credits CLS/Legos)

Lastly, south-east of Crete we can make out the well-known Ierapetra gyre. This is a feature that does not always show up on cue (see An eddy blown by the wind, Image for June 1999). Winds interacting with the topography of the island are believed to be partly responsible for the gyre. Variations from year to year are thought to be due to the winds and the mid-Mediterranean jet along the coast of North Africa.

The Eastern Basin of the Mediterranean in October from 1993 to 1999. The red zone south-east of Crete is the Ierapetra gyre. (Credits CLS/Legos)

See also:

Websites on this subject:

  • MFSPP project: multi-sensors data in near-real time over the Mediterranean Sea