Ierapetra gyre pops in and out

Image of the month - February 2007

Ierapetra gyre is re-appearing in July 2004 after a period when it was missing. Between October 2004 and May 2005, it migrates first South-Westerly (October 2004 - January 2005), then South-Easterly (January 2005 - May 2005), to finish by interacting and disappearing in the current South of the basin.

 

A new gyre created in July 2005 follows a different pasth. Between September 2005 and July 2006, it circles anticyclonically in an area 25-27°E and 33.5-35°N, and finish by merging with a new Ierapetra gyre born in July 2006 at the South-East of Crete. (Credits CLS/MFS)

The Ierapetra gyre is a Mediterranean oceanic feature that pops up more or less regurlarly. This anticyclonic gyre (turning clockwise, since it is in the Northern hemisphere) forms as a result of wind interactions with the relief on Crete and of ocean circulation in the Kasos strait (Image of the Month, June 1999, An eddy blown by the wind). When it exists, it is visible as a "hill" on the ocean topography.

Since 1993, this gyre appeared -- or not -- depending on the periods. Between 1993 and 2001, it is clearly visible (which enabled to study its creation and evolution over several years); it disappeared in 2002, to reappear in July 2004. Since then, its activity is very similar to the one observed between 1993 and 2001: a marked seasonal cycle, with a maximum intensity in September/October.

 

The Ierapetra gyre formed in July 2006 is still visible today (2007/01/27) on Sea level anomalies and Sea surface temperature (AVHRR) maps  (Credits CLS/MFS, CLS)

Long-term monitoring of phenomena such as this Ierapetra gyre allows to better understand ocean circulation and its variations. By continuing the observations, we will better know the variations spanning over periods of several years.

See also:

Websites on this subject:

  • MFS project: Mediterranean Forecasting System

References:

  • Hamad N., Millot C., Taupier-Letage I., 2006, The surface circulation in the eastern basin of the Mediterranean Sea, Scientia Marina 70 (3), 457-503
  • Horton C., Clifford M., Schmitz J., Kantha L.H., 1997, A real time oceanographic nowcast/forecast system for the Mediterranean Sea, J. Geophys. Res. 102, 25123-25156.
  • Larnicol G., Ayoub N., Le Traon P.-Y., 2002, Major changes in the Mediterranean Sea level variability from 7 years of TOPEX/Poseidon and ERS-1/2 data, J. Mar. Sys. 33-34, 63-89
  • Pujol M.-I., 2006, "Analyse de la variabilité de surface en Méditerranée à partir des données altimétriques et comparaison aux simulations MERCATOR et MOG2D", These de l'Universite Paul Sabatier, Toulouse III.