OC4331-Mesoscale Oceanography
Final Project Summary

Topic Area

Meddies

Project Team Member(s)

LT Paula Hildebrand, USN

LT Chris Gabriel, USN

 

Major Findings

Anticyclonic, subsurface eddies are formed when the Mediterranean Undercurrent, originating from the Mediterranean Sea, departs from its path along the south coast of Spain near Cape St. Vincent, in the Iberian Basin. Approximately 17 eddies are formed per year. The eddies are typically 30-160km in diameter, 500-1500m thick, and centered at 1000m below the surface. Meddies are characterized by high salinity (1-2psu) and high temperature (2-4° C) anomalies. Translational speed is approximately 3.0cm/sec, and rotate at approximately 30cm/sec.

The lifespan of a meddy relies heavily on its interaction with the Azores Current, other meddies, and bottom topography. Meddy trajectories can alter and be altered by the Azores Current. Meddies have also been shown to coalesce with other meddies. Approximately 70% of all meddies interact with seamounts, which can lead to a loss in energy and temperature. In some cases, the interaction with a seamount can lead to a steady decline, or more likely a catastrophic destruction of the meddy. Those meddies that avoid interaction can be shown to translate across the North Atlantic Ocean, into the Sargasso Sea.

Meddies also undergo thermohaline mixing during their lifespan, and play an important role in the salt and heat distribution of the North Atlantic Ocean. Interaction with seamounts can lead to significant alterations of the local salt and heat distributions, which in turn can play a part in the overall shape of the Mediterranean salt tongue.

 

References

Prater, M.D., and Sanford, T.B., A Meddy off Cape St. Vincent, Part I: Description, Journal of Physical Oceanography, 24, 1572-1586, 1993.

Richardson, P.L., et al, Tracking Three Meddies with SOFAR Floats, Journal of Physical Oceanography, 19, 371-383, 1988.

Richardson, P.L., and Tychensky, A., Meddy trajectories in the Canary Basin measured during the SEMAPHORE experiment, 1993-1995, Journal of Geophysical Research, 103, 029-046, 1998.

Richardson, P.L., et al, A census of Meddies Tracked by Floats, Manuscript, 1999.