Topic Area

Project Team Member(s)

ENS Jason Deloyd Gipson, USNR
 
 

Major Findings

Subsurface, anticyclonic, submesocale eddies, called Meddies, are a major contributor of salt into the Atlantic Ocean, especially for the maintenance of the Mid-Atlantic Salt Tongue. Meddies are formed from the complex flow of waters entering and exiting through the Straits of Gibraltar; where cool North Atlantic water flows into the Mediterranean and warm, more dense, and saline rich water flows out, under the incoming flow. Anticyclonic vortexes associated with Meddies form through the frictional flow along the Iberian Peninsula. Transiting northwest along the coast of Portugal at a speed of 2-5cm/sec, Meddies eventually propagate southwestward due to anticyclonic shear and interaction with the southward flow of the stronger Canary Current.

Mean lifespan of Meddies is 2-3 years at a rate of 8-12 formed Meddies a year and an upward of 27 Meddies existing at anyone given time. Meddy decay depends heavily on topographic interactions with seamounts, most notably the Great Meteor Seamounts. Catastrophic destruction from sea mounts contributes up to 90% of Meddy death. Meddy decay is also associated with interactions with other meddies and friction. Meddies that do not transit through the Great Meteor Seamounts can exist up to 4-5 years before interacting with elements and weak frictional forces in the western Atlantic.

Meddy propagation south westward is greatly effected by Meddy interaction with the mean flow of the Canary Current and Subtropical Gyre. Due to its small horizontal size, propagation of Meddies by Rossby Wave mechanisms is not higly likely, but has been hypothesized. Meddies also undergo thermohaline mixing as they propagate southwestward, contributing large amounts of salt to the Great Meteor Seamounts after catastrophic Meddy destruction.

References

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

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

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

Fratantoni, D. M., Meddy Collisions with Topography, Woods Hole Oceanographic Institution, http://science.whoi.edu/users/dfratantoni/Meddy/meddy_index.html.