Mediterranean Outflow and Meddies

Co-PIs: Amy Bower, Lawrence Armi (SIO/UCSD), Isabel Ambar (U. Lisbon), and Phil Richardson (WHOI)

The Mediterranean salt tongue is a prominent feature of the North Atlantic Ocean at mid-depths. The discovery of isolated lenses of salty Mediterranean Water (meddies) in the last decade has challenged the traditional view of this tongue as a purely advective/diffusive feature. The role of these meddies in the salt and heat budgets of the North Atlantic is not well-understood. We studied the dispersion of Mediterranean Water into the North Atlantic via meddies and other processes. In 1993-1994, we seeded the Mediterranean Undercurrent near its source with Lagrangian drifters. Forty-nine RAFOS floats were launched sequentially in the Mediterranean Undercurrent south of Portugal and tracked for up to 11 months. Our specific objectives to date have been 1) to identify the most important meddy formation site(s); 2) to make the first direct estimate of the frequency of meddy formation; 3) to document the pathways of meddies and their life histories; and 4) to determine the pathways by which Mediterranean Water which is not trapped in the meddies enters the North Atlantic. The trajectories of floats caught in meddies are easily recognizable due to the persistent and rapid anticyclonic motion associated with these features. As a result of this study, we advanced our understanding of how Mediterranean Water enters the subtropical gyre of the North Atlantic.