On dense water formation criteria and their application to the Mediterranean Sea

Recently proposed criteria to identify sites, periods and characteristics o f dense water formation in the Mediterranean Sea are analyzed. These criter ia were first obtained through tank experiments and numerical and theoretic al analyses. They can be useful for discriminating between processes that r each the sea bottom and those involving only the less thick superficial lay ers. With these criteria, general characteristics of newly formed dense wat er can be inferred from a knowledge only of winter density stratification g ', of the buoyancy increase B due to the violent winter storms, and of the horizontal space scale R of the region of interest, a quantity usually iden tified by a decrease of 0.5-1 degrees C of the SST. For the Mediterranean S ea, these criteria are applied here to the few known field observations and to more indirect "routine" information, namely climatological values of th e stratification, numerical estimates of the buoyancy flux and remotely sen sed SST from satellite imagery. In this way a. stimulating picture of these dramatic phenomena is obtained, giving some insight into the possibility o f forecasting and into other characteristics of dense water formation proce sses. (C) 1999 Elsevier Science Ltd. All rights reserved.