A CENSUS OF EDDIES OBSERVED IN NORTH-ATLANTIC SOFAR FLOAT DATA

SOFAR floats that looped in discrete eddies were studied in order to m ap and describe the distribution and characteristics of eddies in the North Atlantic. One hundred eighteen individual looping float trajecto ries (loopers) were identified, each consisting of two or more consecu tive loops. Each looper was interpreted to be in a discrete eddy, and its characteristics were estimated from the float trajectory. The high est percentage of loopers occurred at 700m in the Newfoundland Basin, where roughly half of the float data were in loopers, mostly cyclones. In the Gulf Stream region, approximately 20% of the float data record ed at 700m were in loopers, again mostly cyclones. Overall, 21% of 700 m data and 6% of 2000m data were in loopers. The fastest swirl speeds, >40cm s-1, were in cyclones south of the Gulf Stream (most of which w ere in Gulf Stream rings), but numerous swift -35cm s-1 anticyclones w ere found there too. Swirl velocity decreased with depth, to roughly h alf as swift at 2000m as at 700m for three eddies in the Sargasso Sea measured simultaneously with floats at these two depths. In the wester n North Atlantic, the average swirl velocity of cyclones and anticyclo nes was the same. Translation velocity of eddies was generally westwar d to southwestward at a few cm s-1. The mean translation velocity of 3 9 eddies in the Sargasso Sea was uBAR = -2.8 +/- 0.4cm s-1, vBAR = -0. 4 +/- 0.4cm s-1. Many of these were located just south of the Gulf Str eam in the region of its recirculation and were probably advected by a westward current there. Near the Gulf Stream and along its extension in the Newfoundland Basin, eddies were often advected downstream with speeds up to 15-20cm s-1 and eddy trajectories were often complicated. South of 30-degrees-N and near the western boundary, 700m eddies were advected northwestward and 1300m and 2000m eddies southeastward by bo undary currents there. Numerous energetic anticyclones were observed s outh of the Gulf Stream; one was tracked for 430 days and its properti es well measured. The formation of these eddies has not been documente d, but they are inferred to have formed near and by the Gulf Stream an d to consist of a thick layer of 18-degrees-C water lying above a depr ession in the thermocline. Analogous anticyclones were observed in the Newfoundland Basin seaward of the Gulf Stream extension there.