GULF-STREAM FLOW-FIELD AND EVENTS NEAR 68-DEGREES-W

The SYNoptic Ocean Prediction (SYNOP) experiment was designed to provi de an accurate understanding of the energetic mesoscale processes in t he Gulf Stream. The Central Array measured velocity and temperature th roughout the water column, with horizontal extent large enough nearly to span the meander envelope and Eulerian mean structure of the jet at 68 degrees W. The 55- to 70-km mooring spacing resolved mesoscale edd y interactions with the Gulf Stream, and the 26-month duration allowed stable estimation of long-term mean fields. Six steep meander troughs propagated into or developed within the array, each lasting around 30 -60 days, thus impressing a small mean trough near 68 degrees W in the predominantly eastward currents at jet level (1000 m and above). At t he deep level (3500 m) the mean how was southwest at the shoreward sit es shallower than 4300 m, but it flowed cyclonically around a mean low -pressure anomaly affecting all the deeper offshore sites. The eddy ki netic energy per unit mass (E(K)) decreased by a factor of about 2.5 w ith each depth increment from 400 to 700 to 1000 m but was only a fact or of 2 smaller at 3500 m than at 1000 m. Values of E(K) in the upper central jet (400 m) were 100 to 230 mJ kg(-1) and were 4-13 mJ kg(-1) at 3500 m. Overall, E(K) in the upper 1000 m at 68 degrees W was highe r than previously published values at 55 degrees W. Two extended case studies of meander propagation through the array demonstrate the devel opment and intensification of deep cyclonic and anticyclonic hows bene ath the Gulf Stream. The cyclonic how at 3500 m, associated with ampli fying meander troughs, often exceeded 0.35 m s(-1), which was much lar ger than the typical 0.05 m s(-1) deep mean velocities.