Soon after it leaves Cape Hatteras, the Gulf Stream transport increases to values in excess of 150 SV, over five times that of the Flordia Current and what is necessary for the interior Sverdrup balance. Little is known about the structure of the recirculation regime responsible for the transport increase or the nature of its variability. Altimeter measurements at the sea surface suggest that the spectrum of variability is brood, encompassing rapid, possibly barotropic shifts in the Gulf Stream with time scales of order a month or less, to annual and interannual variations, which may be both barotropic and baroclinic, the latter associated with the field of mass. We propose to investigate this range of time scales by combining repeated shipboard measurements of the Gulf Stream, mainly using XBT and acoustic Doppler sections, with satellite infraed images and GEOSAT altimeter data. The shipbopard measurements will provide some estimates of the rapid variability of the Gulf Stream system and its vertical structure to depths of 800 m with special emphasis on a line from the continental shelfff south of the Cape Cod to Bermuda. Inverse calculations combining varying subsets of the shipboard data can assess the degree to which the rapid mode of variability affects resulting solutions for mass budgets of the region. Two cruises are envisioned, each of 17-day duration, at times of the year when the Gulf Stream reaches its climatological exetrmes of position and transport. Together with the altimeter data, each cruise will provide an independent estimate of the surface geoid along a track coincident with the GEOSAT altimeter as well as the three dimensional structure of the Gulf Stream system at the time of the cruises. The altimetric measurements will be used to extend the spatial and temproal sampling from the cruises to encompass scales of meanders and annual/interannual variability. The methods employed are analogous to those envisioned for the Topography Experiment for Ocean Circulation (TOPEX and French POSEIDON) and in situ data during the World Ocean Circulation Experiment (WOCE).
