Observation of the circulation in the Newfoundland Basin in winter 1997

A hydrographic survey was performed in January-February 1997 to document th e winter circulation of the North Atlantic Current system in the Newfoundla nd Basin, as part of the Fronts and Atlantic Storm Tracks Experiment (FASTE X). Eighty-seven conductivity-temperature-depth (CTD) stations were occupie d along a four-section trapezoid, which spanned the "Northwest Corner'' and the branching of the North Atlantic Current along 35 degreesW. Realistic s ea surface temperature analyses were produced every 15 days, using all avai lable data collected in this area during the two months of the FASTEX exper iment. These maps were combined with sea level anomaly fields from the TOPE X/Poseidon and ERS-2 satellites at the same time intervals to analyze the f eatures of the main currents in the area and their evolution. These combine d analyses, providing a coherent overview of the fronts and jets identified along the ship track, and the CTD stations are further used to estimate th eir transports. The general pattern is a 15 Sv (Sv equivalent to 10(6) m(3) s(-1)) transport by the North Atlantic Current at 47 degreesN, 43 degreesW , the existence of a recirculating gyre inside the Northwest Corner, and a complex branching of the circulation associated with significant surface fr onts. The recirculating gyre forms a closed circulation, in which a very de ep warm eddy, 100 km wide, was sampled at the end of February: its mixed la yer was 800 m deep and its transport was 27 Sv. Along 35 degreesW, three fr onts were identified between 45 degrees and 52 degreesN: the Northern Subar ctic Front, the Southern Subarctic Front, and the Mid-Atlantic Front, whose origins are precisely located. The currents associated with these fronts t ransport 26 Sv toward the east before crossing the Mid-Atlantic Ridge and s upplying the eastern part of the North Atlantic basin. An important transpo rt (14 Sv) was calculated near 46 degreesN, 37 degreesW, which mostly fed t he current associated with the Mid-Atlantic Front.