The North Atlantic Current


  • W. Krauss


Based on trajectories of satellite-tracked buoys and hydrographic sections, both Dietrich's and Worthington's schemes of the North Atlantic Current are reconsidered. Ninety satellite-tracked buoys have been analyzed in order to distinguish between these schemes. Neither could be confirmed. The North Atlantic Current appears as a superposition of a broad west wind drift and a frontal jet in the western part of the North Atlantic north of 40°N, which becomes independent from the subtropical gyre. Neither a permanent branching, suggested by Dietrich, nor a confinement of the subpolar gyre to the east of Newfoundland (per Worthington) can be found. The North Atlantic Current extends over the entire North Atlantic, carrying more than 20 sverdrups (Sv) toward the north. This northward transport is mainly due to the northward flow around Flemish Cap and a sudden turn of the North Atlantic Current east of the Mid-Atlantic Ridge. The buoy tracks have been used to determine speed and direction in the upper layers (≤ 100 m). We combine these results with hydrographic data in order to obtain an estimate of the mass transport. Transport across the Mid-Atlantic Ridge is based on recent sections (Fahrbach et al., 1985), while transport in the northeastern North Atlantic has been derived from the Erika Dan sections at 53.5°N and 59.5°N. According to these two sections, the return flow occurs mainly below 1000 m after water mass conversion in the northern areas. The results imply that about 7 Sv of Atlantic water are transformed into deep water in the area between 53.5°N and 60°N.