Observations of a warm-core eddy off Oregon, January to March 1978

Abstract

Abstract Observations from a zonal array of current meters moored across the continental margin off central Oregon, CTD sections along the array, and a satellite infrared radiometer image all show the presence of a warm-core eddy off Oregon in January and February 1978. The satellite image, the current vectors, and the dynamic height profiles give consistent estimates of the eddy size (100 km) and position. The eddy penetrated deep into the water column (down to more than 800 m) but not to the bottom. The water in the core of the eddy was significantly warmer and more saline than surrounding water of the same density, implying it had been carried northward from a more southern origin. The eddy center apparently moved northward and offshore from a position over the 800-m isobath at 44°50′N on 5 January to a position beyond the 2000-m isobath at 45°25′N on 6 March. The eddy may have originated on the seaward flank of an unusually strong northward coastal current. Hydrographic data available for other winters suggest that such eddies are unusual off Oregon. Although the moored array was maintained between October 1977 and September 1978, the strong currents associated with the eddy and its persistent presence for at least 2 months dominated the overall estimates of the mean alongshore flow.