Among the many mesoscale eddies found in the northeast Pacific Ocean is a well-developed, anticyclonic baroclinic eddy, situated within a few hundred kilometers of Sitka, Alaska (57°N. 138°W). It has definitely been observed during spring and summer 1958, summer 1960 and summer 1961. Observations made at other times show some evidence of its occurrence also. The trajectories of three NORPAX drifting buoys for April–May 1977 also indicated the probable presence of an eddy there. The eddy, whose diameter ranges from 200 to 300 km and whose depth extends to 100 m and probably to as much as 2000 m, recurs at the same location. The center of the eddy is characterized by the following features: the surface water is less saline and only somewhat warmer than at its periphery; at depths within and below the halocline it is warmer, less saline and contains more dissolved oxygen than at the periphery; and a warm core is situated within the halocline. The halocline is usually depressed by less than 100 m but... Abstract Among the many mesoscale eddies found in the northeast Pacific Ocean is a well-developed, anticyclonic baroclinic eddy, situated within a few hundred kilometers of Sitka, Alaska (57°N. 138°W). It has definitely been observed during spring and summer 1958, summer 1960 and summer 1961. Observations made at other times show some evidence of its occurrence also. The trajectories of three NORPAX drifting buoys for April–May 1977 also indicated the probable presence of an eddy there. The eddy, whose diameter ranges from 200 to 300 km and whose depth extends to 100 m and probably to as much as 2000 m, recurs at the same location. The center of the eddy is characterized by the following features: the surface water is less saline and only somewhat warmer than at its periphery; at depths within and below the halocline it is warmer, less saline and contains more dissolved oxygen than at the periphery; and a warm core is situated within the halocline. The halocline is usually depressed by less than 100 m but...