UPPER OCEAN THERMOHALINE, OXYGEN, NUTRIENT, AND FLOW STRUCTURE NEAR THE DATE LINE IN THE SUMMER OF 1993

An overview is given of the upper ocean geopotential height, zonal flo w, thermohaline, oxygen, and nutrient structures between the Bering Se a and Fiji islands, based on high-resolution field measurements along 179 degrees E. The geopotential topography is dominated by large-ampli tude (2-4 J kg(-1)) mesoscale perturbations in the subarctic and subtr opical gyres and a smoother equatorial ridge-trough system. The fastes t midlatitude zonal flows (40 cm s(-1)) are associated with the Alaska Stream, the Subarctic Current, the Kuroshio Extension, and the North Equatorial Current. Prominent physical and chemical frontal zones are observed between 42 degrees-45 degrees N and 12 degrees-15 degrees N. A pronounced upwelling dome is found south of the Aleutians, which bri ngs dense, nutrient rich waters within 125 m of the sea surface. Well- defined upwelling domes also occur in the northern (5 degrees-10 degre es N) and southern (3 degrees-8 degrees S) doldrums. El Nino condition s prevailed near the equator in August 1993, marked by surface tempera tures of 30 degrees C, low salinities, low nutrient concentrations, ea stward surface flow (30 cm s(-1)), merging of the North Equatorial Cou ntercurrent and Equatorial Undercurrent (50 cm s(-1)), absence of trad e winds and abundant rainfall, and southward displacement of the South Equatorial Countercurrent (20 cm s(-1)). The South Equatorial Current (20 cm s(-1)) has a complex multicore structure and is accompanied by a major physical and chemical frontal zone between 13 degrees-16 degr ees S. A fast coastal eastward jet is observed on the north slope of V anua Levu island; Fiji.