FY 1984

Upper ocean current and temperature observations along the equator west of the Galapagos Islands before and during the 1982–83 ENSO Event

Halpern, D.

In Papers from the 1982–83 El Niño/Southern Oscillation Data Display Workshop, NOAA/AOML, U.S. Government Printing Office, Miami, FL, 3–4 November 1983, 59–91 (1984)

Current and temperature time series measurements made within the uppermost 250 m at two sites (190°30W and 95°W) on the equator in the eastern Pacific west of the Galápagos Islands provide a limited description of the response of the upper ocean thermal and flow fields to the 1982-83 Southern Oscillation event. The 1982-83 El Niño episode involved dynamical variations to at least 250 m; changes found at 100 m were as dramatic as those in the surface layer. The 1982-83 El Niño was remarkable in many ways. The thermocline sank 100 m; the temperature at 100 m, which normally is ~15°C, reached 27.5°C; the time rate of change of the 15-200 m heat content was 500 W m during the August-December 1982 warming phase and -460 W m during the January-February 1983 subsurface cooling phase; the normally westward flowing near-surface South Equatorial Current was much reduced in strength during the August-December warning phase and for several months the 15 m currents were eastward with speeds of about 0.25 m s; and, the Cromwell Current, normally considered to be a permanent feature of the circulation, disappeared during the subsurface cooling phase. The correspondences between our observations and those made by Firing (Firing et al., 1983) at 159°W and by Wyrtki (1983) at Christmas Island and Galápagos Islands are briefly reviewed.