THE NORTHEAST PACIFIC-OCEAN RESPONSE TO THE 1982-1983 EL-NINO

The ocean's response to atmospheric forcing and to forcing along the coast by Kelvin waves is examined in light of nearshore seasonal variability and the major 1982-1983 El Nino. In addition to driving the northeast Pacific gyre and local currents, the wind modifies the depth to the main thermocline, changing the apparent westward phase speed of Rossby waves excited by passing Kelvin waves. The amplitude of the passing Kelvin wave detemines whether the Rossby wave depresses or raises the thermocline while propagating westward. Along the northeast Pacific coast from Oregon to Washington, model results suggest that the wind raises the main thermocline during the 1982-1983 El Nino. Generally, the coastal response off Oregon and Washington appears to be strongly driven by the large-scale atmosphere, while along the California coast and south to the equator, the dominant El Nino signal has an oceanic origin. -from Authors