A modelling study of the 1976 climate regime shift in the North Pacific Ocean

Around 1976, the North Pacific Ocean underwent a climate regime shift, with significant biological consequences. To model the changes in the ocean, an ocean general circulation model was forced by the wind stress and sea surf ace temperature monthly climatology of the 1952-1975 period in one numerica l experiment and the 1976-1988 period in another. Changes in the ocean mode l between the two experiments revealed how the ocean might have changed und er the 1976 climate regime shift. In winter, the intensified post-1976 Aleu tian Low spun up the subarctic gyre and the subtropical gyre, except in the Gulf of Alaska, where the circulation weakened. Upwelling was generally en hanced in the subarctic and downwelling enhanced in the subtropical region, with temperature changes down to 600 m. In the post-1976 period, the merid ional heat transports were also enhanced: poleward in the low latitudes, eq uatorward in the midlatitudes, and poleward in the high latitudes.