SEA-SURFACE TEMPERATURE-CHANGES IN THE NORTHEASTERN PACIFIC-OCEAN DURING THE PAST 20,000 YEARS AND THEIR RELATIONSHIP TO CLIMATE-CHANGE IN NORTHWESTERN NORTH-AMERICA

Modern ocean-atmosphere interactions in the northeastern Pacific Ocean have a significant effect on the climate of the west coast of North A merica. We present radiolarian microfossil-based temperature reconstru ctions for the eastern North Pacific spanning the past 20,000 yr to ex amine possible correlations and linkages between continental climate c hange and changes in sea surface temperature (SST) in the northeastern Pacific Ocean on millennial time scales. The reconstructions indicate that the regional pattern of ocean circulation off the west coast of North America was further south 15,000 cal yr B.P. than it is today, a nd reached its present location 13,000 cal yr B.P. The North Pacific D rift and Transition Zone were further south as a result of a more sout herly North Pacific high pressure cell. prior to 13,000 cal yr B.P. Wh ile two continental paleoclimate records from northwestern North Ameri ca show regional differences, they also can be correlated to the SST c hanges. A coastal site at 48 degrees N shows similar patterns in summe r temperatures, as observed in offshore marine records of SSTs. Howeve r, an inland continental record seems to reflect more-regional-scale c hanges in sea surface conditions showing a thermal maximum centered at 10,000 cal yr B.P which is observed in the marine transect south of 4 2 degrees N. We conclude, based on the pattern of oceanographic change as reflected in radiolarian assemblages, that changes in the past lat itudinal position of the North Pacific Drift played a significant role in controlling continental climate immediately to its east, as it doe s in the present environment. We also conclude that during the past 20 ,000 yr much of the evolution of oceanographic change is related to th e migration of the atmospheric pressure cells (the North Pacific high and Aleutian low) of the northeastern Pacific. (C) 1996 University of Washington.