Holocene and latest Pleistocene paleoceanography of the northeast Pacific and its relationship to climate change in the Pacific Northwest

Graduation date: 1995Northeast Pacific Ocean sediments were analyzed to determine the past\ud relationship between northeast Pacific sea surface conditions and the climate on the\ud adjacent continent, the Pacific Northwest of North America. Studies of modern\ud ocean-atmosphere interactions demonstrate the significant effect sea surface conditions\ud and atmospheric circulation in the Northeast Pacific Ocean has on the climate of the\ud west coast of North America. Thus, it is likely that past continental climate change\ud can be correlated to changes in sea surface temperature in the northeast Pacific Ocean.\ud We analyzed radiolaria from twelve sediment cores, ranging from 33.62°N to\ud 54.42°N latitude along the west coast of North America to reconstruct past sea surface\ud conditions. Relationships between modern radiolaria and mean annual sea surface\ud temperature calibrate equations used to estimate sea surface conditions for the past\ud 20,000 years. Chronology is controlled by radiocarbon ages from planktonic\ud foraminifera and bulk organic carbon.\ud The reconstructions of sea surface conditions from changes in radiolaria\ud assemblages indicate that the upwelling center off the west coast of North America\ud was further south 15,000 years ago than it is today, and reached its present location\ud 13,000 years ago. We infer that the West Wind Drift and Transition Zone were\ud further south in the latest Pleistocene as a result of a more southerly North Pacific\ud High pressure cell prior to 13,000 years ago.\ud Two Pacific Northwest continental records of paleotemperature are well\ud correlated to the sea surface temperature record the northeast Pacific around 48N\ud latitude, with temperatures increasing over the past 20,000 years. Significant\ud temperature minima and glacial expansions occurred at 13,000 and 4,000 years ago in\ud the records examined, as did a minor minimum at 16,000 years ago. We conclude\ud that changes in the past latitudinal position of the West Wind Drift played a significant\ud role in controlling continental climate immediately to its east, as it does in the present\ud day environment