Direct correlation of millennial-scale changes in western North American vegetation and climate with changes in the California current system over the past ∼60 kyr

Abstract

Terrestrial (pollen) and marine climate proxies from seven sediment cores taken on the continental margin of western North America between 32° and 43°N show systematically related short-term changes superposed on Milankovitch-scale oscillations of the past 60 kyr. During oxygen isotope stage 3, brief warming events in California and Oregon appear correlative with interstadial events in waters offshore, as do the rapid climate oscillations of the last glacial transition (∼14∼ 10 ka). Estimated temperature depression of the coastal lowlands ranges from >10°C in southern California to ∼5°C in Oregon during the last glacial. The absence of long-distance migration of Pacific coastal plant assemblages concurs with marine evidence that southward movement of the polar front during the last glacial maximum was limited. Correlative changes in terrestrial and marine ecosystems imply that broad reorganizations of circulation in the northeast Pacific Ocean were synchronous with reorganizations of atmospheric circulation over western North America.