University of California at Santa Barbara, United States

Differences in radiocarbon apparent ages between coexisting planktonic and benthic (B-P) foraminifers in the Santa Barbara Basin contain information about changes in the age (and thus the source) of water entering the basin. The Holocene sequence indicates a greater variability in circulation than previously detected. During the early Holocene, ca. 9 ka, B-P (super 14) C apparent age differences fluctuated between 220 and 560 (super 14) C yr, similar to rapid variations seen during the Younger Dryas and the last glacial episode. During the relatively stable middle Holocene (8.5-2 ka), B-P (super 14) C apparent age differences averaged 440 (super 14) C yr. After 2 ka, the average B-P (super 14) C apparent age difference increased to 620 (super 14) C yr, which has persisted until the present. The shift in B-P (super 14) C apparent age differences likely represents a change in the strength or source of North Pacific Intermediate Water production and is concurrent with changes in regional climate patterns as well as with changes in temperature and accumulation rates measured in the Greenland Ice Sheet Project 2 ice core, suggesting large-scale changes in atmospheric circulation patterns.