Diachronous benthic delta O-18 responses during late Pleistocene terminations

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SEP 23

Benthic delta O-18 is often used as a stratigraphic tool to place marine records on a common age model and as a proxy for the timing of ice volume/sea level change. However, Skinner and Shackleton ( 2005) found that the timing of benthic delta O-18 change at the last termination differed by 3900 years between one Atlantic site and one Pacific site. These results suggest that benthic delta O-18 change may not always accurately record the timing of deglaciation. We compare benthic delta O-18 records from 20 Atlantic sites and 14 Pacific sites to evaluate systematic differences in the timing of terminations in benthic delta O-18. Analysis of sedimentation rates derived from the alignment of benthic delta O-18 suggests a statistically significant Atlantic lead over Pacific benthic delta O-18 change during the last six terminations. We estimate an average Pacific benthic delta O-18 lag of 1600 years for Terminations 1-5, slightly larger than the delay expected from ocean mixing rates given that most glacial meltwater probably enters the North Atlantic. We additionally find evidence of similar to 4000-year Pacific delta O-18 lags at approximately 128 ka and 330 ka, suggesting that stratigraphic correlation of delta O-18 has the potential to generate age model errors of several thousand years during terminations. A simple model demonstrates that these lags can be generated by diachronous temperature changes and do not require slower circulation rates. Most importantly, diachronous benthic delta O-18 responses must be taken into account when comparing Atlantic and Pacific benthic delta O-18 records or when using benthic delta O-18 records as a proxy for the timing of ice volume change.