Neodymium isotope evidence for glacial-interglacial variability of deepwater transit time in the Pacific Ocean.

There is evidence for greater carbon storage in the glacial deep Pacific, but it is uncertain whether it was caused by changes in ventilation, circulation, and biological productivity. The spatial εNd evolution in the deep Pacific provides information on the deepwater transit time. Seven new foraminiferal εNd records are presented to systematically constrain glacial to interglacial changes in deep Pacific overturning and two different εNd evolution regimes occur spatially in the Pacific with reduced meridional εNd gradients in glacials, suggesting a faster deep Pacific overturning circulation. This implies that greater glacial carbon storage due to sluggish circulation, that is believed to have occurred in the deep Atlantic, did not operate in a similar manner in the Pacific Ocean. Other mechanisms such as increased biological pump efficiency and poor high latitude air-sea exchange could be responsible for increased carbon storage in the glacial Pacific.