Millennial-scale deep water oscillations: Reflections of the North Atlantic in the deep Pacific from 10 to 60 ka

Abstract

Northeast Pacific benthic foraminiferal δ18O and δ13C reveal repeated millennial-scale events of strong deep-sea ventilation (associated with nutrient depletion and/or high gas exchange) during stadial (cool, high ice volume) episodes from 10 to 60 ka, opposite the pattern in the deep North Atlantic. Two climate mechanisms may explain this pattern. North Pacific surface waters, chilled by atmospheric transmission from a cold North Atlantic and made saltier by reduced freshwater vapor transports, could have ventilated the deep Pacific from above. Alternatively, faster turnover of Pacific bottom and mid-depth waters, driven by Southern Ocean winds, may have compensated for suppressed North Atlantic Deep Water production during stadial intervals. During the Younger Dryas event (∼11.6-13.0 cal ka), ventilation of the deep NE Pacific (∼2700 m) lagged that in the Santa Barbara Basin (∼450 m) by >500 years suggesting that the NE Pacific was first ventilated at intermediate depth from above and then at greater depth from below. This apparent lag may reflect the adjustment time of global thermohaline circulation.