North Pacific response to millennial‐scale changes in ocean circulation over the last 60 kyr

Abstract

Foraminifera‐based sea surface temperature estimates in the northwest Pacific (Ocean Drilling Program Site 883; 51°N) varied by 4°C on millennial timescales over the last 60,000 calendar (cal) years, with the most prominent amplitudes during marine isotope stage 3. Age control is based on benthic δ18O records, 14C ages, and on geomagnetic intensity variations at Site 883 tuned to the North Atlantic paleointensity stack since 75 ka (NAPIS‐75), in turn, tied to the Greenland Ice Sheet Project 2 (GISP2) ice core chronology. On the basis of this tuning, northwest Pacific warm phases parallel Greenland cold stadials and viceversa. This contrasts with atmospheric heat transfer, expected to produce quasi‐coeval signals across the Northern Hemisphere. The antiphasing may instead stem from variations in global thermohaline circulation. At its North Pacific terminus in the subarctic gyre, any slowdown or shutoff of North Atlantic Deep Water formation during Dansgaard‐Oeschger stadials led to a turnoff or reduction of the upwelling of cold Pacific deepwater and thus, to striking, instantaneous, short‐term warmings of surface water.