Equatorial Pacific Sea‐Air CO<sub>2</sub> Exchange Modulated by Upper Ocean Circulation During the Last Deglaciation
Zhimin Jian, Jimin Yu, Yue Wang, Haowen Dang, Minhan Dai, Chen Li, Xuan Ji, Xingxing Wang, Yue Chen
Abstract
Abstract The eastern equatorial Pacific (EEP) is a source of atmospheric CO 2 during the last deglaciation, but the associated oceanic dynamics in the broader low‐latitude Pacific is not fully understood. Here, we report 30,000‐year‐long surface and subsurface p CO 2 records for the western equatorial Pacific (WEP), based on boron isotopes in two planktonic foraminiferal species from core MD10‐3340. Our results show that the WEP surface became a significant atmospheric CO 2 sink despite that its subsurface waters were enriched by CO 2 during the last deglaciation to early Holocene. Combined with EEP proxy data and model results, we suggest that a deglacial‐early Holocene zonal seesaw of sea‐air CO 2 exchange across the equatorial Pacific led to a net CO 2 outgassing much greater than the modern situation. This can be ascribed to strengthened Subtropical‐Tropical Circulation, resulting in stronger upper ocean stratification in the WEP concurrent with enhanced upwelling of CO 2 ‐rich subsurface waters in the EEP.