GRL: Equatorial Pacific Sea-Air CO2 Exchange Modulated by Upper Ocean Circulation During the Last Deglaciation

Zhimin Jian¹ , Jimin Yu^2,3 , Yue Wang¹ , Haowen Dang¹ , Minhan Dai⁴ , Chen Li¹ ,

Xuan Ji³ , Xingxing Wang¹ , and Yue Chen¹

1State Key Laboratory of Marine Geology, Tongji University, Shanghai, China,

2Laoshan Laboratory, Qingdao, China,

3Research School of Earth Sciences, The Australian National University, Canberra, ACT, Australia,

4State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China

Abstract:The eastern equatorial Pacific (EEP) is a source of atmospheric CO₂ 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 pCO₂ 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 CO₂ sink despite that its subsurface waters were enriched by CO₂ 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 CO₂ exchange across the equatorial Pacific led to a net CO₂ 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 CO₂-rich subsurface waters in the EEP.

Full Article:https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023GL105169