Equatorial Pacific seawater pCO2 variability since the last glacial period

Kaoru Kubota,Toshitsugu Yamazaki,Tsuyoshi Ishikawa,Minoru Ikehara,Takuya Sagawa,Yusuke Yokoyama

doi:10.1038/s41598-019-49739-0

Abstract

The ocean may have played a central role in the atmospheric pCO2 rise during the last deglaciation. However, evidence on where carbon was exchanged between the ocean and the atmosphere in this period is still lacking, hampering our understanding of global carbon cycle on glacial–interglacial timescales. Here we report a new surface seawater pCO2 reconstruction for the western equatorial Pacific Ocean based on boron isotope analysis—a seawater pCO2 proxy—using two species of near-surface dwelling foraminifera from the same marine sediment core. The results indicate that the region remained a modest CO2 sink throughout the last deglaciation.

Highlights

During the last deglaciation, the atmospheric partial pressure of carbon dioxide increased by approximately 80 μatm[1,2,3]
Based on δ11B measurements of the planktonic foraminifera Torilobatus sacculifer in a marine sediment core (ERDC-92, Fig. 1), Palmer and Pearson[12] reported that the surface layer of the western equatorial Pacific (WEP) was a CO2 source during the last deglaciation, which suggested a potential contribution of this region to the deglacial rise in atmospheric CO2
Their reported ranges of δ11B values differ from generally accepted values for T. sacculifer on glacial-interglacial timescales[9,10,13,14,15,16] by as much as 5‰, which is likely due to positive bias, especially when analyzing foraminifera shell using negative thermal ionization mass spectrometry (N-TIMS)[15,17,18,19]

Summary

Introduction

During the last deglaciation (ca. 19.0–10.5 ka), the atmospheric partial pressure of carbon dioxide (pCO2) increased by approximately 80 μatm[1,2,3]. Based on δ11B measurements of the planktonic foraminifera Torilobatus sacculifer in a marine sediment core (ERDC-92, Fig. 1), Palmer and Pearson[12] reported that the surface layer of the WEP was a CO2 source during the last deglaciation, which suggested a potential contribution of this region to the deglacial rise in atmospheric CO2.

Results

Conclusion