| Summary: | Although the eastern equatorial Pacific (EEP) is a source of CO2 to the atmosphere today, it remains unknown how this may have varied in the past. Recently, Lovely et al. (2017) showed that dust fluxes to the EEP increased during the cold Heinrich Events of the last glacial cycle, likely due to an intensification and southward shift of the Intertropical Convergence Zone. As a result, biological productivity in the EEP increased, possibly increasing carbon burial in the deep Pacific. The goal of this project is to determine whether the increased biological productivity stimulated by dust fertilization and enhanced upwelling caused the EEP to switch and become a sink for atmospheric CO2 during cold stadial events. To do this, we measure B/Ca ratios in the planktonic foraminifera Globigerina bulloides from core MV1014-17JC (00º10.83’S, 85º52.00’W; 2846 m water depth) as a proxy for past changes in seawater [CO32-]. To calculate the carbonate chemistry of EEP surface waters, we also measure Mg/Ca ratios as a proxy for sea surface temperature and d18O as a proxy for sea surface salinity using G. bulloides from the same intervals. We then estimate past changes in alkalinity from the modern salinity:alkalinity relationship in the EEP. Our results provide a 25,000-year record of surface water PCO2 and determine when the EEP acted as a source or sink for atmospheric CO2. Increased understanding of the EEP’s influence on atmospheric pCO2 across abrupt climate events will help modelers better predict the region’s response as the global climate continues to warm.
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