Enhanced Tropical Pacific Foraminiferal Carbonate Pump During the Last Deglaciation Linked to Ocean Warming

Abstract Marine calcifying organisms secrete shells of calcium carbonate (CaCO 3 ) that play a crucial role in regulating the oceanic biological pump and atmospheric CO 2 levels. Here, we quantify CaCO 3 production of planktonic foraminifera, which accounts for roughly half of the global pelagic biogenic CaCO 3 flux, in the western tropical Pacific since 46 ka. Foraminiferal CaCO 3 production and its proportion of total biogenic flux both increased from the last deglaciation to early Holocene (19‐8 ka), consistent with the anomalously high CO 2 content of tropical Pacific subsurface water. By analyzing planktonic foraminiferal shell flux, shell size and calcification density, we suggest that the observed enhancement of foraminiferal carbonate pump was primarily driven by deglacial ocean warming, which promoted the proliferation of foraminifera, especially heavily calcified species. Therefore, we infer that the oceanic carbonate pump may have acted as a critical positive global‐warming feedback on glacial‐interglacial timescales.