Glacial‐Holocene calcium carbonate dissolution at the central equatorial Pacific seafloor

Abstract

Holocene sediments in the central equatorial Pacific have lower CaCO3 burial rates relative to sediments deposited during the last glacial period. This change could be related to shifts in the deep‐sea carbonate system and ultimately to the glacial‐interglacial atmospheric CO2 cycle. In this study the glacial‐Holocene sedimentation in the central equatorial Pacific is investigated using a numerical model applied to CaCO3, carbonate 14C, and excess 230Th. We also employ excess 231Pa to 230Th ratios as proxies of past particle fluxes. Although the CaCO3 burial rates decreased by 0.7–2.0 g cm−2 kyr−1, the 231Pa to 230Th ratios indicate that particle and CaCO3 fluxes have either remained nearly constant or increased since the last glacial. This suggests that the reduction in CaCO3 burial rates resulted from an intensification of CaCO3 dissolution. A small to moderate decrease in bottom water carbonate concentration, rather than an increase in sedimentary respiratory‐CO2 production, is the most plausible mechanism for driving the sedimentation changes.