Kevin Geyer Harrison 

Glacial calcium carbonate (CaCO3) shells are larger than interglacial CaCO3 shells. My research explores the consequences of this size difference. Because larger CaCO3 shells sink faster and dissolve more slowly than smaller CaCO3 shells, larger glacial shells underwent less dissolution than smaller interglacial shells. The resulting CaCO3 transport efficiency increase, coupled with observations that CaCO3 delivery to deep-ocean sediments remained about the same between glacial and interglacial times, implies that glacial production of CaCO3 in the mixed layer decreased by ~45%. This decrease helps explain why CO2 levels were lower and why atmospheric radiocarbon levels were higher during glacial times. This research also explores the decrease in CaCO3 transport efficiency caused by ocean acidification. Furthermore, it explains how large CaCO3 shells can form in high-energy environments at high pCO2 levels.