The calcium carbonate counter pump: Fundamentals, evolution through time, and future feedbacks

Because the vertical calcium carbonate (CaCO3) pump transports two units of alkalinity per unit of carbon, its short-term effect is to increase atmospheric CO2. It has therefore been referred to as the CaCO3 counter pump. However, burial of CaCO3 in marine sediments is one of the main mechanisms to reduce atmospheric CO2 in the long term (if the Ca originates from silicate weathering). The calcium carbonate pump can therefore have very different effects on ocean carbon, alkalinity, and atmospheric CO2 on different spatial and temporal scales. This presentation provides insight into the fundamental operation of the calcium carbonate pump. I will also describe how the CaCO3 pump has evolved through time. Furthermore, I will present model results to estimate future effects of changes in dissolution, remineralization, and ocean acidification on the CaCO3 pump. Feedbacks between changes in CaCO3 pumping, ocean carbon cycling, ocean CO2 uptake, and future atmospheric CO2 levels will be explored.