The carbonate pump in the ocean affects the carbon cycle by moving carbon between the surface and deep ocean through processes like calcification and dissolution of calcium carbonate. Researchers used a model to study how this pump influences carbon fluxes and transport between hemispheres. They found that changes in the carbonate pump in future climate scenarios have minimal impact on the upper ocean carbon cycle compared to other factors. By looking at the levels of alkalinity and dissolved inorganic carbon, scientists can better understand the processes shaping the ocean's carbon cycle.