The deep ocean basins are stably stratified, so mixing of surface waters with the deep ocean waters occurs only very slowly. The dissolved CO of the surface waters of the ocean is roughly in equilibrium with the partial pressure of CO in the atmosphere. As atmospheric CO levels are rising, the oceans are absorbing some CO from the atmosphere. When surface waters sink, they carry considerable amounts of CO into the deep oceans, away from the atmosphere. Because these waters are able to contain a large amount of CO, they have helped slow the rise in atmospheric CO concentrations, thus slowing some aspects of climate change.
Climate change could have different effects on ice melt and brine rejection. Previous studies have suggested that as ice cover thins, it will become a weaker insulator, resulting in larger ice production during the autumn and winter. The consequent increase in winter brine rejection will drive ocean ventilation and strengthen the inflow of warm Atlantic waters. Studies of the last glacial maximum have indicated that a drastic reduction in the production of sea ice, and thus reduction of brine rejection, would result in the weakening of the stratification in the global deep oceans and in CO release into the shallow oceans and the atmosphere, triggering global deglaciation.