The ocean can be conceptually divided into a surface layer within which water makes frequent (daily to annual) contact with the atmosphere, and a deep layer below the typical mixed layer depth of a few hundred meters or less, within which the time between consecutive contacts may be centuries. The dissolved inorganic carbon (DIC) in the surface layer is exchanged rapidly with the atmosphere, maintaining equilibrium. Partly because its concentration of DIC is about 15% higher but mainly due to its larger volume, the deep ocean contains far more carbon—it is the largest pool of actively cycled carbon in the world, containing 50 times more than the atmosphere—but the timescale to reach equilibrium with the atmosphere is hundreds of years: the exchange of carbon between the two layers, driven by thermohaline circulation, is slow.
the ocean can be conceptually divided into a surface layer within which water makes frequent (daily to annual) contact with the atmosphere and a deep layer below the typical mixed layer depth of a few hundred meters or less within which the time between consecutive contacts may be centuries the dissolved inorganic carbon (dic) in the surface layer is exchanged rapidly with the atmosphere maintaining equilibrium partly because its concentration of dic is about 15% higher but mainly due to its larger volume the deep ocean contains far more carbon—it is the largest pool of actively cycled carbon in the world containing 50 times more than the atmosphere—but the timescale to reach equilibrium with the atmosphere is hundreds of years the exchange of carbon between the two layers driven by thermohaline circulation is slow