Ocean Carbon Cycle

The ocean contains about 50 times as much carbon (39,000 PgC) as the atmosphere. Net CO₂ transfer across the air-sea interface can occur whenever there is a partial pressure difference between the atmosphere and the ocean. Once in the ocean, the future of an atom of carbon is the result of multiple mechanisms involving chemical reactions (inorganic carbon chemistry), physical processes (advection, mixing), and biological interactions (photosynthesis, respiration, calcification, . . .). As a consequence, on the order of 90 Pg of carbon are exchanged each year and in each direction at the air-sea interface. The ocean carbon cycle is responsible for the large variations (80 ppm) in atmospheric CO₂ during glacialinterglacial cycles, but on shorter timescales, dissolution of atmospheric carbon in the ocean also provides a large sink for anthropogenic CO₂ (~2 PgC a^-1 over 1990-1999). However, the impact of future climate change on the ocean carbon cycle is uncertain and requires further modeling and observational studies.