Query: The amount of carbon dioxide absorbed by the upper layer of the oceans is increasing by about 2 billion tons per year.

Relevant passages:
Oceanic carbon cycle <=SEP=> The oceans contain around 36,000 gigatons of carbon , mostly in the form of bicarbonate ion ( over 90 % , with most of the remainder being carbonate ) .   At the surface of the oceans towards the poles , seawater becomes cooler and more carbonic acid is formed as CO2 becomes more soluble . This is coupled to the ocean 's thermohaline circulation which transports dense surface water into the ocean 's interior ( see the entry on the solubility pump ) .  Although the deep ocean contains much more dissolved inorganic carbon than the surface ocean , the concentration is only 15 % higher in the deep ocean as compared to the surface ocean due to the higher volume of the deep ocean .  In upper ocean areas of high biological productivity , organisms convert reduced carbon to tissues , or carbonates to hard body parts such as shells and tests . These are , respectively , oxidized ( soft-tissue pump ) and redissolved ( carbonate pump ) at lower average levels of the ocean than those at which they formed , resulting in a downward flow of carbon ( see entry on the biological pump ) .  The flux or absorption of carbon dioxide into the world 's oceans is influenced by the presence of widespread viruses within ocean water , that infect many species of bacteria . The resulting bacterial deaths spawn a sequence of events that lead to greatly enlarged respiration of carbon dioxide , enhancing the role of the oceans as a carbon sink .  The balance of dissolved inorganic carbon ( DIC ) : dissolved organic carbon ( DOC ) : particle organic carbon is about 2000:38:1 .  The CaCO3 counter pump increases the partial pressure of CO2 in the ocean , thus leading to higher outgasing of carbon dioxide .  Higher ocean temperatures lead to stronger layering , thus less mixing and less capacity for thermohaline circulation to bring carbon into lower ocean layers .  The weathering of silicate rock ( see carbonate-silicate cycle ) . Carbonic acid reacts with weathered rock to produce bicarbonate ions . The bicarbonate ions produced are carried to the ocean , where they are used to make marine carbonates . Unlike dissolved CO2 in equilibrium or tissues , which decay , weathering does not move the carbon into a reservoir from which it can readily return to the atmosphere .  Much remains to be learned about the cycling of carbon in the deep ocean . For example , a recent discovery is that larvacean mucus houses ( commonly known as `` sinkers '' ) are created in such large numbers that they can deliver as much carbon to the deep ocean as has been previously detected by sediment traps . Because of their size and composition , these houses are rarely collected in such traps , so most biogeochemical analyses have erroneously ignored them .  The amount of dissolved inorganic carbon in the ocean is significantly higher in the deep layer ( below 300 m depth ) . This is caused by the solubility pump and the biological pump .

Carbon dioxide <=SEP=> Carbon dioxide ( chemical formula ) is a colorless gas with a density about 60 % higher than that of air ( 1.225 g/L ) that is odorless at normally encountered concentrations . Carbon dioxide consists of a carbon atom covalently double bonded to two oxygen atoms . It occurs naturally in Earth 's atmosphere as a trace gas at a concentration of about 0.04 percent ( 400 ppm ) by volume . Natural sources include volcanoes , hot springs and geysers , and it is freed from carbonate rocks by dissolution in water and acids . Because carbon dioxide is soluble in water , it occurs naturally in groundwater , rivers and lakes , ice caps , glaciers and seawater . It is present in deposits of petroleum and natural gas .   As the source of available carbon in the carbon cycle , atmospheric carbon dioxide is the primary carbon source for life on Earth and its concentration in Earth 's pre-industrial atmosphere since late in the Precambrian has been regulated by photosynthetic organisms and geological phenomena . Plants , algae and cyanobacteria use light energy to photosynthesize carbohydrate from carbon dioxide and water , with oxygen produced as a waste product .   Carbon dioxide is produced by all aerobic organisms when they metabolize carbohydrates and lipids to produce energy by respiration . It is returned to water via the gills of fish and to the air via the lungs of air-breathing land animals , including humans . Carbon dioxide is produced during the processes of decay of organic materials and the fermentation of sugars in bread , beer and winemaking . It is produced by combustion of wood and other organic materials and fossil fuels such as coal , peat , petroleum and natural gas .   It is a versatile industrial material , used , for example , as an inert gas in welding and fire extinguishers , as a pressurizing gas in air guns and oil recovery , as a chemical feedstock and in liquid form as a solvent in decaffeination of coffee and supercritical drying . It is added to drinking water and carbonated beverages including beer and sparkling wine to add effervescence . The frozen solid form of , known as `` dry ice '' is used as a refrigerant and as an abrasive in dry-ice blasting .   Carbon dioxide is the most significant long-lived greenhouse gas in Earth 's atmosphere . Since the Industrial Revolution anthropogenic emissions - primarily from use of fossil fuels and deforestation - have rapidly increased its concentration in the atmosphere , leading to global warming . Carbon dioxide also causes ocean acidification because it dissolves in water to form carbonic acid .