The Nordic Seas carbon budget: sources, sinks and uncertainties

A carbon budget for the Nordic Seas is derived by combining recent inorganic carbon data from the CARINA database with relevant volume transports. Values of organic carbon in the Nordic Seas' water masses, the amount of carbon input from river runoff, and the removal through sediment burial are taken from the literature. The largest source of carbon to the Nordic Seas is the Atlantic Water that enters the area across the Greenland-Scotland Ridge; this is in particular true for the anthropogenic CO2. The dense overflows into the deep North Atlantic are the main sinks of carbon from the Nordic Seas. The budget show that presently 12.0 {plus minus} 1.4 Gt C yr-1 is transported into the Nordic Seas and that 12.2 {plus minus} 0.9 Gt C yr-1 is transported out, resulting in a net advective carbon transport out of the Nordic Seas of 0.17 {plus minus} 0.06 Gt C yr-1. Taking storage into account, this implies a net air-to-sea CO2 transfer of 0.19 {plus minus} 0.06 Gt C yr-1 into the Nordic Seas. The horizontal transport of carbon through the Nordic Seas is thus approximately two orders of magnitude larger than the CO2 uptake from the atmosphere. No difference in CO2 uptake was found between 2002 and the preindustrial period, but the net advective export of carbon from the Nordic Seas is smaller at present due to the accumulation of anthropogenic CO2.