Anthropogenic carbon dioxide in the Arctic Ocean: Inventory and sinks

Abstract

An inventory and sequestering rate of anthropogenic carbon dioxide CTanthro in the Arctic Ocean, calculated by a plume‐entrainment model, are presented. The plume is initiated by a fraction rj leaving the shelf break at 200 m, followed by an entrainment of rj for every 150 m depth the plume descends. The model is constrained by the CFC‐12 and carbon tetrachloride (CCl4) distributions, with the concentrations of CFC‐12, CCl4, and CTanthro in the source water calculated assuming a water in 100% equilibrium with the atmosphere. The model is run from 1750 to 1991, the latter being the year in which measurements of the transient tracers in the water column of the central Arctic Ocean were made. The output from the model gives sinks of anthropogenic carbon dioxide in 1991 of 0.026±0.009 Gt C yr−1, of which 0.0194 Gt C yr−1 is in the Eurasian Basin and 0.0070 Gt C yr−1 in the Canadian Basin. This amounts to about 1% of the total oceanic uptake of anthropogenic CO2. The Arctic Ocean inventory of anthropogenic carbon dioxide in 1991 was 1.35(+0.12/−0.06) Gt C, which is about 1% of the total oceanic inventory. The sensitivity of the computed sinks and inventories to various model assumptions was estimated.