The Arctic Ocean carbon sink

We present observation based estimates of the transport of dissolved inorganic carbon (DIC) across the four main Arctic Ocean gateways (Davis Strait, Fram Strait, Barents Sea Opening and Bering Strait). Combining a recently derived velocity field at these boundaries with measurements of DIC, we calculated a net summertime pan-Arctic export of 231 ± 49 Tg C yr − 1 . On an annual basis, we estimate that at least 166 ± 60 Tg C yr − 1 of this is due to uptake of CO2 from the atmosphere, although time-dependent changes in carbon storage are not quantified. To further understand the regionʹs role as a carbon sink, we calculated the volume-conserved net DIC transport from beneath a prescribed mixed layer depth of 50 m, referred to as ‘interior transport’, revealing an export of 61 ± 23 Tg C yr − 1 . Applying a carbon framework to infer the sources of interior transport implied that this export is primarily due to the sinking and remineralisation of organic matter, highlighting the importance of the biological pump. Furthermore, we qualitatively show that the present day Arctic Ocean is accumulating anthropogenic carbon beneath the mixed layer, imported in Atlantic Water.