Trends in anthropogenic carbon in the Arctic Ocean

This study evaluates the trends in anthropogenic carbon (C-ant) in the different sub-basins of the Arctic Ocean between 1987 and 2015. Data were extracted from the GLODAPv2 data product as well as two GEOTRACERS cruises in the Arctic Ocean from 2015 and C-ant was evaluated using the transient time distribution (TTD) approach. In the Nansen and Amundsen sub-basins, the C-ant trend in the Atlantic Waters (AW, depths: 200-500 m) and dense AW (dAW, depths: 500-800 m) is about + 0.7 mu mol kg(-1) yr(-1). As we move into the Makarov and West Canadian sub-basins, the C-ant trend in the AW and dAW is smaller. The upper Polar Deep Water (uPDW, depths: 800-1600 m) has a C-ant trend of about +0.4-0.5 mu mol kg(-1) yr(-1) in the Nansen, Amundsen and West Canadian sub-basins. The trend is smallest in the South Canadian sub-basin, with a value of about + 0.2 mu mol kg(-1) yr(-1). Ventilation primarily governs C(ant )trends while the influence of the Revelle factor plays a secondary role. The increase in the C-ant column inventory is estimated to be 0.7-1.0 mol C m(-2) yr(-1) in the Nansen, Amundsen and Makarov sub-basins. By extrapolating the results from our defined sub-basins to the full Arctic Ocean, we estimate an C-ant accumulation of 25 Tg C yr(-1) in the Arctic Ocean and an inventory of about 3.6-3.9 Pg C between 2005 and 2015.