Trends in anthropogenic carbon in the Arctic Ocean

•Anthropogenic carbon trends highest in Eurasian basin.•Ventilation governs anthropogenic carbon trends.•Column inventory increase highest in the Nansen, Amundsen and Makarov basins. This study evaluates the trends in anthropogenic carbon (Cant) 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 Cant was evaluated using the transient time distribution (TTD) approach. In the Nansen and Amundsen sub-basins, the Cant trend in the Atlantic Waters (AW, depths: 200–500 m) and dense AW (dAW, depths: 500–800 m) is about +0.7 µmol kg−1 yr−1. As we move into the Makarov and West Canadian sub-basins, the Cant trend in the AW and dAW is smaller. The upper Polar Deep Water (uPDW, depths: 800–1600 m) has a Cant trend of about +0.4–0.5 µmol 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 µmol kg−1 yr−1. Ventilation primarily governs Cant trends while the influence of the Revelle factor plays a secondary role. The increase in the Cant 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 Cant 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.