Temporal Variability in Surface Water pCO₂ in Adventfjorden (West Spitsbergen) With Emphasis on Physical and Biogeochemical Drivers

Seasonal and interannual variability in surface water partial pressure of CO 2 ( p CO 2 ) and air‐sea CO 2 fluxes from a West Spitsbergen fjord (IsA Station, Adventfjorden) are presented, and the associated driving forces are evaluated. Marine CO 2 system data together with temperature, salinity, and nutrients, were collected at the IsA Station between March 2015 and June 2017. The surface waters were undersaturated in p CO 2 with respect to atmospheric p CO 2 all year round. The effects of biological activity (primary production/respiration) followed by thermal forcing on p CO 2 were the most important drivers on a seasonal scale. The ocean was a sink for atmospheric CO 2 with annual air‐sea CO 2 fluxes of −36 ± 2 and −31 ± 2 g C·m −2 ·year −1 for 2015–2016 and 2016–2017, respectively, as estimated from the month of April. Waters of an Arctic origin dominated in 2015 and were replaced in 2016 by waters of a transformed Atlantic source. The CO 2 uptake rates over the period of Arctic origin waters were significantly higher (2 mmol C·m −2 ·day −1 ) than the rates of the Atlantic origin waters of the following year.