Temporal variability in surface water pCO2 in Adventfjorden (West Spitsbergen) with emphasis on physical and biogeochemical drivers

Abstract

Seasonal and interannual variability in surface water partial pressure of CO₂ (<i>p</i>CO2) and air‐sea CO₂ fluxes from a West Spitsbergen fjord (IsA Station, Adventfjorden) are presented, and the associated driving forces are evaluated. Marine CO₂ 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 <i>p</i>CO₂ with respect to atmospheric <i>p</i>CO₂ all year round. The effects of biological activity (primary production/respiration) followed by thermal forcing on pCO2 were the most important drivers on a seasonal scale. The ocean was a sink for atmospheric CO₂ with annual air‐sea CO₂ 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 CO₂ 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.