Dynamics of pCO2 and related air-ice CO2 fluxes in the Arctic coastal zone (Amundsen Gulf, Beaufort Sea)

We present an Arctic seasonal survey of carbon dioxide partial pressure (pCO₂) dynamics within sea ice brine and related air-ice CO₂ fluxes. The survey was carried out from early spring to the beginning of summer in the Arctic coastal waters of the Amundsen Gulf. High concentrations of pCO₂ (up to 1834 matm) were observed in the sea ice in early April as a consequence of concentration of solutes in brines, CaCO₃ precipitation and microbial respiration. CaCO₃ precipitation was detected through anomalies in total alkalinity (TA) and dissolved inorganic carbon (DIC). This precipitation seems to have occurred in highly saline brine in the upper part of the ice cover and in bulk ice. As summer draws near, the ice temperature increases and brine pCO₃ shifts from a large supersaturation (1834 matm) to a marked undersaturation (down to almost 0 matm). This decrease was ascribed to brine dilution by ice meltwater, dissolution of CaCO₃ and photosynthesis during the sympagic algal bloom. The magnitude of the CO₂ fluxes was controlled by ice temperature (through its control on brine volume and brine channels connectivity) and the concentration gradient between brine and the atmosphere. However, the state of the ice-interface clearly affects air-ice CO₂ fluxes.