Insights into oxygen transport and net community production in sea ice from oxygen, nitrogen and argon concentrations

We present and compare the dynamics (i.e., changes in standing stocks, saturation levels and concentrations) of O2, Ar and N2 in landfast sea ice, collected in Barrow (Alaska), from February through June 2009. The comparison suggests that the dynamic of O2 in sea ice strongly depends on physical processes (gas incorporation and subsequent transport). Since Ar and N2 are only sensitive to the physical processes in the present study, we then discuss the use of O2 / Ar and O2 / N2 to correct for the physical contribution to O2 supersaturations, and to determine the net community production (NCP). We conclude that O2 / Ar suits better than O2 / N2, due to the relative abundance of O2, N2 and Ar, and the lower biases when gas bubble formation and gas diffusion are maximized. We further estimate NCP in the impermeable layers during ice growth, which ranged from -6.6 to 3.6 µmol O2 L-1 d-1, and the concentrations of O2 due to biological activity in the permeable layers during ice decay (3.8 to 122 µmol O2 L-1). We finally highlight the key issues to solve for more accurate NCP estimates in the future