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 O 2, Ar and N 2 in landfast sea ice, collected in Barrow (Alaska), from February through June 2009. The comparison suggests that the dynamic of O 2 in sea ice strongly depends on physical processes (gas incorporation and subsequent transport). Since Ar and N 2 are only sensitive to the physical processes in the present study, we then discuss the use of O 2 / Ar and O 2 / N 2 to correct for the physical contribution to O 2 supersaturations, and to determine the net community production (NCP). We conclude that O 2 / Ar suits better than O 2 / N 2, due to the relative abundance of O 2, N 2 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 O 2 L −1 d −1, and the concentrations of O 2 due to biological activity in the permeable layers during ice decay (3.8 to 122 μmol O 2 L −1). We finally highlight the key issues to solve for more accurate NCP estimates in the future.