Sea surface pCO2 cycles and CO2 fluxes at landfast sea ice edges in Amundsen Gulf, Canada

Abstract

In late fall, spring, and early summer, we measured the surface ocean and atmospheric partial pressures of CO2 (pCO2sw and pCO2atm, respectively) to calculate CO2 gradients (ΔpCO2 = pCO2sw − pCO2atm) and resulting fluxes along the landfast ice regions of southern Amundsen Gulf, Canada. In both the fall and spring seasons we observed positive ΔpCO2caused by wind‐driven upwelling. The presence of a landfast ice edge appeared to be an important factor in promoting this upwelling in some instances. Despite the potential for significant CO2 evasion, we calculated small fluxes during these periods due to high sea ice concentration. In summer, ΔpCO2 became strongly negative across the entire study area. Primary production no doubt played a role in the pCO2swdrawdown, but we found evidence that sea ice melt and dissolution of ice‐bound calcium carbonate crystals may also have been contributing factors. The seasonal ΔpCO2 cycle suggests a net annual sink of atmospheric CO2 for these landfast ice regions, since calculated summer uptake by the ocean was much stronger than fall/spring outgassing and occurred over a longer time period. However, we hypothesize that this balance is highly dependent on the strength of upwelling and the timing of ice formation and decay, and therefore may be influenced by interannual variability and the effects of climate change.