How snow affects air-sea ice CO2 fluxes

Sea ice is a significant contributor to the sink of atmospheric CO2 by polar oceans. Physical and biogeochemical sea ice processes affect partial pressure of CO2 within sea ice, that in turn controls the way and magnitude of air-sea ice CO2 fluxes. Snow cover appears to affect the magnitude of the fluxes. In order to understand the role of snow, we compared chamber and micrometeorological measurements of air-ice CO2 fluxes over snow covered and uncovered sea ice (land fast and pack ice) in both arctic and antarctic. We observed significant differences between fluxes over uncovered and covered sea ice. In addition chamber and micrometeorological measurement show different patterns that are partially due to snow cover. By gathering these observations, we observed at least three effects of snow on air-ice CO2 fluxes. Snow appears to (i) act as transient CO2 reservoir (ii) affect thermal properties of the ice surface (iii) control gas transfer depending on snow structure (superimposed ice, slush).