PIPERS: Role of Polynyas on the Atmospheric Budget of Methane and Carbon Dioxide

Coastal polynyas are areas of anomalous open water and thin ice in regions that are otherwise covered by sea
ice. They frequently occur around the Antarctic continent in response to strong offshore katabatic wind
stresses. The loss of heat from the open ocean to the cold atmosphere can enormously enhance rates of ice
production. In polynya areas, the coupling between the atmosphere, sea ice and ocean is complex, and the role
of ice formation on the budget of the main climate forcing carbon gases remains unknown. During the PIPERS
expedition on the N.B. Palmer from April to June 2017, we performed continuous measurements of methane
and carbon dioxide concentrations in the atmosphere and in the surface water from New Zealand to the
polynyas of the Ross Sea. Discrete sampling was carried out in parallel to calibrate the continuous systems and
to later measure the stable isotope ratios of both gases in the water and in the air. The stable isotope data
enable unravelling the pathways involved in gas formation and removal. While the concentrations of both
gases were relatively low in the surface waters of polynyas, the preliminary atmospheric data show higher
methane and carbon dioxide levels in the atmosphere at locations where sea ice formation was most intense.
These data together with the isotopic ratios of both gases and with meteorological data will be discussed to
better understand the role of sea ice formation on the exchange of climate forcing gases.