Carbon dioxide and methane fluxes in different waterbodies in Inexpressible Island, Ross Sea, East Antarctica.

The Southern Ocean (SO) is one of the most important sinks of atmospheric CO2. However, it is lacking data from the other waterbodies of Antarctic continent. This study investigated in situ CO2 and CH4 fluxes in different waterbodies, including coastal seawater of the Terra Nova Bay (TNB) polynya, Ross Sea, snow/meltwater of Nansen Ice Shelf, and lakes of Inexpressible Island, East Antarctica during summer, 2022-2023. The results indicate that the TNB polynya is a significant atmospheric CO2 sink (-133.7--8.0 mmol m-2 d) and a weak CH4 source (-2.5-13.5 μmol m-2 day-1). In contrast, lakes are weak sinks of atmospheric CO2 and CH4 because of their low biomass mass. However, one exception was observed in the lagoon and ponds of Adélie penguin colony around Seaview Bay, Inexpressible Island, where penguin guano significantly increased carbon emissions. The largest CO2 emission (29.8-114.7 mmol m-2 day-1) was observed in ponds, while the largest CH4 emission (29-50.9 μmol m-2 day-1) was observed in the lagoon, potentially affecting regional carbon emissions. Ponds derived from the meltwater of the Nansen Ice Shelf are weak sinks of atmospheric CO2 and CH4, ranged from -4.9-2.9 mmol m-2 day-1 and -1.3 -0.6 μmol m-2 day-1, with averages of -1.6 mmol m-2 day-1 and -0.5 μmol m-2 day-1, respectively. Considering the extensive occurrence of meltwater in west Antarctica, it is essential to further strengthen observations of carbon at the ice sheet-ocean interface to understand carbon dynamics in the SO.