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 CO. However, it is lacking data from the other waterbodies of Antarctic continent. This study investigated in situ CO and CH 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 CO sink (-133.7--8.0 mmol m d) and a weak CH source (-2.5-13.5 μmol m day). In contrast, lakes are weak sinks of atmospheric CO and CH 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 CO emission (29.8-114.7 mmol m day) was observed in ponds, while the largest CH emission (29-50.9 μmol m day) 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 CO and CH, ranged from -4.9-2.9 mmol m day and -1.3 -0.6 μmol m day, with averages of -1.6 mmol m day and -0.5 μmol m day, 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.