Glacier meltwater, a potential source of methane in West Antarctica Peninsula

During the late Austral summer of 2023, we carried out three surveys in the West Antarctic Peninsula (WAP) from Horseshoe Island (67° 514 south) to the Northern tip of the Peninsula to document the distribution of CH4 in surface waters. We observed a striking feature in Dodman Island in the Grand Didier Channel with a marked supersaturation of methane (up to 400%) in the bay of the island, whereas saturation (maximum of 260%) was observed elsewhere. Our main hypothesis is that this supersaturation is linked to meltwater from the glacier on the island, which acts as a source of methane in the water column. This hypothesis is supported by vertical profiles of CH4 concentration, field observations of sub-glacial water flowing to the surface of the water column, as well as by variations in salinity showing a freshwater inflow. This phenomenon has already been suggested in the Arctic (Lamarche-Gagnon et al., 2019) but does not yet seem to have been demonstrated in the Antarctic. These data show that it would be worthwhile investigating areas with active glaciers to determine whether melting glaciers can be a source of methane for the Antarctic water column.