<p>Dissolved methane (CH<sub>4</sub>) was measured at 9 stations along a transect at 75° S in the Ross Sea during austral summer in January 2020. CH<sub>4</sub> undersaturation (mean: 82 ± 20 %) was found in the water column, with a mean air-sea CH<sub>4</sub> flux density of −0.58 ± 0.48 μmol m<sup>−2</sup> day<sup>−1</sup>, which suggests that the Ross Sea was a net sink for atmospheric CH<sub>4</sub> during the austral summer. Simple box-model calculations revealed that the CH<sub>4</sub> depletion should occur in the surface mixed layer because of CH<sub>4</sub> oxidation and advection of CH<sub>4</sub>-poor waters. We propose that freshwater injection caused by sea-ice melting in summer dilutes CH<sub>4</sub> concentrations within the surface layer and thus increases its potential for atmospheric CH<sub>4</sub> uptake in the Ross Sea. Thus, we argue that both CH<sub>4</sub> consumption and sea-ice melting are important drivers of CH<sub>4</sub> undersaturation, which implies that the high-latitude area of the Southern Ocean is a sink for atmospheric CH<sub>4</sub>. We estimated that the Southern Ocean (> 65° S) takes up about 0.02 % of the global CH<sub>4</sub> emissions and thus represents a minor sink for atmospheric CH<sub>4</sub>.</p>