The concentration of methane (CH4), along with temperature and salinity, were measured in the ice- covered Arctic Ocean within the Eurasian Basin (Verdugo et al., 2016; doi:10.1016/j.dsr.2016.08.016). The transect was conducted across the Nansen-Gakkel Ridge, from the Nansen Basin to the Amundsen Basin, covering depths from the surface (10 m) down to 4300 m. All sampling stations, except for ST 12, were covered by sea ice. Water samples were collected with a CTD-rosette sampler equipped with 24 Niskin Bottles. Gas sampling was carried out directly from 12 L Niskin bottles. Triplicate water samples for CH4 analyses were taken in 20 mL glass vials and preserved with 50 µL of saturated HgCl2. The vials were then sealed with a butyl-rubber septum and an aluminum cap to prevent bubble formation and stored in darkness at room temperature until laboratory analysis. CH4 concentrations were analyzed by creating 5 mL of ultra-pure helium headspace, followed by equilibration in the vial, and then quantified with a gas chromatograph (GC). A Varian 3380 GC, equipped with flame ionization detector (FID) maintained at 250 °C, and a capillary column GS-Q operated at 30 °C was used for analysis. A calibration curve was made with three standard concentrations for CH4 (1, 5, and 10 ppm, provided by Scotty Standards) and dry air.