Distribution Patterns of Methane, Hydrogen, and Helium in the Water Column of the Kara Sea

Estimates of the content of dissolved methane, hydrogen, and helium in seawater of the Kara Sea were obtained. It was found that the methane concentration in the studied areas varied from 1.3 to 27 nmol/L. The highest methane concentrations were detected in the subsurface layers of seawater on the outer shelf, in the zone of freshwater runoff from the Ob and Yenisei rivers. The methane distribution pattern in the water column of the Novaya Zemlya Depression is heterogeneous and most likely controlled by freshwater runoff from Novaya Zemlya. At some stations in the Kara Sea, there is a correlation between the high concentrations of methane (20 nmol/L), hydrogen (8 nmol/L), and helium (5 nmol/L) in the upper layer of the water column (10–70 m). No gas migration from bottom sediments into water was detected at these stations. Most likely, the high gas concentrations are associated with advection from enriched areas.