Dissolved hydrogen in Eurasian Arctic waters

Abstract

The distribution of dissolved hydrogen was studied during YMER-80 in the Arctic Ocean and the northern Barents Sea. Water samples were analyzed from a variety of Arctic environments including stations under complete ice cover and along the retreating ice-edge as well as vertical and horizontal sets obtained apart from the ship. The results show localized hydrogen concentrations well below air-sea equilibrium. Levels of undersaturation resemble those found in the Norwegian Sea. 3-8 nl/l (0.13-0.36 nM). Deep water in the Polar Basin contains 4.5 nl/l (0.20 nM). A section northwest of Franz-Joseph Land contains a prominent subsurface maximum with levels above saturation between 75 and 300 m. Supersaturation is also found in surface waters among ice floes at two coastal sites. In the Barents Sea, hydrogen in surface water is near equilibrium and is highly correlated with salinity. Below the surface. the hydrogen level quickly drops to half the H₂ concentration contained in Norwegian Sea water. This distribution suggests that hydrogen is being consumed throughout the Barents while excess H ₂ is added to surface waters by low salinity intrusion from the retreating ice pack with secondary fluxes across the air-sea interface and from river runoff. The hydrogen mixing ratio in air samples north of Svalbard is 16% below the mixing ratio measured over the Baltic Sea.