Department of Earth System Science

We examined the concentration and δD of atmospheric H₂ in a boreal forest in interior Alaska to investigate the systematics of high latitude soil uptake at ecosystem scale. Samples collected during nighttime inversions exhibited vigorous H₂ uptake, with concentration negatively correlated with the concentration of CO₂ (−0.8 to −1.2 ppb H₂ per ppm CO₂) and negatively correlated with δD of H₂. We derived H₂ deposition rates of between 2 to 12 nmol m⁻² s⁻¹. These rates are comparable to those observed in lower latitude ecosystems. We also derive an average fractionation factor, α = D:H_residual/D:H_consumed = 0.94 ± 0.01 and suggestive evidence that α depends on forest maturity. Our results show that high northern latitude soils are a significant sink of molecular hydrogen indicating that the record of atmospheric H₂ may be sensitive to changes in climate and land use.