Is methane being released from Norwegian glaciers?

Recent research underscores a potential, yet overlooked, positive climate feedback mechanism: the transport of subglacially produced methane (CH₄) to the atmosphere via meltwater. While the majority of research focused on release from beneath the Greenland Ice Sheet, mountain glaciers have been largely understudied, creating a gap in our understanding of the spatial distribution of subglacial CH₄ emissions. Emerging research from glaciers in Iceland, Canada, Alaska, and China suggests the presence of CH₄ release also from glaciers other than the Greenland Ice Sheet.

 

Here, we explore the potential of CH₄ release from outlet glaciers of the Jostedalsbreen ice cap and Midtdalsbreen in central Norway. We investigated whether meltwaters from outlet glaciers of Jostedalsbreen (Tuftebreen, Fåbergstølsbreen, Bøyabreen, Supphelebreen, Austerdalsbreen and Nigardsbreen), along with Midtdalsbreen in Finse, act as a source of CH₄ to the atmosphere. We collected discrete samples for dissolved CH₄ (dCH₄) and CO₂ concentrations at all glacier outlets multiple times throughout the melt season. Additionally, we conducted longer time-series measurements of dCH₄ at Tuftebreen, Fåbergstølsbreen and Midtdalsbreen, utilizing custom-made dCH₄ sensors. Accompanying these measurements were samples analysed for water chemistry and stable isotopes of dCO₂ (δ¹³C-CO₂) in samples where concentrations were elevated compared to atmospheric equilibrium.

 

Our results indicate that dCH₄ concentrations in the meltwater of all studied glaciers remained below atmospheric equilibrium concentrations throughout the melt season. In contrast, dCO₂ concentrations surpassed atmospheric equilibrium levels, suggesting that the studied glacial runoffs do not act as CH₄ source to the atmosphere but might contribute as a small source of CO₂. This dataset of dissolved greenhouse gases enhances our understanding of the spatial distribution of subglacial CH₄ emissions, fostering discussions on carbon cycling beneath glaciers and the factors influencing the presence or absence of CH₄ emissions from the subglacial domain.