BASAL-CH4 : Methane fluxes study at the glacier-ocean interface
© 2025 EPFL, Jérôme Chappellaz
In May 2025, the EPFL SENSE group led by Professor Jérôme Chappellaz launched the project BASAL-CH4 funded by SPI Forel Grants program with the goal to investigate a potentially overlooked contributor to greenhouse gas emissions: methane trapped beneath Greenland's massive ice sheet.
While methane, a greenhouse gas roughly 25 times more potent than carbon dioxide, is known to be produced in oxygen-poor environments beneath glaciers, its pathway to the atmosphere remains poorly understood. Recent research suggests that as Greenland's glaciers retreat due to climate change, this hidden methane source could become increasingly important.
From ocean to atmosphere: A critical transition
Currently, much of Greenland's subglacial meltwater drains directly into the ocean through fjords at marine-terminating glaciers. In these settings, oceanic microbes rapidly consume dissolved methane, oxidizing it before it can reach the atmosphere. However, as glaciers retreat inland, more of this methane-rich water will drain onto land instead, bypassing this natural filter and releasing greenhouse gases directly into the air.
This transition from marine to terrestrial drainage could represent a significant feedback mechanism in climate change that we haven't fully accounted for.
Measuring methane at the source
In July 2025, SENSE's R&D engineer Sebastien Lavanchy embarqued aboard the FOREL vessel on a 2 weeks expedition to Greenland to conduct the first comprehensive investigation of dissolved methane concentrations in subglacial outflows at four major fjord outlets in central-western Greenland (in the sectors of Uummannaq, Ilulissat and Kangerlussuaq). The fieldwork was strategically timed for July, when basal melt rates reach their peak.
The study employed the SubOcean probe, a cutting-edge instrument capable of highly precise, real-time measurements of dissolved methane directly in the field. Combined with our multi-sensor CTD that measures water properties, this technology will allow us to map how methane concentrations vary throughout the water column and track the extent of microbial oxidation in different fjord environments.
The team (Sebastien Lavanchy) recorded thousands of data as one would imagine. The next step is to clean up the raw data to extract methane's profile and unravel or confirm our hypothesis.