The basal environments of ice sheets produce and store large reserves of methane (CH4), which have the potential to raise atmospheric CH4 concentration and thus further climate warming, if released during periods of deglaciation. The Greenland ice sheet (GrIS), the largest ice mass in the Northern Hemisphere, is retreating rapidly, losing mass at over 400 km3 per year. Recent research has shown subglacial CH4 of microbial origin is released at the ice sheet margin. However, no estimate of the CH4 footprint of the entire GrIS currently exists.

A new 5-year project called MARCH4G will quantify the potential of the GrIS bed to produce and release CH4 – a potent greenhouse gas – and affect the global CH4 cycle and climate. The underlying hypothesis is that global climate change and resulting increasing melting of the GrIS causes export of subglacial CH4 of microbial origin to the atmosphere. To test this hypothesis, MARCH4G will 1) map CH4 efflux around the ice sheet using portable high-precision gas measurement technology and determine its origin and age through a combination of radio- and stable isotope techniques, 2) directly access the Greenland ice sheet basal ecosystem via hot-water drilling and retrieve subglacial sediment unaffected by the contact with the atmosphere, 3) constrain the biological sources and sinks of subglacial CH4 and their environmental controls and examine biological CH4 cycling processes at an energetic frontier using a combination of field measurements and laboratory experiments with collected subglacial sediment samples, and 4) use biogeochemical modelling to upscale obtained field and experimental data to estimate CH4 cycling beneath and export from the GrIS and its significance for the global CH4 budget. MARCH4G will integrate formerly separated aspects of Greenland ice sheet research into a large-scale multidisciplinary project and constitute a major leap in our understanding of the fast-changing Arctic ecosystem.

We will collaborate with a number of project partners from Denmark (Aarhus University), Norway (The Arctic University of Norway, Tromsø), Belgium (Université Libre de Bruxelles), and Scotland (NERC Radiocarbon Facility, East Kilbride). Several PhD and postdoc positions will soon be available on this project — please watch this space!