Figure 2
From: Direct isotopic evidence of biogenic methane production and efflux from beneath a temperate glacier
Schematic model of hydrological evolution at Sólheimajökull, Iceland. The headward expansion of the conduit drainage system intersects with the geothermal area, where release of reduced gases determines the sub-oxic meltwater status essential for preserving aqueous methane until the point of emergence from beneath the glacier. (a) Summer season snowpack ablation delivers meltwater to expand the conduit drainage system headwards into the Katla geothermal field. This results in a drainage system well-connected to deep within the geothermal field, delivering water of reducing status. Methane generated within the basal sediments through microbial methanogenesis is preserved during export. (b) Winter season limited surface ablation restricts the conduit drainage system to the lower reaches of the glacier. This results in a drainage system operating close to atmospheric conditions within the vicinity of the glacier snout and poorly connected to deeper beneath the ice mass. Much of the methane generated within the surrounding sediments is oxidised proximal to the channelized drainage system before being exported from beneath the glacier.
