Glacial retreat driving enhanced methane emissions in the high Arctic

Abstract

<p>Permafrost and glaciers in the high Arctic form an impermeable ‘cryospheric cap’ that traps a large reservoir of sub-surface methane and hinders it from reaching the atmosphere. The vulnerability of the cryosphere to climate warming is making releases of this methane possible, but uncertainty in the magnitude and timing makes future predictions of Arctic greenhouse gas emissions difficult. In Svalbard, where air temperatures are rising more than twice as fast as the average for the Arctic, glaciers are retreating and leaving behind an exposed forefield that enables rapid methane escape.</p> <p>We undertook a field survey of unprecedented spatial coverage across central Svalbard to identify methane emission hotspots in glacial forefields, a previously unknown emission source. Here we document how methane-rich groundwater springs that have formed in recently revealed forefields of 78 land-terminating glaciers are bringing deep-seated methane gas to the surface. Waters collected from these springs are supersaturated with methane up to 600,000-times greater than atmospheric equilibration, with strong isotopic evidence of a thermogenic source. We estimate annual emissions of methane degassing from such groundwater springs to be up to 2.31 kt across the Svalbard archipelago. Our findings reveal that climate-driven glacial retreat is facilitating widespread release of methane, a positive feedback loop that is likely to be prevalent across other regions of the rapidly warming Arctic.</p>