Subglacial gas hydrates: ice sheet modulation of methane

Gas hydrates exist within a relatively narrow envelope of thermal and pressure conditions,  small changes in which may lead to widespread dissociation and methane release.  During past glacials, extensive ice sheets covered the continental margins of the Arctic Basin yielding ideal high pressure and low temperature conditions for the sequestration of thermogenic and biogenic methane in hydrate-bearing subglacial sediments.  On ice sheet retreat at the end of the last glacial, these hydrate reservoirs experienced major perturbations in thermal and pressure conditions leading to decomposition and methane mobilization over a variety of magnitude, temporal and spatial scales. Using geophysical data to constrain state-of-the-art ice sheet/gas hydrate modelling, we investigate how past Northern Hemisphere ice sheets modulated carbon sequestration and release.  Our results provide the first quantitative assessment of widespread subglacial hydrate formation and mobilization during the last glacial, yields insights into global carbon cycle dynamics and informs potential future atmospheric greenhouse composition and feedbacks associated with shrinkage of the contemporary cryosphere.