Extreme basal heat flow and presumptive subglacial thermal springs in Northeast Greenland

While subaerial thermal springs are common around Greenland’s ice-free periphery, such springs have not yet been documented beneath the ice that covers ~85% of Greenland. Here, we present evidence that presumptive subglacial thermal springs play a critical role in maintaining two major subglacial lakes beneath Flade Isblink, in Northeast Greenland. The thermogenesis of these subglacial thermal springs may be hitherto undocumented recent volcanism, or exothermic weathering. This latter thermogenesis would be associated with the inflow of oxygenated meltwater and oceanic water into a tectonically fractured, pyrite-rich, carbonaceous mudstone basement beneath the ice cap. We estimate that these springs deliver localized basal heat flows of >960 mW m–2 beneath both lakes. This is extremely elevated relative to background geothermal flow. This heat flow maintains locally thawed ice-bed interfaces at the subglacial lakes, in an otherwise frozen-bedded ice cap. Given the sensitivity of ice flow to basal thermal state, subglacial thermal springs can therefore have a potent influence on local ice dynamics.