Reflections on subglacial megafloods: their possible cause, occurrence, and consequence for the global climate

Abstract

Huge water reservoirs exist subglacially, for instance in the form of lakes. Failure of a wall around such a lake underneath the central part of a large ice mass may result in huge water outbursts. The resulting megafloods will rarely be traceable along the ice front, because much power is lost by friction and because the flood spreads subglacially over a large area. Truly giant meltwater outbursts might, however, still have an enormous power when reaching the marginal area of an ice cap. Such a megaflood may both affect the integrity of the ice mass, and help create a sliding layer over which huge ice masses can be easily transported towards the ocean, thus triggering a Heinrich-like event. This would have great impact on the global climate. Some of the Heinrich events that occurred during the past hundreds of thousands of years may well have been due to giant subglacial water outbursts, and such a situation may equally well occur in the time to come.