Credit: USGS

Glacier lakes bounded by natural ice dams can empty suddenly, causing massive flooding. The floods, which empty along subglacial paths and are known as jökulhlaups, can be very large and last from days to weeks. Predicting the timing and the peak flow of these floods has proven difficult, but now researchers have found that their occurrence is linked to air temperature.

Felix Ng from the University of Sheffield and colleagues have used thermo-mechanical models to study 39 of these events at Merzbacher Lake in the Kyrgyz Republic, a lake that completely empties each time it floods. They found that the maximum flow of water out of the lake is greater when the air is warmer, owing to the faster rate at which meltwater enters the lake. Air temperature also controls the time it takes the lake to refill and therefore influences the timing of the next flood.

As air temperatures increase with climate change, glacier lake outburst floods may become more hazardous, the researchers warn. However, it is also possible that the timing of floods will shift to cooler months as the climate warms, or that the lakes may become smaller as glaciers thin.