Meltwater lakes cause glaciers to retreat much more rapidly

An international team of researchers led by the University of Leeds has estimated how much meltwater lakes, which form at glacier margins, accelerate ice loss. The researchers found that these bodies of water cause glaciers to retreat much farther and faster compared to glaciers that terminate on land. 

According to the researchers, the effects of glacial lakes are not represented in current ice sheet models. This means that predictions of ice loss from lake-terminating glaciers are underestimated. 

“An ice cube in a bowl of water is going to melt much more quickly than an ice cube sitting on a table, and the effect proglacial lakes have on glacier ice is roughly the same,” said study lead author Dr. Jenna Sutherland.

“The simulations show that the influence of a proglacial lake on a glacier predominantly takes place over decades to centuries rather than over millennia, meaning the glacier recedes much faster than it ever could from climatic changes alone.”

Many mountain glaciers now terminate in meltwater lakes, which are formed as water becomes trapped behind ridges of glacier debris. The size and number of glacial lakes have drastically increased in recent years as a result of climate change. However, their impacts on glacial retreat have not been entirely clear. 

Based on computer simulations, the researchers determined that the presence of meltwater causes glaciers to shrink more than four times faster, and accelerates ice flow by up to eight times compared to other glaciers that terminate on land in the same climate. According to the experts, one land-terminating glacier in particular took 1,000 years to recede to the extent that a nearby lake-terminating glacier reached in 100 years.

“Our findings suggest that simulations of past, contemporary or future glaciers ignore the effects of ice-contact lakes and will likely mis-represent the timing and rate of recession, especially the changes to the timing and rate that will occur once a proglacial lake forms,” said study co-author co-author Dr Jonathan Carrivick. “These effects need to be included in all future models and simulations if we are to have an accurate global picture of glacial ice loss.”

The research was focused on the effects of a meltwater lake on the Pukaki Glacier in New Zealand, but the experts said the findings can be applied to all lake-terminating glaciers.

“This study is also critical because the timing of ice retreat is often used to determine the synchrony, or lack thereof, in climate events globally,” said study co-author James Shulmeister. “Major inferences have been made about the roles of phenomena like oceanic circulation in affecting the global climate system from glacial retreat timings. If the timings are wrong, the relationship between these processes may need to be re-examined.”

The research is published in the journal Geophysical Research Letters.

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By Chrissy Sexton, Earth.com Staff Writer