Will Climate Change Be Responsible for More Glacial Lake Outburst Floods?

Image of a Himalayan river bridge that could be swept away in the event of a GLOF from the glaciers above (Source: GRID Arendal/Flickr).

How certain is it that climate change increases the frequency and severity of glacier lake outburst floods or GLOFs? It turns out the answer is complicated and the subject of a new study published in The Cryosphere. Although previous research has examined the nature and characteristics of GLOF events in mountain ranges across the world, this recent study provides the first global assessment of the problems involved in developing a robust attribution argument for climate change and GLOF events.

GlacierHub has covered GLOFs throughout the years including major milestones into understanding their characteristics and an interview with a Peruvian farmer explaining his ongoing lawsuit with a German energy firm over climate risks. However, the GLOFs in this study refer specifically to ones caused by the failure of moraine dams. The formation of these moraine-dammed lakes and resulting GLOFs involve the process of thinning, flow stagnation, and glacier recession. Such moraines often contain a melting ice core built from transported rock debris. And, as stated in the study, “when they fail, large volumes of stored water can be released, producing glacial lake outburst floods.” These floods have already caused hundreds of fatalities across the world, destroying downstream communities and stunting the socio-ecological integrity in their wake.

Evidence of a glacial lake outburst flood in Nepal (Source: Matt W/Flickr).

This study presents an unprecedented global GLOF inventory related to the failure of moraine dams. The motivation behind the focus on GLOFs caused by moraine dams is the clear diagnostic evidence left behind by moraine-dam failures as well as the conventional link between climate change and moraine-dammed lake formation.

Dan Shugar, one of the authors of the study and a geoscientist at the University of Washington Tacoma, explained that these particular glacial lakes don’t tend to reform once they burst. “With ice-dammed lakes that burst, the glacier typically ‘heals’ the breach, and so they can reform and burst again and again,” he said, which allows for clear diagnostic evidence.

Adam Emmer, a fellow author from CzechGlobe, told GlacierHub that the research is the first attempt to link climate change with GLOF patterns on a global level. Christian Huggel, another author and geographer from the University of Zurich, added that this is no trivial task.

“It is reasonable to assume that glacier hazards will increase as the climate warms, and we were somewhat surprised to see that over the past century or so, there has not been a monotonic rise in outburst floods,” Shugar told GlacierHub. “The reality, as usual, is a bit more complicated.”

Aerial image of glaciers in Bhutan at risk of GLOF events in the future (Source: The Ice Age/Twitter).

As simple as it would be to link warming climate to the increased frequency and severity of GLOFs, a number of factors go into a GLOF event. Differences in ground thermal conditions, for example, plus presence or absence of ground ice or permafrost all influence extreme weather. Seismic processes, topography, and glacial history also vary across mountain ranges.

However, as stated in the study, “although we know that GLOFs involve a complex set of dynamics… there must be a relationship here to climatic warming.” The scientists did conclude a lagged time response when it comes to GLOFs and climate change, with outburst flood frequency actually decreasing in recent decades since 1970.

“We suggest that outburst floods will become more frequent in response to contemporary warming, but that there is a lag built into the system,” Shugar explained. Thus, although an attribution of GLOFs to climate change is possible, a suite of factors influencing GLOF occurrence means scientists cannot adequately quantify the attribution as many might hope.

Ultimately, from assessing the timing of climate forcing, lag times in glacier recession, lake formation, and moraine-dam failure, the study predicts an increase in GLOF frequency in the coming decades. But because of the assortment of factors involved in a GLOF event and glacier recession, the study states that GLOF frequency has not fluctuated directly in response to global climate change.

A close connection is certainly present, but the varying response times from mountain to mountain and region to region indicate that the relationship is hidden in messy response time dynamics.Prior to this study, no global database had been created that focused specifically on GLOFs related to the failure of moraine dams. The scientists argue that more studies exploring a global context of GLOFs are necessary to better understand the links to the changing climate and naturally-occurring variability. On the policy level, a better understanding of GLOFs’ relationship to present and future climate change is of great interest at both national and regional government levels due to the devastation potential of these events.

Policymakers are using information on GLOFs to develop early warning systems and small-scale infrastructure projects to mitigate their risks (Source: UNDP Pakistan/Twitter).

This research may also make its way to the courtroom. As Huggel explained to GlacierHub, “The study is certainly very relevant with respect to the ongoing legal case where a Peruvian sued German energy producers for the GLOF risks caused by anthropogenic climate change. In principle, more such court cases could follow.” There is also the question of loss and damages, and whether affected countries could receive compensation (or at least stronger assistance) for the resultant (or potential) damage.