Glacier hazards: Will they change in the future?

THE ISSUE

Glaciers can pose significant hazards (e.g., floods, landslides, ice falls) with disastrous consequences for people and infrastructure, especially as glaciers retreat in response to climate warming. Adverse potential risks are exacerbated as human activities increasingly expand into regions prone to glacier hazards.

WHY IT MATTERS

A wide range of glacier hazards has been reported^1,2:

1. Debris- and ice-dammed lakes can drain suddenly, causing dangerous flooding that temporarily rivals the largest rivers on Earth. These abrupt floods are among the most destructive types of glacier disasters (Figure 1). They have led to significant loss of lives and infrastructure, such as the 2013 flash flood in the Kedarnath area in the Indian Himalaya that killed an estimated 6,000 people.

   Figure 1. Catastrophic drainage from a glacier-dammed lake (here shown prior to draining) on the Mendenhall Glacier in Alaska led to flooding and severe property damage in Juneau, Alaska, in August 2023. Image courtesy University of Alaska Southeast.

   

2. Such floods often mobilize large amounts of sediment and inundate downstream areas with debris layers tens of meters thick.

3. Ice masses breaking off from steep mountain glaciers can cause severe damage in high-mountain regions (Figure 2). Recently deglaciated slopes are less stable and are prone to landslides, debris flows, and catastrophic rock-slope failures. For example, a huge ice/rock failure and subsequent mudflow killed more than 120 people in the Caucasus in 2002.

   Figure 2. A catastrophic ice avalanche in Tibet killed nine people and numerous livestock in 2016. Images are from Landsat-8 on 24 June prior to the glacier collapse (left) and Sentinel-2 on 21 July after the collapse (right). Source: NASA Earth Observatory (https://earthobservatory.nasa.gov/).

   

4. In glaciated regions with active volcanoes, such as Iceland, Alaska, and Kamchatka, the interaction between hot volcanic ash and ice can produce muddy volcanic debris flows (“lahars”). These mudflows can travel several tens of kilometers and reach speeds of more than 60 km per hour. Major cities in the Pacific Northwest, such as Seattle, are within reach of potential lahars.

5. Glacier surges, which involve sudden ice flow speed-ups and often significant advances of individual glaciers of up to several kilometers within a few months, can threaten infrastructure such as roads or pipelines (e.g., in Alaska). On the Pamir Plateau a surge advance in 2015 buried summer pastures.

6. Icebergs breaking off glaciers into the sea can block shipping lanes and threaten ships. An attempt to avoid such icebergs contributed to the infamous Exxon Valdez oil spill. Icebergs regularly block harbors in Greenland, and the rolling of icebergs causes local tsunamis that have led to loss of infrastructure and lives.

7. In some cases, several glacier hazards combine and amplify the negative effects. For example, a surging glacier can dam a river, leading to the formation of glacier lakes that may cause floods, or a landslide facilitated by glacier retreat can cause a glacier-dammed lake to overflow and drain catastrophically.

STATE OF KNOWLEDGE

Though some glacier-related hazards are expected to increase in intensity and frequency in response to global warming, others may decrease as glaciers shrink or even disappear. Recent observations show a significant increase in the number and volume of potentially hazardous moraine-dammed lakes, especially in High Mountain Asia. These moraines are susceptible to collapse when the lake surface reaches a critical level or overtops because they are composed of loose, poorly sorted material eroded by the glacier. As the moraines become more stabilized with time, the risk of outburst flood from these lakes may decline. Failure of such lake dams can also be triggered by earthquakes. Slopes that become exposed as glaciers recede are also expected to be more susceptible to slope instabilities that can have far-reaching effects, including severe damage to towns located even at distances of tens of kilometers from the event. In contrast, the risk of glacier surges may decrease with climate warming as some surge-type glaciers may no longer build up sufficient mass to trigger a surge. The mechanisms for glacier surges are still not well understood, however, making it difficult to predict how climate change will affect the frequency of surging. Hazards due to icebergs are expected to decrease as tidewater glaciers recede onto land but can increase where the glacier front is retreating into deeper water and calving off more icebergs.

WHERE THE RESEARCH IS HEADED

Recent developments in satellite observations have increased our ability to monitor and detect potential glacier hazards including in remote areas. For example, the growth of potentially hazardous glacier lakes or even individual icebergs can be tracked with high precision and in almost real time. However, predicting the timing and magnitude of glacier hazards remains challenging due to incomplete understanding of the processes driving glacier hazards and the irregular and sporadic nature of such events. Very accurate predictions of some impending natural disasters are possible with modern surveying equipment, but they require concerted (and expensive) equipment in the field and recognition that a potentially dangerous situation is developing. Therefore, a major goal of current research is to develop cost-effective operational tools and physically based models that can provide accurate, short-term (hours, days) and longer-term (years to decades) projections of the location, timing, and magnitude of glacier hazards. Efforts are also underway to develop effective remediation in areas affected by glacier hazards.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15230430.2024.2335991.

Additional information

Funding

This work was supported by the Office of Polar Programs, National Science Foundation.