Rising Temperatures May Not Cause More Frequent GLOF Catastrophes

Glacial lake outburst floods, GLOFs for short, are expected to increase in frequency over time as global temperatures warm. These floods can be very sudden, fast-flowing, and powerful enough to form their own seismic signatures. They carry water, rocks, trees, and debris down valleys, destroying homes and sometimes killing people and livestock.

Many glaciers such as ones in the Hindu-Kush, Karakoram, and Himalayas are shrinking rapidly, forming glacial lakes and causing potentially catastrophic floods for tourists and nearby communities. Understanding the influence of climate change on the frequency and intensity of GLOFs will help disaster risk managers in developing early warning systems and disaster response plans.

Glacial lake by the base of Gokyo Ri, a peak on the Ngozumpa glacier, the largest glacier in Nepal (Source: AlexCuby//Pixabay)

Although experts expect these moraine-dammed glacial lakes to grow in size with the addition of glacial meltwater, the risk of GLOFs doesn’t necessarily increase everywhere. In a recent article published in Nature Climate Change, Georg Veh and several of his colleagues from the University of Potsdam and the GFZ German Research Centre for Geosciences examined historical flood occurrences in the the Himalayas that were considered to be hotspot regions for glacier retreat. They aimed to observe GLOF activity for the last few decades, assessing changes in frequency and trend.

Some climate scientists hypothesize that dangerous GLOFs will become more frequent with the growth of moraine-dammed glacial lakes. According to Veh and his colleagues, testing this hypothesis is confounded by incomplete data. Historical reports on GLOF activity are selective, and the researchers speculated that 40 reports on GLOFs in the Hindu-Kush, Karakoram, and Himalayas since 1935 only accounted for large and destructive cases. This suggests that a significant portion of the data might be missing.

To account for reporting bias, the team examined changes in GLOF frequency through a systematic inventory of activity in the Hindu-Kush, Karakoram, and the Himalayas. They were able to identify moraine-dammed lakes and activity in Landsat images from the late 1980s to 2017. Researchers used a random forest model, which was able to generate land-cover maps. These maps provided probabilities for water, cloud, shadow, ice, and land cover across the image tiles. During GLOFs, lakes would abruptly decrease in size, changing from a water to land classification in the Landsat image.

Lake Saiful Muluk in the Karakorum mountain range (Source: Mansoor Haque 199108/Wikimedia Commons)

The research team mined over 8,000 Landsat images of the region. In addition to the 17 GLOFs reported since the 1980s, the researchers added 22 newly detected occurrences. They found that despite increasing rates of meltwater entering glacial lakes, particularly in the central and eastern Himalayas, which observed rates of up to six times higher than the northern basin, GLOF abundance remained low.

The average annual rate of 1.3 GLOFs in the region remained unchanged over the last three decades. The fraction of GLOFs per unit of meltwater area, however, has declined since the 1990s.

“We infer that climate-driven rates of glacier melt and lake expansion may be unsuitable predictors of contemporary outburst potential,” stated the researchers.

Their findings were consistent with research on glacial lakes in the Patagonian Andes.

The scientists inferred that their result may indicate a sort of resilience to climate-driven triggers such as glacier calving and ice avalanches, the most frequently reported cause of GLOFs. Unfortunately the team was unable to identify triggers for the 22 newly identified outburst floods, although 16 of them came from pro-glacial lakes within proximity of their parent glaciers. GLOFs generated by calving and avalanche events become less relevant as glaciers retreat from the lakes they have formed.

They also mentioned the importance in perceiving the role of alternate triggers such as earthquakes and landslides in the formation of outburst floods. They give the example of the 2015 Gorkha earthquake in the Nepalese Himalayas. The 7.8 magnitude earthquake did not provoke GLOFs, but it generated landslides which hit glacial lakes.

Veh said the research demonstrated that climate as a sole driver did not change GLOF frequency over the last decade, but that does not mean that frequency will remain unchanged in the future.

“Reliably projecting the future frequency of outburst floods remains an open issue, given that our current knowledge of triggers is quite vague today,” Veh said. The updated inventory of outburst floods will allow for further examination of these cases in more detail.

“Better knowledge of the processes involved in glacial lake outburst floods will ultimately reduce current uncertainties in hazard and risk assessment,” he added.

The researchers believe new generations of optical and radar sensors may be effective in better recognizing GLOF triggers and determining when the next glacier lake outburst flood might occur.

Read More on GlacierHub:

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South Georgia Island’s Novosilski Glacier Is Retreating Rapidly

Novosilski Glacier is a large tidewater outlet glacier on the west (cloudier) coast of South Georgia,  terminating in Novosilski Bay. It shares a divide with the rapidly retreating Ross and Hindle Glacier on the east coast.  

Gordon et al. (2008) observed that larger tidewater and calving outlet glaciers generally remained in relatively advanced positions from the 1950’s until the 1980s. After 1980 most glaciers receded; some of these retreats have been dramatic.

The change in glacier termini position that have been documented by Cook et al (2010) at British Antarctic Survey in a BAS retreat map identified that 212 of the peninsula’s 244 marine glaciers have retreated over the past 50 years and rates of retreat are increasing.

Pelto (2017) documented the retreat of 11 of these glaciers during the 1989-2015 period.

Here we examine Landsat images from 2001-2018 and the British Antarctic Survey GIS of the island to identify the magnitude of glacier change.

The Novosilski Glacier is seen in Landsat images from 2001 and 2018. The red arrow indicate 2001 terminus location, yellow arrow the 2018 terminus location, pink arrows the fringing grounded sections of marginal ice. The South Georgia BAS map, lower image, indicates glacier margin position and elevation contours.

In 2001 Novosilski Glacier terminated in shallow water just east of a small island that acted as a pinning point (red arrow).  By 2009 the glacier had retreated only a minor amount from this island into deeper water.

A rapid retreat ensued, and by 2016 the glacier had retreated into a narrower fjord reach. The north and south margins featured remnant ice that was based above tidewater (pink arrows). The blue arrows in the 2016 Landsat image indicate the large accumulation area feeding Novosilski.  

The Novosilski Glacier is seen in Landsat image from 2016. The red arrow indicates 2001 terminus location, yellow arrow the 2018 terminus location, pink arrows the fringing grounded sections of marginal ice, and blue arrows the glacier flow directions.

By 2018 the 2-kilometer-wide calving front had retreated 2.5 km from the 2001 position. There is little evident thinning upglacier of the terminus, and there is a significant increase in surface slope suggesting that unless calving rate increases the terminus can remain near its current position.

The snowline is below 500 meters in each of the satellite images of the glacier. This is not a particularly hospitable section of coastline and the BAS has only identified gentoo penguins having colonies in the area.

The Novosilski Glacier is seen in a Landsat image from 2009. The red arrow indicates 2001 terminus location, the yellow arrow shows the 2018 terminus location.

This article originally appeared on From a Glacier’s Perspective, a blog published by the American Geophysical Union.

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Photo Friday: The Shrinking Patagonian Icefield

Typically obscured by cloud cover and mist, it is difficult to study the glaciers of the Southern Patagonian Icefield from space. However, on April 29, May 1, and May 24, 2016, NASA satellites captured clear images of the glaciers. Compiled into striking mosaics, this data reveals a great deal about the shrinking icefield.

For example, the mosaics obviate the differences between the eastern and western parts of the icefield. Heavy precipitation on the landscape west of the icefield keeps the terrain green and lush, while the eastern regions of retreat are characterized by bare, brown rock. Glacial flour, a fine sediment produced when ice grinds over of bedrock, colors the proglacial lakes a distinct turquoise.

Enjoy observing the Patagonian Icefield through the images below.

 

Upsala, Jorge Montt, and Occidental Glaciers, detailed below, shown in relation to one another (Source: NASA).

 

Upsala Glacier, on the eastern edge of the icefield, has retreated constantly since observation began in 1810 (Source: NASA).

 

The density of icebergs in the fjord before Jorge Montt Glacier shows the intense retreat of glaciers in the icefield (Source: NASA).

 

Occidental Glacier has retreated only about 1 kilometer since the 1980s (Source: NASA).

 

 

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Scaling Quelccaya: Depicting Climate Change Through Art

The Quelccaya Ice Cap, located in the Peruvian Andes, is the world’s largest tropical glaciated area. In an effort to conceptualize the scale of the glacier’s retreat, Meredith Leich, M.F.A. in film, video, media, and new animation at SAIC, and Andrew Malone, Ph.D. in glaciology and climatology at the University of Chicago, collaborated on a project in 2016 called “Scaling Quelccaya.” The project combines 30 years of satellite imagery of the Peruvian ice cap, 3-D animation, and gaming software to create a virtual representation of the glacier’s retreat using the city of Chicago as a “metering stick,” allowing viewers to develop a more elaborate sense of Quelccaya’s scale.

The 3-D animation enables viewers to visualize the Peruvian ice cap and virtually “fly” through the Andes by converting satellite data into a Digital Elevation Model, then using a gaming software called Unity to transform it into a 3-D model. “Scaling Quelccaya” was initiated by Leich, who acknowledged having only an incomplete idea about the impact of climate change at the start of the project. Malone’s research of the Quelccaya ice cap was then transformed into the 3-D animation in order to allow the audience to visualize the melting effects on the ice cap, a more effective tool than graphs or charts alone. Malone used satellite data from the Landsat program, a series of satellites that has provided the longest temporal record of data of Earth’s surface, including the Quelccaya Ice Cap, to provide an accurate representation of the amount of ice loss over this period.

Qori Kalis, one section of the Quelccaya Ice Cap, shown in 1978 (left) and 2011 (right) (Source: Edubucher/Creative Commons).

This project allowed Leich and Malone to visually portray the consequences of climate change in ways that viewers could understand intuitively, contrasting the disappearance of the glaciers to a hypothetical disappearance of the Chicago area. In an interview with GlacierHub, Meredith Leich explains the inspiration behind the project’s comparison of Quelccaya with Chicago: “Instead of solely describing numerically how much Qori Kallis (one of Quelccaya’s glacial outlets) had retreated, we could show visually that the glacier had retreated the distance between the Willis Tower and the Tribune Tower in Chicago – a distance that an urban resident would understand viscerally, with embodied memories of walking the city streets.” The name of the project plays on the word scale, since it shows the scale of glacier retreat and allows viewers to scale the summit of a virtual glacier.   

To get a better understanding of Quelccaya’s volume of snow, Leich and Malone began generating DEMs – Digital Elevation Models – from the satellite data obtained from Shuttle Radar Topography Mission (SRTM). The DEM calculated the height of every point on the glacier’s surface. The software then selected a shade of black, gray or white to represent each height. The uppermost height was registered as white, the lowest height as black, and every height in between mathematically assigned a corresponding shade of gray. Next, they generated a 3-D model with a gaming software called Unity by importing height maps as “terrains.” The terrain function read a combination of the DEM to create the virtual 3-D model based on the topography of the land. Finally, they used Maya, an animation and modeling program, to apply texture to the surface of the terrain, add light, and be able to move around the glacier to see it from all angles.

Digital Elevation Model of Quelccaya Ice Cap (Source: Meredith Leich/Tumblr).

Once the model was finished, Leich and Malone removed the equivalent of ice in Quelccaya and placed it on a model of Chicago as snow, with different variations of snow such as fluffy snow, firm snow, ice, and others. New York City (specifically Manhattan) is often chosen as a prime example of the effects of climate change because of its popularity. Rather than compare Quelccaya to New York City, the project focused on Chicago because of its lack of representation, and because the research and creation of “Scaling Quelccaya” took place in Chicago.

When asked about any challenges that they faced in recreating the glaciers through the 3-D technology, Andrew Malone told GlacierHub that “passing information between different softwares was a big challenge.” “We found early that files had to be in particular formats and that each software had its idiosyncrasies. One of our first (technologically) successful 3-D visualizations looked as though someone had taken a buzzsaw to every mountain top,” he said. “When I outputted the digital elevation models (DEMs) to an image in the correct format for Meredith, the QGIS default was truncating the highest and lowest elevations.” Once the models were complete, it allowed for their audience to connect to the glacial scenes and bring two distant entities, Chicago and Quelccaya, into the same space.

The project included a feature that enabled viewers to grasp how much of Quelccaya’s snow would cover Chicago. The city itself was under about 600 feet of snow, extending over almost all of the metropolitan area. According to Leich, the inspiration behind this feature was that this kind of visualization would make the science behind climate change more accessible and visually apparent. “Many stories about climate change also involve a doomsday narrative, and we wanted to convey something more subtle and informative than stoking fears,” she said.

Quelccaya Ice Cap (Source: Edubucher/Creative Commons).

Meredith A. Kelly, a glacial geomorphologist at Dartmouth College, noted in an interview with the New York Times, that “the melting now under way appears to be at least as fast, if not faster, than anything in the geological record since the end of the last ice age.” If the ice cap melts away and disappears, it would leave millions of people in surrounding downstream communities, who rely on this water source for drinking and electricity, with a smaller and less reliable water supply.

In an interview with GlacierHub, Gustavo Valdivia, a Ph.D. student in anthropology at John Hopkins University, explained how some in Peru have been adapting: “People who live in Phinaya, the closest community to Quelccaya, are mostly herders of alpacas and llamas. In the last years, they have been building local irrigation systems, changing their herds’ composition – to include more resistant animals – and also changing their herding techniques.” If the Phinaya community does not have a water supply for their animals, ultimately, their livelihoods will suffer, he added. Projects such as “Scaling Quelccaya” attempt to demonstrate the  effects of climate change to the lay public by bringing effects such as these closer to home.  

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Roundup: Glacier-Fed Lakes, Remote Sensing, and Glacial Succession

Roundup: Glacier-Fed Lakes, Remote Sensing, and Soil

 

Global Warming and Glacier-Fed Lakes

From Freshwater Biology: “Climate warming is accelerating the retreat of glaciers, and recently, many ‘new’ glacial turbid lakes have been created. In the course of time, the loss of the hydrological connectivity to a glacier causes, however, changes in their water turbidity (cloudiness) and turns these ecosystems into clear ones. To understand potential differences in the food-web structure between glacier-fed turbid and clear alpine lakes, we sampled ciliates (single-celled animals bearing ciliates), phyto-, bacterio- and zooplankton in one clear and one glacial turbid alpine lake, and measured key physicochemical parameters. In particular, we focused on the ciliate community and the potential drivers for their abundance distribution.”

Learn more about how global warming affects lakes here:

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A glacier-fed lake (Source: Rodrigo Soldon/Creative Commons).

 

Glacier Remote Sensing Using Sentinel-2

From Remote Sensing: “Mapping of glacier extents from automated classification of optical satellite images has become a major application of the freely available images from Landsat. A widely applied method is based on segmented ratio images from a red and shortwave infrared band. With the now available data from Sentinel-2 (S2) and Landsat 8 (L8) there is high potential to further extend the existing time series (starting with Landsat 4/5 in 1982) and to considerably improve over previous capabilities, thanks to increased spatial resolution and dynamic range, a wider swath width and more frequent coverage.”

Read more about remote sensing here:

Test region 1 in the Kunlun Mountains in northern Tibet using a S2A image from 18 November 2015 (Source: Remote Sensing).
Test region 1 in Tibet using a S2A image from 2015 (Source: Remote Sensing).

 

The Impact of Soil During Glacial Succession

From Journal of Ecology: “Plant–soil interactions are temporally dynamic in ways that are important for the development of plant communities. Yet, during primary succession [colonization of plant life in a deglaciated landscape], the degree to which changing soil characteristics (e.g. increasing nutrient availabilities) and developing communities of soil biota influence plant growth and species turnover is not well understood. We conducted a two-phase glasshouse experiment with two native plant species and soils collected from three ages (early, mid- and late succession) of an actively developing glacial chronosequence ranging from approximately 5 to <100 years in age.”

Learn more about the impact of soil during glacier succession here:

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A photo of Lyman Glacier with different plants growing on its face (Source: Marshmallow/ Creative Commons).

 

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Satellite Images Offer Clues to Causes of Glacial Lake Flooding

(from journal article: Field observations for glacial lakes: (a) the rapidly expanding Lake Longbasaba in 2012; (b) an areally increasing glacial lake at the Middle Rongbu Glacier near Mount Qomolangma (Everest) in 2008.)
(from journal article: Field observations for glacial lakes: (a) the rapidly expanding Lake Longbasaba in 2012; (b) an areally increasing glacial lake at the Middle Rongbu Glacier near Mount Qomolangma (Everest) in 2008.)

Satellites are now allowing us to track the behavior of icy glacial lakes on the Himalayan Mountains–in particular the conditions that lead to glacial lake outburst floods (GLOFs), which have become increasingly frequent in the region over the past 20 years.

Researchers from the Institute of Mountain Hazards and Environment and the State Key Laboratory of Cryosphere Sciences in China published a study in PLOS One in December of last year that catalogued data from lakes in the central Himalayas between 1990 to 2010.

The scientists, Drs. Yong Nie, Qiao Liu, and Shiyin Liu, used images from Landsat scientific satellites to count and measure glacial lakes in the region. As the longest running remote sensing project, Landsat has over 40 years of images available across the globe.

(from journal article: Distribution of glacial lakes in the central Himalayas)
(from journal article: Distribution of glacial lakes in the central Himalayas)

GLOFs – floods that occur when a lake dammed by a glacier or glacial moraine is released – are hazardous to communities located at elevations below the burst lake. Flooding and debris flows damage infrastructure, cause property loss, and can take lives, as GlacierHub has reported in prior posts. It is widely believed that rising temperatures due to climate change and reduced albedo of the ice from cryoconite (also known as carbon dust particles) are melting the glaciers at higher rates and causing lake volumes to rise, which in turn increases the risk of GLOF events. But the specific processes that lead to GLOF outbursts are not well understood.

By looking at lakes at four time points (1990, 2000, 2005 and 2010), at different elevations (from 3,500 to 6,100 meters), of different types (pro-glacial and supraglacial), and of varying sizes, the researchers were able to identify which lakes expanded faster and burst more frequently to understand which ones pose the greatest risk of GLOFs.

A GLOF from above in Alaska’s Kennai Peninsula (Travis S./Flickr, some rights reserved)
A GLOF from above in Alaska’s Kennai Peninsula (Travis S./Flickr, some rights reserved)

Overall, it was found that total lake surface area for the 1,314 lakes in the central Himalayas had increased over the 20-year period. Drs. Nie, Liu and Liu found that more lakes on the northern side of the central Himalayan range were expanding rapidly. They also found that pro-glacial lakes (lakes at the terminus of a glacier) grew faster than supraglacial lakes (lakes on the surface of the glacier). Some pro-glacial lakes are connected directly to glaciers while others are not, but those that were connected grew far faster. Additionally, larger pro-glacial lakes were likely to flood sooner than smaller ones and more changes to glacial lakes occurred at the altitudes between 4,500 and 5,600 meters.

The dynamics of alpine glacial lakes are complex, but this study could help communities monitor lakes at high risk of flooding and to create early-warning systems and disaster preparedness plans.

PAPER DOI: 10.1371/journal.pone.0083973.g002

GLOF aftermath in Peru ( Will McElwain/Flickr, some rights reserved)
GLOF aftermath in Peru (Will McElwain/Flickr, some rights reserved)

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