Roundup: Thwaites Earthquakes, Peru Glacier Collapse Claims Lives, and an Alaskan Streamflow Study

Thwaites Glacier in Antarctica is Now Causing Earthquakes

Thwaites Glacier is one of Antarctica’s largest contributors to sea level rise from Antarctica.  Its rate of loss has doubled in the past three decades, earning it the moniker “doomsday glacier.” Understanding why it’s retreating so quickly has been a challenge, but glaciologists have recently discovered that the glacier is now generating its own seismic activity when it calves (breaks off icebergs into the ocean), which could help in unlocking the physical keys to this process. The findings were published early this year in Geophysical Research Letters. 

Read the full story on Thwaites earthquakes by Grennan Milliken on GlacierHub here.

Icebergs near the terminus of Thwaites Glacier. If it were to collapse it could raise global sea levels by ten feet. (Source: NASA)

A Catastrophic Glacier Collapse and Mudflow in Salkantay, Peru

On 23 February 2020 an enormous, catastrophic debris flow tore down the Salkantay River in Santa Teresa, Peru. This event has killed at least four people, with a further 13 reported to be missing. Given the magnitude of the flow, this number is probably uncertain. The mudflow was captured in an extraordinary video posted to YouTube.

Read the full post on the Salkantay ice/rock avalanche by Dave Petley on GlacierHub here.

A Classification of Streamflow Patterns Across the Coastal Gulf of Alaska

From the plain language abstract: “Streams provide society with many benefits, but they are being dramatically altered by climate change and human development. The volume of flowing water and the timing of high and low flows are important to monitor because we depend on reliable streamflow for drinking water, hydroelectric power, and healthy fish populations. Organizations that manage water supplies need extensive information on streamflow to make decisions. Yet directly measuring flow is cost‐prohibitive in remote regions like the Gulf of Alaska, which drains freshwater from an area greater than 400,000 km2, roughly the size of California. To overcome these challenges, a series of previous studies developed a tool to predict historical river flows across the entire region. In this study, we used 33 years of those predictions to categorize different types of streams based on the amount, variability, and timing of streamflow throughout the year. We identified 13 unique streamflow patterns among 4,140 coastal streams, reflecting different contributions of rain, snow, and glacial ice. This new catalog of streamflow patterns will allow scientists to assess changes in streamflow over time and their impact to humans and other organisms that depend on freshwater.”

Read the full study published by the American Geophysical Union here.

Source: AGU/Sergeant et al

Read More on GlacierHub:

Photo Friday: Norwegian Glacial Ice Preserves Ancient Viking Artifacts

Video of the Week: Animation Shows Frequency of Antarctic Calving Events

Black History Month: Honoring an Arctic Explorer

Thwaites Glacier in Antarctica is Now Causing Earthquakes

Thwaites Glacier is one of Antarctica’s largest contributors to sea level rise from Antarctica.  Its rate of loss has doubled in the past three decades, earning it the moniker “doomsday glacier.” Understanding why it’s retreating so quickly has been a challenge, but glaciologists have recently discovered that the glacier is now generating its own seismic activity when it calves (breaks off icebergs into the ocean), which could help in unlocking the physical keys to this process. The findings were published early this year in Geophysical Research Letters.  

Combing through seismograph readings collected in West Antarctica during a large calving event at Thwaites on February 8th 2014, a team of researchers found evidence of two low frequency earthquakes, each about 10-30 seconds long. Their hunch—that the quakes came from the calving—was confirmed when they matched the seismograph readings with satellite images taken on the same day. 

Thwaites Glacier
The rate of ice loss from Thwaites Glacier has doubled in the last thirty years. (Source: NASA)

They also discovered high frequency blips of seismic activity that chirped on and off in the week preceding the event. Glaciologist and lead author of the study, Paul Winberry, explained to GlacierHub that in these short bursts they were actually “hearing all these little cracks start to propagate.” It was the sound of countless cracks forming and popping apart, heralding the large break about to come. 

“Frequency” refers to the behavior of shockwaves that reverberate out from the source of the earthquake. Waves repeat their motion as they travel in a peak-valley-peak-valley pattern. Waves that do this rapidly are called high-frequency and those that do it slowly are called low frequency. High frequency waves are detectable over short distances; low frequency waves over long distances.       

Thwaites is the only known glacier in Antarctica to exhibit seismic behavior, whereas glaciers in Greenland have been recorded causing earthquakes for some time. This difference can be explained by the fact that the majority of Greenland’s icebergs capsize when they break off into the water. The result is a more boisterous form of calving that produces detectable earthquakes. Why Greenland’s icebergs capsize and Antarctica’s do not has to do with the physical makeup of each landmass’s ice sheets and where they start to float on the water.

Greenland glaciers flow down the island’s mountainous sides and break into icebergs when they hit the water. This behavior is common where a glacier’s terminus is close to where it starts to float—also known as the grounding line. Antarctic glaciers flow outwards horizontally, and continue on into the water as huge floating shelves that stretch miles out to sea. 

“Basically when [Greenland glaciers] start to go afloat, they form icebergs as opposed to Antarctica, where in most places they go afloat they don’t break off instantaneously but they form these big long ice shelves—floating extensions,” said Winberry. “It’s completely different.”

The other key component of capsizing is the physical shape. Greenland’s icebergs are top-heavy. “They’re taller than they are wide. They’re not stable, so when they break off they want to flip over,” said Winberry. 

Tim Bartholomaus, a glaciologist from the University of Idaho who has studied Greenland’s glaciers told GlacierHub that the capsizing icebergs bang into the front of the glacier as they’re flipping over and that generates the earthquake. “As they’re rotating en masse, they’re putting their shoulder against the back of the terminus and giving it an enormous push as they’re rotating.” 

Icebergs near the terminus of Thwaites Glacier. If it were to collapse it could raise global sea levels by ten feet. (Source: NASA)

These collisions don’t normally occur during calving in Antarctica because the ice sheets are far bigger, already floating on the water, and terminate far from the grounding line. “Those icebergs break off and form New England or Delaware-sized chunks. And when that happens they kind of slowly drift away,” said Winberry. That Thwaites is now generating detectable seismic earthquakes means one thing: its icebergs are likely capsizing because its terminus is now close to the grounding line. 

“The fact that Thwaites is now doing this slab capsize style of calving, that means that it is breaking off right at the point where the glacier is hitting the ocean,” said Bartholomaus. 

The capsize calving at Thwaites on February 8th 2014 sent low frequency waves traveling—and shaking—through the ice and land underneath for hundreds of miles. It generated enough energy to show up on seismometers over 900 miles away as a magnitude 3.0 earthquake.  

Over the last three decades, the Thwaites glacier has lost about 600 billion tons of ice. Some scientists fear that with an increased rate of 50 billion tons of ice lost a year in recent times, runaway instability of the glacier may already be underway. Total collapse of the glacier would raise global sea levels by 10 feet. Thwaites’ newfound seismic activity suggests that its retreat has now reached land. 

“It’s lost all of its floating ice,” Winberry told GlacierHub. “The floating extension has basically disappeared. So to understand the future retreat of the glacier, we need to understand this different style of calving behavior.” 

While that may be concerning, it also gives scientists a new tool for better understanding the process of calving at Thwaites. So far, glaciologists have relied heavily on satellite imagery for studying large scale calving events in Antarctica, but satellites usually only take one picture a day or every two days.  “A lot happens between those two days. In these calving events, the flipping of these icebergs and actual breaking apart can happen over minutes to hours,” said Winberry. Being able to “listen” to them unfold in near real time adds a whole new element. 

“That is going to help us unravel the physics of how these icebergs actually form, which is what we need to know to produce better predictions of future retreat of this glacier” said Winberry. 

Read More on GlacierHub:

Video of the Week: Animation Shows Frequency of Antarctic Calving Events

A Catastrophic Glacier Collapse and Mudflow in Salkantay, Peru

Roundup: A New Glacier Surge Study, Three Decades of Caucasus Glacier-Debris Change, and Mining Expansion in Greenland

Roundup: Volcanoes, Cryoseismology and Hydropower

Roundup: Kamchatka, Cryoseismology and Bhutan

 

Activity in Kamchatka’s Glacier-Covered Volcanoes

From KVERT: “The Kamchatka Volcanic Eruption Response Team (KVERT) monitors 30 active volcanoes of Kamchatka and six active volcanoes of Northern Kuriles [both in Russia]. Not all of these volcanoes had eruptions in historical time; however, they are potentially active and therefore are of concern to aviation... In Russia, KVERT, on behalf of the Institute of Volcanology and Seismology (IVS), is responsible for providing information on volcanic activity to international air navigation services for the airspace users.” Many of these volcanoes are glacier-covered, and the interactions between lava and ice can create dramatic ice plumes. Sheveluch Volcano currently has an orange aviation alert, with possible “ash explosions up to 26,200-32,800 ft (8-10 km) above sea level… Ongoing activity could affect international and low-flying aircraft.”

Read more about the volcanic warnings here, or check out GlacierHub’s collection of photos from the eruption of Klyuchevskoy.

Klyuchevskoy, one of the glacier-covered volcanoes in Kamchatka that KVERT monitors, erupting in 1993. (Source: Giorgio Galeotti/Flickr)
Klyuchevskoy, a glacier-covered volcano monitored by KVERT, erupting in 1993 (Source: Giorgio Galeotti/Creative Commons).

 

New Insights Into Seismic Activity Caused by Glaciers 

In Reviews of Geophysics: “New insights into basal motion, iceberg calving, glacier, iceberg, and sea ice dynamics, and precursory signs of unstable glaciers and ice structural changes are being discovered with seismological techniques. These observations offer an invaluable foundation for understanding ongoing environmental changes and for future monitoring of ice bodies worldwide… In this review we discuss seismic sources in the cryosphere as well as research challenges for the near future.”

Read more about the study here.

The calving front of an ice shelf in West Antarctica as seen from above (Source: NASA/Flickr)
The calving front of an ice shelf in West Antarctica (Source: NASA/Creative Commons).

 

The Future of Hydropower in Bhutan

From TheThirdPole.net: An interview with Chhewang Rinzin, the managing director of Bhutan’s Druk Green Power Corporation, reveals the multifaceted challenges involved in hydropower projects in Bhutan. These challenges include the effect of climate change on glaciers: “The glaciers are melting and the snowfall is much less than it was in the 1960s and 70s. That battery that you have in a form of snow and glaciers up there – which melts in the spring months and brings in additional water – will slowly go away…But the good news is that with climate change, many say that the monsoons will be wetter and there will be more discharge,” said Rinzin.

Check out the full interview with Chhewang Rinzin here. For more about hydropower in Bhutan, see GlacierHub’s earlier story.

Hydropower plants are common in rivers fed by melting ice and snow in the Himalayas (Source: Kashyap Joshi/Wikimedia Commons)
A hydropower plant common in rivers fed by melting ice and snow in the Himalayas (Source: Kashyap Joshi/Creative Commons).