Fig. 1: Deriving the bathymetry and temperature of a large supraglacial pond on Khumbu Glacier, Everest region of Nepal. The sonar-equipped unmanned surface vessel nicknamed ‘BathyBot’ (left), and kayak retrieval of temperature loggers (right) [Credit: Scott Watson].
A creeping flux of ice descends Everest, creating the dynamic environment of Khumbu Glacier. Ice and snow tumble, debris slumps, ice cliffs melt, englacial cavities collapse, ponds form and drain, all responding to a variable energy balance. Indeed, Khumbu Glacier is a debris-covered glacier, meaning it features a layer of sediment, rocks and house-sized boulders that covers the ice beneath. Recent advances in understanding debris-covered glacier hydrology come from combining in situ surveys with remotely sensed satellite data.
The dramatic beauty of Nepal’s Everest region attracts a mix of trekkers, climbers, and scientists. Flowing down from the slopes of Mount Everest, the debris-covered Khumbu Glacier has drawn scientists from the mid-1900s, and offers temporary residence for research teams and a myriad of climbers. In some locations, Khumbu Glacier has thinned by up to 80 m in the last three decades, leading to moraines overlooking the glacier with impressive topographic relief and providing an instant visualisation of glacier mass loss for trekkers heading to Everest Base Camp.
Melt at the surface of this glacier is moderated by an undulating debris layer, which insulates the ice beneath, and enhanced locally by dynamic surface features such as supraglacial ponds and ice cliffs thinly veiled by debris. These features contribute disproportionately to melt and lead to the development of hummocky, pitted surface topography. The resulting variable surface topography and melt rates complicate meltwater runoff and flow routing across the glacier. To better understand them, in situ surveying (Fig. 1) is increasingly combined with fine spatial-temporal resolution satellite imagery to reveal the hydrological evolution of debris-covered glaciers, which is closely linked to their mass loss.
Hydrology of Khumbu Glacier
As with debris-free glaciers, water may be routed through supraglacial, englacial, and subglacial pathways, which are conceptually distinct but physically link to one another.
At Khumbu Glacier, surface channels collect and rapidly convey meltwater generated in the upper ablation area (Fig. 2), just below the treacherous Khumbu Icefall, incising at a faster rate than the surface melt. In the middle of the debris-covered area, such streams disappear into the glacier’s interior through cut-and-closure and/or hydrofracture.
Fig.2: The upper ablation area of Khumbu is drained by supraglacial channels which enter the glacier’s interior through hydrofracture and cut-and-closure, while the lower portion is characterised by pitted surface depressions and an increasing density of ponds. Right panel looking east to west shows the hummocky topography and ponding on Khumbu Glacier. [Credit: Evan Miles (left), Ann Rowan (right)].
In areas of low surface gradient , and particularly throughout the hummocky lower reaches of the glacier, supraglacial ponds collect water in surface depressions. These features haveregulate the runoff of debris-covered glaciers by seasonally storing meltwater. The annual melt cycle thus leads to pond expansion and contraction, or their disappearance when the protecting debris layer thaws and relict meltwater conduits become avenues for drainage (Fig 3). The areal fluctuation of ponds can be quantified using satellite images at different times, but cloud cover during the summer monsoon season limits useable imagery at a time when the ponds are most dynamic. Therefore, field-instrumented ponds provide valuable insights into their active melt season behaviour.
Fig. 3: A small 4.5 m deep pond that drained over the course of a year [Credit: Watson et al., 2017a].
Turbid ponds associated with debris influx from ice cliffs are often ephemeral but some can grow to hold vast quantities of water (Fig. 1). Stored water absorbs and transmits solar energy to melt adjacent ice, which generates additional meltwater and leads to pond expansion. The ponds also thermally undercut ice cliffs, leading to both subaqueous and subaerial retreat (Fig. 4). Khumbu Glacier has been developing a growing network of ponds in recent years, which means meltwater is increasingly stored on the surface of the glacier before contributing to downstream river discharge. Ponds that coalesce into larger and more persistent lakes behind unstable deposits of sediment can in some cases pose a hazard to downstream communities. Field and satellite-based techniques are therefore used simultaneously to monitor lake development.
Fig. 4. Supraglacial ponds often exist alongside ice cliffs. These ‘hot spots’ of melt can be observed with repeat point cloud differencing [Credit: Watson et al., 2017b]. An interactive view of the drained pond basin (right) is available here.
What lies beneath?
Ephemeral ponds drain into the ‘black box’ glacier interior, where relatively little is known about the internal structure and hydrology. Scientists have occasionally ventured into the subsurfac e realm through networks of englacial conduits that become exposed as the glacier thins (Fig. 5); such conduits often re-emerge at the glacier surface but may also lead to the bed. The conduits carry meltwater through the glacier but can become dormant if blocked by falling debris or creeping ice, or when the meltwater that sustains them finds a route of lesser resistance. Whilst satellite data can be used to infer the presence of conduits, field-based methods are required for hydrological budgeting and quantifying meltwater transit times. For example, dye tracing can detect the subsurface passage of meltwater where strategically placed fluorometers measure the receipt and dilution of the dye upon re-emergence. Such methods are crucial for developing an improved understanding of the links between, for example, flow in the supraglacial channels up-glacier and discharge at the outlet.
Fig. 5: An exposed conduit on Lirung Glacier (left) [Credit: Miles et al., 2017] and researchers inside a conduit on Ngozumpa Glacier (right) [Credit: Benn et al., 2017].
Multiple teams working across the Himalaya are advancing our understanding of debris-covered glacier hydrology, which is essential to forecast their future and quantify their downstream impact. With the ready availability of increasingly high temporal resolution satellite imagery (e.g. Sentinel-2, Planet Labs), the link between field and spacebourne observations will become increasingly complementary. Developing these links is crucial to upscale observations from specific sites more broadly across the Himalaya.
Scott Watson is a Postdoc at the University of Arizona, USA. He studies glaciers in the Everest region and the surface interactions of supraglacial ponds and ice cliffs. He also investigates natural hazards and the implications of glacial lake outburst floods. Tweets @CScottWatson. Website: www.rockyglaciers.co.uk
Evan Miles is a Research Fellow at the University of Leeds, UK, where he is a part of the EverDrill project’s hot-water drilling at Khumbu Glacier. His recent work has examined the seasonal hydrology and dynamics of debris-covered glaciers, with a focus on the melt associated with dynamic surface features such as supraglacial ice cliffs and ponds. Tweets @Miles_of_Ice
Schematic summary of the dominant observed variations in the cryosphere. [Credit: fig 4.25 from
IPCC (2013) ].
While the first week of COP22 – the climate talks in Marrakech – is coming to an end, the recent election of Donald Trump as the next President of the United States casts doubt over the fate of the Paris Agreement and more generally the global fight against climate change.
In this new political context, we must not forget about the scientific evidence of climate change! Our figure of the week, today summarises how climate change affects the cryosphere, as exposed in the latest assessment report of the Intergovernmental Panel on Climate Change (IPCC, 2013, chapter 4)
Observed changes in the cryosphere
Glaciers (excluding Greenland and Antarctica)
Glaciers are the component of the cryosphere that currently contributes the most to sea-level rise.
Their sea-level contribution has increased since the 1960s. Glaciers around the world contributed to the sea-level rise from 0.76 mm/yr (during the 1993-2009 period) to 0.83 mm/yr (over the 2005-2009 period)
Sea Ice in the Arctic
sea-ice extent is declining, with a rate of 3.8% /decade (over the 1979-2012 period)
The extent of thick multiyear ice is shrinking faster, with a rate of 13.5%/decade (over the 1979-2012 period)
Sea-ice decline sea ice is stronger in summer and autumn
On average, sea ice thinned by 1.3 – 2.3 m between 1980 and 2008.
Ice Shelves and ice tongues
Ice shelves of the Antarctic Peninsula have continuously retreated and collapsed
Some ice tongue and ice shelves are progressively thinning in Antarctica and Greenland.
The Greenland and Antarctic ice sheets have lost mass and contributed to sea-level rise over the last 20 years
Ice loss of major outlet glaciers in Antarctica and Greenland has accelerated, since the 1990s
Since the early 1980s, permafrost has warmed by up to 2ºC and the active layer – the top layer that thaw in summer and freezes in winter – has thickened by up to 90 cm.
Since mid 1970s, the southern limit of permafrost (in the Northern Hemisphere) has been moving north.
Since 1930s, the thickness of the seasonal frozen ground has decreased by 32 cm.
Snow cover declined between 1967 and 2012 (according to satellite data)
Largest decreases in June (53%).
Lake and river ice
The freezing duration has shorten : lake and river freeze up later in autumn and ice breaks up sooner in spring
delays in autumn freeze-up occur more slowly than advances in spring break-up, though both phenomenons have accelerated in the Northern Hemisphere
How much can President Trump impact climate change?
Figure 1: A speleologist descending inside a glacier cave of the Grey Glacier [Credit: Tommaso Santagata/ La Venta]
Chilean Patagonia hosts many of the most inhospitable glaciers on the planet – in areas of extreme rainfall and strong winds. These glaciers are also home to some of the most spectacular glacier caves on Earth, with dazzlingly blue ice and huge vertical shafts (moulins). These caves give us access to the heart of the glaciers and provide an opportunity to study the microbiology and water drainage in these areas; in particular how this is changing in relation to climate variations. Our image of this week shows the entrance to one of these caves on Grey Glacier in the Torres del Paine National Park.
Glaciers in Patagonia are “temperate”, which means that the ice temperature is close to the melting point. As glacial melt-water runs over the surface of this “warm” ice it can easily carve features into ice, which are similar to those formed by limestone dissolution in karstic landscapes. Hence, this phenomenon is called Glacier karstification. It is this process that forms many of the caves and sinkholes that are typically found on temperate glaciers.
From the morphological (structural) point of view, glaciers actually behave like karstic areas, which is rather interesting for a speleologist (scientific cave explorer). Besides caves and sinkholes one often finds other shapes similar to karstic landscapes. For example, small depressions on the ice surface formed by water gathering in puddles, whose appearance resembles small kartisic basins (depressions). Of all the features formed by glacier karstification glacier caves are the most important from a glaciological perspective.
Glacier caves can be divided in two main categories:
Contact caves – formed between the glacier and bed underneath; or at the contact between extremely cold and temperate ice by sublimation processes (Fig. 2a)
Englacial caves – form inside the glacier – as shown in our image of the week today. Most of these caves are formed by runoff, where water enters the glacier through a moulin (vertical shaft) and are the most interesting for exploration and research (Fig. 2b)
Figure 2: Two different types of caves explored on the Grey Glacier. A- Contact formed between the glacier bed and overlying ice [Credit: Tommaso Santagata]. B- Entrance to an englacial cave [Credit: Alessio Romeo/La Venta].
Exploring the moulins of a Patagonian glacier
Located in the Torres del Paine National Park area (see Fig. 3), the Grey glacier was first explored in 2004 by the association La Venta Esplorazioni Geografiche. In April of this year, a team of speleologists went back to the glacier to survey the evolution of the glacier.
Grey glacier begins in the Andes and flows down to it’s terminus in Grey Lake, where it has three “tongues” which float out into the water (Fig, 3). As with many other glaciers, Grey Glacier is retreating, though mass loss is less catastrophic than some of Patagonia’s other glaciers (such as the Upsala – which is glaciologically very similar to the Grey Glacier). Grey Glacier has retreated by about 6 km over the last 20 years and has thinned by an average of 40 m since 1970.
In 2004 research was concentrated on the tongue at the east of this Grey Glacier (Fig. 3 – red dot), which is characterised by a surface drainage network with small-size surface channels that run into wide moulin shafts, burying into the glacier. In this latest expedition, the same area was re-examined to see how it had changed in the last 12 years.
Several moulins were explored during the 2016 expedition, including a shaft of more than 90 m deep and some horizontal contact caves (Fig 2). The glacier has clearly retreated and the surface has lowered a lot from the 2004 expedition. The extent of the thinning in recent years can be easily measured on the wall of the mountains around the glacier. Interestingly the entrance to the caves which were explored in 2004 and in 2016 was in the same position as 12 years ago, although the reasons for this are not yet clear.
The entrance of two of the main moulins which were explored were also mapped in 3D using photogrammetry techniques (see video below). The 3D models produced help us to better understand the shape and size of these caves and to study their evolution by repeating this mapping in the future. For more information about the outcome of this expedition, please follow the Inside the Glaciers Blog.
Information and results from a similar project on Gornergletscher, Switzerland.
Books on the subject:
Caves of the Sky: A Journey in the Heart of Glaciers, 2004, Badino G., De Vivo A., Piccini L.
Encyclopaedia of Caves and Karst Science, 2004, Editor: Gunn J.
Edited by Emma Smith and Sophie Berger
Tommaso Santagata is a survey technician and geology student at the University of Modena and Reggio Emilia. As speleologist and member of the Italian association La Venta Esplorazioni Geografiche, he carries out research projects on glaciers using UAV’s, terrestrial laser scanning and 3D photogrammetry techniques to study the ice caves of Patagonia, the in-cave glacier of the Cenote Abyss (Dolomiti Mountains, Italy), the moulins of Gorner Glacier (Switzerland) and other underground environments as the lava tunnels of Mount Etna. He tweets as @tommysgeo
Field Site, Imja Lake, in November 2015 [Credit: D. Rounce]
Imja Lake is one of the largest glacial lakes in the Nepal Himalaya and has received a great deal of attention in the last couple decades due to the potential for a glacial lake outburst flood. In response to these concerns, the UNDP has funded a project that is currently lowering the level of the lake by 3 m to reduce the flood hazard. The aim of our research efforts is to understand how quickly the glacier is melting and how rapidly the lake is expanding such that we can model the flood hazard in the future. The focus of this research expedition was to install an automatic weather station, measure the thickness of the ice behind the calving front of Imja Lake, and measure the bathymetry of Imja Lake amongst other smaller tasks.
However, before any work could be done, we had to get there first.
The 8-day trek from Lukla to Imja Lake [Credit: GoogleEarth]
The long trek in
Tenzing-Hillary Airport in Lukla, at an altitude of 2,845 m [Credit: D. Rounce]
The launch point for our expedition was Kathmandu, Nepal, where we met with our trekking agency, Himalayan Research Expedition, purchased any last minute supplies, and took a day to kick our jet lag. Then the real trip began with a flight from Kathmandu to Lukla. Depending on the weather, this flight can be smooth and showcase the splendor of the Himalaya or it can be nerve-wracking flying through turbulence and clouds. Unfortunately, we had the latter and spent most of the 30-minute class flying through white clouds. Once our feet touched the ground at Tenzing-Hillary Airport, we were all excited and ready to start trekking.
Located at 5010 m above sea level (a.s.l) in the Everest region of the Himalaya, Imja Lake required 8 days of trekking to reach our base camp. The first 6 days followed the route to Everest Base Camp and provided the first glimpses of Everest, Lhotse, and Ama Dablam among many others. Due to the late start of our trek on May 29th, the monsoon clouds often blocked most of these peaks, so whenever the skies did clear we enjoyed them thoroughly. The 8-day trek also included two rest days (one in Namche and one in Dingboche) that were critical to be properly acclimated. The general rule of thumb that we follow is an acclimatization day for every 1,000 m of elevation gain. After the first rest day at Namche, at 3,400 m.a.s.l., the effects of altitude began to set in. The trekking slowed down as oxygen was a bit harder to come by. By the time we reached Imja Lake, there was about half as much oxygen as there is at sea level.
At 5,000 meters in altitude there is about half as much oxygen as there is at sea level
Imja Lake looked…different
The team at our base camp at Imja Lake [Credit: D. Rounce]
I was beyond excited to be back at Imja Lake. This was my 5th time at the lake and this time I was accompanied by a great team of colleagues. This project is funded by the NSF’s Dynamics of Coupled Natural and Human Systems (CNH) program and is led by Daene McKinney (University of Texas), Alton Byers (University of Colorado Boulder), and Milan Shrestha (Arizona State University). One of the great aspects of this trip was we were all able to be in the field at the same time providing an excellent mix of fieldwork on the glacier and social science work with the communities downstream. My group consisted of myself, Greta Wells from the University of Texas, Jonathan Burton from Brigham Young University, Alina Karki from Tribhuvan University, and eight hard-working individuals from our trekking agency (unfortunately, Daene was with us, but had to leave the expedition early).
The first drastic change that we saw when we got to Imja Lake was the large camp set up by the Army to work on the lake-lowering project. Usually, the only people that we see up here are people at Island Peak base camp, but now the location where were typically set up camp was packed with tents for the workers. The next surprise was seeing a backhoe operating on the terminal moraine (the natural dam comprising sand, rocks, and boulders). Typically, once you get off the plane in Lukla, you don’t see any motorized transportation besides the occasional helicopter flying to Everest Base Camp, so seeing this large piece of construction machinery was quite surprising! The lake lowering project was fascinating to see in progress. A cougher dam has been established to divert the outlet stream such that the typical outlet can be dredged and an outlet gate established, which will reduce the lake level by 3 m. This is a large undertaking due to the difficulty of working at 5,000 m (for both the workers and the machinery), but is an excellent step forward for Nepal in addressing the hazards associated with their glacial lakes.
The lowering project in progress at Imja Lake, with a backhoe working on a terminal moraine [Credit: D. Rounce]
Seeing this large piece of construction machinery [at that altitude] was quite surprising!
Let the work begin
On June 6th, we woke up at 6:00 a.m. to pure fog and limited visibility – not the weather you hope for on your first day of fieldwork. Fortunately, the fog burned off as the sun came up giving us a nice partly cloudy day to perform our reconnaissance of the glacier for the upcoming work. The first task was figuring out how to get onto the glacier from the lateral moraines (the sides of the glacier). This may sound trivial, but the glacier has melted such that the lateral moraines are now over 100 m higher than the debris-covered glacier surface and their slopes are very steep, which makes descending down them quite difficult. Fortunately, we found a good spot near Island Peak base camp, where Laxmi (our guide) set a rope and cleared the path of loose rocks and boulders.
Arduous descent onto the glacier [Credit: D. Rounce]
The glacier has melted such that the lateral moraines are now over 100 m higher
Automatic Weather Station on Imja-Lhotse Shar Glacier [Credit: D. Rounce]
Once on the glacier, we were tasked with determining the location of the weather station and wind tower in addition to finding potential routes for our Ground Penetrating Radar transects. The problem with Imja-Lhotse Shar Glacier is there are very few suitable flat spots. The debris cover on the glacier consists of fine sands, gravel, and boulders with melt ponds and bare ice faces scattered over the surface. The thickness of the debris can range from these bare ice faces to a thin cover of a few centimetres to many meters thick. Needless to say, the heterogeneous terrain can make walking on its surface quite difficult. My initial thought was to use a location where we had installed temperature sensors and ablation stakes two years ago; however, this site had turned into a melt pond ! Hence, we need to select a spot that seems relatively stable such that it won’t be in the middle of a pond when we return!
After many hours of trekking on the glacier, we returned to camp fatigued. The altitude wears you down quickly, especially in the first couple of days, so it’s crucial to stay hydrated, warm, and well rested such that we can work hard for all of the 16 scheduled days that we were out here. I find the first couple days to be the most difficult as my body adjusts to the limited supply of oxygen and for the first 2-3 days I typically have a mild headache in the afternoon. A good meal of dal baht (rice, lentil soup, and typically a meat or vegetable curry) along with a good night’s sleep and a little ibuprofen does the trick to have me feeling refreshed the next day though.
The first task was to set up the weather station and wind tower. The weather station will record meteorological data every 30 minutes that is important for energy balance modelling. This will allow us to model melt rates that can be applied to the entire glacier such that we can understand the evolution of the debris-covered glacier – crucial for future hazard modelling! The wind tower allows us to measure the surface roughness of the topography, which influences the turbulent heat flux transfers, i.e., the transfer of heat and moisture between the surface of the debris and the air – an important debris property to measure for energy balance modelling as well. Additionally, beneath the weather station, we installed temperature and relative humidity sensors within the debris such that we can understand how heat is transferred through the debris. Each piece of equipment has an essential role in the energy balance modelling.
The other large undertaking in the first week was performing ground penetrating radar (GPR) transects on Imja-Lhotse Shar Glacier. GPR is a geophysical technique that is used to measure and detect objects beneath the surface. In our case, we’ll be trying to measure the ice thickness of the glacier.
Ground Penetrating Radar in short
Ground Penetrating Radar survey in action [Credit: D. Rounce]
The quick and dirty of GPR is you have a transmitter and a receiver. The transmitter sends a great deal of energy into the ground, which then reflects off various surface, e.g., we should see a strong reflection at the ice/rock interface, and this reflected signal is then picked up by the receiver. Sounds easy right?
Things become a bit more difficult when you get on the debris-covered glacier and everything must be carried or dragged across the surface. This requires a lot of people such that the antennas don’t get stuck on the boulders, requires everyone to be walking at the same speed, and requires that all the electrical connections, batteries, etc. are secure and operating.
In a nutshell, it is a great deal of work, but provides an excellent dataset to understand the extent to which glacial lakes may grow in the future.
When this ice thickness is paired with lake expansion rates, one can predict the evolution of the glacial lake, which is critical for understanding the future hazard associated with Imja Lake. Two full days were spent climbing over the glacier, around bare ice faces and melt ponds, and attempting to collect transects that provide a good picture of the ice thickness behind the calving front of Imja Lake. During these days, we completed half of our planned transects and were ready for our first day of rest.
A flood and a community meeting
After 6 days of hard work, I was exhausted. The plan was to hike down to Chukung at 4700 m.a.s.l., where we would stay for two nights. A change in 300 m may not sound like a lot, but at altitude, this can provide a great boost in energy. During our “rest day” in Chukung, we were planning to hike down to Dingboche (4400 m.a.s.l.) to help out with a focus group session with the community led by Milan. What happened next was completely unexpected… we witnessed a glacier flood!
We witnessed a glacier flood!
A glacier flood threatened the village of Chukung [Credit: D. Rounce]
Our colleagues Alton and Elizabeth Byers were heading down to Dingboche before us. Along the way, they heard the sound of a landslide and when they checked to see what it was they were surprised to witness the start of a glacier flood. These floods appeared to have originated from the drainage of supraglacial lakes on Lhotse Glacier and appeared to have discharged through a series of englacial conduits. This englacial conduit flood grew rapidly as the initial flood continued to melt the surrounding ice. The videos that Elizabeth took were absolutely remarkable and fortunately everyone in Chukung was safe. By the time we arrived at the typical crossing point around 3:00 p.m., the flood had supposedly diminished by quite a bit, but was still very powerful. We ended up having to an hour detour over an ice bridge (literally a place on the glacier where the flood had carved into the ice and was going underneath the glacier such that we could walk above the flood on the debris-covered surface). It was truly fascinating to witness a flood from a glacier. When we arrived at Chukung, we made the decision to continue hiking to Dingboche such that we were safely out of the potential flooded area.
The energy in Dingboche was electric. Our entire NSF group was in the lodge and eager to talk to one another. The flood had also sparked a great deal of interest with community members as they witnessed the flood coming downstream and were fortunately able to contact members in Chukung to learn that this was not a larger glacial lake outburst flood (GLOF) from Imja Lake, which alleviated a great deal of concern. After a good meal and great conversation, we were all exhausted and went to bed early (not to mention that for the first time in over a week we were able to reconnect and update family and friends on the internet, which was a wonderful treat as well). The next day we were able to sit in on Milan’s focus group session with the members of Dingboche. From my background in engineering, I was fascinated to see first-hand the important work that Milan was conducting with the community. The community member’s interest and questions were very inspiring. For many years, these communities have seen researchers come to Imja Lake and not share any of their results. This has led to a great deal of skepticism and also led to unnecessary fear and/or panic, so every opportunity that we have to share our results and have a dialogue with the community is crucial. It is wonderful to be working with Milan as his work is a wonderful vessel for us to learn about the community’s concerns and vice versa, for us to share our work with them as well. I’m incredibly excited to see how this work progresses and see the field science and the social science come together.
The community of Dingboche [Credit: D. Rounce]
Every opportunity that we have to share our results and have a dialogue with the [local] community is crucial
Finishing off the fieldwork
After a day of “rest” in Dingboche, our team was ready to get back to work at Imja Lake. The first task was more GPR transects on the glacier. The benefit was that we were all feeling rejuvenated from our days at lower elevations and now that this was our 3rd day of GPR things were running smoothly.
The other benefit was that after almost 10 days at 5000 m.a.s.l. our bodies were feeling well adjusted to the limited supply of oxygen. The headaches that came and went over the first couple days were non-existent. The only downfall was we were now getting into the heart of the monsoon season, where clouds came up the valley every morning and it rained almost every afternoon. The work had to go on though, so we simply shifted our wake-up time an hour earlier in an attempt to avoid the rain.
Greta Wells and Jonathan Burton conducting a bathymetric survey on Imja Lake [Credit: G. Wells]
As our days were winding down, it was time to start splitting up the group. Jonathan and Greta became our kayaking experts and quickly became adept at working the sonar system to conduct a bathymetric survey of Imja Lake. The bathymetric survey is a remarkable experience and one that Jonathan and Greta seemed to thoroughly enjoy. The calving front of Imja Lake is ~10-20 m tall, which seems huge from the view of a kayak on the water. Furthermore, the calving front is quite active each year, so there are icebergs floating on the surface that provide some fun obstacles during the survey. They did a wonderful job and I am incredibly thankful for their support.
While the bathymetric survey was being conducted, Alina and I worked on the Structure from Motion (SfM) survey and the operation of the differential GPS (dGPS). Structure from Motion is a technique that allows us to take hundreds of pictures of the debris-covered surface and transform these pictures into a digital elevation model using the software PhotoScan Pro.
differential GPS measurement of a ground control point [Credit: D. Rounce]
This technique requires ground control points, which is where the dGPS comes into play. The differential GPS provides centimetric accuracy of specific points on the glacier (in our case spray painted boulders), which provide the spatial scale for the digital elevation model. We had ~40 ground control points and each point took approximately 10 minutes to measure… hence, the dGPS survey was a great deal of work. Once again, I have to thank my wonderful colleague, Alina, for her hardwork operating the dGPS with me.
The bathymetric survey, SfM, dGPS, and GPR transects occupied all of our remaining time on the glacier. Two days before I left the glacier, I sent our team members off to visit Everest Base Camp and Kala Patthar as the only activities left were finishing off the dGPS survey and downloading the last bit of meteorological data from the weather station. The trek to Everest Base Camp takes about 2 days from our site and I was glad that they would have an opportunity to go visit – they certainly deserved it. Perhaps one of the best surprises of the trip was the day that Jonathan, Greta, and Alina went to Kala Patthar, they had a couple hours of clear skies in the morning such that they were able to see Everest! What a better way to end the trip for them. On my side, the last couple days went very smoothly and I was ecstatic with all the work that we had accomplished. 16 days of hard work paid off and I am anxiously waiting for us to return and collect all the remaining data next year!
A special thanks to the NSF-CNH program for funding this research. Also a big thanks to my colleagues Daene McKinney, Alton Byers, Elizabeth Byers, Milan Shrestha, Greta Wells, Jonathan Burton, and Alina Karki among the countless others who were with Alton and Milan’s groups. Lastly, this work would not be possible without the tremendous effort and support provided by Himalayan Research Expedition and our team of guides, porters, and cooks.
Figure 1: Down-glacier view of debris-covered Miage Glacier, Italy, taken from a low-altitude lightweight UAV in June 2016 (Credit: M. Westoby). As the summer progresses, the melting of winter snow cover prompts the development of a surface drainage network, characterised as a network of streams and ponds, which are concentrated in intermoraine troughs and drain into open crevasses or moulins. Snowmelt in this area will eventually reveal a glacier surface covered by a continuous mantle of supraglacial debris, comprised predominantly of mica-schist
What are debris-covered glaciers?
Many alpine glaciers are covered with a layer of surface debris (rock and sediment), which is sourced primarily from glacier headwalls and valley flanks. So-called ‘debris-covered glaciers’ are found in most glacierized regions, with concentrations in the European Alps, the Caucasus, Hindu-Kush-Himalaya, Karakoram and Tien Shan, the Andes, and Alaska and the western Cordillera of North America. Debris cover is important for ice dynamics for several reasons:
A layer of surface debris thicker than a few centimetres suppresses ice ablation (Brock et al., 2010), as it insulates the underlying ice from atmospheric heat and insolation.
In contrast, a thin layer of debris serves to enhance melt rates through reduced albedo (reflectance) and enhanced heat transfer to underlying ice.
A continuous or near-continuous layer of debris can result in debris-covered glaciers persisting at lower elevations than, and attaining lengths which exceed those of their ‘clean ice’ counterparts (Anderson and Anderson, 2016).
Miage Glacier – the largest debris-covered glacier in the European Alps
The Ghiacciaio del Miage, or Miage Glacier, is Italy’s longest glacier and is the largest debris-covered glacier in the European Alps. It is situated in the Aosta Valley, on the southwest flank of the Mont Blanc/Monte Bianco massif. The glacier descends from ~3800 m to ~1700 m above sea level (a.s.l.) across a distance of around 10 km, and is fed by four tributary glaciers. The glacier surface is extensively debris-covered below ~2400 m a.s.l., and the average surface debris thickness is 0.25 m across the lower 5 km of the glacier (Foster et al., 2012).
Figure 2: Up-glacier view of Miage Glacier, in which three of the glacier’s four tributaries are visible – from upper centre-left: Tête Carée Glacier, Bionnassay Glacier, Dome Glacier.
Glacier surveying using Unmanned Aerial Vehicles
Researchers from Northumbria University, UK, acquired these images of the glacier using a lightweight unmanned aerial vehicle (UAV) during a recent field visit to Miage Glacier. During the visit the team carried out a range of activities including the installation and maintenance of a network of weather stations and temperature loggers across the glacier and geomorphological surveying of the glacier and its catchment, whilst undergraduate students collected data for their final-year research projects. The UAV imagery reveals the emergence of surface debris cover from beneath winter snow cover and the persistence of a channelized hydrological network in the snowpack, characterised as a cascade of streams and storage ponds. A recent study by Fyffe et al. (2015) found that high early-season melt rates and runoff concentration in intermoraine troughs promotes the development of a channelized subglacial hydrological system in mid-glacier areas, whilst the drainage system beneath continuously debris-covered areas down-glacier is largely inefficient due to lower melt inputs and hummocky topography.
(Edited by Emma Smith and Sophie Berger)
Matt Westoby is a postdoctoral researcher at Northumbria University, UK. He is a quantitative geomorphologist, and uses novel high-resolution surveying technologies including repeat UAV-based Structure-from-Motion to quantify surface processes and landscape evolution in glacial and ice-marginal environments. Fieldwork on the Miage Glacier in June 2016 was supported in part by an Early Career Researcher Grant from the British Society for Geomorphology. He tweets as @MattWestoby Contact e-mail: firstname.lastname@example.org
A 15,000 m³ rockfall during the 2015 summer heat wave at Tour de Ronde summit, Mont Blanc Massif. (Photo credit: Ludovic Ravanel.)
This photo captures a rockfall at the summit of Tour de Ronde, 3792 m above sea level in the Mont Blanc Massif. On 27 August 2015, around 15000 m3 of rock fell from the steep walls of the mountain.
Why do mountains crumble ?
Rockfalls such as the one on the photo have been linked to thawing permafrost. The exact mechanism that leads to these events is not fully understood, however, it is thought that areas of the mountain becoming destabilised during thaw periods (Luethi et al, 2015). Records show that during heat waves — as for instance the one that happened in the summer of 2015 in the Mont Blanc Massif — there are many more rockfalls than during colder years. Researchers at the Université Savoie Mont Blanc have been monitoring this area of the Alps for many years, installing a network of temperature sensors on the surface and in boreholes drilled into the rock to try and better understand the link between temperature and rock slope stability (see Magnin et al, 2015).
What can we do about it?
The short answer is that there is not a lot that can be done to prevent it. However, long term monitoring studies, such as the one from Magnin et al (2015), help to better understand what conditions are likely to result in rockfall activity and therefore predict when they are likely to happen. By doing this in the Mont Blanc region the team from Université-Savoie Mont Blanc has been able to put in place an alert network to warn the local community to increased rockfall activity. This means that the potential damage can be minimised, for example, by closing climbing routes in risky areas.
Check out our blog post about how cryospheric research can transform lives.
Magnin, F., Deline, P., Ravanel, L., Noetzli, J., and Pogliotti, P. (2015) : Thermal characteristics of permafrost in the steep alpine rock walls of the Aiguille du Midi (Mont Blanc Massif, 3842 m a.s.l), The Cryosphere, 9, 109-121, doi:10.5194/tc-9-109-2015
Luethi, R., Gruber, S. and Ravanel, L., (2015)Modelling transient ground surface temperatures of past rockfall events: towards a better understanding of failure mechanisms in changing periglacial environments. Geografiska Annaler: Series A, Physical Geography, 97, 753–767. doi: 10.1111/geoa.12114
Three repeat photos of the Muir Glacier, Alaska taken on 13 August 1941, 4 August 1950 and 31 August 2004 . Credit: U.S. Geological Survey
The Muir is a valley glacier (Alaska) that has significantly retreated over the last 2 centuries. The 3 pictures have the same field of view and record the changes that occurred during the 63 years separating 1941 and 2004.
In the 1941, the terminus of the glacier is on the lower right corner of the photo. The Muir is then a tidewater glacier up to 700m thick and is well connected to its tributary, the Riggs Glacier (upper right part of the photo).
9 years later, in 1950, the Muir Glacier has retreated by more than 3 km, is more than 100m thinner but is still connected to Riggs Glacier.
By 2004, the Muir glacier has retreated further inland and its terminus is no longer visible on the picture. The Riggs glacier is now disconnected to the Muir and has retreated by 0.25km. Vegetation has invaded the place.
The photo comes from and the text is inspired from the section “Repeat photography of the Alaskan Glaciers” on U.S. Geological Survey website. Photo 1: W. O. Field, # 41-64, courtesy of the National Snow and Ice Data Center and Glacier Bay National Park and Preserve Archive. Photo 2 : W. O. Field, # F50-R29, courtesy of the Glacier Bay National Park and Preserve Archive. Photo 3: B. F. Molnia, USGS Photograph
The 15th Karthaus Summer School (Credit: C. Reijmer)
After a train, the London Underground, another train, a flight, three more trains and a taxi (shared with people I had met on my way); I had arrived in a small Alpine village in the very north of Italy.
The cross on Kreuz Spitze. (Credit: I. Nias)
The reason for this rather convoluted journey?
To attend the Karthaus Summer School on ice sheets and glaciers in the climate system. I’m pleased to say it was definitely worth the trip getting there!
Nearly every September for the last 20 years, around 35 glaciology students from all around the globe descend on the village of Karthaus for 10 days to learn about all things icy. This year we were a mixture of mostly PhD students, a few postdocs and masters students. We were joined by 11 scientists from institutions around Europe, who were willing to give up some of their valuable research time to lecture students in their area of expertise (maybe the food and wine is enough to persuade them…).
Each morning we had lectures on a range of topics, including continuum mechanics, ice dynamics, numerical modelling, geophysical methods, polar oceanography and climatology; with plenty of coffee breaks in between to keep us alert. The lectures were excellent – I felt that in each topic, the basics were explained in a good amount of detail, enabling us to get a grasp on more complex ideas. I’m sure I will be referring to the lecture material in years to come. In the afternoon (after the three course lunch!) we went on to problem exercises, which we tended to work on in pairs, and group project work. These group projects were a great way to get stuck into a particular problem in more detail, in an area of glaciology that was not directly related to our own research.
The results of our group projects were presented on the last afternoon. It was great to hear what everyone had been working on: from reconstructing glacial history of the Tibetan Plateau to modelling ice on Mars.
… and playing
It wasn’t all work – each evening there was plenty of time before dinner to go for a run, play ping pong, sleep, or sauna. With the exception of perhaps the penultimate evening, when the time was spent making our group project presentations. And there was plenty of post dinner socialising, which mostly involved playing games in the bar.
Making the most of the good weather on our afternoon off. (Credit: I. Nias)
Before I attended Karthaus, there were a number of things previous participants told me about. When I told people I had a place, the most common response was “enjoy the food!”. Despite this, I don’t think I quite appreciated what it was going to be like to eat a three course lunch and a five course dinner every day! It was absolutely delicious though – fresh salad, homemade pasta, and lots of cream and parmesan. And of course bottles of the local wine on every table.
Another thing I was forewarned about was the yearly tango lessons from Hilmar Gudmundsson. I say “warned” because, as someone with zero sense of rhythm, dancing is not a skill I possess. Luckily, I didn’t seem to be alone in finding it a challenge, and seeing as the woman is supposed to “follow” the man, it wasn’t actually my fault when it went wrong (apart from when I got told off for trying to take the lead!). It was great fun and people got very much into it – so much so that we had a couple more dance nights, where we were also taught some German disco fox and Scottish ceilidh!
Excursion – to Hollywood!
Outdoor screening of Everest in the village square. (Credit: I. Nias)
Something that was definitely not expected was the public premier of the movie “Everest” in the village square, a week before it was released to cinemas. It turns out that much of the movie had been filmed in the surrounding mountains and on the glacier we visited on our excursion. This free public viewing was in honour of the help and hospitably the crew received during the filming. They must have done an excellent job in turning the Alps into the Himalayas.
When we took the cable car up to the Hochjochferner glacier the following Wednesday for our excursion, the cloud was so low that for all we knew there could have been Everest looming over us. Lack of snow cover on the ice meant we were unable to walk to the weather station that Carleen Tijm-Reijmer described in her lecture. However, we were still able to get up close (and underneath) the glacier. We had the chance to spot some of the geomorphological features we had learnt about in Arjen Stroeven’s lectures. When you see a large boulder suspended in the basal ice, it is easy to understand how striae are scratched into the underlying bedrock. After an early lunch in a mountain hut (including wine), we were free to go on a hike in the surrounding mountains. My group walked to a rock glacier in a neighbouring valley – the weather made the place feel more like Wales than the Alps, so we warmed ourselves with a Bombardino in another mountain hut.
Excursion to the Hochjochferner Glacier (left). Getting a closer look of the glacier (right). (Credit : I. Nias)
On the last evening, after the five course meal, we were treated to live music by members of the group. We then moved to the village hall for a final night of Karthaus dancing. It was a great evening to end a fantastic 10 days, and the next morning saw all of us (tired and slightly worse for wear) making our way home.
Frank, Carlo and Hans performing on the last night. (Credit: I. Nias)
I highly recommend that anyone who is beginning their career in glaciology applies next year. A huge thank you to Hans Oerlemanns and all the lecturers for creating such a fantastic summer school. Also thanks must go to Paul and Stefanie Grüner and all their staff at the Hotel Goldene Rose for making us feel so welcome!
Edited by Sophie Berger and Nanna Karlsson
Isabel Nias is a PhD student at the Bristol Glaciology Centre, University of Bristol, supervised by Tony Payne. She is using an ice-flow model to investigate grounding-line dynamics of ice streams in the Amundsen Sea Embayment, and how this may impact future sea level. Her work is part of the UK Natural Environment Research Council iSTAR programme, which aims to improve understanding of the stability of the West Antarctic Ice Sheet.
The margin at Hochjochferner in the fog. Credit: N. B. Karlsson.
The margin of the glacier “Hochjochferner” on the border between Austria and Italy. This glacier has been monitored with an Automatic Weather Station for several years by the Institute for Marine and Atmospheric research in Utrecth, NL.It is also the destination of the field trip that takes place during the annual Karthaus summer school in ice and climate. Here, students are exploring the margin of the glacier, where the sound of water rushing under the ice could clearly be heard.
The Tibetan Plateau – area: 2.5 million km2, mean elevation: 4,700 m a.s.l., surrounded by a series of high mountain ranges that are home to some of the world’s highest peaks: Himalayas, Karakoram, Pamir, Kunlun Shan. Considering these characteristics and the unique cultural heritage of Tibet the decision was easy when I was asked if I am interested working in a project on the regional patterns of glacier change on the Tibetan Plateau. And of course, we had to do a lot of field work to collect atmospheric and glaciological data :-). Between 2009 and 2012 we could realise seven field campaigns over three to four weeks to two different glaciers.
The Tibetan Plateau with location of the studied glaciers. The red stars mark the glaciers with in-situ measurements. Map by T. Bolch.
The journey always started at Lhasa airport. When leaving the plane I usually felt a little bit dizzy. Who wonders, air pressure is only 65% of that at sea level. In the following days in Lhasa every single time when walking up to the 3rd floor of our guesthouse at the Institute of Tibetan Plateau Research (ITP) I remembered that I was at 3,700 m a.s.l. By now I was glad that our schedule said that we stay in Lhasa for three nights before heading towards the snow and ice! Enough time to prepare our instruments, food and other equipment and to enjoy the tourist life… including headache and diarrhoea.
Glaciers on the Tibetan Plateau are usually terminating above 5,000 m a.s.l. and are only accessible by foot. Together with Chinese drivers and our colleagues from the ITP we left Lhasa by car, either for a one day ride to the north, to Nam Co Lake, and then another hiking day to Zhadang glacier (5,500 m a.s.l.). Or we went on a three day drive to the west, to the Kailash region, also followed by a one day ascent to Naimona’nyi glacier (5,600 m a.s.l.).
Local Tibetan people at Naimona’nyi glacier. Credit: Benjamin Schröter.
Generally, we spent two to three days in between to adapt to the altitude. With the support of local Tibetan people and yaks or horses we managed to bring all our stuff up to the glacier. I was always thankful only having to carry up myself and a small backpack :-).The torture of the ascent (at least for me) was totally forgotten when the tents were set up and we were rewarded with a great view down to the plateau (see picture at the top; camp at Naimona’nyi glacier. Credit: Benjamin Schröter).
However, we did not walk up to enjoy the landscape but to set up automatic weather stations (AWS) on or near the glacier and to conduct additional glaciological measurements. The AWS measure various atmospheric as well as surface and subsurface parameters. We also set up two time-lapse camera systems that took daily pictures of the glacier over three years. My colleagues at TU Dresden (Germany) geo-referenced and orthorectified these pictures to derive a daily snow line.
AWS at Naimona’nyi glacier in 2011. Credit: Christoph Schneider.
Usually nights up there were cold and restless and the days were quite exhausting. Air pressure drops to 50% of that at sea level. Thus, most of us were really happy when we successfully finished our measurements and repair work and walked down again after a few days to one week at the glacier side.
AWS at Zhadang glacier; left: 2009; right: after the ablation season in 2010. Credit: Christoph Schneider and Fabien Maussion.
When returning home in the office the real work was only just beginning. We set up a physically-based ‘COupled Snowpack and Ice surface energy and MAss balance model’ (COSIMA) that accounts for subsurface processes like melt water percolation, retention and refreezing. The collected in-situ measurements are used to calibrate, run and evaluate the model. Forced with atmospheric model data (High Asia Refined analysis; HAR) we then applied the model to five glaciers on the Tibetan Plateau (see map above). From every regional study we obtained a 10-year time series of glacier-wide surface energy and mass balance components. This data set helps us to further understand the role of the different energy and mass balance components for glacier change in the different climate regions of the Tibetan Plateau. We also hope to increase the knowledge on the various driving mechanisms for energy and mass balance on Tibetan glaciers.
Schematic overview of COSIMA by E. Huintjes.
Illustration of the ‘COupled Snowpack and Ice surface energy and MAss balance model’ (COSIMA). Tair: air temperature; RH: relative humidity; ws: wind speed; N: cloud cover; ρair: air density; SWin: shortwave incoming radiation; SWout: shortwave outgoing radiation; α: albedo; LWin: longwave incoming radiation; LWout: longwave outgoing radiation; Qsens: turbulent sensible heat flux; Qlat: turbulent latent heat flux; Qmelt: energy flux for melting; QC: conductive heat flux; QPS: energy flux from penetrating SW radiation; Ts: surface temperature; Tb: bottom temperature; Ti: temperature of the snow/ice layer i; ρi: density of layer i; wi: liquid water content of layer i.
Eva Huintjes is PostDoc at RWTH Aachen University, Germany. In December 2014 she finished her PhD on ‘Energy and mass balance modelling for glaciers on the Tibetan Plateau – Extension, validation and application of a coupled snow and energy balance model’ supervised by Prof. Christoph Schneider. She is interested in understanding the different regional patterns of glacier surface energy and mass balance components and their driving mechanisms on the Tibetan Plateau and in other glaciated regions. Currently she is applying the model to glaciers in southeastern Tibet to reconstruct Little Ice Age climate conditions and to glaciers in the Tianshan (northwestern China).