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Cryospheric Sciences

glaciers

Image of the Week – Ice-Spy: the launch of ICESat-2

The second generation Ice Cloud and land Elevation Satellite (ICESat-2) from NASA fires 10,000 pulses every second to take elevation measurements up to every 70 cm on-the-ground. This data will offer lots of opportunities for scientists to understand the changing cryosphere in more detail than ever before [Credit: NASA’s Goddard Space Flight Center].

On September 15th, 2018, at 18:02 local time, NASA launched its newest satellite – the second generation Ice, Cloud and land Elevation Satellite (ICESat-2). ICESat-2 only contains one instrument – a space laser that fires 10,000 pulses per second to Earth to measure elevation. Its primary purpose is for monitoring the ever changing cryosphere, so naturally there are plenty of ice enthusiasts that are excited for the data it will provide!


Blast off! ICESat-2 launches successfully from California, on the Delta II Rocket [Credit: NASA / Bill Ingalls].

Space laser?

The space laser is referred to more formally as an ‘altimeter’ (specifically, the Advanced Topographic Laser Altimeter System; ATLAS). Each of the 10,000 pulses per second contain around 20 trillion photons (the elementary unit that makes up light). The instrument works by measuring the time it takes for the photons to travel to Earth, reflect off the surface, and bounce their way back to the receiver. When the land is higher in elevation, there is less distance for the photons to travel, so they arrive back quicker and vice versa. The detector only lets in light at 532 nanometres in the visible spectrum. This means only the target photons are detected and sunlight is filtered out. An on-board clock measures time to a billionth of a second for maximum precision. The 10,000 pulses per second compares to just 40 per second in the original ICESat mission, giving us measurements every 70 cm on-the-ground. ICESat-2 repeats its orbit every 91 days, so we get elevation measurements for everywhere on Earth every 3 months.

What happened to the original ICESat?

ICESat launched in 2003 and lasted 7 years before its mission came to an end when its primary instrument stopped functioning. Its final task was to propel itself into Earth’s atmosphere and burn up on re-entry. In its lifetime, ICESat helped us to quantify decreasing Arctic sea-ice thickness, estimate global above ground biomass using forest canopy height and even find lakes beneath Antarctica. It was such a success that, since 2010, NASA have flown planes (Operation IceBridge) over the cryosphere with the same instruments to bridge the gap in the data loss between the two ICESat missions.

Operation IceBridge flies over ice sheets, ice shelves, glaciers and sea-ice to ensure there is no gap in data between the ICESat missions. You can see more of the stunning imagery collected from Operation IceBridge here! [Credit: NASA’s Goddard Space Flight Center]

What new science will we get from ICESat-2?

The primary purposes of the mission are to measure elevation change of ice sheets, glaciers, sea-ice and the subsequent impacts of sea-level rise. Whereas the original ICESat mission had a single laser beam with 40 pulses per second, ICESat-2 has 6 laser beams with 10,000 pulses per second, which gives an unprecedented level of detail. On the original mission, the orbit may have only provided a single track across a mountain glacier, but the new mission will have significantly more measurements. The higher spatial resolution of ICESat-2 means that the satellite can be used to identify and track icebergs that cross shipping lanes, provide extra measurements of sea-ice thickness for subsistence hunters and detect small topographic changes in potentially active volcanoes. There are many other potential applications of ICESat-2, including for non-cryospheric research, but there will also be many unforeseen applications of the new data that will come about with time.

I’m so excited! When will the first results start coming out?

Whenever satellites are launched with the purpose of earth observation, there is a long period of time when the instruments need to be checked to ensure they are working as intended. NASA will be calibrating ICESat-2 for a few months after launch to ensure the outputs are of the highest possible quality, so don’t expect any publicly available data until early 2019. It’s worth getting it right early in the mission because ICESat-2 has enough fuel on board to last 7 years, so mistakes early on can lead to delays or reduce the overall quality of data collected over the mission. If you can’t wait, however, you can see the first height measurements from Antarctica here!

The first data from NASA’s newest satellite – the second generation Ice Cloud and land Elevation Satellite (ICESat-2). ICESat-2 fires 10,000 pulses every second to take elevation measurements up to every 70 cm on-the-ground. This elevation data shows the first track across the Antarctic ice sheet. Who knows what new science we will discover during its mission! [Credit: NASA’s Goddard Space Flight] Center.

Find out more

Edited by Adam Bateson


Liam Taylor is a PhD student at the University of Leeds and Centre for Polar Observation and Monitoring. His research looks at identifying novel remote sensing methods to monitor mountain glaciers for water resource and hazard management. He is passionate about climate change and science communication to a global audience, as an educator on free online climate courses and through his personal blog. You can find Liam on Twitter.

 

Ice-hot news: The cryosphere and the 1.5°C target

Ice-hot news: The cryosphere and the 1.5°C target

Every year again, the Conference of Parties takes place, an event where politicians and activists from all over the world meet for two weeks to discuss further actions concerning climate change. In the context the COP24, which started this Monday in Katowice (Poland), let’s revisit an important decision made three years ago, during the COP21 in Paris, and its consequences for the state of the cryosphere…


1.5°C target – what’s that again?

Last October, the International Panel on Climate Change (IPCC) released a special report (SR15) on the impacts of a 1.5°C global warming above pre-industrial levels. This target of 1.5°C warming was established during the 21st conference of the parties (COP21), in a document known as the Paris Agreement. In this Agreement, most countries in the World acknowledge that limiting global warming to 1.5°C warming rather than 2°C warming would significantly reduce the risks and impacts of climate change.

But wait, even though achieving this target is possible, which is not our subject today, what does it mean for our beloved cryosphere? And how does 1.5°C warming make a difference compared to the 2°C warming initially discussed during the COP21 and previous COPs?

A reason why the cryosphere is so difficult to grasp is the nonlinear behaviour of its components. What does this mean ? A good basic example is the transition between water and ice. At 99.9°C, you have water. Go down to 0.1°C and the water is colder, but this is still water. Then go down to -0.1°C and you end up with ice. The transition is very sharp and the system can be deeply affected even for a small change in temperature.

As a main conclusion, studies conducted in the context of SR15 show that, below 1.5°C of global warming, most components of the cryosphere will be slightly affected, while above that level of warming, there is more chance that the system may respond quickly to small temperature changes. In this Ice Hot News, we review the main conclusions of the SR15 concerning ice sheets, glaciers, sea ice and permafrost, answering among others the question if achieving the 1.5°C target would prevent us to trigger the potential nonlinear effects affecting some of them.

Ice sheets

The two only remaining ice sheets on Earth cover Greenland and Antarctica. If melted, the Greenland ice sheet could make the sea level rise by 7 m, while the Antarctic ice sheet could make it rise by almost 60 m. A recent review paper (Pattyn et al., 2018), not in SR15 because published very recently, shows that keeping the warming at 1.5°C rather than 2°C really makes the differences in terms of sea level rise contribution by the two ice sheets.

Greenland is a cold place, but not that cold. During the Holocene, the surface of the ice sheet always melted in summer but, in the yearly mean, the ice sheet was in equilibrium because summer melt was compensated by winter accumulation. Since the mid-1990s, Greenland’s atmosphere has warmed by about 5°C in winter and 2°C in summer. The ice sheet is thus currently losing mass from above and its surface lowers down. In the future, if the surface lowers too much, this could accelerate the mass loss because the limit altitude between snow and rainfalls may have been crossed, further accelerating the mass loss. The temperature threshold beyond which this process will occur is about 1.8°C, according to the Pattyn et al., 2018 paper.

Antarctica is a very cold continent, much colder than Greenland, but it has been losing mass since the 1990s as well. There, the source of the retreat is the temperature increase of the ocean. The ocean is in contact with the ice shelves, the seaward extensions of the ice sheet in its margins. The warmer ocean has eroded the ice shelves, making them thinner and less resistant to the ice flow coming from the interior. And if you have read the post about the marine ice sheet instability (MISI), you already know that the ice sheet can discharge a lot of ice to the ocean if the bedrock beneath the ice sheet is deeper inland than it is on the margins (called retrograde). MISI is a potential source of nonlinear acceleration of the ice sheet that, along with other nonlinear effects mentioned in the study, could trigger much larger sea level rise contribution from the Antarctic ice sheet above 2 to 2.7°C.

You can find complementary informations to the Pattyn et al., 2018 paper in SR15, sections 3.3.9, 3.5.2.5, 3.6.3.2 and in FAQ 3.1.

Glaciers crossing the transantarctic mountains, one of them ending up to Drygalski ice tongue (left side) in the Ross sea. The ice tongue is an example of those ice shelves that form as grounded ice flows toward the sea from the interior. Ice shelves are weakened by a warmer ocean, which accelerates upstream ice flow [Credit: C. Ritz, PEV/PNRA]

Glaciers

Over the whole globe, the mass of glaciers has decreased since pre-industrial times in 1850, according to Marzeion et al., 2014. At that time, climate change was a mix between human impact and natural variability of climate. Glacier response times to change in climate are typically decades, which means that a change happening, for instance, today, still has consequences on glaciers tens of years after. Today, the retreat of glaciers is thus a mixed response to natural climate variability and current anthropogenic warming. However, since 1850, the anthropogenic warming contribution to the glacier mass loss has increased from a third to more than two third over the last two decades.

Similarly to the Greenland ice sheet, glaciers are prone to undergo an acceleration of ice mass loss wherever the limit altitude where rainfall occurs more often than snowfall is higher and at the same time the glacier surface lowers. However, as opposed to ice sheets, glaciers can be found all over the world under various latitudes, temperature and snow regimes, which makes it difficult to establish a unique temperature above which all the glaciers in the world will shrink faster in a nonlinear way. There are, however, model-based global estimates of ice mass loss over the next century. The paper from Marzeion et al., 2018, shows that under 1.5-2°C of global warming, the glaciers will lose the two thirds of their current mass, and that for a 1°C warming, our current level of warming since pre-industrial times, the glacier are still committed to lose one third of their current mass. This means the actions that we take now to limit climate change won’t be seen for decades.

You can find complementary informations in SR15, sections 3.3.9, 3.6.3.2 and in FAQ 3.1.

Sea ice

As very prominently covered by media and our blog (see this post and this post), the Arctic sea-ice cover has been melting due to the increase in CO2 emissions in past decades. To understand the future evolution of climate, climate models are forced with the expected CO2 emissions for future scenarios. In summer, the results of these climate model simulations show that keeping the warming at 1.5°C instead of 2°C is essential for the Arctic sea-ice cover. While at 1.5°C warming, the Arctic Ocean will be ice-covered most of the time, at 2°C warming, there are much higher chances of a sea-ice free Arctic. In winter, however, the ice cover remains similar in both cases.

In the Antarctic, the situation is less clear. On average, there has been a slight expansion of the sea-ice cover (see this post). This is, however, not a clear trend, but is composed of different trends over the different Antarctic basins. For example, a strong decrease was observed near the Antarctic peninsula and an increase in the Amundsen Sea. The future remains even more uncertain because most climate models do not represent the Antarctic sea-ice cover well. Therefore, no robust prediction could be made for the future.

You can find all references were these results are from and more details in Section 3.3.8 of the SR15. Also, you can find the impact of sea-ice changes on society in Section 3.4.4.7.

Caption: Sea ice in the Arctic Ocean [D. Olonscheck]

Permafrost

Permafrost is ground that is frozen consecutively for two years or more. It covers large areas of the Arctic and the Antarctic and is formed or degraded in response to surface temperatures. Every summer, above-zero temperatures thaw a thin layer at the surface, and below this, we find the boundary to the permafrost. The depth to the permafrost is in semi-equilibrium with the current climate.

The global area underlain by permafrost globally will decrease with warming, and the depth to the permafrost will increase. In a 1.5°C warmer world, permafrost extent is estimated to decrease by 21-37 % compared to today. This would, however, preserve 2 millions km2 more permafrost than in a 2°C warmer world, where 35-47 % of the current permafrost would be lost.

Permafrost stores twice as much carbon (C) as the atmosphere, and permafrost thaw with subsequent release of CO2 and CH4 thus represents a positive feedback mechanism to warming and a potential tipping point. However, according to estimates cited in the special report, the release at 1.5°C warming (0.08-0.16 Gt C per year) and at 2°C warming (0.12-0.25 Gt C per year) does not bring the system at risk of passing this tipping point before 2100. This is partly due to the energy it takes to thaw large amounts of ice and the soil as a medium for heat exchange, which results in a time lag of carbon release.
The response rates of carbon release is, however, a topic for continuous discussion, and the carbon loss to the atmosphere is irreversible, as permafrost carbon storage is a slow process, which has occurred over millennia.

Changes in albedo from increased tree growth in the tundra, which will affect the energy balance at the surface and thus ground temperature, is estimated to be gradual and not be linked to permafrost collapse as long as global warming is held under 2°C.

The above-mentioned estimates and predictions are from the IPCC special report Section 3.5.5.2, 3.5.5.3 and 3.6.3.3.

Slope failure of permafrost soil [Credit: NASA, Wikimedia Commons].

So, in summary…

In summary, what can we say? Although the 1.5°C and 2°C limits were chosen as a consensus between historical claims based on physics and a number that is easy to communicate (see this article), it seems that there are some thresholds for parts of the cryosphere exactly between the two limits. This can have consequences on longer term, e.g. sea-level rise or permanent permafrost loss. Additionally, as the cryosphere experts and lovers that we are here in the blog team, we would mourn the loss of these exceptional landscapes. We therefore strongly hope that the COP24 will bring more solution and cooperation for the future against strengthening of climate change!

Further reading

Edited by Clara Burgard and Violaine Coulon


Lionel Favier is a glaciologist and ice-sheet modeller, currently occupying a post-doctoral position at IGE in Grenoble, France. He’s also on twitter.

 

 

 

Laura Helene Rasmussen is a Danish permafrost scientist working at the Center for Permafrost, University of Copenhagen. She has spent many seasons in Greenland, working with the Greenland Ecosystem Monitoring Programme and is interested in Arctic soils as an ecosystem component, their climate sensitivity, functioning and simply understanding what goes on below.

 

 

Clara Burgard is a PhD student at the Max Planck Institute for Meteorology in Hamburg. She investigates the evolution of sea ice in general circulation models (GCMs). There are still biases in the sea-ice representation in GCMs as they tend to underestimate the observed sea-ice retreat. She tries to understand the reasons for these biases. She tweets as @climate_clara.

 

Image of the Week – Karthaus Summer School 2018

Beautiful and cozy Golden Rose hotel on the left; blissful and small Italian village, Karthaus, on the right [Credit: Rohi Muthyala].

Nearly every year since the late 90s, during the summer, the picturesque Karthaus has hosted 10-day glaciology course. This school is a platform for glaciologists to explore, learn and expand their knowledge base. This helps researchers become multi-faceted: to view glaciology from the perspective of those specializing in other backgrounds such as hydrology, geomorphology, oceanography, etc. which complement one another in defining glaciology. Along with the intense course work, one can wholeheartedly cherish the exotic food, cozy resort, spellbinding views and delicious wine!


Time to learn

Day used to start at 8 am with a healthy breakfast and then we head out to Katharinaberg to attend the lectures. Morning session of the course composed of four lectures with coffee breaks in between to keep us alert. These lectures were on a gamut of topics including numerical and analytical modeling, continuum mechanics, glacier hydrology, mass balance of the ice sheets, thermodynamics of ice, geophysical methods, geodynamics, ice core analysis, polar oceanography and geomorphology, etc. Lectures began with basics in every topic and gradually evolved into complex concepts, enabling students understand the subject better, irrespective of their specialization. After four hours of lectures, we, surrounded by lustrous green hills, enjoyed a delicious three-course lunch.

Afternoon session was all about application of the concepts learned in the morning into numerical exercises and group projects. We were divided into 12 groups to work as a team for a group project. Each group was assigned a topic and a teacher to work with. Results from the group projects presented on the last day of the course, astonished me by the level of research we could accomplish in 10 days, showing the amount of knowledge gained through the program.

Outdoor afternoon session in Kartharinaberg [Credit: F. Pattyn]

After school

School ended at 5 pm, leaving us with ample time to relax before dinner. While some students enjoyed it hiking, trail running and chilling in the sauna, I spent this time exploring Karthaus with a bunch of friends I made at the school and tried to capture the beauty of nature with my camera. Then was the best part of the evenings – a five-course dinner with lots of wine and stories from our fellow glaciologists. I have never had such an exotic five-course meal, which was so tasty that I couldn’t help but overeat. To top the delicious food, we had musical performances by Frank Pattyn and Johannes Oerlemans. I was amazed to know that most of the teachers have their own specialty with an instrument and that it’s a tradition at Karthaus to enjoy the evenings with their performances. After a two-hour long dinner, we moved to the bar next to the restaurant and continued our entertainment with games, wine and chatting. I wished there were more than 24 hours in a day to spend at Karthaus. This summer school is a complete package of education and entertainment.

Dinners at karthaus, with 5-course meal, wine and music (Frank Pattyn on Piano and Johannes Oerlemans on Bass) [Credit: Rohi Muthyala]

Entertainment after dinner with wine, games, chatting and as you can see, some map reading as well. Apparently, this year students are the most solemn group ever [Credit: Rohi Muthyala].

Adding to the fun, in the middle of the course, we had a day-off that most of us spent by going on an excursion to the Otztal Alps. A bus ride to Kuzras, a cable car to the top of Hochjochferner and hike down into the valley led us to the edge of the glacier where some stepped onto a glacier and/or entered an ice cave for the first time in their life. We stopped by Bellavista (Schonne Aussicht hut) for a hot meal and drinks before hiking higher onto the Italian Alps. Though we had been lucky with perfect clear skies throughout the course, we got a cloudy weather on our day-off to the Alps. Nonetheless, the experience of going well above the clouds in the cable car was the best start for the day.

Hiking on a cloudy day from the top of Hochjochferner gletscher to bellavista [Credit: Rohi Muthyala].

All in all

This summer school would be an intense and beneficial experience for students in all stages of education. Be it a beginner in glaciology or an experienced final year Ph.D. student, I think the course has a lot to offer to every student. Especially to the students with no glaciology background, this could be a place to learn the basics and understand how to look for answers you are trying to find. With three years of experience going to Greenland for research as an Arctic hydrologist, I was still ignorant in some concepts (such as geomorphology, geodynamics, thermodynamics, etc) that are not directly related to my dissertation. This program opened paths for understanding those concepts in a productive way. I highly recommend this summer program to every graduate student studying glaciology and especially to those who are not from Europe, with few opportunities such as this to learn the basics in wide range of topics from glaciology.

Another best outcome of this course was the opportunity to interact with fellow students and build a network for future collaborations. AGU and EGU have been mostly exclusive, and this provided an opportunity for me (from an American university) to get to know my fellow researchers from other parts of the world. I would also like to highlight the women participation in this course (roughly 50%) and appreciate the organizing committee’s effort to encourage more women in this field. Huge thanks to the organizing committee and all the teachers for their effort in making this an incredible experience. Special thanks to the convener, Johannes Oerlemans, for coordinating such a quintessential summer school.

Class photo in Katharinaberg [Credit : W.J. van de Berg]

Edited by Violaine Coulon


Rohi Muthyala is a PhD candidate from Rutgers University (New Jersey, USA), working with Asa Rennermalm. Muthyala comes from a multidisciplinary background of atmospheric, environmental sciences and geography, and currently focuses her research on Arctic hydrology and hydrological modeling. Objective of her dissertation is to model surface hydrological processes influencing the transport of meltwater over the surface of Greenland ice sheet.

Image of the Week – Inspiring Girls!

Image of the Week – Inspiring Girls!

What, you may ask, are this group of 22 women doing standing around a fire-pit and what does this have to do with the EGU Cryosphere blog? This group of scientists, artists, teachers, and coaches gathered 2 weeks ago in Switzerland to learn how to become instructors on an Inspiring Girls Expedition. But what, you may ask again, is an Inspiring Girls Expedition? Well read on to find out more…


What is an Inspiring Girls Expedition?

In 1999 Glaciologist Erin Petit, Geographer Michele Koppes, and 5 high-school girls hiked out onto the South Cascade Glacier in Washington State. For the next week, this motley crew spent their time camped out on a glacier moraine, exploring the landscape and performing scientific experiments by day, and talking and listening to each others thoughts and stories by night – that was the birth of Girls on Ice.

Over the next 13 years, more expeditions took place and more instructors (scientists, artists and mountain guides) started to get involved. In 2012, a second Girls on Ice expedition was born in Alaska and, in the years since, there have been Girls on Ice expeditions in 4 different locations and in 2 different languages! The idea has expanded to other areas of wilderness expedition as well, with new projects starting up: Girls on Rock, Girls in Icy Fjords and Girls on Water – nowadays these expedition are collectively known as Inspiring Girls Expeditions!

But I haven’t really answered the question – what is an Inspiring Girls Expedition? It is a wilderness and science education program for high-school aged girls. Over the course of around 12 days, these girls get the chance to explore a wilderness setting, learn about scientific thinking, increase self-confidence, and push their physical and intellectual boundaries as part of a single-gendered team. And, importantly – it’s FREE – opening it up to girls who might not have the financial means to do something like this otherwise. Everyone who goes on the expedition from scientists to mountain guides and instructors is female, making this expedition pretty unique! I think the philosophy of Inspiring Girls is best described by their mission statement:

Our mission is to bring out your natural curiosity, inspire your interest in science, connect the arts and sciences, free you from gender roles, provide a less competitive atmosphere, and encourage trust in your physical abilities.

The workshop

I’ve been following the work of Girls on Ice for a while, so when I saw a chance to go on an instructor training course, I enthusiastically signed up! Over 4 days in June 2018, a group of women from at least 8 different countries got together in a hiking hut in Switzerland for an Inspiring Girls Instructor Workshop, hosted by Swiss Girls on Ice. We came from a broad range of backgrounds: glaciologists, climate scientists, biologists, artists, architects, professional coaches, teachers (I hope I haven’t forgotten anyone!). We started off by learning more about the Inspiring Girls philosophy, what they expeditions aim to teach, and how they keep the girls safe and deal with any issues that might arise. Then came the thinking part for us…How do you teach in a wilderness setting? How to keep teenage girls engaged in what you are doing? What is a good leader? This gave us a lot of food for thought and we discussed a lot of these issues late into the evenings!

Then the fun part (although we all look rather serious in the pictures – below), working on ideas for new Inspiring Girls Expeditions (the current expeditions are often over-subscribed so there is certainly scope for more expeditions in more places) with the hope of inspiring more girls! So definitely watch this space for more expeditions coming to a mountain, cave or forest near you!

Figure 2: Workshop participants designing new Inspiring Girls Expeditions [Credit: Marijke Habermann]

It was a fantastic few days, with a fantastic bunch of women and I certainly came away feeling inspired myself!

I have to admit, this isn’t your usual Image of the Week blog post, however, I hope the relevance to scientists, science educators, and anyone else that follows the blog is clear! There is a need to show girls and young women that they have the potential to do what they want: be that a glaciologist, a mountain guide (both very much male dominated careers) or something entirely different! This type of expedition, in a single-gendered environment, is a very effective way to help build courage, confidence, and self-reliance!

This sounds cool – how can I get involved?

The team at Inspiring Girls are always looking for new people who are keen and enthusiastic about their project to get involved as volunteers, by donating a bit of cash or simply spreading the word about the expeditions – check their website to see how you can help out!

Edited by Clara Burgard

Image of the Week – Microbes have a crush on glacier erosion

Image of the Week – Microbes have a crush on glacier erosion

Glacier erosion happens at the interface between ice and the ground beneath. Rocks are ground down to dust and landscapes shaped by the flowing ice. While these might be hotspots for erosion, the dark and nutrient-poor sites are unlikely environments for biological activity. However, experiments suggest there may be novel sources of energy powering subglacial microbial life…


Where there is water, there is life…

Glaciers, ice sheets and ice caps cover around 11% of the earth’s land surface. At least 50% of the beds of these ice masses have temperatures at melting point due to the high pressure beneath the weight of the ice masses (Oswald and Gogineni, 2012). Liquid water is therefore present at the ice-bedrock interface in these areas. Additionally, erosion is a frequent feature of larger ice masses, and involves crushing and fracturing of bedrock. Consequently, recently crushed and wetted rock is a common feature of glacier and ice sheet beds. The adage that “where there is water, there is life” holds true for all glacier beds sampled to date, and for the only subglacial lake directly sampled beneath Antarctica, Subglacial Lake Whillans. Still, there is a large spectrum of different aquatic subglacial habitats beneath glaciers and ice sheets. The subglacial environments host genetically and functionally diverse microbial ecosystems capable of accelerating rock weathering (Montross et al., 2013), influencing global carbon cycles (Wadham et al., 2012) and productivity in adjacent oceans (Death et al., 2014).

How long can life survive beneath large ice masses?

However, the maintenance and longevity of these ecosystems is currently an area of uncertainty. Subglacial debris contains chemicals such as sulphides and organic matter that provide energy to sustain subglacial life (Hamilton et al., 2013). This is particularly important in areas close to the margin where melting water from the surface enters through moulins and crevasses and transports O2 and other biologically useful compounds such as DOC (dissolved organic carbon), POC (particulate organic carbon) and nutrients (such as Nitrogen and Phosphorus) to the bed. However, in the interior zones of ice sheets, the direct input of these species to the bed is negligible because hydrological connections between surface and bed do not exist. The O2 that is added to the bed in these locations is limited to gas bubbles in the basal ice which is geothermally melted or melts as regelation waters form and refreeze as ice flows around irregularities of the bedrock . This is problematic for the longer term maintenance of life in subglacial lakes and other aquatic environments beneath the ice sheet interiors, such as swamps and ice stream beds, because there is a lack of dissolved oxygen, and there is little energy derived from oxidants interacting with organic matter and sulphides. Further, the supply of potentially reactive organic matter, for example within former marine sediments, is finite and decreases over time, Therefore, subglacial life beneath ice sheet interiors is destined to expire unless new and sustainable sources of energy can be generated at the bed.

Hydrogen seems to be the miraculous diet!

A major advance in our understanding of the maintenance of life in subglacial environments was the recent discovery that H2 is produced by subglacial crushing. This is an important energy source for microbial food chains, because physical energy is transferred, via surface chemical (free-radical) energy, to biological activity and energy. Experiments show that  around 10-20 nmol H2 is produced per gram of crushed rock after 120 hours (Telling et al., 2015). Even if they sound very small, these concentrations are significant since only sub-nanomolar concentrations of H2 are required to sustain microbial growth near 0°C (Hoehler, 2004). Hydrogen is utilized by many types of microbes, and is generated abiotically via the interaction of silica surface radicals with water.

Next time you look at an otherwise dull grey meltwater stream draining a glacier, think of the crushing and the hydrogen that has been liberated by glacier erosion. The grey coloration arises from suspended sediment concentrations of about 1kg/m3 of meltwaters, and the sediment is typically silt- to clay-sized [Credit: Martyn Tranter].

Production of H2 supports the base of microbial food webs in fault and hydrothermal zones. Therefore, it is no stretch to suppose that this could be the case beneath glaciers. The H2 production rate from experimental rock crushing exceeds that required to support measured rates of methane production in the upper centimetre of South Western Greenland subglacial sediments. Additionally, rates of methane production in these subglacial sediments increased 10 times with the addition of excess H2 at 1°C (Stibal et al., 2012). A range of aerobic and anaerobic bacteria thought to be capable of oxidizing H2 as a source of energy have been found in subglacial sediments. Adding H2 to subglacial sediments from Robertson Glacier provided compelling evidence that the non-biological H2 produced during rock crushing could provide the sustain H2-oxidizing microbes (Telling et al., 2015).

Subglacial Lake Whillans is the first Antarctic subglacial lake to be sampled via a direct access hole. Water and sediment from the lake contain microbial life (Christner et al., 2013). Examination and experimentation on these unique samples is currently ongoing at the University of Bristol, where we hope to show that even already heavily weathered sediment produces hydrogen and supports microbial ecosystems when crushed and wetted. Subglacial microbes really do have a crush on glacier erosion, but don’t say it with chocolate or flowers, say it with hydrogen.

Edited by Joe Cook and Clara Burgard


Martyn Tranter is a polar biogeochemist, resident at the Bristol Glaciology Centre, University of Bristol, UK. Contact Email: m.tranter@bristol.ac.uk.

Image of the Week – Karthaus Summer School 2017

Gloriously cloudless day for the fieldtrip to the Ötztal Alps [Credit: C. Reijmer].

Glaciologists often undertake fieldwork in remote and difficult to access locations, which perhaps explains why they happily travel to similar locations to attend meetings and workshops. The Karthaus Summer School, which focuses on Ice Sheets and Glaciers in the Climate System, is no exception. The idyllic village of Karthaus, located in the narrow Schnalstal valley in Südtirol (Italy), has been hosting this 10-day glaciology course nearly every year since 1995. In September, an international crowd of some 30+ PhD students and postdocs, and 11 lecturers assembled in Karthaus for the 2017 edition of this famous course, for an intensive program of lectures, food, some science, more food (with wine!), and lots of socialising.


The lecture theatre with a backdrop of green hills, on the day the cows came down from the hills [Credit: D. Medrzycka].

The morning sessions

A typical morning of the course involved four hours of lectures, which covered a wide range of topics including continuum mechanics, thermodynamics, ice-ocean interactions, ice cores, geophysics, and geodynamics, with a special focus on numerical modelling and its applications for investigating ice-climate interactions. The lectures covered fundamentals processes, their applications and limitations, and current knowledge gaps for a wide range of complex concepts related to ice dynamics. All our lecturers happily answered our (many) additional questions during the coffee and cake breaks, enjoyed in the fresh mountain air outside the lecture theatre.

 
 
 
 
 
 
 

The biggest challenge was not the group work itself, but trying to not get distracted by the sun and the hills surrounding us [Credit: V. Zorzut].

The afternoon sessions

After a three-course lunch, we spent the afternoon sessions applying the theory learned in the morning lectures. The group projects were designed to get us to go into more detail on certain topics, and work on real-world applications for specific research problems. We presented the results of our work at the end of the course during a 15 minute group presentation. For those who could afford a bit of free time after these sessions, the rest of the afternoon could be spent either hiking or trail running in the steep hills overlooking the village (trying to beat I. Hewitt’s time up Kruezspitze), playing football, chilling in the sauna, or catching up on some sleep before dinner.

 

The evenings

Everyone who has ever attended the Karthaus course mentions the food, complementing both the quality and (legendary) quantity of it. Every evening, we were served a memorable five course meal accompanied by generous amounts of local wine. Dessert was followed by musical entertainment, with inspired performances by Frank Pattyn on the piano. On the last evening, Frank was accompanied by Johannes Oerlemans who treated us to two of his original tango arrangements on the guitar, followed by a passionate rendition of Jacques Brel’s Le port d’Amsterdam by our own Kevin Bulthuis (vocals). We wrapped up each day of the course in the local bar, socialising, playing card games, sampling the local beers, and making our way through the many different flavours of schnaps and grappa. Big thanks to the owners, Paul and Stefania Grüner, and staff (with a special shout-out to Hannes) of the Goldene Rose Hotel, and the village of Karthaus, for taking great care of us!

Frank Pattyn (piano) and Johannes Oerlemans (guitar) performing an original tango arrangement [Credit: D. Medrzycka].


 

Out and about

On the penultimate day of the course the group headed to a number of glaciers in the Ötztal Alps. The excursion, which happened to take place on a perfectly cloudless day, gave us the opportunity to observe first hand the changes affecting glaciers in the region, and the impact of these retreating ice masses on the landscape and humans inhabiting it. It also provided a much needed break from the intense week! After walking down the ski slopes of the Hochjochferner, a small valley glacier accessible by cable car from Kurzras, we stopped to enjoy the sun and have lunch at the Schöne Aussicht (Bellavista) hut (2845 m a.s.l.). Those with more energy scrambled up to the ridge running along the Italian/Austrian border (3270 m a.s.l.), through at times knee-deep snow, to take a peak at the Hintereisferner, a valley glacier on the Austrian side of the border. Four of us continued on along the ridge, and by chance visited the laser scanner (LiDAR) system operated by researchers from the University of Innsbruck, used to monitor changes in surface elevation on the glacier.

Standing on the ridge running along the Italian/Austrian border. View onto the Hintereisferner [Credit: D. Medrzycka].


 

Final thoughts

The 10 day course was certainly an intensive (and intense) experience, and I would recommend it to all glaciology students without reservations, whether they are looking for a basic introduction to ice dynamics, or aiming to fill a few knowledge gaps. Whilst some of the topics covered in the course were only remotely related to my own PhD research (and far out of my comfort zone!), the lectures and project work forced me to think in alternate ways. Although I may have finished the course with more questions than I had at the start, I now know where to go look for the answers!

A big part of the experience was without a doubt the social aspect of the course. Between the never ending and excellent food (as a result of which some of us developed “food babies”), and the long evenings at the local bar (resulting in increasing amounts of sleep deprivation), there were plenty of opportunities to talk science, gain new insights into our ongoing research, and discuss ideas for future projects. As with all great Summer Schools, one of the major perks was the opportunity to hang out with fellow students, expand our network of fellow researchers, and establish the groundwork for continued professional collaborations. Huge thanks to the convenor, Johannes Oerlemans, the village of Karthaus, and all the lecturers and fellow students for a memorable 10 days! I am looking forward to working with all of you in the future.

The crowd of the Karthaus summerschool: 2017 edition [Credit: C. Reijmer].

Edited by Morgan Gibson and Clara Burgard


Dorota Medrzycka is a PhD candidate at the University of Ottawa (Canada), working with Luke Copland. Her research focuses on the dynamics of glaciers and ice caps in the Canadian High Arctic, with a focus on ice flow instabilities (including glacier surging). Her project combines field studies and remote sensing techniques to monitor ice motion, and gain insight into the factors controlling the variability in ice dynamics in the Canadian Arctic. Contact: dorota.medrzycka@uottawa.ca.