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Climate Change & Cryosphere – Why is the Arctic sea-ice cover retreating?

Climate Change & Cryosphere – Why is the Arctic sea-ice cover retreating?

The Arctic Ocean surface is darkening as its sea-ice cover is shrinking. The exact processes driving the ongoing sea-ice loss are far from being totally understood. In this post, we will investigate the different causes of the recent retreat of the Arctic sea-ice cover, using the most updated literature…


Arctic sea ice is disappearing

Due to its geographical position centered around the North Pole, the Arctic Ocean is relatively cold compared to other world oceans. This means that, each winter, ocean temperatures fall below the freezing point, and sea ice forms on top of the ocean surface.

The Arctic sea-ice extent reaches about 15 million km2 in March, at its maximum (see left panel in Fig. 1 and Fig. 2). In spring, the ice starts to melt and reaches its minimum extent in September, which is about three times smaller than its maximum extent (see right panel in Fig. 1 and Fig. 2).

Figure 1: Maps of mean Arctic sea-ice concentration (percentage of sea ice in a given grid cell) in March (left) and September (right), averaged over 1979-2015, from satellite observations. The red line (right panel) shows the sea-ice edge in September 2012 (record minimum) [Credit: Ocean and Sea Ice Satellite Application Facility (OSI SAF)].

Satellite observations clearly show that the Arctic sea-ice cover has been shrinking since the beginning of the satellite record in 1979 (see this post and this post for more information about sea-ice satellite observations). The sea-ice loss is about 13% per decade in September and 3% per decade in March (see this post, this post and this post for further information on recent Arctic sea-ice changes). A recent study using data from a series of different observations (ship reports, airplane surveys, analyses by national services, etc.) shows that the recent Arctic sea-ice loss, as measured by satellites, is unprecedented as far back as 1850.

Figure 2: Seasonal cycle of Arctic sea-ice extent from satellite observations. The solid blue and dashed red lines show the 2019 (ongoing) and 2012 (record minimum) values. The dark gray curve shows the average over the period 1981-2010 with the corresponding uncertainty range in light gray (+/- 2 standard deviations) [Credit: National Snow and Ice Data Center].

The year 2012 was particularly exceptional in the sense that it featured the record minimum in September since the beginning of satellite measurements (dashed red curve in Fig. 2). 2019 was on a ‘good path’ to break this record, but the sea-ice loss rate started to lower from mid-August (blue curve in Fig. 2, see also here).

 

What are the drivers of the Arctic sea-ice loss?

The recent changes in Arctic sea ice have been caused by three main factors:

  1. External forcing: the variability caused by external factors, which can either be human (e.g. anthropogenic greenhouse gas emissions) or natural (e.g. changes in solar activity, volcanic eruptions).
  2. Internal variability: the variability caused by the chaotic nature of processes at work in the climate system. It is internal variability that prevents us to make accurate weather forecasts beyond a few days.
  3. Positive feedbacks: the processes by which a change in the climate can amplify, e.g. the ice-albedo feedback. These feedbacks are described in more detail in this post.

 

External forcing

Several studies have analyzed the links between the changes in external forcing and the recent changes in Arctic sea ice in both observations and models. It has been found that the anthropogenic global warming, caused by increased greenhouse gas concentration in the atmosphere, is the main driver of the long-term sea-ice loss in the Arctic. In particular, Notz and Stroeve (2016) found that for each ton of CO2 released into the atmosphere, the Arctic loses about 3 m2 of sea ice in September, as shown in Fig. 3 below (see this post).

Figure 3: September Arctic sea-ice area against cumulative CO2 emissions since 1850 for the period 1953-2015. Grey circles and diamonds show the results from in-situ (1953-1978) and satellite (1979-2015) observations, respectively. The thick red line shows the 30-year running mean and the dotted red line represents the trend of 3 m2 in sea-ice area loss per ton of CO2 emitted [Credit: D. Notz, based on Notz & Stroeve (2016)].

Other changes in external forcing have had a more limited impact on the recent changes in Arctic sea ice. For example, the volcanic eruptions of El Chichón in 1982 and Mount Pinatubo in 1991 caused a small increase in Arctic sea-ice extent (see this study), but their impact cannot be clearly identified in individual climate models (see here). Similarly, the impact of the solar activity on the recent Arctic sea-ice changes is very small.

 

Internal variability

The sea-ice evolution is also strongly subject to internal variability. A good explanation of the concept of internal variability can be found here and in this study.

Internal variability is often estimated using climate models. Running the same model with exactly the same parameters and external forcing, but with slightly different initial conditions (for example a different sea surface temperature), is a common method to get an idea of the internal variability of the climate system. Figure 4 below shows the evolution of the Arctic sea-ice extent using the Community Earth System Model (CESM) run 40 times with different initial conditions. The spread of the ensemble represents the range of the effect of internal variability.

Figure 4: Evolution of Arctic September sea-ice extent using the Community Earth System Model Large Ensemble (CESM-LE) in the less optimistic scenario (RCP8.5). The blue curves show all the 40 model members. The red curve shows the NSIDC satellite observations [Credit: Fig. 1a of Jahn et al. (2016)].

Variations in heat transport from the Atlantic Ocean due to internal variability have caused strong reductions in sea-ice area in the Barents Sea (see this study and this study), and probably other seas located in the Atlantic sector of the Arctic Ocean (as shown here). Changes in large-scale atmosphere circulation, also associated with internal variability, have contributed to sea-ice reductions as well (see this study).

However, several studies found that internal variability was not the key cause of the recent Arctic sea-ice loss over the past 40 years (e.g. this study). Instead, internal variability acts as an amplifier of the external forcing (see this study), so it only explains a small part of the recent Arctic changes. In the climate models used in the IPCC AR5 report, the impact of internal variability is of maximum 1 million km2 (see this study).

 

Feedbacks

A last cause for the recent changes in Arctic sea ice is the presence of positive feedbacks, which can amplify ongoing changes. One of the main feedbacks acting in the Arctic is the ice-albedo feedback (see this post and this study). Since ice reflects more sunlight than water, if the sea-ice cover decreases, more heat is trapped by the surface of the Arctic Ocean, leading to more ice melting.

However, as we have seen above, there is a clear linear relationship between Arctic sea-ice extent and cumulative CO2 emissions (Fig. 3). If the ice-albedo feedback was important in explaining the recent loss of Arctic sea ice, this linear relationship would break after years of strong or weak ice loss, which is not the case.

In fact, the positive feedbacks (like the ice-albedo feedback) are partly compensated by negative feedbacks that stabilize the climate system (see this previous post for a description of feedbacks in polar regions). Thus, while these feedbacks play a key role in the short term, they cannot explain the bulk part of the sea-ice loss since 1979.

 

The future

In conclusion, the recent loss of Arctic sea ice is strongly linked to anthropogenic global warming, although the changes in atmosphere circulation and ocean heat transport, associated with internal variability, also influence the sea-ice evolution. Research continues on the topic in order to capture the exact contribution of the different causes to the Arctic sea-ice loss.

On the long term, Arctic sea ice will continue disappearing. Based on the current emission rates of greenhouse gas emissions into the atmosphere, it is probable that the Arctic Ocean will be ice free during summer before 2050 (see this post, this study and this study).

Due to its linear relationship with CO2 emissions, the Arctic sea-ice cover is a strong indicator for the pace of current climate change. Its rapid disappearance should be seen as a warning light for other impacts to come…

 

Further reading

Edited by Clara Burgard


David Docquier is a post-doctoral researcher at the Earth and Life Institute of Université catholique de Louvain (UCL) in Belgium. He works on the development of processed-based sea-ice metrics in order to improve the evaluation of global climate models (GCMs). His study is embedded within the EU Horizon 2020 PRIMAVERA project, which aims at developing a new generation of high-resolution GCMs to better represent the climate.

Cryo-adventures – Life and science at a central Greenland ice core drilling camp

How do you get there? Where will you sleep? What work will you do there?These are just a few of the many questions I got from family and friends when I told them that I would join the EastGRIP ice core project this summer. As a paleo climate and ice sheet modeller, I could only repeat the abstract information given to me, very conscious that I actually had no idea how it would be to live and work on top of the Greenland ice sheet. In the numerical models I use for my work, the ice sheet shape and properties are represented by numbers and mathematical equations. Quite different from the vast expanse of empty, flat whiteness around the EastGRIP camp. Inspired by my kids (two boys who love to play with LEGO and watch Ninjago) I took a LEGO ninja and a LEGO scientist with me to the field. I wrote a little scenario involving a villain, a ninja who accidently ends up in Greenland and a scientist. Their adventure is my attempt to describe the travel, life and work in the ice core drilling camp. It became a 94-picture story in comic book format. The full story can be read here, but let me show you some of the highlights.


The travel

How do you get there? [Credit: Petra Langebroek – Map data Credit: Google]

For example, I explained that we travelled from Kangerlussuaq on the west coast of Greenland to EastGRIP by military plane. These special planes can land on normal runways, but also have skies in order to land on EastGRIP’s runway made of compacted snow.

The camp

Where do you sleep? [Credit: Petra Langebroek]

In the camp, most of us sleep in bunk beds in heated tents. Apart from scientists and drillers, there is also a medical doctor, a cook and a mechanic in camp. These people are essential for keeping the camp running, safe and in a good mood. The population in camp varies between about 20 to 40 people, depending on the workload and time within the field season. Being at EastGRIP is a bit like camping on the snow. Even the toilets are located in tents.

Where to go when nature calls? [Credit: Petra Langebroek]

The work

Where do we drill and process the ice core? [Credit: Petra Langebroek]

The primary activity at EastGRIP is of course related to drilling an ice core. In a large trench below the ice, several “rooms” have their own specific purpose, the largest ones are for the drilling and processing of the drilled ice. The latter happens in the “science trench”, where each bench has its own specific tools to either cut the ice or measure properties of the ice. In a conveyer belt-like system, scientists process the drilled ice at a rapid tempo.

The science

Why do we drill ice cores? [Credit: Petra Langebroek]

Of course, at some point the LEGO ninja wonders why we actually drill these ice cores. The LEGO scientist explains the basics of preserving climate information in layers of snow. Layers are compacted and become the ice we drill, with the climate information archived inside.

Why are we drilling a deep ice core at EastGRIP? [Credit: Petra Langebroek – Map data Credit: Google]

The EastGRIP ice core is being drilled at the start of the North East Greenland Ice Stream (NEGIS). This is the largest ice stream in Greenland, and it is still unclear how it exactly originated and why it is there. The surface velocity at EastGRIP is around 51m/yr, which is extremely fast for ice far inland. The main objective of the EastGRIP project is to study the dynamics of this ice stream, both internally in the ice and at its base.

In the end of the LEGO adventure, the ninja knows everything about EastGRIP and upon return to Bergen, captures the villain!

– The End

Further reading

Edited by Violaine Coulon


Dr Petra Langebroek is a senior researcher at the Norwegian Research Centre NORCE and the Bjerknes Centre for Climate Research, in Bergen, Norway. She works with ice sheet and climate models, aiming to understand past changes in ice sheets and climate. Currently she is coordinating a strategic project at the Bjerknes Centre (https://rises.w.uib.no/) focussing on the interactions of Greenland Blocking, ice dynamics and basal hydrology, using geological information from the Scandinavian Ice Sheet as an analogue for future Greenland changes. She is also coordinating the freshly started Horizon 2020 project TiPACCs (https://www.tipaccs.eu/) on tipping points in the Southern Ocean and Antarctic Ice Sheet.

Did you know? – Storms can make Arctic sea ice disappear even faster

Did you know? – Storms can make Arctic sea ice disappear even faster

The increase in air and water temperature due to climate change drives the retreat in the Arctic sea-ice cover. During summer, when sunlight reaches the Arctic, the absorption of heat by the dark ocean water enhances the sea-ice melt through the ice-albedo feedback. During winter, when sunlight does not reach the Arctic, another feedback is at work, as storms enhance the energy transfer between air, ice and water…


How can storms enhance sea-ice melting?

In summer, when the Arctic sea-ice cover is close to its minimum extent, a large storm can rapidly lead to a further decrease in the ice cover. In the case of a storm, the ice breaks up and is pushed together due to the wind-induced waves that quickly develop in the vast areas of open water. Once the storm is over, the resulting small ice pieces drift apart and melt faster than the larger ice pieces would have melted before the storm.

During winter, there is hardly any open water in the Arctic Ocean. An exception is the Barents Sea, where warm ocean water flows in from the North Atlantic and sinks under the surface when it meets the sea ice. Because this inflowing water got warmer over the past couple of decades, the Barents Sea has become nearly ice free in the winter (Polyakov et al, 2017). The “Whaler’s Bay“, north of Svalbard, is experiencing a similar evolution. In this area of open water, where the banks of the bay are formed not by land, but by sea ice, warm ocean water brought by currents sinks under the ice as well. While the effect of the water warming leads to a clear retreat of the ice in both the Barents Sea and Whaler’s Bay, another phenomenon can lead to an even faster retreat: episodic winter storms (e.g. Boisvert et al, 2016) that bring in warm air and push the sea ice northwards.

Until now, scientists observed both processes mainly using ocean moorings and satellite remote sensing sources as winter in-situ observations in this area are very rare.

Fig. 2: N-ICE2015 was based in an ice camp set around RV Lance. The ship was assisted to approx. 84N by an ice breaker and then left to drift out towards the Whaler’s Bay slowly with the sea ice and ocean surface current. [Credit: Paul Dodd, Norwegian Polar Institute].

Observations from the N-ICE 2015 campaign

In early 2015, the Norwegian Polar Institute led a half-a-year-long international expedition in the sea ice north of the Whaler’s Bay (Norwegian Young Sea Ice Cruise, N-ICE2015). During the winter part of the expedition, when air temperatures were typically below -20ºC, six powerful storms brought strong winds and mild temperatures into the region. The atmosphere-ice-ocean measurements recorded by the expedition revealed complex processes of energy transfer resulting in complex combination of thin and snow-covered sea ice, numerous leads, and pressure ridges (see this previous post about sea-ice dynamics).

The observations from N-ICE2015 show that early winter storms deposited a thick snow cover on the ice. Because snow is an excellent insulator, heat from the ocean cannot escape into the atmosphere and the water right under the ice does not cool enough to form further sea ice. This way, the ice stays relatively thin. So thin, that it yields the weight of the deep snow cover and gets submerged under the sea level. Generally, ice floes can be kilometers-wide and have thick steep edges built of pressure ridges that prevent water seeping into the snow from the sides of the floes.

However, each new storm during the observation period came with strong southerly winds that pushed the ice floes northwards with such force that they cracked in much smaller pieces. After the center of the storm passed over the sea ice, the wind direction reverted to southward and the ice stretched again towards Whaler’s Bay. The cracked floes were then less protected from water seeping into the snow from the cracks. Some large cracks even developed into leads with open water. After the storms, northerly winds brought back cold temperatures and cracks, leads, and flooded snow froze rapidly.

At the same time, the motion of the ice floes led to vertical mixing at the ocean’s surface. If this mixing happened right above the sinking warm water, some of the warm water was brought up to the surface and melted the ice from below.

Figure 3: The Arctic Winter Storm Cycle [Adapted from Graham et al. (2019)].

The shallow warm ocean water currents are unique to the Barents Sea and Whaler’s Bay in the Arctic. Further in the Central Arctic, the cold ocean has much less potential to melt sea ice during winter. Still, many powerful storms can reach beyond the North Pole and cross the whole Arctic Ocean. This means that the abundant snowfall, breaking-up of the ice floes, flooding of snow and opening of the leads can be common in large parts of the Arctic Ocean in the winter (for details see Fig. 3 and Graham et al, 2019). This way, a row of passing storms cannot only build a deep snow cover, but also create a broken-up ‘ice-scape’ that is susceptible to melt faster during summer. Moreover, abundance of areas of thin ice which transforms into leads can let enough light into the ocean to trigger large algae bloom earlier than usual in the season (Assmy et al, 2017). In summary, winter storms can make a large cumulative impact that lasts far beyond the short duration of a single storm.

More observations are needed!

Although it provided a lot of new understanding on the importance of storms for the sea-ice evolution, the N-ICE2015 brought some limitations. For example, it ended in June, before we could observe summer melt processes and it was limited to the area north of the Whaler’s Bay. To confirm and further explore the Arctic atmosphere-ice-ocean-ecosystem processes, the international scientific community is launching an even larger expedition in 2019 and 2020.

The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) will be a huge international effort with hundreds of scientists involved in field work, data analysis and research. Its main goal is to collect the data from the ‘new Arctic’ where the sea ice is much thinner than earlier decades. Such data can help improve the climate model projections that still under-represent the recent decline in sea ice extent and volume. MOSAiC will provide observations spanning over the full annual cycle of sea ice, from freeze-up in fall 2019 to melt in summer 2020. Geographically, the expedition will cover vast distances by drifting with the sea ice from the Central Arctic towards the North Atlantic. MOSAiC observations will build on the results from N-ICE2015 and will measure the effects of storms also in the Central Arctic.

Further reading

Edited by Clara Burgard


Polona Itkin is a researcher at the UiT The Arctic University of Norway, Tromsø. She investigates the sea ice dynamics of the Arctic Ocean and its connection to the sea ice thickness and snow depth. In her work she combines the information from in-situ observations, remote sensing and numerical modeling. Polona was a post-doctoral researcher at the Norwegian Polar Institute and one of many early career scientists involved with N-ICE2015. The expedition was highlighted also in their social media project ‘oceanseaiceNPI’: Instagram.com/OceanSeaIceNPI, Twitter.com/OceanSeaIceNPI, Facebook.com/OceanSeaIceNPI, contact Email: polona.itkin@uit.no.

An interview with… Marie Dumont

Snow! Here, Marie is spreading mineral dust on natural snow to investigate how this will change snow evolution (Col du Lautaret, France) [Credit : Maxim Lamare]

This week, we are interviewing Dr Marie Dumont. At the European Geosciences Union (EGU) general assembly in 2019, Marie was awarded the Arne Richter Award for Outstanding Early Career Scientist. Marie is currently a research team leader and deputy scientific director for the Snow Research Centre (part of Centre National de Recherches Meteorologiques, Météo-France & Le Centre national de la Recherche Scientifique [CNRS]) in France. Here, we ask her questions to find out a little more about the snow scientist. 


Let’s start off with an easy question: what is it that you work on? 

My researches are about the optical properties of snow, aka as the color of snow for the visible wavelengths. The “color” of snow is both cause and an effect of the snow cover evolution, it controls a large part of the melt rate and triggers potent climate feedbacks. I am working on how to measure and model the optical properties of snow at differences length scales and how to use this knowledge to better predict the evolution of the snow cover, in the past, now and in the future.

Did you always know you wanted to be a scientist?

Tricky question! Maybe, I knew deep down inside of me. It popped up quite naturally in my career. I hesitated for a while between mountain sports and science, and for some reason (maybe education, maybe something else) I ended up with one being my job and the other being my hobby, so I am quite lucky!

What is it about snow that has inspired you (and prompted four uses of ‘snow’ in your twitter handle)?

Snow snow snow …
Snow is beauty and fairy-like, snow is complex and simple at the same time. To me, it makes everything look great and perfect. As far as I remember, I have always been fascinated by snow. It calms me down and makes me feel incredibly good and peaceful. Maybe, it has also something to do with the fact that snow is ephemeral and somehow bound to melt and disappear and also that it’s changing/evolving continuously, it’s never the same, never boring.

Jon Snow or actual snow?

Jon Snow cause “I know nuthin’”
Jon Snow, except in season 8 …**spoiler alert**.
Kidding … both. I was really happy to see that a worldwide success like Game of Thrones was using snow and winter as part of the (scary) story.  In Game of Thrones, everyone is worrying that the world would end with winter coming. In reality, it was more the contrary. Naively, it made me happy to live in the fiction whilst winter was coming: it somehow distracted me from my sad thoughts on climate change and snow disappearance.

What worries you more: giving an award lecture at EGU, or panicking that you’ve left your tap running once you’ve left for fieldwork?

Giving an award lecture at EGU and knowing that I left the tap running when I left home for the conference… just kidding…. I think I am at bit of a scatterbrain, so I am quite used to leaving home with the tap running, losing my keys, my visa card and my passport. I don’t worry too much about that kind of thing anymore, it’s part of me and I am used to it.
On the contrary, I am not used to giving award lectures at all, so it worried me a lot, really a lot! I thought about it for quite a long time before EGU this year and the thing that worries me the most besides being in the limelight is the fact that I could possibly disappoint people that pushed me to get there and thus put their trust in me.

Marie received her award at the EGU2019 General Assembly in April 2019 [Credit: Olaf Eisen].

You’ve been very successful in both grant funding and winning awards, but what about times of less success? Do you have advice for any Early Career Scientists who’ve recently been rejected?

Usually only success is publicly reported. As anyone, I had, have and will have time of less success: rejected papers, rejected proposals, bad meetings, fully unsuccessful ideas, errors and conflicts with colleagues. I think I learnt, at least equally if not more, from errors and rejection than from success.
Advice? I’m not sure I am the right person to be giving any. This is a bit cliché but: keep trying, be passionate, be open to others, listen to them, listen to their comments and even when they are criticisms.

What do you crave/miss most when in remote locations?

My kids, friends and family, and after a few weeks a hot shower.

Do your kids have an interest in following in your footsteps (Marie is a mother of twins)?

Don’t know 😉 they are five years old! I brought them to one of my favourite field sites when they were two and taught them how to do a snow pit profile. For a while, they thought my job was about tasting snow J I am not really interested in the fact that they follow my footsteps or not. I just want, if I am able to do it, to show them how nature, wild places, and snow are beautiful and I think (ask me again in 10 years) that I would be happy if they are able to find their own passion about something and live it.

They could be the youngest early career scientists in the field of snow research! Do you think science has made advances in supporting women and parents in science? Are there still more things we can work on?

I am always a bit “torn” by this kind of question. On one hand, I think there has been a lot of advances in supporting parents and women in science, and I benefited from that a really a lot and it’s great!
On the other hand, in the push to promote male/female equality, I am always a bit puzzled by the emphasis that is put on supporting women only. There is something contradictory in this.
I think maybe it would make sense not to underline the differences too much. Getting funding, awards, sitting on committees is not all about quota, it should be mainly about skills. I am not at all saying that women, parents and other minorities should not be encouraged and offered new possibilities, as this is happening and is really great. However, there is a weight from history (more men than women in some science topics) that can’t disappear immediately and to some extent, I think pushing women only for quotas is harming the gender equality. Some women (I am part of them) may think they are successful only because of a quota. For example, I have encountered this argument:
XX : “Can you be part of this committee? Can you chair this or that?”
Me : “Why are you asking me ?”
XX: “Because you are a woman …”
Situations like this are frequent and in fact, it can make me quite angry.

You regularly participate and organise summer schools. Do you enjoy teaching? Do you have any advice for someone who might want to start teaching?

Not summer schools, winter schools of course!
I enjoy teaching but it’s also not a large part of my working time and I don’t have a huge experience in teaching. I enjoy teaching because I like sharing with students, learning about them, about their opinion … Advice? Same as above: listen to the students: as kids they teach you as much as you teach them, try to be funny and convincing!

As you spend lots of time in cold places for your work, do you prefer hot/beach holidays or do you still holiday in colder places?

Before having kids, it was really only about cold/mountain places. Now that I am getting older, I do also appreciate hot/beach holidays as long as I can climb or do some sports and that the places are wild and beautiful.

Day to day, what does being a scientist look like?

Coffee, taking kids to school, cycling to work, meetings (I need another coffee), emails, reviews, proposal writing, abstract writing (promising work that I know I will never be able to do before the conference), debugging some programs, discussing ideas with colleagues and students, ticking 2 things on my to-do list and adding 7 new items, trying to fit in two hours of pure science, asking for deadline extensions, meetings again, cycling back home… something like that.

She might look happy but digging snow pits is hard work! Snow pits are often dug to allow scientists to look at the change in snow properties with depth (Col du Lautaret, France) [Credit: François Tuzet].

That sounds busy! And on really cool, awesome-science days, what does being a scientist look like?

Top 10 awesome-science days/moments (with no preference):

  • Field days (even the unsuccessful days and during bad weather)
  • Sharing ideas and debating with colleagues/students when the understanding is beyond words
  • Passionate science/equation discussions in weird places (carparks, planes, trains, …)
  • Exciting new lab measurements that we still don’t know what they are useful for
  • Friday beers when the discussion oscillates between what happened during the past week and what the plans for the weekend are
  • Making at least one person laugh or smile in a conference talk with a nerdy joke
  • Finally getting the figure that demonstrates the hypothesis we were convinced about for a while and realizing a few hours after that there was a bug in the plot routine.
  • Finally finding the bug I was looking for after two weeks
  • Working as a team
  • Making nice figures with nice colours

Fieldwork is a regular part of Marie’s scientific career. Here she is doing spectral albedo measurements with her PhD student, François Tuzet in Col du Lautaret, France. This instrument was developped by Laurent Arnaud and Ghislain Picard (IGE, Grenoble, France) [Credit: Mark Flanner].

We always love a nerdy science joke! What might be the next big break-through in your field? (E.g higher resolution satellite data or a new model or method of observing etc).

The next paper from my student 😉 kidding of course!
I think it’s a combination of the 3 points you mentioned.  On one hand, temporal and spatial resolution of satellite data are getting better and better. For instance, the Sentinel satellites provide us unprecedented means to monitor the state of the snow cover. On the other hand, new observing methods (such as new instruments enabling observations of the snow properties at the microns/millimiters scales) provide new insights on snow evolution (in the lab and in the field) and snow physics that could be implemented in new snow models. So my vision, probably quite biased by what I currently plan to develop, is that a big break-through in snow science can probably be reached by developing modelling-assimilation systems that combine the most advanced knowledge of snow physics and the wealth of high resolution satellite data.

Model, satellite data or in-situ observations, you can only do one for the rest of time… which one?

Sorry, I can’t choose!

Ooo, we will let you off then. Afterall, science is about using the best techniques and data available. Thank you so much for chatting with us Marie!

Interviewed and edited by Jenny Turton


Dr Marie Dumont is a snow scientist at the Snow Research Centre in the Centre National de Recherches Meteorologiques (Météo-France & CNRS). This unit is also associated to the  Observatoire des Sciences de l’Univers de Grenoble – OSUG and  to Univ. Grenoble Alpes in France. Her research focuses on remote sensing and observations of optical snow properties, and uses a range of methods including data assimilation of observations into models and laboratory work. She tweets from @mpneige.

 

 

 

Surviving in cold environments: from microbes under glaciers to queer scientists in the current social context

Surviving in cold environments: from microbes under glaciers to queer scientists in the current social context

On the 5th of July we will celebrate the International Day of LGBTQ+ (lesbian, gay, bisexual, transsexual, queer, and people that do not identify themselves as cis and/or straight) People in Science, Technology, Engineering, and Maths (STEM). Many people will ask: “Why is this day important?” Being a queer scientist in particular, and a queer person in general, can sometimes reminds us of how living organisms feel in extreme environments. In this blog post, I will use the analogy of organisms thriving in harsh environments, to highlight the struggles of LGBTQ+ people in the science community.


I am a geomicrobiologist investigating how microorganisms interact with their surroundings in order to survive and what impact this activity has on the environment in which the microbes live. My PhD focused on the subglacial environment (underneath glaciers), and although it is a well-known fact that microorganisms can survive in extreme conditions, it was not until the late 1990s that the first subglacial bacteria were described (Priscu et al., 1999; Sharp et al., 1999). This discovery led to a shift in the way we regarded the subglacial environment: from a cold, dark, nutrient desert to a microbial oasis, an ironic “hot spot” for life within immense ice masses (Tung et al., 2006), showing a very high abundance of microorganisms (Toubes-Rodrigo et al., 2016).

 

How can microorganisms survive in a carbon poor and dark environment?

In illuminated environments, plants and photosynthetic bacteria are able to get energy from the sunlight, but this resource is not available under meters and meters of ice. At the bottom of glaciers, where the ice is in contact with the underlying ground, debris can entrain into the ice (Hubbard et al., 2009; Knight, 1997). Microorganisms are able to take advantage of the sediment and produce energy from the minerals to create organic matter in a process called chemolithotrophy. In addition, due to physical interactions between sediment and ice, there is always a thin layer of liquid water (even at sub-freezing temperatures) around the sediment grains, and it is well known that water is one of the most limiting factors for life. The bacteria which get their energy from the minerals and water under the glacier are called chemolithotrophs.

This process continues as glaciers flow across the ground. As glaciers flow, fresh minerals are picked up into the ice, becoming a supply for chemolithotrophs, which in turn enrich the sediment with carbon over time (Telling et al., 2015). The extra carbon then allows for the blooming of microorganisms capable of feeding on it (heterotrophs). Therefore, we have an active ecosystem in such a harsh environment.

 

How does this link to the LGBTQ+ Community?

This is a very good analogy for the conditions the LGBTQ+ community finds itself in: we usually find that our surroundings are very cold towards us. Just ask a homosexual person what reaction we receive when we are doing something as normal as holding with our partners or ask a trans person about the reaction they receive for their mere existence. Nevertheless, we queer people are capable of not only thriving but also making an impact and changing the mentality around us. As the visibility and representation of queer people continues to grow, people are becoming more educated about queer lives, queer history and the issues we still face. Much like the microbes that enrich the sediment, we enrich society through our diversity. Therefore, events such as the International Day of LGBTQ+ People in STEM are critical to maintaining and furthering the progress we have already made.

We can imagine glaciers as giant conveyor belts, able to transport sediment from the bedrock underneath the ice and release it downstream. The process of transport will not only affect the location of the sediment, but also the chemical makeup of it, due to the activity of microorganisms over years and years. The sediment released from glacier is richer in some of the nutrients, generating fertile soil. Yet again, this a wonderful metaphor: many people have questioned why LGBTQ+ Pride (in STEM) is needed, as LGBTQ+ rights have advanced so much in recent years. However, it is arguably more important now than ever before as, whilst we have made huge progress, we are still the target of hatred. For example, we still find attacks to queer people in cities such as London and Detroit only last week (see articles below) and in many countries around the world, queer existence is either passively ignored or actively threatened.

A number of museums associated with the University of Cambridge Museums are hosting LGBTQ+ Tours, to highlight research by the LGBTQ+ community and to educate the public. Just recently, the Scott Polar Museum ran the ‘Bridging Binaries Tour’ which included information about same-sex behaviour among penguins, and non-normative gender identities in the ancient world [Credit: University of Cambridge Museums].

How can LGBTQ+ initiatives help?

Initiatives such as Pride, LGBTQ+ people in STEM day or the Bridging Binaries Tours increase the visibility of the community: we prepare the soil for queer people to thrive. It helps internally-struggling individuals accept themselves, and highlights that it is ok to be different and that we exist. A discouraging fact for me when I was growing up was the lack of LGBTQ+ role models in science. A lack of role models has a terrible impact on LGBTQ+ people in STEM. Just to give a couple examples taken from PRIDE in STEM: more than 40% of LGBTQ+ people in STEM remain in the closet, having to disguise a fundamental part of themselves. Furthermore, gay, lesbian, and bisexual students are less likely to follow an academic career. When I first started my PhD, I was asked “edit it down” and be less overt about my sexuality, even by friends. Initiatives such as the International Day of LGBTQ+ People in STEM can make our surroundings more welcoming: it gives us a voice, a place. It gives us a space, in which we can express ourselves, and allows us to inspire the new generations of scientists, technologists, engineers, and mathematicians. As with microorganisms, the whole of society needs to stick together, interact and positively feedback all its members. Just as microorganisms thrive and diversify the community under glaciers, LGBTQ+ people should be able to thrive and add balance to the scientific community. This is why we need to nurture, nourish, and celebrate diversity with days such as International Day of LGBTQ+ (lesbian, gay, bisexual, transsexual, queer) People in Science, Technology, Engineering and Maths (STEM), especially in such politically divided and uncertain times. At the last EGU general assembly, a pride@EGU event was held which provided a meeting point for the LGBTQ+ community and allies (non-LGBTQ+ community members who support them). For more information about LGBTQ+ STEM day, please visit http://lgbtstemday.org.

At the last EGU general assembly, the pride@EGU event was well attended. Another event is being planned for the next general assembly in 2020 [Artwork/photo credit: Dr Stephanie Zihms].

Further reading

Edited by Jenny Turton


Dr Mario Toubes-Rodrigo is a post-doctoral research associate at the Open University, UK. Previously, he completed his PhD at the Manchester Metropolitan University. His research focuses on investigating microorganisms which inhabit extreme environments from the lowest layers of glaciers to sulphate-rich lakes, comparing their production of gases to those in the Martian Atmosphere. Mario is an active twitter user and goes by the handle: @micro_mario.

Image of the Week – Looking to the past for answers

Figure 1 – The lateral moraines of the Khumbu Glacier, Nepal (A+B). Taken from the true right of the glacier and the confluence with Changri Nup/Shar. A shows the original photo; B shows the annotation highlighting different moraines. Numbers assigned based on distance from glacier tongue. Dots represent where rock samples were collected from moraine crests. Yellow circle highlights walkers for scale. [Credit: Martin Kirkbride (photo), mapping and sample collection completed by Jo Hornsey]

We’re only just really starting to comprehend the state and fate of Himalayan glaciers due to a scarcity of research along the monumental mountain range. Climbers and scientists have been observing these lofty glaciers since the 1900s. However, is that looking back far enough? Glacier moraines, featuring in this Image of the Week, can reveal change extending back thousands of years.


You may look at Figure 1 and think ‘what is that?! It’s a mess!’ and you would be right to do so. The only glacier ice visible is where ice cliffs break the debris-covered surface of Khumbu Glacier (Figure 2), which begins in the Western Cwm. If you let your eyes adjust to the medley of rocks and many shades of brown, you can start to pick out lines and shapes. Some are highlighted by the sunlight whilst others take a more discerning eye. If your eyesight is very good, you can spot the people on a path in the lower right area (highlighted by the yellow circle), which give a sense of scale to this landscape. These huge mounds of rock and debris (called moraines), though appearing messy and interwoven, are vital pieces of evidence which show how much the glacier is shrinking; extending thousands of years back beyond the satellite record or human observations.

But why the mess?

The young Himalayan fold mountains produce huge amounts of debris due to the extreme weather and ongoing orogeny. The summer monsoon also provides significant amounts of intense precipitation, which erodes slopes and sediment, causing a highly mobile landscape, and a continual cacophonous supply of rocks and sediment to the Khumbu Glacier (Figure 2); creating a surface blanket known as debris cover. This debris alters how the glacier would normally melt and results in the surface of the glacier lowering through time, rather than the terminus retreating as so often seen on ‘clean’ ice glaciers. Though data collection is improving constantly, access to the Khumbu (nearly a week’s trek with several days of altitude acclimatisation) limits the range of monitoring techniques available and reduced oxygen controls your ability to collect data. Whilst there is observational data, such as satellite imagery and observations from explorers/scientists during the 1900s, it is limited in temporal and spatial resolution. This is where my research on glacier moraines comes in.

A longer time frame

I have spent the last year and ¾ (I am a PhD student; I am counting every second!) mapping the landforms which these great bodies of ice leave behind. This mainly consists of mapping lateral moraines (Figures 1 and2) as these represent the height of the glacier surface at the time it built the moraines and can be used to reconstruct a patterns of glacier evolution. These landforms have differing patterns (size, shape, preservation etc) between glacial valleys, sometimes even within the same valley, telling us that there are local and regional differences in glacier behaviour. To uncover when this all happened, I did what every person thinks I do when I tell them my PhD is based in geography; I went to collect rock samples from the glacier moraines (Figures 1 and 3).

Figure 2 – Mapped moraines. The moraines are identified by the different coloured lines (higher numbers represent older moraines). The dots represent the areas where rocks were sampled for dating. The contemporary glacier outlines were taken from the Randolf Glacier Inventory GLIMS data set. The Digital Elevation Model was taken from the High Mountain Asia 8m resolution data set (Shean, 2017). [Credit: Mapping of moraines and sample collection completed by Jo Hornsey].

Rocks can tell the time?

Well, no; they can’t. But using a technique known as Exposure Dating, we can assign an age to a rock surface if we’re sure that surface has been in that position on that landform since it was put there by the glacier. This means, if we choose rocks on the crests of the moraines (similar to the one I am stood on in Figure 3), we can interpret the age we get from that rock as the time that the glacier surface was there building that landform. If we do it for the mapped moraines of the Khumbu Glacier (Figure 2), then we can start to build a timeline of glacier recession. Thanks to studies in the 1980’s  and to a couple done in the early 2000’s (e.g. Richards, et al., 2000; Finkel, et al., 2003), we’re pretty confident that the most glacier proximal landforms were built around 500 years ago during a hemispheric wide cooling event. This event was significant enough to build the towering lateral moraines which are significantly larger than those mounds you can see bordering them in Figure 1. Importantly, this event occurred before the western industrial revolution. Therefore, by looking at moraine building events before this, we can recreate how glaciers were before humanity’s dependence on fossil fuels developed, i.e. a time where glaciers were able to reach a point of stability and build landforms. By including smaller, distal moraines as well as the mammoth slopes of those most proximal to the glacier, we can construct a chronology of the Khumbu Glacier’s behaviour over the Late Holocene (2500 years ago to present in the Himalaya), into the last point of stability, and onto the behaviour we see today.

So, then what?

I’m glad you asked. Once we have a chronology for the glacier’s behaviour, we can start to compare it to the modern-day behaviour. This can be done using direct comparisons between glacier extent and thickness or using glacier models. Models can be useful as they are able to recreate the behaviour between the moraine building phases. I will be applying my chronology to a dynamic glacier model known as iSOSIA, one that was adapted to be able to simulate the development of debris covered glaciers. The chronology will act as parameters within the model (so that it knows the moraines must be built by a certain time), and the model can then recreate the glaciers behaviour whilst it was building these striking landmarks. We can use the model to improve our understanding of how these glaciers have become debris covered, what they would be like if they weren’t, and what might happen to them as climate change continues.

What is this all for?

Having travelled to the Khumbu valley and spent days staggering around on the debris-covered glacier trying in vain to catch my breath, the sense of our impact on the world hit home quite dramatically. Whilst the Khumbu valley is a particularly busy valley, you’re still days away from any form of infrastructure. The moment you travel off the well-worn path, it’s the most incredibly peaceful landscape. Not because it’s silent; the glacier is constantly making noise as it slowly flows down the valley and debris shifts around the surface. It is because it is entirely natural. When there are no helicopters to be heard, in that moment, you could be the only person alive. In the face of an ever-expanding world, I believe it is important to protect and preserve these natural spaces, and those dependent on them.

Humans will not last forever, or even for a long time in the grand scheme of things, but if we’re not careful, our impact might. I don’t think future populations of any species deserve that.

Figure 3 – Looking back up the valley whilst I contemplate a rock. Pumori summit can be seen to the left of the photograph, and Nuptse summit can be seen on the right. Existential questions on a postcard please. [Credit: Martin Kirkbride]

Further Reading

Edited by Scott Watson


Jo Hornsey is a PhD student at the Department of Geography in Sheffield, UK. She is researching the changing extent of Himalayan glaciers over the last 2500 years with specific focus on the Little Ice Age event ~500 years ago; dating the patterns of glacier retreat in the Khumbu Valley; using this information to improve accuracy of the iSOSIA model; and applying IPCC Climate Scenarios to analyse future glacier behaviour in the Khumbu Valley. In her downtime she can be found walking, climbing, running, acting, playing Dungeons and Dragons, and invariably trying to show you pictures of her cats.
Twitter – @joshornsey
Email – jhornsey1@sheffield.ac.uk

An interview with Jenny Turton, early-career representative for the cryo-division of the EGU

The European Geophysical Union (EGU) has a number of scientific divisions or themes, such as cryosphere, atmospheric sciences and geodesy. Each division has a representative for early career scientists, and often a team of scientists who write and edit blogs and organise events. Today,  Jenny Turton, the new representative for the cryo-division, explains a bit more about the role and what she hopes to achieve.


JT: Hi! I’m Jenny Turton, the new EGU CR ECS rep.

This is me! [Credit: Jenny Turton]

That’s a lot of acronyms, help us out?

JT: It is quite a mouthful. I am the representative for Early Career Scientists (ECS) in the cryosphere (CR) division for the European Geosciences Union (EGU).

Am I an ECS? Are you my rep?

JT: EGU says that an early career scientist is anyone who has finished their highest degree within the last 7 years (or 8 if you’ve had time away for childcare or healthcare). Although I am interested in promoting early career scientists across all physical science disciplines, I am the representative for anyone in the cryospheric sciences. That includes anyone studying/researching ice, snow, cold climates, polar regions, high-mountain glaciers, sea ice, permafrost, atmosphere-ice interactions, ice sheets… and I’m sure I have forgotten some. 56% of the cryosphere community who have an EGU membership are early career scientists!

So what will you do in your new role?

JT: I will be the point of contact between any early career scientists and EGU. I will put forward suggestions from the cryosphere community to the EGU council, on how EGU can better represent and support early career scientists. This includes at the general assembly in Vienna (mostly just known as EGU), but also in EGU journals and other events. More specifically, I have two main avenues I would like to work on during my time. Want to know more?

Yes please!

JT: Firstly, I want to support and develop the early career scientist community in terms of diversity. This includes gender, ethnicity and LGBTQ+ rights. Just 35% of the EGU members are women, and this increases to 42% for early career scientist community. Whilst the EGU cryosphere hasn’t yet analysed their breakdown in terms of gender, just 33% of the American Geosciences Union cryosphere members (our American sister) are women. The number of women in STEM areas (Science, Technology, Engineering and Maths) is increasing, but I want to do more to represent the women we already have in science, and to try and increase the numbers. When organising panel talks, or inviting guest speakers, please think about how you can ensure a more diverse range of backgrounds and routes into science. Read our past blog dedicated to women in science.

We do not have numbers of scientists who categorise themselves as LGBTQ+, however at the general assembly in Vienna in 2019, EGU held their first ‘pride’ event, which was well attended. In this event we discussed what challenges scientists have faced on their career path so far, and how ‘allies’ (people who do not categorise themselves as LGBTQ+ but want to be supporters of those who do) can assist and support in making EGU and science a more diverse place. I will be supporting the organisers of this event again for next year’s General Assembly.

That sounds like a good idea! I follow ‘Polar Pride’ (@PridePolar) on twitter. What’s your second focus point?

The ECS reps and cryo team organise short courses at the general assembly which are well attended and are aimed at the ECS community. Topics include: how to find funding (the picture here), a polar career panel (jointly run with APECS) and presenting tips. [Credit: Jenny Turton]

JT: My second focus is on making strong links between the other EGU early career scientist reps. I have a small confession… I am not wholly within the cryosphere division, I am actually a mixture of cryosphere, atmospheric sciences and climate. There are many scientists (especially scientists who move between topics after their PhDs) whose research does not fall into one category. I research the interactions between the atmosphere and the cryosphere for the 79°N glacier in Northeast Greenland (see this previous blog post). More specifically I have looked at whether there is evidence of climate change in this region (big hint: there is) and run an atmospheric model to investigate the processes that are having an impact on the ice. I know I am not the only person who spans multiple research divisions, but that doesn’t mean you have to feel left out, or as if you’re in no-man’s land. During my time as a rep, I aim to work closely with other reps to create bridges between them. This will include joint social activities and organised short-courses that are of interest to many groups.

You’re going to be a busy bee (or a busy polar bear maybe?). Do you do this alone?

No! Absolutely not. The EGU cryo team includes many people. We have a number of chief editors, many regular editors and authors for our weekly blogs. We have a social media team, who focus on spreading important information and highlighting our blog posts. We also rely on a number of members who help organise and convene the short courses at EGU and organise our other events. We are always looking for new members for our growing team. Get in touch for information on joining us!

How do we know you will get this done? Do you have any experience of this sort of role?

The Networking and Early Career Scientist Zone is a new feature at the EGU general assembly, and is a space for early career scientists to meet their reps, hang out, work in a quiet spot and grab a coffee. There is also an info board with all of the social and off-programme events taking place. [Credit: Jenny Turton]

JT: Actually, yes! I have always been active in outreach, organisation and extra-academia activities throughout my PhD and postdoc. I was the head of education and outreach for the UK Polar Network (the UK Branch of the Association for Polar Early Career Scientists) and have organised student conferences with the Royal Meteorological Society. I’m also pretty organised, and a big fan of to-do lists which keep me on track. I think I am quite well placed to ensure that as many scientists voices with the cryosphere are heard. I completed my PhD in 2017 with the British Antarctic Survey (there’s a lot of cryo scientists there you know) and the University of Leeds. I also keep in contact with the University of Lancaster, where I did my masters and undergraduate degrees. Now, I am based in Erlangen, with two growing teams of scientists with cryosphere interests, and my research is part of a larger German-based project with many cryo-scientists. I’m also an active tweeter (@TurtonJ1990) which means I can often reach out to other early career scientists on the twittersphere.

How can we get in touch with you and how will you give us information?

JT: The best way to contact me is through the EGU cryosphere email (ecs-cr@egu.eu), or on twitter (@TurtonJ1990 or @EGU_CR). During the next EGU general assembly (#EGU20), I will often be in the Networking and ECS lounge, or floating between cryosphere sessions (unless its 6pm, then I’ll be near the beer stand!). The cryo twitter account will inform you of social events and relevant dates for EGU, our blog will keep you informed more informally, and there are the EGU ECS newsletters.

Right, thanks for the info. I’d better get on to publishing this blog.

JT: And I need to do some research. Feel free to get in touch!

Edited by Sophie Berger

Image of the Week – Unravelling the mystery of the 2017 Weddell Polynya

Figure 1: The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired these images of the Maud Rise or Weddell polynya in the eastern Weddell Sea on September 25, 2017. The first image is natural color and the second is false color where areas of ice are in blue and clouds are in white. [Image credit: NASA Earth Observatory].

The mysterious appearance and disappearance of the Weddell Polynya, a giant hole in the ice, has long puzzled scientists. Recent work reveals that it is tightly tied to energetic storms. Read on to find out more…


The eastern side of the Weddell Sea is a region known for its low concentration of sea ice due to the presence of a seamount, an underwater plateau called the Maud Rise. The seamount influences ocean circulation by bringing warm water closer to the surface, preventing the formation of thick ice. In the early 1970s, when satellites first began snapping photos of Earth, scientists noticed a mysterious hole in Antarctica’s seasonal sea ice floating in this area. This phenomenon is known as a polynya, and for decades its occurrence went unexplained. Then in 2017, during the continent’s coldest winter months, when ice should be at its thickest, a giant 9,500-square-kilometre hole suddenly showed up in the same region (Figure 1). Two months later it had grown 740% larger, before merging with the open ocean at the beginning of the melt season.

The Weddell Polynya is a rather famous hole in the ice (see this previous post). Scientists have been investigating such features in the Southern Ocean for decades, but the true reasons for the appearance and disappearance of the Weddell Polynya were still surrounded by mystery – until now.

Why does the Weddell Polynya form?

Recently, our new study found that these mid-sea polynyas can be triggered by strong cyclonic storms. Using satellite observations and reanalysis data, we found that in some winters, atmospheric circulation moves a significant amount of heat and moisture from mid-latitudes to Antarctica, allowing large cyclones to develop over the sea ice pack. When strong cyclones – some as strong as hurricanes – form and spin over the ice pack, the strong cyclonic winds they can drag the floating sea ice in opposite directions away from the cyclone center, creating the opening.

Sea ice typically drifts in a direction turned 30° on average to the left of the atmospheric flow, with a speed amounting to 1–2% of the surface wind speed. Those rules, when applied to a cyclonic wind situation (i.e., two opposing winds around a center), imply divergence in the motion of sea ice leading to open water area within the cyclone center, as in Fig. 2. We can see how such a situation occurs in real life for the Weddell Polynya when looking at Fig. 3, where near-surface winds exceeding 20 m/s are pushing the ice in opposite directions away from the cyclone center, characterized by weak winds, and the hole in the ice underneath it.

Figure 2: Sketch summarizing the mechanisms by which the cyclone can open the polynya [Credit: Francis et al., 2019].

Why does the Weddell Polynya matter?

Once opened, the polynya works like a window through the sea ice, transferring huge amounts of energy during winter between the ocean and the atmosphere. Because of their large size, mid-sea polynyas are capable of impacting the climate regionally and globally. This includes impact on the regional atmospheric circulation, the global overturning circulation, Antarctic deep and bottom water properties, and oceanic carbon uptake. It is important for us to identify the triggers for their occurrence to improve their representation in models and their effects on climate.

What might happen in the future?

Under future warming-climate conditions, previous studies have predicted an intensification of the activity of polar cyclones and a poleward shift of the extratropical storm track. Others have shown that a poleward shift of the cyclone activity can result in a reduced sea ice extent, a situation similar to that observed in 2016 and 2017. When the sea ice extent is reduced, preferable polynya areas (i.e. areas of thinner ice, for example the Maud Rise) located in the ice pack become closer to the ice edge and hence to the cyclogenesis zone. Given the link between polynya occurrence and cyclones, polynya events may thus become more frequent under a warmer climate.

Figure 3 AMSR2‐derived sea ice concentrations on 16 September 2017 at 1200 UTC (colors) and ERA5 10‐m winds less than 20 m/s in black contours, and greater than 20 m/s in red contours.The solid yellow contour is the 15% ERA‐Interim sea ice contour, the dotted yellow contour is the 50% ERA‐Interim sea ice contour, and the dashed white contour is the 15% ice from satellite data delineating the polynya area. [Credit: Francis et al., 2019].

Further reading

Edited by Lettie Roach


Diana Francis is an atmospheric scientist at New York University Abu Dhabi, UAE. She investigates atmospheric dynamics in polar regions with focus on polar meteorology and links to changes in land and sea ice conditions. To this end, she uses regional models together with available observations and reanalyses. She tweets as @drdianafrancis.
Contact Email:  diana.francis@nyu.edu

Climate Change & Cryosphere – Caucasus Glaciers Receding

Climate Change & Cryosphere – Caucasus Glaciers Receding

The Tviberi Glacier valley is located in the Svaneti Region – a historic province of the Georgian Caucasus. Between 1884 and 2011, climate change has led to a dramatic retreat of the ice in this valley. Other glaciers in the Greater Caucasus evolved in a similar way in past decades. We investigated glaciers and their changes both in-situ and with remote sensing techniques in the 53 river basins in the southern and northern slopes of the Greater Caucasus in order to analyze glacier dynamics in combination with climate change over the last decades…


Why are glaciers important for the Caucasus region?

On the one hand, in a high mountain system such as the Greater Caucasus, glaciers are the source of rivers through snow and ice melting. They are therefore an important source of water for agricultural production, for several hydroelectric power stations, for water supply, and for recreational opportunities. Also, the Greater Caucasus glaciers have a positive impact on the economy by being a major tourist attraction. The Svaneti, Racha and Kazbegi regions in Georgia welcome thousands of visitors each year.

On the other hand, glacier hazards are relatively common in this region, leading to major casualties. On the 20th September 2002, for example, Kolka Glacier (North Ossetia) initiated a catastrophic ice-debris flow killing over 100 people, and, on the 17th May 2014, Devdoraki Glacier (Georgia) caused a rock–ice avalanche and glacial mudflow killing nine people (Tielidze and Wheate, 2018).

 

Tviberi Glacier Degradation over the last century

According to our investigation, the Tviberi was the largest glacier of the southern slope of Georgian Caucasus in the end of the 19th century with a total area of 49.0 km2. The glacier terminated at a height of 2030 m above sea level (a.s.l) in 1887 (based on topographical maps, see Fig.2a). Before the 1960s, the largest ice stream – the Kvitoldi Glacier – separated from the Tviberi, and became an independent glacier (Fig. 2b). The 1960 topographical map shows that, as a consequence, the Tviberi Glacier shrinked to an area of 24.7 km2 and the glacier tongue ended at 2140 m a.s.l. (Fig. 2b). Finally, the Landsat 2014 image shows the degradation of the Tviberi Glacier after 1960, as it decomposed into smaller simple-valley glaciers and even smaller cirque glaciers developed (Fig. 2c) (Tielidze, 2016).

Fig.2: a – Tviberi Glacier, topographical map 1887; b – topographical map 1960, 1: Tviberi Glacier, 2: Kvitlodi Glacier; c – Landsat L8 imagery 2014. [Credit: modified from Fig.2 in Tielidzle, 2016]

Latest Caucasus Glacier Inventory

In our remote-sensing survey of glacier change in the Greater Caucasus based on large-scale topographic maps and satellite imagery (Corona, Landsat and ASTER), we show that the evolution of the Tviberi Glacier reflects the evolution of the majority of glaciers in the region. The main aim of this study was to present an updated and expanded glacier inventory at three time periods (1960, 1986, 2014) covering the entire Greater Caucasus (Russia-Georgia-Azerbaijan).

According to our study, glaciers on the northern slope of the Greater Caucasus lost 0.50% of their area per year between 1960 and 2014, while the southern slope glacier area decreased by 0.61% per year. Glaciers located on Mt. Elbrus lost 0.27% of their combined area per year during the same period. Overall, the total ice area loss between 1960 and 2014 was 0.53% per year, while the number of glaciers reduced from 2349 to 2020 for the entire Greater Caucasus (Fig. 3) (Tielidze and Wheate, 2018).

 

Fig.3: Greater Caucasus glacier area decrease by slopes, sections and mountain massifs in 1960–1986, 1986–2014 and 1960–2014 [Credit: Fig.4 in Tielidze and Wheate, 2018]

We have observed strong positive linear trends in the mean annual and summer air temperatures at all selected meteorological stations for the period 1960-2014 (Fig. 4). These climate data suggest that the loss of glacier surface area across the Greater Caucasus between the 1960 and 2014 mostly reflects the influence of rising temperatures in both the northern and southern slopes of the Greater Caucasus. The highest temperature increase was recorded in the eastern Greater Caucasus where the glacier recession was highest at the same time. If the decrease in the surface area of glaciers in the eastern Greater Caucasus continues over the 21st century, many will disappear by 2100 (Tielidze and Wheate, 2018).

 

Fig.4: Mean annual air temperatures at the seven meteorological stations in the years 1960–2014. [Credit: Levan Tielidze]

Want to use these and more data?

This new glacier inventory has been submitted to the Global Land Ice Measurements from Space (GLIMS) database and can be used as a basis data set for future studies.

 

Further reading

Edited by Clara Burgard


Levan Tielidze is a senior research scientist at Institute of Geography, Tbilisi State University. He is also a PhD student of School of Geography, Environmental and Earth Sciences, and Antarctic Research Centre at Victoria University of Wellington. The field of his research is modern glaciers and glacial-geomorphological studies of the mountainous areas in the Quaternary (Late Pleistocene and Holocene). Contact Email: levan.tielidze@tsu.ge/levan.tielidze@vuw.ac.nz.

Image of the Week – The GReenland OCEan-ice interaction project (GROCE): teamwork to predict a glacier’s future

Figure 1: The GROCE project, with 11 working groups and more than 30 scientists from across Germany, aims to understand what the present-day state of the 79°N glacier in Greenland is. On a windy day in May 2019, the GROCE teams met up at the annual update meeting to present findings and discuss the next steps to understand this complex system. Photo credit: Mario Hoppman, AWI


The GROCE project, funded by the German Ministry for Education and Research (BMBF), takes an Earth-System approach to understand what processes are at play for the 79°N glacier (also known as Nioghalvfjerdsfjorden), in northeast Greenland. 79°N is a marine-terminating glacier, meaning it has a floating ice tongue (like an ice shelf) and feeds into the ocean. Approximately 8% of all the ice contained in the Greenland Ice Sheet feeds into the 79°N glacier before it reaches the ocean (Seroussi et al., 2011). Therefore, in a worst-case-scenario where it melted entirely, this would lead to 1.1 m of sea level rise (Mayer et al., 2018). In recent years, the glacier’s ice flow to the ocean has increased in speed (Khan et al., 2014) and at the same time, the atmosphere at the surface in the region has warmed by 3°C over the last 40 years (Turton et al., 2019). This means that the 79°N glacier is being affected by both the warming atmosphere and the warming ocean simultaneously and will therefore be highly sensitive to future climate changes. However, without understanding its current state through accurate monitoring, predicting what the future may hold for this glacier is difficult.

Figure 2: The 79°N glacier and its floating tongue respond to warm waters coming from the surrounding ocean, producing melt-water which circulates underneath the floating tongue. In turn, the less saline melt-water affects and changes the large-scale ocean circulation itself. Simultaneously, at the surface, a warming atmosphere leads to more surface melt-water, some of which drains to the base of the glacier. Infographic credit: Mario Hoppman/AWI/Martin Künsting.

We are 11 different working groups, all attempting to understand the 79°N glacier, each group investigating a different, but complementary, aspect of the glacier. Our investigations include: the interactions between the atmosphere and the ice, the ocean circulation around the ice tongue, melting at the surface of the ice, melting near the bedrock beneath the ice, the location of the grounding line (where the ice meets the ocean and starts to float to form the floating ice tongue), tidal processes and many more (see Figure 2 for some of these processes). The 11 working groups, which includes 34 scientists and PhD students from 8 universities and research institutes, are spread all over Germany: from FAU University of Erlangen-Nürnberg (most southerly) to IOW (Leibniz Institute for Baltic Sea Research Warnemünde) (see Figure 3 for a map of the locations of all the research groups). The project is about to enter its third and final year, which means a lot of exciting new results are emerging from the project and there will be many more to come…

Figure 3: The locations of the 8 main partner universities and research institutions involved in the GROCE project. Figure made with google my maps.

If you’re interested in learning more about the GROCE project, its members or research outcomes, you can find a lot of information on our website: www.groce.de.

Figure 4: Jenny Turton reports on the progress made in regional atmospheric modelling efforts within the last year during the progress meeting in May 2019. Photo credit: Mario Hoppman, AWI

Edited by Marie Cavitte


Jenny Turton is a post-doc researcher in the climate system research group at Friedrich-Alexander University (FAU) in Erlangen. She currently investigates the interaction between the atmosphere and the cryosphere. More specifically, her current research focuses on the link between atmospheric processes and the glacier surface of 79°N glacier in northeast Greenland.