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Cryospheric Sciences

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Image of the Week – The future of Antarctic ice shelves

Percent change in ice shelf melting, caused by the ocean, during the four future projections. The values are shown for all of Antarctica (written on the centre of the continent) as well as split up into eight sectors (colour-coded, written inside the circles). Figure 3 of Naughten et al., 2018 ). ©American Meteorological Society. Used with permission.

Climate change will increase ice shelf melting around Antarctica. That’s the not-very-surprising conclusion of a recent modelling study, resulting from a collaboration between Australian and German researchers. Here’s the less intuitive result: much of the projected melting is actually linked to a decrease in sea ice formation. Learn why in our Image of the Week…


Different types of Antarctic ice

Sea ice is just frozen seawater. But ice shelves (as well as ice sheets and icebergs) are originally formed of snow. Snow falls on the Antarctic continent, and over many years compacts into a system of interconnected glaciers that we call an ice sheet. These glaciers flow downhill towards the coast. If they hit the coast and keep going, floating on the ocean surface, the floating bits are called ice shelves. Sometimes the edges of ice shelves will break off and form icebergs, but they don’t really come into this story (have a look at this and this previous post if you want to read about icebergs nevertheless!).

Climate models don’t typically include ice sheets, or ice shelves, or icebergs. This is due to a combination of insufficient resolution and software engineering challenges, and is one reason why future projections of sea level rise are so uncertain. However, some standalone ocean models, i.e. ocean models without a coupled atmosphere, do include ice shelves. At least, they include the little pockets of ocean beneath the ice shelves – we call them ice shelf cavities – and can simulate the melting and refreezing that happens on the undersides of ice shelves.

Modelling future ice shelf melting

We took one of these ocean/ice-shelf models and forced it with the atmospheric output of regular climate models, which periodically make projections of climate change from now until the end of this century. As forcing, we used the atmospheric output of the Australian model ACCESS 1.0 in two experiments, and the mean of the atmospheric output from 19 other climate models taking part in the Coupled Model Intercomparison Project Phase 5  (Multi-Model Mean or “MMM”) in another two experiments. Each set of experiments considered two different scenarios for future greenhouse gas emissions (“Representative Concentration Pathways” or RCPs), for a total of four simulations. Each simulation required 896 processors on the supercomputer in Canberra. By comparison, your laptop or desktop computer probably has about 4 processors. These are pretty sizable models!

In every simulation, and in every region of Antarctica, ice shelf melting increases over the 21st century. The total increase ranges from 41% to 129% depending on the emissions scenario and choice of climate model. The largest increases occur in the Amundsen Sea region, marked with red circles in our Image of the Week, which also happens to be the region exhibiting the most severe melting in recent observations. In the most extreme scenario, i.e. with the highest future greenhouse gas emissions and the more sensitive climate model, ice shelf melting in this region nearly quadruples.

Understanding the drivers of melting

So what processes are causing this melting? This is where the sea ice comes in. When sea ice forms, it spits out most of the salt from the seawater (brine rejection), leaving the remaining water saltier than before. Salty water is denser than fresh water, so it sinks. This drives a lot of vertical mixing, and the heat from warmer, deeper water is lost to the atmosphere. The ocean surrounding Antarctica is unusual in that the deep water is generally warmer than the surface water. We call this warm, deep water Circumpolar Deep Water, and it’s currently the biggest threat to the Antarctic Ice Sheet. (I say “warm” – it’s only about 1°C, so you wouldn’t want to go swimming in it, but it’s plenty warm enough to melt ice.)

In our simulations, warming winters cause a decrease in sea ice formation. This leads to less brine rejection, causing fresher surface waters, causing less vertical mixing, and the warmth of Circumpolar Deep Water is no longer lost to the atmosphere. As a result of reduced vertical mixing, ocean temperatures near the bottom of the Amundsen Sea increase and this better-preserved Circumpolar Deep Water
finds its way into ice shelf cavities, causing large increases in melting.

 

Slices through the Amundsen Sea – you’re looking at the ocean sideways, like a slice of birthday cake, so you can see the vertical structure. Temperature is shown on the top row (blue is cold, red is warm); salinity is shown on the bottom row (blue is fresh, red is salty). Conditions at the beginning of the simulation are shown in the left 2 panels, and conditions at the end of the simulation are shown in the right 2 panels. At the beginning of the simulation, notice how the warm, salty Circumpolar Deep Water rises onto the continental shelf from the north (right side of each panel), but it gets cooler and fresher as it travels south (towards the left) due to vertical mixing. At the end of the simulation, the surface water has freshened and the vertical mixing has weakened, so the warmth of the Circumpolar Deep Water is preserved. Figure 8 of Naughten et al., 2018, ©American Meteorological Society. Used with permission.

 

Going to the next level

This link between weakened sea ice formation and increased ice shelf melting has troubling implications for sea level rise. The next step is to simulate the sea level rise itself, which requires some model development. Ocean models like the one we used for this study have to assume that ice shelf geometry stays constant, so no matter how much ice shelf melting the model simulates, the ice shelves aren’t allowed to thin or collapse. Basically, this design assumes that any ocean-driven melting is exactly compensated by the flow of the upstream glacier such that ice shelf geometry remains constant.

Of course this is not a good assumption, because we’re observing ice shelves thinning all over the place, and a few have even collapsed. But removing this assumption would necessitate coupling with an ice sheet model, which presents major engineering challenges. We’re working on it – at least ten different research groups around the world – and over the next few years, fully coupled ice-sheet/ocean models should be ready to use for the most reliable sea level rise projections yet.

Further reading

Edited by Clara Burgard


Kaitlin Naughten is a postdoc at the British Antarctic Survey in Cambridge, UK. She is an ocean modeller focusing on interactions between Antarctic ice shelves, sea ice, and the Southern Ocean. Tweets as @kaitlinnaughten Website: climatesight.org

Image of the Week – Making waves: assessing supraglacial water storage for debris-covered glaciers

Fig. 1: Deriving the bathymetry and temperature of a large supraglacial pond on Khumbu Glacier, Everest region of Nepal. The sonar-equipped unmanned surface vessel nicknamed ‘BathyBot’ (left), and kayak retrieval of temperature loggers (right) [Credit: Scott Watson].

A creeping flux of ice descends Everest, creating the dynamic environment of Khumbu Glacier. Ice and snow tumble, debris slumps, ice cliffs melt, englacial cavities collapse, ponds form and drain, all responding to a variable energy balance. Indeed, Khumbu Glacier is a debris-covered glacier, meaning it features a layer of sediment, rocks and house-sized boulders that covers the ice beneath. Recent advances in understanding debris-covered glacier hydrology come from combining in situ surveys with remotely sensed satellite data.


Khumbu Glacier

The dramatic beauty of Nepal’s Everest region attracts a mix of trekkers, climbers, and scientists. Flowing down from the slopes of Mount Everest, the debris-covered Khumbu Glacier has drawn scientists from the mid-1900s, and offers temporary residence for research teams and a myriad of climbers. In some locations, Khumbu Glacier has thinned by up to 80 m in the last three decades, leading to moraines overlooking the glacier with impressive topographic relief and providing an instant visualisation of glacier mass loss for trekkers heading to Everest Base Camp.

Melt at the surface of this glacier is moderated by an undulating debris layer, which insulates the ice beneath,   and enhanced locally by dynamic surface features such as supraglacial ponds and ice cliffs thinly veiled by debris. These features contribute disproportionately to melt and lead to the development of hummocky, pitted surface topography. The resulting variable surface topography and melt rates complicate meltwater runoff and flow routing across the glacier. To better understand them, in situ surveying (Fig. 1) is increasingly combined with fine spatial-temporal resolution satellite imagery to reveal the hydrological evolution of debris-covered glaciers, which is closely linked to their mass loss.

Hydrology of Khumbu Glacier

As with debris-free glaciers, water may be routed through supraglacial, englacial, and subglacial pathways, which are conceptually distinct but physically link to one another.

At Khumbu Glacier, surface channels collect and rapidly convey meltwater generated in the upper ablation area (Fig. 2), just below the treacherous Khumbu Icefall, incising at a faster rate than the surface melt. In the middle of the debris-covered area, such streams disappear into the glacier’s interior through cut-and-closure and/or hydrofracture.

Fig.2: The upper ablation area of Khumbu is drained by supraglacial channels which enter the glacier’s interior through hydrofracture and cut-and-closure, while the lower portion is characterised by pitted surface depressions and an increasing density of ponds. Right panel looking east to west shows the hummocky topography and ponding on Khumbu Glacier. [Credit: Evan Miles (left), Ann Rowan (right)].

In areas of low surface gradient , and particularly throughout the hummocky lower reaches of the glacier, supraglacial ponds collect water in surface depressions. These features haveregulate the runoff of debris-covered glaciers by seasonally storing meltwater. The annual melt cycle thus leads to pond expansion and contraction, or their disappearance when the protecting debris layer thaws and relict meltwater conduits become avenues for drainage (Fig 3). The areal fluctuation of ponds can be quantified using  satellite images at different times, but cloud cover during the summer monsoon season limits useable imagery at a time when the ponds are most dynamic. Therefore, field-instrumented ponds provide valuable insights into their active melt season behaviour.

Fig. 3: A small 4.5 m deep pond that drained over the course of a year [Credit: Watson et al., 2017a].

Turbid ponds associated with debris influx from ice cliffs are often ephemeral but some can grow to hold vast quantities of water (Fig. 1). Stored water absorbs and transmits solar energy to melt adjacent ice, which generates additional meltwater and leads to pond expansion. The ponds also thermally undercut ice cliffs, leading to both subaqueous and subaerial  retreat (Fig. 4). Khumbu Glacier has been developing a growing network of ponds in recent years, which means meltwater is increasingly stored on the surface of the glacier before contributing to downstream river discharge. Ponds that coalesce into larger and more persistent lakes behind unstable deposits of sediment can in some cases pose a hazard  to downstream communities. Field and satellite-based techniques are therefore used simultaneously to monitor lake development.

 

Fig. 4. Supraglacial ponds often exist alongside ice cliffs. These ‘hot spots’ of melt can be observed with repeat point cloud differencing [Credit: Watson et al., 2017b]. An interactive view of the drained pond basin (right) is available here.

What lies beneath?

Ephemeral ponds drain into the ‘black box’ glacier interior, where relatively little is known about the internal structure and hydrology. Scientists have occasionally ventured into the subsurfac e realm through networks of englacial conduits that become exposed as the glacier thins (Fig. 5); such conduits often re-emerge at the glacier surface but may also lead to the bed. The conduits carry meltwater through the glacier but can become dormant if blocked by falling debris or creeping ice, or when the meltwater that sustains them finds a route of lesser resistance. Whilst satellite data can be used to infer the presence of conduits, field-based methods are required for hydrological budgeting and quantifying meltwater transit times. For example, dye tracing can detect the subsurface passage of meltwater where strategically placed fluorometers measure the receipt and dilution of the dye upon re-emergence. Such methods are crucial for developing an improved understanding of the links between, for example, flow in the supraglacial channels up-glacier and discharge at the outlet.

Fig. 5: An exposed conduit on Lirung Glacier (left) [Credit: Miles et al., 2017] and researchers inside a conduit on Ngozumpa Glacier (right) [Credit: Benn et al., 2017].

 

Outlook

Multiple teams working across the Himalaya are advancing our understanding of debris-covered glacier hydrology, which is essential to forecast their future and quantify their downstream impact. With the ready availability of increasingly high temporal resolution satellite imagery (e.g. Sentinel-2, Planet Labs), the link between field and spacebourne observations will become increasingly complementary. Developing these links is crucial to upscale observations from specific sites more broadly across the Himalaya.

Further reading

Edited by Violaine Coulon and Sophie Berger


Scott Watson is a Postdoc at the University of Arizona, USA. He studies glaciers in the Everest region and the surface interactions of supraglacial ponds and ice cliffs. He also investigates natural hazards and the implications of glacial lake outburst floods.
Tweets @CScottWatson. Website: www.rockyglaciers.co.uk

 

 

Evan Miles is a Research Fellow at the University of Leeds, UK, where he is a part of the EverDrill project’s hot-water drilling at Khumbu Glacier. His recent work has examined the seasonal hydrology and dynamics of debris-covered glaciers, with a focus on the melt associated with dynamic surface features such as supraglacial ice cliffs and ponds.
Tweets @Miles_of_Ice

EverDrill website: www.EverDrill.org

Image of the Week — Orange is the new white

Figure 1. True color composite of a Sentinel-2 image showing the dust plume off the coast of Libya on 22-Mar-2018 (see also on the ESA website) [Credit: processed by S. Gascoin]

On 22 March 2018, large amounts of Saharan dust were blown off the Libyan coast to be further deposited in the Mediterranean, turning the usually white snow-capped Mountains of Turkey, Romania and even Caucasus into Martian landscapes.  As many people were struck by this peculiar color of the snow, they started documenting this event on social media using the “#orangesnow hashtag”. Instagram and twitter are fun, but satellite remote sensing is more convenient to use to track the orange snow across mountain ranges. In this new image of the week, we explore dusty snow with the Sentinel-2 satellites…

Марс атакует 🌔 #smurygins_family_trip

A post shared by Alina Smurygina (@sinyaya_ptiza) on


Sentinel-2: a great tool for observing dust deposition

Sentinel-2 is a satellite mission of the Copernicus programme and consists of two twin satellites (Sentinel-2A and 2B). Although the main application of Sentinel-2 is crop monitoring, it is also particularly well suited for characterizing the effect of dust deposition on the snowy mountains because:

  1. Sentinel-2A and 2B satellites provide high-resolution images with a pixel size of 10 m to 20 m (depending on the spectral band), which enables to detect dust on snow at the scale of hillslopes.
  2. Sentinel-2 has a high revisit capacity of 5 days which increases the probability to capture cloud-free  images shortly after the dust deposition.
  3. Sentinel-2 has many spectral bands in the visible and near infrared region of the light spectrum, making easy to separate the effect of dust on snow reflectance — i.e. the proportion of light reflected by snow — from other effects due to snow evolution. The dust particles mostly reduce snow reflectance in the visible, while coarsening of the snow by metamorphism (i.e. the change of microstructure due to transport of vapor at the micrometer scale) tends to reduce snow reflectance in the near infrared (Fig. 2).
  4. Sentinel-2 radiometric observations have high dynamic range and are accurate and well calibrated (in contrast to some trendy miniature satellites), hence they can be used to retrieve accurate surface dust concentration, provided that the influence of the atmosphere and the topography on surface reflectance are removed.

Figure 2: Diffuse reflectance for different types of snowpack. These spectra were computed with 10 nm resolution using the TARTES model (Libois et al, 2013) using the following parameters: snowpack density: 300 kg/m3, thickness: 2 m, fine snow specific surface area (SSA): 40 m2/kg, coarse snow SSA: 20 m2/kg, dust content: 100 μg/g. The optical properties of the dust are those of a sample of fine dust particles from Libya with a diameter of 2.5 μm or less (PM2.5) (Caponi et al, 2017). The Sentinel-2 spectral bands are indicated in grey. [Credit: S. Gascoin]

Dust on snow from Turkey to Spain

The region of Mount Artos in the Armenian Highlands (Turkey) was one of the first mountains to be imaged by Sentinel-2 after the dust event. Actually Sentinel-2 even captured the dust aloft on March 23, before its deposition (Fig. 3)

Figure 3: Time series of three Sentinel-2 images near Mount Artos in Turkey (true color composites of level 1C images, i.e. orthorectified products, without atmospheric correction). [Credit: Contains modified Copernicus Sentinel data, processed by S. Gascoin]

Later in April another storm from the Sahara brought large amounts of dust in southwestern Europe.

Figure 4: Sentinel-2 images of the Sierra Nevada in Spain (true color composites of level 1C images). [Credit: Contains modified Copernicus Sentinel data, processed by S. Gascoin]

This example in the spanish Sierra Nevada nicely illustrates the value of the Sentinel-2 mission since both images were captured only 5 days apart. The high resolution of Sentinel-2 is also important given the topographic variability of this mountain range. This is how it looks in MODIS images, having a 250 m resolution.

Figure 5: MODIS Terra (19) and Aqua (24) images of the Sierra Nevada in Spain. True Color composites of MODIS corrected reflectance. [Credit: NASA, processed by S. Gascoin]

Sentinel-2 satellites enable to track the small-scale variability of the dust concentration in surface snow, even at the scale of the ski runs as shown in Fig. 6.

Figure 6: Comparison of a true color Sentinel-2 image and a photograph of the Pradollano ski resort, Sierra Nevada. [Credit: photograph taken by J. Herrero / Contains modified Copernicus Sentinel data, processed by S. Gascoin]

A current limitation of Sentinel-2, however, is the relative shortness of the observation time series. Sentinel-2A was only launched in 2015 and Sentinel-2B in 2017. With three entire snow seasons, we can just start looking at interannual variability. An example in the Prokletije mountains in Albania is shown in Fig. 7.

Figure 7. Sentinel-2 images of the Prokletije mountains in Albania (true color composites of level 1C images) [Credit: Contains modified Copernicus Sentinel data, processed by S. Gascoin]

These images suggest that the dust event of March 2018 was not exceptional in this region, as 2016 also highlights a similar event. The Sentinel-2 archive will keep growing for many years since the EU Commission seems determined to support the continuity and development of Copernicus programme in the next decades. In the meantime to study the interannual variability the best option is to exploit the long-term records from other satellites like MODIS or Landsat.

Beyond the color of snow, the water resource

Dust on snow is important for water resource management since dust increases the amount of solar energy absorbed by the snowpack, thereby accelerating the melt. A recent study showed that dust controls springtime river flow in the Western USA (Painter et al, 2018).

“It almost doesn’t matter how warm the spring is, it really just matters how dark the snow is.”

said snow hydrologist Jeff Deems in an interview about this study in Science Magazine. Little is known about how this applies to Europe…

Further reading

 Edited by Sophie Berger


Simon Gascoin is a CNRS researcher at Centre d’Etudes Spatiales de la Biosphère (CESBIO), in Toulouse. He obtained a PhD in hydrology from Sorbonne University in Paris and did a postdoc on snow and glacier hydrology at the Centro de Estudios Avanzados en Zonas Áridas (CEAZA) in Chile. His research is now focusing on the application of satellite remote sensing to snow hydrology. He tweets here and blog here.

 

 

Marie Dumont is a researcher, leading the snow processes, observations and modelling research team at the snow study centre (CNRM/CEN, Grenoble, France). Her research focuses on snow evolution mostly in alpine region using numerical modelling and optical remote sensing.

 

 

 

Ghislain Picard is a lecturer working at the Institute of Geosciences and Environment at the University Grenoble Alpes, in the climate and ice-sheets research group. His research focuses on snow evolution in polar regions in the context of climate change. Optical and microwave remote sensing is one of its main tools.

Image of the Week – Polar Prediction School 2018

Image of the Week – Polar Prediction School 2018

Early career scientists studying polar climate are one lucky group! The 29 young scientists who took part in the 10 day Polar Prediction School this year were no exception. They travelled to Arctic Sweden to learn and discuss the challenges of polar prediction and to gain a better understanding of the physical aspects of polar research.


The Year of Polar Prediction

The Year of Polar Prediction (YOPP) was launched on May 15th 2017; a large 2 year project that ‘aims to close gaps in polar forecasting capacity’ and ’lead to better forecasts of weather and sea-ice conditions to improve future environmental safety at both poles’. With these aims in mind, and with the support of the related APPLICATE project and the Association for Polar Early Career Scientists (APECS), a ten day Polar Prediction School took place in Abisko, Sweden in mid-April.

Abisko is a little town of 85 inhabitants, located north of the Arctic Circle (68°N) next to a National Park and a large lake. Due to the interesting habitats found in the region it is an excellent place to undertake polar research. Consequently, a scientific research station is located in the town, where research mainly focuses on biology, ecology, and meteorology.

Heading back to the research station (seen at the back of the picture) after a long hike [Credit: C. Burgard].

The 29 school participants were made up of Master students, PhD students, and PostDocs, with some studying the Arctic and some the Antarctic. The participants had diverse research backgrounds, with research that focused on atmospheric sciences, oceanic sciences, glaciers, sea ice and hydrology of polar regions, and used a range of techniques, from weather or climate models to in-situ or satellite observations. However, in the end, we were all linked together by our interest in the polar regions. Both this diversity and this link in our research helped us to exchange ideas about the common issues and the differences in all our disciplines.

The school programme

The course aimed to broaden students’ knowledge around their very specific PhD area. Therefore, the school covered a huge range of topics including polar lows, polar ocean-sea ice forecasting, remote sensing of the cryosphere, boundary layers, clouds and much more! Each day was made up of a mixture of lectures and practical sessions, which included:

  • Computer modelling exercises, for example using a simple 1D sea ice model
  • Observations, which included measuring temperature and wind from a weather station on the frozen lake next to the station, and daily radiosonde launches at lunchtime, in sync with radiosonde launches worldwide. These results were compared to model predictions each day.
  • Data assimilation, which focused on understanding the shortcomings in reanalysis products that we all use, including sources of uncertainty and error in the products and how they may impact our own work.

After dinner each evening a different group gave an informal weather briefing for the next day, which was often condensed down to how cloudy it would be, the amount of snow predicted (very little), and temperature (which averaged 2-3°C). Not quite the harsh, sub-zero temperatures that most of us had packed for! Each day was broken up by two coffee breaks (always accompanied by an obligatory cinnamon roll!) and meals which were taken all together in the main research building. This dragged everyone out of the lecture room to chat and refresh before the next session.

As is usual for any worthwhile meteorological fieldwork, we installed a small weather mast on the lake [Credit: C. Burgard].

Living Arctic weather for real

The usual weather in Abisko during April is fairly dry with temperatures ranging from 2°C to -6°C. In preparation for the cold, most of us had brought an abundance of wooly jumpers, thick thermal layers and numerous pairs of socks. However, on arrival in Abisko, the sun was shining and it was a balmy 7°C for the first two days. Whilst erecting the meteorology mast many of us were wearing T-shirts and sunglasses, after abandoning our warmer gear. The warm weather was not to last! Cloudy, relatively mild (2°C to -2°C) conditions persisted throughout most of the week, and it remained dry, which made it easier to forecast the weather but we were all hoping for a little snow! Finally, on the final day of the summer school, large snowflakes fell, although sadly it all melted quite quickly.

When we arrived, the whole area was coated in a thick layer of white snow and the frozen lake was covered. However, by the end of our visit, the bare earth was visible, and the top of the lake was slushy puddles of water. The changes in weather throughout the summer school made for interesting observation records. The albedo (reflectivity) of the lake surface went from approximately 0.8 for the fresh, white snow, but was reduced to 0.4 for the darker, water covered lake surface. It was great to see some theory in action!

Exploring the region

Luckily, we were also given a free day , in which we could explore the region, go skiing or just relax. One large group went off hiking, whilst a smaller group went cross country skiing and a few had a walk to the nearby frozen waterfall. But don’t worry, the science still continued! A group of 3 people stayed close by to release the lunchtime radiosonde.

Abisko children launching a radiosonde! [Credit: J. Turton]

Our visit to the area coincided with the exciting annual ice fishing contest! Whilst cars and small DIY tools are common place in many cities, in Abisko it is a snow mobile (or skidoo) and an ice drill, so they were well versed in the art of ice fishing! The majority of the town’s occupants arrived at the lake and started drilling small holes to catch some fish. After two hours, a number of prizes were awarded (e.g for the longest fish caught). Unfortunately, some of the holes were a little too close to our meteorology mast, and some cables were pulled out, but thankfully we still collected some good data!

An important aspect of any research is engaging with the local communities and communicating effectively with them. So all of the summer school attendees gathered by the lake to watch the ice fishing contest, and a large number of the children from Abisko gathered to watch us release the radiosonde, even helping launch one. They found our activities just as exciting as we found theirs!

And we did some science communication as well!

A crucial aspect of science is how you communicate it to a variety of audiences. The way you might discuss your thesis to your viva panel should be completely different to the way you describe your science to your Great Aunt Linda or to a group of 10-year olds who are attending your outreach event. As part of the summer school, we learnt a range of tips and tricks for communicating science, thanks to Jessica Rohde. Jess is the communications officer for IARPC (Interagency Arctic Research Policy Committee) Collaborations and has years of science communication experience under her belt. Each evening we had a short lecture by Jess, which focused on a specific area of communication including presentation slide design, knowing your audience, listening to the audience and finding the story behind your science. Once we had learnt the theory we then put what we had learnt into practice. We did a bit of  improv’, which included 1-minute elevator pitches and tailoring your science to taxi drivers, the Queen of England and models (no not computer models, the Kate Moss variety). An important take-home message was that there is no such thing as the ‘general public’. When designing your outreach event, the ‘general public’ could involve children of all ages (and therefore all learning levels), parents, teachers, professors and pensioners. Therefore, you should listen to the needs of your audience and understand what their motivation is.

You can check out the final results of these sessions here!

In summary…

In the end, although the school was quite intense, everyone was sad to part. We are sure we will all remember this exciting time, where we learnt about the many aspects of polar prediction, and what to consider when tackling science communication. We hope that this school will be organized again in the next years to provide this amazing and unforgettable experience to all those who could not join this year’s Polar Prediction School!

Further reading

Edited by Morgan Jones


Rebecca Frew is a PhD student at the University of Reading (UK). She investigates the importance of feedbacks between the sea ice, atmosphere and ocean for the Antarctic sea ice cover using a hierarchy of climate models. In particular, she is looking at the how the importance of different feedbacks may vary between different regions of the Southern Ocean.
Contact: r.frew@pgr.reading.ac.uk

 

 

Jenny Turton is a post doc working at the institute for Geography at the University of Erlangen-Nuernberg, in the climate system research group. Her current research focuses on the interactions between the atmosphere and surface ice of the 79N glacier in northeast Greenland, as part of the GROCE project. 

 

 

 

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.

Image of the Week — Biscuits in the Permafrost

Fig. 1: A network of low-centred ice-wedge polygons (5 to 20 m in diameter) in Adventdalen, Svalbard [Credit: Ben Giles/Matobo Ltd]

In Svalbard, the snow melts to reveal a mysterious honeycomb network of irregular shapes (fig. 1). These shapes may look as though they have been created by a rogue baker with an unusual set of biscuit cutters, but they are in fact distinctive permafrost landforms known as ice-wedge polygons, and they play an important role in the global climate.


Ice-wedge polygons: Nature’s biscuit-cutter

In winter, cracks form when plummeting air temperatures cause the ground to cool and contract. O’Neill and Christiansen (2018) used miniature accelerometers to detect this cracking, and found that it causes tiny earthquakes, with large magnitude accelerations (from 5 g to at least 100 g (where g = normal gravity)!). Water fills the cracks when snow melts. When the temperature drops, the water refreezes and expands, widening the cracks. Over successive winters, the low tensile strength of the ice compared to the surrounding sediment means that cracking tends to reoccur in the ice. As the cycle of cracking, infilling, and refreezing continues over centuries to millennia, ice wedges develop.

Subsurface ice wedge growth causes small changes in the ground surface microtopography. There are linear depressions, known as troughs, above the ice wedges (fig. 2). Adjacent to the troughs, the soil is pushed up into raised rims. From these raised rims, the elevation drops off into the polygon centre, forming low-centred polygons (fig. 2a).

Shaping Arctic landscapes

Permafrost in the Northern hemisphere is warming due to increasing air temperatures (Romanovsky et al. (2010). As air temperatures rise, the active layer (the ground that thaws each summer and refreezes in winter) deepens.

As permafrost with a high ice content thaws out, the ice melts and the ground subsides. On the other hand, permafrost containing no ice does not experience subsidence. Consequently, permafrost thaw can cause differential subsidence in ice-wedge polygon networks. This re-arranges the surface microtopography: ice wedges melt, the rims collapse into the troughs, and the polygons become flat-centred and then eventually high-centred (fig. 2b and c; Lara et al. (2015)). Wedge ice is ~20 % of the uppermost permafrost volume, and so this degradation could have a big impact on the shape of Arctic landscapes.

Are ice wedge polygons climate amplifiers?

Fig. 2: Schematic diagrams of polygon types and features [Credit: Wainwright et al. (2015)].

The transition from low-centred to high-centred ice-wedge polygons affects water distribution across the polygonal ground. The rims of low-centred polygons tend to block water drainage, whereas the troughs facilitate relatively fast and effective drainage of water from the polygonal networks (Liljedahl et al., 2012). So, during summer, the centres of low-centred polygons are frequently flooded with stagnant water, whereas the central mounds of high centred polygons are well drained (and good to sit on at lunchtime!). The contrast in hydrology influences vegetation, surface energy transfer, and biogeochemistry, in turn influencing carbon cycling and the release of greenhouse gases into the atmosphere.

High-centred polygons can have increased carbon dioxide emissions compared to low-centred polygons, on account of their lower soil moisture, reduced cover of green vascular vegetation and the well-drained soil (Wainwright et al., 2015). On the other hand, once plant growth during peak growing season is accounted for, this can actually cause a net drawdown of carbon dioxide in high-centred polygons (Lara et al., 2015). In contrast, there is general agreement that low-centred polygons are associated with high summer methane flux (Lara et al., 2015; Sachs et al., 2010; Wainwright et al., 2015). This is due to multiple interacting environmental factors. Firstly, low centred polygons have a higher temperature, which increases methane production rates. Secondly, they also have moister soil, which decreases the consumption of methane, owing to the lower oxygen availability. Thirdly, the low-centred polygons often have more vascular plants that help transport the methane away from its production site and up into the atmosphere. Lastly, the low-centred polygons had higher concentrations of aqueous total organic carbon, which provides a good food source for methanogens.

Outlook

As the climate warms, ice wedge polygons will increasingly degrade. The challenge now is to figure out whether the transition from low-centred to high-centred polygons will enhance or mitigate climate warming. This depends on the balance between the uptake and release of methane and carbon dioxide, as well as the rate of transition from high- to low-centred polygons.

Further Reading

Lara, M.J., et al. (2015), Polygonal tundra geomorphological change in response to warming alters future CO2 and CH4 flux on the Barrow Peninsula. Global Change Biology, 21(4), 1634-1651

Liljedahl, A.K., et al. (2016), Pan-Arctic ice-wedge degradation in warming permafrost and its influence on tundra hydrology. Nature Geoscience, 9, 312-316.

Wainwright, H.M., et al. (2015), Identifying multiscale zonation and assessing the relative importance of polygons geomorphology on carbon fluxes in an Arctic tundra ecosystem. Journal of Geophysical Research: Biogeosciences, 707-723.

On permafrost instability: Image of the Week – When the dirty cryosphere destabilizes! | EGU Cryosphere Blog

On polygons in wetlands: Polygon ponds at sunset | Geolog

Edited by Joe Cook and Sophie Berger


Eleanor Jones is a NERC PhD student on the EU-JPI LowPerm project based at the University of Sheffield and the University Centre in Svalbard. She is investigating the biogeochemistry of ice-wedge polygon wetlands in Svalbard. She tweets as @ElouJones. Contact Email: eljones3@sheffield.ac.uk

Image of the Week – Cure from the Cold?

Image of the Week – Cure from the Cold?

Humans rely on antibiotics for survival, but over time they are becoming less effective. So-called ‘superbugs’ are developing resistance to our most important drugs. The key to this global issue may be found in the cryosphere, where extreme microbiologists are hunting for new compounds in the cold that could help us win the war against antimicrobial resistance.


Discovering drugs in Earth’s coldest places

Antimicrobial resistance poses a global threat predicted to cause 10 million deaths per year by 2050.

Alexander Fleming’s 1928 discovery of penicillin- a compound produced from a fungus had an antimicrobial effect transformed life expectancy in the 20th century and kick-started the antibiotic revolution. Since then, most antibiotic drugs have been extracted from soil-dwelling microbes such as bacteria and fungi.

We can exploit these compounds produced by microbes to limit the growth of other microbes that are harmful to humans. The chemical structure of these compounds forms the basis of most antibiotics used today to treat microbial infections. However, soil has become an exhausted environment for drug discovery and researchers are turning to other environments in the search for new antimicrobial drugs.

One of these environments is the cryosphere, where diverse habitats in snow, glaciers, ice sheets and sea ice are dominated by microbes. Multiple stresses such as low temperature, high UV intensity, limited nutrient availability and variable salinity mean this extreme environment naturally favours only the hardiest microbes. In order to thrive, it is likely that microbes produce a variety of chemical warfare against their competitors, making the cryosphere a potentially rich reserve for bioprospecting new antimicrobial compounds.

Glacier microbes: all grown up!

Cultivation (growing microbes in a nutrient-containing growth medium in the laboratory) is a valuable technique for discovering new antimicrobial drugs because it allows scientists to take microbes from the environment and grow them in controlled conditions. In the cryosphere, glacier microbiologists have previously shown that many of the cultivable bacteria from these environments demonstrate potent antimicrobial activity. At least 219 novel natural products have been discovered thus far in polar organisms. In the face of widespread glacier and ice sheet melting, microbiologists must move quickly to find and cultivate these potential ‘cures from the cold’.

Fig. 2: A range of different single colonies isolated from a dilute sample of cryoconite, collected from the Foxfonna glacier, Svalbard in 2016. Samples have been grown on a range of different growth mediums [Credit: A. Debbonaire].

Microbial wars help humanity

Once bacteria have grown, we can exploit them. Any weaponry they produce to fend off competition can be extracted and tested against other microbes. We can assess their array of weapons by placing the growing bacteria under different stresses and seeing what compounds they produce to counteract it. Moreover, bacteria can be grown alongside other bacteria/fungi, increasing the likelihood that they fight each other by producing new chemical warfare that we can then use (Figure 3).

We can also test how powerful these weapons of microbial war are using a simple 24-hour test. By adding them to known concentrations of harmful bacteria such as Staphylococcus aureus (think MRSA) we can then monitor the bacterial growth over time after adding the potential antibiotic compounds. Little growth indicates that the new compounds are wreaking havoc and inhibiting growth – we have a new defence!

Fig. 3: Microbes grown from glacier samples compete with one another in a biochemical arms race [Credit: A. Debbonaire].

Cultivation’s “1% problem”

Cultivation is not the only way to bioprospect in the cold, especially because only 1% of the total microbial diversity of an environment is able to grow on growth media, meaning 99% of that diversity goes undiscovered. Our alternative is a technique known as metagenomics, which has been increasingly applied in the cryosphere over the past few years.

Metagenomics is an expensive but fast method of sequencing all DNA within an environmental sample to identify the microbial population that has been demonstrated to be extremely useful for glacier surface ecosystems and can even now be achieved on-site in extreme locations in the cryosphere in a relatively short time. However, metagenomics will only identify which microbes are present, not necessarily their capability, or more importantly, what compounds they produce when under stress. Both techniques combined are now applicable to exploring the cryosphere and provide the most robust approach to drug discovery in the cryosphere. In the war of microbe versus microbe, metagenomics shows which weapons may, or may not, be used; but cultivation provides a detailed analysis of the battle plan.

In summary…

The battle against drug-resistant microbes may be one of the major challenges facing humanity in the twenty-first century. Traditional sites for drug-discovery are being exhausted and researchers are turning to Earth’s coldest reaches to find stressed-out microbes that could provide us with new weaponry to fight the emerging ‘superbugs’. In this melting biome, researchers must act fast to gather the ‘cures from the cold’, exploiting the microbial life in the cryosphere to tackle a global threat to humanity.

 

Further reading

Edited by Joe Cook and Clara Burgard


Aliyah Debbonaire is a PhD student at the Interdisciplinary Centre for Environmental Microbiology (Aberystwyth University). Her research aims to bioprospect extreme environments for life-saving drug candidates. She tweets as @Gnarliyah.

Image of the week — Making pancakes

A drifting SWIFT buoy surrounded by new pancake floes. [Credit: Maddie Smith]

It’s pitch black and twenty degrees below zero; so cold that the hairs in your nose freeze. The Arctic Ocean in autumn and winter is inhospitable for both humans and most scientific equipment. This means there are very few close-up observations of sea ice made during these times.

Recently, rapidly declining coverage of sea ice in the Arctic Ocean due to warming climate and the impending likelihood of an ‘ice-free Arctic’ have increased research and interest in the polar regions. But despite the warming trends, every autumn and winter the polar oceans still get cold, dark, and icy. If we want to truly understand how sea ice cover is evolving now and into the future, we need to better understand how it is growing as well as how it is melting.


Nilas or thin sheets of sea ice [Credit: Brocken Inaglory (distributed via Wikimedia Commons) ]

Sea ice formation

Sea ice formation during the autumn and winter is complex. Interactions between ocean waves and sea ice cover determine how far waves penetrate into the ice, and how the sea ice forms in the first place. If the ocean is still, sea ice forms as large, thin sheets called ‘nilas’. If there are waves on the ocean surface, sea ice forms as ‘pancake’ floes – small circular pieces of ice. As the Arctic transitions to a seasonally ice-free state, there are larger and larger areas of open water (fetch) over which ocean surface waves can travel and gain intensity. Over time, with the continued action of waves in the ice, pancake ice floes develop raised edges —  as seen in our image of the week — from repeatedly bumping into each other. Pancake ice is becoming more common in the Arctic, and it is already very common in the Antarctic, where almost all of the sea ice grows and melts every year.

Nilas vs pancakes

Nilas and pancake sea ice are different at the crystal level (see previous post), and regions of pancake ice and nilas of the same age may have different average ice thickness and ice concentration. As a result, the interaction of the ocean and atmosphere in these two ice types may be very different. Gaps of open water between pancake ice floes allow heat fluxes to be exchanged between the ocean and atmosphere – which can have very different temperatures during winter. Nilas and pancakes also interact with waves differently – nilas might simply flex with a low-intensity wave field, or break into pieces if disturbed by large waves, while pancakes bob around in waves, causing a viscous damping of the wave field. The two ice types have very different floe sizes (see previous posts here and here). Nilas is by definition is a large, uniform sheet of ice; pancake floes are initially very small and grow laterally as more frazil crystals in the ocean adhere to their sides, and multiple floes weld together into sheets of cemented pancakes.

How to make observations?

Sea ice models have only recently begun to be able to separate different sizes of sea ice. This allows more accurate inclusion of growth and melt processes that occur with the different sea ice types. However, observations of how sea ice floe size changes during freeze-up are required to inform these new models, and these observations have never been made before. Pancake sea ice floes are often around only 10 cm in diameter initially, which is far too small to observe by satellite. This means that observations of pancake growth need to be made close-up, but the dynamic ocean conditions in which pancakes are created makes it difficult to deploy instruments in-situ. So how can we observe pancake sea ice in this challenging environment?

In a recent paper (Roach et al, 2018), we used drifting wave buoys, called SWIFTs, to capture the growth of sea ice floes in the Arctic Ocean. SWIFTs are unique platforms (see image of the week) which drift in step with sea ice floes, recording air temperature, water temperature, ocean wave data and – crucially for sea ice – images of the surrounding ice. Analysis of the series of images captured has provided the first-ever measurements of pancake freezing processes in the field, giving unique insight into how pancake floes evolve over time as a result of wave and freezing conditions. This dataset has been compared with theoretical predictions to help inform the next generation of sea ice models. The new models will allow researchers to investigate whether describing physical processes that occur on the scale of centimetres is important for prediction of the polar climate system.

Edited by Sophie Berger


Lettie Roach is a PhD student at Victoria University of Wellington and the National Institute for Water and Atmospheric Research in New Zealand. Her project is on the representation of sea ice in large-scale models, including model development, model-observation comparisons and observation of small-scale sea ice processes.  

 

 

 

Maddie Smith is a PhD student at the Applied Physics Lab at the University of Washington in Seattle, United States. She uses observations to improve understanding of air-sea interactions in polar, ice-covered oceans.

Image of the Week – Super-cool colours of icebergs

Image of the Week – Super-cool colours of icebergs

It is Easter weekend! And as we do not want you to forget about our beloved cryosphere, we provide you with a picture nearly as colourful as the Easter eggs: very blue icebergs! What makes them so special? This is what this Image of the Week is about…


What are icebergs made of?

Fig.2: An iceberg with ‘scallop’ indentations [Credit: Stephen Warren].

Icebergs are chunks of ice which break off from land ice, such as glaciers or ice sheets (as you’ll know if you remember our previous post on icebergs). This means that they are mostly made up of glacial ice, which is frozen freshwater from accumulated snowfall. However, in some places where ice sheets extend to the coastline, making an ice shelf, icebergs can be made up of a different type of ice too.

 

Ice shelves can descend far down into the ocean. Seawater in contact with the ice at depth in the ocean is cooled to the freezing temperature. Because the freezing temperature decreases with decreasing pressure, if the seawater moves upwards in the ocean, it will have a temperature lower than the freezing temperature at that depth. That means it’s super-cooled – the seawater temperature is below the freezing temperature, but it hasn’t become a solid. The seawater cannot last for long in this state and freezes to the base of ice shelves as marine ice, which is seawater frozen at depth. The marine ice can help stabilize the ice shelf as it is less susceptible to fractures than glacial ice. Icebergs that calve from Antarctic ice shelves can sometimes be mixtures of glacial ice (on the top) and marine ice (on the bottom).

 

What can icebergs tell us?

Icebergs which tip over can tell us about processes that happen at the base of ice shelves. For example, scallops on the ice (the small indentations that can be seen in the second picture) can show the size of turbulent ocean eddies in the ocean at the ice shelf base. Basal cavities or channels show where oceanic melt had a large impact. Any colours visible in the iceberg can also give us information.

Fig.3: Marine ice containing organic matter, giving a greenish appearance [Credit: Stephen Warren].

Why are icebergs different colours?

Like snow (see this previous post), different types of ice appear different colours. A typical iceberg is white because it is covered with dense snow, and snowflakes reflect all wavelengths of ice equally. The albedo of snow, which is the proportion of the incident light or radiation that is reflected by a surface, is very high (nearly 1). Glacial ice is compressed snow, meaning it has fewer light-scattering air bubbles, so light can penetrate deeper than in snow, and more yellows and reds from the visible spectrum are absorbed. This results in a bubbly blue colour, with a slightly lower albedo than snow. Marine ice does not have bubbles, but light can be scattered by cracks, resulting in clear blue ice (see our Image of the Week). However, if the seawater from which the marine ice was formed contained organic matter, like algae and plankton, the resulting marine ice can have a yellowish or even green appearance (Fig. 3). If the marine ice formed near the base of an ice shelf where it meets the sea floor, it could contain sediment, giving it a dirty or black appearance.

So the colour of icebergs can tell us something about how ice was formed hundreds of metres below the ocean surface. You could even say that was super-cool…

Further reading

  • Warren, S. G., C. S. Roesler, V. I. Morgan, R. E. Brandt, I. D. Goodwin, and I. Allison (1993), Green icebergs formed by freezing of organic-rich seawater to the base of Antarctic ice shelves, J. Geophys. Res., 98(C4), 6921–6928, doi:10.1029/92JC02751.
  • Morozov, E.G., Marchenko, A.V. & Fomin, Y.V. Izv. (2015): Supercooled water near the Glacier front in Spitsbergen, Atmos. Ocean. Phys. 51(2), 203-207. https://doi.org/10.1134/S0001433815020115
  • Image of the Week – Ice Ice Bergy
  • Image of the Week – Fifty shades of snow

This post is based on a talk by Stephen Warren presented at AMOS-ICSHMO2018

Edited by Clara Burgard


Lettie Roach is a PhD student at Victoria University of Wellington and the National Institute for Water and Atmospheric Research in New Zealand. Her project is on the representation of sea ice in large-scale models, including model development, model-observation comparisons and observation of small-scale sea ice processes.  

 

Image of the Week – Broccoli on Kilimanjaro!

Image of the Week – Broccoli on Kilimanjaro!

On the plateau of Kilimanjaro, Tanzania, the remnants of a glacier can be found and the ice from that glacier contains a rather interesting feature – Broccoli! Not the vegetable, but bubbles that look a lot like it. Our Image of the Week shows some of these strange “Broccoli Bubbles”. Read on to find out more about where these were found and how we can see them.


Figure 2: Kilimanjaro northern ice field, Tanzania, 5800 m a.s.l. Red arrow indicates where ice samples were collected [Credit: Adapted from a Google Earth image]

There is not much ice left on the mountain plateau of Kilimanjaro (Fig. 2), the highest mountain in Africa (5895 m a.s.l.), which is also a dormant volcano. Very likely the last remnants of glacier ice will have gone soon (Thompson et al., 2009). However, a recent expedition to Kilimanjaro’s Northern Ice Field in 2015 (Bohleber et al., 2017) brought home some ice block samples cut with a chain saw from the accessible southern ice cliff 5800 m a.s.l. (red arrow, Fig. 2) . These block were then studied in  ice laboratory at AWI in Germany and an interesting observation was made…Broccoli bubbles!

These irregularly shaped bubbles, which look like broccoli, were seen in the polished ice slabs using close-up photography and an LASM (Large Area Scan Macroscope). This type of bubble intrigued scientists as it is certainly not a common one! When looking from above onto a horizontal section the broccoli bubbles appear to have pointy tips (Fig. 3.), which are all directed towards the glacier face.

Figure 3: “Broccoli” bubbles seen from above. RHS: A horizontal section of ice, area in image is approx. 2 cm high, image is a close-up photograph with a metal plate in the background. The pointed tips of the bubbles (up in this photo) are directed towards the ice cliff face (from which the samples were taken). LHS: Large Area Scan Macroscope (LASM) cross-section through the sample (LHS). The black pore spaces are the Broccoli bubbles [Credit: Johanna Kerch].

Another type of bubble makes also an appearance: the disk- or bowl-shaped bubble (Fig. 1). It is rather regular but not rounded. Instead it is flattened on one or both sides and a little angular, maybe even leaning towards a hexagonal shape. Disk bubbles found close together are oriented in the same direction, one explanation for this could be that the crystal orientation of the ice (the way the ice crystal align during ice flow) plays a role in the bubble formation.

How do the broccoli and disk bubbles evolve? Although we suspect it has something to do with the temperate ice and some temperature gradient at the ice cliff, we do not know for certain. Nonetheless, it is a marvellous thing to discover – before the Kilimanjaro glacier ice is gone for good!

Edited by Emma Smith


Johanna Kerch is a postdoctoral researcher at Alfred-Wegener-Institute in Bremerhaven. Her research focus is on crystal-preferred orientation and microstructure of glacier ice and how it links to other physical properties in ice and the deformation mechanisms in glacier ice. She has studied cold and temperate glacier ice from various sites in the Alps and has recently been involved in making measurements of the physical properties of the EGRIP ice core. She tweets as @JohannaKerch.

Image of the Week – The colors of sea ice

Image of the Week – The colors of sea ice

The Oscars 2018 might be over, but we have something for you that is just as cool or even cooler (often cooler than -20°C)! Our Image of the Week shows thin sections of sea ice photographed under polarized light, highlighting individual ice crystals in different colors, and is taken from a short video that we made. Read more about what this picture shows and watch the movie about how we got these colorful pictures…


Sea ice can vary in salinity

Sea ice forms differently than fresh water ice due to its salt content. When sea water begins to freeze, the ice crystals aren’t able to incorporate salt into their structure and hence reject salt into the surrounding water. This increases the density of the remaining sea water which sinks (see this previous post). Some salty water gets trapped between the crystals though. This water will also slowly freeze, always rejecting the salts into the remaining water. The saltier the water, the lower its freezing point. This means the remnant very salty water, which we call brine, remains liquid even at temperatures below -20oC!

Sea ice crystals can vary in shape

The first layer of sea ice is typically granular – the crystals are small and round, with a diameter around one centimeter. This is because this layer is formed in open seas, where the crystals which go on to form this layer are spun and broken up by surface waves. This granular structure includes lots of ‘pockets’ of trapped brine. Under this surface ice layer, which is typically 10-30 cm thick, ice starts growing in more sheltered conditions. Such sea ice is columnar. The crystals are flat and elongated – like layers in a vertical cake. The brine is trapped between these layers in brine channels. When ice is relatively warm, for example shortly after freezing or before it starts melting, such channels are wide and can be connected. Brine can then escape from them at the lower end into the ocean. The channels also allow small, hardy microscopic plants and animals to travel through the ice. Often air bubbles are trapped in them too.

Sea ice can vary in how it looks too!

The size and form of sea ice crystals – sea ice texture – impacts various properties of the sea ice including its salt content, density and suitability as a habitat. It also influences the optical properties of ice, however. While pure water ice is transparent (see this previous post), sea ice appears milky. That is because of brine channels and bubbles between the crystals.

When looking at large regions of sea ice from space by sensors mounted on satellites, sea ice texture will be important too. Visible light has a short wavelength and this means it only penetrates into the top millimeter of ice. Images collected in the visible light range (see this previous post) will show features dominated by the surface properties of the ice. In comparison, microwaves have a longer wavelength and can penetrate deeper into the ice. Hence imagery of the sea ice cover collected in the microwave spectrum of light (see this previous post) will display features influenced by the internal structure of the sea ice in addition to the surface features.

 

The video below shows how the sea ice samples are analyzed for texture and how we got the colorful pictures for our Image of the Week…

 

Further reading

Edited by Adam Bateson and Clara Burgard


Polona Itkin is a Post-doctoral Researcher at the Norwegian Polar Institute, Tromsø. She investigates the sea ice dynamics of the Arctic Ocean and its connection to the sea ice thickness. In her work she combines the information from in-site observations, remote sensing and numerical modeling. Polona is part of the social media project ‘oceanseaiceNPI’ – a group of scientists that communicates their knowledge through social media channels: Instagram.com/OceanSeaIceNPI, Twitter.com/OceanSeaIceNPI, Facebook.com/OceanSeaIceNPI, contact Email: polona.itkin@npolar.no