CR
Cryospheric Sciences

Image of the Week

Image of the Week – See sea ice from 1901!

Image of the Week – See sea ice from 1901!

The EGU Cryosphere blog has reported on several studies of Antarctic sea ice (for example, here and here) made from high-tech satellites, but these records only extend back to the 1970s, when the satellite records began. Is it possible to work out what sea ice conditions were like before this time? The short answer is YES…or this would be a very boring blog post! Read on to find out how heroic explorers of the past are helping to inform the future.


During the Heroic Age of Antarctic Exploration (1897–1917), expeditions to the “South” by explorers such as Scott and Shackleton involved a great deal of time aboard ship. Our image of the week shows one such ship – the ship of the German Erich von Drygalsk – captured from a hot air balloon in 1901.

These ships spent many months navigating paths through sea ice and keeping detailed logs of their observations along the way. Climate scientists at the University of Reading, UK have used these logs to reconstruct sea-ice extent in Antarctica at this time – providing key information to extend satellite observations of sea ice around the continent.

Why do we want to know about sea-ice extent 100 years ago?

In the last three decades, satellite records of Antarctic sea-ice extent have shown an increase, in contrast to a rapid decrease in Arctic sea-ice extent over the same period (see our previous post). It is not clear if this, somewhat confusing, trend is unusual or has been seen before and without a longer record, it is not possible to say. This limits how well the sensitivity of sea ice to climate change can be understood and how well climate models that predict future ice extent can be validated.

To help understand this increase in Antarctic sea-ice extent; records of ice composition and nature from ships log books recorded between 1897–1917 have been collated and compared to present-day ice conditions (1989–2014).

What does the study show?

The comparison between sea ice extent in the Heroic Age and today shows that the area of sea ice around Antarctica has only changed in size by a very small amount in the last ~100 years. Except in the Weddell sea, where ice extent was 1.71o (~80 km) further North in the Heroic Age, conditions comparable to present-day were seen around most of Antarctica. This suggests that Antarctic sea-ice extent is much less sensitive to the effects of climate change than that Arctic sea ice. One of the authors of the study, Jonny Day, summarises these findings in the video below:

References and Further Reading

Planet Press

planet_pressThis is modified version of a “planet press” article written by Bárbara Ferreira and originally published on 26th November 2016 on the EGU website .

It is also available in Dutch, Hungarian, Serbian, French, Spanish, Italian and Portuguese! All translated by volunteers – why not consider volunteering to translate an article and learn something interesting along the way?

 

Edited by Sophie Berger

Image of the week – Micro-organisms on Ice!

Image of the week – Micro-organisms on Ice!

The cold icy surface of a glacier doesn’t seem like an environment where life should exist, but if you look closely you may be surprised! Glaciers are not only locations studied by glaciologists and physical scientists, but are also of great interest to microbiologists and ecologists. In fact, understanding the interaction between ice and microbiology is essential to fully understand the glacier system!


Why study micro-organisms on glaciers?

Micro-plants, micro-animals and bacteria live and reproduce in cryoconite ecosystems on the surface of glaciers. Cryoconite is a dark coloured material (Fig. 2) found at the bottom of cylindrical water-filled melt holes (cryoconite holes) on a glacier surface; it consists of dust and mineral powders transported by the wind, and micro-organisms. Cryoconite holes are formed as the dark coloured material causes localised melting, due to reduced albedo (ability of a surface to reflect solar energy).

Figure 2: Example of a Cryoconite hole filled with dark cryoconite material (markers are 10×10 cm) [Credit: Tommaso Santagata – La Venta Esplorazioni Geografiche]

Because organisms in cryoconite thrive in extreme conditions, they are very unique and interesting to study. Information about their genetic makeup and chemical structure can help to inform, for example, medical and pharmaceutical sciences. Currently, however, information on their community structure is still limited.

Cryoconite ecosystems are very isolated and must work together to survive and thrive. Some micro-organisms (e.g. micro-algae) can photosynthesise and are able to live autonomously inside cryoconite holes using atmospheric carbon dioxide, sunlight, water and chlorophyll. By this same mechanism, they can find all the molecules essential for their vital and structural needs and consequently they generate most of the molecules necessary for all other living things. For example, the waste product of photosynthesis, oxygen, is essential for the survival of all organisms living in aerobiosis in these communities. Due to their key role in the ecosystem, the micro-algae are known as “primary producers”.

As around 70% of the earth is covered in water, which is colonised by micro-algae, studying the way they survive in extreme conditions and how they contribute to the ecosystem is of global importance – especially at this time of climate change.

The diversity of highly active bacterial communities in cryoconite holes makes them the most biologically active habitats within glacial ecosystems.

Data collections – Six days on THE glacier

The Perito Moreno glacier (Fig. 3) is known as one of the most important tourist attraction in Argentinian Patagonia (see our previous IOW post). Each day, hundreds of people observe the impressive front of this glacier and wait to see ice detachments and hear the loud sound of it’s impacts in the water of Lake Argentino. The glacier takes it’s name from the explorer Francisco Moreno, who studied the Patagonian region in the 19th century. The glacier is more than 30 km in length and an area of about 250 km2, Perito Moreno is one of the main outlet glaciers of Hielo Patagonico Sur (southern Patagonia icefield).

Figure 3: Aerial view of the Perito Moreno
[Credit : Tommaso Santagata – La Venta Esplorazioni Geografiche]

In April 2017, after several missions to the Greenland Ice Sheet to study extremophilic micro-organisms (organism that thrive in extreme environments) of ice, a team of Italian and French scientists organised a scientific expedition to study the microbiology of Perito Moreno. The expedition was organised by La Venta and Spélé’Ice and included researchers from several French and Italian Universities (see below for full list)

Perito Moreno is very well known, especially to the La Venta team, who have been organising scientific expeditions in Patagonia since 1991. The microbiological research objectives of this mission were to study the micro-organisms that live on the surface of Perito Moreno and compare them to results obtained in the other polar, sub-polar and alpine regions. The multi-disciplinary research team were able to set up a complex field laboratory, which included a microscope and an innovative small tool size capable of DNA sequencing. This meant that samples could be analysed immediately after their extraction from the ice (Fig. 1).

Getting all the equipment and personnel to achieve this expedition onto the ice was not an easy task. The team and their equipment were transported by boat to a site near the front of the glacier. Equipment then needed to be transported to the Buscaini Refugee, a shelter used as a base-camp by the team (Fig. 4). This took two trips, on foot, of about 7 hours (12 km of trail along the lateral moraine and the ice of the glacier with very heavy backpacks) – not an easy start! Luckily this hardship was somewhat mitigated by the absence of extreme cold, in fact, abnormally hot weather tallowed the team to move and work in t-shirts – not bad!

Figure 4: Walking into the field site along the ice of Perito Moreno – part of the 12km of trail to the Buscaini Refugee shelter
[Credit: Alessio Romeo – La Venta Esplorazioni Geografiche]

Thanks to these favourable weather conditions, all the goals were achieved in the short amount of time the team were allowed to camp on the glacier (special permission is needed from the national park to do this). During the five days of activity, many samples were taken and sequenced directly at the camp by the researches. Other important goals, such as morphological comparisons and measurements of the velocity of the glacier through the use of GPS, laser scanning and unmanned aerial vehicles were achieved by another team of researchers (stay tuned for another blog post about this!).

Universities and research institutes involved: University Bicocca of Milan – Italy, University of Milano – Italy, Sciences of the Earth A.Desio – Italy, Natural History Museum of Paris – France, University Diderot of Paris – France, University of Florence – Sciences of the Earth – Italy, University of Bologna – Italy.

Further Reading

Edited by Emma Smith


Tommaso Santagata is a survey technician and geology student at the University of Modena and Reggio Emilia. As speleologist and member of the Italian association La Venta Esplorazioni Geografiche, he carries out research projects on glaciers using UAV’s, terrestrial laser scanning and 3D photogrammetry techniques to study the ice caves of Patagonia, the in-cave glacier of the Cenote Abyss (Dolomiti Mountains, Italy), the moulins of Gorner Glacier (Switzerland) and other underground environments as the lava tunnels of Mount Etna. He tweets as @tommysgeo

Image of the Week – A new way to compute ice dynamic changes

Fig. 1: Map of ice velocity from the NASA MEaSUREs Program showing the region of Enderby Land in East Antarctica [Credit: Fig. 1 from Kallenberg et al. (2017) ].

Up to now, ice sheet mass changes due to ice dynamics have been computed from satellite observations that suffer from sparse coverage in time and space. A new method allows us to compute these changes on much wider temporal and spatial scales. But how does this method work? Let us discover the different steps by having a look at Enderby Land in East Antarctica, for which ice velocities are shown in our Image of the Week…


Mass balance of ice sheets

The mass balance of an ice sheet is the difference between the mass gain of ice, primarily through snowfall, and the mass loss of ice, primarily via meltwater runoff and ice dynamic processes (e.g. iceberg calving, melting below ice shelves). When the mass gain is equal to the mass loss, the ice sheet is in balance. However, if one exceeds the other, the ice sheet either gains or loses mass.

Measuring mass balance changes of ice sheets is crucial due to their potential contribution to sea level rise (see previous post). You can have a look at this nice review for further details about the recent changes in the mass balance of the two biggest ice sheets on Earth, i.e. Antarctica and Greenland.

Ice mass changes from snowfall and meltwater runoff (what we call ‘surface mass balance’ changes) are reasonably well simulated by regional climate models, which give good agreement with observations (see this study for Antarctica and this one for Greenland). Mass changes from ice dynamics are more complex to obtain. They are commonly estimated by combining ice velocity and ice thickness. Ice velocity is measured via satellite radar interferometry, while ice thickness is obtained thanks to airborne radar. Unfortunately, these measurements have sparse temporal and spatial coverage, especially in Antarctica, which makes the computation of mass changes from ice dynamics challenging.

A new method to estimate ice dynamic changes

Kallenberg et al. (2017) conducted a study focussing on Enderby Land in East Antarctica (see our Image of the Week) in which they use a novel approach to estimate ice dynamic changes. This region of Antarctica has experienced a slightly positive mass balance in past years, meaning that the ice sheet has slightly thickened in this region.

Kallenberg et al. (2017) first used satellite observations to compute the total changes in ice sheet mass. They took advantage of two high-technology datasets. The first one, “Gravity Recovery And Climate Experiment” (GRACE), measures changes in the Earth’s gravity field, from which ice mass changes can be derived. A summary explaining how GRACE works can be found in this previous post. The second satellite dataset, “Ice, Cloud, and land Elevation Satellite” (ICESat), measures changes in ice surface elevation, from which changes in ice mass can be computed by using ice density.

However, Kallenberg et al. (2017) were not interested in the total ice mass changes, as obtained from GRACE and ICESat satellites, but rather in ice dynamic changes. They subtracted two quantities from the total mass changes in order to obtain the remaining dynamic changes:

  1. Surface mass balance changes: changes from processes happening at the surface of the ice sheet (e.g. snow accumulation, meltwater runoff). These changes were obtained from model simulations using the Regional Atmospheric Climate Model (RACMO2), for which details can be found in this previous post.
  2. Glacial Isostatic Adjustment: changes in land topography due to ice loading and unloading. These changes were computed from Glacial Isostatic Adjustment models.

What does this study tell us?

The results of this study show that it is possible to compute changes in ice mass resulting from ice dynamics with higher spatial and temporal coverage than before, using a combination of satellite observations and models.

Also, the use of two different satellite datasets (GRACE and ICESat) shows that they agree quite well with each other in the region of Enderby Land (see Fig. 2). This means that using one or the other dataset does not make a big difference.

Finally, this new method also shows that differences between GRACE and ICESat reduce when using the newer version of RACMO2 for computing surface mass balance changes. This tells us that comparing results of ice dynamics from both satellites with different models is a good way to identify which models correctly simulate surface processes and which models do not.

Fig. 2: Ice dynamic changes (dH/dt, where H is ice thickness and t is time) computed from (a) GRACE and (b) ICESat and expressed in meters per year [Credit: Fig. 5 from Kallenberg et al. (2017) ].

Further reading

Edited by Clara Burgard and Emma Smith


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.

Image of the Week – Drilling into a Himalayan glacier

Image of the Week – Drilling into a Himalayan glacier

How water travels through and beneath the interior of debris-covered glaciers is poorly understood, partly because it can be difficult to access these glaciers at all, never mind explore their interiors. In this Image of the Week, find out how these aspects can be investigated by drilling holes all the way through the ice…


Hydrological features of debris-covered glaciers

Debris-covered glaciers can have a range of hydrological features that do not usually appear on clean-ice valley glaciers, such as surface (supraglacial) ponds. These features are produced as a result of the variable melting that occurs across the glacier surface, depending on the thickness of the debris layer on the surface. Melting is reduced where the debris layer is thick (e.g. near the terminus), which leads to mass loss primarily by thinning, rather than terminus retreat like clean-ice glaciers (read more about this process in this previous blog post). This produces a low-gradient surface covered by hummocks and depressions in which ponds can form, often with steep bare ice faces (ice cliffs) surrounding them. The occurrence of ice cliffs and ponds also affects the surface melt rate, as glacier ice in/on/under these features melts considerably faster (up to 10 and 7 times more, respectively) than that of the debris-covered areas surrounding them (Sakai et al., 2000). Consequently, these hydrological features are an important contributing factor to the general trend of surface lowering of debris-covered glaciers (Bolch et al., 2012).

As a result, most hydrological research on debris-covered glaciers to date has focused on the (more accessible) supraglacial hydrological environment, as well as measuring the proglacial discharge of meltwater from these glaciers, which is a vital water resource for millions of people (Pritchard, 2017). Below the debris-covered surface of these glaciers, next-to-nothing is known about their hydrology; do drainage networks exist within (englacial) or beneath (subglacial) these glaciers, can they exist, and how can they be observed in such challenging environments?

A limited amount of direct research has been carried out in attempt to answer some of these questions, such as speleological techniques to investigate shallow englacial systems on a few glaciers (e.g. Gulley and Benn, 2007; Narama et al., 2017). However, all other inferences of subsurface drainage through debris-covered glaciers have come from hydrogeochemical analyses of water samples taken from the proglacial environment (e.g. Hasnain and Thayyen, 1994) or interpretation of observed glacier dynamics from satellite imagery (e.g. Quincey et al., 2009). While relict englacial features can be observed on the surface of many debris-covered glaciers (Figure 2), studying these systems while they are still active is more difficult.

Fig. 2: A relict englacial feature in the centre of an ice cliff on Khumbu Glacier (looking downglacier), through which the associated supraglacial pond is thought to have drained in the past. Following the drainage event, the pond water-level would have dropped, exposing the ice cliffs around its edge and resulting in the pond water-level being too low to sustain a water flow through the channel. The inset shows the same feature from the far side (looking upglacier): on this side, a vast amount of surface lowering of the ice surface has occurred and the previously englacial channel is now visible from the surface. For scale, the feature is approximately 10 metres in height. [Large image credit: Evan Miles; Inset image credit: Katie Miles]

Hot-water drilling to investigate subsurface hydrology

One way in which potential hydrological systems beneath the surface of debris-covered glaciers can be investigated is through the use of hot-water drilling, as was carried out on Khumbu Glacier, Nepal Himalaya this year by the EverDrill team. A converted car pressure-washer was used to produce a small jet of hot, pressurised water, which was sent through a spool of hose into the drill stem to melt the ice below as it was slowly lowered into the glacier (our Image of the Week). The result (if all went well!) was a borehole 10-15 cm in width, that penetrated the ice all the way to the glacier bed (Figure 3). During the field campaign, we managed to drill 13 boreholes at 3 different drill sites across Khumbu Glacier, ranging in length from 12 to 155 metres.

Once the borehole has been drilled, it can be used to investigate the hydrology of the glacier in a number of ways. If the water level suddenly drops while drilling is in progress, it is possible that the borehole has cut through an englacial conduit, through which the excess drill water has drained. If it drops at the base of a borehole drilled to the bed, it can be assumed that some form of subglacial drainage network exists at the base of the glacier, and the excess water drained through this system. Such features can be examined further through the use of an optical televiewer (360° camera that is lowered slowly through the length of the borehole, taking hundreds of images to give a complete picture of the internal surface of the borehole), or by installing a variety of sensors along the hole’s length to collect various types of data.

Fig. 3: A borehole drilled into Khumbu Glacier during the EverDrill field season in Spring 2017. The borehole was approximately 10 cm in width. A small channel (to the left of the borehole) was formed during the drilling process to drain away the excess water as the borehole was drilled. [Credit: Katie Miles]


During the EverDrill fieldwork in Spring 2017, we televiewed three of the drilled boreholes. These boreholes were then instrumented with sensors to measure the temperature of the ice and, where the boreholes reached the bed, a subglacial probe to measure electrical conductivity, temperature, water pressure and suspended sediment concentration (turbidity). We have left these probes in the boreholes, so that we have measurements both through our field season and additionally through the monsoon summer months. This will allow us to see whether any subsurface hydrological drainage systems develop when there is an additional source of water contributing to the melting of these glaciers. We will return in October to collect this data, and hopefully find out a little more about the englacial and subglacial drainage systems of this debris-covered glacier!

Further reading

Edited by Morgan Gibson, Clara Burgard and Emma Smith


Katie Miles is a PhD student in the Centre for Glaciology, Aberystwyth University, UK, studying the internal structure and subsurface hydrology of high-elevation debris-covered glaciers in the Himalaya by investigating boreholes and measurements that can be made within them. She is also interested in the potential of Sentinel-1 SAR imagery in detecting lakes on the surface of the Greenland Ice Sheet. Katie tweets at @Katie_Miles_851, contact email: kam64@aber.ac.uk

Image of the Week – Fifty shades of snow

Image of the Week – Fifty shades of snow

When I think of snow, I tend to either think about the bright white ski slopes in the mountains or the large white areas in the Arctic. However, natural phenomena can lead to colorful snow. Our Image of the Week shows snow can be green! Snow can also turn orange, pinkish, grey and even yellow… But where do these different shades of snow come from?


White

The most common color of snow is white (see Fig. 2). Snow generally appears white when it is pure snow, which means that it is only an aggregate of ice and snow crystals. When sunlight meets the snow surface, all frequencies of the sunlight are reflected several times in different directions by the crystals, leading to a white color of the snowpack.

 

Fig. 2: Fresh powder snow, snow crystals [Credit: Introvert, Wikimedia Commons]

 

 

If other particles or organisms are present in the snow though, they can alter the color of the snow’s surface…

Green

Snow can obtain a green color if it is host to an algal bloom (see our Image of the Week). Depending on the wetness of the snow, sunlight conditions and nutrient availability, unicellular snow algae can develop and thrive on the snow. Although it is not clear exactly how fast snow algae grow, algae populations from temperate regions have been found to grow sixteen-fold in one day! As the algae population increases, the snow turns green as the algae reflect the green light back.

 

Red/Pink

The pink-red-colored snow, commonly called “watermelon snow”, can also be caused by snow algae (see Fig. 3). The snow algae responsible for the pink color are similar to the ones responsible for green color. However, these algae use pigments of red color to protect their cells from high sunlight and UV radiation damage during the summer. Just like how we use sunscreen to protect our skin! The red pigments come either from iron tannin compounds or, more commonly, from orange to red-pigmented lipids.

There is also another origin for pink snow: Penguin poo! Indeed, the krill they eat contain a lot of carotenoids that give their poo a red color.

Fig. 3: Watermelon snow streaks [Credit: Wikimedia Commons].

 

Yellow

Yellow snow is the result of a different process (and no, it is not from Penguin pee!). Fig. 4 shows the Sierra Nevada in Spain before and after dust transported from the Sahara settled down on the snow-covered mountain tops. The dust was lifted up from the Sahara desert and blown north before ending its trip in Spain.

Fig. 4: Snow-covered Sierra Nevadas (Spain) before and after a dust deposition event [Credit: modified from NASA’s Earth Observatory]

 

Do these colors have an influence on snow cover?

In all cases of colored snow, the snow surface is darker than before. The darker surface absorbs more sunlight than a white surface, which causes the snow to melt faster… Therefore, although it looks artistic, colored snow is not necessarily healthy for the snow itself…

 

So, if you don’t like winter because everything is boring and white, just think about the variety of snow colors and try to look out for these special types! 🙂

 

Further reading

Edited by David Rounce

Image of the Week – Summer is fieldwork season at EastGRIP!

Image of the Week – Summer is fieldwork season at EastGRIP!

As the days get very long, summer is a popular season for conducting fieldwork at high latitudes. At the North East Greenland Ice Stream (NEGIS), the East Greenland Ice-core Project (EastGRIP) is ongoing. Several scientists are busy drilling an ice core through the ice sheet to the very bottom, in continuation to previous years (see here and here). This year, amongst others, several members from the European Research Council (ERC) supported synergy project ice2ice are taking part in the work at EastGRIP. Besides sleeping in the barracks that can be seen in our Image of the Week, the scientists enjoy the international and interdisciplinary setting and, of course, the work in a deep ice core drilling camp…


Life at the EastGRIP camp

In total, 22 people live in the camp (see Fig.2): 1 field leader, 5 ice core drillers, 4 ice core loggers, 3 people working with the physical properties of the ice, 2 are doing continuous water isotope analysis, 2 surface science scientists, 2 field assistants, and 1 mechanic, 1 electrical engineer and most important an excellent cook. We cover a variety of nationalities: British, Czech, Danish, French, German, Japanese, Korean, Norwegian, Russian and more. The crew changes every four weeks and the EastGRIP project aims to get as many young scientists (Master and PhD students) into camp as possible, so that it also works as a learning environment for new generations. In total, the number of people that have and will spent time at EastGRIP this season is almost 100, making it a buzzing science hub. This environment leads to extensive science discussions over the dinner table and therefore facilitates the interdisciplinary connections so vital in ice core science.

Fig.2: The current crew at EastGRIP dressed up for the Saturday party (tie and dress obligatory!) [Credit: EastGRIP diaries].

Science at the EastGRIP camp

The main aim of the EastGRIP project is to retrieve an ice core by drilling through the North East Greenland Ice Stream (NEGIS) up to a depth of 2550 m (!). Ice streams are responsible for draining a significant fraction of the ice from the Greenland Ice Sheet (see Fig. 3). We hope to gain new and fundamental information on ice stream dynamics from the project, thereby improving the understanding of how ice streams will contribute to future sea-level change. The EastGRIP project has many international partners and is managed by the Centre for Ice and Climate, Denmark with air support carried out by US ski-equipped Hercules aircraft managed through the US Office of Polar Programs, National Science Foundation.

Fig. 3: Ice velocities from RADARSAT synthetic aperture radar data are shown in color and illustrate the wedge of fast-flowing ice that begins right at the central ice divide and cuts through the ice sheet to feed into the ocean through three large ice streams (Nioghalvfjerds isstrømmen, Zachariae isbræ, and Storstrømmen). [Credit: EastGRIP, data from Joughin et al., 2010]

Currently, four Norwegian and Danish scientists from the ice2ice project have joined the EastGRIP project to conduct field work at the ice core drilling site. The ice2ice project focuses on how land ice and sea ice influence each other in past, present, and future. Thus, being at the EastGRIP site is a great opport

unity for us in ice2ice to learn more about how the fast-flowing ice stream in North East Greenland may influence the stability of the Greenland ice cap and to enjoy the collaborative spirit at an ice core drilling site.

 

This year’s fieldwork at EastGRIP started in May and will continue until August. We aim to make it through the brittle zone of the ice. This is a zone where the gas bubbles get enclosed in the ice crystals and thus the ice is, as the name indicates, more brittle than at other depths. Unfortunately for us, the brittle zone makes it very hard to retrieve the ice in a great quality. This is because of the pressure difference between the original depth of the ice and the surface, that causes the ice to fracture when it arrives at the surface. We are doing our very best to stabilize the core and several optimizations in terms of both drilling and processing of the ice core are being applied.

Fig. 4: Cross-section view of an ice core [Credit: Helle Astrid Kjær].

Still, a large part of the core can already be investigated (see Fig. 4) for water isotopes to get information about past climate. Also, ice crystals directions are being investigated through thin slices of the ice core to help better understanding the flow of the NEGIS. On top of the deep ice core, which is to be drilled to bedrock over the coming years, we are doing an extensive surface program to look at accumulation changes.

In the large white plains…

Despite all the fun science and people, when you are at EastGRIP for more than 4 weeks, you have a very similar landscape everyday and can miss seeing something else than just the great white. About a week ago, a falcon came by to remind us of the rest of the world (see Fig. 5). It flew off after a couple of days. We will follow its path to the greener parts of Greenland when we will soon fly down to Kangerlussuaq. Someone else will then take over our job at EastGRIP and enjoy the wonders of white…

Fig.5: Visit of a falcon [Credit: Helle Astrid Kjær].

Further reading

Edited by Clara Burgard


Helle Astrid Kjær is a postdoc at the Centre for Ice and Climate at the Niels Bohr Institute at University of Copenhagen. When she is not busy in the field drilling and logging ice cores, she spends most of her time in the lab retrieving the climate signal from ice cores. These include volcanic events, sea salts, dust with more by means of Continuous Flow Analaysis (CFA). Further she is hired to manage the ice2ice project.

Image of the Week — High altitudes slow down Antarctica’s warming

Elevations in Antarctica. The average altitude is about 2,500m. [Credit: subset of Fig 5 from Helm et al (2014)]

When it comes to climate change, the Arctic and the Antarctic are poles apart. At the north of the planet, temperatures are increasing twice as fast as in the rest of the globe, while warming in Antarctica has been milder. A recent study published in Earth System Dynamics shows that the high elevation of Antarctica might help explain why the two poles are warming at different speeds.


The Arctic vs the Antarctic

At and around the North Pole, in the Arctic, the ice is mostly frozen ocean water, also known as sea ice, which is only a few meters thick. In the Antarctic, however, the situation is very different: the ice forms not just over sea, but over a continental land mass with rugged terrain and high mountains. The average height in Antarctica is about 2,500 metres, with some mountains rising as high as 4,900 metres.

A flat Antarctica would warm faster

Mount Jackson in the Antarctic Peninsula reaches an altitude of 3,184 m  [Credit: euphro via Flickr]

Marc Salzmann, a scientist working at the University of Leipzig in Germany, decided to use a computer model to find out what would happen if the elevation in Antarctica was more like in the Arctic. He discovered that, if Antarctica were flat, there would be more warm air flowing from the equator to the poles, which would make the Antarctic warm faster.

As Antarctica warms and ice melts, it is actually getting flatter as time goes by, even if very slowly. As such, over the next few centuries or thousands of years, we could expect warming in the region to speed up.

Reference/further reading

planet_pressThis is modified version of a “planet press” article written by Bárbara Ferreira and originally published on 18 May 2017 on the EGU website
(a Serbian version is also available, why not considering adding a new language to the list? 🙂 )

Image of the Week – The birth of a sea-ice dragon!

Image of the Week – The birth of a sea-ice dragon!

Dragon-skin ice may sound like the name of an episode of the Game of Thrones fantasy franchise. However, this fantasy name hides a rare and bizarre type of ice formation that you can see in our Image of the Week. It has been recently observed by the “Polynyas, ice production and seasonal evolution in the Ross Sea” (PIPERS) research team in Antarctica. This bizarre phenomenon caused by strong wind conditions has not been observed in Antarctica since 2007.


PIPERS expedition observed dragon-skin ice

In early April, the Nathan B Palmer icebreaker (see Fig. 2) began its 65-day voyage to Antarctica to study sea ice in the Ross Sea during the autumn period. This expedition, named PIPERS, was carried out by a team of 26 scientists from 9 countries. Its goal was to investigate polynyas, ice production, and seasonal evolution with a particular focus on the Terra Nova Bay and Ross Sea Polynyas (see Fig. 3).

Fig.2 : The Nathan B Palmer icebreaker caught in sea ice [Credit: IMAS ].

A polynya is an area of open water or thin sea ice surrounded by thicker sea ice and is generally located in coastal areas [Stringer and Groves, 1991]. Ice formation in polynyas is strongly influenced by wind conditions whose action can lead to astonishing spatial patterns in sea ice appearance. Special wind conditions probably also lead to what the members of the PIPERS expedition had the opportunity to observe: ice patterns that resemble dragon scales, therefore called dragon-skin ice. Such a sighting is quite remarkable as the last one dates back from a decade. However, the sparsity of observations of dragon-skin ice phenomena is probably a consequence of the relatively small number of expeditions in Antarctica during the autumn and winter seasons…

Fig. 3: The Terra Nova Bay Polynya and Ross Sea Polynya explored by the PIPERS expedition. [Credit: PIPERS ].

Chaotic ice formation caused by strong winds

Dragon-skin ice is a chaotic result of the complex interplay between the ocean and the atmosphere. Coastal polynyas in Antarctica are kept open by the action of strong and cold offshore winds (see Fig. 4) known as katabatic winds, which blow downwards as fast as 100 km/h for several hours [McKnight and Hess, 2000]. Sea ice forming at the cold sea surface gets blown away by these strong winds, preventing a closed sea-ice cover in this area. As the ice is blown away, an area of open water gets in direct contact with the atmosphere, leading to strong cooling and new formation of ice, that gets blown away again, and so on… Therefore, in general, sea ice in polynyas consists of thin pancake ice (see Fig. 5) i.e. round pieces of ice from 0.3 to 3 meters in diameter, which results from the aggregation of ice crystals caused by the wave action. Due to the wind action, the pieces of ice are pushed out by the wind action to the edges of the polynya.  As these pieces push strongly against each other, dragon-like scales appear on sea ice giving birth to the so-called dragon-skin ice.

Fig.4: Formation of coastal polynyas due to the action of katabatic winds [Credit: Wikimedia Commons ].

Figure 5: Sea ice in polynyas takes the form of pancake ice due to the action of water waves [Credit: PIPERS ].

The importance of polynyas for ocean-atmosphere interactions

Besides providing us with dazzling pictures of the cryosphere, investigating sea-ice production and evolution in polynyas is essential to better understand the complex interactions between the ocean and the atmosphere.
As sea water freezes into sea ice, salt is expelled into the ocean, raising its local salinity. The incessant production of sea ice in polynyas leads to water masses with very high salinity inside the polynyas. As sea water cools down, it releases energy in the atmosphere, leading to a warming of the atmosphere in polar regions. Moreover, due to their high density, these masses of cold and salty water sink and mix with lower ocean layers.
First results from the PIPERS mission show that when sea ice is forming, polynyas release greenhouse gases to atmosphere, instead of capturing it, as it was previously assumed! But fully understanding what’s happening there will necessitate more time and analyses….

Further reading

 

Edited by Scott Watson and Clara Burgard
Modified by Sophie Berger on 3 July 2017 to account for remarks of Célia Sapart (Member of the PIPER expedition)


Kevin Bulthuis is a F.R.S.-FNRS Research Fellow at the Université de Liège and the Université Libre de Bruxelles. He investigates the influence of uncertainties and instabilities in ice-sheet models as a limitation for accurate predictions of future sea-level rise. Contact Email:kevin.bulthuis@ulg.ac.be.

Image of the Week – Heat waves during Polar Night!

Fig. 1: (Left) Evolution of 2-m air temperatures from a reanalysis over December 2016. (Right) Time series of temperature at the location of the black cross (Svalbard). Also shown is the 1979-2000 average and one standard deviation (blue). [Credit: François Massonnet ; Data : ERA-Interim]

The winter 2016-2017 has been one of the hottest on record in the Arctic. In our Image of the Week, you can see that air temperatures were positive in the middle of the winter! Let’s talk about the reasons and implications of this warm Arctic winter. But first, let’s take a tour in Svalbard, the gateway to the Arctic…

A breach in the one of the world’s largest seed vaults

The Global Seed Vault on Svalbard (located at the black cross in our Image of the Week) is one of the world’s largest seed banks. Should mankind face a cataclysm, 800,000 copies of about 4,000 species of crops can safely be recovered from the vault. Buried under 120 m of sandstone, located 130 m above sea level, and embedded inside a thick layer of permafrost, the vault can withstand virtually all types of catastrophe – natural or man-made. This means, for example, that it is high enough to stay above sea level in case of a large sea-level rise, or that it is far enough from regions that might be affected by nuclear warfare. But is it really that safe? Last winter, vault managers reported water flooding at the entrance of the cave, after an unexpected event of permafrost melt in the middle of polar night. Not enough to put the seeds at risk (they are safely guarded in individual chambers deeper in the mountainside), but worrying enough to raise concern about how, and why such an event happened…

Fig. 2: Entrance of the Svalbard Global Seed Vault. [Credit: Dag Terje Filip Endresen, Wikimedia Commons ].

Soaring temperatures in the Arctic

The Arctic region is often dubbed the “canary in the coal mine” for climate change: near-surface temperatures there have risen at twice the pace of the world’s average, mainly due to the process of “Arctic Amplification whereby positive feedbacks enhance greatly an initial temperature perturbation. Increases in lower-troposphere Arctic air temperatures have occurred in conjunction with a dramatic retreat and thinning of the sea-ice cover in all seasons, a decrease of continental spring snow cover extent, and significant mass loss from glaciers and ice sheets (IPCC, 2013)

Winter temperatures above freezing point

The last two winters (2015-2016 and 2016-2017) have been particularly exceptional. As displayed in our Image of the Week for winter 2016-2017 and here for 2015-2016 (see also two news articles here and here for an accessible description of the event), temporary intrusions of relatively warm air pushed air temperatures above freezing point in several parts of the Arctic, even causing sea ice to “pause” its expansion at a period of the year where it usually grows at its fastest rate (see Fig. 3).

Fig.3 : Mean Arctic sea ice extent for 1981 to 2010 (grey), and the annual cycles of 1990 (blue), and 2016-2017 (red and cyan, respectively). [Credit: National Snow and Ice Data Center. Interactive plotting is available here ]

Cullather et al. (2016) and Overland and Wang (2016) conducted a retrospective analysis of the 2015-2016 extreme winter and underlined that the mid-latitude atmospheric circulation played a significant role in shaping the observed temperature anomaly for that winter (see also this previous post). Scientists are still working to analyse the most recent winter temperature anomaly (2016 – 2017).

Unusual?

How unusual are such high temperatures in the middle of the boreal winter? It is important to keep in mind that the type of event featured in our Image of the Week results from the superposition of weather and climate variability at various time scales, which must be properly distinguished. At the synoptic scale (i.e., that of weather systems, several days), the event is not exceptional. For example, a similar event was already reported back in 1975! It is not surprising to see low-pressure systems penetrate high up to the Arctic.

At longer time scales (several months), the observed temperature anomaly in the recent two winters is more puzzling. The winter 2015-2016 configuration appears to be connected with changes in the large-scale atmospheric circulation (Overland and Wang, 2016). To understand the large-scale atmospheric circulation, scientists like to map the so-called “geopotential heightfield for a given isobar, that is, the height above sea level of all points with a given atmospheric pressure. The geopotential height is a handy diagnostic because, in a first approximation, it is in close relationship with the wind: the higher the gradient in geopotential height between two regions, the higher the wind speed at the front between these two regions. The map of geopotential height anomalies (i.e., deviations from the mean) for the 700 hPa level in December (Fig. 4) is suggestive of the important role played by the large-scale atmospheric circulation on local conditions. The link between recent Arctic warming and mid-latitude atmospheric circulation changes is a topic of intense research.

Fig.4: Anomaly in 700 hPa geopotential height, December 2016 (with regard to the reference period 1979-2000) [Credit: François Massonnet; Data: ERA-Interim]

Finally, at climate time scales (several years to several decades), this event is not so surprising: the Arctic environment has changed dramatically in the last few decades, in great part due to anthropogenic greenhouse gas emissions. With a warmer background state, there is higher probability of winter air temperatures surpassing 0°C if synoptic and large-scale variability positively interact with each other, as seems to have been the case during the last two winters.

What does this mean for future winters?

The rapid transformation of the Arctic is already having profound implications on ecosystems (Descamps et al., 2016) and indigenous populations (e.g., SWIPA report). To a larger extent, it can potentially affect our own weather: we polar scientists like to say that “what happens in the Arctic, does not stay in the Arctic”. The unusual summers and winters that large parts of Europe, the U.S. and Asia have experienced in recent years might be related to the rapid Arctic changes, according to several scientists – but there is no consensus yet on that matter. One thing is known for sure: the last two winters have been the warmest on record, but this might just be the beginning of a long chain of more extreme events…

Further reading

Edited by Scott Watson and Clara Burgard


François Massonnet is a F.R.S.-FNRS Post-Doctoral Researcher at the Université catholique de Louvain and affiliated at the Barcelona Supercomputing Center (Spain). He is assessing climate models as tools to understand (retrospectively and prospectively) polar climate variability and beyond. He tweets as @FMassonnet. Contact Email: francois.massonnet@uclouvain.be

Image of the Week – When the dirty cryosphere destabilizes!

Image of the Week – When the dirty cryosphere destabilizes!

Ice is usually something you see covering large ocean areas, mountain tops and passes or as huge sheets in polar regions. This type of ice is clearly visible from space or with the naked eye. There is, however, a large volume of ice that is less visible. This ice is distributed over the polar and high alpine permafrost regions; and is the ice hidden below ground. It might be hidden, but that doesn’t mean we should ignore it. If this below-ground ice melts, the ground might collapse!


On solid ground?

To change the surface of a landscape usually requires wind or water, which actively erodes the material around it. In permafrost areas, however, different mechanisms are at work. In these areas, the ground or parts of the ground, are frozen all year round and the formation and melting of below-ground ice changes the landscape in a complicated way. Below-ground ice can have many shapes and sizes depending on moisture availability, sediment type and thermal regime (French, 2007). Because a gram of ice has 9 % higher volume than a gram of water, simply freezing, thawing and re-freezing soil water can make the surface “wobbly” and irregular. Since ice doesn’t drain from a saturated soil, as water does, a permanently frozen soil can also contain moisture in excess of the absorption capacity of the soil – excess ice. This means that ice might take up the majority of the ground volume in ice-rich areas.

Our Image of the Week (Fig. 1) was taken in NE Greenland. The phenomenon shown is a result of ground, which has been frozen for many years, being destabilized. In this photo, the below-ground ice has begun to melt, and the decrease in ice volume has caused the ground to collapse, forming what is known as a thermokarst development (Fig. 1). This is just one type of feature that can be caused by below-ground ice mass loss. Kokelj and Jorgenson (2013) give a nice overview of recognized thermokarst features including: retrogressive thaw slumps, thermokarst lakes and active layer detachment slides. Ice melt might also simply be expressed as a lowering of the land surface (thermal subsidence), as observed in peat (Dyke and Slaten, 2010) and in areas with ice wedge polygons (Jorgenson et al., 2006), or in upraised plateaus (Chasmer et al., 2016).

the decrease in ice volume has caused the ground to collapse

The spatial scales of these types of collapse features span from depressions of 10 cm depth to areas of several square kilometers, with thermokarst features many meters deep. The rates of surface change also vary from sudden detachment and slide of the unfrozen upper active layer on slope, to features developed over centuries and even millennia (e.g. Morgenstern et al., 2013).

The most dramatic surface changes often happen where ground ice content is high, such as in the coastal lowland tundras of Siberia (e.g. Morgenstern et al., 2013) or coastal northern Canada (Fortier, et L., 2007). However, thermokarst development is found also in coastal Greenland (Fig. 1) and even the McMurdo Dry Valleys of Antarctica (Levy et al., 2013).

Why does the ground ice melt?

Many factors can lead to the destabilization of below-ground ice bodies. Notable ones are:

  • Erosion of the surface allows for atmospheric energy to penetrate deeper into the ground.
  • Thermal contraction or other types of cracks might create an easy access to deeper layers for water and energy.
  • Persistent running water might erode physically as well as transfer fresh energy into the system.

Fig. 2 shows a recently opened crack in the ground, close to the karst formation shown in Fig.1. The crack reveals a large body of massive (pure ice) below-ground ice. The opening of the crack, however, also creates a highway for heat energy into the now unstable ice body, which will start degrading.

Figure 2: Looking into a recently opened crack revealing a large ice body just below the summer thaw layer, NE Greenland [Credit: Laura Helene Rasmussen]

“And so what?”

The surface changes somewhat. No big deal. Why investigate where and how and how much and how fast?

For people living in permafrost areas thermal subsidence might happen below the foundation of their house or destabilize the one road leading to their local airport (Fortier, et al., 2011).

Figure 3: Taking a closer (!) look at below-ground ice, NE Greenland [Credit: Line Vinther Nielsen].

Thermal subsidence might also change the hydrology of the area, causing surface water to find new routes (Fortier, et al., 2007) or pool in new places. When water pools in the depressions above frozen ground, the exchange of energy between the atmosphere and the permafrost is altered.

There is increased heat transport downward into the ground in summer (Boike et al., 2015), which can then lead to more melting. Similarly, thermokarst development itself exposes more frozen ground to above-zero temperatures, leading to further thawing (Chasmer et al., 2016)

and crucially mobilising otherwise dormant carbon stored in the permafrost (Tarnocai, et al., 2009).

Reports of an increase in rates of thaw have been linked to recent climatic warming (Kokelj and Jorgenson, 2013), and changes in precipitation patterns (e.g. Kokelj et al., 2015). So expect to see this “dirty“ cryospheric component receiving more attention, and don’t be surprised if you see an increasing number of strange scientists figuratively or literally (!) sticking their heads into cracks in the ground…

Edited by Emma Smith and Clara Burgard


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

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