CR
Cryospheric Sciences

ice sheet

Image of the Week – Antarctica’s Flowing Ice, Year by Year

Fig 1: Map series of annual ice sheet speed from Mouginot et al. (2017). Speeds range from 0 (purple) to 1000+ (dark brown) m/yr. [Credit: George Roth]

Today’s Image of the Week shows annual ice flow velocity mosaics at 1km resolution from 2005 to 2016 for the Antarctic ice sheet. These mosaics, along with similar data for Greenland (see Fig.2), were published by Mouginot et al, (2017) last month as part of NASA’s MEaSUREs (Making Earth System Data Records for Use in Research Environments) program.


How were these images constructed?

The mosaics shown today (Fig 1 and 2) were built by combining optical imagery from the Landsat-8 satellite with radar (SAR) data from the Sentinel-1a/b, RADARSAT-2, ALOS PALSAR, ENVISAT ASAR, RADARSAT-1, TerraSAR-X, and TanDEM-X sensors.

Although the authors used the well-known techniques of feature and speckle tracking to produce their velocities from optical and radar images, respectively, the major novelty of their study lies in the automation and integration of the different datasets.

Fig.2: Mosaics of yearly velocity maps of the Greenland and Antarctic ice sheet for the period 2015-2016.Composite of satellite-derived yearly ice sheet speeds from 2005-2016 for both Greenland and Antarctica. [Credit: cover figure from Mouginot et al. (2017)]

How is this new dataset useful?

Previously, ice sheet modellers have used mosaics composed of satellite data from multiple years to cover the entire ice sheet. However, this new dataset is one of the first to provide an ice-sheet-wide geographic scale, a yearly temporal resolution, and a moderately high spatial resolution (1km). This means that modellers can now better examine how large parts of the Greenland and Antarctic ice sheets evolve over time. By linking the evolution of the ice sheets to the changes in weather and climate over those ice sheets during specific years, modellers can calibrate the response of those ice sheets’ outlet glaciers to different climate conditions. The changes in the speeds of these outlet glaciers have important consequences for the amount of sea level rise expected for a given amount of warming.

How can I start using this data?

The yearly MEaSUREs data is hosted at the NSIDC in NetCDF format. The maps shown in the animated image were made using Quantarctica/QGIS (for more information on Quantarctica, check out our previous post E). QGIS natively supports NetCDF files like these mosaics with no additional import steps. Users can quickly calculate new grids showing speed, changes in velocities between years, and more by using the QGIS Raster Calculator or gdal_calc.

References/ Further Reading

Mouginot, J., Rignot, E., Scheuchl, B., & Millan, R. (2017). Comprehensive Annual Ice Sheet Velocity Mapping Using Landsat-8, Sentinel-1, and RADARSAT-2 Data. Remote Sensing, 9(4), 364. http://dx.doi.org/10.3390/rs9040364

Image of the Week – Quantarctica: Mapping Antarctica has never been so easy!

Image of the Week – A high-resolution picture of Greenland’s surface mass balance

Written with help from Jelte van Oostsveen
Edited by Clara Burgard and Sophie Berger


George Roth is the Quantarctica Project Coordinator in the Glaciology group (@NPIglaciology) at the Norwegian Polar Institute. He has spent the last several years helping researchers with GIS, cartography, and remote sensing in both the Arctic and Antarctic.

Image of the Week – A high-resolution picture of Greenland’s surface mass balance

Image of the Week – A high-resolution picture of Greenland’s surface mass balance

The Greenland ice sheet – the world’s second largest ice mass – stores about one tenth of the Earth’s freshwater. If totally melted, this would rise global sea level by 7.4 m, affecting low-lying regions worldwide. Since the 1990s, the warmer atmosphere and ocean have increased the melt at the surface of the Greenland ice sheet, accelerating the ice loss through increased runoff of meltwater and iceberg discharge in the ocean.


Simulating the climate with a regional model

To understand the causes of the recent ice loss acceleration in Greenland, we use the Regional Atmospheric Climate Model RACMO2.3 (Noël et al. 2015) that simulates the evolution of the surface mass balance, that is the difference between mass gain from snowfall and mass loss from sublimation, drifting snow erosion and meltwater runoff. Using this data set, we identify three different regions on the ice sheet (Fig. 1):

  • the inland accumulation zone (blue) where Greenland gains mass at the surface as snowfall exceeds sublimation and runoff,

  • the ablation zone (red) at the ice sheet margins which loses mass as meltwater runoff exceeds snowfall.

  • the equilibrium line (white) that separates these two areas.

From 11 km to 1 km : downscaling RACMO2.3

To cover large areas while overcoming time-consuming computations, RACMO2.3 is run at a relatively coarse horizontal resolution of 11 km for the period 1958-2015. At this resolution, the model does not resolve small glaciated bodies (Fig. 2a), such as narrow marginal glaciers (few km wide) and small peripheral ice caps (ice masses detached from the big ice sheet). Yet, these areas contribute significantly to ongoing sea-level rise. To solve this, we developed a downscaling algorithm (Noël et al., 2016) that reprojects the original RACMO2.3 output on a 1 km ice mask and topography derived from the Greenland Ice Mapping Project (GIMP) digital elevation model (Howat et al., 2014). The downscaled product accurately reproduces the large mass loss rates in narrow ablation zones, marginal outlet glaciers, and peripheral ice caps (Fig. 2b).

Fig. 2: Surface mass balance (SMB) of central east Greenland a) modelled by RACMO2.3 at 11 km, b) downscaled to 1 km (1958-2015). The 1 km product (b) resolves the large mass loss rates over marginal outlet glaciers [Credit: Brice Noël].

 

The high-resolution data set has been successfully evaluated using in situ measurements and independent satellite records derived from ICESat/CryoSat-2 (Noël et al., 2016, 2017). Recently, the downscaling method has also been applied to the Canadian Arctic Archipelago, for which a similar product is now also available on request.

Endangered peripheral ice caps

Using the new 1 km data set (Fig. 1), we identified 1997 as a tipping point for the mass balance of Greenland’s peripheral ice caps (Noël et al., 2017). Before 1997, ablation (red) and accumulation zones (blue) were in approximate balance, and the ice caps remained stable (Fig. 3a). After 1997, the accumulation zone retreated to the highest sectors of the ice caps and the mass loss accelerated (Fig. 3b). This mass loss acceleration was already reported by ICESat/CryoSat-2 satellite measurements, but no clear explanation was provided. The 1 km surface mass balance provides a valuable tool to identify the processes that triggered this recent mass loss acceleration.

Fig. 3: Surface mass balance of Hans Tausen ice cap and surrounding small ice bodies in northern Greenland before (a) and after the tipping point in 1997 (b). Since 1997, the accumulation zone (blue) has shrunk and the ablation zone (red) has grown further inland, tripling the pre-1997 mass loss [Credit: Brice Noël].

 

Greenland ice caps are located in relatively dry regions where summer melt (ME) nominally exceeds winter snowfall (PR). To sustain the ice caps, refreezing of meltwater (RF) in the snow is therefore a key process. The snow acts as a “sponge” that buffers a large amount of meltwater which refreezes in winter. The remaining meltwater runs off to the ocean (RU) and contributes to mass loss (Fig. 4a).

Before 1997, the snow in the interior of these ice caps could compensate for additional melt by refreezing more meltwater. In 1997, following decades of increased melt, the snow became saturated with refrozen meltwater, so that any additional summer melt was forced to run off to the ocean (Fig. 4b), tripling the mass loss.

Fig. 4: Surface processes on an ice cap: the ice cap gains mass from precipitation (PR), in the form of rain and snow. a) In healthy conditions (e.g. before 1997), meltwater (ME) is partially refrozen (RF) inside the snow layer and the remainder runs off (RU) to the ocean. The mass of the ice cap is constant when the amount of precipitation equals the amount of meltwater that runs off. b) When the firn layer is saturated with refrozen meltwater, additional meltwater can no longer be refrozen, causing all meltwater to run off to the ocean. In this case, the ice cap loses mass, because the amount of precipitation is smaller than the amount of meltwater that runs off [Credit: Brice Noël].

  In 1997, following decades of increased melt, the snow became saturated with refrozen meltwater, so that any additional summer melt was forced to run off to the ocean, tripling the mass loss.

We call this a “tipping point” as it would take decades to regrow a new, healthy snow layer over these ice caps that could buffer enough summer meltwater again. In a warmer climate, rainfall will increase at the expense of snowfall, further hampering the formation of a new snow cover. In the absence of refreezing, these ice caps will undergo irreversible mass loss.

What about the Greenland ice sheet?

For now, the big Greenland ice sheet is still safe as snow in the extensive inland accumulation zone still buffers most of the summer melt (Fig. 1). At the current rate of mass loss (~300 Gt per year), it would still take 10,000 years to melt the ice sheet completely (van den Broeke et al., 2016). However, the tipping point reached for the peripheral ice caps must be regarded as an alarm-signal for the Greenland ice sheet in the near future, if temperatures continue to increase.

Data availability

The daily, 1 km Surface Mass Balance product (1958-2015) is available on request without conditions for the Greenland ice sheet, the peripheral ice caps and the Canadian Arctic Archipelago.

Further reading

Edited by Sophie Berger


Brice Noël is a PhD Student at IMAU (Institute for Marine and Atmospheric Research at Utrecht University), Netherlands. He simulates the climate of the Arctic region, including the ice masses of Greenland, Svalbard, Iceland and the Canadian Arctic, using the regional climate model RACMO2. His main focus is to identify snow/ice processes affecting the surface mass balance of these ice-covered regions. He tweets as: @BricepyNoel Contact Email: b.p.y.noel@uu.nl

Image of The Week – Ice Flows!

Image of The Week – Ice Flows!

Portraying ice sheets and shelves to the general public can be tricky. They are in remote locations, meaning the majority of people will never have seen them. They also change over timescales that are often hard to represent without showing dramatic images of more unusual events such as the collapse of the Larsen B Ice Shelf.  However, an app launched in the summer at the SCAR (Scientific Committee for Antarctic Research) Open Science Conference in Kuala Lumpur set out to change this through a game. Developed by Anne Le Brocq from the University of Exeter, this game is aptly named – Ice Flows!


The game in a nutshell!

Ice Flows is a game that allows the player to control various variables of an ice shelf (floating portion of an ice sheet) environment, such as ocean temperature and snowfall, and see the changes that these cause. For example, increasing the amount of snowfall increases the ice thickness but increasing the ocean temperature causes thinning of the ice shelf. The aim of the game is to help penguins feed by altering the variables to create ice shelf conditions which give them access to the ocean. Although the game is based around penguins, importantly, it is changing the ice shelf environment that the player controls, this allows a player to investigate how changing environmental conditions affect the ice. Our Image of the week shows a still from the game, where the player has created ice conditions which allow the penguins to dive down and catch fish.

What is the educational message?

The polar regions are constantly changing and assigning these changes to either natural cycles or anthropogenic (human induced) climate change can be tricky. Ice shelves tend to only hit the news when large changes happen, such as the recent development of the Larsen C rift which is thought to be unrelated to the warming climate of the region but may still have catastrophic consequences for the ice shelf. Understanding that changes like these can sometimes be part of a natural process can seem conflicting with the many stories about changes caused by warming. That’s why ice flows is a great way to demonstrate the ways in which ice shelves can change and the various factors that can lead to these changes. And the bonus chance to do this with penguins is never going to be a bad thing!

The game allows players to visualise the transformation of ice sheet to ice shelf to iceberg. This is an especially important educational point given the confusing ways that various types of ice can be portrayed by the media; reports, even if factually correct, will often jump from sea ice to ice shelves and back (see this example). It is also common for reports to cloud the climate change narrative by connecting processes thought to be due to natural causes (such as the Larsen C rift) to a warming climate (such as this piece). This confusion is something I often see reflected in people’s understanding of the cryosphere. In my own outreach work I start by explicitly explaining the difference between ice shelves and sea ice (my work is based on ice shelves). Even so, I can usually guarantee that many people will ask me questions about sea ice at the end of my talk.

Xue Long the Snow Dragon Penguin [Credit: Ice Flows game ]

Despite the messages that it is trying to convey, the app doesn’t come across as pushing the educational side too much. There is plenty of information available but the game also has genuinely fun elements. For example, you can earn rewards and save these to upgrade your penguins to some extravagant characters (my favourite has to be Xue Long – the snow dragon penguin!) Although the focus may be drawn towards catching the fish for the penguins while you’re actually playing, it would be hard for anyone to play the game and walk away without gaining an understanding of the basic structure of an ice shelf and how various changing environmental factors can affect it.

Developing the game…

The game was developed by Anne Le Broq in collaboration with games developers Inhouse Visual and Questionable Quality, using funding from the Natural Environment Research Council. Of course, many scientific researchers were also involved to ensure that the game was as scientifically accurate as possible whilst still remaining fun to play.

A key challenge in developing the game was modelling the ice flow. In order to be used in the app, the ice flow model needed to represent scientific understanding as well as being reactive enough to allow the game to be playable. This required some compromise, as one of the scientists involved in the development, Steph Cornford (CPOM, University of Bristol), explains on the CPOM Blog:

On one hand, we wanted the model to reflect contemporary understanding well enough for students to learn about ice sheets, ice shelves, and Antarctica in particular. On the other, the game had to be playable, so that any calculations needed to be carried out quickly enough that the animation appeared smooth, and changing any of the parameters (for example, the accumulation rate) had to lead to a new steady state within seconds, to make the link between cause and effect clear.

— Steph Cornford

The resulting model works really well, creating a fun, challenging and educational game! See for yourself by downloading the free to play game from your app store, or online at www.iceflowsgame.com!

Further reading

  • Find out more about the game on the University of Exeter website or visit the game’s own website here.
  • You can read in more detail about Steph’s modelling here.

Edited by Emma Smith


Sammie Buzzard has recently submitted her PhD thesis where she has developed a model of ice shelf surface melt, focusing on the Larsen C Ice Shelf. She is based at the Centre for Polar Observation and Modelling within the University of Reading’s Department of Meteorology. She blogs about her work and PhD life in general at https://iceandicing.wordpress.com/ and tweets as @treacherousbuzz.

Image of the Week — Hidden lakes in East Antarctica !

Image of the Week — Hidden lakes in East Antarctica !

Who would have guessed that such a beautiful picture could get you interviewed for the national news?! Certainly not me! And yet, the photo of this englacial lake (a lake trapped within the ice in Antarctica), or rather science behind it, managed to capture the media attention and brought me, one of the happy co-author of this study,  on the Belgian  television… But what do we see on the picture and why is that interesting?


Where was the picture taken?

The Image of this Week shows a 4m-deep meltwater lake trapped 4 m under the surface of the Roi Baudouin Ice Shelf (a coastal area in East Antarctica). To capture this shot, a team of scientists led by Stef Lhermitte (TU Delft) and Jan Lenaerts (Utrecht University) went to the Roi Baudouin ice shelf, drilled a hole and lowered a camera down (see video 1).

Video 1 : Camera lowered into borehole to show an englacial lake 4m below the surface. [Credit: S. Lhermitte]

How was the lake formed?

In this region of East Antarctica, the katabatic winds are very persistent and come down from the centre of the ice sheet towards the coast, that is the floating ice shelf (see animation below). The effect of the winds are two-fold:

  1. They warm the surface because the temperature of the air mass increases during its descent and the katabatic winds mix the very cold layer of air right above the surface with warmer layers that lie above.
  2. They sweep the very bright snow away, revealing darker snow/ice, which absorb more solar radiation

The combination leads to more melting of the ice/snow in the grounding zone — the boundary between the ice sheet and ice shelf — , which further darkens the surface and therefore increases the amount of solar radiation absorbed, leading to more melting, etc. (This vicious circle is very similar to the ice-albedo feedback presented in this previous post).

Animation showing the processes causing the warm micro-climate on the ice shelf. [Credit: S. Lhermitte]

All the melted ice flows downstream and collects in depressions to form (sub)surface lakes. Those lakes are moving towards the ocean with the surrounding ice and are progressively buried by snowfalls to become englacial lakes. Alternatively, the meltwater can also form surface streams that drain in moulins (see video 2).

Video 2 : Meltwater streams and moulins that drain the water on the Roi Baudouin ice shelf. [Credit: S. Lhermitte]

Why does it matter ?

So far we’ve seen pretty images but you might wonder what could possibly justify an appearance in the national news… Unlike in Greenland, ice loss by surface melting has  often been considered negligible in Antarctica. Meltwater can however threaten the structural integrity of ice shelves, which act as a plug of the grounded ice from upstream. Surface melting and ponding was indeed one of the triggers of the dramatic ice shelves collapses in the past decades, in the Antarctic Peninsula . For instance, the many surfaces lakes on the surface of the Larsen Ice shelf in January 2002, fractured and weakened the ice shelf until it finally broke up (see video 3), releasing more grounded ice to the ocean than it used to do.

Of course surface ponding is not the only precondition for an ice shelf to collapse : ice shelves in the Peninsula had progressively thinned and weakened for decades, prior their disintegration. Our study suggests however that surface processes in East Antarctica are more important than previously thought, which means that this part of the continent is probably more vulnerable to climate change than previously assumed. In the future, warmer climates will intensify melt, increasing the risk to destabilise the East Antarctic ice sheet.

Video 3 : MODIS images show Larsen-B collapse between January 31 and April 13, 2002. [Credit:NASA/Goddard Space Flight Center ]

Reference/Further reading

Edited by Nanna Karlsson

Polar Exploration: Perseverance and Pea Sausages

Polar Exploration: Perseverance and Pea Sausages

Born on this Day

Portrait of Ludvig Mylius-Erichsen by Achton Friis. [Credit: Danish Arctic Institute].

On this day in 1872 – 145 years ago –Ludvig Mylius-Erichsen, Danish author and polar explorer, was born. He led two expeditions to Greenland and successfully mapped the then unknown northeastern part of the country. The second expedition was his last. The expedition was surprised by an early onset of spring and could no longer use their dog sledges. The two Danes, Mylius-Erichsen and Høeg Hagen died in November 1907 of cold and hunger. Their bodies have never been found. The last remaining expedition member, the Greenlander Brønlund, continued the journey alone but perished a few weeks later. His body and the expedition diary was found in 1908.

Thousands of Pea Sausages

The tin on the image above contains “pea sausage” and was essentially the world’s first ready meal: A mixture of ground peas, beef fat, bacon, spices and salt. Pea sausage was invented in 1867 in Germany and was a common part of military and expedition rations up until the beginning of the 20th century.

Mylius-Erichsen’s expedition brought along 1756 tins of this kind. Each tin contained 6 tablets of pea sausage, that mixed with ¼ water would make a nourishing soup. And the taste? On his first expedition, Mylius-Erichsen wrote:

“The evening meals in the three boxes consisted mainly of different kinds of sturdy soups, black pudding, meat pie, beef, pea sausage and sizeable portions of vegetable such as cabbage, beans and carrots. We only used one third of the evening meal rations on the way out. We did not like the taste of the meat but black pudding, peas and the different kinds of soup were heavenly”.

And later:

“Jørgen and I had dinner at Amarfik’s, and dinner consisted both days of little auks boiled in our last portion of pea sausage – a wonderful dish…”

Members of Mylius-Erichsen’s first expedition: Brønlund, Bertelsen, Mylius-Erichsen, Rasmussen and Moltke. [Credit: Danish Arctic Institute].

Photos and descriptions are from the Danish Arctic Institute (@arktiskinstitut) where you can also see a full 360 degrees photo of the tin.

Check out more historical footage from Greenland in a previous Image of the Week showing aerial photos from the 1930s.

Edited by: Sophie Berger

Image of the Week – It’s all a bit erratic in Yosemite!

Image of the Week – It’s all a bit erratic in Yosemite!

When you think of California, with its sun-soaked beaches and Hollywood glamour, glaciers may not be the first thing that spring to mind – even for ice nerds like us. However, Yosemite National Park in California’s Sierra Nevada is famous for its dramatic landscape, which was created by glacial action. With our latest image of the week we show you some of the features that were left behind by ancient glaciers.


What do we see here?

Although Yosemite is now largely glacier-free the imprint of large-scale glaciation is evident everywhere you look. During the last glacial maximum (LGM), around 26,000 to 18,000 years ago, much of North America was covered in ice. Evidence of this can be seen in the strange landscape, shown in our image of the week. The bedrock surface in this area is polished and smoothed due to a huge ice mass that was moving over it, crushing anything in it’s path. When this ice mass melted rocks and stones it transported were released from the ice and left strewn on the smoothed bedrock surface. These abandoned rocks and stones are know as glacial erratics. Some of these erratics will have travelled from far-away regions to their resting place today.

During the last glacial maximum (LGM), around 26,000 to 18,000 years ago, much of North America was covered in ice.

Glaciers that still remain!

There are still two glaciers in Yosemite, Lyell and Maclure, residing in the highest peaks of the National Park. Park rangers have been monitoring them since the 1930s (Fig. 2), so there is a comprehensive record of how they have changed over this period. Sadly, as with many other glaciers around the world this means a huge amount mass has been lost – read more about it here!

Figure 2: Survey on Maclure Glacier by park rangers in the 1930s [Credit: National Parks Service]

On a more cheerful note – Here at the EGU Cryosphere Blog we think it is rather fantastic that the park rangers of the 1930s conducted fieldwork in a suit, tie and wide-brimmed hat and we are hoping some of you might be encouraged to bring this fashion back! 😀

If you do please make sure to let us know, posting it on social media an tagging us @EGU_CR! Here are a few more ideas of historical “fieldwork fashion” to wet your appetite: Danish explorers in polar bear suits, 1864-65 Belgian-Dutch Antarctic Expedition and of course Shackleton’s Endurance expedition!


Imaggeo, what is it?

You like this image of the week? Good news, you are free to re-use it in your presentation and publication because it comes from Imaggeo, the EGU open access image repository.

Image of the Week — Looking back at 2016

Image of the Week — Looking back at 2016

Happy New-Yearcorn

I cannot believe that a full year has passed since this very cute pink unicorn wished you a Happy New Year.

Yet, over the past  12 months our blog has attracted more than 16,200 visits.  And the blog analytics show that you, our dear readers, are based not only in Europe but literally all over the world!

With 67 new posts published in only 52 weeks, it’s more than likely that you missed a few interesting ones. Don’t worry, today’s Image Of the Week highlights some of the most exciting content written, edited and published by the whole cryo-team during the year 2016!  

Enjoy and don’t forget to vote in the big EGU Blog competition (see below) !
(Remark
: all the images are linked to their original posts)


Get the most of 2016

Last glaciation in Europe, ~70,000-20,000 years ago [By S. Berger].

The 82 research stations in the Antarctic [By S. Berger].

 

 

 

  • We also launched our new “for dummies” category that aims at explaining complex glaciological concepts in simple terms. The first and most read “for dummies” is all about “Marine Ice sheet instability” and explains why West Antarctica could be destabilised.

Marine Ice Sheet Instability [By D. Docquier].

Three other “for dummies” have been added since then. They unravel the mysteries behind Water Masses, Sea Level and Ice Cores.

  • Drilling an ice core [By the Oldest Ice PhD students]

    Another welcomed novelty of 2016 was the first “ice-hot news” post, about the very exciting quest for the oldest ice in Antarctica. In this post — issued at the same time as the press release —  the 3 PhD students currently involved with the project explain how and where to find their holy grail, i.e. the 1 million year old ice!

The list goes on of course, and I could probably spend hours presenting each of our different posts one by one and explain why every single one of them is terrific. Instead, I have decided to showcase a few more posts with very specific mentions!

 

The oddest place for ice : inside a volcano! [By T. Santagata]

The quirkiest ice phenomenon  : ice balls [By E. Smith].

The most romantic picture : Heart-shaped bubbles for ValentICE’s day [By S. Berger]

The creepiest picture: Blood Falls, Antarctica [By E. Smith]

The funniest post : April Fools “do my ice deceive me” [By S. Berger]

The best incidental synchronisation: The Perito Moreno collapsed the day before our the post went live [By E. Smith]

 

The “do they really do that? ” mention for ballooning the ice [By N. Karlsson]

The best fieldwork fail : Skidoos sinking into the slush [By S. Berger]

The most epic story : Shackleton’s rescue [By E. Smith]

The most puntastic title “A Game of Drones (Part 1: A Debris-Covered Glacier” [By M. Westoby].

The most provocative title : “What an ice hole” [By C. Heuzé]

The soundest post where science is converted to music [By N. Karlsson]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Good resolutions for 2017

The beginning of a new year is a great opportunity to look back at the previous year, and one of the logical consequences is to come with good resolutions for the coming year.  Thinking of a good resolution and then achieving it can however be tricky.  This is why we have compiled a few resolutions, that YOU dear cryo-followers could easily make 🙂

 Cryoblog stronger in the E(G)U blog competition

To celebrate the excellent display of science writing across all the EGU blogs, a competition has been launched.

Olaf the snowman begs you to vote for “the journey of a snowflake”

From now until Monday 16th January, we invite you, the cryo-readers, to vote for your favourite post of 2016, which should be “journey of a snowflake” (second-to last option). I am obviously being totally objective but if you’re not convinced, the little guy on the right might be more persuasive. If you’re really adventurous, you could also consider clicking on other posts to check what they look like, after having voted for the cryo-one, of course.

Get involved

Hopefully by now:

  1. You are convinced that the cryosphere is amazing and that the EGU cryoblog enables you to seize some of the cryo-awesomeness
  2. You have read and elected the “journey of a snowflake”  as the best post of 2016
  3. You would like to contribute to the blog (because you would like to be part of this great team or simply because you think your sub-field is not represented well enough).

Not to confuse you with a long speech, the image below explains how to get involved. We always welcome contributions from scientists, students and professionals in glaciology, especially when they are at the early stage of their career.

Thank you for following the blog!

PS: this is one of my favourite tweets from the EGU cryospheric division twitter account. What is yours?

Edited by Nanna Karlsson

Ice-Hot News : The “Oldest Ice” quest has begun

Ice-Hot News : The “Oldest Ice” quest has begun

This is it! The new European horizon 2020 project on Oldest Ice has been launched and the teams are already heading out to the field, but what does “Old Ice” really mean? Where can we find it and why should we even care? This is what we (Marie, Olivier and Brice) will try to explain somewhat.


Why do we care about old ice, ice cores and past climate?

Figure 1: Drilling an ice core [Credit: Brice Van Liefferinge]

Figure 1: Drilling an ice core [Credit: Brice Van Liefferinge]

Unravelling past climate and how it responded to changes in environmental conditions (e.g. radiative forcing) is crucial for our understanding of the current climate and for predicting how climate will likely change in the future.

Ice cores contain unique and quantitative information on the past climate (e.g. atmospheric gas concentration). The caveat is that at the moment, we can “only” go back up to 800,000 years at EPICA Dome C ice core (Parrenin et al, 2007).

Nonetheless, marine records tell us that during the Mid-Pleistocene there was a major climate transition (0.8-1.2 million years ago): a change in the frequency of glacial-interglacial cycles in the Northern Hemisphere. Instead of an ice age every 40,000 year, the climate changed to what is termed a “100,000 year world”. Unfortunately, the time resolution of marine records are too coarse to provide details on the mechanisms behind such climate changes. We must therefore rely on ice cores to obtain a high enough temporal resolution. Furthermore, the ice traps air bubbles and can therefore provide a record of the atmospheric composition that can be used to directly measure the paleo atmosphere through the transition.

The new European project ‘Oldest ice’ was set up for this very objective: crack the Mid-Pleistocene Transition climate. It brings together engineers, experimentalists and modellers from 14 Universities around the world.

In this post, we will focus on the first mission of the project: locating areas with million year old ice in Antarctica. The next steps will be to:

  • develop the drilling technology,

  • improve our geophysical knowledge of the identified site,

  • and finally, reach the “holy grail”: recover ice from the very base of the ice sheet with a target age of 1.5 Million years.

The whole project is anticipated to last 10 years!

The new European project ‘Oldest ice’ was set up for this very objective: crack the Mid-Pleistocene Transition climate

The first mission: “Where to find million year old ice?”

Oldest Ice (ice more than 1 mio. years old) can only be recovered in Antarctica, but where exactly? This question has to be answered in a two-step approach:

  1. On a large scale, we must first narrow down places in Antarctica where Oldest Ice might be found. To do that, we rely on models.

  2. Then, we can focus our analysis on those regions by gathering field data in the form of airborne radar surveys. Further ground-based work is currently taking place.

On a larger scale, Oldest Ice in Antarctica requires:

  1. Thick ice and cold bed. We need thick ice to reconstruct past climate variations with sufficient temporal resolution (e.g. is there enough ice to measure air bubbles or other climate markers). However, the thicker the ice, the higher the basal temperature. If the bottom of the ice is too warm, the ice at the base will start to melt, potentially destroying the Oldest Ice of the ice sheet.
    Finding a suitable drill site hence requires a good trade-off between thickness and cold-bed conditions.

  2. Slow-moving ice. This is found mainly at the centre of the ice sheet. Imagine this: if ice were to flow at as little as 1 m per year over a period of 1.5 Million years, it would have travelled 1,500 km over that time interval! However, there is a catch: slow-moving areas are also low-accumulation areas, and low accumulation means warmer ice. This is because the ice is cooled by the addition of cold snow at the surface that then gets transformed to ice and then travels downwards. Indeed, the greater the accumulation, the deeper the “cold snow” can penetrate into the ice sheet!

  3. Undisturbed ice. In order to obtain an interpretable climate record, the ice recovered from the drill needs to be stratigraphically ordered, i.e. no mixing of the ice can have occurred so that we can assume that time increases with depth when we measure ice composition down the core. Variations in the height of the bedrock can induce such ice mixing.

(more information can be found in Van Liefferinge and Pattyn (2013))

Figure 2. Potential locations of cold bed (basal temperatures 2000 m), slow motion (horizontal flow speeds <2m/yr) The colour bar represents the basal temperature. The two insets focus on Dome C and Dome F, two areas highly likely to store million year old ice. [Credit: Brice Van Lieffering, updated from Van Liefferinge, B. and Pattyn, 2013]

Figure 2. Potential locations of cold bed (basal temperatures 2000 m), slow motion (horizontal flow speeds <2m/yr) The colour bar represents the basal temperature. The two insets focus on Dome C and Dome F, two areas highly likely to store million year old ice. [Credit: Brice Van Lieffering, updated from Van Liefferinge, B. and Pattyn, 2013]

While boundary conditions such as ice thickness and accumulation rates are relatively well constrained, the major uncertainty remains in determining thermal conditions at the ice base. The thermal conditions depend on the geothermal heat flow (the flux of “energy” provided by the Earth which conducts heat into the crust) underneath the ice sheet. But to measure the geothermal heat flow, you need to reach the bed.

We need to find the ideal drilling location which would satisfy all these conditions – a bit of a “Goldilocks’ choice”: thick ice but not too much, low accumulation but not too low, low geothermal heat flow but high enough to not get folded basal ice. To do this we use several models: a simple one which calculates the minimum geothermal heat flow needed to reach the pressure melting point that we can then compare to data sets, and a more complex one resolving in three dimensions the temperature field with thermomechanical coupling (i.e. linking the ice-flow component to the heat-flow component). The combination of modelling approaches shows that the most likely oldest ice sites are situated near the ice divide areas (close to existing deep drilling sites, but in areas of smaller ice thickness) (see Figure 2).

Give it a go: Try to find million year old ice yourself using this Matlab© tool: http://homepages.ulb.ac.be/~bvlieffe/old-ice.html

The combination of modelling approaches shows that the most likely oldest ice sites are situated near the ice divide areas

On finer scales: we need deep radiostratigraphy and age modelling

Radar profiles

Figure 3. Radargram from the new OIA radar survey (Young et al., in review) with isochrones interpreted in red [Credit: Marie Cavitte]

Figure 3. Radargram from the new Oldest Ice A radar survey (Young et al., in review) with isochrones interpreted in red [Credit: Marie Cavitte]

Radargrams (see figure 3) are powerful tools to observe the internal structure of the ice: variations in density, acidity and ice fabric all can create conductivity contrasts, which result in radar visual stratigraphy. Below the firn column (the compacting snow, up to 100 m thick), most returns are related to acidity variations, corresponding to successive depositional events (i.e. snowfall). Radar stratigraphy in this case can be considered isochronal, i.e. every visible line (see figure 3) were formed at the same moment, (Siegert et al., 1999). Such radar isochrones can then be traced for kilometres throughout the ice sheet where radar data has been acquired. When radar lines intersect an ice core site, the radar stratigraphy can then be dated by matching the isochrone-depths to the ice core depths at the site and then transferring the age-depth timescale.

This allows to date entire sub-regions. However, the very bottom of the ice column is often difficult to interpret: radar isochrones cannot always be continuously followed from the ice core.

Radargrams are powerful tools to observe the internal structure of the ice

The newly acquired Oldest Ice A radar survey (Young et al., in review) over the Dome C region (see figure 2 for location) gives very rich stratigraphic information and the proximity of the EPICA Dome C ice core has allowed the dating of the isochrones. The ice sheet in this area could only be dated to ~360,000 years (Cavitte et al., 2016) and not further back in time because deeper isochrones are tricky to tie to the ice core, and other times, there is no clear signal (deep scattering ice, visible near the bedrock, at the bottom of Figure 3). As such, we need an age model to try to describe the age-depth relation below the deepest dated isochrones.

Modelling the ice

Figure 4. More precise analysis of the Dome C Oldest Ice target, with the lines representing the Oldest Ice A airborne survey collected in winter 2015/16 (Young et al., in review). The colours represent the modelled age of the ice 60 meters above the bedrock, in thousands of years. We can see that this whole region has a lot of potential for recovering million year old ice. [Credit: Olivier Passalacqua]

Figure 4. More precise analysis of the Dome C Oldest Ice target, with the lines representing the Oldest Ice A airborne survey collected in winter 2015/16 (Young et al., in review). The colours represent the modelled age of the ice 60 meters above the bedrock, in thousands of years. We can see that this whole region has a lot of potential for recovering million year old ice. [Credit: Olivier Passalacqua]

The age of the ice primarily depends on its vertical velocity, so we can use a simple 1D model to describe the motion of the ice in the vertical direction. We run the model for an ensemble of vertical velocity profiles and basal melt rates, and consider the distribution of the basal ages (i.e. model ages) given by the profiles that reproduce the observations the best (i.e. isochrones ages).

We need an age model to try to describe the age-depth relation below the deepest dated isochrones

After running the model, it appears that many areas of the Oldest Ice A survey region host very old ice (see red and yellow dots on figure 4 which represent ages > 1 million years). A high enough bottom age gradient, provided by the dated isochrones, is required to ensure sufficiently old ice as a drilling target. Following initial calculations, it will probably be a better choice to drill on the flank of the bedrock relief than on its top.

So in the end, where do we find the oldest ice?

We have to find areas which provide a good compromise between thick ice (for the a good temporal resolution in the ice core) but not too thick (to avoid basal melting). The best sites will be the ones close to the surface ridge (to ensure limited displacement of the ice), standing above the surrounding subglacial lakes, and for which a lot of undated isochrones below the last dated isochrone are visible.

To find out more about Beyond EPICA and keep track of progress visit the project  website and follow @OldestIce on twitter!

Edited by Sophie Berger


Brice Van Liefferinge is a PhD student and a teaching assistant at the Laboratoire de Glaciology, Université libre de Bruxelles, Belgium. His research focuses on the basal conditions of the Antarctic ice sheet. He tweets as @bvlieffe.

Marie Cavitte is a PhD student at the Institute for Geophysics at the University of Texas at Austin, Texas. Her research focuses on understanding radar internal stratigraphy and using it as a means to constrain the temporal stability of the East Antarctic Ice Sheet interior.

Olivier Passalacqua is a PhD student at the Laboratoire de Glaciologie et Géophysique de l’Environnement, Grenoble, France.

Members of the consortium

  • Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI, Germany), Coordination
  • Institut Polaire Français Paul Émile Victor (IPEV, France)
  • Agenzia nazionale per le nuove tecnologie, l’energia e lo sviluppo economico sostenibile (ENEA, Italy
  • Centre National de la Recherche Scientifique (CNRS, France)
  • Natural Environment Research Council – British Antarctic Survey (NERC-BAS, Great Britain)
  • Universiteit Utrecht – Institute for Marine and Atmospheric Research (UU-IMAU, Netherlands)
  • Norwegian Polar Institute (NPI, Norway)
  • Stockholms Universitet (SU, Sweden)
  • Universität Bern (UBERN, Switzerland)
  • Università di Bologna (UNIBO, Italy)
  • University of Cambridge (UCAM, Great Britain)
  • Kobenhavns Universitet (UCPH, Denmark)
  • Université Libre de Bruxelles (ULB, Belgium)
  • Lunds Universitet (ULUND, Sweden)

Non-Europan partners

  • Institute for Geophysics, University of Texas at Austin (UTIG, US)
  • Australian Antarctic Division (AAD, Australia)

Image of the Week – Climate Change and the Cryosphere

Image of the Week – Climate Change and the Cryosphere

While the first week of COP22 – the climate talks in Marrakech – is coming to an end, the recent election of Donald Trump as the next President of the United States casts doubt over the fate of the Paris Agreement and more generally the global fight against climate change.

In this new political context, we must not forget about the scientific evidence of climate change! Our figure of the week, today summarises how climate change affects the cryosphere, as exposed in the latest assessment report of the Intergovernmental Panel on Climate Change (IPCC, 2013, chapter 4)


Observed changes in the cryosphere

Glaciers (excluding Greenland and Antarctica)

  • Glaciers are the component of the cryosphere that currently contributes the most to sea-level rise.
  • Their sea-level contribution has increased since the 1960s. Glaciers around the world contributed to the sea-level rise from 0.76 mm/yr (during the 1993-2009 period) to 0.83 mm/yr (over the 2005-2009 period)

Sea Ice in the Arctic

  • sea-ice extent is declining, with a rate of 3.8% /decade (over the 1979-2012 period)
  • The extent of thick multiyear ice is shrinking faster, with a rate of 13.5%/decade (over the 1979-2012 period)
  • Sea-ice decline sea ice is stronger in summer and autumn
  • On average, sea ice thinned by 1.3 – 2.3 m between 1980 and 2008.

Ice Shelves and ice tongues

  • Ice shelves of the Antarctic Peninsula have continuously retreated and collapsed
  • Some ice tongue and ice shelves are progressively thinning in Antarctica and Greenland.

Ice Sheets

  • The Greenland and Antarctic ice sheets have lost mass and contributed to sea-level rise over the last 20 years
  • Ice loss of major outlet glaciers in Antarctica and Greenland has accelerated, since the 1990s

Permafrost/Frozen Ground

  • Since the early 1980s, permafrost has warmed by up to 2ºC and the active layer – the top layer that thaw in summer and freezes in winter – has thickened by up to 90 cm.
  • Since mid 1970s, the southern limit of permafrost (in the Northern Hemisphere) has been moving north.
  • Since 1930s, the thickness of the seasonal frozen ground has decreased by 32 cm.

Snow cover

  • Snow cover declined between 1967 and 2012 (according to satellite data)
  • Largest decreases in June (53%).

Lake and river ice

  • The freezing duration has shorten : lake and river freeze up later in autumn and ice breaks up sooner in spring
  • delays in autumn freeze-up occur more slowly than advances in spring break-up, though both phenomenons have accelerated in the Northern Hemisphere

Further reading

How much can President Trump impact climate change?

What Trump can—and can’t—do all by himself on climate | Science

US election: Climate scientists react to Donald Trump’s victory  | Carbon Brief

Which Trump will govern, the showman or the negotiator? | Climate Home

GeoPolicy: What will a Trump presidency mean for climate change? | Geolog

Previous posts about IPCC reports

Image of the Week — Ice Sheets and Sea Level Rise

Image of the Week —  Changes in Snow Cover

Image of the Week — Atmospheric CO2 from ice cores

Image of the Week — Ice Sheets in the Climate

Edited by Emma Smith

Sea Level “For Dummies”

Sea Level “For Dummies”

Looking out over the sea on a quiet day with no wind, the word “flat” would certainly pop up in your mind to describe the sea surface. However, this serene view of a flat sea surface is far from accurate at the global scale.

The apparent simplicity behind the concept of sea level hides more complex science that we hope to explain in a simple manner in today’s “For Dummies” post, which will give you the keys to understand the important aspects of past sea change, and an ability to look into and understand how sea level is a key factor in the future.

Everyone will be familiar with news stories about current sea level rise, but it can be very confusing to understand what this means in real terms; how fast it is happening and why we should care about it anyway. So to begin with, let’s have a look at what we mean by sea level?


Sea Level – It’s all about gravity!

[Read More]

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