The Cryosphere

the latest in cold climate science from the Arctic to the Antarctic, via the Alps and the Andes

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ESA’s gravity-mapper reveals relics of ancient continents under Antarctic ice

It was five years ago this month that ESA’s GOCE gravity-mapping satellite finally gave way to gravity, but its results are still yieldin

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Karthaus Summer School covering glacier and ice sheet dynamics, for PhD students in September 2017.

APPLICATIONS DUE: Sunday 7th May 2017

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Link an overview of a summer school at UNIS, for PhD and postdocs, concerning the Arctic Ocean and the marginal ice zone.

APPLICATIONS DUE: Monday 8th May 2017

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NASA just snapped the first photos of a mysterious crack in one of Greenland’s largest glaciers

A scientist tweeted satellite photos of a crack in a famous glacier. Pretty soon, NASA had taken its picture.

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Unique Canadian ice core collection suffers catastrophic meltdown

Freezer failure destroys 12.8% of collection

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List of polar and alpine related events occurring in 2017, compiled by the Arctic, Antarctic and Alpine Research (AAAR) journal.

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APECS are hosting a conference to kick-start Polar Week on Monday 20th March. The conference will be held online and focus on alternative solutions to undertaking and communicating polar research. Registration to the sessions and information on the topics to be discussed can be found through the link above - sessions are limited to 100 participants so be quick if you want to get involved.

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If you want to see how the sea ice extent has changed over the years and place the latest figures in context, this interactive graph from NSIDC is a great tool. Data is available for both the Arctic and Antarctic, across the full year and stretching all the way back to 1979.

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Check out the schedule for the CryoSat conference at the end of March, in Banff, Canada. There’s a lot of big names giving talks and presenting their research across some very interesting looking topics.

Today’s the last day to sign up and confirm your place there.

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Fastest glacier on Earth

The fastest glacier on Earth moves 40 metres in a day

Courtesy of the BBC and Sir David Attenborough, this ~3 minute video is rather light on scientific content but contains some stunning imagery of the Jakobshavn Isbræ in Greenland. 

It is well worth checking out, but be warned - the vertiginous shots from atop the glacier as the river of ice prepares to calve are not for those with a fear of heights!

[thecryosphere]

Assessing the Accuracy of Glacier DSMs from UAV imagery

Overview

Digital Surface Models (DSMs) created from UAV-based photogrammetry are being increasingly used to quantify ice volume change and glacier motion. This paper by Gindraux et al. (2017) assesses the accuracy of the created models with specific reference to glacial surfaces.

Study Area & Acquisition

Three glaciers in the Swiss Alps were studied, across Summer, Winter and Autumn. Ground Control Points were measured with a dGPS, the mean accuracy being ~2cm, and the UAV was then flown over the glaciers at an approximate height of 115m, carrying a customised Canon camera, GPS and IMU.

Methodology & Workflow

Results

A vertical accuracy of 0.1-0.25m and horizontal accuracy of 0.03-0.09m can be achieved for DSMs when using an optimal number of Ground Control Points (GCP). Above this density, additional GCPs do not improve the accuracy of the DSM. 

Greater distances to a GCP were found to have a detrimental impact on the accuracy at a rate of 0.09m per 100m, though there is large scatter and other factors are therefore important.

The lack of structure in fresh snow made it impossible to orient the images and therefore the creation of DSMs was not possible. However, snow that was one day old could be orientated in 19 of 20 images. Excluding fresh snow, the surface texture did not have any significant influence on accuracy. 

Similar DSM accuracies can be achieved over all seasons. 

References and Links

Gindraux, S., Boesch, R. & Farinotti, D. (2017) Accuracy Assessment of Digital Surface Models from Unmanned Aerial Vehicles’ Imagery on Glaciers. Remote Sensing, 9, (2), 186. Open Access Article here.

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Assisting Avalanche Search and Rescue Operations with UAV Imagery

Overview

A paper by Bejiga et al. (2017) introduces and investigates the success of an automated system that utilises images captured by an Unmanned Aerial Vehicles (UAV) to detect avalanche victims. 

The Detection System

According to a report by Brugger & Falk (2002), around 60% of avalanche victims have at least some part of their body visible. The present study aims to to detect such victims and therefore help speed up the search part of a Search And Rescue operation by utilising the following automated steps:

- pre-process the images to select regions of interest;

- employ a Convolutional Neural Network technique to identify features within the images;

- train a Support Vector Machine (SVM) to classify what type of object the features are;

- post-process the results, using Hidden Markov Models to compare whether objects appear in successive images as would be expected.

There are currently two possibilities as to how this system would be deployed: either the images are sent to a ground station in near-real-time and processing is achieved there, which is slower but more powerful; or the processing takes place onboard the UAV, and only areas of interest are sent to the station.

And in a little more detail…

Pre-processing: Image segmentation methods split images into areas of snow and non-snow, based on a threshold value that determines their colour.

Convolutional Neural Network: A feed forward neural network - neurons accept input from local neurons in the previous layer, and use weighted operations based around the width, height and depth of the neuron. The convolutional layer is trained to identify features, the pooling layer mitigates against overfitting, and the fully connected layer introduces the weighting of all other neurons from the previous layer.

Support Vector Machine: Identified features from the CNN are classified, using margin maximization (between classes) and error minimization (penalising incorrect classification). The aim is to separate people and skis from trees, shadows and rocks.

Post-processing: Use of HMM to compare successive images. These techniques are used in applications such as speech recognition, molecular biology, and bioinformatics. 

Main Conclusions

The use of a pre-processing step significantly decreases the processing time.

Increasing the resolution of the input data improves the detection success of the system, but also leads to a larger number of false alarms and slows down the processing time.

Increasing the height from which the images are captured reduces the prediction performance.

Suggested Further Work

Investigate a pre-processing step that is more robust at lower resolutions.

Investigate the effects of illumination and wind on the images.

References & Links

Bejiga, M.B., Zeggada, A., Nouffidj, A. & Melgani, F. (2017) A Convolutional Neural Network Approach for Assisting Avalanche Search and Rescue Operations with UAV Imagery. Remote Sensing, 9, 2, 100. Open Access Article here.

Brugger, H. & Falk, M. (2002) Analysis of Avalanche Safety Equipment for Backcountry Skiers. Available online here. Accessed on 26 February 2017.

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Pine Island Glacier calving caught by satellites

A chunk of ice, about 1 square mile in size, broke off the Pine Island Glacier (PIG) in Antarctica towards the end of January 2017. The size of it is nothing special in itself, but the above image of the breakup was captured by NASA’s satellite. A before and after comparison can be found on the NASA Images of Change webpage here.

If you want to read an overview of PIG and see why it is such an important glacier to monitor, check out Bethan Davies’ AntarcticGlaciers.org blog here.

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Rapid growth of a crack in the Larsen C Ice Shelf

The MIDAS project team, a group of UK-based researchers, have filmed a crack that is quickly spreading along the Larsen C ice shelf on the Antarctic Peninsula. The crack is approximately 460m wide and 175km long at the moment, meaning just 20km of ice is holding it to the ice shelf. When it does break away, which could still be anywhere from days to years away, an iceberg approximately twice the size of Luxembourg (>5,000 square km) will be released into the Weddell Sea.

Antarctic Ice Shelves - Larsen C is on the Antarctic Peninsula

What effect will that have?

The calving of icebergs is a normal part of an ice sheet’s life cycle and doesn’t in itself an impact sea level because an ice shelf is already floating on the water. However, there is much speculation about what could happen to the ice that lies behind it - when the iceberg calves, it is no longer providing the glaciers with a protective buttress from the open ocean, and the glaciers in this region could therefore speed up. This was the case with Larsen C’s sister ice shelves, Larsen A and Larsen B, which collapsed in 1995 and 2002 respectively. Links to journal articles detailing those collapses can be found below.

This precedent, however, does not mean that a speed up in the ice flow is guaranteed - it is also possible that the ice will simply regrow and the ice shelf will remain stable. Even if this is the case, the calving event will be of interest to scientists - it is just as interesting to see why the ice doesn’t do something as it see why it does do something.

References and Further Reading

The official blog of the MIDAS project can be found here.

More details can also be found at BAS, Nature, BBC, Scientific American and any number of other media outlets.

A general overview of the Larsen Ice shelves is here.

Larsen A and Larsen B

De Angelis & Skvarca (2003) Glacier surge after ice shelf collapse

Scambos et al. (2004)  Glacier acceleration and thinning after ice shelf collapse in the Larsen B embayment, Antarctica

Glasser & Scambos (2008) A structural glaciological analysis of the 2002 Larsen B ice shelf collapse

Rack & Rott (2004) Pattern of retreat and disintegration of the Larsen B ice shelf, Antarctic Peninsula

Rignot et al. (2004) Accelerated ice discharge from the Antarctic Peninsula following the collapse of Larsen B ice shelf

Rott et al. (2011) The imbalance of glaciers after disintegration of Larsen-B ice shelf, Antarctic Peninsula

Effects of buttressing

Dupont & Alley (2005) Assessment of the importance of ice-shelf buttressing to ice-sheet flow

Pritchard et al. (2012) Antarctic ice-sheet loss driven by basal melting of ice shelves

Royston & Gudmundsson (2016) Changes in ice-shelf buttressing following the collapse of Larsen A Ice Shelf, Antarctica, and the resulting impact on tributaries

[thecryosphere]

Biggest ever Arctic research mission wants to get stuck in the ice

In Autumn 2019, the Polarstern research vessel is to be deliberately left to freeze itself into the Arctic sea ice in order to collect year-round data about key climate processes as it drifts across the frozen ocean.

Why, what and where?

Useful as datasets from Earth observation satellites undoubtedly are, models of the Arctic are not reliably predicting the region’s response to climate change, particularly in terms of the sea ice’s behaviour, so something important must be missing. As part of the MOSAiC research project, it is the Polarstern’s job to enlighten us to what that is on its year-long drift from the East Siberian Sea to the Fram Strait, the passage between Greenland and Svalbard.

Scientific Purpose

The in-situ observations that will be made aim to uncover the underlying processes that couple the atmosphere, ocean, sea ice, bio-geochemistry and ecosystem with one another. This is addressed in 6 broad research questions.

1) What are the seasonally-varying energy sources, mixing process, and interfacial fluxes that affect the heat and momentum budgets of the Arctic atmosphere, ocean and sea ice?

2) How does sea ice formation, drift, deformation and melting couple to atmospheric, oceanic and ecosystem processes?

3) What are the processes that regulate the formation, properties, precipitation and life time of Arctic clouds and their interactions with aerosols, boundary layer structure and atmospheric fluxes?

4) How do interfacial exchange rates of bio-geochemical process-related trace gases trigger the Arctic climate system?

5) How do sea ice and pelagic (open ocean) ecosystems respond to change in Arctic sea ice?

6) How do ongoing changes in the Arctic climate system impact large-scale hear, momentum and mass fluxes, and how do these changes feed back into the Arctic climate and ecosystem?

The science plan for the mission (found here) expands on these questions, providing a literature review that outlines the importance of the topic, and the current knowledge base and ideas of the constituent questions encompassed in each of these broad categories.

Extending the study area

To help answer these questions, the trapped ship will be surrounded by satellite research stations set up on the ice at distances of up to ~50km, a distance chosen to extend the study area to a size that is typical of gridded climate models. These stations, operated either automatically or via remote control from the ship, will allow researchers to see the heterogeneity of their results - i.e. how much do things change within the 50km grids that are used in the models? 

To extend the coverage even further, collaborating research vessels, satellites, UAVS, aircraft and ocean gliders will also play their part. 

Further reading and references

The official website of the MOSAiC project can be here.

A brief introduction to the project from the principal instigators is here.

The science plan is here, in case you missed the link above.

Download an overview presentation here.

A more general overview is also provided through these many media outlets, including: BBC; Telegraph; Guardian, Tert.

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Welcome

Hello! Welcome! This is the Cryosphere! That means all things cold and icy, and here we are going to keep you up-to-date with some of the most interesting cold climate research and goings-ons in the polar and alpine regions of Planet Earth.

We’ll cover everything from sea ice to palaeo-nunataks, and snow cover to winter migrations - if it’s interesting and somehow related to the cold then you’ll find it here. 

There’ll be a focus on the latest articles from research journals, but we’ll also add plenty of background information about ongoing and upcoming research projects, as well as including any interesting press releases, photographs and stories in this field.

We hope you come with us on this journey and learn to love the cryosphere just as much as we do along the way.