Subglacial hydrology at Kronebreen, Svalbard, published in The Cryosphere

The Cryosphere recently published our work on Kronebreen, a fast-flowing tidewater glacier in Svalbard (click here to see the article). The study examines subglacial hydrology and its influence on basal dynamics over the 2014 melt season, with simultaneous observations of water pressure at the bed, supraglacial lake drainage, meltwater plume activity, and glacier surface velocities. In addition, melt/runoff and hydraulic potential were modelled in order to estimate surface melt production, and the routing of meltwater at the bed. This built a nice record from which we could establish a robust, theoretical picture of how water is channeled at the bed.

One of the key findings is the difference in drainage beneath the north and south regions of the glacier terminus, which is linked to spatial variations in surface velocity. The study also shows a consistently high water pressure at the glacier bed throughout the melt season. These readings were collected from a borehole that was drilled approximately 3 km upglacier of the terminus. Borehole records from tidewater glaciers are rare but the few early studies that currently exist, including this one, suggest that bed conditions at tidewater glaciers are persistently pressurised, with a high hydraulic base-level that permits fast flow.

The Cryosphere Kronebreen site map figure

Figure 1 from the TC paper: The site map of Kronebreen, along with the location of the three groups of supraglacial lakes (C1, C2 and C3) that filled and drained during the 2014 melt season. These lakes were monitored by seven time-lapse cameras, which were installed on the rock outcrops surrounding the glacier tongue (denoted by the orange numbered locations). These lakes drained sequentially in an upglacier fashion, similar to the speed-up event at the beginning of the melt season. The starred location is where the borehole was drilled and the pressure sensor was installed.

The Cryosphere Kronebreen maps

Figure 5 from the TC paper: Sequential velocity maps (left) and velocity change maps (right) of Kronebreen, derived from TerraSAR-X imagery. The south region of the glacier tongue is faster flowing than the north region throughout the melt season. We argue that this reflects a difference in drainage efficiency. An early-season speed-up event is  depicted in the velocity change maps, which originates from the terminus and propagates upglacier. Similar speed-up events occur year-on-year at Kronebreen. These may reflect changes at the terminus early in the melt season which promote longitudinal stretching, and/or reflect a seasonal hydraulic overhaul which promotes basal sliding.


Further reading

The Cryosphere paper

Other studies at Kronebreen (here and here) which show early-season speed-up events

Borehole study at a tidewater glacier in Patagonia 

 

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What is going on at Tunabreen?

Tunabreen is a tidewater glacier in Svalbard that has recently been displaying some exciting activity. It is known as a surge-type glacier, with discrete periods where it flows markedly faster and slower. Tunabreen entered a fast-flowing phase in December 2016, which is ongoing at the time of writing. The nature of this fast-flowing phase is atypical for Tunabreen though, throwing into question whether this phase is associated with surge dynamics. What is going on at Tunabreen?!

Tunabreen is an ocean-terminating glacier on the west coast of Svalbard. This glacier is particularly special because of its unique set of dynamics. A large number of the glaciers in Svalbard are known as surge-type glaciers. A surge-type glacier undergoes periods of fast-flow followed by very slow, inactive phases. The nature of this surging pattern is due to the glacier’s inefficiency in transferring mass from its upper regions to its terminus (Sevestre and Benn, 2015). It is an internally-driven process. The trigger of this process is unrelated to external influences (i.e. changes in air temperature, ocean temperature, and precipitation).

Time-lapse at Tunabreen using one image per day

Time-lapse images from the front of Tunabreen. This glacier terminates into a large fjord called Tempelfjorden, hence it is referred to as a marine-terminating glacier. This time-lapse image sequence was constructed using one image per day between July-August 2016. This work is part of Calving Rates and Impact On Sea level (CRIOS) project at UNIS.

Tunabreen is one of few glaciers in Svalbard to have been observed to undergo repeated surge cycles. It has surged in 1870, 1930, 1971, and between 2002-2005. We know these surges happened because each surge phase left a pronounced ridge on the seabed which defines the surge extent (Flink et al., 2015). As these surges have been spaced 30-60 years apart, the next surge was not expected for quite a while (at least until 2030).

Tunabreen was a very slow-moving glacier between 2005 and 2016, flowing between 0.1-0.4 metres per day (m/day). These velocities were largely derived from sequential satellite imagery. Distinct glacial features were tracked from image to image to determine surface velocities on the glacier. The highest velocities (0.4 m/day) were limited to the terminus area, with very little movement (0.1 m/day) in the upper section of the glacier tongue. It was often difficult to track glacial features from image to image because the glacier was moving so slowly.

A marked speed-up was initially observed at Tunabreen in December 2016. The entire glacier tongue suddenly flowed faster. The terminus flowed >3 m/day and velocities in the upper section increased to 0.3-2.0 m/day. This speed-up continues at the time of writing this blog post (March 2017). It is a dramatic difference from the months and years prior to this event. 

Speed-up at Tunabreen. Source: St Andrews Glaciology.

The speed-up at Tunabreen shown from feature-tracking through TerraSAR-X satellite images (from Adrian Luckman, Swansea University). Luckman also tweeted two images from this sequence here which nicely show the difference between 2015 and 2016. Source: St Andrews Glaciology.

So, is this a surge? is the question on everyone’s lips now. In short, we don’t know at the moment and this is a difficult question to answer with the short amount of time that we have witnessed these changes at Tunabreen. At the time of writing, there are 4 key observations that need to be considered:

  1. The timing of this speed-up coincides with record-high temperatures and precipitation for a winter season in Svalbard (as stated in this article by Chris Borstad, a glaciologist at UNIS). This could have had a significant influence on the presence of water at the bed of the glacier, which is understood to lubricate the interface between the ice and the underlying bedrock. This, in turn, promotes sliding and may also cause the glacier to flow faster.
  2. This winter, sea ice did not form in Tempelfjorden and the fjord area directly adjacent to the glacier front. Sea ice and melange is understood to provide a back-stress against the front of a glacier. This acts as an opposing force to ice flow. Without the presence of sea ice, this opposing force is absent at the front of Tunabreen. Lack of sea ice was also observed in the winter of 2015 (as noted here in a previous blog post).
  3. The spatial pattern of this speed-up propagated in an upward fashion i.e. an increase in velocity first occurred at the front of the glacier, with subsequent velocity changes progressing up the glacier tongue. The abundance of crevasses on the glacier surface has increased, with the crevasse field extending much further up the glacier tongue than previously. Also, the terminus has advanced roughly 400 m since December 2016, as shown from the sequence of Sentinel images tweeted by Adrian Luckman (and displayed in a post by St. Andrews Glaciology). These observations are indicative of surging dynamics, as stated by Sevestre and Benn (2015).
  4. This speed-up has occurred 12 years after the previous surge (2002-2005). Surges at Tunabreen have previously been spaced 30-60 years apart from one another. The next surge was not expected until at least 2030. If this speed-up is associated with surge dynamics then it has occurred much earlier than anticipated.
Tempelfjorden. This year we unfortunately could not visit Tempelfjorden and Tunabreen glacier with the students because of the lack of sea ice. Sea ice normally forms in Tempelfjorden up to the ice front over the winter, but this year it has not formed. This also happened in 2006 and 2012. For the first time ever though, there is no sea ice directly in front of Tunabreen, which will have massive repercussions for the glacier's dynamics

Tempelfjorden in March 2015. Sea ice normally forms in Tempelfjorden up to the ice front over the winter, but it did not form in 2015 and 2016. This also happened in 2006 and 2012. As well as having large implications for the dynamics of Tunabreen, this has also impacted on snow scooter routes across Svalbard. The sea ice in Tempelfjorden has previously been used as a major scooter route for tourist groups and for transporting goods.

These observations can be used as arguments for and against this speed-up being associated with surge dynamics. Whilst the behaviour of the glacier indicates that this may be associated with surge dynamics, there have also been significant changes in external factors which could have played a crucial role in this speed-up. It is important to continue monitoring changes to better understand the processes behind the abnormal behaviour at Tunabreen. It will be interesting to see if this speed-up is sustained through the spring of 2017, and to see how much the terminus will continue to advance into Tempelfjorden. One thing is for certain: all eyes will be on Tunabreen and what it does next!

Tunabreen in March 2017

The front of Tunabreen in March 2017. I was lucky enough to visit Tunabreen earlier this month as part of the Glaciology course that runs at UNIS each year. It was incredible to see this glacier again. We have time-lapse cameras positioned on the mountain ridge (Tunafjell) that is visible in this picture. Hopefully they will give us some insight into the dynamics associated with this speed-up.


Further Reading

St. Andrews Glaciology blog: Unexpected ‘surge’ of a Svalbard tidewater glacier

UNIS post by Chris Borstad on the changes at Tunabreen

Sevestre and Benn (2015) – A comprehensive study on surge-type glaciers and their distribution around the world.

Flink et al. (2015) – Past surge extents at Tunabreen determined by topographic features on the sea bed, derived from multibeam-bathymetric surveying over Tempelfjorden.

Tweets by Adrian Luckman showing the speed-up from TerraSAR-X imagery and Sentinel imagery

Using meltwater plumes to infer subglacial hydrology at tidewater glaciers

PhD update: January 2017. Meltwater plumes are the upwelling of fresh water in front of a tidewater glacier. These are known to influence submarine melt rates, which are suggested to have a significant impact on the calving rate of glaciers that terminate in sea water. Recent work has suggested that meltwater plumes can also be used to infer the subglacial hydrology at the front of a glacier.

At land-terminating glaciers, water is evacuated via flow outlets which form large rivers on the adjacent land. It is therefore relatively straightforward to measure the amount of water leaving the glacial system. Things are a bit more complicated at glaciers which terminate in water (i.e. a fjord, sea, or ocean). Fresh water exits from the glacier at depth and interacts with the salty seawater. The fresh water moves upwards due to the density difference between freshwater and saltwater, forming a turbulent column of mixing water. This is a meltwater plume (and can also be referred to as a ‘submarine plume’, or simply just a ‘plume’).

An example of a meltwater plume at Tunabreen, a tidewater glacier in Svalbard

An example of a surfacing meltwater plume at Tunabreen, a tidewater glacier in Svalbard. Note the distinctive shape and the dark colour (indicating sediment content) of the surface expression.

The freshwater in a meltwater plume will continue to flow up through the water column and entrain surrounding saltwater until it is thoroughly mixed (i.e. there is no difference in the density between the plume and the surrounding water). At this point, a meltwater plume will reach its neutral buoyancy and the water will cease flowing upwards and flow horizontally away from the glacier front.

A meltwater plume can reach the sea surface if the neutral buoyancy exceeds the depth of the fjord. The surface expression of a meltwater plume is normally very distinctive, distinguished by its sediment-laden colour and turbulent flow away from the glacier. We have lovely images of meltwater plume activity at Tunabreen, a tidewater glacier in Svalbard, showing a surfacing plume which has entrained very rich red/brown sediment.

The neutral buoyancy point of a meltwater plume is influenced by a number of factors:

  1. The temperature/density difference between the freshwater in the plume and the surrounding saltwater
  2. The geometry of the fjord, such as how deep it is
  3. The stratification of the surrounding saltwater
  4. The rate at which meltwater is exiting the glacier (also referred to as discharge)

The first three of these listed influences undergo relatively little change compared to discharge over short time-scales (e.g. a summer season). Assuming this, the activity of a meltwater plume can be used as a signal for the rate at which meltwater is exiting a glacier over the course of a melt season.

Meltwater typically exits into a fjord/sea/ocean at the bed of a glacier. The meltwater can either be directed through a given number of big channels or a series of intricate, small cavities. Channels can typically accommodate large volumes of meltwater, hence they are known as an efficient drainage system. Linked cavities are not as effective at transporting meltwater and tend to hold water at the bed for much longer durations, so they are aptly referred to as an inefficient drainage system.

Kronebreen (centre) viewed from the west. Kronebreen shares its southern (right) margin with Kongsvegen, a slow-moving surge-type glacier that has been fairly inactive for the past couple of years. The glacier adjacent to Kronebreen, separated by the mountain Collethøgda (left), is called Kongsbreen. Kongsbreen has been retreating from the fjord onto land since approximately 2014 (September 2016)

A meltwater plume at the front of Kronebreen, a fast-flowing tidewater glacier in Svalbard. The surfacing plume  is situated on the north side of the plume (left side of the terminus in this image). This plume entrains sediment which gives it a red/brown colour. A plume also surfaced intermittently on the south side of the terminus during the melt season of 2014 (not pictured here). Photo taken: September 2016.

Timeline of surfacing plume activity at Kronebreen, Svalbard, monitored from time-lapse imagery. Plumes P1, P2 and P3 were present at the north side of the terminus, with P1 being active for the entire monitoring period (gaps are where there was no visibility in the images). Plume P4 surfaced at the south side of the terminus, showing intermittent activity throughout the melt season.

Timeline of surfacing plume activity at Kronebreen, Svalbard, monitored from time-lapse imagery. Activity began on the 23 June and continued through till the end of September. Plumes P1, P2 and P3 were present at the north side of the terminus. P1 (pictured in the above image) was active for the entire monitoring period (gaps are where there was no visibility in the time-lapse imagery). Plume P4 surfaced at the south side of the terminus, showing intermittent activity throughout the melt season.

An efficient drainage system can quickly channel a large volume of meltwater into the adjacent sea water. It is therefore likely that the neutral buoyancy of a meltwater plume from an efficient drainage system can exceed the depth of the fjord, so the plume will surface and will be visible. An inefficient drainage system is much more limited in the rate at which it can deliver meltwater into the adjacent sea water. It is therefore likely that the neutral buoyancy of a meltwater plume from an inefficient drainage system will be at depth, so the plume will not surface and will not be visible. We can thus infer what type of drainage system is present at the front of a glacier by monitoring meltwater plume activity over short durations.

We have been monitoring meltwater plume activity at the front of Kronebreen, a fast-flowing tidewater glacier in Svalbard. Two sets of plumes were present over the 2014 melt season, on the north and south side of the terminus. It is assumed here that a meltwater plume is likely to surface in the fjord if a channel is active based on the known fjord depth (∼80 m) and modelled runoff outputs. The set of plumes on the north side of the terminus persistently surfaced throughout the melt season, whereas the plume on the south side only surfaced intermittently.

A plume may not be able to consistently surface because meltwater is not leaving the glacier through a stable efficient drainage system. This could suggest that two different drainage systems preside at the north and south side of the glacier – a stable efficient drainage system on the north side, and an unstable system that switches between efficient and inefficient drainage on the south side.

Velocity map of Kronebreen over an 11-day period in April 2014 (Luckman et al., 2015)

A velocity map of Kronebreen over an 11-day period in April 2014 (Luckman et al., 2015). These velocities are derived from feature tracking between image pairs, and these images are TerraSAR-X satellite images. Higher surface velocities are present at the central/south side of the terminus compared to the north side. This is possibly related to a difference in subglacial drainage beneath these two regions. Source: UNIS.

In this situation, you would expect to see other differences between the north and south side of the terminus such as surface velocity. A large amount of subglacial meltwater is in contact with the bed in an inefficient drainage system, which enhances lubrication at the bed and promotes ice sliding. In an efficient drainage system, the water is channelled through a discrete area of the glacier and thus there is less basal lubrication as a smaller amount is in contact with the bed.

Surface velocities over the 2014 melt season show a distinct difference between the north and south side of the glacier terminus – the south is much faster flowing than the north, with the south exceeding velocities of 4 metres per day whilst the north remains relatively slow (see an example velocity map above). It is likely that a difference in drainage efficiency could facilitate this difference in surface velocities. The presence of an inefficient drainage system at the south side of the glacier tongue may be promoting faster velocities.

This idea is being further explored with additional datasets to better understand glacier hydrology and dynamics. The main take-home message from this post is that meltwater plume activity could be a reliable signal for meltwater outflow. This activity can be effectively monitored using time-lapse photography. Observations of plume activity can help us to diagnose the nature of subglacial drainage beneath tidewater glaciers, which is not accessible for direct measurements at this time. Kronebreen appears to have two different drainage systems active near the glacier terminus, as reflected in the differing plume activity, and this could be facilitating fast velocities in discrete areas of the glacier.


Further reading

Slater et al., 2017 – A newly-published study looked at meltwater plume activity at Kangiata Nunata Sermia (KNS) in Southwest Greenland using an in-situ time-lapse camera. They predicted from model simulations that a meltwater plume from a single channel should be able to surface in the adjacent fjord water, knowing the rate of discharge through the drainage system. However, the time-lapse imagery showed that the meltwater plume was only visible for brief periods throughout a melt season (May to September 2009). They argued that a plume was not consistently surfacing because meltwater may not leaving the glacier through a stable efficient drainage system. An efficient drainage system may not be able to persist at the front of KNS because it could be repeatedly disrupted by basal deformation, which is facilitated by the fast-flowing nature of the glacier. This paper has been neatly summarised by ice2ice.

Time-lapse sequences from Kronebreen. Note the visible plume activity seen from cameras 1 and 2 through the melt season.

PhD new year resolutions 2017

At the beginning of 2016, I set myself five new year resolutions specifically relating to my PhD work. Now it is the end of the year, I thought I would review these resolutions and set new ones for 2017.

2016 PhD resolution review

1 Write more – over the course of this year I have written 25 blog posts and begun the framework for each of the chapters/papers of my thesis, including a thorough review of terrestrial time-lapse photogrammetry techniques which is currently 10,000 words long. I think I got this one in the bag.

2 Publish something – not quite, but I knew that this goal would be unlikely to achieve by the end of 2016. I am currently writing the first paper from my work on the subglacial hydrology of Kronebreen, so I hope to be submitting it early in the new year.

3 Continue our time-lapse work at Kronebreen glacier in Svalbard – I went back to Svalbard in May 2016 to install the time-lapse cameras at Kronebreen and other glaciers in the Kongsfjorden area. These successfully captured images over the summer melt season and were collected in September 2016. In addition, we installed cameras on the shoreline next to Kronebreen in August 2016 to capture high-frequency time-lapse sequences of calving events. This time-lapse work is likely to continue into 2017, but I now have plenty of data to finish my PhD!

4 Attend a big conference, along with some smaller ones – this year I attended the EGU (European Geosciences Union) General Assembly in Vienna. It was a fantastic experience and I want to do more big conferences like EGU next year (for more, see here). I also attended this year’s IGS (International Glaciological Society) Nordic Branch meeting in Tromso, Norway to present some recent work from Kronebreen. Much of the content that I presented is on my blog here and it was generally well received. I talked with a lot of people about ideas and I greatly benefited from being there.

Attending the EGU General Assembly in Vienna. Despite being in Vienna with glorious sunny weather, a glaciologist will always be able to find a snowman! (April 2016)

Attending the EGU General Assembly this year. Despite being in Vienna with glorious sunny weather, a glaciologist will always be able to find a snowman! (April 2016)

5 Take a holiday – failed. Completely failed. Although I spent a week with my parents in their home in Derbyshire during the summer, I still did work. I don’t think a day has gone by this year where I haven’t at least thought about work. And I fear that this will continue into next year as I enter my final year as a PhD student with paper and thesis deadlines looming overhead. All I can hope for is that I find time to take a break and do not panic!


2017 PhD new year resolutions

1 DO NOT PANIC – leading directly on from the previous paragraph, I think next year will get quite stressful at times as there will be pressure to publish papers and ultimately submit a complete thesis. Exercise has largely kept my panic demons at bay thus far, so maybe one of my resolutions can be to find other ways to relieve stress and anxiety.

Our camera at Kongsbreen... survived and still working! (September 2016)

Re-visiting one of our camera sites in September 2016. In total, I have spent 5 months of this year in Svalbard, making it a total of 15 months (approx.) spent in Svalbard throughout the course of my PhD!

2 Write more… again – write, submit, publish, and repeat. I would also like to keep up on my blog posts, but this may not be manageable at certain points. Publishing papers is the priority for 2017.

3 Think about what to do post-PhD – I have begun thinking about what I want to do after a PhD and plans have been mentioned. It would be nice to have a more concrete plan by the end of 2017, possibly with a position ready to follow on directly after I’ve finished my PhD.

4 Try and enjoy it – easier said than done. Many have said to me that your PhD is the time at which you get the most freedom in your research as you have few other commitments. So I want to try and enjoy it, despite all the stresses. I have already lined up some trips to St. Andrews and Tromso to work with colleagues, and hopefully other fun opportunities will crop up to make this last year enjoyable.

Happy new year everyone!

 

How time-lapse photography works in the study of glacial processes

PhD update: November 2016. Whilst preparing a talk for the Geography research seminar series at the University of Manchester, I decided to include some information on time-lapse methods in glaciology to help introduce the topic.  Within this, I wanted to convey how different glacial processes were visible at specific image intervals. By constructing image sequences with various intervals, I could effectively show the processes that occur at the front of glacier and how different processes operate on different time-scales.
A time-lapse camera installed at Ultunafjella, overlooking the calving front of Tunabreen (August 2015)

One of our time-lapse cameras looking at the calving front of Tunabreen, a surge-type glacier in Svalbard. This camera remained here taking photos every 10 minutes between August 2015 and September 2016. This camera collected 24,136 images in total.

To begin with, we take a camera and place it in front of the glacier we wish to study. Using an external timer (or intervalometer), the camera can take photos at a set interval. We tend to use small intervals, such as every hour or 10 minutes, from which we can extract image sequences with longer intervals (e.g. one image per day). This camera can be left unattended for a period of time, accumulating images of the glacier. We normally leave our cameras for a summer melt season (May to September) because either the memory card is full or the camera system needs servicing. For more information on the elements of a time-lapse camera system and how it is powered, see here.

Once the camera has been collected, the images can be used to construct image sequences from which observations and photogrammetric measurements can be made. These images can either be selected manually to maintain consistency in illumination or based on time interval. Glacial processes are more apparent when illumination is consistent. This is especially beneficial for looking at longer-term processes such as glacier movement. By constructing a sequence using one image per day with consistent illumination, glacier movement is apparent along with changes in terminus position (see below).

An image sequence constructed from one photo a day at the front of Kronebreen glacier in Svalbard. This sequence spans 15 June to 26 July 2016, covering part of summer melt season. During this phase, the glacier is moving approx. 3 metres per day and calving activity is high. The muddy water in the fjord indicates that meltwater is exiting the glacier, forming a submarine plume that interacts with the saline fjord water.

An image sequence constructed from one photo a day at the front of Kronebreen glacier in Svalbard. This sequence spans 15 June to 26 July 2016, covering part of summer melt season. During this phase, the glacier is moving approx. 3 metres per day and calving activity is high. The muddy water in the fjord indicates that meltwater is exiting the glacier, forming a submarine plume that interacts with the saline fjord water.

Over a summer melt season, marked changes at Kronebreen glacier, Svalbard, are visible. As ice in the upper region flows into the fjord, ice breaks off at the front as if it is being ‘nibbled’ away. This is known as the rate of frontal ablation.  The rate of frontal ablation is higher in the area nearer to the camera due to the presence of a submarine plume, creating a small embayment in the glacier front. The region adjacent to this embayment retreats very little, leaving a preserved pinnacle in the middle of the glacier front. Its retreat rate is likely to be the result of a low frontal ablation rate controlled by a rapid delivery of ice to the region and low calving activity. This region of the glacier front also sits on a topographic high in the sea bed, which has pinned the front in a stable location.

We can examine the processes that contribute to these long-term changes in an image sequence constructed from images at shorter intervals. The sequence below is composed from images of Kronebreen every 10 minutes, covering 4 hours (real-time) in total.

One photo every 10 minutes at Kronebreen (2-6pm 1st September 2016)

An image sequence constructed from one photo every 10 minutes at the front of Kronebreen. This sequence spans 4 hours real-time (2-6pm 1st September 2016), showing conditions at the end of the summer melt season. Here, the circulation in the fjord water can be distinguished based on the movement of icebergs, migration of the submarine melt plume is seen, and calving ice from the glacier front is visible.

Compared to the previous image sequence, we see a different picture here. We no longer visibly see glacier movement or change in the glacier front position. Instead we see shorter-term processes such as migration of the submarine melt plume surface expression. This can be used as an arbitrary measure for the amount of meltwater leaving the glacier. We can also observe icebergs moving in the fjord which can be tracked to indicate patterns of small-scale fjord circulation. This can be especially useful for examining submarine melt, specifically how the fjord water interacts with the front of the glacier.

We can isolated events with even shorter interval image sequences. Over the past year, we have been experimenting with high-frequency time-lapse methods, capturing one image every three seconds for short periods at Kronebreen. Image sequences constructed from one image every three seconds can look similar to video, better showing processes in a high level of detail. This has been especially useful for looking at individual calving events and the study of calving mechanisms.

Large calving event at Kronebreen (September 2015), with ice originating from above and below the waterline. Iceberg approx. 100m wide, 50m high (above waterline only)

An image sequence constructed from one photo every three seconds, showing a large calving event at Kronebreen. This sequence covers two minutes real time at the end of the summer melt season 2015 (00.18 to 00.20).The iceberg that breaks off is approx. 100m wide, 50m high (above waterline only).

Above is an example of a large calving event at Kronebreen at the end of the summer melt season 2015. It is visible to distinguish that this calving event is the result of a complete failure through the ice column, with ice breaking off from above and below the waterline. Initial failure at the top of the ice face causes a rotational break-off of the ice below this, which is likely to have been encouraged by a pre-existing weakness in the ice column such as a small crack or crevasse.

Hopefully with these sequences I have illustrated that different sets of glacial processes work on different timescales. One of the main advantages of time-lapse photography and photogrammetry techniques is that we can adjust the interval rate to look at the process we wish to examine, making it much more flexible than other imagery acquisition. We hope that time-lapse techniques will continue to be used in the study of glacial environments. It is likely that with the ongoing development of camera technology, there will soon be more advantages to using time-lapse photography and photogrammetry.

PhD Update: October 2016

It is known that supraglacial lakes on the surface of a glacier fill and drain over the course of a summer melt season. Lake observations from time-lapse photography at Kronebreen glacier in Svalbard show possible links between their drainage and changes at the glacier bed. This month I have been further investigating these lakes using satellite imagery and other data to find that these lakes have formed and drained in similar positions for at least 30 years, indicating that the subglacial environment is relatively consistent year-on-year.

Time-lapse images at Kronebreen show lake drainage at the end of June in both 2014 and 2015. These lakes have a maximum surface area of 18,000 sq m and appear to fill and drain simultaneously, sometimes appearing to be a brown, sediment-heavy colour suggesting that they are directly connected to the glacier bed.

Supraglacial lakes filling and draining in the upper section of Kronebreen glacier, Svalbard. The sequence covers June to July 2015, one image per day.

Supraglacial lakes filling and draining in the upper section of Kronebreen glacier, Svalbard. The sequence covers June to July 2015, one image per day.

These lakes were tracked through time based on pixel intensity and then geo-rectified using the camera position, a three-dimensional representation of the landscape (DEM) and ground control points (GCPs) to map them in real world coordinates. For more on the details of how this method works, see an earlier post here. The three sets of lakes tracked from the 2014 sequence have an upglacier pattern of drainage – the lower lakes fill and drain first, followed by the upper glacier lakes. As it is likely that these lakes are connected to the glacier bed, it is possible that their pattern of drainage show an upglacier-propagating flushing event at the bed. A trigger causes subglacial meltwater near the glacier front to drain which subsequently draws down meltwater from further upglacier, draining the lower surface lakes before the upglacier lakes.

Surface lakes on Kronebreen in the 2014 summer melt season

Surface lakes on Kronebreen in the 2014 summer melt season (the red line indicates the 2014 terminus position). These lakes were mapped from time-lapse imagery acquired from two camera positioned on Collethogda and Garwoodtoppen, the two outcrops to the north and south of the glacier tongue. The lakes are automatically detected based on the pixel intensity in the image and mapped in the image plane. Then the shapes are geo-rectified to place them in real world coordinates. Base map supplied freely by Norsk Polarinstitutt.

Surface lake area tracked through the Kronebreen time-lapse image sequence from 2014.

Surface lake area tracked through the Kronebreen time-lapse image sequence from summer 2014. Here, automatically detected lakes are determined from images every half hour (apart from images with poor illumination or cloud cover). There is slight flickering at the beginning of the sequence when the lakes are at their largest due to changing illumination conditions, but generally the automated detection shows the rapid drainage. After the drainage, the lakes appear to shift upwards (i.e. perpendicular to the ice flow from right to left). This signifies that a significant surface lowering event has taken place, with the lowering appearing as movement towards the time-lapse camera. This supports the idea of a upglacier progression of drainage, with the glacier surface lowering as the system is no longer hydraulically jacked.

As we only have images of these lakes from 2014 and 2015, I had a look at archived Landsat satellite imagery of the area to see if these lakes appear in similar places in earlier years. Overall, I found that lakes consistently appear year-on-year around the same time in the same places, at least back to 1986, which is 30 years ago. From here, we are working on acquiring more satellite imagery  to further investigate whether these lakes are consistent and also whether there are additional lakes in other areas on the glacier tongue. Initial assessment shows that there are other lakes nearer to the terminus that appear infrequently, suggesting that the subglacial system is dynamic and not as consistently configured as we first thought.

Landsat image of Kronebreen from 23rd July 1990, showing surface lakes that appear in a similar region year-on-year.

Landsat image of Kronebreen from 23rd July 1990, showing surface lakes that appear in a similar region year-on-year. Landsat imagery from 2011, 2001, 2000, 1990 and 1986 (i.e. all years without cloud cover or poor imagery) all showed lake formation and drainage in the same area. Landsat imagery freely accessed from the USGS LandsatLook Viewer.

I presented this work at the International Glaciological Society (IGS) Nordic Branch Meeting at the end of this month, which was held at the Norsk Polarinstitutt in Tromsø. Generally the presentation went really well, probably one of the best presentations I have ever done! There were a number of people at the conference working on Kronebreen, so it was especially helpful to see what they were doing and have input from them. We also had a lot of discussions more generally about Kronebreen and the techniques that we are using to acquire data from time-lapse imagery. The conference was very well organised and a great success so I would like to say thank you to those involved in making it happen.

PhD Update: September 2016

I have been in Svalbard (again) for most of September, collecting images from our 14 time-lapse cameras that we have based in Kongsfjorden and Tempelfjorden. We haven’t seen these cameras since May 2016 (Kongsfjorden cameras) and August 2015 (Tempelfjorden cameras) so it was quite nerve-racking to go back and see if everything had worked. We had a couple of disappointments but generally the retrieval was a success, with approximately 130,000 photos collected in total.

Ten time-lapse cameras were deployed in Kongsfjorden last May (click here for more info on the deployment). Eight of these were installed on Collethøgda, overlooking Kronebreen, a fast-flowing marine-terminating glacier at the end of the fjord.  It is hoped that the close array of images from these cameras can be used to generate three-dimensional time-lapse sequences using a technique called Structure-from-Motion (SfM) which uses images from multiple angles to generate 3D point clouds of a target.

The other two cameras were installed by Kongsbreen and Kongsvegen, the two glaciers adjacent to Kronebreen. The data from these cameras form part of a longer-term project to monitor glaciers in the Kongsfjorden area. It was of particular importance to the influence of submarine melting on glacial retreat in this area.

Our camera at Kongsbreen... survived and still working! (September 2016)

Our camera at Kongsbreen… survived and still working! When were first started installing cameras in Svalbard, we would bolt them into the bedrock and use guide wires to stabilise them. Over time we have learnt that building cairns around the tripod legs is just as effective and takes much less time. We had a particularly long time around this camera site in May to build a large cairn… and do some sunbathing.

Due to bad weather, it proved difficult to access the camera sites and were limited to only two days of helicopter time to retrieve data. We had hoped to have enough time to survey and maintain each of the cameras so that they could run over the winter season, but alas! that is the beauty of fieldwork – you have to work with the weather you have. We managed to retrieve all of the memory cards from the cameras in the end, but couldn’t complete the camera surveying.

Previously we had deployed 7 time-lapse cameras in 2014 and 8 cameras in 2015, so we knew we were being ambitious with 10. In total, 6 worked through the entire season collecting images either every 10 minutes or every 30 minutes. We have had better success in the past (5/7 in 2014 and 6/8 in 2015) so we were a little disappointed that we weren’t able to beat our personal best! All of the problems were related to the power supply – temperamental solar controllers did not recharge the batteries from the solar panels, and there were poor connections in the camera boxes that had developed over the duration in the field.

Overall, 48 000 images were collected from the cameras at Kongsfjorden – we have a good sequence from Kongsbreen showing multiple submarine plumes creating inlets in the ice front, good coverage over the front of Kronebreen to look at calving activity and surface velocities over the summer season, and a good sample dataset to begin looking at constructing 3D SfM time-lapse sequences.

As the weather was so limiting on our helicopter time, we also accessed the shoreline next to Kronebreen by boat, where we set up our 4K video camera (left over from the CalvingSEIS project last month) to record calving activity. We recorded an 11-hour 4K video sequence which provides some awesome close-ups on isolated calving events such as the one in the video below.

This work is so important to ensure the safety of tourists and scientists alike. Currently the minimum safe distance from a calving front is 200 metres, but accidents do still happen. The distance that ice can be thrown from a calving event is thought to be controlled by the height of the calving origin and the impact with the water. With this in mind, the minimum safe distance should be different for each calving glacier front in Svalbard. We hope that we can track projectiles from such calving events in this sequence to re-assess the distance that boats should be from calving  glacier fronts in Svalbard. It is likely that glacier calving fronts require different categories of risk based on calving activity (frequency and volume), ice cliff height and ocean temperature.

Preparing for our helicopter ride over to Tunabreen (September 2016)

Preparing for our helicopter ride over to Tunabreen. Mats (pilot, left) is ‘composing himself for the flight’ whilst Harold (technician, centre) is doing routine checks on the helicopter. Chris Borstad (UNIS, right) joined us on this trip to check the time-lapse cameras and survey the glacier surface using a laser scanner to look at crevasse propagation rates in the upper section of the glacier tongue.

After finishing in Kongsfjorden, we flew back from Ny Ålesund to Longyearbyen and got a lucky opportunity to fly to Tunabreen and collect data from 4 time-lapse cameras that have been there for over a year now (see here for information on the installations and other work in this area). They were meant to be collected in September 2015, but the plan had to be abandoned due to poor weather. We also planned to retrieve them at the beginning of this year, but the warm winter had left Tempelfjorden first without sea ice for snow scooter transport and then with too much sea ice for the boat season.

After some manic negotiations with the Sysselmannen (Governor of Svalbard), we got permission for two helicopter landings on Ultunafjell, where the time-lapse cameras were installed. When flying over, it was impressive to see how much the calving front has changed, even over the past couple of months. Normally there is one consistent submarine plume at the west side of the calving front (near to the camera in the image below) that is active throughout the melt season, creating an inlet in the calving front. This year though, it appears that a second strong plume at the east side of the calving front  has created a marked inlet (see far inlet in the image below). The upper section of the glacier tongue has also changed, with the crevasse field extending much further up-glacier than in previous years. Both the growth of the crevasse field and the change in submarine plume activity could indicate a change in the subglacial conditions at Tunabreen.

The calving front of Tunabreen (September 2016)

The calving front of Tunabreen. The muddy water in front of the glacier is where the submarine plume has been strong enough to entrain sediment from the sea bed to the surface through turbulent mixing of freshwater and seawater. This promotes melting of the ice below the waterline, which has created two inlets in the calving front this year – the first is closest to the camera with a very visible plume adjacent, the second is the marked bay on the far side.

Three of the cameras on Ultunafjell were entrained on the calving front and lower section of Tunabreen, all of which had captured images till now. Unfortunately, due to unknown circumstances, two of the cameras were taking images that were out of focus when they came back on in the spring (after hibernating over the winter). It is likely that either someone has been up there, taken a look at the cameras and accidentally knocked the focusing ring on the lenses; or that high winds caused vibrations in the camera box that gradually shifted the focusing ring.

It’s a new set of circumstances for us anyway! From now on, we will fix the focusing ring in position by taping each lens. Luckily, one camera did not experience focus drift so we have three sets of images from August till November 2015, and one set of images from May to September 2016. This is plenty to work with and will give us a nice dataset to extract velocities and calving rate from.

The fourth camera is positioned further up the ridge, looking at the upper section of the glacier tongue where crevasses are begin to form and propagate. It was installed to monitor an array of strain meters that were set out on the glacier surface, measuring the rate at which crevasses were opening and the rate of longitudinal stretching. The relative distance between each strain meter in the images can be used to ensure that the strain meters are accurately measuring changes at the glacier surface. This camera has captured images every 10 minutes from August 2015 till September 2016, which is a great success. The camera has been surveyed and will now continue to take photos through the rest of 2016 into 2017, providing a complimentary dataset for Chris Borstad and the University Centre in Svalbard (UNIS) to use with other on-glacier instruments.

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Sample image from the time-lapse sequence at the upper section of Tunabreen. These images monitor an area that is 497.6 m x 331.7 m. The strain meters are difficult to find in this image, with each strain meter box only represented as a 2 x 2 pixel square!

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A close-up of the strain meters. The people in the image are myself and Doug Benn, part of the team that installed the seven strain meters on Tunabreen in August 2015.

So, in total, we have collected approximately 130,000 images in this month, providing us with a third consecutive year of time-lapse data at Kronebreen, and new insights into processes at Tunabreen and Kongsbreen. From these images, we should be able to extract a record of surface velocities, calving rate, submarine plume activity and crevasse propagation from each glacier. I am now back from Svalbard for this rest of this year to begin processing this data and enjoy Edinburgh in the autumn/winter season.

A tame ptarmigan at Tunabreen (September 2016)

A ptarmigan at Tunabreen. This little guy was walking along with me to visit our third time-lapse camera. Ptarmigans often nest around our cameras at both Tunabreen and Kronebreen – this makes for lovely images, but is a hinderance for photogrammetry processing!


With thanks to the following for making this fieldwork possible: Richard Delf (University of Edinburgh), Jack Kohler (NP), Chris Borstad (UNIS), our helicopter pilots Mats Larsen and Harold Edorsen, our skipper Wojtek Moskal,  and all in the NP Sverdrup station in Ny Ålesund.