A dummies guide to… my PhD thesis on glacier dynamics

Recently my PhD thesis was made available online through the Edinburgh Research Archive, titled ‘Dynamical change at tidewater glaciers examined using time-lapse photogrammetry’. The thesis is 342 pages long which would be a marathon to get through for anyone, so here is a short synthesis.


In a nutshell

Title: Dynamical change at tidewater glaciers examined using time-lapse photogrammetry

Goal: To understand processes linked to dynamical change at tidewater glaciers.

Three main aims:
1. Examine subglacial hydrology and its influence on glacier dynamics at Kronebreen, a fast-flowing, tidewater glacier in Svalbard
2. Investigate controls on terminus conditions and calving processes at Tunabreen, a surge-type, tidewater glacier in Svalbard
3. Develop a suite of photogrammetry tools for obtaining measurements from oblique time-lapse imagery

Techniques used: Monoscopic time-lapse photogrammetry, hot water borehole drilling, bathymetry surveying, satellite feature-tracking, passive seismic monitoring, melt/runoff modelling


Acquiring data from the field

Me at camera site 8b, Kronebreen, Svalbard (May 2015)

An example of one of our time-lapse cameras, installed at Kronebreen

High-detail monitoring of glacier termini is challenging. We decided to employ time-lapse photogrammetry as our primary technique in this study given that it can provide high-resolution data acquisition (e.g. 1 image every 3 seconds, over 24 hours) as well as appropriate acquisition rates for longer-term monitoring where needed (e.g. 1 image every hour over the course of a melt season). Therefore we can acquire different temporal frequencies depending on which aspects of the glacier system we want to examine.

Between 2014 and 2017, we deployed 7 – 14 time-lapse cameras at two glaciers in Svalbard (Kronebreen and Tunabreen) to monitor various aspects of the glacial system – ice flow, terminus retreat, supraglacial lake drainage, meltwater plumes, and local fjord circulation. We combined the findings from these images with other datasets (e.g. borehole measurements, bathymetry surveys) in order to examine dynamical change at a high level of detail.


Finding #1: Spatial variation in Kronebreen’s ice flow is primarily controlled by meltwater routing at the glacier bed

From our time-lapse images over the 2014 melt season, along with borehole data analysis, melt/runoff modelling and hydropotential modelling, we found that spatial variations in ice flow at Kronebreen were primarily controlled by the location of subglacial meltwater channels.

Efficiency in subglacial water evacuation varied between the north and south regions of the glacier tongue, with the north channel configuration draining a large proportion of the glacier catchment through persistent channels, as indicated by hydropotential modelling. Channel configurations beneath the south region of the terminus were vastly different, with rapid hydrological changes evident and cyclic ‘pulsing’ suggested from the observed meltwater plume activity.

These differences in subglacial hydrology are reflected in ice flow, with faster velocities experienced in the south region of the glacier, facilitated by enhanced basal lubrication and sliding. Two speed-up events were observed at the beginning of the 2014 melt season, the second being of significant importance given that it occurred at the end of the melt season and enabled fast flow through the winter season. It is suggested that this event was caused by an abnormal high rainfall event which overwhelmed an inefficient hydrological regime entering its winter phase. This phenomena highlights that the timing of rainfall events at tidewater glaciers is fundamental to their impact on ice flow.

The Cryosphere Kronebreen maps

Sequential velocity maps (left) and velocity change maps (right) of Kronebreen showing the first of two speed-up events experienced during the 2014 melt season.


Finding #2: Terminus stability is inherently linked to both atmospheric and oceanic variability at Tunabreen. In particular, calving activity is primarily facilitated by melt-undercutting

Terminus conditions at Tunabreen were examined on two differing temporal scales:

  1. Over a one month period in peak melt season using time-lapse images acquired every 10 minutes
  2. Over a 28-hour period in August 2015 using time-lapse images acquired every 3 seconds

Over the one-month observation period, the terminus retreated 73.3 metres, with an average retreat rate of 1.83 metres per day. The frontal ablation rate fluctuated between 0 and 8.85 metres per day, and 1820 calving events were recorded of which 115 events were simultaneously detected from passive seismic signatures recorded in Longyearbyen. Overall, strong links were found between terminus position changes and both sea surface temperature and air temperature, suggesting that atmospheric forcing plays a larger role in terminus stability than previously considered.

Calving events at Tunabreen over a 30-hour period in August 2015, captured using high-resolution time-lapse photography (one photo every three seconds). Calving events are categorised as subaerial (i.e. ice falling from the front above the waterline), subaqueous (i.e. ice breaking off from the front beneath the waterline), both (i.e. large calving events which contain both subaerial and subaqueous originating ice) and unknown (caused by concealment or poor visibility).

Calving events at Tunabreen over a 28-hour period in August 2015, captured using high-resolution time-lapse photography (one photo every three seconds). Calving events are categorised as subaerial (i.e. ice falling from the front above the waterline), subaqueous (i.e. ice breaking off from the front beneath the waterline), both (i.e. large calving events which contain both subaerial and subaqueous originating ice) and unknown (caused by concealment or poor visibility)

Calving activity at Tunabreen consists of frequent events, with 358 calving events detected from the 28-hour, high-frequency time-lapse sequence (i.e. 12.8 events per hour). The majority of these calving events (97%) occurred above the waterline despite the fact that 60-70% of the terminus is subaqueous (i.e. below the waterline). This suggests that ice loss below the waterline is dominated by submarine melting, rather than the break off of large projecting ‘ice feet’.  In addition, calving events are twice as frequent in the vicinity of the meltwater plumes, with visible undercutting (approximately 5 metres) revealed from the bathymetry side profiles. Overall, this suggests that enhanced submarine melting causes localised terminus instability at Tunabreen.


Finding #3: PyTrx is a viable Python-alternative toolbox for extracting measurements from oblique imagery of glacier environments

PyTrx velocities

An example of PyTrx’s capabilities in deriving surface velocites at Kronebreen, Svalbard. Velocities are calculated from the image using a sparse feature-tracking approach, with unique corner features identified using Shi-Tomasi corner detection and subsequently tracked using Optical Flow approximation. In this example, 50 000 points have been successfully tracked between an image pair from Kronebreen, producing a dense collection of velocity points.

Time-lapse photogrammetry is a growing method in glaciology for providing measurements from oblique sequential imagery, namely glacier velocity. When we began processing our time-lapse images, we found that there were few publicly available toolboxes for what we wanted and the range of their applications was relatively small. For this reason we decided to develop PyTrx, a Python-alternative toolbox, to process our own data and also aid the progression of glacial photogrammetry with a wider range of toolboxes.

PyTrx is an object-oriented toolbox, consisting of six scripts that can be used to obtain velocity, area and line measurements from a series of oblique images. These six scripts are:

  1. CamEnv: Handles the associated data with the camera environment, namely the Ground Control Points (GCPs), information about the camera distortion, and the camera location and pose
  2. DEM: Handles data related to the scene, or Digital Elevation Model (DEM)
  3. FileHandler: Contains functions for reading in data from files (such as image data and calibration information) and exporting output data
  4. Images: Handles the image sequence and the data associate with each individual image
  5. Measure: Handles the functionality for calculating homography, velocities, surface areas and distances from oblique imagery
  6. Utilities: Contains the functions for plotting and interpolating data

PyTrx has been used to process the data presented previously, and is freely available on GitHub with several example applications also. These examples include deriving surface velocities and meltwater plume footprints from time-lapse images of Kronebreen, and terminus profiles and calving event locations from time-lapse images of Tunabreen.


Related links

This thesis is freely available to download from the Edinburgh Research Archive

How et al. (2017) The Cryosphere – Examining the subglacial hydrology of Kronebreen and its influence on glacier dynamics 

How et al. (In Review) Annals of Glaciology – Observations of calving styles at Tunabreen and the role of submarine melting in calving dynamics

How et al. (2018) Geoscientific Instrumentation, Methods and Data Systems – Presenting the PyTrx toolbox and its capabilities with oblique imagery of glacial environments

PyTrx – PyTrx toolbox code repository, hosted on GitHub

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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 

 

Ptarmigans love time-lapse cameras!

Ptarmigan at Kronebreen 01

We have been setting up time-lapse cameras in Kongsfjorden, Svalbard since 2014 to observe glacier change over time. Ptarmigans have been known to nest by these cameras. One particular camera is their favourite! This camera was set up on a rocky outcrop called Garwoodtoppen to measure velocities over Kronebreen glacier. 

Ptarmigans at Kronebreen 02

Sometimes more than one ptarmigan will come to sit in front of this camera…

Ptarmigans at Kronebreen 03

…And we have noticed changes in their appearance through the season. Their feathers are normally white in colour over the winter and spring, but change to grey/brown in the summer. Over the course of a season (May – September), we capture roughly 20 ptarmigans in our images (out of a possible 6000 images). 

Ptarmigan at Kronebreen 04

Although these images have been useful to monitor ptarmigan activity in this area of Svalbard, they are also a bit of a nuisance for tracking glacier movement. When they are in front of the camera, they block a significant patch of the glacier that we are monitoring. Silly ptarmigans!

 

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!

 

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.