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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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!

 

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

A detailed look at the front of Kronebreen, Svalbard

Thanks to some nice boat trips this September (and a good zoom lens on my camera*), we were able to take a detailed look at the calving front of Kronebreen, a fast-flowing glacier which terminates into Kongsfjorden, an inlet on the west coast of Svalbard. Since 2011, Kronebreen has been retreating significantly faster (approx. 100m per year) and the front (where the ice meets the fjord water) has changed drastically. What is interesting is that the calving front does not appear uniform – the distinctiveness of each section indicates that different processes are active. If this intrigues you then please read on! If not, then sit back, relax, and enjoy the pictures at least!

All photos were taken on the Sony NEX-5R with the Sony E 55-210 mm f/4.3-6.3 lens and the Sony E 20 mm f/2.8 lens.

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)

Kronebreen glacier (centre) viewed from the west this September (2016). 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.

Kronebreen (‘crown glacier’) is a heavily crevassed glacier tongue fed from a large ice field called Hotledahlfonna, flowing between 1-5 metres per day into Kongsfjorden, an inlet on the west coast of Svalbard (see here for more information on Kongsfjorden and Svalbard). The front of Kronebreen is approximately 3 km, forming an impressive ice face that deposits ice into the fjord to form icebergs. This process is called calving and is one of the main processes by which ice is transferred from land to sea. For more information on Kronebreen, please refer to another post I wrote on why small glaciers are important to study here.

In many settings (such as at the large glaciers found in Greenland), the front of a glacier is a tall cliff of ice from which large sections of ice calve off. From studying the front of Kronebreen though, it is apparent that the ice face is not uniform. Certain sections of the ice front look entirely different from one another, suggesting that the controls on calving are also different. There are five sections that are particularly interesting:

Numbered sections of the calving front of Kronebreen (Landsat image from 09/07/2016, downloaded from USGS LandsatLook Viewer)

Numbered sections of the calving front of Kronebreen (Landsat image from 09/07/2016, downloaded from USGS LandsatLook Viewer)

  1. The glacier margin next to Collethøgda
  2. The retreated region around a large submarine plume that forms during the summer melt season each year (since at least 2011)
  3. The pinnacle – the middle section of glacier that is the furthermost point of the ice front
  4. The ‘traditional’ tall ice cliff at the front of the fastest-flowing section of the glacier
  5. The shared margin with Kongsvegen

1. The glacier margin next to Collethøgda

The north margin of Kronebreen. This section tends to move much slower as the ice flows against the land which generates shear stress. A lot of the land (at the foot of Collethøgda) is ice-cored - as the glacier has retreated, ice has been left isolated at the margin which becomes buried over time due to landslides and rockfalls (September 2016)

The north margin of Kronebreen. This section tends to flow much slower as the ice shears against the land from lateral drag. A lot of the land (at the foot of Collethøgda) is ice-cored – as the glacier has retreated, ice has been left isolated at the margin which is buried over time due to landslides and rockfalls from above.

A close-up of the north margin (September 2016)

A close-up of the north margin. The ice face appears broken up because it has been subject to compressive flow deformation further upstream – marginal crevasses form as the ice shears. These crevasses form weaknesses in the ice front when the ice is transferred downstream. Generally the calving activity in this margin zone is caused by exploitation of these weaknesses, producing ice falls and small collapses.


2. Region around a large submarine plume

Undercutting at the waterline exposed during low tide. Turbulence at the interface between the ice face and the fjord water causes undercutting. During low tide, this undercut section is exposed which creates a weakness in the front and promotes calving activity driven by gravitational potential energy (September 2016)

Undercutting at the waterline exposed during low tide. Turbulence at the interface between the ice face and the fjord water causes undercutting. During low tide, this undercut section is exposed which creates a weakness in the front (from the undercutting) and the ice flow marginally increases (from the reduction of hydraulic head). It is thought that there is a correlation between calving activity and tidal patterns, but it has been challenging to thoroughly test this hypothesis. This undercutting occurs over the entire front of Kronebreen, with a tidal range of roughly 1 metre (excluding spring/neap tides). Marked undercutting is noted to occur in areas where a submarine plume is active.

A significant undercut chasm located where a submarine plume emerges from consistently year on year. The submarine plume generates a marked amount of turbulence in the water column which cuts/melts the ice column beneath the waterline and causes small collapses of ice from above the waterline (September 2016)

A significant undercut chasm located where a submarine plume emerges from Kronebreen consistently year on year. In the summer melt season, meltwater is channeled through large tunnel networks in the glacier, exiting into the fjord as large bodies of freshwater. The freshwater rises as it comes into contact with the fjord as freshwater is lighter than salt water, creating a turbulent column of water that promotes melting/cutting in the adjacent ice column below the waterline. The plume is visible at the surface when it is strong enough to generate turbulence through the entire water column (click here to see a visible plume at Tunabreen in August 2015). Turbulence from the plume also can cut back into the ice column as we see at Kronebreen, forming chasms in the ice front where melt-back beneath the waterline causes small collapses above the waterline.


3. The pinnacle – the middle section of glacier that is the furthermost point of the ice front

The 'pinnacle' of the calving front at Kronebreen. The face is not the usual ice cliff you tend to see in marine-terminating settings. Instead, the calving front is composed of ice columns which look separated from above but are connected beneath the waterline (September 2016)

The ‘pinnacle’ of the calving front at Kronebreen (viewed from the north side). The face is not the usual smooth, clean-cut ice cliff you see in marine-terminating settings. Instead, the calving front is composed of ice columns which rest at different orientations to one another. Ice flow from behind the calving front is pushing these columns into the fjord, often causing these columns to calve into the fjord with rotations… and big splashes!

A close up in to the pinnacle section of the calving front. Internal collapses are common at Kronebreen, where ice behind the front collapses (September 2016)

A close up in to the pinnacle section of the calving front. Internal collapses are common at Kronebreen, where ice behind the front collapses. This has been known to form columns of ice which appear isolated from the rest of the calving front, similar to geological sea stacks. Such ice columns are attached to the rest of the front beneath the waterline.

The pinnacle, viewed from the south side of Kronebreen. The front is approx. 50 metres high in this section. For some sense of scale, see the bird perched on the top of the ice column in the centre of the image (September 2016)

The pinnacle, viewed from the south side of Kronebreen. The front is approximately 50 metres high in this section. For some sense of scale, see the bird perched on the top of the ice column in the centre of the image. It is uncertain exactly why this preserved pinnacle exists at Kronebreen. It is likely that the section is pinned to a region of the sea bed, and its shape is exaggerated by two submarine plumes which are active either side of the pinnacle.


4. The ‘traditional’ tall ice cliff at the front of the fastest-flowing section of the glacier

Tall ice cliffs at the fastest-flowing section of the glacier front at Kronebreen (September 2016)

These tall ice cliffs are a common feature of marine-terminating glaciers. The steep profile of the face is maintained by the fast delivery of ice to the front.  At Kronebreen, this part of the ice face is at the front of the fastest-flowing section, reaching velocities of 5 metres per day  in the peak summer melt season. Calving activity is infrequent here, but events are often large with failures through the entire column of ice (at least above the waterline). Click here for an example of a calving event in this area captured in September 2015.


5. The shared margin with Kongsvegen

Dirty ice at the shared margin between Kronebreen and Kongsvegen (September 2016)

At the divide between Kronebreen and Kongsvegen is a section of dirty ice. This is a lateral moraine. As Kongsvegen has flowed into the side of Kronebreen, sediment has been squeezed and thrust to the surface between these two glaciers. The layers of sediment between the ice can easily be exploited and creates weaknesses at the ice front. There are often small ice falls and collapses in this area, with few large failures.

Where Kronebreen meets Kongsvegen (September 2016)

The shared margin from above. This large section of dirty ice is the lateral moraine where Kronebreen (left) meets Kongsvegen (right). A large inlet has formed (since approx. 2014) just to the south of the lateral moraine at the front of Kongsvegen. This inlet is roughly 200 metres deeper than the rest of the calving front, thought to be the result of weaknesses at the lateral moraine. This could be the beginning of Kongsvegen’s separation from Kronebreen. Another explanation is that a large meltwater channel exits the glacier here, exploiting weaknesses in the lateral moraine to create a large channel that has promoted calving activity in the immediate vicinity. From looking at this photograph, it is apparent that part of the inlet has now retreated to land (see the two small black sediment beaches that are in the inlet). The gap between these two beaches could be the location of this channel opening.


* All photos were taken from approx. 500m from the glacier front. It is generally advised to be AT LEAST 200 METRES from the front of any calving glacier in Svalbard. Being close to calving glaciers is dangerous and could result in serious injury or even death if a calving event were to occur. See here for more information issued by the Governor of Svalbard and Norsk Polarinstitutt, or google ‘glacier calving accident’ if you want to scare yourself silly.


Further reading

AntarcticGlaciers.org article on stress and strain in glacial environments

Mauri Pelto’s AGU blog on the mutual margin of Kronebreen and Kongsvegen

Calving activity at Kronebreen by Anne Chapuis et al. (2010)

Submarine plumes in Greenland by Kristin Schild et al. (2016)

Why study Kronebreen and other small glaciers?

There are two motivations behind writing this blog post. One is to document the deployment of our time-lapse cameras for a third consecutive summer season at Kronebreen, which is a fast-flowing tidewater glacier in Svalbard. It is difficult to justify such intensive fieldwork without explaining why we are doing this research though. So the second reason for writing this is to explain why we are studying Kronebreen, and more importantly why findings from smaller glacier systems are just as significant as those from bigger catchments (i.e. Greenland and Antarctica).  The take home message from this is that the study of smaller glaciers is essential to progressing our understanding of glacier dynamics which ultimately feeds into better prediction of future sea level rise.

DISCLAIMER: All opinions are my own and I encourage discussion on the subject matter. I’m all ears!


About Kronebreen and our research

Kronebreen is a heavily crevassed, elongated glacier located in Svalbard, the Arctic archipelago that is situated to the north of Norway. The glacier flows from an expansive ice field to a fjord called Kongsfjorden, which is connected to the Atlantic Ocean. The name Kronebreen literally translates to “crown glacier”, Kongsfjorden means “king’s fjord”, and a lot of the other glaciers in the area are named along this theme – for example, the two neighbouring glaciers to Kronebreen are Kongsbreen (to the north) and Kongsvegen (to the south) which mean “king’s glacier” and “king’s road”.

Satellite imagery of Kronebreen and Kongsvegen in 2011. Where their margins converge is signified by a significant dark debris band. Note how much more crevassed Kronebreen is than Kongsvegen. Source: Google Earth.

Satellite imagery of Kronebreen and Kongsvegen in 2011. Where their margins converge is signified by a significant dark debris band. Note how Kronebreen is much more crevassed than Kongsvegen (to see this contrast in better detail click here). Source: Google Earth.

Where the front of Kronebreen meets the fjord water, a process called calving occurs. Calving is the mechanism by which ice detaches to form isolated icebergs. Calving was once considered a minor component of glacier dynamics, but is now understood to form a significant contribution to future sea level change. There are still many uncertainties concerning when and how calving at tidewater glaciers will occur in the future though, which makes it difficult to accurately predict future sea level change.

There are certain controls on calving which dictate the size of each ice piece that breaks off, and the frequency at which these events occur. Calving activity at Kronebreen is generally characterised as frequent and small (in comparison to larger glacier systems such as those found in Greenland and Antarctica). Calving has increased gradually year-on-year at Kronebreen, and the front has been retreating since the early 1900s (Nuth et al., 2012). Recent work has confidently linked this to warming of the Atlantic Ocean – Kronebreen and other glaciers in the Kongsfjorden are particularly susceptible because they are positioned close to a strong current of water (the West-Spitsbergen Current) which brings warm water from the south to the interior Arctic (Luckman et al., 2015).

Embayment forming between Kronebreen and Kongsvegen

One of our time-lapse cameras (the tiny yellow dot) looking at the front of Kronebreen and Kongsvegen glaciers.

We have been placing time-lapse cameras at Kronebreen for the past 3 years to monitor its calving activity and terminus position, along with its velocity and the presence of lakes on the glacier surface. We previously chose camera locations which produced images that adequately covered the entire glacier surface. This year we have placed our cameras much closer together, focusing on the first kilometre of the glacier front. The reasoning behind this re-shuffle is to ensure adequate overlap in the images from each camera, which we can use to attempt three-dimensional time-lapse. Using a technique called Structure-from-Motion, images taken from multiple angles can be used to form a three-dimensional model of a given object. In this case, we will produce Digital Elevation Models (DEMs), potentially every half an hour. This will give us a highly detailed look at how the front of Kronebreen changes over the summer season.

Myself and my supervisor, Nick Hulton (University of Edinburgh, University Centre in Svalbard), spent a week in Svalbard at the end of April installing our cameras, alongside researchers from Norsk Polarinstitutt who are looking more generally at changes in the Kongsfjorden area. The fieldwork was very successful and we installed 10 time-lapse cameras in total – 8 were installed at Kronebreen, and 2 were positioned at Kongsvegen and Kongsbreen. The weather was our main constraint, meaning we had to squeeze 7 of these installations into one day which took nearly 14 hours. Luckily, Svalbard is in 24-hour daylight at this time of year, which allowed us to work such long hours.

P1060518

Lining up one of our time-lapse camera systems. To generate three-dimensional time-lapse sequences, we had to be very specific about each camera placement and exactly where each camera pointed. Because of this, we dedicated a day to scouting out new sites and generating test photos which we used to produce demo Digital Elevation Models. Photo credit: Nick Hulton.


Why Kronebreen?

In my opinion, one of the biggest misconceptions in glaciology is that research on Greenland and Antarctica (i.e. ‘larger’ glacier systems) is more important than research on smaller glaciers. This is generally because the Greenland and Antarctica ice sheets are the largest contributors to future sea level rise. And yes, in a direct sense this is true, they are extremely important to study. Greenland and Antarctica hold 99% of the world’s freshwater ice and if that all vanished, sea level would rise by approximately 65 metres (IPCC, 2013). Often research on Greenland and Antarctica is published in higher-impact journals because of the direct importance of the findings. Research on smaller glaciers is just as important though, as the findings can have significant implications for larger glacier systems. It is just harder to convey this because the findings are usually limited to indirect implications.

helheim_calving_large.GIF

A big, catastrophic calving event at Helheim glacier, East Greenland, captured by a group of researchers at Swansea University in 2010. The calving event here is approximately 4 km long and the height of the ice cliff above the waterline is 100 metres. Such big calving events like this rarely occur and thus are often not observed or captured. The full video of the calving event can be viewed here. Associated research papers from this work are listed at the end of this article.

krone_big

In contrast, a small calving event at Kronebreen, Svalbard. The calving event here is approximately 50 metres high and spans 50 metres of the glacier front. Such events occur frequently at Kronebreen (approx. 1 every hour) and this is similarly observed at other smaller glaciers.

Research on calving dynamics is a good example where studies have largely focused on Greenland and Antarctica (so far). Calving activity at Greenland and Antarctic mainly consists of rare, catastrophic events, such as calving across the entire ice cliff or complete collapse of an ice shelf (e.g. Larsen B Ice Shelf, Antarctica). Obviously, these types of events have a significant impact on future glacier dynamics and sea level change. Studies have largely focused on understanding this type of calving. This trend may be because this research is still largely in its infancy. The idea that oceans interact with glacier fronts was not considered particularly important until fairly recently (Straneo et al., 2010).

At the other end of the spectrum though, calving events can also be small and frequent. This type of calving has not been as thoroughly studied as larger calving styles so far. Small calving styles are often observed at smaller glaciers which are grounded on the sea bed (i.e. the base of the glacier sits on the sea bed rather than floating). Even though these calving events do not immediately impact the surrounding environment, they do promote instabilities at glacier fronts which can cause larger events (Åström et al., 2014). Again, smaller glaciers that exhibit small calving styles may not produce direct, immediate global impacts, but they are important facilitators for bigger processes and their contribution is significant in the long run.

Landsat satellite imagery of Kronebreen and Kongsvegen from 27/04/2016, showing the significant retreat around the glaciers' conjoining margin which has formed a marked embayment (approx. 200 m deep compared to the rest of the glacier front). Source: USGS Earth Explorer.

Landsat satellite imagery of Kronebreen and Kongsvegen from April 2016, showing the significant retreat around the glaciers’ conjoining margin which has formed a marked embayment (approx. 200 m deep compared to the rest of the glacier front). Source: USGS Earth Explorer.

Kronebreen is specifically being used for this study because it is at a very unique and interesting phase, distinguished in two aspects:

1. Since the 1900s, Kronebreen has retreated year-on-year. Often the front sits in similar position for a number of years (+/- 100 m in one year) and then rapidly retreats (+/- 1000 m in one year) to a new stable position (Schellenberger et al., 2015). For a number of years now, the front of Kronebreen has been gradually retreating. We have recently observed a marked stretching and thinning of the terminus area which happened over the winter season of 2014. It is also known that the bed on which Kronebreen sits is particularly deep in places just behind the glacier front. The combination of a thin terminus and a sudden change in topography make it vulnerable to another of these rapid retreat periods. Although such retreats have often been documented, highly-detailed observations (e.g. frequent satellite images, time-lapse imagery) are seldom recorded.

2. Kronebreen is adjacent to Kongsvegen, both fed from the same ice field and sharing a lateral margin. Kongsvegen is slower-moving than Kronebreen, with considerably less calving activity. The difference between these two glacier is abundantly clear when looking from above at the presence of crevasses on their surfaces – there is a high density of crevasses on Kronebreen compared to the smooth surface of Kongsvegen. Recently there has been greater calving activity around the mutual margin, forming a marked embayment. This is likely to be the beginning of the separation of these two glaciers. Separations like this have not been documented closely because they happen rarely. With the changing climate though, it is highly probable that similar separations will occur at other glaciers around the world. By studying this one, we may be able to detect the initiation of the separation process in the future. For more on this separation, click here.

The embayment at the mutual margin between Kronebreen and Kongsvegen (May 2016). Photo credit: Nick Hulton.

The embayment at the mutual margin between Kronebreen and Kongsvegen (May 2016). Photo credit: Nick Hulton.

Time-lapse imagery acquisition is our best bet of capturing such important changes at Kronebreen. Not only do the time-lapse images offer effective visualisation of these changes, but they can also be used to extract precise, high-frequency measurements. Information on glacier velocity, calving rate, calving style, plume extent, fjord circulation patterns and surface lake estimation can be collected simultaneously. Results (and hopefully publications) will be coming from our previous years’ work soon.


The camera deployment this year would not have been possible without the support of Jack Kohler and the Norsk Polarinstitutt. Thank you Jack.


Further reading

1. This AGU blog post on the initiation of glacier separation by Mauri Pelto is a concise story of the current state of Kronebreen and Kongsvegen (published October 2015).

2. Luckman et al., 2015 is a highly detailed paper on changes in velocity and calving activity at Kronebreen since 2013, in relation to tidal level and ocean temperatures. The paper also draws in other study areas around Svalbard (Tunabreen and Aavatsmarkbreen) and finds confident links between ocean temperatures and the long-term rate of calving. Small calving activity is referred to as “frontal ablation” in an attempt to distinguish it from the large, rare, catastrophic calving styles observed at Greenland and Antarctica. By differentiating the terms, the processes behind them can also be discerned and the influence of one on the other can be better distinguished. This may be a good approach to adopt for future research into calving.

3. Åström et al., 2014 is a great paper that tentatively looks at large calving events in relation to smaller calving events, likening glacier termini to self-organised critical systems which transitions between a state of instability build-up and instability release.

4. Work associated with the time-lapse sequence from Helheim Glacier, Greenland – direct observations of a large buoyant flexure calving event (Murray et al., 2015), changes in glacier surface elevation and basal crevasse propagation before the onset of this kind of calving (James et al., 2015), and modelling buoyant flexure calving (Wagner et al., 2016).


Svalbard photography (Feb-Mar 2016)

For the past month I have been in Svalbard, demonstrating on the Glaciology course (AG-325/825) at the University Centre in Svalbard (UNIS). The course is aimed at Masters and PhD students who want a taste of the Arctic, consisting of four weeks of glaciology lectures  and weekly excursions to glaciers in the local area. I have been supporting the logistical side of the weekly excursions, with the odd bit of teaching here and there. The course ran very successfully and everyone seemed to thoroughly enjoy themselves. Here are a few photos from the course…

The sun rising in Rindersbukta. The sun first rose after the dark season in early March and has created beautiful lighting for the rest of the month (March 2016)

The sun rising over Rindersbukta, taken during the third week of the course. The sun first rose after the dark season in early March and has created beautiful lighting for the rest of the month…

...Like this. This was taken on the way back from our trip to Mohnbukta in the final week of the course.

…Like this. This was taken on the way back from our trip to Mohnbukta in the final week of the course.

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. This year we unfortunately could not visit Tempelfjorden and Tunabreen glacier with the students because of the lack of sea ice (this picture was taken on a rekkie trip to examine the conditions for snow scooter travel). 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.

During the course, I have been lucky enough to have come across four polar bears (safely and in a calm situation). This particular photo shows a male bear that we spotted in Rindersbukta. Shortly after this photo, a second bear was spotted nearby. Before this visit to Svalbard, I had only seen one polar bear (I have been coming to Svalbard since the start of 2014). This might be coincidence, but could also be related to the sea ice conditions and lack of sea ice in certain areas of Svalbard.

During the course, I have been lucky enough to have come across four polar bears (safely and in a calm situation). This particular photo shows a male bear that we spotted in Rindersbukta. Shortly after this photo, a second bear was spotted nearby. Before this visit to Svalbard, I had only seen one polar bear (I have been coming to Svalbard since the start of 2014). This might be coincidence, but could also be related to the sea ice conditions and lack of sea ice in certain areas of Svalbard. Photo credit: Nick Hulton.

Another incredible view

Another incredible view from one of our field excursions. I am often at the back of the student group on these excursions, making sure that the group is okay. I find it very relaxing being at the back as I can happily stop and take pictures like this! 

Another picture from the back of the group, in front of Hayesbreen/Heuglinbreen.

Another picture from the back of the group, in front of Hayesbreen/Heuglinbreen. The students were especially enthusiastic to get up close and personal to the glacier front! As you can probably tell, I am a very (very very very) amateur photographer. For much better photos taken in Svalbard, I would definitely recommend checking out Frede Lamo who, as well as working in the logistics department at UNIS, is a professional photographer and very (very very very) good at taking photos of Svalbard wildlife and scenery.

 

 

Paulabreen

This month I have been in Svalbard, demonstrating on the Glaciology course (AG-325/825) at the University Centre in Svalbard (UNIS). The course is aimed at Masters and PhD students who want a taste of the Arctic. The course consists of four weeks of glaciology lectures  and weekly excursions to glaciers in the local area. I have been supporting the logistical side of the weekly excursions, with the odd bit of teaching here and there. This week we have been to Paulabreen, a surge-type glacier, which has some impressive ice exposures.

Map of Paulabreen, which flows into Rindersbukta, along with Skobreen and Bakaninbreen. The camera labelled on the map is the location of a time-lapse camera installed by researchers at UNIS, which captured the 2003-05 surge of Paulabreen-Skobreen. Source: Kristensen and Benn (2012)

Map of Paulabreen, which flows into Rindersbukta, along with Skobreen and Bakaninbreen. The camera labelled on the map is the location of a time-lapse camera installed by researchers at UNIS, which captured the 2003-05 surge of Paulabreen-Skobreen. Source: Kristensen and Benn (2012)

Paulabreen is a tidewater glacier that calves into Rindersbukta, a sheltered embayment that is situated close to the small mining settlement called Svea. Bakaninbreen and Skobreen are tributary glaciers of Paulabreen. All three of these are a special type of glacier called surging glaciers. A surge-type glacier is classified by its inability to transfer its mass from the upper accumulation region to the lower ablation region in a steady way. In the quiescent phase of a surge,  ice accumulates over time with slow throughput to the front (i.e. low velocities). At a given threshold, the glacier switches and rapidly transfers this large reservoir of accumulated ice, surging forward with velocities up to ten times faster than its slower, inactive phase. To find out more about surging glaciers, why they surge and where they can be found, I recommend reading a series of papers by Heidi Sevestre, whose PhD was specifically looking at surging glaciers – cataloging where they are, and producing a new concept that explains the processes behind surging dynamics.

Paulabreen and Skobreen last experienced a surge from 2003-2005, which was beautifully captured in this time-lapse sequence. The surge initiated at Skobreen, dragging Paulabreen with it as it propagated down into Rindersbukta. Over its surge period, these two glaciers advanced 2800m, with an average velocity of 3.2 m per day. For more information on the Paulabreen-Skobreen surge, click here.

Currently Paulabreen is very slow-moving and experiencing a steady retreat. The position of the glacier front is similar to its position in the 1980s, having advanced and retreated between then and now. Observations from the time-lapse sequence of the surge shows that the ice experienced thrusting and severe ice deformation, which is still seen in the ice today. By examining the ice exposures at the front of Paulabreen, we can get up close and personal to the processes that occurred during its surge phase. There are several features of interest that we could see…

Paulabreen in 1982 Photo credit: Simon Collins @RGSweather

Paulabreen in 1982. Photo credit: Simon Collins @RGSweather

Map of Paulabreen in 1982. Credit: Simon Collins @RGSweather

Map of Paulabreen in 1982. Credit: Simon Collins @RGSweather

Summary of the survey of Paulabreen in 1982. Credit: Simon Collins @RGSweather

Summary of the survey of Paulabreen in 1982. Credit: Simon Collins @RGSweather

Many thanks to Simon Collins (@RGSweather) for sharing his amazing photos and information about Paulabreen in the 1980s. Simon was part of an expedition who surveyed Paulabreen and Vallakrabreen, also taking sediment samples, weather readings and collecting information on the flowering species Alpine Bistort. The expedition consisted of a week-long hike from Longyearbyen to Svea, and then taking small boats across Rindersbukta to the study area. They spent six weeks there in total. 

Check out RGSweather for information on the Reigate Grammar School Weather Station, an automated weather station which collects high-resolution data on temperature, rainfall, barometric pressure, humidity, wind speed, wind direction and sunshine hours in the south of the UK. RGSweather are particularly dedicated to stimulating interest in the weather, with regular blog posts and information. 

The front of Paulabreen, with glaciology students on snow scooters for scale (March 2016)

A section of Paulabreen’s calving front with glaciology students on snow scooters for scale (March 2016)

Glaciology students examining the ice exposure at Paulabreen (March 2016)

Glaciology students examining the ice exposure at west side of Paulabreen (March 2016)

Glaciology students studying a section of the ice exposure at Paulabreen. The section here is approximately 6 m high (March 2016)

Glaciology students studying a section of the ice exposure at Paulabreen. The section here is approximately 6 m high (March 2016)

 

Wind pockets. High-winds exploit small indentations in the ice, creating hollows in the ice face. This process is not associated with the surge at Paulabreen, but is commonly seen at ice faces all over the world.

Wind pockets at Paulabreen (March 2016)

Wind pockets at Paulabreen (March 2016)

Wind pockets at Paulabreen (March 2016)

Wind pockets at Paulabreen. This picture shows approx. 15m ice face (March 2016)

 

‘Wormy’ ice. When ice is warmed by rapid motion, it partially melts. This allows air to move around the ice. It often travels towards ice crystal grain boundaries. This creates the ‘worm’-like veins in the ice. .

Wormy ice at Paulabreen (March 2016)

Wormy ice at Paulabreen. The section shown here is approx. 0.5 x 0.3 m (March 2016)

 

Regelation ice. Ice under a high amount of pressure, squeezing all air out of it to create very clear ice. Regelation ice can form at the bed of a glacier (in a high-pressure environment) or can form when exerted under high pressure. This changes the melting point of the ice and allows it to be partly liquid. During the surge at Paulabreen, sections of ice were pushed on top of one another, creating high amounts of pressure  and liberating the air from the ice.

Regelation ice and glacier ice separated by a debris layer at Paulabreen (March 2016)

Regelation ice (left) and meteoric ice (right) separated by a layer of debris at Paulabreen. Meteoric ice refers to ice derived from precipitation. Regelation ice is modified meteoric ice, transformed in a high-pressure environment. The section here is approx. 2 x 1.5 m (March 2016)

 

Debris entrainment features. Debris (i.e. fine-grained sediment, small pebbles, rocks) is often found in glaciers. This can be inputted on the glacier surface via rock fall and washed into surface meltwater channels. It can also be introduced at the base, entrained as the glacier ice flows over the bed. The size, texture and orientation of the debris entrainment can tell us about its origin and entrainment mechanism.  At Paulabreen, we see a lot of angular debris bands, with small pebbles orientated in the same direction. In this case, the debris has been entrained from the bed as one ice section has thrust over an adjacent stationary section during the 2003-05 surge.

Entrained sediment at Paulabreen (March 2016)

Entrained debris at Paulabreen. This debris band extends to the top of the ice face, with small angular pebbles all orientated in the same direction. This was formed during the surge phase of Paulabreen (March 2016)

Sediment squeezing at Paulabreen (March 2016)

Debris squeeze feature at Paulabreen. The debris here is rounded and sorted, with finer sediment at the top of the feature and larger pebbles and rocks at the bottom. In this case, crevasses and cracks appear at the base of the glacier as it surges rapidly. A slurry of wet mud and stones is then forced into these under the pressure exerted by the weight of the glacier. The debris squeeze feature shown in this image is approx. 3 x 0.5 m  (March 2016)

 

Debris – Regelation ice – Meteoric ice patterns. During the surge of Paulabreen, multiple sections of ice were thrust over each other as the ice was being pushed down Rindersbukta. This created a distinct pattern of debris band, regelation ice and meteoric ice. There is a gradual transition from the regelation ice to meteoric ice, from less bubbly to more bubbly ice. Where the debris passes over the ice, there is a sharp transition from meteoric ice to debris. As a section of ice is thrust over another, debris is entrained from the bed. This creates the debris band. The process of thrusting generates a large amount of pressure that transforms the ice immediately adjacent to the bed into regelation ice. This creates the seciton of regelation ice. On top of this regelation ice is normal unmodified meteoric ice, which has not been subjected to high pressure conditions. Over the period of the surge, multiple ice thrusting events create multiple lines of debris, regelated ice and meteoric ice.

Debris-Regelation ice-glacier ice patterns seen at Paulabreen (March 2016)

Debris-Regelation ice-glacier ice patterns seen at Paulabreen. The section here is approx. 3 x 2 m (March 2016)

Debris-Regelation ice-glacier ice patterns seen at Paulabreen (March 2016)

Debris-Regelation ice-glacier ice patterns seen at Paulabreen (March 2016)

 

Internal ice fractures. Cracks or faults in the ice that relate to cooling of the ice as it meets relatively cold winter air temperatures, and strong pressure gradients near the free ice face. These features are not directly related to the surge of Paulabreen.

Ice fracturing at Paulabreen (March 2016)

Ice fracturing at Paulabreen. Image here shows 1 x 0.6 m section of the ice exposure (March 2016)