GeoLog

Svalbard

Imaggeo on Mondays: Wandering the frozen Svalbard shore

Imaggeo on Mondays: Wandering the frozen Svalbard shore

These ethereal, twisted ice sculptures litter the frozen shoreline of Tempelfjorden, Svalbard, giving the landscape an otherworldly feel and creating a contrast with the towering ice cliff of the glacier and the mountains behind. They are natural flotsam, the scoured remnants of icebergs calved from the Tunabreen glacier, washed up on the shoreline.

These icebergs were calved from the Tunabreen glacier, which flows into Tempelfjorden from its source at the Lomonosovfonna ice cap. Tunabreen is a surge-type glacier, which means that it periodically switches between long periods of slow, stable flow to short-lived periods of very fast flow during which it advances. Tunabreen has historically surged approximately every 35 to 40 years, and its calving front advanced more than 2 kilometres during a surge in 2004.

Tunabreen is one of the glaciers monitored by the Calving Rates and Impact on Sea Level (CRIOS) project, an international initiative that involves several institutions. The glacier tends to slow during the winter months when there is less meltwater available to lubricate the sliding of ice over bedrock. Glaciologists were caught by surprise, therefore, when in late 2016 the glacier was observed to accelerate to speeds in excess of 3 m/day from the more usual 0.4 m/day. This acceleration began at the glacier terminus and spread up to 7km upstream over the following months. Tunabreen appeared to be surging decades earlier than expected!

The causes of this change in the glacier’s behaviour are not certain. However, the onset of this acceleration followed an unusually warm and wet autumn. Sea ice, which usually acts to oppose the flow by applying a resistive pressure against the calving front, also failed to form in Tempelfjorden over the winter. Both of these factors likely contributed. As a result of the flow acceleration, the surface of the glacier has become heavily crevassed, posing a hazard to travellers and glaciologists hoping to cross it!

I was fortunate to be able to visit Tunabreen in March 2017, as part of a glaciology course taught at UNIS, the University Centre in Svalbard. The view of the glacier’s 100ft high calving front framed by the mountains in the background is spectacular, and the trip by snowmobile was a fantastic daytrip. The surge continued throughout 2017 and early 2018, with the calving front advancing by more than a kilometre during that period. Since the summer of 2018, flow velocities have been decreasing, so it appears that the surge may have come to an end. This episode illustrates that there is still much we have to learn about the dynamics of surge-type glaciers, and that they can still take us by surprise!

Matt Trevers, PhD Researcher, Centre for Polar Observation and Modelling, University of Bristol

Further reading

Glaciers On The Move

Tunabreen may be surging decades earlier than expected (The University Centre in Svalbard)

What is going on at Tunabreen? (Penny How)

The recent surge of Tunabreen, Svalbard (Adrian’s glacier gallery) 

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Imaggeo on Mondays: Digging out a glacier’s story

Imaggeo on Mondays: Digging out a glacier’s story

This photograph shows landforms on Coraholmen Island in Ekmanfjorden, one of the fjords found in the Norwegian archipelago, Svalbard. These geomorphic features were formed by Sefströmbreen, a tidewater glacier, when it surged in the 1880s.

Although all glaciers flow, some glaciers undergo cyclic changes in their flow. This is called surging, and glaciers that surge are called surging glaciers. During their active phase, surging glaciers speed up and advance. At this time, glaciers collect, transport and deposit large volumes of sediment. This active phase is then followed by a so-called quiescent phase, when glaciers slowdown and retreat. Sediment carried within the ice is then exposed. Often surge-type glaciers produce a characteristic set of landforms, like the red ridges featured here in this photograph.

Only a small proportion of the world’s glaciers surge. Svalbard is home to many of these surging glaciers, and the length of the surge cycle varies by region. A quiescent phase of surging glaciers in Svalbard can last between 10 and 100 years. An active phase is commonly between 1 and 10 years. Surging glaciers are enigmatic; we still do not fully understand all the processes that cause these glaciers to switch between active and quiescent phases.

When Sefströmbreen surged, it advanced over the fjord and overrode Coraholmen Island. The glacier deposited up to 0.2 km3 of sediment on the western side of the island. As a result, the island doubled in size. The red ridges in the foreground of the photograph were formed when sediment under the glacier was squeezed up into crevasses, large cracks in the ice. Once the ice melted, these crevasse-squeezed ridges were exposed. They contrast in colour with grey Kolosseum Mountain in the background.

Glaciers are useful indicators of past climate and they are used for climate reconstructions. However, surging glaciers are not suitable for such reconstructions. This is because glacier surging is not directly related to climate. When a surging glacier advances during its active phase, it does not mean that the climate is colder. This also holds true for the past. If a surging glacier was bigger at some point in the past, it is not because the climate at the time was colder. If we didn’t know that the glacier surged, we would make a wrong inference about climate. Therefore it is important to know which glaciers are surging-type glaciers.

To document surging behaviour of glaciers, we can use historical sources, glaciological observations and satellite images. If no such records exist or if we are interested in time period that precedes satellite observations, we rely on landforms to tell us the story. We can study these landforms, their appearance, shape, structure, and what they’re made of to learn about past behaviour of glaciers, their dynamics, and processes that go on underneath a glacier where it meets its bed.

The photograph was taken during a field cruise as part of the University Centre in Svalbard’s Arctic Glaciers and Landscapes course.

By Monika Mendelova, University of Edinburgh (UK)

References

Boulton, G.S. et al. Till and moraine emplacement in a deforming bed surge — an example from a marine environment. QSR 15, 961-987. 1996

Evans, D.J.A., & Rea, B.R. Geomorphology and sedimentology of surging glaciers: a land-systems approach. Ann. Glaciol. 27, 75 – 82. 1999

Dowdeswell, J.A. et al. Mass balance change as a control on the frequency and occurrence of glacier surges in Svalbard, Norwegian High Arctic. Geophys. Res. Lett. 22, 2909-2912. 1995

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Imaggeo on Mondays: Arctic cottongrass in Svalbard

Imaggeo on Mondays: Arctic cottongrass in Svalbard

In the High Arctic, where vegetation is limited in height, cottongrass stands out as some of the tallest plant species around.

This photo shows a wispy white patch of Arctic cottongrass growing amongst other tundra vegetation in the Advent river floodplain of Adventdalen, a valley on the Norwegian archipelago island Svalbard.

Svalbard is of particular scientific interest as it is a relatively warm region for its high latitude. This is due to the North Atlantic Ocean, which transports heat from lower latitudes to Svalbard’s shores.

The photo was taken in September 2014, towards the end of the region’s growing season. In the background, you can see that the season’s first snow had already blanketed the valley’s neighboring mountain tops.

Cottongrass generally loves wet conditions and scientists sometimes even use this plant genus (Eriophorum) as an indicator of the ground’s fluctuating water level, especially in areas that begin to develop peat, an accumulation of more of less decomposed plant material in wet environments. The waters feeding this region’s wetland come from melted snow and ice travelling down the adjacent mountains and floodwater from the Advent river, which is primarily meltwater fed.

Arctic cottongrass also can exchange gases with their underground environment through their roots and even have been shown to alter the local carbon budget of regions where they grow. It is therefore a very important species to account for when studying permafrost carbon dynamics.

Gunnar Mallon, currently a teaching fellow at the University of Sheffield (UK), took this photo while on a fieldwork expedition together with Andy Hodson, a glaciology professor at the University Centre in Svalbard, for the LowPerm project.

The LowPerm project aimed to understand how nutrients are transported within permafrost landscapes in Norway and Russia and how that may affect the production of greenhouse gases, such as carbon dioxide (CO2) and methane (CH4). The study brought together scientists from the UK, Norway, Denmark and Russia and results from the extensive field and laboratory work are currently being analysed and made ready for publication.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Volcanic ash layers in Svalbard hold clues to the formation of the North Atlantic

Volcanic ash layers in Svalbard hold clues to the formation of the North Atlantic

This guest post by Dr Morgan Jones (a Researcher in Volcanology at the Centre of Earth Evolution and Dynamics (CEED) at the University of Oslo, Norway) describes the latest findings of his multidisciplinary research into how the North Atlantic formed. His open access study, in collaboration with colleagues at CEED and the Massachusetts Institute of Technology (MIT) is published in the Nature Journal: Scientific Reports. This post is modified from a version which first appeared on John Stevenson’s blog, Volcan01010. Read the original post.

Summary

The Earth’s tectonic plates have pulled apart and come together multiple times during its long history. These processes leave hallmarks of the past layouts of continents, which allow scientists to reconstruct how the plates have moved through time. While we know from the geological record that these movements took place, it is sometimes difficult to work out when key events occurred and their correct order. One such example is just before the formation of the northeast Atlantic Ocean, around 62-55 million years ago, when there were several changes in the relative motions of North America, Greenland, and Eurasia (the combined landmass of Europe and Asia) in just a few million years.

A technique called radioisotopic dating allows us to determine the exact age of volcanic rocks. This study shows that the Greenland plate began to push against part of the Eurasian plate around 61.8 million years ago, leading to the formation of a mountain belt between Greenland and Svalbard. This precise age of first compression occurred at the same time as other changes around the edge of the Greenland plate. For the first time, this study provides evidence that these events are connected.

This gives scientists who work in plate tectonic reconstructions the ability to refine their models to understand how North America and Eurasia began to break apart.

Plate Tectonics in the Palaeocene

The Palaeocene epoch was between 66-55.8 million years ago, occurring after the Cretaceous period. The between the Cretaceous and the Palaeocene 66 million years ago is marked by the well-known catastrophe that led to the extinction of the dinosaurs.

The Palaeocene was also an important time period for plate tectonic motions in the northern hemisphere. At the time when dinosaurs became extinct, the North Atlantic Ocean was still in its infancy and seafloor spreading did not extend further north than Canada and Portugal. Over the course of the next few million years, North America and Eurasia began to break apart, which eventually resulted in a seaway that connected the Atlantic and Arctic Oceans.

However, the break up was a complicated process. As the Atlantic Ocean grew northward, branches opened on either side of southern Greenland (between Canada to the west and Scotland/Norway to the east). The western arm pulled apart first, but at some point both of these rift zones were active, and a mountain range was formed in what is now Svalbard. This meant that for a short period (geologically speaking) Greenland was its own tectonic plate, moving independently of both North America and Eurasia.

The aim of our study is to pinpoint exactly when Greenland and Svalbard began to push together, as this compression is directly related to the rifting further south. This means that understanding the geological history of Svalbard can shed light on when and why Greenland became its own tectonic plate.

The Geology of Svalbard

The rock outcrops in western Svalbard are intensely folded and cut by long faults. They were once part of a mountain chain that formed due to Greenland and Svalbard pushing together. This was followed later by sideways movement as the northeast Atlantic Ocean began to open; pulling Greenland and Svalbard apart.

The rocks in south-central Svalbard, adjacent to this ancient mountain range, are sedimentary deposits that were formed in deltas and shallow seas. Mountain ranges often have low-lying regions alongside them (called basins) where sediments accumulate. Modern examples include the Po Valley next to the Alps in Italy and the Ganges Basin next to the Himalayas in India.

Importantly, these basins form at the same time as the mountains grow, which means that techniques to work out the age of rock formations can be used to accurately date when both the basin and the mountains started to form.

Dating First Compression between Svalbard and Greenland

An important tool for working out the age of a rock is radioisotopic dating. Radioactive isotopes of elements are unstable, meaning that over time they will degrade from one form to another. The half-life (the rate at which radioactive decay occurs) of each system varies from milliseconds to billions of years, which means that different isotope systems can be used for dating, depending on how far back in time your interest lies.

This is an edited version of Figure 5 from the paper, created using the open source plate tectonics software GPlates by Grace Shephard and Morgan Jones. It shows a regional reconstruction of how the tectonic plates were 62 million years ago. The blacked dashed lines show where the plate boundaries between North America, Greenland, and Eurasia are predicted to have been. The light blue areas show the approximate extent of seafloor in the Labrador Sea and in Baffin Bay. The orange areas show the rifting zone to the east of Greenland where the northeast Atlantic would later open. The purple areas show the known extent of magma intrusions and volcanic deposits from the first pulse of the North Atlantic Igneous Province (NAIP). The purple star is where the centre of the mantle plume is predicted to be at this time. The red arrows show the onset of compression between Greenland and Svalbard, beginning at 61.8 million years ago. The volcano symbols mark where the ash layers in Svalbard came from.

When considering millions to billions of years in the past, uranium-lead (U-Pb) dating is used as 238U has a half-life of about 4.5 billion years. Zircon crystals are ideal for this method as they form in cooling magma chambers. Zircons can have a high uranium concentration, which means that if they are found in volcanic deposits such as lavas or volcanic ash layers, they can be used to accurately date those rocks.

The sediments in Svalbard have numerous volcanic ash layers preserved within them. These ash layers are likely to have originated from volcanoes in northern Greenland and Ellesmere Island, now over 1000 km away across the ocean.

Based on the dating of these ash layers it is possible to calculate when sedimentation first began in central Svalbard. This age of valley formation, and therefore the initiation of compression between Greenland and Svalbard, is predicted to be start around 61.8 million years ago.

This age is significant because it overlaps with key events further south. Around 61.6 million years ago there was a dramatic change in the sedimentation in the North Sea from limestone to sandstone and siltstone. The speed of seafloor spreading increased between Canada and Greenland, and many faults were active along the edges of eastern Greenland.

The synchronicity of these events strongly indicates a common driving force affecting all margins of Greenland.

Potential Causes

A remaining mystery is what caused Greenland to change direction.

There are several possible candidates that could have caused the shift, either individually or together.

The acceleration of seafloor spreading in the Labrador Sea has the potential to drive changes in relative plate motions. It is also plausible that events further afield may be important. Greenland was in between the North American and Eurasian plates, so the change in motion may be a result of forces acting on one of these much larger plates.

Another possibility is the arrival of a mantle plume at the base of the crust. Mantle plumes bring considerable heat from deep in the Earth, resulting in widespread crustal melting and volcanic activity. The North Atlantic Igneous Province (NAIP) is one such example. The first pulse of magma arrived at the surface around 62 million years ago and is still causing enhanced melting today to form Iceland.

The scale of volcanic and magmatic products from the NAIP is truly enormous. Current estimates put the total amount of magma at 6 to 10 million cubic kilometres. Much of this activity is still exposed along the edges of the northeast Atlantic, including the British Isles, Faroe Islands, and East Greenland. There are also considerable deposits found in West Greenland. It is therefore possible that the change in plate motions may be connected to this pulse of magma. However, further work is needed to test this hypothesis.

By Dr Morgan Jones, Researcher in Volcanology at the Centre of Earth Evolution and Dynamics (CEED) at the University of Oslo, Norway