The dynamics of Svalbard glaciers
Top image: Kronebreen is one of the fastest moving glaciers in Svalbard. This summer cameras were put up to study the velocity components of the glacier. Photo: Monica Sund/UNIS.
Calving and surging glaciers play a major role in delivering land ice to Arctic waters. Changes in calving frequency might impact sea transport, fisheries and oil exploration in the Arctic. However, these changes are poorly understood. A new PhD project at UNIS aims at increasing the understanding of glacier changes in a shifting climate.
31 October 2007
Text: Monica Sund, UNIS PhD candidate in glaciology
The PhD-project “Dynamics of Calving and Surging Glaciers”, which is a part of the international GLACIODYN (The Dynamic Response of Arctic Glaciers to Global Warming) project and IPY, has successfully retrieved data from two glaciers this season.
Analyzing velocities of Kronebreen
Kronebreen is one of the fastest moving glaciers in Svalbard and calves into the inner part of Kongsfjorden. The high velocities are a result of the very large accumulation area draining through a narrow channel between the mountains Pretender, Garwoodtoppen and Colletthøgda.
In middle of June 2007 two cameras were put up on Colletthøgda in order to obtain high resolution digital photos for studying the velocity components of Kronebreen using ground based stereo photogrammetry technique.
The results will be used to test a new time-dependant model, which predicts changing ice front positions and calving fluxes for tide water glaciers.
In August the cameras were retrieved and contained a dataset of one month with stereo photos of a time lapse of 6 hours.
Understanding rapidly changing glaciers
The goal of the GLACIODYN project is to make a significant contribution to assessments on the impact of climate change in the Arctic region. The focus is on the effect of glaciers on sea level change and on the fresh water input into fjords and embayments. GLACIODYN aims to increase understanding of the mechanisms behind rapid changes in glacier dynamics and develop robust, predictive models that include key dynamic processes.
Change in the volume of glaciers involves two main sets of processes, both of which are temporally and spatially variable: (1) surface mass balance; and (2) ice flow and calving (dynamics). Interaction between these process domains can amplify glacier response to initial forcing, e.g. increased meltwater production can increase basal sliding, delivering more ice to regions of higher melt in a self-reinforcing cycle.
Dynamic feedbacks also play a key role in the behaviour of calving glaciers, which in many parts of the world have undergone sudden thinning, acceleration and retreat. Calving glaciers play a major role in delivering land ice to the world ocean and changes in the frequency of calving events may impact planned infrastructure and traffic related to sea transport, fisheries and oil exploration in the Arctic, where activity is expected to increase significantly over the coming decades.
First field measurements of early stage glacier surge in Svalbard
Another poorly understood aspect of aspect of glacier dynamics concerns glacier surges, which are episodes of fast flow affecting otherwise slowly-moving glaciers. Surging glaciers are concentrated in few areas around the world, among them Svalbard.
Surges of larger glaciers and ice streams can cause massive freshwater supply over a short period. A surge must not be confused with continuous fast flow, like that of Kronebreen, yet the flow regime of a surging glacier has similarities to fast flowing glaciers.
A spectacular example of a large glacier surge could be witnessed in the early 1990s when Fridtjovbreen in the Van Mijenfjorden started advancing and image of the front clearly show the large crevassing and congestation of the ice.
Another incident occurred in 2005 when the tributary glacier Skobreen surged into Paulabreen, causing the front of Paulabreen to move forward at a rapid pace.
Until now no field measurements of the early stage of a surge has been carried out in Svalbard, and the knowledge of the initiation phase of surges is poor. Data from a smaller inland glacier, Kroppbreen, has been obtained this season, to unveil the factors that are important in the switch from slow to fast flow. A longitudinal and transversal profile of 12 stakes has been established and measured to achieve flow velocities. Also GPR (Ground Penetrating Radar) measurements have been carried out to measure the ice thickness and thermal conditions of the glacier.
The preliminary results show a draw down of approx. 50 m of the upper part of the glacier and a mass transfer to the middle part where the ice surface has risen about 50 m since 1990. Currently it seems that the cold terminus is damming the faster ice further upglacier. Thus the large crevasses are limited to the upper part of the glacier, apart from that the crevasses are currently rather small.