A Remote Sensing Investigation into the evolution of Folgefonna Glacier over the last 150 years

TitleA Remote Sensing Investigation into the evolution of Folgefonna Glacier over the last 150 years
Publication TypeThesis
Year of Publication2012
AuthorsRobson, B
Refereed DesignationUnknown
SupervisorsSandven, S, Bakke, J
NERSC SupervisorsSandven, Stein,, Babiker, Mohamed,
Number of Pages130
Date Published06/2012
PublisherUniversity of Bergen, Department of Geography
Thesis TypeMaster
ISBN NumberN/A
Thesis NumberN/A
Abstract

The evolution of Folgefonna, three large maritime ice masses in Hardanger, Western Norway has been assessed over the last 150 years using a variety of remote sensing datasets (optical and microwave satellite images, aerial photography, digital elevation models (DEMs) and old maps). Changes in glacier area, volume and elevation of the transient snowline (TSL), a commonly used glacier mass balance proxy are determined. All three parameters show a similar trend, although the scarcity of glacier volume data points means that changes cannot be resolved in as much detail as the measurements of glacier area or the TSL elevation. Since the Little Ice Age (LIA) maxima at the end of the nineteenth century Folgefonna has been retreating and losing mass with noticeable glacier advances in the 1960s/70s and the 1990s. Since the turn of the millennium Folgefonna has retreated rapidly interrupted only by a short lived advance between 2005 and 2008. In 2011 Nordfonna, Midtfonna and Sørfonna had respective areas of 24.8 km2, 9.1 km2 and 156.7 km2, reductions of 47%, 68% and 20% compared with their LIA maxima sizes in 1860. The TSL mirrors this trend albeit with less magnitude compared with the other observations, it is therefore assumed that in actual fact it the firn line being measured and not the TSL. Absolute ice volume calculations are only possible for Nordfonna where the subglacial topography is known; Nordfonna measured 1.84 km3 in 2010, a reduction of 43% of its 1937 volume. If planar bedrock surfaces beneath 95% of the ice surfaces are assumed then rudimentary percentage losses can be calculated. Over the same time span Midtfonna lost 1441 million kg (50%) of mass, while Sørfonna lost 8268 million kg (18%) between 1987 and 2010, the portion of Sørfonna visible on the 1937 topographic map lost 5658 million kg (21%) between then and 2010. The changes observed remotely in Folgefonna relate well to the in-situ data as well as the climatic data, it is evident that winter precipitation has traditionally been the principle driver of Folgefonna, however recent increases in summer temperature have been responsible for the acceleration in glacier shrinkage. Folgefonna is found to have advanced and retreated roughly in synchronisation with ice masses in Scandinavia, Europe and further afield suggesting that a global force is partly responsible for driving the glacier.

Author Address

Dept of Geography, Uiversity of Bergen

and

NERSC

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