UNIS Ph.D. student Monica Sund and colleagues from the University of Oslo have studied the surface elevation changes of the glacier Nathorstbreen and its tributaries. By using subtraction of repeat digital terrain models the scientists have succeeded in forecasting a surge of the glaciers. The results of this study further support previous findings that the majority of Svalbard glaciers are of surge-type.

Text: Monica Sund, UNIS Ph.D. student in glaciology

On a sample of Svalbard glaciers geometric changes have been studied using subtraction of repeat digital terrain models (DTMs) in order to determine early surge-stage dynamics. The study succeeded in forecasting a surge of Nathorstbreen and its tributary glaciers in the Van Keulen fjord area. The study is currently in press in Annals of Glaciology.

A DTM was compiled from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite images from 2003 and compared with a DTM from 1990.

Three surge stages
The surge development could be followed through three stages, of which the first two are mainly identified from glacier thickness changes and showed little visual evidence and have not been previously described in Svalbard.

The Nathorstbreen glacier in March 2009. (Photo: Marcus Eckerstorfer/UNIS).

In stage 1 initial surface lowering was found in the upper part of the glacier, followed by a thickening further down glacier in stage 2. The third stage represents the period of well developed surge dynamics that is usually reported.

The study revealed that the upper part of the Nathorstbreen glacier systems have started to lower while ice thickness increased further downglacier, several years prior to well known surge signs like heavy crevassing.

The glacier system (initially 480 km²) accelerated and reached the final stage 3 during winter 2008-09 and had by March 2009 advanced 2-3 km in a few months.

New surge indications
In addition a number of new surges were found for glaciers that were not known to have surged previously as some surges ceased at stage 2 as a partial surge and never developed into a fully active surge. These partial surges could be misinterpreted as rapid response to climate change.

The Nathorstbreen glacier in May 2009. (Photo: Geir Moholdt/UiO).

The results of this study further support previous findings that the majority of Svalbard glaciers are of surge-type.

Reference
Sund, Monica (UNIS); Eiken, Trond; Hagen, Jon Ove; and Kääb, Andreas (UiO). Svalbard surge dynamics derived from geometric changes. Annals of Glaciology 50(52) 2009 (in press).