A Short-Time Repeat TLS Survey to Estimate Rates of Glacier Retreat and Patterns of Forefield Development (Case Study: Scottbreen, SW Svalbard)

The study presents findings from comparative analyses of high-resolution differential digital elevation models (DEM of Difference-DoD) based on terrestrial laser scanning (TLS) surveys. The research was conducted on the 0.2 km(2) Scottbreen valley glacier foreland located in the north-western part of Wedel-Jarlsberg Land (Svalbard) in August of 2013. The comparison between DTMs at 3-week intervals made it possible to identify erosion and depositional areas, as well as the volume of the melting glacier's terminus. It showed a considerable recession rate of the Scottbreen (20 m year(-1)) while its forefield was being reshaped by the proglacial Scott River. A study area of 205,389 m(2), 31% of which is occupied by the glacier (clear ice zone), was included in the repeated TLS survey, which was performed from five permanent scan station points (registered on the basis of five target points-TP). The resultant point clouds with a density ranging from 91 to 336 pt m(-2) were converted into DEMs (at a spacing of 0.1 m). They were then put together to identify erosion and depositional areas using Geomorphic Change Detection Software (GCD). During the 3-week interval, the retreat of the glacier's snout ranged from 3 to 9 m (mean of 5 m), which was accompanied by an average lowering of the surface by up to 0.86 m (+/- 0.03 m) and a decrease of ice volume by 53,475 m(3) (+/- 1761 m(3)). The deglaciated area increased by 4549 m(2) (similar to 5%) as a result of the recession, which resulted in an extensive reshaping of the recently deglaciated area. The DEM of Difference (DoD) analyses showed the following: (i) lowering of the glacial surface by melting and ii) predominance of deposition in the glacier's marginal zone. In fact, 17,570 m(3) (+/- 1172 m(3)) of sediments were deposited in the glacier forefield (41,451 m(2)). Also, the erosion of sediment layers having a volume of 11,974 m(3) (+/- 1313 m(3)) covered an area equal to 46,429 m(2) (53%). This occurrence was primarily based on the washing away of banks and the deepening of proglacial stream beds, as well as the washing away of the lower parts of moraine hillocks and outwash fans.

Automated summary

The study compared high-resolution differential digital elevation models based on terrestrial laser scanning surveys to analyze erosion and deposition patterns in a glacier foreland in Svalbard. Results showed significant recession of the glacier and reshaping of the forefield by a proglacial river.