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

Abstract

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 km2 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 m2, 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 m3 (±1761 m3). The deglaciated area increased by 4549 m2 (~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 m3 (±1172 m3) of sediments were deposited in the glacier forefield (41,451 m2). Also, the erosion of sediment layers having a volume of 11,974 m3 (±1313 m3) covered an area equal to 46,429 m2 (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.