Multi-temporal Mapping and Analysis of Ice-marginal Lakes using Sentinel-1: a Case Study from the Southern Margin of the Vatnajökull Ice Cap, Southeast Iceland

Monday, 7 December 2020
Zahra Dabiri, Daniel Hölbling and Lorena Abad, University of Salzburg, Department of Geoinformatics - Z_GIS, Salzburg, Austria
The monitoring of ice-marginal lakes (or proglacial lakes) is important for glaciological and geomorphological studies as well as for hazard and risk assessment. Proglacial lake development is a result of deglaciation and their appearance and increase in size are visible consequences of climate change. Freely available Sentinel-1 C-band synthetic aperture radar (SAR) data allows for monitoring and studying geomorphological features, especially in areas with high cloud coverage. The Vatnajökull ice cap in southeast Iceland has shown a constant evolution of its proglacial lakes, particularly in the southern part. The purpose of this study is to assess the applicability of Sentinel-1 data for multi-temporal analysis of changes in lake area from 2015 to 2020. We selected the ice-marginal lakes of Breiðamerkurjökull and Fjallsjökull, particularly Jökulsárlón, Breiðárlón, and Fjallsárlón for semi-automatically mapping and monitoring their evolution. We use multi-temporal Sentinel-1 VV and VH polarizations and object-based image analysis (OBIA) for change mapping based on the VV and VH intensity bands. Moreover, we assess the suitability of the intensity bands together with polarization-derived products such as entropy, alpha, and anisotropy decomposition for deriving further information about the lakes and their variability, such as changes in sediment load and the density of ice blocks detached from the glacier margins. Our results show a considerable increase in lake areas. Finally, we discuss the potential of using Sentinel-1 data and derived products for semi-automatically mapping ice-marginal lake changes.