Winter mass balance of Drangajökull ice cap (NW Iceland) derived from satellite sub-meter stereo images

Joaquín M C Belart,Ian M Howat,Etienne Berthier,Leif S Anderson,Finnur Pálsson,Guðfinna Aðalgeirsdóttir,Tómas Jóhannesson,Thorsteinn Thorsteinsson,Alexander H Jarosch,Eyjólfur Magnússon

doi:10.5194/tc-11-1501-2017

Abstract

Abstract. Sub-meter resolution, stereoscopic satellite images allow for the generation of accurate and high-resolution digital elevation models (DEMs) over glaciers and ice caps. Here, repeated stereo images of Drangajökull ice cap (NW Iceland) from Pléiades and WorldView2 (WV2) are combined with in situ estimates of snow density and densification of firn and fresh snow to provide the first estimates of the glacier-wide geodetic winter mass balance obtained from satellite imagery. Statistics in snow- and ice-free areas reveal similar vertical relative accuracy (< 0.5 m) with and without ground control points (GCPs), demonstrating the capability for measuring seasonal snow accumulation. The calculated winter (14 October 2014 to 22 May 2015) mass balance of Drangajökull was 3.33 ± 0.23 m w.e. (meter water equivalent), with ∼ 60 % of the accumulation occurring by February, which is in good agreement with nearby ground observations. On average, the repeated DEMs yield 22 % less elevation change than the length of eight winter snow cores due to (1) the time difference between in situ and satellite observations, (2) firn densification and (3) elevation changes due to ice dynamics. The contributions of these three factors were of similar magnitude. This study demonstrates that seasonal geodetic mass balance can, in many areas, be estimated from sub-meter resolution satellite stereo images.

Highlights

Monitoring glacier changes improves understanding of the close connection between glacier mass balance and climate (Vaughan et al, 2013)
The statistics obtained from the difference of DEMs (dDEM) in snow- and icefree areas (Table 2) allow for a quantitative comparison of the different methods and datasets used in the study
This study shows the capabilities of sub-meter satellite stereo images for measuring winter mass balance

Summary

Introduction

Monitoring glacier changes improves understanding of the close connection between glacier mass balance and climate (Vaughan et al, 2013). Monitoring has provided evidence for the continuous retreat and mass loss currently taking place in most glaciated regions on Earth (Vaughan et al, 2013; Zemp et al, 2015). Observations of mass balance provide a valuable shortterm overview of the glacier’s mass budget and its implications for water storage, runoff and regional climate (e.g., Huss et al, 2008; Radicand Hock, 2014). These observations can reveal trends and patterns in glacier mass evolution and are commonly used in glacier modeling (e.g., Huss et al, 2008; Aðalgeirsdóttir et al, 2011). Seasonal records of glacier mass changes, are sparse, and many glaciated areas in the world are not currently monitored due to high cost and logistical challenges (Ohmura, 2011)

Methods

Results

Discussion

Conclusion