Recent Changes to Langjökull Icecap, Iceland: An investigation integrating airborne LiDAR and satellite imagery

• Main Author: Pope, Allen J.
• Format: Master Thesis
• Language: English
• Published: Scott Polar Research Institute, University of Cambridge 2009
• Subjects: Langjökull; Iceland
• Online Access: https://doi.org/10.17863/CAM.11240; https://www.repository.cam.ac.uk/handle/1810/265184

Langjökull, Iceland’s second largest icecap (~950 km$^{2}$), was the subject of an incomplete airborne LiDAR survey in August 2007. This study investigates and evaluates the application of photoclinometry, which employs visible light imagery (here, Landsat ETM+ band 4) to interpolate unmeasured sections of this fragmented data set. A complete digital elevation model (DEM) of Langjökull was produced, and photoclinometry was determined to be a satisfactory and robust technique for topographic interpolation (RMS error = 3.4 m over a 3 km section). Future applications of photoclinometry can ensure optimal results by focusing on the consistent ability of their imager to accurately represent low contrast surfaces; also, consideration of setting characteristic such as solar azimuth, solar elevation, and moderate surface slope will make photoclinometric interpolation more effective. Photoclinometry it is proven to be a current and valuable technique, it is confirmed as a secondary rather than primary tool, and other possible applications of photoclinometry are considered. Using the completed DEM of Langjökull for summer 2007 and a previously prepared corresponding 1997 data set, Langjökull was found to have a specific annual mass balance of -0.99$\pm$0.1 meters per year of water equivalence (m yr$^{-1}$ w.e.), a number which confirms published predictions that Langjökull will likely disappear in the next 200 years. Comparison of remotely-sensed mass balance values and traditional $\textit{in situ}$ measurements revealed a possible systematic disparity; it is hypothesized that field measurements may not be sufficiently constraining behavior of interior areas and that the signal from strongly receding outlet glaciers may be skewing the $\textit{in situ}$ mass balance value calculated for the entire icecap. An additional DEM of outlet Hagafellsjökull Vestari allowed for calculation of specific mass balances of -2.28 m yr$^{-1}$ w.e. for 1997-2001, -3.86 m yr$^{-1}$ w.e. for 2001-2007, and -3.23 m yr$^{-1}$ w.e. for ...