Mapping the Retreat of the Debris-covered Tasman Glacier in the Aoraki-Mount Cook South Island, New Zealand
Presentation Time: Thu, 08/04/2022 - 13:00
Keywords: Tasman, Glacier, SVM, Landsat, Debris, New Zealand, DEM
As anthropogenic global climate change continues to accelerate, glaciers around the world are rapidly retreating. The Tasman Glacier offers a unique opportunity to demonstrate the challenge of mapping a debris covered glacier with a contemporary and rapid loss of ice at the terminus. Landsat 4, ETM+, and 8 OLI satellite Level-2 Reflectance imagery for years 1990, 2000, 2010 and 2022, are utilized for mapping the debris-covered glacier using a semi-automatic Support Vector Machine (SVM) classification. Normalized difference snow and ice index (NDSI) and normalized difference vegetation index (NDVI) are thresholded and used as supplemental data to optimize training samples and for general visualization purposes. To support delineation of the debris-covered glacier at the terminus location, morphometric parameters slope and aspect are derived from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (DEM). In addition to morphometric parameters, the DEM is used to calculate the glacier flow direction for the delineation of the Tasman watershed. A Global Land Ice Measurements from Space (GLIMS) digital glacier outline created for the 2013 Tasman Glacier system, and a 15 m (1/2 pixel) buffer are used to create the final outline of the Tasman Glacier system for each year. Variability of the terminus retreat is quantified by the surface area of resulting debris covered glacier and glacial lake. Post classification data points are created and validated to produce a confusion matrix to assess the quality and performance of the classified image. The average kappa index of agreement is ~ 0.85.
