Abstract
The increased availability of remote sensing platforms with appropriate spatial and temporal resolution, global coverage and low financial costs allows for fast, semi-automated, and cost-effective estimates of changes in glacier parameters over large areas. Remote sensing approaches allow for regular monitoring of the properties of alpine glaciers such as ice extent, terminus position, volume and surface elevation, from which glacier mass balance can be inferred. Such methods are particularly useful in remote areas with limited field-based glaciological measurements. This paper reviews advances in the use of visible and infrared remote sensing combined with field methods for estimating glacier parameters, with emphasis on volume/area changes and glacier mass balance. The focus is on the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor and its applicability for monitoring Himalayan glaciers. The methods reviewed are: volumetric changes inferred from digital elevation models (DEMs), glacier delineation algorithms from multi-spectral analysis, changes in glacier area at decadal time scales, and AAR/ELA methods used to calculate yearly mass balances. The current limitations and on-going challenges in using remote sensing for mapping characteristics of mountain glaciers also discussed, specifically in the context of the Himalaya.
Highlights
IntroductionAn increasing number of glaciologic studies are focusing on monitoring glacier changes using remote sensing in mountain regions experiencing rapid changes in glacier extents, such as Alaska [1], Patagonia [2], the Andes [3,4,5,6], the Alps [7,8,9], the Himalaya [10,11,12,13,14,15,16] and Central Asia [17,18,19]
We describe the various steps involved in estimating these characteristics from satellite imagery, ASTER data and discuss their applicability for Himalayan glaciers: 1) semi-automated glacier delineation algorithms from multi-spectral and topographic data; 2) glacier thickness and volume estimations from satellite data; 3) volumetric changes at decadal time scales using digital elevation models (DEMs) on a pixel by pixel basis and 4)
Advantages over the other sensors include: (1) ASTER's spatial resolution of 15m in visible and near-IR (VNIR) is adequate for regional-scale glacier studies; (2) the high spectral resolution with 3 VNIR bands, 6 mid-IR bands and 5 thermal infra-red (TIR) bands allows for multi-spectral image classification (3) the off-nadir viewing band in the near infrared (NIR) enables high-resolution along-track stereoscopic vision and (4) the adjustable sensor gain settings provide increased contrast over bright areas [43]
Summary
An increasing number of glaciologic studies are focusing on monitoring glacier changes using remote sensing in mountain regions experiencing rapid changes in glacier extents, such as Alaska [1], Patagonia [2], the Andes [3,4,5,6], the Alps [7,8,9], the Himalaya [10,11,12,13,14,15,16] and Central Asia [17,18,19]. Massbalance records show an acceleration of glacial loss in the last decades in many of these sites [20, 21] Such studies show the potential of remote sensing data to provide useful information for glaciologic applications such as: glacier area, length, surface elevation, surface flow fields, accumulation/ablation rates, albedo, equilibrium line altitude (ELA), accumulation area ratio (AAR) and the mass balance gradient δb/δz. Due to intense manual labor, this method has limited applicability in rugged or remote glacierized areas due to logistic difficulties involved in maintaining a monitoring network, lack of logistical support and political or cultural conflicts In such areas, spaceborne remote sensing may offer complementary information on glacier parameters, especially glacier area, surface elevation, ELA and terminus position, from which mass balance can be inferred on various spatial and temporal scales. The emphasis is on the advantages and limitations of remote sensing methods for mass balance estimations at various spatial and temporal scales, and their potential in filling the existing gap in mass balance records in the Himalaya
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