Abstract
Abstract. Positive glacier-mass balances in the Karakoram region during the last decade have fostered stable and advancing glacier termini positions, while glaciers in the adjacent mountain ranges have been affected by glacier recession and thinning. In addition to fluctuations induced solely by climate, the Karakoram is known for a large number of surge-type glaciers. The present study provides an updated and extended inventory on advancing, stable, retreating, and surge-type glaciers using Landsat imagery from 1976 to 2012. Out of 1219 glaciers the vast majority showed a stable terminus (969) during the observation period. Sixty-five glaciers advanced, 93 glaciers retreated, and 101 surge-type glaciers were identified, of which 10 are new observations. The dimensional and topographic characteristics of each glacier class were calculated and analyzed. Ninety percent of nonsurge-type glaciers are shorter than 10 km, whereas surge-type glaciers are, in general, longer. We report short response times of glaciers in the Karakoram and suggest a shift from negative to balanced/positive mass budgets in the 1980s or 1990s. Additionally, we present glacier surface velocities derived from different SAR (synthetic aperture radar) sensors and different years for a Karakoram-wide coverage. High-resolution SAR data enables the investigation of small and relatively fast-flowing glaciers (e.g., up to 1.8 m day−1 during an active phase of a surge). The combination of multitemporal optical imagery and SAR-based surface velocities enables an improved, Karakoram-wide glacier inventory and hence, provides relevant new observational information on the current state of glaciers in the Karakoram.
Highlights
Meltwater from snow cover and glaciers in high mountain areas is a major source for downstream water resources (Gardner et al, 2013; Kaser et al, 2010)
Positive glacier-mass balances in the Karakoram region during the last decade have fostered stable and advancing glacier termini positions, while glaciers in the adjacent mountain ranges have been affected by glacier recession and thinning
We demonstrate the potential of very highresolution synthetic aperture radar (SAR) time series to map changes in ice flow for very small surge-type or advancing glaciers, and complement this analysis with products based on archived scenes from ERS (European remote sensing satellite) SAR and Envisat ASAR
Summary
Meltwater from snow cover and glaciers in high mountain areas is a major source for downstream water resources (Gardner et al, 2013; Kaser et al, 2010). Mass balances for the Karakoram are found to be less negative, or even positive, using the geodetic method (Gardelle et al, 2012, 2013; Gardner et al, 2013; Kääb et al, 2012) Both stable and advancing terminus positions have been described by various authors (e.g., Bhambri et al, 2013; Bolch et al, 2012; Hewitt, 2005; Scherler et al, 2011). Existing surge-type glacier inventories (Barrand and Murray, 2006; Copland et al, 2011; Hewitt, 1998) are updated and refined using Landsat time series (1976–2012), and a detailed analysis of termini-position changes of surge-type, advancing, and retreating glaciers since 1976 is carried out. During the active phase of a surge event, high surface velocities close to the glacier snout support the identification of surge-type glaciers
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