According to the authors, "we conclude on a balanced/positive mass balance in the Karakoram since the 1980s or 1990s, or even earlier, induced by changing climatic conditions since the 1960s.", "Out of 1219 glaciers in the inventory, the vast majority [79%] showed stable terminus positions (969)" and "Glacier recession is found for only 8% of the glaciers in the inventory, indicating decreasing numbers since the beginning of the 21st century, whereas the number of advancing glaciers has increased since then."
Conclusions and outlook
The present study utilizes different remote sensing-based methods to generate an updated glacier inventory for the entire Karakoram region. It provides a new comprehensive dataset on the state of advancing, stable, and retreating glaciers, including the temporal and spatial variations of frontal positions between 1976 and 2012. Out of 1219 glaciers in the inventory, the vast majority [79%] showed stable terminus positions (969). These findings support the assumption of the anomalous behavior of glaciers in the Karakoram in comparison to adjacent mountain ranges, which indicate glacier recession and thinning (Bolch et al., 2012; Hewitt, 2005; Gardelle et al., 2013; Kääb et al., 2012; Scherler et al., 2011). Glacier recession is found for only 8% of the glaciers in the inventory, indicating decreasing numbers since the beginning of the 21st century, whereas the number of advancing glaciers has increased since then. Considering the advance of small glaciers with assumed short response times of about 10–20 years, we conclude on a balanced/positive mass balance in the Karakoram since the 1980s or 1990s, or even earlier, induced by changing climatic conditions since the 1960s (Archer and Fowler, 2004; Bocchiola and Diolaiuti, 2013; Williams and Ferrigno, 2010; Yao et al., 2012).
The Cryosphere, 8, 977-989, 2014
1Institute of Geography, University of Erlangen-Nuremberg, Wetterkreuz 15, 91058 Erlangen, Germany
2Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775-7320, USA
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.