Abstract
ABSTRACTGlacier area changes on the Tibetan Plateau were studied in different drainage basins based on Landsat satellite images from three epochs: 263 in the mid-1970s, 150 in 1999–2002 and 148 in 2013/14. Three mosaics (M1976, M2001 and M2013) with minimal cloud and snow cover were constructed, and the uncertainty due to each epoch having a finite span was accounted for. Glacier outlines (TPG1976, TPG2001 and TPG2013) were digitized manually with guidance from the SRTM DEM v4.1 and Google Earth imagery. To achieve complete multi-temporal coverage in a reasonable time, only debris-free ice was delineated. Area mapping uncertainty was evaluated at three study sites, Mount Qomolangma (Everest), Mount Naimona'Nyi, Mount Geladandong, where the largest differences between present and earlier measurements were within ~±4%. Area differences with previous inventories ranged from −19.6% (TPG1976 minus the first Chinese Glacier Inventory) to −3.6% and −1.1% (TPG2013 and TPG2001, respectively minus the second Chinese Glacier Inventory), while the difference TPG2001 minus the GAMDAM Glacier Inventory was +10.4%. Glacier area on the plateau decreased from 44 366 ± 2827 km2(1.7% of the study area) in the 1970s to 42 210 ± 1621 km2in 2001 and 41 137 ± 1616 km2in 2013. Shrinkage was faster in external drainage basins of the southeast than in the interior basins of the northwest, from a maximum of −0.43% a−1(−1.60% a−1during 1994–2013) in the Mekong catchment down to a minimum of −0.12% a−1in the Tarim interior drainage.
Highlights
Most mountain glaciers have been melting rapidly in recent decades (Gardner and others, 2013; Zemp and others, 2015) and this has been documented, especially in High Mountain Asia (HMA hereafter), in surveys of the whole (Li and others, 2008; Cogley, 2016) or large parts (Bolch and others, 2012; Yao and others, 2012) of the region as well as in basin-scale and single-glacier studies (Fujita and Nuimura, 2011; Wang and others, 2013; Yang and others, 2013)
Comparisons between TPG data and our previous studies show that the differences at all three sites between the series of TPG data and the local studies are within ±4% (Table S2)
The amount of misinterpretation varies with the choice of thresholds and other methodological details, we found that the advantage in productivity offered by automated methods is largely offset by the need for post-processing
Summary
Most mountain glaciers have been melting rapidly in recent decades (Gardner and others, 2013; Zemp and others, 2015) and this has been documented, especially in High Mountain Asia (HMA hereafter), in surveys of the whole (Li and others, 2008; Cogley, 2016) or large parts (Bolch and others, 2012; Yao and others, 2012) of the region as well as in basin-scale and single-glacier studies (Fujita and Nuimura, 2011; Wang and others, 2013; Yang and others, 2013) As reported in these earlier studies, most HMA glaciers showed obvious shrinkage (area loss) and thinning (implying mass loss) except in the west, for example in the Karakoram (Gardelle and others, 2012) and western Kunlun (Neckel and others, 2014; Kääb and others, 2015; Ke and others, 2015). Regions in the interior TP, such as 5Z1, 5Z2, 5Z5, 5Z6 and 5Y5 are less influenced both by the summer monsoon and the westerlies (Yao and others, 2012)
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