A decreasing glacier mass balance gradient from the edge of the Upper Tarim Basin to the Karakoram during 2000\u20132014

Hui Lin,Lan Cuo,Andrew Hooper,Gang Li,Qinghua Ye

doi:10.1038/s41598-017-07133-8

Abstract

In contrast to the glacier mass losses observed at other locations around the world, some glaciers in the High Mountains of Asia appear to have gained mass in recent decades. However, changes in digital elevation models indicate that glaciers in Karakoram and Pamir have gained mass, while recent laser altimetry data indicate mass gain centred on West Kunlun. Here, we obtain results that are essentially consistent with those from altimetry, but with two-dimensional observations and higher resolution. We produced elevation models using radar interferometry applied to bistatic data gathered between 2011 and 2014 and compared them to a model produced from bistatic data collected in 2000. The glaciers in West Kunlun, Eastern Pamir and the northern part of Karakoram experienced a clear mass gain of 0.043 ± 0.078~0.363 ± 0.065 m w.e. yr−1. The Karakoram showed a near-stable mass balance in its western part (−0.020 ± 0.064 m w.e. yr−1), while the Eastern Karakoram showed mass loss (−0.101 ± 0.058 m w.e. yr−1). Significant positive glacier mass balances are noted along the edge of the Upper Tarim Basin and indicate a decreasing gradient from northeast to southwest.

Highlights

Glaciers and ice sheets throughout the world are experiencing degradation and have contributed approximately 29 ± 13% of the observed sea level increase from 2003 to 20091
West Kunlun showed a positive mass balance (0.128 ± 0.055 m w.e. yr−1), and the surrounding area (A-F) experienced a mass gain that varied from 0.043 ± 0.078 to 0.363 ± 0.065 m w.e. yr−1, with a decreasing gradient from northeast to southwest (Fig. 1, Supplementary Fig. S10)
Within the Extended West Kunlun, which is close to the Eastern Karakoram and Spiti-Lahaul (Fig. 1 and Supplementary Fig. S11), the glacier experienced rapid degradation at a rate of −0.286 ± 0.067 m w.e. yr−1

Summary

Methods

We utilized 39 pairs of X-band SAR images (Supplementary Fig. S1) and used SRTM data from Feb 2000 to detect glacier height changes using bistatic SAR interferometry (InSAR). For each sub-region, we applied C- and X-band SRTM to estimate and remove the penetration depth difference on glaciers individually in each 50-m elevation bin (Supplementary Figs S2–S4). To avoid the effects of seasonal snow on the penetration depth estimates, we mainly adopted TSX/TDX images obtained in Jan, Feb and Mar. Four pairs of images obtained during different months, with a region of overlap in West Kunlun, were employed to estimate the seasonal effect (Supplementary Figs S5 and S6). The glacier height change estimates include bias and random error The former includes differences in the penetration depths associated with the C- and X-bands, the off-glacier region datum and seasonal variations. The random error depends on the number of effective measurements at each glacier and on the standard deviation of the elevation differences within the off-glacier region, where no height changes were presumed

Author Contributions

Additional Information