Mass changes of Southern and Northern Inylchek Glacier, Central Tian Shan, Kyrgyzstan, during ∼1975 and 2007 derived from remote sensing data

Abstract

Abstract. Glacier melt is an essential source of freshwater for the arid regions surrounding the Tian Shan. However, the knowledge about glacier volume and mass changes over the last decades is limited. In the present study, glacier area, glacier dynamics and mass changes are investigated for the period ~1975–2007 for Southern Inylchek Glacier (SIG) and Northern Inylchek Glacier (NIG), the largest glacier system in Central Tian Shan separated by the regularly draining Lake Merzbacher. The area of NIG increased by 2.0 ± 0.1 km2 (~1.3%) in the period ~1975–2007. In contrast, SIG has shrunk continuously in all investigated periods since ~1975. Velocities of SIG in the central part of the ablation region reached ~100–120 m a−1 in 2002/2003, which was slightly higher than the average velocity in 2010/2011. The central part of SIG flows mainly towards Lake Merzbacher rather than towards its terminus. The measured velocities at the distal part of the terminus downstream of Lake Merzbacher were below the uncertainty, indicating very low flow with even stagnant parts. Geodetic glacier mass balances have been calculated using multi-temporal digital elevation models from KH-9 Hexagon (representing the year 1975), SRTM3 (1999), ALOS PRISM (2006) and SPOT-5 high-resolution geometrical (HRG) data (2007). In general, a continuous mass loss for both SIG and NIG could be observed between ~1975 and 2007. SIG lost mass at a rate of 0.43 ± 0.10 m w.e. a−1 and NIG at a rate of 0.25 ± 0.10 m w.e. a−1 within the period ~1975–1999. For the period 1999–2007, the highest mass loss of 0.57 ± 0.46 m w.e. a−1 was found for NIG, whilst SIG showed a potential moderate mass loss of 0.28 ± 0.46 m w.e. a−1. Both glaciers showed a small retreat during this period. Between ~1975 and 1999, we identified a thickening at the front of NIG with a maximum surface elevation increase of about 150 m as a consequence of a surge event. In contrast significant thinning (>0.5 m a−1) and comparatively high velocities close to the dam of Lake Merzbacher were observed for SIG, indicating that Lake Merzbacher enhances glacier mass loss.

Characterizing the May 2015 Karayaylak Glacier surge in the eastern Pamir Plateau using remote sensing

“…We estimated the uncertainty of the glacier area using a buffer of half a pixel for images of regions with bare ice and favorable snow conditions (Bolch and others, 2010), but we used a buffer of two pixels for debris-covered sections (Shangguan and others, 2015). This yielded an area uncertainty of 1.8% for the Landsat 8 images and 0.2% for the Gaofen-1 and ZY-1-02C images.…”

“…Multi-temporal images of Landsat 8 OLI images were successfully co-registered by the US Geological Survey to an accuracy of 0.4 pixels; they used the same registration method and the images were suitable as input, as they covered a larger area of the glacier than ASTER images (Nobakht and others, 2014;Shangguan and others, 2015). Hence, we could calculate the uncertainty related to co-registration from Landsat panchromatic images, and the uncertainty was ∼6.0 m. However, uncertainty related to the image resolution was usually less than half a pixel at the image resolution (Bolch and others, 2010).…”

Recent glacier mass balance and area changes in the Kangri Karpo Mountains from DEMs and glacier inventories

“…Glaciers in the eastern Nyainqentanglha mountains are predominantly influenced by the monsoon and have more snow moisture and higher temperatures than the Antarctic ice sheet (Shi and The Cryosphere, 12, 103-121, 2018 www.the-cryosphere.net/12/103/2018/ Another issue relates to data voids in the accumulation area. Different assumptions, or elevation changes in the accumulation regions, were used to fill the data voids and to assess the impact on mass balance (Pieczonka et al, 2013;Shangguan et al, 2015). In this study, information on elevation change exists for all altitudinal zones from 2400 m to 6600 m a.s.l., but the area of data voids was too small to affect the mass balance significantly (0.7 % of the area above 6000 m a.s.l.…”

Changes in ice volume of the Ningchan No.1 Glacier, China, from 1972 to 2014, as derived from in situ measurements

“…The pink polygon is the subset area for comparing geodetic and glaciological mass balance. Shangguan and others, 2015). We assumed that any uncertainty arising from image co-registration could be captured using the buffer method.…”