Glacier Changes and Their Linkage to the Climate-Topographic Context in the Borohoro Mountains, Tian Shan 1977–2018

Yanan Li

doi:10.3390/w12051502

Abstract

Against the backdrop of climate change and socio-ecological sustainability, studying glacier changes provides essential knowledge to the basic water needs and security for regions and populations under such threats, such as Central Asia. Little attention has focused on glaciers in the northern periphery of the Chinese Tian Shan. This study aims to map a recent glacier inventory and examine the glacier area shrinkage and surface elevation change for the central massif of the Borohoro Mountains in the past 41 years. Using declassified Hexagon images (1977), Landsat 5 TM (1994 and 2007), Sentinel 2A (2018) and altimetry data from the Ice, Cloud and Land Elevation Satellite (ICESat) over 2003–2009 with the 30-m Shuttle Radar Topography Mission (SRTM) digital elevation model, multi-temporal glacier fluctuations and the influence of topographic and climatic factors were investigated. Results show that the glacier area decreased from 287.5 ± 8.2 km2 in 1977 to 215.8 ± 4.1 km2 in 2018, at a rate of 0.61 ± 0.01% year−1. Glacier disintegration has led to a gradual increase in the number of glaciers and reached 224 glaciers in 2018. The shrinkage was at the highest rate during the 1994–2007 period and the smallest during 1977–1994. Glacier size, hypsometry, and median, maximum, and range of elevation are the most significantly correlated parameters with the relative area change. The surface elevation changes from two of the largest glaciers revealed a stronger thinning on the southern slope compared to the northern slope. These observations of glacier loss are primarily driven by the marked warming trend since the 1970s and confirmed with the overall pattern of glacier retreat in the Tian Shan from previous studies.

Highlights

As reported in the Intergovernmental Panel on Climate Change (IPCC) special report, mountain surface air temperatures show warming at an average rate of 0.3 ± 0.2 ◦ C/decade, outpacing the global average warming rate of 0.2 ± 0.1 ◦ C/decade [1]
0.02 km2, which had a total area of 215.8 ± 4.1 km2 in the study area; 70% of the glaciers are smaller than 0.5 km2, while only 10 out of 224 glaciers are larger than 5 km2, comprising 47.5% of the total area (Table 2; Table S1)
As the median elevation is commonly used to estimate the balanced-budget equilibrium line altitude (ELA) [54], it is adopted in describing the altitudinal location of individual glaciers and later used in the topographic analysis, instead of using the mean elevation

Summary

Introduction

As reported in the Intergovernmental Panel on Climate Change (IPCC) special report, mountain surface air temperatures show warming at an average rate of 0.3 ± 0.2 ◦ C/decade, outpacing the global average warming rate of 0.2 ± 0.1 ◦ C/decade [1]. This enhanced warming has induced changes to elements and processes in the atmosphere, hydrosphere and biosphere in the mountain environment, and perhaps most prominently, in the cryosphere (glaciers, snow cover, and permafrost) that has responded sensitively to the changing climate. Knowing the glacier fluctuations in this key region is essential because of their importance to the water supply for over

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Conclusion