Multi-Temporal Variations in Surface Albedo on Urumqi Glacier No.1 in Tien Shan, under Arid and Semi-Arid Environment

Xiaoying Yue,Shuang Jin,Feiteng Wang,Huilin Li,Zhongqin Li

doi:10.3390/rs14040808

Abstract

Surface albedo exerts substantial control over the energy available for glacier melting. For Urumqi Glacier No.1 in the Tien Shan Mountains, China, represented as a “summer accumulation” glacier, the variations in albedo driven by surface processes are complex and still poorly understood. In this study, we examined the interannual trends in ablation-period albedo from 2000 to 2021 using MOD10A1 products, evaluated the variation in bare-ice albedo retrieved from 13 end-of-summer Landsat images obtained between 2002 and 2019, and investigated the seasonal variation and diurnal cycle of surface albedo collected near the equilibrium line of the glacier by an AWS from September 2018 to August 2021. During the period of 2000–2021, the average ablation-period albedo presented a slight but not statistically significant downward trend, with a total decrease of 1.87%. Specifically, the decrease in glacier albedo was quicker in July than that in August, and there was a slight increase in May and June. The blackening phenomenon was shown on the east branch glacier, but not on the west branch glacier. For seasonal variability, a bimodal pattern was demonstrated, different from the unimodal seasonal variation in other midlatitude glaciers. The albedo peaks occurred in December and April or May. Under clear sky conditions, the diurnal cycle presented three patterns: a symmetric pattern, an asymmetric pattern, and a progressive decreasing pattern. Air temperature and solid precipitation are the main drivers of variations in glacier albedo, but in different periods of the ablation season, two climate variables affect albedo to varying degrees. The effect of surface albedo reduction enhanced glacier melting by about 20% over the past 20 years. The short-term increase in albedo caused by summer snowfall can considerably reduce glacier melting by as much as 80% in June.

Highlights

Introduction published maps and institutional affilIn arid and semi-arid regions, glaciers and their meltwater play an important role in the regulation of river runoff, and constitute the material and cultural basis for the sustainable development of populations, resources, ecology, the environment, and the socio-economy [1,2,3]
The decrease in glacier albedo was quicker in July than that in August, and there was a slight increase in May and June
Surface mass balance is determined by the snowfall and the melt energy provided by the surface energy balance

Summary

Introduction

In arid and semi-arid regions, glaciers and their meltwater play an important role in the regulation of river runoff, and constitute the material and cultural basis for the sustainable development of populations, resources, ecology, the environment, and the socio-economy [1,2,3]. The current accelerated glacier retreat poses far-reaching challenges to water resources and nature conservation in arid and semi-arid regions. Glacier surface mass balance is the most direct and accurate parameter to determine the contribution of glaciers to regional water resources. Surface mass balance is determined by the snowfall and the melt energy provided by the surface energy balance. The shortwave radiation provides the primary melting energy source on midlatitude glaciers, and the value is as high as 80% or more [4,5,6,7]. The net shortwave radiation is controlled by the surface iations

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