Grey Tienshan Urumqi Glacier No.1 and light-absorbing impurities.

Jing Ming,Cunde Xiao,Feiteng Wang,Zhongqin Li,Yamin Li

doi:10.1007/s11356-016-6182-7

Abstract

The Tienshan Urumqi Glacier No.1 (TUG1) usually shows “grey” surfaces in summers. Besides known regional warming, what should be responsible for largely reducing its surface albedo and making it look “grey”? A field campaign was conducted on the TUG1 on a selected cloud-free day of 2013 after a snow fall at night. Fresh and aged snow samples were collected in the field, and snow densities, grain sizes, and spectral reflectances were measured. Light-absorbing impurities (LAIs) including black carbon (BC) and dust, and number concentrations and sizes of the insoluble particles (IPs) in the samples were measured in the laboratory. High temperatures in summer probably enhanced the snow ageing. During the snow ageing process, the snow density varied from 243 to 458 kg m−3, associated with the snow grain size varying from 290 to 2500 μm. The concentrations of LAIs in aged snow were significantly higher than those in fresh snow. Dust and BC varied from 16 ppm and 25 ppb in fresh snow to 1507 ppm and 1738 ppb in aged snow, respectively. Large albedo difference between the fresh and aged snow suggests a consequent forcing of 180 W m−2. Simulations under scenarios show that snow ageing, BC, and dust were responsible for 44, 25, and 7 % of the albedo reduction in the accumulation zone, respectively.

Highlights

Mountain glaciers, different from the Arctic and Antarctic ice sheets, are geographically much closer to human settlements, such as the mid-latitude glaciers in the Alps, Caucasus, Highmountain Asia, and Southern Andes (Ming et al 2015; Gardner et al 2013; Zeng et al 1984)
Sites are far below the equilibrium line altitude (ELA) of 2013. These sites are all located in strong ablation zone and fresh snow can change to aged snow which would make the Tienshan Urumqi Glacier No.1 (TUG1) look not Bwhite^ any more in a short time (Fig. 2)
0 350 450 550 650 750 850 950 1050 Wavelength and dust in fresh and aged snow imply insoluble particles (IPs) including black carbon (BC) and dust could be aggregated during the post-depositional process and darken the surface of the UR1

Summary

Introduction

Different from the Arctic and Antarctic ice sheets, are geographically much closer to human settlements, such as the mid-latitude glaciers in the Alps, Caucasus, Highmountain Asia, and Southern Andes (Ming et al 2015; Gardner et al 2013; Zeng et al 1984). The optical measurement at each site was conducted randomly three times both for fresh and aged snow surfaces. The instrument could not measure BC in the aged snow samples collected at S4, and S6, probably due to high dust loads in the filters.

Results

Conclusion