Articles | Volume 10, issue 6
The Cryosphere, 10, 2611–2621, 2016
The Cryosphere, 10, 2611–2621, 2016

Research article 07 Nov 2016

Research article | 07 Nov 2016

Concentration, sources and light absorption characteristics of dissolved organic carbon on a medium-sized valley glacier, northern Tibetan Plateau

Fangping Yan1,4,5, Shichang Kang1,3,4, Chaoliu Li2,3, Yulan Zhang1, Xiang Qin1, Yang Li2,4, Xiaopeng Zhang1,4, Zhaofu Hu1,4, Pengfei Chen2, Xiaofei Li1, Bin Qu5, and Mika Sillanpää5,6 Fangping Yan et al.
  • 1Qilian Station for Glaciology and Ecological Environment, State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, 730000 Lanzhou, China
  • 2Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, 100101 Beijing, China
  • 3CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, 100101 Beijing, China
  • 4University of Chinese Academy of Sciences, 100049 Beijing, China
  • 5Laboratory of Green Chemistry, Lappeenranta University of Technology, Sammonkatu 12, 50130 Mikkeli, Finland
  • 6Department of Civil and Environmental Engineering, Florida International University, Miami, FL 33174, USA

Abstract. Light-absorbing dissolved organic carbon (DOC) constitutes a major part of the organic carbon in glacierized regions, and has important influences on the carbon cycle and radiative forcing of glaciers. However, few DOC data are currently available from the glacierized regions of the Tibetan Plateau (TP). In this study, DOC characteristics of a medium-sized valley glacier (Laohugou Glacier No. 12, LHG) on the northern TP were investigated. Generally, DOC concentrations on LHG were comparable to those in other regions around the world. DOC concentrations in snow pits, surface snow and surface ice (superimposed ice) were 332 ± 132, 229 ± 104 and 426 ± 270 µg L−1, respectively. The average discharge-weighted DOC of proglacial stream water was 238 ± 96 µg L−1, and the annual DOC flux released from this glacier was estimated to be 6949 kg C yr−1, of which 46.2 % of DOC was bioavailable and could be decomposed into CO2 within 1 month of its release. The mass absorption cross section (MAC) of DOC at 365 nm was 1.4 ± 0.4 m2 g−1 in snow and 1.3 ± 0.7 m2 g−1 in ice, similar to the values for dust transported from adjacent deserts. Moreover, there was a significant relationship between DOC and Ca2+; therefore, mineral dust transported from adjacent arid regions likely made important contributions to DOC of the glacierized regions, although contributions from autochthonous carbon and autochthonous/heterotrophic microbial activity cannot be ruled out. The radiative forcing of snow pit DOC was calculated to be 0.43 W m−2, demonstrating that DOC in snow needs to be taken into consideration in accelerating melt of glaciers on the TP.

Short summary
DOC release of Laohugou Glacier No. 12 was 192 kg km−2 yr−1, of which 43.2 % could be decomposed and return to atmosphere as CO2 within 28 days, producing positive feedback in the warming process and influencing downstream ecosystems. Radiative forcing of snow pit DOC was calculated to be 0.43 W m−2, accounting for about 10 % of the radiative forcing caused by BC. Therefore, DOC is also a light-absorbing agent in glacierized regions, influencing the albedo of glacier surface and glacier melting.