State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; University of Chinese Academy of Sciences, Beijing 100039, China.
State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100039, China.
Sci Total Environ. 2018 Jun 15;627:579-585. doi: 10.1016/j.scitotenv.2018.01.265. Epub 2018 Feb 2.
In glacierized regions, melting process has a significant effect on concentrations and light absorption characteristics of dissolved organic carbon (DOC), potentially resulting in variations of its radiative forcing, which is not yet relevant research at glacier region of the Tibetan Plateau (TP). In this study, DOC fractionation and its radiative forcing change during the melting process were investigated at Laohugou glacier No. 12 (LHG glacier) in western Qilian Mts., northern TP. DOC concentrations in fresh snow, snowpit and surface ice samples were 0.38 ± 0.06, 0.22 ± 0.11 and 0.60 ± 0.21 mg L, respectively. Their mass absorption cross-section at 365 nm (MAC) were 0.65 ± 0.16, 4.71 ± 3.68 and 1.44 ± 0.52 m g, respectively. The MAC values of snowpit samples showed a significant negative correlation with DOC concentrations, indicating DOC with high MAC values were likely to be kept in snow during the melting process. Topsoil samples of LHG glacierized region likely contributed a lot to snowpit DOC with high MAC values due to their similar absorption spectra. Spatially, the DOC concentration of surface ice samples increased from terminus to the upper part of the glacier. Correspondingly, the MAC value showed decreased trend. In the freezing experiment on surface ice and topsoil samples, small part of DOC with high MAC value was also likely to enter first frozen solid phase. In addition, the radiative forcing caused by snowpit and surface ice DOC increased around 7.64 ± 2.93 and 4.95 ± 1.19 times relative to fresh snow DOC, indicating the snow/ice melting caused by increased light-absorbing DOC needs to be considered in the future research.
在冰川地区，融化过程对溶解有机碳 (DOC) 的浓度和光吸收特性有显著影响，这可能导致其辐射强迫的变化，但目前青藏高原冰川地区还没有相关研究。本研究以祁连山北麓老虎沟 12 号冰川（LHG 冰川）为研究对象，探讨了冰川消融过程中 DOC 分馏及其辐射强迫的变化。新鲜雪、雪坑和表面冰样中的 DOC 浓度分别为 0.38±0.06、0.22±0.11 和 0.60±0.21mg·L-1，其在 365nm 处的质量吸收消光系数（MAC）分别为 0.65±0.16、4.71±3.68 和 1.44±0.52m·g-1。雪坑样品的 MAC 值与 DOC 浓度呈显著负相关，表明在融化过程中，高 MAC 值的 DOC 可能被保留在雪中。LHG 冰川区的表土样品由于其相似的吸收光谱，可能对高 MAC 值的雪坑 DOC 有很大贡献。从空间上看，表面冰样的 DOC 浓度从末端向上部冰川逐渐增加，相应地，MAC 值呈下降趋势。在表面冰和表土样品的冻结实验中，也有一部分高 MAC 值的 DOC 可能首先进入第一冻结固相。此外，雪坑和表面冰 DOC 的辐射强迫分别增加了约 7.64±2.93 和 4.95±1.19 倍，相对于新鲜雪 DOC，表明未来的研究需要考虑由于增加的光吸收 DOC 导致的冰雪融化。
