State Key Laboratory of Cryosphere Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control (AEMPC), School of Environmental Sciences and Engineering, Nanjing University of Information Science and Technology. 219 Ningliu Road, Nanjing 210044, China.
State Key Laboratory of Cryosphere Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China.
Sci Total Environ. 2017 Mar 1;581-582:848-856. doi: 10.1016/j.scitotenv.2017.01.032. Epub 2017 Jan 13.
The Tibetan Plateau (TP) or the third polar cryosphere borders geographical hotspots for discharges of black carbon (BC). BC and dust play important roles in climate system and Earth's energy budget, particularly after they are deposited on snow and glacial surfaces. BC and dust are two kinds of main light-absorbing impurities (LAIs) in snow and glaciers. Estimating concentrations and distribution of LAIs in snow and glacier ice in the TP is of great interest because this region is a global hotspot in geophysical research. Various snow samples, including surface aged-snow, superimposed ice and snow meltwater samples were collected from a typical temperate glacier on Mt. Yulong in the snow melt season in 2015. The samples were determined for BC, Organic Carbon (OC) concentrations using an improved thermal/optical reflectance (DRI Model 2001) method and gravimetric method for dust concentrations. Results indicated that the LAIs concentrations were highly elevation-dependent in the study area. Higher contents and probably greater deposition at relative lower elevations (generally <5000masl) of the glacier was observed. Temporal difference of LAIs contents demonstrated that LAIs in snow of glacier gradually increased as snow melting progressed. Evaluations of the relative absorption of BC and dust displayed that the impact of dust on snow albedo and radiative forcing (RF) is substantially larger than BC, particularly when dust contents are higher. This was verified by the absorption factor, which was <1.0. In addition, we found the BC-induced albedo reduction to be in the range of 2% to nearly 10% during the snow melting season, and the mean snow albedo reduction was 4.63%, hence for BC contents ranging from 281 to 894ngg in snow of a typical temperate glacier on Mt. Yulong, the associated instantaneous RF will be 76.38-146.96Wm. Further research is needed to partition LAIs induced glacial melt, modeling researches in combination with long-term in-situ observations of LAIs in glaciers is also urgent needed in the future work.
青藏高原（TP）或第三极冰雪带是黑碳（BC）排放的地理热点地区。BC 和尘埃在气候系统和地球能量预算中起着重要作用，特别是在它们沉积在雪和冰川表面之后。BC 和尘埃是雪和冰川中两种主要的光吸收杂质（LAIs）。估计 TP 中雪和冰川冰中 LAIs 的浓度和分布非常有趣，因为该地区是地球物理研究的全球热点地区。在 2015 年融雪季节，从玉龙山上的一个典型温带冰川采集了各种雪样，包括表面老化雪、叠加冰和雪融水样本。使用改进的热/光反射率（DRI Model 2001）方法和重量法测定 BC 和有机碳（OC）浓度，以及尘埃浓度。结果表明，在研究区域内，LAIs 浓度高度依赖于海拔。在冰川相对较低的海拔（一般 <5000masl）处观察到更高的含量和可能更大的沉积。LAIs 含量的时间差异表明，随着雪的融化，冰川雪中的 LAIs 逐渐增加。对 BC 和尘埃相对吸收率的评估表明，尘埃对雪反照率和辐射强迫（RF）的影响远大于 BC，特别是当尘埃含量较高时。这一点通过吸收率得到了验证，吸收率<1.0。此外，我们发现，在融雪季节，BC 引起的反照率降低幅度在 2%至近 10%之间，平均雪反照率降低 4.63%，因此对于玉龙山上典型温带冰川雪中的 BC 含量范围为 281 至 894ngg，相关的瞬时 RF 将为 76.38-146.96Wm。需要进一步研究来划分 LAIs 引起的冰川融化，未来的工作还需要结合冰川中 LAIs 的长期原位观测进行建模研究。
