Record Low Sea-Ice Concentration in the Central Arctic during Summer 2010

The Arctic sea-ice extent has shown a declining trend over the past 30 years. Ice coverage reached historic minima in 2007 and again in 2012. This trend has recently been assessed to be unique over at least the last 1450 years. In the summer of 2010, a very low sea-ice concentration(SIC) appeared at high Arctic latitudes—even lower than that of surrounding pack ice at lower latitudes. This striking low ice concentration—referred to here as a record low ice concentration in the central Arctic(CARLIC)—is unique in our analysis period of 2003–15, and has not been previously reported in the literature. The CARLIC was not the result of ice melt, because sea ice was still quite thick based on in-situ ice thickness measurements.Instead, divergent ice drift appears to have been responsible for the CARLIC. A high correlation between SIC and wind stress curl suggests that the sea ice drift during the summer of 2010 responded strongly to the regional wind forcing. The drift trajectories of ice buoys exhibited a transpolar drift in the Atlantic sector and an eastward drift in the Pacific sector,which appeared to benefit the CARLIC in 2010. Under these conditions, more solar energy can penetrate into the open water,increasing melt through increased heat flux to the ocean. We speculate that this divergence of sea ice could occur more often in the coming decades, and impact on hemispheric SIC and feed back to the climate.

青藏高原湖泊状态与丰度

湖泊的数量与面积变化及其丰度和大小分布对区域及全球水资源、生物地球化学循环和气候变化的评估具有重要的意义．本研究利用Landsat数据，对青藏高原过去40年大于1km^2的湖泊数量与面积变化进行了详细的研究．

Lakes' state and abundance across the Tibetan Plateau

Understanding the changes in number and areal extent of lakes,as well as their abundance and size distribution is important for assessments of regional and global water resources,biogeochemical cycles,and changes in climate.In this study,changes in lake area greater than 1 km2are mapped using Landsat datasets,spanning the 1970s,1990,2000,and 2010.In addition,high-resolution images(GeoCover Landsat mosaic 2000,with a pixel size of 14.25 m)are used for the first time to map lakes as small as 0.001 km2across the entire Tibetan Plateau(TP).Results show that the numbers and areal extent of individual lakes[1 km2in size show a slight decrease between the 1970s and 1990,followed by a clear increase from 1990 to 2010.Ninety-nine new lakes are identified between the 1970s and 2010,71 of which are found between 1990 and 2010.This indicates the accelerated glacier melt and/or increased difference of precipitation minus evaporation since the 1990s.More than 80%of the lakes show an increase in their area between the 1970s and2010.The lake census,using 2000 imagery,shows that there are 32,843 lakes with a total area of 43,151.08±411.49 km2,which makes up 1.4%of the total area of the TP.Around 96%of all lakes are small,with an area\1 km2,while the 1,204 large lakes([1 km2)account for96%of the total lake area.The TP is subdivided into 12greater drainage basins,and of these the inner TP dominates in terms of the number of lakes(55.03%),the total area of lakes(66%),and lake density(0.026/km2compared to the mean,0.011/km2).A plot of lake abundance against size shows that the size distribution of lakes departs from a typical power-law distribution,but displays such a distribution at the mean elevation(4,715 m),with an r2value of 0.97 and a slope of-0.66.The slopes of the abundance-size equations from each of the 12 greater basins,and from all basins together,are larger than-1,supporting the inference that larger lakes,rather than the small lakes,contribute more to the total lake surface area across the TP.The lake inventory provided in this study,along with the assessment of lake size distribution,have important implications for estimates of water balance,for water resource management,and for lake area estimations in the TP.

A novel solution for outlier removal of ICESat altimetry data： a case study in the Yili watershed, China

Due to the influence of cloud and saturated waveforms, ICESat data contain many contaminated elevation data that cannot be directly used in examining surface elevation and change. This study provides a novel solution for removing bad data and getting clean ICESat data for land applications by using threshold values of reflectivity, saturation, and gain directly from ICESat＇s GLAS （Geoscience Laser Alteimeter System） 01, 05, and 06 products. It is found that each laser campaign needs different threshold compositions to assure qualified ICESat data and that bad data removal rates range from 9.6% （laser 2A） to 62.3% （laser 2B） for the test area in the Yili watershed, China. These thresholds would possibly be used in other regions to extract qualified ICESat footprints for land applications. However, it is recommended to use the steps proposed here to further examine the transferability of threshold values for other regions of different elevations and climate regimes. As an example, the resulting ICESat data are applied to examine lake level changes of two lakes in the study area.

用于柔性和图案化电致变色器件的二维聚苯胺的喷墨打印研究

基于有机共轭聚合物的电致变色器件(ECD)在数字和彩色显示器中具有广阔的应用前景.然而,制备兼具优异电致变色性能、柔韧性和定制化图案的ECD仍然是一个挑战.本文报道了利用喷墨打印技术制备二维层状聚苯胺(PANI)基柔性图案化ECD的方法.层状PANI均匀分散在甲酸中,能够实现高精度、稳定的喷墨打印.同时,层状PANI的纳米级厚度、适当的掺杂比例,以及无添加剂的墨水成分,使得打印后的PANI电极和器件保持较高的电致变色性能和电化学特性.喷墨打印所得电极不仅表现出优异的光学对比度(76%,750 nm波长)、良好的着色效率(259.1 cm^(2)C^(-1))、较短的着色/褪色时间(1.8/2.4 s),而且具有赝电容特性与机械柔韧性.此外,本文所开发的二维层状PANI墨水可以定制化设计并打印成各种图案,并以此制备电化学控制的可寻址电致变色显示器.这种二维层状PANI电致变色材料可进一步用于柔性和图案化ECD,在新型光电显示领域具有较好的应用前景.