Analysis of flute forming conditions using ice sheet reconstructions and field techniques

Basal shear stress and sediment strength associated with the development of glacial flutes exposed during the 20th century in the Saskatchewan Glacier Valley Alberta, Canada, were determined by comparing reconstructed ice thicknesses, basal shear stresses, and field properties of sediments with the morphologically similar Kiwa Glacier Valley, British Columbia, Canada, where flutes are absent. Reconstructed subglacial conditions in these two valleys were compared to understand why flutes were developed in the former and not the latter. Using an existing topographic map of each glacier, equations for a series of longitudinal profile lines were determined to represent the existing ice surface. A previous ice surface, identified by trimlines along the valley walls, was reconstructed by applying the equations of longitudinal profile lines from the existing ice surface to a previous terminus between 5 and 10 km downvalley. After subtracting the elevation of the land surface (determined from topographic maps) from the reconstructed glacier surface, and calculating former ice surface slope, ice thickness and basal shear stress distributions were determined. Sediment texture and the location of flutes on a morainal topographic high, downglacier from a proglacial lake basin, allowed high porewater pressures to develop as glaciers extended to terminus positions in the Saskatchewan Glacier Valley. Sediment strength was reduced sufficiently below values of reconstructed shear stress plots to allow deformation creating flutes. The absence of a similar topographic high and different sediment textural characteristics in the Kiwa Glacier Valley resulted in lower porewater pressures and consequently less reduction in sediment strength preventing the development of glacial flutes despite higher shear stress values here. Results indicate that the degree to which sediment characteristics and porewater pressure allow reduction of subglacial sediment strength relative to basal shear stress is important in determining conditions when flutes may develop.     

Recent behaviour of the Debeli Namet glacier,Durmitor, Montenegro

A small cirque glacier is present in a north‐east facing cirque on the mountain of ?ljeme (2455 m a.s.l.) in the Durmitor massif, Montenegro. Sediment ridges in front of this glacier are interpreted as moraines and can be attributed to recent glacier activity over the past 130 years. Lichenometry was applied to determine the relative ages of different moraines using Aspicilia calcarea agg. One set of moraines dates from about 1878 AD, whilst another set of inner moraines dates from about 1904 AD. The most recent moraines appear to have formed within the last 11 years in front of an active glacier margin. Copyright © 2007 John Wiley & Sons, Ltd.     

中国天山冰川变化脆弱性研究

冰川是重要的淡水资源,对社会经济发展和生态环境影响显著,而其变化的脆弱性也关乎区域生态服务和经济可持续发展。本文以中国天山为例,基于脆弱性的暴露度、敏感性、适应能力构建涵盖自然地理特征、人口状况、社会经济水平、农业发展和社会服务等因素的冰川变化脆弱性框架,并以此针对性构建评价指标体系,探析天山冰川变化脆弱性的空间特征,采用地理探测器模型探讨自然、社会、经济和人口等因素对冰川变化适应能力的影响及交互作用。结果表明：① 脆弱性等级由西部地区向东部地区呈降低趋势,且水平差异显著。天山东部地区脆弱性最低、中部地区次之、西部地区较高。② 暴露度、敏感性和适应能力在空间上分别存在明显正相关与负相关,表明区域范围内冰川变化具有高暴露、高敏感地区往往适应能力较低,进而导致脆弱性较高;反之,脆弱性较低。③ 天山应对冰川变化能力的空间异质性是自然、社会、经济和人口因素共同作用的结果。其中,第二、三产业产值、城镇人口数、城镇固定资产投资与年末单位从业人员等因素具有主导作用。     

基于无人机摄影测量的梅里雪山明永冰川末端表面高程动态监测

位于横断山区的梅里雪山地区,受地形与气候的影响,该地区光学遥感及微波遥感应用较为受限。论文基于大疆精灵4RTK无人机搭配中海达UBase,于2018年11月9日和2019年11月12日对梅里雪山地区明永冰川末端开展了2期摄影测量,估算冰川消融区表面高程变化,监测冰川动态变化。研究结果表明:冰川区表面形态在不同位置有显著差别,航测冰川区中下部大量表碛覆盖,有少量沿冰川主流线方向发育的裂隙;航测冰川区中上部表碛覆盖较少,大量横向裂隙发育。2018年11月至2019年11月,明永冰川末端表面高程平均变化-1.67 m。冰川表面高程变化空间分布差异显著,在航测冰川区上部高程差存在正负交替现象,航测冰川区中部以减薄为主,而航测冰川区下部以增厚为主。与高亚洲地区其他山系冰川变化对比,梅里雪山地区是冰川表面高程变化最显著的地区。     

Vulnerability of glacier change in the Tianshan Mountains region of China

The glacier is a crucial freshwater resource in arid and semiarid regions,and the vulnerability of the glacier change is intimately linked to regional ecological services and so-cio-economic sustainability.Taking the Tianshan Mountains region in China as an example,a basic framework for studying the vulnerability of glacier change was constructed so as to address factors such as physical geography,population status,socio-economic level,agri-cultural development,and social services.The framework was based on key dimensions,that is,exposure,sensitivity,and adaptability,and this constituted a targeted evaluation index system.We examined the spatial structure and spatial autocorrelation of the glacier change vulnerability using ArcGIS and GeoDa software.The influence and interaction of natural,so-cial,economic,population and other factors on glacier change adaptability was examined using the GeoDetector model.The results suggested the following:(1) The vulnerability level decreased from the western region to the eastern region with significant differences between the two regions.The eastern region had the lowest vulnerability,followed by the central re-gion,and then western region which had the highest vulnerability.(2) Significant positive and negative correlations were found between exposure,sensitivity,and adaptability,indicating that the areas with high exposure and high sensitivity to glacier change tended to have a low adaptive capacity,which led to high vulnerability,and vice versa.(3) The spatial heterogeneity regarding the ability to cope with glacier change reflected the combined effects of the natural,social,economic,and demographic factors.Among them,factors such as the production value of secondary and tertiary industries,the urban population,urban fixed-asset investment,and the number of employees played major roles regarding the spatial heterogeneity of glacier change.     

天山南坡科其喀尔冰川作用区CO2通量观测研究

冰川融水径流的发育和形成过程中,存在大量水化学侵蚀,尤其是K/Na长石及碳酸盐的水解作用,可能消耗水体中H⁺,促使大气CO₂溶于水形成重碳酸盐,影响区域碳循环。2015年7月21日-2017年7月18日选取相对平坦开阔的西天山科其喀尔冰川表碛物覆盖区,利用涡度相关法进行CO₂通量监测。结果表明：大气CO₂通量介于-17.99~3.59 g·m^-2·d^-1之间,平均值为-2.58 g·m^-2·d^-1,说明研究区是一个显著的碳汇。净冰川区系统CO₂交换量主要受大气CO₂通量支配,但日内变化显著,白天因冰雪消融导致大气CO₂沉降于融水中促进区域水化学侵蚀,而夜间因太阳辐射减少,冰雪消融减弱甚至停止,抑制了区域CO₂沉降,甚至再生冰的形成引起溶解于液态水中的CO₂释放。净冰川区系统CO₂交换量与气温呈显著的负相关关系,即气温升高,大气CO₂沉降量增加;当降水量小于8.8 mm时,交换量随降水量变化不显著,而降水量大于8.8 mm时,CO₂沉降量随降水量增加而减少。净冰川区系统CO₂交换量随日径流量的变率遵循：积雪消融期 > 积雪积累期 > 冰川消融前期 > 冰川消融后期 > 冰川消融峰期,意味着积雪消融存在时,系统CO₂交换量随日径流量变率较大,可能是因积雪本身的阻尼作用或积雪期水文通道不发育,积雪融水较冰川冰融水汇集相对较慢,为可溶性物质化学反应提供充分时间,增强了CO₂沉降。     

东帕米尔高原昆盖山跃动冰川遥感监测研究

冰川跃动是冰川周期性地快速运动,给下游生命财产安全带来巨大威胁。对已经发现的跃动冰川进行监测不仅有助于提高对冰川跃动机理的认识,而且对冰川跃动灾害预警预报和风险评估都具有重要的意义。在中国第二次冰川编目中发现,1963-2009年东帕米尔高原昆盖山的5Y663L0023冰川末端发生大幅前进。本文利用Landsat影像、ASTER立体像对等数据对该冰川前进过程进行监测研究。结果表明：该冰川于1990-1992年和2007-2013年分别前进81±30 m和811±30 m,其中2007-2013年的前进属于跃动引发的前进。其中跃动最高峰在2007年8月21日-2008年10月26日,期间32.7×10⁶ m³的冰体发生卸载,导致末端前进了704±30 m,面积扩张了0.34 km²。针对东帕米尔地区跃动冰川周期研究的空白,本文认为该冰川跃动周期中跃动期为4 a,平静期最短为15 a左右。该冰川属于多温型冰川,跃动受热力学机制影响的可能性较大,但液态降水、冰雪融水的增加也是影响因素。     

中国天山冰川生态服务功能及价值评估

山岳冰川是干旱区生态环境和社会经济可持续发展的物质基础和特色文化基础,具有独特且无法替代的生态服务功能,而目前对冰川调节生态环境和提供人类福祉等方面服务功能和价值估算研究很少。本文基于第一、二次冰川编目数据,分析中国天山冰川面积和冰储量变化特征;梳理并构建山岳冰川生态服务功能体系,结合单位面积服务功能价格法和当量因子法,评估中国天山冰川年生态服务价值。结果显示：① 1970-2010年间,中国天山冰川面积减少1274 km²,退缩了13.9%,年平均冰川储量减少约4.08×10⁹ m³。高海拔区（> 5200 m）冰川面积出现增加,可能是由于该区域降水增加对冰川积累的作用大于气温上升对冰川消融作用造成的。② 中国天山冰川年生态服务价值为602亿元,气候调节、水文调节和淡水资源供给价值分别占总价值的66.4%、21.6%和9.3%,水力发电的年均生态服务价值约为3.5亿元,其他类型的调节和服务功能价值约12.8亿元。③ 比较分析冰川、森林、草地和湿地生态系统不同服务价值所占总价值比例发现,淡水资源供给/实物生产和生态调节功能在生态系统中均占比例较大,冰川单位面积生态服务价值高于其他类生态系统。本文以期能提高冰川对人类福祉和维持生态环境等方面的认知,服务于冰冻圈生态安全、环境保护以及资源的可持续利用规划与管理。     

近期哈尔里克山脉冰川变化遥感监测

哈尔里克山脉冰川的快速退缩已经影响到吐鲁番坎儿井的水量,先前关于该区冰川研究不够细致,且最新资料报道较为短缺。以哈尔里克山脉冰川为研究对象,基于Landsat TM/ETM+和OLI影像（1992、2002、2010、2016年）,通过比值阈值法、目视解译结合GIS技术,提取了该地区四期冰川边界,同时对研究区周边气温、降水以及日照时数进行线性趋势分析,研究其与冰川的响应关系。结果表明：（1）1992-2016年,哈尔里克山脉冰川总体呈现出持续退缩趋势,面积退缩了13.18%,年均退缩率为0.56%,近年来退缩速率有所减缓。（2）近似估算的冰储量在过去25 a间减少了18.33%,冰川物质亏损将对该区短缺的水资源提供了危险的信号。（3）冰川退缩率与冰川规模呈指数函数变化趋势;低海拔区冰川存在明显的末端升高趋势;N和NW向的冰川占明显优势,但N向退缩率最慢。（4）分形理论分析表明该地区冰川未来退缩将趋于一种稳定状态。该区气温和日照时数的显著上升导致其冰川退缩,同时冰川规模、海拔和坡向分布也是冰川变化的重要因素;对比发现该区冰川退缩速率较天山其他区域慢。