大高加索山脉冰川反照率时空分布及与物质平衡的关系

利用MOD10A1和MYD10A1冰雪反照率数据, 分析了大高加索山脉地区加拉巴西冰川和德扬库特冰川的反照率时空分布特征, 并使用五种反照率聚合方法, 对这两条冰川2002—2019年夏季反照率与物质平衡关系开展相关性研究.结果表明, 加拉巴西冰川和德扬库特冰川反照率随年份增加而明显减小, 两条冰川在夏季都出现了最低反照率, 加拉巴西冰川在冬季出现最高反照率, 而德扬库特冰川则出现在春季; 加拉巴西冰川夏季高海拔和低海拔区域的反照率差异较德扬库特冰川更为明显; 两条冰川夏季反照率均与夏季物质平衡表现出一定的正相关性, 其中加拉巴西冰川的相关性更加显著, 使用平均最小反照率方法时两者相关系数最大可达0.874(p＜0.05), 德扬库特冰川使用加权平均反照率方法时两者相关系数最大为0.765(p＜0.05).德扬库特冰川反照率与物质平衡相关性较低的原因可能是坡向和低海拔导致了其更易受暖湿气流影响, 冰川消融中短波辐射能占比较低, 反照率对其消融的影响小.

     

利用黏弹性有限元模型研究挪威北海北部地区末次冰期以来的冰后回弹和应力演化

挪威北海北部在末次冰期存在较大范围的冰盖,其冰盖的加载和卸载会对地表变形和内部应力调整产生重要影响.本文基于Maxwell黏弹性本构关系,根据初应力法自主开发了一套Maxwell黏弹性体有限元程序,它可以考虑重力和构造加载、地球介质弹性的纵向和横向不均匀性以及黏性的分层性,可以计算冰川载荷变化引起的地球表面变形及内部应力状态的变化.利用它研究了挪威北海北部1.1 Ma以来的冰川载荷变化、特别是两万多年以来冰盖的消退引起的地表冰后回弹.结果表明,自2万年以来,冰后回弹效应在冰盖载荷变化的不同阶段呈现明显的时空变化,现今地表垂直变化速率为几个毫米/年,与观测结果一致.下地壳和上地幔的黏弹性松弛效应明显,上地壳的应力状态在现今海岸线两侧存在差异性,水平和垂直正应力变化可达几十兆帕,剪应力变化有一个先增加后迅速减小至零的过程,与古地震、现今地震时空分布及应力测量结果也比较符合,研究结果有助于加深对冰后回弹的动力学过程的认识.

     

青藏高原色林错流域区冰川消融对湖泊水量变化的影响

青藏高原大部分湖泊近年来持续扩张,湖泊水位和水量明显增加.冰川消融是流域水量平衡和水循环的重要影响因素,直接导致湖泊水量变化.由于缺乏大范围的冰川质量平衡观测结果,青藏高原冰川消融对湖泊水量变化的影响仍存在较大争议.本文选择青藏高原内流区的色林错流域区（水系编号5Z2）作为研究对象,利用SRTM DEM和TanDEM-X双站InSAR数据,精确估算该流域三个主要冰川区（普若岗日、格拉丹东和西念青唐古拉）2000-2012年的冰川质量平衡,依次为：-0.020±0.030、-0.128±0.049、-0.143±0.032 m·w.e.·a^-1.并据此采用面积加权法准确推估出5Z2流域的冰川质量变化为：-0.166±0.021 Gt·a^-1.综合ICESat和Cryosat-2卫星测高数据,计算该流域2003-2012年湖泊水量变化速率（3.006±0.202 Gt·a^-1）,并定量评估冰川质量变化对5Z2流域湖泊水量增加的贡献为：5.52%±1.07%,因此在青藏高原色林错流域区,冰川消融不是导致21世纪初期湖泊水位上升的主要因素.

     

Impacts of Yulong Mountain glacier on tourism in Lijiang

Introduction The mountain tourism has been repeatedly identified as potentially vulnerable to global climate change and has received greater research attention. Implications of climate change can be seen, for example, in less snow, receding glaciers, melt…     

高亚洲冰川系统物质平衡特征及其对全球变化响应研究进展与展望

分布在高亚洲的大量现代冰川,是亚洲中部干旱半干旱地区最重要的淡水资源.高亚洲各区因环境差异,各区冰川系统物质平衡及其对全球气候变化的响应就表现出不同特点,需进一步应用冰川系统理论和方法对高亚洲冰川系统进行合理分区,研究各分区冰川系统的结构特征、物质平衡特征及其对气候变化的响应过程.通过总结国内外高亚洲冰川系统研究的现状,找出了国内外研究的优势及不足;在此基础上,从高亚洲冰川系统的等级划分、气候地形背景、结构特征、物质平衡特征、对全球变化的响应以及冰川系统径流变化对冰川灾害及环境影响的评估等方面进行了研究展望.并认为需要根据各区气候、地理条件划分不同的次级冰川系统,然后分别对不同冰川系统的冰川变化进行预测,根据冰川变化趋势,制定最优利用冰川水资源方案和冰川灾害防范措施.     

冰川物质平衡模式及其对比研究——以祁连山黑河流域十一冰川研究为例

冰川物质平衡是冰川连结气候和水资源的纽带, 对其的观测和模拟始终是冰川与气候变化研究领域的重点和前缘之一. 以祁连山黑河流域十一冰川为参照冰川, 结合实测物质平衡验证资料, 建立了基于冰川表面能量平衡的冰川物质平衡模型(物理模型)和基于温度参数、温度-辐射参数和温度-辐射-水汽压参数的三种度日因子模型(统计模型), 并对模拟结果进行了分析及评估. 结果表明: 净辐射是冰川表面最主要的能量来源, 占能量收入的82.3%; 其次为感热供热, 占收入的17.7%. 净长波辐射基本为负, 吸收的热量主要通过融化和蒸发/升华方式消耗, 分别占能量支出的84.7%和15.3%. 加入净短波辐射和水汽压参数的度日因子-物质平衡模型的模拟效果提高显著, 相对误差为7%, 与能量平衡模型的模拟误差6.7%, 相差不大. 研究表明, 能量-物质平衡模型的物理意义明确, 模拟能力强大, 尤其在日尺度上有绝对的优势; 统计物质平衡模型在特定的地理条件和气候条件下表现出不佳, 对于一些极端值的模拟能力欠缺, 但是具有输入变量少, 计算简单的优点. 研究结果对黑河流域乃至整个祁连山地区的冰川物质平衡模拟方法的建立具有参考意义.     

Second-Order Modelling of Turbulence in Katabatic Flows

A complete one-dimensional second-order closure model is used to simulate katabatic flows observed on glaciers and ice caps. The model is tested with two different closure assumptions for the viscous dissipation, one based on a prognostic equation for and the other on a diagnostic buoyant length scale. Both formulations give quite similar results. Model simulations are compared to observations made over sloping ice surfaces during periods dominated by katabatic flow. In general, good agreement is found for both mean wind and temperature profiles as well as eddy correlation measurements. It is also found that the turbulent transport terms play an important role in katabatic flows as opposed to the classical stable boundary layer where these terms are usually ignored. Even the turbulent transport of temperature variance, which leads to the well-known countergradient term in unstable boundary layers, is relatively important for modelling the observed temperature profiles. The effect of these terms on the flux-profile relationships, using observed and simulated profiles, is also discussed.     

Subglacial drainage system changes of the Gulkana Glacier,Alaska: discharge and sediment load observations and modelling

Hydrological characteristics of englacial and subglacial drainage systems in Gulkana Glacier, Alaska, were examined by analysing temporal variations of discharge and sediment load in the proglacial Phelan Creek in 2001. From data plots on semi‐log paper, it appeared appropriate to separate both discharge and sediment load into fast and slow components. The two components were possibly produced by two different drainage systems: an englacial and subglacial, ‘channellized’ system in the ablation zone, and a subglacial, ‘distributed’ system in the accumulation zone. The data indicate the occurrence of an event during which part of the ‘distributed’ drainage system changed into the ‘channellized’ drainage system. The daily time‐series of discharge and sediment load were represented using a tank model. In the model, the drainage from an additional tank was added, supposing that a subglacial reservoir full of water and sediment collapsed slowly when the subglacial drainage system changed from distributed to channellized. The simulation with the collapsed tank gave much more reasonable results than those with no collapsed tank. The contribution of the collapsed tank to total sediment load is 24%, which is much larger than 9% to total discharge. Copyright © 2006 John Wiley & Sons, Ltd.     

Surface exposure dating of the Great Aletsch Glacier Egesen moraine system,western Swiss Alps,using the cosmogenic nuclide 10Be

Egesen moraines throughout the Alps mark a glacial advance that has been correlated with the Younger Dryas cold period. Using the surface exposure dating method, in particular the measurement of the cosmogenic nuclide ¹⁰Be in rock surfaces, we attained four ages for boulders on a prominent Egesen moraine of Great Aletsch Glacier, in the western Swiss Alps. The ¹⁰Be dates range from 10 460±1100 to 9040±1020 yr ago. Three ¹⁰Be dates between 9630±810 and 9040±1020 yr ago are based upon samples from the surfaces of granite boulders. Two ¹⁰Be dates, 10 460±1100 and 9910±970 yr ago, are based upon a sample from a quartz vein at the surface of a schist boulder. In consideration of the numerous factors that can influence apparently young ¹⁰Be dates and the scatter within the data, we interpret the weighted mean of four boulder ages, 9640±430 yr (including the weighted mean of two ¹⁰Be dates of the quartz vein), as a minimum age of deposition of the moraine. All ¹⁰Be dates from the Great Aletsch Glacier Egesen moraine are consistent with radiocarbon dates of nearby bog‐bottom organic sediments, which provide minimum ages of deglaciation from the moraine. The ¹⁰Be dates from boulders on the Great Aletsch Glacier Egesen moraine also are similar to ¹⁰Be dates from Egesen moraines of Vadret Lagrev Glacier on Julier Pass, in the eastern Swiss Alps. Both the morphology of the Great Aletsch Glacier Egesen moraine and the comparison with ¹⁰Be dates from the inner Vadret Lagrev Egesen moraine support the hypothesis that the climatic cooling that occurred during the Younger Dryas cold episode influenced the glacial advance that deposited the Great Aletsch Glacier Egesen moraine. Because of the large size and slow response time of Great Aletsch Glacier, we suggest that the Great Aletsch Glacier Egesen moraine was formed during the last glacial advance of the multiphased Egesen cold period, the Kromer stage, during the Preboreal chron. Copyright © 2004 John Wiley & Sons, Ltd.