吉林省季节冻土冻结深度变化及对气候的响应

为了掌握季节冻土冻结深度的变化对气候的响应,利用1961-2015年吉林省46个气象站的逐日平均气温、地表温度、积雪深度、冻土冻结深度等数据,采用线性倾向估计、突变分析等方法,研究了吉林省季节冻土冻结深度的时空演变规律及其与气温、积雪的关系。结果表明：吉林省季节冻土最大冻结深度呈由西向东逐渐减小的空间分布特征,绝大多数站最大冻结深度呈减小趋势。基本上在10月开始冻结,次年3月达到最深,6月完全融化。西部冻土冻结深度变幅较大,其次是中部,东部最小。1961-2015年季节冻土最大冻结深度以-5.8 cm·（10a）^-1的速率显著减小（P<0.01）。最大冻结深度基本上呈逐年代减小的趋势,从20世纪90年代开始,最大冻结深度明显减小。最大冻结深度在1987年发生了突变,突变后平均最大冻结深度比突变前平均最大冻结深度减小了22.2 cm。通过分析气温和积雪深度对冻结深度的影响,认为冻土冻结深度对气温变化较为敏感,绝大多数站最大冻结深度与平均气温呈负相关关系。在年际变化上,气温的上升是最大冻结深度减小的主要原因。在季节冻土稳定冻结期,积雪深度超过10 cm,保温作用逐渐变强;当积雪深度达到20 cm时,保温作用显著,冻土冻结深度变浅。     

A near‐annual palaeohydrological study based on testate amoebae from a sub‐alpine mire: surface wetness and the role of climate during the instrumental period

We present the first testate amoeba‐based palaeohydrological reconstruction from the Swiss Alps, and the first depth to the water table (DWT) calibration dataset for this region. Compared to existing models, our new calibration dataset performs well (RMSEP = 4.88), despite the length of the water table gradient covered (53 cm). The present‐day topography and vegetation of the study mire Mauntschas suggest that it is partly ombrotrophic (large Sphagnum fuscum hummocks, one of which was the coring site) but mostly under the minerotrophic influence of springs in the mire and runoff from the surrounding area. Ombrotrophic Sphagnum fuscum hummocks developed at the sampling site only during the last 50 years, when testate amoebae indicate a shift towards dry and/or acid conditions. Prior to AD 1950 the water table was much higher, suggesting that the influence of the mineral‐rich water prevented the development of ombrotrophic hummocks. The reconstructed DWT correlated with Pinus cembra pollen accumulation rates, suggesting that testate amoebae living on the mire and P. cembra growing outside of it partly respond to the same factor(s). Finally, temperature trends from the nearby meteorological station paralleled trends in reconstructed DWT. However, contrary to other studies made on raised bogs of northwestern Europe, the highest correlation was observed for winter temperature, despite the fact that testate amoebae would more logically respond to moisture conditions during the growing season. The observed correlation with winter temperature might reflect a control of winter severity on surface moisture during at least the first part of the growing season, through snow melt and soil frost phenomena influencing run‐off. More ecohydrological work on sub‐alpine mires is needed to understand the relationships between climate, testate amoebae and peatland development. Copyright © 2009 John Wiley & Sons, Ltd.     

三江平原沼泽湿地区道路冻害

三江平原沼泽湿地区,在自然和人为影响下,发育着五种不同类型的道路翻浆,某些路段产生雪阻,冰糊(涎流冰)、路面挂冰等道路冻害,严重影响交通运输,采取相应防治措施维持运营。     

Palaeotemperature reconstructions of the European permafrost zone during marine oxygen isotope Stage 3 compared with climate model results

A palaeotemperature reconstruction based on periglacial phenomena in Europe north of approximately 51 °N, is compared with high‐resolution regional climate model simulations of the marine oxygen isotope Stage 3 (Stage 3) palaeoclimate. The experiments represent Stage 3 warm (interstadial), Stage 3 cold (stadial) and Last Glacial Maximum climatic conditions. The palaeotemperature reconstruction deviates considerably for the Stage 3 cold climate experiments, with mismatches up to 11 °C for the mean annual air temperature and up to 15 °C for the winter temperature. However, in this reconstruction various factors linking climate and permafrost have not been taken into account. In particular a relatively thin snow cover and high climatic variability of the glacial climate could have influenced temperature limits for ice‐wedge growth. Based on modelling the 0 °C mean annual ground temperature proves to be an appropriate upper temperature limit. Using this limit, mismatches with the Stage 3 cold climate experiments have been reduced but still remain. We therefore assume that the Stage 3 ice wedges were generated during short (decadal time‐scale) intervals of extreme cold climate, below the mean temperatures indicated by the Stage 3 cold climate model simulations. Copyright © 2003 John Wiley & Sons, Ltd.     

Mapping exposure to snow in a developing African context: implications for human and livestock vulnerability in Lesotho

Alpine cryospheric hazards are becoming increasingly prominent under current global/regional climate change scenarios and receiving wide scientific coverage from, in particular, northern hemisphere mountain regions associated with glaciers, permafrost, and extensive seasonal snow cover. However, there is a general paucity of knowledge and attention on cryospheric hazards associated with mountain environments only occasionally/rarely impacted by heavy seasonal snowfalls or severe frost events, particularly those in developing and southern hemisphere regions. Prolonged snow cover in the Lesotho Highlands sometimes carries the consequence of human and livestock deaths owing to isolation and exposure in this developing region. We use daily Moderate Resolution Imaging Spectroradiometer snow cover images for the period 2003–2010, to establish the frequency, extent, and timing of snowfalls across Lesotho. In addition, a digital shape file containing the location, name, and district attributes of 2,016 villages across Lesotho was used to assist in the construction of a village exposure to snow index. A ranking system was applied to each village according to the seasonal duration of snow cover, and the accessibility and proximity to the nearest road. Snowfalls occur on average between 1 and 8 times per annum, with village exposure to snow (potential vulnerability) being generally low, particularly for the lowlands and Senqu River Valley. However, the study identifies that some high-altitude (>2,500 m) villages such as Thoteng, Letseng-la-Terae, and Mabalane are, on occasion, highly exposed to prolonged snow cover, and particularly so during the mid-snow season of July/August. We demonstrate the importance of applying spatiotemporal assessments on infrequent snow occurrences (which carry associated hazards) in developing mountain regions such as Lesotho, with implications to reduce livelihood risks through improved disaster preparedness and a well-informed, focused emergency response.     

青藏高原雪盖对亚洲季风影响研究进展

资料分析和数值模拟均表明,青藏高原作为一个特殊的抬高了的下垫面,其上雪盖面积和积雪日数等的异常均与亚洲夏季风的强弱及起讫有关．雪盖面积大、积雪日数多的年份,亚洲季风弱且爆发迟,推进慢;雪盖面积小、积雪日数少的年份,亚洲季风强且爆发早,推进快．但也存在不同的看法     

Slope hummock development, Fosheim Peninsula, Ellesmere Island, Nunavut, Canada

Slope hummocks, a type of nonsorted patterned ground, are composed of stratified, organic, silty sand, and develop through the interaction of niveo-eolian deposition, solifluction, slopewash, and vegetation growth. Fields of hummocks show consistent patterns: forms on convex slopes increase in height downslope until the channel is reached, whereas those on convexo-concave slopes increase on the upper convexity but are buried by niveo-eolian deposition downslope of the snowbank remnant. These trends can be reproduced using a simple numerical model based on measured slope and snow depth profiles, sediment concentrations in the snow and solifluction rates. The model indicates that hummocks transit slopes of 20-40 m in about 2-4 ka, a time-frame that is plausible given site emergence, measured rates of solifluction, and published dates for organic horizons within hummocks on northern Ellesmere Island. Sensitivity analyses show that long-term effect of climate warming on hummock heights may differ depending on whether it is accompanied by precipitation increase or decrease. The required combination of two-sided freezing to promote plug-like movement, incomplete vegetation cover and thin snow that enable eolian erosion during winter and spring, and vegetation growth in snow-bed sites to stabilize niveo-eolian deposits may explain why these forms are important regionally but apparently are not present throughout the Arctic.     

从第三极到北极： 积雪变化研究进展

在全球气候变化背景下, 第三极和北极地区积雪是地表最活跃的自然要素之一, 其动态变化对气候环境和人类生活产生重要影响。通过回顾第三极和北极积雪研究进展, 阐述了降雪、 积雪范围、 积雪日数、 积雪深度和雪水当量在第三极和北极地区的时空分布特征和变化趋势。结果表明： 近50年, 特别是进入21世纪以来, 第三极和北极地区降雪比率均呈下降趋势; 积雪范围、 积雪日数、 积雪深度、 雪水当量总体均呈减小趋势, 融雪首日有所提前。同时就积雪变化对生态系统与气候系统的影响进行了论述, 评估了积雪的反馈作用。通过总结第三极和北极积雪变化研究进展, 凝练研究中存在的不足和未来发展趋势, 为提升积雪对气候变化及经济社会发展影响的认识提供重要科学支撑。     

Periglacial phenomena and their significance as climatic and edaphic indicators

As formed by frost-action and the presence of intensely frozen ground periglacial phenomena, especially microrelief features, are good examples for geomorphic phenomena as being clearly dependent upon specific climatic conditions. Whereas climate controls and delimits the formation and occurrence of periglacial phenomena at a zonal and regional scale, non-climatic vegetational, topographical and edaphic factors are significant within the climatically defined boundary conditions at a smaller scale. It can be shown that each type of periglacial phenomenon is dependent on specific climatic and edaphic conditions. Data on these conditions are compiled in several tables. On the other hand, because of this dependence on specific environmental conditions periglacial phenomena are at the same time diagnostic indicators for such conditions. As to climate they are indicators for specific climatically defined types of frozen ground and for thermal conditions in terms of mean values, such as mean air temperatures, freezing and thawing indexes. Spatial associations of genetically different types of periglacial phenomena indicate the extent and regional subdivision of the periglacial environment and its climatic limits. The definition of the climate-diagnostic value of present periglacial phenomena is an essential perequisite for the palaeoclimatic interpretation phenomena are sensitive to climatic variations of small amplitude and as such they are also indicators of recent short-term climatic changes. As to edaphic conditions they indicate frost-action potential of the groud and various soil properties which have practical implications. As edaphic indicators periglacial phenomena are of significance for terrain evaluation programmes in the Arctic for practical purposes.     

寒区灌丛与积雪关系研究进展

在气候变化的背景下, 寒区灌丛与积雪的相互关系成为寒区水文循环研究的重要环节. 综述近几十年来寒区灌丛-积雪相互关系的国内外研究现状, 并对未来研究提出了展望. 寒区灌丛过去几十年来覆盖面积和生物量等呈现增加趋势, 灌丛的增加可截留积雪, 改变积雪重分布, 影响积雪消融过程; 积雪可增加灌丛区地温, 制约灌丛区融雪时空变化过程, 影响寒区灌丛的生理生态过程. 灌丛与积雪同为寒区自然生态系统和环境的重要组成部分, 二者相互作用使地面太阳辐射和地表水分分配过程复杂化, 从而间接地影响寒区冻土环境变化. 最后, 指出了未来研究需要重点关注的几个问题: 寒区灌丛区积雪分布的精确估计; 灌丛-积雪-冻土连续体的研究; 耦合灌丛-积雪作用的寒区水文模型的构建.     

积雪大尺度气候效应综述

本综述了积雪大尺度气候效应研究在相关分析、天气气候学诊断以及数值以得的重要进展、评论了前人研究中存在的主要问题，强调指出准确而详尽的积雪空间分布、季节变化与年际波动是揭示积雪对气候影响物理机制所必不可缺少的。向欧亚大陆或青藏高原积血可对东亚季风产生持续性影响这一被广泛接受的看法提出了挑战。全球海气异常，东亚季风和欧亚大陆积雪之间的相互关系，有待用真实的积雪变化做进一步探讨。     

结合全球气候模型预测结果概率分析融化深度

A probabilistic approach may be adopted to predict freeze and thaw depths to account for the variability of (1) material properties, and (2) contemporary and future surface energy input parameters (e.g.air temperatures, cloud cover, snow cover) predicted with global climate models. To illustratc the probabilistic approach, an example of the prediction of thaw depths in Fairbanks, Alaska, is considered, More specifically, the Stefan equation is used together with the Monte Carlo simulation technique to make a probabilistic prediction of thaw penetration. The simulation results indicate that the variability in material properties, surface energy input parameters, and temperature data can lead to significant uncertainty in predicting thaw penetration. The Taylor series method was performed to determine the mean and standard deviation of thaw penetration and the results were compared to the Monte Carlo simulation results. The close comparison of the results suggests that the simpler Taylor series method may be applied to many cold regions problems to account for the variability of input parameters.     

山西大同、内蒙古鄂尔多斯冰楔、砂楔群的发现及其环境意义

研究了山西大同、内蒙古东胜和乌审旗地区发现的大量冰楔假型、砂楔、寒冻裂隙和南部白城子附近的冰卷泥.根据这些冰缘现象,并参考前人工作成果,划定了晚更新世晚期末次冰期时多年冻土的南界,并根据所获得的年代资料划分了4次冰缘期:33ka BP,30～26ka BP,20～16ka BP和8ka BP左右,当时的温度比今天分别降低8.4℃,12～13℃,10℃和7～10℃.     

Periglacial phenomena in the wooded areas of Northern Sweden - relicts from the Tärendö Interstadial

Frost-shattered bedrock and ventifacts interpreted to be abraded by drifting snow or ice particles occur frequently in the wooded areas of northernmost Sweden. Ice-wedge casts and periglacial involutions are encountered more sporadically. The phenomena cannot be explained by the present or the Holocene climate and demonstrably pre-date the last deglaciation. The relation to glacial and non-glacial stratigraphy, and to ice flow during the latest glacial stade, strongly suggests that the periglacial activity dates from the local Tärendö Interstadial, tentatively correlated with Odderade. The presence of the periglacial features implies not only that different morphological formations survived the erosive impact of the last continental ice sheet but also that in wide areas the very ground surface, including ventifacts in primary position, is the same today as during the interstadial. A similar situation appears to prevail in northernmost Dalecarlia and parts of Härjedalen and Jämtland in central Sweden.     

Rethinking the fourth of July Valley site: A study in glacial and periglacial geoarchaeology

The Fourth of July Valley site (5BL120) occupies the crest and inner slope of a Satanta Peak (latest Pleistocene) terminal moraine above timberline in the Indian Peaks Wilderness Area, Colorado Front Range. Excavations in 1971 suggested that a Late Paleo‐Indian lithic tradition marked by lanceolate and stemmed projectile points with parallel‐oblique flaking persisted at high altitude during the Altithermal, long after its disappearance from drought‐susceptible lowlands. Analysis of a sediment column collected in 2001 casts doubt on this interpretation. Large charred sclerotia (the resting stages of mycorrhizal fungi) show that tree islands colonized the moraine soon after deglaciation, fueling Early and Middle Holocene wildfires. Conditions became increasingly periglacial ca. 3340 yr B.P., when a lobate rock glacier advanced to the south margin of the site, altering snow‐accumulation patterns, eliminating trees, supplying meltwater that fueled ice‐lens formation, and initiating deposition of humus‐rich, snowbed loess. Large waste flakes and artifacts were frost‐sorted to the existing ground surface, where they became mixed with 6240‐year‐old wildfire charcoal in a pseudo‐occupation layer. Microflakes were too small to participate in vertical frost sorting, so remained in their original stratigraphic locations. The association of thermally altered microflakes with 8920‐year‐old charcoal in a deeply buried stratigraphic context suggests that the site was occupied during the Early Holocene and is irrelevant to the Altithermal refugium hypothesis. © 2005 Wiley Periodicals, Inc.     

Consistent seasonal snow cover depth and duration variability over the Western Himalayas (WH)

Precipitation in solid form, i.e., snow, during winter season over the Western Himalayas (WH) leads to the build-up of seasonal snow cover. Seasonal snow cover build-up (snow cover depth and duration) largely depends on atmospheric variables such as temperature, precipitation, radiation, wind, etc. Integrated (combined) influence of atmospheric variables on seasonal snow cover gets reflected in terms of spatial and temporal variability in seasonal snow cover build-up pattern. Hence spatial and temporal variability of seasonal snow cover build-up can serve as a good indicator of climate change in high altitude mountainous regions like the WH. Consistent seasonal snow cover depth and duration, delay days and early melt days of consistent seasonal snow cover at 11 stations spread across different mountain ranges over the WH were analyzed. Mean, maximum and percentiles (25th, 50th, 75th, 90th and 95th) of consistent seasonal snow cover depth and duration show decline over the WH in the recent past 2–3 decades. Consistent seasonal snow cover is found to melt early and snow cover build-up pattern is found to show changes over the WH. Decline in consistent seasonal snow cover depth, duration and changing snow cover build-up pattern over the WH in recent decades indicate that WH has undergone considerable climate change and winter weather patterns are changing in the WH.     

新疆开都河流域季节性冻土特征的控制和影响因子分析

全球变暖使季节性冻土范围逐渐缩小,而季节性冻土对春季径流,尤其是春季洪峰的影响使得该方面的研究更为重要。为了分析季节性冻土广泛分布的山区不同海拔高度条件下季节性冻土发育和融化期影响因子的差异,采用通径分析方法对开都河流域不同海拔高度季节性冻土最大冻结深度和解冻日数的影响因子进行了分析。结果表明,不同海拔高度这两者的影响因子差异不大,但其控制因子存在差异。季节性冻土最大冻结深度的控制因子由低海拔处的负积温和最大积雪深度转为中高海拔处的平均相对湿度;解冻日数的控制因子由低海拔处的平均风速和最大冻结深度转变为高海拔处的平均相对湿度。该差异主要由不同海拔高度的地理位置和局地气候条件等决定。     

Climate and material controls on periglacial soil processes: Toward improving periglacial climate indicators

One of the distinguished efforts of A.L. Washburn was to reconstruct mean annual air temperature using periglacial features as climate indicators. This paper reviews existing periglacial indicators and proposes a strategy to improve their thermal resolution based on recent periglacial process studies, with a focus on solifluction and thermal contraction cracking and associated landforms/structures. Landforms resulting from solifluction reflect both the depth subjected to freeze-thaw and the thickness of frost-susceptible soils. The thickness of a solifluction structure can be used to infer the dominant freeze-thaw regime and minimum seasonal frost depth. Ice-wedge pseudomorphs have limited potential as a climate indicator because (1) they mainly reflect extreme winter temperatures, (2) their thermal thresholds depend on the host material, and (3) they need to be distinguished from frost wedges of other origin produced under different thermal and/or material conditions. Monitoring studies of currently active ice wedges suggest that ice-wedge cracking requires a combination of low temperature and large temperature gradients in the frozen active layer. Further field monitoring of periglacial processes and their controlling factors under various climate conditions and in various materials are needed, however, to improve the resolution of periglacial paleoclimate indicators.     

2007-2011年西藏纳木错流域积雪时空变化及其影响因素分析

通过2007-2011年纳木错站人工积雪观测资料,对西藏纳木错流域MODIS两种积雪产品(MOD10A1和MOD10A2)进行了精度验证,分析了纳木错流域积雪累积和消融的空间差异,以及流域积雪覆盖率的时空变化;利用纳木错站人工积雪观测资料及自动气象站资料,分析了纳木错流域积雪要素(积雪深度、雪水当量、积雪密度)的时间变化及其与气候参数(气温、降水量、风速等)的关系.结果表明：纳木错流域MOD10A2数据的积雪识别精度(67.1%)高于MOD10A1(42.2%),总识别精度(73.0%)略低于MOD10A1数据(78.4%).纳木错流域积雪累积和消融存在空间差异,积雪在流域南部的念青唐古拉山脉最先累积,之后为流域东部,最后为流域西部;积雪消融的空间变化则相反.由此导致流域积雪日数南部最大、东部次之、西部及西北部最小.纳木错流域各积雪要素的年内变化存在双峰值特征,峰值分别出现在10-11月和1月,积雪在10-11月受降水和气温共同作用,12月至次年3月主要受气温影响.纳木错流域的平均积雪覆盖率为21.9%,受湖泊效应影响区域(主要为东部地区)达到50.6%,而其他区域仅为18.3%.同时,受湖泊效应影响,纳木错平均积雪深度、积雪水当量均显著大于周边地区.