Regional modelling of present,past and future potential distribution of discontinuous permafrost based on a rock glacier inventory in the Bagnes‐Hérémence area (Western Swiss Alps)

A regional model was used to draw the permafrost distribution in the 200 km 2 of the Bagnes-Hérémence area (Western Swiss Alps). The model is based on the fact that permafrost distribution depends mainly on altitude and orientation and that the minimal altitude of active/inactive rock glaciers can be used as an indicator of the lower limit of discontinuous permafrost. The lower limit of relict rock glaciers is also used as an indicator of past distribution of permafrost. An inventory of rock glaciers was therefore made in the study area. The lower limit of permafrost during the Younger Dryas was determined by comparing the position of relict rock glaciers and glacier extension during the Older Dryas. The model was then applied to four periods (Younger Dryas, Little Ice Age, current period and future) in order to show the temporal evolution of permafrost distribution and glacier extension.     

Lake-Level Fluctuations and Small-Scale Vegetation Patterns During the Late Glacial in The Netherlands

Late glacial changes in the vegetation were studied in and around a former lake on the southeastern side of a coversand ridge near Milheeze (southern Netherlands). Analyses of microfossils and macroremains and AMS ¹⁴C dating were performed on four sediment cores along a transect from sand ridge to the lake centre. Small-scale vegetation patterns and lake-level fluctuations were reconstructed in detail based on the information provided by the transect. For the first time in The Netherlands, cores along a transect within one lake were used to reconstruct the amplitude of late glacial lake-level fluctuations. Near Milheeze, a small and shallow lake was formed during the Bølling. The large increase in the water level during the Bølling and early Allerød, and the transition to more eutrophic conditions at the start of the Allerød, were probably related to the disappearance of permafrost. During the Allerød, open birch and pine woodlands developed in the area. In the lake, organic deposits accumulated, and the lake size and depth fluctuated. At the start of the Younger Dryas, higher lake water levels were recorded and woodlands became more open as a result of both a drop in the temperature and an increase in the effective precipitation. During the late Younger Dryas the lake water level dropped as the climate became drier and temperatures slightly increased. Accumulation of organic deposits in the lake ceased at the end of the Younger Dryas, which was caused by a drop in the water level in combination with the hydroseral succession process within the lake itself. The climatic signal reflected in the late glacial flora and lake-level fluctuations agree well with other published data from The Netherlands.     

The late-glacial and early-Holocene palaeoecology of cladoceran microfossil assemblages at Kråkenes, western Norway, with a quantitative reconstruction of temperature changes

Cladoceran microfossil remains were analysed from a sediment core taken from a lake basin at Kråkenes, western Norway. The sequence included immediate post-glacial conditions (ca. 12,300 ¹⁴C BP), the Allerod, Younger Dryas, and early Holocene to approximately 8,500 ¹⁴C BP. The interpretation of changes in the cladoceran assemblages is based on the known ecology of the taxa, the documented environmental history of the study sequence, the variations in the organic content of the sediment, the radiocarbon dates, and the results of analyses of other biotic groups, including diatoms, macrophytes, and chironomids. In addition, a quantitative reconstruction of changes in air temperature is presented for the study period. This reconstruction is based on transfer functions developed from a separate Swiss surface-sediment cladoceran data set.The cladoceran assemblages throughout the sequence are dominated by littoral chydorid taxa. Bosmina, Daphnia, and Simocephalus represent the open-water component of the zooplankton. Chydorus piger and Daphnia were the only immediate post-glacial pioneer taxa. A rapid proliferation of the open-water and littoral cladoceran taxa began with the onset of the Allerod and persisted for approximately 1,000 yrs. At the start of the Younger Dryas a local glacier formed and drained into the lake, causing a sudden decline in chydorid diversity, with only Chydorus sphaericus and Acroperus harpae persisting throughout this period. Chydorid diversity started to recover in the upper Younger Dryas and continued in the early Holocene. Progressive acidification and oligotrophication are also discernible from the cladoceran assemblages present in the Holocene.The reconstructed mean summer air temperature was from 8-21 °C, with prediction errors of 1.8-2.5 °C. The Allerod was only slightly warmer than the Younger Dryas period, but a progressive increase in temperature is apparent during the early Holocene. In conclusion, the results of this study provide a further demonstration of the value of cladocera as indicators of a variety of palaeoenvironmental parameters, including temperature.     

Late-glacial and early-Holocene Trichoptera (Insecta) from Kråkenes Lake, western Norway

Fossil Trichoptera (caddisfly) remains have been identified and quantitatively recorded in the late-glacial and early-Holocene sediments from Kråkenes Lake, western Norway. The sediment sequence was deposited between 12,300 and 8850 ¹⁴C BP, covering the Allerød, Younger Dryas, and early-Holocene periods. The first Trichoptera were recorded at 12,000 ¹⁴C BP, and during the Allerod a diverse assemblage of Limnephilidae taxa developed in the lake. By about 11,400 ¹⁴C BP the relatively thermophilous Polycentropus flavomaculatus and Limnephilus rhombicus were present, suggesting that the summer water temperature was at least 17 °C. This temperature fell by 5-8 °C at the start of the Younger Dryas, and the thermophilous taxa were replaced within 20-40 ¹⁴C yrs by Apatania spp., including the arctic-alpine A. zonella, suggesting a maximum summer water temperature of 10-12 °C. The Trichoptera assemblage was impoverished in numbers and in diversity over the next 200 yrs as the severe conditions of the Younger Dryas developed. As soon as temperatures rose and glacial meltwater and silt input ended about 700 ¹⁴C yrs later, the resident Apatania assemblage expanded immediately, within 10 yrs. About 130 yrs later, thermophilous taxa replaced Apatania, and a much more diverse assemblage than in the Allerod occupied the varied habitats made available by the development of the Holocene lake ecosystem. The 130 yr delay may have been caused by a gradual temperature increase crossing a critical threshold, or by the time taken for thermophilous taxa to migrate from their Younger Dryas refugia.     

Chironomid-inferred late-glacial and early-Holocene mean July air temperatures for Kråkenes Lake, western Norway

A chironomid data-set calibrated to July air temperatures, based on 44 lakes in western Norway, is used to reconstruct mean July air temperatures from late-glacial and early-Holocene fossil chironomid assemblages at Kråkenes Lake. The calibration function is based on Weighted Averaging Partial Least Squares regression and has a root mean square error of prediction (RMSEP) of 1.13 °C, a r² of 0.69, and a maximum bias of 2.66 °C. All these statistics are based on leave-one-out cross-validation. A calibration function based on summer surface-water temperatures has a poorer performance (RMSEP = 2.22 °C, r² = 0.30, maximum bias = 5.29 °C). The reconstructed July air temperatures at Kråkenes rise to 10.5 °C soon after deglaciation, are about 11.5 °C in the Allerød, decrease to 9.5-10 °C in the Younger Dryas, and rise rapidly within 15 yrs to 11.5 °C at the onset of the Holocene. There is a two-step rise to 13 °C or more in the early-Holocene. The likely over-estimation of Younger Dryas temperatures and under-estimation of early-Holocene temperatures probably result from the limited temperature range represented by the existing calibration set. The data set is currently being expanded to include lakes with warmer air temperatures (> 14 °C) and with colder air temperatures (< 8 °C).     

Soil temperatures and stability of ice-cemented ground in the McMurdo Dry Valleys, Antarctica

Year-round temperature measurements at 1600 m elevation during 1994 in the Asgard Range Antarctica, indicate that the mean annual frost point of the ice-cemented ground, 25 cm below the surface, is -21.7 +/- 0.2 degrees C and the mean annual frost point of the atmosphere is -27.5 +/- 1.0 degrees C. The corresponding mean annual temperatures are -24.9 degrees C and -23.3 degrees C. These results imply that there is a net flux of water vapour from the ice to the atmosphere resulting in a recession of the ice-cemented ground by about 0.4-0.6 mm yr-1. The level of the ice-cemented permafrost is about 12 cm below the level of dry permafrost. The summer air temperatures would have to increase about 7 degrees C for thawing temperatures to just reach the top of the subsurface ice. Either subsurface ice at this location is evaporating over time or there are sporadic processes that recharge the ice and maintain equilibrium over long timescales.     

A model of permafrost formation and occurrences in the intracontinental mountains

The proposed method of permafrost distribution mapping entails the use of a computer-based model that takes into account the specific conditions of arid mountains for permafrost formation and occurrence. In the intracontinental arid mountains, incoming short-wave solar radiation, mean annual temperature and evaporation are the main influences on the distribution of permafrost. Coarse debris is widespread in the high mountains and greatly influences the thermal state of the ground. The model can compute heat transfer in the coarse debris, which is considered a porous body, and it can be used for permafrost distribution mapping with various degrees of spatial resolution. As a result, the GIS-based map of permafrost distribution for the Bolshaya Almatinka River basin, Kazakhstan, was generated.     

Midge-inferred temperature reconstructions and vegetation change over the last ~15,000?years from Trout Lake, northern Yukon Territory, eastern Beringia

Two cores from Trout Lake, northern Yukon, yielded quantitative estimates of summer air temperatures using fossil midge larvae. Warming began around 14,400?cal?yr BP, with inferred mean July air temperatures reaching values warmer than present by 12,800?cal?yr BP. A 1?°C cooling from 12,200 to 11,200?cal?yr BP closely corresponds with the Younger Dryas chronozone. A broad temperature maximum occurred between 10,800 and 9,800?cal?yr BP, with mean July air temperature about 2.2?°C warmer than present. This represents an early Holocene thermal maximum and coincides with increased organic content of the sediment. Both the shallow- and deep-water cores show similar temperature trends for their overlapping periods. The inferred rise in mean July air temperature at 14,200?cal?yr BP coincides with a shift in vegetation from an herb- to shrub-dominated landscape. In contrast, the increase in Alnus pollen at 6,400?cal?yr BP does not coincide with a change in temperature, but may be a response to a rise in precipitation.     

A comparison of permafrost prediction models along a section of Trail Ridge Road, Rocky Mountain National Park, Colorado, USA

The distribution of mountain permafrost along Trail Ridge Road (TRR) in Rocky Mountain National Park, Colorado, was modeled using ‘frost numbers’ and a ‘temperature of permafrost model’ (TTOP) in order to assess the accuracy of prediction models. The TTOP model is based on regional observations of air temperature and heat transfer functions involving vegetation, soil, and snow; whereas the frost number model is based on site-specific ratios of ground temperature measurements of frozen and thawed degree-days. Thirty HOBO© temperature data loggers were installed near the surface as well as at depth (30 to 85 cm). From mid-July 2008 to 2010, the mean annual soil temperature (MAST) for all surface sites was − 1.5 °C. Frost numbers averaged 0.56; TTOP averaged − 1.8 °C. The MAST was colder on western-facing slopes at high elevations. Surface and deeper probes had similar MASTs; however, deeper probes had less daily and seasonal variation. Another model developed at the regional scale based on proxy indicators of permafrost (rock glaciers and land cover) classified 5.1 km² of permafrost within the study area, whereas co-kriging interpolations of frost numbers and TTOP data indicated 2.0 km² and 4.6 km² of permafrost, respectively. Only 0.8 km² were common among all three models. Three boreholes drilled within 2 m of TRR indicate that permafrost does not exist at these locations despite each borehole being classified as containing permafrost by at least one model. Addressing model uncertainty is important because nutrients stored within frozen or frost-affected soils can be released and impact alpine water bodies. The uncertainty also exposes two fundamental problems: empirical models designed for high latitudes are not necessarily applicable to mountain permafrost, and the presence of mountain permafrost in the alpine tundra of the Colorado Front Range has not been validated.     

黄河源区多年冻土空间分布变化特征数值模拟

基于IPCC第五次评估报告预估的气温变化情景,采用数值模拟的方法对黄河源区典型冻土类型开展模拟,推算过去及预测未来黄河源区冻土分布空间变化过程和发展趋势。结果表明：1972-2012年源区多年冻土只有少部分发生退化,退化的冻土面积为833 km²,季节冻土主要集中在源区东南部的热曲谷地、小野马岭以及两湖流域南部的汤岔玛地带;RCP 2.6、RCP 6.0、RCP 8.5情景下,2050年多年冻土退化为季节冻土的面积差别不大,分别为2224 km²、2347 km²、2559 km²,占源区面积的7.5%、7.9%、8.6%;勒那曲、多曲、白马曲零星出现季节冻土,野牛沟、野马滩以及鄂陵湖东部的玛多四湖所在黄河低谷大片为季节冻土;2100年多年冻土退化为季节冻土的面积分别为5636 km²、9769 km²、15548 km²,占源区面积的19%、32.9%、52.3%;星宿海、尕玛勒滩、多格茸的多年冻土发生退化,低温冻土变为高温冻土,各类年平均地温出现了不同程度的升高。到2100年,RCP 2.6情景下源区多年冻土全部退化为季节冻土主要发生在目前年平均地温高于-0.15 oC的区域,而-0.15~-0.44 oC的区域部分发生退化;RCP 6.0、RCP 8.5情景下目前年平均地温分别为高于-0.21 oC以及-0.38o C的区域多年冻土全部发生退化,而-0.21~-0.69 oC以及-0.38~-0.88 oC的区域部分发生退化。     

Younger Dryas时期东亚季风气候和中国东部沙区沙漠变化

位于沙漠／黄土过渡带的杨桃峁剖面,高分辨率地记录了ＹｏｕｎｇｅｒＤｒｙａｓ时期东亚季风气候和沙漠变化历史。在ＡＭＳ１４Ｃ测年基础上,磁化率、粒度和有机质含量等替代性气候指标的测试结果分析表明,ＹｏｕｎｇｅｒＤｒｙａｓ时期东亚季风气候在全球气候变化的影响下,总的表现为与北半球高纬度地区相同的干寒特征,即沙漠总的具有扩大的趋势;但又与南北半球大气相互作用,特别是赤道太平洋地区气压异常引起亚洲季风气候的不稳定有关,表现出降水变化特点,沙漠出现逆过程变化,存在短暂成壤固定时期。     

THE EASTERN MARGIN OF GLACIATION IN THE BRITISH ISLES DURING THE YOUNGER DRYAS: THE BIZZLE CIRQUE, SOUTHERN SCOTLAND

ABSTRACT. Geomorphological and sedimentological evidence of former glaciation in the Bizzle valley in the Cheviot Hills of northern England and southern Scotland was used to reconstruct the dimensions of a small topographically constrained glacier with an equilibrium line altitude (ELA) of 535 m. This was interpreted as having formed during Younger Dryas cooling; this is the only glacier to have been described from the area and is the most easterly site of Younger Dryas glaciation in the British Isles. Whilst glaciation at this time was extensive in the Lake District to the southwest, the restricted nature of Cheviot ice cover suggests that a steep west–east precipitation gradient existed in this region during the Younger Dryas.     

Evaluation of the permafrost stability degradation from 1980 to 2010 in China

The degradation of permafrost stability in China over the past 30 years is evaluated using a new, high-resolution near-surface air temperature reanalysis dataset. Results show that the permafrost extent clearly decreased by 22% from 1980 to 2010, that is, a loss of 12.68⁴;104 km². The degradation occurred not only in the transition regions between permafrost and seasonally frozen ground, but also and more importantly, in the interior of the permafrost regions. The degradation in the interior of permafrost regions accounted for 87% of the total degraded areas. The degradation occurred mainly during the 1980s to 1990s in the northeast permafrost area and the Qilian Mountains, and during the 1990s to 2000s in most areas of the Qinghai-Tibet Plateau (QTP). This degradation will have systemic impacts on engineered infrastructures in permafrost regions, the water balance, and the global carbon budget. A more robust physical model should be used to evaluate the permafrost thermal stability at finer resolution in the future.     

The sand wedges of the last ice age in the Hexi Corridor, China: paleoclimatic interpretation

Sand wedges, formed mainly in a Late Pleistocene alluvial gravel in the Hexi Corridor are described in detail in this paper. ¹⁴C ages of the infilling eolian sand indicate that the sand wedges were products of the Last Ice Age. During the period of formation, the mean annual air temperature in the Hexi Corridor was about −5.3 °C, i.e. 12.6–14.6 °C lower than that of the present day. This estimated value is coincident with the fall in mean air temperature of 13 °C, which is predicated from a mirabilite (Na₂SO₄·10H₂O) sedimentary layer, and also agrees with research on the estimated amplitude of air temperature lowering in middle and high latitudes of the Northern Hemisphere during the last glacial period. The annual precipitation in the Western Hexi Corridor at that time was probably 100–200 mm, about 100 mm more than at present.     

长江三角洲城市带扩展对区域温度变化的影响

Based on non-radiance-calibrated DMSP/OLS nighttime light imagery from 1992 to 2003, urban land area statistical data, meteorological data and land surface temperature data retrieved by MODIS and NOAA/AVHRR data, the influence of urbanization on regional cli- matic trend of temperature in the Yangtze River Delta (YRD) was analyzed. Conclusions are as follows: 1) There is a significant urbanization process from 1992 to 2003 in the YRD. Four city clusters of Nanjing–Zhenjiang–Yangzhou, Suzhou–Wuxi–Changzhou, Shanghai and Hangzhou Bay form a zigzag city belt. The increase rate of annual mean air temperature in city-belt is 0.28–0.44℃/10a from 1991 to 2005, which is far larger than that of non-city-belt. 2) The urban heat island (UHI) effect on regional mean air temperature in different seasons is summer>autumn>spring>winter. 3) The UHI intensity and the urban total population logarithm are creditably correlated. 4) The UHI effect made the regional annual mean air temperature increased 0.072℃ from 1961 to 2005, of which 0.047℃ from 1991 to 2005, and the annual maximum air temperature increased 0.162℃, of which 0.083℃ from 1991 to 2005. All these indicating that the urban expansion in the YRD from 1991 to 2005 may be regarded as a serious climate signal.     

试论青藏高原多年冻土类型的划分

本文采用综合分析与主导因素相结合的原则，以干燥度作为主要指标并参考年降水量，年平均相对湿度及气温较差等，结合地形因素将青藏庙的多年冻土划分为：湿润，亚湿润，半干旱，干旱和极干旱５种类型，并对各类型代表性和冻土地区进行分别论述。     

Younger Dryas Glaciation in Söderåsen, South Sweden: An Analysis of Meteorologic and Topographic Controls

In Söderåsen, South Sweden, various geomorphological investigations indicate that small, local glaciers were initiated at very low altitudes within the Skäralid rock canyon during the Younger Dryas period. Wind polish on boulders indicates that this period was characterised by easterly winds and drifting snow. Some new field observations are presented and the Söderåsen Younger Dryas reglaciation hypothesis is tested by means of empirical knowledge on glacier equilibrium line climate and an analytic geographical information system (GIS) experiment. The GIS analysis demonstrates that the deeply incised rock canyon represents a pronounced radiation shelter, while the empirical analysis emphasises the importance of strong snow drift from the east during the winter. Together, the two analyses indicate that the inferred Söderåsen Younger Dryas reglaciation is possible from a palaeoclimatic point of view, although conditions for glaciation may have been marginal to those of rock glacier initiation.     

Geographical patterns of the summer thermal regime of soils in Transbaikalia

Long-term temperature data on a soil layer 3.2 m in thickness have been used in the differentiation of a topographically highly complicated permafrost on the territory of Transbaikalia. It was found that the geographical ranges are most clearly identified from mean annual temperature values. The schematic map displays the areas with the temperatures –4 to–1°C,–1 to 1°C and 1 to 4°C which are in good agreement with the permafrost distribution pattern (continuous and discontinuous permafrost, and permafrost islands). A classification of the thermal conditions of soils is carried out according to the highest mean monthly temperature at all depths. We identified four types which are characterized by the qualitative assessment as warm, moderately warm, cold and very cold. A relevant cartographic model shows the distribution of the thermal regime of soils for a warm season. The dot method was used to provide a clear display of available information on soil temperature, and it was possible to show the existence of small areas of the types of thermal regime and their fragmentation. Current changes in soil temperature were determined for August, which are in good agreement with regional changes in ground air temperature. In either case, we observed positive linear trends. Assessments of thermal resources of the soil layer and their geographical patterns belonging to the widespread depression-valley and valley natural systems as well as to the relatively planate surfaces of Transbaikalia can be used for scientific and practical purposes.     

Late-Glacial/Holocene succession of the chironomid and cladoceran fauna of the Soppensee (Central Switzerland)

Remains of chironomids and cladocerans were studied in a profundal sediment core, which covered a time period since the Oldest Dryas. The aim was to observe long-term variability in the structure of the aquatic fauna. The most dramatic change in the chironomid fauna occurred at the end of the Younger Dryas when the predominating cold-stenothermal Sergentia coracina disappeared due to both climatic amelioration and eutrophic conditions. The chydorids showed a distinct response to the changing temperature at the end of the Oldest Dryas as evidenced by an increase in species diversity, whereas no effect was discernible in the Younger Dryas. A decrease in the proportion of clear water species occurred in the Boreal. In the planktonic Cladocera,Bosmina longispina became extinct in the Atlantic and two Eubosmina morphs of uncertain taxonomic state very recently invaded the lake.     

Climatic characteristics of high temperature in East China during 1961–2005

Based on the daily maximum temperature data covering the period 1961-2005, temporal and spatial characteristics and their changing in mean annual and monthly high temperature days（HTDs）and the mean daily maximum temperature（MDMT）during annual and monthly HTDs in East China were studied.The results show that the mean annual HTDs were 15.1 and the MDMT during annual HTDs was 36.3℃in the past 45 years.Both the mean annual HTDs and the MDMT during annual HTDs were negative anomaly in the1980s and positive anomaly in the other periods of time,oscillating with a cycle of about 12-15 years.The mean annual HTDs were more in the southern part,but less in the northern part of East China.The MDMT during annual HTDs was higher in Zhejiang,Anhui and Jiangxi provinces in the central and western parts of East China.The high temperature process（HTP） was more in the southwestern part,but less in northeastern part of East China.Both the HTDs and the numbers of HTP were at most in July,and the MDMT during monthly HTDs was also the highest in July.In the first 5 years of the 21st century,the mean annual HTDs and the MDMT during annual HTDs increased at most of the stations,both the mean monthly HTDs and the MDMT during monthly HTDs were positive anomalies from April to October,the number of each type of HTP generally was at most and the MDMT in each type of HTP was also the highest.