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1.
This study investigated the thermal regime of shallow groundwater in the Turin area (NW Italy), where the large energy demand has motivated a new interest for renewable sources, such as the use of ground-source heat pumps for domestic heating and cooling. The vertical variability of the groundwater temperature between the ground surface and 10–20 m was detected: deeper temperatures were higher than shallow temperatures in spring, while a decrease with depth occurred in autumn. These variations are connected with the heating and cooling cycles of the ground surface due to the seasonal temperature oscillation. Variations below the seasonal oscillation are likely to be connected with the presence of advective heat transport due to the groundwater flow, according to the hydraulic features of a shallow aquifer. Temperature values mostly ranged between 12 and 14 °C in rural areas, while the values were between 14 and 16 °C below the Turin city. This groundwater warming is attributed to a widespread urban heat island phenomenon linked to warmer land surface temperatures in Turin city. Sparse warm outliers are connected with point heat sources and site-specific conditions of land and subsurface use, which may cause the aquifer temperature to rise. A relatively stable temperature below the seasonal fluctuation zone combined with high productivity and legislated limits for deeper groundwater use represent favourable conditions for a large-scale diffusion of groundwater heat pumps within the shallow aquifer. Moreover, this heat surplus should be regarded as a resource for future geothermal installations.  相似文献   

2.
The Laguna Lagunillas basin in the arid Andes of northern Chile exhibits a shallow aquifer and is exposed to extreme air temperature variations from 20 to ?25 °C. Between 1991 and 2012, groundwater levels in the Pampa Lagunillas aquifer fell from near-surface to ~15 m below ground level (bgl) due to severe overexploitation. In the same period, local mean monthly minimum temperatures started a declining trend, dropping by 3–8 °C relative to a nearby reference station. Meanwhile, mean monthly maximum summer temperatures shifted abruptly upwards by 2.7 °C on average in around 1996. The observed air temperature downturns and upturns are in accordance with detected anomalies in land-surface temperature imagery. Two major factors may be causing the local climate change. One is related to a water-table decline below the evaporative energy potential extinction depth of ~2 m bgl, which causes an up-heating of the bare soil surface and, in turn, influences the lower atmosphere. At the same time, the removal of near-surface groundwater reduces the thermal conductivity of the upper sedimentary layer, which consequently diminishes the heat exchange between the aquifer (constant heat source of ~10 °C) and the lower atmosphere during nights, leading to a severe dropping of minimum air temperatures. The observed critical water-level drawdown was 2–3 m bgl. Future and existing water-production projects in arid high Andean basins with shallow groundwater should avoid a decline of near-surface groundwater below 2 m bgl and take groundwater-climate interactions into account when identifying and monitoring potential environmental impacts.  相似文献   

3.
The impact of groundwater heat pumps on groundwater temperature is simulated by means of a 2D numerical groundwater model in the Leibnitzer Feld aquifer, Austria. The model provides a basis for assessing the regional use of groundwater temperature as an energy source. Since the groundwater table is shallow, the air temperature represents the main source controlling the groundwater temperature. A temperature input function depending on the depth of the groundwater table is delineated from an observed soil temperature profile and the air temperature. Given the diffuse and ubiquitous nature of the heat input, the heat exchange is implemented as a third type boundary condition to enable two-way heat transfer. The temperature of the reinjected water is limited to a decrease of 5 K and an absolute minimum of 5°C by Austrian law. The pumping rates needed to cover the heat requirements of three typical users are determined for selected locations. It is shown that the reduction of the ambient groundwater temperature approximately 300 m downstream of the reinjection wells is less than 0.5°C. Thus it can be concluded that aquifers in similar settings show substantial potential to provide heating and warm water supply for buildings without deteriorating the regional groundwater temperature regime.  相似文献   

4.

Urban areas are major contributors to the alteration of the local atmospheric and groundwater environment. The impact of such changes on the groundwater thermal regime is documented worldwide by elevated groundwater temperature in city centers with respect to the surrounding rural areas. This study investigates the subsurface urban heat island (SUHI) in the aquifers beneath the Milan city area in northern Italy, and assesses the natural and anthropogenic controls on groundwater temperatures within the urban area by analyzing groundwater head and temperature records acquired in the 2016–2020 period. This analysis demonstrates the occurrence of a SUHI with up to 3 °C intensity and reveals a correlation between the density of building/subsurface infrastructures and the mean annual groundwater temperature. Vertical heat fluxes to the aquifer are strongly related to the depth of the groundwater and the density of surface structures and infrastructures. The heat accumulation in the subsurface is reflected by a constant groundwater warming trend between +0.1 and?+?0.4 °C/year that leads to a gain of 25 MJ/m2 of thermal energy per year in the shallow aquifer inside the SUHI area. Future monitoring of groundwater temperatures, combined with numerical modeling of coupled groundwater flow and heat transport, will be essential to reveal what this trend is controlled by and to make predictions on the lateral and vertical extent of the groundwater SUHI in the study area.

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5.
This study was conducted to reveal the trends of the air temperature and soil temperature for 51 years (1960–2010) and their relationship in four of Korea’s largest metropolitan cities (Seoul, Incheon, Busan and Daejeon). Also, the trends of the air and soil temperatures between the studied metropolitan cities and a rural area (Chupungryong) were compared to examine the effect of urban heat. Among the metropolitan cities, the long-term mean soil temperatures (depth 0.0, 0.5, 1.0, 1.5, 3.0, 5.0 m) were lowest (13.34–14.80 °C) in Seoul and highest (16.24–16.54 °C) in Busan, which is mainly the effect of the latitude. The soil temperature exponentially increased with depth in the three cities except for Busan and was closely related to the air temperature. The soil temperatures responded well to the air temperature change (maximum correlation coefficients 0.88–0.98) but this response was slightly delayed with depth. The air and soil temperatures increased at the rates of 0.24–0.40 and 0.11–0.73 °C/decade, respectively, for the period. The increasing rate of the soil temperature was the largest in Daejeon as 0.39–0.73 °C/decade, which was almost 2–4 times greater than those of the other cities (0.11–0.40 °C/decade), and it rose with depth. The increase of the soil temperature was coincident with the increase of the air temperature, which indicates that the soil temperature was largely affected by the increasing of the air temperature. In contrast, the increase in air temperature in Chupungryong (0.06 °C/decade) was significantly lower than in the metropolitan cities. In addition, the increase of the soil temperature in the rural area (0.13 °C/decade) was also much lower than that in the inland cities (0.20–0.27 °C/decade) while it showed no substantial difference from that in the coastal cities (0.11–0.15 °C/decade). Therefore, it is inferred that the soil temperature of the metropolitan cities increased with the increase of the air temperature due to global warming as well as the anthropogenic urban heat.  相似文献   

6.
Oxygen isotope compositions of phosphate in tooth enamel from large mammals (i.e. horse and red deer) were measured to quantify past mean annual air temperatures and seasonal variations between 145 ka and 33 ka in eastern France. The method is based on interdependent relationships between the δ18O of apatite phosphate, environmental waters and air temperatures. Horse (Equus caballus germanicus) and red deer (Cervus elaphus) remains have δ18O values that range from 14.2‰ to 17.2‰, indicating mean air temperatures between 7°C and 13°C. Oxygen isotope time series obtained from two of the six horse teeth show a sinusoidal-like signal that could have been forced by temperature variations of seasonal origin. Intra-tooth oxygen isotope variations reveal that at 145 ka, winters were colder (? 7 ± 2°C) than at present (3 ± 1°C) while summer temperatures were similar. Winter temperatures mark a well-developed West–East thermal gradient in France of about ? 9°C, much stronger than the ?4°C difference recorded presently. Negative winter temperatures were likely responsible for the extent and duration of the snow cover, thus limiting the food resources available for large ungulates with repercussions for Neanderthal predators.  相似文献   

7.
《Comptes Rendus Geoscience》2014,346(9-10):213-222
Two and a half decade (1985–2009) surface air temperature from Giovanni database available for the Naradu valley at High Himalaya Mountain range of Himachal Pradesh has been analysed to determine the changes in the maximum, minimum and mean air temperatures. The analysis was subjected for seasonal, annual and monthly basis and revealed a tendency towards warmer years all around, with significantly warmer winter and more significant increase in minimum temperatures. The annual maximum, minimum and mean temperatures have increase by 1,41 °C, 1,63 °C and 1,49 °C, respectively. The seasonal analysis indicates that the tendency is more pronounced in winter followed by post-monsoon, pre-monsoon and monsoon season. The trends were also examined on a maximum temperatures, and it showed a significant warning in all the months in annual mean, minimum and maximum temperatures, except February during the period of 1985–2009 in the valley. Different trend detection statistical tools have been exercised by using variety of non-parametric tests and all are in agreement.  相似文献   

8.
To assess whether reaches of the Motueka River (New Zealand) that gain water from groundwater were likely to represent significant cold-water refugia for brown trout during periods of high water temperatures, water temperature was monitored for more than 18 months in two gaining reaches of the Motueka River and three reaches that were predicted to be losing water to groundwater. These data were used to predict brown trout (Salmo trutta) growth in gaining and losing reaches. Groundwater inputs had a small effect on water temperature at the reach-scale and modelling suggests that the differences observed were unlikely to result in appreciable differences in trout growth. Several coldwater patches were identified within the study reach that were up to 3.5°C cooler than the mainstem, but these were generally shallow and were unlikely to provide refuge for adult trout. The exception was Hinetai Spring, which had a mean water temperature of close to 16°C during the period January–March, when temperatures in the mainstem regularly exceeded 19°C. Trout were observed within the cold-water plume at the mouth of Hinetai Stream, which would allow them to thermoregulate when mainstem temperatures are unfavourable while still being able to capitalise on food resources available in the mainstem.  相似文献   

9.
The use of renewable energy can be enhanced by utilising groundwater reservoirs for heating and cooling purposes. The urbanisation effect on the peak heating and peak cooling capacity of groundwater in a cold groundwater region was investigated. Groundwater temperatures were measured and energy potentials calculated from three partly urbanised aquifers situated between the latitudes of 60° 25′N and 60° 59′N in Finland. The average groundwater temperature below the zone of seasonal temperature fluctuations was 3–4 °C higher in the city centres than in the rural areas. The study demonstrated that due to warmer groundwater, approximately 50–60 % more peak heating power could be utilized from populated areas compared with rural areas. In contrast, approximately 40–50 % less peak cooling power could be utilised. Urbanisation significantly increases the possibility of utilising local heat energy from groundwater within a wider region of naturally cold groundwater. Despite the warming in urban areas, groundwater still remains attractive as a source of cooling energy. More research is needed in order to determine the long-term energy capacity of groundwater, i.e. the design power, in urbanised areas of cold regions.  相似文献   

10.
Wang  Zejun  Zhou  Hong  Wen  Zhang  Luo  Mingming  Kuang  Ye 《Hydrogeology Journal》2021,29(8):2821-2835

Temperature, discharge, and stable isotope ratios of five karst springs in a mountainous area of Zigui County, Hubei Province, Central China, were analyzed. The purpose was to illustrate the heat exchanges linked to circulation depth in the exposed karst water systems through the development of a method for estimating heat input and heat flux during a rainstorm. Meteorological water in the study area conformed to a local meteoric water line (δD?=?8.37 δ18O?+?12.99) with a mean δ18O elevation gradient of ?4.0‰ km?1, which was used to estimate mean circulation depths of 209–686 m. The mean spring temperatures defined a vertical gradient of ?5.4 °C km?1, which resembled that of the stable atmosphere of the Earth, indicating that the thermal response patterns are mainly controlled by surface air temperature. Thermal convection after rainfall events dominated heat exchange between baseflow and recharge water, leading to a warmer and colder recharge during summer and winter, respectively, whereas thermal conduction dominated the heat exchange only between groundwater, surrounding geology, and the interface air under a condition of no rainfall, resulting in only small temperature variations of the baseflow. Successful application of the method for estimating heat exchange showed that the characteristics of shallow circulation, strong karstification, and well-developed epikarst readily allowed disruption of the thermal balance of the Yuquandong system, resulting in a poor heat regulation capacity, a larger variation of heat input, a lower mean heat flux, and lower baseflow temperatures compared to those of the Dayuquan system.

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11.
Exploration of Perth's geothermal potential has been performed by the Western Australian Geothermal Centre of Excellence (WAGCoE). Detailed vertical temperature and gamma ray logging of 17 Western Australia Department of Water's (DoW) Artesian Monitoring (AM) wells was completed throughout the Perth Metropolitan Area (PMA). In addition, temperature logs from 53 DoW AM wells measured in the 1980s were digitised into LAS format. The logged data are available in the WAGCoE Data Catalogue.

Analysis of the gamma ray logs yielded the first estimates of radiogenic heat production in Perth Basin formations. Values by formation ranged between 0.24 and 1.065 μW m?3. The temperature logs provide a picture of true formation temperatures within shallow sediments in the Perth Basin. A three-dimensional model of the temperature distribution was used to produce maps of temperature at depth and on the top of the Yarragadee aquifer.

The temperature data were interpreted with a one-dimensional conductive heat model. Significant differences between the model and the observations was indicative of heat moving via non-conductive mechanisms, such as advection or convection. Evidence of non-conductive or advective heat flow is demonstrated in most formations in the region, with significant effects in the aquifers. Average conductive geothermal gradients range from 13°C km?1 to 39°C km?1, with sandstone formations exhibiting average gradients of approximately 25°C km?1, while insulating silt/shale formations show higher average gradients of over 30°C km?1.

To produce preliminary heat flow estimates, temperature gradients were combined with thermal conductivities measured elsewhere. The geometric mean heat flow estimates range between 64 mW m?2 to 91 mW m?2, with the standard deviation of the arithmetic mean heat flow ranging between 15 and 23 mW m?2.

The study characterises the shallow temperature regime in the Perth Metropolitan Area, which is of direct relevance towards developing commercial geothermal projects.  相似文献   

12.
Annually resolved June–July–August (JJA) temperatures from ca. 570 BC to AD 120 (±100 a; approximately 690 varve years) were quantified from biogenic silica and chironomids (Type II regression; Standard Major Axis calibration‐in‐time) preserved in the varved sediments of Lake Silvaplana, Switzerland. Using 30 a (climatology) moving averages and detrended standard deviations (mean–variability change, MVC), moving linear trends, change points and wavelets, reconstructed temperatures were partitioned into a warmer (+0.3°C; ca. 570–351 BC), cooler (?0.2°C; ca. 350–16 BC) and moderate period (+0.1°C; ca. 15 BC to AD 120) relative to the reconstruction average (10.9°C; reference AD 1950–2000 = 9.8°C). Warm and variable JJA temperatures at the Late Iron Age–Roman Period transition (approximately 50 BC to AD 100 in this region) and a cold anomaly around 470 BC (Early–Late Iron Age) were inferred. Inter‐annual and decadal temperature variability was greater from ca. 570 BC to AD 120 than the last millennium, whereas multi‐decadal and lower‐frequency temperature variability were comparable, as evident in wavelet plots. Using MVC plots of reconstructed JJA temperatures from ca. 570 BC to AD 120, we verified current trends and European climate model outputs for the 21st century, which suggest increased inter‐annual summer temperature variability and extremes in a generally warmer climate (heteroscedasticity; hotspot of variability). We compared these results to MVC plots of instrumental and reconstructed temperatures (from the same sediment core and proxies but a different study) from AD 1177 to AD 2000. Our reconstructed JJA temperatures from ca. 570 BC to AD 120 showed that inter‐annual JJA temperature variability increased rapidly above a threshold of ～10°C mean JJA temperature. This increase accelerated with continued warming up to >11.5°C. We suggest that the Roman Period serves with respect to inter‐annual variability as an analogue for warmer 21st‐century JJA temperatures in the Alps. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

13.
The Tongue Creek watershed lies on the south flank of Grand Mesa in western Colorado, USA and is a site with 1.5 km of topographic relief, heat flow of 100 mW/m2, thermal conductivity of 3.3 W m–1 °C–1, hydraulic conductivity of 10-8 m/s, a water table that closely follows surface topography, and groundwater temperatures 3–15°C above mean surface temperatures. These data suggest that convective heat transport by groundwater flow has modified the thermal regime of the site. Steady state three-dimensional numerical simulations of heat flow, groundwater flow, and convective transport were used to model these thermal and hydrological data. The simulations provided estimates for the scale of hydraulic conductivity and bedrock base flow discharge within the watershed. The numerical models show that (1) complex three-dimensional flow systems develop with a range of scales from tens of meters to tens of kilometers; (2) mapped springs are frequently found at locations where contours of hydraulic head indicate strong vertical flow at the water table, and; (3) the distribution of groundwater temperatures in water wells as a function of surface elevation is predicted by the model.  相似文献   

14.
Numerical techniques were used to study chironomid distribution and abundance in lakes from a 1000 km transect in Finland, with special interest on the effect of local summer air temperatures on chironomid assemblages. The final aim of the study was to develop a chironomid‐based palaeotemperature inference model. The dataset consisted of 82 lakes (of which 77 were used in the model after deletion of outliers), with catchments spanning from boreal coniferous forests to mountain birch woodland and tundra vegetation. Numerical analysis showed that the mean July air temperature was the most significant variable explaining the distribution and abundance of chironomids in Finnish lakes. Weighted‐averaging partial least squares techniques were used to develop a palaeotemperature inference model for mean July air temperature reconstructions. The model performance statistics were favourable, with cross‐validated coefficient of determination (r2) of 0.78, root mean squared error of prediction of 0.721°C and maximum bias of 0.794°C. Based on these values, the transfer function is a valid means of performing quantitative palaeotemperature estimates in downcore studies. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

15.
河北汤泉地热田地温场分布及其控制因素研究   总被引：5，自引：4，他引：1       下载免费PDF全文
汤泉位于河北省遵化市西北部,为山前丘陵地貌,地热资源丰富。本文对汤泉地热田内分布的诸多基岩热水井进行了钻孔测温,利用测温结果对该地热田地温场分布特征及控制因素进行了研究。研究发现:钻孔温度明显受地下水流的影响,绝大部分测温井表现为对流传热特征,个别表现为传导为主的传热特征;地温异常区域位于汤泉福泉宫和疗养院一带,异常中心呈两极分布,地热异常中心50 m埋深水温为51~54℃,100 m埋深水温可达60~67℃;该地热系统中地热水系地下水在深循环过程中,在正常的大地热流背景下被围岩逐渐加热所致;由花岗岩隔水底板构造形态所形成的隐伏盆地,构成了福泉宫至疗养院一带的蓄水构造;由于断裂构造切割花岗岩体,造成深部的热流沿断裂上升,混合并加热赋存于福泉宫至疗养院一带蓄水构造中的片麻岩裂隙水,形成该地段的地热异常现象;福泉宫地区和疗养院地区片麻岩含水层裂隙发育,使得深部热量能够快速到达浅部地层,并在浅部出现局部异常高温;汤泉地热田片麻岩热储层地热流体属于含岩盐地层溶滤的陆相沉积水,主要来源于大气降水。  相似文献   

16.
The urban heat island (UHI) is a result of urbanization, causing local microclimatologic changes such as increase in ambient temperature. Factors causing the UHI effect are anthropogenic energy release, energy absorption by concrete, tarmac structures and traffic, although the main factor is the replacement of vegetation with man-made structures. These factors cause heating of not only local air but also subsurface and groundwater. Observations of groundwater temperatures from the urban, southern part of Istanbul (Turkey) and the rural, northern part of Istanbul revealed that the urban groundwater temperatures were 3.5°C higher than the rural. Urbanization is a direct consequence of improvements in technology and modern life. However, this comes at the cost of an ever-increasing demand for energy. Exploitation of low-enthalpy geothermal energy is an attractive alternative to fossil fuel based energies. From the environmental point of view, clean and cheap energy is the most preferable, with heat pumps being the best choice for recovery purposes. Usage of elevated groundwater temperature in the heat pumps in urban areas increases the efficiency of the heat pump system and yields more thermal energy than that of rural groundwater. This system may be applicable to Istanbul.  相似文献   

17.
Surface air temperature is one of the main factors that can be used to denote climate change. Its variation in the westerly and monsoon-influenced part of China (i.e., North-West and East China) were analyzed by using monthly data during 1961–2006 from 139 and 375 meteorological stations over these two regions, respectively. The method of trend coefficient and variability was utilized to study the consistency and discrepancy of temperature change over North-West and East China. The results suggest that whether for the annual or the seasonal mean variations of temperature, there were consistent striking warming trends based on the background of global warming over North-West and East China. The most obvious warming trends all appeared in winter over the two regions. Except for the period in spring, the annual and seasonal mean warming trends in North-West China are more obvious than those in East China. The annual mean temperature warming rates are 0.34°C per decade and 0.22°C per decade over North-West and East China, respectively. The average seasonal increasing rates in spring, summer, autumn, and winter are 0.22°C per decade, 0.24°C per decade, 0.35°C per decade, and 0.55°C per decade in North-West China, respectively. At the same time, they are 0.25°C per decade, 0.11°C per decade, 0.22°C per decade, and 0.39°C per decade in East China, respectively. The temperature discrepancies of two adjacent decades are positive over the westerlies and monsoonal region, and they are bigger in the westerlies region than those in the monsoonal region. The most significant warming rate is from the North-East Xinjiang Uygur Autonomous Region of China to West Qinghai Province of China in all seasons and annually over the westerlies region. The North and North-East China are the main prominent warming areas over the monsoonal region. The warming rate increases with latitude in the monsoonal region, but this is not the case in the westerlies region.  相似文献   

18.
The efficiency of heat recovery in high-temperature (>60 °C) aquifer thermal energy storage (HT-ATES) systems is limited due to the buoyancy of the injected hot water. This study investigates the potential to improve the efficiency through compensation of the density difference by increased salinity of the injected hot water for a single injection-recovery well scheme. The proposed method was tested through numerical modeling with SEAWATv4, considering seasonal HT-ATES with four consecutive injection-storage-recovery cycles. Recovery efficiencies for the consecutive cycles were investigated for six cases with three simulated scenarios: (a) regular HT-ATES, (b) HT-ATES with density difference compensation using saline water, and (c) theoretical regular HT-ATES without free thermal convection. For the reference case, in which 80 °C water was injected into a high-permeability aquifer, regular HT-ATES had an efficiency of 0.40 after four consecutive recovery cycles. The density difference compensation method resulted in an efficiency of 0.69, approximating the theoretical case (0.76). Sensitivity analysis showed that the net efficiency increase by using the density difference compensation method instead of regular HT-ATES is greater for higher aquifer hydraulic conductivity, larger temperature difference between injection water and ambient groundwater, smaller injection volume, and larger aquifer thickness. This means that density difference compensation allows the application of HT-ATES in thicker, more permeable aquifers and with larger temperatures than would be considered for regular HT-ATES systems.  相似文献   

19.
Human alteration of Puget Sound shorelines is extensive yet its ecological consequences are largely undocumented. This study evaluates differences between natural and heavily modified beaches in terms of microclimate and one aspect of biological condition. Electronic data laggers were placed at a tidal height of approximately 3.7 m (12 ft) above mean lower low water during July 16–20, 2001, to monitor light intensity, substrate and air temperatures, and humidity. Substrate samples were collected at the end of the monitoring period to evaluate condition and density of eggs from surf smelt (Hypomesus pretiosus), a forage fish species that spawns on gravel-sand beaches in the upper intertidal zone. The modified beach had significantly higher daily mean light intensity, air temperature and substrate temperature, and significantly lower daily mean relative humidity. Particularly striking were the differences in substrate temperature which, on the natural beach, ranged from 12.1°C to 18.2°C (mean=14.1°C) and on the modified beach ranged from 14.4°C to 29.4°C (mean=18.8°C). In addition to these different means and more extreme values, microclimate conditions on the modified beach were more variable, indicative of a less buffered environment. The proportion of smelt eggs containing live embryos on the altered beach was approximately half that of the natural beach.  相似文献   

20.
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.  相似文献   

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