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Lucien von Gunten Oliver Heiri Christian Bigler Jacqueline van Leeuwen Carlo Casty André F. Lotter Michael Sturm 《Journal of Paleolimnology》2008,39(3):283-299
We analysed a 42 cm long sediment record from Lej da la Tscheppa, a high-altitude lake (2,616 m a.s.l.) in the Upper Engadine
valley (Switzerland) for subfossil diatoms, chironomids and pollen. The chronology of the top 21 cm of the record was established
using 210Pb analysis using a constant-rate-of-supply model, and validated with 137Cs measurements and the content of spheroidal carbonaceous particles. A tentative chronology for the lower part of the core
was obtained through extrapolation of the sedimentation rates in the uppermost part of the record. Pollen assemblages in the
record reflect regional changes in forestation and land-use patterns in the Upper Engadine valley and show no evidence of
significant local human activity in the lake’s catchment. Diatom assemblages record a distinct increase in planktonic taxa
since the early 19th century, suggesting a decrease in the duration of ice-cover. In contrast, chironomid assemblages remained
stable during a large part of the record. We applied an established chironomid-based July air temperature transfer function
and a newly developed diatom-based spring air temperature transfer function to reconstruct past seasonal air temperature changes
at Lej da la Tscheppa. The reconstructions indicate a diatom-inferred warming trend in spring temperatures during the past
ca. 400 years, whereas chironomid-inferred summer temperatures suggest a slight cooling trend. These biota-based reconstructions
are in good agreement with the centennial-scale temperature trend in an independent reconstruction of regional temperatures
in the Upper Engadine region based on instrumental records and documentary proxy evidence from the Alps. Our results suggest
that, in high-altitude lakes, independent chironomid- and diatom-based seasonal temperature reconstruction is possible and
can be successfully used to track seasonal temperature trends. 相似文献
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This paper reviews the past history of comparisons between lacustrine records of chironomid-inferred summer temperatures (CI-T) and peat bog-derived records of surface wetness (BSW), and develops a new summer temperature record for the mid-late Holocene for Northern Britain from Bigland Tarn, Cumbria. The CI-T reconstruction is well dated, and corresponds well with the only two other CI-T records for Britain. Comparisons are made with BSW records from northern Britain, which show consistent similarities over centennial to millennial timescales, demonstrating that at this resolution cooler summers equated with a wetter climate, at least during the mid- to late-Holocene. 相似文献
4.
A climatic variation observed in permafrost temperature at Kangiqsualujjuaq in northern Quebec 
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下载免费PDF全文 Permafrost temperatures from the surface down to about 9 m from 3 boreholes distributed around Kangiqsualujjuaq village on the coast of Hudson Strait were recorded and analyzed for the period 1989 1998. The results indicate that the permafrost is getting warm along the southern shore of Hudson Strait from 1993 to 1998 though it became cooling for the past 40 a or more. The observed trend in the order of 0.098℃/a at the 9 m depth is consistent with the long term regional warming observed in air temperatures. It also coincides with that all the global circulation models predict an enhanced warming in polar regions associated with the increase in concentration of greenhouse gases in the atmosphere. 相似文献
5.
We examine some issues related to a classification of climates. A climatic regionalization has been carried out, and a brief characteristic given to the identified types of climate. It has been found that the relationship of the sums of mean daily ground air temperatures above 10 °C and the dryness index show a clearly pronounced zonal distribution. The combination of sums of mean daily air temperatures below ?10 °C and the depth of snow in the northern part of the plain is characterized by a horizontal distribution, and only in the middle and southern parts of the plain do these indices acquire zonal regularities. An analysis is made of the long-term dynamics of air temperature to reveal that some climate warming during 1981–2010 was mainly caused by a rise in winter air temperature. 相似文献
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Summary. A non-steady-state theoretical model is used to predict the present variation of temperature with depth in two boreholes in the Devon Island ice cap, Arctic Canada. The boreholes are 300 m apart and one of them reaches bedrock. The heat transfer equation is solved numerically with the record of past temperatures obtained from measurements of the variations of oxygen—isotope ratio with depth in the cores as surface boundary condition. The effects of ice advection, refreezing of meltwater percolating from the surface (the amount of which is recorded in the cores), heating due to firn compaction and ice deformation, and heat flow in the bedrock below the ice sheet are all included in the model. The free parameters are geothermal heat flux, present surface temperature and heat loss at the surface which depends on the depth of meltwater penetration and other factors. Agreement between observed and predicted temperature—depth profiles is very close. Latent heat released by percolating meltwater is the predominating factor in determining the temperature distribution in the upper half of each borehole. The temperature distribution is insensitive to the value of the factor used to convert oxygen—isotope ratio to temperature. 相似文献
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中国城市扩展对气温观测的影响及其高估程度(英文) 总被引：3，自引：1，他引：2
Since the implementation of the reform and opening up policy in China in the late 1970s, some meteorological stations ’entered’ cities passively due to urban expansion. Changes in the surface and built environment around the stations have influenced observations of air temperature. When the observational data from urban stations are applied in the interpolation of national or regional scale air temperature dataset, they could lead to overestimation of regional air temperature and inaccurate assessment of warming. In this study, the underlying surface surrounding 756 meteorological stations across China was identified based on remote sensing images over a number of time intervals to distinguish the rural stations that ’entered’ into cities. Then, after removing the observational data from these stations which have been influenced by urban expansion, a dataset of background air temperatures was generated by interpolating the observational data from the remaining rural stations. The mean urban heat island effect intensity since 1970 was estimated by comparing the original observational records from urban stations with the background air temperature interpolated. The result shows that urban heat island effect does occur due to urban expansion, with a higher intensity in winter than in other seasons. Then the overestimation of regional air temperature is evaluated by comparing the two kinds of grid datasets of air temperature which are respectively interpolated by all stations’ and rural stations’ observational data. Spatially, the overestimation is relatively higher in eastern China than in the central part of China; however, both areas exhibit a much higher effect than is observed in western China. We concluded that in the last 40 years the mean temperature in China increased by about 1.58℃, of which about 0.01℃ was attributed to urban expansion, with a contribution of up to 0.09℃ in the core areas from the overestimation of air temperature. 相似文献
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Glen M. MacDonald David F. Porinchu Nicolas Rolland Konstantine V. Kremenetsky Darrell S. Kaufman 《Journal of Paleolimnology》2009,41(1):129-141
Instrumental climate records from the central Canadian treeline zone display a pattern of variation similar to general Northern
Hemisphere temperature trends. To examine whether this general correspondence extends back beyond the instrumental record,
we obtained a sediment core from Lake S41, a small lake in the Northwest Territories of Canada at 63°43.11′ N, 109°19.07′ W.
A radiocarbon-based chronology was developed for the core. The sediments were analyzed for organic-matter content by loss-on-ignition
(LOI), biogenic-silica content (BSi), and chironomid community composition to reconstruct July air temperature and summer
water temperature. The paleolimnological records were compared with records of atmospheric CO2 concentration, solar variability, and hemispheric temperature variations over the past 2000 years. The results of the analyses
suggest that widely-documented long-term variations in Northern Hemisphere temperature associated with radiative forcing,
namely the cooling following the medieval period during the Little Ice Age (LIA), and twentieth century warming, are represented
in the central Canadian treeline zone. There is also evidence of a brief episode of warming during the eighteenth century.
As evidenced by LOI and BSi, the twentieth century warming is typified by increased lake productivity relative to the LIA.
Depending upon the measure, the increased productivity of the twentieth century nearly equals or exceeds that of any other
period in the past 2000 years. In contrast, the rate of chironomid head capsule accumulation decreased and remained low during
the twentieth century. Although the chironomid-inferred temperature reconstructions indicate cooling during the LIA, they
present no evidence of greatly increased temperatures during the twentieth century. Warming during the twentieth century might
have enhanced lake stratification, and the response of the chironomid fauna to warming was attenuated by decreased oxygen
and lower temperatures in the hypolimnion of the more stratification-prone lake.
相似文献
| Glen M. MacDonaldEmail: |
9.
BY FREDRIK CHARPENTIER LJUNGQVIST 《Geografiska Annaler: Series A, Physical Geography》2009,91(1):11-29
Proxy data are our only source of knowledge of temperature variability in the period prior to instrumental temperature measurements. Until recently, very few quantitative palaeotemperature records extended back a millennium or more, but the number is now increasing. Here, the first systematic survey is presented, with graphic representations, of most quantitative temperature proxy data records covering the last two millennia that have been published in the peer-reviewed literature. In total, 71 series are presented together with basic essential information on each record. This overview will hopefully assist future palaeoclimatic research by facilitating an orientation among available palaeotemperature records and thus reduce the risk of missing less well-known proxy series. The records show an amplitude between maximum and minimum temperatures during the past two millennia on centennial timescales ranging from c. 0.5 to 4°C and averaging c. 1.5–2°C for both high and low latitudes, although these variations are not always occurring synchronous. Both the Medieval Warm Period, the Little Ice Age and the 20th century warming are clearly visible in most records, whereas the Roman Warm Period and the Dark Age Cold Period are less clearly discernible. 相似文献
10.
The evolution of ground thermal state has been studied to assess impacts of current climatic warming on permafrost in Central Yakutia. The analysis of long-term data of regional weather stations has revealed one of the highest increasing trends in mean annual air temperature in northern Russia. A forecast of surface air temperature fluctuations has been made by applying a frequency analysis method. Monitoring of ground thermal conditions allows us to identify inter-annual and long-term variability among a wide range of natural conditions. Experimental research has indicated a long-term dynamics of ground thermal state evolution： ground temperatures at the depth of zero annual amplitude and seasonally thawed layer depth. Long-term variability of thaw depth shows near-zero to weak positive trends in small valleys in contrast to weak negative trends on slopes. With significant climatic warming, the thermal state of near-surface layers of permafrost demonstrates steadiness. Anthropogenic impacts on ground thermal regime in various terrain types have been qualitatively evaluated. Clear-cutting, ground cover stripping, and post-fire deforestation in inter-alas type terrains result in a significant increase of temperature and seasonal ground thaw depth, as well as adverse cryogenic processes. The dynamics of mean annual ground temperature in slash and burn sites have been evaluated in reference to stages of successive vegetation recovery. 相似文献
11.
Jessica L. Conroy Diane M. Thompson Aaron Collins Jonathan T. Overpeck Mark B. Bush Julia E. Cole 《Journal of Paleolimnology》2014,52(4):331-347
Genovesa Crater Lake is a remote, hypersaline lake in the northern Galápagos archipelago that contains a finely laminated sediment record. This sediment record has the potential to provide a high-resolution history of past climate variability in the eastern tropical Pacific. Here we present modern climate, lake, and sediment observations from 2009 to 2012 to explore how local climate variability influences Genovesa Crater Lake and its sediments. Surface lake temperature is strongly linked to air temperature and is highly seasonal. Temperature stratification is strongest during the warm season, whereas temperature becomes more uniform through the water column in the cool season. Deeper and earlier mixing occurred during the 2010 La Niña, which subsequently delayed 2011 cool season mixing and maximum warm season surface temperatures in 2011 and 2012. Lake salinity changes are influenced by precipitation, evaporation and persistent seawater influx. The largest declines in subsurface salinity follow months after the rainy season, when temperatures cool and fresher surface water from the previous warm/wet season mixes into the subsurface. Between 2009 and 2012, more calcium carbonate precipitated during a period of higher salinity. The period of highest calcium carbonate abundance measured in sediment records that span the late nineteenth to twentieth century coincides with the failure of two consecutive rainy seasons in 1988 and 1989 as well as the coldest monthly sea surface temperature measured at Puerto Ayora in 1989. More calcium carbonate-rich laminae from AD 1550 ± 70 to 1675 ± 90 may indicate a greater frequency of prolonged droughts or cooler temperatures, although enhanced productivity may also modulate carbonate precipitation. More Ca-rich laminae in Genovesa coincide with dry conditions inferred from other Galápagos sediment proxies, as well as prolonged dry and cool conditions inferred from reconstructions of the Southern Oscillation Index and NINO3 sea surface temperatures. 相似文献
12.
Surface air temperature and precipitation records for the years 1958-1999 from ten meteorological stations located throughout West Siberia are used to identify climatic trends and determine to what extent these trends are potentially attributable to the Arctic Oscillation (AO). Although recent changes in atmospheric variability are associated with broad Arctic climate change, West Siberia appears particularly susceptible to warming. Furthermore, unlike most of the Arctic, moisture transport in the region is highly variable. The records show that West Siberia is experiencing significant warming and notable increases in precipitation, likely driven, in part, by large-scale Arctic atmospheric variability. Because this region contains a large percentage of the world's peatlands and contributes a significant portion of the total terrestrial freshwater flux to the Arctic Ocean, these recent climatic trends may have globally significant repercussions. The most robust patterns found are strong and prevalent springtime warming, winter precipitation increases, and strong association of non-summer air temperatures with the AO. Warming rates for both spring (0.5-0.8 °C/decade) and annual (0.3-0.5°C/decade) records are statistically significant for nine often stations. On average, the AO is linearly congruent with 96% (winter), 19% (spring), 0% (summer), 67% (autumn) and 53% (annual) of the warming found in this study. Significant trends in precipitation occur most commonly during winter, when four of ten stations exhibit significant increases (4-13 %/decade). The AO may play a lesser role in precipitation variability and is linearly congruent with only 17% (winter), 13% (spring), 12% (summer), 1% (autumn) and 26% (annual) of precipitation trends. 相似文献
13.
根据河西走廊地区深层地温观测时间最长、资料完整的酒泉、张掖及武威3个地面气象站1980年1月～2011年2月的逐月80、160、320 cm地温资料,运用线性拟合、滑动平均和Mann-Kendall方法进行趋势和突变分析。研究表明：近31 a来河西走廊地区80、160、320 cm深层地温均呈显著的波动上升趋势,其中各深层地温夏季增温速率最大,春季次之,冬季最小,各季各深层地温均发生了暖突变。各深层地温年时间序列中存在3 a波动周期,且表现为前期冷,后期暖的演变趋势,线性增温速率显著,80 cm地温增温速率0.55 ℃/10 a,暖突变出现在1994年;160 cm地温增温速率0.59 ℃/10 a,暖突变出现在1995年;320 cm地温增温速率0.60 ℃/10 a,暖突变出现在1996年。说明年深层地温随着深度的增加,暖突变出现时间存在滞后现象。气温对深层地温的影响作用明显,深层地温受气温升高的影响也呈升高趋势。但随着深度的增加气温与地温的相关性略有降低,这是由于深层地温的变化存在滞后性所致。 相似文献
14.
Reconstructing air temperature at eleven remote alpine and arctic lakes in Europe from 1781 to 1997 AD 总被引：3，自引：0，他引：3
Pristine and sensitive environments, such as remote alpine and arctic lakes, are particularly susceptible to the effects of climate change. However, these remote environments do not have sufficiently long instrumental climate records to support studies on contemporary climate change. The issue of the scarcity of instrumental climate data at remote regions is addressed by reconstructing monthly mean air temperatures from 1781 to 1997 AD at eleven remote alpine and arctic lakes in Europe, as part of the MOuntain LAke Research (MOLAR) project. Stepwise multiple regression is applied to establish linear transfer functions of temperatures between each of eleven upland records and twenty homogenised long lowland records. Twelve monthly transfer functions are obtained for each lake. The skill of these transfer functions is found to range typically between 60 and 99%. The lower skill values generally correspond to winter months. The temperature reconstructions obtained using the transfer functions need to be corrected with vertical temperature gradients. Air-temperature lapse rates were obtained for each lake region by spatial interpolation of radiosonde air-temperature data (1990–1997). The resulting reconstructions at each lake were checked using air-temperature data (1996–1997) from automatic weather stations installed at the lakes during the MOLAR project. We estimate the typical reconstruction errors to be about 1.3 °C for low-sun months and about 0.98 °C for high-sun months. Trend analyses on the reconstructed annual mean air temperatures at the lakes show two distinct types of trends for the 19th and 20th centuries. During the period 1801–1900, the western European lakes show no significant trend whereas annual mean air temperatures at the eastern European lakes decrease significantly. The period 1901–1997 presents a warming trend at all but the Fennoscandian lakes. Our results are in good agreement with previous studies on the spatial distribution and magnitude of temperature change in Europe. Principal component analysis performed on the reconstructed annual mean air temperature reveals two different regimes of trends for the past two centuries. It also allows a regional clustering of the inter-annual variability of air temperature at the lakes to be identified. 相似文献
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北极地区20世纪温度变化趋势的不确定性 总被引：2，自引：0，他引：2
北极作为地球的冷源之一,对于地球气候系统起着重要的调节作用.本研究通过分析和总结北极地区器测数据和模拟集成结果,以及最近2 000 a来的温度记录,得出如下结果：1）格陵兰冰盖表层大气温度记录显示,20世纪存在1923—1965年和1994年—至今2个相对温暖时段,且前者更为温暖,温度变化幅度远大于北半球的平均温度.2）北极地区20世纪温度上升是客观存在的,其夏季温度和年平均温度呈现一致变化,未发现明显的温度异常信号.3）定量重建的古气候记录显示了北极地区20世纪升温的特征,但不同记录揭示的升温幅度存在差异.与器测结果不同,多条重建记录未能揭示自1994年至今的升温阶段,反映了古气候载体对气候响应的复杂性,揭示出北极地区未来气候变化趋势存在不确定性.在全球变化备受关注的背景下,北极地区对气候变化研究的重要性日益显现,在做出明确结论之前,需要进一步加大研究力度. 相似文献
17.
ZHANG Yongjun KANG Shichang QIN Dahe REN Jiawen ZHANG Yulan Bjorn GRIGHOLM Paul MAYEWSKI 《地理学报》2007,17(4):431-441
A 70-year history of precipitation δ18O record has been retrieved using an ice core drilled from a plat portion of the firn area in the Guoqu Glacier (33o34′37.8″ N, 91o10′35.3″ E, 5720 m a.s.l.) on Mt. Geladaindong (the source region of Yangtze River) during October and November, 2005. Based on the seasonality of δ18O records and the significant positive rela-tionships between monsoon/non-monsoon δ18O values and summer/spring air temperature from the nearby meteorological stations, the history of summer and spring air temperature have been reconstructed for the last 70 years. The results show that both summer and spring air temperature variations present similar trends during the last 70 years. Regression analysis indicates that the slope of the temperature-δ18O relationship is 1.3℃/‰ for non-monsoon δ18O values and spring air temperature, and 0.4℃/‰ for monsoon δ18O values and summer air temperature. Variation of air temperature recorded in the ice core is consistent with that in the Northern Hemisphere (NH), however, the warming trend in the Geladaindong region is more intense than that in the NH, reflecting a higher sensitivity to global warming in the high elevation regions. In addition, warming trend is greater in spring than in summer. 相似文献
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利用气象站点1981—2011年逐日0
cm土壤温度和气温数据，运用基本统计、线性回归、累积距平和信噪比分析了川南山区6个分区地温和气温的空间分布、变化趋势以及突变特征，分析并对比了地温和气温的关系。结果表明：川南山区年均地、气温变化范围分别在15.6~20.5 ℃和12.2~17.2 ℃之间，呈现出北低南高、高山低河谷高的空间分布格局。31 a来6个分区的年均地、气温均有显著上升趋势，但季节变化差异明显，冬季地、气温的增温率高于夏季。从不同区域来看，高山地带(Ⅵ区)的年、季增温趋势最为显著，是其他区域的2~6倍，且地、气温在1990年左右发生突变；河谷地带(Ⅱ区)的年、季温度变化最小且未发生突变。各区地温和气温呈极显著正相关(P<0.01)，具有较高的一致性，但也存在非对称增温现象。山地(Ⅲ、Ⅴ、Ⅵ区)的年均、季均地温和河谷(Ⅰ区)的春季地温增温比气温更加强烈，故地气温差出现显著上升趋势，甚至发生突变。 相似文献
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对气候变暖问题争议的分析 总被引：50，自引：8，他引：50
综合评述和分析了近年来关于全球气候变暖问题的研究。重点是有关气候变暖的一些争议。目前的结论是:(1)19世纪中期以来全球平均地表气温上升了0.4～0.8℃;(2)全球气候变暖的论断得到了海洋温度、大气温度、钻孔温度、陆地雪盖、海冰及冰川资料的支持;(3)1998年是近一个半世纪有观测资料以来最暖的一年,对1961～1990年平均的距平为0.55℃。20世纪变暖的趋势为0.066℃/10a;(4)1990′s是20世纪最暖的10年,平均气温距平0.35℃,也可能是500a或者甚至1000a来最暖的10年。所以,20世纪气候的变暖是无可怀疑的。人类活动影响很可能是20世纪气候变暖的主要原因,至少是主要原因之一。 相似文献
20.
Comparisons between climate proxies and instrumental records through the last two centuries are often used to understand better the controls on palaeoarchives and to find relationships that can be used to quantify changes in pre-instrumental climate. Here we compare an 80-year-long annually resolved oxygen isotope record from Nar Gölü, Turkey, a varved lake sequence, with instrumental records of temperature, precipitation, wind speed, relative humidity and calculated values of evaporation, all of which are known to be possible controls on lake oxygen isotope systems. Significant relationships are found between the isotope record and summer temperatures and evaporation suggesting these are dominant controls on the isotope hydrology of this non-outlet lake. Modelling the stable isotope hydrology of the lake system allows these relationships to be tested independently. We show that the isotope record follows the same trends in the temperature and evaporation records but that, even when combined, these two climatic factors cannot fully explain the magnitude of change observed in the isotope record. The models show the lake system is much less sensitive to changes in evaporation and temperature than the climate calibration suggests. Additional factors, including changes in the amount of precipitation, are required to amplify the isotope change. It is concluded that proxy-climate calibrations may incorrectly estimate the amplitude of past changes in individual climate parameters, unless validated independently. 相似文献