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991.
992.
Evidence and Implications of Recent Climate Change in Northern Alaska and Other Arctic Regions 总被引:19,自引:0,他引:19
Larry D. Hinzman Neil D. Bettez W. Robert Bolton F. Stuart Chapin Mark B. Dyurgerov Chris L. Fastie Brad Griffith Robert D. Hollister Allen Hope Henry P. Huntington Anne M. Jensen Gensuo J. Jia Torre Jorgenson Douglas L. Kane David R. Klein Gary Kofinas Amanda H. Lynch Andrea H. Lloyd A. David McGuire Frederick E. Nelson Walter C. Oechel Thomas E. Osterkamp Charles H. Racine Vladimir E. Romanovsky Robert S. Stone Douglas A. Stow Matthew Sturm Craig E. Tweedie George L. Vourlitis Marilyn D. Walker Donald A. Walker Patrick J. Webber Jeffrey M. Welker Kevin S. Winker Kenji Yoshikawa 《Climatic change》2005,72(3):251-298
The Arctic climate is changing. Permafrost is warming, hydrological processes are changing and biological and social systems
are also evolving in response to these changing conditions. Knowing how the structure and function of arctic terrestrial ecosystems
are responding to recent and persistent climate change is paramount to understanding the future state of the Earth system
and how humans will need to adapt. Our holistic review presents a broad array of evidence that illustrates convincingly; the
Arctic is undergoing a system-wide response to an altered climatic state. New extreme and seasonal surface climatic conditions
are being experienced, a range of biophysical states and processes influenced by the threshold and phase change of freezing
point are being altered, hydrological and biogeochemical cycles are shifting, and more regularly human sub-systems are being
affected. Importantly, the patterns, magnitude and mechanisms of change have sometimes been unpredictable or difficult to
isolate due to compounding factors. In almost every discipline represented, we show how the biocomplexity of the Arctic system
has highlighted and challenged a paucity of integrated scientific knowledge, the lack of sustained observational and experimental
time series, and the technical and logistic constraints of researching the Arctic environment. This study supports ongoing
efforts to strengthen the interdisciplinarity of arctic system science and improve the coupling of large scale experimental
manipulation with sustained time series observations by incorporating and integrating novel technologies, remote sensing and
modeling. 相似文献
993.
South Australian rainfall variability and climate extremes 总被引:1,自引:0,他引:1
Rainfall extremes over South Australia are connected with broad-scale atmospheric rearrangements associated with strong meridional
sea surface temperature (SST) gradients in the eastern Indian Ocean. Thirty-seven years of winter radiosonde data is used
to calculate a time series of precipitable water (PW) and convective available potential energy (CAPE) in the atmosphere.
Principle component analysis on the parameters of CAPE and PW identify key modes of variability that are spatially and seasonally
consistent with tropospheric processes over Australia. The correlation of the leading principle component of winter PW to
winter rainfall anomalies reveal the spatial structure of the northwest cloudband and fronts that cross the southern half
of the continent during winter. Similarly the second and third principle components, respectively, reveal the structures of
the less frequent northern and continental cloudbands with remarkable consistency. 850 hPa-level wind analysis shows that
during dry seasons, anomalous offshore flow over the northwest of Australia inhibits advection of moisture into the northwest,
while enhanced subsidence from stronger anticyclonic circulation over the southern half of the continent reduces CAPE. This
coincides with a southward shift of the subtropical ridge resulting in frontal systems passing well to the south of the continent,
thus producing less frequent interaction with moist air advected from the tropics. Wet winters are the reverse, where a weaker
meridional pressure gradient to the south of the continent allows rain-bearing fronts to reach lower latitudes. The analysis
of SSTs in the Indian Ocean indicate that anomalous warm (cool) waters in the southeast Indian Ocean coincide with a southward
(northward) shift in the subtropical ridge during dry (wet) seasons. 相似文献
994.
995.
Natural hazards in Australia: droughts 总被引:3,自引:0,他引:3
996.
Jason P. Evans 《Theoretical and Applied Climatology》2010,99(3-4):389-402
In this study, the ability of a regional climate model, based on MM5, to simulate the climate of the Middle East at the beginning of the twenty-first century is assessed. The model is then used to simulate the changes due to global warming over the twenty-first century. The regional climate model displays a negative bias in temperature throughout the year and over most of the domain. It does a good job of simulating the precipitation for most of the domain, though it performs relatively poorly over the southeast Black Sea and southwest Caspian Sea. Using boundary conditions obtained from CCSM3, the model was run for the first and last 5 years of the twenty-first century. The results show widespread warming, with a maximum of ~10 K in interior Iran during summer. It also found some cooling in the southeast Black Sea region during spring and summer that is related to increases in snowfall in the region, a longer snowmelt season, and generally higher soil moisture and latent heating through the summer. The results also show widespread decreases in precipitation over the eastern Mediterranean and Turkey. Precipitation increases were found over the southeast Black Sea, southwest Caspian Sea, and Zagros mountain regions during all seasons except summer, while the Saudi desert region receives increases during summer and autumn. Changes in the dominant precipitation-triggering mechanisms were also investigated. The general trend in the dominant mechanism reflects a change away from the direct dependence on storm tracks and towards greater precipitation triggering by upslope flow of moist air masses. The increase in precipitation in the Saudi desert region is triggered by changes in atmospheric stability brought about by the intrusion of the intertropical convergence zone into the southernmost portion of the domain. 相似文献
997.
Computer simulations of the topographic evolution of the proposed post‐mining rehabilitated landform for the ERA Ranger Mine, showed that for the unvegetated and unripped case, the landform at 1000 years would be dissected by localized erosion valleys (maximum depth = 7·6 m) with fans (maximum depth = 14·8 m) at the outlet of the valleys. Valley form simulated by SIBERIA has been recognized in nature. This indicates that SIBERIA models natural processes efficiently. For the vegetated and ripped case, reduced valley development (maximum 1000 year depth = 2·4m) and deposition (maximum 1000 year depth = 4·8m) occurred in similar locations as for the unvegetated and unripped case (i.e. on steep batter slopes and in the central depression areas of the landform). For the vegetated and ripped condition, simulated maximum valley depth in the capping over the tailings containment structure was c. 2·2 m. By modelling valley incision, decisions can be made on the depth of tailings cover required to prevent tailings from being exposed to the environment within a certain time frame. A reduction in thickness of 1 m of capping material over tailings equates to c. 1 000 000 Mm3 over a 1 km2 tailings dam area. This represents a saving of c. $1 500 000 in earthworks alone. Incorporation of SIBERIA simulations in the design process may result in cost reduction while improving confidence in environmental protection mechanisms. Copyright 2000 © Environmental Research Institute of the Supervising Scientist, Commonwealth of Australia. 相似文献
998.
The geology of southwest Lleyn comprises two Late Precambrian terranes: the Gwna Mélange in the west and the Sarn Complex in the east, separated by the Lleyn Shear Zone. The location of the terrane boundary is poorly constrained due to the limited exposure. We undertook a ground magnetic survey and also measured four gravity profiles with the original intention of investigating the cause of a positive aeromagnetic anomaly previously recorded close to the terrane boundary at grid reference [SH 2200 3000]. This ‘Sarn anomaly’ appears to be associated with a shallow body within the Sarn Complex, which is known to be a heterogeneous plutonic igneous unit. Of greater interest was the identification of a much larger-amplitude magnetic anomaly striking roughly N–S for over 7 km close to the mapped position of the Lleyn Shear Zone. It can be modelled as a near-vertical discontinuous body of overall dyke-like form, and is too narrow to have been resolved by the aeromagnetic survey. We discovered a previously unreported outcrop of gabbro at Brynhunog Bach [2100 3127] located on this high-amplitude ‘Brynhunog anomaly’. It seems likely that the whole anomaly is due to a gabbroic body which is an original constituent of the Sarn Complex, but an alternative possibility is that it is a later intrusion along the Lleyn Shear Zone. © 1997 John Wiley & Sons, Ltd. 相似文献
999.
1000.