排序方式： 共有38条查询结果，搜索用时 31 毫秒
1.
2.
Henry P. Huntington Michelle Boyle Gwenn E. Flowers John W. Weatherly Lawrence C. Hamilton Larry Hinzman Craig Gerlach Rommel Zulueta Craig Nicolson Jonathan Overpeck 《Climatic change》2007,82(1-2):77-92
Human activities in the Arctic are often mentioned as recipients of climate-change impacts. In this paper we consider the
more complicated but more likely possibility that human activities themselves can interact with climate or environmental change
in ways that either mitigate or exacerbate the human impacts. Although human activities in the Arctic are generally assumed
to be modest, our analysis suggests that those activities may have larger influences on the arctic system than previously
thought. Moreover, human influences could increase substantially in the near future. First, we illustrate how past human activities
in the Arctic have combined with climatic variations to alter biophysical systems upon which fisheries and livestock depend.
Second, we describe how current and future human activities could precipitate or affect the timing of major transitions in
the arctic system. Past and future analyses both point to ways in which human activities in the Arctic can substantially influence
the trajectory of arctic system change. 相似文献
3.
A one-dimensional, time-dependent numerical cloud model is used to analyze the factors in the dynamic and thermodynamic equations which lead to a steady-state or nonsteady-state solution for the cloud vertical motion, buoyancy, precipitation, and cloud water fields. ‘Bulk water’ microphysical techniques are used for the cloud, rain, and hail variables. An atmospheric sounding from a severe storm situation is used as initial and environmental conditions, yielding model updrafts of 40 m sec?1 maximum and more than 10 m sec?1 over the entire cloud region. ‘Early conversion’ of the cloud water to rain leads to loading of lower portions of the updraft by rain, the formation of appreciable amounts of hail by freezing of the supercooled rain, and subsequent loading of the middle and upper portions of the updraft so that the updraft erodes throughout the cloud depth and the cloud dissipates, yielding a vigorous rain shower. A delay in the conversion of the cloud water to rain results in a steady-state solution, no rain or hail falling through the updraft. A two-dimensional cloud simulation of this same case shows rain and hail in the upper cloud regions recycled in the two-dimensional flow into the updraft near cloud base and a breakdown of the updraft with resultant rainout (negligible hail reaching the ground). The breakdown of the updraft has profound effects on the temperature field within the cloud, causing the lapse rate to deviate from the steady-state condition and approach the initial environmental conditions. The results emphasize the fact that the local change in temperature (and other dependent variables as well) is not independent of the vertical velocity, in general. This has implications for the interpretation of measurements made within clouds. 相似文献
4.
Linking Inuit knowledge and meteorological station observations to understand changing wind patterns at Clyde River,Nunavut 总被引：1，自引：1，他引：0
Shari Gearheard Matthew Pocernich Ronald Stewart Joelie Sanguya Henry P. Huntington 《Climatic change》2010,100(2):267-294
Connecting indigenous and scientific observations and knowledge has received much attention in the Arctic, not least in the
area of climate change. On some levels, this connection can be established relatively easily, linking observations of similar
phenomena or of various effects stemming from the same cause. Closer examinations of specific environmental parameters, however,
can lead to far more complex and difficult attempts to make those connections. In this paper we examine observations of wind
at Clyde River, Nunavut, Canada. For Inuit, many activities are governed by environmental conditions. Wind, in particular,
is identified by Inuit as one of the most important environmental variables, playing a key role in driving sea ice, ocean,
and weather conditions that can either enable or constrain hunting, travel, or other important activities. Inuit observe wind
patterns closely, and through many means, as a result of their close connection to the land and sea. Inuit in many parts of
Nunavut are reporting changes in wind patterns in recent years. At Clyde River, a community on the eastern coast of Baffin
Island, Inuit have observed that at least three key aspects of wind have changed over the last few decades: wind variability,
wind speed, and wind direction. At the same time, wind observations are also available from an operational weather station
located at Clyde River. An analysis of this information shows little change in wind parameters since the mid-1970s. Though
the station data and Inuit observations correspond in some instances, overall, there is limited agreement. Although the differences
in the two perspectives may point to possible biases that may exist from both sources—the weather station data may not be
representative of the region, Inuit observations or explanations may be inaccurate, or the instrumental and Inuit observations
may not be of the same phenomena—they also raise interesting questions about methods for observing wind and the nature of
Arctic winds. 相似文献
5.
K. Yang J. F. Huntington J. W. Boardman P. Mason 《Australian Journal of Earth Sciences》2013,60(6):915-922
Hydrothermal alteration mapping with spaceborne hyperspectral data was simulated in the Comstock mining district, Nevada in order to evaluate the mineral mapping capabilities of the proposed Australian Resource Information and Environment Satellite (ARIES‐1). As a result, a suite of hydrothermal alteration minerals, including kaolinite, dickite, illite, chlorite, alunite and carbonate was identified from the simulated data in the 0.4–2.5 μm wavelength region and their areal abundance variations mapped accordingly. The recognised alteration zoning shows a major change in alteration assemblages across the Comstock and Silver City Faults, and a gradual variation from north to south along the faults. In the bleached Miocene volcanic rocks, dickite, kaolinite, illite and alunite were recognised. Coexistence of dickite of relatively high temperature, high‐crystallinity kaolinite of medium temperature and low‐crystallinity kaolinite of low temperature suggests supergene processes overprinting earlier hypogene alteration. The bleached rocks probably represent hydrothermal alteration in the fluid up‐flow zones in the central and shallower parts of the hydrothermal system. Illite in the bleached zones is characterised by relatively short AI–OH band wavelengths (2190–2200 nm), indicating no or very low Fe and/or Mg contents. Fault‐controlled propylitic alteration is mapped in the central part of the district mainly in the footwall of the Comstock Fault. The associated illite is characterised mainly by medium AI–OH band wavelengths (2200–2208 nm). This propylitic alteration may be contemporaneous with Au–Ag mineralisation. Additional and more extensive propylitic zones, containing illite with long AI–OH band wavelengths (2204–2216 nm), were mapped in the southern part of the district. These zones resulted from either a pre‐mineralisation propylitic alteration, or the peripheral hydrothermal alteration in the fluid down‐flow zones of the Miocene hydrothermal system. 相似文献
6.
Sarah F. Trainor Monika Calef David Natcher F. Stuart Chapin III A. David McGuire Orville Huntington Paul Duffy T. Scott Rupp La'Ona DeWilde Mary Kwart Nancy Fresco & Amy Lauren Lovecraft 《Polar research》2009,28(1):100-118
This paper explores whether fundamental differences exist between urban and rural vulnerability to climate-induced changes in the fire regime of interior Alaska. We further examine how communities and fire managers have responded to these changes and what additional adaptations could be put in place. We engage a variety of social science methods, including demographic analysis, semi-structured interviews, surveys, workshops and observations of public meetings. This work is part of an interdisciplinary study of feedback and interactions between climate, vegetation, fire and human components of the Boreal forest social–ecological system of interior Alaska. We have learned that although urban and rural communities in interior Alaska face similar increased exposure to wildfire as a result of climate change, important differences exist in their sensitivity to these biophysical, climate-induced changes. In particular, reliance on wild foods, delayed suppression response, financial resources and institutional connections vary between urban and rural communities. These differences depend largely on social, economic and institutional factors, and are not necessarily related to biophysical climate impacts per se. Fire management and suppression action motivated by political, economic or other pressures can serve as unintentional or indirect adaptation to climate change. However, this indirect response alone may not sufficiently reduce vulnerability to a changing fire regime. More deliberate and strategic responses may be required, given the magnitude of the expected climate change and the likelihood of an intensification of the fire regime in interior Alaska. 相似文献
7.
Summary This paper is concerned with the simulation of deep convection for the CCOPE 19 July 1981 case study. Clark's three-dimensional (3D) cloud model modified to use the bulk water parameterization scheme of Lin et al. has been used in the simulation of the CCOPE 19 July 1981 case in coarse mesh, fine mesh, and interactive grid nested schemes, respectively. Comparisons with observations show this 3D grid nested cloud model is capable of both capturing both the dynamic and microphysical properties of the cloud.In the nested grid fine mesh model simulation, the timing and mode of cloud growth, the diameter of liquid cloud, the cloud top rate of rise, the maximum cloud water content, and the altitude of first radar echo are consistent with observations. The simulated thunderstorm begins to dissipate, after precipitation reaches the ground as indicated by the decreasing values of maximum updraft and maximum liquid cloud water content, and ends as a precipitating anvil as was observed in the actual thunderstorm. The model precipitation developed through ice phase processes consistent with the analysis of observations from the actual thunderstorm.Qualitative comparisons of the actual radar RHIs with simulated reflectively patterns from the 3D model show remarkable similarity, especially after the mature stage is reached. Features of the actual RHI patterns, such as the weak echo region, upshear anvil bulge, strong upwind reflectivity gradients, and the upwind outflow region near the surface are reproduced in the simulation. Comparison of the actual radar PPIs with horizontal cross sections of radar reflectivity simulated by the 3D model, however, show modest differences in the storm size with the 3D simulated thunderstorm being 1–2 km longer in the west-east direction than the actual thunderstorm. The model-predicted maximum updraft speed is smaller than the 2D model-predicted maximum updraft speed, but still greater than what was observed.Comparisons among the nested grid fine mesh model (MB), nested grid coarse mesh model (MA), fine mesh model (FM), coarse mesh model (CM), and 2D model results previously published show that the nested grid fine mesh model (MB) gives the best simulation result. The various 3D model simulation results are generally similar to each other except for the difference in the domain maximum values. The domain maximum values in the fine mesh models (MB and FM) are generally higher than the coarse mesh models as a result of averaging over a smaller area.With 7 Figures 相似文献
8.
D. Arne E. House S. Pontual J. Huntington 《Australian Journal of Earth Sciences》2016,63(8):1003-1025
HyLogger hyperspectral data obtained from seven orogenic gold deposits in central Victoria, including Bendigo, Ballarat, Maldon, Fosterville, Costerfield, Castlemaine and Wildwood, are presented. The data demonstrate that fresh diamond drill core displays substantial mineralogical variation that can be attributed to the effects of cryptic hydrothermal alteration that might not otherwise be recognised. The most significant hyperspectral response lies in the white mica compositions, which vary in a systematic manner between high-Al muscovitic zones (Al–OH absorption around 2208 nm) that define a phyllic alteration halo around mineralised structures, and low-Al phengitic–chlorite zones (Al–OH absorption >2014 nm) inferred to represent either more distal alteration or possibly regional metamorphic background. An extensive ferroan dolomite alteration halo overlaps the phyllic and sulfidic alteration zones and extends beyond the sampled core in most instances. This ferroan dolomite halo has previously been defined petrographically, geochemically and using carbonate staining techniques, and is further characterised using thermal infrared hyperspectral data in drill core from the Ballarat goldfield. The mineralogical trends identified by the hyperspectral data are best developed in diamond drill core from the Costerfield, Fosterville and Ballarat goldfields, and are less pronounced at the other deposits. At Bendigo and Castlemaine the reasons for this are not immediately clear, but may be related to the close timing of gold mineralisation relative to peak metamorphism. The Maldon area lies within the contact aureole of the Harcourt Batholith and so has been thermally overprinted leading to the recrystallisation of earlier hydrothermal assemblages. The Wildwood deposit is similar to the Magdala deposit at Stawell and differs from the other goldfields in its geological setting, host rock lithologies and style of hydrothermal alteration, with the development of Fe-rich chlorite closely associated with gold mineralisation. The results demonstrate how hyperspectral data can be used to define large hydrothermal alteration footprints associated with orogenic gold mineralisation in central Victoria that are of direct benefit to mineral explorers, as well as independently characterising lithological variations in drill core. 相似文献
9.
Over the next several decades, arctic marine mammals will face threats from six areas of human influence: climate change, environmental contaminants, offshore oil and gas activities, shipping, hunting, and commercial fisheries. This paper reviews these factors, the nature and magnitude of the threats they pose, current scientific understanding and management of those threats, and the potential for effective conservation action. Climate change, offshore oil and gas activities, and commercial fisheries likely pose the greatest threats. Addressing the combined effects of all six factors, however, will be particularly difficult but essential to prevent declines beyond those that have already occurred. 相似文献
10.
We analyzed long-term records of ice thickness on the Piscataquis River in central Maine and air temperature in Maine to determine whether there were temporal trends that were associated with climate warming. The trend in ice thickness was compared and correlated with regional time series of winter air temperature, heating degree days (HDD), date of river ice-out, seasonal center-of-volume date (SCVD) (date on which half of the stream runoff volume during the period 1 Jan. to 31 May has occurred), water temperature, and lake ice-out date. All of these variables except lake ice-out date showed significant temporal trends during the 20th century. Average ice thickness around 28 February decreased by about 23 cm from 1912 to 2001. Over the period 1900 to 1999, winter air temperature increased by 1.7 °C and HDD decreased by about 7.5%.Final ice-out date on the Piscataquis River occurred earlier (advanced), by 0.21 days yr–1 over the period 1931 to 2002, and the SCVD advancedby 0.11 days yr–1 over the period 1903 to 2001. Ice thickness was significantly correlated (P-value <0.01) with winter air temperature, HDD, river ice-out, and SCVD. These systematic temporal trends in multiple hydrologic indicator variables indicate a coherent response to climate forcing. 相似文献