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1.
Permafrost warming in the Tien Shan Mountains, Central Asia   总被引:4,自引:0,他引:4  
The general features of alpine permafrost such as spatial distribution, temperatures, ice content, permafrost and active-layer thickness within the Tien Shan Mountains, Central Asia are described. The modern thermal state of permafrost reflects climatic processes during the twentieth century when the average rise in mean annual air temperature was 0.006–0.032 °C/yr for the different parts of the Tien Shan. Geothermal observations during the last 30 yr indicate an increase in permafrost temperatures from 0.3 °C up to 0.6 °C. At the same time, the average active-layer thickness increased by 23% in comparison to the early 1970s. The long-term records of air temperature and snow cover from the Tien Shan's high-mountain weather stations allow reconstruction of the thermal state of permafrost dynamics during the last century. The modeling estimation shows that the altitudinal lower boundary of permafrost distribution has shifted by about 150–200 m upward during the twentieth century. During the same period, the area of permafrost distribution within two river basins in the Northern Tien Shan decreased approximately by 18%. Both geothermal observations and modeling indicate more favorable conditions for permafrost occurrences and preservation in the coarse blocky material, where the ice-rich permafrost could still be stable even when the mean annual air temperatures exceeds 0 °C.  相似文献   

2.
This research presents a precise evaluation of the Tien Shan glacier's recession based on data of geodetic surveys 1861–1869, aerial photographs from 1943, 1963, 1977, 1981, 1:25,000 scale topographic maps, SRTM, and ASTER data from 2000/2003 for the Akshiirak glacierized massif in the central Tien Shan with 178 glaciers covering 317.6 km2, and for the Ala Archa glacier basin in the northern Tien Shan with 48 glaciers covering 36.31 km2.The Tien Shan glaciers retreated as much as 3 km from the 1860s to 2003. From 1943 to 1977, Akshiirak and Ala Archa shrunk 4.2% and 5.1% respectively, and from 1977 to 2003 the area shrunk 8.6% and 10.6%, respectively. The volume of the Akshiirak glaciers was reduced by 3.566 km3 from 1943 to 1977 and 6.147 km3 from 1977 to 2000.The total reduction of the Tien Shan glacier is 14.2% during the last 60 yr. The northern and central Tien Shan have not experienced a significant increase of precipitation during the last 100 yr, but they have experienced an increase in summer air temperatures, especially observable since the 1970s, which caused an acceleration of the Tien Shan glaciers recession.  相似文献   

3.
This paper presents a synopsis of recently published studies by the co-authors, which show that several land surface characteristics unique to Northern Eurasia are responsible for facilitating a causal relationship between autumn snow anomalies in this region and subsequent hemispheric winter climate patterns. The large size and extratropical location of the contiguous Eurasian land mass results in broad, continental-scale interannual snow cover extent and depth variations throughout autumn and winter, and corresponding diabatic heating anomalies. These surface anomalies occur in the presence of a large region of stationary wave activity, produced in part by the orographic barriers that separate northern/central Eurasia from southern/eastern Eurasia. This co-location of snow-forced anomalies and ambient wave energy is unique to Northern Eurasia, and initiates a teleconnection pathway involving stationary wave–mean flow interaction throughout the troposphere and stratosphere, ultimately resulting in a modulation of the winter Arctic Oscillation (AO). Complementary new results are also presented which show that partial snow cover extent or snow depth only anomalies in Northern Eurasia are insufficient to initiate the teleconnection pathway and produce a winter AO signal. This synopsis provides a useful interpretation of the earlier studies in the specific context of Northern Eurasia regional climate and environmental change.  相似文献   

4.
Snow algae in a 45.97-m-long ice core from the Tyndall Glacier (50°59′05″S, 73°31′12″W, 1756 m a.s.l.) in the Southern Patagonian Icefield were examined for potential use in ice core dating and estimation of the net accumulation rate. The core was subjected to visual stratigraphic observation and bulk density measurements in the field, and later to analyses of snow algal biomass, water isotopes (18O, D), and major dissolved ions. The ice core contained many algal cells that belonged to two species of snow algae growing in the snow near the surface: Chloromonas sp. and an unknown green algal species. Algal biomass and major dissolved ions (Na+, K+, Mg2+, Ca2+, Cl, SO42−) exhibited rapid decreases in the upper 3 m, probably owing to melt water elution and/or decomposition of algal cells. However, seasonal cycles were still found for the snow algal biomass, 18O, D-excess, and major ions, although the amplitudes of the cycles decreased with depth. Supposing that the layers with almost no snow algae were the winter layers without the melt water essential to algal growth, we estimated that the net accumulation rate at this location was 12.9 m a− 1 from winter 1998 to winter 1999, and 5.1 m from the beginning of winter to December 1999. These estimates are similar to the values estimated from the peaks of 18O (17.8 m a− 1 from summer 1998 to summer 1999 and 11.0 m from summer to December 1999) and those of D-excess (14.7 m a− 1 from fall 1998 to fall 1999 and 8.6 m a− 1 from fall to December 1999). These values are much higher than those obtained by past ice core studies in Patagonia, but are of the same order of magnitude as those predicted from various observations at ablation areas of Patagonian glaciers.  相似文献   

5.
The potential energy curves for theX 2 Σ+ andB 2 Σ+ states of CO+ have been constructed by the Rydberg-Klein-Rees (RKR) method as modified by van der Sliceet al. The dissociation energy is estimated to be 7.70±0.19 eV by the method of curve fitting using the five parameter Hulburt-Hirschfelder’s function. The estimated value is in good agreement with the value (7.839 eV) given by Misraet al. Carefull observation of the results reveals that accurateD 0 value for CO+ is 8.33 eV  相似文献   

6.
The generation and development of dust storms are controlled by land surface conditions and atmospheric circulations. The latter, in turn, is influenced by the global ice–snow cover. In this study, we examine the relationship between the characteristics of dust storm activities in north China and the changes of global climate patterns. In particular, we are interested in whether Arctic ice–snow cover is related to the dust storm frequencies and intensities in north China. Our analysis, based on the monthly data for the period from 1954 to 1994, shows that this is indeed the case. This result suggests that the Arctic ice–snow cover can be used for the long-term prediction of dust storm activities in north China, and dust storm activities also serve as an indicator of global climate change.  相似文献   

7.
Changes in the extent of glaciers and rates of glacier termini retreat in the eastern Terskey–Alatoo Range, the Tien Shan Mountains, Central Asia have been evaluated using the remote sensing techniques. Changes in the extent of 335 glaciers between the end of the Little Ice Age (LIA; mid-19th century), 1990 and 2003 have been estimated through the delineation of glacier outlines and the LIA moraine positions on the Landsat TM and ASTER imagery for 1990 and 2003 respectively. By 2003, the glacier surface area had decreased by 19% of the LIA value, which constitutes a 76 km2 reduction in glacier surface area. Mapping of 109 glaciers using the 1965 1:25,000 maps revealed that glacier surface area decreased by 12.6% of the 1965 value between 1965 and 2003. Detailed mapping of 10 glaciers using historical maps and aerial photographs from the 1943–1977 period, has enabled glacier extent variations over the 20th century to be identified with a higher temporal resolution. Glacial retreat was slow in the early 20th century but increased considerably between 1943 and 1956 and then again after 1977. The post-1990 period has been marked by the most rapid glacier retreat since the end of the LIA. The observed changes in the extent of glaciers are in line with the observed climatic warming. The regional weather stations have revealed a strong climatic warming during the ablation season since the 1950s at a rate of 0.02–0.03 °C a− 1. At the higher elevations in the study area represented by the Tien Shan meteorological station, the summer warming was accompanied by negative anomalies in annual precipitation in the 1990s enhancing glacier retreat. However, trends in precipitation in the post-1997 period cannot be evaluated due to the change in observational practices at this station. Neither station in the study area exhibits significant long-term trends in precipitation.  相似文献   

8.
Ice divide–dome behaviour is used for ice sheet mass balance studies and interpretation of ice core records. In order to characterize the historical behaviour (last 400 yr) of Dome C and Talos Dome (East Antarctica), ice velocities have been measured since 1996 using a GPS system, and the palaeo-spatial variability of snow accumulation has been surveyed using snow radar and firn cores. The snow accumulation distribution of both domes indicates distributions of accumulation that are non-symmetrical in relation to dome morphology. Changes in spatial distributions have been observed over the last few centuries, with a decrease in snow accumulation gradient along the wind direction at Talos Dome and a counter-clockwise rotation of accumulation distribution in the northern part of Dome C. Observations at Dome C reveal a significant increase in accumulation since the 1950s, which could correlate to altered snow accumulation patterns due to changes in snowfall trajectory. Snow accumulation mechanisms are different at the two domes: a wind-driven snow accumulation process operates at Talos Dome, whereas snowfall trajectory direction is the main factor at Dome C. Repeated GPS measurements made at Talos Dome have highlighted changes in ice velocity, with a deceleration in the NE portion, acceleration in the SW portion and migration of dome summit, which are apparently correlated with changes in accumulation distribution. The observed behaviour in accumulation and velocity indicates that even the most remote areas of East Antarctica have changed from a decadal to secular scale.  相似文献   

9.
On February 1, 1994, a large meteoroid impacted over the Pacific Ocean at 2.6° N, 164.1° E. The impact was observed by space based IR sensors operated by the US Department of Defense and by visible wavelength sensors operated by the US Department of Energy. During entry the object broke into several pieces, one of which detonated at 34 km and another at 21 km altitude. The entry velocity of the object is estimated to be 24–25 km/sec. Based on the visible wavelength data, the integrated intensity of the radiated energy of the fireball was approximately 1.3 × 1013 joules. Assuming a 6000 K black body and a 30% efficiency for the conversion of the kinetic energy of the body into visible light, we estimate the mass of the body to be between 1.6×105 kg and 4.4×106 kg, and to have a diameter of between 4.4 and 13.5 meters. The object entered at a 45° angle, traveling on a heading of approximately 300°, i.e. from the southeast to the northwest. Calculations using a gross-fragmentation model indicate that the body was most likely a stony object larger than 10 m with an Apollo orbit prior to impact.E T Space SystemsSandia National LaboratoriesOndejov Observatory  相似文献   

10.
Based on the theory of the radio evolution of supernova remnants and the theory of x-ray emission, we have derived an expression for the energy of supernova eruption directly in terms of the observed radio flux density and x-ray luminosity. This method is used to estimate the energy of the supernova explosions in LMC and SMC. Our calculated values fall in the range 1049 – 1051 ergs, with the values for Type I supernovae systematically smaller than those for Type II, at about 1049 ergs. We point out that the most likely cause for the discrepancy between the statistical and theoretical N-D relations is incompletness of data. We also point out, in the two clouds, the vast majority of large sources are still in the phase of adiabatic expansion.  相似文献   

11.
The Hubble constant is split into two terms H = H1 + H2 , where H1 is a decreasing function due to the Big Bang and the subsequent gravitational interaction that slows the expansion of the Universe and H2 is an increasing function that corresponds to dark energy which accelerates this expansion. For T = 13.7 Gyr we prove that H2(T) > 5 m/(yr AU). This is a quite large number and thus the impact of dark energy, which is spread almost everywhere uniformly, should be observable not only on large scales, but also in our Solar system. In particular, we show that Earth, Mars and other planets were closer to the Sun 4.5 Gyr ago. The recession speed ≈5.3 m/yr of the Earth from the Sun seems to be just right for an almost constant influx of solar energy from the origin of life on Earth up to the present over which time the Sun’s luminosity has increased approximately linearly. This presents further support for the Anthropic Principle. Namely, the existence of dark energy guarantees very stable conditions for the development of intelligent life on Earth over a period of 3.5 Gyr.  相似文献   

12.
The total kinetic energy of the Galaxy is estimated from the potential energy by applying the virial theorem. The limits of the potential energy depend strongly on the value of the local escape velocity. They are estimated to be between −7. 1016 MȮ km2s−2 and −1. 1016 MȮ km2s−2 (escape velocity approximately between 450 km s−1 and 600 km s−1). The specific kinetic energy of the Galaxy as a whole is most likely about 21 000 km2s−2, being equally distributed among the subsystems if the local escape velocity is near its lower limit; the higher the local escape velocity is, the higher is the specific kinetic energy of the Galaxy due to the influence of the dark corona. The specific kinetic energy of the dark corona tends to become equal to that of the Galaxy as a whole for very high values of the local escape velocity. For the purpose of estimating the totl potential energy of the Galaxy, inter alia, a new model of the Milky Way is developed, which yields both the potential and the density analytically so that it is suitale for calculating the galactocentric orbits.  相似文献   

13.
The development of an ultra high energy air shower has an intrinsic energy fluctuation due both to the first interaction point and to the cascade development. Here we show that for a given primary energy this fluctuation has a lognormal distribution and thus observations will estimate the primary energy with a lognormal error distribution. We analyze the UHECR energy spectrum convolved with the lognormal energy error and demonstrate that the shape of the error distribution will interfere significantly with the ability to observe features in the spectrum. If the standard deviation of the lognormal error distribution is equal or larger than 0.25, both the shape and the normalization of the measured energy spectra will be modified significantly. As a consequence, the GZK cutoff might be sufficiently smeared as not to be seen (without very high statistics). This result is independent of the power law of the cosmological flux. As a conclusion we show that in order to establish the presence or not of the GZK feature, not only more data are needed but also that the shape of the energy error distribution has to be known well. The high energy tail and the sigma of the approximate lognormal distribution of the error in estimating the energy must be at the minimum set by the physics of showers.  相似文献   

14.
In this work we study how the turbulent component of the Galactic magnetic field (GMF) affects the propagation of ultrahigh energy heavy nuclei. We investigate first how the images of individual sources and of the supergalactic plane depend on the properties of the turbulent GMF. Then we present a quantitative study of the impact of the turbulent field on (de-)magnification of source fluxes, due to magnetic lensing effects. We also show that it is impossible to explain the Pierre Auger data assuming that all ultrahigh energy nuclei are coming from Cen A, even in the most favorable case of a strong, extended turbulent field in the Galactic halo.  相似文献   

15.
The classical Kepler Problem consists in the determination of the relative orbital motion of a secondary body (planet) with respect to the primary body (Sun), for a given time. However, any natural system tends to have minimum energy and is subjected to differential gravitational or tidal forces (called into play mainly due to the finite size and deformability of the secondary body). We formulate the Kepler Problem taking into account the finite size of the secondary body and consider an approximation which tends towards minimum energy orbits, by increasing the dimensionality of the problem. This formulation leads to a conceivable natural explanation of the fact that the planetary orbits are characterized by small eccentricities.  相似文献   

16.
Based on spacecraft observations of the giant planets we call attention to an apparent regular mass-luminosity relation for the large planets (giant planets plus Earth). It can provide important clues and constraints on the question of their energy source, including various relevant theories and their difficulties. We describe in some detail a new thermonuclear reaction mechanism, valid for plasma fusions at both super—high and low temperatures, and including the original thermonuclear mechanism as a particular case. It can explain not only the internal energy souce of the large planets, but also many anomalous fusion phenomena observed in the laboratory and in astronomical bodies. Although these appear in various guises, their basic principle is the same, that is, they can all be understood in terms of the new mechanism.  相似文献   

17.
Due to the action of the intervening cosmic magnetic fields, ultra-high energy cosmic rays (UHECRs) can be deflected in such a way as to create clustered energy-ordered filamentary structures in the arrival direction of these particles, the so-called multiplets. In this work we propose a new method based on the spherical wavelet transform to identify multiplets in sky maps containing arrival directions of UHECRs. The method is illustrated in simulations with a multiplet embedded in isotropic backgrounds with different numbers of events. The efficiency of the algorithm is assessed through the calculation of Type I and II errors.  相似文献   

18.
This study uses experimentally determined plagioclase‐melt D values to estimate the trace element concentrations of Sr, Hf, Ga, W, Mo, Ru, Pd, Au, Ni, and Co in a crystallizing lunar magma ocean at the point of plagioclase flotation. Similarly, experimentally determined metal‐silicate partition experiments combined with a composition model for the Moon are used to constrain the concentrations of W, Mo, Ru, Pd, Au, Ni, and Co in the lunar magma ocean at the time of core formation. The metal‐silicate derived lunar mantle estimates are generally consistent with previous estimates for the concentration of these elements in the lunar mantle. Plagioclase‐melt derived concentrations for Sr, Ga, Ru, Pd, Au, Ni, and Co are also consistent with prior estimates. Estimates for Hf, W, and Mo, however, are higher. These elements may be concentrated in the residual liquid during fractional crystallization due to their incompatibility. Alternatively, the apparent enrichment could reflect the inappropriate use of bulk anorthosite data, rather than data for plagioclase separates.  相似文献   

19.
The accelerated expansion of the Universe was proposed through the use of Type-Ia supernovae (SNe) as standard candles. The standardization depends on an empirical correlation between the stretch/color and peak luminosity of the light curves. The use of Type-Ia SNe as standard candles rests on the assumption that their properties (and this correlation) do not vary with redshift. We consider the possibility that the majority of Type-Ia SNe are in fact caused by a Quark-Nova detonation in a tight neutron-star-CO-white-dwarf binary system, which forms a Quark-Nova Ia (QN-Ia). The spin-down energy injected by the Quark-Nova remnant (the quark star) contributes to the post-peak light curve and neatly explains the observed correlation between peak luminosity and light curve shape. We demonstrate that the parameters describing QN-Ia are NOT constant in redshift. Simulated QN-Ia light curves provide a test of the stretch/color correlation by comparing the true distance modulus with that determined using SN light curve fitters. We determine a correction between the true and fitted distance moduli, which when applied to Type-Ia SNe in the Hubble diagram recovers the ΩM = 1 cosmology. We conclude that Type-Ia SNe observations do not necessitate the need for an accelerating expansion of the Universe (if the observed SNe Ia are dominated by QNe Ia) and by association the need for dark energy.  相似文献   

20.
Evidence in X-rays, gamma rays and ultra high energy cosmic rays (UHCR) suggests the existence of active centers in extragalactic space which eject high energy particles and quanta. A concentration of these highest energy sources in the direction of the Local Supercluster indicates that the brightest apparent magnitude AGN's such as 3C274 (M87), 3C273, 3C279 and Markarian 421 are the only candidate sources for this radiation. A theoretical model of mass creation in the Local Supercluster based on a Machian theory of gravitation is described as a possible mechanism for production of the high energy while at the same time allowing the AGN's to be at the relatively close distance of the Supercluster. The fact that infrared photons fill intergalactic space limits the distance to the UHCR sources at a little over twice the distance to the center of the Local Supercluster strongly localizing the highest energy radiation to this relatively close distance.  相似文献   

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