Impact of global warming rate on permafrost degradation

The IAP RAS climate model of intermediate complexity is used to analyze the sensitivity of the area of continuous potential permafrost S _cont to the rate of global temperature variation T _gl in experiments with greenhouse-gas increases in the atmosphere. The influence of the internal variability of the model on the results is reduced by conducting ensemble runs with different initial conditions and analysis of the ensemble means. Idealized experiments with a linear or exponential dependence of the concentration of carbon dioxide in the atmosphere have revealed an increase in the magnitude of the temperature-sensitivity parameter of the area of continuous potential permafrost, k _cont (= S _{cont, 0} ^t-1 dS _cont/dT _gl, where S _{cont, 0} is the present value of S _cont). With a decrease in the linear trend coefficient of T _gl from about 3 to about 2 K/100 yr, this parameter varies from approximately ?0.2 to ?0.4 K^?1. With an even slower change in global temperature, k _cont virtually does not vary and remains close to the value obtained from paleoreconstructions of the past warm epochs. Such a dependence of k _cont on the rate of global warming is related mainly to the fact that the more rapid increase in T _gl leads to a slower response over high-latitude land. The contribution from changes in the annual temperature cycle, though comparable in the order of magnitude, is about one-third as large as the contribution from the variation of the latitudinal structure of the response of annual mean temperature. The total reduction in the annual cycle of temperature during warming partly compensates for the effect of the annual mean temperature rise, thus decreasing the magnitude of k _cont. In numerical experiments with greenhouse gas changes in accordance with SRES scenarios A2 and B2 and scenario IS92a, there is also a monotonic increase in the magnitude of the normalized parameter of temperature sensitivity of the area of continuous permafrost with a decrease in the growth rate of global temperature. For scenarios A2-CO2, IS92a-GHG, IS92a-CO2, B2-GHG, and B2-CO2, its value is almost indistinguishable from the steady-state asymptotic value of ?0.4 K^?1. For A2-GHG, the magnitude of k _cont turns out to be far less (k _cont ≈ ?0.3 K^?1).     

Relationship Between the H5 Chondrite Composition,Structure and Mechanical Properties from the Example of NWA 12370 and Pultusk

Solar System Research - The peculiarities of the composition and internal structure of chondrite NWA 12370, petrological type H5 S1 W1, were studied by means of Raman spectroscopy, XRF, and...     

Impact of non-Gaussian statistics of atmospheric variables on extreme intramonth anomalies

The analysis of asymmetry of probability distribution functions (PDF) is carried out for key atmospheric variables using the JRA-55 reanalysis data in the troposphere of the Northern Hemisphere for 1976–2014. The nonzero asymmetry of the PDF indicates the deviation of the PDF from the normal distribution. The analysis was carried out for two time-scale intervals: synoptic variability (SV) of 2–7 days and low-frequency variability (LV) of 9–30 days. Statistically significant deviations from the normal probability distribution occur in the regions of the most frequent formation of atmospheric baroclinic perturbations, i.e., over the western parts of the oceans in midlatitudes and downstream in the atmosphere. In the SV time-scale interval, a negative asymmetry of the vertical velocity is revealed in isobaric coordinates for the entire thickness of the free troposphere, which agrees with the overall dominance of cyclonic anomalies in this interval of time scales. In the LV interval, the asymmetry of this variable in the entire free troposphere is positive, which indicates the dominance of anticyclonic anomalies at these time scales. For the zonal velocity, temperature, and geopotential, the asymmetry sign of the PDF for variability with time scales of 2–7 days is different for the upper and lower free troposphere. The asymmetry of the PDF for atmospheric variables indicates the important role of the intermode interaction in the formation of baroclinic perturbations. The corresponding deviations of synoptic variability from the normal distribution, which is found in the upper troposphere of the subpolar and polar latitudes, can be related to the interaction of these perturbations with the winter polar vortex. These deviations of PDF from the normal distribution substantially increase the probability of the appearance of large (in absolute value) anomalies as compared to the case of the Gaussian PDF.     

On the very-high-energy gamma-ray flux from the galaxy Mrk 421 in 2004

The galaxy Mrk 421 was observed with the GT-48 Cherenkov telescope in 2004. The observations revealed a very-high-energy gamma-ray flux at a confidence level of 4.8 σ. Comparison with the constant gamma-ray flux from the Crab Nebula yielded an estimate of the total flux from Mrk 421, 1.7 ± 0.7 Crab (E ≥ 1 TeV).     

Precise positions of selected minor planets from the observations of 1991–1993

We present two catalogues of positions of selected asteroids in the system of the Tycho Reference Catalogue from the photographic observations carried out on Mt. Maidanak with the AFR-1 wide-field astrograph (D = 230 mm, F = 2300 mm) and in Zvenigorod with the Zeiss wide-field astrograph (D = 400 mm, F = 2000 mm) in 1991–1993. The catalogue obtained on Maidanak contains 109 positions of selected asteroids; the one obtained in Zvenigorod contains 177 asteroid positions. The two catalogues are compared to show that they are uniform. The one-position mean square errors in the Maidanak and Zvenigorod catalogues are calculated: 0.306″, 0.153″ and 0.370″, 0.219″.     

Nitrogen cycle in the earth climatic system and its modeling

Investigations into the nitrogen cycle in the climatic system of the earth are reviewed with special emphasis on the biospheric nitrogen cycle. Approaches to modeling the biogeochemical nitrogen turnover are described. Excluding the nitrogen cycle from consideration when probable consequences of climate change are analyzed can lead to inaccurate estimates of the ecosystem response, in particular, for regions where mineral compounds of soil nitrogen are a limiting factor for the development of vegetation cover. Numerical experiments with climatic models point to a substantial influence of the nitrogen turnover on the feedback between climatic characteristics and the carbon cycle. Models of the combined dynamics of carbon and nitrogen make it possible to obtain realistic estimates of present-day resources and fluxes of these elements in ecosystems, as well as to estimate their changes during possible climatic changes.     

Carbon cycle–climate feedback sensitivity to parameter changes of a zero-dimensional terrestrial carbon cycle scheme in a climate model of intermediate complexity

Summary A series of sensitivity runs have been performed with a coupled climate–carbon cycle model. The climatic component consists of the climate model of intermediate complexity IAP RAS CM. The carbon cycle component is formulated as a simple zero-dimensional model. Its terrestrial part includes gross photosynthesis, and plant and soil respirations, depending on temperature via Q ₁₀-relationships (Lenton, 2000). Oceanic uptake of anthropogenic carbon is formulated is a bi-linear function of tendencies of atmospheric concentration of CO₂ and globally averaged annual mean sea surface temperature. The model is forced by the historical industrial and land use emissions of carbon dioxide for the second half of the 19th and the whole of the 20th centuries, and by the emission scenario SRES A2 for the 21st century. For the standard set of the governing parameters, the model realistically captures the main features of the Earth’s observed carbon cycle. A large number of simulations have been performed, perturbing the governing parameters of the terrestrial carbon cycle model. In addition, the climate part is perturbed, either by zeroing or artificially increasing the climate model sensitivity to the doubling of the atmospheric CO₂ concentration. Performing the above mentioned perturbations, it is possible to mimic most of the range found in the C4MIP simulations. In this way, a wide range of the climate–carbon cycle feedback strengths is obtained, differing even in the sign of the feedback. If the performed simulations are subjected to the constraints of a maximum allowed deviation of the simulated atmospheric CO₂ concentration (pCO_2(a)) from the observed values and correspondence between simulated and observed terrestrial uptakes, it is possible to narrow the corresponding uncertainty range. Among these constraints, considering pCO_2(a) and uptakes are both important. However, the terrestrial uptakes constrain the simulations more effectively than the oceanic ones. These constraints, while useful, are still unable to rule out both extremely strong positive and modest negative climate–carbon cycle feedback.     

Estimates of climate changes in the 20th-21st centuries based on the version of the IAP RAS climate model including the model of general ocean circulation

Numerical experiments are analyzed for 1860–2100 with the version of the climate model of intermediate complexity of the Obukhov Institute of Atmospheric Physics of the Russian Academy of Sciences (IAP RAS) including the model of general ocean circulation as the oceanic module (CM IAP RAS-GOC) taking account of concentration variations of anthropogenic greenhouse gases and tropospheric sulfate aerosols from the data of observations and reconstructions for the second half of the 19th and for the 20th century and, according to SRES scenarios, in the 21st century. In the 20th century, the model simulates realistically the variations of surface atmospheric temperature, characteristics of heat absorption by the ocean, and oceanic meridional heat transport. The linear trend of global surface atmospheric temperature in the 20th century (in its last 30 years) in this version of the model amounts to 0.5 ± 0.1 K/100 years (0.22 ± 0.05 K/10 years) that is agreed with the observational data. In the 21st century, the global increase in the surface temperature amounts to 2.5 K (3.5 and 4.1 K) for SRES B1 scenario (for SRES A1B and SRES A2 scenarios, respectively). The increase in the surface temperature is the most significant in high latitudes, especially in the Northern Hemisphere and it is higher, on the whole, over the land than over the ocean. The warming near the surface is larger in winter than in summer. The maximum warming is observed in the Arctic and over the land of subpolar latitudes of the Northern Hemisphere reaching 6–10 K by the end of the 21st century in these regions as compared with the end of the 20th century depending on the anthropogenic impact scenario. At the increase in surface temperature in the 20th–21st centuries, the increase in the heat flow to the ocean and the weakening of the heat transport by the ocean from the tropics to the polar area by 1.5–2 times are registered, on the whole. At the warming, the CM IAP RAS-GOC gives the general increase in the annual precipitation amount which is especially appreciable in the tropics and in the storm-track regions. At the global averaging, the precipitation in the 21st century increase by 20–25%.