Estimating climate changes in the northern hemisphere in the 21st century under alternative scenarios of anthropogenic forcing

Possible changes in the climate characteristics of the Northern Hemisphere in the 21st century are estimated using a climate model (developed at the Obukhov Institute of Atmospheric Physics (OIAP), Russian Academy of Sciences) under different scenarios of variations in the atmospheric contents of greenhouse gases and aerosols, including those formed at the OIAP on the basis of SRES emission scenarios (group I) and scenarios (group II) developed at the Moscow Power Engineering Institute (MPEI). Over the 21st century, the global annual mean warming at the surface amounts to 1.2?C2.6°C under scenarios I and 0.9?C1.2°C under scenarios II. For all scenarios II, starting from the 2060s, a decrease is observed in the rate of increase in the global mean annual near-surface air temperature. The spatial structures of variations in the mean annual near-surface air temperature in the 21st century, which have been obtained for both groups of scenarios (with smaller absolute values for scenarios II), are similar. Under scenarios I, within the extratropical latitudes, the mean annual surface air temperature increases by 3?C7°C in North America and by 3?C5°C in Eurasia in the 21st century. Under scenarios II, the near-surface air temperature increases by 2?C4°C in North America and by 2?C3°C in Eurasia. An increase in the total amount of precipitation by the end of the 21st century is noted for both groups of scenarios; the most significant increase in the precipitation rate is noted for the land of the Northern Hemisphere. By the late 21st century, the total area of the near-surface permafrost soils of the land of the Northern Hemisphere decreases to 3.9?C9.5 10⁶ km² for scenarios I and 9.7?C11.0 × 10⁶ km² for scenarios II. The decrease in the area of near-surface permafrost soils by 2091?C2100 (as compared to 2001?C2010) amounts to approximately 65% for scenarios I and 40% for scenarios II. By the end of the 21st century, in regions of eastern Siberia, in which near-surface permafrost soils are preserved, the characteristic depths of seasonal thawing amount to 0.5?C2.5 m for scenarios I and 1?C2 m for scenarios II. In western Siberia, the depth of seasonal thawing amounts to 1?C2 m under both scenarios I and II.     

Specific features of the 2010 summer heat formation in the European territory of Russia in the context of general climate changes and climate anomalies

Specific features of the extreme summer heat of 2010 in the European part of Russia are analyzed against the background of global and regional climate changes taking into account antropogenic influences and natural anomalies related, in particular, to the El Niño/La Niña phenomena. The tendencies of the characteristics of the activity of blocking anticyclones (blockings) responsible for the formation of drought regimes and the increase in the fire hazard at midlatitudes are estimated in connection with climate changes.     

Native ytterbium of regolith AS Luna-24

Native ytterbium first identified in a single brownish orange glass fragment collected from the deepest part (184–189 cm) of the bore core delivered from the Mare Crisium of the Moon to the Earth by the Luna-24 Automatic Station is described. As follows from X-ray elemental maps, the ytterbium grain is metallic. Possible mechanisms of its formation and reasons for its elevated corrosion stability are discussed.     

Assessment of the response of subaqueous methane hydrate deposits to possible climate change in the twenty-first century

Doklady Earth Sciences -     

Analytical estimate of the critical global-warming level for the Antarctic ice sheet mass gain-to-loss transition

We suggested a relatively simple model describing changes in the total balance of the ice sheet mass due to global climate change. Taking into account the basic mechanisms behind change in the ice sheet mass and their relations with temperature, we obtained a nonlinear analytical dependence of the ice sheet thickness on the global near-surface temperature. The behavior of the ice sheet can be split into six regimes. Implementation of some regime or another depends essentially on the initial (present-day) value of the mass balance and the sensitivity parameters of precipitation and ice melt to the temperature. Based on this model, we obtained an analytical estimate of the critical level in global warming, in excess of which the regime of the Antarctic ice sheet gain due to snow accumulation changes to sheet degradation due to more intense growth in ice melting.     

Relationship between metamorphism and ore formation at the Sukhoi Log gold deposit hosted in black slates from the data of U-Th-Pb isotopic SHRIMP-dating of accessory minerals

The formation conditions and age of the Sukhoi Log gold deposit are considered on the basis of new isotopic-geochemical data. The U-Pb isotopic study of zircon and monazite from high-grade ore and host black slates at the Sukhoi Log deposit was carried out with SIMS technique using a SHRIMP II instrument. Two generations of monazite are distinguished on the basis of optical and scanning electron microscopy, cathodoluminescence, and micro X-ray spectroscopy. Monazite I is characterized by black opaque porphyroblasts with microinclusions of minerals pertaining to metamorphic slates and structural attributes of pre- and synkinematic formation. Monazite II occurs only within the ore zone as transparent crystals practically free of inclusions and as rims around monazite I. The REE contents are widely variable in both generations. Porphyroblastic monazite I differs in low U and Th (0.01–0.7 wt % ThO₂) contents, whereas transparent monazite II contains up to 4 wt % ThO2. The average weighted U-Pb isotopic age of monazite I is 650 ± 8.1 Ma (MSWD = 1.6; n = 9) and marks the time of metamorphism or catagenesis. The U-Pb age estimates of synore monazite II cover the interval of 486 ± 18 to 439 ± 17 Ma. Zircons of several populations from 0.5 to 2.6 Ga in age are contained in the ore. Most detrital zircon grains have porous outer rims composed of zircon and less frequent xenotime with numerous inclusions of minerals derived from slates. The peaks of ²⁰⁶Pb/²³⁸U ages in the most abundant zircon populations fall on 570 and 630 Ma and correspond to the age of newly formed metamorphic mineral phases. The discordant isotopic ages indicate that the U-ThPb isotopic system of ancient detrital zircons was disturbed 470–440 Ma ago in agreement with isotopic age of monazite II and the Rb-Sr whole -rock isochron age of black slates (447 ± 6 Ma). The new data confirm the superimposed character of the gold-quartz-sulfide mineralization at the deposit. Black shales of the Khomolkho Formation of the Bodaibo Synclinorium were affected by metamorphism over a long period; the peaks of metamorphism and catagenesis are dated at 570 and 650–630 Ma. The high-temperature ore formation was probably related to a hidden granitic pluton emplaced 450–440 Ma ago, that is, 200 Ma later than the events of greenschist metamorphism. Hercynian granitoid magmatism (320–270 Ma) did not exert a substantial effect on the U-Th-Pb isotopic system in accessory minerals from the ore and could not have been a major source of ore-forming fluids.     

Microstructure investigations of Kamchatka geyserites

This paper discusses the results of examining solid geyserite specimens from two present-day Kamchatkan hydrothermal systems: from geysers of the Academy of Sciences and from the Eastern Thermal Field in the caldera of the Uzon Volcano. These studies were performed using methods of IR spectroscopy, XR spectral analysis, and electron microscopy. Three types of geysers were discriminated: underwater, subaerial, and those that originated under the ground surface. All geyserite varieties consist of amorphous opal, and differences between them are caused by the shape, dimensions, and distribution character of silica aggregates. Most examined geyserites enclose silicified microfossil remnants.     

Satellite-derived peculiarities of total ozone field under atmospheric blocking conditions over the European part of Russia in summer 2010

Based on the AIRS satellite spectrometer data (the Aqua platform), the peculiarities are studied of the field of total ozone (TO) under prolonged blocking conditions over the European part of Russia in summer 2010. It is revealed that the spatial distribution of TO values during the period of blocking was characterized by negative TO anomalies (up to -37 DU on the first ten days of August) over the western and northern peripheries of the blocking anticyclone and by positive TO anomalies (up to 60 DU) over the troughs adj oinmg the anticyclone. Possible mechanisms of the formation of TO anomalies are discussed. The results are presented of the validation of TO measurements with the AIRS spectrometer in May-September 2010 obtained from the data of TO measurements with Brewer spectrophotometers at Kislovodsk and Obninsk stations of the global ozone network.