A flow-foliated ignimbrite related to the Åland rapakivi granite in SW Finland

A flow-foliated felsic ignimbrite constitutes the uppermost lithological unit of the 1.58 Gyr anorogenic magmatic rocks in SW Finland. The ignimbrite is derived from an explosive eruption of hot (≅ 950 °C) phenocryst-bearing A-type (rapakivi-type granite magma.
The ignimbrite is close in composition to subvolcanic rapakivi granites that occur in the margins of the kand rapakivi batholith. The subvolcanic granites crystallized under a pressure of ≅ 1 kbar and at temperatures of about 650–700 °C. However, both major and rare earth elements show that the ignimbrite- forming magma was more fractionated than the magma forming the subvolcanic varieties.
Supported by evidence of mafic-felsic magma mingling, it is suggested that injection of hot mafic magma into a shallow magma chamber produced the high temperature of the ignimbrite-forming magma. This injection increased the magmatic and the volatile pressure that caused the eruption of the dry felsic magma.     

Relation between macroseismic intensity and instrumental parameters of strong motions — A statistical approach

One hundred and twenty-eight strong ground motion CALTECH (Earthquakes in the U.S.A., 1940–1971) records of five Californian earthquakes, recorded at ground level and in basements, for which the modified Mercalli macroseismic intensities are known, were statistically processed to calculate 165 wave parameters. Correlation of the peak values of particle acceleration, velocity and displacement, energy, impulse and root-mean-square amplitude of the vibrations, durations of vibrations for certain levels of the peak amplitude, and spectral energies of 10 frequency windows with macroseismic intensity are discussed from the viewpoint of classification of ground-motion records.Paper presented at the 21st General Assembly of the European Seismological Commission held in Sofia 1988.     

Atmospheric and Coupled Model Intercomparison in Terms of Amplitude Phase Characteristics of Surface Air Temperature Annual Cycle

A model intercomparison in terms of surface air temperature annual cycle ampitude-phase characteristics(SAT AC APC)is performed. The models included in the intercomparison belong to two groups:five atmospheric models with prescribed sea surface temperature and sea ice cover and four coupled models forced by the atmospheric abundances of anthropogenic consituents (in total six coupled model simulations). Over land, the models, simulating higher than observed time averaged SAT,also tend to simulate smaller than observed amplitude of its annual and semiannual harmonics and (outside the Tropics laterthan-observed spring and autumn moments. The models with larger(smaller) time averaged amplitudes of annual and semiannual harmonics also tend to simulate larger(smaller)interannual standard deviations. Over the oceans, the coupled models with larger interannual standard deviations of annual mean SAT tend to simulate larger interannual standard deviations of both annual and semiannual SAT harmonics amplitudes. Most model errors are located in the belts 60°-70°N and 60°-70°S and over Antarctica. These errors are larger for those coupled models which do not employ dynamical modules for sea ice.No systematic differences are found in the simulated time averaged fields of the surface air temperature annual cycle characteristics for atmospheric models on one hand and for the coupled models on the other. But the coupled models generally simulate interannual variability of SAT AC APC better than the atmospheric models (which tend to underestimate it). For the coupled models, the results are not very sensitive to the choice of the particular scenario of anthropogenic forcing.There is a strong linear positive relationship between the model simulated time averaged semiannual SAT harmonics amplitude and interannual standard deviation of annual mean SAT.It is stronger over the tropical oceans and is weaker in the extratropics. In the tropical oceanic areas, it is stronger for the coupled than for the atmospheric models.     

Investigation of the formation of vertical structure of biogenic elements fields in the Black Sea, using the method of spatial isopycnic analysis

The method of two-dimensional isopycnic analysis is applied to study the distribution of inorganic phosphates and nitrates in the Black Sea. The effect of winter-time ventilation in the central sea on the formation of chemical fields is examined, as well as the outcropping of biogenic elements from the layer of high concentrations (σ _t∼14.5–16.0). It is demonstrated that the amount of nitrates entering the upper active layer of the sea as a result of winter-time convective ventilation may attain values comparable with their overall annual input by river discharge, and that they control the intensity of winter-spring phytoplankton blooming in the central sea. The spatial variability of the vertical phosphate distribution is analysed. For the annual cycles with fairly cool winter conditions, an occurrence of three peaks on the phosphates vertical profile in spring has been documented over a vast sea area where the rim current represents an external dynamic boundary. Translated by Vladimir A. Puchkin.     

Modeling stalagmite growth by first principles of chemistry and physics of calcite precipitation

Growth rates and morphology of stalagmites are determined by the precipitation kinetics of calcite and the supply rates of water to their apex. Current modeling attempts are based on the assumption that precipitation rates decrease exponentially with distance along the surface. This, however, is an arbitrary assumption, because other functions for decrease could be used as well. Here we give a process-oriented model based on the hydrodynamics of a water sheet in laminar radial flow spreading outwards from the apex, and the well known precipitation rates F = α(c − c_eq); c is the actual calcium concentration at distance R from the growth axis, c_eq the equilibrium concentration of calcium with respect to calcite, and α is a kinetic constant. This enables us to calculate the concentration profile c(R) for any point of an actual surface of a stalagmite and consequently the deposition rates of calcite there. The numerical results show that under conditions constant in time the stalagmite grows into an equilibrium shape, which is established, when all points of its surface are shifting vertically by the same distance during a time interval. We also show this by strict mathematical proof. This new model is based entirely on first principles of physics and chemistry. The results show that the modeled precipitation rates can be approximated by a Gaussian decrease along the equilibrium surface. In general from the mathematical proof one finds a relation between the equilibrium radius of the stalagmite, Q the supply rate of water, and α the kinetic constant. This is also verified by numerical calculations. An interesting scaling law is found. Scaling all stalagmites by 1/R_eq and presenting them with the origin at their apex yields identical shapes of all. The shapes of the modeled stalagmites are compared to natural ones and show satisfactory agreement. Finally we explore the effect of varying water supply Q and kinetic constant α on the shape of a growing stalagmite, and estimate the minimum period of change that can be imprinted into the morphology of the stalagmite.     

δC profiles along growth layers of stalagmites: Comparing theoretical and experimental results

The isotopic carbon ratio of a calcite-precipitating solution flowing as a water film on the surface of a stalagmite is determined by Rayleigh distillation. It can be calculated, when the -concentration of the solution at each surface point of the stalagmite and the fractionation factors are known. A stalagmite growth model based entirely on the physics of laminar flow and the well-known precipitation rates of a supersaturated solution of calcite, without any further assumptions, is employed to obtain the spatial distribution of the -concentration, which contributes more than 95% to the dissolved inorganic carbon (DIC). The δ¹³C profiles are calculated along the growth surface of a stalagmite for three cases: (A) isotopic equilibrium of both CO₂ outgassing and calcite precipitation; (B) outgassing of CO₂ is irreversible but calcite precipitation is in isotopic equilibrium. (C) Both CO₂ outgassing and calcite precipitation are irreversible. In all cases the isotopic shift δ¹³C increases from the apex along the distance on a growth surface. In cases A and B, calcite deposited at the apex is in isotopic equilibrium with the solution of the drip water. The difference between δ¹³C at the apex and the end of the growth layer is independent of the stalagmite’s radius, but depends on temperature. For case A, it is about half the value obtained for cases B and C. In case C, the isotopic composition of calcite at the apex equals that of the drip water, but further out it becomes practically identical with that of case B. The growth model has been applied to field data of stalagmite growth, where the thickness and the δ¹³C of calcite precipitated to a glass plate located on the top of a stalagmite have been measured as function of the distance from the drip point. The calculated data are in good agreement to the observed ones and indicate that deposition occurred most likely under conditions B, eventually also C. A sensitivity analysis has been performed, which shows that within the limits of observed external parameters, such as drip rates and partial pressure of carbon dioxide P_CO2 in the cave, the results remain valid.     

Modelling of thermochemical plumes and implications for the origin of the Siberian traps

Thermochemical plumes form at the base of the lower mantle as a consequence of heat flow from the outer core and the presence of local chemical doping that decreases the melting temperature. Theoretical and experimental modelling of thermochemical plumes show that the diameter of a plume conduit remains practically constant during plume ascent. However, when the top of a plume reaches a refractory layer, whose melting temperature is higher than the melt temperature in the plume conduit, a mushroom-shaped plume head develops. Main parameters (melt viscosity, ascent time, ascent velocity, temperature differences in the plume conduit, and thermal power) are presented for a thermochemical plume ascending from the core–mantle boundary. In addition, the following relationships are developed: the pressure distribution in the plume conduit during the ascent of a plume, conditions for eruption-conduit formation, the effect of the P–T conditions and controls on the shape and size of a plume top, heat transfer between a thermochemical plume and the lithosphere (when the plume reaches the bottom of a refractory layer in the lithosphere), and eruption volume versus the time interval t₁ between plume formation and eruption. These relationships are used to determine thermal power and time t₁ for the Tunguska syneclise and the Siberian traps as a whole.

The Siberian and other trap provinces are characterized by giant volumes of lavas and sills formed a very short time period. Data permit a model for superplumes with three stages of formation: early (variable picrites and alkali basalts), main (tholeiite plateau basalts), and final (ultrabasic and alkaline lavas and intrusions). These stages reflect the evolution of a superplume from the ascent of one or several independent plumes, through the formation of thick lenses of mantle melts underplating the lithosphere and, finally, intrusion and extrusion of differentiated mantle melts. Synchronous syenite–granite intrusions and bimodal volcanism abundant in the margins of the Siberian traps are the result of melting of the lower crust at depths of 65–70 km under the effect of plume melts.     

Explaining the eventual transient saturation of climate-carbon cycle feedback

Background

Coupled climate-carbon cycle simulations generally show that climate feedbacks amplify the buildup of CO₂ under respective anthropogenic emission. The effect of climate-carbon cycle feedback is characterised by the feedback gain: the relative increase in CO₂ increment as compared to uncoupled simulations. According to the results of the recent Coupled Climate-Carbon Cycle Model Intercomparison Project (C⁴MIP), the gain is expected to increase during the 21st century. This conclusion is not supported by the climate model developed at the A.M. Obukhov Institute of Atmospheric Physics at the Russian Academy of Sciences (IAP RAS CM). The latter model shows an eventual transient saturation of the feedback gain. This saturation is manifested in a change of climate-carbon cycle feedback gain which grows initially, attains a maximum, and then decreases, eventually tending to unity.

Results

Numerical experiments with the IAP RAS CM as well as an analysis of the conceptual framework demonstrate that this eventual transient saturation results from the fact that transient climate sensitivity decreases with time.

Conclusion

One may conclude that the eventual transient saturation of the climate-carbon cycle feedback is a fundamental property of the coupled climate-carbon system that manifests itself on a relevant time scale.     

An evaluation of the economic,social, and ecological risks of China-Mongolia-Russia high-speed railway construction and policy suggestions

The construction of China-Mongolia-Russia high-speed railways is a strategic move to promote transportation infrastructure inter-connectivity between these countries, which will accelerate the implementation of the China-Mongolia-Russia Economic Corridor. However, well-planned China-Mongolia-Russia high-speed railways demand accurately identifying construction risks, scientifically evaluating risk levels, and mapping the spatial distribution of these risks. Therefore, this study established the integrated risk evaluation model (IREM) to scientifically evaluate the economic, social, and ecological risks of China-Mongolia-Russia high-speed railway construction and determine their magnitude and spatial distribution pattern. Based on this analysis, we propose designs for the east and west China-Mongolia-Russia high-speed railways and policy suggestions to mitigate construction risks. Suggestions include developing innovative cooperation of the "high-speed railway for resources and market", strengthening communication and technology dissemination, and applying innovative engineering techniques and setting buffers; establishing collaborative prevention and control systems to mitigate the three major ecological risks in the China, Mongolia, and Russia trans-border areas; and promoting economic integration by improving strategic coordination. In summary, this study provides scientific support for designing the China-Mongolia-Russia high-speed railways minimizing construction risks.     

Mesoscale distribution and advection of overwintering Calanus finmarchicus off the shelf of northern Norway

Data collected on a cruise in January 2008, using a laser optical plankton counter, conductivity–temperature–depth sensors, and a lowered acoustic Doppler current profiler, was used to study the mesoscale distribution and advection of overwintering Calanus finmarchicus in its deep water winter habitat off the shelf of northern Norway. The overwintering animals were generally located immediately below the Atlantic Water (AW) in Arctic Intermediate Water (AIW), in the 600–1200 m depth range. The depth of the interface between AW and AIW varied considerably in the area and this was clearly reflected in the C. finmarchicus distribution. Maximum abundance varied from about 80 ind m^?3 to more than 200 ind m^?3 at the different stations. Current measurements showed the richness of mesoscazle eddies, with speeds exceeding 70 cm s^?1 at the surface and rapidly decreasing with depth. In the main overwintering layer the eddy features were also clearly seen, but with speeds generally below 20 cm s^?1. C. finmarchicus were found in the whole survey area, but they were not homogeneously distributed. Advection of the copepods resulted in relatively high local rates of change in overwintering C. finmarchicus abundance with mean value of 8% per day in the area. It is clear that mesoscale physical processes greatly contribute to the variability in the abundance of overwintering C. finmarchicus off the shelf of northern Norway. The collected data are also a valuable addition to the generally sparse datasets on the C. finmarchicus winter distribution and the role of the Lofoten basin in the large scale system is also discussed.