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

Frank Gaardsted  Meng Zhou  Vladimir Pavlov  Alexey Morozov  Kurt S. Tande 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(11):1465-1473

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.  相似文献   

Sulfur cycling in a stratified euxinic lake with moderately high sulfate: Constraints from quadruple S isotopes   总被引：1，自引：0，他引：1  

Aubrey L. Zerkle  Alexey Kamyshny Jr.  Lee R. Kump  James Farquhar  Harry Oduro  Michael A. Arthur 《Geochimica et cosmochimica acta》2010,74(17):4953-154

We present a 3-year study of concentrations and sulfur isotope values (δ³⁴S, Δ³³S, and Δ³⁶S) of sulfur compounds in the water column of Fayetteville Green Lake (NY, USA), a stratified (meromictic) euxinic lake with moderately high sulfate concentrations (12-16 mM). We utilize our results along with numerical models (including transport within the lake) to identify and quantify the major biological and abiotic processes contributing to sulfur cycling in the system. The isotope values of sulfide and zero-valent sulfur across the redox-interface (chemocline) change seasonally in response to changes in sulfide oxidation processes. In the fall, sulfide oxidation occurs primarily via abiotic reaction with oxygen, as reflected by an increase in sulfide δ³⁴S at the redox interface. Interestingly, S isotope values for zero-valent sulfur sampled at this time still reflect production and recycling by phototrophic S-oxidation. In the spring, sulfide S isotope values suggest an increased input from phototrophic oxidation, consistent with a more pronounced phototroph population at the chemocline. This trend is associated with smaller fractionations between sulfide and zero-valent sulfur, suggesting a metabolic rate control on fractionation similar to that for sulfate reduction. Comparison of our data with previous studies indicates that the S isotope values of sulfate and sulfide in the deep waters are remarkably stable over long periods of time, with consistently large fractionations of up to 58‰ in δ³⁴S. Models of the δ³⁴S and Δ³³S trends in the deep waters (considering mass transport via diffusion and advection along with biological processes) require that these fractionations are a consequence of sulfur compound disproportionation at and below the redox interface in addition to large fractionations during sulfate reduction. The large fractionations during sulfate reduction appear to be a consequence of the high sulfate concentrations and the distribution of organic matter in the water column. The occurrence of disproportionation in the lake is supported by profiles of intermediate sulfur compounds and by lake microbiology, but is not evident from the δ³⁴S trends alone. These results illustrate the utility of including minor S isotopes in sulfur isotope studies to unravel complex sulfur cycling in natural systems.  相似文献   

Relations between integrable systems in plane and curved spaces   总被引：1，自引：0，他引：1  

Alexey V. Borisov  Ivan S. Mamaev 《Celestial Mechanics and Dynamical Astronomy》2007,99(4):253-260

We consider trajectory isomorphisms between various integrable systems on an n-dimensional sphere S ⁿ and a Euclidean space . Some of the systems are classical integrable problems of Celestial Mechanics in plane and curved spaces. All the systems under consideration have an additional first integral quadratic in momentum and can be integrated analytically by using the separation of variables. We show that some integrable problems in constant curvature spaces are not essentially new from the viewpoint of the theory of integration, and they can be analyzed using known results of classical Celestial Mechanics.  相似文献   

Russia's 2020 GHG emissions target: Emission trends and implementation     

Anna Korppoo  Alexey Kokorin 《Climate Policy》2013,13(2):113-130

This article provides an overview of the recent modelling results on Russia's GHG emission trends, and reviews the success of mitigation policies in order to establish whether Russia's domestic target seems feasible. Various Russian GHG emission scenarios indicate that Russia's domestic target – emissions 25% below the 1990 level by 2020 – is not far from the business-as-usual emissions trajectory. In particular, two factors could deliver the required emissions reductions: the currently declining gross domestic product (GDP) growth and ongoing domestic mitigation policies. The former is more likely to secure the target level of emissions, because GDP growth has been contracting significantly in comparison to earlier forecasts of 3–5% annual growth, and this trend is expected to continue. The latter option – success with domestic mitigation measures – seems less likely, given the various meta-barriers to policy implementation, and the marginality of mitigation policies, problems with law-making processes, bureaucratic tradition, and informality of legislative and implementation systems.

Policy relevance

This article provides an assessment of the stringency of Russia's domestically set emissions limitation target by 2020 and the chances of Russia, the fourth largest GHG emitter in the world, achieving it. We base our assessment on a number of recent key sources that analyse Russia's GHG emission paths by applying socio-economic models, which have only been available in the Russian language prior to this publication. This knowledge is applicable for use by other negotiation parties to compare Russia's efforts to mitigate climate change to their own, and thus makes a contribution to facilitating a more equal burden-sharing of climate commitments under the future climate change agreement.  相似文献   

Figures of equilibrium of an inhomogeneous self-gravitating fluid     

Ivan A. Bizyaev  Alexey V. Borisov  Ivan S. Mamaev 《Celestial Mechanics and Dynamical Astronomy》2015,122(1):1-26

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Peri-Gondwanan Ordovician crustal fragments in the high-grade basement of the Eastern Rhodope Massif,Bulgaria: evidence from U-Pb LA-ICP-MS zircon geochronology and geochemistry     

Nikolay Bonev  Maria Ovtcharova-Schaltegger  Robert Moritz  Peter Marchev  Alexey Ulianov 《Geodinamica Acta》2013,26(3-4):207-229

Field, geochemical, and geochronologic data of high-grade basement metamafic and evolved rocks are used to identify the nature and timing of pre-Alpine crustal growth of the Rhodope Massif. These rocks occur intrusive into clastic-carbonate metasedimentary succession. Petrography and mineral chemistry show compositions consistent with Alpine amphibolite-facies metamorphism that obliterated the original igneous textures of the protoliths. Bulk-rock geochemistry identifies low-Ti tholeiitic to calc-alkaline gabbroic-basaltic and plagiogranite precursors, with MORB-IAT supra-subduction zone signature and trace elements comparable to modern back-arc basalts. The U-Pb zircon dating revealed a mean age of 455 Ma for the magmatic crystallization of the protoliths that contain inherited Cambrian (528–534 Ma) zircons. Carboniferous, Jurassic, and Eocene metamorphic events overprinted the Ordovician protoliths. The radiometric results of the metamorphic rocks demonstrate that Ordovician oceanic crust was involved in the build-up of the Rhodope high-grade basement. Dating of Eocene-Oligocene volcanic rocks overlying or cross-cutting the metamorphic rocks supplied Neoproterozoic, Ordovician and Permo-Carboniferous xenocrystic zircons that were sampled en route to the surface from the basement. The volcanic rocks thus confirm sub-regionally present Neoproterozoic and Paleozoic igneous and metamorphic basement. We interpret the origin of the Middle-Late Ordovician oceanic magmatism in a back-arc rift-spreading center propagating along peri-Gondwanan Cadomian basement terrane related to the Rheic Ocean widening. The results highlight the presence of elements of Cadomian northern Gondwana margin in the high-grade basement and record of Rheic Ocean evolution. The eastern Rhodope Massif high-grade basement compared to adjacent terranes with Neoproterozoic and Cambro-Ordovician evolution shares analogous tectono-magmatic record providing a linkage among basement terranes incorporated in the Alpine belt of the north Aegean region.  相似文献   

Sea Ice Dynamics Induced by External Stochastic Fluctuations     

Dmitri V. Alexandrov  Irina A. Bashkirtseva  Alexey P. Malygin  Lev B. Ryashko 《Pure and Applied Geophysics》2013,170(12):2273-2282

The influence of stochastic fluctuations in the atmosphere and in the ocean caused by different occasional phenomena (noises) on dynamic processes of sea ice growth with a mushy layer is studied. It is shown that atmospheric temperature variances substantially increase the sea ice thickness, whereas dispersion variations of turbulent flows in the ocean to a great extent decrease the ice content produced by false bottom evolution.  相似文献   

The tidal and wind induced hydrodynamics of the composite system Adriatic Sea/Lagoon of Venice     

Tomas Lovato  Alexey Androsov  Dmitry Romanenkov  Angelo Rubino 《Continental Shelf Research》2010

A shallow water hydrostatic 2D hydrodynamic numerical model, based on the boundary conforming coordinate system, was used to simulate aspects of both general and small scale oceanic features occurring in the composite system constituted by the Adriatic Sea and the Lagoon of Venice (Italy), under the influence of tide and realistic atmospheric forcing. Due to a specific technique for the treatment of movable lateral boundaries, the model is able to simulate efficiently dry up and flooding processes within the lagoon. Firstly, a model calibration was performed by comparing the results of the model, forced using tides and ECMWF atmospheric pressure and wind fields, with observations collected for a set of 33 mareographic stations uniformly distributed in the Adriatic Sea and in the Lagoon of Venice. A second numerical experiment was then carried out by considering only the tidal forcing. Through a comparison between the results obtained in the two experiments it was possible to assess the reliability of the estimated parameter through the composite forcing. Model results were then verified by comparing simulated amplitude and phase of each tidal constituent as well as tidal velocities simulated at the inlets of the lagoon and in the Northern Adriatic Sea with the corresponding observed values. The model accurately reproduces the observed harmonics: mean amplitude differences rarely exceed 1 cm, while phase errors are commonly confined below 15°. Semidiurnal and diurnal currents were correctly reproduced in the northern basin and a good agreement was obtained with measurements carried out at the lagoon inlets. On this basis, the outcomes of the hydrodynamic model were analyzed in order to investigate: (i) small-scale coastal circulation features observed at the interface between the adjoining basins, which consist often of vortical dipoles connected with the tidal flow of Adriatic water entering and leaving the Lagoon of Venice and with along-shore current fields connected with specific wind patterns; (ii) residual oscillations, which are often connected to meteorological forcing over the basin. In particular, it emerges that small-scale vortical features generated near the lagoon inlet can be efficiently transported toward the open sea, thus contributing to the water exchange between the two marine regions, and a realistic representation of observed residual oscillations in the area would require a very detailed knowledge of atmospheric as well as remote oceanic forcing.  相似文献   

Geochemistry of late Cenozoic lavas on Kunashir Island, Kurile Arc     

Alexey Y.  Martynov  Jun-Ichi  Kimura  Yuri A.  Martynov  Alexsander V.  Rybin 《Island Arc》2010,19(1):86-104

Middle Miocene to Quaternary lavas on Kunashir Island in the southern zone of the Kurile Arc were examined for major, trace, and Sr–Nd–Pb isotope compositions. The lavas range from basalt through to rhyolite and the mafic lavas show typical oceanic island arc signatures without significant crustal or sub-continental lithosphere contamination. The lavas exhibit across-arc variation, with increasingly greater fluid-immobile incompatible element contents from the volcanic front to the rear-arc; this pattern, however, does not apply to some other incompatible elements such as B, Sb, and halogens. All Sr–Nd–Pb isotope compositions reflect a depleted source with Indian Ocean mantle domain characteristics. The Nd and Pb isotope ratios are radiogenic in the volcanic front, whereas Sr isotope ratios are less radiogenic. These Nd isotope ratios covary with incompatible element ratios such as Th/Nd and Nb/Zr, indicating involvement of a slab-derived sediment component by addition of melt or supercritical fluid capable of mobilizing these high field-strength elements and rare earth elements from the slab. Fluid mobile elements, such as Ba, are also elevated in all basalt suites, suggesting involvement of slab fluid derived from altered oceanic crust. The Kurile Arc lavas are thus affected both by slab sediment and altered basaltic crust components. This magma plumbing system has been continuously active from the Middle Miocene to the present.  相似文献   

A comparison of continuous mass‐lumped finite elements with finite differences for 3‐D wave propagation     

Elena Zhebel  Sara Minisini  Alexey Kononov  Wim A. Mulder 《Geophysical Prospecting》2014,62(5):1111-1125

The finite‐difference method on rectangular meshes is widely used for time‐domain modelling of the wave equation. It is relatively easy to implement high‐order spatial discretization schemes and parallelization. Also, the method is computationally efficient. However, the use of finite elements on tetrahedral unstructured meshes is more accurate in complex geometries near sharp interfaces. We compared the standard eighth‐order finite‐difference method to fourth‐order continuous mass‐lumped finite elements in terms of accuracy and computational cost. The results show that, for simple models like a cube with constant density and velocity, the finite‐difference method outperforms the finite‐element method by at least an order of magnitude. Outside the application area of rectangular meshes, i.e., for a model with interior complexity and topography well described by tetrahedra, however, finite‐element methods are about two orders of magnitude faster than finite‐difference methods, for a given accuracy.  相似文献