http://www.sciencedirect.com/science/article/pii/S1674987113001606

The paper reviews previous and recently obtained geological, stratigraphic and geochronological data on the Russian-Kazakh Altai orogen, which is located in the western Central Asian Orogenic Belt （CAOB）, between the Kazakhstan and Siberian continental blocks. The Russian-Kazakh Altai is a typical Pacific-type orogen, which represents a collage of oceanic, accretionary, fore-arc, island-arc and continental margin terranes of different ages separated by strike-slip faults and thrusts. Evidence for this comes from key indicative rock associations, such as boninite- and turbidite （graywacke）-bearing volcanogenic-sedimentary units, accreted pelagic chert, oceanic islands and plateaus, MORB-OIB-protolith blueschists. The three major tectonic domains of the Russian-Kazakh Altai are： （1） Altai-Mongolian terrane （AMT）; （2） subduction-accretionary （Rudny Altai, Gorny Altai） and collisional （Kalba-Narym） terranes; （3） Kurai, Charysh-Terekta, North-East, Irtysh and Char suture-shear zones （SSZ）. The evolution of this orogen proceeded in five major stages： （i） late Neoproterozoic-early Paleozoic subduction-accretion in the Paleo-Asian Ocean; （ii） Ordovician-Silurian passive margin; （iii） Devonian-Carboniferous active margin and collision of AMT with the Siberian conti- nent; （iv） late Paleozoic closure of the PAO and coeval collisional magmatism; （v） Mesozoic post-collisional deformation and anarogenic magmatism, which created the modern structural collage of the Russian- Kazakh Altai orogen. The major still unsolved problem of Altai geology is origin of the Altai-Mongolian terrane （continental versus active margin）, age of Altai basement, proportion of juvenile and recycled crust and origin of the middle Paleozoic units of the Gorny Altai and Rudny Altai terranes.     

Modelling the impact of climate change on Pacific skipjack tuna population and fisheries

IPCC-type climate models have produced simulations of the oceanic environment that can be used to drive models of upper trophic levels to explore the impact of climate change on marine resources. We use the Spatial Ecosystem And Population Dynamics Model (SEAPODYM) to investigate the potential impact of Climate change under IPCC A2 scenario on Pacific skipjack tuna (Katsuwonus pelamis). IPCC-type models are still coarse in resolution and can produce significant anomalies, e.g., in water temperature. These limitations have direct and strong effects when modeling the dynamics of marine species. Therefore, parameter estimation experiments based on assimilation of historical fishing data are necessary to calibrate the model to these conditions before exploring the future scenarios. A new simulation based on corrected temperature fields of the A2 simulation from one climate model (IPSL-CM4) is presented. The corrected fields led to a new parameterization close to the one achieved with more realistic environment from an ocean reanalysis and satellite-derived primary production. Projected changes in skipjack population under simple fishing effort scenarios are presented. The skipjack catch and biomass is predicted to slightly increase in the Western Central Pacific Ocean until 2050 then the biomass stabilizes and starts to decrease after 2060 while the catch reaches a plateau. Both feeding and spawning habitat become progressively more favourable in the eastern Pacific Ocean and also extend to higher latitudes, while the western equatorial warm pool is predicted to become less favorable for skipjack spawning.     

Parameter estimation for basin-scale ecosystem-linked population models of large pelagic predators: Application to skipjack tuna

A Spatial Ecosystem and Population Dynamic Model (SEAPODYM) is used in a data assimilation study aiming to estimate model parameters that describe dynamics of Pacific skipjack tuna population on ocean-based scale. The model based on advection–diffusion–reaction equations explicitly predicts spatial dynamics of large pelagic predators, while taking into account data on several mid-trophic level components, oceanic primary productivity and physical environment. In order to improve its quantitative ability, the model was parameterized through assimilation with commercial fisheries data, and optimization was carried out using maximum likelihood estimation approach. To address the optimization task we implemented an adjoint technique to obtain an exact, analytical evaluation of the likelihood gradient. We conducted a series of computer experiments in order to (i) determine model sensitivity with respect to variable parameters and, hence, investigate their observability; (ii) estimate observable parameters and their errors; and (iii) justify the reliability of the computed solution. Parameters describing recruitment, movement, habitat preferences, natural and fishing mortality of skipjack population were analysed and estimated. Results of the study suggest that SEAPODYM with achieved parameterization scheme can help to investigate the impact of fishing under various management scenarios, and also conduct forecasts of a given species stock and spatial dynamics in a context of environmental and climate changes.     

On Conditions of Phytoplankton Blooms in the Coastal Waters of the North-Western East/Japan Sea

Seasonal changes of abundance of the main phytoplankton groups of species (diatoms, dinoflagellates, chrysophytes, small flagellates and cryptophytes) and a set of environmental parameters were investigated in coastal and preestuarine waters of Peter the Great Bay (East/Japan Sea) in May-October of 1998 and 1999. Three periods of mass development were revealed: spring, summer and autumn blooms, with successive change of species. The conditions favourable for each group of species were determined. Driving mechanisms of the succession include nutrients transport through seasonal pycnocline by turbulent mixing, terrestrial nutrients supply by monsoon floods, nutrients supply by upwellings, and light control by the thickness of upper mixed layer. Summer succession could be explained by a simple SST-MLD diagram similar to Pingree S-kh diagram with sea surface temperature as indicator of stratification (S) and mixed layer depth as indicator of light availability (kh).     

An analytical interpretation of liquid injection induced microseismicity in porous reservoirs

The paper presents a rigorously derived analytical method to describe and interpret the low-magnitude earthquakes caused by injection of the borehole fluids into surrounding porous reservoirs. Microseismicity is induced due to changes in the pore pressure, which, in turn, is influenced mainly by the low-frequency slow Biot (P2) wave. The classical Biot model is used to obtain the distribution of pore pressure in a reservoir. The constructed solution to the Biot system of equations and the spatio-temporal cloud of microseismic events allow one to assess the critical value of the pore pressure, sufficient for the generation of a microearthquake, and the values of hydromechanical parameters (e.g. permeability) of a saturated porous rock.     

April sea ice extent in the Barents Sea, 1850–2001

Three observational data sets are used to construct a continuous record (1850-2001) of April ice edge position in the Barents Sea: two sets of Norwegian ice charts (one from 1850 to 1949 and the other from 1966 to 2001) and Soviet aircraft reconnaissance ice extent charts from 1950 to 1966. The 152-year April ice extent series is subdivided into three sub-periods: 1850-1899, 1900-1949 and 1950-2001. For each of these study sub-periods, a mean April ice edge and a set of anomalies (differences in position between a given April and the mean April ice edge) are computed. The calculations show the mean ice edge position retreated north-eastward over the 152-year period, with the greater retreat seen in the changes from the 1850-1899 sub-period to the 1900-1949 sub-period. The distribution of the standard deviation of the ice edge anomaly over the linear distance along the mean ice edge shows no substantial difference between any of the three periods of the study. Within each study period, the maximum variation is observed in the sector bounded by the 25°E and 49° E meridians, which covers the main pathway of the warmer water flow from the Norwegian Sea.     

Magmatic evolution of the ultramafic–mafic Kharaelakh intrusion (Siberian Craton, Russia): insights from trace-element, U–Pb and Hf-isotope data on zircon

The ultramafic–mafic Kharaelakh intrusion in the northwestern part of the Siberian Craton (Russia) hosts major economic platinum-group-element (PGE)–Cu–Ni sulphide deposits. In situ U–Pb, REE and Hf-isotope analyses of zircon from these rocks, combined with detailed study of crystal morphology and internal structure, identify four zircon populations. U–Pb ages of these populations cover a significant time span (from 347 ± 16 to 235.7 ± 6.1 Ma) suggesting multiple magmatic events that cluster around 350 and 250 Ma, being consistent with two recognised stages of active tectonism in the development of the Siberian Craton. The oldest zircon population, however, represents previously unknown stage of magmatic activity in the Noril’sk area. Epsilon-Hf values of +2.3 to +16.3 in the analysed zircons reflect a dominant role of mantle-derived magmas and suggest that juvenile mantle material was the main source for the ultramafic–mafic Kharaelakh intrusion. A significant range in initial ¹⁷⁶Hf/¹⁷⁷Hf values, found in zircons that cluster around 250 Ma, indicate mixing between mantle and crustal magma sources. Our findings imply that economic intrusions hosting PGE–Cu–Ni deposits of the Noril’sk area have a far more complex geological history than is commonly assumed.     

An assessment of the potential and impacts of winter water banking in the Sokh aquifer, Central Asia

The dynamics of artificial recharge of winter surface flows coupled with increased summer groundwater use for irrigation in the Sokh aquifer (Central Asia) have been investigated. Water release patterns from the giant Toktogul reservoir have changed, as priority is now given to hydropower generation in winter in Kyrgyzstan. Winter flows have increased and summer releases have declined, but the Syr Darya River cannot pass these larger winter flows and the excess is diverted to a natural depression, creating a 40?×?10⁹m³ lake. A water balance study of all 18 aquifers feeding the Fergana Valley indicated the feasibility of winter groundwater recharge in storage created by summer abstraction. This modeling study examines the dynamics of the process in one aquifer over a 5-year period, with four scenarios: the current situation; increased groundwater abstraction of around 625 million (M) m³/year; groundwater abstraction with an artificial recharge of 144 Mm³/year, equivalent to the volume available in low flow years in the Sokh River; and with a larger artificial recharge of 268 Mm³/year, corresponding to high flow availability. Summer surface irrigation diversions can be reduced by up to 350 Mm³ and water table levels can be lowered.