Automatic determination of 3D orientations of fossilized oyster shells from a densely packed Miocene shell bed

International Journal of Earth Sciences - Shell beds represent a useful source of information on various physical processes that cause the depositional condition. We present an automated method to...     

Dormant stages of crustaceans as a mechanism of propagation in the extreme and unpredictable environment in the Crimean hypersaline lakes

A pool of dormant stages of planktonic organisms in saline lakes is a substantial component in the plankton communities;we need to take it into account to understand plankton dynamics.Hypersaline water bodies in Crimea,the largest peninsula in the Black Sea,constitute a very characteristic and peculiar habitat type in the region.We examined the presence of crustacean resting stages in sediments of dried up sites of the Crimean hypersaline lakes.Sediment samples were taken in 9 different lakes.Experiments performed on the hatching of these resting stages showed the presence of Moina salina(Cladocera),parthenogenetic Artemia and Artemia urmiana(Anostraca),Eucypris mareotica( inflata)(Ostracoda),and Cletocamptus retrogressus(Harpacticoida).Comparing the experimental results obtained with clean dried brine shrimp cysts and those kept in sediment samples,it was noted that clean cysts hatched much faster than those from sediments did.Some components in bottom sediments slow down and desynchronize hatching from resting eggs in different groups of crustaceans.The sediments of different lakes inhibited the nauplii output from Artemia and ostracod resting eggs to different degrees.More data are needed before we can discuss the reasons of this inhibition.The nonsynchronous output of active stages from the bottom resting ones may be an adaptation that allows crustacean species to exist in extreme and unpredictably changing environments,avoiding the risk that all may emerge at once under unsuitable conditions.     

Quantifying barriers to decarbonization of the Russian economy: real options analysis of investment risks in low-carbon technologies

Russia has significant potential for reducing its carbon emissions. However, investment in new low-carbon technologies has significant risks. Ambiguous energy and climate policy in Russia, along with deterioration of the country's investment climate, create investment barriers that are well described in qualitative terms in the literature. This paper attempts to provide a quantitative analysis of these barriers. For this numerical experiment, we apply the RU-TIMES model. Using a real options methodology, we estimate the risk-adjusted cost of capital in the Russian energy sector (including energy production and consumption technologies represented in the TIMES framework) to be approximately 43% (including a risk-free interest rate) and demonstrate the high risk of investment into energy-efficient and low-carbon technologies. Any future low-carbon emissions pathway depends on the ability of the Russian government to reduce climate and energy policy uncertainties, and to reduce financial risks through improvements of the general investment climate.

Key policy insights

• The high cost of capital investment into Russian energy production and consumption may prevent the adoption of new energy-efficient and low-carbon technologies.

• These investment risks, if not addressed, will delay Russia's low-carbon transition for the coming decades.

• Adopting a clear and unambiguous long-term climate and energy policy is important to reduce these risks and alleviate some of the barriers to the new technologies.

• The first step could be ratification of the Paris Agreement and adoption of a long-term emission target for the period up to 2050.

     

Geochemistry and origin of the Mirny field kimberlites,Siberia

Here we present new data from a systematic Sr, Nd, O, C isotope and geochemical study of kimberlites of Devonian age Mirny field that are located in the southernmost part of the Siberian diamondiferous province. Major and trace element compositions of the Mirny field kimberlites show a significant compositional variability both between pipes and within one diatreme. They are enriched in incompatible trace elements with La/Yb ratios in the range of (65–300). Initial Nd isotope ratios calculated back to the time of the Mirny field kimberlite emplacement (t = 360 ma) are depleted relative to the chondritic uniform reservoir (CHUR) model being 4 up to 6 ɛNd(t) units, suggesting an asthenospheric source for incompatible elements in kimberlites. Initial Sr isotope ratios are significantly variable, being in the range 0.70387–0.70845, indicating a complex source history and a strong influence of post-magmatic alteration. Four samples have almost identical initial Nd and Sr isotope compositions that are similar to the prevalent mantle (PREMA) reservoir. We propose that the source of the proto-kimberlite melt of the Mirny field kimberlites is the same as that for the majority of ocean island basalts (OIB). The source of the Mirny field kimberlites must possess three main features: It should be enriched with incompatible elements, be depleted in the major elements (Si, Al, Fe and Ti) and heavy rare earth elements (REE) and it should retain the asthenospheric Nd isotope composition. A two-stage model of kimberlite melt formation can fulfil those requirements. The intrusion of small bodies of this proto-kimberlite melt into lithospheric mantle forms a veined heterogeneously enriched source through fractional crystallization and metasomatism of adjacent peridotites. Re-melting of this source shortly after it was metasomatically enriched produced the kimberlite melt. The chemistry, mineralogy and diamond grade of each particular kimberlite are strongly dependent on the character of the heterogeneous source part from which they melted and ascended.

     

Depositional history of the Miocene Lake Sinj (Dinaride Lake System,Croatia): a long-lived hard-water lake in a pull-apart tectonic setting

Early Miocene transpressional wrenching yielded a series of NW–SE-elongated pull-apart basins in the Dinarides of Croatia and Bosnia and Herzegovina. They accommodated a huge lake system that gave rise to spectacular endemic mollusk radiation. Lake Sinj, moderately sized at 342 km², flooded the south-westernmost basin of this system. Due to the karstic environment, the hard-water, alkaline, long-lived lake developed a sediment infill with an average thickness of 370 m, dominated by authigenic limestone. The studied section represents the upper third of the basinal infill and provides detailed insights into the critical period of the lake and of the basinal evolution during the final stages of its filling. It comprises two large-scale, shallowing-upward cycles, both starting with fossil-poor limestones, gradually passing into coal-bearing carbonate rocks and coal seams. The fossil-poor intervals are interpreted as phases of repetitive acidification events due to changing lake level, which induced periodic drying and flooding of the uppermost littoral zone inhabited by starfruit (Damasonium) meadows. The flooding of the aerated, limy mud plain introduced H+ ions from organic-matter decay reactions into the shallow lake. This decreased its pH level, with catastrophic consequences for its biota. The ecosystem then stabilized during the orbitally-forced, dry climate phases. Based on the mollusk record, streams still influenced the marginal lake environment and rich organic-matter production created swamps and mires. The onset of mollusk radiation in the section correlates with stabilized lake alkalinity, as indicated by the disappearance of starfruits, ongoing authigenic carbonate production and by coal seams representing textbook examples for coal formation in alkaline environments. The inferred basinal setting fits well with the pull-apart basin model, pointing to the presence of an extended shallow ramp in front of a steep, fault-induced hillside of the hinterland.     

Long-Term Temperature Trends and Tree Growth in the Taymir Region of Northern Siberia

The northernmost conifers in the world are located well above the Arctic Circle in the Taymir region of northern Siberia and have been recording the thermal environment for centuries to millennia. The trees respond to temperatures beyond the narrow season of actual cambial cell division by means of root growth, photosynthesis, lignification of cell walls, and other biochemical processes. Data from annual tree-ring widths are used to reconstruct May–September mean temperatures for the past four centuries. These warm-season temperatures correlate with annual temperatures and indicate unusual warming in the 20th century. However, there is a loss of thermal response in ring widths since about 1970. Previously the warmer temperatures induced wider rings. Most major warming and cooling trends are in agreement with other high-latitude temperature reconstructions based on tree-ring analyses with some regional differences in timing of cooling in the late 18th century and of warming in the late 19th century.     

Seasonal Cycle of the Near-Surface Diurnal Wind Field Over the Bay of La Paz,Mexico

The results of numerical simulations of the troposphere over the Bay of La Paz, calculated for the months of January, April, July and October during the period 2006–2010 with the Weather Research and Forecast (WRF v3.5) regional model, are used to describe the seasonal features of the diurnal cycle of planetary boundary-layer winds. Two distinct near-surface diurnal flows with strong seasonal variability were identified: (1) a nocturnal and matutinal breeze directed from the subtropical Pacific Ocean, over the Baja California peninsula and the Bay of La Paz, into the Gulf of California that is associated with the regional sea-surface temperature difference between those two major water bodies; and (2) a mid to late afternoon onshore sea-breeze related to the peninsula’s daily cycle of insolation heating that evolves with counter-clockwise rotation over the Bay of La Paz. The model results reveal the interaction over Baja California of opposing afternoon sea-breeze fronts that originate from the subtropical Pacific Ocean and the Gulf of California, with a convergence line forming over the peaks of the peninsula’s topography and the associated presence of a closed vertical circulation cell over the Bay of La Paz and the adjacent Gulf. The collision of the opposing sea-breeze fronts over the narrow peninsula drives convection that is relatively weak due to the reduced heat source and only appears to produce precipitation sporadically. The spatial structure of the sea-breeze fronts over the Bay of La Paz region is complex due to shoreline curvature and nearby topographic features. A comparison of the numerical results with available meteorological near-surface observations indicates that the modelling methodology adequately reproduced the observed features of the seasonal variability of the local planetary boundary-layer diurnal wind cycle and confirms that the low-level atmospheric circulation over the Bay of La Paz is dominated by kinetic energy in the diurnal band. The strongest (weakest) diurnal flows occur during the summer (winter) in response to the seasonally varying magnitudes of the daily land–sea thermal contrast and the regional subtropical Pacific Ocean–Gulf of California sea-surface temperature difference.     

On the response of the oceanic wind-driven circulation to atmospheric CO2 increase

A global, flux-corrected climate model is employed to predict the surface wind stress and associated wind-driven oceanic circulation for climate states corresponding to a doubling and quadrupling of the atmospheric CO₂ concentration in a simple 1% per year CO₂ increase scenario. The model indicates that in response to CO₂ increase, the position of zero wind stress curl in the mid-latitudes of the Southern Hemisphere shifts poleward. In addition, the wind stress intensifies significantly in the mid-latitudes of the Southern Hemisphere. As a result, the rate of water circulation in the subpolar meridional overturning cell in the Southern Ocean increases by about 6 Sv (1 Sv=10⁶ m³ s⁻¹) for doubled CO₂ and by 12 Sv for quadrupled CO₂, implying an increase of deep water upwelling south of the circumpolar flow and an increase of Ekman pumping north of it. In addition, the changes in the wind stress and wind stress curl translate into changes in the horizontal mass transport, leading to a poleward expansion of the subtropical gyres in both hemispheres, and to strengthening of the Antarctic Circumpolar Current. Finally, the intensified near-surface winds over the Southern Ocean result in a substantial increase of mechanical energy supply to the ocean general circulation.     

Predicting Patterns of Near-Surface Air Temperature Using Empirical Data

The signal of recent global warming has been detected in meteorological records, borehole temperatures and by several indirect climate indicators. Anthropogenic warming continues to evolve, and various methods are used to study and predict the changes of the global and regional climate. Results derived from GCMs, palaeoclimate reconstructions, and regional climate models differ in detail. An empirical model could be used to predict the spatial pattern of the near-surface air temperature and to narrow the range of regional uncertainties. The idea behind this approach is to study the correlations between regional and global temperature using century-scale meteorological records, and to evaluate the regional pattern of the future climate using regression analysis and the global-mean air temperature as a predictor. This empirical model, however, is only applicable to those parts of the world where regional near-surface air temperature reacts linearly to changes of the global thermal regime. This method and data from a set of approximately 2000 weather stations with continuous century-scale records of the monthly air temperature was applied to develop the empirical map of the regional climate sensitivity. Data analysis indicated that an empirical model could be applied to several large regions of the World, where correlations between local and global air temperature are statistically significant. These regions are the western United States, southern Canada, Alaska, Siberia, south-eastern Asia, southern Africa and Australia, where the correlation coefficient is typically above 0.9. The map of regional climate sensitivity has been constructed using calculated coefficients of linear regression between the global-mean and regional annual air temperature. As long as the correlations between the local and global air temperature are close to those in the last several decades, this map provides an effective tool to scale down the projection of the global air temperature to regional level. According to the results of this study, maximum warming at the beginning of the 21st century will take place in the continental parts of North America and Eurasia. The empirical regional climate sensitivity defined here as the response of the mean-annual regional temperature to 1 °C global warming was found to be 5–6 °C in southern Alaska, central Canada, and over the continental Siberia, 3–4 °C on the North Slope of Alaska and western coast of the U.S.A., and 1–2 °C in most of the central and eastern U.S.A. and eastern Canada. Regions with negative sensitivity are located in the southeastern U.S.A., north-western Europe and Scandinavia. The local tendency towards cooling, although statistically confirmed by modern data, could, however, change in the near future.