Assessment of interpolated ERA-40 reanalysis temperature and precipitation against observations of the Balkan Peninsula

Due to their ready availability and temporal and spatial consistency, reanalysis data are widely used within the climate community. Nevertheless, higher spatial resolutions are often required and statistical interpolation techniques are applied to increase the data resolution. This work aims to derive a set of high spatial resolution data through three-dimensional interpolation of daily temperature and precipitation. Thin plate spline interpolation has been chosen and used to interpolate ERA-40 temperature and precipitation from a coarse grid (110 km) into a finer one of 1-km spatial resolution. The study evaluates the method by comparing the simulated variables with available in situ meteorological measurements. The chosen stations are distributed over the study region and, most importantly, contain information from a range of altitudes. The results indicate that accounting for the topography in the interpolation process improves the comparisons, with the biggest improvements being evident in the most mountainous areas. The method is found to be better in estimating temperature than precipitation fields. Moreover, the method performs better for maximum temperature in high altitudes and for minimum temperature in low altitudes.     

An assessment of Canadian prairie drought: past, present, and future

Within Canada, the Canadian Prairies are particularly drought-prone mainly due to their location in the lee of the western cordillera and distance from large moisture sources. Although previous studies examined the occurrence of Canadian Prairie droughts during instrumental, pre-instrumental and to a lesser extent, future periods, none have specifically focused on all time three scales. Using two different drought indicators, namely the Palmer Drought Severity Index (PDSI) and Standardized Precipitation Index (SPI), this investigation assesses the variability of summer drought duration and intensity over a core region of the Prairies during (a) the pre-instrumental record extending back several centuries (inferred from tree rings), (b) the instrumental record (1901–2005), and (c) the twenty-first century using statistically downscaled climate variables from several Atmosphere–Ocean Global climate models with multiple emission scenarios. Results reveal that observed twentieth century droughts were relatively mild when compared to pre-settlement on the Prairies, but these periods are likely to return (and even worsen) in the future due to the anticipated warming during the course of the twenty-first century. However, future drought projections are distinctly different between the two indices. All PDSI-related model runs show greater drought frequency and severity mainly due to increasing temperatures. Conversely, the precipitation-based SPI indicates no significant changes to future summer drought frequency although there tends to be a higher persistence of multi-year droughts in central and southern portions of Canadian Prairies. These findings therefore stress the importance of considering anticipated warming trends when assessing future regional-scale drought, especially given the uncertainties and lack of consistency in future precipitation signals among climate models. This study can be considered an initial step toward quantifying and understanding Canadian Prairie drought occurrence and severity over several centuries as determined from paleo, instrumental, and climate model data sources.     

Vegetation responses and feedbacks to climate: a review of models and processes

Vegetation changes both in stationary and changing climates. Such changes can significantly affect hydrological and climate dynamics. Probabilistic, inferential, empirical, statistical, threshold, ecophysiological, and mechanistic vegetation models provide tools and ideas to construct coupled climate and vegetation schemes to study climate/vegetation feedbacks. Their logic is discussed, typical applications are presented, and their usefulness is assessed. Developing coupled climate and vegetation schemes also implies tackling scaling issues explicitly. Just as the Courant-Friedrichs-Lewy (CFL) criterion guarantees that information is not transferred faster through space than time in climate models, information should be transmitted fast enough in vegetation models for the landscape to register vegetation responses. To guarantee that this is the case, a migration criterion, or m criterion, is proposed. The CFL criterion and the m criterion set formal constraints on the design of coupled atmosphere and vegetation schemes. In particular, the ratio of climate and vegetation space scales should be approximately five orders of magnitude less than the ratio of climate and vegetation time scales.     

Mechanisms of fine extinction band development in vein quartz: new insights from correlative light and electron microscopy

Fine extinction bands (FEBs) (also known as deformation lamellae) visible with polarized light microscopy in quartz consist of a range of nanostructures, inferring different formation processes. Previous transmission electron microscopy studies have shown that most FEB nanostructures in naturally deformed quartz are elongated subgrains formed by recovery of dislocation slip bands. Here we show that three types of FEB nanostructure occur in naturally deformed vein quartz from the low-grade metamorphic High-Ardenne slate belt (Belgium). Prismatic oriented FEBs are defined by bands of dislocation walls. Dauphiné twin boundaries present along the FEB boundaries probably formed after FEB formation. In an example of two sub-rhombohedral oriented FEBs, developed as two sets in one grain, the finer FEB set consists of elongated subgrains, similar to FEBs described in previous transmission electron microscopy studies. The second wider FEB set consists of bands with different dislocation density and fluid-inclusion content. The wider FEB set is interpreted as bands with different plastic strain associated with the primary growth banding of the vein quartz grain. The nanometre-scale fluid inclusions are interpreted to have formed from structurally bounded hydroxyl groups that moreover facilitated formation of the elongate subgrains. Larger fluid inclusions aligned along FEBs are explained by fluid-inclusion redistribution along dislocation cores. The prismatic FEB nanostructure and the relation between FEBs and growth bands have not been recognized before, although related structures have been reported in experimentally deformed quartz.     

Global significance of oxygen and carbon isotope compositions of pedogenic carbonates since the Cretaceous

Few global syntheses of oxygen and carbon isotope composition of pedogenic carbonates have been attempted,unlike marine carbonates.Pedogenic carbonates represent in-situ indicators of the climate conditions prevailing on land.The δ~(18)O and δ~(13)C values of pedogenic carbonates are controlled by local and global factors,many of them not affecting the marine carbonates largely used to probe global climate changes.We compile pedogenic oxygen and carbon isotopic data(N= 12,167) from Cretaceous to Quaternary-aged paleosols to identify potential trends through time and tie them to possible controlling factors.While discrete events such as the PaleoceneEocene Thermal Maximum are clearly evidenced,our analysis reveals an increasing complexity in the distribution of the δ~(18)O vs δ~(13)C values through the Cenozoic.As could be expected,the rise of C_4 plants induces a shift towards higher δ~(13)C values during the Neogene and Quaternary.We also show that the increase in global hypsometry during the Neogene plays a major role in controlling the δ~(18)O and δ~(13)C values of pedogenic carbonates by increasing aridity downwind of orographic barriers.Finally,during the Quaternary,an increase of 3‰ inδ~(18)O values is recorded both by the pedogenic carbonates and the marine foraminifera suggesting that both indicators may be used to track global climate signal.     

U-Pb geochronology on zircon and columbite-group minerals of the Cap de Creus pegmatites,NE Spain

Mineralogy and Petrology - The Cap de Creus granitic pegmatites in the eastern Catalan Pyrenees were dated using in situ U-Pb geochronology by laser ablation ICP-MS on zircon and columbite-group...     

Mouvements actuels des blocs tectoniques dans l’arc Bético-Rifain à partir des mesures GPS entre 1999 et 2005

GPS velocities and seismicity across the Betic–Rif Arc structural domains (Morocco and Iberia) provide a basis to evaluate present-day seismotectonic processes between different deformation belts. The results show asymmetric movements in the complex Alboran system accommodating the convergence between the African (Nubian) and Eurasian plates. While the Betic Mountains are attached to Iberia, moving toward the southeast with respect to Africa, the Rif is divided into three blocks with distinct displacements relative to Nubia: (1) the Tangier block moving southeastward, (2) the Central Rif block moving SSW, and (3) the Oriental Rif block undergoing clockwise rotation. GPS-derived motions decrease in rate from the Rif nappes complex to the foreland.     

The Pleistocene hominid site of Ternifine, Algeria: New results on the environment, age, and human industries

A new multidisciplinary research program, started in 1981, provided new data on the stratigraphy, fauna, and human industries, as well as the first results on paleomagnetism and sedimentology, for the Ternifine site in Algeria, which yielded the earliest hominid remains known in North Africa. The fossils were deposited in a swamp or lake surrounded by a very open, dry environment. The lake was fed by artesian springs that raised the underlying Miocene sands. Although nothing suggests a camp or butchery site, we discovered the first undisputable bone artifact in this site, the earliest known in this part of Africa. According to paleontological data, 700,000 yr B.P. is a likely age for the Ternifine deposits, which is consistent with the paleomagnetic results.     

Tectonic record of convergence changes in a collision area: the Boso and Miura peninsulas, Central Japan

Late Cenozoic formations in Boso and Miura have been affected by several tectonic events. Tectonic analysis enables us to reconstruct six different paleostress types: (1) early extension affecting the Oligocene/early Miocene Mineoka Group, (2) and (3), relatively minor compressional and extensional events probably early Pliocene in age, (4) major NNE-SSW compression dominating prior to 2 or 3 Ma ago, and (5) and (6) more recent major NNW-SSE compression to the west and WNW-ESE extension to the east, both types affecting the Pleistocene and prevailing since 1–2 Ma ago. The counterclockwise change from NNE-SSW to NNW-SSE compression is not accurately dated, but very likely occurred between 2 and 3 Ma ago; it is compared to similar evolutions in other areas of the Izu collision zone. We conclude that it corresponds to a major counterclockwise change in the direction of plate convergence (from SSE-NNW to SE-NW). The relationships between the directions of convergence and the distributions of Plio-Quaternary compressional paleostresses in and around the collision zone are described through a simple analogy, for the two stages of Plio-Quaternary collision. This counterclockwise change in stress fields and relative motions, also described in the Taiwan collision zone along the same Philippine Sea plate-Eurasia boundary, is interpreted as a major event at the scale of the plate. The possible significances of the other paleostress types identified in Boso are discussed. We conclude that tectonic analysis in and along collision boundaries provides a key for understanding kinematic evolution.