Analytical modelling of wintertime coastal jets in the Adriatic Sea

Two diagnostic models, reproducing circulation generated in a marginal sea by variable density, have been developed. The models’ domain is a 2D transverse section for which analytical solutions have been obtained. They describe the winter situation in the northern Adriatic, with a strong vertical mixing present and the density maximum dominating the centre of the basin. Both models employ Boussinesq-type parametrisation of friction and linear slip at the bottom. The first model allows for frictional departure from hydrostatic equilibrium and includes vertical friction only. The second one is hydrostatic but allows for lateral friction as well. The results obtained by the two models are similar and to some extent dependent on the vertical and bottom friction. They reproduce several well known characteristics of the Adriatic circulation (cyclonic surface flow, downwelling in the central and larger part of the basin compensated by upwelling in the coastal zone) but also predict some phenomena that are still not well understood. A conspicuous feature of the model results are coastal jets, which were observed in the Adriatic on several occasions. The present models show that the distance of jets from the coasts depends on lateral friction: it is found to vary from 1 up to 10 km on the Italian side and between 2 and 15 km on the Croatian side. Both models reproduce the west–east asymmetry, with the wider current on the east side of the basin. The asymmetry is a subject on which conflicting empirical results exist in the Adriatic. In the two models cyclonic flow occupies the whole water column, which disagrees with some recent theoretical findings of the near-bottom anticyclonic flow and thus leaves the issue open.     

A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa

International Journal of Earth Sciences - In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such...     

Local Imbalance of Turbulent Kinetic Energy in the Surface Layer

We utilize experimental data collected in 2002 over an open field in Hanford, Washington, USA, to investigate the turbulent kinetic energy (TKE) budget in the atmospheric surface layer. The von Kármán constant was determined from the near-neutral wind profiles to be 0.36 ± 0.02 rather than the classical value of 0.4. The TKE budget was normalized and all terms were parameterized as functions of a stability parameter z/L, where z is the distance from the ground and L is the Obukhov length. The shear production followed the Businger–Dyer relation for −2 < z/L < 1. Contrary to the traditional Monin–Obukhov similarity theory (MOST), the shear, buoyancy and dissipation terms were found to be imbalanced due to a non-zero vertical transport over all stabilities. Motivated by this local imbalance, modified parameterizations of the dissipation and the turbulent transport were attempted and generated good agreement with the experimental data. Assuming stationarity and horizontal homogeneity, the pressure transport was estimated from the residual of the TKE budget.     

In situ micro‐Raman and X‐ray diffraction study of diamonds and petrology of the new ureilite UAE 001 from the United Arab Emirates

Abstract— A new olivine‐pigeonite ureilite containing abundant diamonds and graphite was found in the United Arab Emirates. This is the first report of a meteorite in this country. The sample is heavily altered, of medium shock level, and has a total weight of 155 g. Bulk rock, olivine (Fo_79.8–81.8) and pyroxene (En_73.9–75.2, Fs_15.5–16.9, Wo_8.8–9.5) compositions are typical of ureilites. Olivine rims are reduced with Fo increasing up to Fo_96.1–96.8. Metal in these rims is completely altered to Fehydroxide during terrestrial weathering. We studied diamond and graphite using micro‐Raman and in situ synchrotron X‐ray diffraction. The main diamond Raman band (LO = TO mode at ?1332 cm^?1) is broadened when compared to well‐ordered diamond single crystals. Full widths at half maximum (FWHM) values scatter around 7 cm^?1. These values resemble FWHM values obtained from chemical vapor deposition (CVD) diamond. In situ XRD measurements show that diamonds have large grain sizes, up to >5 μm. Some of the graphite measured is compressed graphite. We explore the possibilities of CVD versus impact shock origin of diamonds and conclude that a shock origin is much more plausible. The broadening of the Raman bands might be explained by prolonged shock pressure resulting in a transitional Raman signal between experimentally shock‐produced and natural diamonds.     

Provenance of the HP–HT subducted margin in the Variscan belt (Cabo Ortegal Complex,NW Iberian Massif)

The Variscan Upper Allochthon is a continental‐affinity terrane that recorded a Cambrian–Ediacaran magmatic arc generation, a subsequent transition to a passive margin, and a collision‐related high‐P metamorphism during the Devonian–Carboniferous amalgamation of Pangea. The objective of this article is to decipher which continental margin subducted in the Devonian high‐P–high‐T (HP–HT) event. To do so, a provenance study is presented using combined U–Pb (n = 613) and Lu–Hf (n = 463) isotopic LA–ICP–MS zircon analyses and Sm–Nd whole–rock (n = 5) determinations. These analyses have been performed on five samples of the Banded Gneisses (Cabo Ortegal Complex, NW Iberia), which forms a part of the HP–HT bottom member of the Upper Allochthon. Palaeozoic–Neoproterozoic zircon ages (34.7%) have a maximum abundance at 522–512 Ma, peaks at 575, 561, 545 Ma and minor abundance peaks between 780 and 590 Ma, and show from their Lu–Hf compositions a volcanic arc mixing pattern. This arc was probably related to the Cadomian arc system. The Mesoproterozoic population is scarce and scattered (2.8%), and due to its Lu–Hf pattern, it is proposed that this population is also West Africa Craton derived. The Paleoproterozoic population (39.6%) is concentrated at 2.07 Ga and it is linked to the Eburnean Orogeny, where depleted mantle derived magmas intruded an Archean craton margin. This craton is represented by the Archean population (22.8%), which is grouped at 3.0, 2.68‐2.61 and 2.52‐2.48 Ga, and shows long‐term reworking processes and at least two juvenile magma intrusions. These data show that the Variscan Upper Allochthon has a West African provenance and therefore, it strongly suggests that the NW Iberian allochthonous complexes and their correlative European terranes are also West Africa derived. These results allow us to finally clarify that the first high‐P event, recorded during the eo‐Variscan amalgamation of Pangea, was attained by the subduction of the margin of Gondwana under Laurussia.     

Landslides at a uranium mill tailing deposit site Boršt (Slovenia) detected by radar interferometry

This paper presents a comparison of persistent scatterer interferometry (PSI) monitoring results with in situ displacement measurements at the November 1990 landslide at the Bor?t uranium mill tailing deposit site after heavy rain. Although the landslide did not directly endanger people, site remediation works were undertaken due to the subsequent environmental problems. Additionally, in situ monitoring with benchmarks was established in order to detect the ground motion of the landslide body. PSI campaigning in the ?kofjelo?ko-Cerkljansko area, where the uranium mill tailing is situated, performed for the purpose of measuring displacements of natural targets near the active landslide area, also detected displacements, most probably indicating a creeping process. When comparing the pre- and post-remediation velocities at the benchmarks located on the landslide with persistent scatterers (PSs) located near the landslide, the rates could be regarded as background. The results show that the remediation works in the form of a drainage tunnel were very effective as post-remediation velocities at the landslide closer to the PSs resembled the velocities of the PSs, while the velocities of the landslide mass above the drainage tunnel slowed down, even to below the background velocities. The high correlation values between the movements of the benchmarks and the PSs also confirm that the remediation works were effective as the fluctuations in the displacement values of the landslide were very similar to those of the PSs. Nevertheless, although there are several limitations in comparing the two different datasets, the PSI technique can be complementary to conventional in situ methods.     

Small icebergs and iceberg fragments off Newfoundland: Relationships to deterioration mechanisms and the regional iceberg population

Abstract

Several sets of previously compiled data on iceberg size distributions in areas between North America and Greenland are compared and analyzed. The obtained results indicate that populations of icebergs with lengths L ≥ 20 m are well‐described by log‐normal and gamma distributions together with statistical parameters which are compatible with existing understanding of regional iceberg deterioration and change processes. A lesser amount of data on size distributions in Newfoundland icebergs with L < 20 m show occurrence probabilities which increase exponentially with decreasing iceberg length. Evidence is presented to show that these data are most consistent with the dominance of fracture processes in determining iceberg occurrence versus length relationships. Physical arguments are presented to suggest that the key fracture events are initiated in the larger icebergs by coincidences of wave‐generated bending stress maxima and randomly distributed structural flaws. Similar considerations and use of a simple sequential fracture model imply that size distributions in icebergs (and iceberg fragments) with L < 20 m are more consistent with the presence of an alternative, spontaneous failure mechanism also acting at randomly distributed structural defects. The implications of these results for forecasting and monitoring populations of small icebergs are discussed.     

Content of the potentially harmful elements in soil around the major coal-fired power plant in Serbia: relation to soil characteristics,evaluation of spatial distribution and source apportionment

The concentrations and spatial distribution of nine potentially harmful elements (PHEs), namely Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn, and their relation to soil properties were investigated in thirty soil profiles (0–50 cm depth) sampled around the largest Serbian coal-fired power plant (CFPP) “Nikola Tesla A.” Soil properties were determined following standard procedures, and total contents of PHEs were analyzed by atomic absorption spectrometer. Concentrations of Cd, Co, Fe, Mn, Pb and Zn were the highest in soil profiles sampled 1 km away from the CFPP, concentrations of Ni and Cu gradually increased up to 4 km, and the highest Cr concentrations were measured in samples taken 6 km away from the CFPP. The highest concentration of PHEs analyzed, except Mn, corresponded with predominant wind directions. Depth did not show significant impact on distribution of any PHEs investigated. Among soil properties, the total organic carbon showed the closest relationship with the PHEs. Data were processed by a principal component analysis which enabled distinguishing anthropogenic from natural influences on soil properties and PHE contents. Although the impact of CFPP operations is obvious, assets of principal component analysis did not allow clear distinction of CFPP’s contribution from parent material in enrichment of PHE contents in the soil in the study area.