A conceptual framework for the integral management of marine protected areas

A general conceptual framework for the management of marine protected areas (MPAs) was developed. The driver-pressure-state-impacts-response (DPSIR) framework was used to determine the elements affecting MPAs. The developed evaluation framework helped to select an appropriate suite of indicators to support an ecosystem approach, an assessment of the MPAs functioning and policy decisions. Gaps derived from the management and policy responses in the MPAs were also outlined. It was concluded that the DPSIR framework can help to simplify the complexity of MPA management. This document is a tool for policy makers, scientists and general public on the relevance of indicators to monitor changes and MPAs management.     

Physical properties of asteroid 433 Eros

Newly available photometric, polarimetric, spectroscopic, thermal-radiometric, radar, and occultation results are synthesized in order to derive a coherent model for Eros. The geometric albedo is 0.19±0.01 at the visual wavelength, and the overall dimensions are approximately 13 × 15 × 36km. The rotation is about the short axis, in the direct sense, with a sidereal period of 5^h16^m13^s.4. The pole of rotation lies within a few degrees of ecliptic coordinates λ = 16° and β = + 11°.Eros is uniformly coated with a particulate surface layer several millimeters thick. It has an iron-bearing silicate composition, similar to that of a minority of main-belt asteroids, and probably identifiable with H-type ordinary chondrites.     

Upstream and downstream controls of recent avulsions on the Taquari megafan,Pantanal, south‐western Brazil

Avulsion, the natural relocation of a river, is a key process in the evolution of subaerial fans, river floodplains and deltas. The causes of avulsion are poorly understood, which is partly due to the scarcity of field studies of present avulsions. At present, two avulsions are occurring on the middle and lower Taquari megafan, Pantanal basin, south‐western Brazil. Here we present an analysis of the causes of these avulsions based on field and remote sensing data and show that avulsions on megafans can be controlled by both upstream and downstream processes. The middle fan avulsion (started in 1997–1998) is a result of upstream control: overbank aggradation was caused by the (variable) input of sandy sediment into the system, which caused channel‐belt superelevation and also created an easily erodible subsurface favouring bank retreat, crevassing, and scour of deep floodplain channels. The sandy subsurface in this area is inferred to have been a major factor in the causation of this avulsion under conditions of little gradient advantage. The lower fan avulsion (started c. 1990) results from interplay of upstream and downstream controls, the latter being related to the local base level (the Paraguay River floodplain) at the toe of the fan. Channel and overbank aggradation on the lower fan was influenced by fan sub‐lobe progradation and channel backfilling. Fan sub‐lobe progradation caused a significant gradient advantage of the avulsion channel over the parent channel. Avulsions are commonly supposed to be preferentially triggered by high‐magnitude floods, when there is considerable channel‐belt superelevation. However, both avulsions studied by us were triggered by small to average floods, with modest channel‐belt superelevation. We conclude that flood magnitude and channel‐belt superelevation have been overrated as causes of avulsion, and demonstrate additional causes that influence the growth of crevasses into avulsions. Copyright © 2012 John Wiley & Sons, Ltd.     

The role of meteorological forcing and snow model complexity in winter glacier mass balance estimation,Columbia River basin,Canada

Glaciers are commonly located in mountainous terrain subject to highly variable meteorological conditions. High resolution meteorological (HRM) data simulated by atmospheric models can complement meteorological station observations in order to assess changes in glacier energy fluxes and mass balance. We examine the performance of two snow models, SnowModel and Alpine3D, forced by different meteorological data for winter mass balance simulations at four glaciers in the Canadian portion of the Columbia Basin. The Weather Research and Forecasting model (WRF) with resolution of 1 km and the North American Land Data Assimilation System with ~12 km resolution, provide HRM data for the two snow models. Evaluation is based on the ability of the snow models to simulate snow depth at both point locations (automated snow weather stations) and over the entire glacier surface (airborne LiDAR [Light Detection and Ranging] surveys) during the 2015/2016 winter accumulation. When forced with HRM data, both models can reproduce snow depth to within ±15% of observed values. Both models underestimate winter mass balance when forced by HRM data. When driven with WRF data, SnowModel underestimates winter mass balance integrated over the glacier area by 1 and 10%, whilst Alpine3D underestimates winter mass balance by 12 and 22% compared with LiDAR and stake measurements, respectively. The overall results show that SnowModel forced by WRF simulated winter mass balance the best.     

Incision of alluvial channels in response to a continuous base level fall: Field characterization, modeling, and validation along the Dead Sea

The dramatic lake level drop of the Dead Sea during the twentieth century ( 30 m) provides a field-scale experiment in transport-limited incision of gravel-bed channels in response to quasi-continuous base level fall at approximately constant rate. We apply a one-dimensional numerical incision model based on a linear diffusion equation to seven ephemeral channels draining into the Dead Sea. The model inputs include the measured twentieth century lake level curve, annual shoreline location (i.e., annual channel lengthening following the lake level drop), reconstructed longitudinal profiles of each of the channels based on mapped and surveyed terraces, and the current profiles of the active channels. The model parameters included the diffusion coefficient and the upstream-derived sediment flux. Both were first calibrated using a set of longitudinal profiles of known ages and then validated using additional sets of longitudinal profiles.The maximum at-station total incision observed at each of the studied channels was significantly less then the total lake level drop and varied in response to both drainage area and lake bathymetry. The model applied predicted degradation rates and the pattern of degradation with high accuracy. This suggests that sediment flux in the modeled channels is indeed linearly dependent on slope. Further support for this linear dependency is provided by a linear correlation between the diffusion coefficient and the mean annual rain volume over each basin (a proxy for discharge). The model presented could be a valuable tool for planning in rapid base level fall environments where incision may risk infrastructure.     

Sources of continental magmatism adjacent to the late Archean Kolar Suture Zone,south India: distinct isotopic and elemental signatures of two late Archean magmatic series

 Conspicuous Nd, Sr and Pb isotopic differences exist between the Archean gneiss terranes adjoining the suture at the Kolar Schist Belt, south India. These gneisses, which are the deformed equivalents of plutonic and volcanic rocks, have known or inferred igneous ages of 2630 to 2530 Ma. Initial isotopic ratios of Nd, Sr and Pb suggest that metaplutonic gneisses west of the Kolar Schist Belt were emplaced into, and variably contaminated by, an evolved continental crust that formed prior to 3200 Ma. Felsic metaigneous gneisses that occur as slivers on the western margin of the schist belt have an isotopic character similar to that of the metaplutonic rocks on the same side of the Kolar Schist Belt. On the east side of the Kolar Schist Belt the isotopic evidence suggests that the 2530 Ma granitic gneisses were not derived from or contaminated by an older continental crust. Their source probably evolved with a Nd isotopic composition similar to that of typical Archean mantle, but became light rare earth element enriched after 2900 to 2700 Ma. The inferred tectonic setting for the west side of the Kolar Schist Belt is an Andean continental magmatic arc. For the east side of the Kolar Schist Belt, a possible Phanerozoic analog is an evolved island arc, such as Japan. Received: 24 June 1994/Accepted: 9 January 1995     

Anomalous echoes observed with the EISCAT UHF radar at 100-km altitude

We have observed a number of strong echoes with the European incoherent-scatter (EISCAT) UHF (930-MHz) radar at angles 83.5° and 78.6° with the geomagnetic field and at about 100-km altitude north in the auroral zone. The echoes are shortlived and occur in single 2- or 10-s data dumps. They are offset by 125–130 kHz with respect to the transmitted frequency. In most cases the offset compares well with the frequency of gyro lines in the incoherent-scatter spectrum, as given by the standard linear dispersion relation. But sometimes the measured offsets deviate significantly from the model calculations, and the interpretation in terms of gyro lines becomes questionable. The discrepancy could possibly be explained by local deviations in the magnetic field from the model (IGRF 1987), which are generated by incoming particle beams. A more serious problem with the gyro-line theory is how the line can be excited at altitudes where the collisional damping is substantial. The high intensity and short lifetime of the signal point to a fast-growing plasma instability as the likely excitation mechanism, if the gyro-line interpretation is correct. The cause of the instability could be the same particle beams as those causing the disturbances in the magnetic field. Alternatively, the observations may be interpreted as meteor head echoes. The large Doppler shifts, the short lifetimes and the altitudes of the signals support this explanation. The main difficulty is that the distribution of measured offsets appears to be different in magnetically active conditions and in less active conditions. Also, the occurrence of echoes does not seem to follow the expected changes in meteor density. More observations in different conditions are needed to decide between the two interpretations. As it is, we are inclined to believe in the meteor head echo theory, the objections to the gyro-line theory being more fundamental.     

Silicifications pédogénétiques dans les dépôts hamadiens du piémont de Boudenib (Maroc)

Résumé

— Le système de piémont atlasique du Sud marocain, d’âge tertiaire, est constitué dans le secteur de Boudenib de deux unités distinctes. La llamada de Boudenib forme l’unité inférieure et se caractérise par d’importants encroûtements carbonatés, riches en dolomite et attapulgite. L’unité supérieure de la llamada du Cuir marque une reprise de l’érosion et le dépôt de matériaux relativement peu altérés.

Des silicifications affectent les différents faciès de l’unité inférieure, ainsi que les grès crétacés sous-jacents, et jalonnent une surface d’érosion intra-fonnationnelle. Ces silicifications sont précoces, puisque remaniées dans les dépôts ultérieurs. Les illuviations d’opale et les accumulations gramdaires intercalées entre les concrétionnements successifs de silice attestent d’environnements pédologiques. La silicification plus forte vers la partie supérieure des coupes, ainsi que l’association fréquente des faciés silicifiés avec des niveaux hioturhés et altérés sont également à rapporter à des dispositions pédologiques. Ce sont des silcréles pédogénétiques.

L’étude micrographique montre que la silicification procède par épigénie des argiles et des carbonates, ainsi que par des cristallisations dans les vides. C’est à partir des vides existants (fentes, bioturbations et porosité intergranulaire) que se développe la silicification, montrant ainsi le rôle primordial des circulations. En particulier, l’épigénie des carbonates par la silice semble limitée par la diffusion de la silice à partir des vides, où le renouvellement des solutions est assuré. Les séquences de cristallisation des différentes formes de silice (allant de l’opale vers les quartz automorphes) peuvent être interprétées en terme d’évolution du milieu au cours de la silicification. Au fur et à mesure que des dépôts de silice se font sur les parois des vides, les solutions nourricières sont isolées de la roche encaissante, elles se chargent alors moins en cations étrangers, et la cristallisation de plus grands cristaux peut intervenir.

Les silicifications se développent pendant une période de stabilité tectonique et s’installent dans un paysage de glacis et sous des climats chauds à saisons alternées. Leur reconnaissance à l’échelle régionale peut constituer un repère lithostratigraphique précieux.