The efficiency of the spiral-in of a black hole to the Galactic Centre

We study the efficiency at which a black hole or dense star cluster spirals in to the Galactic Centre. This process takes place on a dynamical friction time-scale, which depends on the value of the Coulomb logarithm (ln Λ). We determine the accurate value of this parameter using the direct N -body method, a tree algorithm and a particle-mesh technique with up to two million plus one particles. The three different techniques are in excellent agreement. Our measurement for the Coulomb logarithm appears to be independent of the number of particles. We conclude that  ln Λ= 6.6 ± 0.6  for a massive point particle in the inner few parsec of the Galactic bulge. For an extended object, such as a dense star cluster, ln Λ is smaller, with a value of the logarithm argument Λ inversely proportional to the object size.     

Barotropic tidal mixing effects in a coupled climate model: Oceanic conditions in the Northern Atlantic

Impacts of mixing driven by barotropic tides in a coupled climate model are investigated by using an atmosphere–ocean–ice–land coupled climate model, the GFDL CM2.0. We focus on oceanic conditions of the Northern Atlantic. Barotropic tidal mixing effects increase the surface salinity and density in the Northern Atlantic and decrease the RMS error of the model surface salinity and temperature fields related to the observational data.     

Palaeolimnological studies of the eutrophication of volcanic Lake Albano (Central Italy)

We use palaeolimnological techniques to reconstruct the eutrophication history of a volcanic lake (Lake Albano, central Italy) over the past three centuries. The presence of annual varves down to the bottom of the core (c. 1700 A.D.) indicated the lack of bioturbation and likely long-term meromixis. Sedimentation rates were estimated by varve counts (calcite/diatom couplets), indicating a mean rate of 0.15 cm yr^–1. The reconstruction of eutrophication was traced using past populations of algal and photosynthetic bacteria (through their fossil pigment), and geochemistry, as well as fossil remains of chironomids. Phaeophorbidea and the red carotenoid astaxanthin were used to detect past zooplankton development.The first sign of trophic change related to human activities is datedc. 1870 A.D. From that period onward a sharp increase of authigenic CaCO₃, nitrogen, N:P ratio, and dinoxanthin, a characteristic carotenoid of Chrysophyceae and Dinophyceae, is observed.Chironomid analyses showed the near absence of a deep water fauna throughout the core length. The populations of chironomid larvae are restricted to oxygenated littoral zones. In fact, the few fossil remains found are primarily of littoral origin, representing shallow water midges that were transported to profundal waters. The reduction of total chironomid in the uppermost layers of the core is to be related to human land uses.     

Die Tektonik der Dolomiten im Rahmen des Südalpinen Baues

Zusammenfassung Die Struktur der Dolomiten paßt ausgezeichnet in das tektonische Bild der südlichen Alpen, wenn auch das Vorhandensein der permischen Porphyrplatte stellenweise häufig Brüche verursacht hat.Die Dislokationen der Dolomiten folgen im allgemeinen Falten und Faltenverwerfungen, die von Westen nach Osten verlaufen und vorwiegend eine Vergenz nach Süden aufweisen.Die permische Porphyrplatte und die markanten Linsen der Dolomitriffe machen diese Gegend zu einem klassischen Beispiel selektiver Tektonik.Die Tektonik der Dolomiten beruht z. T. auf Ablösungs- und Gleiterscheinungen an geneigten Flächen. Es gibt zahlreiche Falten und Brüche im kristallinen Unterbau, die anscheinend durch Druck entstanden sind.

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The structure of the Dolomite-unit easily fits into the tectonic framework of the Southern Alps even if the Permian porphyry plate locally produced more fracturing.The dislocations of the Dolomites, in general, corresponds to West-Eastorientated folds and faulted overfolds. The porphyry plate mentioned and the rigid lenses of the Dolomites reefs have produced classic examples of selective tectonics.Tectonic of the Dolomites is due in part to decollements and sliding from inclined planes, but decollement surfaces of a regional nature are excluded, and the dislocations of the Dolomites-region are not only epidermic.Numerous folds and fractures intersect the basement as well and seem compressive.

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Résumé La structure des Dolomites s'intègre remarquablement bien dans le plan tectonique des Alpes Méridionales, bien que la présence de la dalle porphyrique permienne ait fréquemment, par endroit, provoqué des ruptures. Les dislocations des Dolomites font suite en général à des plis et à des plis-failles avec axes allant d'Ouest en Est et montrant de façon prédominante un déversement vers le Sud.La dalle porphyrique permienne et les lentilles des récifs des Dolomites font de cette région un exemple classique de «tectonique sélective». La tectonique des Dolomites repose en partie sur des phénomènes de décollement et de glissement le long de surfaces inclinées. Il y a de nombreux plis et fractures dans le soubassement cristallin qui, semble-t-il, résultent d'une compression.

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Phase relations in the partial melting of the Baldissero spinel-lherzolite (Ivrea-Verbano zone,Western Alps,Italy)

The occurrence of various types of mobilizates in the Baldissero spinel lherzolite is due to partial melting of the same body. The study of the relationships between the peridotite and its mobilizates demonstrates that olivine did not take an active part in the fusion. Estimates of the degree of partial melting vary from 10% for the average composition, to 20% for the most depleted samples. These values refer to an initial pyrolitic composition, and thus are relative, as they can vary depending on the actual primary composition.The calculated composition of the liquid generated by partial melting is quite similar to that of a picritic basalt, and is practically the same irrespective of the 10% and 20% fusion. This fact provides strong evidence that melting took place at a unique invariant point of the natural system, producing a liquid with a remarkably constant composition.Projection of the liquid in the fo-an-di-si diagram is fairly well aligned with the modal compositions of the solid residua, but does not coincide with the minimum of the simplified system. The proposed solution is based on the enlargement of the spinel field (at constant pressure), due to the Cr content in this phase. Therefore, the position of the invariant minimum is not fixed, but rather controlled by the Cr content of the spinel. Is is suggested that, by an increase in the Cr content, spinel might at a given moment become refractory. Thus, saturated or over-saturated magmas are produced depending on the phase relations between olivine, orthopyroxene and clinopyroxene. This would happen in the case of very advanced fusions or in the case of fusion of already depleted peridotites.The relationships between mobilizates of different generations suggest a non adiabatic mantle upwelling.     

Impact of climate warming on upper layer of the Bering Sea

The impact of climate warming on the upper layer of the Bering Sea is investigated by using a high-resolution coupled global climate model. The model is forced by increasing atmospheric CO₂ at a rate of 1% per year until CO₂ reaches double its initial value (after 70 years), after which it is held constant. In response to this forcing, the upper layer of the Bering Sea warms by about 2°C in the southeastern shelf and by a little more than 1°C in the western basin. The wintertime ventilation to the permanent thermocline weakens in the western Bering Sea. After CO₂ doubling, the southeastern shelf of the Bering Sea becomes almost ice-free in March, and the stratification of the upper layer strengthens in May and June. Changes of physical condition due to the climate warming would impact the pre-condition of spring bio-productivity in the southeastern shelf.     

Real-time multi-model decadal climate predictions

We present the first climate prediction of the coming decade made with multiple models, initialized with prior observations. This prediction accrues from an international activity to exchange decadal predictions in near real-time, in order to assess differences and similarities, provide a consensus view to prevent over-confidence in forecasts from any single model, and establish current collective capability. We stress that the forecast is experimental, since the skill of the multi-model system is as yet unknown. Nevertheless, the forecast systems used here are based on models that have undergone rigorous evaluation and individually have been evaluated for forecast skill. Moreover, it is important to publish forecasts to enable open evaluation, and to provide a focus on climate change in the coming decade. Initialized forecasts of the year 2011 agree well with observations, with a pattern correlation of 0.62 compared to 0.31 for uninitialized projections. In particular, the forecast correctly predicted La Niña in the Pacific, and warm conditions in the north Atlantic and USA. A similar pattern is predicted for 2012 but with a weaker La Niña. Indices of Atlantic multi-decadal variability and Pacific decadal variability show no signal beyond climatology after 2015, while temperature in the Niño3 region is predicted to warm slightly by about 0.5 °C over the coming decade. However, uncertainties are large for individual years and initialization has little impact beyond the first 4 years in most regions. Relative to uninitialized forecasts, initialized forecasts are significantly warmer in the north Atlantic sub-polar gyre and cooler in the north Pacific throughout the decade. They are also significantly cooler in the global average and over most land and ocean regions out to several years ahead. However, in the absence of volcanic eruptions, global temperature is predicted to continue to rise, with each year from 2013 onwards having a 50 % chance of exceeding the current observed record. Verification of these forecasts will provide an important opportunity to test the performance of models and our understanding and knowledge of the drivers of climate change.