Tree-ring growth variability in the Austrian Alps: the influence of site, altitude, tree species and climate

We present an extensive new network of ring-width chronologies, comprising data from 100 sites within the Austrian Eastern Alps, made up of multiple tree species. Principal components analysis and cluster analysis were used to identify five separate high-frequency tree-growth signals from these data. Tree-growth variability at these sites is explained by site altitude and species differences that moderate the effects of the annually varying climatic forcing on tree growth. Recently developed, two-century long gridded climate data sets for the Greater Alpine Region were used to assess the relationship between climate and tree growth. Tree growth at low altitudes is controlled mainly by spring-summer moisture availability. At high altitudes precipitation is no longer a limiting factor and growth is mostly determined by summer temperature. In the intermediate altitudinal range, we did not find any direct relationships with specific climatic variables. High-altitude chronologies suitable for reconstructing past temperatures and low-altitude chronologies suitable for reconstructing past precipitation were identified.     

Flow of Canadian basin deep water in the Western Eurasian Basin of the Arctic Ocean

The LOMROG 2007 expedition targeted the previously unexplored southern part of the Lomonosov Ridge north of Greenland together with a section from the Morris Jesup Rise to Gakkel Ridge. The oceanographic data show that Canadian Basin Deep Water (CBDW) passes the Lomonosov Ridge in the area of the Intra Basin close to the North Pole and then continues along the ridge towards Greenland and further along its northernmost continental slope. The CBDW is clearly evident as a salinity maximum and oxygen minimum at a depth of about 2000 m. The cross-slope sections at the Amundsen Basin side of the Lomonosov Ridge and further south at the Morris Jesup Rise show a sharp frontal structure higher up in the water column between Makarov Basin water and Amundsen Basin water. The frontal structure continues upward into the Atlantic Water up to a depth of about 300 m. The observed water mass division at levels well above the ridge crest indicates a strong topographic steering of the flow and that different water masses tend to pass the ridge guided by ridge-crossing isobaths at local topographic heights and depressions. A rough scaling analysis shows that the extremely steep and sharply turning bathymetry of the Morris Jesup Rise may force the boundary current to separate and generate deep eddies.     

Reconstruction of food conditions for Northeast Atlantic bivalve species based on Dynamic Energy Budgets

Required assimilated energy to support observed growth was reconstructed for four common bivalve species (Mya arenaria, Cerastoderma edule, Mytilus edulis and Macoma balthica) from various Northeast Atlantic coastal areas, along the species distributional range. The approach applied was based on the Dynamic Energy Budget (DEB) theory whereby observed growth patterns in the field, in combination with prevailing temperatures, were used to reconstruct the average food intake experienced in the field scaled to the maximum possible. For all species, results suggest food limitation over the range of locations. In general, reconstructed food intake indicated better conditions for C. edule compared to the other species, while M. edulis presented the lowest food conditions in all the areas. Despite the indications for a latitudinal trend in primary production, no clear pattern or relationship between reconstructed food conditions and latitude was observed suggesting that any trend may be overruled by local conditions.     

Dynamo-based scheme for forecasting the magnitude of solar activity cycles

In this paper we present a general framework for forecasting the smoothed maximum level of solar activity in a given cycle, based on a simple understanding of the solar dynamo. This type of forecasting requires knowledge of the Sun's polar magnetic field strength at the preceeding activity minimum. Because direct measurements of this quantity are difficult to obtain, we evaluate the quality of a number of proxy indicators already used by other authors which are physically related to the Sun's polar field. We subject these indicators to a rigorous statistical analysis, and specify in detail the analysis technique for each indicator in order to simplify and systematize reanalysis for future use. We find that several of these proxies are in fact poorly correlated or uncorrelated with solar activity, and thus are of little value for predicting activity maxima.We also present a scheme in which the predictions of the individual proxies are combined via an appropriately weighted mean to produce a compound prediction. We then apply the scheme to the current cycle 22, and estimate a maximum smoothed International sunspot number of 171 ± 26, which can be expressed alternatively as a smoothed 2800 MHz radio flux (F _10.7) of 211 ± 23 × (10^–22 Wm^–2Hz^–1), or as a smoothed sunspot area of 2660 ± 430 millionths of a solar disk. Once the actual maximum for cycle 22 has been established, we will have both additional statistics for all the proxy indicators, and a clearer indication of how accurately the present scheme can predict solar activity levels.     

Geochronology of the medium to high-grade metamorphic units of the Peloritani Mts., Sicily

The Peloritani Mountains are a fragment of an orogen variably attributed to the Alpine or Hercynian orogeny. On the basis of ³⁹Ar-⁴⁰Ar, U-Pb and Rb-Sr dating, the main metamorphism of the two medium–high grade metamorphic units, the Mela and Aspromonte Units, and most of the thrusting responsible for stacking the orogenic edifice are seen to be Hercynian. The main thrusting of the Aspromonte Unit over the lower grade units took place at 301±2 Ma. Brittle deformation during Tertiary reactivation of Hercynian thrust planes did not generate any rejuvenation of white micas in the studied sector. Our dataset shows a great complexity and we propose to unravel it by considering different levels of information. To first order, the Mela and Aspromonte Units differ in their metamorphic paths and their geochronological evolution. The Mela Unit shows generally younger ages (Carboniferous) than the Aspromonte Unit and, unlike the latter, was extensively retrogressed in greenschist facies. The Aspromonte Unit is itself geochronologically heterogeneous. Proterozoic ages are preserved both in titanite and in amphibole relics of one tectonic subunit; Devonian to Carboniferous amphibole ages are found in different other subunits; tertiary overprint is minor and spatially limited. We propose to consider the chronologically heterogeneous subunits as accreted pre-Hercynian terranes amalgamated late during the Hercynian orogeny. Micas in both units give scattered Mesozoic ³⁹Ar-⁴⁰Ar and Rb-Sr ages, with evidence for heterochemical mica generations. We interpret them as a result of widespread hydrothermal circulation event(s). Tertiary overprint is generally absent, with the exception of a small area near Messina where biotite and muscovite underwent a complex recrystallisation history in the interval between 48 and 61 Ma.An erratum to this article can be found at     

EUDOSSO: a space project for solar oscillations and long term variability relevant to climatic changes

The basic design and the scientific aims of the EUDOSSO project are described. EUDOSSO is a space instrument conceived for achieving very high accuracy and long term stability in measuring solar diameter time variations. Therefore it is suitable for measuring long periodg-modes, oblateness and long-term diameter variations possibly relevant to climatic changes.     

Piles under axial and torsional loads

An analysis of axially and torsionally loaded piles is presented in which the pile is treated as an elastic bar supported on two series of interacting non-linear axial and torsional springs. The characteristics of these springs depend on the soil properties and the diameter of the pile as well as on the interaction between the axial and torsional response. Predicted pile responses are compared to the results of model tests conducted on piles installed in a soft clay bed and loaded with combined axial and torsional loads. Both experimental results and theoretical predictions show that a torque applied to the pile head affects significantly the settlement and the axial bearing capacity of the pile.