Chironomid-inferred temperature changes of the last century in anoxic Seebergsee,Switzerland: assessment of two calibration methods     

Isabelle Larocque-Tobler  Roberto Quinlan  Monique M. Stewart  Martin Grosjean 《Quaternary Science Reviews》2011,30(13-14):1770-1779

Chironomids (non-biting midges) can provide accurate climate reconstructions from the Late Glacial to the present. Until now, anoxic lakes have been avoided for temperature reconstructions since chironomid assemblages are sensitive to changes in oxygen concentrations in the hypolimnion. However, anoxic lakes may have varved sediments, providing the possibility for near-annual climate reconstructions. Here, we tested the applicability of two calibration methods to reconstruct mean July air temperatures from chironomid assemblages preserved in the sediments of the anoxic Seebergsee located in the northern Swiss Alps: a calibration-in-space approach and a calibration-in-time approach. The calibration-in-space approach (i.e. chironomid assemblages from surficial lake sediments (0–1 cm) calibrated against meteorological data) provided accurate inferences (i.e. similar temperature changes as measured at the closest meteorological station, and at regional stations) in the Seebergsee stratigraphy until anoxia increased in the lake. With the increase of anoxia, the chironomid-inferred temperatures were generally colder than measured temperatures. A calibration-in-time approach (i.e. calibration of chironomid assemblages in a time series against instrumental data from the closest meteorological station) provided accurate reconstructions (i.e. similar to the regional records) for the past 100 years, including the time period of inferred anoxia. However, its applicability should be further tested on longer temporal scales.  相似文献   

A new experimental technique for extracting liquids from peridotite at very low degrees of melting: application to partial melting of depleted peridotite   总被引：4，自引：0，他引：4  

Didier?LaporteEmail author  Michael?J.?Toplis  Monique?Seyler  Jean-Luc?Devidal 《Contributions to Mineralogy and Petrology》2004,146(4):463-484

A new technique that allows extraction of liquids from peridotite at degrees of melting as low as 0.2 wt% is presented. Microfractures that formed in the graphite sample container at the beginning of the experiments were used as traps for the liquid phase. Glass-filled cracks (or 'microdikes') unaffected by quench crystallisation were produced in all experiments and were analysed using standard electron microprobe techniques. Reversal experiments demonstrated that, at moderate degrees of melting (4.4 and 6.5 wt%), the segregated liquid was in equilibrium with the neighbouring peridotite. At very low degrees of melting (0.3 wt%), the liquid in the microdikes failed to fully equilibrate with the peridotite after 5 days and the sandwich technique was used in combination with the microdike technique to approach more closely the equilibrium composition of near-solidus partial melts. The microdike technique was used to study melting of a depleted peridotite at 1 GPa and 1,220 to 1,360 °C.Editorial responsibility: T.L. Grove  相似文献   

On the errors on Ω₀: Monte Carlo simulations of the EMSS cluster sample     

Jamila Oukbir  Monique Arnaud 《Monthly notices of the Royal Astronomical Society》2001,326(2):453-462

We perform Monte Carlo simulations of synthetic EMSS cluster samples, to quantify the systematic errors and the statistical uncertainties on the estimate of Ω₀ derived from fits to the cluster number density evolution and to the X-ray temperature distribution up to z =0.83 . We identify the scatter around the relation between cluster X-ray luminosity and temperature to be a source of systematic error, of the order of Δ_systΩ₀=0.09 , if not properly taken into account in the modelling. After correcting for this bias, our best Ω₀ is 0.66. The uncertainties on the shape and normalization of the power spectrum of matter fluctuations imply relatively large uncertainties on this estimate of Ω₀, of the order of Δ_statΩ₀=0.1 at the 1 σ level. On the other hand, the statistical uncertainties due to the finite size of the high-redshift sample are twice as small. Therefore, what is needed in order to improve the accuracy of Ω₀ estimates based on cluster number density evolution is a more reliable measure of the local temperature function and a better understanding of the cluster observed properties both in the local Universe and at high redshift, that is the relation between cluster mass, temperature and luminosity. This requires detailed observations of X-ray selected cluster samples, in comparison with hydrodynamic simulations including refined physics.  相似文献   

Influence of bioturbation by the polychaete Nereis diversicolor on the structure of bacterial communities in oil contaminated coastal sediments   总被引：1，自引：0，他引：1  

Cuny P  Miralles G  Cornet-Barthaux V  Acquaviva M  Stora G  Grossi V  Gilbert F 《Marine pollution bulletin》2007,54(4):452-459

Patterns of change in the structure of bacterial communities monitored by ribosomal intergenic spacer analysis (RISA) in oil contaminated sediments inhabited or not by the marine polychaete Nereis diversicolor were studied during 45 days under laboratory conditions. Results supported by principal component analysis showed a marked response of the bacterial communities to the oil contamination and to the presence of N. diversicolor. Phylogenetic affiliation of specific RISA bands showed that, in the contaminated sediments, the presence of the marine polychaetes favoured the development of bacteria which may play an active role in natural bioremediation processes of oil polluted environments.  相似文献