Winter synoptic-scale variability over the Mediterranean Basin under future climate conditions as simulated by the ECHAM5   总被引：3，自引：1，他引：2  

Christoph Cornelius Raible  Baruch Ziv  Hadas Saaroni  Martin Wild 《Climate Dynamics》2010,35(2-3):473-488

Changes of the winter climate in the Mediterranean Basin (MB) for future A2 conditions are investigated for the period 2071–2100 and compared with the control period 1961–1990. The analysis is based on time-slice simulations of the latest version of the ECHAM model. First, the control simulation is evaluated with reanalysis data. The emphasis is given to synoptic and large-scale features and their variability in the MB. The model is found to be capable of reproducing the main features of the MB and southern Europe in the winter season. Second, the A2 simulation is compared with the control simulation, revealing considerable changes of the synoptic variability. Focusing on the synoptic spatio-temporal scale aims to unfold the dynamic background of the climatic changes. The Mediterranean cyclones, which are individually detected and tracked, decrease by 10% in the Western Mediterranean (WM) whereas no significant change is found in the Eastern Mediterranean. The cyclone intensity is slightly reduced in the entire region. To understand these changes, the underlying dynamical background is analyzed. It is found that changes in baroclinicity, static stability, transformation from eddy kinetic energy to kinetic energy of the mean flow and stationary wave activity are significant in particular in the WM and the coastline of North Africa. The reduction of cyclonic activity severely impacts the precipitation mainly in the southern part of the WM.  相似文献   

10Be and 26Al exposure‐age dating of bedrock surfaces on the Aran ridge,Wales: evidence for a thick Welsh Ice Cap at the Last Glacial Maximum     

Neil F. Glasser  Philip D. Hughes  Cassandra Fenton  Christoph Schnabel  Henrik Rother 《第四纪科学杂志》2012,27(1):97-104

This paper presents results of the analysis of paired cosmogenic isotopes (¹⁰Be and ²⁶Al) from eight quartz‐rich samples collected from ice‐moulded bedrock on the Aran ridge, the highest land in the British Isles south of Snowdon. On the Aran ridge, comprising the summits of Aran Fawddwy (905 m a.s.l.) and Aran Benllyn (885 m a.s.l.), ²⁶Al and ¹⁰Be ages indicate complete ice coverage and glacial erosion at the global Last Glacial Maximum (LGM). Six samples from the summit ridge above 750–800 m a.s.l. yielded paired ¹⁰Be and ²⁶Al ages ranging from 17.2 to 34.4 ka, respectively. Four of these samples are very close in age (¹⁰Be ages of 17.5 ± 0.6, 17.5 ± 0.7, 19.7 ± 0.8 and 20.0 ± 0.7 ka) and are interpreted as representing the exposure age of the summit ridge. Two other summit samples are much older (¹⁰Be ages of 27.5 ± 1.0 and 33.9 ± 1.2 ka) and these results may indicate nuclide inheritance. The ²⁶Al/¹⁰Be ratios for all samples are indistinguishable within one‐sigma uncertainty from the production rate ratio line, indicating that there is no evidence for a complex exposure history. These results indicate that the last Welsh Ice Cap was thick enough to completely cover the Aran ridge and achieve glacial erosion at the LGM. However, between c. 20 and 17 ka ridge summits were exposed as nunataks at a time when glacial erosion at lower elevations (below 750–800 m a.s.l.) was achieved by large outlet glaciers in the valleys surrounding the mountains. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Deciphering signals of late Holocene fluvial and aeolian supply from a shelf sediment depocentre off Senegal (north‐west Africa)     

Jean Nizou  Till J.J. Hanebuth  Christoph Vogt 《第四纪科学杂志》2011,26(4):411-421

High‐resolution climatic records of the late Holocene along the north‐west African continental margin are scarce. Here we combine sediment grain size, elemental distribution and mineral assemblage data to trace dust and riverine sources at a shallow‐marine sediment depocentre in the vicinity of the Senegal River mouth. The aim is to understand how these terrigenous components reflect climate variability during the late Holocene. Major element contents were measured and mineral identification was performed on three sub‐fractions of our sediment core: (i) fluvial material < 2 µm, (ii) aeolian material of 18–63 µm and (iii) a sub‐fraction of dual‐origin material of 2–18 µm. Results show that more than 80% of the total Al and Fe terrigenous bulk content is present in the fluviogenic fraction. In contrast, Ti, K and Si cannot be considered as proxies for one specific source off Senegal. The Al/Ca ratio, recording the continental river runoff, reveals two dry periods from 3010 to 2750 cal a BP and from 1900 to 1000 cal a BP, and two main humid periods from 2750 to 1900 cal a BP and from 1000 to 700 cal a BP. The match between (i) intervals of low river runoff inferred by low Al/Ca values, (ii) reduced river discharge inferred by integrated palynological data from offshore Senegal and (iii) periods of enhanced dune reactivation in Mali confirms this interpretation. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Tropical glacier fluctuations in the Cordillera Blanca,Peru between 12.5 and 7.6 ka from cosmogenic 10Be dating     

Neil F. Glasser  Samuel Clemmens  Christoph Schnabel  Cassandra R. Fenton  Lanny McHargue 《Quaternary Science Reviews》2009,28(27-28):3448-3458

We report cosmogenic surface exposure ¹⁰Be ages of 21 boulders on moraines in the Jeullesh and Tuco Valleys, Cordillera Blanca, Peru (～10°S at altitudes above 4200 m). Ages are based on the sea-level at high-latitude reference production rate and scaling system of Lifton et al. (2005. Addressing solar modulation and long-term uncertainties in scaling secondary cosmic rays for in situ cosmogenic nuclide applications. Earth and Planetary Science Letters 239, 140–161) in the CRONUS-Earth online calculator of Balco et al. (2008. A complete and easily accessible means of calculating surface exposure ages or erosion rates from ¹⁰Be and ²⁶Al measurements. Quaternary Geochronology 3, 174–195). Using the Lifton system, large outer lateral moraines in the Jeullesh Valley have a ¹⁰Be exposure age of 12.4 ka, inside of which are smaller moraine systems dated to 10.8, 9.7 and 7.6 ka. Large outer lateral moraines in the Tuco Valley have a ¹⁰Be exposure age of 12.5 ka, with inner moraines dated to 11.3 and 10.7 ka. Collectively, these data indicate that glacier recession from the Last Glacial Maximum (LGM) in the Cordillera Blanca was punctuated by three to four stillstands or minor advances during the period 12.5–7.6 ka, spanning the Younger Dryas Chronozone (YDC; ～12.9–11.6 ka) and the cold event identified in Greenland ice cores and many other parts of the world at 8.2 ka. The inferred fluctuations of tropical glaciers at these times, well after their withdrawal from the LGM, indicate an increase in precipitation or a decrease in temperature in this region. Although palaeoenvironmental records show regional and temporal variability, comparison with proxy records (lacustrine sediments and ice cores) indicate that regionally this was a cold, dry period so we ascribe these glacier advances to reduced atmospheric temperature rather than increased precipitation.  相似文献   

Chronology of the Last Glacial Maximum in the Salzach palaeoglacier area (Eastern Alps)     

Reinhard Starnberger  Helena Rodnight  Christoph Spötl 《第四纪科学杂志》2011,26(5):502-510

A chronostratigraphy based on luminescence data was established at a key loess profile (Duttendorf) in the northern alpine foreland of Austria. The data help to constrain the timing and duration of the Last Glacial Maximum (LGM) in the area of one of the largest east Alpine piedmont glaciers, the Salzach palaeoglacier. Climate deterioration and maximum advance of this glacier were coeval with the beginning of the main loess accumulation phase in the glacier forefield at ～29–30 ka. A late LGM‐outwash gravel layer deposited on top of the loess profile marks the end of the LGM glacier activity at ～20 ka. The geomorphological setting around the loess profile provides evidence of a major glacier oscillation during the course of the LGM, a phenomenon qualitatively known from other alpine palaeoglaciers but never interpreted in terms of palaeoclimate. A LGM glacier oscillation similar to that of the Salzach palaeoglacier was reported recently from the south Alpine Tagliamento palaeoglacier, suggesting a common forcing. The onset of loess deposition at Duttendorf and the tentatively contemporal advance of the Salzach palaeoglacier reflect, as do other data, the drastic cooling in Europe as a result of Heinrich event 3. The first glacier maximum is not well constrained in the study area but a correlation with the better dated Tagliamento amphitheatre suggests a possible response to Heinrich 2. The second re‐advance occurred synchronously (within dating uncertainties) in both palaeoglaciers forefields (at ～21 ka) but the forcing mechanism remains unknown. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Coupling Size-Exclusion Chromatography and ICP-MS to Investigate the Speciation of Platinum-Group Elements in Environmental Samples     

Christoph M. Menzel  Zsolt Berner  Doris Stüben 《Geostandards and Geoanalytical Research》2001,25(2-3):239-251

The applicability of size-exclusion chromatography (SEC) coupled online with a high resolution ICP-MS (HR-ICP-MS) to investigate the speciation of the platinum-group elements (PGE), Rh, Pd and Pt, was evaluated. Experiments were carried out to determine the efficiency of different hydrophilic and hydrophobic size-exclusion gel materials to select the optimal eluent in respect of resolution, recovery, reproducibility and limit of detection. The suitability of HR-ICP-MS as a reliable detection instrument at low pg ml⁻¹ levels was investigated by examining possible mass interferences with Rh, Pd and Pt. Laboratory experiments demonstrated the interaction and capability of forming complexes of humic substances with PGE, demonstrating the potential role of these ubiquitous natural substances in the mobilisation of PGE in the environment.  相似文献   

Zur Messung der Fahrt über Grund an Bord von Schiffen     

Peter Christoph 《Ocean Dynamics》1958,11(3):113-124

Zusammenfassung Es wird gezeigt, wie mit einem Zweikreiselsystem, das gleichzeitig die Nordrichtung und den Horizont liefert, ein Trägheits-Navigationssystem unter Verwendung von Beschleunigungsmessern und eines Rechenaggregates aufgebaut werden kann. Die Beschleunigungsmesser werden von einer kreiselstabilisierten Plattform getragen, die über Stützmotore in den drei Freiheitsgraden parallel zum Zweikreiselsystem gehalten wird.

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On measuring a ship's speed over ground from board of ships

Summary The following paper explains how to assemble an inertial navigation system with the aid of accelerometers, a calculating unit and a two gyro system that simultaneously indicates the north direction and the horizon. The accelerometers are carried by a gyro stabilized platform that, on its part, is kept in the three degrees of freedom parallel to the two gyro system by three torques generators.

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Sur la mesure à bord d'un bâtiment pour déterminer la vitesse par-dessus le fond de la mer

Résumé Le travail suivant expose de quelle manière on peut construire un système de navigation d'inertie en joignant des accéléromètres, un aggrégat à calculer et un système à deux gyroscopes; ce dernier fournit simultanément la direction nord et l'horizon. Une plate-forme, également stabilisée par un système à deux gyroscopes, porte les accéléromètres. Cette plate-forme se maintient à l'aide de trois génératrices du moment de couple dans les trois degrés de. liberté parallèle au système à deux gyroscopes.

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On the sensitivity of theφ m function tok: A corrected illustration for “the turbulent kinetic energy budget in the asl”     

Paul Frenzen  Christoph A. Vogel 《Boundary-Layer Meteorology》1994,68(4):439-442

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Durch Fahrtmanöver verursachte Anzeigefehler beim nicht-Schuler-abgestimmten Einkreiselkompaß mit Ballistik     

Dr. Peter Christoph  Günter Chodinski 《Ocean Dynamics》1978,31(4):107-120

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Natural and synthetic ferroglaucophane     

Christoph Hoffmann 《Contributions to Mineralogy and Petrology》1972,34(2):135-149

Amphiboles approximating the composition of the ferroglaucophane end member, Na₂Fe₃Al₂Si₈O₂₂(OH)₂, have not been found in nature prior to 1969. Chemical, physical and petrologic data of four specimens of that mineral are given, two from Southern Italy and two from New Caledonia (Black, 1970). The ferroglaucophane end member was synthesized in seeded runs at 500° C, 5000 bars fluid pressure with oxygen fugacity defined by the wüstite-magnetite (WM) buffer. X-ray data and cell dimensions (a=9.686 Å, b=17.89, c=5.317, β=103° 45.2′ V=894.9 ų) are presented along with microprobe data that confirm the end member composition. Under these conditions of synthesis the ferroglaucophane grew metastably, however. Stability relations of the synthetic end member and of one natural specimen were investigated in a temperature range from 250° C to 500° C and at 3 and 5 kb with different oxygen buffers. At relatively low oxygen fugacities (WM buffer, QFM buffer) ferroglaucophane breaks down above 350–360° C. Under more oxidizing conditions (HM buffer) ferroglaucophane may not be stable even at very low temperatures. Mineral facies and chemical bulk composition of rocks that would favor the natural occurrence of ferroglaucophane are discussed. As assemblages with ferroglaucophane can have crystallized only below a very specific upper temperature limit, it is proposed to direct some attention towards that mineral.  相似文献