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311.
In search of the Earth‐forming reservoir: Mineralogical,chemical, and isotopic characterizations of the ungrouped achondrite NWA 5363/NWA 5400 and selected chondrites
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Christoph Burkhardt Nicolas Dauphas Haolan Tang Mario Fischer‐Gödde Liping Qin James H. Chen Surya S. Rout Andreas Pack Philipp R. Heck Dimitri A. Papanastassiou 《Meteoritics & planetary science》2017,52(5):807-826
High‐precision isotope data of meteorites show that the long‐standing notion of a “chondritic uniform reservoir” is not always applicable for describing the isotopic composition of the bulk Earth and other planetary bodies. To mitigate the effects of this “isotopic crisis” and to better understand the genetic relations of meteorites and the Earth‐forming reservoir, we performed a comprehensive petrographic, elemental, and multi‐isotopic (O, Ca, Ti, Cr, Ni, Mo, Ru, and W) study of the ungrouped achondrites NWA 5363 and NWA 5400, for both of which terrestrial O isotope signatures were previously reported. Also, we obtained isotope data for the chondrites Pillistfer (EL6), Allegan (H6), and Allende (CV3), and compiled available anomaly data for undifferentiated and differentiated meteorites. The chemical compositions of NWA 5363 and NWA 5400 are strikingly similar, except for fluid mobile elements tracing desert weathering. We show that NWA 5363 and NWA 5400 are paired samples from a primitive achondrite parent‐body and interpret these rocks as restite assemblages after silicate melt extraction and siderophile element addition. Hafnium‐tungsten chronology yields a model age of 2.2 ± 0.8 Myr after CAI, which probably dates both of these events within uncertainty. We confirm the terrestrial O isotope signature of NWA 5363/NWA 5400; however, the discovery of nucleosynthetic anomalies in Ca, Ti, Cr, Mo, and Ru reveals that the NWA5363/NWA 5400 parent‐body is not the “missing link” that could explain the composition of the Earth by the mixing of known meteorites. Until this “missing link” or a direct sample of the terrestrial reservoir is identified, guidelines are provided of how to use chondrites for estimating the isotopic composition of the bulk Earth. 相似文献
312.
Keywan Riahi Shilpa Rao Volker Krey Cheolhung Cho Vadim Chirkov Guenther Fischer Georg Kindermann Nebojsa Nakicenovic Peter Rafaj 《Climatic change》2011,109(1-2):33-57
This paper summarizes the main characteristics of the RCP8.5 scenario. The RCP8.5 combines assumptions about high population and relatively slow income growth with modest rates of technological change and energy intensity improvements, leading in the long term to high energy demand and GHG emissions in absence of climate change policies. Compared to the total set of Representative Concentration Pathways (RCPs), RCP8.5 thus corresponds to the pathway with the highest greenhouse gas emissions. Using the IIASA Integrated Assessment Framework and the MESSAGE model for the development of the RCP8.5, we focus in this paper on two important extensions compared to earlier scenarios: 1) the development of spatially explicit air pollution projections, and 2) enhancements in the land-use and land-cover change projections. In addition, we explore scenario variants that use RCP8.5 as a baseline, and assume different degrees of greenhouse gas mitigation policies to reduce radiative forcing. Based on our modeling framework, we find it technically possible to limit forcing from RCP8.5 to lower levels comparable to the other RCPs (2.6 to 6 W/m2). Our scenario analysis further indicates that climate policy-induced changes of global energy supply and demand may lead to significant co-benefits for other policy priorities, such as local air pollution. 相似文献
313.
A swarm of earthquakes of magnitudes up to M
L = 3.8 stroke the region of West Bohemia/Vogtland (border area between Czechia and Germany) in October 2008. It occurred in
the Novy Kostel focal zone, where also all recent earthquake swarms (1985/1986, 1997, and 2000) took place, and was striking
by a fast sequence of macroseismically observed earthquakes. We present the basic characteristics of this swarm based on the
observations of a local network WEBNET (West Bohemia seismic network), which has been operated in the epicentral area, on
the Czech territory. The swarm was recorded by 13 to 23 permanent and mobile WEBNET stations surrounding the swarm epicenters.
In addition, a part of the swarm was also recorded by strong-motion accelerometers, which represent the first true accelerograms
of the swarm earthquakes in the region. The peak ground acceleration reached 0.65 m/s2. A comparison with previous earthquake swarms indicates that the total seismic moments released during the 1985/1986 and
2008 swarms are similar, of about 4E16 Nm, and that they represent the two largest swarms that occurred in the West Bohemia/
Vogtland region since the M
L = 5.0 swarm of 1908. Characteristic features of the 2008 swarm are its short duration (4 weeks) and rapidity and, consequently,
the fastest seismic moment release compared to previous swarms. Up to 25,000 events in the magnitude range of 0.5 < M
L < 3.8 were detected using an automatic picker. A total of nine swarm phases can be distinguished in the swarm, five of them
exceeding the magnitude level of 2.5. The magnitude–frequency distribution of the complete 2008 swarm activity shows a b value close to 1. The swarm hypocenters fall precisely on the same fault portion of the Novy Kostel focal zone that was activated
by the 2000 swarm (M
L ≤ 3.2) in a depth interval from 6 to 11 km and also by the 1985/1986 swarm (M
L ≤ 4.6). The steeply dipping fault planes of the 2000 and 2008 swarms seem to be identical considering the location error
of about 100 m. Furthermore, focal mechanisms of the 2008 swarm are identical with those of the 2000 swarm, both matching
an average strike of 170° and dip of 80° of the activated fault segment. An overall upward migration of activity is observed
with first events at the bottom and last events at the top of the of the activated fault patch. Similarities in the activated
fault area and in the seismic moments released during the three largest recent swarms enable to estimate the seismic potential
of the focal zone. If the whole segment of the fault plane was activated simultaneously, it would represent an earthquake
of M
L ~5. This is in good agreement with the estimates of the maximum magnitudes of earthquakes that occurred in the West Bohemia/Vogtland
region in the past. 相似文献
314.
R. Volkmer O. von der Lühe C. Denker S.K. Solanki H. Balthasar T. Berkefeld P. Caligari M. Collados A. Fischer C. Halbgewachs F. Heidecke A. Hofmann M. Klvaa F. Kneer A. Lagg E. Popow D. Schmidt W. Schmidt M. Sobotka D. Soltau K.G. Strassmeier 《Astronomische Nachrichten》2010,331(6):624-627
The integration and verification phase of the GREGOR telescope reached an important milestone with the installation of the interim 1 m SolarLite primary mirror. This was the first time that the entire light path had seen sunlight. Since then extensive testing of the telescope and its subsystems has been carried out. The integration and verification phase will culminate with the delivery and installation of the final 1.5 m Zerodur primary mirror in the summer of 2010. Observatory level tests and science verification will commence in the second half of 2010 and in 2011. This phase includes testing of the main optics, adaptive optics, cooling and pointing systems. In addition, assuming the viewpoint of a typical user, various observational modes of the GREGOR Fabry‐Pérot Interferometer (GFPI), the Grating Infrared Spectrograph (GRIS), and high‐speed camera systems will be tested to evaluate if they match the expectations and science requirements. This ensures that GREGOR will provide high‐quality observations with its combination of (multi‐conjugate) adaptive optics and advanced post‐focus instruments. Routine observations are expected for 2012 (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
315.
Seaports are located in vulnerable areas to climate change impacts: on coasts susceptible to sea-level rise and storms or at mouths of rivers susceptible to flooding. They serve a vital function within the local, regional, and global economy. Their locations in the heart of sensitive estuarine environments make it an imperative to minimize the impacts of natural hazards. Climate impacts, like a projected SLR of .6?m to 2?m and doubling of Category 4 and 5 hurricanes by 2100, will result in more extreme events at many seaports. To assess the current state of knowledge on this issue, we surveyed port authorities from around the world about how administrators felt climate change might impact their operations, what sea-level change would create operational problems, and how they planned to adapt to new environmental conditions. The planned rapid expansion of ports reported by the survey respondents indicates that adaptation measures should be considered as ports construct new infrastructure that may still be in use at the end of the century. Respondents agreed that the ports community needs to address this issue and most felt relatively uninformed about potential climate impacts. Although most ports felt that SLR would not be an issue at their port this century, sea-level rise was nevertheless an issue of great concern. Our results suggest opportunities for the scientific community to engage with port practitioners to prepare proactively for climate change impacts on this sector. 相似文献
316.
317.
Tianjun Zhou Stefan Brönnimann Thomas Griesser Andreas M. Fischer Liwei Zou 《Climate Dynamics》2010,34(4):573-585
The authors present a reconstruction of summer (June–July–August) mean dynamic Indian monsoon index (DIMI) back to 1880 based
on a large number of historical surface observation data as well as information from the upper air data. The reconstruction
shows a satisfying skill in terms of both the value of reduction of error and an evaluation against other independent monsoon
indices. The skill of reconstruction increases over time with more predictor data (in particular upper-level data) becoming
available. A comparison with the observed all Indian summer monsoon rainfall index (AIRI) shows a high consistence in both
inter-decadal and inter-annual variability. The reconstruction shows stronger than normal monsoon during the 1880s, 1915–1925
(around 1920) and 1930–1945 (around 1940) as the AIRI. The El Nino/Southern Oscillation (ENSO)—monsoon relationship is reasonably
captured in the reconstruction. Powers concentrating within quasi-biennial band stand out in the reconstruction as well as
in the AIRI. A comparison of the reconstruction against an atmospheric general circulation model simulation with specified
SST and external forcing agents spanning 1901–1999 indicates a slightly higher reproducibility of monsoon circulation than
monsoon rainfall in terms of interannual variability. The relationship between the Asian continent warming and the ENSO–monsoon
connection is also discussed by using the new dynamic index. 相似文献
318.
Anthropogenic greenhouse gas emissions are expected to lead to more frequent and intense summer temperature extremes, not only due to the mean warming itself, but also due to changes in temperature variability. To test this hypothesis, we analyse daily output of ten PRUDENCE regional climate model scenarios over Europe for the 2071–2100 period. The models project more frequent temperature extremes particularly over the Mediterranean and the transitional climate zone (TCZ, between the Mediterranean to the south and the Baltic Sea to the north). The projected warming of the uppermost percentiles of daily summer temperatures is found to be largest over France (in the region of maximum variability increase) rather than the Mediterranean (where the mean warming is largest). The underlying changes in temperature variability may arise from changes in (1) interannual temperature variability, (2) intraseasonal variability, and (3) the seasonal cycle. We present a methodology to decompose the total daily variability into these three components. Over France and depending upon the model, the total daily summer temperature variability is projected to significantly increase by 20–40% as a result of increases in all three components: interannual variability (30–95%), seasonal variability (35–105%), and intraseasonal variability (10–30%). Variability changes in northern and southern Europe are substantially smaller. Over France and parts of the TCZ, the models simulate a progressive warming within the summer season (corresponding to an increase in seasonal variability), with the projected temperature change in August exceeding that in June by 2–3 K. Thus, the most distinct warming is superimposed upon the maximum of the current seasonal cycle, leading to a higher intensity of extremes and an extension of the summer period (enabling extreme temperatures and heat waves even in September). The processes driving the variability changes are different for the three components but generally relate to enhanced land–atmosphere coupling and/or increased variability of surface net radiation, accompanied by a strong reduction of cloudiness, atmospheric circulation changes and a progressive depletion of soil moisture within the summer season. The relative contribution of these processes differs substantially between models. 相似文献
319.
F. Kucharski A. A. Scaife J. H. Yoo C. K. Folland J. Kinter J. Knight D. Fereday A. M. Fischer E. K. Jin J. Kröger N.-C. Lau T. Nakaegawa M. J. Nath P. Pegion E. Rozanov S. Schubert P. V. Sporyshev J. Syktus A. Voldoire J. H. Yoon N. Zeng T. Zhou 《Climate Dynamics》2009,33(5):615-627
The ability of atmospheric general circulation models (AGCMs), that are forced with observed sea surface temperatures (SSTs),
to simulate the Indian monsoon rainfall (IMR) variability on interannual to decadal timescales is analyzed in a multimodel
intercomparison. The multimodel ensemble has been performed within the CLIVAR International “Climate of the 20th Century”
(C20C) Project. This paper is part of a C20C intercomparison of key climate time series. Whereas on the interannual timescale
there is modest skill in reproducing the observed IMR variability, on decadal timescale the skill is much larger. It is shown
that the decadal IMR variability is largely forced, most likely by tropical sea surface temperatures (SSTs), but as well by
extratropical and especially Atlantic Multidecadal Oscillation (AMO) related SSTs. In particular there has been a decrease
from the late 1950s to the 1990s that corresponds to a general warming of tropical SSTs. Using a selection of control integrations
from the World Climate Research Programme’s (WCRP’s) Coupled Model Intercomparison Project phase 3 (CMIP3), it is shown that
the increase of greenhouse gases (GHG) in the twentieth century has not significantly contributed to the observed decadal
IMR variability. 相似文献
320.
Uncertainties in the climate response to a doubling of atmospheric CO2 concentrations are quantified in a perturbed land surface parameter experiment. The ensemble of 108 members is constructed by systematically perturbing five poorly constrained land surface parameters of global climate model individually and in all possible combinations. The land surface parameters induce small uncertainties at global scale, substantial uncertainties at regional and seasonal scale and very large uncertainties in the tails of the distribution, the climate extremes. Climate sensitivity varies across the ensemble mainly due to the perturbation of the snow albedo parameterization, which controls the snow albedo feedback strength. The uncertainty range in the global response is small relative to perturbed physics experiments focusing on atmospheric parameters. However, land surface parameters are revealed to control the response not only of the mean but also of the variability of temperature. Major uncertainties are identified in the response of climate extremes to a doubling of CO2. During winter the response both of temperature mean and daily variability relates to fractional snow cover. Cold extremes over high latitudes warm disproportionately in ensemble members with strong snow albedo feedback and large snow cover reduction. Reduced snow cover leads to more winter warming and stronger variability decrease. As a result uncertainties in mean and variability response line up, with some members showing weak and others very strong warming of the cold tail of the distribution, depending on the snow albedo parametrization. The uncertainty across the ensemble regionally exceeds the CMIP3 multi-model range. Regarding summer hot extremes, the uncertainties are larger than for mean summer warming but smaller than in multi-model experiments. The summer precipitation response to a doubling of CO2 is not robust over many regions. Land surface parameter perturbations and natural variability alter the sign of the response even over subtropical regions. 相似文献