Quantifying the AMOC feedbacks during a 2×CO2 stabilization experiment with land-ice melting   总被引：1，自引：0，他引：1  

D. Swingedouw  P. Braconnot  P. Delecluse  E. Guilyardi  O. Marti 《Climate Dynamics》2007,29(5):521-534

The response of the Atlantic Meridional Overturning Circulation (AMOC) to an increase in atmospheric CO₂ concentration is analyzed using the IPSL-CM4 coupled ocean–atmosphere model. Two simulations are integrated for 70 years with 1%/year increase in CO₂ concentration until 2×CO₂, and are then stabilized for further 430 years. The first simulation takes land-ice melting into account, via a simple parameterization, which results in a strong freshwater input of about 0.13 Sv at high latitudes in a warmer climate. During this scenario, the AMOC shuts down. A second simulation does not include this land-ice melting and herein, the AMOC recovers after 200 years. This behavior shows that this model is close to an AMOC shutdown threshold under global warming conditions, due to continuous input of land-ice melting. The analysis of the origin of density changes in the Northern Hemisphere convection sites allows an identification as to the origin of the changes in the AMOC. The processes that decrease the AMOC are the reduction of surface cooling due to the reduction in the air–sea temperature gradient as the atmosphere warms and the local freshening of convection sites that results from the increase in local freshwater forcing. Two processes also control the recovery of the AMOC: the northward advection of positive salinity anomalies from the tropics and the decrease in sea-ice transport through the Fram Strait toward the convection sites. The quantification of the AMOC related feedbacks shows that the salinity related processes contribute to a strong positive feedback, while feedback related to temperature processes is negative but remains small as there is a compensation between heat transport and surface heat flux in ocean–atmosphere coupled model. We conclude that in our model, AMOC feedbacks amplify land-ice melting perturbation by 2.5.  相似文献   

Global Positioning System measurements of strain accumulation and slip transfer through the restraining bend along the Dead Sea fault system in Lebanon   总被引：1，自引：0，他引：1  

Francisco Gomez  Gebran Karam  Mohamad Khawlie  Simon McClusky  Philippe Vernant  Robert Reilinger  Rani Jaafar  Charles Tabet  Kamal Khair  Muawia Barazangi 《Geophysical Journal International》2007,168(3):1021-1028

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Synchronicity in Climate and Vegetation Transitions Between Europe and North America During the Holocene     

K. Gajewski  André E. Viau  Michael Sawada  David E. Atkinson  Philippe Fines 《Climatic change》2006,78(2-4):341-361

Interpreting the postglacial climate history of the European continent using pollen data has proven difficult due in part to human modification of the landscape. Separating climate from human-caused changes in the vegetation requires a strategy for determining times of change across the entire region. We quantified transitions in the vegetation across Europe during the past 12,000 years using a mixture model approach on two datasets: radiocarbon dates from pollen diagrams and zone boundaries from selected reference sites. Major transitions in the vegetation, as recorded in pollen diagrams, appear synchronous across the continent. These transitions were also synchronous with those identified in North America pollen diagrams and major environmental changes recorded in North Atlantic marine records and Greenland ice cores. This synchronicity suggests that the major vegetation transitions in Europe during the Holocene and late glacial were primarily caused by large-scale atmospheric circulation change. These climate changes may have caused some of the cultural, political and migration changes in European societies during the Holocene.  相似文献   

Past and future polar amplification of climate change: climate model intercomparisons and ice-core constraints   总被引：2，自引：2，他引：2  

V. Masson-Delmotte  M. Kageyama  P. Braconnot  S. Charbit  G. Krinner  C. Ritz  E. Guilyardi  J. Jouzel  A. Abe-Ouchi  M. Crucifix  R. M. Gladstone  C. D. Hewitt  A. Kitoh  A. N. LeGrande  O. Marti  U. Merkel  T. Motoi  R. Ohgaito  B. Otto-Bliesner  W. R. Peltier  I. Ross  P. J. Valdes  G. Vettoretti  S. L. Weber  F. Wolk  Y. YU 《Climate Dynamics》2006,26(5):513-529

Climate model simulations available from the PMIP1, PMIP2 and CMIP (IPCC-AR4) intercomparison projects for past and future climate change simulations are examined in terms of polar temperature changes in comparison to global temperature changes and with respect to pre-industrial reference simulations. For the mid-Holocene (MH, 6,000 years ago), the models are forced by changes in the Earth’s orbital parameters. The MH PMIP1 atmosphere-only simulations conducted with sea surface temperatures fixed to modern conditions show no MH consistent response for the poles, whereas the new PMIP2 coupled atmosphere–ocean climate models systematically simulate a significant MH warming both for Greenland (but smaller than ice-core based estimates) and Antarctica (consistent with the range of ice-core based range). In both PMIP1 and PMIP2, the MH annual mean changes in global temperature are negligible, consistent with the MH orbital forcing. The simulated last glacial maximum (LGM, 21,000 years ago) to pre-industrial change in global mean temperature ranges between 3 and 7°C in PMIP1 and PMIP2 model runs, similar to the range of temperature change expected from a quadrupling of atmospheric CO₂ concentrations in the CMIP simulations. Both LGM and future climate simulations are associated with a polar amplification of climate change. The range of glacial polar amplification in Greenland is strongly dependent on the ice sheet elevation changes prescribed to the climate models. All PMIP2 simulations systematically underestimate the reconstructed glacial–interglacial Greenland temperature change, while some of the simulations do capture the reconstructed glacial–interglacial Antarctic temperature change. Uncertainties in the prescribed central ice cap elevation cannot account for the temperature change underestimation by climate models. The variety of climate model sensitivities enables the exploration of the relative changes in polar temperature with respect to changes in global temperatures. Simulated changes of polar temperatures are strongly related to changes in simulated global temperatures for both future and LGM climates, confirming that ice-core-based reconstructions provide quantitative insights on global climate changes. An erratum to this article can be found at  相似文献   

Soil surface characteristics influence on infiltration in black marls: application to the Super‐Sauze earthflow (southern Alps,France)     

Jean‐Philippe Malet  Anne‐Veronique Auzet  Olivier Maquaire  Bruno Ambroise  Luc Descroix  Michel Esteves  Jean‐Pierre Vandervaere  Emmanuel Truchet 《地球表面变化过程与地形》2003,28(5):547-564

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On the Origin of Near-Surface Streaks in the Neutrally-Stratified Planetary Boundary Layer     

Philippe Drobinski  Ralph C. Foster 《Boundary-Layer Meteorology》2003,108(2):247-256

The dynamics of near-surface streak formation in the neutrallystratified, rotating planetary boundary layer areinvestigated. The purpose of this note is to compare large-eddysimulation results to theoretical predictions suggesting thatstreaks are associated with non-normal mode optimal perturbations.Streaks are regions near the surface of alternating high and lowspeed fluid organized into nearly linear bands, with horizontalspacing of several hundred metres, oriented up to 30° relativeto the geostrophic wind, that evolve through a continuous cycle ofgeneration, growth, decay and reformation. We find that the earlystages of streak formation and growth are consistent with thelinear theory.  相似文献   

Comparative geochemistry of cadmium, rhenium, uranium, and molybdenum in continental margin sediments     

BjØrn Sundby  Philippe Martinez  Charles Gobeil 《Geochimica et cosmochimica acta》2004,68(11):2485-2493

The concentrations of authigenic phases of Cd, Re, U, and Mo increase with depth in four 45-cm-long sediment box cores collected along the axis of the Laurentian Trough, Gulf of St. Lawrence. Average authigenic accumulation rates, estimated from element inventories, are similar to rates in other continental margin environments. Strong regional variations in sediment accumulation rate and sulfide concentration have little influence on the accumulation rates of Cd and Re. This suggests that slow precipitation kinetics controls the accumulation of Cd and Re in these sediments. The accumulation rate of authigenic U is more variable; it may be tied to the kinetics of microbially mediated U reduction and be controlled by the availability of reactive organic matter. Authigenic Mo is distinguished by a sharp subsurface concentration minimum, above which Mo cycles with manganese. Mo released to pore water upon reduction of Mn oxides diffuses downward and enriches the subsurface sediment. Mo accumulates most rapidly in the sediment with the highest sulfide content. Slow conversion of molybdate to thiomolybdate may explain the much slower Mo accumulation rate in the less sulfidic sediments. A component of authigenic Mo accumulates with pyrite in an approximately constant Mo:Fe ratio. The accumulation rate of pyrite and associated Mo is insensitive to AVS abundance. Pyrite formation may be limited by the reactivity of iron oxide minerals.  相似文献   

From rifting to spreading in the eastern Gulf of Aden: a geophysical survey of a young oceanic basin from margin to margin   总被引：1，自引：0，他引：1  

Sylvie Leroy  Pascal Gente  Marc Fournier  Elia d'Acremont  Philippe Patriat  Marie-Odile Beslier  Nicolas Bellahsen  Marcia Maia  Angelina Blais  Julie Perrot  Ali Al-Kathiri  Serge Merkouriev  Jean-Marc Fleury  Pierre-Yves Ruellan  Claude Lepvrier  Philippe Huchon 《地学学报》2004,16(4):185-192

A geophysical survey in the eastern Gulf of Aden, between the Alula–Fartak (52°E) and the Socotra (55°E) transform faults, was carried out during the Encens–Sheba cruise. The conjugate margins of the Gulf are steep, narrow and asymmetric. Asymmetry of the rifting process is highlighted by the conjugate margins (horst and graben in the north and deep basin in the south). Two transfer fault zones separate the margins into three segments, whereas the present‐day Sheba Ridge is divided into two segments by a transform discontinuity. Therefore segmentation of the Sheba Ridge and that of the conjugate margins did coincide during the early stages of oceanic spreading. Extensive magma production is evidenced in the central part of the western segment. Anomaly 5d was identified in the northern and southern parts of the oceanic basin, thus confirming that seafloor spreading in this part of Gulf of Aden started at least 17.6 Ma ago.  相似文献   

History and origin of aubrites     

S. Lorenzetti  O. Eugster  K. Marti  T. McCoy 《Geochimica et cosmochimica acta》2003,67(3):557-571

The cosmic ray exposure (CRE) ages of aubrites are among the longest of stone meteorites. New aubrites have been recovered in Antarctica, and these meteorites permit a substantial extension of the database on CRE ages, compositional characteristics, and regolith histories. We report He, Ne, and Ar isotopic abundances of nine aubrites and discuss the compositional data, the CRE ages, and regolith histories of this class of achondrites. A Ne three-isotope correlation reveals a solar-type ratio of ²⁰Ne/²²Ne = 12.1, which is distinct from the present solar wind composition and lower than most ratios observed on the lunar surface. For some aubrites, the cosmic ray-produced noble gas abundances include components produced on the surface of the parent object. The Kr isotopic systematics reveal significant neutron-capture-produced excesses in four aubrites, which is consistent with Sm and Gd isotopic anomalies previously documented in some aubrites. The nominal CRE ages confirm a non-uniform distribution of exposure times, but the evidence for a CRE age cluster appears doubtful. Six meteorites are regolith breccias with solar-type noble gases, and the observed neutron effects indicate a regolith history. ALH aubrites, which were recovered from the same location and are considered to represent a multiple fall, yield differing nominal CRE ages and, if paired, document distinct precompaction histories.  相似文献   

Response to the comment by R. H. Byrne on “Solubility of platinum in aqueous solutions at 25°c and pHs 4 to 10 under oxidizing conditions” (2001) Geochim. Cosmochim. Acta65, 4453-4466     

Mohamed Azaroual  Bruno Romand  Philippe Freyssinet 《Geochimica et cosmochimica acta》2003,67(13):2511-2513

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