Mid-Holocene and Last Glacial Maximum climate simulations with the IPSL model—part I: comparing IPSL_CM5A to IPSL_CM4   总被引：1，自引：0，他引：1  

Masa Kageyama  Pascale Braconnot  Laurent Bopp  Arnaud Caubel  Marie-Alice Foujols  Eric Guilyardi  Myriam Khodri  James Lloyd  Fabien Lombard  Véronique Mariotti  Olivier Marti  Tilla Roy  Marie-Noëlle Woillez 《Climate Dynamics》2013,40(9-10):2447-2468

The climates of the mid-Holocene (MH), 6,000 years ago, and of the Last Glacial Maximum (LGM), 21,000 years ago, have extensively been simulated, in particular in the framework of the Palaeoclimate Modelling Intercomparion Project. These periods are well documented by paleo-records, which can be used for evaluating model results for climates different from the present one. Here, we present new simulations of the MH and the LGM climates obtained with the IPSL_CM5A model and compare them to our previous results obtained with the IPSL_CM4 model. Compared to IPSL_CM4, IPSL_CM5A includes two new features: the interactive representation of the plant phenology and marine biogeochemistry. But one of the most important differences between these models is the latitudinal resolution and vertical domain of their atmospheric component, which have been improved in IPSL_CM5A and results in a better representation of the mid-latitude jet-streams. The Asian monsoon’s representation is also substantially improved. The global average mean annual temperature simulated for the pre-industrial (PI) period is colder in IPSL_CM5A than in IPSL_CM4 but their climate sensitivity to a CO₂ doubling is similar. Here we show that these differences in the simulated PI climate have an impact on the simulated MH and LGM climatic anomalies. The larger cooling response to LGM boundary conditions in IPSL_CM5A appears to be mainly due to differences between the PMIP3 and PMIP2 boundary conditions, as shown by a short wave radiative forcing/feedback analysis based on a simplified perturbation method. It is found that the sensitivity computed from the LGM climate is lower than that computed from 2 × CO₂ simulations, confirming previous studies based on different models. For the MH, the Asian monsoon, stronger in the IPSL_CM5A PI simulation, is also more sensitive to the insolation changes. The African monsoon is also further amplified in IPSL_CM5A due to the impact of the interactive phenology. Finally the changes in variability for both models and for MH and LGM are presented taking the example of the El-Niño Southern Oscillation (ENSO), which is very different in the PI simulations. ENSO variability is damped in both model versions at the MH, whereas inconsistent responses are found between the two versions for the LGM. Part 2 of this paper examines whether these differences between IPSL_CM4 and IPSL_CM5A can be distinguished when comparing those results to palaeo-climatic reconstructions and investigates new approaches for model-data comparisons made possible by the inclusion of new components in IPSL_CM5A.  相似文献   

The effects of brine disposal on a subtidal meiofauna community     

Rodrigo Riera  Fernando Tuya  Alicia Sacramento  Eva Ramos  Myriam Rodríguez  Óscar Monterroso 《Estuarine, Coastal and Shelf Science》2011

Desalination plants generate notable (>1,000 s m³) quantities of hypersaline brine which potentially affect the biological communities in the receiving area. We assessed whether proximity to a brine discharge point located off Gran Canaria (Canary Islands, eastern Atlantic) altered patterns in the abundance and assemblage structure of subtidal, soft-bottom, meiofauna. Samples were collected twice (May 2008 and January 2009) at 0, 15 and 30 m away from the brine discharge point, corresponding to a change in salinity from 45 to 36. Proximity to the brine discharge point affected overall meiofaunal abundances: lowest abundances were observed at 0 m (64.55 ± 39.86 ind 10 cm⁻², mean ± SD) than at 15 (210.49 ± 121.01 ind 10 cm⁻²) and 30 m (361.88 ± 102.64 ind 10 cm⁻²) away from the brine discharge point. This pattern was particularly notable for the most conspicuous meiofaunal groups: nematodes and copepods, and meiofaunal assemblage structure also differed with varying proximity to the brine discharge point. Although multivariate techniques identified changes in salinity as a relevant driver of patterns in meiofaunal assemblage structure with varying proximity to the brine outfall, a shift in particle size composition between May 2008 and January 2009 also contributed to explain differences in meiofaunal abundances and assemblage structure with varying proximity to the brine discharge point. Hence, meiofauna can be considered a suitable tool to monitor environmental impacts derived from the discharge of hypersaline effluents on subtidal, soft-bottom, assemblages if potential confounding drivers, i.e. here temporal changes in particle size composition, are accounted for to avoid possible confusing interpretations.  相似文献   

“传统”农业景观旅游保护困局的反思（英文）   总被引：1，自引：0，他引：1  

BobMc KERCHER 《资源与生态学报(英文版)》2013,4(3):242-249

全球范围对"文化景观"重新燃起兴趣需要从多维方式来解释。传统栖息地,人民和他们在特殊环境里的生活方式的价值改变过程是和与遗产地有关的"文化、社会和经济建设"的引入密不可分的。自上世纪90年代开始,文化景观作为一种新型遗产列入联合国教科文组织世界遗产名录,它强调人类与环境相互作用的重要性,需要了解景观在时空上的动态性。观念的变化产生了对标志性景观和传统社区的"动态保护"。从交叉学科的视角来理解这一交互过程对规划和保护可持续遗产景观至关重要。遍及全世界的各试点项目和案例研究都引起了关于遗产景观的可持续性和旅游的至高无上作用的批判性反思。全球重要农业文化遗产(GIAHS)能否受益于旅游产生的经济资源,需要基于研究的方法来分析机会和预期,评估其战略政策和自上而下的政策。  相似文献   

Evolution of sea‐surface conditions on the northwestern Greenland margin during the Holocene     

Myriam Caron  Andr Rochon  Jean‐Carlos Montero‐Serrano  Guillaume St‐Onge 《第四纪科学杂志》2019,34(7):569-580

Reconstructions of sea‐surface conditions during the Holocene were achieved on two sediment cores from the northwest Greenland margin (AMD14‐204) and Kane Basin (AMD14‐Kane2B) based on dinoflagellate cyst assemblages. On the northwest Greenland margin, sea‐surface conditions were cold with an extended sea ice cover prior to 7750 cal a bp associated with the end of the deglaciation. A major change occurred around ca. 7750 cal a bp with enhanced influence of warmer water from the West Greenland Current, and optimal sea‐surface conditions were observed around 6000 cal a bp . After 3350 cal a bp , results reflect the establishment of the modern assemblages. In the Kane Basin, sea‐surface conditions were not favourable for dinocyst productivity prior to 7880 cal a bp , as the basin was still largely covered by ice. The presence of warmer water is recorded between 7880 and 7200 cal a bp and the highest primary productivity between 5200 and 2100 cal a bp , but sea‐surface conditions remained cold with an extended sea ice cover throughout the Holocene. Overall, the results from this study revealed the strong influence of meltwater discharges and oceanic current variability on the sea‐surface conditions. Copyright © 2019 John Wiley & Sons, Ltd.  相似文献   

Holocene chronostratigraphy of northeastern Baffin Bay based on radiocarbon and palaeomagnetic data     

Myriam Caron  Guillaume St‐Onge  Jean‐Carlos Montero‐Serrano  Andr Rochon  Eleanor Georgiadis  Jacques Giraudeau  Guillaume Mass 《Boreas: An International Journal of Quaternary Research》2019,48(1):147-165

The northeastern Baffin Bay continental margin, which experiences high sediment accumulation rates, is an excellent location to study Holocene sedimentary variations. However, it is often difficult to obtain reliable chronologies of the sediment archives using traditional methods (δ¹⁸O and radiocarbon) due to specific oceanographic conditions (e.g. corrosive bottom waters). Here we propose a chronostratigraphy of three cores collected on the northwestern Greenland margin (AMD14‐204, AMD14‐210 and AMD14‐Kane2B) based on a combination of radiocarbon dating and palaeomagnetic records. Geophysical properties of discrete samples were used to verify the reliability of the palaeomagnetic records. Palaeomagnetic analyses indicate a strong and stable natural remanent magnetization carried by low coercivity ferrimagnetic minerals (magnetite) in the pseudo‐single domain grain size range. Correlation of the full palaeomagnetic vector (inclination, declination, and relative palaeointensity) was used to establish a reliable chronostratigraphical framework for two of the cores (AMD14‐204 and AMD14‐210) and to propose an original palaeomagnetic record for the previously ¹⁴C‐dated core AMD14‐Kane2B that covers most of the Holocene. Overall, this new chronostratigraphy allowed improvement of the timing of the main palaeoenvironmental changes that occurred in this area during the Holocene.  相似文献   

Distribution and morphology of mud volcanoes and other fluid flow-related lake-bed structures in Lake Baikal, Russia     

Myriam Cuylaerts  Lieven Naudts  Robbert Casier  Andrey V. Khabuev  Oleg V. Belousov  Eugene E. Kononov  Oleg Khlystov  Marc De Batist 《Geo-Marine Letters》2012,32(5-6):383-394

New high-resolution multibeam bathymetry data recorded in 2009 in the deepest lake in the World, Lake Baikal, Siberia, enabled a better understanding of the morphology of ten known lake-bed structures—the Bolshoy, Malenki, Malyutka and Stari mud volcanoes in the South Baikal Basin, the K1–4 structures in the Selenga delta, and the Novosibirsk and St. Petersburg structures in the Central Baikal Basin—and also the discovery of 29 new lake-bed structures. These new structures are the S1, Tolstiy, mTSG and S2 in the South Baikal Basin, the P1–P4, P6–P19 and K5–K8 in the Selenga delta accommodation zone, and the C1, C3 and C4 edifices in the Central Baikal Basin. In all, 39 positive relief structures were identified and their large-scale distribution mapped. Based on their typical shape, the observation of high-reflectivity areas on side-scan sonar data records, and evidence of feeder channels on subsurface data, these structures can be classified as mud volcanoes. This has already been confirmed in other publications for the Bolshoy, Malenki and K2 structures, by the recovery of mud breccias in sediment cores. Most structures occur on or near faults and have orientations parallel with the major faults and main stress orientations in the basins, suggesting a strong structural control on the formation of the mud volcanoes. Their slopes are generally steeper than 5°, consistent with interpretation as mud cones formed by high-viscosity, stiff mud plugs. Only few structures appear to be characterised by a crater, in which case this apparent crater seems to be formed by the coalescence of several single cones, leaving a depression in the centre. Some structures have a moat, which has probably an erosional origin. Furthermore, three depressions have been found, named P5, P20 and C2, which are suggested to be pockmarks.  相似文献   

EXOTIME: searching for planets around pulsating subdwarf B stars     

Sonja Schuh  Roberto Silvotti  Ronny Lutz  Björn Loeptien  Elizabeth M. Green  Roy H. Østensen  Silvio Leccia  Seung-Lee Kim  Gilles Fontaine  Stéphane Charpinet  Myriam Francœur  Suzanna Randall  Cristina Rodríguez-López  Valerie van Grootel  Andrew P. Odell  Margit Paparó  Zsófia Bognár  Péter Pápics  Thorsten Nagel  Benjamin Beeck  Markus Hundertmark  Thorsten Stahn  Stefan Dreizler  Frederic V. Hessman  Massimo Dall’Ora  Dario Mancini  Fausto Cortecchia  Serena Benatti  Riccardo Claudi  Rimvydas Janulis 《Astrophysics and Space Science》2010,329(1-2):231-242

In 2007, a companion with planetary mass was found around the pulsating subdwarf B star V391 Pegasi with the timing method, indicating that a previously undiscovered population of substellar companions to apparently single subdwarf B stars might exist. Following this serendipitous discovery, the EXOTIME (http://www.na.astro.it/~silvotti/exotime/) monitoring program has been set up to follow the pulsations of a number of selected rapidly pulsating subdwarf B stars on time scales of several years with two immediate observational goals:

1. determine $\dot{P}$ of the pulsational periods P
2. search for signatures of substellar companions in O–C residuals due to periodic light travel time variations, which would be tracking the central star’s companion-induced wobble around the centre of mass

These sets of data should therefore, at the same time, on the one hand be useful to provide extra constraints for classical asteroseismological exercises from the $\dot{P}$ (comparison with “local” evolutionary models), and on the other hand allow one to investigate the preceding evolution of a target in terms of possible “binary” evolution by extending the otherwise unsuccessful search for companions to potentially very low masses. While timing pulsations may be an observationally expensive method to search for companions, it samples a different range of orbital parameters, inaccessible through orbital photometric effects or the radial velocity method: the latter favours massive close-in companions, whereas the timing method becomes increasingly more sensitive toward wider separations. In this paper we report on the status of the on-going observations and coherence analysis for two of the currently five targets, revealing very well-behaved pulsational characteristics in HS?0444+0458, while showing HS?0702+6043 to be more complex than previously thought.  相似文献   

Short-Term Response of a Downstream Marine System to the Partial Opening of a Tidal-River Causeway     

Travis G. Gerwing  Diana J. Hamilton  Myriam A. Barbeau  Katy Haralampides  Gordon Yamazaki 《Estuaries and Coasts》2017,40(3):717-725

The spillway gates of the Petitcodiac Causeway, a hydraulic structure ~35 km upstream of the mouth of the Petitcodiac River in New Brunswick, Canada, were permanently opened in April 2010. The short-term effect opening the spillway gates had on downstream intertidal mudflats of the upper Bay of Fundy was investigated. Specifically, a multivariate before-after-control-impact design was used to determine if opening the spillway gates affected the invertebrate community (crustaceans, polychaetes, and molluscs), abiotic sediment conditions (sediment water content, mean particle size, penetrability, and depth of the apparent redox potential discontinuity), or resource availability (sediment chlorophyll a concentration and organic matter content) of five intertidal mudflats (two impacted sites, three reference sites) spanning Chignecto Bay, the northern arm of the upper Bay of Fundy, up to 5 months post-opening. No biologically or statistically meaningful differences were detected between impacted and reference sites for any of the measured variables. This suggests that opening the causeway did not have a quantifiable impact on these intertidal mudflats, at least within half a year of the opening. This is likely a result of the macrotidal nature of the Bay of Fundy that overwhelmed any immediate changes to hydrodynamics that occurred after the opening of the causeway gates.  相似文献   

Seismic Microzonation: A Comparison between Geotechnical and Seismological Approaches in Pointe-à-Pitre (French West Indies)   总被引：1，自引：0，他引：1  

Benoit LeBrun  Anne-Marie Duval  Pierre-Yves Bard  Olivier Monge  Myriam Bour  Sylvain Vidal  Hubert Fabriol 《Bulletin of Earthquake Engineering》2004,2(1):27-50

Pointe-à-Pitre, the main city of Guadeloupe in the French West Indies, has on several occasions been partially destroyed by major historical earthquakes. Moreover, a post-seismic assessment of the damage from the 1985 Montserrat earthquake indicates that the town is prone to site effects. Consequently, from 1996 to 1998, BRGM conducted a seismic microzonation study based on geotechnical and geological data. At the same time, three seismological studies were being conducted – two based on earthquake recordings using a time-series analysis and the classical spectral ratio (CSR) method (CETE/LCPC and BRGM), and the third based on noise measurement at 400 points using the horizontal-to-vertical noise ratio (HVNR) method (CETE/LCPC). The objective of this paper is not to carry out a new microzonation study by taking into account all the results, but rather to show in what respects the results of these different methods are in agreement or not. A comparison of the results of the seismological studies with the geotechnical microzonation shows that they are in fairly good agreement, albeit with some discrepancies. The results indicate that the seismological methods and the geotechnical data are highly complementary and should be used together in compiling seismic transfer-function microzonation maps. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Joint Electrical and Time Domain Electromagnetism (TDEM) Data Inversion Applied to the Super Sauze Earthflow (France)     

Myriam Schmutz  Yves Albouy  Roger Guérin  Olivier Maquaire  Jacques Vassal  Jean-Jacques Schott  Marc Descloîtres 《Surveys in Geophysics》2000,21(4):371-390

In order to evaluate the risk of an earthflow to evolve abruptly into torrential surge, knowledge of its internal structure is necessary. This study deals with the internal structure of the Super Sauze earthflow developed in black marls in the southern French Alps. Difficulties in this study area are a rough topography, surface heterogeneities and a large thickness variability of the earthflow mass. These conditions hamper the application of geotechnical methods as a preferred investigation mean. Moreover, they pose problems to geophysical investigations and their interpretation.This paper shows the advantage offered by the joint inversion of Time Domain ElectroMagne-tism data (TDEM) and data obtained from Direct Current soundings (DC). The results of the joint inversions are checked using geotechnical data. The internal structure of the earthflow interpreted on the basis of joint inversion data is comparable to that obtained from geotechnical results. Moreover, contrary to separate electrical and TDEM inversions, a satisfactory joint inversion model can be derived without supplying additional a priori information.  相似文献