Hurricane interaction with the upper ocean in the Amazon-Orinoco plume region   总被引：1，自引：0，他引：1  

Yannis Androulidakis  Vassiliki Kourafalou  George Halliwell  Matthieu Le Hénaff  Heesook Kang  Michael Mehari  Robert Atlas 《Ocean Dynamics》2016,66(12):1559-1588

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Experimental investigation of flow pattern and sediment deposition in rectangular shallow reservoirs     

Sébastien ERPICUM 《国际泥沙研究》2010,25(3):258-270

This paper reports the experimental investigation of flow pattern, preferential regions of deposition and trap efficiency as a function of the length of rectangular shallow reservoirs. Four flow patterns were identified (from longer to shorter reservoirs): an asymmetric flow with two reattachment points, an asymmetric flow with one reattachment point, an unstable flow, and a symmetric flow without any reattachment point. Using dye visualizations, the median value and the temporal variability of the reattachment lengths were precisely measured for the asymmetric flows. For each stable flow, sediment tests with plastic particles were carried out. The regions of deposition on the bed of the reservoir were clearly a function of the flow pattern. The transition from an asymmetric flow pattern to a symmetric flow pattern was responsible for an abrupt decrease of the trap efficiency; a number of regression laws were discussed to take it into account.  相似文献   

On early Solar System chronology: Implications of an heterogeneous spatial distribution of Al and Mn     

Matthieu Gounelle  Sara S. Russell 《Geochimica et cosmochimica acta》2005,69(12):3129-3144

Early Solar System chronology is usually built with the assumption that the distribution of short-lived radionuclides was homogeneous through the solar accretion disk. At present, there is no unambiguous evidence for a homogeneous distribution of short-lived radionuclides in the solar accretion disk, while some data point to a heterogeneous distribution of short-lived radionuclides. In this paper, we explore a possible chronology based on a heterogeneous distribution of ²⁶Al and ⁵³Mn in the accretion disk. Our basic assumption is that the different abundances of extinct short-lived radionuclides in calcium-aluminium-rich inclusions (CAIs) and chondrules are due to spatial rather than temporal differences. We develop a simple model where CAIs and chondrules form contemporaneously, in different spatial locations, and are characterised by distinct initial ²⁶Al and ⁵³Mn abundances. In this model, all evolved bodies are supposed to be originally chondritic, i.e., to be made of a mixture of CAIs, chondrules, and matrix. This mixture determines the initial content in ²⁶Al and ⁵³Mn of a chondritic parent-body as a function of its CAI and chondrule abundance fraction. This approach enables us to calculate coherent ²⁶Al and ⁵³Mn ages from the agglomeration of the parent-body precursors (CAIs and chondrules) until the isotopic closure of ²⁶Al and ⁵³Mn, thereafter called ²⁶Al-⁵³Mn age. We calculate such ²⁶Al-⁵³Mn ages for a diversity of evolved objects, with the constraint that they should be found for realistic chondritic parent-body precursors, i.e., objects having similar or identical petrograpy to the existing chondrite groups. The so defined age of the d’Orbigny angrite is 4.3 ± 1.1 Myr, for the Asuka-881394 eucrite 2.8 ± 1.0 Myr, for the H4 chondrite Sainte Marguerite ∼3 Myr, and for H4 Forest Vale ∼5 Myr. The calculated ²⁶Al-⁵³Mn ages give timescales for the evolution of the respective parent-bodies/meteorites that can be investigated in the light of further petrographic studies. We anchor the calculated relative chronology to an absolute chronology using absolute Pb-Pb ages and relative Hf-W ages of the objects under scrutiny. The precursors of Sainte Marguerite and Forest Vale agglomerated at the same time (∼4565.8 ± 1.2 Ma ago). The precursors of eucrites (Asuka-881394) agglomerated 4564.8 ± 1.2 Ma ago. The precursors of angrites agglomerated late (4561.5 ± 1.8 Ma ago). Our model provides a fully compatible Al-Mg/Mn-Cr/Pb-Pb chronology, and is shown to be robust to reasonable changes in the input parameters. The calculated initial ²⁶Al/²⁷Al ratios are high enough to have ²⁶Al as a possible heat source for differentiation.  相似文献   

Volcano-structural evolution of Piton des Neiges,Reunion Island,Indian Ocean     

L. Chevallier  N. Vatin-Perignon 《Bulletin of Volcanology》1982,45(4):285-298

Four volcano-structural stages have accompanied the building of Piton des Neiges: 1) Emergent growth stage of the island. The major eruptive system is a rift zone trending N 120°, associated with dextral strike-slip faults trending N 30° and en-echelon extensional fissures trending N 70°. Breccias and lava tubes produced by aerial and phreatomagmatic activity are injected with outward-dipping dike-swarms along ring fractures suggesting a mechanism analogous to cauldron subsidence. 2) Shield building stages of growth are related to fissures along the main rift zone and three minor rifts trending N 160°, N 45° and N 10°. The summit of the basaltic shield volcano is stretched and collapsed in a graben-like caldera depression along normal and antithetic faults. 3) Differentiated lavas are erupted during two stages separated by the opening of a new caldera corresponding to an explosive activity, a silicic cone-sheet system and a collapse structure. 4) Younger volcanic activity restricted to the inside caldera, has presumably emptied the underlying magma reservoir, building a central volcano collapsed along ring internal dip fractures. The relationships between magnetic anomalies and transform faults in the Mascarene basin and observed fissure and faults on Piton des Neiges suggest that volcanism would be structurally controlled. Active volcanism occurring possibly as a result of tension at the intersection of an northeast-southwest fracture zone with the paleorift axis (dated by the magnetic anomaly 27). Models illustrating the gradual evolution of Piton des Neiges would explain successive caldera collapses controlled by the size, the shape and the depth of the magma reservoir.  相似文献   

Influence of Indian Ocean Dipole and Pacific recharge on following year’s El Niño: interdecadal robustness   总被引：1，自引：1，他引：0  

Takeshi Izumo  Matthieu Lengaigne  Jérôme Vialard  Jing-Jia Luo  Toshio Yamagata  Gurvan Madec 《Climate Dynamics》2014,42(1-2):291-310

The Indian Ocean Dipole (IOD) can affect the El Niño–Southern Oscillation (ENSO) state of the following year, in addition to the well-known preconditioning by equatorial Pacific Warm Water Volume (WWV), as suggested by a study based on observations over the recent satellite era (1981–2009). The present paper explores the interdecadal robustness of this result over the 1872–2008 period. To this end, we develop a robust IOD index, which well exploits sparse historical observations in the tropical Indian Ocean, and an efficient proxy of WWV interannual variations based on the temporal integral of Pacific zonal wind stress (of a historical atmospheric reanalysis). A linear regression hindcast model based on these two indices in boreal fall explains 50 % of ENSO peak variance 14 months later, with significant contributions from both the IOD and WWV over most of the historical period and a similar skill for El Niño and La Niña events. Our results further reveal that, when combined with WWV, the IOD index provides a larger ENSO hindcast skill improvement than the Indian Ocean basin-wide mode, the Indian Monsoon or ENSO itself. Based on these results, we propose a revised scheme of Indo-Pacific interactions. In this scheme, the IOD–ENSO interactions favour a biennial timescale and interact with the slower recharge-discharge cycle intrinsic to the Pacific Ocean.  相似文献   

Ocean feedback to tropical cyclones: climatology and processes   总被引：1，自引：0，他引：1  

Swen Jullien  Patrick Marchesiello  Christophe E. Menkes  Jérôme Lefèvre  Nicolas C. Jourdain  Guillaume Samson  Matthieu Lengaigne 《Climate Dynamics》2014,43(9-10):2831-2854

This study presents the first multidecadal and coupled regional simulation of cyclonic activity in the South Pacific. The long-term integration of state-of the art models provides reliable statistics, missing in usual event studies, of air–sea coupling processes controlling tropical cyclone (TC) intensity. The coupling effect is analyzed through comparison of the coupled model with a companion forced experiment. Cyclogenesis patterns in the coupled model are closer to observations with reduced cyclogenesis in the Coral Sea. This provides novel evidence of air–sea coupling impacting not only intensity but also spatial cyclogenesis distribution. Storm-induced cooling and consequent negative feedback is stronger for regions of shallow mixed layers and thin or absent barrier layers as in the Coral Sea. The statistical effect of oceanic mesoscale eddies on TC intensity (crossing over them 20 % of the time) is also evidenced. Anticyclonic eddies provide an insulating effect against storm-induced upwelling and mixing and appear to reduce sea surface temperature (SST) cooling. Cyclonic eddies on the contrary tend to promote strong cooling, particularly through storm-induced upwelling. Air–sea coupling is shown to have a significant role on the intensification process but the sensitivity of TCs to SST cooling is nonlinear and generally lower than predicted by thermodynamic theories: about 15 rather than over 30 hPa °C^?1 and only for strong cooling. The reason is that the cooling effect is not instantaneous but accumulated over time within the TC inner-core. These results thus contradict the classical evaporation-wind feedback process as being essential to intensification and rather emphasize the role of macro-scale dynamics.  相似文献   

Unprecedented recent warming rate and temperature variability over the east Tibetan Plateau inferred from Alpine treeline dendrochronology     

Shi  Chunming  Masson-Delmotte  Valérie  Daux  Valérie  Li  Zongshan  Carré  Matthieu  Moore  John C. 《Climate Dynamics》2015,44(5-6):1367-1379

Climate Dynamics - Despite instrumental records showing recent large temperature rises on the Tibetan Plateau (TP), only a few tree-ring temperature reconstructions do capture this warming trend....  相似文献   

What role for climate negotiations on technology transfer?     

Matthieu Glachant  Antoine Dechezleprêtre 《Climate Policy》2013,13(8):962-981

Little progress has been made in climate negotiations on technology since 1992. Yet the diffusion of climate change mitigation technologies to developing countries (non-Annex I) has increased dramatically over the last twenty years. The shift has mostly concerned emerging economies, which are now reasonably well connected to international technology flows. This is good news, as the bulk of emissions increases are expected to take place in these countries in the near future. In contrast, the least developed countries still appear to be excluded from international technology flows, mostly because of their negligible participation in the recent economic globalization. This article focuses on the policy implications of the contribution of climate negotiations to international technology diffusion.

Policy relevance

The discrepancy between the small amount of progress made in climate negotiations on technology since 1992 and the steady increase in the international diffusion of climate mitigation technologies leads to the perhaps controversial view that the diffusion of climate mitigation technologies does not need strong international coordination over technology issues under the UNFCCC. However, climate negotiations can play a key role in stimulating the demand for low-carbon technologies by setting ambitious emission reductions targets and policies.  相似文献   

Land use change effects on runoff and erosion from plot to catchment scale on the basaltic plateau of Southern Brazil     

Nilza Maria Dos Reis Castro  Anne‐Vronique Auzet  Pierre Chevallier  Jean‐Claude Leprun 《水文研究》1999,13(11):1621-1628

In the region of the basaltic plateau in Southern Brazil, problems of runoff and erosion on the deep ferrallitic soils are becoming increasingly recognized. Land use change from conventional tillage using disk plough to no‐tillage on residues without terracing occurred at the beginning of the 1990s and it spread very quickly. Measurements of runoff and sediment concentrations on 1 m² plots receiving natural rainfall and simulated rainfall under different crops with different stages of growth and different tillage systems, field surveys and measurements of rills and gullies in nested experimental catchments indicate a relative decrease of runoff on slopes but an increase of subsurface flow, and a marked decrease of sheet and rill erosion and soil loss from plot to catchment scales. Nevertheless, the extension of parts of the gully system is still continuing, strongly influenced by extreme rainfall. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Behaviour of colloidal trace metals (Cu, Pb and Cd) in estuarine waters: An approach using frontal ultrafiltration (UF) and stripping chronopotentiometric methods (SCP)     

Matthieu Waeles  Virginie Tanguy  Gaëtane Lespes  Ricardo D. Riso 《Estuarine, Coastal and Shelf Science》2008,80(4):538-544

The frontal cascade ultrafiltration (UF) technique in conjunction with stripping chronopotentiometry (SCP) has been evaluated for determining the colloidal distribution of Cu, Pb and Cd in estuarine waters. Metallic concentrations in seven size fractions (0.45 μm–0.22 μm; 0.22 μm–300 kDa; 300–50 kDa; 50–30 kDa; 30–10 kDa; 10–5 kDa; <5 kDa) were determined with the aim to investigate their changes along the salinity gradient of the Penzé system (NW France). These data, completed by analysis of the total dissolved metals at 10 stations over the whole freshwater–seawater mixing zone, provided some insights in the removal and addition processes that affect Cu, Pb and Cd in estuaries.  相似文献