Present-day trends of vertical ground motion along the coast lines     

Émilie Ostanciaux  Laurent Husson  Gaël Choblet  Cécile Robin  Kevin Pedoja 《Earth》2012,110(1-4):74-92

Vertical ground motion (VGM) rates stand as crucial information, either for predicting the impact of the actual sea level rise along low-lying coasts or refining geodynamic problems. Because present day VGM rates have a magnitude smaller than 10 mm/yr, they remain challenging to quantify and often elusive. We focus on the quantification of global-scale VGM rates in order to identify global or regional trends. We computed VGM rates by combining tide gauges records and local satellite altimetry, which yield a new dataset of 634 VGM rates. We further compare this database to previous studies that use geodetic techniques and tide gauges records in order to evaluate the consistency of both our results and previous ones. The magnitudes differ by less than 5 mm/yr, and similar subsidence and uplift general tendencies appear. Even if the asset of our database stands in the greater number of sites, the combination of all studies, each with different pros and cons, yields a hybrid dataset that makes our attempt to extract VGM trends more robust than any other, independent study. Fennoscandia, the West coast of North America, and the eastern coast of Australia are uplifting, while the eastern coast of North America, the British Isles and Western Europe, the eastern Mediterranean Sea, Japan, and the western coast of Australia are subsiding. Glacial Isostatic Adjustment (GIA) is expected to provide a major contribution to the present-day signal. Aside from Fennoscandia, observed VGM often depart from the GIA model predictions of Peltier (2004). This either results from an underestimate of the model predictions or from the influence of other processes: indeed, the influence of the geodynamic setting appears in particular along the coasts of western North America or Japan, where the alternation of transform faults and subduction zones makes it possible to assign contrasted behaviours to the local geodynamic context. Local mechanisms like anthropogenic processes or sediment compaction, also contribute to VGM. This remains true for the critical cases of Venice, the Gulf of Mexico, the Ganges delta, and the Maldives, which are particularly exposed to the current sea level rise.  相似文献   

Sumixam maximus gen. and sp. nov., a New Pennsylvanian Species of Archaeorthoptera (Neoptera; Indiana, USA)     

Olivier BéTHOUX  Christin GROSSMANN 《《地质学报》英文版》2011,85(3):515-520

A new Mazon-Creek-type fossil specimen is described as Sumixam maximus gen. and sp. nov., assigned to the taxon Archaeorthoptera Béthoux and Nel, 2002 (composed of Orthoptera and some fossil relatives): it exhibits one of the diagnostic character states of this taxon, which is the fusion of CuA (emerging from M + CuA) with CuP, or a branch of it. A more precise taxonomic assignment is out of reach. The new taxon exhibits a fusion of the anterior branch of MA with RP, and a point of divergence of MA and MP located near the point of divergence of CuA (from M + CuA), but lack a branching of CuPa. This unique combination of character states is probably derived with respect to a number of contemporaneous species. Sumixam maximus gen. and sp. nov. is most likely the closest known relative of the panorthopterans, which include all the recent Archaeorthoptera.  相似文献   

GROUND THERMAL CONDITIONS AT CHACHANI VOLCANO,SOUTHERN PERU     

NURIA ANDRÉS  DAVID PALACIOS  JOSE ÚBEDA  JESÚS ALCALÁ 《Geografiska Annaler: Series A, Physical Geography》2011,93(3):151-162

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Type III radio burst productivity of solar flares     

M. PoquÉrusse  P. S. McIntosh 《Solar physics》1995,159(2):301-323

We study the occurrence probability of type III radio bursts during flares as a function of the flare position on the Sun. We find that this probability peaks around 30° east of the central meridian, which points to a reciprocal tilt of the average radiation pattern of type IIIs. We argue that anisotropic scattering of the radiation by overdense coronal fibers parallel to the magnetic field is the dominant factor determining the orientation of radiation patterns. It follows that the average magnetic field appears to be tilted 30° west from the vertical. We also find that within a given active region, the average type III production rate of flares peaks 1° west of the center of gravity of all the flares of this active region.We infer that the coronal magnetic field above active regions presents a strong east-west asymmetry, resulting from the well known asymmetry at the photospheric level. As the west side of an active region covers a smaller area with stronger magnetic field than the east side, western flares are generally closer to open field lines than eastern flares. As a consequence, accelerated particles on the trailing (east) side of active regions usually stay trapped in magnetic loops, while on the leading (west) side they are more likely to escape along open lines into interplanetary space. As a result of the initial westward tilt of these open lines, we estimate that the corresponding Archimedean spiral is on average (apparently) rooted 15° west of the flare.  相似文献   

Vegetation,fire and climate history of the Lesser Caucasus: a new Holocene record from Zarishat fen (Armenia)          下载免费PDF全文

SÉBASTIEN JOANNIN  ADAM A. ALI  VINCENT OLLIVIER  PAUL ROIRON  ODILE PEYRON  SAMY CHEVAUX  SAMUEL NAHAPETYAN  PETROS TOZALAKYAN  ARKADI KARAKHANYAN  CHRISTINE CHATAIGNER 《第四纪科学杂志》2014,29(1):70-82

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COMMENTS ON THE PAPER: RECALCULATION OF H-Lα SKY SURVEYS: NO NEED FOR ANISOTROPIC SOLAR WIND MASS OUTFLOWS?     

Bertaux  Jean-Loup  QuÉmerais  Eric  Lallement  Rosine  KyrÖlÄ  Erkki  Summanen  Tuula 《Solar physics》1997,170(2):365-370

In a recently published paper, Scherer and Fahr (1995) claimed that the departures of sky L emission measured by Prognoz 5 and 6 from an optically thin model can be attributed entirely to deficiencies of the optically thin approximation, and are not due to variations of solar wind ionization rate with latitude, as advocated since many years by our research group. They base their claim on the result of their new sophisticated model of L radiation transport.It is shown here that their new model, in the simple case of isotropic solar wind, predicts a distribution of intensity in a simple geometry which is completely contradicted by the observations: they find a minimum of intensity near the upwind direction, where a maximum has been observed consistently by all L instruments. Therefore, their conclusion based on an erroneous model must be rejected.  相似文献   

Transformation of Irradiance Measurements into Spectral Actinic Flux for Photolysis Rates Determination     

HÉLÈNE COTTE  CLAUDE DEVAUX  PATRICK CARLIER 《Journal of Atmospheric Chemistry》1997,26(1):1-28

The actinic flux is the only radiometric quantity suitable for photolysisfrequency determination. It is derived from solar spectral irradiancemeasurements performed by a portable spectroradiometer in the 300–850nm wavelength range. The spectral irradiance is first divided into a directpart and a diffuse part, according to the atmospheric conditions, and thenconverted into the corresponding actinic flux quantity. As an intermediary,the ratio of diffuse actinic flux to diffuseirradiance is calculated by the spherical harmonics radiative code withrespect to wavelength, solar zenith angle, surface albedo, and aerosolproperties.The results of extensive sensitivity studies of asa function of the main atmospheric parameters are discussed and lead to theconclusion that aerosol optical depth is the major critical value for aprecise determination. The global algorithm totransform spectral irradiance into actinic flux is finally applied forphotodissociation rate calculations by convolution of the obtained actinicflux spectra with the absorption cross-sections and quantum yields of themolecule studied. Photolysis rates of different atmospheric photooxidants havebeen measured with this spectroradiometric method during the summers of 1993and 1994 in Brittany and in Portugal. The ozone and nitrogen dioxidephotodissociation rates obtained present a good agreement with thej(O₃) and j(NO₂) actinometerresults, for the same experimental conditions in Brittany.  相似文献   

DEFORMATIONAL BEHAVIOURS OF ALLUVIAL UNITS DETECTED BY ADVANCED RADAR INTERFEROMETRY IN THE VEGA MEDIA OF THE SEGURA RIVER,SOUTHEAST SPAIN          下载免费PDF全文

CARMELO CONESA‐GARCÍA  ROBERTO TOMÁS  GERARDO HERRERA  FRANCISCO LÓPEZ‐BERMÚDEZ  MIGUEL CANO  FRANCISCA NAVARRO‐HERVÁS  PEDRO PÉREZ‐CUTILLAS 《Geografiska Annaler: Series A, Physical Geography》2016,98(1):15-38

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Sea‐surface hydrographical conditions off South Faeroes and within the North‐Eastern North Atlantic through MIS 2: the response of dinocysts     

CLÉMENCE CAULLE  AURÉLIE PENAUD  FRÉDÉRIQUE EYNAUD  SÉBASTIEN ZARAGOSI  DIDIER M. ROCHE  ELIZABETH MICHEL  SÉBASTIEN BOULAY  THOMAS RICHTER 《第四纪科学杂志》2013,28(3):217-228

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Postglacial chironomid assemblage succession in northernmost Ungava Peninsula,Canada     

Émilie Saulnier‐Talbot  Reinhard Pienitz 《第四纪科学杂志》2010,25(2):203-213

Sediment cores spanning the postglacial period were recovered from two coastal freshwater basins located 300 km apart in northernmost Ungava (Nunavik, Canada). A basal date from the sequence recovered near Wakeham Bay suggests that the region was ice‐free by as early as 9600 cal. a BP. The initial development of both investigated lacustrine ecosystems was characterised by chironomid assemblages strongly dominated by the Subtribe Tanytarsina. These early postglacial assemblages showed greatly reduced diversity but much greater abundance than during subsequent periods of lake evolution. An abrupt and distinct turnover in sedimentary chironomid assemblage composition and productivity, marked by a switch to a dominance of Orthocladiinae, occurred around 6 ka BP. This turnover likely corresponds with a significant disturbance in the regional environment, which could be linked to the final disappearance of the last remnants of the Laurentide Ice Sheet. These findings, based on the first palaeolimnological investigations undertaken in northernmost Ungava, provide new insights into lateglacial and postglacial faunal recolonisation patterns in aquatic ecosystems of the eastern Canadian Arctic. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献