Organochlorine contaminants in endangered Hawaiian monk seals from four subpopulations in the Northwestern Hawaiian Islands     

Ylitalo GM  Myers M  Stewart BS  Yochem PK  Braun R  Kashinsky L  Boyd D  Antonelis GA  Atkinson S  Aguirre AA  Krahn MM 《Marine pollution bulletin》2008,56(2):231-244

We analyzed blubber and blood samples for organochlorines (OCs) from 158 Hawaiian monk seals (Monachus schauinslandi) at four of their six primary breeding colonies in the Northwestern Hawaiian Islands. Levels of OCs in blubber were lower in adult females compared to juveniles or adult males, evidently owing to the transfer of these lipophilic compounds to pups by pregnant and lactating females. Concentrations of SigmaPCBs and p,p'-DDE in blubber generally increased with age until seals were sexually mature and then continued to increase with age in males after puberty. Average levels of PCBs and PCB toxic equivalents (TEQs) in blubber were significantly higher in adult male and juvenile seals at Midway Atoll than the same age class of seals at the other colonies. Unlike concentrations of OCs in blubber, circulating levels of OCs in blood did not vary consistently among age classes of seals or among breeding colonies. Though the concentrations of OCs measured in Hawaiian monk seals were generally equal to or lower than those reported for other pinniped species in the North Pacific Ocean, they were high enough in a few seals to potentially affect their health.  相似文献   

Glacial isostatic adjustment at the Laurentide ice sheet margin: Models and observations in the Great Lakes region     

Alexander Braun  Chung-Yen Kuo  C.K. Shum  Patrick Wu  Wouter van der Wal  Georgia Fotopoulos 《Journal of Geodynamics》2008,46(3-5):165

Glacial Isostatic Adjustment (GIA) modelling in North America relies on relative sea level information which is primarily obtained from areas far away from the uplift region. The lack of accurate geodetic observations in the Great Lakes region, which is located in the transition zone between uplift and subsidence due to the deglaciation of the Laurentide ice sheet, has prevented more detailed studies of this former margin of the ice sheet. Recently, observations of vertical crustal motion from improved GPS network solutions and combined tide gauge and satellite altimetry solutions have become available. This study compares these vertical motion observations with predictions obtained from 70 different GIA models. The ice sheet margin is distinct from the centre and far field of the uplift because the sensitivity of the GIA process towards Earth parameters such as mantle viscosity is very different. Specifically, the margin area is most sensitive to the uppermost mantle viscosity and allows for better constraints of this parameter. The 70 GIA models compared herein have different ice loading histories (ICE-3/4/5G) and Earth parameters including lateral heterogeneities. The root-mean-square differences between the 6 best models and the two sets of observations (tide gauge/altimetry and GPS) are 0.66 and 1.57 mm/yr, respectively. Both sets of independent observations are highly correlated and show a very similar fit to the models, which indicates their consistent quality. Therefore, both data sets can be considered as a means for constraining and assessing the quality of GIA models in the Great Lakes region and the former margin of the Laurentide ice sheet.  相似文献   

Catalogue of Shakhbazian compact groups of galaxies. VI.     

D. Stoll  H. Tiersch  M. Braun 《Astronomische Nachrichten》1996,317(5):315-332

The sixth part of the catalogue of Shakhbazian compact groups of galaxies contains the positions and references of all the galaxies of the following 48 groups (north of δ > +2°30''): Shkh 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107. For the estimation of the coordinates the Digitized Sky Survey was used.  相似文献   

Stochastic Seismic Emission from Acoustic Glories and the Quiet Sun     

Donea  A.-C.  Lindsey  C.  Braun  D.C. 《Solar physics》2000,192(1-2):321-333

Helioseismic images of multipolar active regions show enhanced seismic emission in 5-mHz oscillations in a halo surrounding the active region called the `acoustic glory'. The acoustic glories contain elements that sustain an average seismic emission 50% greater than similar elements in the quiet Sun. The most intense seismic emitters tend to form strings in non-magnetic regions, sometimes marking the borders of weak magnetic regions and the separation between weak magnetic regions of opposite polarity. This study compares the temporal character of seismic emission from acoustic glories with that from the quiet Sun. The power distribution of quiet-Sun seismic emission far from solar activity is exponential, as for random Gaussian noise, and therefore not perceivably episodic. The distribution of seismic power emanating from the most intense elements that comprise the acoustic glories is exponential out to approximately 4 times the average power emitted by the quiet Sun. Above this threshold the latter distribution shows significant saturation, suggesting the operation of a hydromechanical non-linearity that sets limits on the acoustic power generated by the convection zone. This could give us considerable insight into the physical mechanism of seismic emission from the near subphotosphere.  相似文献   

Petrography,Geochemistry and Physical Properties of a Continuous Extrusive Section from the Sarami Massif,Semail Ophiolite     

Einaudi  Florence  Pezard  Philippe A.  Cochemé  Jean-Jacques  Coulon  Christian  Laverne  Christine  Godard  Marguerite 《Marine Geophysical Researches》2000,21(3-4):387-408

As opposed to ocean crustal drilling that often yields a discontinuous core, ophiolites provide a unique opportunity to study continuous sections of oceanic basalts. In order to provide high frequency constraints on the construction of the upper oceanic crust, a continuous 280 m thick volcanic transect was sampled in the Semail ophiolite in Oman. The analyzed section is located in the Sarami Massif, in the central part of the ophiolite, and exposed along Wadi Shaffan. A multidisciplinary study was carried out after sampling in the field. Core measurements including porosity, grain density, compressional velocity, magnetic susceptibility and electrical resistivity for over 100 samples from this transect have been made. Geochemical analyses including major, trace and Rare Earth Elements were also performed on 23 selected samples from this transect. The Wadi Shaffan transect appears as composed of two main petrological and geochemical members providing the main lithostratigraphic signal. The boundary between the two sequences is marked by the presence of a massive flow unit equating to the most primitive lava and across which significant changes in mineralogy and texture are observed. The physical properties equally record significant changes. In all, the section is characterized by chemical compositions coherent with that of V1-Geotime volcanism and appears as built through two main sequences of volcanic activity. The magnetic susceptibility profile correlated to geochemical variations present the most detailed evolution allowing to individualize a succession of at least 4 volcanic phases. These phases are interpreted as magmatic cycles characterized by differentiation processes, allowing one to place high frequency constraints on the volcanic behavior of fast spreading ridges. Some of the physical properties also reflect this series of differentiation trends, as noticed in the past from downhole measurements recorded in the context of deep ocean drilling into the crust.  相似文献   

Soil production and hillslope transport in mid‐latitudes during the last glacial–interglacial cycle: a combined data and modelling approach in northern Ardennes          下载免费PDF全文

Benoît Bovy  Jean Braun  Alain Demoulin 《地球表面变化过程与地形》2016,41(12):1758-1775

The relative efficiency of various hillslope processes through Quaternary glacial–interglacial cycles in the mid‐latitudes is not yet well constrained. Based on a unique set of topographic and soil thickness data in the Ardennes (Belgium), we combine the new CLICHE model of climate‐dependent hillslope evolution with an inversion algorithm in order to get deeper insight into the ways and timing of hillslope dynamics under one such climatic cycle. We simulate the evolution of a synthetic hill reproducing the slope, curvature, and contributing area distributions of the hillslopes of a ~ 2500 km² real area under a simple two‐stage 120‐kyr‐long climatic scenario with linear transitions between cold and warm stages. The inversion method samples a misfit function in the model parameter space, based on estimates of the fit of topographic derivative distributions in classes of soil thickness and of the relative frequencies of the predicted soil thickness classes. Though the inversion results show remarkable convergence patterns for most parameters, no unique solution emerges. We obtain five clusters of good fits, whose centroids are taken as acceptable model solutions. Based on the predicted time series of average denudation rate and soil thickness, plus snapshots of the soil distribution at characteristic times, we discuss these solutions and, comparing them with independent data not involved in the misfit function, we identify the most realistic scenario. Beyond providing first‐order estimates of several parameters that compare well with published data, our results show that denudation rates increase dramatically for a short time at both warm–cold and cold–warm transitions, when the mean annual temperature passes through the [0, ?5 °C] range. We also point to the overwhelming importance of solifluction in shaping hillslopes and transporting soil, and the role of depth‐dependent creep (including frost creep) throughout the climatic cycle, whereas the contributions of simple creep and overland flow are minor. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Comparison of Snow Data Assimilation System with GPS reflectometry snow depth in the Western United States          下载免费PDF全文

J. J. Braun  J. L. McCreight  F. G. Nievinski 《水文研究》2015,29(10):2425-2437

In this study, we compare gridded snow depth estimates from the Snow Data Assimilation System (SNODAS) with snow depth observations derived from GPS interferometric reflectometry (GPS‐IR) from roughly 100 Plate Boundary Observatory sites in the Western United States spanning four water‐years (2010–2013). Data from these sites are not assimilated by SNODAS; thus, GPS‐IR measurements provide an independent data set to evaluate SNODAS. Our results indicate that at 80% of the sites, SNODAS and GPS‐IR snow depth agree to better than 15‐cm root mean square error, with correlation coefficients greater than 0.6. Significant differences are found between GPS‐IR and SNODAS for sites that are distant from other point measurements, are located in complex terrain or are in areas with strong vegetation heterogeneities. GPS‐IR estimates of snow depth are shown to provide useful error characterization of SNODAS products across much of the Western United States and may have potential as an additional data assimilation source that could help improve SNODAS estimates. © 2014 The Authors. Hydrological Processes published by John Wiley & Sons Ltd.  相似文献   

Sediment Yield During Late Glacial and Holocene periods in the Lac Chambon Watershed,Massif Central,France     

Jean-Jacques Macaire  Gilles Bossuet  Alain Choquier  Constantin Cocirta  Patrick de Luca  Andr Dupis  Isabelle Gay  Eric Mathey  Pascal Guenet 《地球表面变化过程与地形》1997,22(5):473-489

A sediment budget for the Late Glacial and Holocene periods was calculated for the Lac Chambon watershed which is located in a formerly glaciated temperate crystalline mountain area. It appears that over 15 500 years: (1) 69 per cent of eroded particles have been displaced by gravity processes and then stored within the watershed, compared to 31 per cent that have been displaced by running water and evacuated outward; (2) the mean mechanical erosion due to gravity processes on the slopes amounted to 16·1 ±6 m and only developed on a quarter of the watershed surface, whereas the mean mechanical erosion due to running water amounted 1·24 ± 0·37 m and involved the whole watershed surface. The mean sediment yields due to gravity processes on slopes were 2300 ± 1360, 1770 ± 960 and 380 ± 100 m³ km⁻³ a⁻¹, respectively, for basalts, and basic and acidic trachyandesites. Values of sediment yield due to running water were 49±15, 120±36 and 79±24 m³ km⁻² a⁻¹, respectively, during the Bôlling–Allerôd, the Younger Dryas and the Pre-Boreal–Boreal periods. They were 56±17 and 166±50 m³ km⁻² a⁻¹ during the Sub-Atlantic period before and after 1360 a BP , respectively. These values reflect variations in the natural environment and the impact of human-induced deforestation. © 1997 by John Wiley & Sons, Ltd.  相似文献   

The initiation of pull‐apart basins and transform continental margins: results from numerical experiments of kinematic partitioning in divergent settings          下载免费PDF全文

Christophe Basile  Jean Braun 《地学学报》2016,28(2):120-127

We present a set of numerical models to investigate how transform faults initiate in pull‐apart basins or transform continental margins. The model represents an elastic plate with three aligned weak spots. Applying strain on the edge of the model firstly propagates extensional cracks from the pre‐existing damaged spots. The subsequent evolution depends on the angle (obliquity) between the applied strain and the alignment of the damaged spots. For obliquity <50°, transform faults form to connect en‐échelon divergent cracks; for obliquity >60°, transtensional transfer zones connect the divergent cracks and no transform fault forms. These experiments suggest that pull‐apart basins do not form as previously assumed by connection of overlapping transform faults, but that transform faults form as connections of extensional areas.  相似文献   

Regolith mass balance inferred from combined mineralogical, geochemical and geophysical studies: Mule Hole gneissic watershed, South India   总被引：3，自引：0，他引：3  

Jean-Jacques Braun  Marc Descloitres  Jean Riotte  Simon Fleury  Jean-Loup Boeglin  Eva Lacarce  M. Sekhar  M.S. Mohan Kumar  S. Subramanian  Bernard Dupré 《Geochimica et cosmochimica acta》2009,73(4):935-24

The aim of this study is to propose a method to assess the long-term chemical weathering mass balance for a regolith developed on a heterogeneous silicate substratum at the small experimental watershed scale by adopting a combined approach of geophysics, geochemistry and mineralogy. We initiated in 2003 a study of the steep climatic gradient and associated geomorphologic features of the edge of the rifted continental passive margin of the Karnataka Plateau, Peninsular India. In the transition sub-humid zone of this climatic gradient we have studied the pristine forested small watershed of Mule Hole (4.3 km²) mainly developed on gneissic substratum. Mineralogical, geochemical and geophysical investigations were carried out (i) in characteristic red soil profiles and (ii) in boreholes up to 60 m deep in order to take into account the effect of the weathering mantle roots. In addition, 12 Electrical Resistivity Tomography profiles (ERT), with an investigation depth of 30 m, were generated at the watershed scale to spatially characterize the information gathered in boreholes and soil profiles. The location of the ERT profiles is based on a previous electromagnetic survey, with an investigation depth of about 6 m. The soil cover thickness was inferred from the electromagnetic survey combined with a geological/pedological survey.Taking into account the parent rock heterogeneity, the degree of weathering of each of the regolith samples has been defined using both the mineralogical composition and the geochemical indices (Loss on Ignition, Weathering Index of Parker, Chemical Index of Alteration). Comparing these indices with electrical resistivity logs, it has been found that a value of 400 Ohm m delineates clearly the parent rocks and the weathered materials. Then the 12 inverted ERT profiles were constrained with this value after verifying the uncertainty due to the inversion procedure. Synthetic models based on the field data were used for this purpose. The estimated average regolith thickness at the watershed scale is 17.2 m, including 15.2 m of saprolite and 2 m of soil cover.Finally, using these estimations of the thicknesses, the long-term mass balance is calculated for the average gneiss-derived saprolite and red soil. In the saprolite, the open-system mass-transport function τ indicates that all the major elements except Ca are depleted. The chlorite and biotite crystals, the chief sources for Mg (95%), Fe (84%), Mn (86%) and K (57%, biotite only), are the first to undergo weathering and the oligoclase crystals are relatively intact within the saprolite with a loss of only 18%. The Ca accumulation can be attributed to the precipitation of CaCO₃ from the percolating solution due to the current and/or the paleoclimatic conditions. Overall, the most important losses occur for Si, Mg and Na with −286 × 10⁶ mol/ha (62% of the total mass loss), −67 × 10⁶ mol/ha (15% of the total mass loss) and −39 × 10⁶ mol/ha (9% of the total mass loss), respectively. Al, Fe and K account for 7%, 4% and 3% of the total mass loss, respectively. In the red soil profiles, the open-system mass-transport functions point out that all major elements except Mn are depleted. Most of the oligoclase crystals have broken down with a loss of 90%. The most important losses occur for Si, Na and Mg with −55 × 10⁶ mol/ha (47% of the total mass loss), −22 × 10⁶ mol/ha (19% of the total mass loss) and −16 × 10⁶ mol/ha (14% of the total mass loss), respectively. Ca, Al, K and Fe account for 8%, 6%, 4% and 2% of the total mass loss, respectively.Overall these findings confirm the immaturity of the saprolite at the watershed scale. The soil profiles are more evolved than saprolite but still contain primary minerals that can further undergo weathering and hence consume atmospheric CO₂.  相似文献