a lisflood fp hydraulic model of the middle reach of the congo abstract in this paper we attempt to produce a first hydrodynamic model of the middle reach of the congo river system in order to understand what controls this river s unique bimodal flood pulse the model covers the area between kisangani and kinshasa on the main stem and includes the major tributaries and the cuvette centrale wetland one of the world s largest and most understudied lowland regions a mixture of in situ discharges and modelled discharge from a basin wide catchment hydrology model were used to force a four kilometre resolution hydrodynamic simulation developed using the lisflood fp model river channels are represented as sub grid scale features and their width is therefore decoupled from that of the over lying floodplain grid unknown channel friction and bathymetry parameters were calibrated using ers 2 and envisat satellite altimetry measurements of channel water level the calibrated model simulated channel water surface elevations across the domain with a bias and root mean square error of 0 185 and 0 842 m respectively the value for root mean squared error is close to that obtained for comparisons of ers 2 and envisat satellite altimetry to in situ water elevation data in similar basins 0 79 m and 0 47 m respectively the model results imply that the bimodal annual pattern of congo river discharge is predominantly a hydrological rather than hydraulically controlled feature with the channel floodplain interactions and river constrictions having only a modest impact on the flood wave propagation nevertheless and counter to current understanding we find that interactions between channels and floodplains do however occur extensively with over 2100 km of the 13 000 km of channel network in the model identified as zones where water is actively exchanged between channels and floodplains whilst the water volume that is exchanged with the floodplain is substantially less than for other large rivers our results imply that channel floodplain interactions are a significant feature of congo flood wave propagation overall the model provides insights into the hydraulics of this understudied system that can next be tested both in the field and through more detailed modelling studies

comparison between the hot spot and geomagnetic field reference frames hot spots are located on the earth s surface and are caused by hot plumes of upwelling mantle material they manifest themselves by volcanic activity which changes its location in response to the movement of the lithosphere over the mantle plume it has been suggested1 3 that hot spots are relatively stationary with respect to each other and also that they represent a frame of reference with which to measure the absolute movement of the lithospheric plates over the surface of the earth another frame of reference can be partially defined by the position of the mean magnetic dipole field of the earth as the dipolar field is believed to be closely related to the spin axis this frame of reference automatically gives information about the palaeolatitude and orientation of the lithospheric plates but since the position of the ancient dipole field of the earth does not give any information about palaeolongitude and since in many cases the definition of the field is relatively poor due to less than adequate rock collections during the time of interest hot spot reference frames have been favoured by many people we now report a comparison of the two frames of reference and show that over the past 200 myr there has been relative movement between the two frames of reference of about 20 and that this motion has not been constant with time

chemical stability of the atmosphere and ocean abstract the earth system processes most of the chemical components of its atmosphere and oceans in geologically short periods of time it does this in a regulated way one that maintains a remarkably constant surface environment this we know primarily from the fossil record of uninterrupted complex life on earth that extends over the last billion years we are only beginning to understand the feedbacks that control the chemistry of the oceans and atmosphere numerical models of biogeochemical cycles are most stable when there is feedback between the amount of a chemical component in the ocean or atmosphere and its transfer to or from that reservoir coupling of subsystem especially of those operating on different time scales enhances stability an example of the role of feedback in stabilizing earth s chemical environment is the mechanism of control of atmospheric oxygen there appears to be no strong relationship between oxygen level and oxygen consumption however oxygen production may be a function of oxygen level the burial rate of organic carbon oxygen production in marine sediments may be sensitive to bottom water oxygenation levels also combustion may be an effective mechanism of transferring nutrients namely phosphorus from efficient terrestrial ecosystems to less efficient marine ecosystems when o2 rises fires become more frequent and p is transferred to the ocean stimulating marine organic carbon burial but depressing global burial rates global o2 production rates decline as does the o2 level a negative feedback models of ocean chemical composition are presently incapable of reproducingthe temporal constancy indiated by geological observations these models do not incorporate ion exchange equilibria as important processes in marine geochemical cycles when included these equilibria significantly damp the fluctuations in ion ratios calculated by the extant models

shear wave splitting in the upper mantle wedge above the tonga subduction zone summary intermediate period seismograms of shear waves from deep earthquakes are examined for shear wave splitting diagnostic of seismic velocity anisotropy in the upper mantle wedge between the subducting tonga slab and stations in the fiji islands earthquakes with near vertical incidence angles are selected to minimize complications of converted phases and the free surface horizontal component seismograms for 25 deep earthquakes recorded at station lak on the lau ridge show splitting of up to 0 9 s with an average of 0 45 0 25 s between fast and slow s wave components anisotropy in the upper mantle is the most likely cause of the splitting the ese orientation of the fast velocity direction at station lak corresponds to an axis of symmetry of the anisotropic mantle and is approximately perpendicular to magnetic lineations in the lau basin and the northeastern portion of the south iiji basin the observations are consistent with a model of flow alignment of olivine 100 and orthopyroxene 001 axes parallel to the direction of basin extension seismograms for eight deep earthquakes at station sva on viti levu show up to 1 0 s splitting with an average of 0 65 0 29 s and a weak nne preferred orientation of fast velocity polarizations of shear wave particle motions corrected for anisotropy are within 36 5 26 of polarixations predicted for nine moment tensor solutions the magnitude of shearwave splitting and estimates of the thickness of the lithosphere in the fiji region imply that the anisotropy cannot be contained in the lithosphere alone either the anisotropy is distributed in both the lithosphere and asthenosphere or the asthenosphere alone is anisotropic

iron water reaction under high pressure and its implication in the evolution of the earth we have established by experiments and thermodynamical calculations that a large amount of hydrogen can be dissolved in iron under high hydrogen pressure causing appreciable reduction of density and melting point more recent experiments have shown that the reaction of fe with hydrous silicates under high pressure and temperatures 5 gpa 1200 c 20 min yields iron hydride fehx olivine and pyroxene and that coagulation of iron particles is greatly facilitated in the partially molten state of the silicates on the basis of these experimental findings on fe h and fe h2o systems we propose that the fe h2o reaction should have played a crucial role in the evolution of the earth including in particular the core mantle separation and dissolution of hydrogen in the earth s core a tentative calculation on the mass flow in the evolution process was made by assuming a 10 90 mixture of low temperature lt and high temperature ht components for the primordial material and fe fe mg 0 11 for the whole mantle the composition of the core thus deduced together with compressibility data at high pressures is found to give reasonable values for the density deficit of the outer core if conversely we adopt the density reduction as input the composition of the outer core is estimated to be feh0 25c0 05o0 13s0 03 finally some implications of the present picture on other terrestrial planets are examined briefly

azimuthally anisotropic model of the oceanic upper mantle abstract a mixed form of forward and backward modelings of azimuthally anisotropic oceanic upper mantle is attempted for a data set of surface wave velocities of periods 30 100 s one of the basic configurations of the anisotropy postulated in the lid and lvz is axial symmetry of elastic properties with a horizontal axis parallel to the spreading direction as found in ultramafic rocks from ophiolite complexes of the bay of islands and oman basic features of the resulting model are a thin lithosphere of 45 km a decrease of s wave velocities and an increase of p wave velocities and of partial melting dislocation relaxation with depth in the lvz this single model explains the overall features of anisotropy observations in the pacific ocean p n velocity anisotropy sh sv anisotropy and azimuthal anisotropy of surface waves and scs polarization anisotropy this fact leads us to a conclusion that the ultramafic rocks from the ophiolite complexes can explain the seismic properties of the oceanic lid and lvz

icesat derived inland water surface spot heights accurate measurement of water surface height is key to many fields in hydrology and limnology satellite radar and laser altimetry have been shown to be useful means of obtaining such data where no ground gauging stations exist and the accuracy of different satellite instruments is now reasonably well understood past validation studies have shown water surface height data from the icesat instrument to have the highest vertical accuracy mean absolute errors of 10 cm for icesat compared for example with 28 cm from envisat yet no freely available source of processed icesat data currently exists for inland water bodies here we present a database of processed and quality checked icesat derived inland water surface heights iwsh for water bodies greater than 3 arc sec 92 m at the equator in width four automated methods for removing spurious observations or outliers were investigated along with the impact of using different water masks we find that the best performing method ensures that observations used are completely surrounded by water in the srtm water body data using this method for removing spurious observations we estimate transect averaged water surface heights at 587 292 unique locations from 2003 to 2009 with the number of locations proportional to the size of the river

efficient incorporation of channel cross section geometry uncertainty into regional and global scale flood inundation models this paper investigates the challenge of representing structural differences in river channel cross section geometry for regional to global scale river hydraulic models and the effect this can have on simulations of wave dynamics classically channel geometry is defined using data yet at larger scales the necessary information and model structures do not exist to take this approach we therefore propose a fundamentally different approach where the structural uncertainty in channel geometry is represented using a simple parameterisation which could then be estimated through calibration or data assimilation this paper first outlines the development of a computationally efficient numerical scheme to represent generalised channel shapes using a single parameter which is then validated using a simple straight channel test case and shown to predict wetted perimeter to within 2 for the channels tested an application to the river severn uk is also presented along with an analysis of model sensitivity to channel shape depth and friction the channel shape parameter was shown to improve model simulations of river level particularly for more physically plausible channel roughness and depth parameter ranges calibrating channel manning s coefficient in a rectangular channel provided similar water level simulation accuracy in terms of nash sutcliffe efficiency to a model where friction and shape or depth were calibrated however the calibrated manning coefficient in the rectangular channel model was 2 3 greater than the likely physically realistic value for this reach and this erroneously slowed wave propagation times through the reach by several hours therefore for large scale models applied in data sparse areas calibrating channel depth and or shape may be preferable to assuming a rectangular geometry and calibrating friction alone

wetland mapping in the congo basin using optical and radar remotely sensed data and derived topographical indices article i nfo this study reports results of a classification tree approach to mapping the wetlands of the congo basin focusing on the cuvette centrale of the congo river watershed an area of 1 176 000 km 2 regional expert knowledge was used to train passive optical remotely sensed imagery of the landsat thematic mapper tm and enhanced thematic mapper plus etm sensors jers 1 active radar l band imagery and topographical indices derived from 3 arc sec elevation data of the shuttle radar topography mission srtm all data inputs were resampled to a common 57 m resolution grid a classification tree bagging procedure was employed to produce a final map of per grid cell wetland probability thirty bagged trees were ranked and the median result was selected to produce the final wetland probability map thresholding the probability map at 0 5 yielded a proportion of wetland cover for the study area of 32 equivalent to 360 000 km 2 wetlands predominate in the carpe lake tele lake tumba landscape located in the western part of the democratic republic of the congo and the south eastern republic of congo where they constitute 56 of the landscape local topography depicting relative elevation for sub catchments proved to be the most valuable discriminator of wetland cover however all sources of information i e optical radar and topography featured prominently in contributing to the classification tree procedure reinforcing the idea that multi source data are useful in the characterization of wetland land cover the method employed freely available data and a fully automated process except for training data collection comparisons to existing maps and in situ field observations indicate improvements compared to previous efforts

mantle upflow under north america and plate dynamics in the development of plate dynamics there are two fundamental questions first do the plates slide over a passive asthenosphere or are they driven by a convecting upper mantle second are all ocean ridges passive pull apart plate margins or do some lie above upcurrents in the mantle and in that sense become active margins the combination of stress orientations in the crust of north america with other geophysical and geological information favours an active mantle interpretation both for the north american plate and for the mantle upflow which lay beneath the east pacific rise in tertiary times and which now lies beneath the western united states

geophysiology of mineral deposits a model for a biological driving force of global changes through earth history the upper mantle crust hydrosphere and atmosphere of earth are kept in a geophysical geochemical and thermodynamical state far from astrophysical and planetary equilibrium the system oscillates around a quasi stable centre following laws governing dissipative or dynamic systems the energy and materials necessary for such global pseudo equilibria are fed in stored and released on a geological time scale by a the energy and electron channelling processes of photosynthesis respiration and fermentation b biologically controlled accumulation of energy and matter into crustal reservoirs and much later c release of the latter from crust and upper mantle into surface related geotectonical and geochemical cycles phototrophic and chemorganotrophic bacterial microorganisms of microbial mats potential stromatolites or microbialites are capable of anoxygenic and oxygenic photosynthesis of aerobic and anaerobic respiration and of organic and inorganic fermentation i e disproportioning of energy rich molecules in this way large amounts of photosynthate are transformed on a global scale into hydrocarbons and sulphides sulphate serving as electron acceptor for anaerobic respiration or fermentation inorganic reduced compounds produced by the same processes of photosynthesis followed by respiration and fermentation are stored as sulphides of iron lead zinc silver gold etc all the aforementioned microbial processes can transfer energies and matter at a global scale thus disparities of the earth s crust and mantle from the geochemical equilibrium may not be caused solely by internal temperature radioactivity and gravity gradients but increasingly by life processes the biogenic formation of energy rich compounds on a global scale delivers huge amounts of energy and electrons to the crust which are recycled through geological time the quantities of energy involved appear in themselves to be sufficient to provide the driving force for geotectonic processes thus a model of geophysiological equilibration of geochemical cycles and geotectonics is proposed in which the biota play the role of energy and matter transmitters for geodynamic processes living matter controls and transfers more than 10 of the earth s mass in this system with turnover times of up to 500 million years the transfer speed of each individual atom according to the model must have gradually decreased since the precambrian while the amounts of energy and matter stored and cycled have in turn increased as also witnessed by the increase in the thickness of the crust earth as a bioplanet has come of age

test of tectonic models by great circle rayleigh waves summary a large set of published great circle rayleigh wave phase velocities in the period range 125 350s is used to compare three recent tectonic models okal leveque jordan prior to any regionalization the symmetry property of the great circle integrals is used to obtain a lower limit of the signal noise ratio in the data it turns out that the signal is responsible for at least 30 per cent of the data variance in the period range 175 300s a standard regression method is applied for computing the pure path velocities and the model efficiency is derived from a variance analysis it is shown that even at great depth none of the three models explains more than 60 per cent of the energy due to the long wavelength lateral heterogeneities 6500 km the three models have nearly the same efficiency for explaining the short period data t 125s between 200 and 300s the higher performance of okal s model indicates that it is important to separate the subduction zones from the other orogenic zones by perturbing the lateral extension of the subduction zones it comes out that they constitute on both sides of the subducting slabs wider anomalies than often assumed suggesting large downgoing flows on the contrary the effect of surface features such as marginal seas are restricted to a close region in front of the trenches finally the anomalous ellipticity values deduced directly from great circle data are partly explained by a coupling between tectonics and ellipticity

characterization of complex fluvial systems using remote sensing of spatial and temporal water level variations in the amazon congo and brahmaputra rivers the surface water and ocean topography swot satellite mission will provide global space based estimates of water elevation its temporal change and its spatial slope in fluvial environments as well as across lakes reservoirs wetlands and floodplains this paper illustrates the utility of existing remote sensing measurements of water temporal changes and spatial slope to characterize two complex fluvial environments first repeat pass interferometric sar measurements from the japanese earth resources satellite are used to compare and contrast floodplain processes in the amazon and congo river basins measurements of temporal water level changes over the two areas reveal clearly different hydraulic processes at work the amazon is highly interconnected by floodplain channels resulting in complex flow patterns in contrast the congo does not show similar floodplain channels and the flow patterns are not well defined and have diffuse boundaries during inundation the amazon floodplain often shows sharp hydraulic changes across floodplain channels the congo however does not show similar sharp changes during either infilling or evacuation second shuttle radar topography mission measurements of water elevation are used to derive water slope over the braided brahmaputra river system in combination with in situ bathymetry measurements water elevation and slope allow one to calculate discharge estimates within 2 3 accuracy these two studies illustrate the utility of satellite based measurements of water elevation for characterizing complex fluvial environments and highlight the potential of swot measurements for fluvial hydrology copyright 2010 john wiley sons ltd

a multi sensor approach towards a global vegetation corrected srtm dem product abstract we develop the first global bare earth digital elevation model dem based on the shuttle radar topography mission srtm for all landmasses between 60n and 54s our new bare earth srtm dem combines multiple remote sensing datasets including point ground elevations from nasa s laser altimeter icesat a database of percentage of tree cover from the modis satellite as a proxy for penetration depth of srtm and a global vegetation height map in order to remove the vegetation artefacts present in the original srtm dem we test multiple methods of removing vegetation artefacts and investigate the use of regionalization our final bare earth srtm product shows global improvements greater than 10 m in the bias over the original srtm dem in vegetated areas compared with ground elevations determined from icesat data with a significant reduction in the root mean square error from over 14 m to 6 m globally therefore our dem will be valuable for any global applications such as large scale flood modelling requiring a bare earth dem

spatiotemporal variations in hydrological regimes within central africa during the xxth century abstract using several statistical tests we divided into homogeneous segments the xxth century long discharges data series and the rainfall data series of the congo river and of several of its right bank sub catchments these tests revealed that the river congo at brazzaville experienced a phase of so called stable discharge from the beginning of the xxth century until 1960 a phase of surplus discharge during the 1960s testimony to its centennial flooding and then from 1971 onwards two successive phases of lower discharge the second one stretching from 1980 up to now being the most accentuated with a 10 drop in the total series interannual discharge 40 600 m 3 s 1 it has only been very recently in 1990 that the river dropped to its lowest level of the century the dates at which hydrological discontinuities appear are observed to be globally similar within practically all of the tributaries studied the most significant being that of 1970 already well known in west africa during the second half of the century these discontinuities occur roughly every ten years at the beginning of the 1960s 1970s and 1980s rainfall discontinuities are not as numerous as discharges ones they separate homogeneous phases whose variations between them are less pronounced than that of those separated by discharges discontinuities this underlines the major importance of the geographical location and of the physiographical characteristics of river basins on hydrological spatiotemporal variations lastly we show that the effects of the recent drought are more visible and pronounced in the northern areas of this vast basin than in the southern ones

the earth as a planet paradigms and paradoxes the independent growth of the various branches of the earth sciences in the past two decades has led to a divergence of geophysical geochemical geological and planetological models for the composition and evolution of a terrestrial planet evidence for differentiation and volcanism on small planets and a magma ocean on the moon contrasts with hypotheses for a mostly primitive still undifferentiated and homogeneous terrestrial mantle in comparison with the moon the earth has an extraordinarily thin crust the geoid which should reflect convection in the mantle is apparently unrelated to the current distribution of continents and oceanic ridges if the earth is deformable the whole mantle should wander relative to the axis of rotation but the implications of this are seldom discussed the proposal of a mantle rich in olivine violates expectations based on evidence from extraterrestrial sources these and other paradoxes force a reexamination of some long held assumptions

the modern geoid and ancient plate boundaries abstract the non hydrostatic geoid is dominated by three large anomalies an area of high gravity potential in the equatorial pacific another stretching from greenland through africa to the southwest indian ocean and a semi continuous low region passing from hudson s bay through siberia to india and on to antarctica none of these three high amplitude greater than 60 m and long wavelength anomalies corresponds to present day plate boundaries however if the modern geoid is plotted over the positions of continents and plate boundaries at 125 ma b p reconstructed relative to hotspots a strong correlation emerges the modern geoidal low corresponds in position to the areas of subduction surrounding the pacific 125 ma ago the geoidal high now centered on africa is entirely contained within ancient pangaea and the equatorial pacific high overlies the location of the spreading centers preserved in the magnetic anomalies of the central pacific the most plausible cause of the large geoidal undulations is lower mantle convection only weakly coupled to plate motions the correspondence between modern geoid and ancient plate boundaries implies either that the coupling was much more intimate in the past or that there is a lag of at least 100 ma in response of the lower mantle to upper mantle conditions

structure and evolution of the intracratonic congo basin 1 surface wave tomography heat flow and crustal thickness measurements have demonstrated that the thickness of the continental lithosphere varies by at least a factor of 2 since the thermal time constant of the lithosphere depends upon the square of its thickness subsidence records of extensional sedimentary basins offer a potential way of extending these observations into the past here we examine the congo basin a large and iconic intracratonic sedimentary basin in central africa this roughly circular basin covers an area in excess of 1 4 106 km2 with more than 5 km thickness of sedimentary rocks the oldest parts of which are late precambrian in age first we assess the thickness of the lithosphere we have estimated its thickness across africa using maps of shear wave velocity obtained by inversion of fundamental and higher mode surface waveforms the congo basin sits on 220 30 km thick lithosphere and appears to be part of a southern core to the continent encompassing both archean cratons and proterozoic mobile belts this thickness is consistent with published estimates from kimberlites reappraisal of legacy seismic reflection images demonstrates that the sedimentary section is underlain by a late precambrian rift zone and that the basin is still subsiding today subsidence modeling of two deep wells is consistent with uniform extension and cooling of the lithosphere by a factor of 1 2 during latest precambrian and cambrian time we argue that the exceptional 0 55 ga history of the basin is a direct consequence of the lithospheric thermal time constant being a factor of 4 longer than normal today the basin coincides with a long wavelength 30 to 40 mgal gravity anomaly we interpret this gravity anomaly as the surficial manifestation of 400 600 m of recent mantle convective drawdown in response to the onset of upwelling plumes around the flanks of the southern african continent the alternative explanation that it is the static manifestation of locally thick lithosphere is inconsistent with global trends of mantle density depletion our interpretation is consistent with fast seismic velocities observed throughout the sublithospheric upper mantle underneath the basin and recent geodynamic modeling

cenozoic latitudinal shift of the hawaiian hotspot and its implications for true polar wander abstract pacific plate equatorial sediment facies provide estimates of the northward motion of the pacific plate that are independent of paleomagnetic data and hotspot tracks analyses of equatorial sediment facies consistently indicate less northward motion than analyses of the dated volcanic edifices of the hawaiian emperor chain the discrepancy is largest 60 70 ma b p the 60 to 70 ma equatorial sediment facies data agree with recent paleomagnetic results from deep sea drilling on suiko seamount 1 and from a northern pacific piston core 2 equatorial sediment facies data and paleomagnetic data combined with k ar age dates along the emperor chain 3 indicate a position of the spin axis at 65 ma b p of 82 n 205 e in the reference frame in which the pacific ocean hotspots are fixed this pole agrees well with the position of the spin axis in the reference frame in which the atlantic ocean hotspots and the indian ocean hotspots are fixed 4 5 supporting the joint hypotheses that 1 the pacific ocean hotspots are fixed with respect to the hotspots in other oceans 2 the hotspots have shifted coherently with respect to the spin axis and 3 the time average of the earth s magnetic field 65 ma b p was an axial geocentric dipole global neogene paleomagnetic data suggest that a shift of the mantle relative to the spin axis has been occurring during the neogene in the same direction as the shift between 65 ma b p and the present all data are consistent with a model in which the hotspots and by inference the mantle have shifted with respect to the spin axis about a fixed euler pole at a constant rate of rotation for the last 65 ma

secular rotational motions and the mechanical structure of a dynamical viscoelastic earth we give a survey of the analytical methods for computing the linear responses of the rotational axis of a layered viscoelastic earth to surface loading the two classes of eigenspectra involving isostatic relaxation of the mantle and readjustment of the spin axis are emphasized as being essential for a uniformly valid description of polar wander the rotational responses due to the application of an equilibrium phase or a chemically layered boundary condition at the 670 km discontinuity are studied the displacement fields associated with rotational deformation are affected to a much greater extent by the amount of chemical enrichment than are the eigenfunctions associated with isostatic relaxation the present polar motion data from international latitude service i l s can be fit equally well by a pure chemical or an equilibrium phase boundary with a 9 change in density across the interface on the other hand responses from models with a smaller amount of chemical stratification 7 are not compatible with the data the secular variation of the earth s gravitational harmonic j2 is insensitive to the chemical nature of the 670 km discontinuity from the rotational data it is not possible to rule out the existence of a high viscosity region with values of o 1023 p at the bottom 500 km of the mantle although a solution with a relatively uniform viscosity profile o 1022p still can be found inferences of the globally averaged thickness of the elastic lithosphere from rotational data are not affected too much by the particular density stratification used for the lithosphere and upper mantle they lie in the range between 120 and 170 km

numerical study of creep in two phase aggregates with a large rheology contrast implications for the lower mantle it is generally accepted that the earth s lower mantle is dominated by two minerals magnesiowustite mg fe o mw and mg fe sio3 perovskite mg pv which are thought to exhibit very different rheological properties in order to assess the respective role of those phases in the mechanical properties of the assemblage we have carried out 3d finite element modelling of a model two phase aggregate an isotropic random polycrystal has been built from a voronoi mosaic then each grain has been attributed a hard or weak behavior in such a way that the hard phase represents a volume fraction of 70 the creep law introduced for both phases is a simple power law creep without hardening a contrast of 35 is chosen between the strain rates of both phases under a shear stress of 10 mpa a representative volume element of 470 grains has been shown to provide a satisfactory description of the mechanical response of the aggregate with a relative precision equal to 3 numerical creep experiments conducted under a constant macroscopic shear stress of 10 mpa suggest that the creep rate of lower mantle assemblages would be dominated by the mechanical behavior of the harder phase mg pv the finite element model allows one to extract the individual behavior of the two phases within the aggregate it is shown that during creep the harder mg pv phase carries most of the stress whereas the softer mw phase is responsible for most of the accumulated strain this result should have implications for the development of shape and lattice preferred orientations of mw within the aggregate thus for seismic anisotropy of the lower mantle

recent advances in wavelet analyses part 2 amazon parana orinoco and congo discharges time scale variability this paper is devoted to illustrating new wavelet analysis methods in the field of hydrology new wavelet indicators are applied to long term hydrological and climatologic proxies they are first applied to four atlantic large river monthly discharges amazon parana orinoco and congo and then applied to two well known long term climatologic indexes the southern oscillation and the north atlantic oscillation this approach makes it possible to suggest physical explanations for time scale dependant relationships six month variability is present in all the rivers except in the parana in the congo river this signal is near stationary with strong entropy the strength of this scale coincides with higher discharge variability before 1920 and over the orinoco basin with higher discharge values between 1940 and 1955 an annual cycle is present in all the rivers but is much stronger along with the entropy in the rivers with a large tropical basin as in the amazon and the orinoco this annual signal is not permanent in the congo and much more intermittent in the parana where the annual recharge appears as very irregular a quasi biennial variability is apparent in all the equator ward rivers and a nearly permanent 2 year coherence is found between soi and the amazon discharge a 3 6 year oscillation typical of enso variability is observed in all the rivers it is intermittent observed before 1930 in all the rivers and after 1980 mostly in the amazon river these peaks of activity correspond to periods of major soi variability an 8 year variability is particularly strong in the parana river before 1940 and around 1970 and to a lesser extent in the orinoco river during the low nao index period between 1940 and 1970 the congo river exhibits that time scale around 1970 a 13 year variability common to soi nao and the south atlantic ocean circulation is observed in the parana and congo discharges in all the rivers the greatest entropy is observed at bi and multi decadal time scales with the greatest coherence with both nao and soi a near 20 year time scale is observed in most of the series around 1970 although it is strongest in amazon and parana discharges finally a 30 year time scale is observed between 1940 and 1970 it is to be noted that most of the time scale dominant activities in all the rivers may have been influenced by the interdecadal shifts that took place around 1940 and 1970 in the pacific and in the atlantic therefore in this contribution the application of new wavelet indicators combined continuous and multi resolution analysis wavelet entropy wavelet coherence wavelet cross correlation leads to several improvements in the analysis of these global hydrological signal fluctuations and of their mutual time varying relationships it is demonstrated that wavelets should be used more systematically in preference to the classical fourier analysis notably in hydrology

oxygen isotopic compositions of enstatite chondrites and aubrites oxygen isotopic compositions have been measured for ten eh chondrites eight el chondrites and nine aubrites the mean 18o and 17o values are 5 31 and 2 74 5 57 and 2 96 5 24 and 2 70 respectively within the eh group more equilibrated meteorites are fractionated toward higher heavy isotope abundances than the less equilibrated meteorites small departures of individual meteorites from a common mass fractionation occur for some of the eh samples the aubrites may be genetically related to either the eh or el group or to both almost all of the measured isotopic compositions are indistinguishable from the terrestrial oxygen isotope fractionation line suggesting a genetic relationship among the earth the moon and the enstatite the meteorites

a new formula to compute apparent resistivities from marine magnetometric resistivity data magnetometric resistivity mmr is an electromagnetic em exploration method that has been used successfully to investigate electrical resistivity structures below the seafloor apparent resistivity derived from the observed azimuthal component of the magnetic field often is used as an approximation to the resistivity of a layered earth two commonly used formulas to compute the apparent resistivity have their own limitations and are invalid for a deep sea experiment in this paper we derive an apparent resistivity formula based upon the magnetic field resulting from a semi infinite electrode buried in a 1d layered earth this new formula can be applied to both shallow and deep marine mmr surveys in addition we address the effects that arise from the transmitter receiver tx rx depth difference and the choice of the normalized range the radial distance between transmitter and receiver divided by the thickness of seawater on data interpretation and survey design the performance of the new formula is shown by processing synthetic and field data

worldwide distribution of group velocity of mantle rayleigh waves as determined by spherical harmonic inversion we have determined the worldwide distribution of group velocity of mantle rayleigh waves for periods between 100 and 300 sec without assuming any regionalization group slowness 1 u is expressed by spherical harmonics and the coefficients up to angular order 7 have been determined from travel times of rayleigh waves by a least squares method from these u has been synthesized since we cannot obtain information about the odd terms of the expansion from one circuit measurements around the world we have used group velocities of mainly r 2 and r 3 the overall pattern of u for periods between 100 and 200 sec is consistent with results of previous pure path and regional studies group velocities for tectonically active regions are low and those of the shields and the northwestern pacific are high

paleoclimate and polar wander abstract fossil faunas floras and 18 o temperatures indicate that weak or no meridional temperature gradients existed over the continents from triassic to eocene for much of this time tropical pacific 18 o temperatures were some ten degrees colder than at present while arctic and antarctic regions apparently enjoyed warm temperate to semitropical climates polar wander involving displacement of the poles to what are now tropical marine latitudes is offered to explain this uniformly warm paleoclimate this hypothesis is supported by a theoretical model which is discussed

gravitational circulation in the upper mantle implications for crustal and mantle evolution abstract officer and drake 1983 have given an quantitative description of upper mantle convection and related plate dynamics in which the principal driving force is the longitudinal density gradient within the upper mantle between the spreading ridge and the subduction zone the principal objective here is to consider an additional component of flow in the upper mantle between the warmer and less dense spreading ridge and the cooler and more dense deep continental regions

komatiites and picrites evidence that the plume source is depleted high temperature magmas such as picrites and komatiites are candidates for the material in the hot axial region of mantle plumes in current plume theories these magmas should have an enriched ocean island basalt oib type chemistry high mgo magmas however are often more like depleted mid ocean ridge basalts morb in trace element and isotopic chemistry this is a paradox for deep mantle plume or primitive mantle theories but is expected if hotspots and morb share a common depleted source and the transition to oib chemistry involves shallow level cooling crystal fractionation and contamination ancient komatiites appear to have come from the same deep depleted reservoir as modern picrites and morb

water levels in the amazon basin derived from the ers 2 and envisat radar altimetry missions article i nfo this study sets out to analyze the stages of water bodies in the amazon basin derived from the processing of ers 2 and envisat satellite altimetry data for envisat gdr measurements for both ice 1 and ice 2 tracking algorithms were tested for ers 2 the ice 2 data produced by the oscar project was used water level time series over river segments of very different width from several kilometers to less than a hundred of meters were studied the water level time series that can be derived from narrow riverbeds are enhanced by off nadir detections conversely the off nadir effect may degrade the series over large bodies if not properly accounted for comparison at crossovers and with in situ gauges shows that the quality of the series can be highly variable from 12 cm in the best cases and 40 cm in most cases to several meters in the worse cases cautious data selection is clearly a key point to achieve high quality series indeed low quality series mostly result from inclusion of outliers in the data set finally retained for the computation of the series ice 2 and ice 1 tracking algorithms in the envisat data perform almost equally well envisat altimetry is clearly an improvement on ers 2 altimetry

petrology geochemistry and origin of a major australian 1880 1840 ma felsic volcano plutonic suite a model for intracontinental felsic magma generation in australia a major period of felsic volcanism and granite emplacement occurred between 1880 and 1840 ma towards the end of the early proterozoic these volcanics and granites covering at least 37 000 km2 are compositionally uniform over large areas the felsic magmas are predominantly i type being derived from infracrustal sources which have never been exposed to surficial weathering processes when compared with early archaean and phanerozoic i type granites the 1880 1840 ma suite has distinctively high levels of k2o rb zr la ce th u and low mgo and cao contents even at relatively low sio2 levels of 60 65 the 1880 1840 ma rocks are characterized by low initial 87sr 86sr ratios and negative nd values chemical and isotopic modelling on these volcanics and granites suggest that they formed from mantle derived sources that are around 2300 2000 ma old there is no evidence of a major archaean component in these granites the sources are interpreted to have formed as a result of polygonal small scale mantle convection which led to extensive underplating of archaean crust during this underplating event large volumes of incompatible element enriched mantle derived material accreted to the base of the lower crust and fractionated significantly the more fractionated part of this source was remelted between 1880 1840 ma to produce the voluminous felsic volcanics and comagmatic granites present in nearly every proterozoic domain of australia the actual underplating event between 2300 2000 ma is believed to have triggered the formation of early proterozoic sedimentary basins which occur in a polygonal pattern and appear to wrap around archaean nuclei the composition of these felsic melts and the tectonic setting operating during their emplacement precludes genesis by contemporaneous subduction of oceanic crust all are generated by processes of vertical accretion in an intracontinental environment

a subgrid channel model for simulating river hydraulics and floodplain inundation over large and data sparse areas 1 this paper presents a new computationally efficient hydraulic model for simulating the spatially distributed dynamics of water surface elevation wave speed and inundation extent over large data sparse domains the numerical scheme is based on an extension of the hydraulic model lisflood fp to include a subgrid scale representation of channelized flows which allows river channels with any width below that of the grid resolution to be simulated the scheme is shown to be numerically stable and scalable before being applied to an 800 km reach of the river niger in mali the niger application focused on the performance of four different model structures a model without channels two dimensional 2 d model a model without a floodplain one dimensional 1 d model a model of the main channels and floodplain 1 d 2 d model and the subgrid approach developed here inclusion of both the channel network and the floodplain was shown to be essential meaning that large scale models of this region including routing models for land surface schemes will require a floodplain component including subgrid scale channels on the floodplain changed inundation dynamics over the delta significantly and increased simulation accuracy in terms of water level wave propagation speed and inundation extent furthermore only the subgrid model showed a consistent parameterization when calibrated against either gauge or icesat water level data suggesting that connectivity provided by small channels is a strong control on the hydraulics of the floodplain or at the very least that low resolution gridded hydraulic models require additional connectivity to represent the delta flow dynamics

a hydrologic routing model suitable for climate scale simulations of arctic rivers application to the mackenzie river basin in this study the hillslope river routing hrr model was modified for arctic river basin applications and used to route surface and subsurface run off from the community land model clm in the mackenzie river basin mrb for the period 2000 2004 the hrr modelling framework performs lateral surface and subsurface run off routing from hillslopes and channel floodplain routing the hrr model was modified here to include a variable subsurface active layer thickness alt permafrost to enable subsurface water to resurface a distributed surface storage component to store and attenuate the rapid generation of snowmelt water compound hillslopes to account for the low relief near rivers and floodplains and reservoir routing to complete the total surface and subsurface water storage accounting to illustrate the new hrr model components a case study is presented for the mrb the basin is discretized into 5077 sub basins based on a drainage network derived from the global digital elevation model dem developed from the advanced spaceborne thermal emission and reflection radiometer aster sensor on board nasa s terra satellite and river widths extracted from landsat images the median hillslope land area is 68 5 km2 with a flow length of 2 8 km gridded clm surface and subsurface run offs are remapped to the hrr model s irregular sub basins the role of each new model component is quantified in terms of peak annual streamflow magnitude and timing at select locations and basin wide total water storage anomalies the role of distributed surface storage is shown to attenuate the relatively rapid generation of snowmelt water impact the annual peak hydrograph reduced peaks by 30 and detailed peak by 20 days and account for 20 of the monthly total water storage anomalies averaged over the year and ranging from 14 to 25 10 to 30 mm throughout the year although additional research is needed to dynamically link spatially distributed alt to hrr the role of alt is shown to be important a basin wide uniform 1 m alt impacts the annual peak hydrograph reduced peaks by 9 and detailed peak by 8 days and trends in total water storage anomalies copyright 2014 john wiley sons ltd

estimation of multiple inflows and effective channel by assimilation of multi satellite hydraulic signatures the ungauged anabranching negro river abstract with the upcoming swot satellite mission which should provide spatially dense river surface elevation width and slope observations globally comes the opportunity to assimilate such data into hydrodynamic models from the reach scale to the hydrographic network scale based on the hivdi hierarchical variational discharge inversion modeling strategy larnier et al 2020 this study tackles the forward and inverse modeling capabilities of distributed channel parameters and multiple inflows in the 1d saint venant model from multisatellite observations of river surface it is shown on synthetic cases that the estimation of both inflows and distributed channel parameters bathymetry friction is achievable with a minimum spatial observability between inflows as long as their hydraulic signature is sampled next a real case is studied 871 km of the negro river amazon basin including complex multichannel reaches 21 tributaries and backwater controls from major confluences an effective modeling approach is proposed using i ws elevations from envisat data and dense in situ gps flow lines moreira 2016 ii average river top widths from optical imagery pekel et al 2016 iii upstream and lateral flows from the mgb large scale hydrological model paiva et al 2013a the calibrated effective hydraulic model closely fits satellite altimetry observations and presents real like spatial variabilities flood wave propagation and water surface observation frequential features are analyzed with identifiability maps following brisset et al 2018 synthetic swot observations are generated from the simulated flowlines and allow to infer model parameters 436 effective bathymetry points 17 friction patches and 22 upstream and lateral hydrographs given hydraulically coherent prior parameter values inferences of channel parameters carried out on this fine hydraulic model applied at a large scale give satisfying results using noisy swot like data at reach scale inferences of spatially distributed temporal parameters lateral inflows give satisfying results as well with even relatively small scale hydrograph variations being inferred accurately on this long reach this study brings insights in i the hydraulic visibility of the signatures of multiple inflow hydrographs at a large scale with swot ii the simultaneous identifiability of spatially distributed channel parameters and inflows by assimilation of satellite altimetry data iii the need for prior information iv the need to further tailor and scale network hydrodynamic models and assimilation methods to improve the fusion of multisource information and potential information feedback to hydrological modules in integrated chains