eof analysis and modeling of gps tec climatology over north america an empirical ionospheric model of the total electron content tec over north america 20 60 n 40 140 w is constructed using the gps tec data collected by massachusetts institute of technology mit haystack observatory during the years 2001 2012 this model is based on an analysis of quiet time monthly averages using the empirical orthogonal function eof decomposition technique allowing for separation of spatial and temporal variations the importance of different types of spatial temporal variations to the overall tec variability can be well represented by the characteristics of eof basis functions and associated principal components coefficients with various modes the mode one eof decomposition constitutes 97 5 of the total variance and therefore represents the essential feature of north america spatial and diurnal variation of the tec the mode two eof as reported in an earlier study reveals a large and significant symmetric longitudinal variation of the ionosphere organized with respect to magnetic declination the mode three eof decomposition shows midlatitude latitudinal structure that varies with season in a manner very similar to the so called winter anomaly because of the quick convergence of eof decomposition modes the first four eof modes are utilized for constructing a tec empirical model for each of the eof modes the temporal variations are expressed analytically in terms of local time season and solar activity and the spatial variations by cubic spline functions an analysis of accuracy and quality indicates that this regional empirical tec model can reflect the majority of the quiet time monthly means and represent characteristic temporal spatial variations in the north america

long period variations in gravity field caused by mantle anelasticity a numerical perturbation approach is used to assess the effect of mantle anelasticity on the earth s zonal response coefficient the zonal geopotential coefficient j2 and the orbital node of geodetic satellites the theoretical predictions are used to compare solutions of elastic ocean tide models and tides observed by geodetic satellites for mr m m ssa and s a the discrepancies between the satellite observed tides and the solution from schwiderski and recent altimetric ocean tide models can be partly explained by the predicted effect of mantle anelasti city at mf and m m frequencies approximately 80 of the observed semiannual variation in 2 by geodetic satellites can be attributed to the tidal deformation from anelasticity and from the classical equilibrium ocean the predicted for the 18 6 year tide was computed for an earth with an anelastic mantle and a nonequilibrium ocean the range of the lower and upper bounds of for the 18 6 year tide is from 0 345 to 0 377 in amplitude and from 6 o to 3 o in phase with preferred amplitude of 0 365 and phase of 0 o8

long period perturbations in starlette orbit and tide solution continuous and dynamically consistent orbits have been computed using satellite laser ranging slr data to starlette for a one year period during 1976 and 1977 and the three year period from 1983 through 1985 a low degree and order ocean tide solution consisting of a total of 66 tidal parameters from 14 tidal constituents was obtained in a combined solution using both the one and three year starlette orbits an enhanced model of the schwiderski 1980 tide solution was used both as the a priori and the background tide model the model contains 368 tidal coefficients from 21 tidal constituents yearly values for the second degree annual tides sa which produce seasonal variations on the starlette node were obtained also these variations were found to have year to year fluctuations of more than 25 about the mean value and produced significant long period perturbations in the starlette orbit the starlette tide solution is in good agreement with the schwiderski tide solutions and with other satellite solutions including multi satellite tide solutions the average uncertainties are approximately 0 1 cm for the estimated semidiurnal and diurnal tides and 0 4 cm for the long period tides the discrepancies of effective k2 inferred from the starlette tide solution and other tide solutions are less than 0 01 the tide solutions were evaluated using orbit fits of a three year lageos and a one year starlette long arc the results indicate that the starlette tide solution produces significantly improved orbit fits for both lageos and starlette the uncertainties for the estimated tide model coefficients were used to predict tidal errors for the lageos orbit and were found to be consistent with the apparent tidal errors present in this orbit the computed secular change in the moon s mean motion due to tidal dissipation is 24 8 0 8 arc second century2 which is in good agreement with the results obtained from other investigations

large scale mass redistribution in the oceans 1993 2001 1 a recent study of satellite laser ranging measurements by cox and chao 2002 indicates that large scale mass redistribution has caused a rapid change in earth s dynamic oblateness j2 since 1998 using satellite altimeter observations and two runs of an ocean general circulation models ogcm we examine mass variations in the oceans and their estimated effect on j2 combined altimeter and ogcm results indicate variations similar to the j2 changes in 1998 and predict considerably larger oceanic effects on the j2 anomaly than purely ogcm estimates suggesting that the oceans should not be ruled out by any means as a significant source of this interesting geodetic anomaly until they have been studied further

ice mass loss in antarctica and stiff lower mantle viscosity inferred from the long wavelength time dependent gravity field 1 long wavelength time variations of the gravity field detected by means of laser tracking of geodetic satellites provide nowadays the unique opportunity to infer simultaneously the upper and lower mantle viscosity and the mass imbalance between ice accumulation and loss in antarctica and greenland here we show that mantle viscosity inversion based on stratified viscoelastic earth models of the pleistocene deglaciation on two independent satellite laser ranging slr solutions for the even and odd zonal components of the geopotential and on true polar wander tpw indicate that present day ice mass loss in antarctica amounts to about 250 gt yr equivalent to a global sea level rise of 0 7 mm yr and that the lower mantle is more viscous than the upper mantle the odd zonals of the two slr solutions and tpw indicate two admissible upper mantle viscosities close to 1020 pa s and to 1021 pa s respectively

compositional data analysis in the geosciences from theory to practice since karl pearson wrote his paper on spurious correlation in 1897 a lot has been said about the statistical analysis of compositional data mainly by geologists such as felix chayes the solution appeared in the 1980s when john aitchison proposed to use iogratios since then the approach has seen a great expansion mainly building on the idea of the natural geometry of the sample space statistics is expected to give sense to our perception of the natural scale of the data and this is made possible for compositional data using iogratios this publication will be a milestone in this process this book will be of interest to geologists using statistical methods it includes the intuitive justification of the methodology convincing through case studies and presenting user friendly software which includes a section for those who need to see the proof of the mathematical consistency of the methods used

influence of possible inner core motions on the polar motion and the gravity field abstract provided that the figure axis of the inner core coincides with the dipole axis of the geomagnetic field the relative rotation of the oblate inner core with respect to the outer core and the mantle can be determined because of the density difference between the inner and outer core the assumed precessional motion of the inner core relative to the mantle is accompanied by a mass redistribution causing variations of polar motion assuming standard density models it is found that variations of polar motion caused by variations of relative inner core rotation due to that of the real dipole axis are similar to the decadal variations derived from observed pole coordinates calculations of the gravity potential show that the assumed relative rotation of the inner core causes gravity changes which may be detectable by modern satellite methods during the next decade

the use of mineral interfaces in sand sized rock fragments to infer ancient climate the kinds of mineral interfaces preserved in rock fragments of modern plutoniclastic sand are closely correlated with climate and topography in the source area stepwise linear regression analysis of the relationship among environmental and petrographic parameters for sand collected from 16 drainages of varying morphology developed on five granodiorite plutons demonstrates that sand composition varies systematically with temperature and precipitation and drainage steepness and area for small drainages in temperate climates the durability of each kind of mineral interface in sand sized rock fragments derived from the plutons depends on mechanical chemical and textural factors interfaces are mechanically stressed by differential expansion of minerals during unroofing interfaces between minerals of similar expansibility compressibility are more likely to remain uncracked and thus survive weathering the rate and extent of chemical dissolution of interfaces depends on the crystallography and chemistry of adjoining minerals interfaces between minerals of similar structure that have short atomicbond lengths are more likely to survive mineral inclusions are texturally isolated from rock disaggregating processes and thus more likely to survive interfaces of opaque with tectosilicate minerals are enriched relative to other interfaces by progressive disaggregation the rate and extent of which increase with increasing temperature interfaces of biotite with tectosilicates are depleted relative to other interfaces with increasing precipitation regression analysis yields statistically plausible testable models of the dependence of modem sand composition on modern climate such models can be used to quantitatively estimate ancient mean annual air temperature and precipitation based on ancient sand composition

geodynamic parameters derived from 7 years of laser data on lageos seven years 1984 through 1990 of laser data on lageos have been analysed to recover absolute stations velocities and j2 relative motions between stations located in stable tectonic regions agree well with the nuvel 1 model predictions within 5 mm yr rms relative motion across the san andreas fault is found to be 33 1 mm yr solution for the secular variation of j2 is 2 8 0 04 10 11 yr

geological and mechanical study of argillaceous north sea chalk implications for the characterisation of fractured reservoirs abstract argillaceous chalk intervals from the north sea are characterised by matrix permeabilities lower than 0 2 md and therefore they are defined as tight chalks hence fracture networks within these chalks are of major importance to predict fluid flow and reservoir or seal behaviour this study aims to understand the geological parameters controlling the chalk petrophysical and mechanical properties using the outcrop analogue of the cenomanian chalk at cap blanc nez northern france sedimentological petrographic and petrophysical analyses were performed and show that the combination of the depositional environment and diagenetic imprint control the microtexture non carbonate content is ranging from 5 to 40 within the studied samples and is critical for the diagenetic imprint the fracture behaviour of the chalk was studied using a mechanical stratigraphy approach throughout the 70 m thick succession where a transition between lower cenomanian argillaceous chalk and middle upper cenomanian pure chalk is exposed twenty two mechanical units are distinguished and the amount of fractures crosscutting initiating and terminating on mechanical interfaces quantified manual scanlines show that fracture spacing ranges from 17 to 232 cm mechanical interfaces are associated with lithological heterogeneities with strong microtextural contrasts related to the non carbonate content and or degree of cementation the mechanical units are thus defined either by deposition or diagenesis the fracturing behaviour of about 10 m homogeneous pure chalk interval units defined as dfz densely fractured zones differs significantly from the rest of the succession large sigmoidal shaped fractures are confined to those intervals and a dense fracture network developed because of their plastic behaviour clay layers are able to accommodate part of the stress whereas homogeneous pure chalk show a more brittle behaviour

postglacial rebound observed by lageos and the effective viscosity of the lower mantle sixty four observations of the orbital node made by the lageos satellite over a five year time interval reveal an acceleration of 8 1 or 1 8 x 10 to the 8 power arcseconds day 2 due to a source which is not presently modeled in the geodyn orbit determination computer program this acceleration cannot be explained by the ocean tide with 18 6 year period assuming it to be an equilibrium tide instead it seems to be due to postglacial rebound which changes the j 2 coefficient in the spherical harmonic expansion of the earth s gravitational field at the rate of 8 2 or 18 x 10 to the 19th power s this in turn accelerates the node this rate does not agree with the 32 x 10 to the 19th power s predicted by wu and peltier s 1982 l2 model which has upper and lower mantle effective viscosities of 10 to the 21st and 22nd powers pa s respectively it does agree well with their l1 model which gives about 10 x 10 to the 19th power s since the effective viscosity is 10 to the 21st power pa s throughout the entire mantle in the l1 model the results support the contentions that the efective viscosity is near 10 to the 21st power pa s everyhere in the mantle and this relatively low value for the effective viscosity may have permitted several degrees of polar wander due to glaciation during the quaternary ice age previously announced in star as n84 13705

effect of melting glaciers on the earth s rotation and gravitational field 1965 1984 summary yearly mass balance data for 85 glaciers in 13 of the 31 mountain glacier systems designated in meier s 1984 paper are averaged for the years 1965 1984 average rates of volume change for the 13 regions are compared to meier s 1984 estimates of glacial melting these data cover regions that account for about 74 per cent of the volume change estimated to have occurred in all the 31 mountain glacier systems from 1900 to 1984 the volume changes in the 13 regions tend to be less than those calculated by using changes in the volume of glaciers between 1900 and 1961 meier 1984 although the reason for this difference is not well known it could result from melting during the first half of the 20th century of ice accumulated during earlier periods or a decrease in the rise in atmospheric temperatures from 1945 to 1980 spatial and temporal empirical orthogonal functional analysis is used to bring out the similarities and differences among the 13 regions and identify those regions contributing most to the variance of the data set these regions are not necessarily those with the greatest average rates of volume change enough spatial variability is present to support the hypothesis that satellites may eventually be able to discern changes in the earth s glaciers through the gravitational field even though the signal from the mass change is small and changes in the gravitational field of the earth are contaminated with gravity signals from other mass changes on the earth s surface and interior zonal coefficients of the spherical harmonic expansion of the gravitational potential are calculated for yearly mass changes for these 13 regions up to i 8 there is little similarity at decadal periods between the polar motion excitation from mountain glacier systems and the observed excitation the majority of observed polar motion excitation could be due to other surface mass changes including continental water storage see for example chao 1988 the amplitude of the interannual excitation due to the glacial signal computed here is less than 10 per cent of the observed excitation and the secular trend of the excitation from melting glaciers in the 13 regions is about one quarter of that of the observed excitation yearly changes in the length of day lod are calculated from the glacial signals and compared to the observed yearly alod excess lod signal the contribution of glaciers to the total excess lod signal is less than one part in 150 of the observed signal as alod is caused mainly by core mantle coupling at decadal periods and atmospheric coupling at shorter periods the contributions to displacement of the centre of mass of the solid earth as seen by a satellite tracked from the earth s surface are calculated for the mountain glaciers and an 80 year record of global sea level for the glaciers the average displacements are as much as 1 mm over 20 years and for sea level the z coordinate of the average displacement is 5mm over its 80 year record interannual signals

recent results on modelling the spatial and temporal structure of the earth s gravity field the earth s gravity field plays a central role in sea level change in the simplest application a precise gravity field will enable oceanographers to capitalize fully on the altimetric datasets collected over the past decade or more by providing a geoid from which absolute sea level topography can be recovered however the concept of a static gravity field is now redundant as we can observe temporal variability in the geoid due to mass redistribution in or on the total earth system temporal variability associated with interactions between the land oceans and atmosphere can be investigated through mass redistributions with for example flow of water from the land being balanced by an increase in ocean mass furthermore as ocean transport is an important contributor to the mass redistribution the time varying gravity field can also be used to validate global ocean circulation models this paper will review the recent history of static and temporal gravity field recovery from the 1980s to the present day in particular mention will be made of the role of satellite laser ranging and other space tracking techniques satellite altimetry and in situ gravity which formed the basis of gravity field determination until the last few years with the launch of challenging microsatellite payload and gravity and circulation experiment grace our knowledge of the spatial distribution of the earth s gravity field is taking a leap forward furthermore grace is now providing insight into temporal variability through monthly gravity field solutions prior to this data we relied on satellite tracking global positioning system and geophysical models to give us insight into the temporal variability we will consider results from these methodologies and compare them to preliminary results from the grace mission

continental scale erosion and transport laws a new approach to quantitatively investigate macroscale landscapes and associated sediment fluxes over the geological past although critical to a variety of issues in earth sciences paleotopography remains poorly constrained over the geological past indeed sediments preserve a record of the history of the earth surface but deconvolving these archives remains a challenge in the absence of a proper quantification of surface processes at the large spatial and temporal resolution imposed by these data to solve for this we propose a set of simple bedrock erosion and sediment transport laws that apply over large spatial 100 km and temporal 1 10 ma scales these laws are tested in light of physical experiments of landscape evolution under different tectonic and climatic forcings and are calibrated using present day large scale earth topography and sediment fluxes in rivers we subsequently implement these processes into a numerical code toposed that is able to predict the evolution of macroscale topography sediment fluxes paleogeographies and bedrock exhumation given a tectonic and climatic input scenario the results of such simulations can be directly compared to sedimentary or thermochronological data to test the plausibility of the input tectonics and predicted topography a series of tests on the sensitivity of such predictions to the uncertainties on input parameters shows that it should be possible from sedimentary data to invert for paleouplift rates and also for paleotopographies during periods covering major tectonic or climatic events although this code is meant to be refined in the future as we improve our understanding of surface processes at these macroscales toposed provides a powerful tool to put constraints on past geodynamic processes such as dynamic topography by extracting quantitative information on the evolution of the earth surface from sedimentary data

ionospheric local model and climatology from long term databases of multiple incoherent scatter radars empirical ionospheric local models have been developed from long term data sets of seven incoherent scatter radars spanning invariant latitudes from 25 to 75 in american european and asian longitudes at svalbard tromso sondrestrom millstone hill st santin arecibo and shigaraki these models as important complements to global models represent electron density ion and electron temperatures and ion drifts in the e and f regions giving a comprehensive quantitative description of ionospheric properties a case study of annual ionospheric variations in electron density and ion temperature is presented based on some of these models clear latitudinal longitudinal and altitude dependency of annual and semiannual components are found

annual and semiannual variations of the earth s gravitational field from satellite laser ranging and champ 1 temporal variability in the earth s gravity field has been estimated from 4 years of satellite laser ranging slr to five geodetic satellites lageos 1 and 2 stella starlette and ajisai supplemented by over 2 years of champ precise orbital positioning attitude quaternions and accelerometry the study considers variability at the annual and semiannual periodicities in the full field of degrees 2 6 a singular value decomposition has been employed in an attempt to recover variability from stand alone champ data temporal gravity field variability from slr and from slr and champ has been computed and compared against geophysical models for surface mass redistribution for a 4 4 field best agreement of the annual variation results in an rms geoid difference of 0 76 mm with correlation coefficients above 0 85 on extending to a 6 6 field agreement decreases to about 1 5 mm rms in geoid height with correlations of 0 6 at the annual cycle for the extended field the ocean mass redistribution from ocean circulation and climate advanced modeling project and topex is seen to be deficient with near comparable correlations being obtained by neglecting the ocean contribution the semiannual signal is weaker and less well determined for the 4 4 field correlations are no better than 0 6 with rms of 1 mm between the slr and geophysical models results show that champ has a positive effect on the annual variation for a 4 4 field but marginal for the extended 6 6 field champ has a negative impact at the semiannual frequency

global geodetic signatures of the antarctic ice sheet four scenarios of present day antarctic ice sheet mass change are developed from comprehensive reviews of the available glaciological and oceanographic evidence the gridded scenarios predict widely varying contributions to secular sea level change ranging from 1 1 to 0 45 mm yr and predict polar motion and time varying low degree gravitational coefficients that differ significantly from earlier estimates a reasonably linear relationship between the rate of sea level change from antarctica a and the predicted antarctic is found for the four scenarios this linearity permits a series of forward models to be constructed that incorporate the effects of ice mass changes in antarctica greenland and distributed smaller glaciers as well as postglacial rebound assuming the ice 3g deglaciation history with the goal of obtaining optimum reconciliation between observed constraints on and sea level rise numerous viable combinations of lower mantle viscosity and hydrologie sources are found that satisfy observed in the range of 1 to 2 2 5 mm yr and observed for degrees 2 3 and 4 in contrast rates of global sea level rise above 2 5 mm yr are inconsistent with available observations the successful composite models feature a pair of lower mantle viscosity solutions arising from the sensitivity of to glacial rebound the paired values are well separated at mm yr but move closer together as is increased and in fact merge around 2 2 5 mm yr revealing an intimate relation between and preferred lower mantle viscosity this general pattern is quite robust and persists for different solutions for variations in source assumptions and for different styles of lower mantle viscosity stratification tighter constraints for l 2 may allow some viscosity stratification schemes and source assumptions to be excluded in the future for a given total observed the sea level rise from antarctica a is tightly constrained and ranges from 0 to 1 mm yr corresponding to an ablating ice sheet as estimates of are raised from 1 to 2 5 mm yr however when the degree 3 zonal harmonic constraint is removed the solutions show little sensitivity to antarctic mass balance emphasizing the need for a well determined odd degree secular zonal harmonic for determining polar ice mass balance

simultaneous inversion for the earth s mantle viscosity and ice mass imbalance in antarctica and greenland redistribution of mass in the earth due to pleistocene deglaciation and to present day glacial melting induces secular changes in the earth s gravitational field the earth is affected today by the former mechanism because of the viscous memory of the mantle and by the latter because of ongoing surface mass redistribution and related elastic response a self consistent procedure allows us to invert simultaneously for the lower and upper mantle viscosity and for the present day mass imbalance in antarctica and greenland using the observed time variations of the long wavelength gravity field from satellite laser ranging slr analyses the procedure is based on our normal mode relaxation theory for the forward modeling and a newly developed inversion scheme based on the levenberg marquardt method we obtain a large viscosity increase across the 670 km depth transition zone separating the upper and the lower mantle with the lower mantle viscosity varying over the range 5 1021 to 1022 pa s and the less resolved upper mantle viscosity of the order of 1020 pa s when antarctica is the only present day source its rate of melting is 240 gt yr 1 corresponding to a sea level rise of 0 7 mm yr 1 when greenland is added as a source of ice loss the rates of melting are 280 gt yr 1 for antarctica and 60 gt yr 1 for greenland corresponding to sea level rises of 0 8 and 0 2 mm yr 1 slr data indicate that ice melting in the polar regions of the earth is ongoing

starlette geodynamics the earth s tidal response the starlette satellite was launched by the french centre national d etudes spatiales in 1975 the primary objective of this project was to further knowledge of the solid earth and ocean tides and other long period gravitational perturbations in the present study starlette laser ranging data for 1980 have been analyzed to map the tidal response of the earth to about 0 01 in the effective solid earth love number k2 these results are based upon the solution of normal equations by processing the laser ranging data in 5 day orbital arc segments the resonant response near the k1 tidal frequency is clearly shown this is mostly due to the nonrigid body character of the earth s internal structure and is the expected type of response considering modern earth models if we assume the wahr free space potential for the solid earth tidal response the recovered values for the k1 o1 m2 n2 s2 and m ocean tidal coefficients are in good agreement with those of the conventional nonsatellite techniques schwiderski and parke and with those derived from long period orbital evolution studies

magnetic declination and zonal wind effects on longitudinal differences of ionospheric electron density at midlatitudes 1 a prominent ionospheric longitudinal variation at midlatitudes in particular over the continental us was found recently this variation is characterized as a higher east side electron density in the evening and a higher west side electron density in the morning and with clear seasonal and solar activity dependencies a combined effect of geomagnetic declination and changing zonal winds was proposed to explain it this paper represents a comprehensive investigation of this effect by examining climatology for both electron density longitudinal differences and the nighttime zonal winds in the eastern us electron density is from incoherent scatter radar extra wide coverage experiments during 1978 2011 over millstone hill for which the spatial separation of the data can be up to 50 in longitude the thermospheric zonal wind is from the on site fabry perot interferometer measurements during 1989 2001 the observed zonal wind climatology is found to be perfectly consistent with the expectation based on the east west electron density differences in terms of local time seasonal and solar cycle dependencies the correlation between the zonal wind and the east west differential ratio is extremely high with an overall correlation coefficient of 0 93 the observed time delay of 3 hours in the response of electron density differences to zonal winds is a marked feature thus these results confirm positively the declination zonal wind mechanism and provide new insight into longitudinal variations at midlatitudes for other geographic sectors

mechanical models of fracture reactivation and slip on bedding surfaces during folding of the asymmetric anticline at sheep mountain wyoming abstract we use finite element methods to investigate the reactivation of fractures opening and shearing and the development of bedding surface slip during the deformation of the asymmetric anticline at sheep mountain wyoming a series of numerical simulations were run to show the effect of mechanical stratigraphy layer thickness slip on bedding surfaces and tectonic shortening of the fold on the response of a representative three layer ductile brittle ductile two dimensional system the model uses large deformation frictional contact mechanics to capture the response of existing fractures and slip along bedding surfaces and considers both elastic and elastoplastic layer properties the computational results demonstrate the relationships among overall configuration of the multilayer slip on bedding surfaces and the sequence and mode of deformation opening versus shearing of bed perpendicular fractures we show that fractures located in the hinge are mainly reactivated as joints and that those in the forelimb are predominantly reactivated as thrust faults a flexural slip mechanism develops during folding when the layers bounded by frictional bedding surfaces have similar stiffnesses in contrast when the difference in the layer stiffnesses is significant softer outer layers the deformation is accommodated within the softer units without exceeding the frictional strength of the bedding surfaces a reduction of the middle layer thickness from 100 m to 10 m has a minor quantitative effect on the slip along the bedding surfaces we compare the numerical results with fracture data collected at sheep mountain anticline and discuss the similarities and differences between the field observations and the model results

effects of nonlinear rheology on degree 2 harmonic deformation in a spherical self gravitating earth 1 the effect of non linear rheology on surface displacements gravitational potential perturbation and tj2 or j2 dot for a self gravitating spherical earth is studied using a finite element code coupled to poisson s equation four earth models investigated are a model with uniform linear rheology throughout the mantle and three others containing nonlinear rheology in the whole mantle upper mantle and lower mantle respectively the effect of self gravitation is shown to be non negligible the effects of nonlinear rheology in different parts of the mantle on surface displacements and potential have also been shown to be large tj2 due to cyclic glaciation of the laurentian fennoscandian barents sea and antarctic ice sheets over realistic oceans is also computed for all four rheology models the model with nonlinear lower mantle cannot be ruled out by the observed data

the slr secular gravity variations and their impact on the inference of mantle rheology and lithospheric thickness a long history of slr satellite laser ranging observations of the geodetic satellites lageos i lageos ii starlette and stella have been analyzed in order to estimate the time series of the low degree zonal coefficients in the earth gravity field up to degree six and derive their secular drifts the paper will point out the critical aspects of the analysis process and will compare the estimated zonal rates with other published results comparison of these zonal rates with the results of global viscoelastic earth models forced by pleistocenic deglaciation shows that the slr retrieved zonals and the lumped odd zonals can be used to infer the upper mantle viscosity and lithospheric thickness discrepancies in the viscosity profiles required to reproduce the different zonals seem to indicate ongoing mass redistribution over the earth

spectroscopic analysis of global tide gauge sea level data summary yearly and monthly tide gauge sea level data from around the globe are fitted to numerically generated tidal data to search for the 18 6 yr lunar nodal tide and 14 month pole tide both tides are clearly evident in the results with amplitudes and phases that are consistent with a global equilibrium response global atmospheric pressure data are fitted to global monthly sea level data to study the response of the ocean to pressure fluctuations the global response of sea level to pressure is found to be inverted barometer at periods greater than 2 months a large coherence at 437 days between pressure and sea level data is found for the north sea baltic sea and the gulf of bothnia the results are not entirely conclusive but they tend to support o connor s 1986 suggestion that the apparent enhanced pole tide in these basins may be due to meteorological forcing rather than to a basin scale resonance finally global averages of tide gauge data after correcting for the effects of post glacial rebound on individual station records reveal an increase in sea level over the last 80 yr of between 1 1 and 1 9 mm yr as part of the process of removing the effects of post glacial rebound we fit those effects to the global tide gauge data and obtain very good agreement with results predicted from post glacial rebound models this tends to support the post glacial model results and it suggests that the global tide gauge data are indeed capable of resolving changes in sea level at the mm yr level

midlatitude ionospheric plasma temperature climatology and empirical model based on saint santin incoherent scatter radar data from 1966 to 1987 ionospheric plasma temperature variations have recently been studied based on incoherent scatter radar isr observations at a lower midlatitude site shigaraki in east asia otsuka et al 1998 and millstone hill a typical subauroral midlatitude site in north america zhang and holt 2004 the french saint santin isr with a geographic latitude slightly higher but an apex latitude 14 lower than millstone collected bistatic and quadristatic measurements for over two solar cycles beginning in september 1965 a database of these data containing observations between 1966 and 1987 has been used in this study in order to establish the midlatitude ionospheric climatology in particular that of the upper atmosphere thermal status as well as empirical models for space weather applications this paper presents in comparison with the millstone hill results variations of ion and electron temperatures ti and te with solar activity season time of the day and altitude the f2 region te at st santin is found to be lower than at millstone between march and july when the st santin electron density ne is relatively higher the midday te below 300 km increases with f10 7 as at millstone hill above 300 km it tends to decrease with f10 7 at st santin while it increases in summer at millstone hill ti between 250 and 350 km peaks midway between spring and summer we have also created st santin ionospheric models for ne te and ti using a bin fit technique similar to that used for the millstone hill models comparisons with corresponding iri predications indicate good agreement in ti at high solar activity and above the f2 peak te from the iri tends to be higher than both the st santin and millstone hill models

the joint gravity model 3 an improved earth geopotential model complete to spherical harmonic degree and order 70 has been determined by combining the joint gravity model 1 jgm 1 geopotential coefficients and their associated error covariance with new information from slr doris and gps tracking of topex poseidon laser tracking of lageos 1 lageos 2 and stella and additional doris tracking of spot 2 the resulting field jgm 3 which has been adopted for the topex poseidon altimeter data rerelease yields improved orbit accuracies as demonstrated by better fits to withheld tracking data and substantially reduced geographically correlated orbit error methods for analyzing the performance of the gravity field using high precision tracking station positioning were applied geodetic results including station coordinates and earth orientation parameters are significantly improved with the jgm 3 model sea surface topography solutions from topex poseidon altimetry indicate that the ocean geoid has been improved subset solutions performed by withholding either the gps data or the slr doris data were computed to demonstrate the effect of these particular data sets on the gravity model used for topex poseidon orbit determination

from gullies to mountain belts a review of sediment budgets at various scales this paper reviews the state of the art in the concept as well as in the application of sediment budgets in sedimentary research sediments are a product of mass dispersal at the earth surface and take part in global cycles sediment budgets aim at quantifying this mass transfer based on the principle of mass conservation and are the key to determine ancient fluxes of solid matter at the earth surface this involves fundamental questions about the interplay of uplift climate and denudation in mountain belts and transfer of sediments from the continents to the oceans as well as applied issues such as soil and gully erosion reservoir siltation and coastal protection first after introducing basic concepts relevant scales and methodologies the different components of quaternary routing systems from erosion in headwaters river systems glacial and paraglacial systems lakes deltas estuaries coasts shelves epicontinental seas and deep sea fans are discussed in terms of their sediment budget most suitable are sedimentologically closed or semi closed depositional environments e g alluvial fans lakes deltas and deep sea fans in a second step the dynamics of passive active and collisional tectonic settings and sediment budgets in related sedimentary basins are explored and new concepts of sediment portioning at large geodynamic scales are introduced ancient routing systems are more or less incomplete and may be intensively fragmented or destroyed in active tectonic settings in terms of sedimentary basin types rifts intracontinental and epicontinental settings are preferred objects of sediment budgets because of their persistence and relatively simple overall sedimentary architecture however closing basins such as foreland forearc retroarc piggy back and wedge top basins may provide excellent snapshots of orogenic sediment fluxes in a third step the large long lived routing systems of the amazon the ganges brahmaputra and the rhine are reviewed for each system estimates of either sediment volumes mass or sediment fluxes of continental and marine subsystems have been compiled in order to receive a complete routing in terms of mass conservation for specific time periods since the late glacial maximum as well as the cenozoic following lessons can be taken from these case studies i depositional centers and fluxes show strong shifts in space and time and call for caution when simply looking at subsystems ii the response times of these large systems are within the milankovich time interval thus lower than predicted from diffusion models iii cyclic routing of sediments in continental basins is much more dominated by climate human control than by eustacy and iv at long time scales ultimate sinks win over intermittent storage it is concluded from this review that the quantitative understanding of global sediment cycling over historic and geologic time and its response to allogenic forcing is still in its infancy and further research is needed towards a holistic view of sediment routing systems at various temporal and spatial scales and their coupling with global biogeochemical cycles this includes i to better determine response times of large routing systems by linking quaternary with cenozoic sediment budgets and continental with marine sub systems ii to combine advanced provenance techniques with sediment budgets in order to reconstruct ancient systems iii to study sediment partitioning at the basin scale iv to reconcile continental supply dominated sequence stratigraphy with the eustatic dominated marine concept and iv to account for non actualism of ancient systems with respect to their erosion and transport mode in particular during glaciations and pronounced arid intervals glacial and eolian sediment routing may cross over hydrologic boundaries of drainage basins thus challenging the principle of mass conservation

a statistical study of the subauroral polarization stream over north american sector using the millstone hill incoherent scatter radar 1979 2019 measurements this work conducts a statistical study of the subauroral polarization stream saps feature in the north american sector using millstone hill incoherent scatter radar measurements from 1979 to 2019

an improved experimental determination of cosmogenic 10be 21ne and 26al 21ne production ratios in quartz abstract the confidence in surface exposure dating and related research such as erosion rate studies or burial dating strongly depends on the accuracy and precision of the currently used production rates of in situ produced cosmogenic nuclides reducing the uncertainties of nuclide production rates by more accurate calibrations with independently dated natural rock surfaces is crucial for further improving the quantification of earth surface processes here we use surface samples from the 760 2 ka old bishop tuff in eastern california to quantify the 10 be 21 ne and 26 al 21 ne production rate ratios in quartz our determination is based on 1 measured nuclide concentrations of cosmogenic 10 be 21 ne and 26 al 2 a conservative estimate for the erosion of the tuff in the volcanic tableland area which we base on our previously published 21 ne concentrations goethals m m niedermann s hetzel r fenton c r 2009 determining the impact of faulting on the rate of erosion in a low relief landscape a case study using in situ produced 21 ne on active normal faults in the bishop tuff california geomorphology 103 401 413 and a conservative estimate for the uncertainty of the 21 ne production rate and 3 the assumption of steady state erosion other assumptions such as the applied scaling procedure the muon contribution to nuclide production or the attenuation lengths of neutrons and muons in rock do not substantially affect the results based on 13 samples the following average production rate ratios and conservative uncertainty estimates are obtained for sea level high latitude open sky and rock surface 0 249 0 009 or 0 232 0 009 for 10 be 21 ne using 10 be half lives of 1 51 and 1 39 ma respectively and 1 80 0 09 for 26 al 21 ne for an 26 al half life of 0 72 ma the 10 be 21 ne and the 26 al 21 ne production ratios are consistent with currently used production rates but the ratios are much more precise than previous determinations the resulting 26 al 10 be production ratio of 7 23 0 45 for a 10 be half life of 1 51 ma or 7 76 0 49 for a 10 be half life of 1 39 ma is high when compared to previously published values we discuss reasons for this difference amongst them the possibility that 26 al analyses in general might be compromised by artefacts affecting the stable al concentration measurements when combined with a 10 be production rate of 5 01 at g 1 a 1 for the 1 51 ma half life or 4 61 at g 1 a 1 for the 1 39 ma half life our production ratios convert to 21 ne and 26 al production rates of 20 1 and 36 2 at g 1 a 1 or 19 9 and 35 7 at g 1 a 1 respectively

the storage of bed material in mountain stream channels as assessed using optically stimulated luminescence dating abstract a detailed understanding of channel forming and maintenance processes in mountain streams requires some measurement and or prediction of bed load transport and sediment mobility traditional field based measurements of such processes are problematic because of the high formative discharges characteristic of such streams the application of optically stimulated luminescence osl dating is proposed here as a new way of determining actual residency times of fine sediments and consequently validating selected predictions for the entrainment of sediment in these streams model predictions of sediment mobility for selected step pool and plane bed channels in a mountain catchment in south eastern australia are initially calculated using equations of hydraulic competence and the one dimensional hec ras model results indicate that floods exceeding bankfull with recurrence intervals up to 13 years are competent to mobilise the maximum overlying surface grain sizes at both sites osl minimum age model results from 7 samples of well bleached quartz in the fine matrix particles indicate general agreement with selected competence equations the apparent long 100 1400 y burial age of most of the mineral quartz however suggests that competent flows are not able to flush all subsurface fine bed material the depth of maximum bed load exchange flushing was limited to twice the depth of the overlying d 90 grain size application of osl in this study provides important insight into the nature of storage and flushing of matrix material in mountain streams

workflow for analysis of compositional data in sedimentary petrology provenance changes in sedimentary basins from spatio temporal variation in heavy mineral assemblages the field of provenance analysis has seen a revival in the last decade as quantitative data acquisition techniques continue to develop in the 20th century many heavy mineral data were collected these data were mostly used as qualitative indications for stratigraphy and provenance and not incorporated in a quantitative provenance methodology even today such data are mostly only used in classic data tables or cumulative heavy mineral plots as a qualitative indication of variation the main obstacle to rigorous statistical analysis is the compositional nature of these data which makes them unfit for standard multivariate statistics to gain more information from legacy data a straightforward workflow for quantitative analysis of compositional datasets is provided first 1 a centred log ratio transformation of the data is carried out to fix the constant sum constraint and non negativity of the compositional data next 2 cluster analysis is followed by 3 principal component analysis and 4 bivariate log ratio plots several 5 proxies for the effects of sorting and weathering are included to check the provenance significance of observed variations and finally a 6 spatial interpolation of a provenance proxy extracted from the dataset can be carried out to test this methodology available heavy mineral data from the southern edge of the miocene north sea basin are analysed the results are compared with available information from literature and are used to gain improved insight into miocene sediment input variations in the study area

characterizing carbonate reservoir fracturing from borehole data a case study of the visean in northern belgium abstract fractured carbonate rocks are widely used as hydrocarbon or geothermal reservoirs to provide a better understanding of the distribution and characteristics of such fractures a general workflow will be presented for the characterization of fracturing from borehole data by exploration and statistical analyses of integrated datasets in a case study of visean limestones in a belgian borehole both cores and geophysical well logs were used to investigate which factors control the characteristics of partially open veins which contribute to permeability relationships between multiple variables were tested statistically lithology geochemistry and geophysical well log values were taken into account as well as quantified veins vugs and stylolites from cores although natural joint frequencies appeared hard to quantify from the available data partially open vein characteristics could be well quantified the results show that differential compaction controlled the development of fractures fracturing occurred preferentially in massive reefal buildup boundstones in contrast to layered wacke to grainstones layer parallel slip along bedding surfaces could also have reduced fracture development in the latter limestones frequencies of cemented veins and partially open veins are positively correlated which suggests that the partially open veins result from either re opening by dissolution or re opening due to a later fracturation phase in summary this multi source study provides a workflow for fracture characterization from boreholes as well as insights into the factors controlling the distribution and characteristics of partially open veins which enhance reservoir permeability

physically based model of downstream fining in bedrock streams with lateral input 1 bed load particles in bedrock streams receiving lateral input from hillslopes may or may not show a clear monotonic pattern of size reduction in the downstream direction both abrasion and selective sorting may play important roles in generating downstream fining the objective of this study is to develop a physically based model of downstream fining in bedrock streams with lateral input based on both processes a surface based gravel transport relation for the size mixture is employed to account for the effect of selective sorting differential transport while the model produces silt and sand by abrasion it is also assumed to loosely capture particle fracturing via a lumped abrasion coefficient embodied in sternberg s law the model is here tested against field data from vieux habitants river in guadeloupe island which is located in the caribbean sea the river shows clear downstream fining and this pattern is captured reasonably well by the model the model results indicate that abrasion including fracturing is solely responsible for the downstream fining pattern for most of the study reach of the vieux habitants river sensitivity analysis of the model has also been performed the model results suggest that in general selective sorting by differential transport can play a role in downstream fining only in cases of streams with relatively fine gravel sizes and lower slopes the results also indicate that abrasion including fracturing and selective sorting can be equally important for downstream fining in bedrock rivers the results also suggest that future work should explicitly consider fracturing comminution separately from abrasion wear rather than lumping them in a sternberg type coefficient

a new framework for modeling sediment fining during transport with fragmentation and abrasion 1 a new framework for modeling sediment fining during transport is proposed the model is based on a physical description of both abrasion and fragmentation processes it attempts to describe and explain the changes in the grain size distribution of sediments during their transport in a water flow abrasion and fragmentation are modeled through the use of breakage frequency functions and daughter size distributions these functions are determined experimentally for the specific case study which is presented comparison between the predictions from the model and experimental data from the case study show that 1 both abrasion and fragmentation are involved in the degradation 2 fragmentation efficiency decreases during the experiment and 3 the shape of the pebbles provides feedback between abrasion and fragmentation this type of model is therefore appropriate for explaining degradation mechanisms which is promising for a future application to rivers

geomorphometric attributes of the global system of rivers at 30 minute spatial resolution in this paper we explore the geomorphometric characteristics and integrity of a 30 0 longitude latitude spatial resolution representation of the global system of potentially flowing rivers we quantify several geomorphometric attributes of digital simulated topological network stn 30p depicting potential flow pathways across the entire non glacierized surface of the earth this data set was examined with respect to several metrics describing individual grid cells river segments and complete drainage systems nearly 60 000 grid cells constitute the global non glacierized land mass the cells are organized into more than 30 000 distinct river segments belonging to approximately 6200 drainage basins stn 30p flow paths and drainage basins are classified as order one through six using the classification system of strahler stn 30p flow pathways depict rivers draining a global land area of 133 1 10 6 km 2 these pathways show a total length of 3 24 10 6 km at 30 0 spatial resolution the relationships between stn 30p order and interior river segment numbers accumulated sub basin areas and accumulated length within individual basins yield high correlation coefficients average r 2 0 96 for continents and globe mean values across individual continents and river orders for the bifurcation ratio 3 15 to 4 44 drainage area ratio 3 74 to 5 77 and basin length ratio 2 02 to 3 27 fall well within the ranges tabulated at finer spatial scales a basin shape index sba l a 0 5 defined as a function of potential mainstem length and drainage area varies between 1 0 and 5 0 for basins 25 000 km 2 and shows a global mean of 2 12 the structure of stn 30p potential river systems is consistent with those of rivers analyzed at finer spatial scales as demonstrated by the numerical similarity of the several geomorphometric indices analyzed however for a particular basin indices from stn 30p will be based on a condensed set of river orders relative to those derived at finer scales a first order stn 30p river is roughly equivalent to an order five to six river derived from 1 62 500 scale maps while 30 0 spatial resolution was found to represent well the 522 basins with areas 25 000 km 2 that drain 82 of the land mass it cannot be used with high confidence in characterizing the geomorphometry of the remaining smaller basins for global climate and biogeochemical studies a composite of the 30 0 resolution and finer spatial resolutions appears to be necessary q 2000 elsevier

coordinated stable auroral red arc observations relationship to plasma convection during the march 20 22 1990 magnetic storm millstone hill radar and dmsp satellite observations detailed the conditions surrounding the occurrence of a sar arc which was observed continuously through an 8 hour interval from dusk till past midnight in the north american sector all sky imaging with a 630 0 nm imager continually monitored the two dimensional position and magnitude of the sar arc emission while radar scans and satellite overflights measured magneto spheric inputs and ionospheric response the arc was colocated with a deep narrow plasma trough and a region of enhanced westward plasma convection of similar width simate3 immediately equa torward of the low latitude extent of plasma sheet particle precipitation a region of low energy ion precipitation was observed at the equatorward edge of the sar arc during a period of spatial tem poral coincident satellite radar observations near the millstone hill longitude the width of the sar arc and related phenomena was of the order of 2 o and the 200 r emission was associated with an electron temperature of 3500ok and a 10x reduction of plasma density at an altitude of 450 kin the best fit model for the emission intensities of both the sar arc and the background airglow suggests that either the electron temperature at the center of the sar arc was somewhat higher than observed by the radar 4000ok or the neutral densities 0 2 and o were increased by factors of 2 and 4 respectively with respect to the msis values the ionospheric trough and a colocated region of enhancext sunward convection 500 1700 m s 1 were observed in conjugate hemispheres through out the local time range 18 02 mlt the convection feature seen in association with the sar arc had many of the characteristics of a subauroral ion drifts said event we report here the first long duration observations of a colocated said sar arc event a narrow ionospheric trough developed during the interval when the said velocity was 1000 m s and was accompanied by a weak 100 r 630 0 nm emission as the velocity fell to 700 m s 1 the density in the trough recovered some what and the arc intensity rose to 300 r above background this brighter period of the sar arc occurred within a fossil trough said we conclude that there is a close spatial and temporal associ ation among these three types of subauroral low altitude phenomena the sar arc the said even and the fossil convection related trough and that this is indicative of the interrelationship of the

ice sheet collapse and sea level change at the end of the last ice age the melting of large ice sheets led to substantial sea level rises but the sea level changes were not even in time or space in his perspective sabadini 1 explains how clark et al 2 use the geographic patterns of sea level change to deduce the pattern of ice sheet melting and hence of climatic change during deglaciation 1 http www sciencemag org cgi content full 295 5564 2376 2 http www sciencemag org cgi content short 295 5564 2438

inversion of gravity data to determine the terrain density distribution in southwest japan we propose a new method of inverting gravity data for the lateral density variation of the terrain above sea level the density variation is modeled by a piecewise step function we impose an a priori condition that the bouguer anomaly distribution expressed by a third order spline function is smooth relative to the topographic distribution no a priori condition is imposed on the density distribution the akaike s bayesian information criterion is used to obtain optimum trade off parameters controlling the smoothness of the bouguer anomaly surface against its fitness to the observed anomaly values we apply the method to about 45 000 gravity observations in southwest japan the calculated density distribution in general correlates well with major geologic features the density of sedimentary volcanic or granitic units increases as their age increases in a way consistent with laboratory measurements of rock density and age in some regions however where the geologic features described in the literature are likely to be surficial and to be underlain by other geologic units the estimated densities deviate from this general trend some active faults sharply offset topography and geology resulting generally in a step in the bouguer anomaly in such cases the estimated densities tend to be unreasonably large or small synthetic tests indicate that a larger number of data points and spline knots are required near the offset to eliminate this problem

mechanical stratigraphic controls on natural fracture spacing and penetration abstract fine grained low permeability sedimentary rocks such as shale and mudrock have drawn attention as unconventional hydrocarbon reservoirs fracturing both natural and induced is extremely important for increasing permeability in otherwise low permeability rock we analyze natural extension fracture networks within a complete measured outcrop section of the ernst member of the boquillas formation in big bend national park west texas results of bed center dip parallel scanline surveys demonstrate nearly identical fracture strikes and slight variation in dip between mudrock chalk and limestone beds fracture spacing tends to increase proportional to bed thickness in limestone and chalk beds however dramatic differences in fracture spacing are observed in mudrock a direct relationship is observed between fracture spacing thickness ratio and rock competence vertical fracture penetrations measured from the middle of chalk and limestone beds generally extend to and often beyond bed boundaries into the vertically adjacent mudrock beds in contrast fractures in the mudrock beds rarely penetrate beyond the bed boundaries into the adjacent carbonate beds consequently natural bed perpendicular fracture connectivity through the mechanically layered sequence generally is poor fracture connectivity strongly influences permeability architecture and fracture prediction should consider thin bed scale control on fracture heights and the strong lithologic control on fracture spacing

core mantle boundary deformations and j 2 variations resulting from the 2004 sumatra earthquake summary the deformation at the core mantle boundary produced by the 2004 sumatra earthquake is investigated by means of a semi analytic theoretical model of global coseismic and postseismic deformation predicting a millimetric coseismic perturbation over a large portion of the core mantle boundary spectral features of such deformations are analysed and discussed the time dependent postseismic evolution of the elliptical part of the gravity field j 2 is also computed for different asthenosphere viscosity models our results show that for asthenospheric viscosities smaller than 10 18 pa s the postseismic j 2 variation in the next years is expected to leave a detectable signal in geodetic observations

impact of interlayer slip on fracture prediction from geomechanical models of fault related folds understanding and interpreting the timing location orientation and intensity of natural fractures within a geologic structure are commonly important to both exploration and production planning activities here we explore the application of finite element based geomechanical models to fracture prediction our approach is based on the idea that natural fractures can be interpreted or inferred from the geomechanical model derived permanent strains for this analysis we model an extensional fault tip monocline developed in a mechanically stratified limestone and shale sequence because field data exist that can be directly compared with model results the approach and our conclusions however are independent of the specific structural geometry the presence or absence of interlayer slip is shown to strongly control the distribution and evolution of strain and this control has important implications for interpreting fractures from geomechanical models

observations of ion neutral coupling associated with strong electrodynamic disturbances during the 2015 st patrick s day storm we use incoherent scatter radar observations at millstone hill mho and arecibo ao and topside ionosphere in situ dmsp observations during the great geomagnetic storm on 17 18 march 2015 to conduct a focused study on ion neutral coupling and storm time ionosphere and thermosphere dynamics some of these observations were made around the time of large ionospheric drifts within a sub auroral polarization stream saps during the storm main phase we identify multiple disturbance characteristics in the north american late afternoon and dusk sector 1 strong sub auroral westward drifts occurred between 20 24 ut near mho accompanied by a storm enhanced density plume passage over mho in the afternoon with a poleward upward ion drift the strongly westward flow reached 2000 m s speed near the poleward plume edge 2 prompt penetration electric field signatures appearing as poleward upward ion drifts on the dayside over both mho and ao were consistent with dmsp vertical drift data and contributed to plume development 3 meridional wind equatorward surges occurred during daytime hours at mho followed by 2 3 hr period oscillations at both mho and ao the zonal electric field at ao was strongly correlated with the wind oscillation 4 large ion temperature enhancements as well as 50 m s upward ion drifts throughout the e and f regions were observed during the saps period these were presumably caused by strong frictional heating due to large plasma drifts the heating effects appeared to drive significant atmospheric upwelling and corresponding ion upflow was also observed briefly this study highlights some of the important effects of fast plasma transport as well as other disturbance dynamics on ion neutral coupling during a single intensification period within a great geomagnetic storm

postseismic signature of the 2004 sumatra earthquake on low degree gravity harmonics 1 we perform an extensive analysis of the low degree gravity field harmonics measured by the grace mission in order to find a signature of the postseismic relaxation following the 2004 sumatra earthquake we find a statistically significant perturbation in the secular trend of low degree zonal coefficients jl in correspondence of the 2004 sumatra earthquake and a similar perturbation but with weak associated statistical significance also in the nonzonal coefficients technical features and results of such analysis are discussed the time dependent postseismic evolution of harmonic coefficients is modeled for various asthenosphere viscosity values using a theoretical model of global postseismic deformation the observed change in secular trend is found to be consistent with our modeling results but it cannot be used to discriminate between viscosities a forward modeling of the perturbations to time dependent zonal variation rates following the sumatra earthquake for various asthenospheric viscosities is provided as a result an evident signature of the sumatra earthquake on l time series is expected for asthenospheric viscosity values below 1018 pa s therefore long term l time histories from satellite laser ranging will be able to put constraints on the asthenosphere viscosity if such a signature is evidenced from data or at least put lower limits if no significant perturbation will be observed

ice age earth rotation modern predictions of the rotational stability of an ice age earth reflect a convergence of two classic problems in geophysical analysis the modeling of the glacial isostatic adjustment gia process and the rotational stability of terrestrial planets recent theoretical advances in this area have been motivated not by conventional applications such as the inference of earth s deep mantle viscosity but rather by efforts to address vexing problems in global climate change research these advances have demonstrated that traditional calculations of the ongoing motion of the rotation pole relative to the surface geography or true polar wander tpw driven by ice age loading have systematically overestimated this motion by up to a factor of 4 by underestimating by 1 the background flattening of earth s oblate form the physics of this sensitivity is related to concepts that appear in canonical mid twentieth century discussions of earth rotation and avoiding the associated inaccuracy resolves numerous p

reanalysis of ancient eclipse astronomic and geodetic data a possible route to resolving the enigma of global sea level rise predictions of the earth s response to the ice age appear to simultaneously reconcile a set of astronomical geodetic and ancient eclipse observations related to changes in rotation thus ruling out ice melting as a major contributor to 20th century sea level rise we demonstrate that the reconciliation disappears when an improved theory of rotational stability is applied furthermore our reanalysis of longer satellite records renders previous estimates of the secular change in rotation rate suspect the updated ice age predictions and observations permit an anomalous 20th century ice flux of 1 mm yr equivalent sea level rise thus the full suite of earth rotation observations are consistent with a connection between climatic warming and recent melting of ice reservoirs

variations in the earth s oblateness during the past 28 years 1 analysis of satellite laser ranging slr data indicates that the earth s dynamic oblateness j2 has undergone significant variations during the past 28 years the dominant signatures in the observed variations in j2 are 1 a secular decrease with a rate of approximately 2 75 10 11 yr 1 2 seasonal annual variations with a mean amplitude of 2 9 10 10 3 significant interannual variations with timescales of 4 6 years and 4 a variation with period of 21 years and an amplitude of 1 4 10 10 with minimum in december 1988 two large interannual variations are related to the strong el nino southern oscillation events during the periods of 1986 1991 and 1996 2002 and it appears that another interannual cycle may have started in late 2002 the superposition of the decadal variation on the interannual signal makes the j2 fluctuation appear to be anomalously large during the 1996 2002 period contemporary models of the mass redistributions in the atmosphere ocean and surface water can explain a major part of the 4 to 6 year fluctuations however the cause of the decadal variation remains unknown

uses and misuses of compositional data in sedimentology this paper serves two goals the first part shows how mass evolution processes of different nature become undistinguishable once we take a size limited noisy sample of its compositional fingerprint processes of exponential decay mass mixture and complementary accumulation are simulated and then samples contaminated with noise are extracted the aim of this exercise is to illustrate the limitations of typical graphical representations and statistical methods when dealing with compositional data i e data in percentages concentrations or proportions the second part presents a series of concepts tools and methods to represent and statistically treat a compositional data set attending to these limitations the aim of this second part is to offer a state of the art compositional data analysis this includes descriptive statistics and graphics the biplot ternary diagrams with confidence regions for the mean regression and analysis of variance models to explain compositional variability and the use of compositional information to predict environmental covariables or discriminate between groups all these tools share a four step algorithm 1 transform compositions with an invertible log ratio transformation 2 apply a statistical method to the transformed scores 3 back transform the results to compositions and 4 interpret results in relative terms using these techniques a data set of sand petrographic composition has been analyzed highlighting that finer sands are richer in single crystal grains in relation to polycrystalline grains and that grain size accounts for almost all compositional variability a stronger water flow river discharge favors mica grains against quartz or rock fragment grains possibly due to hydrodynamic sorting effects a higher relief ratio implies shorter residence times which may favor survival of micas and rock fragments relatively more labile grains

mechanical stratigraphic controls on fracture patterns within carbonates and implications for groundwater flow abstract groundwater flow in low matrix permeability carbonate rocks is largely controlled by fracture networks the stratigraphic features that control fracture initiation and termination within a sequence of sedimentary rock strata define the mechanical stratigraphy of the sequence we investigate the effectiveness of various types of stratigraphic horizons in terminating opening mode fractures in two different carbonate rock sequences a relatively homogeneous dolomite sequence in door county wi and an interbedded chalk and marl sequence within the austin chalk tx additionally we present analog and numerical modeling results that delineate the specific mechanisms that facilitate fracture termination the combination of model results and empirical relationships between observed sedimentary features and mechanical stratigraphy shows 1 fractures terminate at weak contacts e g thin organic layers shallowly buried contacts or thick fine grained units adjacent to thin fractured beds 2 fractures propagate across strong contacts e g intracycle contacts between different lithology and thin fine grained units adjacent to thick fractured beds and 3 fractures step over at moderate strength contacts we use these guidelines to predict fracture network from sedimentary stratigraphy by qualitatively assessing the mechanical stratigraphy of a portion of the relatively complex cretaceous shelf margin sequence at sant corneli spain this predictive demonstration illustrates the utility of assessing the mechanical stratigraphy of subsurface strata within which fractures are not directly observable we conclude that for a variety of carbonate mechanical stratigraphic sequences dominant fluid flow characteristics such as horizontal high flow zones and flow compartmentalization can be evaluated using fracture spacing and connectivity within fracture networks that is predicted from sedimentary stratigraphy although the resulting heterogeneous flow networks do not rely on every fracture present they are highly dependent on the mechanical stratigraphy

detection of a large scale mass redistribution in the terrestrial system since 1998 earth9s dynamic oblateness j2 had been undergoing a decrease according to space geodetic observations over the past 25 years until around 1998 when it switched quite suddenly to an increasing trend that has continued to the present the secular decrease in j2 resulted primarily from the postglacial rebound in the mantle the present increase whose geophysical cause s are uncertain thus signifies a large change in global mass distribution with a j2 effect that considerably overshadows that of mantle rebound

secular variations in zonal harmonics of earth s geopotential and their implications for mantle viscosity and antarctic melting history due to the last deglaciation

seasonal variations of the ionospheric electron densities retrieved from constellation observing system for meteorology ionosphere and climate mission radio occultation measurements 1 we collected the ionospheric electron density ne profiles from the formosat 3 cosmic f3 c radio occultation measurements to investigate the seasonal behaviors of daytime ne in the altitude range of 200 560 km harmonic analysis of the ne at different altitudes provides unprecedented detail of the seasonal behaviors of ne at low solar activity lsa global maps of seasonal harmonic components indicate that there are strong annual and semiannual variations in daytime ne which have distinct latitudinal and altitudinal dependency the semiannual component predominates over the annual variation in the equatorial regions and at high latitudes in the east asian and south atlantic sectors at low altitudes and at higher altitudes the semiannual component predominates in the equatorial region but recedes in other regions the semiannual variation peaks in equinoctial months in most regions while it has maxima in solstice months first in the south pacific region around 30 s 120 w at 250 km altitude and expanding over the south pacific and south atlantic oceans at higher altitudes moreover there is a region around 45 s 30 w with a dominant semiannual component moving toward east north with increasing altitude in the range of 200 270 km these two interesting features are novel but are not reported yet the relative amplitude of the annual component of ne has hemispheric asymmetry which is prominent at high altitudes in the southern hemisphere the winter seasonal anomaly widely exists in the northern hemisphere and southern low latitudes and in indian ocean region at low altitudes but gradually disappears at higher altitudes further in equatorial regions a new finding is the obvious wave like pattern in the longitudinal structure of the amplitudes of seasonal harmonic components in equatorial regions which supports possible couplings of sources with lower atmospheric origins in the longitudinal variations of ne

detrital modes in sedimenticlastic sands from low order streams in the iberian range spain the potential for sand generation by different sedimentary rocks the composition of modern stream sands derived from sedimentary source rocks in the iberian range has been analyzed in order to evaluate the contributions of the different bedrock types mainly sandstones limestones and dolostones temperate to subhumid climate and short transport conditions promote a weathering limited denudation regime as expected sand composition proved to be essentially quartzolithic with variable amounts of penecontemporaneous carbonates sand compositional data were compared with the exposure areas of the different bedrocks in the drainage sub basins considered for semi quantitative assessment of the sand generation potential of each bedrock type siliciclastic formations sandstones appear to be by far the most significant sand producers with sand generation indices sgis in the medium sand fraction ranging from 4 to 20 i e 4 to 20 times greater than the sgi of carbonate rocks composition and texture are the main factors controlling carbonate sand generation sparitic limestones yield higher sgis 2 8 to 20 when source terrains are constituted exclusively by carbonate rocks high sparite grain content in the sands is enhanced by supplies from additional sources such as calcitized dolostones dolomicrite sources are strongly under represented in the sands analyzed very low sgi whereas the proportion of micritic limestone grains tends to be an accurate reflection of that bedrock at the source even though the results presented here refer to the first stage of sand generation with negligible transport effects we think they may be helpful in the analysis and reconstruction of source terrains in ancient sedimenticlastic deposits

station coordinates baselines and earth rotation from lageos laser ranging 1976 1984 satellite laser range slr measurements to lageos from may 1976 to january 1984 have been used to compute earth rotation parameters and the geocentric positions of 57 laser tracking station sites occupied during this interval the station position determinations were part of a simultaneous solution which includes lageos orbit elements in 15 day arcs and earth rotation parameters in 3 day subarcs using residuals from a 7 7 year lageos long arc lla 8402 systematic differences between the terrestrial reference frames implied by the university of texas station coordinate solution lsc 8402 and by previous solutions computed at the university of texas ut and at goddard space flight center gsfc are reviewed the new solution resolves a 0 72 m z axis difference between the terrestrial reference system origins inferred from the gsfc solution sl5 and the previous ut solution lsc 8112 the implied origins of the lsc 8402 solution and the sl5 solution are consistent to less than 60 mm in all components and after removing orientation and scale differences the coordinates for 26 common tracking stations have an rms difference of less than 80 mm the rms difference in baseline length for 22 station pairs used in the recent crustal dynamics project very long baseline interferometry vlbi slr intercomparison experiment is 50 mm between the gsfc and ut laser solutions and 40 mm between the ut laser solution and the vlbi solution the earth rotation parameters computed in 3 day intervals have an internal precision of 2 marc sec 62 mm at the earth s surface for xp and yp and 0 15 ms 70 mm at the equator for ut1 the estimated accuracy of the series based on dual baseline vlbi intercomparisons is approximately 2 marc sec for xp and yp and 0 2 ms for ut1 the effects of plate motion on the determination of the secular drift in polar motion using the 7 7 year series is shown to be at the level of 1 marc sec yr finally baseline changes have been investigated by repeated station coordinate determinations using 60 day subsets of the 7 7 year interval of the lageos data set in each 60 day solution interval orbit elements were estimated at 15 day intervals and earth rotation parameters were determined at 5 day intervals for the 4 year period beginning in january 1980 baseline length changes inferred by the successive 60 day solutions were found to be in general agreement with the motions predicted by the am1 2 plate motion model of minster and jordan

stylolites a review abstract stylolites are ubiquitous geo patterns observed in rocks in the upper crust from geological reservoirs in sedimentary rocks to deformation zones in folds faults and shear zones these rough surfaces play a major role in the dissolution of rocks around stressed contacts the transport of dissolved material and the precipitation in surrounding pores consequently they play an active role in the evolution of rock microstructures and rheological properties in the earth s crust they are observed individually or in networks in proximity to fractures and joints and in numerous geological settings this review article deals with their geometrical and compositional characteristics and the factors leading to their genesis the main questions this review focuses on are the following how do they form how can they be used to measure strain and formation stress how do they control fluid flow in the upper crust geometrically stylolites have fractal roughness with fractal geometrical properties exhibiting typically three scaling regimes a self affine scaling with hurst exponent 1 1 0 1 at small scale up to tens or hundreds of microns another one with hurst exponent around 0 5 to 0 6 at intermediate scale up to millimeters or centimeters and in the case of sedimentary stylolites a flat scaling at large scale more complicated anisotropic scaling scaling laws depending of the direction of the profile considered is found in the case of tectonic stylolites we report models based on first principles from physical chemistry and statistical physics including a mechanical component for the free energy associated with stress concentrations and a precise tracking of the influence of grain scale heterogeneities and disorder on the resulting micro structures experimental efforts to reproduce stylolites in the laboratory are also reviewed we show that although micrometer size stylolite teeth are obtained in laboratory experiments teeth deforming numerous grains have not yet been obtained experimentally which is understandable given the very long formation time of such geometries finally the applications of stylolites as strain and stress markers to determine paleostress magnitude are reviewed we show that the scalings in stylolite heights and the crossover scale between these scalings can be used to determine the stress magnitude its scalar value perpendicular to the stylolite surface during the stylolite formation and that the stress anisotropy in the stylolite plane can be determined for the case of tectonic stylolites we also show that the crossover between medium millimetric scales and large pluricentimetric scales in the case of sedimentary stylolites provides a good marker for the total amount of dissolution which is still valid even when the largest teeth start to dissolve which leads to the loss of information since the total deformation is not anymore recorded in a single marker structure we discuss the impact of the stylolites on the evolution of the transport properties of the hosting rock and show that they promote a permeability increase parallel to the stylolites whereas their effect on the permeability transverse to the stylolite can be negligible or may reduce the permeability depending on the development of the stylolite

deceleration in the earth s oblateness 1 for over three decades satellite laser ranging slr has recorded the global nature of the long wavelength mass change within the earth system analysis of the most recent time series of 30 day slr based estimates of earth s dynamical oblateness characterized by the gravitational degree 2 zonal spherical harmonic j2 indicates that the long term variation of j2 appears to be more quadratic than linear in nature the superposition of a quadratic and an 18 6 year variation leads to the unknown decadal variation reported by cheng and tapley 2004 although the primary trend is expected to be linear due to global isostatic adjustment there is an evident deceleration j 2 18 1 10 13 yr2 in the rate of the decrease in j2 during the last few decades likely due to changes in the rate of the global mass redistribution from melting of the glaciers and ice sheets as well as mass changes in the atmosphere and ocean

ipy observations of ionospheric yearly variations from high to middle latitude incoherent scatter radars 1 upper atmospheric research during the 2007 international polar year features unprecedented yearlong observations by incoherent scatter radars this valuable data set collected under very low solar and magnetic activity conditions from a set of four radars spanning middle millstone hill auroral poker flat and higher latitudes sondrestrom and svalbard enables us to address a fundamental question of background climatology on ionospheric yearly variations the main focus of this paper is on the noon time baseline annual and semiannual variations with an emphasis on the less known height dependency for those geophysically important areas the radar measurements of ion drifts allow us to examine dynamic effects which have not been well addressed previously high latitude ionospheric climatology shows some interesting features in particular the two semiannual peaks of electron density ne the two peaks neither of which is near summer solstice are essentially of equinoctial symmetry at very high latitude sites where downward ion drifts are strong in summer thus causing ne reduction the symmetry vanishes at the midlatitude site clear phase progression is seen from the topside to the f2 peak at the midlatitude site comparisons of millstone hill data from this period and prior solar minima indicate decreases in the ion temperature throughout the f2 peak and the topside ionosphere these decreases do not seem to be associated with solar flux and magnetic activity effects

present day secular variations in the zonal harmonics of earth s geopotential we develop a new formalism for the prediction of secular variations in the gravitational potential field of a spherically symmetric self gravitating maxwell viscoelastic planetary model subjected to an arbitrary surface load which may include a gravitationally self consistent ocean loading component the theory is applied to generate the most accurate predictions to date of the present day secular variations in the zonal harmonics of the geopotential the so called for degree arising as a consequence of the late pleistocene glacial cycles in this respect we use the very recent ice 3g reconstruction of the last late pleistocene deglaciation event tushingham and peltier 1991 a comparison of these predictions with those generated using simplified disk models of the ice sheets which have been used in all previous studies of the harmonics 2 indicates that the disk model approximation introduces unacceptably large errors at all spherical harmonic degrees except perhaps 2 predictions have also been made using a eustatic loading approximation also used in previous studies in place of a gravitationally self consistent ocean loading component and we have found that the resulting discrepancy is largest at degrees 2 8 and 10 in the case of the magnitude of the error incurred using the eustatic approximation can be as large as order 10 15 of the predicted value we have attributed this discrepancy to the present day net flux of water away from the equatorial regions arising from the remnant present day adjustment associated with the late pleistocene glacial cycles the effect represents a heretofore unrecognized contribution to the harmonics or alternatively the nontidal acceleration of earth s axial rate of rotation in terms of the latter the maximum anomaly in the length of day is approximately 1 7 s yr we also consider the sensitivity of the data to variations in the radial mantle viscosity profile by using a suite of forward calculations and an examination of frechet kernels the theory required for the computation of those kernels is described herein we find that the radial variation in sensitivity can be a strong function of the viscosity model used in the calculations for models with a uniform upper mantle viscosity um of 1021 pa s forward predictions of the harmonics exhibit a pronounced peak when a wide enough range of lower mantle viscosities lm are considered we denote the lm value at this peak as at the lowest degrees 4 frechet kernels computed for a series of increasing lm values 1021 pa s lm 1023 pa s indicate a migration of the dominant sensitivity of the data to variations in viscosity from regions below approximately 1200 km depth for to regions above this depth in the lower mantle for the sensitivity of the data to variations in the viscosity profile in the shallowest parts of the lower mantle for the case is also reflected in a set of forward calculations described herein as an example predictions made using earth models in which the viscosity above 1200 km depth is constrained to be 1021 pa s do not exhibit the multiple solutions characteristic of the um 1021 pa s calculations the same is true of earth models in which the upper mantle viscosity is weakened an order of magnitude to 1020 pa s the theory described herein is also applied to compute the signal 10 arising from the retreat of small ice sheets and glaciers described by meier 1984 and also from any potential variations in the mass of the antarctic and greenland ice sheets the present day signal due to the late pleistocene glacial cycles dominates the signal from meier s sources at all degrees except 3 in contrast the signal arising from mass variations in the antarctic and greenland ice sheets is potentially comparable to the former a comparison of observational constraints on the data with predictions of the postglacial rebound signal described in this paper in order to infer mantle rheology cannot proceed until constraints are placed on the present day mass flux of these large polar ice sheets we show that the constraints required are weakest at degrees 2 and 4 finally we outline a potentially important procedure for incorporating predictions of the signal due to the late pleistocene glacial cycles and meier s sources with an observational constraint on the datum to yield bounds on the present day net mass flux from the antarctic and greenland ice sheets a rigorous application of this procedure must wait until observational constraints on are reestablished in the literature

mechanical stratigraphy and palaeo karstification of the murge area apulia southern italy the cretaceous apulia platform exposed in the murge area southern italy suffered intense palaeo karstification this study focuses on the controlling factors of karstification with emphasis on fracturing mechanical stratigraphy was used to calculate the fracture density withindifferent sedimentarysequences several mechanical unitswere defined and a characteristic relationship was found between unit thicknesses and fracture density that is fracture density increases if layer thickness decreases in some of the quarries studied sedimentary cycles are clearly present that are also reflected in the fracture density logs the degree of karstification withina mechanical unit is proportional to the mean fracture spacing based on fracture orientation data extracted from lidar scans different orientation clusters were observed between fractures thatarekarstifiedandfracturesthatarenotkarstified post datingkarstification theclustersofkar stified fractures are related to the compression of the southern apennines the fractures became dissolution enlarged during the pleistocene uplift caused by bulging of the apulia platform this main karstification phase occurred prior to late pleistocene deposition and before the for mation of orthogonal fracture sets

quantitative models of sediment generation and provenance state of the art and future developments abstract an overview of quantitative approaches to analysis and modelling of sediment generation and provenance is presented with an emphasis on major framework components as determined by means of petrographic techniques conceptual models of sediment provenance are shown to be consistent with two classes of numerical statistical models i e linear mixing models and compositional linear models these cannot be placed within a common mathematical framework because the former requires that sediment composition is expressed in terms of proportions whereas the latter requires that sediment composition is expressed in terms of log ratios of proportions additivity of proportions a fundamental assumption in linear mixing models cannot be readily expressed in log ratio terms linear mixing models may be used to describe compositional variability in terms of physical and conceptual un mixing models of physical un mixing are appropriate for describing compositional variation within transport invariant subpopulations of grains as a result of varying rates of supply of detritus from multiple sources conceptual un mixing governs the relations among chemical mineralogical and petrographic characteristics of sediments which represent different descriptive levels within a compositional hierarchy compositional linear process models may be used to describe compositional and or textural evolution resulting from selective modifications induced by sediment transport as well as chemical and mechanical weathering current approaches to modelling of surface processes treat the coupled evolution of source areas and sedimentary basins in terms of bulk mass transfer only and do not take into account compositional and textural sediment properties moving from the inverse modelling approach embodied in provenance research to process based forward models of sediment generation which provide detailed predictions of sediment properties meets with considerable albeit not insurmountable problems strategies for developing more advanced parameterizations of sediment properties and for simulating their evolution are proposed and expansion of current data acquisition protocols is discussed in the light of data requirements for such advanced sediment generation models inclusion of sediment generation modules in models of landscape evolution and basin filling will mark a significant step towards full fledged source to sink simulations of earth surface processes

drilling induced core fractures and in situ stress the relationship between the shapes of drilling induced core fractures and the in situ state of stress is developed the stress concentrations at the well bore bottom are first determined using a complete three dimensional finite element analysis existing in situ compressional stresses generate large tensions in the immediate vicinity of the bottom hole which are sufficient to rupture the rock tensile fracture trajectories within these concentrated stress fields are predicted using a simple model of fracture propagation these modeled fracture trajectories resemble well the observed shapes of drilling induced core disking petal and petal centerline fractures further this agreement suggests that both the shape of the drilling induced fracture and the location at which it initiates depends on the in situ stress state existing in the rock mass prior to drilling the core fractures contain substantial information on in situ stress conditions in all faulting regimes the coring induced fractures initiate near the bit cut except for most cases under thrust faulting regime where the fracture initiates on the well bore axis further under thrust faulting conditions only disk fractures appear possible both petal and disking fractures can be produced in strike slip and normal faulting regimes depending upon the relative magnitudes between the least compressive horizontal principal stress and the vertical overburden stress the predicted fracture shapes are in good qualitative agreement with observations of drilling induced fractures described in the literature from laboratory experiments and field programs in which in situ stresses are measured by other means the relationship of the morphology of coring induced fractures and in situ stresses suggests that the fractures can be used as independent complementary indicators in identifying stress regimes

the process of ghost rock karstification and its role in the formation of cave systems abstract this paper presents an extensive review of the process of ghost rock karstification and highlights its role in the formation of cave systems the process integrates chemical weathering and mechanical erosion and extends a number of existing theories pertaining to continental landscape development it is a two stage process that differs in many respects from the traditional single stage process of karstification by total removal the first stage is characterised by chemical dissolution and removal of the soluble species it requires low hydrodynamic energy and creates a ghost rock feature filled with residual alterite the second stage is characterised by mechanical erosion of the undissolved particles it requires high hydrodynamic energy and it is only then that open galleries are created the transition from the first stage to the second is driven by the amount of energy within the thermodynamic system the process is illustrated by detailed field observations and the results of the laboratory analyses of samples taken from the karstotype area around soignies in southern belgium thereafter a series of case studies provide a synthesis of field observations and laboratory analyses from across western europe these studies come from geologically distinct parts of belgium france italy and the united kingdom the process of ghost rock karstification challenges a number of axioms associated with the process of karstification by total removal on the basis of the evidence presented it is argued that it is no longer acceptable to use karst morphologies as a basis with which to infer specific karstogenetic processes and it is no longer necessary for a karst system to relate to base level as ghost rock karstification proceeds along transmissive pathways in the rock there is also some evidence to suggest that ghost rock karstification may be superseded by karstification by total removal and vice versa according to the amount of energy within the thermodynamic system the proposed chemical weathering and subsequent mechanical erosion of limestone suggest that the development of karst terrain is related far more closely to the geomorphological development of aluminosilicate and siliceous terrains than is generally supposed it is now necessary to reconsider the origin of many karst systems in light of the outlined process of ghost rock karstification

ionospheric climatology and variability from long term and multiple incoherent scatter radar observations climatology in eastern american sector 1 ionospheric climatology and variability studies are conducted using long term incoherent scatter radar isr observations from seven sites around the world these studies result in an empirical model system the isr ionospheric model isrim which represents local and regional ionospheric climatology and variability of the ionosphere this paper addresses some new climatological features revealed by the model for latitudes spanning 18 70 n over the eastern american sector the latitudinal change of the f2 layer electron density exhibits a clear depletion near millstone hill latitudes when solar activity is median or low accompanied by a te enhancement and electron density peaks at 10 both to the north and south of millstone hill possible explanations are discussed we also characterize several types of variation in plasma temperatures in this region including ion temperature elevation for quiet conditions in the auroral zone and electron temperature increases toward higher latitudes

recent changes in the earth s oblateness driven by greenland and antarctic ice mass loss 1 we use temporal gravity variations from grace to investigate changes in a 34 year time series of earth s oblateness j2 observed by satellite laser ranging slr we use 2002 2010 grace data to compute the effects of greenland and antarctic ice mass variations on j2 2 0 and 1 7 10 11 year respectively their combined effect on the j2 trend during the grace mission is 3 7 10 11 year which agrees well with the gia corrected slr j2 trend over the same time period the results suggest that at least since 2002 ice loss from greenland and antarctica has been the dominant contributor to the current gia corrected j2 trend which apparently began sometime in the 1990s

mechanical and fracture stratigraphy using examples from core studies this article shows that separate identification of mechanical stratigraphy and fracture stratigraphy leads to a clearer understanding of fracture patterns and more accurate prediction of fracture attributes away from the wellbore mechanical stratigraphy subdivides stratified rock into discrete mechanical units defined by properties such as tensile strength elastic stiffness brittleness and fracture mechanics properties fracture stratigraphy subdivides rock into fracture units according to extent intensity or some other observed fracture attribute mechanical stratigraphy is the by product of depositional composition and structure and chemical and mechanical changes superimposed on rock composition texture and interfaces after deposition fracture stratigraphy reflects a specific loading history and mechanical stratigraphy during failure because mechanical property changes reflect diagenesis and fractures evolve with loading history mechanical stratigraphy and fracture stratigraphy need not coincide in subsurface studies current mechanical stratigraphy is generally measurable but because of inherent limitations of sampling fracture stratigraphy is commonly incompletely known to accurately predict fractures in diagenetically and structurally complex settings we need to use evidence of loading and mechanical property history as well as current mechanical states

the effects of mantle anelasticity on nutations earth tides and tidal variations in rotation rate summary we model the effects of mantle anelasticity on luni solar nutations on tidal deformation on tidal variations in rotation rate and on the eigenfrequency of the free core nutation our results can be used to invert observations to solve for the anelastic contributions to the shear and bulk moduli of the upper and lower mantle we use specific anelastic models to numerically estimate the effects of anelasticity on these geodetic observables we compare our nutation estimates with observational results among our conclusions 1 mantle anelasticity is likely to be the most important source of damping for the free core nutation 2 present vlbi nutation results are in principle accurate enough to usefully bound anelasticity at diurnal periods but the discrepancy between the vlbi observed nutations and the 1984 iau nutation model cannot be explained by anelasticity and is not yet well enough understood to allow anelasticity to be determined from the data

ionospheric signatures of plasmaspheric tails 1 we make direct comparisons between gps maps of total electron content tec over the north american continent millstone hill radar observations of storm enhanced density and low and high altitude satellite measurements of the perturbation of the outer plasmasphere during the march 31 2001 geomagnetic storm we find that storm enhanced density sed and plumes of greatly elevated tec are associated with the erosion of the outer plasmasphere by strong sub auroral polarization electric fields the sed tec plumes identified at low altitude map closely onto the magnetospheric determination of the boundaries of the plasmapause and plasmaspheric tail determined by euv imaging from the image spacecraft characteristics of the sed tec plumes tails for the march 31 2001 event are tec 100 tecu f region sunward velocity 1000 m s sunward flux 5 1024 ions s 1 total transport to dayside magnetopause merging region 3 hr event 5 1028 ions

gia induced secular variations in the earth s long wavelength gravity field influence of 3 d viscosity variations abstract predictions of present day secular variations in the earth s long wavelength geopotential driven by glacial isostatic adjustment gia have previously been analyzed to infer the radial profile of mantle viscosity and to constrain ongoing cryospheric mass balance these predictions have been based on spherically symmetric earth models we explore the impact of lateral variations in mantle viscosity using a new finite volume formulation for computing the response of 3 d maxwell viscoelastic earth models the geometry of the viscosity field is constrained from seismic to mographic images of mantle structure while the amplitude of the lateral viscosity variations is tuned by a free parameter in the modeling we focus on the zonal j l harmonics for degrees l 2 8 and demonstrate that large scale lateral viscosity variations of two to three orders of magnitude have a modest 5 10 impact on predictions of j 2 in contrast predictions of higher degree harmonics show a much greater sensitivity to lateral variation in viscosity structure we conclude that future analyses of secular trends for degree l 2 estimated from ongoing grace champ satellite missions must incorporate gia predictions based on 3 d viscoelastic earth models

low degree gravity changes from grace earth rotation geophysical models and satellite laser ranging 1 several independent time series of variations c 21 s 21 and c 20 in earth s gravity field are compared for the period april 2002 to may 2007 we examine estimates from the gravity recovery and climate experiment grace earth rotation variations climate models and satellite laser ranging slr recently released grace solutions show significant improvement relative to earlier results especially for c 21 and s 21 at the annual period all estimates agree remarkably well and good correlation is found among time series at intraseasonal periods in general earth rotation values for c 21 and s 21 and slr values for c 20 agree best with grace estimates grace c 20 time series are contaminated by aliased ocean tide model errors slr c 21 and s 21 time series have been reported without an ocean pole tide opt correction and with an older solid earth pole tide sept model after correcting for opt and sept deficiencies slr c 21 and s 21 time series show improved agreement with other estimates

regional and local ionospheric models based on millstone hill incoherent scatter radar data 1 local and regional statistical models to describe millstone hill incoherent scatter radar observations of electron density electron temperature and ion temperature since 1976 are developed using a bin fit technique the local models generate ionospheric variations with local time day number and altitude from 150 1000 km the prior day s f107 and the ap index from the previous 3 hour period are keyed inputs to specify solar and geomagnetic activity the regional models have a latitude coverage of 32 55 geodetic and an altitude coverage of 200 600 km these climatology models are capable of reproducing primary ionospheric variation features seen in previous studies as well as several newly revealed features such as the semiannual variation of electron density they are accessible through the world wide web at the url http www openmadrigal org

determination of long term changes in the earth s gravity field from satellite laser ranging observations temporal changes in the earth s gravity field have been determined by analyzing satellite laser ranging slr observations of eight geodetic satellites using data spanning an interval of over 20 years the satellites used in the analysis include starlette lageos 1 and 2 ajisai etalon 1 and 2 stella and be c geophysical parameters related to both secular and long period variations in the earth s gravity field including the geopotential zonal rates and and the 18 6 year tide parameter were estimated the estimated values for these parameters are centimeters and s18 6 20 0 1 0 2 centimeters the amplitude and phase for the 18 6 year tide are in general agreement with the effects predicted by the earth s mantle anelasticity the solution accuracy was evaluated by considering the effects of errors in various non estimated dynamical model parameters and by varying the data span and data sets used in the solution estimates for from individual lageos 1 and starlette slr data sets are in good agreement the lumped sum values for and are very different for lageos 1 and starlette the zonal rate determination is limited to degree 6 with the current slr data sets analysis of the sensitivity of the solution for the zonal rates to the satellite tracking data span suggests that the temporal extension of the current slr data sets will enhance the solution of zonal rates beyond degree 6

postglacial rebound and sea level contributions to changes in the geoid and the earth s rotation axis summary the rate of change of the spherical harmonic degree 2 component of the earth s gravitational potential coa 20 and polar wander velocity are two signals which are sensitive to late pleistocene deglaciation current changes in sea level and deep mantle viscosity diierent load and earth models have been used in earlier papers to predict the component of these geophysical signals caused by the collapse of the last great ice sheets and recent melting of polar ice caps in this paper we present a systematic analysis of the dependence of the predictions on parameters of the ice and earth model we show that the key parameters of the ice model which govern the predictions are the mass the location of the centre of mass and the midpoint of the deglaciation phase of secondary importance is the length of the deglaciation phase and the mean ice load prior to the last glacial maximum these conclusions enable us to make a more robust inference of mantle viscosity than has been made before allowing for the uncertainties in the model of late pleistocene and present deglaciation as previous authors have shown the lower mantle viscosity is the most important rheological parameter and therefore thecoa 20 observation complements sea level observations which are primarily sensitive to lithospheric thickness and the viscosity of the upper part of the mantle using realistic constraints on the sizes locations and timing of deglaciation of the late pleistocene ice sheets and current changes in polar ice caps the observation of coa 20 is used to infer lower mantle viscosity as a function of the present rate of sea level change if the present rate of non steric sea level change is 1 mm yr 1 and that change has been occurring for less than 1000 years then the lower mantle viscosity satis es log10 glm 21 82 0 15 which is consistent with inferences drawn from recent sea level analyses and con rms other analyses of thecoa 20 observation if the polar wander signal is produced entirely by postglacial rebound and current sea level change no more than 20 per cent of the present contribution to global sea level change comes from greenland the above conclusions also hold if the density discontinuities at 420 and 670 km are modelled as phase boundaries rather than material chemical boundaries

present day secular variations in the low degree harmonics of the geopotential sensitivity analysis on spherically symmetric earth models 1 we predict present day rates of change of the long wavelength components of the earth s geopotential due to the late pleistocene glacial cycles hereinafter referred to as glacial isostatic adjustment or gia these predictions are generated using spherically symmetric self gravitating maxwell viscoelastic earth models previous studies have generally considered only zonal i e azimuthally independent harmonics or the so called coefficients we extend these efforts to focus on the nonzonal harmonics and explore the sensitivity of our predictions to changes in a variety of model inputs as an example we examine the influence on the gia predictions of ignoring rotational perturbations and assuming an elastically incompressible model and find that these assumptions can have a significant impact on the degree 2 order 1 coefficients while the other harmonics are generally affected by 10 though the gia predictions are generally insensitive to variations in lithospheric thickness and upper mantle viscosity reasonable variations in either lower mantle viscosity or the late pleistocene ice history will have a more significant effect mindful of upcoming dedicated gravity missions we show that predictions of the gia induced changes of the geoid can vary by at least 0 5 mm yr 1 over a plausible range of earth and ice models

twentieth century sea level an enigma changes in sea level relative to the moving crust are associated with changes in ocean volume mostly thermal expansion and in ocean mass melting and continental storage t steric t eustatic t recent compilations of global ocean temperatures by levitus and coworkers are in accord with coupled ocean atmosphere modeling of greenhouse warming they yield an increase in 20th century ocean heat content by 2 1023 j compared to 0 1 1023 j of atmospheric storage which corresponds to greenhouse 2000 3 cm the greenhouse related rate is accelerating with a present value greenhouse 2000 6 cm century tide records going back to the 19th century show no measurable acceleration throughout the late 19th and first half of the 20th century we take historic 18 cm century the intergovernmental panel on climate change attributes about 6 cm century to melting and other eustatic processes leaving a residual of 12 cm of 20th century rise to be accounted for the levitus compilation has virtually foreclosed the attribution of the residual rise to ocean warming notwithstanding our ignorance of the abyssal and southern oceans the historic rise started too early has too linear a trend and is too large melting of polar ice sheets at the upper limit of the intergovernmental panel on climate change estimates could close the gap but severe limits are imposed by the observed perturbations in earth rotation among possible resolutions of the enigma are a substantial reduction from traditional estimates including ours of 1 5 2 mm y global sea level rise a substantial increase in the estimates of 20th century ocean heat storage and a substantial change in the interpretation of the astronomic record