high resolution sar interferometry estimation of local frequencies in the context of alpine glaciers synthetic aperture radar sar interferometric data offer the opportunity to measure temperate glacier surface topography and displacement the increase of the resolution provided by the most recent sar systems has some critical implications for instance a reliable estimate of the phase gradient can only be achieved by using interferogram local frequencies in this paper an original two step method for estimating local frequencies is proposed the 2 d phase signal is considered to have two deterministic components corresponding to low resolution lr fringes and high resolution hr patterns due to the local microrelief respectively the first step of the proposed algorithm consists in the lr phase flattening in the second step the local hr frequencies are estimated from the phase 2 d autocorrelation function computed on adaptive neighborhoods this neighborhood is the set of connected pixels belonging to the same hr spatial feature and respecting the ldquolocal stationarityrdquo hypothesis results with both simulated terrasar x interferograms and real airborne e sar images are presented to illustrate the potential of the proposed method

relating the occurrence of crevasses to surface strain rates the presence of crevasses on the surface of ice masses indicates that a fracture criterion has been met understanding how crevasses form will provide information about the stress and strain rate fields in the ice this study derives a relationship between measurements of strain rate and observations of crevassing on the surface of ice masses a literature search yielded 17 polar and alpine locations where strain rates had been measured and crevassing recorded by plotting strain rates converted to stresses using a creep law using axes representing the surface parallel principal stresses failure envelopes were derived by enclosing measurements where surface crevassing was absent the derived failure envelopes were found to conform well to theoretical ones predicted by the coulomb and the maximum octahedral shear stress von mises theories of failure the derived failure envelopes were scaled by the tensile strength which was found to vary from 90 to 320 kpa there was no systematic variation of tensile strength with either temperature at 10 m depth or the method used to locate the crevasses the observed variation in tensile strength could result from variations in ice properties e g crystal size impurity content or density or could be related to uncertainty in the constitutive relation creep flow and fracture share a very similar temperature dependence suggesting similar crystal scale processes are responsible for both the observed relationship will provide a supplementary tool with which to verify and test models of ice dynamics against remotely sensed imagery the study also indicates that a temperature rise of a few degrees throughout the ice column will not result directly in any increase in calving rates from the large antarctic ice shelves such as the filchner ronne or ross ice shelves

an inversion strategy for hydraulic tomography coupling travel time and amplitude inversion summary we present a hydraulic tomographic inversion strategy with an emphasis on the reduction of ambiguity of hydraulic travel time inversion results and the separation of the estimated diffusivity values into hydraulic conductivity and specific storage our tomographic inversion strategy is tested by simulated multilevel interference slug tests in which the positions of the sources injection ports and the receivers observation ports isolated with packers are varied simulations include the delaying effect of wellbore storage on travel times which are quantified and shown to be of increasing importance for shorter travel distances for the reduction of ambiguity of travel time inversion we use the full travel time data set as well as smaller data subsets of specified source receiver angles the inversion results of data subsets show different resolution characteristics and improve the reliability of the interpretation the travel time of a pressure pulse is a function of the diffusivity of the medium between the source and receiver thus it is difficult to directly derive values for hydraulic conductivity and specific storage by inverting travel times in order to overcome this limitation we exploit the great computational efficiency of hydraulic travel time tomography to define the aquifer structure which is then input into the underlying groundwater flow model modflow 96 finally we perform a model calibration amplitude inversion using the automatic parameter estimator pest enabling us to separate diffusivity into its two components hydraulic conductivity and specific storage

chaotic solute advection by unsteady groundwater flow 1 solute mixing in fluids is enhanced significantly by chaotic advection the phenomenon in which fluid pathlines completely fill the spatial domain explored by a laminar flow steady groundwater flows are in general not well conditioned for this phenomenon because darcy s law confines them spatially to nonintersecting stream surfaces unsteady groundwater flows however may in principle induce chaotic solute advection if their time dependence is periodic and produces frequent reorientation of pathlines an effect connected closely to the development of high solute mixing efficiencies in this paper a simple two dimensional model groundwater system is studied theoretically to evaluate the possibility of inducing chaotic solute advection in the flow field near a recirculation well whose pumping behavior is time periodic in the vernacular of dynamical systems theory the model studied is an example of a hamiltonian system thus allowing a mathematical formulation that facilitates consideration of whether chaotic advection can occur when the model system is driven time periodically by alternate operation of the production and injection components of the recirculation well numerical simulations of the fluid pathlines indicate that regions of chaotic solute advection will indeed develop in the flow field near the well with expected major improvement in plume spreading

combining airborne photographs and spaceborne sar data to monitor temperate glaciers potentials and limits monitoring temperate glacier activity has become more and more necessary for economical and security reasons and as an indicator of the local effects of global climate change remote sensing data provide useful information on such complex geophysical objects but they require specific processing techniques to cope with the difficult context of moving and changing features in high relief areas this paper presents the first results of a project involving four laboratories developing and combining specific methods to extract information from optical and synthetic aperture radar sar data two different information sources are processed namely 1 airborne photography and 2 spaceborne c band sar interferometry the difficulties and limitations of their processing in the context of alpine glaciers are discussed and illustrated on two glaciers located in the mont blanc area the results obtained by aerial triangulation techniques provide digital terrain models with an accuracy that is better than 30 cm which is compatible with the computation of volume balance and useful for precise georeferencing and slope measurement updating the results obtained by sar differential interferometry using european remote sensing satellite images show that it is possible to measure temperate glacier surface velocity fields from october to april in one day interferograms with approximately 20 m ground sampling this allows to derive ice surface strain rate fields required to model the glacier flow these different measurements are complementary to results obtained during the summer from satellite optical data and ground measurements that are available only in few accessible points

the origin of endothermy in synapsids and archosaurs and arms races in the triassic abstract birds and mammals are key elements of modern ecosystems and many biologists explain their great success by their endothermy or warm bloodedness new palaeontological discoveries point to the origins of endothermy in the triassic and that birds archosaurs and mammals synapsids likely acquired endothermy in parallel here a further case is made that the emergence of endothermy in a stepwise manner began in the late permian but accelerated in the early triassic the trigger was the profound destruction wrought by the permian triassic mass extinction ptme in the oceans this was the beginning of the mesozoic marine revolution mmr and a similar revolution occurred on land termed here the triassic terrestrial revolution ttr among tetrapods both synapsids and archosaurs survived into the triassic but numbers were heavily depleted however the survivors were marked by the acquisition of endothermy as shown by bone histology isotopic analyses and the acquisition of insulating pelage both groups before the ptme had been sprawlers after the event they adopted parasagittal erect gait the new posture and the new physiology enabled both groups to compete in their ecosystems at a faster rate than before the ptme the new world of the triassic was characterised by a fast paced arms race between synapsids and archosauromorphs in which the latter as both dinosaurs and pterosaurs initially prevailed

perspectives on proterozoic surface ocean redox from iodine contents in ancient and recent carbonate abstract the proterozoic eon hosted the emergence and initial recorded diversification of eukaryotes oxygen levels in the shallow marine settings critical to these events were lower than today s although how much lower is debated here we use concentrations of iodate the oxidized iodine species in shallow marine limestones and dolostones to generate the first comprehensive record of proterozoic near surface marine redox conditions the iodine proxy is sensitive to both local oxygen availability and the relative proximity to anoxic waters to assess the validity of our approach neogene quaternary carbonates are used to demonstrate that diagenesis most often decreases and is unlikely to increase carbonate iodine contents despite the potential for diagenetic loss maximum proterozoic carbonate iodine levels are elevated relative to those of the archean particularly during the lomagundi and shuram carbon isotope excursions of the paleo and neoproterozoic respectively for the shuram anomaly comparisons to neogene quaternary carbonates suggest that diagenesis is not responsible for the observed iodine trends the baseline low iodine levels in proterozoic carbonates relative to the phanerozoic are linked to a shallow oxic anoxic interface oxygen concentrations in surface waters would have at least intermittently been above the threshold required to support eukaryotes however the diagnostically low iodine data from mid proterozoic shallow water carbonates relative to those of the bracketing time intervals are consistent with a dynamic chemocline and anoxic waters that would have episodically mixed upward and laterally into the shallow oceans this redox instability may have challenged early eukaryotic diversification and expansion creating an evolutionary landscape unfavorable for the emergence of animals

the evolution of respiratory systems in theropoda and paracrocodylomorpha the end triassic extinction and the role of late triassic atmospheric o2 and co2 abstract during the late triassic period 235 201 3 ma paracrocodylomorpha and theropoda switched predatory roles with the former filling the subsidiary predator niche and the latter filling the top predator niche at the end triassic extinction reasons for the transition in predator guilds remain unknown but atmospheric conditions during this time which involved high co2 and low o2 concentration levels may be associated with the event evidence of bird like pneumatic post crania present in both groups as foramina and fossae correlates with an avian like respiratory system this may have allowed organisms to cope with declining atmospheric o2 environments of the late triassic this study estimated po2 throughout the late triassic using organic carbon isotope measurements from newark hartford basin paleosols and examined the morphological change in skeletal remains of theropoda focusing on pneumatic bones compared with paracrocodylomorpha during the late triassic and across the triassic jurassic boundary with data compiled from the paleobiology database and published anatomical literature the change of pneumaticity in taxa is quantified by a pneumatic index pi in which the number of pneumatized units is divided by the total number of bones examined patterns of pneumaticity are individually scored for the presence or absence of pneumatic bones morphological data are compared to corresponding femur length estimated atmospheric o2 and co2 level reconstructions and an ancestral state reconstruction depicting how pi values change throughout various clades our results suggest that pi values in theropoda and paracrocodylomorpha correspond with the vacillating po2 and pco2 throughout the late triassic and into the jurassic high pi values are prevalent in advanced theropod taxa while paracrocodylomorpha pi values vary by clade with a generally negative trend throughout the triassic ancestral state reconstruction analysis highlights the increasing pi values within theropoda and clade dependent trends in paracrocodylomorpha this study is instrumental in reconstructing how theropoda became evolutionarily successful and perhaps how and why the avian like respiratory system originated

satellite radar interferometry for monitoring ice sheet motion application to an antarctic ice stream satellite radar interferometry sri provides a sensitive means of monitoring the flow velocities and grounding line positions of ice streams which are indicators of response of the ice sheets to climatic change or internal instability the detection limit is about 1 5 millimeters for vertical motions and about 4 millimeters for horizontal motions in the radar beam direction the grounding line detected by tidal motions where the ice goes afloat can be mapped at a resolution of 0 5 kilometer the sri velocities and grounding line of the rutford ice stream antarctica agree fairly well with earlier ground based data the combined use of sri and other satellite methods is expected to provide data that will enhance the understanding of ice stream mechanics and help make possible the prediction of ice sheet behavior

estimation of hydraulic conductivity from borehole flowmeter tests considering head losses abstract recent numerical studies have demonstrated that the conventional interpretation of the borehole flowmeter test bft may lead to considerable errors in estimates of the horizontal hydraulic conductivity k r due to neglect of head loss across the electromagnetic borehole flowmeter ebf even in uniform aquifers the conventional interpretation underestimates k r at the base and overestimates k r at the top of the aquifer in this paper we derive exact analytical solutions for hydraulic head and streamlines induced by the bft in a confined homogeneous aquifer the solutions explicitly consider head loss across the ebf the derived analytical solutions for head distribution in the vicinity of the pumping well and for volumetric flux to the well sections above and below the ebf can be used to interpret field bft data in uniform aquifers this approach can be applied to obtain estimates of k r from the conventional interpretation applications of this approach to the bft field data set from a highly heterogeneous aquifer indicate that the constraint of aquifer homogeneity limits the applicability of this approach but it can provide useful insights into the mechanism of flux redistribution near the borehole during the bft

satellite image derived velocity field of an antarctic ice stream the surface velocity of a rapidly moving ice stream has been determined to high accuracy and spatial density with the use of sequential satellite imagery variations of ice velocity are spatially related to surface undulations and transverse velocity variations of up to 30 percent occur such large variations negate the concept of plug flow and call into question earlier mass balance calculations for this and other ice streams where sparse velocity data were used the coregistration of images with the use of the topographic undulations of the ice stream and the measurement of feature displacement with cross correlation of image windows provide significant improvements in the use of satellite imagery for ice flow determination

geostatistical analysis of the borden aquifer hydraulic conductivity field abstract a total of 11 vertical cores spaced 1 m apart along a single transect were extracted from the borden aquifer at a location 60 m north northeast from the site studied by sudicky previously examination of these cores shows the upper 1 5 2 0 m of the aquifer to be comprised of relatively unstructured fine to medium sands underlain by a 0 1 0 8 m thick peaty layer and a 0 1 m thick organic rich horizon between depths of 3 05 and 6 10 m the aquifer is comprised of clean horizontally bedded fine to medium sands similar to those examined by sudicky previously statistical analysis of 642 subsamples of 5 cm length from this interval suggests that the permeability data may follow a log normal distribution with a mean lntransformed permeability m 2 of 25 67 and a variance of 0 585 no consistent trend with depth was detected for ln k or for the mean and variance of ln k on a core by core basis exponential spherical and gaussian models all provided excellent fits to the vertical experimental variogram calculated using the classical estimator without the removal of outliers these fits produced correlation scales ranging from 0 16 to 0 23 m of the three theoretical models only the gaussian model produced a reasonable fit to the horizontal experimental variogram with a correlation scale of 4 8 m a linear model was also found to fit the experimental variogram data well in comparison with earlier results of sudicky and woodbury and sudicky it can be concluded that similar deposits were examined in this study particularly with respect to correlation structure on the basis of statistical tests however it cannot be concluded that the mean and variance of ln k are stationary over the 60 m distance between the cores examined in this study and those of sudicky the results of this study indicate that the borden hydraulic conductivity field is relatively uniform over the scale examined but that it cannot be characterized by a single spatially invariant statistical distribution

flow of glaciar moreno argentina from repeat pass shuttle imaging radar images comparison of the phase correlation method with radar interferometry high resolution radar images of glaciar moreno argentina acquired by the shuttle imaging radar c sir c on 9 and 10 october 1994 at 24 cm wavelength l band are utilized to map the glacier velocity both interferometrically and using the phase correlation method the precision of the interferometric ice velocities is 1 8 cm d 1 6 m a 1 1 the phase correlation method measures ice velocity with a precision of 14 cm d 1 50 m a 1 with image data at a 6 m sample spacing acquired 1 day apart averaged strain rates are measured with a precision of 10 4 d 1 at a 240 m sample spacing with the phase correlation method and 10 5 d 1 with radar interferometry the phase correlation method is less precise than radar interferometry but it performs better in areas of rapid flow is more robust to temporal changes in glacier scattering and measures the glacier velocity in two dimensions with only one image pair using this technique we find that glaciar moreno flows at 400 m a 1 in the terminal valley and 800 m a 1 at the calving front in agreement with velocities recorded a decade ago assuming steady state flow conditions the vertical strain rates measured by sir c are combined with prior data on mass ablation to estimate the glacier thickness and ice discharge the calculated discharge is 0 6 0 2 km3 ice a 1 at 300 m elevation and 1 1 0 2 km3 ice a 1 at the equilibrium line elevation 1150 m which yields a balance accumulation of 6 1m ice a 1

transient flow to a large diameter well in an aquifer with storative semiconfining layers the hantush theory of leaky aquifers with storge in the semiconfining layers is combined with large diameter well theory to produce equations that can be used in the analysis of pumped well and observation well data for stratified formations included in the equations are storage in the pumped well and a linear resistance to flow at the sand face or well bore skin three cases proposed by hantush are considered these depend upon whether the upper boundary of the overlying semiconfining layer or the lower boundary of the underlying semiconfining layer are constant head or no flow boundaries laplace transform solutions valid for the complete time domain are given for each of the three cases for the hydraulic head in the pumped well the aquifer and each of the semiconfining layers type cures obtained by numerical inversion are selected to illustrate the effects of well bore storage well bore skin and leakage although several dimensionless parameters are involved these parameters tend to influence the character of different portions of the type curves suggesting that unique matches are possible the type curves show that well bore storage in a large diameter well may completely obliterate effects of leakage derived from compressible storage in semiconfining layers for the purposes of aquifer testing it may be possible to reduce the magnitude of well bore storage in a large diameter well and thus reveal the presence of leaky semiconfining layers this may help to prevent erroneous interpretation of the well test data and incorrect evaluation of the aquifer parameters

phanerozoic atmospheric oxygen new results using the geocarbsulf model modifications of the geocarbsulf model for phanerozoic atmospheric oxygen have been made to account for new carbon isotopic data reconsideration of the fractionation of carbon isotopes between carbonate and organic matter deposited in sediments and different rates of weathering of volcanic rocks versus granitic rocks results indicate distinctly higher o2 values than geocarbsulf for the mesozoic and cenozoic lack of an appreciable drop in o2 below 15 percent at any time and a small late cenozoic decline of o2 to the present

a method to estimate hydraulic conductivity from bulk geochemical compositions a new method has been developed to estimate the hydraulic conductivity in unconsolidated aquifers the method uses bulk geochemical compositions correlated with hydraulic conductivities measured by pumping tests the concept is based on a general rule that hydraulic conductivity is principally controlled by grain size distribution and particle shape both of which relate to mineralogical composition using a minlith algorithm normative mineralogical compositions can be derived from bulk geochemical compositions economically and expediently and then correlated to the hydraulic conductivity determined by pumping tests in the field in this study 202 sediment samples from nine unconsolidated aquifers were analyzed by x ray fluorescence although hydraulic conductivity does not show a definite relationship with geochemical compositions it does demonstrate a linear logarithmic equation to the content of normative earthy minerals however linear regressed equations should not be applied to aquifers composed of medium to coarse sand and gravel sizes due to interference from lithic fragments in addition this equation tends to overestimate hydraulic conductivity possibly because the effect of compaction is ignored in this study

stable carbon isotopes of c3 plant resins and ambers record changes in atmospheric oxygen since the triassic estimating the partial pressure of atmospheric oxygen po2 in the geological past has been challenging because of the lack of reliable proxies here we develop a technique to estimate paleo po2 using the stable carbon isotope composition d 13 c of plant resins including amber copal and resinite from a wide range of localities and ages triassic to modern plant resins are particularly suitable as proxies because their highly cross linked terpenoid structures allow the preservation of pristine d 13 cs ignatures over geological timescales the distribution of d 13 c values of modern resins n 126 indicates that a resin producing plant families generally have a similar fractionation behavior during resin biosynthesis and b the fractionation observed in resins is similar to that of bulk plant matter resins exhibit a natural variability in d 13 c of around 8 d 13 cr ange 31 to 23 m ean 27 which is caused by local environmental and ecological factors e g water availability water composition light exposure temperature nutrient availability to minimize the effects of local conditions and to determine long term changes in the d 13 co f resins we used mean d 13 c values d 13 c resin for each geological resin deposit fossil resins n 412 are generally enriched in 13 c compared to their modern counterparts with shifts in d 13 c resin of up to 6 these isotopic shifts follow distinctive trends through time which are unrelated to post depositional processes including polymerization and diagenesis the most enriched fossil resin samples with a d 13 c resin between 22 and 21 formed during the triassic the mid cretaceous and the early eocene experimental evidence and theoretical considerations suggest that neither change in pco2 nor in the d 13 c of atmospheric co2 can account for the observed shifts in d 13 c resin the fractionation of 13 c in resin producing plants d 13 c instead is primarily influenced by atmospheric po2 with more fractionation occurring at higher po2 the enriched d 13 c resin values suggest that atmospheric po2 during most of the mesozoic and cenozoic was considerably lower po2 10 20 than today po2 21 in addition a correlation between the d 13 c resin and the marine d 18 o record implies that po2 pco2 and global temperatures were inversely linked which suggests that intervals of low po2 were generally accompanied by high pco2 and elevated global temperatures intervals with the lowest inferred po2 including the mid cretaceous and the early eocene were preceded by large scale volcanism during the emplacement of large igneous provinces lips this suggests that the influx of mantle derived volcanic co2 triggered an initial phase of warming which led to an increase in oxidative weathering thereby further increasing greenhouse forcing this process resulted in the rapid decline of atmospheric po2 during the mid cretaceous and the early eocene greenhouse periods after the cessation in lip volcanism and the decrease in oxidative weathering rates atmospheric po2 levels continuously increased over tens of millions of years whereas co2 levels and temperatures continuously declined these findings suggest that atmospheric po2 had a considerable impact on the evolution of the climate on earth and that the d 13 c of fossil resins can be used as a novel tool to assess the changes of atmospheric compositions since the emergence of resin producing plants in the paleozoic

multi level slug tests in highly permeable formations 2 hydraulic conductivity identification method verification and field applications abstract using the developed theory and modified springer gelhar sg model an identification method is proposed for estimating hydraulic conductivity from multi level slug tests the computerized algorithm calculates hydraulic conductivity from both monotonic and oscillatory well responses obtained using a double packer system field verification of the method was performed at a specially designed fully penetrating well of 0 1 m diameter with a 10 m screen in a sand and gravel alluvial aquifer msea site shelton nebraska during well installation disturbed core samples were collected every 0 6 m using a split spoon sampler vertical profiles of hydraulic conductivity were produced on the basis of grain size analysis of the disturbed core samples these results closely correlate with the vertical profile of horizontal hydraulic conductivity obtained by interpreting multi level slug test responses using the modified sg model the identification method was applied to interpret the response from 474 slug tests in 156 locations at the msea site more than 60 of responses were oscillatory the method produced a good match to experimental data for both oscillatory and monotonic responses using an automated curve matching procedure the proposed method allowed us to drastically increase the efficiency of each well used for aquifer characterization and to process massive arrays of field data recommendations generalizing this experience to massive application of the proposed method are developed

comment on plume spreading in groundwater by stretching and folding by d c mays and r m neupauer the recent paper of mays and neupauer 2012 presents one such novel methodology for the acceleration of plume spreading with punctuated injection protocols that result in fluid stretching and folding which are the hallmarks of chaotic dynamics in continuous systems this protocol shows excellent promise as a means to accelerate dispersion for groundwater remediation recovery and so on our comment regarding this paper does not directly pertain to this method but rather corrects an erroneous statement that has important implications for a wide class of intervention methods which involve recycled injection whereby extracted fluid is reinjected elsewhere in the subsurface to impart continuous fluid flow and deformation

plume spreading in groundwater by stretching and folding 1 this paper proposes a new approach to the hydraulics of in situ groundwater remediation in situ remediation promotes reactions between an injected treatment solution and the contaminated groundwater but without a hydraulic mechanism to promote spreading the laminar flows characteristic of porous media will keep the two fluids in approximately the same relative configuration as they travel through the aquifer limiting the opportunity for reactions to occur to address this fundamental limitation this paper borrows a key result from the fluid mechanics literature spreading in laminar flows is optimized by chaotic advection previous studies have applied this result to groundwater remediation using the pulsed dipole model but that model depends on reinjection of fluid which presents a number of theoretical and practical limitations accordingly this paper proposes a new conceptual model for plume spreading by chaotic advection using an engineered sequence of extractions and injections of clean water at an array of wells which generates plume spreading by stretching and folding the fluid interface between the injected treatment solution and the contaminated groundwater but does not require reinjection the paper includes an overview of the analytical techniques poincare sections periodic points stable and unstable manifolds heteroclinic points and lyapunov exponents used to demonstrate chaotic advection in the limiting case in which diffusion is negligible numerical simulations show that spreading by stretching and folding is complimentary to spreading resulting from aquifer heterogeneity

measurement of ice sheet topography using satellite radar interferometry detailed digital elevation models dems do not exist for much of the greenland and antarctic ice sheets radar altimetry is at present the primary in many cases the only source of topographic data over the ice sheets but the horizontal resolution of such data is coarse satellite radar interferometry uses the phase difference between pairs of synthetic aperture radar sar images to measure both ice sheet topography and surface displacement we have applied this technique using ers 1 sar data to make detailed i e 80 m horizontal resolution maps of surface topography in a 100 km by 300 km strip in west greenland extending northward from just above jakobshavns isbrae comparison with a 76 km long line of airborne laser altimeter data shows that we have achieved a relative accuracy of 2 5m along the profile these observations provide a detailed view of dynamically supported topography near the margin of an ice sheet in the final section we compare our estimate of topography with phase contours due to motion and confirm our earlier analysis concerning vertical ice sheet motion and complexity in ers 1 sar interferograms

ice sheet motion and topography from radar interferometry both topography and motion information are present in repeat pass ers 1 interferograms over ice sheets the authors demonstrate that the topography is separable from the surface displacement field when a sequence of radar images are available if the velocity field is constant over the time span of observation the topography can be derived from differential interferograms formed from sequential observations with this measurement a pure displacement field can then be obtained by removal of the topographic contribution to the interferometric phase at each pixel further they discuss how the vertical and horizontal components of displacement affect the interferometrically derived motion field they illustrate their approach with four successive 3 day repeat ers 1 images of a flow feature in northeastern greenland

variations in ice velocities of pine island glacier ice shelf evaluated using multispectral image matching of landsat time series data abstract pine island glacier pig in west antarctica drains out to the amundsen sea through pine island glacier ice shelf pigis as changes in ice velocities on pigis are strongly linked to changes in ice mass discharge from the west antarctic ice sheet it is very important to evaluate the spatiotemporal variations in ice velocities on the ice shelf this research estimated ice velocities of pigis from an ensemble of image matching of landsat time series multispectral data obtained from 2000 to 2014 orientation correlation was adopted for the image matching of blue green red near infrared panchromatic and the first principal image of the landsat multispectral data from which the results were combined and averaged the multispectral image matching proposed in this research produced 35 more ice velocity vectors than the use of a single band i e panchromatic band image matching the erroneous matches were filtered through simple but rigorous statistical evaluations the ice velocity of pigis accelerated by 55 during 2000 2010 and the acceleration of the image northing velocity component 1 3 km a 1 was higher than that of the image easting velocity component 0 8 km a 1 during 2010 2012 the ice velocity of pigis slowed down by 10 the ice velocity in 2014 increased by 5 from 2012 but was still lower than the peak values observed in 2010 the surface strain rate fields of pigis were derived from the ice velocity fields the longitudinal ice compression was observed near the grounding line and the geographically northern part of the central ice shelf of pigis while a fast flowing band was observed near the southern margin of the ice shelf the transverse strain rate showed that ice divergence in the hinge zone of the central ice shelf has increased since 2000 the width of the shear margins of the central ice shelf of pigis is 25 km which has been stable since 2000

measurement of glacier geophysical properties from insar wrapped phase a method is presented for calculating longitudinal glacier strain rates directly from the wrapped phase of an interferometric synthetic aperture radar insar interferogram assuming the ice flow path is known this technique enables strain rates to be calculated for scenes lacking any velocity control points or areas within a scene where the phase is not continuously unwrappable from a velocity control point the contributions to the error in the estimate of the strain rate are evaluated and recommendations for appropriate sar and insar parameters are presented an example using radarsat 1 insar data of an east antarctic ice stream demonstrates the technique for calculating longitudinal strain rate profiles and estimating tensile strength of ice 186 215 kpa from locations of crevasse initiation the strain rate error was found to be 17 corresponding to a tensile strength of ice error of 5 3

thermal attenuation and lag time in fractured rock theory and field measurements from joint heat and solute tracer tests the modelling and prediction of heat transfer in fractured media is particularly challenging as hydraulic and transport properties depend on a multiscale structure that is difficult to resolve in addition to advection and dispersion heat transfer is also impacted by thermal attenuation and lag time which results from fracture matrix thermal exchanges here we derive analytical expressions for thermal lag time and attenuation coefficient in fractured media which quantify the effect of fracture geometry on these key factors we use the developed expressions to interpret the results of single well thermal tracer tests performed in a crystalline rock aquifer at the experimental site of ploemeur h observatory network thermal breakthrough was monitored with fiber optic distributed temperature sensing fo dts which allows temperature monitoring at high spatial and temporal resolution the observed thermal response departs from the conventional parallel plate fracture model but is consistent with a channel model representing highly channelized fracture flow these findings which point to a strong reduction of fracture matrix exchange by flow channeling show the impact of fracture geometry on heat recovery in geothermal systems this study also highlights the advantages to conduct both thermal and solute tracer tests to infer fracture aperture and geometry

interferometric radar observations of glaciares europa and penguin hielo patagonico sur chile repeat pass l band interferometric synthetic aperture radar insar data for part of hielo patagonico sur chile were collected by the space shuttle based spaceborne imaging radar c sir c over a 4 day span in october 1994 three co registered complex sar images are used to generate phase coherence maps a digital elevation model dem and an ice velocity map the phase coherence maps indicate low coherence in the 5 15 km approaching the termini due to large displacements ice deformation and melting however the coherence is high over nearly all of the remaining imaged icefield ice velocity precision is greater than 2 cm d 1 while the dem is good to about 25 m a flow divide between two of the glaciers is mapped by locating a narrow band of near zero ice velocity horizontal ice surface velocity profiles calculated along flowlines show there is a high degree ofspatial variability reaching a peak value of 5 5 m d 1 located 3 5 km from the terminus of glaciar europa longitudinal strain rates along the center lines calculated from these velocities at the locations of the initiation of crevassing are used to compute the tensile strength of ice 169 224 kpa

tracer advection by steady groundwater flow in a stratified aquifer the perfectly stratified aquifer has often been investigated as a simple tractable model for exploring new theoretical issues in subsurface hydrology adopting this approach we show that steady groundwater flows in the perfectly stratified aquifer are always confined to a set of nonintersecting permanent surfaces on which both streamlines and vorticity lines lie this foliation of the flow domain exists as well for steady groundwater flows in any isotropic spatially heterogeneous aquifer in the present model example it is a direct consequence of the existence of a stream function we then demonstrate that tracer plume advection by steady groundwater flow in a perfectly stratified aquifer is never ergodic regardless of the initial size of the tracer plume this nonergodicity which holds also for tracer advection in any isotropic spatially heterogeneous aquifer implies that stochastic theories of purely advective tracer plume movement err in assuming ergodic behavior to simplify probabilistic calculations of plume spatial concentration moments

identifying hydraulically conductive fractures with a slow velocity borehole flowmeter the u s geological survey used a recently developed heat pulse flowmeter to measure very slow borehole axial water velocities in granitic rock at a site near lac du bonnet manitoba canada the flowmeter was used with other geophysical measurements to locate and identify hydraulically conducting fractures contributing to the very slow vertical water flow in the two boreholes selected for study the heat pulse flowmeter has no moving parts and operates on the tag trace principle it is an improved version of the flowmeter developed by the water research centre in england in 1975 the u s geological survey s heat pulse flowmeter has a flow measuring range in water of 0 06 6 m min and can resolve velocity differences as slow as 0 01 m min this is an order of magnitude slower than the stall speed of spinner flowmeters the flowmeter is 1 16 m long and 44 mm in diameter it was calibrated in columns of 76 and 152 mm diameter to correspond to the boreholes studied the heat pulse flowmeter system is evalu

ice flow of humboldt petermann and ryder gletscher northern greenland radar interferometry ice penetrating radar profiles and an elevation model are used to determine the velocity fields rates of ice discharge approximate states of balance and catchment area for three large outlet glaciers in northeast greenland discharge through flux gates is calculated for humboldt and petermann gletscher which are found to be in balance at the level that the accumulation is known a large difference between the measured and estimated fluxes for ryder gletscher may be a reflection of unsteady flow behavior for this glacier the patterns ofice flow for the three glaciers considered are each unique showing that the nature of ice discharge varies substantially from basin to basin controlled by bed conditions and the presence of subglacial troughs and obstructions

development of an antarctic digital elevation model by integrating cartographic and remotely sensed data a geographic information system based approach we present a high resolution digital elevation model dem of the antarctic it was created in a geographic information system gis environment by integrating the best available topographic data from a variety of sources extensive gis based error detection and correction operations ensured that our dem is free of gross errors the carefully designed interpolation algorithms for different types of source data and incorporation of surface morphologic information preserved and enhanced the fine surface structures present in the source data the effective control of adverse edge effects and the use of the hermite blending weight function in data merging minimized the discontinuities between different types of data leading to a seamless and topographically consistent dem throughout the antarctic this new dem provides exceptional topographical details and represents a substantial improvement in horizontal resolution and vertical accuracy over the earlier continental scale renditions particularly in mountainous and coastal regions it has a horizontal resolution of 200 m over the rugged mountains 400 m in the coastal regions and approximately 5 km in the interior the vertical accuracy of the dem is estimated at about 100 130 m over the rugged mountainous area better than 2 m for the ice shelves better than 15 m for the interior ice sheet and about 35 m for the steeper ice sheet perimeter the antarctic dem can be obtained from the authors

field study of dispersion in a heterogeneous aquifer 3 geostatistical analysis of hydraulic conductivity observations of the spatial variability of hydraulic conductivity at a tracer test site located at columbus air force base in mississippi are presented direct measurements of hydraulic conductivity of the heterogeneous alluvial aquifer at the site were made using borehole flowmeter logging slug tests and a laboratory permeameter to test undisturbed soil cores indirect methods estimating hydraulic conductivity were also evaluated including soil grain size analyses surface geophysical surveys and mapping of sediment facies the spatial covariance of the 2187 hydraulic conductivity values obtained with the borehole flowmeter method was examined the log hydraulic conductivity variance ln2k and the horizontal and vertical correlation scales h and v of 4 5 12 8 m and 1 6 m respectively were estimated assuming second order stationarity of the conductivity field the covariance parameters are uncertain with bounding values that are 24 76 above or below the estimate covariance parameters estimated with more limited nonflowmeter data were within the same magnitude as those obtained using the extensive flowmeter data suggesting that data from a variety of methods may be used to provide approximate values of the autocovariance parameters nonstationarity of the ln k field was examined by removing three dimensional polynomial trend surfaces and calculating variograms of the residuals significantly lower estimates for ln2k h and v of 2 7 4 8 m and 0 8 m respectively were obtained from the third order log conductivity residuals after trend removal the bounding parameter values differ 15 44 from the estimated values accounting for unsteady flow and the uncertainty in the covariance parameters of the third order log conductivity residuals the calculated longitudinal and horizontal transverse macrodispersivities ranged from 1 5 m to 1 8 m and 0 3 m to 0 6 m respectively

engineered injection and extraction to enhance reaction for improved in situ remediation 1 during in situ remediation a treatment solution is often injected into a contaminated aquifer to degrade the groundwater contaminant since contaminant degradation reactions occur only at locations where the treatment solution and groundwater contaminant overlap mixing of the treatment solution and the contaminated groundwater is necessary for reaction to occur mixing results from molecular diffusion and pore scale dispersion which operate over small length scales thus mixing during in situ remediation can only occur where the separation distance between the treatment solution and contaminated groundwater is small to promote mixing advection can be used to spread the treatment solution into the contaminated groundwater to increase the extent of the region where the two solutions coexist a certain degree of passive spreading is the natural consequence of aquifer heterogeneity which is manifested as macrodispersion an alternative mechanism is active spreading in which unsteady flows lead to stretching and folding of plumes active spreading can be accomplished by engineered injection and extraction eie in which clean water is injected and extracted at wells surrounding a contaminant plume to create unsteady flow fields that stretch and fold the treatment solution and contaminant plumes for a model system in which nested plumes of two reactants undergo scalar transport and instantaneous reaction the simulation results reported here indicate that eie enhances degradation of groundwater contamination in homogeneous and heterogeneous aquifers compared to baseline models without eie furthermore this study shows that the amount of reaction provided by the spreading due to eie is greater than the amount of reaction due to spreading from heterogeneity alone

conservative solute approximation to the transport of a remedial reagent in a vertical circulation flow field summary this study presents a novel mathematical model for describing the transport of the remedial reagent in a vertical circulation flow field in an anisotropic aquifer to develop the mathematical model the radial and vertical components of the pore water velocity are calculated first by using an analytical solution for steady state drawdown distribution near a vertical circulation well next the obtained radial and vertical components of the pore water velocity are then incorporated into a three dimensional axisymmetrical advection dispersion equation in cylindrical coordinates from which to build the reagent transport equation the laplace transform finite difference technique is applied to solve the three dimensional axisymmetrical advection dispersion equation with spatial variable dependent coefficients the developed mathematical model is used to investigate the effects of various parameters such as hydraulic conductivity anisotropy longitudinal and transverse dispersivities the placement of the extraction and injection screened intervals of the vertical circulation well and the injection modes on the transport regime of the remedial reagent results show that those parameters have different degrees of impacts on the distribution of the remedial reagent the mathematical model provides an effective tool for designing and operating an enhanced groundwater remediation in an anisotropic aquifer using the vertical circulation well technology

chaotic advection and reaction during engineered injection and extraction in heterogeneous porous media during in situ remediation of contaminated groundwater a treatment solution is often injected into the contaminated region to initiate reactions that degrade the contaminant degradation reactions only occur where the treatment solution and the contaminated groundwater are close enough that mixing will bring them together degradation is enhanced when the treatment solution is spread into the contaminated region thereby increasing the spatial extent of mixing and degradation reactions spreading results from local velocity variations that emerge from aquifer heterogeneity and from spatial variations in the external forcings that drive flow certain patterns in external forcings have been shown to create chaotic advection which is known to enhance spreading of solutes in groundwater flow and other laminar flows this work uses numerical simulations of flow and reactive transport to investigate how aquifer heterogeneity changes the qualitative and quantitative aspects of chaotic advection in an aquifer and the extent to which these changes enhance contaminant degradation we generate chaotic advection using engineered injection and extraction eie an approach that uses sequential injection and extraction of water in wells surrounding the contaminated region to create time dependent flow fields that promote plume spreading we demonstrate that as the degree of heterogeneity increases both plume spreading and contaminant degradation increase however the increase in contaminant degradation is small relative to the increase in plume spreading our results show that the combined effects of eie and heterogeneity produce substantially more stretching than either effect separately

the dipole flow test a new single borehole test for aquifer characterization a new single borehole measurement technique for confined aquifers the dipole flow test yields the vertical distributions of the horizontal hydraulic conductivity the vertical hydraulic conductivity and the specific storativity when applied to different borehole intervals the test utilizes straddle packers to isolate two chambers in the borehole pressure transducers to monitor drawdown in them and a small pump to create a dipole flow pattern in the aquifer by pumping water at a constant rate from the aquifer into one chamber transferring it within the well to the next chamber and finally injecting it back to the aquifer a mathematical model describing the drawdown in each chamber is derived for the transient as well as the steady state cases the aquifer parameters may be estimated from data produced by the dipole flow test alone or in conjunction with conventional pumping tests the dipole flow regime reaches a steady state relatively quickly especially in well permeable aquifers a robust computational methodology for estimating the aquifer parameters suitable for automatization is based on the newton raphson algorithm applied to a system of up to three nonlinear equations each describing the well drawdown at a different judiciously chosen time due to the relatively small drawdownmore it invokes the dipole flow test may be applicable to unconfined aquifers as well less

insar observations of the 1993 95 bering glacier alaska u s a surge and a surge hypothesis time varying accelerations were observed on bagley icefield during the 1993 95 surge of bering glacier alaska u s a using repeat pass synthetic aperture radar interferometry observations were from datasets acquired during winter 1991 92 pre surge winter 1993 94 during the surge and winter 1995 96 post surge the surge is shown to have extended 110 km up the icefield from bering glacier to within 15 km or less of the flow divide acceleration and step like velocity profiles are strongly associated with an along glacier series of central phase bull s eyes with diameters of 0 5 4 km these bull s eyes are interpreted to represent glacier surface rise fall events of 3 30 cm during 1 3 day observation intervals and indicate possible migrating pockets of subglacial water we present a surge hypothesis that relates late summer climate to englacial water storage and thence to the subglacial water dynamics pressurization hydraulic jacking depressurization and migration suggested by our observations

theory of dipole flow in uniform anisotropic aquifers a theory of dipole flow is developed to model flow induced by a vertical circulation well consisting of injection and extraction chambers in a single borehole included in the theory are an analytical description of the kinematic flow structure around a vertical circulation well and the drawdown in the well chambers using stokes stream function simple criteria are derived to determine the region of intensive recirculation this region extends from the dipole center approximately five distances between chamber centers in the radial direction and two distances between chamber centers in both vertical directions the vertical scale does not depend on anisotropy of hydraulic conductivity and the radial scale is corrected for anisotropic aquifers based on these estimates criteria are given for the selection of the appropriate aquifer model to employ in five settings including infinite semi infinite confined semi infinite unconfined finite confined and finite unconfined aquifers applications of dipole flow theory are given for analytical estimation of the capture zone for recirculation wells and for simultaneous measurement of horizontal and vertical hydraulic conductivity in uniform anisotropic aquifers using steady state measurements of drawdown in the well chambers

kinematic structure of minipermeameter flow minipermeameters are rapidly becoming a popular tool for collecting localized measurements of permeability in both laboratory and field studies while one of the main advantages of minipermeameters is their ability to collect data on various support volumes there have been only limited attempts to analyze their size and geometry we define the support volume of minipermeameter measurements as a region containing 90 of the total gas flow i e a region bounded by the 10 streamline using our new semianalytical solutions for the stokes stream function we demonstrate that the support volume has a shape of the semitoroid adjacent to the sample surface hence there is a blind spot directly below the minipermeameter which is not probed by the measurement we demonstrate that the support volume of the minipermeameter measurements decreases with the tip seal s ratio a ratio of the inner tip seal radius to the outer tip seal radius while the size of the corresponding blind spot increases

ice sheet velocity mapping a combined interferometric and speckle tracking approach the first and second radarsat antarctic mapping missions amm 1 and 2 have now acquired interferometric synthetic aperture radar sar overmuch of the ice sheet the radarsat 24 day repeat cycle is nearly ideal for measuring slow ice motion e g 1 but application of sar interferometry is limited in faster moving areas with a 1day repeat period ers 1 2 tandem sar data are much better matched to fast motion but are not always available fortunately several authors have demonstrated the ability to measure velocity in fast moving areas by tracking sar speckle from image to image which works well even in the absence of visible features while these estimates have intrinsically lower resolution and poorer accuracy than direct phase measurements they serve well in areas where there are no data suitable for conventional interferometry this paper describes algorithms i have developed for merging interferometric and speckle tracking data from multiple swaths to form a single seamless mosaic of velocity at each point in the mosaic all the available data are combined to produce estimates of the velocity and the associated error this technique is demonstrated using radarsat data collected over lambert glacier antarctica during amm 1 and 2

atmospheric pco2 perturbations associated with the central atlantic magmatic province the effects of a large igneous province on the concentration of atmospheric carbon dioxide pco2 are mostly unknown in this study we estimate pco2 from stable isotopic values of pedogenic carbonates interbedded with volcanics of the central atlantic magmatic province camp in the newark basin eastern north america we find pre camp pco2 values of 2000 parts per million ppm increasing to 4400 ppm immediately after the first volcanic unit followed by a steady decrease toward pre eruptive levels over the subsequent 300 thousand years a pattern that is repeated after the second and third flow units we interpret each pco2 increase as a direct response to magmatic activity primary outgassing or contact metamorphism the systematic decreases in pco2 after each magmatic episode probably reflect consumption of atmospheric co2 by weathering of silicates stimulated by fresh camp volcanics

surface velocity determination on large polar glaciers by aerial photogrammetry aerial photogrammetric block triangulation a standard and well developed technique for extending accurate control for mapping into the interior of a region from a few points of known position on its perimeter can be readily adapted to determine surface velocities on bodies of ice which are too large and often too crevassed to be studied effectively by conventional ground surveying velocities are calculated from the changes in positions of the same natural surface features determined from photography of two or more epochs and the elapsed time this method is capable of providing many uniformly spaced measurements over the whole moving ice surface thus allowing the production of maps of velocity and strain rate which are valuable in analyzing the ice flow regime results from measurements completed some years ago on byrd glacier one of the largest outlet glaciers from the east antarctic plateau are presented as an example of what the method can yield by means of doppler satellite surveying relative positions of control points for each photography epoch can be determined with sub meter accuracy making the technique suitable also in regions where no fixed land features exist a brief description of a project under way in such an area on ice stream b in west antarctica is given

interferometric radar observations of glaciar san rafael chile interferometric radar observations of glaciar san rafael chile were collected in october 1994 by nasa s spaceborne imaging radar c sir c at both l 24 cm and c band frequency 5 6 cm with vertical transmit and receive polarization the c band data did not yield good geophysical products because the temporal coherence of the signal was significantly reduced after 24 h the l band data were however successfully employed to map the surface topography of the icefield with a 10 m uncertainty in height and measure ice velocity with a precision of 4 mm d 1 or 1 4 ma 1 the corresponding error in strain rates is 0 05 a 1 at a 30 m horizontal spacing the one dimensional interferometric velocities were subsequently converted to horizontal displacements by assuming a flow direction and complemented by feature tracking results near the calving front the results provide a comprehensive view of the ice flow dynamics of glaciar san rafael the glacier has a core of rapid flow 4 5 km in width and 3 5 in average slope surrounded by slowermoving ice not by rock ice velocity is 2 6 m d 1 or 0 95 km a 1 near the equilibrium line altitude 1200 m increasing rapidly before the glacier enters the narrower terminal valley to reach 17 5 m d 1 or 6 4 km a 1 at the calving front strain rates are dominated by lateral shearing at the glacier margins 0 4 0 7 a 1 except for the terminal valley section where longitudinal strain rates average close to 1 a 1 this spectacular longitudinal increase in ice velocity in the last few kilometers may be a fundamental feature of tidewater glaciers

geocarbsulf a combined model for phanerozoic atmospheric o2 and co2 abstract a model for the combined long term cycles of carbon and sulfur has been constructed which combines all the factors modifying weathering and degassing of the geocarb iii model berner r a kothavala z 2001 geocarb iii a revised model of atmospheric co2 over phanerozoic time am j sci 301 182 204 for co2 with rapid recycling and oxygen dependent carbon and sulfur isotope fractionation of an isotope mass balance model for o2 berner r a 2001 modeling atmospheric o2 over phanerozoic time geochim cosmochim acta 65 685 694 new isotopic data for both carbon and sulfur are used and new feedbacks are created by combining the models sensitivity analysis is done by determining 1 the effect on weathering rates of using rapid recycling rapid recycling treats carbon and sulfur weathering in terms of young rapidly weathering rocks and older more slowly weathering rocks 2 the effect on o2 of using different initial starting conditions 3 the effect on o2 of using different data for carbon isotope fractionation during photosynthesis and alternative values of oceanic 13c for the past 200 million years 4 the effect on sulfur isotope fractionation and on o2 of varying the size of o2 feedback during sedimentary pyrite formation 5 the effect on o2 of varying the dependence of organic matter and pyrite weathering on tectonic uplift plus erosion and the degree of exposure of coastal lands by sea level change 6 the effect on co2 of adding the variability of volcanic rock weathering over time berner r a 2006 inclusion of the weathering of volcanic rocks in the geocarbsulf model am j sci 306 in press results show a similar trend of atmospheric co2 over the phanerozoic to the results of geocarb iii but with some differences during the early paleozoic and for variable volcanic rock weathering lower co2 values during the mesozoic atmospheric oxygen shows a major broad late paleozoic peak with a maximum value of about 30 o2 in the permian a secondary less broad peak centered near the silurian devonian boundary variation between 15 and 20 o2 during the cambrian and ordovician a very sharp drop from 30 to 15 o2 at the permo triassic boundary and a more or less continuous rise in o2 from the late triassic to the present

large scale natural gradient tracer test in sand and gravel cape cod massachusetts 3 hydraulic conductivity variability and calculated macrodispersivities hydraulic conductivity k variability in a sand and gravel aquifer on cape cod massachusetts was measured and subsequently used in stochastic transport theories to estimate macrodispersivities nearly 1500 k measurements were obtained by borehole flowmeter tests and permeameter analyses of cores the geometric mean for the flowmeter tests 0 11 cm s is similar to that estimated from other field tests the mean for the permeameter tests 0 035 cm s is significantly lower possibly because of compaction of the cores the variance for the flowmeter 0 24 is also greater than that for the permeameter 0 14 geostatistical analyses applying negative exponential models with and without nuggets reveal similar spatial correlation structures for the two data sets estimated correlation scales range from 2 9 to 8 m in the horizontal and from 0 18 to 0 38 m in the vertical estimates of asymptotic longitudinal dispersivity b 35 0 78 m are similar in magnitude to that observed in the natural gradient tracer test 0 96 m previously conducted at this site

estimation of ice sheet motion using satellite radar interferometry method and error analysis with application to humboldt glacier greenland satellite radar interferometry provides glaciologists with an important new tool for determining the motion and topography of large ice sheets we examine the sources of error in interferometrically derived ice motion measurements including those errors due to inaccurate estimates of the interferometric baseline several simulations are used to assess baseline accuracy in terms of tie point error and the number and distribution of tie points these results give insight into how best to select tie points and also demonstrate the level of accuracy that can be achieved examination of two representative cases likely to occur in mapping ice sheet motion leads to the conclusion that with adequate tie point information ice velocity can be measured accurately to within a few meters per year a method to correct horizontal velocity estimates for the effect of vertical displacement using surface slopes is also developed finally we estimate the single component velocity field for an area on humboldt glacier northern greenland using interferograms formed from ers i sar images we estimate that these velocity measurements are accurate to within 2 3 m year 1

the origin and early radiation of dinosaurs abstract dinosaurs were remarkably successful during the mesozoic and one subgroup birds remain an important component of modern ecosystems although the extinction of non avian dinosaurs at the end of the cretaceous has been the subject of intense debate comparatively little attention has been given to the origin and early evolution of dinosaurs during the late triassic and early jurassic one of the most important evolutionary radiations in earth history our understanding of this keystone event has dramatically changed over the past 25 years thanks to an influx of new fossil discoveries reinterpretations of long ignored specimens and quantitative macroevolutionary analyses that synthesize anatomical and geological data here we provide an overview of the first 50 million years of dinosaur history with a focus on the large scale patterns that characterize the ascent of dinosaurs from a small almost marginal group of reptiles in the late triassic to the preeminent terrestrial vertebrates of the jurassic and cretaceous we provide both a biological and geological background for early dinosaur history dinosaurs are deeply nested among the archosaurian reptiles diagnosed by only a small number of characters and are subdivided into a number of major lineages the first unequivocal dinosaurs are known from the late carnian of south america but the presence of their sister group in the middle triassic implies that dinosaurs possibly originated much earlier the three major dinosaur lineages theropods sauropodomorphs and ornithischians are all known from the triassic when continents were joined into the supercontinent pangaea and global climates were hot and arid although many researchers have long suggested that dinosaurs outcompeted other reptile groups during the triassic we argue that the ascent of dinosaurs was more of a matter of contingency and opportunism dinosaurs were overshadowed in most late triassic ecosystems by crocodile line archosaurs and showed no signs of outcompeting their rivals instead the rise of dinosaurs was a two stage process as dinosaurs expanded in taxonomic diversity morphological disparity and absolute faunal abundance only after the extinction of most crocodile line reptiles and other groups

groundwater flow near vertical recirculatory wells effect of skin on flowgeometry and travel times with implications for aquifer remediation abstract flow structure around a recirculation well in a uniform anisotropic aquifer is investigated using potential theory and stokes stream function techniques a vertical recirculation well consists of two screened sections chambers separated by an impermeable casing one section extracts water from the aquifer and the other section injects the water back into the aquifer analytical formulae are derived for the drawdown and the stream function for a model in which the extraction and injection chambers of the well are modeled as uniformly distributed cylindrical sinks and sources respectively travel times are analyzed for water particles traveling from the injection chamber to the extraction chamber along streamlines containing various percentages of the flow we consider a disturbed zone skin having properties which are different from those in the uniform anisotropic aquifer owing to disturbance of the area near the well during installation the effects of this skin on the streamlines and travel times are analyzed for various lengths separating the chambers and for various skin conductivities the method completely eliminates the use of numerical finite difference or finite element methods and can be used for optimization of technological parameters in a remediation system

modeling atmospheric o2 over phanerozoic time a carbon and sulfur isotope mass balance model has been constructed for calculating the variation of atmospheric o2 over phanerozoic time in order to obtain realistic o2 levels rapid sediment recycling and o2 dependent isotope fractionation have been employed by the modelling the dependence of isotope fractionation on o2 is based for carbon on the results of laboratory photosynthesis experiments and for sulfur on the observed relation between oxidation reduction recycling and s isotope fractionation during early diagenetic pyrite formation the range of fractionations used in the modeling agree with measurements of phanerozoic sediments by others results derived from extensive sensitivity analysis suggest that there was a positive excursion of o2 to levels as high as 35 during the permo carboniferous high o2 at this time agrees with independent modeling based on the abundances of organic matter and pyrite in sediments and with the occurrence of giant insects during this period the cause of the excursion is believed to be the rise of vascular land plants and the consequent increased production of o2 by the burial in sediments of lignin rich organic matter that was resistant to biological decomposition

a field proof of concept of tomographic slug tests in an anisotropic littoral aquifer hydraulic tomography is increasingly recognized as a characterization approach that can image pathways or barriers to flow as well as their connectivity in this study we assess the performance of a transient analysis of tomographic slug test head data in estimating heterogeneity in horizontal hydraulic conductivity kh hydraulic conductivity anisotropy the ratio between vertical and horizontal hydraulic conductivity kv kh and specific storage ss under actual field conditions the tomographic experiment was carried out between two wells in a moderately heterogeneous and highly anisotropic silt and sand littoral aquifer in this field proof of concept the inversion of the two dimensional 2d head dataset was computed with a 2d radial flow algorithm that considers kh kv kh ss and wellbore storage effects this study demonstrated that a transient analysis of tomographic slug tests is able to capture the key features of the littoral environment of the test the vertical profiles of kh and kv are indeed in agreement with those from other field and laboratory tests and ss values exhibit physically plausible profiles furthermore the simulation of independent inter well hydraulic tests slug and pumping tests screened over the entire aquifer using resolved kh kv kh and ss tomograms produce responses very close to field observations this study demonstrates that the effects of fine scale heterogeneity that induces k anisotropy at larger scales can be captured through a transient analysis of tomographic slug tests which are very difficult to quantify otherwise with conventional hydraulic tests thus allowing a better representation of properties controlling flow and transport in aquifer systems