re analysis of faunal assemblages from the haua fteah and other late quaternary archaeological sites in cyrenaican libya in preliminary reports based on approximately 5000 identified bones from the haua fteah cyrenaica e s higgs concluded that changes in the abundance of bovines versus barbary sheep reflected climatic change from drier last interglaciation to wetter last glaciation and back to drier present interglaciation higgs also reported the earliest occurrence of domestic caprines in africa in haua fteah neolithic layers dated to about 6800 bp a new analysis based on roughly 9000 identified specimens supports the broad pattern of faunal change that higgs found but suggests that it reflects wetter when higgs proposed drier and vice versa the new analysis failed to confirm the early date for domestic caprines mainly because of uncertainty concerning the stratigraphic provenience of key specimens finally the new analysis produced some additions to the species list most notably eland and provided previously unavailable information on skeletal part representation and on the ages of animals at time of death with respect to skeletal parts smaller ungulates tend to be represented by a wider variety than larger ones a contrast that is almost universal in stone age sites with regard to age profiles the largest and most reliable one for barbary sheep from the neolithic layers implies the animals were captured by driving over cliffs or into other traps restudy of small additional samples from the cyrenaican sites of hagfet et tera hagfet ed dabba and sidi el hajj creiem fully supports taxonomic and paleoenvironmental conclusions drawn earlier by higgs and bate

grounding line movement and ice shelf buttressing in marine ice sheets 1 understanding the dynamics of marine ice sheets is integral to studying the evolution of the antarctic ice sheet in both the short and long terms an important component of the dynamics grounding line migration has proved difficult to represent in numerical models and most successful attempts have made use of techniques that are only readily applicable to flow line models however to capture the stress transmission involved in another important component the buttressing of a marine ice sheet by its ice shelf the transverse direction must also be resolved we introduce a model that solves the time dependent shelfy stream equations and makes use of mesh adaption techniques to overcome the difficulties typically associated with the numerics of grounding line migration we compare the model output with a recent benchmark for flow line models and show that our model yields an accurate solution while using far less resources than would be required without mesh adaption we also show that the mesh adapting techniques extend to two horizontal dimensions experiments are carried out to determine how both ice shelf buttressing and ice rises affect the marine instability predicted for an ice sheet on a foredeepened bed we find that buttressing is not always sufficient to stabilize such a sheet but collapse of the grounded portion is still greatly delayed we also find that the effect of an ice rise is similar to that of narrowing the ice shelf

atmospheric oxygen 18 and sea level changes past isotopic composition of atmospheric oxygen 18oatm can be inferred from the analysis of air bubbles trapped in ice caps the longest record covers the last 420 ka thousand of years at the vostok site in east antarctica it shows a strong modulation by the precession and striking similarities but also noticeable differences with the deep sea core oxygen 18 record from which changes in the oxygen content of sea water 18osw and in sea level can be derived indeed 18oatm is driven by complex fractionation processes occuring during respiration and photosynthesis both 18oatm and its difference with respect to 18osw the dole effect are influenced by factors such as the ratio of oceanic and terrestrial productivities which may have significantly changed between different climates also the response time of 18oatm to oceanic changes should be taken in consideration but this parameter itself depends on biospheric activity we review the various aspects of the link between the 18oatm and the 18osw signals we also examine the approach followed by shackleton science 2000 for deriving sea level change from the 18oatm vostok record assuming that the phase between this record and insolation changes is constant and that the dole effect is a fraction of the precessional component of the 18oatm signal glaciological constraints on the vostok chronology and the complexity of the dole effect show that those two assumptions are quite probably too simplistic

volume loss from antarctic ice shelves is accelerating the floating ice shelves surrounding the antarctic ice sheet restrain the grounded ice sheet flow thinning of an ice shelf reduces this effect leading to an increase in ice discharge to the ocean using 18 years of continuous satellite radar altimeter observations we have computed decadal scale changes in ice shelf thickness around the antarctic continent overall average ice shelf volume change accelerated from negligible loss at 25 64 cubic kilometers per year for 1994 2003 to rapid loss of 310 74 cubic kilometers per year for 2003 2012 west antarctic losses increased by 70 in the past decade and earlier volume gain by east antarctic ice shelves ceased in the amundsen and bellingshausen regions some ice shelves have lost up to 18 of their thickness in less than two decades

sustained increase in ice discharge from the amundsen sea embayment west antarctica from 1973 to 2013 we combine measurements of ice velocity from landsat feature tracking and satellite radar interferometry and ice thickness from existing compilations to document 41 years of mass flux from the amundsen sea embayment ase of west antarctica the total ice discharge has increased by 77 since 1973 half of the increase occurred between 2003 and 2009 grounding line ice speeds of pine island glacier stabilized between 2009 and 2013 following a decade of rapid acceleration but that acceleration reached far inland and occurred at a rate faster than predicted by advective processes flow speeds across thwaites glacier increased rapidly after 2006 following a decade of near stability leading to a 33 increase in flux between 2006 and 2013 haynes smith pope and kohler glaciers all accelerated during the entire study period the sustained increase in ice discharge is a possible indicator of the development of a marine ice sheet instability in this part of antarctica key points sustained ase mass flux increase 77 since 1973 thwaites accelerated by 33 during the last 6 years speed changes are pervasive and rapid major implications for ice flow modeling 2014 american geophysical union all rights reserved

modeling the instantaneous response of glaciers after the collapse of the larsen b ice shelf following the disintegration of the larsen b ice shelf antarctic peninsula in 2002 regular surveillance of its 20 tributary glaciers has revealed a response which is varied and complex in both space and time the major outlets have accelerated and thinned smaller glaciers have shown little or no change and glaciers flowing into the remnant scar inlet ice shelf have responded with delay in this study we present the first area wide numerical analysis of glacier dynamics before and immediately after the collapse of the ice shelf combining new datasets and a state of the art numerical ice flow model we simulate the loss of buttressing at the grounding line and find a good qualitative agreement between modelled changes in glacier flow and observations through this study we seek to improve confidence in our numerical models and their ability to capture the complex mechanical coupling between floating ice shelves and grounded ice

the holocene archaeological sequence and sedimentological processes at ifri oudadane ne morocco abstract the coastal site of ifri oudadane is one of the most important sites in the mediterranean maghreb recent excavations have provided a stratigraphy featuring the transition from epipalaeolithic hunter gatherers to neolithic food producers this transitional process could be defined by various features the sedimentological field description revealed a change from homogenous sediment to more structured deposits and similar to the so called fumiers that are characteristic of animal husbandry in caves and shelters around the mediterranean sedimentary units identified in the deposits were confirmed by geochemical and micromorphological studies within the early neolithic deposits coprolites and calcite spherulites testify to the penning of ovicaprides inside the shelter radiocarbon analyses date the change from epipalaeolithic to neolithic to approximately 7 6 ka calbp preliminary results from archaeozoological and archaeobotanical studies prove the existence of domesticated species in neolithic deposits finally together with pottery and notched blades new artefact categories appear reflecting changing settlement behaviour associated with neolithic lifeways given the richness of the archaeological material from ifri oudadane which is still under study the sequence is a key site for the mediterranean zone of nw africa it has a considerable role to play in the development of future neolithisation models for the western mediterranean

characteristics of high resolution hydraulic head profiles and vertical gradients in fractured sedimentary rocks summary accurately identifying the position of vertical hydraulic conductivity k v contrasts is critical to the delineation of hydrogeologic units that serve as the basis for conceptual and numerical models of groundwater flow high resolution head profiles have identified the position and thickness of k v contrasts in clayey aquitards but this potential has not yet been thoroughly evaluated in sedimentary rocks this paper describes an experiment in which head profiles with the highest technically feasible resolution were obtained using westbay multilevel systems mls installed in 15 cored holes at three sedimentary rock research sites with contrasting geologic and flow system conditions mlss were installed to maximum depths between 90 and 260 m with 2 5 monitoring zones per 10 m head profiles were measured over multiyear periods the vertical component of hydraulic gradient i e vertical gradient was calculated for each pair of adjacent monitoring intervals in every mls and then categorized based on its repeatability to facilitate interpretation of k v contrasts and comparisons within boreholes between boreholes at the same site and between sites the head and vertical gradient profiles from all three sites display systematic i e simple geometric shapes defined by repeatable intervals of no to minimal vertical gradient indicating relatively high k v units bounded by shorter depth intervals with large up to 50 m m vertical gradients indicating relatively low k v units the systematic nature of the profiles suggests flow in regular and interconnected fracture networks rather than dominated by a few key fractures with irregular orientations the low k v units were typically thin with their positions and thicknesses not predicted by lithostratigraphy or detailed lithologic geophysical and horizontal hydraulic conductivity data hence the position and thickness of units with contrasting k v would not be evident if mlss with the conventional number of monitoring zones had been used furthermore the detailed profiles can be strongly diagnostic of hydrogeologic unit boundaries or layers and can be used to improve the quantitative assessment of flow system conditions that is foundational to understanding contaminant plume migration

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

a tutorial on the use of control methods in ice sheet modeling control methods are recommended as an efficient means to estimate undetermined physical parameters and boundary conditions and in so doing to improve the fidelity of a given ice sheet flow model to specific ice sheet velocity observations to accomplish this task the underlying dynamics of the model are inverted this permits model tuning adjustments to be represented explicitly in terms of model observation misfit

deeply incised submarine glacial valleys beneath the greenland ice sheet the bed topography beneath the greenland ice sheet controls the flow of ice and its discharge into the ocean a combination of sparse radar soundings of ice thickness and high resolution ice motion data suggest that many submarine ice covered valleys extend significantly deeper below sea level and farther inland than thought

groundwater in fractured bedrock environments managing catchment and subsurface resources an introduction hard rocks including crystalline igneous metamorphic and strongly cemented sedimentary and carbonate rocks cover about 50 of the earth s land surface singhal gupta 2010 globally the volume of groundwater contained in hard rock aquifers is not well constrained comte et al 2012 but locally they can be important aquifers macdonald et al 2012 albeit with low groundwater storage and poor primary porosity and permeability groundwater flow in these hard rocks is commonly observed to be associated with water bearing discontinuities such as fractures joints and faults mazurek 2000 berkowitz 2002 font capo et al 2012 and in the weathered regolith wright 1992 chilton foster 1995 deyassa et al 2014 structural elements such as fault zones also strongly govern the behaviour of these systems forster evans 1991 lopez smith 1995 bense et al 2013 the nature abundance orientation and connectivity of these water bearing features are largely governed by the history and nature of structural deformation of the bedrock and commonly impose strong anisotropic flow and transport parameters on these bedrock aquifers hsieh et al 1985 bour davy 1997 mortimer et al 2011 weathering processes furthermore lead to an alteration of bedrock composition and associated aquifer properties resulting in enhanced fracture connectivity and an overall vertical stratification zonation of bulk aquifer properties ranging from highly altered shallow regolith horizons to more competent sparsely fractured bedrock at depth dewandel et al 2006 krasn sharp 2007 lachassagne et al 2011

wet phases in the sahara sahel region and human migration patterns in north africa the carbon isotopic composition of individual plant leaf waxes a proxy for c3 vs c4 vegetation in a marine sediment core collected from beneath the plume of sahara derived dust in northwest africa reveals three periods during the past 192 000 years when the central sahara sahel contained c3 plants likely trees indicating substantially wetter conditions than at present our data suggest that variability in the strength of atlantic meridional overturning circulation amoc is a main control on vegetation distribution in central north africa and we note expansions of c3 vegetation during the african humid period early holocene and within marine isotope stage mis 3 50 45 ka and mis 5 120 110 ka the wet periods within mis 3 and 5 coincide with major human migration events out of sub saharan africa our results thus suggest that changes in amoc influenced north african climate and at times contributed to amenable conditions in the central sahara sahel allowing humans to cross this otherwise inhospitable region

identifying fracture zone geometry using simulated annealing and hydraulic connection data a new approach is presented to condition geostatistical simulation of high permeability zones in fractured rock to hydraulic connection data a simulated annealing algorithm generates three dimensional 3 d realizations conditioned to borehole data inferred hydraulic connections between packer isolated borehole intervals and an indicator fracture zone or background k bedrock variogram model of spatial variability we apply the method to data from the u s geological survey mirror lake site in new hampshire where connected high permeability fracture zones exert a strong control on fluid flow at the hundred meter scale single well hydraulic packer tests indicate where permeable fracture zones intersect boreholes and multiple well pumping tests indicate the degree of hydraulic connection between boreholes borehole intervals connected by a fracture zone exhibit similar hydraulic responses whereas intervals not connected by a fracture zone exhibit different responses our approach yields valuable insights into the 3 d geometry of fracture zones at mirror lake statistical analysis of the realizations yields maps of the probabilities of intersecting specific fracture zones with additional wells inverse flow modeling based on the assumption of equivalent porous media is used to estimate hydraulic conductivity and specific storage and to identify those fracture zone geometries that are consistent with hydraulic test data

context of modern human occupations in north africa contribution of the temara caves data el harhoura 2 and el mnasra caves are located in the region of temara on the atlantic coast of morocco which was occupied by human populations since the beginning of the late pleistocene around 120 ka bp until the middle holocene around 6 ka bp recent excavations yielded human and faunal remains as well as exceptional archaeological objects middle upper palaeolithic and neolithic industries ceramics ornaments in nassarius sp shells bone tools pigments associated with anthropic structures the continuous sedimentary sequence of these sites covers the last climatic cycle from the eemian interglacial to the present one and is studied in a renewed context from several points of view geology stratigraphy chronology cultures anthropology palaeontology taphonomy and zooarchaeology today there is no equivalent of such regional data for the whole late pleistocene in north africa the study of small and large faunal remains associated with chronological data allowed us to obtain significant data on palaeoenvironments and human carnivore occupations of the temara caves these data are included in a broader view of human occupations and their environmental context throughout north africa during the late pleistocene and holocene

a multidisciplinary fractured rock characterization study at raymond field site raymond ca abstract a dedicated field site was developed and a suite of experiments were conducted in the sierra nevada foothills near the town of raymond ca to develop and test a multi disciplinary approach to the characterization of groundwater flow and transport in fractured rocks a wealth of geologic hydrologic and geophysical data was collected at the site using a variety of unique tools a cluster of nine approximately 90 m deep boreholes were drilled at the site in a v shaped pattern with an angle of 60 the boreholes are spaced 7 5 15 30 and 60 m from the central borehole various geophysical and hydrologic tests were conducted in and between these boreholes integration of cross hole radar and seismic tomography borehole flow surveys and images from a new digital borehole scanner indicated that groundwater flow is mainly confined to a few sub horizontal fracture zones a unique suite of hydraulic tests were conducted in which three to four intervals in each of the nine boreholes were isolated using pneumatic packers some 130 injection tests were conducted and more than 4100 cross hole transient pressure measurements were obtained a computer algorithm was developed to analyze such massive interference data systematically as a result of the analysis an image of the fracture connections emerged which is consistent with the geophysical data high precision tiltmeters were effective in remotely characterizing the preferential flow path several radial convergent tracer tests were conducted by injecting a mixture of several conservative tracers and one sorbing tracer deuterium fluorescein lithium bromide and polystyrene micro spheres some differences between the breakthrough curves are observed which may be due to possible differences among so called conservative tracers some characterization tools were found to be more effective than others in locating flowing fractures however no single tool was almighty characterization of fractured rock is extremely challenging and requires a stepwise and well thought approach which is basically a good old scientific approach prediction of transport based on the characterization results is even more challenging and one should always bear in mind that it is virtually impossible to uniquely characterize a fractured rock

representation of sharp rifts and faults mechanics in modeling ice shelf flow dynamics application to brunt stancomb wills ice shelf antarctica ice shelves play a major role in buttressing ice sheet flow into the ocean hence the importance of accurate numerical modeling of their stress regime commonly used ice flow models assume a continuous medium and are therefore complicated by the presence of rupture features crevasses rifts and faults that significantly affect the overall flow patterns here we apply contact mechanics and penalty methods to develop a new ice shelf flow model that captures the impact of rifts and faults on the rheology and stress distribution of ice shelves the model achieves a best fit solution to satellite observations of ice shelf velocities to infer the following 1 a spatial distribution of contact and friction points along detected faults and rifts 2 a more realistic spatial pattern of ice shelf rheology and 3 a better representation of the stress balance in the immediate vicinity of faults and rifts thus applying the model to the brunt stancomb wills ice shelf antarctica we quantify the state of friction inside faults and the opening rates of rifts and obtain an ice shelf rheology that remains relatively constant everywhere else on the ice shelf we further demonstrate that better stress representation has widespread application in examining aspects affecting ice shelf structure and dynamics including the extent of ice melange in rifts and the change in fracture configurations all are major applications for better insight into the important question of ice shelf stability

a spatially adjusted elevation model in dronning maud land antarctica based on differential sar interferometry in this paper a new digital elevation model dem is derived for the ice sheet in western dronning maud land antarctica it is based on differential interferometric synthetic aperture radar sar from the european remote sensing 1 2 ers 1 2 satellites in combination with icesat s geoscience laser altimeter system glas a dem mosaic is compiled out of 116 scenes from the ers 1 ice phase in 1994 and the ers 1 2 tandem mission between 1996 and 1997 with the glas data acquired in 2003 that served as ground control using three different sar processors uncertainties in phase stability and baseline model resulting in height errors of up to 20 m are exemplified atmospheric influences at the same order of magnitude are demonstrated and corresponding scenes are excluded for validation of the dem mosaic covering an area of about 130 000 km2 on a 50 m grid independent icesat heights 2004 2007 ground based kinematic gps 2005 and airborne laser scanner data als 2007 are used excluding small areas with low phase coherence the dem differs in mean and standard deviation by 0 5 10 1 1 1 6 4 and 3 1 4 0 m from icesat gps and als respectively the excluded data points may deviate by more than 50 m in order to suppress the spatially variable noise below a 5 m threshold 18 of the dem area is selectively averaged to a final product at varying horizontal spatial resolution apart from mountainous areas the new dem outperforms other currently available dems and may serve as a benchmark for future elevation models such as from the tandem x mission to spatially monitor ice sheet elevation

a last interglacial fauna from the eastern sahara abstract recent work on the middle paleolithic at bir tarfawi in the hyperarid eastern sahara

trichloroethene dnapl flow and mass distribution in naturally fractured clay evidence of aperture variability a cylindrical sample 0 5 m in diameter and length was obtained by excavation from 3 7 4 2 m depth below ground surface in a surficial deposit of fractured glaciolacustrine clay the sample was enclosed in a triaxial cell in a cold room to impose conditions close to field temperature and stress hydraulic testing using a hydraulic gradient of 2 provided a saturated hydraulic conductivity of 7 10 10 m s which is only slightly larger than the matrix hydraulic conductivity the cubic law provided a mean hydraulic aperture of 5 6 m for the four continuous vertical fractures in the sample a column of immiscible phase trichloroethene tce imposed incrementally at the top of the sample provided an entry pressure derived aperture equal to 17 m for a parallel plate fracture tce dense nonaqueous phase liquid dnapl that flowed through the sample produced dissolved phase diffusion haloes in the matrix that indicated the preferential fracture pathways these haloes indicated that dnapl flowed through only 5 15 of the visible oxidation stained fractures hence natural fractures had variable apertures along their length and the larger aperture regions provided channels for fluid flow using the hydraulic test results and applying the cubic law only to the aperture segments of confirmed dnapl flow an equivalent hydraulic aperture of 8 11 m was obtained which is greater than the conventional mean hydraulic aperture and smaller than the local aperture determined from the dnapl entry pressure these differences are large in the context of fluid flux which is proportional to the aperture cubed

groundwater flow characterization in a fractured bedrock aquifer using active dts tests in sealed boreholes summary in recent years wireline temperature profiling methods have evolved to offer new insight into fractured rock hydrogeology important advances in wireline temperature logging in boreholes make use of active line source heating alone and then in combination with temporary borehole sealing with flexible impervious fabric liners to eliminate the effects of borehole cross connection and recreate natural flow conditions here a characterization technique was developed based on combining fiber optic distributed temperature sensing dts with active heating within boreholes sealed with flexible borehole liners dts systems provide a temperature profiling method that offers significantly enhanced temporal resolution when compared with conventional wireline trolling based techniques that obtain a temperature depth profile every few hours the ability to rapidly and continuously collect temperature profiles can better our understanding of transient processes allowing for improved identification of hydraulically active fractures and determination of relative rates of groundwater flow the advantage of a sealed borehole environment for dts based investigations is demonstrated through a comparison of dts data from open and lined conditions for the same borehole evidence for many depth discrete active groundwater flow features under natural gradient conditions using active dts heat pulse testing is presented along with high resolution geologic and geophysical logging and hydraulic datasets implications for field implementation are discussed

antarctic ice rise formation evolution and stability antarctic ice rises originate from the contact between ice shelves and one of the numerous topographic highs emerging from the edge of the continental shelf while investigations of the raymond effect indicate their millennial scale stability little is known about their formation and their role in ice shelf stability here we present for the first time the simulation of an ice rise using the bisicles model the numerical results successfully reproduce several field observable features such as the substantial thinning downstream of the ice rise and the successive formation of a promontory and ice rise with stable radial ice flow center showing that ice rises are formed during the ice sheet deglaciation we quantify the ice rise buttressing effect found to be mostly transient delaying grounding line retreat significantly but resulting in comparable steady state positions we demonstrate that ice rises are key in controlling simulations of antarctic deglaciation

enhancement factors for grounded ice and ice shelves inferred from an anisotropic ice flow model polar ice is known to be one of the most anisotropic natural materials for a given fabric the polycrystal viscous response is strongly dependent on the actual state of stress and strain rate within an ice sheet grounded ice parts and ice shelves have completely different stress regimes so one should expect completely different impacts of ice anisotropy on the flow the aim of this work is to quantify through the concept of enhancement factors the influence of ice anisotropy on the flow of grounded ice and ice shelves for this purpose a full stokes anisotropic marine ice sheet flowline model is used to compare isotropic and anisotropic diagnostic velocity fields on a fixed geometry from these full stokes results we propose a definition of enhancement factors for grounded ice and ice shelves coherent with the asymptotic models used for these regions we then estimate realistic values for the enhancement factors induced by ice anisotropy for grounded ice and ice shelves

ephemeral grounding as a signal of ice shelf change interferometric synthetic aperture radar insar observations of ice shelf tidal deformation reveal the wide transition between grounded and floating ice as well as local areas where the ice shelf is only grounded at low tide a condition that we call ephemeral grounding ephemeral grounding creates a subtle local disturbance on the vertical motion field of the ice shelf surface in response to changes in occanic tide which is detected with millimetric precision using insar these ice shelf features are however not expected to produce a noticeable disturbance on the ice shelf velocity field to illustrate the influence of ephemeral grounding on ice shelf creep flow we use a finite element model in which ephemeral grounding is incorporated through a variable basal friction coefficient the results show that while ice rises permanently grounded areas have a pronounced influence on the ice shelf velocity field areas of ephemeral grounding have a vanishingly small influence what is thus of most interest is the capacity for observations of ephemeral grounding to reveal subtle changes in ice shelf thickness over time we discuss an example in the thwaites glacier area west antarctica where multi year data show how ice rises become ephemeral grounding and subsequently disappear this result is consistent with the grounding line retreat and ice thinning of thwaites glacier

glacier acceleration and thinning after ice shelf collapse in the larsen b embayment antarctica 1 ice velocities derived from five landsat 7 images acquired between january 2000 and february 2003 show a two to six fold increase in centerline speed of four glaciers flowing into the now collapsed section of the larsen b ice shelf satellite laser altimetry from icesat indicates the surface of hektoria glacier lowered by up to 38 6 m in a six month period beginning one year after the break up in march 2002 smaller elevation losses are observed for crane and jorum glaciers over a later 5 month period two glaciers south of the collapse area flask and leppard show little change in speed or elevation seasonal variations in speed preceding the large post collapse velocity increases suggest that both summer melt percolation and changes in the stress field due to shelf removal play a major role in glacier dynamics

an analysis of the influence of fracture geometry on mass transport in fractured media a stochastic modeling technique has been developed to investigate mass transport within a network of discrete fractures the fracture network is composed of two orthogonal fracture sets with fracture length location and aperture characterized by appropriate probability distributions emphasis is placed on understanding how fracture geometry influences mass transport within a network of discontinuous fractures the network is aligned in such a manner that one fracture set set one forms the dominant pathway for transport the primary role of the second fracture set is to provide connecting pathways between the discontinuous fractures of set one results suggest that mass transport can be described in terms of the directness of the connection between the upstream and downstream boundaries variations in fracture geometry which have the effect of increasing the probability that a relatively indirect or circuitous pathway exists through the network generally lead to an increase in both the mean and the standard deviation in the arrival time of various breakthrough fractions examples include a reduction in the number of fractures forming the set aligned with the direction of the hydraulic gradient or a decrease in the average length of fractures forming that set variations in fracture geometry which have the effect of increasing the probability that a relatively direct pathway will exist through the network have the opposite effect transport is sensitive to the variability in fracture aperture the connectivity of the fracture network is also shown to influence the magnitude of dispersive effects

the control of an uncharted pinning point on the flow of an antarctic ice shelf antarctic ice shelves are buttressed by numerous pinning points attaching to the otherwise freely floating ice from below some of these kilometric scale grounded features are unresolved in antarctic wide datasets of ice thickness and bathymetry hampering ice flow models to fully capture dynamics at the grounding line and upstream we investigate the role of an 8 7 km 2 pinning point at the front of the roi baudouin ice shelf east antarctica using ers interferometry and alos palsar speckle tracking we derive on a 125 m grid spacing surface velocities deviating by 5 2 4 5 m a 1 from 37 on site global navigation satellite systems derived velocities we find no evidence for ice flow changes on decadal time scales and we show that ice on the pinning point virtually stagnates deviating the ice stream and causing enhanced horizontal shearing upstream using the bisicles ice flow model we invert for basal friction and ice rigidity with three input scenarios of ice velocity and geometry we show that inversion results are the most sensitive to the presence absence of the pinning point in the bathymetry surface velocities at the pinning point are of secondary importance undersampling of pinning points results in erroneous ice shelf properties in models initialised by control methods this may impact prognostic modelling for ice sheet evolution in the case of unpinning

impact of bedrock description on modeling ice sheet dynamics recent glaciological surveys have revealed a significant increase of ice discharge from polar ice caps into the ocean in parallel ice flow models have been greatly improved to better reproduce current changes and forecast the future behavior of ice sheets for these models surface topography and bedrock elevation are crucial input parameters that largely control the dynamics and the ensuing overall mass balance of the ice sheet for obvious reasons of inaccessibility only sparse and uneven bedrock elevation data is available this raw data is processed to produce digital elevation models dems on a regular 5 km grid these dems are used to constrain the basal boundary conditions of all ice sheet models here by using a full stokes finite element code we examine the sensitivity of an ice flow model to the accuracy of the bedrock description in the context of short term ice sheet forecast we show that in coastal regions the bedrock elevation should be known at a resolution of the order of one kilometer conversely a crude description of the bedrock in the interior of the continent does not affect modeling of the ice outflow into the ocean these findings clearly indicate that coastal regions should be prioritized during future geophysical surveys they also indicate that a paradigm shift is required to change the current design of dems describing the bedrock below the ice sheets they must give users the opportunity to incorporate high resolution bedrock elevation data in regions of interest

antarctic subglacial conditions inferred from a hybrid ice sheet ice stream model abstract subglacial conditions of large polar ice sheets remain poorly understood despite recent advances in satellite observation major uncertainties related to basal conditions such as the temperature field are due to an insufficient knowledge of geothermal heat flow here a hybrid method is presented that combines numerical modeling of the ice sheet thermodynamics with a priori information using a simple assimilation technique additional data are essentially vertical temperature profiles measured in the ice sheet at selected spots as well as the distribution of subglacial lakes in this way geothermal heat flow datasets are improved to yield calculated temperatures in accord with observations in areas where information is available results of the sensitivity experiments show that 55 of the grounded part of the antarctic ice sheet is at pressure melting point calculated basal melt rates are approximately 65 gt year 1 which is 3 of the total surface accumulation although these sensitivity experiments exhibit small variations in basal melt rates the impact on the ice age of basal layers is quite important in areas that are characterized by relatively low melt rates this may lead to standard deviations up to 50 in a model run over a period of 10 6 years subglacial water flow is concentrated underneath the large outlet glaciers of antarctica the larger subglacial lakes are perched at the head of these subglacial water systems an exception however is the lake system of the recovery ice stream catchment that receives a substantial amount of subglacial melt water from the upstream catchment

combined use of straddle packer testing and flute profiling for hydraulic testing in fractured rock boreholes summary a combination of high resolution hydraulic tests using straddle packers and transmissivity t profiling using the flute flexible liner method liner profiling in densely fractured rock boreholes is shown to be efficient for the determination of the vertical distribution of t along the entire hole the liner t profiling method takes a few hours or less to scan the entire borehole length resulting in a t profile under favorable conditions this method has good reliability for identifying the highest t zones identified by distinct decreases in liner velocity when these zones are covered by the descending liner in contrast for one short test interval e g 1 2 m the multiple test straddle packer method takes a few hours to measure t with good precision and accuracy using a combination of steady state and transient tests e g constant head step tests slug tests and constant rate pumping tests because of the time consuming aspect of this multiple test method it is most efficient in each borehole to conduct straddle packer testing only in priority zones selected after assessment of other borehole data collected prior to packer testing the t profile from the liner method is instrumental in selecting high permeable zones for application of the multiple test method using straddle packers which in turn refines the t estimation from the liner profile results from three boreholes in densely fractured sandstone demonstrate this approach showing the synergistic use of the methods with emphasis on information important for determining hydraulic apertures

ice flow of the antarctic ice sheet we present a reference comprehensive high resolution digital mosaic of ice motion in antarctica assembled from multiple satellite interferometric synthetic aperture radar data acquired during the international polar year 2007 to 2009 the data reveal widespread patterned enhanced flow with tributary glaciers reaching hundreds to thousands of kilometers inland over the entire continent this view of ice sheet motion emphasizes the importance of basal slip dominated tributary flow over deformation dominated ice sheet flow redefines our understanding of ice sheet dynamics and has far reaching implications for the reconstruction and prediction of ice sheet evolution

modeling thermodynamic ice ocean interactions at the base of an ice shelf abstract models of ocean circulation beneath ice shelves are driven primarily by the heat and freshwater fluxes that are associated with phase changes at the ice ocean boundary their behavior is therefore closely linked to the mathematical description of the interaction between ice and ocean that is included in the code an hierarchy of formulations that could be used to describe this interaction is presented the main difference between them is the treatment of turbulent transfer within the oceanic boundary layer the computed response to various levels of thermal driving and turbulent agitation in the mixed layer is discussed as is the effect of various treatments of the conductive heat flux into the ice shelf the performance of the different formulations that have been used in models of sub ice shelf circulation is assessed in comparison with observations of the turbulent heat flux beneath sea ice formulations that include an explicit parameterization of the oceanic boundary layer give results that

basal friction of ice stream e west antarctica we use surface velocity derived from sequential landsat imagery and a control method to estimate the basal friction distribution of a major west antarctic ice stream the area averaged basal stress is approximately 1 4 10 4 pa or about 29 of the area averaged driving stress of 4 9 10 4 pa uncertainty of the derived area averaged basal stress is difficult to assess and depends primarily on spatial variation of the flow law rate factor in the constitutive law spatial variation associated with depth averaged temperature variation gives an uncertainty of approximately 10 3 pa approximately 60 of the ice stream has a basal stress magnitude less than 10 4 pa and approximately 30 has less than 10 3 pa these characteristics suggest the presence of a mechanically weak water charged subglacial till small scale sticky spots where basal friction exceeds the area averaged driving stress are scattered irregularly across the subglacial regime and comprise approximately 15 of the ice stream area sticky spots cluster in regions where landsat imagery suggests structural features in the underlying bedrock

simulated climate and biomes of africa during the late quaternary comparison with pollen and lake status data new compilations of african pollen and lake data are compared with climate ccm1 ncar boulder and vegetation biome 1 2 gsg lund simulations for the last glacial maximum lgm and early to mid holocene emh the simulated lgm climate was ca 4 c colder and drier than present with maximum reduction in precipitation in semi arid regions biome simulations show lowering of montane vegetation belts and expansion of southern xerophytic associations but no change in the distribution of deserts and tropical rain forests the lakes show lgm conditions similar or drier than present throughout northern and tropical africa pollen data indicate lowering of montane vegetation belts the stability of the sahara and a reduction of rain forest the paleoenvironmental data are consistent with the simulated changes in temperature and moisture budgets although they suggest the climate model underestimates equatorial aridity emh simulations show temperatures slightly less than present and increased monsoonal precipitation in the eastern sahara and east africa biome simulations show an upward shift of montane vegetation belts fragmentation of xerophytic vegetation in southern africa and a major northward shift of the southern margin of the eastern sahara the lakes indicate conditions wetter than present across northern africa pollen data show an upward shift of the montane forests the northward shift of the southern margin of the sahara and a major extension of tropical rain forest the lake and pollen data confirm monsoon expansion in eastern africa but the climate model fails to simulate the wet conditions in western africa

enhanced detection of hydraulically active fractures by temperature profiling in lined heated bedrock boreholes summary the effectiveness of borehole profiling using a temperature probe for identifying hydraulically active fractures in rock has improved due to the combination of two advances improved temperature sensors with resolution on the order of 0 001 c and temperature profiling within water inflated flexible impermeable liners used to temporarily seal boreholes from hydraulic cross connection the open hole cross connection effects dissipate after inflation so that both the groundwater flow regime and the temperature distribution return to the ambient background condition this paper introduces a third advancement the use of an electrical heating cable that quickly increases the temperature of the entire static water column within the lined hole and thus places the entire borehole and its immediate vicinity into thermal disequilibrium with the broader rock mass after heating for 4 6 h profiling is conducted several times over a 24 h period as the temperature returns to background conditions this procedure referred to as the active line source als method offers two key improvements over prior methods first there is no depth limit for detection of fractures with flow second both identification and qualitative comparison of evidence for ambient groundwater flow in fractures is improved throughout the entire test interval the benefits of the als method are demonstrated by comparing results from two boreholes tested to depths of 90 and 120 m in a dolostone aquifer used for municipal water supply and in which most groundwater flow occurs in fractures temperature logging in the lined holes shows many fractures in the heterothermic zone both with and without heating but only the als method shows many hydraulically active fractures in the deeper homothermic portion of the hole the identification of discrete groundwater flow at many depths is supported by additional evidence concerning fracture occurrence including continuous core visual inspection acoustic televiewer logs and tests for hydraulic conductivity using straddle packers as well as rock core voc data where available that show deep penetration and many migration pathways confidence in the use of temperature profiles and the conceptual model is provided by numerical simulation and the demonstrated reproducibility of the evolution of the temperature signal measured in the lined holes with and without heating this approach for using temperature profiling in lined holes with heating is a practical advance in fractured rock hydrogeology because the liners are readily available the equipment needed for heating is low cost and rugged and the time needed to obtain the profiles is not excessive for most projects

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

antarctic ice rises and rumples their properties and significance for ice sheet dynamics and evolution locally grounded features in ice shelves called ice rises and rumples play a key role buttressing discharge from the antarctic ice sheet and regulating its contribution to sea level ice rises typically rise several hundreds of meters above the surrounding ice shelf shelf flow is diverted around them on the other hand shelf ice flows across ice rumples which typically rise only a few tens of meters above the ice shelf ice rises contain rich histories of deglaciation and climate that extend back over timescales ranging from a few millennia to beyond the last glacial maximum numerical model results have shown that the buttressing effects of ice rises and rumples are significant but details of processes and how they evolve remain poorly understood fundamental information about the conditions and processes that cause transitions between floating ice shelves ice rises and ice rumples is needed in order to assess their impact on ice sheet behavior targeted high resolution observational data are needed to evaluate and improve prognostic numerical models and parameterizations of the effects of small scale pinning points on grounding zone dynamics

marine resources exploitation by palaeolithic hunter fisher gatherers and neolithic tribal societies in the historical region of the strait of gibraltar this work has been financially supported by the benzu project spanish ministry of culture and ceuta government158 08 pv benzu cv the project dges har2008 06477 c03 02 the aecid hispanic moroccan projects pci a 2893 05 a 6317 06 and a 010823 07 and junta de andalucia project p07 hum 03015 authors are grateful to carol and paul beven and ana durante for their editorial assistance and to the anonymous referees for their helpful suggestions also we are grateful to ivan briz and marco madella for the corrections and suggestions

early to middle pleistocene homo dispersals from africa to eurasia geological climatic and environmental constraints abstract although the pleistocene human dispersal is one of the most intriguing issues of paleoanthropology large sectors along possible migratory pathways are ill defined or poorly documented this paper examines the geological geomorphological climatic and environmental conditions that could have determined hominin transit from their motherland in the east africa rift valley toward the circummediterranean regions or arabian peninsula for their choice between these two alternatives the danakil depression afar rift immediately north of the ethiopian rift valley was a strategic area they could reach the mediterranean sea through a northern route along the nile river valley the trans sahara megalake or riverine belts or else navigate an eastern route into the arabian peninsula after crossing the bab el mandeb straits it is assumed all of these pathways were possible during convenient geological climatic and or sea level conditions hominins had three additional choices once they arrived at the mediterranean sea shores with eurasia as their final destination the levant corridor was the easiest because walkable and almost always under favorable conditions two other possibilities were the sicily channel and the strait of gibraltar these sea arms are located in two extremely active settings of the mediterranean sea and were at their embryonic stage during the early pleistocene because large scale deformations of the sea floor were associated to prolonged sea level lowstands these two sea arms could have been passable similar considerations apply to the bab el mandeb straits region for the trans mediterranean and the trans red sea routes of dispersal the environmental conditions and the submarine and terrestrial topographical features that could have made sea transit possible even without land bridges are underscored to track the dispersal relations between northern africa and eurasia three schematic maps are presented to show the distribution of the archeological and paleoanthropological sites currently regarded as reliably dated they document three groups of dates between 2 0 and 1 5 ma 1 4 and 0 7 ma and 0 6 and 0 1 ma their distribution is matched with coeval paleoclimatic proxies such as marine oxygen isotope stages aeolian dust in the atlantic ocean and sapropels levels and dust fluxes in the eastern mediterranean dispersal was temporally arranged into cycles of four major exodus waves 2 0 1 6 ma 1 4 1 2 ma 1 0 0 8 ma and 0 6 0 1 ma controlled by climatic and environmental changes

antarctic grounding line mapping from differential satellite radar interferometry 1 the delineation of an ice sheet grounding line i e the transition boundary where ice detaches from the bed and becomes afloat in the ocean is critical to ice sheet mass budget calculations numerical modeling of ice sheet dynamics ice ocean interactions oceanic tides and subglacial environments here we present 15 years of comprehensive high resolution mapping of grounding lines in antarctica using differential satellite synthetic aperture radar interferometry dinsar data from the earth remote sensing satellites 1 2 ers 1 2 radarsat 1 and 2 and the advanced land observing system alos palsar for years 1994 to 2009 dinsar directly measures the vertical motion of floating ice shelves in response to tidal oceanic forcing with millimeter precision at a sample spacing better than 50 m simultaneously over areas several 100 km wide in contrast with earlier methods that detect abrupt changes in surface slope in satellite visible imagery or altimetry data on stagnant and slow moving areas we find that breaks in surface slope are reliable indicators of grounding lines but on most fast moving glaciers and ice streams our dinsar results reveal that prior mappings have positioning errors ranging from a few km to over 100 km a better agreement is found with icesat s data also based on measurements of vertical motion but with a detection noise one order of magnitude larger than with dinsar overall the dinsar mapping of antarctic grounding lines completely redefines the coastline of antarctica

cultural and human dynamics in southern arabia at the end of the middle paleolithic abstract the arabian peninsula has long been considered as a region devoid of long term human settlement until the holocene period as a result of drastic climatic changes throughout the pleistocene it might be expected that the area was deserted during hyper arid and arid periods and populated by new migrant groups during humid events according to a push and pull phenomenon although this scenario may be perfectly valid for a large part of the peninsula a set of recent data points to the persistence of populations in several regions which may have served as refugia for human groups who developed their own technological traditions such a scenario is suggested by 1 the succession of dense human occupations under arid conditions between ca 60 and 50 ka in the wadi surdud basin a small sedimentary basin in the foothills of the yemeni western highlands this archaeological site complex encompasses several successive human settlements characterized by a middle paleolithic tradition which significantly differs from the middle paleolithic and middle stone age contemporaneous traditions from neighboring regions 2 the regional diversity of the middle paleolithic throughout the saharo arabian arid belt during mis 3 expressed by an array of local techno typological facies that likely relate to distant and disconnected source regions where populations contracted when climate worsened together with a set of high resolution archaeological contexts recently discovered in the arabian peninsula and dated to mis 5 these data suggest that the major human expansion waves which occurred in the region during the upper pleistocene are correlated with the wet phases of mis 5 while populations probably contracted into a few refugia areas at the beginning of mis 3

glacier motion estimation using sar offset tracking procedures two image to image patch offset techniques for estimating feature motion between satellite synthetic aperture radar sar images are discussed intensity tracking based on patch intensity cross correlation optimization and coherence tracking based on patch coherence optimization are used to estimate the movement of glacier surfaces between two sar images in both slant range and azimuth direction the accuracy and application range of the two methods are examined in the case of the surge of monacobreen in northern svalbard between 1992 and 1996 offset tracking procedures of sar images are an alternative to differential sar interferometry for the estimation of glacier motion when differential sar interferometry is limited by loss of coherence i e in the case of rapid and incoherent flow and of large acquisition time intervals between the two sar images in addition an offset tracking procedure in the azimuth direction may be combined with differential sar interferometry in the slant range direction in order to retrieve a two dimensional displacement map when sar data of only one orbit configuration are available

mechanical analysis of pinning points in the ross ice shelf antarctica ice shelves regulate the rate of ice sheet discharge along much of the antarctic coastline pinning points sites of localised grounding within floating ice can in turn regulate the flow and thickness of an ice shelf while the net resistive effect of ice shelves has been quantified in a systematic way few extant pinning points have been examined in detail here complete force budgets are calculated and examined for ice rises and rumples in the ross ice shelf west antarctica the diverse features have different effects on ice shelf mechanics that do not depend simply on their size but may we conclude depend on the properties of seafloor materials

detailed hydraulic head profiles as essential data for defining hydrogeologic units in layered fractured sedimentary rock this paper describes a study in southern wisconsin where vertical hydraulic head profiles measured in exceptional detail provided the key data for defining hydrogeologic units hgus in a layered sequence of sandstone siltstone shale and dolostone the most important data were obtained from corehole mp 6 which was cored 131 m into bedrock and instrumented using a westbay multilevel system with 36 depth discrete monitoring intervals the resulting head profile is consistant over time and shows eight distinct inflections in hydraulic head several of the inflections occur between adjacent permeable units and are likely due to poor vertical connectivity of fracture sets rather than distinct lower permeability layers or aquitards in the conventional sense no other type of data was capable of identifying the position of such distinct hydrogeologic features these zones of abrupt head loss provide the primary dataset for delineation of eleven hgus at mp 6 and are supported by less detailed head profiles at other locations although the detailed head profiles are essential core logs and geophysical logs from other boreholes are nessessary to fully establish the lateral continuity of the hgus

evolution of derwael ice rise in dronning maud land antarctica over the last millennia ice rises situated in the ice shelf belt around antarctica have a spatially confined flow regime with local ice divides beneath the divides ice stratigraphy often develops arches with amplitudes that record the divide s horizontal residence time and surface elevation changes to investigate the evolution of derwael ice rise dronning maud land antarctica we combine radar and gps data from three consecutive surveys with a two dimensional full stokes thermomechanically coupled transient ice flow model we find that the surface mass balance smb is higher on the upwind and lower on the downwind slopes near the crest the smb is anomalously low and causes arches to form in the shallow stratigraphy observable by radar in deeper ice arches are consequently imprinted by both smb and ice rheology raymond effect the data show how arch amplitudes decrease as along ridge slope increases emphasizing that the lateral positioning of radar cross sections is important for the arch interpretation using the model with three rheologies isotropic with n 3 4 5 and anisotropic with n 3 we show that derwael ice rise is close to steady state but is best explained using ice anisotropy and moderate thinning our preferred albeit not unique scenario suggests that the ice divide has existed for at least 5000 years and lowered at approximately 0 03 m a 1 over the last 3400 years independent of the specific thinning scenario our modeling suggests that derwael ice rise has exhibited a local flow regime at least since the mid holocene

marine ice sheet collapse potentially under way for the thwaites glacier basin west antarctica resting atop a deep marine basin the west antarctic ice sheet has long been considered prone to instability using a numerical model we investigated the sensitivity of thwaites glacier to ocean melt and whether its unstable retreat is already under way our model reproduces observed losses when forced with ocean melt comparable to estimates simulated losses are moderate 1 mm per year of sea level rise collapse in the different simulations within the range of 200 to 900 years

human occupation of northwest africa a review of middle palaeolithic to epipalaeolithic sites in morocco abstract this paper provides a summary of all available numerical ages from contexts of the moroccan middle palaeolithic to epipalaeolithic and reviews some of the most important sites particular attention is paid to the so called aterian albeit those so labeled assemblages fail to show any geographical and chronological pattern for this reason this phenomenon should not be considered a distinct culture or techno complex and is referred to hereinafter as middle palaeolithic of aterian type whereas anatomical modern humans amh are present in northwest africa from about 160 ka onwards according to current research some middle palaeolithic inventories are more than 200 ka this confirms that for this period it is impossible to link human forms with artifact material perforated shell beads with traces of ochre documented from 80 ka onwards certainly suggest changes in human behavior the transition from middle to upper palaeolithic here termed early upper palaeolithic at between 30 and 20 ka remains the most enigmatic era however the still scarce data from this period requires careful and fundamental revision in the frame of any future research by integrating environmental data in reconstruction of population dynamics clear correlations become obvious high resolution data are lacking before 20 ka and at some sites this period is characterized by the occurrence of sterile layers between middle palaeolithic deposits possibly indicative of shifts in human population after heinrich event 1 there is an enormous increase of data due to the prominent late iberomaurusian deposits that contrast strongly from the foregoing accumulations in terms of sedimentological features fauna and artifact composition the younger dryas shows a remarkable decline of data marking the end of the palaeolithic environmental improvements in the holocene are associated with an extensive epipalaeolithic occupation

possible shell beads from the middle stone age layers of sibudu cave south africa recent excavations at sibudu cave kwazulu natal south africa uncovered an iron age horizon below which is a complex 3 m thick middle stone age sequence with post howiesons poort howiesons poort still bay and pre still bay layers available osl ages indicate that the howiesons poort occupation is older than 60 ky and the still bay older than 70 ky here we present the archaeological context and the taphonomic analysis of six afrolittorina africana three of which bear perforations from the still bay and howiesons poort layers of this site the single specimen from the latter cultural horizon comes from the lowermost layer attributed to this technocomplex this and the depositional context of this layer suggest that this shell derives as do the other five from the still bay occupation layers taphonomic analysis of the archaeological specimens based on present day afrolittorina africana biocoenoses microscopic examination morphometry experimental perforation of modern shells and a review of the natural agents that may accumulate marine shells at inland sites indicate probable human involvement in the collection transport modification and abandonment of afrolittorina africana in sibudu if confirmed by future discoveries these shells would corroborate the use of personal ornaments already attested at blombos cave western cape province by still bay populations the apparent absence of ornaments at howiesons poort sites raises the question of the mechanisms that have led to cultural modernity since it seems to contradict the scenario according to which cultural innovations recorded at middle stone age sites reflect a process of continuous accretion and elaboration interpreted as the behavioural corollary of the emergence of anatomically modern humans

the sensitivity of west antarctica to the submarine melting feedback we use an ice sheet model with realistic initial conditions to forecast how the amundsen sea sector of west antarctica responds to recently observed rates of submarine melting in these simulations we isolate the effects of a positive feedback driven by submarine melt in new ocean cavities flooded during retreat by allowing the present climate calving front and melting beneath existing ice shelves to persist over the 21st century even without additional forcing from changes in climate ice shelf collapse or ice cliff collapse the model predicts slow sustained retreat of west antarctica driven by the marine ice sheet instability and current levels of ocean driven melting when observed rates of melting are included in new subglacial ocean cavities the simulated sea level contribution increases and for sufficiently intense melting it accelerates over time conditional bayesian probabilities for sea level contributions can be derived but will require improved predictions of ocean heat delivery

mammalian faunas as indicators of environmental and climatic changes in spain during the pliocene quaternary transition abstract the study of mammal communities provides useful knowledge of paleoenvironments and paleoclimates during the quaternary period and better documentation about the main fossil sites is making this task easier paleoecological reconstructions of this study are based on i rodent evolution and species richness ii the cenogram method and iii methods for quantifying climatic parameters these analyses applied to a pliocene quaternary faunal sequence of spain indicate that a climatic change occurred at the end of the pliocene when considerable cooling led to the onset of the glacial interglacial cycles subsequently during the quaternary period alternating environmental patterns occurred with a rather open and arid environment during the cold phases that contrasts with a somewhat more closed and comparatively wet environment during warmer phases these observations are generalized from spain to the remainder of the continent noting that climatic conditions were less harsh and more arid in spain than elsewhere in europe

african climate change and faunal evolution during the pliocene pleistocene abstract environmental theories of african faunal evolution state that important evolutionary changes during the pliocene pleistocene interval the last ca 5 3 million years were mediated by changes in african climate or shifts in climate variability marine sediment sequences demonstrate that subtropical african climate periodically oscillated between markedly wetter and drier conditions paced by earth orbital variations with evidence for step like 0 2 ma increases in african climate variability and aridity near 2 8 ma 1 7 ma and 1 0 ma coincident with the onset and intensification of high latitude glacial cycles analysis of the best dated and most complete african mammal fossil databases indicates african faunal assemblage and perhaps speciation changes during the pliocene pleistocene suggesting more varied and open habitats at 2 9 2 4 ma and after 1 8 ma these intervals correspond to key junctures in early hominid evolution including the emergence of our genus homo pliocene pleistocene shifts in african climate vegetation and faunal assemblages thus appear to be roughly contemporary although detailed comparisons are hampered by sampling gaps dating uncertainties and preservational biases in the fossil record further study of possible relations between african faunal and climatic change will benefit from the accelerating pace of important new fossil discoveries emerging molecular biomarker methods for reconstructing african paleovegetation changes tephra correlations between terrestrial and marine sequences as well as continuing collaborations between the paleoclimatic and paleoanthropological communities

using flowmeter pulse tests to define hydraulic connections in the subsurface a fractured shale example cross borehole flowmeter pulse tests define subsurface connections between discrete fractures using short stress periods to monitor the propagation of the pulse through the flow system this technique is an improvement over other cross borehole techniques because measurements can be made in open boreholes without packers or previous identification of water producing intervals the method is based on the concept of monitoring the propagation of pulses rather than steady flow through the fracture network in this method a hydraulic stress is applied to a borehole connected to a single permeable fracture and the distribution of flow induced by that stress monitored in adjacent boreholes the transient flow responses are compared to type curves computed for several different types of fracture connections the shape of the transient flow response indicates the type of fracture connection and the fit of the data to the type curve yields an estimate of its transmissivity and storage coefficient the flowmeter pulse test technique was applied in fractured shale at a volatile organic contaminant plume in watervliet new york flowmeter and other geophysical logs were used to identify permeable fractures in eight boreholes in and near the contaminant plume using single borehole flow measurements flowmeter cross hole pulse tests were used to identify connections between fractures detected in the boreholes the results indicated a permeable fracture network connecting many of the individual boreholes and demonstrated the presence of an ambient upward hydraulic head gradient throughout the site