cenozoic ice rafting history of the central arctic ocean terrigenous sands on the lomonosov ridge the cenozoic ice rafted debris ird history of the central arctic is reconstructed utilizing the terrigenous coarse sand fraction in iodp 302 cores from 0 to 273 meters composite depth this holocene middle eocene quantitative record of terrigenous sand accumulation on the lomonosov ridge along with qualitative information on grain texture and composition confirms the interpretation that ice initiation sea ice and glacial ice occurred 46 ma in the arctic and provides a long term pattern of arctic ice expansion and decay since the middle eocene ird mass accumulation rates range from 0 to 0 13 g cm2 ka in the middle eocene and from 0 to 0 36 g cm2 ka in the neogene ird mass accumulation rate mar maxima in the miocene and pliocene cooccur with either glacial initiation or intensification in the sub arctic the 46 25 ma ird onset in the central arctic slightly precedes the earliest evidence of ice in the antarctic and compares in timing with a 1000 ppm decrease in atmospheric concentrations of co2 the decline of pco2 in the middle eocene may have driven both poles across the temperature threshold that enabled the nucleation of glaciers on land and partial freezing of the surface arctic ocean especially during times of low insolation

alaska landfast sea ice links with bathymetry and atmospheric circulation 1 using radarsat synthetic aperture radar sar imagery of northern alaska and northwestern canada we calculated a mean climatology of the annual landfast ice cycle for the period 1996 2004 we also present the monthly minimum mean and maximum landfast ice extents throughout the study area these data reveal where and when the landfast is most stable and which sections of the coast are susceptible to midseason breakout events stabilization of landfast ice is strongly related to the advance of the seaward landfast ice edge slie into waters around 18 m deep isobaths near this depth are a good approximation for midseason landfast ice extent comparison with work from the 1970s suggests a reduced presence of landfast ice in this region of the arctic due to later formation and earlier breakup this will likely lead to an increase in coastal erosion and may also have profound effects upon subsistence activities which are intimately linked to the timing of marine mammal migration patterns interannually landfast ice formation correlates with the incursion of pack ice into coastal waters suggesting that the later mean date of formation in recent years may be related to the increasingly northward location of the perennial sea ice edge the timing of breakup correlates well with onset of thawing air temperatures analysis of regional data shows a multidecadal trend toward earlier thaw onset which suggests that the observed change in breakup dates may be part of a longer term trend

inversion of pack ice elastic wave data to obtain ice physical properties geophones mounted on floating ice sheets can potentially provide data for a robust method to monitor mechanical properties of the ice the technique relies on the measurement and inversion of low frequency elastic waves propagating in the ice to test this hypothesis several geophone systems were deployed on the arctic ice as part of the office of naval research sea ice mechanics initiative simi including a winter over system of 20 triaxial geophones at the fall 1993 simi camp an inversion technique is discussed here through references to the literature and by analysis of geophone data specifically those data collected on clean first year ice off resolute bay canada and on highly irregular multiyear ice found at the fall simi camp for undeformed first year ice the inversion technique gave an estimate of ice properties that agreed well with known values although extensive work remains to determine the effects of anisotropy and inhomogeneity the geophone data for the nonuniform ice at the simi camp were very complex and difficult to analyze the inversion yielded only trends in what can at best be termed effective ice thickness and bending rigidity it is uncertain how these relate to actual ice properties the simi geophone system demonstrated the feasibility of performing autonomous measurements of the characteristics of propagating waves in the arctic ice with continued study it seems evident that such systems can be used in clean first year ice to monitor ice properties however extensive research is required to make this technique useful in multiyear or complex first year ice

effects of sedimentary heterogeneity on groundwater flow in a quaternary pro glacial delta environment joining facies analysis and numerical modelling abstract we present the sedimentological survey of quaternary sediments developed in glacio fluvial to glacio lacustrine delta environments and exposed at an abandoned quarry in northern italy this outcrop is considered an analogue of sedimentary structures that could form a real aquifer we recognise the following sedimentary units i colluvial sediments with human artefacts less than 2 m thick ii gravelly sands with oversized pebbles 2 5 5 5 m thick bounded at the base by a roughly flat composite disconformity surface iii and iv gravelly sand foresets which form two bodies with different dips that are separated by an inclined almost planar erosional surface from past observations in the surrounding area and a geoelectrical survey we estimate that the minimum total thickness of the delta system is 20 m we have analysed the sedimentary characteristics of two well exposed areas which are located within units ii iii and iv and covering areas of 115 and 95 m2 using detailed sedimentological surveys along six vertical sections with the aid of a topographic survey we have reconstructed the distribution of textural units based on sedimentary facies and including information about grain size distribution sorting and packing we have constructed a sedimentary model for the two areas using orthogonal cells of 10 10 cm attributing the dominant textural unit to each cell the distribution of sedimentary textural units is used to estimate the distribution of hydraulic conductivity for the two areas of this aquifer analogue we have determined the hydraulic conductivity by assigning different values to the different textural units according to laboratory measurements of porosity and grain size distribution kozeny carman s equation and literature data we have modelled groundwater flow in the two areas approximating the balance equation with finite differences using a regular grid with 10 cm spacing and we have performed some numerical experiments first we have evaluated the equivalent conductivity tensor for the two areas secondly we have considered a coarse grid with 1 5 m spacing and at this scale we have analysed the validation of the discrete form of darcy s law usually introduced in finite difference modelling the results of the numerical experiments show the anisotropic behaviour of the medium especially for unit ii composed of sandy beds some of which lead to a preferential path for groundwater flow in the horizontal direction the deeper sedimentary units iii and iv are characterised by a lower anisotropy ratio for hydraulic conductivity because the layered structures of these units have different dips finally we show that the discrete form of darcy s law at a scale length of 1 5 m is a first order approximation only

a note on infragravity waves in the arctic ocean long period 20 50 s surface gravity waves were recorded in the eastern arctic 83 n 10 e using tiltmeters deployed on the ice and an acoustical current meter deployed a few meters below the ice during the spring of 1989 the waves caused ice tilt of a few microradians and horizontal velocity of the water just beneath the ice of order 10 4 m s 1 the unprecedented sensitivity of the velocity measurements is the result of a path averaging technique based on reciprocal transmission along 200 m horizontal paths the measurements indicate that infragravity waves and low frequency swell penetrate the arctic ocean through the pram strait and that they are freely propagating and not tied to groups of short waves it is suggested that these waves could provide a method to measure ice thickness distribution in the arctic ocean

the physiography of high arctic cross shelf troughs abstract a comprehensive inventory of high arctic cross shelf troughs is compiled from international bathymetric chart of the arctic ocean ibcao bathymetric data v 3 0 the location of 75 cross shelf troughs is presented alongside a synthesis of their key physiographic characteristics and available glacial geological evidence the troughs are interpreted to have been occupied intermittently and eroded by marine terminating ice streams that traversed the shelf during at least one and often many quaternary full glacial periods considerable variation in cross shelf trough physiography exists in the high arctic trough lengths range between 35 and 1400 km widths from 12 to 260 km and maximum depths from 200 to 1000 m the longest cross shelf troughs extend through inter island channels on the beaufort sea queen elizabeth islands and barents kara sea margins the gradient of the upper slope beyond high arctic glacial troughs which ranges between 0 3 and 13 is shown to have a negative relationship with palaeo ice stream drainage basin area and trough length glacial sedimentary depocentres or trough mouth fans tmfs are inferred on the basis of bathymetric and where available seismic evidence to exist beyond the majority of high arctic cross shelf troughs evidence of shelf progradation or tmf development is absent from the slope beyond several high arctic troughs probably as a result of limited sediment supply to the margin and or sediment by passing of the upper slope on the south greenland continental margin it is likely that steep slopes prevented the development of significant glacial sedimentary depocentres beyond cross shelf troughs or that glacigenic debris has been removed from the upper slope by submarine slope failure

ocean surface wave evolvement in the arctic basin 1 recent basin scale changes to the compactness and thickness of arctic sea ice foreshadow that encroaching swells and locally generated waves will exert more influence there in the future indeed it is conceivable that waves may have already hastened the adjustments observed by breaking up ice floes yet waves advancing in sea ice attenuate due to being scattered from ice thickness variations and damped by ice inelasticity turbulence and friction while past research focuses on scattering by unnaturally perfect features in the ice the model reported herein assimilates realistic basin scale swathes of heterogeneous ice and parameterizes damping by way of example we show how an ocean wave train evolves during its passage in an 1670 km long arctic sea ice profile obtained from submarine

swell and sea in the emerging arctic ocean ocean surface waves sea and swell are generated by winds blowing over a distance fetch for a duration of time in the arctic ocean fetch varies seasonally from essentially zero in winter to hundreds of kilometers in recent summers using in situ observations of waves in the central beaufort sea combined with a numerical wave model and satellite sea ice observations we show that wave energy scales with fetch throughout the seasonal ice cycle furthermore we show that the increased open water of 2012 allowed waves to develop beyond pure wind seas and evolve into swells the swells remain tied to the available fetch however because fetch is a proxy for the basin size in which the wave evolution occurs thus both sea and swell depend on the open water fetch in the arctic because the swell is regionally driven this suggests that further reductions in seasonal ice cover in the future will result in larger waves which in turn provide a mechanism to break up sea ice and accelerate ice retreat

implications of fractured arctic perennial ice cover on thermodynamic and dynamic sea ice processes decline of the arctic summer minimum sea ice extent is characterized by large expanses of open water in the siberian laptev chukchi and beaufort seas and introduces large fetch distances in the arctic ocean long waves can propagate deep into the pack ice thereby causing flexural swell and failure of the sea ice this process shifts the floe size diameter distribution smaller increases floe surface area and thereby affects sea ice dynamic and thermodynamic processes the results of radarsat 2 imagery analysis show that a flexural fracture event which occurred in the beaufort sea region on 6 september 2009 affected 40 000 km2 open water fractional area in the area affected initially decreased from 3 7 to 2 7 but later increased to 20 following wind forced divergence of the ice pack energy available for lateral melting was assessed by estimating the change in energy entrainment from longwave and shortwave radiation in the mixed layer of the ocean following flexural fracture 11 54 mj m 2 of additional energy for lateral melting of ice floes was identified in affected areas the impact of this process in future arctic sea ice melt seasons was assessed using estimations of earlier occurrences of fracture during the melt season and is discussed in context with ocean heat fluxes atmospheric mixing of the ocean mixed layer and declining sea ice cover we conclude that this process is an important positive feedback to arctic sea ice loss and timing of initiation is critical in how it affects sea ice thermodynamic and dynamic processes

triggering of the hinlopen yermak megaslide in relation to paleoceanography and climate history of the continental margin north of spitsbergen 1 on the basis of the detailed sedimentological record of the key core ps66 309 1 and a review of open literature we present an assessment of the paleoenvironmental conditions as well as trigger mechanism of the hinlopen yermak megaslide north of spitsbergen the svalbard archipelago is characterized by strong inflow of atlantic water accompanied by rapidly falling sea level rapidly growing svalbard barents sea ice sheet and associated increasing glaciotectonic activity during the time window around 30 calendar kyr b p of this catastrophic failure event thus the potential trigger mechanisms include sediment buoyancy and excess pore pressure hydrate stability and tectonic glaciotectonic processes while the common scenarios seem to fail to explain this unique submarine megaslide we focus on glacial processes and their consequences for the regional tectonic framework we conclude that the hinlopen yermak megaslide has been the consequence of the rapid onset of late weichselian glaciation resulting in a drastic sea level drop asymmetrical ice loading and a forebulge development leading to enhanced tectonic movements along the hinlopen fault zone as the final trigger we assume a strong earthquake positioned below or close to the se sophia basin

observations and analyses of an intense waves in ice event in the sea of okhotsk 1 ice draft ice velocity ice concentration and current profile data gathered at an array of eight continental shelf monitoring sites east of sakhalin island were analyzed in conjunction with regional meteorological data to document and explain intense wave occurrences several hundred kilometers inside the sea of okhotsk ice pack the studied event was associated with the 19 21 march 1998 passage of an intense cyclone which produced waves with amplitudes in excess of 1 m at the most offshore monitoring location the relatively monochromatic character of the waves allowed extraction of wave intensity time series from ice draft time series data spatial and temporal variations in these data were used to establish directions and speeds of wave energy propagation for comparisons with an earlier interpretation liu and mollo christensen 1988 of an antarctic intense waves in ice event it was concluded that although both events are compatible with a two stage process in which initially slowly advancing wave activity increases subsequent ice cover wave transmissivity the first stage of the sea of okhotsk event was not explicable in terms of the static stress induced changes in the waves in ice dispersion relationship proposed by liu and mollo christensen an alternative explanation is offered that eschews the linkage between wave group velocities and the observed slow rates of wave energy propagation and attributes the subsequent transition to more normal wave propagation behavior to ice pack divergence

modeling heterogeneity of gravel sand braided stream alluvial aquifers at the facies scale abstract the coarse grained alluvial aquifers are recurrently considered as almost homogeneous and isotropic media nevertheless water flow through these sediments is controlled by internal architecture therefore a better knowledge is necessary to understand the effects of facies heterogeneity on the conductivity magnitude and anisotropy within these aquifers in this work we search interactions at the facies scale within a glacio fluvial aquifer among sedimentary heterogeneity distribution of permeability and anisotropy the case study concerns pleistocene sequences of the ticino basin northern italy where three model blocks dug into real sediments at a quarry site have been investigated at the meter scale these model blocks represent the most diffuse facies associations 1 sand gravel dunes 2 gravel bedforms and 3 poorly sorted mass gravity deposits facies maps with 2 cm resolution were obtained for each block and used to condition 3d geostatistical simulation of the sediment volumes with a hierarchical modification of sisim conductivities of samples were either measured with laboratory tests or estimated with empirical formulas conductivity values were finally introduced as input data into the numerical flow model to compute the upscaled tensor of equivalent conductivity at the model block scale the results of field infiltration tests were used to verify the outcomes of upscaling experiments which identified the primary influence on the most permeable facies open framework gravel on both conductivity magnitude and anisotropy ratio the latter property is unrelated to the abundance of this facies but is controlled by its spatial distribution within the blocks as the connectivity of open framework gravel increases model blocks become more anisotropic on the other hand the low permeable sand facies of dunes do not produce significant anisotropy at the block scale these results show the importance of introducing the hierarchical assemblage of different rank depositional units in conceptual aquifer models in addition we identified the most significant depositional units to forecast the spatial distribution of aquifer heterogeneity at different scales

the innuitian ice sheet configuration dynamics and chronology abstract portrayal of north american ice cover during the last glacial maximum is dominated by the laurentide ice sheet leaving little detail for the adjacent innuitian ice sheet iis four decades of geological fieldwork across the queen elizabeth islands now warrant specific treatment of the iis including its chronology configuration dynamics and retreat this reconstruction is relevant to the sedimentary history of the arctic ocean and to high latitude climate forcing the iis was composed of both an alpine and lowland sector the advance of the alpine sector occurred as recently as 19 14 c ka bp geological evidence configures outflow from alpine and lowland divides that produced several palaeo ice streams one extending northwestward across the canadian arctic archipelago to the polar continental shelf retreat of the iis commenced along its southwest margin 11 6 14 c ka bp however most of the ice sheet remained on the continental shelf during the younger dryas by 10 14 c ka bp marine based ice experienced widespread calving through the western and central archipelago in response to holocene warming and ongoing eustatic sea level rise the sea penetrated the eastern archipelago by 8 5 14 c ka bp gutting the alpine sector of the iis regional isobases record the glacioisostatic signature of the ice sheet and are congruent with the primary geological evidence the delayed buildup of the iis was out of phase with the growth of the laurentide ice sheet that occasioned climatic and glacio eustatic forcing in the innuitian region recent modelling experiments reinforce the hypothesis that growth of the laurentide ice sheet culminated in a split jet stream that temporarily favoured augmented precipitation and growth of the iis

numerical estimation of effective permeability in sand shale formations a numerical approach is used to estimate effective permeability in sand shale formations under steady state uniform flow conditions permeability is modeled as a binary second order stationary random function taking on two possible values kss and ksh in sandstone and shale respectively this model is realistic since experience with sandstone reservoirs has shown that randomly dispersed low permeability shales are the single dominant heterogeneity affecting flow behavior the cases of both spatially correlated and uncorrelated permeabilities are considered for the case of spatially correlated permeability an autocovariance model was fitted to data from the assakao fluvial sandstone which outcrops in the tassili region of the central sahara the turning bands method was used to simulate the spatially correlated permeabilities of blocks discretizing the flow field effective permeability was found to depend on the shale volume fraction the spatial covariance structure and the dimensionality of the flow system existing analytical methods for estimating effective permeability in a two phase medium are found to be inaccurate when compared to numerical results or unapplicable to stratified environments in addition to providing a check of analytical work the numerical approach is found to be a useful tool for exploring the effects of reservoir heterogeneity on flow behavior in a qualitative sense

waves in frazil and pancake ice and their detection in seasat synthetic aperture radar imagery a theoretical model of waves propagating into an ice cover composed of frazil and pancake ice is developed and compared with measurements of wavelength and direction derived from synthetic aperture radar sar imagery obtained from seasat in october 1978 the theoretical model is based on the concept that ice of these types which consists of small crystals or cakes has only a mass loading effect on the water surface we derive the dispersion relation for phase and group velocities finding that there is an upper frequency limit for propagation into the ice from the reflection coefficient at the ice edge we derive the wave radiation pressure exerted on the ice showing that it will cause a slick of frazil ice backed by thicker floes to become more dense or thick with increasing penetration the implications for radar scattering enabling detection on sar are that the bragg resonant wavelength corresponds to waves above the frequency limit for propagation so that a frazil slick appears dark on an sar image when the frazil ice becomes transformed into pancake ice through slick compression or other means the raised edges of the pancakes cause the ice to appear bright despite the fact that there are no waves present at the bragg wavelength these results are applied to a seasat sar image obtained from the chukchi sea the appearance of the ice in the image corresponds to what we expect for frazil ice gradually transforming itself into pancake ice backed by thicker floes we derive directional wave number spectra outside and inside the ice cover by digital fourier analysis of image subscenes and we find that the change of wavelength and angle of refraction of the dominant wave entering the ice field are both characteristic of the dispersion relation derived theoretically mean ice thicknesses extracted from the theory correspond to thicknesses expected for such slicks the technique offers a possible means of extracting the thickness of fields of frazil and pancake ice from sar imagery this may be of considerable utility when ers 1 sar is used to study the advancing winter ice edge in the antarctic which consists of vast areas of these ice types

sea ice thickness measurement based on the dispersion of ice swell the dispersion of flexural waves propagating in the arctic sea ice cover is exploited in order to locally measure the ice thickness the observed dispersion for waves filtered in the 4 20 s period interval at up to 4 broad band seismometers deployed in spring 2007 near the north pole is compared to a parameterized model that accounts for a complex wavefield made of a superposition of independent plane waves with different amplitudes and back azimuth angles the parameterization that includes finding the best modeled ice thickness is performed by using the cross correlation functions between the seismometers the ice thickness is estimated to 2 5 0 2 m for the 1 km large floe the seismic stations were deployed on which is coherent with other independent measurements at this site this study thus demonstrates the feasibility of using broad band seismometers deployed on the sea ice in order to passively measure the ice thickness without requiring active sources nor human intervention

hierarchical dynamic stratigraphy in various quaternary gravel deposits rhine glacier area sw germany implications for hydrostratigraphy the approach of dynamic stratigraphy aims to understand genetic processes that form stratigraphic units in a hierarchy of spatial and temporal scales this approach was used to investigate quaternary gravel deposits in terms of their sedimentology and in order to characterize the various sedimentary units in terms of their hydrogeological properties facies analysis within 62 gravel pits laboratory permeability measurements of field samples and geophysical surveys 3 d georadar 2 d seismic reflection led to the detection and classification of sedimentary heterogeneity according to the following six scales whereby each scale can be translated into defined hydrostratigraphic units 1 particles and pores micro scale that reflect depositional and diagenetic fluid dynamics as well as source material behaviour e g grain size roundness lithological composition this was found to be important for the hydrogeochemistry of groundwater in gravel aquifers e g higher sorption capacity of carbon rich limestone particles for organic pollutants 2 strata meso scale contain the recognition of sorting fabric texture and stratinomic features which can give an indication of transport and depositional dynamics five major lithofacies groups for example were distinguished within fluvial gravel bed deposits their variable hydraulic properties led to their subdivision into 12 hydrofacies types they form the smallest mappable hydrostratigraphic units which may result in either preferred pathways for fluid flow or flow barriers 3 depositional elements macro scale enable reconstruction of sedimentary geomorphic elements and their dynamics within a depositional system e g gravel bed braided river systems are dominated by gravel sheet gravel dunes and scour pool depositional elements hydrostratigraphically the architecture of depositional elements influences the hydraulic connectivity and local permeability structure distribution within an aquifer body five types of depositional elements in fluvial gravel bed deposits were distinguished and their geometries dimensions quantified 4 facies bodies mega scale composed of a stack of depositional elements and strata recording distinct environmental systems and their dynamics e g a coarse grained prograding delta system hydrostratigraphically facies bodies represent major compartments of an aquifer six major types of meltwater controlled facies bodies were identified in the study area 5 genetic sequences mega scale reflect the shifts of depositional environments caused by allocyclic changes e g glacial advance recorded by a coarsening upward sequence or autocyclic changes of landscape shaping events these sequences may form separate hydrostratigraphic units or aquifer storeys 6 basin fill giga scale comprising the lateral and vertical stacking of facies bodies and genetic sequences controlled by either long term glacier dynamics or short term flood events the regional distribution of permeable gravel units and for example less permeable diamicts builds the larger scale hydrostratigraphy

seabed erosion on the lomonosov ridge central arctic ocean a tale of deep draft icebergs in the eurasia basin and the influence of atlantic water inflow on iceberg motion 1 the submarine lomonosov ridge which bisects the arctic ocean is covered by 450 m of hemipelagic sediments high resolution chirp sonar and side scan data have documented erosion of a section of the ridge here we present multichannel seismic and chirp sonar data which show removal of unconsolidated sediments along the eurasia basin side of the lomonosov ridge where the central ridge is shallower than 1000 m the incomplete erosion of the hemipelagic drape and probable topographic control of ice motion suggest that the deepest draft glacier ice which reached the central arctic ocean from the eurasia basin was in the form of armadas of large icebergs embedded in sea ice rather than a single continuous floating ice shelf massive rapid discharge of glacier ice was probably required to produce the deepest draft 800 m icebergs eastward and northward drift trajectories from a likely iceberg source area on the kara barents sea margin would reflect the relative strength of atlantic inflow through the fram strait however only icebergs with drafts exceeding bathymetric thresholds on the lomonosov ridge would leave an erosive imprint on the seabed advection of atlantic water may have been relatively strong at times of discharge from the saalian ice sheet icebergs exiting the arctic ocean caused massive erosion and redeposition of the hemipelagic sediments on top of yermak plateau

seven million years of glaciation in greenland glacial till glaciomarine diamictites and ice rafted detritus found in marine cores collected off the shore of southeast greenland record multiple late cenozoic glaciations beginning in the late miocene distinct rock assemblages and seismic stratigraphic control correlate the diamictites with glaciation of the southeast greenland margin glaciers advanced to the sea during several intervals in the pliocene and pleistocene north atlantic glaciation may have nucleated in southern greenland rather than further north because of the high mountains and the high levels of precipitation in this region

asynchronous deposition of ice rafted layers in the nordic seas and north atlantic ocean instabilities in ice stream flow within the north american laurentide ice sheet leading to the periodic release of armadas of icebergs into the north atlantic ocean over the past 60 000 years have produced extensive layers of coarse grained iceberg rafted debris heinrich layers in north atlantic sediments1 2 correlation of these layers with iceberg discharge events from the ice sheets on greenland iceland and scandinavia suggested in previous studies for some heinrich layers and in some areas3 4 5 would imply that ice sheet instability had been synchronous across the north atlantic presumably in response to a common environmental cause here we show a lack of widespread systematic correlations both between ice rafted debris layers in different sediment cores from the nordic seas and between the nordic layers and the north atlantic heinrich layers this suggests that the full glacial nordic ice sheets did not exhibit unstable behaviour coincident with iceberg discharge from the vast hudson bay drainage basin of the laurentide ice sheet6 7 off the hudson strait significant ice sheet discharge of melt water is indicated by size sorted sandy and muddy turbidite sediments different from the poorly sorted debris flows which dominate sedimentation on the margins of the nordic seas8 9 10 together these results suggest that the dynamics of quaternary ice sheets surrounding the nordic seas were different from the outlet glacier draining the hudson bay basin and they provide evidence against a common circum north atlantic mechanism driving the discharge of icebergs

mapping arctic landfast ice extent using l band synthetic aperture radar interferometry in recent years methods have been developed to extract the seaward landfast ice edge from series of remote sensing images with most of them relying on incoherent change detection in optical infrared or radar amplitude imagery while such approaches provide valuable results some still lack the required level of robustness and all lack the ability to fully automate the detection and mapping of landfast ice over large areas and long time spans this paper introduces an alternative approach to mapping landfast ice extent that is based on coherent processing of interferometric l band synthetic aperture radar sar data the approach is based on a combined interpretation of interferometric phase pattern and interferometric coherence images to extract the extent and stability of landfast ice due to the low complexity of the base imagery used for landfast ice extraction significant improvements in automation and reduction of required manual interactions by operators can be achieved a performance analysis shows that l band interferometric sar insar data enable the mapping of landfast ice with high robustness and accuracy for a wide range of environmental conditions

the attenuation rates of ocean waves in the marginal ice zone during field operations in the greenland and bering seas in 1978 1979 and 1983 a number of experiments were carried out in which wave energy was measured along a line of stations running from the open sea deep into an icefield wave buoys in the water and accelerometer packages on floes were the instruments employed with airborne vertical photography to supply information on floe size distribution it was found that the decay of waves is exponential with a decay coefficient which generally increases with frequency except for a roll over at the highest frequencies the observations can be fitted reasonably well to a theory of one dimensional scattering

soil property trends and classification of alluvial floodplains south carolina coastal plain abstract alluvial soils derived from sediments of piedmont origin occur in the atlantic coastal plain of the southeastern u s in south carolina high order rivers receiving sediment are savannah sv congaree cn wateree wa santee st lynches ly and great pee dee pd this study investigated distribution of soil properties on natural levee valley flat and backswamp landforms within and among the six river floodplains and compared results to the taxonomic classifications used historically during soil survey production this study also investigated the contribution of sediment sources to soil characteristics data were compiled for 65 soil pedons sampled from 16 soil survey areas during a 41 year time period pedons were located in three major land resource areas mlras and the results should aid in development of both land resource area and ecological site concepts data analyses centered on clay and silt contents mineralogy base saturation bs and cation exchange activity cea classes evaluation of data from the six river floodplains revealed common properties among soils on fluvial landscapes across multiple mlras four soil systems each derived from a predominant rock type composed the piedmont drainage basin of each river the absolute area of each soil system differed between rivers but sediment supplied typically did not result in great soil texture variation per landform the land area proportion of the carolina slate belt soil system had a close relationship to silt contents of the alluvial soils on the valley flat landform of five floodplains particle size control section pscs median clay content ranged only between 302 g kg 1 and 405 g kg 1 among all valley flats median pscs silt content ranged between 361 g kg 1 and 511 g kg 1 slight positive downriver trends for clay were observed on sv wa and pd and for silt on sv and wa although local bs variation could be high between pedons slight positive downriver bs trends on valley flats were observed on sv wa and st negative bs trends were seen on ly and pd kaolinite was the dominant clay mineral in soils of all landforms on the six floodplains weatherable primary minerals in sand and silt fractions resulted in higher bs except for the ly soils where resistant minerals composed sand and silt fractions the semiactive cea class occurred predominantly on all three landforms taxonomic analysis supported soil assignment to the suborders aquepts or udepts on all floodplains great group level eutrudepts in south carolina are first reported here and they occur extensively enough on sv cn wa and pd to warrant recognition in soil map units because most soil properties showed little variability for soils occurring in floodplains for all six rivers botanical assessments will be needed to determine the magnitude of the role the properties have toward defining ecological sites ultimately the alluvial systems may be aggregated as a single land resource area within the coastal plain

reconstruction of the glacial ice covers of greenland and the canadian arctic islands by three dimensional perfectly plastic ice sheet modelling a three dimensional perfectly plastic ice sheet model developed for determining the surface elevations and the flow pattern of an ice sheet with given bottom topography and ice margin positions is applied to the reconstruction of the glacial ice covers of greenland and the canadian arctic islands in the northern regions two different reconstructions have been performed with ice margins along the present 600 and 200 m sea depth contours respectively in central greenland the ice margin is considered to be at the outermost ice margin deposits on the coastal shelf to the west and at the present 200 m sea depth contour to the east the main conclusions to be drawn from the reconstructions are 1 the flow pattern of the glacial ice cover of greenland shows a great resemblance to the present one the central ice divide being displaced less than 50 km from its present position and being no more than 200 m higher than today 2 the main ice divide of the ice sheet covering the canadian arctic islands the innuitian ice sheet was located over the highlands of eastern ellesmere island with local domes positioned over the present ice caps indicating that even the deep ice of wisconsin age in these ice caps is of local origin this is also the case for the devon island ice cap 3 even in the not very likely case of a rather extensive glacial ice cover in north west greenland the ice flow pattern upstream of the camp century deep drill site would not have changed radically compared to the present flow pattern thus it is concluded that even advanced ice margins in late wisconsin time could at most have resulted in an elevation of the deposition site of the late wisconsin ice at camp century 600 m higher than at present the consequences of this conclusion are discussed

submarine slope stability on high latitude glaciated svalbard barents sea margin abstract slope stability is evaluated at two locations on high latitude deep sea fans along the svalbard barents sea margin based on available samples and using an infinite slope analysis the stability evaluation uses the mohr coulomb failure criterion and a semi analytical approach based on gibson s formulation for determining the excess pore pressure build up due to sedimentation the main results are presented in the form of contour plots of slope safety factors in a diagram with axes of time and thickness of deposit the results show that during rapid sedimentation which mostly takes place during periods of maximum glaciation with the ice front located along the shelf edge slope failure will occur with a frequency varying between 95 and 170 years only part of the upper sedimented layer will be mobilised 10 30 m while the remaining thickness 40 70 m will remain at the initial sedimentation site these results may explain why the continental slope is characterised by relatively uniform sediment thickness from upper to lower slope

hydrogeophysical imaging of alluvial aquifers electrostratigraphic units in the quaternary po alluvial plain italy the integration of surface geological and geomorphological information with borehole point data and geophysical e g geoelectrical images of the subsurface yields spatially consistent representations of alluvial aquifers heterogeneity at different scales from depositional systems to basin fills such an approach requires a conceptual framework to match the stratigraphic units with their evidence from ground based dc resistivity methods to effectively fill the gaps between sparse borehole data and to obtain valid representations of sedimentary heterogeneities such an approach is applied to characterize two sites of the quaternary aquifers of the central po plain italy which represent 1 the middle upper pleistocene braided to meandering river depositional systems sitting on southalpine crust and 2 their down current counterparts where they are involved by the latest uplift and deformation due to the tectonic activity of the apennine frontal thrusts electrical resistivity was considered as a proxy of the litho textural properties of hydrofacies and their major hierarchical association at depth and was interpreted in accordance with the depth decreasing resolution of ground based resistivity methods thus it was possible to identify the geophysical signature of hydrostratigraphic units through electrostratigraphic units i e sedimentary volumes identified by resistivity contrasts that spatially preserve the vertical polarity hydrostratigraphy and electrostratigraphy were then joined together through a site specific relationship between electrical resistivity and hydraulic conductivity which takes into account the prevailing process of current conduction the litho textural properties of hydrofacies and the groundwater electrical conductivity at the scales of aquifer systems and complexes this approach permitted to establish the conceptual framework to match hydrostratigraphy electrostratigraphy average hydrodynamic properties and distribution of heterogeneities

block hydraulic conductivity of cross bedded fluvial sediments this paper concerns the three dimensional block hydraulic conductivity of blocks of limited size in cross bedded sediments of meandering rivers based on a simplified sedimentological model of a single point bar a stochastic model is proposed to simulate the spatial distribution of core scale conductivities within point bar deposits the required parameters for these simulations are obtained from actual hydraulic conductivity measurements and sedimentological field data the simulations are then used to calculate the three dimensional block conductivity tensor with a numerical upscaling procedure the stochastic simulation model is used to investigate the influence of slope and aspect angle of the cross beds and the core scale anisotropy ratio on the block hydraulic conductivity it is expected that the off diagonal elements of the block conductivity tensor generally cannot be neglected the core scale anisotropy ratio which reflects the small scale layering within the cross beds can potentially have a significant impact on the elements of the block conductivity tensor

ocean waves across the arctic attenuation due to dissipation dominates over scattering for periods longer than 19 s the poorly understood attenuation of surface waves in sea ice is generally attributed to the combination of scattering and dissipation scattering and dissipation have very different effects on the directional and temporal distribution of wave energy making it possible to better understand their relative importance by analysis of swell directional spreading and arrival times here we compare results of a spectral wave model using adjustable scattering and dissipation attenuation formulations with wave measurements far inside the ice pack in this case scattering plays a negligible role in the attenuation of long swells specifically scattering dominated attenuation would produce directional wave spectra much broader than the ones recorded and swell events arriving later and lasting much longer than observed details of the dissipation process remain uncertain average dissipation rates are consistent with creep effects but are 12 times those expected for a laminar boundary layer under a smooth solid ice plate

characterization of the reactivity of riverine heterogeneous sediments using a facies based approach the rhine meuse delta the netherlands large groundwater resources are found in densely populated lowland areas which consist often of young unconsolidated and reduced sediments when anthropogenic activities lead to oxygenation of the aquifer breakdown of the main reduced fractions i e sedimentary organic matter som and pyrite could lead to severe groundwater deterioration such as acidification heavy metal mobilization and increased hardness the characterization of the reactive properties of these sediments is important in predicting groundwater deterioration but is often complicated by the high degree of heterogeneity of these sediments in this study the potential reduction capacity prc based on som and pyrite content the potential buffer capacity pbc based on carbonate content potential acidification capacity pac based on the potential acid production by sulfide oxidation and the measured reduction capacity mrc of five facies which are typical of the riverine sediments in the rhine meuse delta the netherlands were determined a universal facies classification model was used to classify the deposits into more homogeneous sub units based on lithologic and geogenic properties with a further sub division into oxic or anoxic redox environment based upon groundwater data and field observations the bulk chemical data show strong variation across facies for the median values of prc 186 9093 mmol o2 kg 1 pbc 17 132 mmol o2 kg 1 and pac 36 1530 mmol h kg 1 the mrc was measured as reactivity to molecular o2 exposure and was 0 5 567 3 mmol o2 kg 1 steady state oxidation rates were in the wide range of 0 001 10 355 mmol o2 kg 1 day 1 but were typically about 3 8 times faster in fine facies than in coarse facies both the prc and mrc depend strongly on grain size but also on the syn post depositional environment and redox conditions the main part of the prc consists of som but pyrite reactivity is higher than som reactivity as shown by the relative depletion of pyrite in oxic subfacies and the preferential oxidation during the oxidation experiments some facies are very prone to acidification because the pac is higher than the pbc but the oxidation experiments also show that acidification could already start before the prc is fully exhausted this study is one of the few that combines bulk chemical data groundwater data and reactivity measurements and shows that a facies based approach is a practical tool in characterizing the reactivity of heterogeneous deposits 2007 elsevier ltd all rights reserved

modeling hydraulic conductivity of a complex confining layer at various spatial scales the spatial variation of the hydraulic conductivity of a complex confining layer in the netherlands is modeled at four different scales the scale of sediment cores 10 1 100 m the scale of the numerical model blocks 101 102 m the local scale 102 103 m and the regional scale 103 105 m two stochastic methods are combined 1 conditional multiple indicator simulation of texture classes to obtain three dimensional images of the lithology of the confining layer from borehole descriptions and 2 the statistical upscaling procedure of indelman and dagan 1993a b to derive the first and second order statistics of hydraulic conductivities at the scale of the numerical model blocks when the upscaling of the core scale conductivities is ignored the local and regional scale groundwater flow through the confining layer is predicted wrongly

ice streaming in the laurentide ice sheet a first comparison between data calibrated numerical model output and geological evidence 1 despite the importance of rapidly flowing ice streams to ice sheet mass balance their incorporation into numerical ice sheet models is a major scientific challenge this introduces large uncertainties in model output and inhibits a more complete understanding of the role of ice streams in overall ice sheet stability recent computational advances have enabled more realistic representations of ice streaming but few studies have attempted to compare model output against known locations of ice streams this paper compares predictions of ice streaming derived from a large ensemble analysis of a glacial systems model of the laurentide ice sheet against independent geological evidence compiled from previously published studies although the precise dating of paleo ice stream locations is problematic our analysis includes comparisons at six different time steps 18 to 10 cal ka bp during deglaciation results indicate that the model is successful in predicting all of the major marine terminating ice streams but there is mixed success in simulating terrestrial ice streams in the right place and at the right time which is vital in guiding future model development the model also reveals that whilst some ice streams persist throughout deglaciation the focus of mass loss associated with ice streaming switches through time with dynamic changes in ice stream catchments and tributaries this implies that major changes in ice stream activity are to be expected in a deglaciating ice sheet with important implications for contemporary ice sheet dynamics

late quaternary sequence stratigraphy as a tool for groundwater exploration lessons from the po river basin northern italy sequence stratigraphy typically used for hydrocarbon exploration in ancient strata can be applied to late quaternary successions to decipher complex spatial relations among their aquifers late pleistocene holocene strata of the po basin were investigated using a sequence stratigraphic approach to produce a high resolution model for guiding groundwater exploitation because facies tend to be diachronous across depositional basins facies analysis was done within the conformable intervals of strata revealed by sequence stratigraphy to accurately interpret and map coeval lateral facies relations volumetric assessments sand distribution mapping hydraulic characterization of facies and spatial variations of hydraulic parameters revealed two aquifer systems the lowstand systems tract lst and the highstand systems tract hst vertically separated by an aquitard the transgressive systems tract tst the lst aquifer consists of amalgamated fluvial sands average transmissivity 3 5 e 3 m2 s 37 7 e 3 ft2 s with considerable width 25 km 16 mi preferentially elongated downstream the widespread tst aquitard is dominated volumetrically 57 by low permeability estuarine deposits the hst aquifer average transmissivity 5 4 e 5 m2 s 58 1 e 5 ft2 s is 5 10 km 3 6 mi wide elongated parallel to the modern shoreline sequence stratigraphic analysis at the parasequence scale revealed an almost unprecedented level of detailed insight into aquifer or aquiclude dimensions and the complex distribution of hydraulic parameters in the subsurface showing that similar facies have different permeabilities depending on systems tract in contrast lithostratigraphic mapping obscures subsurface connectivity and directional trends and has minimal predictive power away from control these insights should be useful for guiding correlation and mapping of the deep subsurface and for hydrocarbon reservoir modelers

transport modeling in heterogeneous aquifers 1 statistical description and numerical generation of gravel deposits transport of solutes in groundwater is decisively influenced by the heterogeneity of the aquifer the goal of the present work is the numerical generation of synthetic heterogeneous aquifer models based on a statistical description of heterogeneities in gravel aquifers large unweathered outcrops in several gravel pits in northeastern switzerland were investigated in this context on the basis of sedimentological observations it was possible to specify distinct sedimentary structures appearing as lenses or layers all structures have been identified in each of the investigated outcrops by inspecting and analyzing photographs of the outcrops it was possible to estimate the probability density functions pdf of the geometrical attributes of the sedimentary structures disturbed and undisturbed samples were taken from these structures to estimate the pdf of their hydraulic properties that is the hydraulic conductivity and the porosity the information obtained is used to generate distinct numerical realizations by unconditional stochastic simulation of synthetic aquifers having the same statistical properties with respect to hydraulic conductivity and porosity as the investigated deposits

wave measurements on sea ice developments in instrumentation traditional methods of measuring the propagation of waves originating from ocean swell and other sources have relied on wire strain gauges accelerometers or tiltmeters all methods required constant attention to keep in range while data recovery has demanded that the instrument site be revisited in this paper we describe the use of ultra sensitive tiltmeters and novel re zeroing techniques to autonomously gather wave data from both polar regions a key feature of our deployments has been the use of the iridium satellite communications system as a way of ensuring continuous data recovery and remote control of the instrumentation currently four instruments have been successfully reporting from the arctic ocean for over 18 months with two further units deployed in 2005 one in the weddell sea antarctica and one additional unit in the arctic

sedimentary and hydraulic characterization of a heterogeneous glaciofluvial deposit application to the modeling of unsaturated flow abstract flows in the unsaturated zones of alluvial deposits are often poorly understood at the scale of structures such as stormwater infiltration basins the heterogeneous nature of the sediment inherent to this type of formation can lead to preferential flows the difficulty of quantifying them lies in obtaining hydrodynamic parameters representative of the soil structure in situ when the latter is inaccessible this study proposes a method of estimating the hydrodynamic parameters of the lithofacies composing a glaciofluvial deposit east lyon france and their integration in a 2d flow model to model flow in the unsaturated zone the approach developed comprises a sedimentological study based on the miall code carried out to determine the analogy between the lithofacies of the study site and those of two glaciofluvial reference sites currently in the process of formation chamonix france breidamerkurjokull iceland thereby permitting easy access to all the lithofacies identified on the study site the water retention and hydraulic conductivity curves were obtained on the reference sites by using beerkan type infiltration tests for finely textured materials completed by the arya and paris model and data from the literature for coarser materials thus hydrofacies corresponding to all the lithofacies were characterized these hydrofacies were used to model a drainage phase on the study site at the scale of a trench 13 50 m long 2 50 m deep the model highlighted the importance of the role played by the spatial distribution of hydrofacies on flows with a pronounced capillary barrier effect of the very coarse lithofacies and a sand lens leading to funneled flows by assuming that there is a direct link between the sedimentary lithological heterogeneity and the unsaturated hydrodynamic properties of the materials composing its different structures it was possible to perform a detailed hydrodynamic characterization of the unsaturated zone that could then be used to model flows and in particular highlight preferential flows

a hydrostratigraphic simplification approach to build 3d groundwater flow numerical models example of a quaternary deltaic deposit aquifer the construction of 3d hydrogeological models for unconsolidated sedimentary aquifers remains particularly challenging especially in quaternary deposits simplifications at small or large scale are part of groundwater flow modeling and are often required due on the usual inherent complexity of the stratigraphic systems this study analyzes the effects of hydrostratigraphic simplifications on the accuracy of 3d numerical groundwater flow models such investigation is conducted from an initial detailed model of an aquifer located in the saguenay lac st jean region in canada and the considered simplifications are based on using the equivalent hydraulic conductivity concept different levels or approaches of simplification are applied to numerical simulated models and the results of the different scenarios are compared a root mean square rms calibration result of 3 79 m on the groundwater levels is obtained for the most detailed model while the rms ranges between 4 01 and 4 83 m with the simplified models such results illustrate a gain obtained in the calibration of the model with increasing level of hydrostratigraphic details but that this gain is relatively limited the proposed methodology for simplifying the hydrostratigraphic settings could be used by hydrogeological modellers for a wide variety of aquifers constituted of sedimentary granular material

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

dynamical contrasts between pancake and pack ice investigated with a drifting buoy array 1 the motion of pancake ice was investigated using an array of specialised drifting buoys deployed into the advancing ice edge of the weddell sea in april 2000 the buoys remained in the ice as the pancakes consolidated into a coherent ice sheet and the study examined the contrasts in dynamics for equivalent periods before and after consolidation drift velocities were largely determined by the meridional component perpendicular to the ice edge prior to consolidation these showed significantly elevated magnitudes at high frequencies periods shorter than six hours scalar velocities were higher than previously reported values reducing with time and distance from the ice edge the same trends were not evident from in situ wind data derivation of momentum transfer parameters wind factor turning angle was hampered by a lack of reliable wind directions from the outermost buoys however relative motions between buoys were investigated using differential kinematic parameters these displayed high amplitude high frequency oscillations in unconsolidated ice with rms invariant values up to two orders of magnitude higher than normally reported for weddell sea pack ice the values were found to be strongly dependent on sampling interval increasing further at intervals less than one hour in situ winds did not display an equivalent variation suggesting that wind forcing was not responsible and translation under wave action either internal or surface gravity was postulated as the forcing

a wave based model for the marginal ice zone including a floe breaking parameterization 1 the marginal ice zone miz is the boundary between the open ocean and ice covered seas where sea ice is significantly affected by the onslaught of ocean waves waves are responsible for the breakup of ice floes and determine the extent of the miz and floe size distribution when the ice cover is highly fragmented its behavior is qualitatively different from that of pack ice with large floes therefore it is important to incorporate wave ice interactions into sea ice ocean models in order to achieve this goal two effects are considered the role of sea ice as a dampener of wave energy and the wave induced breakup of ice floes these two processes act in concert to modify the incident wave spectrum and determine the main properties of the miz a simple but novel parameterization for floe breaking is derived by considering alternatively ice as a flexible and rigid material and by using current estimates of ice critical flexural strain and strength this parameterization is combined with a wave scattering model in a one dimensional numerical framework to evaluate the floe size distribution and the extent of the miz the model predicts a sharp transition between fragmented sea ice and the central pack thus providing a natural definition for the miz reasonable values are found for the extent of the miz given realistic initial and boundary conditions the numerical setting is commensurate with typical ice ocean models with the future implementation into two dimensional sea ice models in mind

assessing small scale deformation and stability of landfast sea ice on seasonal timescales through l band sar interferometry and inverse modeling abstract rapid environmental change and increases in use of shorefast ice by industry and coastal communities highlight the need for an approach to accurately assess landfast sea ice stability on seasonal timescales while stability can sometimes be inferred from field measurements current methods are lacking robustness and the ability to be automated and applied over large areas and long time scales to ensure safety and document change in the context of transportation indigenous ice uses and industrial development this paper introduces an inverse model capable of reconstructing three dimensional deformation fields from one dimensional interferometric l band synthetic aperture radar sar phase patterns we apply this method at three landfast ice locations on the alaska beaufort sea coast near barrow and prudhoe bay we find the small scale displacements estimated from the model consistent with regional patterns of ice motion our study suggests that interferometry can provide planning and decision support information for ice road development and structures operating within ice moreover insar can potentially increase our understanding of sea ice on a fundamental level in terms of large scale stability and long term changes in ice dynamics

reorganization of ice sheet flow patterns in arctic canada and the mid pleistocene transition 1 evidence for the evolution of laurentide ice sheet lis basal thermal regime patterns during successive glaciations is poorly preserved in the geologic record here we explore a new approach to constrain the distribution of cold based ice across central baffin island in the eastern canadian arctic over many glacial interglacial cycles by combining till geochemistry and cosmogenic radionuclide crn data parts of the landscaped with geomorphic evidence for limited glacial erosion are covered by till characterized by high chemical index of alteration cia values and crn concentrations requiring complicated burial exposure histories till from regions scoured by glacial erosion have cia values indistinguishable from local bedrock and crn concentrations that can be explained by simple exposure following deglaciation crn modeling results based on these constraints suggest that the weathered tills were deposited by 1 9 to 1 2 ma and by that time the fiorded baffin island coastline must have developed close to its modern configuration as piracy of ice flow by the most efficient fiord systems resulted in a major shift in the basal thermal regime across the northeastern lis the resultant concentration of ice flow in fewer outlet systems may help explain the cause of the mid pleistocene transition from 41 to 100 kyr glacial cycles

meso and microscale sea ice motion in the east siberian sea as determined from ers 1 sar data synthetic aperture radar sar derived ice motion vectors and sar interferometry were used to study the sea ice conditions in the region between the coast and 75 n 560 km in the east siberian sea in the vicinity of the kolyma river ers 1 sar data were acquired between 24 december 1993 and 30 march 1994 during the 3 day repeat ice phase of the satellite the time series of the ice motion vector fields revealed rapid 3 day changes in the direction and displacement of the pack ice longer term 1 month trends also emerged which were related to changes in large scale atmospheric circulation on the basis of this time series three sea ice zones were identified the near shore stationary ice zone a transitional ice zone and the pack ice zone three 3 day interval and one 9 day interval interferometric sets amplitude correlation and phase diagrams were generated for the end of december the begining of february and mid march they revealed that the stationary ice zone adjacent to the coast is in constant motion primarily by lateral displacement bending tilting and rotation induced by atmospheric oceanic forcing the interferogram patterns change through time as the sea ice becomes thicker and a network of cracks becomes established in the ice cover it was found that the major features in the interferograms were spatially correlated with sea ice deformation features cracks and ridges and major discontinuities in ice thickness

high resolution aquifer analog of fluvial aeolian sediments of the guarani aquifer system the guarani aquifer system gas represents one of the biggest aquifers in the world and is the most relevant groundwater resource in south america for the first time by combining field and laboratory measurements a high resolution aquifer analog model of fluvial aeolian sediments of the gas in sao paulo state brazil is constructed three parallel sections of frontal outcrops 28 m 5 8 m and two parallel sections of lateral outcrops 7 m 5 8 m are recorded during open pit mining of sandy sediments and describe in detail the three dimensional distribution of the local lithofacies and hydrofacies variations of hydraulic conductivity k and porosity n are resolved on the centimeter scale and the most permeable units of the fluvial aeolian facies association are identified the constructed aquifer analog model shows moderate hydraulic heterogeneity and a mean k value of 1 36 10 4 m s which is greater than the reported range of k values for the entire gas in sao paulo state the results suggest that the examined sedimentary unit constitutes a relevant portion of the gas in sao paulo state in the context of groundwater extraction and pollution moreover the constructed aquifer analog is considered an ideal basis for future numerical model experiments aiming at in depth understanding of the groundwater flow and contaminant transport patterns at this gas portion or at comparable fluvial aeolian facies associations

determination of the effective hydraulic conductivity for heterogeneous porous media using a numerical spectral approach 1 method using the numerical spectral method described in the companion paper dykaar and kitanidis this issue the effective conductivity of a three dimensional isotropic stationary lognormally distributed hydraulic conductivity is computed six cases were investigated for variances in log conductivity ranging between 1 and 6 the results show that averaging volumes of at least 30 integral scales are required before the effective conductivity reaches its asymptotic value the results support matheron s 1967 hypothesis that ke kg exp y2 6 where ke is the effective hydraulic conductivity and kg and y2 are the geometric mean and variance respectively of the hydraulic conductivity field we also find that for a gaussian covariance function heterogeneities smaller than about 1 3 integral scales do not significantly contribute to the effective conductivity in two dimensions averaging volumes of more than 80 integral scales are required before the effective conductivity reaches the analytic infinite domain result of the geometric mean while the effective conductivity is insensitive to heterogeneities less than 2 integral scales in size the method is also applied to data from a shale and sandstone formation and the results are compared with those from other methods