seasonal climatic forcing of alpine glaciers revealed with orbital synthetic aperture radar the evolution of four dynamic radar glacier zones at the surface of an alpine icefield in british columbia is monitored using a time series of 35 first european remote sensing satellite ers 1 synthetic aperture radar sar images acquired from 1992 to 1994 these zones result from changing wetness and textural properties and appear to represent 1 cold snow with no liquid water present 2 an initial melt front with an upper boundary near the elevation of the 0 isotherm 3 metamorphosed rapidly melting first year snow with a rough or pitted surface and 4 bare ice this interpretation is aided by temperature and runoff data air photographs and field measurements of snowpack properties acquired simultaneously with two ers i sar scenes ice surface elevations derived from 1 50 000 topographic maps and simulations of radar backscatter from a geometric optics model of surface scattering meltwater production is affected by the development of zones 2 3 and 4 which form migrate up elevation and disappear each year between april and september

remote sensing of the albedo and detection of the slush line on the greenland ice sheet advanced very high resolution radiometer images of a section of the greenland ice sheet western part between 64 5 and 70 5 n with a size of 667 n s by 700 w e km were processed in order to retrieve the surface albedo the images were for the summer seasons of 1990 1997 inclusive and results were compared to simultaneous mass balance measurements carried out along the transect 67 n the main findings are as follows first many images show a distinct transition from low spatial variability of the albedo at higher elevations to higher spatial variability of the albedo at lower elevations it is argued that these transitions most likely correspond to transitions at the surface slush line in short from the area that is uniformly covered by snow to a mosaic of snow patches slush and ice second 70 of the interannual variations in the mean specific mass balance can be explained by interannual variations in the maximum elevation of the slush line i e the slush limit however a higher percentage 82 can be explained by interannual variations in the sum of positive degree days third in 3 years with a relatively large amount of melt the inland migration of the slush line stopped or slowed considerably down at a fixed distance from the ice sheet margin we believe that this so called maximum slush line coincides with an abrupt change in the density profile the maximum slush line forms an important limitation for the use of satellite data to monitor interannual variations in the mass balance its position is a climate indicator and was determined for the entire section of the greenland ice sheet investigated

significant effect of sediment cohesion on delta morphology delta morphology is thought to be controlled by factors such as river discharge tides and waves numerical modelling shows that sediment cohesion also strongly influences the development of a delta s characteristics the morphologies of the world s deltas are thought to be determined by river discharge tidal range and wave action 1 more recently sea level rise 2 3 and human engineering4 have been shown to shape delta evolution the effects of factors such as sediment type and the overall amount of sediment carried by rivers are considered secondary4 5 6 in particular the role of sediment cohesion which is controlled by sediment size and type of vegetation is unclear here we use a numerical flow and transport model7 8 9 10 to show that sediment cohesiveness also strongly influences the morphology of deltas we find that holding all other factors constant highly cohesive sediments form bird s foot deltas with rugose shorelines and highly complex floodplains whereas less cohesive sediments result in fan like deltas with smooth shorelines and flat floodplains in our simulations sediment cohesiveness also controls the number of channels that form within the deltas and the average angle of bifurcation of those channels as vegetation generally acts as a cohesive agent we suggest that deltas that formed before the expansion of land plants in the devonian period should show fan like characteristics a finding consistent with the limited data from the sedimentological record11

glacier recession on kilimanjaro east africa 1912 89 the varying ice extent on the kibo cone of kilimanjaro east africa this century was reconstructed from terrestrial photogrammetric mappings in 1912 and 1953 and satellite images in 1976 and 1989 these were all conformed to the official 1 50 000 topographic sheet the ice distribution on kibo is characterized by lower ice margins on the southern than on the northern flanks and deepest reaching glaciers to the west contrasting with least ice cover on the eastern crater rim the meridional contrast appears to be related to the more abundant precipitation on the southern side the even more striking zonal asymmetry in ice cover is favored by the vigorous diurnal circulations with enhanced afternoon cloudiness blocking insolation on the western slopes the total ice cover diminished from 12 058 to 6675 to 4171 to 3305 x 10 3 m 2 between the years 1912 1953 1976 and 1989 and the three large coherent ice bodies disintegrated into numerous smaller ice fragments

the ainsa fold and thrust oblique zone of the central pyrenees kinematics of a curved contractional system from paleomagnetic and structural data this work was funded by the project intectosal cgl2010 21968 c02 01 and by the grup de recerca de geodinamica i analisi de conques 2009sgr1198 secretaria d universitat i recerca del departament d economia i coneixement de la generalitat de catalunya josep poblet acknowledges financial support by research projects geociencias en iberia estudios integrados de topografia y evolucion 4d topo iberia csd2006 041 and desarrollo de fracturas y venas asociadas al plegamiento fraveple cgl2011 23628 funded by spanish ministries

arsenic toxicity of groundwater in parts of the bengal basin in india and bangladesh the role of quaternary stratigraphy and holocene sea level fluctuation arsenic toxicity in groundwater in the ganges delta and some low lying areas in the bengal basin is confined to middle holocene sediments dissected terraces and highlands of pleistocene and early holocene deposits are free of such problems arsenic rich pyrite or other arsenic minerals are rare or absent in the affected sediments arsenic appears to occur adsorbed on iron hydroxide coated sand grains and clay minerals and is transported in soluble form and co precipitated with or is scavenged by fe iii and mn iv in the sediments it became preferentially entrapped in fine grained and organic rich sediments during mid holocene sea level rises in deltaic and some low lying areas of the bengal basin it was liberated subsequently under reducing conditions and mediated further by microbial action intensive extraction of groundwater for irrigation and application of phosphate fertilizer possibly triggered the recent release of arsenic to groundwater this practice has induced groundwater flow mobilizing phosphate derived from fertilizer as well as from decayed organic matter which has promoted the growth of sediment biota and aided the further release of arsenic however the environment is not sufficiently reducing to mobilize iron and arsenic in groundwater in the ganges floodplains upstream of rajmahal thus arsenic toxicity in the groundwater of the bengal basin is caused by its natural setting but also appears to be triggered by recent anthropogenic activities

a method for monitoring glacier mass balance using satellite albedo measurements application to vatnajskull iceland we compare satellite albedo images of vatnajokull iceland with mass balance measurements for the years 1991 99 we find that the equilibrium line is mostly not visible when it is located above its position of the previous year s equilibrium line detection is further hindered by clouds and a gradual transition between ice and firn or snow consequently firn line elevation at the end of the melting season is not particularly useful for estimating the annual mass balance instead we propose to study the mean albedo of the entire ice cap throughout the melting season so that all available information about the surface albedo is taken into account the mean net potential global radiation which can be estimated from the mean surface albedo alone both depends on and influences summer melt it also depends on winter precipitation and integrated over the melting season is found to relate linearly to the specific mass balance b r 0 87 and 0 94 for different outlets of vatnajokull b can be estimated quantitatively when this relation is known and qualitatively when it is not the uncertainty in the satellite derived value of b is 0 5 0 8 m w e which for vatnajokull corresponds to about 27 of the interannual variability of b

mass balance of himalayan glaciers using aar and ela methods the accumulation area ratio aar for himalayan glaciers representing zero mass balance is substantially lower than for north america and europe regression analysis suggests 0 44 for the aar representing zero mass balance in the western himalaya a good correlation was observed when this method was applied to individual glaciers such as gara and gor garang in himachal pradesh india the correlation coefficients r using 6 and 7 years of data respectively were 0 88 and 0 96 for gara and gor garang glaciers respectively however when data from six western himalayan glaciers were correlated the correlation was 0 74 the aar was also estimated by using landsat images which can be useful in obtaining a trend in mass balance for a large number of himalayan glaciers for which very little information exists a higher correlation was observed between equilibrium line altitude ela and mass balance the field data from gara and gor garang glaciers shows a high correlation coefficient i e 0 92 and 0 94 respectively the ela values obtained from the landsat satellite images combined with topographic maps suggest positive mass balance for the year 1986 87 and negative for 1987 88

predicting delta avulsions implications for coastal wetland restoration river deltas create new wetlands through a continuous cycle of delta lobe extension avulsion and abandonment but the mechanics and timing of this cycle are poorly understood here we use physical experiments to quantitatively define one type of cycle for river dominated deltas the cycle begins as a distributary channel and its river mouth bar prograde basinward eventually the mouth bar reaches a critical size and stops prograding the stagnated mouth bar triggers a wave of bed aggradation that moves upstream and increases overbank flows and bed shear stresses on the levees an avulsion occurs as a time dependent failure of the levee where the largest average bed shear stress has been applied for the longest time r 2 0 93 these results provide a guide for predicting the growth of intradelta lobes which can be used to engineer the creation of new wetlands within the delta channel network and improve stratigraphic models of deltas

quantifiable effectiveness of experimental scaling of river and delta morphodynamics and stratigraphy laboratory experiments to simulate landscapes and stratigraphy often suffer from scale effects because reducing length and time scales leads to different behaviour of water and sediment classically scaling proceeded from dimensional analysis of the equations of motion and sediment transport and minor concessions such as vertical length scale distortion led to acceptable results in the past decade many experiments were done that seriously violated these scaling rules but nevertheless produced significant and insightful results that resemble the real world in quantifiable ways here we focus on self formed fluvial channels and channel patterns in experiments the objectives of this paper are 1 to identify what aspects of scaling considerations are most important for experiments that simulate morphodynamics and stratigraphy of rivers and deltas 2 to establish a design strategy for experiments based on a combination of relaxed classical scale rules theory of bars and meanders and small scale experiments focussed at specific processes we present a number of small laboratory setups and protocols that we use to rapidly quantify erosional and depositional types of forms and dynamics that develop in the landscape experiments as a function of detailed properties such as effective material strength and to assess potential scale effects most importantly the width to depth ratio of channels determines the bar pattern and meandering tendency the strength of floodplain material determines these channel dimensions and theory predicts that laboratory rivers should have 1 5 times larger width to depth ratios for the same bar pattern we show how floodplain formation can be controlled by adding silt sized silicaflour bentonite medicago sativa alfalfa or partially hydrolyzed polyacrylamide a synthetic polymer to poorly sorted sediment the experiments demonstrate that there is a narrow range of conditions between no mobility of bed or banks and too much mobility the density of vegetation and the volume proportion of silt allow well controllable channel dimensions whereas the polymer proved difficult to control the theory detailed methods of quantification and experimental setups presented here show that the rivers and deltas created in the laboratory seem to behave as natural rivers when the experimental conditions adhere to the relaxed scaling rules identified herein and that required types of fluvio deltaic morphodynamics can be reproduced based on conditions and sediments selected on the basis of a series of small scale experiments

estimating the mass balance of vatnajokull iceland from noaa avhrr imagery we investigate the possibility of obtaining the mass balance of vatnajo kull iceland from us national oceanic and atmospheric administration noaa advanced very high resolution radiometer avhrr albedo images for the years 1991 2002 de ruyter de wildt and others 2002 demonstrated that the mean potential absorbed radiation averaged over the melting season correlates well with the mean specific mass balance and that can be estimated from the evolution of the surface albedo here we improve the retrieval method of de ruyter dewildt and others 2002 by introducing the more realistic 6s atmospheric transfer model and by adding the latest narrowto broadband ntb albedo conversion equations bidirectional reflectance distribution functions for both ice and snow are used where appropriate we show that the choice of the ntb conversion equations greatly influences the calculated measured mass balance correlates well with if enough cloud free images can be found through the year and if the spatial variation in measured mass balances is high enough the correlation coefficient for all drainage basins combined is 0 92 with a residual standard deviation of 0 18mw e we present an estimated mass balance series for the whole of vatnajo kull based on our findings switching between different avhrr instruments over time may cause serious errors in the calculated mass balance

firn line detection on austre okstindbreen norway with airborne multipolarization sar we examine the ability of synthetic aperture radar sar to detect the equilibrium line on the glacier austre okstindbreen norway using multipolarization sar images in c and l band acquired with the electromagnetic institute of the technical university of denmark s airborne emisar sensor during the european multisensor airborne campaign emac 95 the late summer snowline approximating the equilibrium line cannot be seen on the sar images instead photographs from austre okstindbreen show that a distinct boundary visible on the c band sar images corresponds to the firn line created by old snow from many previous years this is better seen on the cross polarized sar images hv and vh which in general reveal more detail than the hh and vv polarized images we model the stratigraphy from net balance and glacier velocity data to calculate the firn line altitude fla modelled fla and the observed boundary are separated by 50 m in elevation but considering errors during co registration and modelling we conclude that the observed boundary on austre okstindbreen is the firn line monitoring fla rather than equilibrium line altitude ela for mass balance studies with remote sensing is therefore suggested

strike variability of clastic depositional systems does it matter for sequence stratigraphic analysis current sequence stratigraphic models are two dimensional in nature and predict variability in depositional dip sections strike and dip variability of sediment supply to clastic depositional systems causes significant changes to sequence architecture so that contrasting yet coeval stacking patterns result these changes ultimately affect prediction potential based on fixed systems tract stacking patterns and relation to relative sea level curves identification of key surfaces in sequences rather than stacking patterns is the most reliable indicator of relative sea level history

platform sedimentation and collapse in a carbonate dominated margin of a foreland basin jaca basin eocene southern pyrenees the eocene jaca basin is a foreland basin with well exposed carbonate platforms in the distal margin this margin underwent alternating periods of stable platform growth and platform drowning periods of drowning were accompanied by large scale collapses with generation of shelf edge truncations and resedimentation of carbonate megabreccias into a terrigenous turbiditic trough these features caused a stepped retreat of the platforms and are related to episodic variations of tectonic loading in the hinterland and correlative flexural bending of the distal basin

advances in borehole imaging technology and applications abstract borehole imaging devices are currently available for both wireline and logging while drilling lwd environments for use in both openhole and cased wells most wireline and all lwd devices provide indirect images that are derived from a high density grid of electrical or ultrasonic acoustic measurements optical techniques such as television and photography provide direct images of the borehole imaging devices consist of 1 a rotating sensor acoustic or electrical that scans the borehole with each revolution 2 multiple azimuthally placed sensors or 3 a downhole television or photographic camera advances in digital acquisition and processing permit real time display and evaluation of images of the open borehole or the inside of casing the resolution and borehole coverage of microelectrode devices has increased with newer designs that allow additional measurement sensors per pad additional pad segments on a four arm tool and the introduction of six arm imaging tools in nonconductive borehole fluids a four arm microinduction device can provide crude images macroelectrode imaging tools laterolog type wireline provide lower resolution electrical images from either an azimuthal arrangement of sensors around a mandrel wireline or from azimuthally sensitive sensors logging while drilling that scan the borehole during rotation of the bottomhole assembly in acoustic imaging recent devices incorporate design changes that provide improved image resolution and operate in a wider range of borehole conditions ultrasonic transducers now use lower transmitting frequencies and spherical focusing and these tools also offer surface selectable acquisition parameters acoustic and microresistivity imaging techniques measure different physical properties and these data are complementary one recently introduced wireline service combines microresistivity and acoustic imaging devices in a single tool for simultaneous single pass acquisition recent advances in cable and sonde design permit downhole video in a wider range of petroleum environments in flowing wells and in tubing openhole image interpretation involves qualitative visual identification and quantitative characterization of strike and dip on planar features lithology bedding fractures and vugs when core is available features identified on log derived images can be correlated or calibrated to it or when core is absent images may serve as a substitute borehole images are useful in formation evaluation when calibrated sedimentology stratigraphy and structural analysis current applications include core orientation reconstructing missing core identification and characterization of fractures and depositional features e g bedforms reservoir architecture bedding grain size porosity permeability net sand and net pay counts faults folds and fractures hydrocarbon water geothermal wells and in rock engineering evaluation of borehole stress borehole stability directional placement of wellbore for optimal drainage fractured reservoirs evaluation of fracture stimulations and perforation control cased hole applications include cement evaluation casing inspection detection of fluid entry identifying production blockages and assisting in fishing operations

integration of outcrop and borehole image logs for high resolution facies interpretation example from a fluvial fan in the ebro basin spain electrical borehole image logs yield high resolution information about variations in micro resistivity along the borehole wall to interpret these variations in terms of sedimentary structures and lithofacies types calibration with real rock is needed normally the only real rock available is core and this only provides one dimensional information in this paper the interpretation of fluvial facies types from borehole image logs was established by direct comparison with outcrops four fluvial facies associations were established in an outcrop study of a low net to gross fluvial succession i meandering rivers ii braided rivers iii crevasse deltas and iv crevasse splays the lithofacies characteristics and palaeocurrent distributions of each fluvial facies association were established two 200 m deep wells were drilled behind the cliff face outcrops one well was cored to a depth of 150 m and borehole image logs were recorded in both wells the wells were correlated with the outcrop the borehole image logs were analysed by their vertical colour succession and the dipmeter pattern image log facies were established and these were interpreted in terms of the fluvial facies associations encountered in the corresponding outcrops the study of borehole image logs yields a set of diagnostic criteria for a detailed fluvial facies interpretation and the establishment of depositional trends and thus provides a powerful tool for the direct interpretation of fluvial facies in a reservoir setting

combining geologic process models and geostatistics for conditional simulation of 3 d subsurface heterogeneity 1 the goal of simulation of aquifer heterogeneity is to produce a spatial model of the subsurface that represents a system such that it can be used to understand or predict flow and transport processes spatial simulation requires incorporation of data and geologic knowledge as well as representation of uncertainty classical geostatistical techniques allow for the conditioning of data and uncertainty assessment but models often lack geologic realism simulation of physical geologic processes of sedimentary deposition and erosion process based modeling produces detailed geologically realistic models but conditioning to local data is limited at best we present an aquifer modeling methodology that combines geologic process models with object based multiple point and variogram based geostatistics to produce geologically realistic realizations that incorporate geostatistical uncertainty and can be conditioned to data first the geologic features of grain size or facies distributions simulated by a process based model are analyzed and the statistics of feature geometry are extracted second the statistics are used to generate multiple realizations of reduced dimensional features using an object based technique third these realizations are used as multiple alternative training images in multiple point geostatistical simulation a step that can incorporate local data last a variogram based geostatistical technique is used to produce conditioned maps of depositional thickness and erosion successive realizations of individual strata are generated in depositional order each dependent on previously simulated geometry and stacked to produce a fully conditioned three dimensional facies model that mimics the architecture of the process based model we demonstrate the approach for a typical subsea depositional complex

variations in snowpack melt on the greenland ice sheet based on passive microwave measurements a simple microwave emission model is used to simulate 37 ghz brightness temperatures associated with snowpack melt conditions for locations across the greenland ice sheet the simulated values are utilized as threshold values and compared to daily gridded smmr and ssm i passive microwave data in order to reveal regions experiencing melt the spatial extent of the area classified as melting is examined on a daily monthly and seasonal may august basis for 1979 91 the typical seasonal cycle of melt coverage shows melt beginning in late april a rapid increase in the melting area from mid may to mid july a rapid decrease in melt extent from late july through mid august and cessation of melt in late september seasonal averages of the daily melt extents demonstrate an apparent increase in melt coverage over the 13 year period of approximately 3 8 annually significant at the 95 confidence interval this increase is dominated by statistically significant positive trends in melt coverage during july and august in the west and southwest of the ice sheet we find that a linear correlation between microwave derived melt extent and a surface measure of ablation rate is significant in june and july but not august so caution must be exercised in using the microwave derived melt extents in august nevertheless knowledge of the variability of snowpack melt on the greenland ice sheet as derived from microwave data should prove useful in detecting climate change in the arctic and examining the impact of climate change on the ice sheet

architecture of the tectonically influenced sobrarbe deltaic complex in the ainsa basin northern spain abstract the syn tectonic sobrarbe deltaic complex eocene of the ainsa basin spanish pyrenees is confined by lateral thrust ramps and influenced by intra basinal growth anticlines six facies associations have been distinguished within the deltaic complex i slope marls and turbidite sandstones ii distal delta front silty and bioturbated sandstones iii proximal delta front and delta plain deposits tidal inlet tidal flat mouth bar bay distributary channel and floodplain environments iv biogenic deposits at flooding surfaces v collapse zone sediments and vi nummulite dominated shallow marine carbonates the deltaic complex comprises four composite sequences which each contain a number of minor sequences of the genetic maximum flooding surface bounded type regressive unconformities and their correlative surfaces separate the composite sequences cs and each cs can be divided into lowstand transgressive and highstand components at the base the comaron cs is a wnw prograding deltaic complex containing six minor sequences characterized by basinward stepping sandstone wedges separated by transgressive mudstones double regressive unconformities are often associated with these sandstone wedges proximally in the basin growth of the intra basinal arcusa anticline caused gentle folding of the comaron cs and syn growth strata at the base of the overlying las gorgas cs contain a prominent forced regressive sandstone wedge the las gorgas sandbody and display thinning of bedsets onto the crest of the anticline moreover it can be demonstrated that relative sea level rise took place in the growth synclines at the same time as a fall in relative sea level occurred on the growth anticlines the tectonic deformation caused a shift in the direction of deltaic progradation towards the north northwest as demonstrated by the well developed clinoforms in the highstand sequence set of the las gorgas cs a second phase of tectonic activity this time triggering large scale collapse of the delta front occurred at the transition between the las gorgas and barranco el solano cs tilting of the basin floor led to the development of coeval transgressive and regressive strata separated by a fulcrum line of zero net vertical movement of the shoreline in the post tilt phase reduced sediment supply and accelerated subsidence led to widespread transgression and a change from clastic to carbonate dominated sedimentation this phase was terminated by a gradual increase in sediment supply causing progradation of a mixed clastic carbonate system dominated by large nummulite banks and bioturbated shoreface marls and sandstones finally a pronounced fall in relative sea level associated with the transition to the buil cs triggered slope instabilities and eventually established fluvial conditions all over the study area with the exception of the anticline crests the relatively high rate of tectonic subsidence in the study area suppressed relative sea level falls resulting in development of discontinuous lowstand strata and bounding surfaces the segmented nature of many regressive unconformities may be related to incremental growth of thrust related structures and each segment is separated from neighbouring segments by gaps of limited vertical and lateral displacement precursors of progressive unconformities are seen in the upper proximal part of the comaron cs by downdip fanning and updip convergence of minor sequences these differentially tilted stratal units provide reliable indicators of syn sedimentary tectonism

assessment of the surface mass balance along the k transect greenland ice sheet from satellite derived albedos this paper explores the potential of using satellite derived albedos to estimate the surface mass balance of the kangerlussuaq transect k transect greenland ice sheet we first retrieved surface albedos from advanced very high resolution radar data by using among other techniques a new cloud detection algorithm based on the relation between brightness temperature and surface elevation we then computed the satellite derived mass balance bsat from the mean albedo for the transect by taking fixed values for atmospheric transmissivity and the longwave and turbulent fluxes we found that bsat explains 71 of the variance in 13 years of stake mass balance measurements bm our method also provides good estimates of the magnitude of the interannual variability in bm the performance of the method degrades considerably without correction for anisotropic reflection at the surface and recalibration of the satellite sensors with dry snow at the top of the ice sheet sensitivity tests indicate that the method s performance is hardly sensitive to uncertainties in parameters therefore we expect that the method could be successfully applied on other glaciers and parts of ice sheets and ice caps especially where accumulation rates are relatively small we show that the investigated method performs best just below the mean equilibrium line altitude

glacier snow line mapping using ers 1 sar imagery abstract this article paper evaluates the effectiveness of ers 1 synthetic aperture radar sar imagery for mapping movement of the transient snow line in a temperate glacier basin during an ablation season the two primary objectives of this study are to normalize the topographically induced distortions radiometric and geometric inherent in sar imagery of rugged terrain and to delineate the snow line in the normalized imagery the radiometric distortions are normalized with a cosine correction and the image texture is enhanced to take advantage of the spatial distribution of tonal variations within each image to minimize geometric distortions and georeference the imagery each cosine corrected texture enhanced sar image is orthorectified to an error of approximately 60 m using a dem and satellite orbital and ephemeris data a supervised classification is performed on the orthorectified imagery to map the spatial distribution of snow and glacial ice within the basin the visual boundary between the wet snow and glacier ice surfaces on the orthorectified images is within 75 m horizontally of the snow line obtained from field data the glacier boundary is also discernible to within 75 m of the surveyed glacier outline several isolated bare ice areas on the lower glacier give a low return similar to wet snow resulting in some confusion between glacier ice and wet snow it is speculated that the incident wave is lost within the crevasses and surface runoff runnels due to specular reflection within the features despite the localised confusion between glacier ice and wet snow the wet snow line and can be mapped reasonably well and in a timely manner using ers i sar imagery

quantitative models of sedimentary basin filling summary quantitative modelling of the filling of sedimentary basins was begun in earnest in the 1960s dozens of themes and variations have been proposed since then and have yielded an abundance of idealized stratigraphic patterns as functions of both imposed changes and basin properties post plate tectonic modelling began with rigid lid models which show the stratigraphic signature of subsidence variation this work introduced the connection between stratigraphy and the rheology of the lithosphere rigid lid models are the simplest type of geometric model in which the sediment surface is assigned prescribed geometries usually corresponding to different depositional environments these can reproduce many aspects of overall stratal geometry but are formally restricted to relatively long timescales for which quasi steady surface topography can be assumed so called dynamic models attempt to represent the morphodynamics of the sediment surface by abstracting and averaging short term transport processes most of the dynamic models proposed to date can be seen as special cases of a single general morpho dynamic equation the most important result of the first wave of quantitative basin filling models is that even relatively simple models can produce reasonable stratal patterns we now have a wide array of tools for exploring scenarios searching for general behaviours and effects and making initial quantitative predictions we have also learned that basin response to external forcing as recorded in stratigraphy can be as sensitive to the characteristics of the basin as to the forcing the main brake on the development of basin modelling is not computing power but lack of methods and data for testing the models we have already developed physical experiments which are only just beginning are one means of doing this experimental stratigraphy is a bridge to quantitative field tests which will require collaboration among academic researchers from a wide range of areas and between academia and industry on projects of greater scale and degree of integration than we have seen so far the advancement of quantitative sedimentary geology will also require significant changes in the way the subject is taught at all levels

comparison of avhrr derived and in situ surface albedo over the greenland ice sheet abstract this paper discusses a methodology for computing the clear sky surface albedo over the greenland ice sheet by using advanced very high resolution radiometer avhrr global area coverage visible and near infrared reflectances this approach is then used to map the monthly changes in albedo over the entire greenland ice sheet during the spring and summer months the methodology includes corrections for the intervening atmosphere by using the 6s radiative transfer model additional corrections for the anisotropic nature o f snow reflectance and the conversion from a marrow into a broadband albedo are made based on in site measurements from the swiss federal institute of technology university of colorado camp at 69 34 n 49 18 w comparison with surface albedo field ineasureinents indicates that before the onset of snoic melt agreement is good between the satellite derived and measured surface albedo after melt begins it is difficult to compare the satellite values with the field data owing to melt water ponding on the ice sheet surface with appropriate modifications the 6s radiative transfer model is suitable for atmospherically correcting avhrr visible and near infrared radiances atmospherically polar regions

evaluation of remote sensing techniques to measure decadal scale changes of hofsjokull ice cap iceland dynamic surficial changes and changes in the position of the firn line and the areal extent of hofsjokull ice cap iceland were studied through analysis of a time series 1973 98 of synthetic aperture radar sar and landsat data a digital elevation model of hofsjokull which was constructed using sar interferometry was used to plot the sar backscatter coefficient vs elevation and air temperature along transects across the ice cap seasonal and daily patterns are caused by freezing or thawing of the ice cap surface and abrupt changes in are noted when the air temperature ranges from 5 to 0 c late summer 1997 sar and reflectance landsat boundaries agree and appear to be coincident with the firn line and a sar boundary that can be seen in the january 1998 sar image in january 1994 through 1998 the elevation of this boundary on the ice cap was quite stable ranging from 1000 to 1300 m while the equilibrium line altitude as measured on the ground varied considerably thus the equilibrium line may be obscured by firn from previous years techniques are established to measure long term changes in the elevation of the firn line and changes in the position of the ice margin

scaling relationships and evolution of distributary networks on wave influenced deltas 1 no genetic model can explain the variability in distributary network pattern on modern deltas here we derive scaling relationships for two processes known to create distributary channels and with these laws construct a simple model for distributary network evolution the first process is mouth bar deposition at the shoreline and subsequent channel bifurcation the second is avulsion the wholesale abandonment of a channel in favor of a new path the former creates relatively small networks with power law distributions of channel length the latter generates relatively few backwater scale distributaries frequency magnitude plots of channel length on natural deltas agree with theoretical predictions and show a clear separation in scale that reflects these processes mouth bar distributary lengths scale with the width of the parent channel and avulsive distributary lengths scale with the backwater length intermediate channel lengths are relatively rare wave energy controls network topology by suppressing mouth bar development thereby preferentially eliminating smaller scale distributaries

the use of remote sensing data for mass balance studies at mýrdalsjokull ice cap iceland a series of satellite images of myrdalsjokull iceland was analyzed in view of their value for mass balance investigations a combination of optical satellite images from the aster sensor and synthetic aperture radar data from ers 2 and envisat asar proved very useful the glacier margin of myrdalsjokull was delineated on aster images from summer and winter 2004 with a time series of summer asar images it was possible to monitor the temporal and spatial development of the transient snowline tsl throughout the year 2004 as well as the firn line fl at the end of the balance year an inverse function was applied to visually enhance detail in the radar imagery winter radar images were not useful for mass balance observations because of frequent surface melting which prevented the transparency of the snow cover for c band microwaves interannual mass balance fluctuations were observed by comparing three radar images acquired in late summer 1998 1999 and 2004 respectively these fluctuations follow the same trend as the annual mean air temperature which shows a strong increasing trend between 1999 and 2004 an accumulation area ratio of 0 43 was determined for 2004 indicating clear negative mass balance conditions monitoring the tsl fl with radar summer images for mass balance studies rather than the equilibrium line el is suggested for large ice caps in maritime climates

spatial and temporal variations of the surface albedo and other factors influencing urumqi glacier no 1 in tien shan china glacier albedo controls the surface energy budget the variability of which affects the glacier surface melt rate and in turn impacts the mass balance of the glacier during 2013 and 2014 spatial and temporal variations of albedo were investigated using 18 landsat images of urumqi glacier no 1 factors influencing these spatiotemporal profiles were analyzed an established retrieval process including geolocation radiometric calibration atmospheric topographic and anisotropic correction and narrow to broadband conversion was applied for the first time to landsat 8 images differences between landsat image derived albedo values and albedo values measured using a handheld spectroradiometer ranged from 0 024 to 0 049 spatial and temporal variations of surface albedo were significant especially in the ablation area the variability of the values of ice albedo ranged from 0 06 to 0 44 due to topographic effects and light absorbing impurities the results suggest that this retrieval method can be used to investigate the spatial and temporal variability of surface albedo from landsat 8 images on mountain glaciers moreover as constant albedo values for ice and snow cannot be assumed the distribution of albedo was not completely dependent on altitude under conditions of more intense ablation and by reason of light absorbing impurities during the melt season

groundwater flow in an arsenic contaminated aquifer mekong delta cambodia abstract to advance understanding of hydrological influences on as concentrations within groundwaters of southeast asia the flow system of an as rich aquifer on the mekong delta in cambodia where flow patterns have not been disturbed by irrigation well pumping was examined monitoring of water levels in a network of installed wells extending over a 50 km2 area indicates that groundwater flow is dominated by seasonally variable gradients developed between the river and the inland wetland basins while the gradient inverts annually net groundwater flow is from the wetlands to the river hydraulic parameters of the aquifer k 10 4 ms 1 and overlying clay aquitard k 10 8 ms 1 were determined using grain size permeameter and slug test analyses when coupled with observed gradients they indicate a net groundwater flow velocity of 0 04 0 4 ma 1 downward through the clay and 1 13 ma 1 horizontally within the sand aquifer producing aquifer residence times on the order 100 1000 a the results of numerical modeling support this conceptual model of the flow system and when integrated with observed spatial trends in dissolved as concentrations reveal that the shallow sediments upper 2 10 m of fine grained material are an important source of as to the underlying aquifer

large scale fluvial grade as a nonequilibrium state in linked depositional systems theory and experiment 1 a graded river conveys its sediment load without net aggradation or degradation grade is thought to represent the equilibrium state of a river system subject to steady allogenic forcing we address the concept of grade in linked depositional systems through a combination of mathematical modeling and flume experiments we develop a moving boundary morphodynamic model of fluviodeltaic sedimentation and use it to quantify the conditions necessary for a state of sustained grade in an alluvial deltaic system developing on a uniformly sloping shelf to test our theory we conducted a series of flume experiments in which we constructed laboratory scale fluviodeltaic systems under specific relative sea level histories on large spatiotemporal scales our theoretical and experimental results suggest an alternative view of grade as an intrinsically nonequilibrium state that requires a fall in relative sea level under conditions of stillstand or rise in relative sea level the equilibrium graded profile does not exist and the alluvial river will always aggrade with a steady sediment supply alluvial grade can be sustained if relative sea level falls with a specific square root of time dependence common sequence stratigraphic conceptualizations of alluvial river response to sea level change suggest that rivers aggrade and degrade in response to relative sea level rise and fall respectively we show that rivers can remain aggradational if the rate of sea level fall is sufficiently small the boundary between aggradational and degradational states is the graded state described here that associated with a relative sea level fall that varies with the square root of time

controls on river delta formation insights from numerical modelling abstract primary hydraulic and sedimentary controls on river deltas were previously postulated in classification schemes in the field of sedimentary geology based on many field observations however detailed mechanistic models were restricted to the river dominated delta class analogous to the concept of morphological conditioning here we show that antecedent stratigraphy controls morphometrics of prograding river dominated delta distributary networks under steady sea level further we use coupled hydrodynamic morphodynamic stratigraphic detailed numerical modelling to assess the influence of wind generated waves and tides on clastic river delta formation our synthetic simulations show that deltas forming under mere riverine forcing prograde via sequences of mouth bar induced flow bifurcation and upstream channel shifting windwave action suppresses sequestration of fine sediments on the developing delta plain entailing relatively smooth shorelines perturbed by a limited number of distributary channels in contrast tide influenced river deltas are found to prograde mainly via lengthening of initially formed relatively stable distributaries as well as being characterized by cyclicity in deposits interbedding of sands and silts these results provide a framework for physics based river delta modelling under various environmental conditions particularly our findings suggest that relatively low energetic basin conditions can already significantly impact morphological and stratal patterns of prograding river deltas

validation of avhrr and modis derived albedos of snow and ice surfaces by means of helicopter measurements we describe the validation of surface albedos of snow and glacier ice as derived from advanced very high resolution radiometer avhrr and moderate resolution imaging spectrometer modis satellite data for this purpose we measured surface albedos from a helicopter over vatnajokull iceland and the kangerlussuaq transect western part of the greenland ice sheet in thematic mapper tm bands 2 and 4 and avhrr bands 1 and 2 and converted these values to measured albedos in three modis bands relative to other validation methods our helicopter measurements have the advantages of larger spatial coverage and of almost direct measurements in satellite sensor spectral bands we found the smallest differences between the satellite derived and helicopter albedos for the kangerlussuaq transect for avhrr data a mean difference of 0 01 in both bands with the satellite in near nadir position and for two modis images a mean difference of 0 00 0 02 for bands 2 and 4 and 0 03 for band 1 for two avhrr images of vatnajokull we found mean differences of up to 0 06 differences are primarily due to errors in the satellite derived albedos which in turn are mainly caused by errors in the calibration coefficients of the satellite sensors and insufficient knowledge of the angular distribution of the radiation reflected by snow and ice satellite data obtained from view zenith angles larger than 50 55 appeared to be unsuitable

influence of steady base level rise on channel mobility shoreline migration and scaling properties of a cohesive experimental delta 1 here we describe results from an alluvial delta physical experiment with and without steady base level rise using a unique cohesive sediment mixture that promotes the development of persistent channels and a rugose shoreline we quantitatively characterize channel network properties as a function of base level rise in a distributary system that reproduces many aspects of the geometry of natural deltas analysis of the experimental data shows clear dynamical differences between the predominantly progadational and aggradational phases of the experiment the experiment was conducted in two phases a first in which the delta prograded into standing water of constant depth in the absence of base level rise and a second during which steady base level rise was imposed on the system forcing a twofold increase in topset aggradation due to greater sediment retention in the fluvial reach the shift in sediment mass balance to enhanced fluvial deposition in the second phase caused channel network mobility to increase reducing the autogenic channel time scale from 23 5 to 12 5 h and supporting a positive correlation between deposition and channel avulsion frequency an independent shoreline time scale that characterizes the dominant time over which shoreline regression is persistent closely correlates with measurements of the channel network 28 3 h during fan progradation and 9 5 h during fan aggradation these metrics suggest a strong coupling between channel network and shoreline kinematics and a more active fluvial surface during fan aggradation by a factor of 2 to 3 similar to the increase in aggradation rate spatial scaling of shoreline roughness reveals that maximum shoreline variability is set by the scale of distributary lobes strong coupling exists between delta growth and shoreline geometry during progradation during aggradation however shoreline variability is not solely due to distributary lobe growth but is also set by shoreline transgression over inactive portions of the delta illustrating a decoupling between fan kinematics and fan geometry this decoupling together with the matched increase in channel network mobility and fluvial aggradation suggest the stratigraphic architecture may not be a strong geometric signal of different fluvial surface conditions either

hypsometry and sensitivity of the mass balance to changes in equilibrium line altitude the case of the southern patagonia icefield we study the relation between glacier hypsometry and sensitivity of mass balance rate to changes in equilibrium line altitude ela our aim is to assess whether hypsometry can be reliably used as an estimator of the sensitivity of unmeasured glaciers to changes in ela we express the sensitivity of mass balance rate to ela d dot b dela as a function of accumulation area ratio aar its derivative against altitude daar dela and mass balance functions of ela we then apply the concept to 139 glaciers in the southern patagonia icefield for which we derive hypsometry and aar and analyze the influence of hypsometry on their mass balance rate sensitivity we confirm that glaciers where the bulk of area is located above the ela are the least sensitive whereas those where the bulk of area is located below the ela are the most sensitive glaciers with unimodal hypsometric curves where the peak of area fraction is around the present ela and glaciers with bi or multimodal area distributions with the ela located approximately between the bulges have intermediate sensitivities we conclude that hypsometry can be used as a first order estimator of the mass balance rate sensitivity to ela change

narrowband to broadband albedo conversion for glacier ice and snow based on aircraft and near surface measurements this article presents albedo measurements of snow and glacier ice at vatnajokull iceland and the kangerlussuaq transect greenland radiative fluxes were measured in the broadband and in four narrowbands namely thematic mapper tm bands 2 and 4 and advanced very high resolution radiometer avhrr bands 1 and 2 the incoming fluxes were measured near the ground and the outgoing fluxes from a helicopter extracts of the data collected over snow ice supraglacial moraines supraglacial lakes and tundra are discussed using the data sets from iceland and greenland and data sets with entirely ground based albedo measurements from the morteratschgletscher switzerland and scharffenbergbotnen antarctica new equations for narrowband to broadband ntb conversion were developed they have a residual standard deviation of 0 011 for tm and 0 008 for avhrr and can be applied without having to classify the surface the helicopter data are also used to develop criteria for distinguishing different types of surfaces which are needed for the application of bidirectional reflectance distribution functions brdfs snow can be distinguished from ice by defining a threshold for a single narrowband albedo the ratio of the albedos in tm4 and tm2 and to a lesser extent the ratio of the albedos in avhrr2 and avhrr1 may serve as a proxy for the surface characteristics of glacier ice in terms of concentrations of water debris and dust

comparison of satellite derived with ground based measurements of the fluctuations of the margins of vatnajokull iceland 1973 92 vatnajokull iceland is the earth s most studied ice cap and represents a classical glaciological field site on the basis of s palsson s seminal glaciological field research in the late 18th century since the 19th century vatnajokull has been the focus of an array of glaciological studies by scientists from many nations including many remote sensing investigations since 1951 landsat derived positions of the termini of 11 outlet glaciers of vatnajokull were compared with frontal positions of six of these 11 outlet glaciers determined by field observations during the period 1973 92 the largest changes during the 19 year period 1973 92 occurred in the large lobate surge type outlet glaciers along the southwestern western and northern margins of vatnajokull tungnaarjokull receded 1413 112 m 1380 1 m from ground observations and bruarjokull receded 1975 191 m 2096 5 m from extrapolated ground observations between 1973 and 1992 satellite images can be used to delineate glacier margin changes on a time lapse basis if the glacier margin can be spectrally discriminated from terminal moraines and sandur deposits and if the advance recession is larger than maximum image pixel size local knowledge of glaciers is critically important however in the accurate delineation of glacier margins on landsat images

backwater controls of avulsion location on deltas river delta complexes are built in part through repeated river channel avulsions which often occur about a persistent spatial node creating delta lobes that form a fan like morphology predicting the location of avulsions is poorly understood but it is essential for wetland restoration hazard mitigation reservoir characterization and delta morphodynamics following previous work we show that the upstream distance from the river mouth where avulsions occur is coincident with the backwater length i e the upstream extent of river flow that is affected by hydrodynamic processes in the receiving basin to explain this observation we formulate a fluvial morphodynamic model that is coupled to an offshore spreading river plume and subject it to a range of river discharges results show that avulsion is less likely in the downstream portion of the backwater zone because during high flow events the water surface is drawn down near the river mouth to match that of the offshore plume resulting in river bed scour and a reduced likelihood of overbank flow furthermore during low discharge events flow deceleration near the upstream extent of backwater causes enhanced deposition locally and a reduced channel fill timescale there both mechanisms favor preferential avulsion in the upstream part of the backwater zone these dynamics are fundamentally due to variable river discharges and a coupled offshore river plume with implications for predicting delta response to climate and sea level change and fluvio deltaic stratigraphy

temporal and spatial variation of the surface albedo of the morteratschgletscher switzerland as derived from 12 landsat images this investigation uses landsat images from 12 days in 1999 and 2000 to study the spatial and temporal variation in surface albedo of a glacier with a rugged topography morteratschgletscher switzerland our retrieval method considers all processes that substantially influence the relationship between the satellite signal and the surface albedo the correction for the anisotropy of the reflected radiation field of ice and snow ranges up to 0 10 depending on wavelength band solar zenith angle and surface type we analyzed the uncertainties in the retrieval method and mainly expect errors in satellite derived albedos for areas with large variation in topography and high albedos the latter is due to application of bidirectional reflectance distribution function brdf parameterizations for the anisotropic correction to albedos outside the parameterizations validity on average satellite derived albedos exceed the measured surface albedo by 0 03 the glacier tongue is characterized by bands of low and high albedo relating to ice with higher and lower concentrations of debris the ice albedo shows no dependence on altitude except at 2000 2200 m a s l it increases during summer which is likely associated with rainfall as concluded from a comparison between summer rainfall and measured albedos

limitations in identifying the equilibrium line altitude from the optical remote sensing derived snowline in the tien shan china optical remote sensing derived end of summer snowline altitude sla has long been employed on glaciers as an indicator of the equilibrium line altitude ela in the tien shan northwest china both accumulation and ablation of glaciers occur mainly in the warm season making it difficult to obtain the representative snowline highest snowline in the area the high spatio temporal resolution of hj 1 satellite images enables the highest snowline to be acquired in this paper we compare image derived sla and measured in situ ela for two adjacent glaciers in the tien shan over the period 2009 10 results indicate that 1 in 2009 there was a substantial difference between sla and ela on one glacier suggesting inconsistent applicability in using sla to identify ela over a large area and 2 in 2010 an intense ablation year the field data derived ela surpassed the glacier peak in this situation there is no theoretical relationship between sla and ela and the image derived snowline actually indicates the boundary between ice and firn from previous years in summary errors will arise from the discrepancies between individual glaciers and from intensive ablation when using sla to identify ela over a large area

geochemistry of secondary copper minerals from proterozoic porphyry copper deposit malanjkhand india abstract three assemblages of ores have been recognized at the proterozoic porphyry copper deposit malanjkhand india they are 1 primary ore containing chalcopyrite and pyrite 2 moderately oxidized ore containing chalcocite covellite bornite and other secondary copper sulfides and 3 intensely oxidized ore containing copper sulphates carbonates chlorides oxides and native copper the malanjkhand chalcopyrite alters by continued oxidation to the following sequence of minerals chalcopyrite cufes2 bornite cu5fes4 idaite cu3fes4 covellite cus yarrowite cu9s8 spionkopite cu39s28 geerite cu1 60s anilite cu1 75s djurleite cu1 943s chalcocite cu2s the alteration beyond chalcocite follows the reverse sequence to covellite i e chalcocite djurleite anilite geerite spionkopite yarrowite covellite the excess copper from the reverse sequence produces copper sulphates carbonates oxides chlorides and native copper additional formation of copper sulphates carbonates etc is due to variable conditions of eh ph mineral solubilities in water and dissolution of pyrite at relatively high eh ph values these factors give rise to different complex ions such as so42 cu oh 2 cu so 4 cu co3 22 and cucl the chalcopyrite in the primary ore tarnishes by the formation of films of feo oh bornite idaite covellite anilite and chalcocite the tarnish varies in color from deep yellow purple yellow purple violet orange pink blue peacock blue and dark grey to black the alteration of malanjkhandchalcopyrite has been considered to be due to galvanic interactions probable and possible stability relations among various phases are suggested in terms of eh ph and attendant galvanic reactions in oxygenated and carbonated waters percolating through the rock and orebody several electrochemical equations are proposed for the reactions and stability fields of the minerals are constructed using available thermodynamic data

accumulation and hoar effects on microwave emission in the greenland ice sheet dry snow zones the relationships between accumulation and microwave emissivity in the dry snow regions of the greenland ice sheet are studied with special focus on hoar formation with the use of a discrete ordinate radiative transfer model the relative contributions of hoar and accumulation to microwave emission are examined the results show that the link between microwave emission and accumulation rates in the dry snow area ofthe greenland ice sheet is significant however the emissivity is also dependent on the extent of hoar development as a result accumulation estimates based on passive microwave observations in the low accumulation dry snow areas will require successful parameterization of hoar formation furthermore the increasing t b trends that were observed during the 1980s which have been hypothesized to be related to accumulation changes may be strongly related to variations in hoar development other possible explanations for these observed trends such as slight surface melt or atmospheric conditions are also discussed

space based mapping of glacier changes using aster and gis tools we describe an investigation that combines space based observations of glacier parameters with historical glaciological data derived by traditional means to predict changes in ice extent and volume for the ak shirak range in the interior tien shan of central asia a variety of geographic information systems and photogrammetric tools are used to extract glacier outlines derive of a digital elevation model and compute area versus elevation distribution functions from data acquired by the advanced spaceborne thermal emission and reflection radiometer these products are then used in a glaciological methodology that can predict the response of glacier systems to changes in local climate

mass balance of south east alaska and north west british columbia glaciers from 1976 to 1984 methods and results the annual surfllce mass balance for 1983 and 1984 and the 10 year cumulative mass balances for 1975 85 were calculated for 60 south east alaskan and north west british columbia glaciers at present the mass balance is positive on nine at equilibrium on nine and negative on 42 glaciers the ratio of glaciers with positive and equilibrium mass balance to glaciers with negative mass balance has not changed significantly since 1946 however the magnitude of negative balances has declined on 39 of the 42 glaciers the annual mass balance of south east alaska and north west british columbia glaciers cannot be measured on more than a few glaciers this paper presents the methods and results for a mass balance model using as input local weather records juneau icefield field studies and satellite imagery the primary variable in mass balance from one glacier to another is the budget gradient the budget gradient varies predictably according to three parameters ocean proximity surface slope and valley width valley height the annual fluctuation of the budget gradient can be determined by examination of local weather records determination of activity indexes and delineation of the equilibrium line gradient from the maritime to the conti nental part of each ice field the latter two variables are determined using largely satellite imagery keyed to topographic maps this procedure where applicable yielded mass balance errors of 0 16 q 22 m and 10 year cumulative mass balance