minor and trace element export from a glacierized alpine headwater catchment haut glacier d arolla switzerland major ion concentrations in meltwaters draining glacial environments have been widely reported however concentrations of minor and trace elements have received scant attention this study presents trace and minor element variations in bulk meltwaters draining haut glacier d arolla switzerland based on twice daily sampling throughout the 1999 ablation season which represents the most detailed meltwater quality dataset to date in order to assess the mode of export from the catchment these elements are partitioned into i dissolved and ii particulate associated minor and trace element components a computer based speciation model phreeqci was applied to the bulk meltwater data suggesting that ba be cd cu li rb and sr exist primarily as mobile monovalent or divalent dissolved cations which may be involved in interactions with suspended sediment surfaces conversely the model predicts the precipitation of fe al mn and cr oxi hydroxides suggesting these species may be predominantly transported as colloids which may remove other minor and trace elements from solution by co precipitation reactions laboratory leaching experiments on suspended sediments and fresh rock powder suggests that minor and trace element concentrations may also be influenced by oxy hydroxide precipitation and adsorption desorption reactions with suspended sediment surfaces the quantity and transport mode of trace and minor elements may influence their bioavailability downstream of glacierized headwater catchments further the enrichment of many dissolved minor and trace elements in meltwaters compared with world stream waters coupled with the timing of water and sediment delivery during the summer months may have implications for downstream aquatic environments copyright 2001 john wiley sons ltd

climatology of upper tropospheric lower stratospheric utls jets and tropopauses in merra abstracta global climatology 1979 2012 from the modern era retrospective analysis for research and applications merra shows distributions and seasonal evolution of upper tropospheric jets and their relationships to the stratospheric subvortex and multiple tropopauses the overall climatological patterns of upper tropospheric jets confirm those seen in previous studies indicating accurate representation of jet stream dynamics in merra the analysis shows a northern hemisphere nh upper tropospheric jet stretching nearly zonally from the mid atlantic across africa and asia in winter spring this jet splits over the eastern pacific merges again over eastern north america and then shifts poleward over the north atlantic the jets associated with tropical circulations are also captured with upper tropospheric westerlies demarking cyclonic flow downstream from the australian and asian monsoon anticyclones and associated easterly jets multiple tropopauses associated with the thermal tropopause break

relationship between cyclone tracks anticyclone tracks and baroclinic waveguides abstract this study presents observational results concerning the structure and evolution of high frequency fluctuations with periods shorter than 6 days in the geopotential height field the results are based on a statistical analysis of 1000 500 and 250 mb height fields derived from twice daily nmc final analyses over the northern hemisphere for the 20 winters 1964 65 through 1983 84 the disturbances assume the form of waves elongated in the meridional direction with a mean wavelength of 4000 km a westward tilt with height and a mean eastward phase propagation of 12 1 5 m s 1 these results support an interpretation in terms of finite amplitude baroclinic waves whose structure and evolution varies with geographical location over the continents and especially along the eastern slopes of the rockies and the tibetan plateau the waves show marked departures in structure and evolution from those over the oceans in particular we find evidence of a systematic influence of the terrain in steering the

causes of reduced north atlantic storm activity in a cam3 simulation of the last glacial maximum abstract the aim of this paper is to determine how an atmosphere with enhanced mean state baroclinity can support weaker baroclinic wave activity than an atmosphere with weak mean state baroclinity as a case study a last glacial maximum lgm model simulation previously documented to have reduced baroclinic storm activity relative to the modern day climate simulated by the same model despite having an enhanced midlatitude temperature gradient is considered several candidate mechanisms are evaluated to explain this apparent paradox a linear stability analysis is first performed on the jet in the modern day and the lgm simulation the latter has relatively strong barotropic velocity shear it was found that the lgm mean state is more unstable to baroclinic disturbances than the modern day mean state although the three dimensional jet structure does stabilize the lgm jet relative to the eady growth rate next feature tracking was used to assess the storm track seeding and temporal growth of distur

interannual and decadal modulations recently observed in the pacific storm track activity and east asian winter monsoon abstract interannual variability of the north pacific storm track observed over 17 recent winters is documented the local storm track activity is measured by a meridional flux of sensible heat associated with the lower tropospheric subweekly fluctuations the interannual variability in the heat flux over the northwestern nw pacific is found to be strongest in midwinter the first empirical orthogonal function of the interannual variability in midwinter captures the decadal tendency toward the enhanced storm track activity in midwinter over the nw pacific in association with the decadal weakening of the east asian winter monsoon siberian high and the aleutian low that occurred in the late 1980s the most marked signature of this enhancement is that the midwinter minimum in the storm track activity which had been apparent in the early to mid 1980s almost disappeared afterward as opposed to linear theory of baroclinic instability the enhanced activity occurred despite the weakening of the pacific j

wave packets and life cycles of troughs in the upper troposphere examples from the southern hemisphere summer season of 1984 85 abstract in this paper reanalysis data for the southern hemisphere summer season of 1984 85 produced by the european centre for medium range weather forecasts have been analyzed to examine wave packets and life cycles of baroclinic waves a semiobjective algorithm has been devised to track wave packets it is found that the perturbations in the upper troposphere are dominated by wave packets some of these wave packets can be tracked for several weeks during which they can make up to two trips around the latitude circle the energy life cycles of waves that make up several of these wave packets were analyzed and apart from the incipient waves that started the wave packets most of the subsequent wave development was found to be dominated by convergence and divergence of energy fluxes rather than due to baroclinic or barotropic conversions demonstrating that these wave packets are indeed coherent entities that propagate due to downstream development or dispersion the energy life cycle of the most

evidence for a till layer beneath storglaciaren sweden based on electrical resistivity measurements evidence for a till layer beneath storglaciaren sweden based on electrical resistivity measurements

storm track dynamics this paper reviews the current state of observational theoretical and modeling knowledge of the midlatitude storm tracks of the northern hemisphere cool season observed storm track structures and variations form the first part of the review the climatological storm track structure is described and the seasonal interannual and interdecadal storm track variations are discussed in particular the observation that the pacific storm track exhibits a marked minimum during midwinter when the background baroclinicity is strongest and a new finding that storm tracks exhibit notable variations in their intensity on decadal timescales are highlighted as challenges that any comprehensive storm track theory or model has to be able to address physical processes important to storm track dynamics make up the second part of the review the roles played by baroclinic processes linear instability downstream development barotropic modulation and diabatic heating are discussed understanding of these processes forms the core of our current theoretical knowledge of storm track dynamics and provides a context within which both observational and modeling results can be interpreted the eddy energy budget is presented to show that all of these processes are important in the maintenance of the storm tracks the final part of the review deals with the ability to model storm tracks the success as well as remaining problems in idealized storm track modeling which is based on a linearized dynamical system are discussed perhaps on a more pragmatic side it is pointed out that while the current generation of atmospheric general circulation models faithfully reproduce the climatological storm track structure and to a certain extent the seasonal and enso related interannual variations of storm tracks in depth comparisons between observed and modeled storm track variations are still lacking

geometry bed topography and drainage system structure of the haut glacier d arolla switzerland as part of an integrated study of the hydrology meltwater quality and dynamics of the haut glacier d arolla switzerland the glacier s drainage network structure was determined from patterns of dye recovery in 342 injection experiments conducted from 47 moulins distributed widely across the glacier this structure was compared with theoretical predictions based upon reconstructed patterns of water flow governed by a the subglacial hydraulic potential surface and b the subglacial bedrock surface these reconstructions were based on measurements of ice surface and bedrock topography obtained by a combination of ground survey and radio echo sounding techniques the two reconstructions simulate the drainage system structures expected for a closed channels in which water is pressurized by the overlying ice and b gravity driven open channel flow the closed channel model provides the best fit to the observed structure even though theoretical calculations suggest that under summer discharge conditions open channel flow may be widespread beneath the glacier possible reasons for this apparent discrepancy are discussed

a synthesis of the levantine basin circulation and hydrography 1985 1990 abstract the levantine basin circulation derived from recent data consists of a series of sub basin scale to mesoscale eddies interconnected by jets the basin scale circulation is masked by eddy variability that modulates and modifies it on seasonal and interannual time scales long term qualitative changes in the circulation are reflected in the bifurcation pattterns of ther mid basin jets relative strengths of eddies and the hydrographic properties at the core of these eddies confinement within the basin geometry strongly influences the co evolution of the circulation features surface measurements satellite images and the mass field indicate an entire range of scales of dynamical features in the region the complexity of the circulation is consistent with the basin wide and mesoscale heterogeneity of the hydrographic properties the interannual variability of liw levantine intermediate water formation in the region appears correlated with the changes in the circulation wintertime convective overturning of water masses reach intermediate depths and constitute a dominant mechanism of liw formation especially in anticyclonic eddies and along the coasts of the northern levantine basin

mechanisms controlling the downstream poleward deflection of midlatitude storm tracks abstractthe atlantic and pacific storm tracks in the northern hemisphere are characterized by a downstream poleward deflection which has important consequences for the distribution of heat wind and precipitation in the midlatitudes in this study the spatial structure of the storm tracks is examined by tracking transient cyclones in an idealized gcm with a localized ocean heat flux the localized atmospheric response is decomposed in terms of a time and zonal mean background flow a stationary wave and a transient eddy field the lagrangian tracks are used to construct cyclone composites and perform a spatially varying pv budget three distinct mechanisms that contribute to the poleward tilt emerge transient nonlinear advection latent heat release and stationary advection the downstream evolution of the pv composites shows the different role played by the stationary wave in each region in the region where the tilt is maximized all three mechanisms contribute to the poleward propagation of the

new gravity wave treatments for giss climate models previous versions of giss climate models have either used formulations of rayleigh drag to represent unresolved gravity wave interactions with the model resolved flow or have included a rather complicated treatment of unresolved gravity waves that while being climate interactive involved the specification of a relatively large number of parameters that were not well constrained by observations and also was computationally very expensive here the authors introduce a relatively simple and computationally efficient specification of unresolved orographic and nonorographic gravity waves and their interaction with the resolved flow comparisons of the giss model winds and temperatures with no gravity wave parameterization with only orographic gravity wave parameterization and with both orographic and nonorographic gravity wave parameterizations are shown to illustrate how the zonal mean winds and temperatures converge toward observations the authors also show that the specifications of orographic and nonorographic gravity waves must be different in the northern and southern hemispheres then results are presented where the nonorographic gravity wave sources are specified to represent sources from convection in the intertropical convergencezoneandspontaneousemissionfromjetimbalances finally astrategytoincludetheseeffectsin a climate dependent manner is suggested

theory and numerical modeling of electrical self potential signatures of unsaturated flow in melting snow 1 we have developed a new theory and numerical model of electrical self potential sp signals associated with unsaturated flow in melting snow the model is applicable to continuous natural melt as well as transient flow phenomena such as meltwater pulses and is tested using laboratory column experiments sp signals fundamentally depend on the temporal evolution of snow porosity and meltwater flux electrical conductivity ec and ph we infer a reversal of the sign of the zeta potential a fundamental electrical property of grain surfaces in porous media consistent with well known elution sequences of ions that cause progressive increases and decreases in meltwater ph and ec respectively injection of fully melted snow samples containing the entire natural range of ions into melting snow columns caused additional temporary reversals of the sign of the zeta potential widely used empirical relationships between effective saturation meltwater fraction ec and ph as well as snow porosity grain size and permeability are found to be robust for modeling purposes thus nonintrusive sp measurements can serve as proxies for snow meltwater fluxes and the temporal evolution of fundamental snow textural hydraulic or water quality parameters adaptation of automated multisensor sp acquisition technology from other environmental applications thus promises to bridge the widely acknowledged gap in spatial scales between satellite remote sensing and point measurements of snow properties sp measurements and modeling may therefore contribute to solving a wide range of problems related to the assessment of water resource availability avalanche or flood risk or the amplification of climatic forcing of ice shelf ice sheet or glacier dynamics

influence of subglacial drainage conditions on the velocity distribution within a glacier cross section substrate properties and hydrological conditions at the base of haut glacier d arolla switzerland are nonuniform the thickness and grain size of subglacial sediment vary on length scales less than one ice thickness whereas hydrological conditions vary seasonally and on length scales of about one ice thickness transverse to ice motion there is a close relationship between the annually averaged velocity field and this nonuniformity of bed conditions basal motion dominates in an area with large water level variations in boreholes whereas ice deformation contributes significantly to total movement elsewhere localized enhanced basal motion occurs primarily in summer especially during a july spring event but this motion is barely discernible in annually averaged surface velocity measurements because transverse coupling suppresses surface expression of the basal motion discontinuity these results highlight the need to include representations of bed nonuniformity in models of glacier flow and to consider ice deformation and basal motion as interdependent processes

seasonal reorganization of subglacial drainage inferred from measurements in boreholes the effect of the formation of a major subglacial drainage channel on the behaviour of the subglacial drainage system of haut glacier d arolla switzerland was investigated using measurements of borehole water level and the electrical conductivity and turbidity of basal meltwaters electrical conductivity profiles were also measured within borehole water columns to identify the water sources driving water level changes and to determine patterns of water circulation in boreholes prior to channel formation boreholes showed idiosyncratic and poorly coordinated behaviour diurnal water level fluctuations were small and driven by supraglacial englacial water inputs even when boreholes were connected to a subglacial drainage system this system appeared to consist of hydraulically impermeable patches interspersed with storage spaces and transmitted a very low water flux drainage reorganization which occurred around 31 july 1993 in response to rapidly rising meltwater and rainfall inputs seems to have involved the creation of a connection between an incipient channel and a well established channelized system located further down glacier once a major channel existed within the area of the borehole array borehole water level fluctuations were forced by discharge related changes in channel water pressure although a diversity of responses was observed these included i synchronous ii damped and lagged iii inverse and iv alternating inverse lagged responses synchronous responses occurred in boreholes connected directly to the channel while damped and lagged responses occurred in boreholes connected to it by a more resistive drainage system pressure variations within the channel resulted in diurnal transfer of mechanical support for the ice overburden between connected and unconnected areas of the bed producing inverse and alternating patterns of water level response 1998 john wiley sons ltd

alpine subglacial hydrology abstract the size and shape of subglacial flow pathways exert a strong influence over the pressure and speed at which meltwaters are routed through glaciers these characteristics in turn influence glacier sliding velocity and the quantity and quality of bulk meltwaters discharging from glaciers in this paper we summarise four empirical research approaches that have been developed to improve our understanding of the subglacial hydrology of predominantly temperate based alpine glaciers investigations of bulk meltwater discharge and chemistry tracer studies proglacial bedrock investigations and borehole investigations as a result of linking these studies to conceptual or numerical models three arborescent and four non arborescent or distributed subglacial drainage configurations are described these drainage networks may be neither spatially nor temporally persistent but may compete with and replace each other on a seasonal basis a qualitative model of the temporal and spatial evolution of a typical alpine subglacial drainage system is advanced on the basis of research conducted at haut glacier d arolla switzerland

subglacial electrical phenomena the subglacial electrical environment is surprisingly complex owing to the variety of processes that promote spatial and temporal variability possible sources of variability are the chemical evolution of subglacial water and the structural and morphological evolution of the drainage configuration such changes contribute to changes in the apparent resistivity of the glacier bed less obvious but possibly more interesting are those electrical phenomena associated with the natural transport of water and charge in the subglacial drainage system streaming potentials are generated by water flow through subglacial sediment and these potentials are closely associated with the subglacial water pressure field to explore these effects we have monitored induced and natural electrical responses in the deforming material beneath trapridge glacier yukon canada several arrays of electrodes were placed at the ice bed interface and data were recorded over a period of several years data from these experiments indicate that natural potentials can be used to monitor water pressure gradients and that the bulk resistivity of the glacier bed can be altered by changing the hydraulic regime we present evidence that temporal variations in streaming potentials can indicate fluctuations in subglacial water flow rate and that spatial variations can be related to variations in bed elevation water pressure and hydraulic connectivity

water storage and subglacial drainage conditions inferred from borehole measurements on gornergletscher valais switzerland measurements of change in length of a borehole or displacements of poles and of subglacial water pressure were combined with drainage tests and electrode tests in boreholes in experiments near the northern margin of gornergletscher valais switzerland at the upstream side of an overdeepening the measurements suggest that the subglacial drainage system consisted of discrete conduits at that location presumably linked cavities on clean bedrock changes in subglacial water pressure were followed by variations in subglacial water storage together with similar variations in elevation of a pole the variations in subglacial water storage caused changes in cross sections of subglacial passageways and thereby changed the frequencies of slug test oscillations similar experiments conducted near the center line of the glacier revealed different subglacial conditions impeded drainage through a sediment layer and different depths of water levels in different boreholes these results are discussed in relation to previous studies

hydrogeological analysis of slug tests in glacier boreholes slug testing allows estimation of subglacial hydraulic properties by evaluating the response of a coupled borehole subglacial flow system to an artificial displacement of its steady state hydraulic head however existing models developed specifically for application to slug test data collected in glacier boreholes are challenging to apply in practice here we demonstrate that conventional linear methods which are relatively readily applicable and widely used in groundwater studies can also be used to estimate subglacial hydraulic properties overdamped underdamped and critically damped slug test data were recorded in fluctuating boreholes drilled to the bed of haut glacier d arolla valais switzerland we find that non linear effects in the data are negligible supporting the application of conventional hydrogeological methods results suggest that the hydraulic conductivity of the unconsolidated sediments within the area influenced by a major subglacial drainage channel is enhanced several 10 2 ms 1 typical of gravelly sand compared to areas outside the zone of influence 0 1 10 2 ms 1 typical of silty sand a distance to a flow boundary within the subglacial aquifer inferred on the basis of slug test analysis was found to coincide with the actual location of the subglacial channel sensitivity analyses reveal that uncertainties in borehole and filter radii as well as the storage coefficient of the subglacial aquifer are more likely to affect the accuracy of the hydraulic and distance estimates than uncertainties regarding the repeatability of the slug test responses and curve fitting procedures involved in the conventional hydrogeological methods

how strong are the southern hemisphere storm tracks 1 the real strength of the southern hemisphere sh storm tracks is poorly known as the ncep ncar and ecmwf reanalyses differ significantly in this measure in this work the cosmic gps radio occultation dataset is used to investigate this issue the ratio of the strength of the sh storm tracks to that in the northern hemisphere nh based on the cosmic dataset can be regarded as close to the true inter hemisphere ratio since the dataset has similar biases and errors in both hemispheres comparing this ratio with that based on the reanalysis it is found that the strength of the sh storm tracks in the ncep ncar reanalysis is significantly biased low by at least 25 at 300 hpa while those in the ecmwf reanalyses are much closer to that inferred from cosmic observations but era40 may be biased low by 5 10

vertical distribution of marine cyanobacteria synechococcus spp in the black marmara aegean and eastern mediterranean seas abstract the vertical distributions of the unicellular cyanobacteria synechococcus were studied in several highly contrasting seas the black sea sea of marmara aegean sea and mediterranean sea cell abundances varied significantly on both vertical and horizontal scales in all physically and spatially discrete water masses epifluorescence microscope cell counts from all seas clearly showed that majority of the population remains suspended in the surface mixed layer and decreases gradually towards the base of the euphotic zone surface spatial distributions in the black sea were heterogeneous salinity rather than temperature seemed to have the greatest impact on the surface distribution of cells in this highly eutrophic sea changes in abundance in the mixed layer were small compared to the abrupt changes below the halocline especially in the black sea and the sea of marmara in contrast to the black sea the major population remains suspended above the depth of fluorescence maximum in the aegean and eastern mediterranean seas significant correlations r p 0 01 were observed between cell counts and physical and chemical parameters with depth in the black sea in all seas cells at subsurface chlorophyll a maximum layer scml reflected brighter and longer fluorescence than those present at the surface and below cell size derived from flow cytometry indicated the presence of larger cells at the surface mixed layer compared to those at depth

the impact of wave packets propagating across asia on pacific cyclone development abstract in this paper ecmwf 40 yr reanalysis data have been examined to study the influence of upper level wave packets propagating across asia into the pacific on surface cyclone development over the pacific previous studies have shown that in winter wave packets propagate across asia over two branches a northern branch over siberia and a southern branch along the subtropical jet across southern asia results presented here show that subsequent to the presence of wave packets on either branch the frequency of occurrence of deep cyclones defined as cyclones with central pressure below 960 hpa as well as explosively deepening cyclones those with a deepening rate of 1 bergeron or more are significantly enhanced this enhancement also clearly follows the wave packet eastward as it propagates across the pacific wave packets from the two branches are found to interfere with each other such that if wave packets of the appropriate configuration are present on both the northern and southern branch s

structure and characteristics of submonthly scale waves along the indian ocean itcz this study examines wave disturbances on submonthly 6 30 day timescales over the tropical indian ocean during southern hemisphere summer using japanese reanalysis jra25 jcdas products and national oceanic and atmospheric administration outgoing longwave radiation data the analysis period is december february for the 29 years from 1979 1980 through 2007 2008 an extended empirical orthogonal function eeof analysis of daily 850 hpa meridional wind anomalies reveals a well organized wave train pattern as a dominant mode of variability over the tropical indian ocean daily lagged composite analyses for various atmospheric variables based on the eeof result show the structure and evolution of a wave train consisting of meridionally elongated troughs and ridges along the indian ocean intertropical convergence zone itcz the wave train is oriented in a northeast southwest direction from sumatra toward madagascar the waves have zonal wavelengths of about 3 000 5 000 km and exhibit westward and southwestward phase propagation individual troughs and ridges as part of the wave train sequentially travel westward and southwestward from the west of sumatra into madagascar meanwhile eastward and northeastward amplification of the wave train occurs associated with the successive growth of new troughs and ridges over the equatorial eastern indian ocean this could be induced by eastward and northeastward wave energy dispersion from the southwestern to eastern indian ocean along the mean monsoon westerly flow in addition the waves modulate the itcz convection correlation statistics show the average behavior of the wave disturbances over the tropical indian ocean these statistics and other diagnostic measures are used to characterize the waves obtained from the composite analysis the waves appear to be connected to the monsoon westerly flow the waves tend to propagate through a band of the large meridional gradient of absolute vorticity produced by the mean monsoon westerly flow this suggests that the monsoon westerly flow provides favorable background conditions for the propagation and maintenance of the waves and acts as a waveguide over the tropical indian ocean the horizontal structure of the wave train may be interpreted as that of a mixture of equatorial rossby waves and mixed rossby gravity wavelike gyres

vertical structure and dominant horizontal scales of baroclinic waves in the nasa dao and ncep reanalyses abstract the reanalyses of the data assimilation office dao of the national aeronautics and space administration nasa are compared to those of the national centers for environmental prediction ncep with regard to the vertical structure and important horizontal scales of the baroclinic transients attention is focused on the eight northern hemisphere winters of 1985 86 1992 93 and on bandpass transients of timescales 2 8 days the local seasonal mean vertical shear normalized by the square root of the static stability is very similar between the two sets of analyses the upper level vorticity gradient dominated by the meridional derivative also shows little sensitivity to which reanalysis is used the condition for barotropic instability change of sign of total vorticity gradient is satisfied the vertical structure of bandpass kinetic energy meridional sensible heat flux and variance of temperature gradient all show consistent differences between the ncep and nasa reanalyses with the ncep

time lapse imaging of subglacial drainage conditions using three dimensional inversion of borehole electrical resistivity data we recorded electrical resistivity data at the base of four boreholes drilled through haut glacier d arolla switzerland the data were acquired repetitively every hour over two diurnal hydrological cycles in the late melt season separated by 10 days constrained three dimensional 3 d data inversion allowed reconstruction of hourly variations in bulk resistivity in the subglacial sediment layer inverted resistivity models reflect the establishment of channelized subglacial drainage in the study area between the two hydrological cycles in agreement with previous work daily variations in bulk and water resistivity are in phase and bulk resistivity amplitudes decrease away from the subglacial channel using selected electrical hydraulic relationships we estimate metre scale changes in the hydraulic conductivity and porosity of the subglacial sediment layer accounting for increasing clay content and decreasing median grain radius with distance from the channel hydraulic conductivity and porosity were respectively calculated to decrease from 6 4 2 1 10 2 m s 1 and 0 34 0 01 at the channel to 3 3 2 2 10 2 m s 1 and 0 26 0 01 at a distance of 5 m from it the hydraulic conductivity estimates are in agreement with previously inferred values and the porosity estimates fall within the expected range for unlithified subglacial sediments we conclude that collection and inversion of repeat 3 d subglacial resistivity data is feasible and has the capacity to generate multidimensional images of subglacial hydraulic processes and properties

diesel transport monitoring in simulated unconfined aquifers using miniature resistivity arrays the principal aim of this study is to assess the scope of monitoring diesel plume migration in a scaled aquifer model with a miniaturised electrical resistivity array respectively 1000 and 500 ml of diesel were injected in both the unsaturated and water saturated zones of a sand body overlying a clay aquitard and diesel migration was monitored with a miniature electrode array and an off the shelf resistivity meter inverted time lapse electrical resistivity tomography ert data reflect downward and lateral spreading of the diesel plume away from the injection point in the unsaturated zone diesel was also imaged to spread upwards and laterally away from the injection point in the saturated zone as controlled by capillary rise in both cases later time ert images reflected preferential pooling of diesel on the water table as well as vertical smearing of pooled diesel in response to simulated water table fluctuations repeat fluid electrical conductivity ec and dissolved oxygen do measurements validate the observed changes in bulk resistivity caused by both diesel injections artefacts introduced by 2d inversion of 3d contaminant transport were abound time lapse ert imaging of diesel transport is therefore inferred to be feasible and well suited to complementing conventional techniques of intrusive site investigation although time lapse 3d or 4d ert imaging is strongly advocated

orographic control of storm zones on mars low pressure cyclones and their accompanying frontal systems in the middle latitudes of the earth s troposphere develop travel eastwards and decay preferentially within latitudinally and longitudinally confined geographical regions known as storm zones1 these zones can be readily identified in the circulation statistics of terrestrial weather systems2 mars like the earth is a rapidly rotating solid planet and has a seasonally varying shallow atmosphere large scale orography and in a broadly defined context continental structures3 although there are also important differences between the two planets travelling weather systems do exist on mars3 this raises the question of whether storm zones also occur there and if so by what mechanisms here we report the results of numerical simulations of global atmospheric circulation patterns on mars we find that storm zones can exist during the northern winter and that continental scale orography rather than surface thermal contrasts is the main factor determining the development of these zones storm zones on mars should play an important role in the martian climate cycle4 5 by influencing the transport of for example heat momentum water vapour and atmospheric dust3 6 8 towards the poles

northeast atlantic winter storminess 1875 1995 re analysed northeast atlantic winter storminess is analysed for the period 1875 1995 using a new dataset consisting of multi daily mean sea level pressure observations from a selected set of stations in the northeast atlantic an analysis of storminess is presented based on the high pass filtered signal from these observations from which selected percentiles are calculated for each winter this method avoids potential inhomogeneity problems artificial trends or jumps our finding is an increase however not a dramatic one during the past 2 3 decades in the northeasternmost part of the storm track but the dominant features are inter annual and decadal variations furthermore the variations in storminess are found to be statistically linked to low frequency circulation variations represented by the winter average of the msl pressure field over the north atlantic it is argued that the existence of this link could have dynamical consequences for the response of the atmosphere to external forcing

statistical evaluation of glacier boreholes as indicators of basal drainage systems between 1988 and 1992 closely spaced arrays of boreholes were drilled at small river glacier british columbia the borehole arrays have been used to investigate the interannual and spatial consistency of patterns of basal hydraulics beneath the glacier a simple robust classification was devised identifying unconnected high standing low standing and dry base water levels in boreholes spatial and interannual comparisons were made using a simple nearest neighbour statistic corrected for differences in frequency of different borehole types and evaluated using monte carlo confidence intervals to compensate for array form arrays in the lower ablation zone showed spatial and interannual coherence with three distinct areas characterized by low water pressure till associated non connection and high pressure there was no indication of a dominant conduit slightly higher up glacier borehole patterns were less coherent and varied from year to year probably a result of subglacial karst capturing basal waters at a number of low pressure points at the bed therefore both the upper and lower arrays at small river glacier appear to encompass unusual drainage conditions the nearest neighbour analysis provides valuable constraints on more specific interpretation

earth tide forcing of glacier drainage 1 fourier analysis reveals that winter electrical self potential sp water pressure pw and electrical conductivity ec time series collected beneath haut glacier d arolla switzerland are forced by earth and atmospheric tides forcing is dominant during periods of expanding bedrock consistent with glacier substrate deformation periodically driving water from the ice body into the bed this may modify the strength of subglacial sediments and could therefore influence glacier drainage and motion on a global scale

assessing the paradigm shift deformable glacier beds abstract during the mid 1980s glaciologists recognised that many glaciers and ice masses overlie soft sediments rather than hard bedrock these sediments are typically weaker than glacier ice and may therefore deform this realisation was heralded as a paradigm shift in glaciology since this realisation a wide body of theoretical and field based research has been undertaken to assess the mechanical and hydrological significance of such substrates we review the techniques and results of this work and attempt to assess this paradigm shift in glaciology and in particular its importance for quaternary scientists we suggest areas of research that remain unanswered and identify those in which glacial geology in particular may be able to inform glaciologists

review of subglacial hydro mechanical coupling trapridge glacier yukon territory canada abstract the interaction of basal processes with the subglacial drainage system is a critical issue in understanding glacier dynamics since the recognition that many glaciers and ice masses overlie soft sediments rather than hard bedrock much research has been undertaken to investigate how mechanical and hydrological conditions of a deformable substrate control the coupling at the ice bed interface and thus affect fast ice flow and glacier surging in research undertaken on trapridge glacier a small surge type glacier in the st elias mountains yukon territory canada we have combined extensive field investigations using novel measurement techniques and theoretical modelling to study hydro mechanical coupling processes measurements of subglacial water pressure indicate that the basal water system can be dramatically inhomogeneous both spatially and temporally since ice bed coupling is strongly influenced by subglacial water pressure the stresses at the bed are also markedly heterogeneous and are expected to form a patchwork distribution which mimics the pressure distribution of the basal water system this heterogeneity in the stress field at the ice bed interface introduces a pronounced variability to the basal motion mechanics as such basal sliding and subglacial sediment deformation are not steady and continuous processes instead the variability of the subglacial water system leads to a spatial and temporal interplay of increased ice bed coupling at low water pressures at one site or time with ice bed decoupling during rising water pressures at other sites or times thus on the one hand there is downglacier shear deformation of the bed and accumulation of elastic strain in ice and sediment while on the other hand there is enhanced slip sliding of the glacier and upglacier shear motion of the bed due to an elastic relaxation of the sediment

patterns of vertical velocity induced by eddy distortion in an ocean model vertical motions within eddies play an important role in the exchange of properties and energy between the upper ocean and the ocean interior here we analyze alternating upward and downward cells in anticyclonic eddies in the east australian current region using a global eddy resolving model the cells explain over 50 of the variance of vertical velocity within these eddies we show that the upward and downward cells relate to eddy distortion defined as the change in eddy shape over time in anticyclonic eddies in the southern hemisphere an inward distortion is associated with upward motion and an outward distortion is associated with downward motion we discuss two mechanisms that link eddy distortion to vertical velocity one mechanism relates to changes in stratification and relative vorticity in the eddy interior the other mechanism relates to divergence of the horizontal flow in different quadrants of the eddy we show that mesoscale changes in sea level anomaly can be used to infer the vertical motion within eddies

trapping of synoptic scale disturbances into the north pacific subtropical jet core in midwinter 1 over the northwestern nw pacific a subtropical jet stream develops at 30 n in midwinter as the east asian winter monsoon intensifies eddies with subweekly periods propagating through the midlatitude tropopause into the nw pacific storm track tend to be trapped into the jet core 1000 km away from a surface baroclinic zone at 40 n while lifted up by 3 km the trapping appears to weaken the interaction of the upper level eddies with the baroclinic zone thus acting against eddy amplification and thereby contributing to the midwinter minimum in the eddy activity as observed before the late 1980s since then under the reduced trapping effect by the weakened jet upper level eddies tended to propagate right above the surface baroclinic zone while strongly interacting it even in midwinter as in fall and spring this midwinter tendency acted to enhance the eddy amplification that led to the recent disappearance of the activity minimum

inter borehole electrical resistivity imaging of englacial drainage borchole based electrical resistivity surveys have the capacity to enhance our understanding of the structure of englacial drainage pathways in temperate ice we summarize inter borehole electrical resistivity tomography ert as currently used in hydrogeological investigations and as adapted for imaging englacial drainage ert connections were success for the first time in glacier ice following artificial mineralization of borehole waters haut glacier d arolla switzerland here two types of electrical connection were made between boreholes spaced up to 10 m apart and drilled to depths of between 20 and 60 m most tests indicated the presence of resistively homogencous ice with uniform bulk resistivities of 10 10 9 m however ert was also successfully used to identify and characterize a hydraulically conductive englacial fracture that intersected two boreholes at a depth of 13 m below the glacier surface the presence of this connecting void as suggested by drilling records and verified by dual borehole impulse testing the reconstructed tomogram for these boreholes is characterized by a background ice resistivity field of 10 9 m that is disrupted at a depth of 13 m by a sharp sub horizontal low resistivity zone 10 1 m inter borehole ert therefore has the capacity to image both uniform and fractured temperate glacier ice

seasonality and interannual variability of the westerly jet in the tibetan plateau region abstract in this study 40 yr ecmwf re analysis era 40 data are used for the description of the seasonal cycle and the interannual variability of the westerly jet in the tibetan plateau region to complement results based on the analysis of monthly mean horizontal wind speeds an occurrence based jet climatology is constructed by identifying the locations of the jet axes at 6 hourly intervals throughout 1958 2001 thus a dataset describing the highly transient and localized features of jet variability is obtained during winter and summer the westerly jet is located respectively to the south and north of the tibetan plateau during the spring and autumn seasons there are jet transitions from south to north and vice versa the median dates for these transitions are 28 april and 12 october the spring transition is associated with large interannual variations while the fall transition occurs more reliably within a 3 week period the strength of the jet exhibits a peculiar seasonal cycle during northw

dynamics of the enso teleconnection and nao variability in the north atlantic european late winter abstractthe winter extratropical teleconnection of el nino southern oscillation enso in the north atlantic european nae sector remains controversial concerning both the amplitude of its impact

spatial patterns and intensity of the surface storm tracks in cmip5 models abstractto improve the understanding of storm tracks and western boundary current wbc interactions surface storm tracks in 12 cmip5 models are examined against era interim all models capture an equatorward displacement toward the wbcs in the locations of the surface storm tracks maxima relative to those at 850 hpa an estimated storm track metric is developed to analyze the location of the surface storm track it shows that the equatorward shift is influenced by both the lower tropospheric instability and the baroclinicity basin scale spatial correlations between models and era interim for the storm tracks near surface stability sst gradient and baroclinicity are calculated to test the ability of the gcms match reanalysis an intermodel comparison of the spatial correlations suggests that differences relative to era interim in the position of the storm track aloft have the strongest influence on differences in the surface storm track position however in the north atlantic biases in the surf

interdecadal variations in northern hemisphere winter storm track intensity abstract in this paper the interannual variations in the northern hemisphere winter storm tracks have been examined based on 51 winters december january february of ncep ncar reanalysis data the leading empirical orthogonal function eof corresponds to the simultaneous strengthening weakening of both the pacific and atlantic storm tracks interannual and month to month variations in the pacific and atlantic storm tracks are found to be significantly correlated the principal component associated with the leading hemispheric eof exhibits pronounced interdecadal variability there appears to be a transition during the early 1970s from a weak storm track state prior to 1972 73 to a strong storm track state subsequently decadal mean storm track intensity during the 1990s is about 30 stronger than that during the late 1960s and early 1970s the relationship between variations in storm track intensity and low frequency seasonal mean flow anomalies has also been examined it is shown that storm track va

the signature of the midlatitude tropospheric storm tracks in the surface winds abstract storm track analysis is applied to the meridional winds at 10 m and 850 hpa for the winters of 1999 2006 the analysis is focused on the north atlantic and north pacific ocean basins and the southern ocean spanning the region south of the indian ocean the spatial patterns that emerge from the analysis of the 850 hpa winds are the typical free tropospheric storm tracks the spatial patterns that emerge from the analysis of the surface winds differ from the free tropospheric storm tracks the spatial differences between the surface and free tropospheric storm tracks can be explained by the influence of the spatial variability in the instability of the atmospheric boundary layer strongly unstable boundary layers allow greater downward mixing of free tropospheric momentum momentum mixing and this may be the cause of the stronger surface storm tracks in regions with greater instability in the time mean principal component analysis suggests that the basin scale variability that is reflected in th

cross coupled flow modeling of coincident streaming and electrochemical potentials and application to subglacial self potential data 1 this study aims to demonstrate that self potential measurements can yield unique information about subglacial drainage conditions which has so far been doubtful at the bed of warm based glaciers arborescent and distributed drainage systems interact and streaming and electrochemical potentials coincide a key secondary aim of this study is therefore the development of a mathematical framework for the analysis of self potentials generated by such interacting flow systems we consider cross coupling between hydraulic electrical and chemical driving forces and apply the resulting model solution to self potential data recorded beneath haut glacier d arolla switzerland we find that 1 the streaming and electrochemical contributions to the total self potential signal can be separated mathematically 2 streaming potentials directly reflect the direction of water flow at the glacier bed 3 combination of streaming potentials with hydraulic conductivity estimates from slug tests allows estimation of in situ subglacial water flow velocities 4 the subglacial zeta potential calculated from estimated values of the streaming coupling coefficient is small 0 022 v due to systematic flushing of clay minerals from the channel area during the melt season and 5 uncertainties in exact electrode location in the borehole are unlikely to produce self potential noise self potential measurements may therefore yield unique information about subglacial drainage conditions and especially the direction and velocity of in situ subglacial water flow are difficult to obtain by other methods we further anticipate that our mathematical framework will be applicable to other areas of subsurface hydrology especially where spatially distributed seepage feeds preferential flow pathways

water flow through temperate glaciers understanding water movement through a glacier is fundamental to several critical issues in glaci ology including glacier dynamics glacier induced floods and the prediction of runoff from glacierized drainage basins to this end we have synthesized a conceptual model of water movement through a temper ate glacier from the surface to the outlet stream pro cesses that regulate the rate and distribution of water input at the glacier surface and that regulate water movement from the surface to the bed play important but commonly neglected roles in glacier hydrology where a glacier is covered by a layer of porous perme able firn the accumulation zone the flux of water to the glacier interior varies slowly because the firn tempo rarily stores water and thereby smooths out variations in the supply rate in the firn free ablation zone in con trast the flux of water into the glacier depends directly on the rate of surface melt or rainfall and therefore varies greatly in time water moves from the surface to the bed through an upward branching arborescent net work consisting of both steeply inclined conduits formed by the enlargement of intergranular veins and gently inclined conduits spawned by water flow along the bottoms of near surface fractures crevasses engla cial drainage conduits deliver water to the glacier bed at a limited number of points probably a long distance downglacier of where water enters the glacier englacial conduits supplied from the accumulation zone are quasi steady state features that convey the slowly varying water flux delivered via the firn their size adjusts so that they are usually full of water and flow is pressurized in contrast water flow in englacial conduits supplied from the ablation area is pressurized only near times of peak daily flow or during rainstorms flow is otherwise in an open channel configuration the subglacial drainage system typically consists of several elements that are distinct both morphologically and hydrologically an up glacier branching arborescent network of channels in cised into the basal ice conveys water rapidly much of the water flux to the bed probably enters directly into the arborescent channel network which covers only a small fraction of the glacier bed more extensive spatially is a nonarborescent network which commonly includes cav ities gaps between the glacier sole and bed channels incised into the bed and a layer of permeable sediment the nonarborescent network conveys water slowly and is usually poorly connected to the arborescent system the arborescent channel network largely collapses during winter but reforms in the spring as the first flush of meltwater to the bed destabilizes the cavities within the nonarborescent network the volume of water stored by a glacier varies diurnally and seasonally small temper ate alpine glaciers seem to attain a maximum seasonal water storage of 200 mm of water averaged over the area of the glacier bed with daily fluctuations of as much as 20 30 mm the likely storage capacity of subglacial cavities is insufficient to account for estimated stored water volumes so most water storage may actually occur englacially stored water may also be released abruptly and catastrophically in the form of outburst floods

a diagnostic study of waves on the tropopause the spatial structure and phase velocity of tropopause disturbances localized around the subpolar jet in the southern hemisphere are investigated using 6 hourly european centre for medium range weather forecasts reanalysis data covering 15 yr 1979 93 the phase velocity and phase structure of the tropopause disturbances are in good agreement with those of an edge wave vertically trapped at the tropopause however the vertical distribution of the ratio of potential to kinetic energy exhibits maxima above and below the tropopause and a minimum around the tropopause in contradiction to edge wave theory for which the ratio is unity throughout the troposphere and stratosphere this difference in vertical structure between the observed tropopause disturbances and edge wave theory is attributed to the effects of a finite depth tropopause together with the next order corrections in rossby number to quasigeostrophic dynamics

borehole water level variations and the structure of the subglacial hydrological system of haut glacier d arolla valais switzerland late summer subglacial water pressures have been measured in a dense array of boreholes in the ablation area of haut glacier d arolla switzerland interpolated surfaces of minimum diurnal water pressure and diurnal water pressure variation suggest the presence of a subglacial channel within a more widespread distributed drainage system the channel flows along the centre of a variable pressure axis vpa some tens of metres wide that is characterized by low minimum diurnal water pressures frequently atmospheric and high diurnal water pressure variations these characteristics are transitional over a lateral distance of c 70 m to higher and more stable subglacial water pressures in the adjacent distributed system water pressure variations recorded in boreholes located close to the centre of the vpa reflect the delivery of surface derived meltwater to the glacier bed and result in a diurnally reversing transverse hydraulic gradient that drives water out from the channel into the distributed system during the afternoon and back to the channel overnight subglacial observations suggest that such flow occurs through a vertically confined sediment layer borehole turbidity records indicate that the resulting diurnal water flows are responsible for the mobilization and transport of fine debris in suspension analysis of the propagation velocity and amplitude attenuation of the diurnal pressure waves suggests that the hydraulic conductivity of the sediment layer decreases exponentially with distance from the channel falling from c 10 4 m s 1 at the channel boundary to c 10 7 ms 1 70m away these apparent hydraulic conductivities are consistent with darcian flow through clean sand and typical glacial till respectively we suggest that fine material is systematically flushed from basal sediments located adjacent to large melt season drainage channels beneath warm based glaciers this process may have important implications for patterns of glacier erosion hydrochemistry and dynamics

global characteristics of medium scale tropopausal waves observed in ecmwf operational data global characteristics and seasonal variation of medium scale zonal wavelengths of 2000 3000 km waves observed around the midlatitude tropopause are examined using 6 hourly european centre for medium range weather forecasts operational data over four years 1990 93 covering both hemispheres medium scale waves and synoptic scale waves are extracted using time filters and their characteristics are compared hovmoller diagrams indicate the existence of medium scale waves in the southern hemisphere as well as in the northern hemisphere the zonal wavelengths of medium scale waves are slightly larger in the southern hemisphere than in the northern hemisphere medium scale waves are mostly active in three regions the north atlantic in winter dec jan feb the north pacific in spring mar apr may mam and the south indian ocean in autumn mam these regions are roughly corresponding to and slightly downstream of storm tracks where synoptic waves are dominant significant differences in seasonal variation of the intensity between the two kinds of waves are also found the maximum of wave amplitudes is seen around the tropopause at latitudes slightly higher than the jet stream axis where the meridional gradient of the quasigeostrophic potential vorticity qpv is maximized the positive large qpv gradient is attributed to the atmospheric structure around the midlatitude tropopause that is located in vertical westerly shear of the jet stream this fact suggests that the medium scale waves are waves trapped around the midlatitude tropopause

seasonal dependence of coupling between storm tracks and sea surface temperature in the southern hemisphere midlatitudes a statistical assessment abstracttwo way coupling between sea surface temperature sst variations in the midlatitude southern oceans and changes of synoptic scale 2 8 day eddy activities in the lower and upper troposphe

inversion of induced polarization data we present an algorithm for inverting induced polarization ip data acquired in a 3 d environment the algorithm is based upon the linearized equation for the ip response and the inverse problem is solved by minimizing an objective function of the chargeability model subject to data and bound constraints the minimization is carried out using an interior point method in which the bounds are incorporated by using a logarithmic barrier and the solution of the linear equations is accelerated using wavelet transforms inversion of ip data requires knowledge of the background conductivity we study the effect of different approximations to the background conductivity by comparing ip inversions performed using different conductivity models including a uniform half space and conductivities recovered from one pass 3 d inversions composite 2 d inversions limited aim updates and full 3 d nonlinear inversions of the dc resistivity data we demonstrate that when the background conductivity is simple reasonable ip results are obtainable without using the best conductivity estimate derived from full 3 d inversion of the dc resistivity data as a final area of investigation we study the joint use of surface and borehole data to improve the resolution of the recovered chargeability models we demonstrate that the joint inversion of surface and crosshole data produces chargeability models superior to those obtained from inversions of individual data sets

diabatic damping of zonal index variations abstractzonal index variations or north south shifts of the midlatitude jet are the dominant mode of zonal wind variability in the southern hemisphere previous studies have shown that synoptic time scale eddy momentum flux provides a positive feedback and acts to increase the persistence and low frequency variance of the zonal index however the impact of diabatic heating due to the precipitation associated with these eddies has not been investigated in this study regression analyses have been conducted to demonstrate that a robust precipitation anomaly can be found to accompany the jet and eddy momentum flux anomalies associated with a poleward shift of the jet with enhanced precipitation on the poleward flank of the jet and reduced precipitation on the equatorward flank diabatic heating associated with such a precipitation anomaly is expected to reduce the temperature gradient across the jet anomaly thus decreasing eddy generation and damping the anomaly this expectation is confirmed by three

subglacial till a physical framework for its properties and processes the continuum theory of mixtures provides a framework around which present knowledge of subglacial till can be organized the proposed framework is provisional in two senses the constitutive description of till will require improvement and not all potentially significant processes have been included till is treated as a three component mixture of water clasts coarse grained solids and fine grained matrix solids these components obey mass balance equations and their behavior is subject to constitutive relations that describe such processes as darcian water transport fine grained sediment transport consolidation shear deformation dilatancy and comminution five state variables uniquely determine the compressibility permeability shear strength and other physical properties numerical solutions of the state evolutions equations illustrate that the properties of till are highly responsive to changes in the subglacial environment

compressional velocity and porosity in sand clay mixtures laboratory measurements of porosity and compressional velocity were conducted on unconsolidated brine saturated clean ottawa sand pure kaolinite and their mixtures at various confining pressures a peak in p velocity versus clay content in unconsolidated sand clay mixtures at 40 percent clay by weight was found the peak in velocity is 20 30 percent higher than for either pure clay or clean sand a minimum in porosity versus clay content at 20 40 percent clay by weight is also observed such behavior is explained using a micro geometrical model for mixtures of sand and clay in which two classes of sediments are considered 1 sands and shaley sands in which clay is dispersed in the pore space of load bearing sand and thus reduces porosity and increases the elastic moduli of the pore filling material and 2 shales and sandy shales in which sand grains are dispersed in a clay matrix for these sediments the model reproduces the extrema in velocity and porosity and accounts for much of the scatter in