some observations on suspended sediment dynamics in storbregrova jotunheimen observations are reported of the dynamics of suspended sediment transport in the meltstream of storbreen in the jotunheimen fine sediment is transferred from the subglacial to the proglacial environment during low flow meltdominated periods and then removed from the catchment during high flow rainfall controlled events both diurnal and storm period sediment load discharge relationships involve clockwise hysteresis but separate multivariate rating curves define variations of load with streamflow according to 1 the relative importance of meltwater and rainfall runoff and 2 changes in the sediment source areas contributing to the stream at different times particle size variations in the suspended sediment also reflect varying source area influences

coupling of the surface and near bottom currents in the gulf of mexico coupling between the surface and near bottom currents in the gulf of mexico gom has been reported in many case studies however geographical variations of this coupling need more examination in this study surface geostrophic currents derived from satellite observed sea surface height and subsurface currents from a collection of deep ocean moorings are used to examine the surface and bottom coupling in different parts of the gom the short period 30 90 days fluctuations generated by the loop current lc and the lc eddies lces have a more vertically coherent structure and stronger deep ocean expressions than the long period fluctuations 90 days in addition the strength of the coupling is modulated by the long period variations of the lc and lce sheddings moreover the surface and bottom coupling varies geographically in the lc region the surface fluctuations along the eastern side of the lc are important in causing the bottom current fluctuations through baroclinic instability under the lc and through traveling topographic rossby waves trws north of the lc in the central deep gom the bottom currents are affected by the upper fluctuations of the northern lc through both local baroclinic instability and remote trw propagation in the northwestern gom the bottom current fluctuations are largely related to the remote surface variability from the west side of the lc by trws propagating northwestward this study will help us better understand mechanisms of the bottom current fluctuations that are important for the dispersal of deep ocean materials and properties

comparison of near surface mean and eddy flows from two numerical models of the south atlantic ocean the near surface mean and eddy flows simulated by two eddy permitting models of the south atlantic s coordinate primitive equation model spem and ocean parallel opa model are compared these models are intrinsically different by virtue of their vertical discretizations versus geopotential coordinates respectively so that their solutions differ essentially through the representation of current topography interactions the path of the agulhas current the generation process the characteristics and the subsequent trajectory of the agulhas rings are differently affected by topography in the two models along the american western boundary spem traps a larger part of the antarctic circumpolar current acc around the falkland plateau and consequently produces a stronger malvinas current which overshoots far to the north inshore of a rather realistic brazil current and confluence regime in contrast opa allows a large part of the acc to flow across the scotia sea produces a weaker malvinas current traps the brazil and malvinas currents along the american coast and tends to distort the complex dynamics of the confluence region and the zapiola anticyclone some of these differences can be attributed to the particularities of each vertical coordinate system and to the representation of topographic slopes staircases in opa and facettes in spem more generally the topographic constraint trapping of boundary currents and interaction of mean and eddy flows with bathymetry is stronger in spem than in opa the topographic smoothing usually performed in sigma coordinate models removes mesoscale topographic roughness and reduces topographic slopes this treatment is probably responsible for several of the differences observed in the numerical solutions

hydrological characteristics of the drainage system beneath a surging glacier a rare combination of natural circumstances permits assessment of current theories on water flow beneath glaciers outburst floods from the subglacial lake grimsvotn in iceland took place before during and after surging of skei ararjokull the glacier beneath which the outburst floods drain the observable drainage patterns associated with these floods show the different nature of the basal water conduit system of the glacier during surge and non surge phases during surge conditions basal water is dispersed slowly across the bed in a distributed drainage system but when the glacier is not surging water is transported rapidly through a system of tunnels

characterization of glacial silt and clay using automated mineralogy glacial erosion produces vast quantities of fine grained sediment that has a far reaching impact on earth surface processes to gain a better understanding of the production of glacial silt and clay we use automated mineralogy to quantify the microstructure and mineralogy of rock and sediment samples from 20 basins in the st elias mountains yukon canada sediments were collected from proglacial streams while rock samples were collected from ice marginal outcrops and fragmented using electrical pulse disaggregation for both rock fragments and sediments we observe a log normal distribution of grain sizes and a sub micrometer terminal grain size we find that the abrasion of silt and clay results in both rounding and the exploitation of through going fractures the abundance of inter versus intragranular fractures depends on mineralogy and size unlike the relatively larger grains where crushing and abrasion are thought to exploit and produce discrete populations of grain sizes the comminution of fines leads to a grain size composition and rounding that is continuously distributed across size and highly dependent on source rock properties

karakoram glacier surge dynamics quincey d j braun m glasser n f bishop m p hewitt k luckman a 2011 geophysical research letters 38 article number l18504

particle interaction in fjord suspended sediment abstract glacial flour enters the surface layer of howe sound a fjord in southwestern british columbia as a sediment plume which moves quickly down inlet while gradually mixing with the sea water flocculation occurs in the lower brackish waters of the surface layer although mixing and diffusion are the dominant processes for sediment to enter the marine water once in the underlying marine water zooplankton pelletization and biologic agglomeration of inorganic floccules predominate this generates a response in the order of days between the two layers in terms of sedimentation of particulate matter most particles settling in the fjord environment fall as 1 sand and silt grains containing attached clay particles 2 clay clasts possibly related to river mudballs 3 mineral bearing fecal pellets from pelagic zooplankton 4 large grain inorganic and colloidal floccules and 5 inorganic biogenic agglomerates analysis of sediment trap data has led to the following conclusions 1 water turbidity cannot be used to infer the downward flux of particles 2 size distributions of sediment deposited on the sea bed are a function of non lognormal size distributions from particles composing sub laminae

a m gurnell and m j clark eds 1987 glacio fluvial sediment transfer an alpine perspective chichester etc john wiley and sons ltd

barotropic rossby wave radiation from a model gulf stream 1 the barotropic rossby wave field in the north atlantic ocean is studied in an eddy resolving ocean model simulation the meandering model gulf stream radiates barotropic rossby waves southward through preferred corridors defined by topographic features the smoother region between the bermuda rise and the mid atlantic ridge is a particularly striking corridor of barotropic wave radiation in the 20 50 day period band barotropic rossby waves are also preferentially excited at higher frequencies over the bermuda rise suggesting resonant excitation of topographic rossby normal modes the prevalence of these radiated waves suggests that they may be an important energy sink for the equilibrium state of the gulf stream

application of image cross correlation to the measurement of glacier velocity using satellite image data abstract image to image cross correlation software is applied to pairs of digital satellite images to map the velocity field of moving ice this technique uses small scale glacial surface features such as crevasse scars and snow dunes as markers on the surface of the moving ice displacements of the surface features are mapped by selecting small image areas centered on distinct features or by dividing a large area of densely featured glacial surface into a grid of areas and searching a subsequent image for matching areas using a cross correlation algorithm interpolation of the peak correlation values allows the displacements to be measured to subpixel accuracy resulting in very precise velocity measurements cross correlation is also applied to provide image coregistration in areas devoid of bedrock exposures in such areas subtle large scale topographic undulations in the ice surface related to underlying bedrock structure may be correlated by using large image areas and low pass filtered images both types of applications are demonstrated using ice stream d and ice stream e in west antarctica as test areas a high resolution map of the velocity field of the central portion of ice stream e generated by the displacement measuring technique is presented the use of cross correlation software is a significant improvement over previous manually based photogrammetric methods for velocity measurement and is far more cost effective than in situ methods in remote polar areas

karakorum hindukush western himalaya assessing high altitude water resources the high mountains of central and south asia provide irrigation water for their adjacent lowlands the indus irrigation scheme depends on approximately 50 of its runoff originating from snowmelt and glacier melt from the eastern hindukush karakorum and western himalaya the atlas of pakistan indicates that these mountains gain a total annual rainfall of between 200 and 500 mm amounts that are generally derived from valley based stations and not representative for elevated zones high altitude snowfall seems to be neglected and is obviously still rather unknown estimates derived from accumulation pits runoff above 4000 m range from 1000 mm to more than 3000 mm depending on the site and time of investigation as well as on the method applied to assess the vertical spatio temporal distribution of total annual precipitation a combined approach is presented this approach links in situ measurements of snow depth and water equivalent 10 year time series derived from automatic weather stations at elevations between 1500 and 4700 m a s l the spatial distribution and period of snow coverage remotely sensed data and digital elevation models and the runoff characteristics of streams originating from snow or snow ice covered watersheds modified snowmelt runoff model including intermediate snowfall and glacier runoff based on conservative assumptions the vertically changing seasonal ratio between liquid and solid precipitation is calculated using a combined snow cover and ablation model total annual amounts of precipitation are derived for different altitudinal zones amounts of modelled and measured runoff complement the investigation horizontal gradients along the indus gilgit hunza transect indicate the varying dominance of seasonal precipitation regimes monsoonal mediterranean and continental disturbances south of nanga parbat between nanga parbat and batura wall west karakorum rainfall regime 1500 1800 mm year 1 at 5000 m and areas north of batura central asian rainfall regime 600 mm year 1 at 5000 m copyright 2005 john wiley sons ltd

particle size analysis of the sediment suspended in a proglacial stream glacier de tsidjiore nouve switzerland hourly at a point samples of suspended sediment taken from the outflow stream of glacier de tsidjiore nouve switzerland over a 60 day sampling period n 1440 are shown to be dominantly composed of silt sized particles particle size sem and xrd analyses indicate a subglacial provenance for the suspended sediment temporal variations in particle size and sorting correspond poorly to fluctuations in water discharge being dominated by erratic hour to hour fluctuations and clockwise hysteresis over diurnal flow events examination of grain size and sorting dynamics over snowmelt and icemelt related ablation events during precipitation events and during glacier drainage events enables some inferences to be drawn regarding sediment source areas and supply regimes we conclude that although the bulk of the suspended sediment in the proglacial stream of glacier de tsidjiore nouve is derived directly from subglacial sources with occasional contributions from the valley train during rapid snowmelt and heavy rainfall periods a portion of the suspended load undergoes intermittent flush fall transfer through the proglacial zone which acts as a sediment source during rising flows and as a sink during periods of waning flow

hydroclimatic influence on particle size distribution of suspended sediments evacuated from debris covered chorabari glacier upper mandakini catchment central himalaya abstract sediments released from high altitude glaciers exhibit varying evacuation patterns and transport characteristics owing to the presence of thick debris cover over the glacier despite the recent needs for integrated hydrometeorological studies in the himalaya little is known about the impacts of suspended sediment on hydropower generation reservoir sedimentation and abrasion of turbine components present study involves analysis of particle size distribution of suspended sediments to understand sediment evacuation patterns and transport characteristics in variable energy conditions during the ablation season peak suspended sediments were evacuated during extreme rainfall events the estimated seasonal modern sediment erosion rate varies from 0 6 to 2 3 mm y 1 for the study period 2009 2012 the analysis shows dominance of medium silt sized to fine sand sized particles having sediment size of 0 0156 0 25 mm corresponding to 70 80 without any significant seasonal variation these transported sediments show that they are poorly sorted coarser in nature with a nearly symmetrical to coarse skewed texture and kurtosis analysis suggesting mesokurtic distribution of sediments the particle size fraction ranges between 4 65 and 5 23 which is dominantly medium to coarse silty in texture results indicate that suspended sediments are evacuated in highly variable energy conditions through subglacial transport pathways because of increase in availability of meltwater with the progressive ablation season bulk geochemical characterization has been carried out to differentiate the source of suspended sediments and intensity of weathering chemical index of alterations cia values of sediment flux range from 54 68 to 55 18 compared to the upper continental crust ucc 50 indicating moderate intensity of weathering mean seasonal 2009 2012 elemental fluxes and their contribution to the suspended sediment flux reflect that si and al are responsible for about 85 of the total detrital elemental flux trace elements show high concentrations of radioactive elements like u th pb and rb that suggest their high anomalous presence in the catchment lithology an overall study indicates that the hydroclimatic conditions over the debris covered glacier play a dominant controlling factor in erosion transportation and evacuation of suspended sediments during the ablation season

spatially variable response of himalayan glaciers to climate change affected by debris cover the present state and future evolution of himalayan glaciers has been controversial an analysis of remotely sensed frontal changes and surface velocities from glaciers in the greater himalaya between 2000 and 2008 shows large regional variability in the responses of himalayan glaciers to climate change

particle size characteristics of suspended sediment transported in meltwater from the gangotri glacier central himalaya an indicator of subglacial sediment evacuation abstract proglacial meltwater streams draining out of the himalayan glaciers carry considerable amounts of suspended sediment with a variety of particle sizes because of the supraglacial englacial and subglacial debris as well as formation of sediments from erosion by the movement of the ice this paper examines particle size transported in the proglacial meltwater stream of gangotri glacier for seven consecutive melt seasons may october 2000 2006 in order to provide information on i temporal variations in the particle size distribution ii texture and mineralogy of the sediments and iii origin and evacuation pattern of the sediments our results indicate dominance of silt size 0 002 0 06 mm particles 71 followed by sand size 0 06 0 6 mm particles 24 and clay size

glacier surge propagation by thermal evolution at the bed bakaninbreen southern svalbard began a prolonged surge during 1985 in 1986 an internal reflecting horizon on radio echo sounding data was interpreted to show that the position of the surge front coincided with a transition between areas of warm unfrozen and cold frozen bed ground penetrating radar lines run in 1996 and 1998 during early quiescence show that the basal region of the glacier is characterized by a strong reflection interpreted as the top of a thick layer of sediment rich basal ice down glacier of the present surge front features imaged beneath the basal reflection are interpreted as the bottom of the basal ice layer the base of a permafrost layer and local ice lenses this indicates that this region of the bed is cold up glacier of the surge front a scattering zone above the basal reflection is interpreted as warm ice there is no evidence for this warm zone down glacier of the surge front nor do we see basal permafrost up glacier of it thus as in early surge phase the location of the surge front is now at the transition between warm and cold ice at the glacier bed we suggest that the propagation of the front is associated with this basal thermal transition throughout the surge because propagation of the front occurs rapidly and generates only limited heat basal motion during fast flow must have been restricted to a thin layer at the bed and occurred by sliding or deformation localized at the ice bed interface

transport of suspended particulate matter in an antarctic fjord abstract vertical profiles of temperature salinity and light attenuation were used in conjunction with underwater photography and water samples to characterize the nature and dynamics of particle transport in an antarctic fjord most of the particles are sand sized 0 1 2 mm floccules comprised of individual grains in the 5 to 50 m size range the quartz silt grains are derived from basal debris laden meltwater originating from beneath the submerged valley glacier the meltwater buoyantly rises to form cold water interflows at mid water depths turbulent mixing near the seafloor also plays a role in the transport and break up of floccules together the midwater cold tongues and near bottom turbidity account for 87 of the total sediment load thus attesting to the importance of non surface transport mechanisms in polar fjords

influences of a rough bottom topography on flow kinematics in an eddy resolving circulation model we report a study of a coastal frontal zone of the southeastern united states based on a field experiment and numerical modeling the study was conducted in the spring of 1985 during weak to moderate wind stress and strong input of buoyancy from solar radiation and river discharge the study confirms that the structure and slope of the frontal zone depends on a combination of wind stress and cross shelf advection of buoyancy a cross shelf depth two dimensional x y time dependent numerical model illustrated the response of the frontal zone to the local wind stress regimes a comparison of model results with field data showed that the model successfully predicted onsets of stratification and mixing when alongshore wind stress was negative southward isopycnals in the frontal zone steepened due to a combination of horizontal advection and vertical convection when stress was positive northward the offshore advection of low density water flattened the isopycnals and potential energy decreased demonstrating that horizontal advection terms are important in the equation of conservation of buoyancy the model predicts die offshore advection of lenses of less dense water during upwelling favorable wind stress these lenses are of the order of 20 km in cross shelf scale and represent an efficient mechanism to export nearshore water the lenses consist of a mixture of low salinity coastal water and continental shelf water originating further offshore and advected onshore along the bottom the mean flow inside the frontal zone opposed the mean alongshore wind stress part of the alongshore flow was in geostrophy with the cross shore pressure gradient the other part was due to an alongshore pressure gradient force kinematic of about 1 10 6 m s 2 equivalent sea surface slope 1 10 7 which was trapped along the coast with an offshore width scale of o 10 km it is likely that the alongshore extent of this pressure gradient was governed by the scale at which freshwater is injected to the continental shelf i e 20 30 km the pressure gradient force immediately outside of the frontal zone was about 5 10 7 m s 2 in the direction of the mean alongshore wind stress it is hypothesized that as a result of wind setup and freshwater influx the northward pressure gradient forced over outer shelf slope by the gulf stream decreases in magnitude onshore and can even change sign across a nearshore frontal zone of o 10 km the implied flow field near the frontal zone is therefore highly three dimensional with v y u x where u v are velocities in the cross shore x and alongshore y directions respectively

glacier motion dominated by processes deep in underlying till black rapids glacier is a 40 km long surge type glacier in the central alaska range in spring 1997 a wireline drill rig was set up at a location where the measured surface velocities are high and seasonal and annual velocity variations are large the drilling revealed a layer of subglacial till up to 7 m thick that is believed to be water saturated at one location a string of instruments containing three dual axis tiltmeters and one piezometer was successfully introduced into the till the tiltmeters monitored the inclination of the borehole at the ice till interface and at 1 and 2 m into the till for 410 days they showed that no significant deformation occurred in the upper 2 m of the till layer and no significant amount of the basal motion was due to sliding of the ice over the till the measured surface velocity at the drill site is about 60 m a 1 of which 20 30 m a can be accounted for by ice deformation almost the entire amount of basal motion 30 40 m a 1 was taken up at a depth of 2 m in the till possibly in discrete shear layers or as sliding of till over the underlying bedrock we propose that the large scale mobilization of such till layers is a key factor in initiating glacier surges

correlations of suspended sediment size with bedrock lithology and glacier dynamics the hypothesized link between glacier surging and bedrock geology motivates this study of the suspended sediment size distributions sssd from surge type and non surge type glaciers we analyze sssds from proglacial streams in 20 individual basins comprising various fractions of metasedimentary ms and felsic plutonic rocks we compare the size distributions by performing tests of significance on the distribution statistics and a principal component analysis on discrete grain sizes we find that surge type and non surge type glaciers underlain solely by ms rocks have significantly different sssds while surge type glaciers as a whole have remarkably similar sssds regardless of the underlying bedrock geology these observations hint at a relationship between sediment characteristics and glacier surging though causation in either direction cannot be established without additional data

flow thermal structure and subglacial conditions of a surge type glacier temperature measurements in a subpolar surge type glacier reveal a distinctive thermal structure associated with the boundary between the ice reservoir and receiving areas in the receiving area the glacier is cold based but bottom temperature has increased as much as 0 5 c between 1981 and 1982 and the basal heat flux is roughly 10 times the expected geothermal flux water percolation through permeable subglacial material is the probable energy source deformation of the substrate could destroy this drainage system and trigger a surge

on eddy scales in the eastern and northern north atlantic ocean as a function of latitude infrared satellite images and two ensembles of satellite tracked buoys have been used to analyze eddy scales in the central and eastern north atlantic between 35 n and 60 n both data sets yield eddy scales which decrease northward from the subtropical atlantic and can be closely related to the rossby radius of the first baroclinic mode

thermally controlled glacier surging bakaninbreen in svalbard and trapridge glacier in yukon territory canada are two prominent examples of surging glaciers which are thought to be controlled by their thermal regime both glaciers have developed large bulges which have propagated forward as travelling wave fronts and which are thought to divide relatively stagnant downstream cold based ice from faster moving warm based upstream ice additionally both glaciers are underlain by a wet metres thick layer of deforming till we develop a simple model for the cyclic surging behaviour of these glaciers which interrelates the motion of the ice and till through a description of the subglacial hydrology we find that oscillations surges can occur if the subglacial hydrological transmissivity is sufficiently low and the till layer is sufficiently thin and we suggest that these oscillations are associated with the development and propagation of a travelling wave front down the glacier we therefore interpret the travelling wave fronts on both trapridge glacier and bakaninbreen as manifestations of surges in addition we find that the violence of the surge in the model is associated with the resistance to ice flow offered by undulations in the bed and the efficiency with which occasional hydrological events can release water accumulated at the glacier sole

the recent evolution of liligo glacier karakoram pakistan and its present quiescent phase liligo glacier in the central eastern karakoram pakistan is a small south to north flowing glacier situated in a transverse valley on the left south side of baltoro glacier new processing of satellite imagery enables a better quantification of terminus oscillations over the past 30 years from the beginning of the 1970s to the beginning of the 21st century liligo glacier advanced about 2km 60m a 1 the progress was characterized by a significant evolution of terminus morphology similar to that observed on the same glacier during the advance event near the beginning of the 20th century and to those of many other karakoram glaciers this suggests indications of a surge type mechanism field observations performed in 2004 indicated there was probably no confluence at that time between liligo and baltoro glaciers and that a quiescent phase had started in the early years of the 21st century

characteristics of surge type glaciers glaciers can be divided into two classes according to their flow behavior normal relatively steady annually averaged flow rate and surge type pronounced cyclic flow variations having a typical periodicity of 10 100 years we have examined the population statistics of 2356 glaciers in the st elias mountains yukon territory canada and estimate that 151 6 4 of these glaciers are surge type to explore how various glacier attributes are associated with surging we compare the probability of surging associated with various subsets of the complete population to appropriate reference values in this way potential influences on surge tendency can be examined for the 55 drainage basins analyzed there is a pronounced spatial variation in the concentration of surge type glaciers but no obvious environmental control can be evinced within the study area the greatest concentration lies in the northern st elias mountains a region of high topographic elevation that is experiencing rapid tectonic uplift analysis of the influence of length on surge tendency reveals that long glaciers have a significantly greater probability of being surge type than short glaciers the surge probability increases monotonically from 0 61 for very short glaciers 0 1 km to 65 1 for long glaciers 10 75 km this result suggests that ice sheets and ice caps or at least portions of them should have a high probability of surging tributary glaciers have a greater tendency to surge than trunk glaciers presumably because they may themselves be surge type and may additionally participate in surges of the trunk glacier the nonrandom geographical distribution of surge type glaciers is not simply a consequence of the variation from basin to basin of the glacier length distribution surge type glaciers tend to have a higher overall elevation than normal glaciers the elevation of the highest point of the accumulation zone the elevation of the snow line and the elevation of the lowest point of the ablation zone on average exceed the corresponding elevations for normal glaciers there is no significant difference between the overall slopes of surge type and normal glaciers although there is a tendency for surge type glaciers to have greater slope in the accumulation zone and lesser slope in the ablation zone than normal glaciers although the prevalent flow direction for glaciers in the yukon data set is to the north surge type glaciers tend to flow to the east and southeast this orientation influence is probably explained by the fact that many of the longest glaciers also flow to the east and southeast

from soil aggregates to riverine flocs a laboratory experiment assessing the respective effects of soil type and flow shear stress on particles characteristics particles eroded from hillslopes and exported to rivers are recognized to be composite particles of high internal complexity their architecture and composition are known to influence their transport behaviour within the water column relative to discrete particles to date hillslope erosion studies consider aggregates to be stable once they are detached from the soil matrix however lowland rivers and estuaries studies often suggest that particle structure and dynamics are controlled by flocculation within the water column in order to improve the understanding of particle dynamics along the continuum from hillslopes to the lowland river environment soil particle behaviour was tested under controlled laboratory conditions seven flume erosion and deposition experiments designed to simulate a natural erosive event and five shear cell experiments were performed using three contrasting materials two of them were poorly developed and as such can not be considered as soils whilst the third one was a calcareous brown soil these experiments revealed that soil aggregates were prone to disaggregation within the water column and that flocculation may affect their size distribution during transport large differences in effective particle size were found between soil types during the rising limb of the bed shear stress sequence indeed at the maximum applied bed shear stress the aggregated particles median diameter was found to be three times larger for the well developed soil than for the two others differences were smaller in the falling limb suggesting that soil aggregates underwent structural changes however characterization of particles strength parameters showed that these changes did not fully turn soil aggregates into flocs but rather into hybrid soil aggregate floc particles copyright 2013 john wiley sons ltd

controls on the distribution of surge type glaciers in svalbard we analyzed the possible controls on the distribution of surge type glaciers in svalbard using multivariate logit models including 504 glaciers and a large number of glacial and geological attributes specifically we examined the potential effect of geological boundaries mass balance conditions and thermal regime on surging it was found that long glaciers with relatively steep slopes overlying young fine grained sedimentary lithologies with orientations in a broad arc clockwise from northwest to southeast are most likely to be of surge type no relation between lithological boundaries and surge potential could be established possible explanations for length being conducive to surging are transport distance related substrate properties distance related attenuation of longitudinal stresses and the possible relation between thermal regime and glacier size analysis of glaciers with recorded radioecho sounding reveals that a polythermal regime accumulation area ratios close to balance and a large elevation span increase the surge potential the logit models also enabled us to detect 19 new surge type glaciers to reclassify six glaciers as normal and to identify unusual surge type glaciers our model results suggest that a polythermal regime and fine grained potentially deformable beds are conducive to the surge potential of svalbard glaciers

how much do we really know about glacier surging some of the ideas about glacier surging are considered mainly but not entirely in the light of observations of temperate glaciers in alaska u s a made within the last 15 years climate has an influence on surge recurrence interval climate and weather also affect surge initiation termination and magnitude regional studies lead to the speculation that subglacial till plays a key role in surging and it has been found under all surge type glaciers studied so far including black rapids and variegated glaciers alaska in most of the glaciers studied till deformation processes dominate the motion in quiescence the linked cavity model of surge triggering and rapid motion is not consistent with these observations but the limited coverage of the observations does not rule it out under parts of the glaciers studied the till observations in alaska raise old questions about the interaction between till and the hydraulic systems of temperate glaciers the role of stored water which observations show to be active even in winter on black rapids glacier is noted

a surge of bualtar glacier karakoram range pakistan a possible landslide trigger bualtar glacier karakoram range northern pakistan surged during the spring and early summer of 1987 this followed a major episode of three landslides which impacted part of the glacier ablation zone on 30 31 july 1986 in may 1987 surface velocities of 7 m d 1 were measured at one profile down glacier from the landslide deposits where in 1986 velocities were an order of magnitude less surface and hydrological characteristics of the glacier in and down glacier from the landslide deposit were also indicative of surge like behavior in 1987 and a return to pre surge conditions by 1988

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

particle size and mineralogical composition of inorganic colloids in glacier melting water and overlying ice in an alpine glacier oberaargletscher switzerland

composite suspended sediment particles and flocculation in glacial meltwaters preliminary evidence from alpine and himalayan basins research over the last decade has shown that the suspended sediment loads of many rivers are dominated by composite particles these particles are also known as aggregates or flocs and are commonly made up of constituent mineral particles which evidence a wide range of grain sizes and organic matter the resulting in situ or effective particle size characteristics of fluvial suspended sediment exert a major control on all processes of entrainment transport and deposition the significance of composite suspended sediment particles in glacial meltwater streams has however not been established existing data on the particle size characteristics of suspended sediment in glacial meltwaters relate to the dispersed mineral fraction absolute particle size which for certain size fractions may bear little relationship to the effective or in situ distribution existing understanding of composite particle formation within freshwater environments would suggest that in stream flocculation processes do not take place in glacial meltwater systems because of the absence of organic binding agents however we report preliminary scanning electron microscopy data for one alpine and two himalayan glaciers that show composite particles are present in the suspended sediment load of the meltwater system the genesis and structure of these composite particles and their constituent grain size characteristics are discussed we present evidence for the existence of both aggregates or composite particles whose features are largely inherited from source materials and flocs which represent composite particles produced by in stream flocculation processes in the absence of organic materials the latter may result solely from electrochemical flocculation in the meltwater sediment system this type of floc formation has not been reported previously in the freshwater fluvial environment further work is needed to test the wider significance of these data and to investigate the effective particle size characteristics of suspended sediment associated with high concentration outburst events such events make a major contribution to suspended sediment fluxes in meltwater streams and may provide conditions that are conducive to composite particle formation by flocculation copyright 2002 john wiley sons ltd

glacier velocities across the central karakoram optical matching of aster advanced spaceborne thermal emission and reflection radiometer satellite image pairs is used to determine the surface velocities of major glaciers across the central karakoram the aster images were acquired in 2006 and 2007 and cover a 60 120 km region over baltoro glacier pakistan and areas to the north and west the surface velocities were compared with differential global position system gps data collected on baltoro glacier in summer 2005 the aster measurements reveal fine details about ice dynamics in this region for example glaciers are found to be active over their termini even where they are very heavily debris covered the characteristics of several surge type glaciers were measured with terminus advances of several hundred meters per year and the displacement of trunk glaciers as surge glaciers pushed into them this study is the first synthesis of glacier velocities across this region and provides a baseline against which both past and future changes can be compared

the potential of satellite radar interferometry and feature tracking for monitoring flow rates of himalayan glaciers abstract the stagnation of himalayan glaciers will only be exacerbated by a warming climate increasing hazards associated with glacier lake development frontal recession is a poor indicator of negative balance in this region where most glaciers are debris covered but reduced glacier flow rates provide a valuable warning of stagnation in situ measurements of velocity are understandably rare and remote sensing measurements have hitherto been limited by severe topography and lack of suitable data in this paper we compare two techniques to measure flow rates in everest region glaciers firstly satellite radar interferometry sri has recently become more viable because of improved digital elevation data and precision orbit models which now allow snapshots of velocities to be retrieved from ers imagery in the mid 1990s without ground control information secondly feature tracking between synthetic aperture radar sar images is found to be successful even on the small glaciers of this region because of the patterning associated with debris cover this technique extends through the 1990s and beyond the time frame over which velocities can be measured using the examples of the khumbu glacier flowing south into nepal and the kangshung glacier flowing east into china from the everest massif we compare sri and sar feature tracking in ers images consider the errors in these techniques and examine the potential to monitor flow rates across the region the techniques are found to be highly complementary and appropriate for monitoring flow rates in this region suggesting that routine monitoring of himalayan glaciers is possible the kangshung glacier appears to sustain relatively high flow rates of up to 10 cm day which along with a convex topographic profile indicates a healthy glacier not exhibiting significant negative mass balance in comparison much of the khumbu glacier appears to have stagnated the surface velocity at gorak shep is only 20 of a field based measurement in the 1970 s and the concave surface profile confirms the downwasting associated with a debris covered glacier in recession

the significance of particle aggregation in the overbank deposition of suspended sediment on river floodplains abstract the effects of suspended sediment aggregation on rates of overbank deposition and on the grain size composition of deposited sediment were investigated using a combined field measurement and numerical modelling approach measurements of the in situ grain size characteristics of the suspended sediment load termed the effective size distribution of the river culm devon were obtained using a custom built water elutriation system samples of suspended sediment and of sediment deposited on the floodplain were analysed in the laboratory to determine the size distributions of their constituent discrete mineral particles termed the ultimate size distribution interpretation of these field data was aided by the development of a two dimensional finite difference model of flood hydraulics and suspended sediment dispersion and deposition field measurements and model predictions show that particle aggregation results in higher relative contributions of fine size fractions to overbank deposits aggregation may also provide a mechanism for explaining the poor agreement between theoretical and observed trends in relationships between mean deposit grain size and distance from the main channel suspended sediment aggregation is shown to cause significant increases in rates of floodplain deposition increases in deposition rates resulting from aggregation may however be less than expected because of the effects of aggregate shape and density the latter may offset increases in particle size so that the settling velocities of the largest aggregates do not increase appreciably with particle diameter

how topographic smoothing contributes to differences between the eddy flows simulated by sigma and geopotential coordinate models abstract the characteristics of the mesoscale turbulence simulated at a resolution of by a sigma coordinate model spem and a geopotential coordinate model opa of the south atlantic differ significantly these two types of models differ with respect to not only their numerical formulation but also their topography smoothed in spem as in every sigma coordinate application in this paper the authors examine how these topographic differences result in eddy flows that are different in the two models when the topography of the agulhas region is smoothed locally in opa as is done routinely in spem the production mechanism of the agulhas rings their characteristics and their subsequent drift in the subtropical gyre are found to converge toward those in spem furthermore the vertical distribution of eddy kinetic energy eke everywhere in the basin interior becomes similar in spem and opa and according to some current meter data becomes more realistic when mesoscale topographic roughness is re

composite suspended sediment particles in river systems their incidence dynamics and physical characteristics most of the existing data on the effective particle size characteristics of fluvial suspended sediment derive from instantaneous sampling methods that may not be representative of the overall suspended sediment loads this presents difficulties when there is a need to incorporate effective particle size data into numerical models of floodplain sedimentation and sediment associated contaminant transfer we have used a field based water elutriation apparatus wea to assemble a large 36 flood database on the time integrated nature of the effective and absolute particle size characteristics of suspended sediment in four subcatchments of the river exe basin of southwest england these catchments encompass a wide range of terrains and fluvial environments that are broadly representative of much of the uk and temperate low relief northwest europe the wea provides important data on the physical characteristics of composite particles that are not attainable using other methods this dataset has allowed for the first time detailed interbasin comparisons of the time integrated particle size characteristics of suspended sediment and reliable estimates of the contribution of five effective size classes to the mean annual suspended sediment load of the study catchments the suspended sediment load of each river is dominated by composite rather than primary particles with for example almost 60 by mass of the sediment load of the river exe at thorverton transported as composite particles 16 m in size all the effective size classes contain significant clay components a key outcome of this study is the recognition that each catchment has a distinctive time integrated effective particle size signature in addition the time integrated effective particle size characteristics of the suspended loads in each of the catchments display much greater spatial variability than the equivalent absolute particle size distributions this indicates that the processes producing composite particles vary significantly between these catchments and this has important implications for our understanding of the dynamics of suspended sediment properties copyright 2007 john wiley sons ltd

glacial sediment production and development of hydro electric power in glacierized areas by jim bogen glaciology section norwegian water resources and energy administration p o box 5091 majorstua n 0301 oslo 3 norway abstract this paper discusses the results of a sediment monitoring programme carried out in connection with hydro electric power development plans in the river basins surrounding the jostedalsbreen ice cap in norway whereas the highest suspended sediment transport rates occur during years with several flash flood events the bed load is more dependent upon the duration of large magnitude flood events bed load transport has been obtained from annual measurements of deltaic growth in small lakes at the front of glaciers during the years 1968 86 the mean ratio of bed load to total load amounted to 0 30 0 50 of the total load but in years with large magnitude floods this ratio decreased the mean annual suspended sediment yield of norwegian glaciers ranges from 100 tonnes km2 a i to 1300 tonnes km2 a i valley glaciers cause the highest erosion rates with the exception of the small cirque glacier trollbergdalsbreen which is thought to be a soft bed glacier the investigation programme undertaken involved monitoring the volume of suspended sediments together with the size distribution mineralogy and shape of grains in general the valley glaciers supply more sand than the smaller cirque glaciers whereas particles in the fine sand and silt size ranges in almost all of the glaciers are angular in shape methods of comparing the abrasive capacity of the sediment load at various intakes in a power plant are discussed long term sediment supply from the glaciers was investigated by studies of varves and rythmites in sediment cores from glacier fed lakes introduction during the last few years several glacier areas in norway have been developed for hydro electric power in this paper the results of a sediment monitoring programme carried out in connection with hydro electric power plans in the river basins surrounding the jostedalsbreen ice cap are discussed the hydro electric power plans on the western side the breheimen stryn project involve diversions of water at 32 intakes fig

glacier surge mechanism 1982 1983 surge of variegated glacier alaska the hundredfold speedup in glacier motion in a surge of the kind the kind that took place in variegated glacier in 1982 1983 is caused by the buildup of high water pressure in the basal passageway system which is made possible by a fundamental and pervasive change in the geometry and water transport characteristics of this system the behavior of the glacier in surge has many remarkable features which can provide clues to a detailed theory of the surging process the surge mechanism is akin to a proposed mechanism of overthrust faulting

flocculation a key process in the sediment flux of a large glacier fed lake this study investigates the consequences of flocculation for sediment flux in glacier fed lillooet lake british columbia based on density fractal dimension in situ profiles of sediment concentration and size distribution and settling velocity equations presented in the literature sediment flux attributed to macroflocs during the late spring and summer accounts for a significant portion of sediment flux in the lake equivalent to at least one quarter of the average annual sediment flux fine sediment is reaching the lake floor faster in flocs than occurs if settling as individual grains this flux varies both spatially and temporally over the observation period suggesting a link between deposition via flocculation and the properties of bottom sediments macrofloc flux increased through june reached a peak during july and then declined into august macrofloc flux was greatest in the distal end of the first basin approximately 10 km from the point of inflow relatively high excess densities 0 1 g cm 3 at 500 m for flocs in situ are consistent with a composition dominated by inorganic primary particles microlaminations within lillooet lake varves have been linked by earlier workers to discharge events and the action of turbidity currents emanating from the lillooet river while turbidity currents undoubtedly occur in lillooet lake these results demonstrate flocculation as an adjunct process linking discharge lake level macrofloc flux bulk density and microlaminations in situ measurements of sediment settling velocity in glacier fed lakes are required to better constrain flux rates and permit comparison between flocculation in lacustrine environments with existing studies of estuarine marine and fluvial flocculation copyright 2009 john wiley sons ltd

eddy induced heat transport in a coupled ocean atmospheric anomaly model the midlatitude meridional heat transport in the ocean can be partitioned into a transport by the mean flow and an eddy transport this heat transport has been studied in several ocean only models surprisingly it was found that eddy resolving and coarse resolution models have similar total heat transport this is caused by a compensation mechanism in which poleward eddy transport is counterbalanced by an eddy induced meridional circulation recently it was shown that this compensation depends on details of the atmospheric forcing and in fact only occurs for weak thermal coupling where thermal coupling is defined as the rate of change of the surface heat flux with respect to the sea surface temperature sst the thermal coupling varies with the spatial scale of the sst anomaly to study the actual strength of this coupling on the eddy length scale the authors have coupled an isopycnic ocean model with embedded mixed layer to an atmospheric anomaly model by comparing coarse resolution and eddy resolving simulations it is found that 1 the thermal coupling is strong on the eddy length scale and 2 the aforementioned compensation does not occur consequences for the temperature boundary condition in ocean only models the gent and mcwilliams eddy parameterization and climate modeling are discussed

ice velocity and climate variations for baltoro glacier pakistan quincey dj copland l mayer c bishop m luckman a belo m 2009 ice velocity and climate variations for the baltoro glacier pakistan journal of glaciology 55 194 1061 1071 sponsorship rcuk us national science foundation us national geographic society natural sciences and engineering research council of canada canadian foundation for innovation ontario research fund university of ottawa

tributary glacier surges an exceptional concentration at panmah glacier karakoram himalaya four tributaries of panmah glacier have surged in less than a decade three in quick succession between 2001 and 2005 since 1985 13 surges have been recorded in the karakoram himalaya more than in any comparable period since the 1850s ten were tributary surges in these ten a full run out of surge ice is prevented but extended post surge episodes affect the tributary and main glacier the sudden concentration of events at panmah glacier is without precedent and at odds with known surge intervals for the glaciers interpretations must consider the response of thermally complex glaciers at exceptionally high altitudes and of high relief to changes in a distinctive regional climate it is suggested that high altitude warming affecting snow and glacier thermal regimes or bringing intense short term melting episodes may be more significant than mass balance change

tracing organic matter sources in riverine suspended sediment implications for fine sediment transfers abstract the study of sediment transport in riverine systems has historically focussed on the inorganic fluxes although the suspended load is known to incorporate both inorganic and organic material research on freshwater flocculation indicates that sediment morphology and behaviour depend on both components as biologic material can alter the hydrodynamic and charge properties of composite particles which has implications for fine sediment transport and storage in stream systems this study evaluates both the supply and the quality of the organic matter comprising the suspended sediment in a salmon bearing stream in northern british columbia canada seasonally changing hydrodynamic and biologic conditions are considered in the context of suspended sediment seston size seston samples were collected in an event based design for analysis of organic matter sources suspended particulate inorganic and organic matter concentrations spm sim and som and effective particle size distributions epsd organic matter sources were assessed using carbon nitrogen c n ratios and the associated stable isotopic signals samples and environmental measurements were taken during spring melt pre spawn low flows active salmon spawning post spawn and select rainstorms spm and sim were elevated during active salmon spawning compared to that expected for the given hydrologic conditions seasonal patterns of c n ratios and stable isotopes indicate that organic matter types can be differentiated in seston samples and these sources of organic material exhibit changing dominance in the seston over time the isotopic signature of seston increases in salmon derived nutrients when live and decaying salmon are present within the study stream the largest suspended particles are observed during the period of active spawning when both live and rotting salmon modify instream conditions this appears to be a function of the combined influence of high sim low shear stress and low c n ratios the generation of increased floc or seston size is of ecological importance in this stream and riverine systems elsewhere as it regulates the freshwater transfers of locally derived nutrients and sediments out of the fluvial system