weathering rates of historic sandstone structures in semiarid environments ebro basin ne spain abstract long term weathering rates of sandstones were obtained for well dated from 400 to 1100 years bp historic structures wall sections of the alberuela castle in a semiarid environment of the central ebro basin ne spain using an exclusive movable contour plotting frame this sandstone has a low durability controlled mainly by textural properties differences observed in weathering rates are clearly controlled by the age of building as well as the orientation of the studied sandstone wall sections weathering processes related to insolation control the asymmetric spatial pattern of weathering rates in surfaces exposed for since 1100 bp which are higher in southeast facing sandstone wall sections 8 4 mm 100 years than in southwestern 4 4 mm 100 years and northern faces 3 9 mm 100 years in addition exponential increase in weathering rates with time from 1 6 2 2 mm 100 years in surfaces exposed for since 800 400 bp to 8 4 mm 100 years in surfaces exposed for since 1100 bp in southeastern faces may be probably related to environmental changes during the last millennium

salt weathering simulation using a single immersion technique samples of concrete were subjected in an environmental cabinet to six different diurnal cycles of temperature and humidity change representative of desert surface conditions in the presence of a range of saturated salt solutions the samples were not subjected to repeated immersion or continuous partial immersion as has been the case in most previous experiments breakdown did occur nonetheless the two most effective cycles were one from egypt with a very high daytime maximum and one from the negev with high nocturnal humidity conditions cycles with relatively modest temperature and humidity cycles were ineffective in causing debris liberation

the effect of rock strength on weathering rates of sandstone used for angkor temples in cambodia abstract this study determined the weathering rates from the depths of hollows formed by the deterioration of sandstone blocks used to build angkor temples in the 7th 12th centuries due to capillary processes these hollows generally develop at the bases of building components such as doorframes false doorframes window frames and pillars in this study 55 locations in 29 temples were selected to measure maximum hollow depth based on the ages of the temples the weathering rate was calculated to be in the range 7 92 mm ka 1 the weathering rate was found to be independent of building component type and aspect the calculated weathering rate corresponds to the physical weathering rate of sandstone caused by the wetting drying cycles that result from the tropical environment along with the dry season an equation that can estimate the maximum depth of a hollow in a sandstone block was proposed based on temple age and the coefficient obtained from two types of rock hardness values the equation coefficient is an effective index that can help predict the deterioration of stone cultural artifacts such as the angkor temples

ross ice shelf oxygen isotopes and west antarctic climate history the ross ice shelf 18o profile at station j 9 covers at least the last 30 000 yr it identifies the depth in the core of ice from i the last glacial interglacial transition 266 to 286 m and ii the 1000 m surface elevation about 140 m various processes contribute to the 18o change observed in the core i climatic warming mainly caused by a decrease in winter sea ice extent around antarctica of about 6 latitude early in the glacial interglacial transition ii decreasing ice sheet thickness later in the glacial interglacial transition and during the holocene and iii decreases in elevation and effective distance from the open ocean as the source of the ice in the core shifts along the flow line toward j 9 average 18o values of the last 3000 yr imply a fairly stable climate yet shorter 102 to 103 yr 18o climatic oscillations up to 6 are seen in both the holocene and the glacial portion of the record

engineering aspects and time effects of rapid deterioration of sandstone in the tropical environment of sabah malaysia cut slopes in rock masses start to deteriorate directly after excavation due to stress relief and weathering the deterioration is a time dependent process that depends on the local climate and the rock mass including its history and the environment the amount of deterioration per time unit the weathering intensity rate is not a constant over time but is for most rock masses larger when the mass is less weathered and becomes smaller with further progressing weathering a study has been carried out to establish the relationship between weathering intensity rate and exposure time for the intact rock strength irs of sandstone in humid tropical areas the data set for the study was collected in and near kota kinabalu sabah malaysia which has a humid tropical climate the geology in the area consists of thick sequences of sandstone and shale beds of the crocker formation results show that the best relationship between intact rock strength irs and exposure time t is by a logarithmic function irs t 105 34 log 1 t this relationship can likely be used for prediction of the intact rock strength development of similar sandstone over the engineering lifetime of man made slopes in tropical areas

weathering rates of sandstone in a semi arid environment hunter valley australia the rate of sandstone weathering in the semi arid climate of the hunter valley new south wales australia has been estimated from observations of gravestone weathering in the area the gravestone data points to two distinct stages in the weathering process the first stage covering the first century of exposure is characterised by a relatively low recession rate of 0 5 mm 100 years this is followed by a second stage in which the rate of weathering increases sharply to ca 2 5 mm 100 years the non linear nature of the weathering trends over time suggests that during the first century of exposure structural changes took place within the sandstone material which lay the foundation for accelerated weathering after further exposure laboratory trials were also conducted to identify the effectiveness of different weathering processes in the decay of sandstone in this region of the four processes examined only the freeze thaw cycle produced a significant degree of mass loss and is therefore most likely a strong contributor to the weathering of sandstone in this region

evidence for platelet ice accretion in arctic sea ice development moderate quantities of platelet ice are reported in ice cores obtained from floes in the central and western beaufort sea arctic ocean the crystal structure characteristics include a fabric of long thin ragged edged crystals with randomly oriented c axes the cellular substructure that is characteristic of congelation ice is not evident in individual platelet ice crystals but they do occur together with congelation ice in layers ranging from 0 05 to 0 6 m thick platelet ice crystals are observed primarily in second year and multiyear floes the structural characteristics of arctic platelet ice are similar to those of antarctic platelet ice the platelet ice layers have a minimum 18o value of 5 3 and in some cases the platelet ice layers have more negative 18o values than the ice layers above and below them the salinity of platelet ice layers is not significantly different from other ice layers a number of platelet ice growth mechanisms and sources are discussed processes associated with the ellesmere ice shelves nearshore processes such as anchor ice growth in shallow waters off the north coast of alaska and ice growth in freshwater impounded behind grounded ice dams might be locally important but are unlikely to contribute significant quantities of platelet ice to pack ice floes two processes probably account for the presence of platelet ice the first is growth in underice melt ponds which form in inverted depressions at the base of floes when meltwater floes off the ice surface the second is the operation of ice pumps in which ice that is melted off the deeper parts of floes and ridges is deposited as platelet ice at a higher level in either case initially loose accumulations of platelet crystals are entrained in the floes by the growth of congelation ice the widespread occurrence of platelet ice in the central and western beaufort sea suggests that ice growth in both underice melt ponds and associated with the operation of ice pumps might be more common than was previously realized

stable isotope 18o 16o tracing of fresh brackish and sea ice in multi year land fast sea ice ellesmere island canada la salinite de la glace et les rapports 18 o 16 o ont ete mesures sur 12 carottes de glace prelevees sur la glace marine au large de la cote nord de ellesmere island canada les 3 types de glace douce saum tre et marine ont ete identifies dans les carottes en utilisant les rapports isotopiques 18 o 16 o l utilisation des mesures 18 o pour identifier la glace marine et saum tre est discutee la proportion de chaque type de glace presente est etablie et les implications pour les proprietes et la structure de l eau sous glaciaire sont presentees

the evidence for paraglacial sedimentation and its temporal scale in the deglacierizing basin of small river glacier canada abstract spatially sampled suspended sediment data from extra channel surfaces of different ages during rainfall events were used to infer the timescale of landscape adjustment to little ice age lia deglacierization at small river glacier canada surface ages were determined by aerial photograph interpretation turbidimeters were installed in three ephemeral channels on young mature and old surfaces and their response to rainfall events of different magnitudes recorded results showed young ice proximal surfaces exposed since 1977 were increasingly vulnerable to mobilization during rainfall events a suspended sediment response from old surfaces exposed since 1910 was recorded for only three events with 5 and 30 year return periods the intensity and duration of rainfall events therefore had to increase in magnitude to mobilize sediment on surfaces of increasing maturity hysteresis in the channel suspended sediment response further confirmed the dependence of surface response on rainfall event magnitude the rapid temporal decline in surface response indicated that surface armoring or sediment exhaustion is stabilizing surfaces within decades of exposure from the lia maximum ca 1910 at small river glacier however further perturbation for example by glacial advance or extreme climatic events would likely modify the pattern of suspended sediment yields by changing terrain surface mobilization thresholds and reconfiguring channel sediment stores we therefore suggest that it is difficult to determine when paraglacial sedimentation ceases to influence suspended sediment yields and therefore significantly limiting the usefulness of the term to describe the period of suspended sediment yield adjustment following deglacierization

arctic ice shelves and ice islands origin growth and disintegration physical characteristics structural stratigraphic variability and dynamics ice shelves are thick floating ice masses most often associated with antarctica where they are seaward extensions of the grounded antarctic ice sheet and sources of many icebergs however there are also ice shelves in the arctic primarily located along the north coast of ellesmere island in the canadian high arctic the only ice shelves in north america and the most extensive in the north polar region the ellesmere ice shelves originate from glaciers and from sea ice and are the source of ice islands the tabular icebergs of the arctic ocean the present state of knowledge and understanding of these ice features is summarized in this paper it includes historical background to the discovery and early study of ice shelves and ice islands including the use of ice islands as floating laboratories for polar geophysical research growth mechanisms and age the former extent and the twentieth century disintegration of the ellesmere ice shelves and the processes and mechanisms of ice island calving are summarized surface features thickness thermal regime and the size shape and numbers of ice islands are discussed the structural stratigraphic variability of ice islands and ice shelves and the complex nature of their growth and development are described large scale and small scale dynamics of ice islands are described and the results of modeling their drift and recurrence intervals are presented the conclusion identifies some unanswered questions and future research opportunities and needs

scale issues in weathering studies a review of the major scale issues in weathering studies reveals concerns over the fundamental spatio temporal distributions of weathering phenomena as well as issues of upscaling microscope based observations and linking different scales of observations in explanations of landform development various strategies are proposed which can be used to tackle these issues many rooted in non linear dynamical systems ideas as an initial step spatio temporal scale distributions are estimated here for weathering processes landforms and controls based on a range of empirical data two case studies of phytokarst in grand cayman and blistering and scaling of building stones are presented to illustrate the types of data that might be used to establish more convincing scale linkages in weathering investigations

effects of aspect on weathering anomalous behaviour of sandstone gravestones in southeast england rocks in the humid temperate zone tend to weather more severely on faces exposed to the prevailing winds than on their more sheltered leeward faces in southeast england however gravestones composed of a non local quartz rich sandstone exhibit a reverse weathering pattern the east facing lee sides exhibit a much greater depth and areal extent of weathering than the west sides which face the westerly wind and rain possible reasons for the asymmetric pattern of weathering are discussed copyright 2000 john wiley sons ltd

the interaction between armouring and particle weathering for eroding landscapes the interaction between particle weathering and surface armouring and its effect on erosion has been investigated the effect of soil armouring is to decrease sediment transport with time by preferentially stripping away fine particles on the other hand the effect of weathering which breaks down the particles in the armour is generally believed to increase erosion by extending an existing armouring model armour and using a variety of published weathering mechanisms this interaction has been explored the model predicts that while this is generally true in some cases erosion can be decreased by weathering when the particles generated by weathering were approximately of equal diameter erosion increased while armouring decreased when weathering produced very fine particles by spalling erosion increased and armouring also increased when weathering produced a range of particles from fine to coarse the armour layer broke down and erosion decreased relative to the no weathering case this latter decrease in erosion was due to the high entrainment of coarser transportable materials from the bed decreasing the sediment transport capacity of the flow in these studies clear regimes could be identified where erosion was limited by either the energy of the flow alone i e transport limited or the rate of weathering weathering limited however for some mechanisms there was an interaction between the two which we called weathering transport limited copyright 2006 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

the freshwater budget and under ice spreading of mackenzie river water in the canadian beaufort sea based on salinity and 18o 16o measurements in water and ice observations of salinity and oxygen isotope composition 18o were made for the beaufort shelf mackenzie estuary waters in september 1990 just prior to ice formation and for both the water column and ice in april may 1991 at the end of winter these measurements are used to determine the apportioning of fresh water in the estuary between its two main sources runoff and sea ice melt changes in disposition of water between seasons and amounts frozen into the growing ice sheet are also derived two domains are considered in order to construct a freshwater budget for the mackenzie shelf the nearshore within which landfast ice grows in winter and the outer shelf most of the winter inflow from the mackenzie river appears to remain impounded as liquid under the ice within the landfast zone at the end of winter and about 15 of it is incorporated into the landfast ice oxygen isotopes 18o in ice cores collected from across the shelf record the progress beneath the ice of new mackenzie inflow as it invades the nearshore throughout winter rates of spreading are about 0 2 cm s 1 away from the coast and 1 3 cm s 1 along the coast as this inflow spreads across the shelf it progressively shuts off convection driven by brine production at locations within the landfast ice salinity and 18o in the offshore water column suggest that about 3 m of sea ice was formed in the outer shelf domain since both brine and newly formed sea ice can be advected off the shelf a complete budget for brine or sea ice production cannot be established without first measuring the advection of one of these two components

determining sediment source areas in a tropical river basin costa rica abstract four hydrologic events were studied at three gauging stations in the pejibaye river basin costa rica the sediment sources were determined by comparing the timing of the sedigraph at the gauging station and the timing of rainfall in the catchment with addition of time for the new water to flow from different land use districts along the main rivers to the gauging stations the rainfall was recorded in the basin upstream of pejibaye gauging station which was therefore the only station where the sedigraph rainfall method could be properly used for determining sediment sources on three occasions the sediment discharges at the pejibaye station were of about equal height the sedigraph rainfall method indicated that on two of these occasions the sediment came mainly from the pasture and sugar districts and in one case from the forested middle basin on the fourth occasion rainfall amounts and intensities were locally high in the forested upper basin but water and sediment discharges were small re erosion of material deposited in the channel increased the width of clockwise sediment concentration discharge loops in one storm the concentration discharge loop changed from an eight shaped loop at the upper station to a counter clockwise loop at the downstream station explained by the lagging of the sediment after the water

the weathering rates of some sandstone cliffs central weald england short term 1 30 months weathering rates were obtained for steep cliffs of cretaceous ardingly sandstone in southern england using a new photographic method mean rates for an exposed and a sheltered outcrop were 0 11 and 0 033 mm a 1 respectively significant p 0 1 positive correlations were obtained with illumination and algal biomass and a significant negative correlation p 0 05 with slope angle there was no correlation with grain size porosity or mean surface temperature highest weathering rates were observed on south and west facing exposed cliffs the results are discussed with reference to algal growth climate and wind direction

using gravestones to assess changing rates of weathering in the united kingdom weathering rates were calculated using the height difference between lead lettering and marble on gravestones at three sites in the uk comparison of their regression lines and residuals suggested that two of the sites portsmouth and wolverhampton had similar amounts and rates of weathering over the last 100 150 years gravestones in swansea appear to have weathered much more and much faster than gravestones at the other two sites these differences may be the result of the differing pollution and rainfall histories of the three sites

salt weathering and experimental desalination treatment of building sandstone sydney australia local sandstone used in nineteenth century buildings in sydney has been affected by salt weathering and surface crust formation this study trialled two approaches namely washing and vacuuming and poulticing to salt removal treatment of weathered sandstone blocks from the sydney hospital and australian museum both treatments removed solutes from the stones in laboratory tests icp titration of sampled scrapings at depths of 0 2 2 5 and 50 mm showed substantial between sample variation with no significant difference being recorded in solute levels after treatment mann whitney u test except for sulfur and sodium sulfur levels increased at the surface 0 2 mm following washing and vacuuming but not poulticing for the hospital and museum samples sodium levels increased at the surface 0 2 mm following poulticing but not washing and vacuuming for the hospital samples the presence of surface crusts may have contributed to some of the variation in desalination responses

salt weathering influence of evaporation rate supersaturation and crystallization pattern micro and macroscale experiments which document the dynamics of salt damage to porous stone have yielded data which expose weaknesses in earlier interpretations previously unexplained differences are found in crystal morphology crystallization patterns kinetics and substrate damage when comparing the growth of mirabilite na2so4 10h2o and thenardite na2so4 versus halite nacl the crystallization pattern of sodium sulphate was strongly affected by relative humidity rh while a lesser rh effect was observed for sodium chloride macroscale experiments confirmed that mirabilite crystallizing at rh 50 per cent and thenardite crystallizing at rh 50 per cent tend to form subflorescence in highly localized areas under conditions of constant rh and temperature this crystallization pattern was more damaging than that of halite since halite tended to grow as efflorescence or by filling the smallest pores of the stone in a homogeneous fashion a result which contradicts wellman and wilson s theoretical model of salt damage low rh promoted rapid evaporation of saline solutions and higher supersaturation levels resulting in the greatest damage to the stone in the case of both sodium sulphate and sodium chloride crystallization at any particular crystallization condition sodium chloride tended to reach lower supersaturation levels resulting in the crystallization of isometric crystals and created negligible damage while sodium sulphate reached higher supersaturation ratios resulting in non equilibrium crystal shapes resulting in significant damage esem showed no damage from sodium sulphate due to hydration instead after water condensation on thenardite crystals rapid dissolution followed by precipitation of mirabilite took place resulting in stone damage by means of crystallization pressure generation it is concluded that salt damage due to crystallization pressure appears to be largely a function of solution supersaturation ratio and location of crystallization these key factors are related to solution properties and evaporation rates which are constrained by solution composition environmental conditions substrate properties and salt crystallization growth patterns when combined with a critical review of salt damage literature these experiments allow the development of a model which explains variations in damage related to combinations of different salts substrates and environmental conditions

weathering of coastal defensive structures in southwest england a 500 year stone durability trial historic structures can be viewed as exposure trials of the stone of which they are constructed as such they represent a geomorphological weathering experiment several structures of henrician sixteenth century and greater age on the coast of southwest england have been exposed to coastal salt weathering for 500 600 years long term weathering rates on five different rock groups are derived from careful study of weathering depths and forms there is significant variation in weathering rate between five major rock groups rank ordering of weathering rate values reveals a durability order of these rock groups which is confirmed by local juxtapositions controls on rock durability in the coastal weathering environment include both mechanical and mineralogical characteristics specific density and combined quartz and muscovite content are positively related to durability high feldspar and chlorite content are associated with low durability copyright 2000 john wiley sons ltd

18o concentrations in sea ice of the weddell sea antarctica we present data on ice texture salinity and delta o 18 obtained from identical sections of ice cores during the winter weddell sea project 1986 on rv polarstern from july through august 1986 in the longitude range between 5 degrees w and 7 degrees e we find no uniquely definable relationship between delta o 18 values and ice texture in a particular section however most of the snow ice as well as some sections of frazil ice ar found to have negative delta o 18 concentrations this is due to varying degrees of admixtures of meteoric ice snow and sea water during formation of snow ice in contrast to common assumptions our results seem to indicate that a snow cover contributes positively to sea ice growth rather than slowing down the overall growth rate based on a simple model we have estimated the contributions of meteoric ice mean of 3 3 and the combined meteoric ice sea water fraction a minimum of 7 6 to the total ice thickness for the majority of the sampled floes although this is only a moderate contribution to the overall mass balance in the absence of congelation growth it nevertheless enhances ice growth in general this hypothesis is dependently supported by our snow and ice thickness data wadhams and others 1987 which demonstrate that the depression of the snow ice interface below the water line i e a negative freeboard and the formation of snow ice is a common occurrence in the weddell sea therefore we hypothesize that the major part of the observed apparent increase in ice thickness between our inbound and outbound tracks of wwsp 86 may not be derived from regular thermodynamically driven congelation growth but rather from the snow ice component in floes of the weddell sea

paraglacial redistribution of glacial sediments in the vestfold hills east antarctica abstract the vestfold hills landscape is dominated by bare rock slopes and unconsolidated deposits form a minor component of the surficial geology the principal objectives of the study were to explain the distribution of unconsolidated deposits determine the nature and timing of sedimentary processes during and after deglaciation and the impact of these processes on landscape development observations of late quaternary glaciation and deglaciation of the area and contemporary depositional processes are reported and a conceptual model of geomorphological change since deglaciation is presented the model attempts to reconcile the types and rates of contemporary depositional processes with the distribution of deposits and landforms and to explain why unconsolidated deposits cover less than 20 of the hills despite the effects of recent glaciation the lack of unconsolidated deposit in the landscape can be attributed to the combined effects of low debris volumes in the ice and the redistribution of debris during and after deglaciation redistribution of debris can be explained by paraglacial processes which are non glacial sedimentary processes that are directly conditioned by glaciation paraglacial sedimentation is a response to rapid adjustment of the debris system after the dominance of glacial conditions and is characterized by disequilibrium between sediment supply and transportation of sediment by nonglacial processes evidence from the vestfold hills suggests paraglacial sedimentary processes are dominated by mass movement of glacial debris from slopes and the formation of stable valley fills and that the main sediment transfers occur within a few thousand years of deglaciation

on the isotopic composition in δd and δ18o of water and ice during freezing experiments on progressive unidirectional freezing are coi1 ducted to determine rhe evol ution in 00 and 51 bo of successive water samples and ice layers ta ken during the course of freezing r es ults indicate t hal lhi s evoluti on takes pl ace in a bd bibo diagram a long a strai ght line wi th a characteri sti c slope this slope different from that due to the precip itation effec t gives a finger print of the occurrence of a freezing or of a melt ing refreez ing process in the stud ied reservoir residual water was sampled at the beginning of the experiment after 40 80 85 90 and 95 of the material had frozen when the freezing process was complete the ice core was recovered and sectioned the samples covered the freezing ranges from 0 to 10 10 to 20 20 to 50 50 to 60 60 to 70 70 to 80

stable oxygen and carbon isotopes in planktic foraminifers from arctic ocean surface sediments reflection of the low salinity surface water layer planktic foraminifers neogloboquadrina pachyderma sin from 87 eastern and central arctic ocean surface sediment samples were analyzed for stable oxygen and carbon isotope composition additional results from 52 stations were taken from the literature the lateral distribution of 18o full size image 33 atlantic waters entering the arctic ocean through the fram strait 18o values decrease both to the barents shelf and to the north pole in accordance with the decreasing salinities of the halocline waters in the nansen basin a strong n s 18o gradient is in contrast with a relatively low salinity change and suggests contributions from different freshwater sources i e salinity reduction from sea ice meltwater in the south and from light isotope waters meteoric precipitation and river runoff in the northern part of the basin north of the gakkel ridge 18o and salinity gradients are in good accordance and suggest less influence of sea ice melting processes the 13c full size image 1 k values of n pachyderma sin from arctic ocean surface sediment samples are generally high 0 75 0 95 lower values in the southern eurasian basin appear to be related to the intrusion of atlantic waters the high 13c values are evidence for well ventilated surface waters because the perennial arctic sea ice cover largely prevents atmosphere ocean gas exchange ventilation on the seasonally open shelves must be of major importance lack of 13c gradients along the main routes of the ice drift from the siberian shelves to the fram strait suggests that primary production i e co2 consumption does probably not change the co2 budget of the arctic ocean significantly

frost and salt weathering further experimental results a laboratory experiment has been conducted to examine the effects of frost and salt weathering i e physical breakdown by the freezing of salt solutions on a limestone results show that the presence of certain salts in solution can inhibit frost damage these findings are in direct conflict with those presented by goudie 1974 and more recently williams and robinson 1981 comparison of the experimental methods used in each of these three studies suggests that opposing results can be explained in terms of the different experimental procedures which were employed if salt supply is frequent and plentiful then it seems likely that rock breakdown will be enhanced this is the case represented by the experiment of williams and robinson conversely if the salt supply is limited and the amounts of salt remain more or less constant then rock breakdown will be inhibited the case of the present experimental study caution is therefore advocated when attempting to extrapolate laboratory derived results to infer on the behaviour of rocks under natural conditions several environmental situations in which frost and salt weathering may be a possibility are dsiscussed but it is concluded that further field data especially concerning temperature regimes and salt availability at and below rock surfaces in cold regions would be necessary before more definite statements could be made about the efficacy of this process

new evidence for the incision history of the liuchong river southwest china from cosmogenic 26al 10be burial ages in cave sediments cosmogenic nuclides be 10 and al 26 have been analyzed for sediments from the multilevel riverside caves along the liuchong river at the southeastern margin of the tibetan plateau the liuchong river is the northern origin of wujiang river which passes through the northwestern guizhou plateau and cuts down hundreds of meters into the bedrock leaving behind an abundance of multilevel caves the measured al 26 be 10 ratios produced the apparent burial ages in range of 0 49 2 85 ma taking into account of geomorphic and geological backgrounds the dashi cave located at the highest level along the liuchong river system formed around 0 75 ma ago which probably suggests the initial formation age of the modern wujiang river the resulted incision rate of similar to 480 m ma in guizhou in the last 0 75 ma is slightly higher than those in adjacent areas this feature implies an intensive downcutting history of the liuchong river during the quaternary which might be primarily caused by the uplift of tibetan plateau cut through of the three gorges and soluble carbonate bedrock c 2013 elsevier ltd all rights reserved

ice island detection and characterization with airborne synthetic aperture radar a 1 300 000 scale airborne synthetic aperture radar sar image of an area of the arctic ocean adjacent to the queen elizabeth islands canadian high arctic is examined to determine the number and characteristics of ice islands in the image and to assess the capability of airborne and satellite sar to detect ice islands twelve ice islands have been identified and their dimensions range from as large as 5 7 km by 8 7 km to as small as 0 15 km by 0 25 km a significant sar characteristic of the shelf ice portions of ice islands is a return with a ribbed texture of alternating lighter and darker grey tones resulting from the undulating shelf ice surfaces of the ice islands the appearance of the ribbed texture varies according to the ice islands orientation relative to the illumination direction and consequently the incidence angle some ice islands also include extensive areas of textureless dark tone attached to the shelf ice the weak returns correspond to 1 multiyear landfast sea ice that was attached to the front of the ward hunt ice shelf at the time of calving and which has remained attached since then and 2 multiyear pack ice that has become attached and consolidated since the calving indicating that ice islands can increase their area and mass significantly as they drift other sar characteristics include straight bright returns along the edges arising from sea ice pressure ridges or shelf ice cliffs other physical characteristics of ice islands that make them identifiable in sar images include their greater size and shapes longer thinner and more angular than those of surrounding pack ice floes it is evident that ice islands are easily discernible in sar images and for the future sar represents a promising technique to obtain a census of ice islands in the arctic ocean however any sar based census probably will be conservative because ice islands smaller than 300 400 m across are likely to remain undetected particularly in areas of heavy ice ridging which produces strong sar clutter

linking weathering and rock slope instability non linear perspectives weathering is linked complexly to the erosion and evolution of rock slopes weathering influences both the strength of rock slopes and the stresses that act upon them while weathering has often been portrayed in an over simplified way by those studying rock slope instability in reality it consists of multiple processes acting over different spatial and temporal scales with many complex inter linkages through a demonstration of the sources of non linearities in rock slope weathering systems and their implications for rock slope instability this paper proposes five key linkages worthy of further study copyright 2012 john wiley sons ltd

stable isotope clues to the formation and evolution of refrozen melt ponds on arctic sea ice author posting american geophysical union 2018 this article is posted here by permission of american geophysical union for personal use not for redistribution the definitive version was published in journal of geophysical research oceans 123 12 2018 8887 8901 doi 10 1029 2018jc013797

anti clockwise hysteresis in suspended sediment concentration during individual storms holbeck catchment yorkshire england abstract analysis of the flow sediment hysteresis shape may assist in determining the sediment source area in a small basin a clockwise hysteresis occurs when sediment is derived from the bed and banks of the channel or areas adjacent to the channel whereas an anti clockwise hysteresis occurs when the upper part of the slopes is the sediment source area

the ice cover in the greenland and norwegian seas the seasonal sea ice cover of the northern north atlantic is reviewed comprising the ice of the east greenland current the ice cover around svalbard and the ice of the barents sea as far east as franz josef land the review considers various types of ice cover 1 the fast ice along the coasts and in fjords including sikussak or very old fast ice of exceptional thickness 2 the transition zone between the fast ice and the main pack including the positions and causes of recurring winter polynyas and the nature of the shear zone in ne greenland 3 the constitution dynamics and seasonal extent of the drifting pack ice including interannual variations 4 the processes of air ice ocean interaction which occur in the marginal ice zone where the pack ice is influenced by an open ocean boundary

paraglacial debris cone formation on recently deglaciated terrain western norway five debris cones have formed on terrain deglaciated since ad 1750 75 in bergsetdalen western norway three were surveyed and studied in detail two accumulated over 108 215 years and the third over 57 108 years accumulation on all three appears to have effectively ceased around or slightly before ad 1965 through exhaustion of readily entrainable sediment in source areas upslope the volumes of the three cones range from c 9500 m3 to 403 600 m3 and imply average sediment accumulation rates of 8 44 mm yr 1 sediment erosion at one site was calculated to be 37 93 mm yr 1 averaged over the entire sediment source area paraglacial reworking of glacial drift by debris flows appears to have been the main agent of cone development at two sites but snow avalanches are thought to represent the main process of sediment transport at the largest cone these findings indicate that substantial debris cones may form and become inactive within 100 200 years of deglaciation implying that many late pleistocene parag

spatial scale dependence of sediment dynamics in a semi arid badland drainage basin abstract problems of spatial scale transference are of key interest in drainage basin research the objective of this study was to investigate the spatial scale dependence of sediment dynamics in semi arid badland drainage basins simulated rainfall experiments indicated that on microscale plots runoff generation and sediment entrainment occurred when total rainfall exceeded 0 5 to 6 mm on pediment surfaces 1 5 to 4 mm on sandstone surfaces and 8 to 25 mm on shale surfaces the sediment concentration discharge relationship for two mesoscale basins displayed a change from clockwise to counterclockwise hysteresis when total rainfall exceeded the threshold rainfall for the initiation of flow in deep tunnel systems the initiation of tunnel flow causes counterclockwise hysteresis due to a delayed increase in sediment concentrations during a runoff event this contrasts with the clockwise hysteresis caused by flushing in the early stages of runoff for smaller rainstorms comparison of micro and mesoscale sediment dynamics indicates that microscale thresholds are not by necessity in evidence at the mesoscale in addition at the mesoscale elements exist which are non existent at the microscale e g a deep tunnel system the behaviour of the mesoscale basin is dominated by these elements rather than by the microscale components it contains

snowfall and oxygen isotope variations off the north coast of ellesmere island n w t canada snow pack along the lan d fast ice fringe off the north coast of ellesmere island was generally characterized by depth hoar overl ain by dense snow and wind slab mean snow depth in the study area was 0 54 m 1982 85 and the mean 6180 value of the sno w pack was 31 3 0 00 isotope data were not obtained previously for this geographic region and therefore complement a previous study of 6180 variations in high arctic snow koer ner 1979 the data are consistent with an arctic ocean moisture source the 6180 profiles show seasonal variat ions with winter snow being more depleted in 180 than fall and spring snow however the 6180 profiles are dominated by a trend to higher 6180 values with increasing depth this is attributed to a decrease in 6180 values as conden sation temperatures fall during the autumn winter acc umulation period during this time there is also a chan ge from relatively open to almost complete ice cover in the arctic ocean the change in evaporation conditions and consequent effect on 6 values gives rise to a sharp dis continuity in the 6180 prof iles and a bi m odal 6180 freq uency dist ribution the bi modal distribution is reinforced by a secon dary isotope fracti onation that occurs during dept h hoar formation this isotope effect leads to a wider 6180 range but does not signific antly alter the mean 6180 value

geomorphology s role in the study of weathering of cultural stone abstract great monumental places petra giza angkor stonehenge tikal macchu picchu rapa nui to name a few are links to our cultural past they evoke a sense of wonderment for their aesthetic fascination if not for their seeming permanence over both cultural and physical landscapes however as with natural landforms human constructs are subject to weathering and erosion indeed many of our cultural resources suffer from serious deterioration some natural some enhanced by human impact groups from the united nations to local civic and tourism assemblies are deeply interested in maintaining and preserving such cultural resources from simple rock art to great temples geomorphologists trained in interacting systems process and response to thresholds rates of change over time and spatial variation of weathering processes and effects are able to offer insight into how deterioration occurs and what can be done to ameliorate the impact review of recent literature and case studies presented here demonstrate methodological and theoretical advances that have resulted from the study of cultural stone weathering because the stone was carved at a known date to a baseline or zero datum level some of the simplest methods e g assessing surface weathering features or measuring surface recession in the field provide useful data on weathering rates and processes such data are difficult or impossible to obtain in natural settings cultural stone weathering studies demonstrate the importance of biotic and saline weathering agents and the significance of weathering factors such as exposure microclimate and human impact more sophisticated methods confirm these observations but also reveal discrepancies between field and laboratory studies this brings up two important caveats for conservators and geomorphologists for the conservator are laboratory and natural setting studies really analogous and useful for assessing stone damage for the geomorphologist does cultural stone data have any real relevance to the natural environment these are questions for future research and debate in any event cultural stone weathering studies have been productive for both geomorphologists and conservators continued collaboration and communication between the geomorphic historic preservation archaeological and engineering research communities are encouraged

stratigraphy stable isotopes and salinity in multi year sea ice from the rift area south george vi ice shelf antarctic peninsula results from a detailed profile in a 5 54m multi year sea ice core from the rift area in the southern part of george vi ice shelf are presented stratigraphy stable isotopes and na content are used to investigate the growth processes of the ice cover and to relate them to melting processes at the bottom of the ice shelf the thickest multi year sea ice in the sampling area appears to be second year sea ice that has survived one melt season combined salinity stable isotope analyses show large scale sympathetic fluctuations that can be related to the origin of the parent water brackish ice occurs between 450 and 530cm in the core it is demonstrated that this results from the feezing of brackish water formed by mixing of normal sea water with melted basal shelf ice with dilution percentages of maximum 80 fresh water from authors

arctic ocean water mass balance from isotope data the distributions of the oxygen 18 and tritium isotopes and of salinity yield a residence time of 10 years for the surface and halocline waters of the arctic basin we find a yearly net production of 0 59 m of sea ice and an input of 1 16 m of freshwater from continental river runoff local precipitation and bering strait salinity deficiency using the basin area value with these numbers gives long term average total net production and transport rates of 0 15 sv of ice and 0 18 sv of meteoric component bering strait water not included if in addition a reasonable depth profile of relative current velocity is assumed for the outflow a yearly input of 2 8 sv of atlantic and bering strait water is needed to replenish the upper and halocline waters these numbers should be good to 20 and are multiyear averages the isotope data clearly indicate that the barents sea is an inflow area for atlantic water to the basin but that net export of ice occurs there

reconstructing hydrographic change in petersen bay ellesmere island canada inferred from sar imagery abstract synthetic aperture radar sar satellite imagery was used to reconstruct the change in limnological conditions adjacent to an arctic ice shelf by examining the backscatter values of coastal ice in mid winter scenes high sar backscatter values 6 db suggest that an ice dammed lake was present adjacent to the south coast of petersen bay from 1992 until 2005 following a large calving event of the adjacent petersen ice shelf 8 07 km2 in august 2005 the lake drained through a region where the ice shelf had separated from the coastline this loss of freshwater and replacement of lake ice with sea ice along the southern coast of petersen bay were confirmed from analyses of ice core samples and conductivity temperature depth ctd profiles the exception to this pattern was one distinct area where terrestrial streams entered the edge of petersen bay and freshwater continued to collect from 2006 to 2008 however this ephemeral area of freshwater has not reformed since 2009 due to the persistence of open water events in petersen bay observed in optical satellite imagery which likely facilitated mixing of freshwater with sea water based on the continued break ups of petersen ice shelf and the frequency of open water events it is unlikely that this ice dammed lake will reform the results of this study underscore the utility of sar for reconstructing past hydrographic conditions in the water column below

variable weathering response in sandstone factors controlling decay sequences differences in weathering response characteristics of fine and coarse grained stanton moor sandstone samples were assessed in a laboratory weathering simulation experiment using a variable combination of salt weathering and freeze thaw cycles preliminary analysis of permeability characteristics identified similar mean values for each type of stanton sandstone but significant differences in the range of values between the two sample sets with coarse grained samples of stanton moor sandstone displaying a restricted range of values in comparison to fine grained samples which showed much greater within block variation data indicated that the greater the range in initial permeability values the greater the potential for salt and moisture ingress and retention and hence eventual disruption of the fabric of the stone experimental data also identified different stages in decay sequences with significant structural change occurring during the initial preparatory stage before material breakdown and loss became apparent evidence suggests that relatively minor structural and mineralogical differences between samples of the same stone type can have a significant influence on weathering behaviour resulting in distinct rates and patterns of breakdown copyright 2005 john wiley sons ltd

contrasting weathering rates in coastal urban and rural areas in southern britain preliminary investigations using gravestones weathering rates were calculated using the height differences between lead lettering on marble gravestones from inland urban inland rural coastal urban and coastal rural sites within southern britain all sites exhibit similar amounts and variations in rainfall over the study period for which gravestone measurements are available comparison of mean weathering rates suggested that the coastal urban site of clacton had a similar weathering rate to the nearby coastal rural site the other urban sites of oxford lodge hill and portsmouth had similar weathering rates despite their diverse locations and histories the inland rural site had a significantly lower mean weathering rate than any other site analysis of covariance confirms that there are similarities between some sites linear and curvilinear regression of depth of loss against age suggests that a linear regression adequately describes the relationship over the period for which data are available although there are problems with this simple interpretation copyright 2000 john wiley sons ltd

paraglacial modification of slope form the morphological consequences of paraglacial modification of valley side drift slopes are investigated at six sites in norway here paraglacial slope adjustment operates primarily through the development of gully systems whereby glacigenic sediment is stripped from the upper drift slope and redeposited in debris cones downslope this results in an overall lowering of average gradient by up to 4 5 along gully axes in general slope profile adjustment appears to be characterized by a convergence of slope profiles towards an equilibrium form with an upper rectilinear slope gradient at 29 4 and a range of concavities of approximately 0 0 to 0 4 after initial rapid incision further gully deepening is limited but gullies become progressively wider as sidewall gradients decline to c 25 after which parallel retreat appears to predominate the final form of mature paraglacial gully systems consists of an upper bedrock floored source area a mid slope area of broad gullies whose sidewalls rest at stable moderate gradients and a lower slope zone where gullies discharge onto the surfaces of debris cones and fans some gullies appear to have attained this final form and have stabilized following exhaustion of readily entrainable sediment within decades of gully initiation at most sites paraglacial activity has transformed steep drift mantled valley sides into gullied slopes where an average of c 2 3 m of surface lowering has taken place at the most active sites these average amounts imply minimum erosion rates averaging c 90 mm a 1 since gully initiation which highlights the extreme rapidity of paraglacial erosion of deglaciated drift mantled slopes copyright 1999 john wiley sons ltd

patterns of damage in igneous and sedimentary rocks under conditions simulating sea salt weathering a saline spray artificial ageing test was used to simulate the effects produced in granites and sedimentary rocks calcarenites micrites and breccia under conditions in coastal environments three main points were addressed in this study the durability of the different kinds of rock to salt decay the resulting weathering forms and the rock properties involved in the weathering processes for this mineralogical and textural characterization of each of the different rocks was carried out before and after the test the soluble salt content at different depths from the exposed surfaces was also determined two different weathering mechanisms were observed in the granite and calcareous rocks physical processes were involved in the weathering of granite samples whereas dissolution of calcite was also involved in the deterioration of the calcareous rocks we also showed that microstructural characteristics e g pore size distribution play a key role in salt damage because of their influence on saline solution transport and on the pressures developed within rocks during crystallization copyright 2003 john wiley sons ltd

laboratory simulation of the salt weathering of schist 1 weathering of schist blocks in a seasonally wet tropical environment data describing sediment generation focusing on the temporal evolution of size gradation are required for the prediction of long term landform evolution this paper presents such data for the salt weathering of a quartz chlorite schist obtained from the ranger uranium mine in northern australia rock fragment samples are subjected to three different climate regimes 1 a dry season climate 2 a wet season climate both based on observations at the ranger site and 3 an oven drying sequence designed to test the sensitivity of the weathering process by exposing the rocks to more extreme temperatures two mgso4 salt solutions are applied one being typical of wet season runoff and the other a more concentrated solution salt solution is applied daily in the wet season experiments and once only at the beginning of the dry season experiments results of the experiments reveal four stages of weathering the kinetics of each stage are described and related to the formation of sediment of different sizes wet season climate conditions are shown to produce greater moisture variability and lead to faster weathering rates however salt concentrations in the wet season are typically lower and so when climate is combined with observed salt concentrations the dry and wet season experiments weather at approximately equal rates finally small variations in rock properties were shown to have a large impact on weathering rates leading to the conclusion that rock weathering experiments need to be carefully designed if results are to be used to help predict weathering behaviour at the landscape scale copyright 2006 john wiley sons ltd

sandstone weathering a century of research and innovation abstract a review of sandstone weathering research particularly in the past 100 years reveals a trajectory of enquiry from early description and classification of features to development of process based explanations to decreasing scales of investigation and a disparity between understanding of process es and explanations of the genesis of sandstone weathering features developments in expositions on mesoscale weathering features on sandstone surfaces are discussed demonstrating a range of approaches to weathering phenomena field based and laboratory based that must be linked to provide an explanation of observed features on a landform scale throughout the twentieth century a thematic chronology highlights certain trends in research description of forms often in arid and semi arid environments single process form models an emphasis on experimentation difficulties in measuring weathering rates and a persistent emphasis on physical causes of breakdown a new research agenda is promoted in which biodeterioration and chemical processes gain parity a holistic approach based on conceptual modeling of weathering systems gains prominence and scale issues are addressed more rigorously

the role of moisture cycling in the weathering of a quartz chlorite schist in a tropical environment findings of a laboratory simulation long term weathering of a quartz chlorite schist via wetting and drying was studied under a simulated tropical climate cubic rock samples 15 mm 15 mm 15 mm were cut from larger rocks and subjected to time compressed climatic conditions simulating the tropical wet season climate at the ranger uranium mine in the northern territory australia fragmentation moisture content and moisture uptake rate were monitored over 5000 cycles of wetting and drying to determine the impact of climatic variables five climatic regimes were simulated varying water application temperature and drying one of the climatic regimes reproduced observed temperature and moisture variability at the ranger uranium mine but over a compressed time scale it is shown that wetting and drying is capable of weathering quartz chlorite schist with changes expected over a real time period of decades while wetting and drying alone does produce changes to rock morphology the incorporation of temperature variation further enhances weathering rates although little fragmentation occurred in experiments significant changes to internal pore structure were observed which could potentially enhance other weathering mechanisms moisture variability is shown to lead to higher weathering rates than are observed when samples are subjected only to leaching finally experiments were conducted on two rock samples from the same source having only subtle differences in mineralogy the samples exhibited quite different weathering rates leading to the conclusion that our knowledge of the role of rock type and composition in weathering is insufficient for the accurate determination of weathering rates copyright 2005 john wiley sons ltd

a one dimensional model for simulating armouring and erosion on hillslopes 1 model development and event scale dynamics this paper presents an erosion model armour which simulates time varying runoff erosion deposition and surface armour evolution down a hillslope either as a result of a single erosion event or as the cumulative impact of many events over periods up to decades armour simulates sediment transport for both cohesive and non cohesive soil and dynamically differentiates between transport limited and source limited processes a variety of feasible processes for entrainment of different size classes can be modelled and evaluated against data the generalized likelihood of uncertainty estimation glue technique was used to calibrate and validate armour using data collected during rainfall simulator experiments at two contrasting sites 1 non cohesive stony sediments at ranger uranium mine northern territory australia and 2 cohesive silty sediments at northparkes gold mine nsw australia the spatial and temporal variations of model predictions within the individual runoff events showed that some entrainment processes could not model the spikes in concentration and subsequent depletion while the hiding model of andrews and parker best simulated the concentration trends for both calibrated and independent runoff events armour also successfully captured the coarsening of the surface material though small over the duration of the rainfall simulator trials this was driven by the depletion of the finest size class of the soil for a constant discharge armour simulated higher sediment flux at the start of the storm with the sediment flux and concentration diminishing with time for natural rainfall a power law relationship between sediment flux and discharge was observed the calibration exercise showed that sediment concentration and discharge alone are insufficient to calibrate all aspects of the physics in particular the armour depth this appears to be because the armouring during the short duration events is driven by depletion of the finest classes of the sediments diameters less then 62 5 mm which are not normally measured copyright 2006 john wiley sons ltd

drifting arctic sea ice archives changes in ocean surface conditions 18o profiles in drifting arctic sea ice are coupled with back trajectories of ice drift and an ice growth model to reconstruct the surface hydrography of the arctic ocean interior the results compare well with 18o values obtained by traditional oceanographic methods and known water mass distributions analysis of the stable isotopic composition of sea ice floes sampled at strategic and relatively accessible locations e g fram strait could aid in mapping spatial and temporal variations in arctic ocean surface waters