growth by extension and reworking of a south western kalahari linear dune optically stimulated luminescence osl dating studies of linear longitudinal dunes have been used extensively to elucidate late quaternary environments and climates in arid or formerly arid regions yet understanding of the development of such dunes is incomplete in particular conflicting opinions have been presented regarding the propensity of linear dunes to migrate laterally the degree to which they rework their own sediment during accumulation and whether they form primarily by extension as opposed to lateral sand movement from adjacent interdunes this study focuses on this last point although the importance of the other controversies is discussed in context a simple linear dune in the south western kalahari which has a prominent termination on a pan playa surface provides an opportunity to directly test hypotheses of dune extension chronostratigraphy along a 600 m transect along the crest of the dune constrained by 42 osl ages reveals that the dune grew by extension on occasions in the late pleistocene and early holocene but has also been subject to reworking along its length which has continued until recent times dune development by extensional growth is suggested to operate under environmental conditions more conducive to net accumulation whereas reworking is largely independent of conditions throughout the last 18 ka and may represent seasonal fluctuations in the position of the dune crest the relative significance of these two modes of development is suggested to be a key control on the efficacy of linear dunes as archives of environmental and climatic change copyright 2011 john wiley sons ltd

middle holocene aeolian activity on the high plains of west central kansas the uppermost surficial stratigraphic unit south of the arkansas river in the kansas high plains is a previously unidentified middle holocene or younger loess the unit fits both a loess thickness and a particle size model for loess distribution with increasing distance from source a soil immediately below this unit is radiocarbon dated 6000 to 6700 years bp the radiocarbon ages indicate that the loess unit is younger than the commonly reported ranges for bignell loess in the great plains and demonstrate a need for re examining holocene loess stratigraphy of the great plains in some locations closest to the arkansas valley source this middle holocene unit is overlain by or interfingers with dune sands the presence of these aeolian sands indicates that following a period of relative landscape stability and soil development a shift toward a middle holocene climate in which aeolian processes dominated occurred about 6000 years ago on the high plains of west central kansas

topographic controls on the surface energy balance of a high arctic valley glacier 1 this paper presents the results of a distributed two dimensional surface energy balance model used to investigate the spatial and temporal variations in the surface energy balance of midre lovenbreen a small valley glacier in northwest spitsbergen svalbard over the summer of 2000 we utilize high resolution airborne lidar data to derive a digital elevation model of the glacier and surrounding topography on which a surface energy balance is computed driven by meteorological data obtained from a meteorological station located on the glacier and a synoptic station maintained at the nearby ny alesund research base given the high resolution topographic data we focus particularly on whether the long duration of sunshine at high latitudes compensates for the higher solar zenith angles on the season long energy balance and whether shading by the surrounding topography plus glacier surface slope and aspect play an increased role in the patterns of solar radiation receipt and hence melt over the glacier surface the model results are validated using a combination of mass balance data from the glacier measured surface lowering at the glacier meteorological station and by comparing a derived energy balance component from the model with a measured energy flux overall the model performance is very good glacier topography is found to play a fundamental role in determining the surface energy balance topographic shading slope and aspect and correction of the surface albedo for high solar zenith angles are found to play a crucial role in determining spatial patterns of surface energy balance and therefore melt

spatial and temporal variations of albedo on nine glaciers in western china from 2000 to 2011 this research demonstrates the spatiotemporal variations of albedo on nine glaciers in western china during 2000 2011 by the albedo derived from two types of datasets landsat tm etm images and mod10a1 product then the influence factors of glacier albedo and its relationship with glacier mass balance are also analyzed by the correlation approach which is frequently used in geostatistics the paper finds that there are different spatiotemporal variations over the glaciers in western china 1 for a single glacier the albedo varies gently with altitude on its tongue and increases fast in the middle part while in the accumulation zones the albedo value appears in the form of fluctuation this could provide a quantitative method to retrieve the snowline by determining the threshold albedo value of snowpack and bare ice 2 for the glaciers in western china the albedo decreases with distance to the center of tibetan plateau tp this may relate to the elevation of glacier for the speed of glacier retreat highly depends on air temperature 3 in the summer period albedo on most glaciers declines over the last 12years and it decreases much faster in southeastern tp than other regions for which air temperature overwhelms the black carbon concentration in addition the trend of glacier albedo in summer is greatly correlated with that of measured glacier mass balance which implies that the long term albedo datasets by remote sensing technology could be used to monitor and predict the change of glacier mass balance in the future 2013 john wiley sons ltd

measurement and parameterization of albedo variations at haut glacier d arolla switzerland spatial and temporal variations of surface albedo on haut glacier d arolla switzerland during the 1993 and 1994 ablation seasons are described correlation and regression analyses are used to explain the albedo variations in terms of independent meteorological and surface property variables parameterizations are developed which allow estimation of albedo variation in surface energy balance models snow albedo is best estimated from accumulated daily maximum temperatures since snowfall on deep snow 0 5 cm w e depth a logarithmic function is used while on shallow snow 0 5 cm w e depth an exponential function is used to enable the albedo to decay to the underlying ice or debris albedo the transition from deep to shallow snow is calculated as a function of decreasing snow depth combined r 2 0 65 this new parameterization performs better than earlier schemes because accumulated daily maximum temperatures since snowfall correlate strongly with snow grain size and impurity concentration the main physical controls on snow albedo ice albedo may be parameterized by its relationship to elevation r 2 0 28 but this approach results in only a small improvement over the assumption of a constant mean ice albedo

discussion of the relationship between dustfall grain size and the desert border taking the southern border of the tengger desert and the southern dust deposit area as an example abstract in northern china high spatial and temporal instability exists in the southern desert border since the region is very sensitive to the changes of global climate and the migration of the southern desert border threatens the survival of surrounding inhabitants it is very important to strengthen the research about the migration of the southern desert border of northern china the dust in the downwind of the desert contains relevant information of the desert evolutionary history in order to investigate the relationship between dustfall grain size and the southern border of northern china desert we collected 56 eolian surface soil samples from the south of the tengger desert selected two near north south transects from these samples and used the grain size class standard deviation method we finally obtained three sensitive grain size components ranking by degree of sensitivity from high to low 61 8 185 4 m 18 2 61 8 m and 2 3 18 2 m the values of the three sensitive grain size components from the 56 eolian surface soil samples and the three commonly used grain size indicators which are the median grain size 20 m and 63 m particle content have been converted to the grain size contour figures in the six grain size contour figures the contour of the 61 8 185 4 m particle content component has the highest degree of similarity with the southern border of the tengger desert followed by the 63 m particle content component and then the components of the median grain size 18 2 61 8 m particle content 20 m and 2 3 18 2 m particle content in turn relative to the 20 m and 63 m particle content indicators the indicator of 61 8 185 4 m particle content is not only the most sensitive one in theory but also has the highest degree of similarity between its contour and the southern desert border in practical terms moreover this indicator is further defined as the upper limit of coarse grain size since the coarse grains in the eolian deposits are mainly from the near source desert the component of 61 8 185 4 m particle content within the loess to the south of the tengger desert could be regarded as the indicator of the migration of the southern desert border which could be used to quantitatively reconstruct the desert palaeo border in the future

elongation and migration of sand dunes two distinct processes are known to act on dynamic dunes the process of migration by erosion on the windward side and deposition on the lee side typical for transverse dunes and the process of elongation typical for linear dunes these two processes are determined by wind direction relative to the dune alignment this article reviews the assertion that linear dunes experience lateral displacement in addition to elongation fieldwork on vegetated linear dunes vlds and gis work on seif dunes indicates no lateral migration for these dunes linear dunes can shift laterally only when a slip face formed on the lee side reaches the plinth of the dune the winds from both sides of the seif dune are never symmetric usually winds from one direction are more dominant and effective the outcome is the formation of peaks and saddles along the dune the strongest winds create a slip face on the lee side of the peak segments of the dune oblique to the dune alignment which reaches the base of the dune and displaces the peak downwind along the dune alignment the internal structure of the seif dune is formed mostly by this dominant wind direction and gives the impression that the dune has shifted laterally on the other hand there are cases in which the wind directions relative to dune alignment fall between those of transverse and seif dunes in such cases both processes act on the dune which subsequently experiences migration as well as elongation

retreating alpine glaciers increased melt rates due to accumulation of dust vadret da morteratsch switzerland the automatic weather station aws on the snout of the vadret da morteratsch switzerland has delivered a unique 12 year meteorological dataset from the ablation zone of a temperate glacier this dataset can be used to study multi annual trends in the character of the surface energy budget since 2003 there has been a substantial darkening of the glacier tongue due to the accumulation of mineral and biogenic dust the typical surface albedo in summer has dropped from 0 32 to 0 15 we have analysed the implications of the lowered albedo for the energy balance and the annual ablation for the 4 year period 2003 06 the decreased albedo caused an additional removal of about 3 5 m of ice calculations with an energy balance model show that the same increase in ablation is obtained by keeping the ice albedo fixed to 0 32 and increasing the air temperature by 1 7 k our analysis confirms that for retreating glaciers the deposition of dust from exposed side moraines on the glacier surface constitutes an important feedback mechanism the mineral dust stimulates the growth of algae lowers the surface albedo enhances the melt rates and thereby facilitates the further retreat of the glacier snout

albedo variations and the impact of clouds on glaciers in the chilean semi arid andes albedo variations are presented at two on glacier sites in the semi arid andes chile with 3 years of continuous measurements although 2 km apart and at similar elevations the sites show significantly different albedo cycles whereas toro 1 exhibits a clear seasonal cycle guanaco reveals a more complicated pattern as exposed ice can occur in any month of the year daily albedo values are as low as 0 18 for debris covered toro 1 while minima are higher on guanaco 0 38 a method is presented to discern cloud free from cloudy conditions using measured incoming shortwave radiation only a cloud climatology is provided showing very low cloudiness values we see that effective cloud cover relates inversely to cloud occurrence i e either more but thin or fewer but thick clouds the cloud free diurnal albedo cycle is pronounced with lowest values around noon clouds increase albedo by 0 04 as a median hourly value and 0 20 for the 95 quantile there is a positive relationship between effective cloud cover and resulting albedo rise calculations as to whether the diurnal albedo cycle or the effect of clouds on albedo should be considered in energy balance estimations show that the former is necessary whereas the latter can be neglected in the semi arid andes

palaeoclimate interpretations of late pleistocene vegetated linear dune mobilization episodes evidence from the northwestern negev dunefield israel abstract the vegetated linear dune vld field of the northwestern nw negev desert situated at the downwind eastern end of the northern sinai nw negev erg constitutes an ideal setting for dating and interpreting its late quaternary dune encroachment episodes this study builds upon the results of roskin et al age origin and climatic controls on vegetated linear dunes in the northwestern negev desert israel quaternary science reviews 30 2011 1649 1674 that presented the stratigraphy of 35 sections and 97 optically stimulated luminescence osl ages from the nw negev dunefield here we refine our analysis of the negev late pleistocene dune mobilizations and stabilizations and interpret their palaeoclimatic controls in light of regional and global sediment records and proxies while initial dune encroachment into and stabilization in the nw negev took place during the last glacial maximum lgm at 23 18 ka spatial and statistical analyses of the osl dataset suggest that since the lgm negev dune activity was concentrated in two significant mobilization stabilization episodes a main episode at 16 13 7 ka and a minor one at 12 4 11 6 ka when the dunes reached their maximum spatial extent and stabilized these episodes include rapid dune encroachment and accretion events and coincide with the heinrich 1 and younger dryas cold events respectively the late pleistocene sand transporting winds were characterized by a westerly direction that resulted in west east vld elongation dune mobilizations may have occurred in response to wintertime east mediterranean cyclonic systems that brought storms of rainfall and strong winds the rapid dune mobilization events and their concurrence with the heinrich 1 and younger dryas cold events suggest a more global control despite the rainfall the elongating vlds were probably sparsely vegetated because of the high wind power their stabilization resulted from a decrease in storminess with the onset of a more arid holocene climate other global low latitude dune mobilizations and stabilizations are concentrated at the end of the late pleistocene leading us to suggest that these were also controlled mainly by global cold events and subsequent changes in windiness the recurring discontinuous aeolian sedimentation pattern found in osl dated vlds provides new and important chronological and sedimentological insight into prominent dune mobilization and stabilization processes the suggested link between global drops in cold event windiness and low latitude dune stabilization episodes emphasizes the prevalence of winds over aridity regarding major dune mobilizations for low latitude dunes even if vegetated

age origin and climatic controls on vegetated linear dunes in the northwestern negev desert israel abstract the stabilized northwestern nw negev vegetated linear dunes vld of israel extend over 1300 km 2 and form the eastern end of the northern sinai nw negev erg this study aimed at identifying primary and subsequent dune incursions and episodes of dune elongation by investigating dune geomorphology stratigraphy and optically stimulated luminescence osl dating thirty five dune and interdune exposed and drilled section were studied and sampled for sedimentological analyses and osl dating enabling spatial and temporal elucidation of the nw negev dunefield evolution in a global perspective the nw negev dunefield is relatively young though sporadic sand deposition has occurred during the past 100 ka dunes began to accumulate over large portions of the dunefield area only at 23 ka three main chronostratigraphic units corresponding to three osl age clusters were found throughout most of the dunefield indicating three main dune mobilizations late to post last glacial maximum lgm at 18 11 5 ka late holocene 2 0 8 ka and modern 150 8 years the post lgm phase is the most extensive and it defined the current dunefield boundaries it involved several episodes of dune incursions and damming of drainage systems dune advancement often occurred in rapid pulses and the orientation of vld long axes indicates similar long term wind directions the late holocene episode included partial incursion of new sand reworking of late pleistocene dunes as well as limited redeposition the modern sand movement only reactivated older dunes and did not lengthen vlds this aeolian record fits well with other regional aeolian sections we suggest that sand supply and storage in sinai was initiated by the late pleistocene exposure of the nile delta sands late pleistocene winds substantially stronger than those usually prevailing since the onset of the holocene are suggested to have transported the dune sands across sinai and into the northwestern negev our results demonstrate the sensitivity of vegetated linear dunes located along the northern fringe of the sub tropical desert belt to climate change i e wind and sediment supply

spatial distribution of surface ablation in the terminus of rhonegletscher switzerland the spatial pattern of glacier surface melt was measured with a resolution of 20 100 m within a region extending 1 km up glacier from the terminus of rhonegletscher switzerland the melt rate was monitored from 6 july to 6 september 2009 using 44 ablation stakes we also measured the surface albedo near the stakes to investigate the importance of this parameter for the melt rate distribution the melt rate varied from 32 8 to 71 9 mm w e d 1 in the study area our measurements suggest that the spatial variation of the melt rate can be explained by 1 shading of the ice surface by neighbouring mountains 2 surface albedo and 3 effects of microclimate e g radiation from side walls on the surface energy balance the observed melt rate distribution was compared to the results of a temperature index melt model which takes into account shading of direct solar illumination but not the other two effects the model reproduces some important features of the field data but its spatial variations are generally less than the measured values our study shows the importance of albedo and other local conditions in the accurate estimation of the small scale melt rate distribution

mass balance model parameter transferability on a tropical glacier we explore the small scale spatial and temporal transferability of model parameters between two points in the ablation zone of tropical glaciar shallap cordillera blanca peru 9 s 77 w 4800 m a s l in order to provide a robust assessment of the performance of a process based glacier mass balance model relative surface height change is calculated at hourly time steps and cumulative values are compared to surface height measurements made at irregular intervals 14 64 days over the course of two continuous hydrological years august 2006 august 2008 best performing parameter combinations were determined for each point from the outcome of 1000 model simulations for which parameters were varied randomly within a defined range with these parameter combinations measurements for a specific location and time span are well reproduced transferring the parameter combination as optimized for one location to the other location in the ablation zone increases the errors of modeled cumulative mass balance by 5 1326 mm ice eq a 1 transferring the parameter combinations as optimized for one year to the other year increases the modeled errors in cumulative mass balance by 18 3179 mm ice eq a 1 model errors generally increase during periods with frequent snowfall and snow cover this could reflect either the inherent difficulty of modeling complex snow processes or the inability of the model to correctly capture the pattern of albedo evolution at this site the magnitude of errors associated with parameter transfer in space and time highlights the need for improving model performance for robust climatological and or hydrological analyses on tropical glaciers

radiative fluxes and their impact on the energy balance of the greenland ice sheet a meteorological experiment was carried out during the summer months of 1990 and 1991 near the mean equilibrium line altitude ela on the western slope of the greenland ice sheet eth camp 69 34 n 49 17 w 1155 m a s l as a part of the project the energy fluxes at the surface including all components of the radiation balance atmospheric profiles with a tower and radiosondes and the cloud conditions were investigated in detail results from the radiative fluxes are compared with observations made at other locations in order to derive general characteristics of the radiation conditions on the greenland ice sheet and their relation to the climate of the ice sheet at eth camp albedo values obtained at ground level 2 m and from a high tower 27 m are similar during the melt season late may to mid august and slightly different during pre and post melt seasons due to the interplay of inhomogeneous surface conditions and solar elevation during the melt period the decrease in global radiation due to increasing cloud amount is compensated for by an increase in longwave incoming radiation because of the steady values of longwave outgoing radiation net radiation at the surface is characterized mainly by the albedo and its variation the regional net radiation for summer months on the greenland ice sheet is determined mainly by three facts 1 a strong increase in albedo from the ablation area to the ela and a smaller increase from the ela to the accumulation area 2 a large increase in longwave outgoing radiation in the ablation area and at the ela in june and july compared to the accumulation area 3 a larger amount of cloud of the stratus type at lower areas

a study of ablation variations on the tongue of hintereisferner austrian alps austria here we discuss the interpretation of detailed ablation measurements on the tongue two profiles are considered one along the glacier axis and one across the glacier tongue at the crossing an energybalance station was operated providing the necessary meteorological data at all stakes the albedo was measured several times with a simple light weight instrument described separately in the appendix the absorption of solar radiation was calculated for all stake positions taking into account local albedo slope aspect and shading effects it appears that the differences in ablation can be explained almost entirely by the differences in surface albedo both along and across the glacier tongue

distributed modeling of ablation 1996 2011 and climate sensitivity on the glaciers of taylor valley antarctica here the mcmurdo dry valleys of antarctica host the coldest and driest ecosystem on earth which is acutely sensitive to the availability of water coming from glacial runoff we modeled the spatial variability in ablation and assessed climate sensitivity of the glacier ablation zones using 16 years of meteorological and surface mass balance observations collected in taylor valley sublimation was the primary form of mass loss over much of the ablation zones except for near the termini where melt primarily below the surface dominated microclimates in 10 m scale topographic basins generated melt rates up to ten times higher than over smooth glacier surfaces in contrast the vertical terminal cliffs on the glaciers can have higher or lower melt rates than the horizontal surfaces due to differences in incoming solar radiation the model systematically underpredicted ablation for the final 5 years studied possibly due to an increase of windblown sediment surface mass balance sensitivity to temperature was 0 02 m w e k 1 which is among the smallest magnitudes observed globally we also identified a high sensitivity to ice albedo with a decrease of 0 02 having similar effects as a 1 k increase in temperature and a complex sensitivity to wind speed

hydrometeorological relationships on haig glacier alberta canada we investigate the relationships between meteorological hydrological and glaciological data collected at haig glacier alberta canada for the 2002 and 2003 ablation seasons correlation lag cross correlation and multivariate regression analyses are employed to assess the seasonal evolution of relationships between temperature temperature residuals total daily radiation albedo accumulation area ratio aar and total daily discharge qi early season melt is temperature dependent when aar remains high and the hydraulic properties of the snowpack limit both diurnal discharge variability and a rapid hydrologic response as the melt season progresses a decreasing aar and ripening of the snowpack induce a glacier wide decrease in albedo and a structured radiation discharge response is observed radiation detrended temperature values offer modest improvements over physical temperature values in multivariate regression models estimating daily discharge values using a detrended temperature indexed melt model we assess the transport efficiency of the glacial hydrologic system through a comparison of total modelled daily melt and observed discharge transport efficiency values support the notion of a purge effect during freezing events and at the end of the ablation season and suggest that it is the evolution of the supraglacial drainage system that controls diurnal discharge variability

areal melt and discharge modelling of storglaciaren sweden a grid based glacier melt and discharge model was applied to storglaciaren a small valley glacier 3 km 2 in northern sweden for the melt seasons of 1993 and 1994 the energy available for melt was estimated from a surface energy balance model using meteorological data collected by automatic weather stations on the glacier net radiation and the turbulent heat fluxes were calculated hourly for every grid point of a 30 m resolution digital terrain model using the measurements of temperature humidity wind speed and radiative fluxes on the glacier two different bulk approaches were used to calculate the turbulent fluxes and compared with respect to their impact on discharge simulations discharge of storglaciaren was simulated from calculated meltwater production and precipitation by three parallel linear reservoirs corresponding to the different storage properties of firn snow and ice the performance of the model was validated by comparing simulated discharge to measured discharge at the glacier snout depending on which parameterization of the turbulent fluxes was used the timing and magnitude of simulated discharge was in good agreement with observed discharge or simulated discharge was considerably underestimated in one year

a comparison of empirical and physically based glacier surface melt models for long term simulations of glacier response we investigate the performance of five glacier melt models over a multi decadal period in order to assess their ability to model future glacier response the models range from a simple degree day model based solely on air temperature to more sophisticated models including the full shortwave radiation balance in addition to the empirical models the performance of a physically based energy balance eb model is examined the melt models are coupled to an accumulation and a surface evolution model and applied in a distributed manner to rhonegletscher switzerland over the period 1929 2012 at hourly resolution for calibration seasonal mass balance measurements 2006 12 are used decadal ice volume changes for six periods in the years 1929 2012 serve for model validation over the period 2006 12 there are almost no differences in performance between the models except for eb which is less consistent with observations likely due to lack of meteorological in situ data however simulations over the long term 1929 2012 reveal that models which include a separate term for shortwave radiation agree best with the observed ice volume changes indicating that their melt relationships are robust in time and thus suitable for long term modelling in contrast to more empirical approaches that are oversensitive to temperature fluctuations

effects of clouds on surface melting of laohugou glacier no 12 western qilian mountains china we analyzed a 2 year time series of meteorological data january 2011 december 2012 from three automatic weather stations on laohugou glacier no 12 western qilian mountains china air temperature humidity and incoming radiation were significantly correlated between the three sites while wind speed and direction were not in this work we focus on the effects of clouds on other meteorological parameters and on glacier melt on an average 18 of top of atmosphere shortwave radiation was attenuated by the clear sky atmosphere and clouds attenuated a further 12 most of the time the monthly average increases in net longwave radiation caused by clouds were larger than decreases in net shortwave radiation but there was a tendency to lose energy during the daytime when melting was most intense air temperature and wind speed related to turbulent heat flux were found to suppress glacier melt during cloudy periods while increased water vapor pressure during cloudy days could enhance glacier melt by reducing energy loss by latent heat from these results we have increased the physical understanding of the significance of cloud effects on continental glaciers

climate sensitivity of storglaciaren sweden an intercomparison of mass balance models using era 40 re analysis and regional climate model data estimates of glacier contributions to future sea level rise are often computed from mass balance sensitivities derived for a set of representative glaciers our purpose is to investigate how mass b

variations of ablation albedo and energy balance at the margin of the greenland ice sheet kronprins christian land eastern north greenland a meteorological and glaciological experiment was carried out in july 1993 at the margin of the greenland ice sheet in kronprins christian land eastern north greenland within a small area about 100 m 2 daily measurements were made on ten ablation stakes fixed in light and dark ice and were compared to each other simultaneously the components of the energy balance including net radiation sensible heat flux latent heat flux and conductive heat flux in the ice were determined global radiation longwave incoming radiation and albedo were measured and longwave outgoing radiation was calculated by assuming that the glacier surface was melting sensible and latent heat fluxes were calculated from air temperature humidity and wind speed conductive heat flux in the ice was estimated by temperature profile measurements in the uppermost ice layer net radiation is the major source of ablation energy and turbulent fluxes are smaller energy sources by about three times while heat flux into the ice is a substantial heat sink reducing energy available for ice melt albedo varies from 0 42 to 0 56 within the experimental site and causes relatively large differences in ablation at stakes close to each other small scale albedo variations should therefore be carefully sampled for large scale energy balance calculations

distributed mass balance modelling on two neighbouring glaciers in ortles cevedale italy from 2004 to 2009 a 6 year application of an enhanced temperature index mass balance model to careser and la mare glaciers eastern italian alps is presented the two glaciers exhibit very different characteristics and a comprehensive dataset of distributed mass balance measurements was used to test the model performance the model was run using meteorological data acquired outside the glaciers the work was focused on two main aspects 1 the development of a morphological redistribution procedure for snow and 2 the comparison of three different melt algorithms proposed in the literature the results show that the simple method proposed for snow redistribution can greatly improve simulation of winter balance and further improvements would be achievable by collecting data on inaccessible and high altitude areas all three melt formulations displayed a good skill level and very similar results in modelling the mass balance distribution over glacier areas with slightly better results from a multiplicative algorithm in capturing the vertical balance gradient the simulation errors are related to aspect and elevation and tend to be spatially aggregated some assumptions concerning the spatial and temporal distribution of air temperature and incoming solar radiation although reasonable and widely used in the literature may be responsible for this aggregation hence there is a need to further investigate the processes that regulate the distribution of melt energy and that appear to control the current deglaciation phase in this area

sedimentological characteristics and morphology of the aeolian sand dunes in the eastern part of the uae a case study from ar rub al khali abstract the umm az zimul al wijan area is located in the southeastern part of the uae and covers about 1600 km 2 it is bounded to the east by the oman mountains and to the south and west by the extensive dune area of ar rub al khali field investigation revealed the common occurrence of parallel to sub parallel sand ridges with a general east west orientation also present but less frequent are barchan barchanoid and star dunes interdune areas are classified into four types that include dolomite mixed ancient sabkha and ophiolitic rock fragments mixed sand sheet and ophiolitic rock fragments and recent sabkha the textural characteristics of the sand forming the dunes are unimodal with a modal class in fine sand size moderately to very well sorted positively skewed and mesokurtic quartz grains are mainly subrounded to subangular the similarity in roundness properties in different dune types in the eastern province of the uae seems not to be influenced by dune form based on the heavy mineral suites and the angularity of quartz grains it is believed that the sand sediments are mostly derived from the ultrabasic rocks forming the ophiolitic sequence of the oman mountains acidic rocks of iran and from the coastal area

energy and mass balance of zhadang glacier surface central tibetan plateau climate variables that control the annual cycle of the surface energy and mass balance on zhadang glacier in the central tibetan plateau were examined over a 2 year period using a physically based energy balance model forced by routine meteorological data the modelled results agree with measured values of albedo incoming longwave radiation surface temperature and surface level of the glacier for the whole observation period the radiation component dominated 82 the total surface energy heat fluxes this was followed by turbulent sensible 10 and latent heat 6 fluxes subsurface heat flux represented a very minor proportion 2 of the total heat flux the sensitivity of specific mass balance was examined by perturbations of temperature 1 k relative humidity 20 and precipitation 20 the results indicate that the specific mass balance is more sensitive to changes in precipitation than to other variables the main seasonal variations in the energy balance were in the two radiation components net shortwave radiation and net longwave radiation and these controlled whether surface melting occurred a dramatic difference in summer mass balance between 2010 and 2011 indicates that the glacier surface mass balance was closely related to precipitation seasonality and form proportion of snowfall and rainfall

particle size fractionation of eolian sand along the sinai negev erg of egypt and israel eolian sand fractions along the west east transport system of the northern sinai peninsula northwestern negev erg of egypt and israel were analyzed in this study with regard to source dune geomorphology eolian transport and paleoclimate the studied erg is composed of active linear seif dunes in northern sinai western part and stabilized vegetated linear dunes in the nw negev dune field eastern part linear seif dunes differ from vegetated linear dunes in their vegetation cover linearity internal structure and dynamics sand samples were analyzed for sand grain morphology and particle size distribution although both dune types are continuous landforms with similar orientations and sand grain roundness values the linear dunes of sinai are coarser grained than the negev vegetated linear dunes the vegetated linear dunes have a variable but higher proportion of very fine sand 50 125 m content and a varying but lower sand fining ratio defined as the ratio of fine sand percentage to very fine sand percentage from these observations we infer that fractionation of sand occurred along the studied eolian transport path during periods of enhanced windiness very fine sands are suggested to have been transported by saltation and low suspension from source deposits and sand sheets we suggest that a significant proportion of the very fine sand fraction of nile delta sands has been transported downwind through northern sinai during the late pleistocene especially when linear dunes reached the nw negev due to last glacial period windiness and probably larger sediment supply generally decreasing wind velocities and increasing precipitation along the west east dune transport path enhanced vegetative cover in the northern negev and enabled deposition of the very fine sand component within the dunes and probably further downwind our results suggest that particle size distribution can elucidate much about erg history over time scales of a glacial interglacial cycle especially in cases where the sand provenance is of a single dominant source

a simple energy balance model to calculate ice ablation at the margin of the greenland ice sheet apres avoir etabli les relations donnees climatiques taux d enlevement de la glace dans 2 glaciers du groenland un modele simple de bilan energetique est effectue pour calculer le taux d enlevement de la glace aux bordures du glacier

sensitivity of mass balance and equilibrium line altitude to climate change in the french alps assessment of the sensitivity of surface mass balance and equilibrium line altitude ela to climate change is crucial for simulating the future evolution of glaciers such an assessment has been carried out using an extensive dataset comprising numerous measurements of snow accumulation and snow and ice ablation made on four french glaciers over the past 16 years winter mass balance shows a complicated pattern with respect to altitude with no clear linear relationship although the ratios of winter mass balance to valley precipitation differ considerably from site to site they are relatively constant over time relationships between snow ice ablation and temperature are stable with no link with altitude the mean snow and ice positive degree day pdd factors are 0 003 and 0 0061 m w e c 1 d 1 this analysis shows that at a given site ablation depends mainly on the amount of snow precipitation and on cumulative pdds the sensitivity of annual ablation to temperature change increases almost linearly from 0 25 m w e c 1 at 3500 m to 1 55 m w e c 1 at 1650 m ela sensitivity to temperature change was found to range from 50 to 85 m c 1

near surface hydraulic conductivity of northern hemisphere glaciers the hydrology of near surface glacier ice remains a neglected aspect of glacier hydrology despite its role in modulating meltwater delivery to downstream environments to elucidate the hydrological characteristics of this near surface glacial weathering crust we describe the design and operation of a capacitance based piezometer that enables rapid economical deployment across multiple sites and provides an accurate high resolution record of near surface water level fluctuations piezometers were employed at 10 northern hemisphere glaciers and through the application of standard bail recharge techniques we derive hydraulic conductivity k values from 0 003 to 3 519 m day 1 with a mean of 0 185 0 019 m day 1 these results are comparable to those obtained in other discrete studies of glacier near surface ice and for firn and indicate that the weathering crust represents a hydrologically inefficient aquifer hydraulic conductivity correlated positively with water table height but negatively with altitude and cumulative short wave radiation since the last synoptic period of either negative air temperatures or turbulent energy flux dominance the large range of k observed suggests complex interactions between meteorological influences and differences arising from variability in ice structure and crystallography our data demonstrate a greater complexity of near surface ice hydrology than hitherto appreciated and support the notion that the weathering crust can regulate the supraglacial discharge response to melt production the conductivities reported here coupled with typical supraglacial channel spacing suggest that meltwater can be retained within the weathering crust for at least several days not only does this have implications for the accuracy of predictive meltwater run off models but we also argue for biogeochemical processes and transfers that are strongly conditioned by water residence time and the efficacy of the cascade of sediments impurities microbes and nutrients to downstream ecosystems because continued atmospheric warming will incur rising snowline elevations and glacier thinning the supraglacial hydrological system may assume greater importance in many mountainous regions and consequently detailing weathering crust hydraulics represents a research priority because the flow path it represents remains poorly constrained

significance of primary hilltop loess in reconstructing dust chronology accretion rates and sources an example from the negev desert israel 1 although high latitude loess sequences have been studied extensively for reconstructing past climates loess in desert margins has been mostly overlooked moreover many low latitude loess studies have focused on secondary reworked sequences for which paleoclimatic inferences are complicated owing to postdepositional processes acting under local control in this respect the spatial distribution of the loess and its different types are crucial in this study we differentiate primary and secondary loess using remote sensing and field criteria we present remote sensing and geographic information system procedures for mapping loess distribution in general and for identifying pristine hilltop loess sequences in particular then we present the mineralogical and textural analyses combined with optically stimulated luminescence ages of one such primary hilltop loess sequence in the negev desert that show that the late pleistocene negev loess started accumulating at 95 ka much earlier than previously proposed 70 ka it was preceded by a previously unknown middle pleistocene period of loess formation at 180 130 ka the ages also suggest that the threshold of dust accretion rate needed for loess formation is 0 02 mm a 1 30 g m 2 a 1 a factor of 2 or more lower than previously thought 0 04 to 1 0 mm a 1 our results also provide insights into causes of late pleistocene loess accretion and its close association with regional dune field activity the methodology for mapping the loess distribution may potentially be generalized to help understanding loess formation in other more remote desert areas

late holocene dune mobilizations in the northwestern negev dunefield israel a response to combined anthropogenic activity and short term intensified windiness abstract the study of the effects of past climates on ancient cultures is usually based on geologic records pertaining to rainfall and temperature fluctuations and shifts this study proposes a paradigm of anthropogenic activity and windiness fluctuations to explain aeolian sedimentation and dune mobilization in the northwestern nw negev desert dunefield israel the proposed paradigm contributes a different approach to estimating the effect of climate changes on the unprecedented agricultural and urban settlement expansion during the late roman to early islamic period in the northern and central negev desert this study builds upon the late holocene cluster of luminescence ages coupled with analysis of archaeological finds and historical texts whereas the nw negev dunefield was generally stable during the holocene intermittent dune mobilization during the late holocene at 1 8 ka and mostly 1 4 1 1 ka 600 900 ce are linked to periods of human occupation the idea that the last glacial dune encroachments alone that formed the nw negev dunefield is connected to cold event windy climates that may have intensified east mediterranean cyclonic winter storms cannot explain the late holocene dune mobilizations a conceptual model indicates a connection between late holocene dune mobilization widespread anthropogenic occupation and activity and windiness historic grazing and uprooting shrubs for fuel in the past by nomads and sedentary populations led to decimation of dune stabilizers biogenic soil crusts and vegetation causing dune erodibility and low grade activity short term events of amplified wind power in conjunction with periods of augmented anthropogenic activity that triggered major events of dune mobilization elongation and accretion have been preserved in the dune chronostratigraphy because they were short lived the dune mobilization events corresponding windiness and probable dustiness which were examined affected the northern negev landscape differentially however they cannot be shown to have affected the environment sufficiently to influence the decline of the late byzantine and early islam agricultural establishment this study demonstrates the sensitivity of dunes in arid and semi arid regions to a combination of local and short term fluctuations in windiness at times of widespread grazing anthropogenic activity the results indicate that in similar future scenarios sand mobilization may be similarly retriggered to varying degrees

abrasion derived sediments under intensified winds at the latest pleistocene leading edge of the advancing sinai negev erg abstract quaternary desert loess and sandstone loessite relationships in the geological record raise questions regarding causes and mechanisms of silt formation and accretion in the northern sinai negev desert carbonate terrain only sand abrasion in active erg could have produced the large quantities of quartzo feldspathic silts constituting the late quaternary northwestern negev loess in the continuum of source medium to fine sand of dunes to sink silts in loess the very fine sand is unaccounted for in the record this weakens the sand abrasion model of silt formation as a global process here we demonstrate that as predicted by experiments abrasion by advancing dunes generated large quantities of very fine sand 60 110 m deposited within the dune field and in close proximity downwind this very fine sand was generated 13 11 ka possibly synchronous with the younger dryas under gusty sand dust storms in the southeastern mediterranean and specifically in the northern sinai negev erg these very fine sands were washed down slope and filled small basins blocked by the advancing dunes outside these sampling basins it is difficult to identify these sands as a distinct product we conclude that ergs are mega grinders of sand into very fine sand and silt under windy quaternary and ancient aeolian desert environments

the surface energy balance of an active ice covered volcano villarrica volcano southern chile the energy balance of bare snow and tephra covered ice near the glacier equilibrium line elevation on villarrica volcano southern chile was investigated during 2004 and 2005 combining meteorological surface temperature and ablation measurements with energy balance modelling a tephra thermal conductivity of 0 35 w m 1 k 1 and a critical tephra thickness of 0 1 m tephra windblown tephra impurities lowered snow albedo but increased snowmelt by only an estimated 0 28 m w e over the same period the net mass balance impact of supraglacial tephra at villarrica volcano is therefore positive as thick ash and lapilli mantle most of the glacier ablation zones probably reducing annual ablation by several metres w e in the accumulation seasons frequent melting events were recorded with modelled daily snowmelt rates of up to 50 mm w e

which empirical model is best suited to simulate glacier mass balances based on an extensive dataset of surface mass balances smb from four glaciers in the french alps for the period 1995 2012 and in the framework of enhanced temperature index models we investigate the sensitivity of seasonal glacier smb to temperature solar radiation precipitation and topographical variables our results reveal strong correlations between winter smb and precipitation although the precipitation gradient cannot explain the high accumulation rates based on the available point measurements we found no relevant relationship between winter smb and topographical variables temperature was found to be the main driver of ice snow ablation while solar radiation was found to strongly influence the spatial distribution of summer smb we compared the ability of several enhanced temperature index models to accurately simulate point smb and glacier wide mb our analyses revealed that the uncertainties in the simulated annual smb due to winter smb uncertainties are larger than differences between models and prevented us from concluding which model is the most suitable in contrast with results of previous studies including solar radiation in melt models did not improve the performances when modelling glacier wide mb we conclude that a classical degree day model is sufficient to simulate the long term glacier wide mb if the underlying processes are not required to be resolved

a distributed surface energy balance model for a small valley glacier i development and testing for haut glacier d arolla valais switzerland this paper describes the development and testing of a distributed surface energy balance model used to calculate rates of surface melting at haut glacier d arolla valais switzerland the model uses a digital elevation model dem of the glacier surface and surrounding topography together with meteorological data collected at a site in front of the glacier to determine hourly or daily totals of the energy balance components and hence of melting over the entire surface of the glacier with a spatial resolutio of 20 m the model can also be used to determine temporal and spatial variations in snow depth snow line position and glacier surface albedo calculations from the model are compared with observations made along the glacier centre line in 1990 and in general the model performs very well the correlation coefficients between calculated and measured snow line elevation albedo and ablation are 0 99 0 85 and 0 81 respectively the main source of error between modelled and measured values of these variables is probably inadequacies in the parameterization of albedo used in the model

melt and surface sublimation across a glacier in a dry environment distributed energy balance modelling of juncal norte glacier chile previous estimates of melt and surface sublimation on glaciers of the subtropical semiarid andes 29 34 s have been obtained at few specific locations but it is not clear how ablation components vary across the entire extent of a glacier in this dry environment here we simulate the distributed energy and mass balance of juncal norte glacier 33 s during a 2 month summer period forcing fields of near surface air temperature and wind speed are generated using two methods accounting for the main physical processes that shape their spatial variations simulated meteorological variables and ablation agree well with observations on the glacier tongue and reveal complex patterns of energy and mass fluxes ablation decreases from 70 mm w e d 1 at the low albedo glacier terminus 3000 m where almost 100 of total ablation corresponds to melt to 75 of total ablation our simulations provide the first glacier scale estimates of ablation components on a glacier in the study region and better reproduce the observed and expected spatial variations of melt and surface sublimation in comparison with more simple assumptions such as linear gradients and uniform wind speeds

including debris cover effects in a distributed model of glacier ablation 1 distributed glacier melt models generally assume that the glacier surface consists of bare exposed ice and snow in reality many glaciers are wholly or partially covered in layers of debris that tend to suppress ablation rates in this paper an existing physically based point model for the ablation of debris covered ice is incorporated in a distributed melt model and applied to haut glacier d arolla switzerland which has three large patches of debris cover on its surface the model is based on a 10 m resolution digital elevation model dem of the area each glacier pixel in the dem is defined as either bare or debris covered ice and may be covered in snow that must be melted off before ice ablation is assumed to occur each debris covered pixel is assigned a debris thickness value using probability distributions based on over 1000 manual thickness measurements locally observed meteorological data are used to run energy balance calculations in every pixel using an approach suitable for snow bare ice or debris covered ice as appropriate the use of the debris model significantly reduces the total ablation in the debris covered areas however the precise reduction is sensitive to the temperature extrapolation used in the model distribution because air near the debris surface tends to be slightly warmer than over bare ice overall results suggest that the debris patches which cover 10 of the glacierized area reduce total runoff from the glacierized part of the basin by up to 7

neglecting ice atmosphere interactions underestimates ice sheet melt in millennial scale deglaciation simulations dynamic and thermodynamic interactions between the atmosphere and underlying ice sheets are generally not represented in the traditional one way boundary condition forcing used to drive ice sheet models this shortcoming is investigated through a series of idealized millennial scale deglaciation simulations designed to isolate the mechanisms regulating the deglaciation timescale of the laurentide ice sheet sensitivity experiments indicate that the conventional use of one way non interactive atmospheric forcing fields leads to an unrealistically insensitive melt response in the ice sheet model even when atmospheric carbon dioxide is set to modern preindustrial levels and earth s angle of obliquity is set to its early holocene value a more realistic deglaciation timescale is obtained only through the application of a new two way interactive asynchronous ice atmosphere coupling scheme and a seasonal ice albedo parameterization that accounts for the observed darkening of ice in the moist summertime ablation zone

surface mass balance of glaciers in the french alps distributed modeling and sensitivity to climate change a new physically based distributed surface mass balance model is presented for alpine glaciers based on the crocus prognostic snow model it resolves both the temporal 1 hour time step and spatial 200 m grid step variability of the energy and mass balance of glaciers mass balance reconstructions for the period 1981 2004 are produced using meteorological reconstruction from the safran meteorological model for glacier de saint sorlin and glacier d argentiere french alps both glaciers lost mass at an accelerated rate in the last 23 years the spatial distribution of precipitation within the model grid is adjusted using field mass balance measurements this is the only correction made to the safran meteorological input to the glacier model which also includes surface atmospheric temperature moisture wind and all components of downward radiation independent data from satellite imagery and geodetic measurements are used for model validation with this model glacier sensitivity to climate change can be separately evaluated with respect to a full range of meteorological parameters whereas simpler models such as degree day models only account for temperature and precipitation we provide results for both mass balance and equilibrium line altitude ela using a generic alpine glacier the sensitivity of the ela to air temperature alone is found to be 125 m c 1 or 160 m c 1 if concurrent stefan boltzmann longwave radiation change is taken into account

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

sediment export transient landscape response and catchment scale connectivity following rapid climate warming and alpine glacier recession abstract in the face of rapid climate warming rapid glacier recession should lead to a marked increase in the spatial extent of the paraglacial zone in glaciated drainage basins the extent of the paraglacial zone has been well established to be transient but there are very few studies of this transient response and what it means for sediment export there is good reason to expect that glacier recession could increase basin scale sediment connectivity as sediment becomes less dependent on glacier surface transport proglacial streams are more able to migrate laterally than subglacial streams and so access sediment for transport and glacier debuttressing may aid the development of gullies that can dissect moraines and so aid hillslope to proglacial zone connectivity by using records of the flushing of hydroelectric power installations we were able to develop a record of coarse sediment sand and gravel export from a basin with a rapidly retreating valley glacier the haut glacier d arolla from 1977 to 2014 modelling suggested that these data could only be partially controlled by transport capacity implying an important role for sediment supply and potentially for the influence of changing sediment connectivity indeed there was evidence of the effects of glacial debuttressing upon gullying processes and hence a possible increase in the ease of connection of upstream basins to the proglacial area more recently we were able to show possible temperature control on sediment export which may only have become apparent because of the progressive development of better sediment connectivity however whilst rapid glacier recession should result in theory in a progressive increase in connectivity of sediment sources to the basin outlet the supply to capacity ratio does not increase continually with glacier recession until maximum capacity is reached we identified two possible examples of why first gullying was also accompanied by the sediment accumulation at the base of moraines that was too coarse to be transported by the proglacial stream maintaining disconnection of the upper basins second the sediment capacity ratio appeared to be elevated during periods of more rapid retreat and we attribute this to the importance of a continued supply of unworked glacial till before fluvial reworking and sorting of freshly exposed sediment increased the resistance of sediment to entrainment and hence export rates thus the transient geomorphic response of glaciated basins to glacier recession may involve negative feedbacks that can reduce the extent to which increases in connectivity elsewhere in the basin lead to increased sediment export

characterisation of aeolian sediments from the strzelecki and tirari deserts australia implications for reconstructing palaeoenvironmental conditions abstract in arid environments dominated by desert dunes aeolian sediments represent a major source of potential palaeoenvironmental information however the extent to which dune sedimentology can be used for past environmental reconstruction is unclear this paper assesses the value of dune sediments as palaeoenvironmental indicators by investigating the sedimentological characteristics of linear dunes in the strzelecki and tirari deserts of central australia we use thin section microscopy particle size analysis and x ray diffractometry xrd mineralogy to characterise the sediments occurring within the dunefields of the region and examine the stratigraphic record in the context of dune preservation and sediment reworking we find that it is rarely possible to reconstruct past environmental change within desert dunefields purely on the basis of sedimentological evidence however limited palaeoenvironmental information is preserved within dune sediments which can be combined with additional arid zone proxies and geochronological techniques to enable the most reliable reconstruction of past conditions paleosols provide the most informative and unambiguous palaeoenvironmental indicators within dune sediments acting as markers of relative environmental stability paleosols are characterised by pedogenic carbonates and gypsum and illuviated clays in the form of intact grain coatings the potential for incomplete stratigraphic preservation within dunes is a critical consideration for reconstructing palaeoenvironments however the preservation of paleosols indicates that the dunes in this region have not been completely reworked grain coatings provide important evidence both for pedogenesis when they are intact and for aeolian reworking when they are partially abraded abraded cutans are ubiquitous across the region studied linear dune mineralogy of the strzelecki and tirari deserts is dominated by quartz with minor feldspar and clay minerals the latter in the form of grain coatings and aggregates the occurrence of intact sand sized aggregates composed of clay and silt particles at several sites indicates incipient rather than peak aridity and may within this geomorphic context indicate reduced stream discharges grain size shows a regional bias although silt sized material is most likely to have been deposited as long travelled dust the regional grain size characteristics combined with local occurrences of rock fragments and high feldspar content suggest that sediments are mostly derived from local sources

2 m temperatures along melting mid latitude glaciers and implications for the sensitivity of the mass balance to variations in temperature in calculations of the variation in the 2 m temperature along glaciers the lapse rate is generally assumed to be constant this implies that the ratio of changes in the 2 m temperature above a glacier to changes in the temperature outside the thermal regime of that glacier climate sensitivity is equal to 1 however data collected during the ablation season on several mid latitude glaciers show that this sensitivity is smaller than 1 the lowest measured value 0 3 was obtained on the tongue of the pasterze a glacier in austria the measured temperature distribution along the pasterze cannot be described by a constant lapse rate either however there is almost a linear relationship between potential temperature and the distance along die glacier this paper introduces a simple analytical thermodynamic glacier wind model which can be applied to melting glaciers and which explains the observed climate sensitivities and temperature distributions much better than calculations based on a constant lapse rate this way of modelling the 2 m temperatures has implications for the sensitivity of the surface mass balance to atmospheric warming outside the thermal regime of the glacier the magnitude of this sensitivity is computed with a surface energy balance model applied to the pasterze when a constant lapse rate is used instead of the proposed glacier wind model to compute changes in the 2 m temperature along the glacier the negative change in mass balance due to 1 c warming is overestimated by 22

climate sensitivity of glaciers in southern norway application of an energy balance model to nigardsbreen hellstugubreen and alfotbreen three glaciers in southern norway with very different massbalance characteristics are studied with an energy balance model of the ice snow surface the model simulates the observed mass balance profiles in a satisfactory way and can thus be used with some confidence in a study of climate sensitivity calculated changes in equilibrium line altitude for a 1 k temperature increase are 110 108 and 135 in for nigardsbreen hellstugubreen and alfotbreen respectively the corresponding changes in mass balance averaged over the entire glacier area are 0 88 0 715 and 1 11 in year water equivalent runs with an ice flow model for nigardsbreen to which calculated mass balance profiles are imposed predict that the front will advance by 3 km for a 1 k cooling and will retreat by as much as 6 5 km for a 1 k warming the response to a 10 increase in precipitation would be a 2 km advance of the snout whereas a 4 km retreat is predicted for a 10 decrease this large sensitivity as compared to many other glaciers is to a large extent due to the geometry of nigardsbreen

pliocene pleistocene climate of the northern margin of saharan arabian desert recorded in speleothems from the negev desert israel abstract the middle late pliocene climate was 2 3 c warmer than today but with similar levels of atmospheric co2 this period reflects climate conditions expected in the near future and is therefore an important target for current data modeling studies this study reconstructs the pliocene quaternary evolution of arid conditions on the northern margin of the saharan arabian desert using radiometrically u pb dated periods of speleothem deposition from three caves of the negev desert israel speleothem growth started between 3 75 and 3 ma at the end of the first significant tectonic uplift of the western shoulder of the dead sea rift major speleothem deposition indicating wet conditions occurred during the pliocene around 3 1 ma with subsequent aridity during the last 3 myr punctuated by short wet episodes the pleistocene negev humid periods nhp the oldest dated nhp occurred between 1 7 and 1 25 ma and other short humid episodes continued intermittently later speleothem 18o values 6 9 to 11 2 show that the humid episodes were associated with periods of low global ice volume and warm temperatures after correction for rainfall 18o changes associated with ice volume and temperature effects the observed relative constancy of speleothem 18o values from pliocene to late pleistocene indicates rainfall was from a common source most probably the eastern mediterranean sea the humid pliocene conditions could be generated by more southerly position of the mediterranean coast allowing the access of mediterranean precipitation to the negev as well as by warmer atlantic sea surface temperatures that weakened the azores high pressure cell maximum amounts of precipitation were 500 600 mm a during the pliocene and 300 mm a during pleistocene nhp the pliocene and the earliest pleistocene nhp are associated with formation of lakes in the negev low 87sr 86sr ratios of 0 7078 in the pliocene speleothems are indicative of low dust supply low water residence time in the vadose zone and relatively high weathering rates of the cave host rock increase of 87sr 86sr ratios to 0 7082 0 7083 in the pleistocene suggest an increased supply of desert dust high water residence time in the vadose zone and reduced host rock weathering

the surface albedo of the greenland ice sheet satellite derived and in situ measurements in the sondre stromfjord area during the 1991 melt season the temporal and spatial variation in the surface albedo of the greenland ice sheet during the ablation season of 1991 is investigated the study focuses on an area east of sondre stromfjord measuring 200 km by 200 km and centred at 67 5 n 48 13 w the analysis is based on satellite radiance measurements carried out by the advanced very high resolution radiometer avhrr the broad band albedo is estimated from the albedos in channel 1 visible and channel 2 near infrared the results are calibrated with the surface albedo of sea and dry snow satellite derived albedos are compared with gimex ground measurements at three stations there is a high degree of consistency in temporal variation at two of the three stations large systematic differences are attributed to albedo variations on subpixel scale in the course of the ablation season four zones appear each parallel to the ice edge it is proposed that these are in order of increasing altitude i clean and dry ice ii ice with surface water iii superimposed ice and iv snow an extensive description of these zones is given on the basis of the situation on 25 july 1991 zones i iii and iv reveal fairly constant albedos 0 46 0 65 and 0 75 on average whereas zone ii is characterised by an albedo minimum 0 34 survey of the western margin of the greenland ice sheet up to 71 n shows that the zonation occurs between 66 and 70 n

permanent quaternary hyperaridity in the negev israel resulting from regional tectonics blocking mediterranean frontal systems although various episodes of wet quaternary climates have been suggested in studies of the negev desert here we demonstrate that reg soils developed on flat alluvial surfaces and sensitive to minor changes in precipitation indicate that the southern negev has been permanently hyperarid at least since the middle pleistocene the wetter episodes were restricted to the northern negev currently mildly arid gypsic saline reg soils that de veloped on stable surfaces during 200 k y in the southern negev are cumulative and polygenetic but none exhibits even the weakest development of calcic horizons under current climate conditions in the negev calcic soils are widespread in areas with rainfall 80 mm yr 21 the fact that the hyperarid 50 mm yr 21 southern negev lacks any calcic horizons indicates that it never experienced an average rainfall of 80 mm yr 21 during the middle late pleistocene whereas the northern negev was wetter this negev dichotomy is explained by the main physical features controlling rainfall over the negev i e the southward decreasing depth of the atmospheric boundary layer with distance from the mediterranean and the altitude of the central negev highland 1000 m the interaction between these two features often prevents the passage of rain clouds into the southern negev the holocene and pleistocene gypsic salic soil distribution across the negev closely matches the current circumstances we suggest that hyperaridity has prevailed over the southern negev since the last stages of the uplift of the central negev highland in the late pliocene early pleistocene

self similarity in glacier surface characteristics catchment wide information on glacier snow cover depth surface albedo and surface roughness is important input data for distributed models of glacier energy balance in this study we investigate the small scale mm to 100 m spatial variability in these properties with a view to better simulating this variability in such models data were collected on midre lovenbreen a 6 km 2 valley glacier in northwest svalbard the spatial variability of all three properties was found to be self similar over the range of scales under investigation snow depth and albedo exhibit a correlation length within which measurements were spatially autocorrelated late winter and summer properties of snow depth differed with smaller depths in summer due to melt and shorter correlation lengths similar correlation lengths for snow depth and surface albedo may suggest that snow depth variation is an important control on the small scale spatial variability of glacier surface albedo for surface roughness the data highlight a possible problem in energy balance studies which use microtopographic surveys to calculate aerodynamic roughness in that the scale of the measurements made affects the calculated roughness value this suggests that further investigations of the relationships between surface form and aerodynamic roughness of glacier surfaces are needed

visible and near infrared reflectivity during the ablation period on peyto glacier alberta canada models for calculating glacier mass balance are sensitive to surface reflectivity variation fieldwork carried out on peyto glacier alberta canada contributes to the data set available for ice reflectivity parameterization in such models hemispherical reflectivity in the visible and near infrared parts of the solar spectrum was obtained for rock snow and three contrasting glacier surfaces to examine temporal and spatial variations glacier ice near infrared reflectivity displays only minor spatial variation 0 12 0 17 in comparison with the visible range 0 23 0 40 the latter being influenced primarily by surface impurity content surface roughness is of minor importance compared with impurities temporal variation of reflectivity was weak at all glacier ice and rock locations slight variations observed were due to changes in either solar zenith angle or cloud amount snow reflectivity displayed pronounced diurnal asymmetry and a larger response to cloud cover the minimal temporal variation in glacier ice reflectivity simplifies its parameterization this behaviour is additionally useful for satellite based measurements of the reflectivity field on larger glaciers as images obtained within a 6 h window centred on solar noon are likely to yield values which are within 2 3 of daily mean values

spatial and temporal variations in albedo on storglaciaren sweden extensive albedo data from storglaciaren sweden during nine summers are analyzed focusing on the effect of surface slope on measurements and on the influence of clouds on albedo of both snow and ice surfaces on clear sky days albedo continuously dropped throughout the day by 0 3 when derived from measurements in a horizontal plane over the slightly sloping surface when we correct for the tilt effect over frozen surfaces the apparent decrease in albedo largely disappeared while over melting surfaces it became significantly less pronounced this emphasizes the need to correct horizontally measured data for slope when they are used for example as ground truth for satellite derived albedo or in high resolution glacier melt runoff models albedo varied by 0 1 due to cloud fluctuations to quantify cloud effects albedo changes between successive half hourly and daily data were regressed against corresponding changes in cloudiness expressed by the ratio of global radiation to top of atmosphere solar radiation the resulting relationship over snow explains 66 of oberved albedo changes using hourly and 4 using daily time steps over ice the corresponding values arc 28 and 0 hence cloudiness is a dominating factor in determining short term variability of albedo over snow whereas over ice the observed large day to day variability 20 is mainly attributed to changes in the physical characteristics of the weathering crust results suggest that cloud effects should be incorporated into models treating snow and ice surfaces separately

mechanisms of loess sized quartz silt production and their relative effectiveness laboratory simulations the production of loess sized quartz silt is frequently ascribed to glacial grinding mechanisms in this study a series of laboratory simulations was set up the purpose of which was to demonstrate that a range of geomorphic mechanisms are capable of producing silt under laboratory conditions the geomorphic mechanisms investigated were aeolian abrasion fluvial comminution glacial grinding salt weathering and frost weathering the results confirmed that under laboratory conditions all of these mechanisms were capable of producing silt the relative effectiveness of these mechanisms at producing silt under laboratory conditions was then calculated in order to provide a starting point for a consideration of their potential effectiveness within the natural environment these results indicate that fluvial and aeolian activity are highly effective at producing quartz silt over short time periods in a dust storm of four days duration 287 g of silt could potentially be produced from every kilogram of sand entrained while fluvial comminution in a turbulent fluvial environment could potentially produce 900 g of silt from every kilogram of sand entrained within 32 h over longer periods of time the glacial grinding and weathering mechanisms represent more continuous and hence more effective silt producing mechanisms although it is realised that the relative importance of each silt producing mechanism will differ spatially and temporally due to differences in climate relief geology and geomorphic history the findings from this work do have implications for the genesis of loess deposits they demonstrate that glacial and cold weathering processes are not solely responsible for fine particle formation and that efficient silt producing mechanisms can operate within a variety of environments under suitable conditions weathering together with episodic contributions from aeolian and fluvial mechanisms could be responsible for a considerable proportion of global quartz silt production

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

sources and transport routes of fine detritus material to the late quaternary dead sea basin abstract the sources and routes of transport of fine detritus material fdm to the lakes filling the late quaternary dead sea basin were studied by petrographic mineralogical grain size chemical and sr nd isotope analyses on sediments of the late quaternary lacustrine formations including river flood material dust and loess from the lake watershed the lacustrine formations comprise two sedimentary facies one that consists of alternating laminae of primary aragonite and silty detritus material aad facies and another that consists mainly of laminated detritus particles and generally lacks aragonite ld facies the aad facies characterizes the glacial intervals e g mis2 and 4 when lake levels were high while the ld facies characterizes interglacials e g mis1 5 and warmer glacial intervals e g mis3 when lake levels were low the detritus of both aad and ld facies show similar mineralogy mainly quartz and calcite grains with minor feldspars and clays but distinct grain sizes 8 10 m and 50 60 m respectively and distinct 87 sr 86 sr and end 0 711 0 712 and 7 to 8 versus 0 709 0 710 and 5 respectively the aad and ld fdm comprise desert dust of mixed granitic basaltic composition that was blown from the sahara desert and from the nile delta to the northern negev desert e g the loess deposits and the judean mountains bordering the dead sea basin mainly during glacial intervals along with enhanced mediterranean rain fronts the aad fdm reflects an enhanced transport of saharan granitic dust to the vicinity of the lake mainly during glacials the ld fdm was recycled from the loess surface cover of the negev desert mainly during interglacials and warm glacial intervals

spatial and temporal transferability of a distributed energy balance glacier melt model abstract modeling melt from glaciers is crucial to assessing regional hydrology and eustatic sea level rise the transferability of such models in space and time has been widely assumed but rarely tested to investigate melt model transferability a distributed energy balance melt model debm is applied to two small glaciers of opposing aspects that are 10 km apart in the donjek range of the st elias mountains yukon territory canada an analysis is conducted in four stages to assess the transferability of the debm in space and time 1 locally derived model parameter values and meteorological forcing variables are used to assess model skill 2 model parameter values are transferred between glacier sites and between years of study 3 measured meteorological forcing variables are transferred between glaciers using locally derived parameter values 4 both model parameter values and measured meteorological forcing variables are transferred from one glacier site to the other treating the second glacier

a 1 year record of global radiation and albedo in the ablation zone of morteratschgletscher switzerland we analyse data on solar radiation measured with an automatic weather station on morteratschgletscher switzerland for the period 1 october 1995 30 september 1996 the station is in the lower ablation zone due to shading by surrounding mountains and atmospheric attenuation only 49 of the annual extraterrestrial irradiance mean 292 w m 2 reaches the glacier surface about 48 of this is absorbed at the surface mean 79 w m 2 annual albedo of 0 53 we present a simple albedo scheme for use in glacier mass balance models we fit the model to the 1 year dataset by optimizing five control parameters optimal values in brackets albedo of snow 0 75 albedo of firn 0 53 albedo of ice 0 34 e folding constant for effect of ageing on snow albedo 21 9 days and e folding constant for effect of snow depth on albedo 3 2 cm the input consists of daily albedo snow depth and dates of snowfall events the correlation coefficient between observed and simulated albedo is 0 931 the corresponding rms difference being 0 067

the nature and origin of the aeolian mantles of central northern nigeria abstract evidence is presented here to show that the upland soils of central northern nigeria are formed in aeolian mantles deposited by two aeolian processes aeolian suspension or dust deposition and aeolian saltation or dune sand deposition the soils to the south and west of kano are largely the product of harmattan dust deposition whereas the northern soils appear to originate from dune sand migration from the quaternary dune fields to the east of the study area the spatial pattern of particle size populations or quanta and quartz grain roundness characteristics within the mantles and dune sands indicates that considerable mixing of dune sands and dust has occurred in the formation of these mantles

interdecadal variability of degree day factors on vestari hagafellsjokull langjokull iceland and the importance of threshold air temperatures the skill of degree day glacier melt models is highly dependent on the choice of degree day factor ddf which is often assumed to remain constant in time here we explore the validity of this assumption in a changing climate for two locations on vestari hagafellsjokull 1979 2012 using a surface energy balance seb approach that isolates the effect of changes in the prevailing weather on the ddf at lower elevation we observe stable ddf during the period of study however at higher elevation ddf is noted to be more variable and a statistically significant downward trend is observed this is found to result from an inappropriate threshold air temperature t crit from which to initiate the positive degree day sum and is removed by setting t crit to 1 83 c rather than the usual value of 0 c used in degree day melt models the stationarity of ddf once t crit is adjusted contradicts previous research and lends support to the use of constant ddf for projecting future glacier melt optimizing t crit also improves the skill of melt simulations at our study sites this research thus highlights the importance of t crit for both melt model performance and the evaluation of ddf stationarity in a changing climate

temporal and spatial variations in spectral reflectance and characteristics of surface dust on gulkana glacier alaska range spectral reflectances in the visible to near infrared wavelength range 350 1050 nm were measured on the surface of gulkana glacier alaska range alaska usa at six different elevations from may to september 2001 the measurements showed variable spectral reflectances on the glacier surface and the spectra changed over time and elevation the spectra in may were those of a typical wet snow surface the reflectance ranged approximately from 0 4 to 0 8 and generally decreased as the wavelength increased as snowmelt proceeded the reflectance gradually fell and specific absorptions appeared in the spectrum at wavelength ranges of 400 600 and 670 680 nm corresponding to a red snow surface due to snow algal bloom as the ice surface was exposed the spectrum finally shifted to a lower 0 1 0 4 and flat reflectance curve typical of an ice surface contaminated with dust analyses of the dust on the glacier surface showed that its quantity and characteristics changed spatially and seasonally and were correlated with spectral albedo the results showed that the temporal and spatial variations in spectral reflectance on this glacier are due not only to physical properties of the glacier surface but also to biogenic materials on the surface e g red colored snow algal cells and cryoconite

microbiotic crusts as biomarkers for surface stability and wetness duration in the negev desert microbiotic crusts play an important role in arid and semi arid regions yet very little information exists regarding the factors that impact their development in an attempt to assess the main factors that may determine their growth measurements of the amount of fines silt and clay rain moisture content wetness duration and wind erosion and deposition were carried out along a 12 station transect within a partially crusted dune field in the western negev desert and compared to the crust cover and chlorophyll content surface stability was the only variable that exhibited significant relationship with crust cover while daylight wetness duration exhibited strong positive relationship r2 0 92 0 99 with the crust s chlorophyll content the data point out that microbiotic crusts may serve as a useful biomarker for surface stability while wetness duration and wind will control crust cover and the crust chlorophyll content in semi stable habitats with absolute annual change in sand level of 2 3 mm stable habitats absolute change 1 mm will be controlled primarily by moisture while habitats with low surface stability absolute change of tens and hundreds of millimeters will be primarily controlled by wind furthermore owing to the strong positive relationship between daylight wetness duration and the crust s chlorophyll content the crust may serve as a useful biomarker for the quantification of surface wetness duration copyright 2009 john wiley sons ltd

a distributed surface energy balance model for complex topography and its application to storglaciaren sweden a grid based surface energy balance mass balance model has been developed to simulate snow and ice melt in mountainous regions with an hourly resolution the model is applied to storglaciaren a valley glacier in sweden using a 30 m resolution digital elevation model emphasis is directed towards computing the radiation components these are modelled individually considering the effects of slope angle aspect and effective horizon a new parameterization for snow albedo is suggested modifying the albedo of the preceding hour as a function of time after snowfall air temperature and cloudiness the model is used to provide the meltwater input for discharge modelling and to assess the influence of the individual components on melt results are validated by means of observed melt rates patterns of snow line retreat and proglacial discharge in general simulations are in good agreement with observations in particular the diurnal and seasonal fluctuations of discharge are simulated remarkably well

evidence of active dune sand on the great plains in the 19th century from accounts of early explorers eolian sand is extensive over the great plains of north america but is at present mostly stabilized by vegetation accounts published by early explorers however indicate that at least parts of dune fields in nebraska colorado kansas new mexico and texas were active in the 19th century based on an index of dune mobility and a regional tree ring record the probable causes for these periods of greater eolian activity are droughts accompanied by higher temperatures which greatly lowered the precipitation to evapotranspiration ratio and diminished the cover of stabilizing vegetation in addition observations by several explorers and previous historical studies indicate that rivers upwind of great plains dune fields had shallow braided sandy channels as well as intermittent flow in the 19th century wide braided sandy rivers that were frequently dry would have increased sand supplies to active dune fields we conclude that dune fields in the great plains are extremely sensitive to climate change and that the potential for reactivation of stabilized dunes in the future is high with or without greenhouse warming

mass balance gradients and climatic change it is generally assumed that the mass balance gradient on glaciers is more or less conserved under climatic change in studies of the dynamic response of glaciers to climatic change one of the following assumptions is normally made i the mass balance perturbation is independent of altitude or ii the mass balance profile does not change it simply shifts up and down observational evidence for such an approach is not convincing on some glaciers the inter annual changes in mass balance seem to be independent of altitude on others not at all moreover it is questionable whether inter annual variation can be projected on different climatic states to see what a physical approach might contribute we developed an altitude dependent mass balance model it is based on the energy balance of the ice snow surface where precipitation is included in a parameterized form and numerical integrations are done through an entire balance year with a 30 min time step atmospheric temperature snowfall and atmospheric transmissivity for solar radiation are all dependent on altitude so a mass balance profile can be calculated slope and exposure of the ice snow surface are taken into account and the effects of these parameters studied in general the calculations were done for 100 m elevation intervals climatological data from the sonnblick observatory austria 3106 m a s l and from vent 2000 m a s l oetztal alps austria served as input for a number of runs simulation of the mass balance profiles for hinterseisferner north easterly exposure and kesselwandferner southeasterly exposure yields reasonable results the larger balance gradient on kesselwandferner is produced by the model so exposure appears to be an important factor here sensitivity of mass balance profiles to shading effects different slope and exposure are systematically studied another section deals with the sensitivity to climatic change perturbations of air temperature cloudiness albedo and precipitation are imposed to see their effects on the mass balance profiles the results clearly show that in general mass balance perturbations depend strongly on altitude they generally increase down glacier and are not always symmetric about the reference state for typical climatic conditions in the alps we found that a 1 k temperature change leads to a change in equilibrium line altitude of 130 m three factors contribute to this large value turbulent heat flux longwave radiation from the atmosphere and fraction of precipitation falling as snow here the albedo feed back increases the sensitivity in a significant way

rapid quantification of cryoconite granule geometry and in situ supraglacial extents using examples from svalbard and greenland supraglacial dust cryoconite is an important but poorly understood component of the glacial system there is a lack of primary data on cryoconite form extent and dynamics here we present a suite of rapid low cost methodologies for quantification of granule geometry and supraglacial cryoconite coverage using image data captured by commercially available digital cameras we develop robust transferable protocols for analysis of 1 cryoconite granule geometry major axis feret diameter circularity 2 centimetre metre scale supraglacial extent m2 cryoconite m 2 surface and 3 temporal change in supraglacial extent at hourly intervals over several days image processing methodologies were developed using the public domain software imagej manual supervised controls were used to estimate sources of error and measurements then automated using simple scripting tools macros fully automated processing successfully identified 90 of a sample of isolated granules ranging between 2 5 and 39 2 mm with uncertainties of 20 particle sphericity inferred from circularity decreased as particle size increased supraglacial cryoconite extent was obtained with a mean uncertainty of 37 and 22 for data from field sites in greenland and svalbard respectively these methods will facilitate acquisition and analysis of datasets for cryoconite across a range of spatial scales supporting research into cryoconite impacts on supraglacial hydrological connections nutrient and carbon cycling and initiation of primary succession in deglaciating environments

an enhanced temperature index glacier melt model including the shortwave radiation balance development and testing for haut glacier d arolla switzerland an enhanced temperature index glacier melt model incorporating incoming shortwave radiation and albedo is presented the model is an attempt to combine the high temporal resolution and accuracy of physically based melt models with the lower data requirements and computational simplicity of empirical melt models represented by the degree day method and its variants the model is run with both measured and modelled radiation data to test its applicability to glaciers with differing data availability five automatic weather stations were established on haut glacier d arolla switzerland between may and september 2001 reference surface melt rates were calculated using a physically based energy balance melt model the performance of the enhanced temperature index model was tested at each of the four validation stations by comparing predicted hourly melt rates with reference melt rates predictions made with three other temperature index models were evaluated in the same way for comparison the enhanced temperature index model offers significant improvements over the other temperature index models and accounts for 90 95 of the variation in the reference melt rate the improvement is lower but still significant when the model is forced by modelled shortwave radiation data thus offering a better alternative to existing models that require only temperature data input

a distributed energy balance melt model of an alpine debris covered glacier distributed energy balance melt models have rarely been applied to glaciers with extensive supraglacial debris cover this paper describes the development of a distributed melt model and its application to the debris covered miage glacier western italian alps over two summer seasons sub debris melt rates are calculated using an existing debris energy balance model deb model and melt rates for clean ice snow and partially debris covered ice are calculated using standard energy balance equations simulated sub debris melt rates compare well to ablation stake observations melt rates are highest and most sensitive to air temperature on areas of dirty crevassed ice on the middle glacier here melt rates are highly spatially variable because the debris thickness and surface type varies markedly melt rates are lowest and least sensitive to air temperature beneath the thickest debris on the lower glacier debris delays and attenuates the melt signal compared to clean ice with peak melt occurring later in the day with increasing debris thickness the continuously debris covered zone consistently provides 30 of total melt throughout the ablation season with the proportion increasing during cold weather sensitivity experiments show that an increase in debris thickness of 0 035 m would offset 1 c of atmospheric warming

assessing the transferability and robustness of an enhanced temperature index glacier melt model we investigate the transferability of an enhanced temperature index melt model that was developed and tested on haut glacier d arolla switzerland in the 2001 season the model s empirical parameters temperature factor tf and shortwave radiation factor srf are recalibrated for 1 other locations on haut glacier d arolla 2 subperiods of distinct meteorological conditions 3 different years on haut glacier d arolla and 4 other glaciers in different years the model parameters are optimized against simulations of an energy balance model validated against ablation observations results are compared with those obtained with the original parameters the model works very well when applied to other sites seasons and glaciers with the exception of overcast conditions differences are due to underestimation of high melt rates the parameter values are associated with the prevailing energy balance conditions showing that high srf are obtained on clear sky days whereas higher tf are typical of locations where glacier winds prevail and turbulent fluxes are high we also provide a range of parameters clearly associated with the site s location and its meteorological characteristics that could help to assign parameter values to sites where few data are available

monitoring ice capped active volcan villarrica southern chile using terrestrial photography combined with automatic weather stations and global positioning systems volc an villarrica 39 25 12 s 71 56 27 w 2847ma s l is an active ice capped volcano located in the chilean lake district the surface energy balance and glacier frontal variations have been monitored for several years using automatic weather stations and satellite imagery in recent field campaigns surface topography was measured using javad gps receivers daily changes in snow ice and tephra covered areas were recorded using an automatic digital camera installed on a rock outcrop in spite of frequently damaging weather conditions two series of consecutive images were obtained in 2006 and 2007 these photographs were georeferenced to a resampled 90m pixel size srtm digital elevation model and the reflectance values normalized according to several geometric and atmospheric parameters the resulting daily maps of surface albedo are used as input to a distributed glacier melt model during a 12 day mid summer period the spatial pattern of cumulative melt is complex and controlled by the distribution of airfall and wind blown tephra with extremely high melt rates occurring downwind of the crater and exposed ash banks the camera images are also used to visualize the pattern of glacier crevassing the results demonstrate the value of terrestrial photography in understanding the energy and mass balance of the glacier including the generation of meltwater and the potential value of the technique for monitoring volcanic activity and potential hazards associated with ice volcano interactions during eruptive activity

grain size distribution function of polymodal sediments in hydraulic and aeolian environments and numerical partitioning of the sedimentary components most continental sediments are polymodal composed of overlapping components of which the grain size generally obeys some type of natural distribution the grain size components and their function types can be determined from frequency and cumulative curve plots in order to define the function formula of the grain size distribution the function parameters can be estimated by fitting a defined function formula to the measured grain size data of the sample which simultaneously achieves numerical partitioning of the sedimentary components genetic analysis of grain size components of hydraulic and aeolian sediments demonstrates the following environmental implications fluvial sediment is composed of isolated saltation and suspension components the sediments in closed lake basins are dominated by a suspension silt clay component with a small proportion of saltation sand the fine sand component makes up the majority of desert sand overlapping with a small proportion of fine dust aeolian loess is composed of two overlapping components a short suspension time silt component and a long suspension time fine component aeolian material in the north pacific deep sea sediments is dominated by long suspension time fine dust the fine component in aeolian sediments shows a consistent grain size distribution and genetic connection from the desert sand loess of northern china to the north pacific ocean which is mainly transported by westerly winds and is dispersed in the atmosphere forming a background dust c 2002 elsevier science b v all rights reserved

a 5 year record of surface energy and mass balance from the ablation zone of storbreen norway a 5 year record of data from an automatic weather station aws operating in the ablation zone of storbreen norway has been used to calculate the local surface energy and mass balance the aws observations cover five mass balance years with an unusually strong mass deficit on storbreen the average energy flux q contributing to melt for the period 2001 06 is 113wm 2 of this the net shortwave radiation flux is the dominant contributor 92wm 2 followed by the sensible heat flux 20 wm 2 and the latent heat flux 9 w m 2 the net longwave radiation 6w m 2 and the subsurface heat flux 2 w m 2 contribute negatively to the budget net radiation thus produces 76 of the melt while the turbulent fluxes and the subsurface heat flux produce 24 of the total melt the seasonal mean incoming shortwave radiation is remarkably constant between the years whereas variations in temperature and reflected shortwave radiation albedo explain most of the interannual variation in melt the modelled ablation compares well with the measured ablation from stake readings the sensitivity of the energy balance model was examined by varying the surface roughness length of momentum and the sensitivity of the calculated melt by perturbations of temperature wind speed and relative humidity

trace element and pb isotope variability during rainy events in the nw mediterranean constraints on anthropogenic and natural sources abstract rain samples collected over the period 1995 1999 on the french mediterranean coast have been analyzed for their trace elements and pb isotopic compositions both in the dissolved and particulate loads our results show that metal enrichment factors ef relative to upper erodable crust are high for cu pb zn and cd and comparable to values reported about 10 years ago for north western mediterranean rains overall unradiogenic pb isotopic compositions indicate the still visible influence of french gasoline lead on both dissolved and particulate loads this influence is also seen on aerosols although more variable the examination of air mass trajectories allows us to distinguih the pb isotopic signatures of main sources in particular marseille north italy north africa rains collected and analyzed sequentially show intra rain variations for metal contents metal ef and pb isotopes which may also be related to the main paths and altitudes of the air masses metal efs and pb isotopic data on rains from southern france in the late 1990s are similar to recent data published on french aerosols or sediments which are interpreted as reflecting the phasing out of leaded gasoline in the atmosphere