climate swings in the northern red sea over the last 150 000 years from end and mg ca of marine sediments abstract the end and mg ca compositions of terrigenous material from a meridional transect of seven marine sediment cores located between the northern red sea and the gulf of aqaba together with modern dust sample compositions reveal the temporal and spatial changes in precipitation and dust sources over the last 150 kyrs and are further used to discuss the late quaternary climate history of this region two recent glacial periods marine isotopes stages mis 6 and 2 are characterized by low end values associated with a saharan dust source 12 while mg ca ratios suggest increased transport of dust containing authigenic clays during the last deglacial which most likely originated from the arabian peninsula by contrast mis5e sediments are characterized by an abrupt basin wide shift of end values toward the local arabian nubian shield end member 2 that are exposed around the red sea this shift stems from intense fluvial events and is coeval with other regional paleo precipitation records that all point to an extensive northward shift of precipitation from the tropics during mis5e considering model simulations and regional precipitation dynamics we conclude that although the african summer monsoon probably intensified and extended somewhat northward during mis5e it was not the driver of significant precipitation and the main contribution of precipitation to the northern red sea was due to increased frequency and possible intensity of tropical plumes and red sea troughs that triggered massive fluvial floods within the red sea catchment considering mis5e as an analogue to a future warmer world this currently hyperarid region could be exposed over the coming decades to an increased impact of extreme rainfall events with critical implications for water availability and infrastructure sustainability

coupling the wrf model with a temperature index model based on remote sensing for snowmelt simulations in a river basin in the altay mountains north west china

saharan wind regimes traced by the sr nd isotopic composition of subtropical atlantic sediments last glacial maximum vs today new nd sr isotopic data on the 30 m lithic particles of surface and last glacial maximum sediments recovered along the african margin between the equator and the gibraltar strait are presented in combination with grain size measurements this 30 m size fraction allows us to eliminate any hemipelagic contribution that could occur in the coarser fractions in the eolian fraction both sr and nd isotopic tracers reveal the same major northwestern origin mauritania mali southern algeria and morocco the archaean formations of the western saharan shield could be the source of the very unradiogenic ratios observed here the more southern regions senegal guinea act only as secondary sources a similar pattern is observed for the lgm lithic particles are mostly transported by both trade and saharan air layer sal winds along an approximate ne sw axis this main feature matches the southern plume characterizing the dust transport observed during winter no significant latitudinal shift of the belt winds is observed between the lgm and today at the lgm however dust fluxes were 2 4 times higher than today leading to a more archaean type imprint in the deposits we do not observe any clear relationship between the latitudinal variability of the upwelling systems identified in this region at the lgm and the location of the major wind systems both enhanced aridity on the continent and increased wind speed probably occurred together over western tropical africa during the last glacial period

the role of corsica in initiating nocturnal offshore convection in the region of corsica located in the western mediterranean sea the mean daily lightning activity as an indicator for deep convection in late summer and autumn shows a distinct maximum in mid afternoon and a secondary maximum at night during the night most of the lightning activity is located offshore and near the island s coastline currently there are no observational data which could be used to explain this nocturnal offshore convection but understanding its formation mechanism is important for accurately forecasting the regional weather in this article we explore two possible mechanisms initiating nocturnal offshore convection i convergence with subsequent lifting due to the interaction between drainage winds and the synoptic flow over the sea and ii dynamically induced lee side convergence due to the island barrier effect to this end we perform numerical simulations with the consortium for small scale modeling cosmo model at a convection permitting horizontal grid spacing of 2 8 km for two cases with different synoptic conditions and low level wind directions the simulation results show that the island s drainage flow can either favour or hinder the development of deep convection furthermore convective initiation is very sensitive to terrain elevation and model initialisation time and small changes of these parameters can determine whether deep convection can be successfully simulated

tracing dust sources and transport patterns using sr nd and pb isotopes continental dust transported through the atmosphere can be a tracer of atmospheric circulation and transport as well as being a source of information about climate in the dust s source area this information about the provenance of dust transported from desert areas and deposited elsewhere on the oceans and continents can be evaluated using several observational techniques satellite imagery has been used to this end in recent decades and air mass back trajectories have been calculated to trace dust deposits back to their source area another method consists of analysis of the concentration and composition of certain tracers in the dust itself and comparing them to soils and sediments from possible source areas this method has the advantage of being useable for paleo atmospheric circulation and paleo dust transport studies whereas satellite imagery and air mass back trajectories are restricted to relatively recent times we review here different kinds of isotopic tracers that have been used to trace dust provenance but special attention is focused on the use of sr nd and pb isotopes we evaluate their use in studies of both spatially as well as temporally varying continental dust source and transport

morning precipitation peak over the strait of malacca under a calm condition abstract this paper describes the formation mechanism of morning maximum in the diurnal cycle of precipitation at the strait of malacca under a calm condition with a nonhydrostatic mesoscale numerical model and ship based observational data the morning precipitation peak at the strait is induced by the convergence of two cold outflows that have been produced by the precipitation systems in the previous evening over sumatra and the malay peninsula the outflows converge at the strait of malacca around midnight a new precipitation system is thus generated and reaches its peak in the early morning sensitivity experiments using the numerical model suggest that the timing and position of the morning precipitation peak are affected by the width of the strait in the case of the strait of malacca its width favors the formation of the morning precipitation system around the center of the strait which explains why its diurnal cycle of precipitation can be observed much clearer than those in other coastal ar

glacial regime of the highest tien shan mountain pobeda khan tengry massif major processes controlling the existence of a large sub continental glacier system were identified on the basis of glaciological meteorological and isotopic analyses using expeditionary and long term data observations were made on the southern inylchek glacier located in the pobeda khan tengry massif the largest sub continental glacier system on the northern periphery of central asia more than 1200 glaciers with a total area of about 4320 km comprise the massif melt is for the most part caused by radiation and is most intensive during periods of anticyclonic weather with fohn development the proportion of solar radiation input in relation to heat balance is more than 90 evaporation and condensation are negligible during most times and comprise 7 of heat expenditure accumulation was associated with cold cyclonic weather four ice formation zones were identified the upper boundary of liquid runoffis at 5200 m and the recrystallization zone is above 5900 m the calculated net glacier mass is negative 318 kg m 2 a 1 and indicates the degradation of modern pobeda khan tengry glaciers

late quaternary changes in desert dust inputs to the red sea and gulf of aden from 87sr 86sr ratios in deep sea cores abstract strontium isotope ratios of the hcl insoluble residue isr and foraminifera of cores from the red sea and gulf of aden are used to monitor effects of hydrothermal fluvial and desert dust transport to these regions during the past 0 5 ma while the gulf of aden was open ocean during low glacial sea levels the red sea was a semi isolated basin allowing the possibility to study the effects regional versus global inputs during glacial interglacial cycles the isr from the gulf of aden and the red sea display different ranges of 87 sr 86 sr ratios of 0 7085 0 7107 and 0 7062 0 7085 respectively these reflect mixtures between three components granitic hydrothermal and loess strontium with representative 87 sr 86 sr of 0 711 0 706 and 0 7085 respectively gulf of aden isr represent mixtures of the loess and granitic sources while red sea isr are mixtures of the loess and sea floor hydrothermal sources in the gulf of aden loess sources dominate during glacials indicating intensification of the ne moonsonal wind regime and granitic sources dominate during interglacials reflecting wetter conditions related to an enhanced regional sw monsoon red sea isr show no clear glacial interglacial distinction but display a general temporal increase in 87 sr 86 sr ratios over the past 380 ka toward loess like values indicating increasing loess contributions toward the present day the ranges of isr 87 sr 86 sr ratios in the red sea and the gulf of aden were distinct prior to the last glacial period 87 sr 86 sr ratios following major climate transitions at 10 80 130 190 240 and 330 ka bp that coincide with sapropel episodes in the eastern mediterranean which originated from the african monsoonal system and indicate enhanced wetness in the desert belt 87 sr 86 sr ratios of foraminifera show a very narrow range from 0 70912 to 0 70917 over 530 ka and in most samples are consistent with the contemporaneous global ocean in the red sea foraminifera and pteropods show slightly more variability than the gulf of aden a few red sea samples fall slightly above the seawater trend in marine isotope stages 5 and 9 and below during the last deglaciation suggesting local effects that occurred when the flow of surface ocean water from the gulf of aden to the red sea was limited and the red sea behaved like an amplifier basin

enhanced saharan dust input to the levant during heinrich stadials abstract the history of dust transport to the levant during the last glacial period is reconstructed using the isotope ratios of pb sr nd and hf in sediments of lake lisan the last glacial dead sea exposed marginal sections of the lisan formation were sampled near masada the perazim valley and from a core drilled at the deep floor of the modern lake bulk samples and size fractions display unique isotopic fingerprints the finest detritus fraction 87 sr 86 sr and lower end values 0 710 0 713 and 7 0 to 9 8 respectively relative to the coarser fractions 5 20 m and 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb ratios 18 26 19 02 15 634 15 68 and 38 25 38 82 respectively are systematically higher in the finest detritus fraction relative to corresponding coarser fractions and bulk samples the 87 sr 86 sr and end values of the finest fraction correspond with those of atmospheric dust originating from the sahara desert while those of the coarse fractions are similar to loess deposits exposed in the sinai and negev deserts pronounced excursions in the sr nd pb isotope ratios toward more sahara like values coincide with the heinrich h stadials 6 5 and 1 reflecting significant increases in saharan dust fluxes during regionally arid intervals reflected by sharp lake level drops moreover during h6 the dust came from different saharan sources than during h1 and h5 while the relatively wet glacial climate in the levant suppressed the transport of dust to the lake watershed short term hyper arid spells during h stadial intervals were accompanied by enhanced supply of fine sahara dust to this region

winter monsoon convection in the vicinity of north borneo part i structure and time variation of the clouds and precipitation abstract radar and satellite observations in the vicinity of northern borneo obtained during the international winter monsoon experiment wmonex showed that the convection in that region underwent an extremely regular diurnal cycle over the sea to the north of borneo the general level of convective activity was increased during monsoon surges and during the passages of westward propagating near equatorial disturbances convective activity was decreased during monsoon lulls the diurnal cycle was well defined regardless of whether the general level of convective activity was enhanced or suppressed by synoptic scale events the cycle of convection over the sea was especially well documented it was typically initiated at about midnight when an offshore low level wind began where this wind met the monsoonal northeasterly flow usually just off the coast convective cells formed after midnight the convection continued to develop and by 0800 lst it had evolved into an organized mesoscale system with a

pyroclast snow interactions and thermally driven slurry formation part 1 theory for monodisperse grain beds lahars are often produced as pyroclastic flows move over snow this phenomenon involves a complicated interplay of mechanical and thermal pro cesses that need to be separated to get at the funda mental physics the thermal physics of pyroclast snow interactions form the focus of this paper a theoretical model is developed of heat and mass transfer at the interface between a layer of uniformly sized pyroclasts and an underlying bed of snow for the case in which there is no relative shear motion between pyroclasts and snow a microscale view of the interface is required to properly specify boundary conditions the physical model leads to the prediction that the upward flux of water vapor which depends upon emplace ment temperature pyroclast grain size pyroclast layer thickness and snow permeability is sometimes suffi cient to fluidize the pyroclasts uniform fluidization is usually unstable to bubble formation which leads to vigorous convection of the pyroclasts themselves thus predicted threshold conditions for fluidization are tantamount to predicted thresholds for particle convection such predictions are quantitatively in good agreement with results of experiments described in part 2 of this paper because particle convection commonly causes scour of the snow bed and transfor mation of the pyroclast layer to a slurry there exists a thermal scour process for generating lahars from pyroclastic flows moving over snow regardless of the possible role of mechanical scour

the effect of dust deposition on the soils of the land of israel abstract loess and aeolian dust affected soil formation to different degrees in most parts of the land of israel in the arid desert the loess was re eroded from slopes and sedimented as fluvial loess in along the valleys by flood water in areas with slight precipitation loess remains on slopes sedimentation rates are slower and loessial serosems are formed in the mildly arid areas in the northern negev the loess covers most of the landscape and occurs in thick sequences intercalated with several superimposed strongly developed loessial brown soils sedimentary and weathering processes occurred simultaneously and sediment palaeosols profiles up to 12 m thick were formed in areas further away from the desert aeolian deposition decreased as a result loessial brown soils grade into dark brown grumic soils and grumusols aeolian dust input also affected soils of the sand dunes of the coastal plain and in the terra rossa soils of the mountainous region

sensitivity of deep convection to terrain forcing over mediterranean islands the influence of mountainous islands on the initiation of deep convection is investigated using the consortium for small scale modeling cosmo model a case study and sensitivity analysis is performed for 26 august 2009 when moist convection occurred over both corsica and sardinia islands in the western mediterranean sea sensitivity runs with systematically modified topography are explored to evaluate the relative importance of the land sea contrast and the terrain height for convection initiation whereas no island precipitation is simulated when the islands are completely removed all simulations that represent these land surfaces develop convective precipitation although convection initiates progressively earlier in the day over taller islands the precipitation rates and accumulations do not show a fixed relationship with terrain height this is due to the competing effects of different physical processes firstly whereas the forcing for low level ascent increases over taller islands the boundary layer moisture supply decreases which diminishes the conditional instability and precipitable water secondly whereas taller islands enhance the inland propagation speeds of sea breeze fronts they also block these fronts mechanically and prevent them from reaching the island interior as a result the island precipitation is rather insensitive to island terrain height except for one particular case in which the island precipitation increases considerably due to an optimal superposition of the sea breeze and upslope flow comparing the two islands convective precipitation develops earlier over corsica due to its increased terrain height and reduced convective inhibition however precipitation amounts are substantially larger over sardinia where a stronger land sea contrast gives rise to a more intense and organized line of sea breeze convergence these results demonstrate the complexity of interactions between sea breezes and orography and reinforce that an adequate representation of detailed topographic features is necessary to account for thermally induced wind systems that initiate deep convection

multiple dust sources in the sahara desert the importance of sand dunes 1 we determine the current sources of dust in the sahara desert using quantitative correlation between the number of days with dust storms nds derived from remote sensing data of high temporal resolution with the distribution of the soil types and geomorphic units during 2006 8 the source of over 90 of the nds was found to be sand dunes leptosols calcisols arenosols and rock debris in contrast to previous studies only few dust storms originated from playas and dry lake beds land erodibility was estimated by regressing the nds to the number of days with high speed wind events and was found to be high for sand dunes clay and fine silt grains and aggregates are scarce in sand dunes which most likely produce dust particles through aeolian abrasion of sand grains thus saltating sand grains impacting clay aggregates on playa surfaces cannot be the sole process for generating dust in the sahara

measurements of mid winter spatial distribution of meltwater saturation under melt freeze conditions crusts may evolve within a snowpack which may favour avalanche initiation by forming a hard bed surface for weakly bonded faceted grains we used a parallel probe saturation profiler ppsp to record the distribution of water contents within the snowpack diurnal effects of melt freeze action on the growth of crusts were monitored with the help of the ppsp device saturation profiles were collected from a partially wet snow cover snow stratigraphy was conducted manually in the morning after overnight freezing to identify the location and the granular compositions of the crusts that had evolved a one to one correspondence between the saturation spikes collected using the ppsp and the actual positions of the crusts was established the ppsp was also used to monitor three dimensional variations in the maximum percolation depths within a south facing snowpack the operation of the ppsp is faster than existing dielectric measurement techniques so it was applied to study the spatial variability of maximum percolation depths on the slopes of different aspects

the micromorphology of gypsum and halite in reg soils the negev desert israel gypsum and halite are the most common salts in reg soils developed on alluvial parent material under extremely arid conditions in the negev desert israel the aim of this paper is to document the changes in the micromorphology of these salts at different stages of reg soil development on two alluvial fan chronosequences the micromorphological analyses included thin section observations and scanning electron microscope and electron microprobe analyses in this arid soil environment gypsum and halite possess a variety of crystal forms which may change with depth in a single profile and or between profiles of different ages the variety of crystal forms results from changes in the microenvironmental conditions that occur in desert reg soils over time poikilitic lenticular gypsum is found in all reg soils and is distributed throughout the profiles the conditions needed for such crystals to form are high ionic impurities and deposition in a void system where space is not limiting microcrystalline alabastrine gypsum is only found in mature reg soils and is crystallized when the profile has high amounts of fine material and a well developed desert pavement in a well developed reg soil profile indicators such as a well developed desert pavement and high amounts of fine earth limit the leaching depth and cause gypsum deposition from supersaturated soil solutions under high evaporation rates close to the surface prismatic and fibrous gypsum are less common low amounts of prismatic gypsum are found in young and mature soils while fibrous gypsum is found only in mature soils in re cemented shattered gravel the halite crystal form is mainly cubic with low amounts of host material incorporated into the crystal it occurs predominantly in mature reg soil profiles through the crystallization from supersaturated soil solutions at the depth of maximum water penetration although the alabastrine prismatic and fibrous gypsum and cubic halite are deposited in a displacive manner no correlation was found between their occurrence and the distribution of shattered gravel in the soil profile

soils in the mediterranean region what makes them different mediterranean climates are characterized by winter rains with some months of excess rainfall over evatranspiration warm and dry summer months with moisutre deficits drying out soils and their annual vegetation xeric moisture regime they are found on western parts of all continents between the cooler temperature zone and the hot dry desert zone the largest mediterranean region surrounding the mediterranean sea extends over 4 300 000 km2 and exhibits a wide variety of soils and geo ecosystems characteristics landscape attributes are the high proportion of mountains with sleep slopes significant additions of saharan desert dust to practically all soils of the region and a large proportion of limestone and other calcareous rocks as soil parent materials characteristics soil behavior features are moderate weathering with pervection leaching lessivage of mostly 2 1 clays into b horizons xeralfs luvisols hematite induced reddening of the clays due to summer dehydration of free iron oxyhydroxides carbonate dissolution and reprecipitation with prevalence of calcic horizons xerolls calcisols in semiarid regions and development of vertisols mostly in lowlands where deep layers of swelling cracking clays have sedimented shallows soils on nearly bare slopes mostly a result of erosion subsequent to deforestation are frequent leptosols cambiosols inceptisols entisols red or brown mediterranean soils are no longer used as a separate classification group in modern well defined soil property controlled taxonomies soil taxonomy fao system but were partially replaced by duchaufour s term fersiallitic soils in some classification systems terra rossa continues to be used in some classification for hard limestone derived red soils mostly shallow the effects of man s past and current interference with the lanscape are pervasive in most regions and predictions for possible future effects on the soils and ecosystems due to greenhouse gas induced warming and rainfall change are partly negative partly still too uncertain

dust transport and synoptic conditions over the sahara arabia deserts during the mis6 5 and 2 1 transitions from grain size chemical and isotopic properties of red sea cores abstract the red sea situated between the sahara and arabia deserts is a natural trap for fine grained particles transported by winds and floods from weathered materials in these deserts derived from the proterozoic crustal granitic and basaltic terrains and phanerozoic carbonates the accumulated fine particles provide valuable information on the climate conditions in the source regions and modes of atmospheric circulation over the red sea region here we report on the grain size mineralogy chemical composition and nd and sr isotope ratios of fine grained insoluble residues ir from acid leaching that were recovered from two deep sea cores kl23 and kl11 drilled in the northern and central red sea respectively we focus on the mis6 5 and mis2 1 transitions kl23 samples are closer to the sahara granitoids field and display significant variations during the mis6 5 transition between end of 7 to 2 and 87sr 86sr of 0 7096 to 0 7114 smaller variations occurred during the mis2 1 transition between end of 5 to 6 and 87sr 86sr of 0 7104 to 0 7118 the kl11 values are closer to the blue nile field which comprises mixtures of granitoid and basalt derived particles during the mis6 5 transition their end varies from 4 to 1 and in 87sr 86sr from 0 7059 to 0 7091 during periods equivalent to sapropels s5 and s1 both cores appear to converge to similar isotope ratios of e nd 2 and 87sr 86sr 0 7095 indicating derivation from the granitoid terrains of the arabian nubian shield occurring adjacent to the red sea and possibly distributed by runoff in terms of synoptic conditions the data indicate that during glacials dust was blown to the northern red sea from the northern sahara desert in association with the mediterranean winter cyclones and to the central red sea from the ethiopian plateau by southern winds that are associated with monsoonal circulation during interglacials especially sapropel intervals monsoonal rains caused erosion and flooding at the arabian nubian shield margins of the red sea during the heinrich events associated with the studied intervals h11 and h1 dust from mixed basaltic granitic terrains was blown from all of the regional sources in the red sea region reflecting severe regional aridity and transport of dust by regional winds when monsoonal activity and mediterranean cyclone activity were weak

synoptic conditions of fine particle transport to the last interglacial red sea dead sea from nd sr compositions of sediment cores abstract the sediments deposited at the depocenter of the dead sea comprise high resolution archive of hydrological changes in the lake s watershed and record the desert dust transport to the region this paper reconstructs the dust transport to the region during the termination of glacial marine isotope stage 6 mis 6 135 129 ka and the last interglacial peak period mis5e 129 116 ka we use chemical and nd and sr isotope compositions of fine detritus material recovered from sediment core drilled at the deepest floor of the dead sea the data is integrated with data achieved from cores drilled at the floor of the red sea thus forming a red sea dead sea transect extending from the desert belt to the mediterranean climate zone the dead sea accumulated flood sediments derived from three regional surface cover types settled desert dust mountain loess soils and loess soils filling valleys in the dead sea watershed termed here valley loess the valley loess shows a distinct 87sr 86sr ratio of 0 7081 1 inherited from dissolved detrital calcites that originate from dried waterbodies in the sahara and are transported with the dust to the entire transect our hydro climate and synoptic conditions reconstruction illustrates the following history during glacial period mis6 mediterranean cyclones governed the transport of saharan dust and rains to the dead sea watershed driving the development of both mountain soils and valley loess then at heinrich event 11 dry western winds blew saharan dust over the entire red sea dead sea transect marking latitudinal expansion of the desert belt later when global sea level rose the dead sea watershed went through extreme aridity the lake retreated depositing salt and accumulating fine detritus of the valley loess during peak interglacial mis 5e enhanced flooding activity flushed the mountain soils and fine detritus from all around the dead sea and red sea marking a significant contraction of the desert belt at the end of mis 5e the effect of the regional precipitation diminished and the dead sea and red sea areas re entered sever arid conditions with extensive salt deposition at the dead sea

100 000 years of african monsoon variability recorded in sediments of the nile margin abstract multiproxy analyses were performed on core ms27pt recovered in hemipelagic sediments deposited on the nile margin in order to reconstruct nile river palaeohydrological fluctuations during the last 100 000 years the strontium and neodymium isotope composition of the terrigenous fraction and the major element distribution reveal large and abrupt changes in source oscillating between a dominant aeolian saharan contribution during arid periods and a dominant nile river contribution during pluvial periods iron content shows a strong correlation with strontium and neodymium isotopes this allows the use of a high resolution continuous fe record as a proxy of blue nile sediment input over the last 100 000 years the detailed fe record with approximately 10 years resolution during pluvial periods is consistent with subtropical african records of well dated lake level fluctuations and thus constitutes a first continuous high resolution record of the east african monsoon regime intensity over ethiopia the detailed fe record shows the two main known pluvial periods attributed to strengthening of the african monsoon over ethiopia the nabtian period from 14 to 8 ka cal bp and the saharan period from 98 to 72 ka bp for the first time the last glacial period marine isotope stage mis 2 3 and 4 is documented with a continuous record showing large oscillations between high and low east african palaeo monsoon regimes the end of the nabtian period occurred at 8 ka in core ms27pt i e much earlier than on the east equatorial african region where it ended around 5 5 ka we interpret this as evidence that the southward shift of the rain belt occurred 3000 years earlier over the eastern ethiopian highland and propose that the gradual southward migration of the rain belt was associated with highly variable intensity and longer rainy seasons from 8 to 5 ka during the last glacial period two wet periods are present around 60 50 ka bp and 38 30 ka bp these two humid periods are in phase with the rise of atmospheric ch4 concentrations suggesting that wetland tropical african area was one of the sources of the atmospheric ch4 during the mis 3 during the last glacial maximum and mis 4 high saharan aeolian influxes in phase with records of aeolian dust deposited in east antarctica are documented this study highlights the importance of reconstructions of monsoon rainfall fluctuation at high temporal resolution to better understand the link between low and high latitude climate variability at millennial timescales

distribution of natural and anthropogenic lead in mediterranean soils abstract the concentrations and isotopic composition of pb have been combined with a selective sequential dissolution procedure to track the distribution of anthropogenic and natural pb in the soil of semiarid climate and the penetration pathway of petrol pb within the soil profile soil samples were collected from soil profiles adjacent to a major highway 8 23 m and from soil profiles 500 m away from the same highway the selective sequential dissolution procedure was used to determine the distribution of pb between the different soil components soil carbonate organic matter fe oxides and hydrous oxides and aluminosilicates natural pb is associated mainly with aluminosilicates 60 and fe oxides 30 and only a small fraction with the soil carbonate and organic matter 10 in contrast to the distribution of natural pb the distribution of anthropogenic pb which accumulates mainly in the upper part of the soil profile is 40 with the soil carbonate 10 with organic matter 35 with fe oxides and only 15 with aluminosilicates on the basis of concentration and isotopic composition of total pb the deeper horizon of the roadside soil 10 30 cm and the soil sampled 500 m from the highway seem uncontaminated however the isotopic composition of the labile components in the soil pbcarb pborg and pbfe ox indicates that these soils are actually contaminated this contamination implies that over the period of vehicle pollution 40 yr petrol pb has penetrated through the entire roadside soil profile 25 30 cm furthermore pb isotopes in aluminosilicates of the upper part of the roadside soil indicate that this pb too is anthropogenic measurements of pb concentration and isotopic composition in roadside soil profiles sampled in 1997 and archived samples collected at the same location in 1982 provided a unique opportunity to trace petrol pb penetration into the soil

ice layer and surface crust permeability in a seasonal snow pack ice layers in snowpacks are thought to retard or obstruct gas and melt water flow through the pack yet there has been little published information on the permeability of ice layers in seasonal snow in this paper investigations of ice layer permeabilities are reported for prominent ice layers 1 to 3 mm thick in a seasonal snowpack for distinct fairly solid ice layers 1 to 3 mm thick permeabilities ranged from 1 to 19 x 10 10 m 2 these values are significantly lower than values for the surrounding snow within 24 h early in the melt season the permeability of the surface crust increased 160 from approximately 70 to 120 x 10 10 m 2 this increase in permeability was accompanied by a small increase in grain size and a decrease in albedo the snow air interface can exhibit dramatic changes in transport properties over relatively short periods of time even without precipitation events these changes driven by the surface meteorology affect transport properties such as permeability as well as albedo

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

tracing the transport of anthropogenic lead in the atmosphere and in soils using isotopic ratios the isotopic composition of lead in aerosols and soils in israel is used to characterize the sources of anthropogenic lead in the region to ascertain the isotopic composition of natural rock derived lead in specific areas and to determine rates of anthropogenic lead migration in soils the isotopic composition of lead currently emitted from cars in israel 206pb207pb 1 115 2 is controlled by alkyl lead produced in france and germany in addition to petrol lead two more sources of anthropogenic lead can be detected in sampled aerosols the first one has low concentrations of lead 4 ng m3 and 206pb207pb 1 157 and is most likely lead emitted in turkey that traveled across the eastern mediterranean basin the second type of aerosols contains a mixture of lead emitted in several countries including turkey greece and ukraine 206pb207pb value of 1 155 1 160 pb 20 30 ng m3 anthropogenic lead is more accessible for acid leaching than natural lead therefore it is more labile in the soil the isotopic composition of lead in the acid leached fraction of near road soil profiles record the histor of alkyl lead emission in the country based on changes in the isotopic composition of lead with soil depth it is estimated that anthropogenic lead migrates into the soil at approximately 0 5 cm y a soil profile from a relatively remote area is less contaminated by anthropogenic lead and displays a different distribution of lead isotopic values with depth the isotopic composition of lead suggests that natural lead in soils developed on carbonate bedrock is derived from clays either from the rock esidue the clay fraction in the carbonate bedrock or from airborne clay but not from lead released from the carbonate fraction in the rock

bulk composition of northern african dust and its source sediments a compilation abstract this paper presents a review of bulk compositional data of northern african dust and its potential source sediments and includes elemental isotope and mineralogical data northern african dust represents about one half of the total global atmospheric mineral dust burden and its uplift transport and deposition have strong impacts on climate and various terrestrial and marine ecosystems the chemical data set shows that an average northern african dust exhibits comparable si fe and mn contents with respect to the average composition of the upper continental crust is slightly depleted in the alkali metals k and na and enriched in ti and p however the complete data set yields clear evidence that northern african dust and its source sediments are compositionally heterogeneous on a regional scale and that this heterogeneity can be used to differentiate between major potential source areas on the basis of so called source markers an evaluation of these compositional fingerprints shows that the following parameters and especially their combination are effective in the discrimination of the most active source areas in northern africa ratio of ca mg fe wt calcite or carbonate content palygorskite occurrence and abundance illite kaolinite ratio nd 0 value and 87sr 86sr ratio for example the data set corroborates previous ideas which assign carbonate illite and palygorskite rich mineral dusts to north west ern source regions because most of the above listed source markers do not change substantially during transport even far traveled dusts may be assigned to specific potential source areas in northern africa some limitations of the presented data set are also discussed our compilation reveals some substantial gaps in the knowledge of the composition of source sediments and mineral dusts from important potential source areas that should be filled in the future the here compiled data set can be used as a reference frame when incorporating the composition of source sediments e g mineralogy into global or regional dust transport models and can be compared with source analysis by remote sensing or back trajectory analysis however source apportionment studies supported by our data set will not only be useful for actual dust samples but will also be helpful for the understanding of paleo wind directions and hence paleo climatological conditions through the investigation of quaternary eolian sediments deposited in and around northern africa

quaternary fluctuations in the northern hemisphere trade winds and westerlies the mass accumulation rate and grain size of the total colian component isolated from pelagic sediment in two north pacific cores piston core kk75 02 under the prevailing westerlies and deep sea drilling project site 503 beneath the trade winds have been used to evaluate changes in the intensity of atmospheric circulation and source area aridity over the past 700 000 yr the eolian grain size a direct indicator of wind intensity fluctuates at periodicities similar to those calculated for the earth s orbital parameters of precession obliquity and eccentricity both sites display greater variability in wind intensity prior to 250 000 yr ago eolian accumulation rates an indicator of source area aridity fluctuate at periodicities similar to those of the glacial interglacial cycles lower eolian accumulation rates during colder glacial times most likely reflect increased glacial age humidity at central asian and central american source areas

elemental and isotopic composition of surface soils from key saharan dust sources saharan dust contains significant amount of p an important macronutrient to all living organisms which has been shown to exert large effects on nearby and remote ecosystems located across the dust transport pathways the biological effect of saharan dust depends on the amount and nature of the p speciation of the dust however thus far relatively small numbers of samples from potential source areas psa has been analyzed here we report the p speciation resin p hcl p fe bound p and organic p the 18op values the elemental composition and the 87sr 86sr and 143nd 144nd of the fine fraction and bulk soil from 5 important psas across northern africa we found the hcl p concentrations between different source areas were relatively constrained but that these concentrations were higher in the fine fraction which here is used a surrogate for dust the 18op values for soils from sand dunes varied from 15 0 to 21 4 which is in the range of phosphate minerals from sedimentary origin the 18op values of soils from dry lakes were significantly higher 24 0 28 5 probably since their p is derived from fossilized plankton that lived in the lake as it dried up the 87sr 86sr and end values ranged from 0 7219 to 0 7276 and 12 7 to 14 0 in eastern samples and from 0 7146 to 0 7185 and 11 9 to 13 4 in western samples suggesting a different source for the siliciclastic material of eastern and western samples our analysis indicates that the 18op values are decoupled from the sr and nd isotopic systems together the new chemical and isotope data are specific for different psas and thus are used for source apportionment purposes such data can be used to provide more accurate estimates of the flux of potentially bioavailable p to marine and terrestrial ecosystems these estimates can be used in global climate models to determine the magnitude and distribution of p control on carbon uptake

meltwater movement in a deep snowpack 2 simulation model a numerical simulation model is developed describing the one dimensional flow of meltwater in a snowpack based on established methods of modeling unsaturated groundwater flow the results of field observations of snowmelt and meltwater flow are used to determine parameters describing the hydraulic properties of the snowpack and surface energy balance measurements are used as input to the model tests of the performance of the model show a high sensitivity to the saturated hydraulic conductivity of the snowpack and to liquid water content of the snow saturated hydraulic conductivity can be measured with acceptable precision by simple field methods however measurement of liquid water content is more difficult and constitutes the major limitation affecting calibration of the model the model is relatively insensitive to exponents in the power law equations relating conductivity capillary pressure and liquid water content meltwater wave speeds predicted by the model are somewhat slower than those observed in the field observations of snowpack layering and horizontal inhomogeneity of flow suggest that these features affect transient storage of meltwater and consequently cause meltwater wave speeds to differ from those predicted by a one dimensional model

dissolved rare earth elements in the southern ocean cerium oxidation and the influence of hydrography abstract analysis of dissolved ree distributions in the southeastern atlantic ocean has revealed that progressive oxidative removal of dissolved ce from deepwater 1 km occurs over the mixing time of the oceans ce anomaly ce ce values measured in deep waters from the southeastern atlantic are similar to but slightly higher than those from deep ocean stations throughout the indian and pacific oceans typically falling in the range 0 08ce ce 0 12 only deepwater samples from the north atlantic exhibit values greater than ce ce 0 12 with the exception of southeastern atlantic bottomwaters which are influenced by antarctic bottomwater covariation of dissolved ree concentrations with salinity and or dissolved si concentrations at this site has allowed dissolved ree compositions for various southern ocean water masses to be predicted end member concentrations for antarctic bottom water aabw derived in this way indicate high dissolved ree concentrations similar to average pacific deep water but with significantly enhanced dissolved ce concentrations and less pronounced hree enrichment this result is consistent with the proximity of our study site to active aabw deepwater formation and evolution of that water mass during transport to the pacific ocean

mobilization of fine detritus to the dead sea basin during the late glacial and early holocene abstract the mineralogical grain size and geochemical properties e g nd and sr isotopes mg al ratios of fine detritus that accumulated in the dead sea during the late glacial to early holocene time 22 7 ka are used to identify its sources and modes of transport and to reconstruct the hydroclimate conditions in the dead sea watershed samples were retrieved from the dsddp 5017 1a core that was drilled in the deep floor of the lake and from various exposures of surface cover in the lake s watershed the data show that during most of the late glacial detrital particles were either directly blown mostly from the north sahara desert or were washed from the surface cover loessial soils of the north negev desert and judea desert this picture changed during the end of the last glacial to the early holocene 14 7 ka when the fine detritus showed evidence for contribution from surface cover that contained basaltic soils the contribution of basaltic soils to the fine detritus inventory of the dead sea and to terraces in the jordan valley indicates a period of intense erosion in the northern highlands of the dead sea watershed at an interval that partly coincides with sapropel s1 in contrast during the last interglacial sapropel s5 fine detritus was mostly mobilized to the lake from southern and eastern region of the watershed the formation and accumulation of terraces from this basaltic derived material could be an important factor in the establishment of early agriculture settlements in the jordan valley

estimation of equivalent permeability of snowpack using a snowmelt lysimeter at patsio northwest himalaya the meltwater percolation process through the snowpack greatly influences its physical and mechanical properties the percolation process is important for understanding the spring avalanche phenomenon as well as the meltwater runoff for basin hydrology studies the permeability of individual snow layers depends on parameters such as porosity pore connectivity and the geometrical shape of the pores snowpack equivalent permeability plays an important role in governing the transmission of meltwater through the different layers of the snowpack in this paper we present the design fabrication and installation of a snowmelt lysimeter at patsio field research station himachal pradesh india and determine the snowpack equivalent permeability using lysimeter discharge data the snowmelt lysimeter having a collector area of 6 25 m 2 and a high capacity snowmelt measuring tipping bucket was installed on flat ground near the observatory with a data acquisition system snowmelt discharge measurements were made for two melt seasons 2006 07 and 2007 08 snow and meteorological data were collected at 15 min intervals using a semi automatic weather station the hourly surface snowmelt was estimated using an energy balance approach the maximum daily discharge was 2 mm w e h 1 for most of the observation period the daily mean wave speed of the meltwater front varied from 109 to 285 mm h 1 for a daily mean discharge range of 0 6 1 8 mm w e h 1 while wave speeds for a particular melt flux of 2 mm w e h 1 varied between 113 and 486 mm h 1 the pore size distribution index was estimated using the power fit relation between wave speed and discharge the equivalent permeability of the snowpack was found to vary between 3 4 x 10 8 and 9 9 x 10 12 m 2

clay mineral accumulation rates in the arabian sea during the late quaternary abstract the regional variations in clay mineral concentrations in 39 turbidite free and undisturbed deep sea sediment cores from the arabian sea are compared with distribution patterns of clay mineral accumulation rates during the holocene and the last glaciation dust plumes from the red sea area arabia mesopotamia iran and pakistan can be traced by accumulation rates of mineral specific dust loads during the late quaternary the major proportions of aeolo marine sediments in the western arabian sea were derived from arabia during the summer season the clay mineral assemblage in these dust plumes consists of illite smectite kaolinite chlorite and palygorskite in decreasing order of abundance the distribution pattern of palygorskite in particular reveals that dust transport from southern arabia occurs mainly with northwesterly to westerly winds in the mid troposphere dust plumes from iran and pakistan which are characterized by high chlorite content are dispersed by northwesterly winds over the northwestern arabian sea dust contributions from the red sea area which are rich in smectite and characterized by the occurrence of amphiboles are transported to the gulf of aden the amount of dust related to northeast monsoon winds during the winter season appears to be negligible when compared to the proportions borne on other dust bearing winds in addition to aeolian contributions we distinguish two fluvial contributions a chlorite illite kaolinite and quartz rich assemblage from oman and pakistan into the gulf of oman and a smectite rich assemblage which is dominant off southern india originating from rivers that drain the indian subcontinent the significant difference between the holocene and glacial accumulation rates of wind transported clay minerals consist in the higher abundance of quartz illite and chlorite in the northwestern arabian sea during the last glaciation this pattern indicates intensified dust contributions by northwesterly winds from the persian gulf area which was dry during glacial times

tropical plumes over eastern north africa as a source of rain in the middle east tropical plumes tps reflect tropical extratropical interaction associated with the transport of moisture from the tropics to extratropical latitudes they are observed in satellite images as continuous narrow cloud bands ahead of upper level subtropical troughs at times when the subtropical jet is highly perturbed rainstorms usually develop in the exit regions of tps so their presence over northern africa has an impact on the precipitation regime in the southeastern mediterranean based on satellite images and rainfall measurements from israel 10 tps over eastern north africa between 1988 and 2005 in which considerable rain was recorded were selected using the ncep ncar reanalysis data the structure and evolution of these tps were characterized and their regional canonical features were identified a typical tp that occurred in march 1991 is described in detail the main canonical characteristics are as follows the tp development is preceded by an incubation period expressed either as a stationary upper level trough persisting 2 6 days or as two consecutive tp pulses the preferred location for tp origin is 5 15 n 5 w 15 e the tp is separated from the underlying dry saharan pbl the subtropical trough undergoes a phase locking with the lower tropical trough the cloudiness in the tp induced rainstorm is mostly stratified with continuous moderate rain originating from midlevel moisture and the tp tends to be followed by a midlatitude cyclogenesis over the eastern mediterranean this analysis proposes several explanations for the efficiency of the tps in transporting moisture over a 2000 km distance

why precipitation is mostly concentrated over islands in the maritime continent abstract high resolution observations and regional climate model simulations reveal that precipitation over the maritime continent is mostly concentrated over islands analysis of the diurnal cycles of precipitation and winds indicates that this is predominantly caused by sea breeze convergence over islands reinforced by mountain valley winds and further amplified by the cumulus merger processes comparison of a regional climate model control simulation to a flat island run and an all ocean run demonstrates that the underrepresentation of islands and terrain in the maritime continent weakens the atmospheric disturbance associated with the diurnal cycle and hence underestimates precipitation the implication of these regional modeling results is that systematic errors in coarse resolution global circulation models probably result from insufficient representation of land sea breezes associated with the complex topography in the maritime continent it is found that precipitation in the maritime continent

flow and mixing in new mexico mountain cumuli abstract convection and cloud formation over mountains during weak winds and strong insolation were studied using an instrumented aircraft previous studies in cloudless situations had shown the existence of convergence over the mountain range at low levels and divergence aloft the present observations indicate that cumulus clouds and even thunderstorms in their early stages do not significantly affect the strength of the low level convergence furthermore net divergence was found around clouds up to at least 6 km msl this favors the vertical mixing model of a cumulus cloud over the lateral entrainment model in one case the convergent low level heat island circulation over the mountain was observed to change to an almost non divergent asymmetric circulation as a thunderstorm over the mountain reached maturity

correlation lengths of meltwater flow through ripe snowpacks colorado front range usa the flowpaths of meltwater through snow is known to be an inhomogeneous process the spatial distribution of meltwater flowing from the bottom of melting snowpacks is the result of horizontal and vertical flow paths within the snowpack the ability to characterize the spatial distribution of these meltwater flowpaths would be useful in developing models of snow melt runoff which could better characterize snow melt hydrographs we analyzed near infrared aerial photos of melting snow using a moving window analysis which can characterize correlation lengths in the reflectance of the snow surface near infrared is sensitive to snow grain size which in turn may indicate higher amounts of meltwater the grains grow faster if the liquid water content is higher correlation lengths were live to seven metres and the probability of finding such correlation lengths increased from 0 22 in may 1997 when the melt had just started to 0 68 by late june when melt was well established liquid water content at the snow surface was sampled with a dielectric sensor at 0 5 m intervals on 100 m 2 and 75 m 2 grids semi variograms showed a sill at five to six metres the liquid water measurements at the snow surface suggest that the correlation lengths derived from the infrared aerial photos represent surface expressions of higher flow density through the melting snowpack a circular array of 16 snow melt lysimeters each with areas of 0 2 m 2 was operated for two years at niwot ridge in the colorado front range variograms indicated that flows were correlated over a distance of five to seven metres these three independent methods all suggest a spatial organization of five to seven metres for flowpaths draining ripe snowpacks in the rocky mountains

a numerical study of three catastrophic precipitating events over southern france ii mesoscale triggering and stationarity factors in the western mediterranean basin large amounts of precipitation can accumulate in less than a day when a mesoscale convective system mcs stays over the same area for several hours heavy precipitating events hpes in this region especially southern france are not only characterized by significant precipitation rates typically more than 200 mm in less than 24 or 48 hours but also by quasi stationary behaviour the aim of this present study is to use realistic simulations of past events to analyze and better understand the physical mechanisms which lead to the stationarity of hpes over southern france using a high resolution 2 5 km non hydrostatic mesoscale atmospheric model we focused on three hpes 13 14 october 1995 the cevennes case 12 13 november 1999 the aude case and 8 9 september 2002 the gard case the experimental design for simulating realistic structures and evolutions of the hpes with the meso nh model has been presented in a companion paper in that study the evolution of the synoptic patterns in which the hpes occurred were analysed in this paper the importance of mesoscale ingredients such as the moist and conditionally unstable low level jet llj is examined in terms of their ability to focus the deep convection over the same area for several hours the cevennes case is typical of a so called cevenole event in france for which orographic forcing is the primary mechanism which acts to continuously generate convective cells upwind of the massif central the unusual location of the gard event is explained by a cold pool induced by the evaporation of precipitation which acts as a relief like feature to force the conditionally unstable and moist llj to rise this constitutes a quasi stationary forcing as the cold pool is blocked in the rhone valley for the third case diabatic cooling and the massif central act to enhance the precipitation but have almost no impact on the location of the anchoring point of the precipitating system

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

the modern and last glacial maximum hydrological cycles of the eastern mediterranean and the levant from a water isotope perspective abstract the isotopic composition of precipitation p is one of the most widely used and informative terrestrial paleoclimate proxies p integrates a series of hydrological processes therefore any interpretation of paleohydrology using p requires a thorough understanding and quantification of the full hydrological cycle in this paper we use modern data to analytically model the full isotopic hydrological cycle of the eastern mediterranean and the southern levant including oceanic evaporation distillation during transport and precipitation over land this model allows us to determine the important factors controlling this system the model results underscore the significance of the isotopic distillation process driven by the land sea temperature gradient as a significant factor controlling the long term average isotopic composition of precipitation across israel based on the understanding of the processes that govern the modern system we model the isotopic composition of precipitation from the last glacial maximum lgm using published data for speleothem oxygen isotopes in calcite oxygen and hydrogen isotopes in fluid inclusions and clumped isotope values from soreq cave and the isotopic composition of east mediterranean planktonic foraminifera g ruber the data and model results indicate two plausible scenarios for the lgm that entail changes in the magnitude of distillation over israel in normalized humidity over the mediterranean and possible shifts of the moisture trajectories over the mediterranean the results presented in the paper illustrate the importance of understanding the full local hydrological cycle when reconstructing and interpreting the isotopic composition of precipitation

revised chronology of the icdp dead sea deep drill core relates drier wetter drier climate cycles to insolation over the past 220 kyr abstract the dead sea deep drilling project drilled 456 meters into the deepest floor of the dead sea and recovered a record of the past 220 kyr of the levant hydroclimate history that is marine isotope stages 1 7 including the last three interglacials and the last two glacials we present an updated chronology of the core from dsddp hole 5017 1 a from the dead sea s deepest basin that refines our previous chronology torfstein et al 2015 based on new information the updated chronology uses the following approaches 1 radiocarbon ages of kitagawa et al 2017 2 correlation of specific layers in the core with u th dated sediments on the dead sea margin particularly during the interval of glacial lake lisan mis 2 3 4 3 tuning of the 18o data of dsddp core aragonite to the u th dated oxygen isotopes of regional cave speleothems and 4 tuning of the dsddp aragonite 18o data to summer insolation curves when the cave 18o chronology is less clear the updated chronology reveals a strong relationship between the sedimentary facies comprising the core and northern hemisphere summer insolation variations it shows that sequences of sediments marking drier wetter drier climate conditions in the lake s watershed e g salt muds salt respectively appear across the flank peak flank segments of several summer insolation peaks in particular the transition from drier to wetter sedimentary facies during mid latitude insolation peaks coincides with the intervals of sapropel conditions in the mediterranean reflecting enhanced nile flow due to intense african monsoonal conditions and marking the impact of the tropical precession cycles on eastern mediterranean hydroclimate this pattern was lost during mis 2 3 4 when mostly sequences of primary aragonite are punctuated by gypsum precipitation during heinrich events marking the strong impact of the north atlantic on the last glacial levant hydroclimate

strontium isotopic chemical and sedimentological evidence for the evolution of lake lisan and the dead sea precise strontium isotope ratios combined with chemical analyses and sedimentological information are used to monitor the water sources and the evolution of the dead sea and its late pleistocene precursor lake lisan 70 18 kyr b p the materials analyzed include bulk aragonite water leached soluble salts and residual aragonite and gypsum from the lisan formation in the perazim valley near the sw shore of the dead sea the residual aragonite and the associated soluble salts display systematic fluctuations in 17sr86sr ratios between 0 70803 and 0 70806 and from 0 70805 to 0 70807 respectively in individual soluble salt residual aragonite pairs the soluble salt displays a higher 87sr86sr ratio gypsum samples yield 17sr86sr ratios similar to the soluble salts from adjacent layers in the section this shows that in individual samples the source of sr in aragonite was distinct from that in soluble salts and the gypsum the sterility of the lisan sediments their strictly nonbioturbated fine lamination and their high content of chloride salts indicate that lake lisan was a saline or even hypersaline water body in the absence of alternative sources of hco3 and s042 the abundance of primary aragonite and gypsum in the lisan column reflects an import of very large volumes of freshwater into the otherwise saline lake resulting in a density stratification of this water body the history of the upper water layer and that of the lower brine is reflected in the chemical and strontium isotope composition of the aragonite and in that of the associated soluble salts and in the gypsum samples respectively whereas the bicarbonate and much of the ca2 required for aragonite crystallization were supplied by the freshwater the complementary ca2 and sr 2 were added by the lower brine the upper water layer of lake lisan acted as a so42 capacitor during the lake s rise periods it was removed therefrom as prominent gypsum beds upon climatic induced drier period mixing or even complete overturn of the lake the evolution of lake lisan took place between two distinct modes the first was characterized by an extensive supply of freshwater and resulted in a rise of the lake s level a density layered structure and precipitation of aragonite the second mode was marked by a diminishing freshwater input resulting in mixing or complete overturn of its water and precipitation of gypsum these two modes reflect the climatic evolution of the region in the late pleistocene which fluctuated between drier and wetter periods the transition to the holocene is accompanied by the dry up of lake lisan and its contraction to the present dead sea

rapid development of negative ce anomalies in surface waters and contrasting ree patterns in groundwaters associated with zn pb massive sulphide deposits ground and surface waters collected from two undisturbed zn pb massive sulphide deposits the halfmile lake and restigouche deposits and active mines in the bathurst mining camp bmc nb canada were analysed for the rare earth elements ree ree contents are highly variable in waters of the bmc with higher contents typical of waters with higher fe and lower ph there are significant differences between ground and surface waters and between groundwaters from different deposits the ree contents of surface waters are broadly similar within and between deposit areas although there are spatial variations reflecting differences in ph and redox conditions surface waters are characterised by strong negative ce anomalies ce ce nasc as low as 0 08 produced by oxidation of ce3 to ce4 and preferential removal of ce4 from solution upon leaving the shallow groundwater environment groundwaters and seeps typically lack significant ce anomalies reflecting generally more reducing conditions in the subsurface environment and indicating that ce oxidation is a rapid process in the surface waters deeper groundwaters at the halfmile lake deposit are characterised by ree patterns that are similar to the host lithologies whereas most groundwaters at the restigouche deposit have lree depleted patterns compared to nasc halfmile lake deposit groundwaters have generally lower ph values whereas restigouche deposit groundwaters show greater heavy ree complexation by carbonate ions shallow waters at the halfmile lake and stratmat main zone deposits have unusual patterns which reflect either the adsorption of light ree onto colloids and fracture zone minerals and or precipitation of ree phosphate minerals middle ree enrichment is typical for ground and surface waters and is highest for neutral ph waters the labile portion of stream sediments are generally more middle ree enriched than total sediment and surface waters indicating that the ree are removed from solution by adsorption to fe and mn oxyhydroxides in the order middle ree light ree heavy ree

short residence time and fast transport of fine detritus in the judean desert clues from 7be in settled dust 1 the cosmogenic isotope 7be t1 2 53 3d was measured in sediments collected from dust traps deployed in the judean desert which is part of the dead sea drainage basin the results show that a the 7be dry deposition flux in the dead sea region is 2 0 0 6 104 atoms cm 2 y 1 during summer and winter and 5 3 0 7 104 atoms cm 2 y 1 during fall b the residence time of dust in the dead sea drainage basin is less than one year c the recycled component of the cosmogenic isotope 10be t1 2 1 39 106y in judean desert dust is potentially small and d the 7be inventory atoms cm 2 in dust settled in the drainage basin did not reach steady state between consecutive rare events of desert winter floods suggesting a short transport rate of fine detritus material from the marginal terraces into the dead sea provided 10be behaves similarly as implied by the common geochemistry and cosmogenic origin of 7be and 10be we suggest 10be in lake lisan pleistocene dead sea detrital sediments as a potential proxy for paleo flood frequency and dust transport

hydrological cycles on the north and south peripheries of mountain glacial basins of central asia four high mountain glacial basins of the northern and southern periphery of central asia were studied to determine their interaction with the external hydrological cycle over the eurasian continent two of them located in the northern periphery are closed drainage basins with continental climate and the other two are open basins located in the southern periphery calculations of mass energy exchange glacial runoff and components of the hydrological cycles were conducted for glaciers with a continental climate the calculations of snow ice melt and runoff were based on solar parameters for glaciers with a marine climate regime glacier melt and runoff were based on air temperature the relative errors of simulated annual flows were on average 8 14 the components of the regional hydrological cycles precipitation condensation runoff and evaporation were quantified for each glacial system and their share in total atmospheric moisture was determined the closed basins of the northern periphery in central asia stored annually about 0 1 2 4 of the total external atmospheric moisture in the aralo caspian and tarim hydrographic systems about 0 22 0 24 of the external water cycle is transferred annually in open glacial basins of the southern periphery the glaciers of these regions return 0 25 0 30 of the external water cycle per year to the pacific and indian oceans 0 03 and 0 06 of this external moisture is taken from the glacial resources of the gongga and xixibangma glaciers

ree mobility and fractionation during shale weathering along a climate gradient abstract we systematically investigated six soil profiles developed on a climosequence of gray shale to constrain the mobility and fractionation of rare earth elements ree during chemical weathering processes in addition one site developed on black shale marcellus formation was included to document ree behaviors in organic rich versus organic poor shale end members under the same environmental conditions our study shows that ree are mobilized intensively during shale weathering and the extent of depletion is larger under warm humid climates however the integrated release rates calculated from six soil profiles are not directly correlated to mean annual precipitation or temperature instead the primary control might be the ree concentrations in the most reactive minerals ree bearing phases in shale sulfides phosphates and organic matter probably react quickly at first mobilizing ree following that ree are then released more slowly during dissolution reactions of clay minerals consistent with this interpretation black shale weathers much faster and releases more ree than gray shale under the same climate conditions due to the higher organic matter and sulfide contents and lower soil ph ree are not 100 depleted in any of the investigated soil sites in northern sites depletion is minimal whereas in the southern warm and humid sites surface depletion is higher and re deposition is observed at depth retention of ree is likely caused by adsorption to mineral surfaces as ph increases and dissolved organic matter content decreases with depth this case study quantified loss redistribution and fractionation of ree during shale weathering improved our understanding of ree mobility in surficial environments and contributed to the exploration of ree as strategic mineral resources

geochemical characterization of contemporary fine detritus in the dead sea watershed abstract reconstruction of paleo synoptic conditions e g past atmospheric circulation involves tracing the origins and routes of transport of particles comprising eolian archives i e desert dust lacustrine deposits that accumulated in the quaternary lakes filling the dead sea basin include remobilized eolian desert dust that was washed to the lakes by floods here we analyze the mineralogical chemical compositions e g mg al ratios and 87sr 86sr and 143nd 144nd end values isotope ratios of fine siliciclastic particles that form the modern surface cover of the dead sea watershed e g loess mountain soils and flood particles that are mobilized to the lake during distinct synoptic conditions the data comprises reference data set that can be used for paleo synoptic interpretation enhancing our ability to decipher the paleoclimate history during the quaternary in the levant the end values and 87sr 86sr ratios of the fine detritus lie between 8 and 6 and 0 7035 to 0 7188 reflecting the values of erosional products of granitoids that are exposed in the sahara and arabia deserts and the unradiogenic sr from local soils in the dead sea watershed particles with low mg al ratios i e 0 17 0 31 are transported by the western winds associated with the mediterranean cyclones transporting dust from the sahara while particles with high mg al ratios 0 27 0 68 are associated with storms blowing dusts from east to the dead sea watershed saudi arabia and syrian deserts during red sea trough synoptic conditions fine particles blown from the sahara deserts during winter storms are rapidly washed to the lake by subsequent floods whereas the particles blown during dry storms associated with red sea trough synoptic conditions accumulate on the surface of the dead sea watershed and can be washed later to the lake during extensive rain events

geochemical and isotopic characterization of the bodele depression dust source and implications for transatlantic dust transport to the amazon basin the bodele depression chad in the central sahara sahel region of northern africa is the most important source of mineral dust to the atmosphere globally the bodele depression is purportedly the largest source of saharan dust reaching the amazon basin by transatlantic transport here we have undertaken a comprehensive study of surface sediments from the bodele depression and dust deposits chad niger in order to characterize geochemically and isotopically sr nd and pb isotopes this dust source and evaluate its importance in present and past african dust records we similarly analyzed sedimentary deposits from the amazonian lowlands in order to assess postulated accumulation of african mineral dust in the amazon basin as well as its possible impact in fertilizing the amazon rainforest our results identify distinct sources of different ages and provenance in the bodele depression versus the amazon basin effectively ruling out an origin for the amazonian deposits such as the belterra clay layer by long term deposition of bodele depression material similarly no evidence for contributions from other potential source areas is provided by existing isotope data sr nd on saharan dusts instead the composition of these amazonian deposits is entirely consistent with derivation from in situ weathering and erosion of the precambrian amazonian craton with little if any andean contribution in the amazon basin the mass accumulation rate of eolian dust is only around one third of the vertical erosion rate in shield areas suggesting that saharan dust is consumed by tropical weathering contributing nutrients and stimulating plant growth but never accumulates as such in the amazon basin the chemical and isotope compositions found in the bodele depression are varied at the local scale and have contrasting signatures in the silica rich dry lake bed sediments and in the calcium rich mixed diatomites and surrounding sand material this unexpected finding implies that the bodele depression material is not pre mixed at the source to provide a homogeneous source of dust rather different isotope signatures can be emitted depending on subtle vagaries of dust producing events our characterization of the bodele depression components indicate that the bodele calcium rich component identified here is most likely released via eolian processes of sand grain saltation and abrasion and may be significant in the overall global budget of dusts carried out by the harmattan low level jet during the winter

palygorskite occurrences and genesis in calcisol and groundwater carbonates of the tensift al haouz area central morocco abstract palygorskite has been identified as a major constituent of the clay fraction in carbonate soils of arid and semi arid regions this fibrous clay has a great significance as a paleoclimatic indicator and is of fundamental importance for a more complete understanding of conditions under which petrocalcic horizons and groundwater carbonates precipitate the present study was undertaken in order to evaluate the occurrence the genesis as well as the micromorphological aspects of palygorskite in calcisol and groundwater carbonates the samples were analyzed by x ray diffraction xrd scanning electron microscopy sem and chemical analysis xrf two modes of genesis for palygorskite were identified 1 in the petrocalcic horizons the palygorskite is the dominant clay mineral palygorskite fibers and fiber bundles extend from euhedral or subhedral calcite crystals showing an authigenic origin of palygorskite the palygorskite is formed in the vadose environment from infiltrating soil water through the intense evaporation of subsurface water after calcite precipitation 2 in the groundwater carbonates smectite flakes appear to terminate palygorskite fibers suggesting formation of palygorskite through the alteration of precursor smectite the increasing aridity would have caused the intense evaporation conducive to the precipitation of calcite and an increase in ph which lead to dissolution of smectite and formation of palygorskite

radar observations of the diurnally forced offshore convective lines along the southeastern coast of taiwan this study documents offshore convective lines along the southeastern coast of taiwan a frequent but poorly understood mesoscale phenomenon that influences coastal weather during the taiwan mei yu season doppler radar and surface observations were gathered from a specially chosen period 11 15 may 1998 when the offshore convective lines were active off the southeastern coast of taiwan these observations were used to show the basic character structure and possible formative processes of offshore convective lines the synoptic environment accompanying these events was found to be relatively undisturbed and featured uniformly prevailing southerly south southeasterly winds in the boundary layer with southwesterlies westerlies aloft examination of radar data during the study period indicates that the lines generally occurred 10 30 km offshore and were characterized by an elongated narrow zone 5 10 km wide of heavy precipitation the lines were oriented roughly parallel to the coastline and generally did not move significantly the intensity of the radar reflectivity associated with the lines exhibited a marked diurnal variation and was closely related to the coastal offshore flow developing at night detailed analyses of an event on 14 15 may 1998 further show the important physical link between the offshore flow and the development of the line the offshore line was found to be located near and immediately ahead of the seaward extent of the offshore flow particularly a very narrow zone 2 km of low level heavy precipitation 40 45 dbz coincided with regions of strong updrafts and convergence where the prevailing southerly onshore flow encountered the cool offshore flow nearshore this offshore flow induced convergence given a stable thermodynamic condition in the lowest 1 km in the inflow region was a crucial low level forcing that provided lifting to trigger moist deep convection in this case the line s precipitation tilt eastward was confined primarily to the warmer inflow side rather than feeding the offshore flow to the west of the line no consistent upshear tilt of updrafts throughout the storm layer was observed which is consistent with the presence of a strong westerly shear in the line s environment both of these observations explain a relatively strong weak modification of low level onshore offshore flow by precipitation additionally a combination of surface and doppler radar observations indicates that the leading edge of the offshore flow moved seaward very slowly at 0 7 m s 1 and possessed a frontal character with notable discontinuities in near surface wind and temperature instead of pressure and dewpoint temperature

climatology of heavy precipitation over corsica in the period 1985 2015 the island of corsica in the western mediterranean is frequently struck by devastating heavy precipitation events hpes which endanger property and lives alike in the framework of the hymex hydrological cycle in the mediterranean experiment project multiple hpes from 2012 were observed and studied and to provide context a climatology for hpes based on 31 years 1985 2015 of surface observations was derived based on 173 events hpes 100 mm d 1 strike the island around 5 6 times a year and show a distinct seasonal cycle they occur predominantly during autumn with more than half of the hpes occurring from september to december and almost 20 in october the most active month the eastern half of the island is most affected by hpes composite fields for all events show a cyclone over the western mediterranean west of corsica and warm and moist low level air upstream of the orography predominantly over the tyrrhenian sea southeast of the island the events are classified using their synoptic and mesoscale environment obtained from era interim data using equivalent orthogonal functions eofs and a principal component pc analysis together with the k means clustering algorithm three clusters of events are identified each has a different seasonal cycle dominant wind direction and precipitation distribution warm southeasterly events occur predominantly in autumn produce the most extreme events and affect the coasts and slopes of eastern corsica alike cool southeasterly events occur predominantly in winter and affect mostly the slopes along the east side of the orography southwesterly events are more often associated with large scale atlantic cyclones and occur throughout almost the entire year and with the highest precipitation over the mountains

clay distribution over the landscape of israel from the hyper arid to the mediterranean climate regimes abstract the current study evaluates clay distribution in modern surface sediments mainly soils to which desert dust is a major contributor the mineralogical composition of the clay fraction of seventy seven samples was analyzed by x ray diffraction twenty nine soil and dust samples were also analyzed for their bulk chemical composition the samples are settled dust soils developed on various sedimentary rocks stream and lake sediments they were collected along a climate gradient from hyper arid to mediterranean regimes in israel the purpose of the study is to decipher the main factors that control variable clay distribution along this gradient including annual precipitation substrate type and topography the common clay composition for most samples of all sources is illite smectite is kaolinite illite trace amounts of chlorite palygorskite goethite and quartz might be present pedogenic processes are recognized even under arid climate where loessial soils display kaolinite depletion and more illitic is phases than dust two main processes shape clay composition under a mediterranean climate regime regardless of the parent material a smectitization process occurs in leached low permeable clayey soils and reaches optimum evolution with 90 smectite or smectitic is this evolutionary trend is also recognized in poorly drained soils of catenary chains that are related to other soil types like terra rossa hamra and pale rendzina kaolinitization and apparently illite pedogenic formation occur in well drained red mediterranean soils of the terra rossa and hamra types to the detriment of smectitic is phases of parent materials in the most evolved terra rossa and hamra soils kaolinite becomes the principal mineral and illite is significantly enriched pedogenic evolution of the clay fraction mineralogical composition affects bulk chemical composition of most soil types clay inheritance from the bedrock is rather limited in leached soils it is widely recognized in pale rendzina soils by the presence of smectite or smectite and palygorskite derived from late cretaceous or eocene chalks respectively streams clay composition like that of dust is fairly uniform as streams average various sources across their drainage basins however composition variations can be attributed to local contribution from certain sources

mineralogical and chemical variability of mountain red brown mediterranean soils the purpose of the current study was to quantitatively explore the dynamics of clay pedogenesis in red brown soils of the terra rossa type and associated soils mainly rhodoxeralfs of the mediterranean region with respect to bedrock and dust composition and the impact of the vegetation translocated elements silicon and potassium fifteen non cultivated shallow and leached mountain pedons were sampled in israel along three transects that represent various rainfall ranges and bedrock lithologies bulk and clay fraction chemical and mineralogical compositions as well as grain size were determined quantitative relative analysis of clay minerals displayed a large variability that was largely affected by leaching leaching was dependent on rainfall amount and bedrock soil permeability in general if the better soils were drained and leached the higher were the amounts of both kaolinite and illitic phases soil clay assemblages lay between two mineralogical end members one with dominance of smectite and the second with high values of kaolinite and illitization parameters potassium and silicon were mobile in soils relative to aluminum but under high rainfall or certain vegetation translocation by vegetation reached a degree that promoted illite or smectite formation local combinations of rainfall bedrock soil permeability and vegetation translocation of potassium and silicon dictated a large variability in clays including illite formation within a restricted group of red brown mediterranean soils

the permeability of a melting snow cover data from snow lysimeters in california and vermont are used to find the saturated permeability of a melting snow cover in the range of 10 40 10 10 m2 depending on snow density the unsaturated permeability increases as about the third power of liquid saturation the gravity flow theory is shown to be an accurate representation of meltwater drainage from snow covers in two diverse areas even though the snow covers are treated as homogeneous units the variation of saturated permeability with snow density occurs about as predicted by shimizu s formula for dry snow although ice layers decrease the permeability somewhat

chemical and textural controls on the formation of sepiolite palygorskite and dolomite in volcanic soils abstract a 3 m deep soil profile from gran canaria canary islands has been studied the profile is interesting because soil development on mafic tephra produced a pattern of clay mineral and carbonate distribution carbonates precipitated abundantly increasingly towards the bottom making up 20 90 wt of the soil sepiolite and calcite are dominant at the top whereas palygorskite and dolomite are the major components at the lower part of the profile quartz is present in low amounts in most of the profile and smectite and non crystalline partially altered tephra occur in low amounts towards the bottom mineralogical chemical and textural investigations indicate that sepiolite and calcite precipitated in the space between the original tephra grains from ca mg and si dissolved in situ and transported in the runoff palygorskite and smectite precipitated within tephra grains from in situ tephra weathering as well as dolomite the distribution of the clay minerals is due to clay composition and ion mobility sepiolite consisting only of si and mg precipitated outside tephra grains where the mobile si and mg ions were abundant in the interstitial waters palygorskite and smectite contain si al fe and mg and only precipitated within the tephra grains where the immobile al and fe were available calcite precipitation in solution is kinetically favored over that of dolomite and thus calcite precipitated between the grains dolomite precipitated within altering tephra grains and spherical clay structures because tephra and clay generated a viscous medium where dolomite supersaturation increased and the kinetic barrier for precipitation was overcome these results are relevant to the dolomite problem as they illustrate how dolomite can precipitate in surface conditions and to co 2 sequestration because dolomite can immobilize higher co 2 amounts both ca and mg are involved and not only ca and in a much more stable manner dolomite is eight orders of magnitude less soluble than calcite

chemical characterization of atmospheric dust from a weekly time series in the north red sea between 2006 and 2010 abstract atmospheric dust loads and chemical compositions serve as a key link between global climate patterns and marine biogeochemical cycles the primary source of atmospheric dust in the world today is the sahara arabian desert belt although this source was also active during the quaternary the interpretation of paleo dust records and their effects on marine ecosystems is complicated by the scarcely reported atmospheric load patterns of bioavailable phases i e water and acid leachable phases and present day contamination of anthropogenic components this study reports a multi annual time series of atmospheric dust loads 2006 2016 and their chemical compositions 2006 2010 collected in the north gulf of aqaba north red sea at a weekly to bi weekly resolution major and trace element abundances in each sample are reported for three fractions water soluble salts carbonates and oxides weak acid leach and al silicates dust loads vary seasonally from low values in late summer 20 30 g m 3 to higher values in the fall and highest values in late winter and early spring 150 250 g m 3 major and trace element abundances allow to distinguish between the sources and chemical compositions that dominate high and low dust loads in each season the water leachable fraction l0 is relatively enriched in na ca k and mg the acid leachable fraction l1 is enriched in ca as well as na al mg zn cd and pb and the silicate residue l2 in al and fe high dust loads occurring mainly during winter and spring months are characterized by low mg ca l1 l2 low k al and na al l1 and high ca al l1 high mg al l2 and relatively un weathered l2 contents high dust load intervals during winter months are characterized by low passing air masses originating from the sahara while the ambient winter dust low dust load is associated with proximal source regions from the east sahara and arabian peninsula during late winter and spring months high dust loads originate from central and west sahara and to a lesser extent from north sahara low dust loads characterize the summer with limited compositional variability relative to winter spring months summer dust is generally characterized by high k al l1 ratios relative to late winter and spring it is also relatively high in anthropogenic trace elements in the l0 and l1 fractions e g zn al pb al cr al ni al and v al whereby back trajectories indicate the source of these components is primarily from south and east europe the total load ng m 3 of anthropogenic trace elements however remains higher during winter and spring stemming from the overall significantly higher dust loads characterizing this time window the temporal load patterns of important micronutrients such as fe cd zn cu ni and others in the bio available phases l0 l1 are not correlated with major nutrients or chlorophyll a sea surface concentrations suggesting that the atmospheric dust plays a limited role in driving primary productivity in the oligotrophic surface waters of the gulf of aqaba on a wider scale the results provide unique chemical fingerprinting of sahara arabian dust that can be applied to reconstruct past trends in dust loads recorded in deep sea cores and other geological archives from this and other regions

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

provenance of the various grain size fractions in the negev loess and potential changes in major dust sources to the eastern mediterranean abstract the isotopic composition of sr and nd and elemental concentrations e g na k ca mg al of three primary negev loess sequences trace the relative contributions of desert dust sources over the past 180 000 yr to the southeastern mediterranean we focused on the geochemical signature of the fine 20 m grain size modes of the loess to identify their respective provenances the isotopic composition of the coarse fraction falls on a mixing line of sources feeding the nile and its delta the chemical compositions of the coarse fraction and the sinai negev sand dunes are similar indicating that this fraction is the product of aeolian abrasion of the adjacent sinai negev sands in turn these sands are derived from the nile delta and transported inland the fine fraction has less negative end values and slightly deviates from the mixing line indicating an additional end member the higher end values and mg al ratios of the fine fraction are relatively well correlated r2 0 64 and point to arabian dust as an additional source temporal changes in the geochemical composition of loess over time reflect changes in climates of source areas and the eastern mediterranean shifts from saharan to arabian fine dust dominated intervals indicate wetter conditions in the southern sahara that weaken dust fluxes from this source relative to the arabian fluxes

kinematic wave modelling of vertical movement of snowmelt water through a snowpack vertical movement of snowmelt water through snowpacks is modelled by applying the kinematic wave theory analytical solutions are obtained for moisture flux particle velocity time history and velocity of meltwater front and total moisture content for a single melt event assuming that the melt rate is constant these solutions are extended to the case involving more than one event

the sharav cyclone observations and some theoretical considerations a special study of the sharav cyclones indicates that they are the result of large scale weak baroclinicity enhanced by vigorous boundary layer baroclinicity between the north african coast and the mediterranean it is illustrated how the jet stream plays a major role in the vertical circulation in producing a complex cyclonic circulation dominated by at least three mechanisms large scale interior baroclinicity boundary layer baroclinicity and jet stream related circulations the main characteristics of the sharav cyclone also called the saharan depression or khamsin depression in the mediterranean are reviewed unlike the cold winter cyclone the sharav cyclone is a spring cyclone its tracks lie mainly along the north african coast and turn to the north near the southeastern mediterranean its warm front is active and is sometimes associated with extremely high surface temperatures its cold front is shallow the sharav cyclone moves eastward relatively fast typically faster than 10 m s 1 and with a small speed variability in general there is an upper level trough to the west of the surface low and the surface horizontal scale is of the order of 500 1000 km finally it is frequently associated with heavy dust sand storms and low visibilities some of these features are illustrated in a case study of the april 28 30 1986 cyclone vertical cross sections indicate a deep circulation associated with the exit region of an upper level jet in addition to presenting evidence that the sharav cyclone is a deep tropospheric circulation it is shown that the transverse indirect circulation at the exit region of the jet is a major component of its circulation the classic two level baroclinic model phillips 1954 is applied the effects of the major diabatic heating due to the sensible heat flux above the north african desert and the large north to south temperature gradients are incorporated through the thermal wind of the basic state the model predicts the fast eastward motion the relatively smaller horizontal scale and the fast growth rate furthermore the model predicts an annual maximum growth rate in april and a secondary peak in october which agrees with the frequency of occurrences of the sharav cyclones

what is the mechanism for the modification of convective cloud distributions by land surface induced flows abstract the aim of this study is to determine the mechanism that modulates the initiation of convection within convergence zones caused by land surface induced mesoscale flows an idealized modeling approach linked quantitatively to observations of vegetation breezes over tropical benin was used a large eddy model was used with a prescribed land surface describing heterogeneities between crop and forest over which vegetation breezes have been observed the total surface fluxes were constant but the bowen ratio varied with vegetation type the heterogeneous land surface created temperature differences consistent with observations which in turn forced mesoscale winds and convection at the convergence zones over the crop boundaries at these convergence zones optimum conditions for the initiation of convection were found in the afternoon the equivalent potential temperature was higher in the convergence zones than over anywhere else in the domain due to reduced entrainment and the mesoscale convergence

a comprehensive mass flux scheme for cumulus parameterization in large scale models abstract observational studies indicate that a mass flux approach may provide a realistic framework for cumulus parameterization in large scale models but this approach through the introduction of a spectral cloud ensemble leads normally to rather complex schemes in this paper the question is addressed whether much simpler schemes can already provide realistic values of the thermal forcing by convection under various synoptic conditions this is done through verifying such a scheme first on data from field experiments for periods of tropical penetrative convection gate marshall islands tradewind cumuli atex bomex and extratropical organized convection sesame 79 and then in a nwp model the scheme considers a population of clouds where the cloud ensemble is described by a one dimensional bulk model as earlier applied by yanai et al in a diagnostic study of tropical convection cumulus scale downdrafts are included various types of convection are represented i e penetrative convection in c

how mineralogy and slope aspect affect ree release and fractionation during shale weathering in the susquehanna shale hills critical zone observatory abstract to understand the factors that control rare earth elements ree release and fractionation during shale weathering we investigate the ree contents in solid bedrock regolith stream sediments and natural waters stream and pore waters from a first order catchment developed entirely on gray shales in central pennsylvania usa up to 65 of the ree relative to parent bedrock is depleted from the weathering profiles in the acidic and organic rich soils due to chemical leaching in addition newly formed fine particles were also lost along with the down slope movement of soil waters weathering profiles on the south facing slope show less depletion of ree than those on the north facing slope 33 vs 45 on average we hypothesize that the different degrees of ree depletion on the two transects reflect a history of different chemical weathering rates and possible different surface erosion rates controlled by contrasting slope aspect induced microclimate conditions in addition weathering profiles natural waters and sequential extractions all show a preferential removal of middle ree up to 22 more relative to light ree and heavy ree during shale weathering due to preferential release of mree from rhabdophane furthermore the long term phosphate mineral dissolution rates e g rhabdophane were estimated at 10 15 to 10 14 mol m 2 s 1 under field conditions based on ree depletion profiles strong positive ce anomalies average ce ce n value 1 79 observed in the regolith stream sediments and regolith extractions point to the fractionation and preferential precipitation of ce as compared to other ree due to the generally oxidizing conditions during release transport and redistribution of ree in the surface and subsurface environments positive eu anomalies average eu eu n value 1 30 observed in the natural waters of the catchment are attributed to weathering of plagioclases in the shale bedrock this study highlights the use of ree as natural tracers for low temperature geochemical processes

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

the effects of palygorskite on chemical and physico chemical properties of soils a review abstract very little was known about how palygorskite affects soil properties when it constitutes a significant component of the soil clay fraction this constituted a serious impediment for the proper management of palygorskite containing soils under irrigated agriculture the present review is intended to summarize studies on the effects of palygorskite on chemical and physico chemical properties of soils carried out in recent years and to discuss future research required in this area when palygorskite containing soils are involved in irrigation practices release of mg from palygorskite into the soil solution will occur magnesium as an exchangeable cation in turn is known to decrease aggregate stability and to enhance the dispersivity of the soil clay fractions on the other hand magnesium as a dissolved cation is known to improve phosphorus availability in arid soils knowledge of factors affecting rheological properties of soil clay suspensions is essential for understanding of mechanisms of water and solid particle transfer through the soil profile the rheological behavior of soil clay suspensions is however complex and cannot be predicted from that of suspensions of standard clays although the flocculation value of palygorskite at near neutral ph is significantly lower than that of smectite the presence of palygorskite in the soil clay fraction will not affect the flocculation value of the soil clay since smectite which is always present in the clay fraction of palygorskite containing soils has a dispersive effect on palygorskite palygorskite has the strongest disaggregation potential and the highest ability to migrate in the soil among common phyllosilicates such as smectite and kaolinite palygorskite particles are thus likely to move preferentially over smectite and kaolinite downward in the soil profile and eventually to clog soil pores disaggregation and migration of palygorskite from the surface soil during rainfall and or irrigation may have an effect on the degree of erosion as well palycretes duripans in which the cementing material is dominantly composed of palygorskite can be formed in some landscapes where palycretes occur close to the surface plant growth is severely impeded palycretes also reduce water permeability of the soils creating water logged conditions that necessitate drainage installation although some progress has been made recently in understanding the effects of palygorskite on chemical and physico chemical properties of soils much research remains to be done performing some additional studies on disaggregation potential and migration ability of palygorskite under conditions close to those in the field is strongly desirable scanning electron microscopy observations on possible changes in aggregation of palygorskite in soils following intensive irrigation might be useful studies of the rheological behavior of soil clays with different mineralogical composition and palygorskite containing soil clays in particular are strongly encouraged there is a need as well to study interactions of various contaminants both organic and inorganic with palygorskite containing soil clays