dust a diagnostic of the hydrologic cycle during the last glacial maximum dust concentrations in ice of the last glacial maximum lgm are high in ice cores from greenland and antarctica the magnitude of the enhancements can be explained if the strength of the hydrologic cycle during the lgm was about half of that at present this notion is consistent with a large decrease 5 c in ocean temperature during the lgm as recently deduced from measurements of strontium and calcium in corals

sr nd isotope composition and clay mineral assemblages in eolian dust from the central philippine sea over the last 600 kyr implications for the transport mechanism of asian dust dust transport to the tropical subtropical northwestern pacific over the past 600 kyr was investigated using radiogenic isotopes 87sr 86sr and end together with the clay mineral composition of eolian dust preserved in a sediment core obtained from the philippine sea 12 30 n 134 60 e these data revealed the influence of two prevailing dust sources namely the asian deserts and nearby volcanic arcs e g the luzon arc with average contributions of around 70 and 30 respectively from each the clay mineral composition of the core resembled dust from the central asian deserts cads e g the taklimakan desert as in the north central pacific but published aerosol data collected near the study site during winter spring have the mineralogical signature of dust originating from the east asian deserts eads these data indicate that the relative contribution of ead dust increases with the northeasterly surface winds associated with the east asian winter monsoon eawm during winter spring but the prevailing westerlies and trade winds that carry dust from the cads is the dominant transport agent in the overall dust budget of the study site the results of this study contradict the prevailing view that direct dust transport by the eawm winds in spring dominates the annual flux of eolian dust in the northwest pacific

quantitative mineralogy of surface sediments on the iceland shelf and application to down core studies of holocene ice rafted sediments abstract quantitative x ray diffraction analyses on the 2 mm sediment fraction from the iceland shelves are reported for subglacial diamictons seafloor surface sediments and the last 2000 cal yr bp from two cores the overall goal of the paper is to characterize the spatial variability of the mineralogy of the present day surface sediments 18 non clay minerals and 7 clay minerals compare that with largely in situ erosional products typified by the composition of subglacial diamictons and finally examine the late holocene temporal variability in mineral composition using multi mineral compositions the subglacial diamictons are dominated in the non clay mineral fraction by the plagioclase feldspars and pyroxene with 36 7 6 1 and 17 9 3 5 wt respectively with smectites being the dominant clay minerals the surface seafloor sediments have similar compositions although there are substantial amounts of calcite plus there is a distinct band of sites from nw to n central iceland that contain 1 6 wt of quartz this latter distribution mimics the modern and historic pattern of drift ice in iceland waters principal component analysis of the transformed wt log ratio non clay minerals is used to compare the subglacial surface and down core mineral compositions fifty eight percent of the variance is explained by the first two axes with dolomite microcline and quartz being important foreign species these analyses indicate that today the nw n central iceland shelf is affected by the import of exotic minerals which are transported and released from drift ice the down core mineralogy indicates that this is a process that has varied over the last 2000 cal yr bp

influence of patagonian glaciers on antarctic dust deposition during the last glacial period dust deposition over antarctica was much higher during the last glacial period but the causes of this flux remain unclear an analysis of the composition and age of glacial outwash sediments indicates that growth and decay of glaciers in patagonia may have influenced dust transport to antarctica at that time

seasonal variability in the origin of recent atmospheric mineral dust at northgrip greenland abstract isotopic sr and nd and mineralogical analyses of dust extracted from snow deposits from the last decade at the northgrip greenland ice camp 75 1 n 042 3 w confirm the eastern asian source for greenland dust and extend it to the present day the 1998 and 1999 samples which represent a 2 4 month resolution of dust deposition show that there are at least two east asian sources for the greenland dust that vary seasonally the provenance of dust during the major spring summer deposition is the takla makan desert of northwest china

characterization of late glacial continental dust in the greenland ice core project ice core twelve glacial dust samples extracted from the greenland ice core project ice core have been characterized in terms of mineralogy sr and nd isotopic composition and rare earth element concentrations the ice samples are taken from the younger dryas the bolling the last glacial maximum and both cold and mild glacial periods back to 44 kyr b p a comparison with samples from possible dust source areas determines eastern asia as being the main source area at all times hereby confirming and extending earlier results biscaye et al 1997 this finding is partly in agreement with recent atmospheric general circulation model simulations of glacial atmospheric dust transport andersen et al 1998 mahowald et al 1999 a low intersample variability in tracer characteristics is discussed in the context of a volcanogenic influence grain size dependence and variability in the conti nental dust source areas the clay mineralogy of the ice core dust shows a weak climatic de pendence while the isotopic composition of sr and nd does not correlate with climate this is interpreted as a geographical variation of source areas on a regional scale within asia two ice dust samples were size fractionated at 2 gm and the grain size dependence on tracer characteristics is in accordance with the literature

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

new insights into the magnetic variations of aeolian sands in the tarim basin and its paleoclimatic implications abstract the tarim basin where aeolian activity is widespread has been regarded as a major source for global dust production therefore knowledge about variation of magnetic parameters in aeolian sands from the tarim basin has a global significance systematic rock magnetic studies of aeolian sands from this region are still scarce because of the vast area and poor accessibility of the basin in this paper multi parameter rock magnetic investigations of a larger number of aeolian sand samples from a wide area in the tarim basin have been conducted we find that magnetic properties of aeolian sands are controlled by changes in the concentration of larger pseudo single domain and multidomain magnetite grains which are produced by weathering and erosional processes in the surrounding mountain regions in addition aeolian sands collected from different geographic regions of the tarim basin exhibit different magnetic properties suggesting that selective wind and river transport and low temperature oxidation might play a critical role for the magnetic properties of aeolian sands in the tarim basin our study also provides a better understanding of the complex relationships between magnetic properties and source materials for pliocene deposits in the basin

distributions of lead isotopes with grain size in aeolian deposits lead pb isotopes are a powerful tool for identifying aeolian dust sources and reconstructing atmospheric circulation patterns however the grain size dependence of pb isotopes has not been well documented this study demonstrates the grainsize effect on the pb isotopes in four loess samples and one contemporary dust fall sample the results indicate that the pb isotopes show significant variation with grain size with no specific trend for all types of aeolian deposits the pb and neodymium nd isotopes with grain size fractions indicate that the potential sources of aeolian deposits from the sichuan basin the chinese loess plateau and the tibetan plateau probably differ from one another

comparing dust flux records from the subarctic north pacific and greenland implications for atmospheric transport to greenland and for the application of dust as a chronostratigraphic tool we present a new record of eolian dust flux to the western subarctic north pacific snp covering the past 27 000 years based on a core from the detroit seamount comparing the snp dust record to the north greenland ice core project ngrip ice core record shows significant differences in the amplitude of dust changes to the two regions during the last deglaciation while the timing of abrupt changes is synchronous if dust deposition in the snp faithfully records its mobilization in east asian source regions then the difference in the relative amplitude must reflect climate related changes in atmospheric dust transport to greenland based on the synchronicity in the timing of dust changes in the snp and greenland we tie abrupt deglacial transitions in the 230th normalized 4he flux record to corresponding transitions in the well dated ngrip dust flux record to provide a new chronostratigraphic technique for marine sediments from the snp results from this technique are complemented by radiocarbon dating which allows us to independently constrain radiocarbon paleoreservoir ages we find paleoreservoir ages of 745 140 years at 11 653 year b p 680 228 years at 14 630 year b p and 790 498 years at 23 290 year b p our reconstructed paleoreservoir ages are consistent with modern surface water reservoir ages in the western snp good temporal synchronicity between eolian dust records from the subantarctic atlantic and equatorial pacific and the ice core record from antarctica supports the reliability of the proposed dust tuning method to be used more widely in other global ocean regions

control of dust emissions by geomorphic conditions wind environments and land use in northern china an examination based on dust storm frequency from 1960 to 2003 the degree to which dust emissions are controlled by geomorphic conditions wind environments and land use was investigated using the dust storm frequency dsf and data from more than 300 meteorological stations throughout northern china our analysis showed that most dust emissions originated in gobi deserts that developed in piedmont alluvial fans of the kunlun qilian and helan mountains dust emissions are low from other gobi desert regions such as the northern gurbantunggut and eastern taklimakan where high vegetation coverage restrained dust emissions or where dust size particles are not abundant after a long period of strong wind erosion sandy deserts with relatively high vegetation coverage or an extensive cover by mobile sands are not a major dust source although the highest dust emissions did not appear in regions with the highest wind energy dsf trends in each region from 1960 to 2003 were closely related to local wind activity dsf was low in regions with high levels of human activity where the mean dsf from 1960 to 2003 did not exceed 4 days year even from the 1960s to the early 1970s the period with the greatest dsf frequency did not exceed 8 days year which indicates that extensive land use did not contribute to dsf the low dsf in these areas might result from the fact that although land use could produce abundant fine soil fractions vegetation coverage and soil moisture remained higher than in the gobi deserts of arid china thereby decreasing dust storm occurrence

sr nd hf isotopic analysis of 10 mg dust samples implications for ice core dust source fingerprinting combined sr nd hf isotopic data of two reference materials agv 1 bcr2 and 50 10 and 5 mg aliquots of carbonate free fine grain 10 lm separates of three loess samples central europe nus china bei usa jud are presented good agreement between measured and reference sr nd hf isotopic compositions ics demonstrate that robust isotopic ratios can be obtained from 5 to 10 mg size rock samples using the ion exchange mass spectrometry techniques applied while 87sr 86sr ratios of dust aluminosilicate fractions are affected by even small changes in pretreatments nd isotopic ratios are found to be insensitive to acid leaching grain size or weathering effects however the nd isotopic tracer is sometimes inconclusive in dust source fingerprinting bei and nus both close to end 0 10 hafnium isotopic values 10 lm fractions are homogenous for nus while highly variable for bei this heterogeneity and vertical arrays of hf isotopic data suggest zircon depletion effects toward the clay fractions 2 lm monte carlo simulations demonstrate that the hf ic of the dust 10 lm fraction is influenced by both the abundance of zircons present and maturity of crustal rocks supplying this heavy mineral while the 2 lm fraction is almost unaffected thus ehf 0 variations in the clay fraction are largely controlled by the hf ic of clays heavy minerals having high lu hf and radiogenic 176hf 177hf ic future work should be focused on hf ic of both the 10 and 2 lm fractions of dust from potential source areas to gain more insight into the origin of last glacial dust in greenland ice cores

sr and nd isotope compositions of atmospheric mineral dust at the summit of mt sefuri north kyushu southwest japan a marker of the dust provenance and seasonal variability abstract we analyzed rb sr nd isotope ratios of mineral dust in total aerosol load collected with rainwater continuously from 1998 to 2006 at the summit of mt sefuri northern kyushu southwestern japan during this period the total mass of the dust generally increased in late winter peaked in early spring and then decreased 87sr 86sr in atmospheric mineral dust varied from 0 7096 to 0 7180 and end 0 chur from 19 9 to 3 5 during heavy deposition periods the dust had high 87sr 86sr isotope ratios and low to middle end 0 chur values respectively these compositions are comparable to those of sand and loess in arid areas of northeast china takla makan and western beijing such particles were transported by westerlies from those areas to northern kyushu in winter and spring in summer and autumn the isotopic compositions of the dust varied greatly however during light deposition periods the sr isotope composition was low in these seasons the contributions to the dust from japanese soils and volcanic ash transported by southern winds were relatively larger than in winter and spring because of decreased mineral dust particle transport from the continent nevertheless fine sandy desert particles and loess in general accounted for most mineral dust deposition in northern kyushu year round even in summer local soils derived from weathered granite and volcanic ash were minor components only the net mass of water insoluble inorganic matter in the collected mineral dust fluctuated from year to year deposition on mt sefuri was relatively large before 2001 decreased from 2002 to 2005 and increased greatly in spring 2006 these year to year differences probably reflected changes in the strength of the westerlies and in climate conditions in the arid source areas

timescales for dust variability in the greenland ice core project grip ice core in the last 100 000 years the calcium representing dust concentration record of the last 100 000 years from the greenland ice core project grip ice core shows a huge dynamic range factor 100 the relationship between dust concentrations and temperature represented by the oxygen isotope ratio is not a simple one as has often been assumed a rapid alternation factor of 5 10 between low concentrations during the dansgaard oeschger interstadial periods and high levels in colder periods is superimposed on a long term trend encompassing a further factor of 5 10 within climate periods there is only a very weak relationship between ca concentration and temperature previous authors biscaye et al 1997 have suggested that the most likely source for the increased dust is eastern asia for the first time we consider each possible cause of both rapid and slow increases from source to deposition we suggest that to account for the size and rapidity of the fast changes significantly higher wind speed in the source area is required although changes in atmospheric residence time could also play a role for the slower long term variability changes in transport speed or possibly route are probably also involved changes in the size of the source area could give some change on longer time periods the probable importance of changes in source area wind speed almost simultaneous with greenland temperature changes confirms that climatic parameters in high and low latitudes were strongly coupled through the atmosphere during glacial climatic changes this adds to evidence that the atmospheric circulation system underwent almost instantaneous large scale changes during the last glacial period

ice core evidence for a very tight link between north atlantic and east asian glacial climate 1 corresponding millennial scale climate changes have been reported from the north atlantic region and from east asia for the last glacial period on independent timescales only to assess their degree of synchrony we suggest interpreting greenland ice core dust parameters as proxies for the east asian monsoon systems this allows comparing north atlantic and east asian climate on the same timescale in high resolution ice core data without relative dating uncertainties we find that during dansgaard oeschger events north atlantic region temperature and east asian storminess were tightly coupled and changed synchronously within 5 10 years with no systematic lead or lag thus providing instantaneous climatic feedback the tight link between north atlantic and east asian glacial climate could have amplified changes in the northern polar cell to larger scales we further find evidence for an early onset of a younger dryas like event in continental asia which gives

the size distribution of microparticles from selected segments of the greenland ice core project ice core representing different climatic periods the size distribution of insoluble microparticles dust in the particle size interval 0 4 6 0 m radius has been measured in more than 1400 samples from the greenland ice core project grip deep ice core from summit greenland the samples were taken from ice core segments representing 32 climatic periods including ice from the eem interglacial and ice from below the eemian ice the mean dust volume distributions from the climatic periods are compared and the relationship of total dust mass to the concentration of ca2 and to the stable isotopic composition 18o is investigated the dust volume distributions are found to be lognormal in the size interval 0 4 2 0 m with nearly identical shapes changes of the lognormal part of the volume distributions are found to be connected to the total dust mass in a systematic way the total dust mass is correlated to the ca2 concentration and data do not show any enrichment in ca2 from exposed continental shelves due to lower sea levels during the last glacial maximum the total dust mass is strongly connected to 18o the volume distribution of the particles in the size interval 2 0 6 0 m is found to be almost the same in most periods the exceptions are the cold periods in the last part of the last glacial period where the volume of these particles is higher than in most periods and the periods from the eemian and just above the eemian where the volume of these particles is lower the volume distributions of both the eemian warm periods and the cold eemian events are different from the distributions in ice from both below and above the eemian ice climate changes appear to have modified the processes of production transport modification and deposition of the dust aerosol in the same way over the last 120 000 years or more

the chemical composition of cold events within the eemian section of the greenland ice core project ice core from summit greenland selected segments from the eemian period of the greenland ice core project grip core from summit greenland have been analyzed by ion chromatography and coulter multisizer the results will be discussed with special emphasis on the sudden cooling events event 1 and event 2 in the record as observed in the 18o profile grip members 1993 dansgaard et al 1993 whether the sudden cooling events of the eemian represent a real climatic signal or they are a consequence of disturbed ice core st ratigraphy is still a matter of debate chappellaz et al this issue however several features of the chemical profiles across these cooling events are difficult to explain if they were a result of disturbed stratigraphy we will focus our discussion on the unique profiles of nitrate methane sulfonic acid msa and ammonium across event 1 and argue that even if we allow for movement of ions by diffusion or displacement of ions by physical or chemical interactions events 1 and 2 are not likely to consist of ice from other climatic periods which have been inserted in the eemian strata by folding processes furthermore our records do not show any layers in the vicinity of the eemian strata which can be a possible source of the ice in event 1 we believe that the events represent a climate signal and we will discuss other possible explanations of the profiles our conclusion that the cold events in the eemian represent a real climatic signal runs counter to other evidence from gas measurements however whatever their cause the unusual chemical signals require further discussion and explanation

toward a geochemical mass balance of major elements in lake qinghai ne tibetan plateau a significant role of atmospheric deposition abstract sediments in lake qinghai archive important information about past environmental changes in order to faithfully interpret the sediment records and constrain the elemental cycles it is critical to trace various sources of sediments in the lake the results show that the elemental input output budgets are imbalanced for most major elements between riverine fluxes and mass accumulation rate mar of lake qinghai sediments a realistic model must include contributions of dry wet atmospheric deposition that allow the major element mass balance for the lake to be defined the budget estimation is based on mass balances of si and al which are relatively immobile and carried to the lake via particulate forms estimated annual budget of dry atmospheric deposition is 1 3 0 3 103 kt a accounting for 65 of the total inputs to the lake sediments assuming local loess within the catchment as a candidate for dry atmospheric deposition to the lake the resultant flux of 300 45 g m2 a falls within the flux average of the desert area 400 g m2 a and the loess plateau 250 g m2 a consistent with the geographical setting of lake qinghai the role of atmospheric deposition would be more significant if wet deposition via rainfall and snow were taken into account this highlights the potential importance of dust as a significant source for sediment preservation flux for other catchments worldwide the results also indicate that nearly all ca input was preserved in the lake sediments under modern conditions consistent with ca2 supersaturation of the lake water

seeking a holocene drift ice proxy non clay mineral variations from the sw to n central iceland shelf trends regime shifts and periodicities quantitative x ray diffraction analysis of the 2 mm sediment fraction was carried out on 1257 samples from the seafloor and 16 cores from the iceland shelf west of 18 w all but one core b997 347pc were from transects along troughs on the nw to n central shelf an area that in modern and historic times has been affected by drift ice the paper focuses on the non clay mineralogy of the sediments excluding calcite and volcanic glass quartz and potassium feldspars occupy similar positions in an r mode principal component analysis and oligoclase feldspar tracks quartz these minerals are used as a proxy for ice rafted detritus ird accordingly the sum of these largely foreign minerals q k to icelandic bedrock is used as a proxy for drift ice a stacked equi spaced 100 a record is developed which shows both low frequency trends and higher frequency events the detrended stacked record compares well with the flux of quartz mg cm 2 a 1 at md99 2269 off n iceland the multi taper method indicated that there are three significant frequencies at the 95 confidence level with periods of ca 2500 445 and 304 a regime shift analysis pinpoints intervals when there was a statistically significant shift in the average q k weight and identifies four ird rich events separated by intervals with lower inputs there is some association between peaks of ird input less dense surface waters from 18o data on planktonic foraminifera and intervals of moraine building copyright 2009 john wiley sons ltd

magnetization of polar ice a measurement of terrestrial dust and extraterrestrial fallout abstract laboratory induced remanent magnetization of polar ice constitutes a measurement of the magnetization carried by the ferromagnetic dust particles in the ice this non destructive technique provides a novel kind of information on the dust deposited on the surface of polar ice sheets measurements made on ice samples from greenland north grip ice core and antarctica vostok and epica dome c ice cores allowed the recognition of a fraction of magnetic minerals in ice whose concentration and magnetic properties are directly related to that of insoluble dust the source of this fraction of magnetic minerals thus appears closely related to terrestrial dust transport and deposition and its magnetic properties are informative of the dust provenance areas the rock magnetic properties of the dust may reflect distinct changes of dust source areas from glacial to interglacial periods in agreement with and adding further information to the isotopic 87 sr 86 sr and 143 nd 144 nd analyses a second magnetic fraction consists of particles of nanometric size which are superparamagnetic at freezer temperature and whose concentration is independent of the mass of aerosol dust found in the ice the source of these nanometric sized magnetic particles is ascribed to fallout of meteoric smoke and their concentration in ice was found to be compatible with the extraterrestrial fallout inferred from ir concentrations the diameter of the smoke particles as inferred from magnetic measurements is in the range of about 7 20 nm

dust sources in arid and semiarid china and southern mongolia impacts of geomorphological setting and surface materials abstract analysis of the geomorphological settings and surface materials in arid and semiarid china and southern mongolia revealed that the dominant dust sources are gobi deserts and alluvial fans adjacent to gobi deserts in the piedmonts of the kunlun qilian helan and gobi altai mountains these areas have persistent supplies of dust sized particles deposited by intermittent floods from the mountains and fine materials are also generated by weathering and aeolian processes acting on the coarse fractions of gobi surfaces clear spatial differences in mineral types and contents and in the salt contents of surface materials also strongly affected the intensity of dust emissions inconsistencies in monitoring simulation and calculation of dust emissions in previous studies of northern china and mongolia may have been caused by insufficiently detailed considerations of variations in the geomorphological setting where the geomorphological settings in these areas are not considered in sufficient detail deviations arise in the estimation and prediction of dust using current models although the present study did not quantify the persistence and replenishment of dust sources in the study area our conclusions about the importance of geomorphology can improve future studies of dust sources and controlling factors improve assessments of the effects of climate change on dust emissions and facilitate the interpretation of paleoclimate records

the contemporary physical and chemical flux of aeolian dust a synthesis of direct measurements of dust deposition abstract the deposition of aeolian or windblown dust is widely recognized as an important physical and chemical flux to ecosystems dust deposition adds exogenous mineral and organic material to terrestrial surfaces and can be important for the biogeochemical cycling of nutrients there have been many studies that characterize the physical and chemical composition of dust however few studies have synthesized these observations in order to examine patterns geochemical fluxes we have compiled observations of dust deposition rates particle size distributions psd mineralogy and bulk elemental and organic chemistry the rates of dust deposition observed across the globe vary from almost 0 to greater than 450 g m 2 yr 1 sites receiving dust deposition can be partitioned into broad categories based on there distance from dust source regions when compared to global dust models our results suggest some models may underestimate dust deposition rates at the regional and local scales the distance from the source region that dust is deposited also influences the particle size distributions mineralogy and chemical composition of dust however more consistent dust sampling and geochemical analyses are needed to better constrain these spatial patterns on average the concentrations of most major elements si al fe mg ca k in aeolian dust tend to be similar 20 to the composition of the upper continental crust ucc but there is substantial variability from sample to sample in contrast some elements tend to be depleted na or enriched ti in dust likely as a result of soil weathering processes prior to dust emissions trace elements especially heavy metals are consistently enriched in dust relative to the ucc ecologically important nutrients such as n and p are also present in dust deposition the geochemical flux attributable to dust deposition can be substantial in ecosystems located proximal to dust source regions we calculate estimates of elemental flux rates based on the average chemical composition of aeolian dust and varying rates of deposition these estimated flux rates are useful as a rough gauge of the degree to which dust deposition may influence biogeochemical cycling in terrestrial ecosystems and should be utilized to better constrain deposition estimates of global dust models

possible deposit of soil dust from the 1930 s u s dust bowl identified in greenland ice 1 we have identified a dust storm deposit in the gisp2 ice core that most likely originated from the great plains region of the united states during the 1930 s dust bowl era these results indicate that the central u s can be a significant source of dust to the greenland ice sheet especially when the source area is affected by intense drought conditions

using mg isotope ratios to trace cenozoic weathering changes a case study from the chinese loess plateau abstract the magnesium isotope system is a useful tracer of weathering processes due to its sensitivity to secondary mineral formation we present elemental and isotopic data in bulk loess and paleosol sediments from the luochuan profile in the chinese loess plateau clp due to a relatively constant pre weathering mineralogy changes in the sediment chemistry with depth can be interpreted to reflect changes in weathering processes that are ultimately controlled by climate we find that the luochuan sediments are all enriched in light mg relative to the upper continental crust ucc 0 22 the isotopically light signature is a result of three way mixing between mg sourced from silicate calcite and dolomite changes in 26 mg between loess and paleosol reflect the higher weathering intensities during pedogenesis and corresponding loss of easily leachable calcite enriched in light mg isotopes from the loess layers this is confirmed by the results of a simple leaching procedure in which the leachate phase contains high ca concentrations and isotopically light 26 mg values of up to 2 any isotopic fractionation of mg imparted by isotopically heavy clay mineral formation appears to be insignificant and is obscured by the presence of detrital dolomite that is resistant to acid leaching and is isotopically light the isotopic composition of mg at luochuan broadly follows the magnetic susceptibility record in that loess layers are relatively isotopically light and have lower magnetic susceptibilities than their adjacent paleosol as such the changes in 26 mg values with depth do correspond to changes in chemical weathering however the driving factor behind these changing 26 mg values is carbonate preservation which in itself is not a highly sensitive paleoclimate proxy from a global perspective the 26 mg value of luochuan loess is similar to other loess sediments which are often isotopically light relative to the ucc we have recalculated the average 26 mg value of global loess sediments to be 0 58 1 18 this reflects the fact that 26 mg values in loess are highly heterogeneous and are generally enriched in 24 mg compared to typical ucc rocks due to preservation of high amounts of isotopically light carbonate minerals for this reason loess sediments cannot be used to approximate the isotopic composition of mg in the earth s crust

multiple sources supply eolian mineral dust to the atlantic sector of coastal antarctica evidence from recent snow layers at the top of berkner island ice sheet the sr and nd isotopic composition of dust extracted from recent snow layers at the top of berkner island ice sheet located within the filchner ronne ice shelf at the southern end of the weddell sea enables us for the first time to document dust provenance in antarctica outside the east antarctic plateau eap where all previous studies based on isotopic fingerprinting were carried out berkner dust displays an overall crust like isotopic signature characterized by more radiogenic 87sr 86sr and much less radiogenic 143nd 144nd compared to dust deposited on the eap during glacial periods differences with eap interglacial dust are not as marked but still significant indicating that present day berkner dust provenance is distinct at least to some extent from that of the dust reaching the eap the fourteen snow pit sub seasonal samples that were obtained span a two year period 2002 2003 and their dust sr and nd isotopic composition reveals that multiple sources are at play over a yearly time period southern south america patagonia in particular likely accounts for part of the observed spring summer dust deposition maxima when isotopic composition is shifted towards younger isotopic signatures in the spring possible additional inputs from australian sources would also be supported by the data most of the year however the measured isotopic signatures would be best explained by a sustained background supply from putative local sources in east antarctica which carry old crust like isotopic fingerprints whether the restricted east antarctic ice free areas produce sufficient eolian material has yet to be substantiated however the fact that large 5 mu m particles represent a significant fraction of the samples throughout the entire time series supports scenarios that involve contributions from proximal sources either in patagonia and or antarctica possibly including snow free areas in the antarctic peninsula and other areas as well this also indicates that additional dust transport which does not reach the eap must occur at low tropospheric levels to this coastal sector of antarctica

geochemical and magnetic characteristics of aeolian transported materials under different near surface wind fields an experimental study by combining field investigations field sampling wind tunnel experiments and laboratory measurements the relationships between near surface winds and the geochemical and magnetic characteristics of windtransported materials were statistically analyzed our study was conducted using bulk surface samples from a major potential dust source area in central asia the ala shan plateau under near surface wind velocities ranging from 8 to 22 m s the coefficients of variation ranged between 1 6 and 14 9 for chi if 1 4 and 11 0 for chi arm and 0 7 and 123 for sirm of the transported materials for the 26 elements and oxides investigated the coefficients of variation of ti cr as zr ce pb and cu in the samples were greater than 10 no consistent patterns were found between magnetic characteristics and elemental and iron oxide concentrations as a function of variations in near surface wind velocities in potential dust source areas under near surface wind velocities there are variations in the relationships between magnetic and geochemical characteristics in the fine fractions of transported materials with different particle sizes given the wide variation in magnetic and geochemical characteristics of aeolian transported materials under different near surface winds their use as proxies for past climate reconstruction must be carefully appraised c 2015 elsevier b v all rights reserved

using nd sr isotopes and rare earth elements to study sediment provenance of the modern radial sand ridges in the southwestern yellow sea abstract the radial sand ridges rsrs in the southwestern yellow sea off the jiangsu coast east china have been intensively studied at least since 1975 despite decades of studies the provenance of the rsr sediments remains uncertain in this study the nd sr isotopic and ree geochemical compositions of residual sediments i e the acid insoluble fractions were investigated to determine the provenance of the rsr sediments the nd isotopic composition paas normalized ree patterns and characteristic parameters e g sm nd la sm n gd yb n were merely associated with source rocks but not with particle sorting while the sr isotopic composition and ree contents of residual sediments were affected by particle sorting in addition to source rocks the onshore rsr sediments originated mainly from mixing of the fine grained sediments from various parts of the offshore rsr in terms of ree geochemical and isotopic analyses isotopic and ree geochemical comparison further reveals that the rsrs off the jiangsu coast were fed chiefly by the dispersal of surface sediments from the yangtze river mouth surface sediments from the yangtze river mouth were directly dispersed to the rsrs along the jiangsu coast and significantly affected the seaward part of the offshore rsr and the old yellow river delta area by a northward branch of the changjiang diluted freshwater plume only minor quantities of surface sediments from the modern yellow river mouth were introduced into the rsrs by the jiangsu coastal current and mainly contaminated the landward part of the offshore rsr area our findings highlighted the potential of the nd isotopes with ree geochemistry to trace the provenance of coastal sediments

asian dustfall in the st elias mountains yukon canada in april 2001 a major atmospheric dustfall event occurred in the st elias mountains yukon territory canada field samples were collected and analyzed for particle size mineralogy chemical composition and sr nd and pb isotopes dusts found above 3000 m had their source in the gobi desert region of northern china and inner mongolia and were transported to the yukon following a series of major dust storms that took place in early april dusts found below 3000 m had local yukon or mixed source s the asian dusts had a modal volume diameter of 4 m typical of far traveled mineral aerosols however larger 10 m particles were also found at 5000 m suggesting a very rapid trans pacific transport in the mid troposphere we estimate that the april 2001 event deposited from 5500 to 6335 tons of dust over an area of 21 000 km2 in the southwestern yukon most of which probably fell within a week our findings are consistent with instrumental observations and model simulations of the april 2001 event while the dust cloud was reportedly mixed with volatile pollutants from asia we found no evidence of metal pollution associated with the dustfall in the yukon our findings contribute to clarify the dynamics and the geochemical impact of asian dust long range transport events and to better estimate eolian fluxes of dustborne elements e g fe to the ocean associated with such events they may also assist in identifying past asian dust events in ice cores drilled from the st elias mountains icefields to develop a long term record of their frequency magnitude and source s

clay sized hf nd sr isotopic composition of mongolian dust as a fingerprint for regional to hemispherical transport hf nd sr isotopic fingerprinting has been employed as a powerful method for distinguishing dust sources however the hf and sr isotopic compositions of dust are highly dependent on particle size to accurately identify dust provenance here we compare the hf nd sr isotopic compositions of clay sized fractions from dust sources the mongolian plateau to sinks beijing and greenland our results document that clay sized hf nd sr isotopic compositions of mongolian dust are controlled by two isotopic geochemical provinces southern mongolian gobi smg and northern mongolian plateau nmp our data indicate that the smg is potentially an important dust source to the loess in beijing and hulun buir and could be a contributing source of dust to greenland whereas the nmp contributes little dust to the chinese loess and the greenland furthermore we demonstrate that the deserts of northwest china are one of the main dust contributors to beijing and greenland but not to hulun buir

a change in seasonality in greenland during a dansgaard oeschger warming a new sub seasonal chemical record is presented from the north greenland icecore project northgrip ice core during the onset of one of the longest and strongest interstadials of the last glacial period dansgaard oeschger event 8 approximately 38 000 years ago this is the first time that a record of such resolution has been achieved over several metres of deep glacial ice and provides a unique opportunity for using additional parameters to carry out accurate dating using annual layer counting the very high resolution chemical data were used to assess the phasing of various ions and determine changes in the seasonal strength of chemical deposition and the shape of the seasonal cycle the study shows that a change in seasonality accompanied the dramatic warming transition from stadial to interstadial conditions in greenland thickness due to the exceptionally small sample size a new cutting method using a microtome device and a low volume ion chromatography method was developed the section of ice used in this study was from the outer most part of the ice core the outer surfaces were removed using a bandsaw to prevent contamination from drilling fluid and handling a sledge microtome was then used to cut 2 mm samples using several passes of the blade to cut a succession of 40 mm shavings with no ice loss that were placed in clean coulter accuvettes for melting and then transferred into clean ion chromatography auto sampler vials for analysis powder free gloves and protective clothing were worn throughout to minimize contamination ion chromatography ic was used to determine five anions chloride cl fluoride f methanesulphonate msa nitrate no3 and sulphate so4 2 the system used was a reagent free dionex ics 2500 with a 2 mm column and a 250 ml sample loop a potassium hydroxide eluent generator cartridge egc oh was used to reduce operational errors and contamination associated with eluent preparation the flow was set to 0 25 ml min 1 with an isocratic elution of 23 mm koh four cations calcium ca 2 potassium k sodium na and magnesium mg were analyzed using a reagent free dionex ic 2000 3 mm column and 250 ml sample loop the cation system is equipped with an msa eluent generator cartridge and the method followed set the flow to 0 5 ml min 1 with an isocratic elution of 20 mm msa a sequential flow method was used to analyze both anions and cations from the same sample vial using a dionex as50 auto sampler thus minimizing sample volume requirements the sample and the anion eluent are passed from the ics 2500 system into the ic 2000 system tests of this method were made using frozen ultra pure water to show that the blanks were negligible 5 of glacial concentration levels for all ions thomas 2006

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

the chronological position of the lohne soil in the nussloch loess section re evaluation for a european loess marker horizon abstract the loess section of nussloch in southwestern germany is a key profile for the reconstruction of the terrestrial palaeo environment of central europe at the time of the last glacial and interglacial recently the significance of the site for palaeo environmental and geoarchaeological research increased additionally with the discovery of unique palaeolithic cultural remains from anatomically and culturally modern humans that invaded southwestern germany during the weichselian wurmian pleniglacial period at nussloch a chrono stratigraphical key position is taken by a middle pleniglacial cambisol remain which under the designation lohne soil serves as an important pedostratigraphic marker horizon for the greater area repeatedly greenland interstadial gis 8 was suggested as a likely period of soil formation for the lohne soil this interpretation is yet not justified on the basis of published chronometric data critical assessment of the data points to a later period of soil formation likely during gis7 to gis5 this conclusion is supported by a new set of radiocarbon ages for the nussloch site which are presented here for the first time consequences of a revised chronology for correlations of pleniglacial cryosols below and above the lohne soil with greenland interstadials are discussed the implications are important for european loess research as the nussloch section serves as a reference base for loess sections throughout europe

six millennia of atmospheric dust deposition in southern south america isla navarino chile to characterize dust deposition in southern south america for the holocene a 542 cm long core from a peat bog in southern chile oreste bog isla navarino was studied peat formation started 11 160 14c yr before present bp the titanium ti concentration in bulk peat combined with dry bulk density and peat accumulation rate were used to calculate the mineral accumulation rate mar in the oreste bog the distribution of calcium ca manganese mn and titanium ti showed that mineral accumulation for the last c 6000 yr was predominantly atmospheric with a record of effectively constant deposition 0 43 0 12 g m2 per yr similarly ti and zirconium zr concentrations in the acid insoluble ash aia were also effectively constant and agreed well with the mar for the last six millennia except at c 4200 cal yr bp where zr was enriched relative to ti here scanning electron microscope sem micrographs showed that the aia was dominated by volcanic particles 20 40 m with the mt burney

antarctic dome c ice core dust at 18 k y b p isotopic constraints on origins we have determined the source area from which dusts from the last glacial maximum lgm section of the dome c ice core were derived by comparing their strontium and neodymium isotopic ratios with those of samples from potential source areas the87sr 86sr and143nd 144nd isotope ratios of the dusts deposited 18 k y b p at the east antarctic dome c site were compared with potential antarctic australian southern african and south american sources the isotope ratios clearly define the patagonian provenance of the dust with the other potential source areas being at most minor contributors contributions by volcanic ash and tephra to the dust sample were also determined to be minimal based on the patterns of rare earth elements knowing the source of the dusts places constraints on the aeolian trajectory by which it was transported to antarctica and this serves as a test of the simulation of southern hemispheric circulation by atmospheric global circulation models during the lgm

the application of neodymium isotope as a chronostratigraphic tool in north pacific sediments it has been suggested that dust generation was closely linked to the development of global ice sheets and or cooling this feature has allowed asian dust to be a potential chronostratigraphic tool in north pacific ocean npo sediments the orbital scale age control in npo sediments is usually established by adjusting the benthic foraminiferal 18o to the global 18o stack lr04 however it would become difficult if the sediments did not contain enough foraminifera this study investigates sr and nd isotopes trace elements mineralogy and grain size of the operationally defined aeolian dust oded extracted from the sediments recovered at ocean drilling program odp site 1209b on the shatsky rise in the npo covering the past five glacial interglacial cycles the geochemical results show that the oded at site 1209b is actually a mixture of asian dust and volcanic ash the variation of nd isotope mimics the cycles of glacial interglacial ice sheets as revealed by the global benthic foraminifera s oxygen isotope stack lr04 over the past 500 ka the low high nd values corresponded with the cool warm periods we propose that nd variation reflects the evolving aeolian dust in site 1209 sediments the excellent agreement between nd values at site 1209b and lr04 stack over the past 500 ka allows establishing the orbital timescale age control by tuning nd to the lr04 curve we thus propose that nd isotope provides a chronostratigraphic technique in npo sediments especially for sediments with a limited amount of foraminifera

the δ18o record along the greenland ice core project deep ice core and the problem of possible eemian climatic instability over 70 000 samples from the 3029 m long greenland ice core project grip ice core drilled on the top of the greenland ice sheet summit have been analyzed for 8o a highly detailed and continuous 8o profile has thus been obtained and is discussed in terms of past temperatures in greenland we also discuss a three core stacked annual 8o profile for the past 917 years the short term 50 years variability of the annual 8o signal is found to be 1 in the holocene and estimates for the coldest parts of the last glacial are 3 or higher these data also provide insights into possible disturbances of the stratigraphic layering in the core which seems to be sound down to the onset of the eemian spectral analysis of highly detailed sequences of the profile helps determine the smoothing of the 8o signal which for the holocene ice is found to be considerably stronger than expected we suggest this is due to a process involving diffusion of water molecules along crystal boundaries in the recrystallizing ice matrix deconvolution techniques were employed for restoring with great confidence the highly attenuated annual 8o signal in the holocene we confirm earlier findings of dramatic temperature changes in greenland during the last glacial cycle abrupt and strong climatic shifts are also found within the eem sangamon interglaciation which is normally recorded as a period of warm and stable climate in lower latitudes the stratigraphic continuity of the eemian layers is consequently discussed in section 3 of this paper in terms of all pertinent data which we are not able to reconcile

westward pacific drift and the tectonics of eastern asia abstract the tectonics of southeast asia is attributed to the flow of mantle material away from a region of accumulation in the mantle at the west pacific margin the accumulation is dynamically maintained by the continuous introduction of material from the east in the form of the westward drifting pacific plate the region bounded on the north by southern siberia and on the south by southern indonesia is experiencing westward displacement as a result of slow flow in the mantle the displacement is fastest in low latitudes resulting in the westward embayment of the equatorial west pacific margin besides the westward displacement of sundaland in the fashion described by powell and johnson 1980 the model calls for the encroachment of southeast asia upon northern burma and india the geoidal features upon which the model is based are attributed to mantle mass anomalies rather than to core mantle topography the pressure gradient associated with the western slope of the west pacific geoidal high results in the flow of mantle material in that direction

continuous dust concentration profile of pre holocene ice from the greenland ice sheet project 2 ice core dust stadials interstadials and the eemian in this paper we present and discuss the pre holocene dust profile of the greenland ice sheet project 2 gisp2 ice core retrieved from central greenland measured using laser light scattering lls from ice and compare it with the electrical conductivity method and oxygen isotope profiles we describe how we dated the pre holocene ice using the annual dust peaks observed with lls starting from the accepted chronology to 2250 m and obtained a chronology in substantial accord with the gas age dating of the ice we also show that the gisp2 ice core penetrated the eemian and that a record of a 10 2 kyr penultimate glaciation is present in the gisp2 core

sub millennial variability of asian monsoon intensity during the early mis 3 and its analogue to the ice age terminations abstract although the initiation and continuation of orbital and millennial climate transitions were reported to be roughly similar little is yet known about the extent to which their sequences of climate events are linked together in the same physical processes here we present a stalagmite isotope record from wulu cave southwestern china based on 1200 oxygen isotope data and 15 230 th ages registering a detailed history of the asian monsoon am from 61 3 to 50 5 ka bp with an average resolution of 12 yr two replicated high resolution calcite 18 o profiles show four millennial scale strong summer monsoon events analogous in timing and structure to chinese interstadials a 17 a 14 cis a 17 a 14 as recorded elsewhere in china and greenland interstadials 17 14 gis 17 14 these events exhibit two distinct phases consistent with multi decadal centennial shifts in greenland temperature and storminess this relationship reveals a tight coupling between high and low latitude climates at sub millennial scales implying a role for westerly winds in linking greenland temperature and the am around the marine isotope stage mis 4 3 boundary successive am events resemble but in higher frequency structure of the bolling younger dryas yd surrounding termination i along with evidence from similar shifts in bipolar temperature and atmospheric ch 4 we suggest that the recurrence of similar climate structure worldwide is likely caused by changes in atlantic meridional overturning circulation amoc at various timescales under thresholds of global ice volume boundaries as predicted by the bipolar seesaw model

delineation of carbonate dust aluminous dust and sea salt deposition in a greenland glaciochemical array using positive matrix factorization 1 high resolution trace element records from polar ice cores are fundamental to identifying spatial and temporal variability in dust and sea salt aerosols here we developed high temporal resolution glaciochemical records over recent centuries from an array of seven recently collected greenland ice cores positive matrix factorization pmf was used to assess apportionment of trace elements between three unique sources which were identified as proxies of carbonate dust aluminous dust and sea salt the three pmf factors agree well with literature values and represent the first time carbonate and aluminous dust sources have been quantifiably differentiated using high resolution glaciochemistry the concentrations of all three sources varied with ice core site however the large array of ice cores provided a regional scale understanding of the sources and magnitude of dust and sea salt impurities deposited on the greenland ice sheet at the regional level all three sources varied on seasonal annual and multiyear timescales the seasonal deposition of sea salt impurities reached a maximum in the winter followed by spring peaks of carbonate and aluminous dust over the 331 year composite record only aluminous dust exhibited a long term increasing trend that peaked in the 1930s and was followed by a 20 decline in recent decades

microparticle concentration variations linked with climatic change evidence from polar ice cores the microparticle concentrations in three deep ice cores reveal a substantial increase in the concentration of insoluble particles in the global atmosphere during the latter part of the last major glaciation the ratio of the average particle concentration in the late glacial strata to that in the holocene strata is 6 1 for the core from dome c antarctica 3 1 for the core from byrd station antarctica and 12 1 for the core from camp century greenland whether this temporal correlation between increased atmospheric particle load and the lower surface temperatures is directly causal is unknown however the variations in these two parameters must be satisfactorily resolved in any successful hypothesis that addresses the causes of climatic change

sr isotopic and elemental characteristics of calcites in the chinese deserts implications for eolian sr transport and seawater sr evolution abstract calcite content sr concentrations and isotopes of calcites in the chinese deserts are systematically studied in this paper calcite contents which are calculated according to acid soluble ca contents in the deserts are generally higher in the sandy deserts than in the sandy lands and decrease roughly from northwest to northeast of china acid soluble sr is well correlated with calcite in the chinese deserts implying acid soluble sr comes mainly from the calcite dissolution sr concentrations in calcites calculated on the basis of calcite contents and acid soluble sr concentrations in the deserts have an inverse relation to calcite contents essentially mirroring the degree of sr substitution for ca in the calcite development desert calcites have regional variations in sr isotopic ratios calcite sr isotopic ratios depend on geological settings and chemical weathering the badain jaran and tengger deserts are probably affected by additional factors such as the remote groundwater cycle or overturning of underlying sand deposits only four deserts taklimakan qaidam badain jaran and tengger appear to be potential sources of eolian deposits in the chinese loess plateau clp isotopic signatures of calcite sr and silicate nd further indicate that the tengger desert was not an important source for eolian deposits in the clp eolian calcite was probably enriched due to wind sorting from the potential sources to the clp and suffered weathering leaching after it accumulated in the clp sr isotopic compositions and ca sr molar ratios of calcites are different between the deserts and the lingtai profile due to the integrated effect of wind sorting and weathering leaching it is essential to calculate accurately the 87sr 86sr ratio and sr concentration of eolian calcite entering the oceans according to geochemical data of the chinese deserts because of the importance of the chinese deserts in the global dust cycle the calculated sr concentration and 87sr 86sr ratio of eolian calcite entering the north pacific ocean are 11 75 mol g and 0 71032 respectively the calculated values in this study are close to the recommended values by jacobson jacobson a d 2004 has the atmospheric supply of dissolved calcite dust to seawater influenced the evolution of marine 87sr 86sr ratios over the past 2 5 million years geochem geophys geosyst 5 12 1 9 q12002 doi 10 1029 2004gc000750 using the same model as that of jacobson 2004 the effect of asia dust on the evolution of seawater sr isotopes is evaluated 87sr 86sr seawater increases by 0 3 10 5 if the lower dust flux of 2 34 108 mol sr yr is used in the model suggesting the little effect of asian dust on the seawater sr record in the quaternary the increase in 87sr 86sr seawater is 1 5 10 5 if the higher value of 1 17 109 mol sr yr is used as observed in the quaternary sr record these results further support the suggestions of jacobson 2004

salts in the clay playas of china s arid regions gone with the wind in china s arid regions aeolian salts are transported along with dust aerosols but their contents and the emission rates are poorly understood using samples with undisturbed surfaces and artificially disrupted surfaces to simulate human disturbances such as reclamation planting trampling by animals and other activities the transport rates for windblown material and the salt contents of clay playa surfaces were investigated in a wind tunnel the results showed that under wind velocities ranging from 8 to 22 m s wind erosion rates ranged between 0 009 and 0 066 g m2 s for the undisturbed surfaces and between 0 011 and 0 048 g m2 s for the artificially disrupted playa surfaces although the amount of wind transported material that was captured was too small to allow an analysis of individual salt contents using the available equipment electrical conductivity measurements and correlation analysis revealed mean total salt contents of 9 59 g kg in the transported materials collected above the sealed playa surfaces versus 3 38 g kg in materials from the same surfaces that were artificially cracked after testing the sealed surfaces given the large areas containing clay playas in china s arid regions these results will improve our understanding of aeolian salt transport in arid china and will facilitate interpretation of the sources of aeolian salts

natural vs anthropogenic sources supply aeolian dust to the miaoergou glacier evidence from sr pb isotopes in the eastern tienshan ice core abstract the compositions of sr and pb isotopes in the soluble and insoluble dust in six samples from the miaoergou ice core in eastern tienshan china were measured the six samples were dated from top to bottom as follows 2000 ad 1991 ad 1983 ad 1977 ad 1962 ad and 1958 ad the 87sr 86sr ratios in the soluble fraction ranged from 0 709984 to 0 711031 the isotopic ratios of pb in the soluble and insoluble dust were between 17 962 18 182 and 18 198 18 409 for 206pb 207pb 15 540 15 606 and 15 560 15 581 for 208pb 207pb and 37 994 38 173 and 38 179 38 384 for 208pb 204pb respectively these isotopic results for insoluble dust allowed us to document the origins of the dust in the miaoergou glacier in eastern tienshan the major sources of the natural aeolian deposits were the taklamakan and gobi deserts natural and anthropogenic pb sources were assessed using a simple ternary model in which deserts lead ore and coal served as the primary sources of insoluble dust lead ore coal combustion and the use of leaded gasoline in the surrounding area may represent additional anthropogenic sources of soluble dust thus anthropogenic sources could be further investigated by using the dust free soluble fractions the pb concentration and pb isotopic compositions from the high asia ice cores provided distinct evidence of the positive influences of anthropogenic factors associated with industrial development and the prevailing atmospheric circulation patterns in these regions

variations in trace element including rare earth element concentrations with grain sizes in loess and their implications for tracing the provenance of eolian deposits the concentrations of rare earth elements rees and other 28 trace elements were determined in seven grain size fractions from four loess samples collected from the tibetan plateau the sichuan basin and the chinese loess plateau the results indicate that concentrations of rees except for heavy rare earth elements hrees are almost grain size independent however rees show clear fractionation with grain size middle rare earth element mree depletion increases with decreasing grain size whereas hree enrichment increases with decreasing grain size excluding rees and y most of the other trace element concentrations tend to increase with decreasing grain sizes the trace element geochemistry indicates that the potential sources of eolian deposits from the sichuan basin the chinese loess plateau and the tibetan plateau differ from one another this comparative study confirmed that the eolian materials from the asian continent are the source of the terrigenous component of the central north pacific sediments and the loess from the chinese loess plateau could represent the average composition of eolian dust from the asian continent in contrast the eolian deposits in the sichuan basin and in the tibetan plateau are mainly of local origin with short distance eolian transport

grain size in sediments from lake sugan a possible linkage to dust storm events at the northern margin of the qinghai tibetan plateau samples of surface deposits in the lake sugan catchment as well as surface lake sediments eolian materials occulted in the lake ice cover and airborne dust were collected for grain size analysis the results show that the coarse fraction of the lake sediments could be transported by ambient winds and to a lesser extent by river flow in the study area sediment cores were retrieved from lake sugan in december 2000 and 210pb and 137cs dating and grain size analyses were performed on these samples 210pb ages and the volume percentage of the fraction of lake sediments 63 m were used to reconstruct the dust storm history from 1957 to 2000 observational data for dust storm events collected at a local meteorological station largely agrees with the reconstructed trend for the past 44 years suggesting that lake sediments can be employed to trace the dust storm history of the northern qinghai tibetan plateau

isotopic tracing sr nd u and hf of continental and marine aerosols in an 18th century section of the dye 3 ice core greenland determining the sources and pathways of atmospheric mineral dust and marine aerosols remains a difficult problem in order to address this problem the radiogenic isotopic composition of the dust and soluble ice components of greenland ice has been determined and used as a source tracer for mineral dust and marine aerosols sr and nd isotopic composition was measured with a yearly to seasonal resolution on both the bulk dust and soluble fractions of a section of the dye 3 1988 ice core from greenland in the age range of 1786 1793 a d hf isotopic composition was also measured for three of the dust samples as a complementary tracer of dust origin the first direct measurement of hf in paleo atmospheric dust measured nd and sr isotopic composition of the dust corrected for carbonate contributions are compared to literature potential source area psa data 6 e units and are decoupled from dust composition indicating that the nd composition of seawater is preserved in the ice the end of the ice suggests variable mixing of aerosols from arctic sea salts with another more radiogenic source during transport

glacial interglacial change in chlorite concentration from the lingtai section in the chinese loess plateau over the past 1 2 ma and its possible forcing mechanisms high precision concentrations of chlorite minerals from the lingtai section in the chinese loess plateau and the surrounding deserts are presented through a mineral liberation analyzer technique variations in chlorite concentration over the last 0 5 ma display a typical pattern of glacial interglacial changes with its bulk content in loess units approximately twice that in paleosol units this climate driven chlorite change is more pronounced in the fine size fraction 5 20 m of the loess deposits evidence from changes in hornblende and muscovite along the same profile suggests that the glacial interglacial oscillations were likely controlled by changes in atmospheric circulation and shifts in the dust provenance instead of postdepositional weathering a relatively high chlorite content in several deserts near mt qilian compared with the other desert basins suggests that a transport pathway in the west east direction associated with southward shifts of the winter monsoons may play an important role in modulating the chlorite records in addition enhanced saltation and transportation of dust materials is thought to be a main driver of the pronounced changes in the fine size fraction finally we discuss a possible forcing mechanism behind different long term trends between the chlorite and its secondary weathering products we observed here

asian provenance of glacial dust stage 2 in the greenland ice sheet project 2 ice core summit greenland samples of dust from the greenland ice sheet project 2 gisp2 ice core summit greenland dated within marine isotope stage 2 between 23 340 and 26 180 calendar years b p around the time of the coldest local last glacial temperatures have been analyzed to determine their provenance to accomplish this we have compared them with approximately coeval aeolian sediments mostly loesses sampled in possible source areas psas from around the northern hemisphere the 5 m grain size fraction of these samples was analyzed on the basis that it corresponds to the atmospheric dust component of that time and locale which was sufficiently fine grained to be transported over long distances on the basis of comparison of the clay mineralogy and sr nd and pb isotope composition with ice dust and psas and assuming that we have sampled the most important psas we have determined that the probable source area of these gisp2 dusts was in eastern asia the dust was not derived from either the midcontinental united states or the sahara two more proximal areas that have been suggested as potential sources based on atmospheric circulation modeling except for a brief period during an interstadial when dust transport was exceptionally low for glacial times and had a mineralogical composition indicative of a slightly more southern provenance the source area of the dust did not change significantly during times of variably higher fluxes of dust with larger mean grain size or lower fluxes of dust with smaller mean grain size this includes the high dust period that correlates with the heinrich 2 period of major iceberg discharge into the north atlantic variable wind strengths must therefore be invoked to account for these abrupt and significant changes in dust flux and grain size

two possible source regions for central greenland last glacial dust dust in greenland ice cores is used to reconstruct the activity of dust emitting regions and atmospheric circulation however the source of dust material to greenland over the last glacial period is the subject of considerable uncertainty here we use new clay mineral and 10 m sr nd isotopic data from a range of northern hemisphere loess deposits in possible source regions alongside existing isotopic data to show that these methods cannot discriminate between two competing hypothetical origins for greenland dust an east asian and or central european source in contrast hf isotopes 10 m fraction of loess samples show considerable differences between the potential source regions we attribute this to a first order clay mineralogy dependence of hf isotopic signatures in the finest silt clay fractions due to absence of zircons as zircons would also be absent in greenland dust this provides a new way to discriminate between hypotheses for greenland dust sources

evolution of the arid climate in high asia since 1 ma evidence from loess deposits on the surface and rims of the tibetan plateau the formation and development of the arid climate in high asia remain controversial this is largely because of the scarcity of continuous high resolution geological records from the asian interior region thick loess sequences deposited on the surface of the tibetan plateau and its rims provide great potential to reconstruct a high resolution history of the formation and evolution of high asia arid climate based on detailed investigations of the grain size and carbonate content of representative loess sequences in high asia a persistent drying of high asia occurred in the past 1 ma and two major rapid drying events occurred at about 0 9 0 8 ma and 0 5 ma persistent and rapid stepwise uplifts of the tibetan plateau since the mid pleistocene might play a dominant role in the drying of high asia although the mid pleistocene global cooling may partially contribute to the event

quartz and k feldspar luminescence dating of a marine isotope stage 5 megalake in the juyanze basin central gobi desert china abstract the juyanze basin in the central gobi desert of china contains one of three terminal lakes of the heihe river the second largest inland river in china the paleoenvironmental record of the region is important since it is a significant global dust source region in this study a newly developed post infrared ir stimulated luminescence irsl pirir dating technique together with traditional quartz optically stimulated luminescence osl dating was applied to shoreline and deep water sediments obtained from a buried shoreline at 927 m in the ejina basin 33 m above the basin floor the reliability of k feldspar pirir dating was confirmed by internal checks of a dose recovery test an anomalous fading test and a residual dose test internal checks of the quartz osl dating and comparison to k feldspar pirir ages indicate that the single aliquot regenerative dose protocol was reliable for samples from the shoreline but that quartz ages older than 60 ka may be underestimated our results indicate that three lacustrine sequences separated by erosional unconformities and eolian deposition span a period from 122 to 73 ka covering most of marine isotope stage mis 5 at a depth of 33 m 927 m elevation the paleolake covered more than 1800 km2 in the juyanze basin during this period but fluctuated frequently whether or not this mis 5 lake filled the entire ejina basin or merely overflowed the juyanze basin to partially fill the other ejina sub basins remains unknown regardless the presence of such a large mis 5 paleolake in the ejina basin suggests its lake history closely matches those from other closed basin drainages originating in the qilian mountains we suggest that the high stands appearing during mis 5 in the juyanze basin likely were a response to moist climatic conditions during the last interglacial period

nd and sr isotopic characteristics of chinese deserts implications for the provenances of asian dust silicate nd sr isotopes of the fine grained fractions of the 10 major deserts and sandy lands in north china and the loess in chinese loess plateau were systematically investigated wide ranges in nd sr isotopic compositions have been observed the results of the 7 0 b the deserts on the northern margin of tibetan plateau with end 0 ranging from 11 9 to 7 4 and c the deserts on the ordos plateau with the lowest end 0 11 5 the distribution of the threes isotopic regions is controlled by the tectonic setting in north china which implies that the materials of the deserts are derived from the locally eroded rocks from the surrounding mountains and the nd sr isotopic signatures of these deserts could be quit stable over the past million years on the sub tectonic time scales if there is any desert at those times the nd sr isotopic compositions of the loess are mostly close to those of the deserts in isotopic region b suggesting that the main source regions of the last glacial loess in the chinese loess plateau are badain jaran desert tengger desert and qaidam desert also the comparison between the nd sr isotopes of the 5 lm silicate fractions of the deserts and the ancient dust falls in the north pacific and greenland show that the asian end members of these dust falls are derived most from the deserts in the isotopic region b and less from those in the isotopic region c

contemporary glacigenic inputs to the dust cycle the importance of glacigenic dust in the earth s system during glacial periods is widely acknowledged under contemporary conditions the world s largest dust sources are in low lying hot arid regions and this is where most aeolian research is focused however the processes of dust production and emissions are still operating in cold climate regions particularly in proglacial areas this paper assesses current understanding of the relationship between glacierised landscapes and dust emissions and inputs to the global dust cycle it focuses on how elements in the glacial and aeolian geomorphic sub systems interact to determine the magnitude frequency and timing of aeolian dust emissions and on feedback mechanisms between the systems where they have been measured dust emission intensity and deposition rates in glacierised catchments are very high in some cases far exceeding those in lower latitudes however few studies span long time scales the impact of future glacier retreat on the balance between sediment supply availability and aeolian transport capacity and implications for glacigenic dust emissions is also considered this balance depends on relative spatial and temporal changes in meltwater suspended sediment concentration and wind strengths which promote dust emissions and patterns and rates of soil development and vegetation succession on recently deglaciated terrain which protect sediments from deflation retreat of the antarctic ice sheet could mean that in future glacigenic contributions to the dust cycle exceed those of non glacigenic sources in the southern hemisphere copyright 2012 john wiley sons ltd

seasonal variability in the input of lead barium and indium to law dome antarctica lead pb isotopic compositions and concentrations and barium ba and indium in concentrations have been determined at monthly resolution in five law dome coastal eastern antarctica ice core sections dated from 1757 ad to 1898 ad natural background pb concentrations in 1757 ad average 0 2 pg g 1 and can be attributed to mineral dust and volcanic emissions with 206pb 207pb ratios reaching up to 1 266 0 002 from 1887 ad to 1898 ad pb concentrations reached 5 pg g 1 and 206pb 207pb ratios decreased to 1 058 0 001 as a result of additional inputs of pb from anthropogenic sources seasonal variability in the late 1880s has been investigated by decoupling volcanic pb from the total measured pb concentrations revealing spring and autumn maxima and consistent winter minima in anthropogenic pb and mineral dust ba concentrations we link this variability to the annual cycle in the position and strength of the antarctic circumpolar trough and the southern ocean westerly winds to the north of the trough region during the autumn and spring seasons these systems increase in strength transporting more impurity laden air from the southern hemisphere continental regions to eastern antarctica and law dome as this pb is isotopically identical to that emitted from south eastern australia broken hill port pirie this implies a relatively direct air trajectory pathway from southern australia to law dome eastern antarctica

sr and nd isotopic composition of dust in dunde ice core northern china implications for source tracing and use as an analogue of long range transported asian dust abstract this study presents the sr and nd isotopic composition of dust from a shallow dunde ice core 38 06 n 96 24 e 5325 m a s l northern china in order to trace its source regions and the provenance of long range transported lrt asian dust dunde dust samples show similar sr 87 sr 86 sr averages 0 719982 and varies between 0 715220 and 0 721874 and nd e nd 0 averages 10 6 and ranges from 11 1 to 9 9 isotopic composition to desert sand from taklimakan and qaidam revealing that the tarim and qaidam basins are the most possible source areas for dunde dust while the contribution from badain jaran and tengger seems very small or unlikely our results indicate that materials from taklimakan can be entrained from the tarim basin and transported to qilian shan by westerlies under the present climate the sr nd isotopic composition of dunde dust which is a good analogue for the long range transported asian dust resembles that of north pacific and greenland dust indicating that the important provenance of end members of the asian dust seems to be taklimakan on a regional scale

regional variability of ice core dust composition and provenance in greenland 1 mineralogical and isotopic composition sr and nd of six dust samples obtained from six widely spread ice coring sites in greenland were analyzed in order to investigate the regional geographic variability of dust provenance we show that long range transport from eastern asian deserts provides mineral dust with essentially the same composition to all elevated interior sites dye 3 site a grip and northgrip while most material deposited at sites located closer to the edge and at lower altitude hans tausen and renland derives from proximal source regions no contribution from other sources is apparent at any of the interior sites from the mineralogical and isotopic composition of the dust samples each of which represents several decades of dust deposition during the 17th 18th century these results provide additional evidence that african and north american deserts do not play a significant role in the dust deposited over greenland which has implications for ice core record interpretation and atmospheric dust transport model validation

evidence for early 12 7 ma eolian dust impact on river chemistry in the northeastern tibetan plateau abstract as one of the largest dust sources on the earth s surface dryland in central asia gives rise to thick eolian deposits over east asia e g the chinese loess plateau clp and significantly influences the regional hydrochemistry in the downwind drainage areas however the formation of thick eolian dust deposits requires not only climatic prerequisites for dust emission and transport but also climatic and topographic conditions favourable for deposition and accumulation the scarcity of widespread eolian deposition around the clp before 7 8 ma hinders a full understanding of the processes and mechanisms of central asian aridification the deposition of eolian dust also impacts the hydrogeochemistry of fluvial systems and the precipitation of authigenic phases in continental sedimentary systems could be an archive for studying eolian dust dynamics when pure eolian deposits are scarce here we present the ca mg sr concentrations and 87sr 86sr isotope compositions of bulk carbonates in a new fluvial sequence 12 7 4 8 ma of the xining basin the mg ca and sr ca ratios of the carbonate describe a power law relationship with a power coefficient of 0 8 lower than the coefficient characteristic of prior calcite precipitation pcp an input of eolian dust with the dissolution of mg rich carbonate is likely responsible for the deviation from a pure pcp process the bulk carbonates also show a general decrease of 87sr 86sr ratios from 12 7 to 4 8 ma with a transition around 8 6 ma revealed by lower sr mg ratios the comparison of these proxies to a previously reported fluvial section 12 2 5 1 ma in the linxia basin 200 km to the southeast shows that the 87sr 86sr ratios of the bulk carbonates and water soluble salts in the linxia basin are around 0 7098 which is 0 0018 lower than those in the xining basin before 8 6 ma but shows a significant rise between 8 6 and 7 0 ma the two basins share the same range of carbonate 87sr 86sr ratios when sediments are younger than 7 ma for the last 7 myrs the evolution of the 87sr 86sr ratios in bulk carbonates of fluvial sediments and pliocene quaternary eolian deposits found in the xining basin are similar to those in typical eolian red clays loess palaeosol sequences on the clp these results suggest a transition of the hydrochemical regime at 8 6 ma in the linxia basin from a catchment only influenced by the weathering of its bedrock to one significantly impacted by eolian dust input in the xining basin the carbonate elemental and 87sr 86sr ratios are consistent with a hydrochemistry more impacted by the presence of the eolian dust there the dust input occurred earlier at 12 7 ma though it has strengthened since 8 6 ma the eolian dust impact on fluvial systems in the xining basin was much earlier than in the linxia basin and also preceded the initial accumulation of widespread eolian red clays on the clp 7 8 ma suggesting a temporally propagating and spatially stepwise expansion of eolian dust delivery across the asian inland during the late cenozoic

nd sr isotope geochemistry of fine grained sands in the basin type deserts west china implications for the source mechanism and atmospheric transport abstract the basin type deserts of west china are among the greatest dust emission areas in the world mineral dust that is emitted from the deserts is transported and deposited in east central china and even in far east regions this study investigates the nd sr isotopic compositions of fine grained surface sands nd 0 10 9 to 15 and 87 sr 86 sr 0 714 to 0 718 while those of the dune sands from the gurbantunggut desert range from e nd 0 4 5 to 6 and 87 sr 86 sr 0 711 to 0 713 the isotopic compositions of the fine grained surface sands are not spatially uniform within each desert and are controlled by the lithological characteristics of the tectonic units in which the deserts are located the isotopic comparison of the dune sands with other sediments indicates that tectonic denudation and fluvial processes are the main mechanisms of fine particle production of the modern desert sands in terms of isotope analyses and forward trajectory results it is further found that the mineral dust is deposited not only in proximal areas such as the hexi corridor the chinese loess plateau and the tibet qinghai plateau but also in distal regions such as japan the pacific ocean and greenland once it is blown out of the taklimakan desert however the transport and sinks of mineral dust vary with the atmospheric currents

continuous record of microparticle concentration and size distribution in the central greenland ngrip ice core during the last glacial period 1 a novel laser microparticle detector used in conjunction with continuous sample melting has provided a more than 1500 m long record of particle concentration and size distribution of the ngrip ice core covering continuously the period approximately from 9 5 100 kyr before present measurements were at 1 65 m depth resolution corresponding to approximately 35 200 yr particle concentration increased by a factor of 100 in the last glacial maximum lgm compared to the preboreal and sharp variations of concentration occurred synchronously with rapid changes in the 18o temperature proxy the lognormal mode of the volume distribution shows clear systematic variations with smaller modes during warmer climates and coarser modes during colder periods we find 1 7 m diameter during lgm and 1 3 m during the preboreal on timescales below several 100 years and the particle concentration exhibit a certain degree of independence present especially during warm periods when generally is more variable using highly simplifying considerations for atmospheric transport and deposition of particles we infer that 1 the observed changes of in the ice largely reflect changes in the size of airborne particles above the ice sheet and 2 changes of are indicative of changes in long range atmospheric transport time from the observed size changes we estimate shorter transit times by roughly 25 during lgm compared to the preboreal the associated particle concentration increase from more efficient long range transport is estimated to less than one order of magnitude

the influence of near surface winds on the sr isotope composition of aeolian sediments a wind tunnel experiment article we used wind tunnel experiments to simulate the effect of near surface wind velocity on the silicate stron tium sr isotopic compositions of the fractions b10 m in windblown dust using intact surface samples obtained from a potential dust source area in arid northern china our results showed that the 87 sr 86 sr ratios of the silicate fractions in the windblown dust varied with near surface wind speed and with the total amount of the fraction b10 m for the five samples that we analyzed the variances of the 87 sr 86 sr ratio under a range of wind velocities were 0 00014 0 00004 0 00052 0 00151 and 0 00012 in addition although most samples were collected at the same site and were treated in the same way there were still differences in the 87 sr 86 sr ratios with an intersample variance of up to 0 00409 these observations suggest that although

long distance transport of pollen to greenland 1 four pollen traps were recently placed at coastal sites in east and west greenland in order to assess long distance transport of pollen to the arctic domain by identifying potential vegetation source areas associated with air mass pathways we were able to produce the first detailed record of pollen transport from eastern north america to narsarsuaq southern greenland the record is based on observations and on a transport and dispersion model used to calculate back trajectories of the air masses the evidence points to the pollen being transported northward by the air mass over newfoundland and the labrador sea before reaching narsarsuaq at this point the air mass was at an altitude of 3000 m deposition of pollen grains occurred with downward air movements associated with a 0 5 mm h rain the source areas for these pollen grains differ from those of dust and certain other aerosols that reach the summit of the greenland ice sheet the results demonstrate the need for continued maintenance and analysis of the greenland pollen trap data in order to improve our understanding of atmospheric circulation and transport to high northern latitudes

geochemical and magnetic characteristics of fine grained surface sediments in potential dust source areas implications for tracing the provenance of aeolian deposits and associated palaeoclimatic change in east asia abstract we investigated the geochemical and magnetic characteristics of fine grained surface sediments fractions

esr signal intensity and crystallinity of quartz from gobi and sandy deserts in east asia and implication for tracing asian dust provenance 1 electron spin resonance esr signal intensity and crystallinity index ci of fine 16 m quartz were measured in surface samples from the taklimakan desert in western china the badain juran tengger and mu us deserts in northern china and the gobi desert in southern mongolia to evaluate whether these geophysical parameters can serve as reliable provenance tracers of asian dust the results indicate that spatial variability of both esr signal intensity and ci is evident within the taklimakan deserts and the mongolian gobi but less significant in the three deserts of northern china coarse grained quartz from the mongolian gobi and northern china deserts can be differentiated from the taklimakan desert using the esr signal intensity fine grained quartz originating from three major asian dust sources i e the gobi sandy deserts in western china northern china and southern mongolia can be distinguished effectively using the combination of esr and ci signals our results suggest that esr signal intensity and ci can discriminate the sources of fine grained quartz better than coarse grained quartz providing an effective approach to trace the provenance of fine grained dust deposition on the land and in the ocean

changes in atmospheric circulation and ocean ice cover over the north atlantic during the last 41 000 years high resolution continuous multivariate chemical records from a central greenland ice core provide a sensitive measure of climate change and chemical composition of the atmosphere over the last 41 000 years these chemical series reveal a record of change in the relative size and intensity of the circulation system that transported air masses to greenland defined here as the polar circulation index pci and in the extent of ocean ice cover massive iceberg discharge events previously defined from the marine record are correlated with notable expansions of ocean ice cover and increases in pci during stadials without discharge events ocean ice cover appears to reach some common maximum level the massive aerosol loadings and dramatic variations in ocean ice cover documented in ice cores should be included in climate modeling

a 2000 year dust storm record from lake sugan in the dust source area of arid china 1 arid northwestern china is considered to be a major source of atmospheric dust supply to the northern hemisphere however dust storm evolution and dust emission processes in the past remain unclear due to the scarcity of geologic archives in this region hydrologically closed lakes in dust source areas act as a trap providing the opportunity to trace the history of dust emission or eolian activity here we present the results of dust storm proxies and a dust storm history from lake sugan in the qaidam basin a dust source area on the northern qinghai tibetan plateau grain size analyses of the materials deposited during modern dust storms and of the lake surface sediments demonstrate that the coarse component of the lake sediments was transported primarily by ambient winds when dust storms occurred in combination with a sediment chronology generated by counting annual laminations a 2000 year dust storm history was reconstructed on the basis of changes in the coarse component and magnetic susceptibility of the lake sediments frequent and or intensive dust storms occurred during the intervals ad 300 500 ad 1180 1240 and ad 1500 1700 the occurrence of dust storms largely coincided with the strengthening of the siberian high with colder air masses from high latitudes such as during the little ice age frequently encroaching into the dust source areas in northwestern china our results suggest that wind strength plays an important role in dust emissions in arid source areas however dust storms in the late 20th century are most likely associated with disturbance of the ground surface caused by petroleum exploitation in the qaidam basin

horizontal wind erosion flux and potential dust emission in arid and semiarid regions of china a major source area for east asia dust storms abstract arid and semiarid regions of china are important sources of dust for storms that affect east asia and the western pacific ocean however little is known about the process spatial variation and quantity of the emission and transportation of windblown sand dust from such areas in 2009 a large number of passive sand traps were set on different landscape surfaces across the arid and semiarid regions of china to monitor the horizontal wind erosion flux and establish the potential of dust emission the monitoring data suggest that the taklamakan desert has the greatest wind erosion flux the mean wind erosion flux of the marginal sand seas hinterland sand seas gobi type desert and degraded land of oases in this area is 45 07 32 37 31 11 and 19 83 kg day 1 m 2 respectively during the aeolian transport process the mean limit of a suspended load particle size is 0 066 mm aeolian sediment mean grain size and sorting are 0 11 mm and 1 40 respectively and potential pm10 dust emission rate is 0 969 kg day 1 m 2 the qaidam basin and dunhuang areas and the hexi corridor and alax areas also have strong wind erosion flux the mean wind erosion flux for the gobi type deserts in these areas is 11 57 and 39 16 kg day 1 m 2 respectively while for the degraded land of oases it is 14 78 and 12 68 kg day 1 m 2 respectively during the aeolian sediment transport process the mean limit of a suspended load particle size is 0 083 mm aeolian sediment mean grain size and sorting are 0 18 mm and 1 82 respectively and potential pm10 dust emission rate is 1 011 kg day 1 m 2 the mu us sandy land steppes of the northern yinshan mountains hunshandake sandy land and its surrounding steppes and horqin sandy land have the weakest wind erosion flux the mean value of which is 10 53 5 43 2 88 and 1 94 kg day 1 m 2 respectively during the aeolian sediment transport process the mean limit of a suspended load particle size is 0 12 mm aeolian sediment mean grain size and sorting are 0 25 mm and 2 1 respectively and potential pm10 dust emission rate is 0 103 kg day 1 m 2

the significance of gobi desert surfaces for dust emissions in china an experimental study a series of experiments to determine the direct emission of dust sized particles from gobi surfaces by clean wind wind without sand and the potential for aeolian abrasion of gobi surfaces and beds of gravel and mobile sand to produce fine 100 m in diameter and then pm10 by sedimentation was acquired the gobi surface provided most of the emitted fine particles during the initial dust emission processes but subsequently release of the clay coatings of particles by abrasion becomes the dominant source of fine materials under sand laden winds pm10 production rates produced by aeolian abrasion of gobi surfaces ranged between 0 002 and 0 244 of blown materials after removal of sand silt or clay with low resistance to erosion from the gobi surfaces by the wind the pm10 production rates caused by aeolian abrasion were similar to those from gravel and sand beds the results also indicated that after the dust sized particles with low resistance to erosion were removed the production of dust sized particles was unrelated to wind velocity under aeolian processes gobi deserts in this region therefore play a major role in dust emissions from arid and semiarid china

magnetization of greenland ice and its relationship with dust content 1 we estimate the concentration of fine magnetic particles in ice samples from the north greenland ice core project core from the central greenland ice sheet using lowtemperature 77k isothermal remanent magnetization irm analysis and compare it with the mass concentration of aerosol dust samples were taken from six climatic intervals spanning the time from the holocene preboreal back to the last glacial dansgaard oeschger cycle 5 the mean irm intensity of the ice varies by a factor of 3 from glacial to interglacial stages being lower during interglacials the irm acquisition curves of the ice do not quite saturate at the maximum available field of 0 8 t and show a relatively broad coercivity which is compatible with a mixture of maghemite or magnetite and hematite comparison of the irm intensity and total dust mass shows a remarkably good correlation but also reveals a large background magnetization which may be essentially constant over the different climatic stages irm suggests that the dust properties are independent of the background signal and that the dust aerosol has a magnetization within about 30 of pristine loess from the chinese loess plateau which is considered to have the same source in the same east asian deserts as dust in greenland ice ice contamination and the flux of extraterrestrial dust particles were considered in order to explain the origin of the background magnetization nevertheless we could not find a convincing explanation for this signal which represents a considerable part of the irm signal and is the dominant component during interglacial intervals without invoking the presence of undetected dust mass the alternative hypothesis of a varying magnetization of the ice dust at different climatic periods would suggest that different sources of aerosol are active during different climatic periods this however has not proven to be the case so far for studies of the provenance of dust in greenland ice index terms 0305 atmospheric composition and structure aerosols and particles 0345 4801 0399 atmospheric composition and structure general or miscellaneous 0394 atmospheric composition and structure instruments and techniques keywords magnetization irm greenland ice core northgrip aerosol

a search in north greenland for a new ice core drill site a new deep ice core drilling site has been identified in north greenland at 75 12 n 42 30 w 316 km north northwest nnw of the grip drill site on the summit of the ice sheet the ice thickness here is 3085 m the surface elevation is 2919 m the north grip ngrip site is identified so that ice of eemian age 115 130 ka bp calendar years before present is located as far above bedrock as possible and so the thickness of the eemian layer is as great as possible an ice flow model similar to the one used to date the grip ice core is used to simulate the flow along the nnw trending ice ridge surface and bedrock elevations surface accumulation rate distribution and ratio echo sounding along the ridge have been used as model input the surface accumulation rate drops from 0 23 m ice equivalent year 1 at grip to 0 19 m ice equivalent year 1 50 km from grip over the following 300 km the accumulation is relatively constant before is starts decreasing again further north ice thickness up to 3250 m bring the temperature of the basal ice up to the pressure melting point 100 250 km from grip the ngrip site is located 316 km from grip in a region where the bedrock is smooth and the accumulation rate is 0 19 m ice equivalent year 1 the modeled basal ice here has always been a few degrees below the pressure melting point internal radio echo sounding horizons can be traced between the grip and ngrip sites allowing us to date the ice down to 2300 m depth 52 ka bp an ice flow model predicts that the eemian age ice will be located in the depth range 2710 2800 m which is 285 m above the bedrock this is 120 m further above the bedrock and the thickness of the eemian layer of ice is 20 m thicker than at the grip ice core site

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds