holocene dust in east antarctica provenance and variability in time and space in this paper we provide a comprehensive overview of the state of knowledge of dust flux and variability in time and space in different sectors of east antarctica during the holocene by integrati

lead isotopic evidence for an australian source of aeolian dust to antarctica at times over the last 170 000 years abstract systematic analysis of pb sr and nd isotopes of 32 fluvial clay samples 6 km 2 murray darling basin mdb located in semiarid southeastern australia displays similar isotopic values between some mdb clays and dust from several ice core samples from the epica dome c in antarctica close scrutiny of several ratios of the four pb isotopes and in particular 208 pb 207 pb versus 206 pb 207 pb shows that several samples from the darling sub basin of the mdb display similar values for the same isotopes for dome c samples from different ages and more particularly during wet phases in australia marine isotopic stages 5e 3 and 1 the combination of nd and sr isotopic ratios from the same mdb fluvial clays clearly eliminates the murray sub basin and supports the darling sub basin as a potential source of aeolian material to antarctica overall the australian dust supply to antarctica predominantly occurred during interglacial periods the work presented here shows that aerosols generated in southeastern australia can travel to parts of west antarctica and this is supported by atmospheric observations and models in addition evidence of australian dust in antarctic ice cores further implies dust deposition in the southern ocean would have occurred in the past current meteorological observations also imply that the western pacific and indian ocean sector of the southern ocean would frequently receive aeolian dust components originating from southeastern australia

identifying regional dust transport pathways application of kinematic trajectory modelling to a trans tasman case pi kinematic trajectory model is used to investigate potential pathways of dust transport from australia to new zealand historically these have been assumed to follow rather direct west east trajectories spanning 2 to 3 days often resulting in red snow events in the southern alps of new zealand however results from the present study which examined the route taken by air parcels originating in southern australia during dust storms on 24 and 25 may 1994 indicate that trans tasman dust transport trajectories are more diverse than previously thought and display considerable variation during single events these mon divergent pathways tie in more closely with aeolian dust sedimentation patterns identified by ocean coring in the tasman sea and may account for the deposition of australian dust on sub antarctic islands located well south of the australian continent copyright 2000 john wiley sons ltd

greater supply of patagonian sourced detritus and transport by the acc to the atlantic sector of the southern ocean during the last glacial period reconstructing past detrital flux and provenance in the southernocean provides information about changes in source regions associated with climate variations and transport pathways we present a lastglacial maximum lgm to holocene comparison of 230th normalised fluxes combined with sediment provenance data pb nd and sr isotopes from a latitudinal core transect in the eastern atlanticsector of the southernocean odp leg 177 cores we compare the radiogenic isotopic composition ic of detritus in these cores to that of cores proximal to potential source areas we observe a well defined latitudinal holocene gradient in both detrital flux and provenance of sediment high detrital fluxes in the north are associated with terrigenous material derived from southern africa while low detrital fluxes in the south are associated with supply from southern south america west antarctica and the south sandwich islands the data suggest that this well defined holocene gradient in detrital flux and sediment provenance is controlled by the flow of the antarctic circumpolar current acc and the position of its frontal zones the lgm is characterised by 2 to 6 times higher than modern detrital fluxes at most odp leg 177 sites the lgm detrital fluxes do not show a latitudinal trend and suggest a greatersupply of glaciogenic detritussourced from southern south america glacialpatagonian outwash sediments 5 m fraction were analysed and compared to the bulk compositions of the marine sediments the pb ic of the patagonian sediments is very similar to the glacial ic of sediments in the scotia sea and at 49 s latitude in the eastern atlanticsector we propose that the glacial ic of sediments is controlled by increased delivery of patagoniandetritus initially supplied by glaciers and then transported at depth via the acc

the effects of continental margins and water mass circulation on the distribution of dissolved aluminum and manganese in drake passage a total of 232 samples were analyzed for concentrations of dissolved aluminum al and manganese mn in drake passage both al and mn were extremely low similar to 0 3 and 0 1 nm respectively in the surface layer of the middle drake passage most likely due to limited input and biological uptake scavenging elevated al 14 nm and mn 2 nm over the south american continental shelf are related to land run off whereas elevated concentrations 1 nm and 2 nm respectively near the antarctic peninsula are most likely related to sediment re suspension re suspension of sedimentary particles and pore waters influences the distribution of al and mn over the continental slopes on both sides of drake passage the influence of the continental margins and accumulated dust input potentially explains the higher al observed eastward in the atlantic section of the southern ocean in the northern drake passage elevated al similar to 0 8 nm and mn similar to 0 3 nm near the seafloor are most likely the result of bottom sediment re suspension by the relatively strong currents in the deep southern drake passage sediment re suspension associated with the inflow of weddell sea deep water appears to cause elevated al 1 nm and mn similar to 0 4 nm in the deep northern drake passage north atlantic deep water brings in elevated al and southeast pacific deep slope water brings in the signature of pacific hydrothermal vents elevated mn and delta he 3 were correlated in this water layer and are most likely originating from the volcanically active ridges in the pacific ocean

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

glacial interglacial co2 change the iron hypothesis several explanations for the 200 to 280 ppm glacial interglacial change in atmospheric co2 concentrations deal with variations in southern ocean phytoplankton productivity and the related use or nonuse of major plant nutrients an hypothesis is presented herein in which arguments are made that new productivity in today s southern ocean 7 4 1013g yr 1 is limited by iron deficiency and hence the phytoplankton are unable to take advantage of the excess surface nitrate phosphate that if used could result in total southern ocean new production of 2 3 1015 g c yr 1 as a consequence of fe limited new productivity holocene interglacial co2 levels preindustrial are as high as they were during the last interglacial 280 ppm in contrast atmospheric dust fe supplies were 50 times higher during the last glacial maximum lgm because of this fe enrichment phytoplankton growth may have been greatly enhanced larger amounts of upwelled nutrients may have been used and the resulting stimulation of new productivity may have contributed to the lgm drawdown of atmospheric co2 to levels of less than 200 ppm background information and arguments in support of this hypothesis are presented

toward understanding the dust deposition in antarctica during the last glacial maximum sensitivity studies on plausible causes 1 understanding the plausible causes for the observed high dust concentrations in antarctic ice cores during the last glacial maximum lgm is crucial for interpreting the antarctic dust records in the past climates and could provide insights into dust variability in future climates using the geophysical fluid dynamics laboratory gfdl general circulation models we conduct an investigation into the various factors modulating dust emission transport and deposition with a view toward an improved quantification of the lgm dust enhancements in the antarctic ice cores the model simulations show that the expansion of source areas and changes in the antarctic ice accumulation rates together can account for most of the observed increase of dust concentrations in the vostok dome c and taylor dome cores but there is an overestimate of the lgm present ratio in the case of the byrd core the source expansion due to the lowering of sea level yields a factor of 2 3 higher contribution than that due to the reduction of continental vegetation the changes in other climate parameters e g sh precipitation change are estimated to be relatively less important within the context of this sensitivity study while the model simulated lgm surface winds yield a 20 30 reduction rather than an increase in dust deposition in antarctica this research yields insights toward a fundamental understanding of the causes for the significant enhancement of the dust deposition in the antarctic ice cores during the lgm

maximum horizontal stress orientations in the cooper basin australia implications for plate scale tectonics and local stress sources summary borehole breakouts and drilling induced tensile fractures ditfs were interpreted in 61 wells in the cooper basin indicating an average maximum horizontal stress orientation of 101 n a total of 890 borehole breakouts and 608 ditfs were interpreted in the cooper basin the approximately east west maximum horizontal stress orientation is consistent over much of the basin except in the patchawarra trough where maximum horizontal stress rotates to a northwest southeast orientation this rotation in maximum horizontal stress orientation is consistent with in situ stress data to the northwest of the cooper basin the stress field in the cooper basin appears to mark the apex of a major horseshoe shaped rotation in maximum horizontal stress direction across central eastern australia finite element modelling of the in situ stress field of the indo australian plate iap using a range of plate scale tectonic forces is able to match the regional maximum horizontal stress orientation over most of australia reasonably well including the mean east west maximum horizontal stress orientation in the cooper basin however plate boundary scale modelling does not adequately match the horseshoe shaped stress rotation across central eastern australia the average east west maximum horizontal stress orientation in the cooper basin indicates that stresses from tensional forces acting along the tonga kermadec subduction zone are not transmitted into the interior of the australian plate the majority of the tensional forces associated with the tonga kermadec subduction zone are most likely accommodated along the numerous spreading centres within the lau havre backarc basin a number of more localized stress anomalies have also been identified these cannot be explained by plate scale tectonic forces and are possibly a result of geological structure and or density contrasts locally perturbing the stress field

iron and other transition metals in patagonian riverborne and windborne materials geochemical control and transport to the southern south atlantic ocean abstract the bulk of particulate transition metals transported by patagonian rivers shows an upper crustal composition riverine particulate 0 5 n hcl leachable trace metal concentrations are mainly controlled by fe oxides complexation of fe by dissolved organic carbon doc appears to be an important determinant of the phases transporting trace metals in patagonian rivers in contrast aeolian trace elements have a combined crustal and anthropogenic origin aeolian materials have fe mn and al contents similar to that found in regional topsoils however seasonal concentrations of some metals e g co pb cu and zn are much higher than expected from normal crustal weathering and are likely pollutant derived we estimate that patagonian sediments are supplied to the south atlantic shelf in approximately equivalent amounts from the atmosphere 30 10 6 t yr 1 and coastal erosion 40 10 6 t yr 1 with much less coming from the rivers 2 0 10 6 t yr 1 low trace metal riverine fluxes are linked to the low suspended particulate load of patagonian rivers inasmuch most of it is retained in pro glacial lakes as well as in downstream reservoirs based on our estimation of aeolian dust fluxes at the patagonian coastline the high nutrient low chlorophyll sub antarctic south atlantic could receive 1 0 to 4 0 mg m 2 yr 1 of leachable 0 5 n hcl fe past and present volcanic activity in the southern andes through the ejection of tephra must be highlighted as another important source of fe to the south atlantic ocean based on the 1991 hudson volcano eruption it appears that volcanic events can contribute several thousand fold the mass of leachable fe to the ocean as is introduced by annual patagonian dust fallout

glacial interglacial changes of southern hemisphere wind circulation from the geochemistry of south american dust abstract the latitudinal displacement of the southern westerlies and associated climate systems is a key parameter for understanding the variations of southern hemisphere atmospheric circulation during the late quaternary period to increase understanding of past atmospheric circulation and of the paleo environmental conditions associated with continental dust sources we dig deeper into dust provenance in paleo archives of the southern hemisphere we present here a sr nd isotopic and rare earth element study of surface sediments collected along a 4000 km latitudinal band from arid and semi arid terrains in southern south america findings from terrains that served as paleo dust suppliers are compared with modern dust collected from monitoring stations along the same latitudinal band which affords a test on how actual present day aeolian compositions compare to those of the past potential source areas moreover the comparison between past and present day datasets is useful for understanding present day atmospheric circulation armed with a new comprehensive dataset we revise previous interpretations of the provenance of dust trapped in the antarctic ice and sediments deposited in the south atlantic sector of the southern ocean these comparisons support multiple source regions in southern south america that changed with climates the findings reveal that although patagonia plays an important role in contributing dust to the higher latitudes central western argentina and to a lesser extent the southern puna region also emerge as potentially important dust sources during glacial times the southern altiplano appears to be a major contributor during interglacial periods as well we rely in part on an understanding of modern wind dust activities to conclude that the possible presence of southern south america source regions other than patagonia in east antarctic ice is consistent with an overall equatorward displacement during glacial times of both the mid latitude westerlies and the subtropical jet stream

export production in the new zealand region since the last glacial maximum increased export production ep in the subantarctic zone saz of the southern ocean due to iron fertilisation has been proposed as a key mechanism for explaining carbon drawdown during the last glacial maximum lgm this work reconstructs marine ep since the lgm at four sites around new zealand for the first time in this region 230 thorium normalised fluxes of biogenic opal carbonate excess barium and organic carbon are presented in subtropical waters and the saz these flux variations show that ep has not changed markedly since the lgm the only exception is a site currently north of the subtropical front here we suggest the subtropical front shifted over the core site between 18 and 12ka driving increased ep to understand why ep remained mostly low and constant elsewhere lithogenic fluxes at the four sites were measured to investigate changes in dust deposition at all sites lithogenic fluxes were greater during the lgm compared to the holocene the positive temporal correlation between the antarctic dust record and lithogenic flux at a site in the tasman sea shows that regionally increased dust deposition contributed to the high glacial lithogenic fluxes additionally it is inferred that lithogenic material from erosion and glacier melting deposited on the campbell plateau during the deglaciation 18 12ka from these observations it is proposed that even though increased glacial dust deposition may have relieved iron limitation within the saz around new zealand the availability of silicic acid limited diatom growth and thus any resultant increase in carbon export during the lgm therefore silicic acid concentrations have remained low since the lgm this result suggests that both silicic acid and iron co limit ep in the saz around new zealand consistent with modern process studies

re evaluation of the composition of sediments from the murray darling basin of australia as a potential source area for airborne dust to epica dome c in antarctica reply to comment on lead isotopic evidence for an australian source of aeolian dust to antarctica at times over the last 170 000 years by p de deckker m norman i d goodwin a wain and f x gingele

earth s rotation variations a wavelet analysis historical to up to date data of the minute variations in the solid earth s rotation are subjected to a comprehensive time frequency wavelet analysis the length of day for the period 1962 2012 confirms the presence of a prominent robust 6 year periodicity and reveals an anomalously strong 18 6 year tidal oscillation as well as a 13 year quasi periodic signal the polar motion excitation for the period 1900 2012 validates the existence of the 26 year markowitz wobble and shows an 8 year quasi periodic signal but no appreciable 18 6 year periodicity although it is known that exchanges of angular momentum with the geophysical fluids are responsible for the rotational variations of the solid earth the exact physical mechanisms involved on interannual to decadal timescales are still far from understood

distribution and provenance of wind blown se pacific surface sediments article i nfo the reconstruction of low latitude ocean atmosphere interactions is one of the major issues of paleo environmental studies the trade winds extending over 20 to 30 of latitude in both hemispheres between the subtropical highs and the intertropical convergence zone are major components of the atmospheric circulation and little is known about their long term variability on geological time scales in particular in the pacific sector we present the modern spatial pattern of eolian derived marine sediments in the eastern equatorial and subtropical pacific 10 n to 25 s as a reference data set for the interpretation of se pacific paleo dust records the terrigenous silt and clay fractions of 75 surface sediment samples have been investigated for their grain size distribution and clay mineral compositions respectively to identify their provenances and transport agents dust delivered to the southeast pacific from the semi to hyper arid areas of peru and chile is rather fine grained 4 8 m due to low level transport within the southeast trade winds nevertheless wind is the dominant transport agent and eolian material is the dominant terrigenous component west of the peru chile trench south of 5 s grain size distributions alone are insufficient to identify the eolian signal in marine sediments due to authigenic particle formation on the sub oceanic ridges and abundant volcanic glass around the galapagos islands together with the clay mineral compositions of the clay fraction we have identified the dust lobe extending from the coasts of peru and chile onto galapagos rise as well as across the equator into the doldrums illite is a very useful parameter to identify source areas of dust in this smectite dominated study area

transport and deposition of heavy metals in the ross sea region antarctica emissions and long range transport of toxic metals and metalloids pose a global threat to ecosystems and human health global industrialization occurring from the late nineteenth century releases large quantities of pollutants into the earth s atmosphere despite international efforts to mitigate emissions accumulation of metals is still observed in the most remote regions of the planet new baseline studies are needed to determine i natural background concentration of pollutants ii contributions of anthropogenic emissions and iii potential remobilization of previously deposited metals constructing such records requires distinguishing source strength from transport efficiency to the recording site and accounting for local depositional effects here we investigate the sensitivity and representation of southern hemisphere atmospheric concentrations of heavy metals fe al mn pb tl and as in the roosevelt island climate evolution rice ice core a new coastal antarctic ice core site concentration variability with precipitation is explored in daily surface snow samples collected over 70 days while seasonal deposition is investigated through snow pit sampling we find that snow sample concentrations increase with particular snow precipitation types rime and fog and enhanced meridional atmospheric transport to the site snow pit heavy metals peak in summer and also show variable intraannual peaks seasonal airmass modeling based on era interim reanalysis data indicates a synoptic shift during the spring and summer months we conclude that modern heavy metal concentrations are influenced by transport efficiency and scavenging behavior and thus time series records from rice have the potential to provide representative data of regional changes in heavy metals

quantitative estimates of the effect of climate change on dust storm activity in australia during the last glacial maximum quantitative estimates are made of the effect of climate change upon dust activity during the last glacial maximum lgm which peaked 18 000 years ago using present day measurements of the occurrence of dust storms recalculated in the light of information on lgm climatic change dust activity was increased by 57 in northeast australia and by 52 in the southeast in relation to present day dust storm seasons were lengthened and dust paths were modified estimates based upon climate alone without considering the increased supplies of sediment to dust source areas during the lgm however probably underestimate lgm dust activity

soluble iron inputs to the southern ocean through recent andesitic to rhyolitic volcanic ash eruptions from the patagonian andes patagonia due to its geographic position and the dominance of westerly winds is a key area that contributes to the supply of nutrients to the southern ocean both through mineral dust and through the periodic deposits of volcanic ash here we evaluate the characteristics of fe dissolved into soluble and colloidal species from volcanic ash for three recent southern andes volcanic eruptions having contrasting features and chemical compositions contact between cloud waters wet deposition and end members of andesitic hudson volcano and rhyolitic chaiten volcano materials was simulated results indicate higher fe release and faster liberation rates in the andesitic material fe release during particle seawater interaction dry deposition has higher rates in rhyolitic type ashes rhyolitic ashes under acidic conditions release fe in higher amounts and at a slower rate while in those samples containing mostly glass shards fe release was lower and faster the 2011 puyehue eruption was observed by a dust monitoring station puyehue type eruptions can contribute soluble fe to the ocean via dry or wet deposition nearly reaching the limit required for phytoplankton growth in contrast the input of fe after processing by an acidic eruption plume could raise the amount of dissolved fe in surface ocean waters several times above the threshold required to initiate phytoplankton blooms a single eruption like the puyehue one represents more than half of the yearly fe flux contributed by dust

deciphering color reflectance data of a 520 kyr sediment core from the southern ocean method application and paleoenvironmental implications sediment color reflectance contains important information on paleoenvironmental changes such data are routinely measured on sediment cores from the southern ocean their usefulness however is undervalued here for the first time color reflectance of an 520 kyr sediment core retrieved off prydz bay east antarctica was intensively investigated to correlate sediment color changes to changes in sediment compositions total carbon total organic carbon x ray fluorescence derived fe ti and br ti ratios water content and mineral composition of sediment from this core and color reflectance of another two sediment cores retrieved nearby were analyzed in this study the raw reflectance data were transformed into their first order derivatives and subjected to factor analysis algorithms a four factor model was selected to unmix the data set explaining 80 of the total data variance its robustness is supported by similar factor analysis results from the other two cores the four factors represent from factors 1 4 pulses of sedimentary mn enrichment and fe3 fe2 changes in clay minerals relative content changes of colorless components hematite and goethite and water respectively scores of factor 1 show high spikes at glacial terminations recording enhanced deglacial ventilation in the abyssal southern ocean scores of factor 2 mainly reflect biogenic components and chlorite but are further complicated by refractory terrigenous organic carbon and mn oxides hydroxides higher scores of factor 3 occur mainly at peak interglacial intervals associated with enhanced transport of sediment of antarctic origin by oceanic currents water content factor 4 in the core sediment was significantly influenced by opal content and sediment grain size compositions

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

trajectory modeling of modern dust transport to the southern ocean and antarctica aerosol deposition over the southern ocean and antarctica has the potential to alter marine productivity and thus ocean carbon uptake while also impacting radiative balance due to scattering and absorption from atmospheric particulates quantification of modern emission transport and deposition of terrestrial dust and other airborne material from southern hemisphere sources is challenging due to low emission levels and poor detection from remote sensing platforms here forward trajectory modeling is used to explore atmospheric transport independent of deposition processes from 1979 to 2013 trajectories are initiated from known arid dust source areas in south america patagonia australia and southern africa with detailed consideration of new zealand as a potential source results suggest that patagonian and new zealand dust and other aerosol emissions share strong atmospheric transport during all seasons allowing even potentially small new zealand emissions to contribute significantly to southern ocean and antarctic aerosol loading we find that atmospheric transport controlling distribution of dust and other aerosols shows distinct spatial variability new zealand and patagonia rapidly contribute a high proportion of trajectories to west antarctica while in interior east antarctica source contributions are limited and highly mixed the sensitivity of existing deep ice core sites to modern atmospheric transport is discussed finally interannual variability of poleward trajectory extension over the pacific and atlantic sectors of the southern ocean highlights the association of both tropical pacific sea surface temperature and high latitude wind variability e g the southern annular mode with transport of dust and other aerosols to the southern ocean and antarctica

distribution transport and deposition of mineral dust in the southern ocean and antarctica contribution of major sources 1 a model based investigation of the transport distribution and deposition of mineral dust in the southern hemisphere sh is performed by using the gfdl atmospheric model am2 the study represents an attempt to quantify the contribution of the major sources by tagging dust based on its origin we evaluate the contribution of each source to the emission distribution mass burden and deposition of dust in the southern ocean and antarctica and show that each source produces distinctive meridional transport vertical distribution and deposition patterns the dust in sh originates primarily from australia 120 tg a 1 patagonia 38 tg a 1 and the inter hemispheric transport from northern hemisphere 31 tg a 1 a small fraction of it 7 tg a 1 is transported and deposited in the southern ocean and antarctica where dust from south america australia and northern hemisphere are essentially located in the boundary layer mid troposphere and upper troposphere respectively these three sources contribute to nearly all the dust burden in the southern ocean and antarctica south america and australia are the main sources of the dust deposition but they differ zonally with each one dominating half of a hemisphere along 120 e 60 w the half comprising the atlantic and indian oceans in the case of the south american dust and the pacific half in the case of the australian dust our study also indicates a potentially important role of northern hemisphere dust as it appears to be a significant part of the dust burden but contributing little to the dust deposition in antarctica

dust sources and deposition during the last glacial maximum and current climate a comparison of model results with paleodata from ice cores and marine sediments mineral dust aerosols in the atmosphere have the potential to affect the global climate by influencing the radiative balance of the atmosphere and the supply of micronutrients to the ocean ice and marine sediment cores indicate that dust deposition from the atmosphere was at some locations 2 20 times greater during glacial periods raising the possibility that mineral aerosols might have contributed to climate change on glacial interglacial time scales to address this question we have used linked terrestrial biosphere dust source and atmospheric transport models to simulate the dust cycle in the atmosphere for current and last glacial maximum lgm climates we obtain a 2 5 fold higher dust loading in the entire atmosphere and a twenty fold higher loading in high latitudes in lgm relative to present comparisons to a compilation of atmospheric dust deposition flux estimates for lgm and present in marine sediment and ice cores show that the simulated flux ratios are broadly in agreement with observations differences suggest where further improvements in the simple dust model could be made the simulated increase in high latitude dustiness depends on the expansion of unvegetated areas especially in the high latitudes and in central asia caused by a combination of increased aridity and low atmospheric co2 the existence of these dust source areas at the lgm is supported by pollen data and loess distribution in the northern continents these results point to a role for vegetation feedbacks including climate effects and physiological effects of low co2 in modulating the atmospheric distribution of dust

dry lake beds as sources of dust in australia during the late quaternary a volumetric approach based on lake bed and deflated dune volumes abstract dust affects earth s climate ecology and economies across a broad range of scales both temporally and spatially and is an integral part of the earth s climate system previous studies have highlighted the importance of inland lake beds to dust emissions both locally and globally this study aims to explore the relative volumetric importance of ephemeral lakes that emit dust to the australian southeastern dust path over the last glacial cycle srtm dems and gis analyses of long term up to 80 ka lake bed deflation volumes and deposition of sand sized sediment onto downwind source bordering dunes were used to derive estimates of transported dust mass a strong power relationship was found between lake area and the mass of deflated lake bed sediments total dust masses for the largest 53 lakes in southeastern australia were derived using the relationship between lake area and dust mass and used to determine an upper value for total dust mass deflated from lake beds in southeastern australia ephemeral lake derived dust was found to represent at most 13 of the dust derived from southeastern australia deposited in the southern pacific over the last 80 ka or 22 over the last 40 ka lake eyre the largest lake has contributed at most 3 of the australian southeast dust plume these results imply that there are significant additional sources of dust in australia over these timescales such as floodplains or dunefields and that modelling must allow for diverse climatic and geomorphic controls on dust production

impact of anthropogenic pb and ocean circulation on the recent distribution of pb isotopes in the indian ocean abstract pb and pb isotope ratios in the modern ocean have been altered significantly by anthropogenic pb inputs over the past century most studies of anthropogenic pb in the ocean have focused on the north atlantic and north pacific oceans and the impact of anthropogenic pb inputs to the indian ocean and processes controlling the distribution of pb in the indian ocean are poorly known this study presents the pb and pb isotopic composition 206 pb 207 pb 208 pb 207 pb of 11 deep stations from the indian ocean japanese geotraces cruise kh 09 5 from the bay of bengal and arabian sea to the southern ocean 62 s the pb isotope ratios of the indian ocean range 1 140 1 190 for 206 pb 207 pb and 2 417 2 468 for 208 pb 207 pb with lower ratios appearing in the shallow waters of the northern indian ocean and higher ratios appearing in the deep layers of the southern ocean this result agrees with a previous study on pb concentrations echegoyen et al 2014 showing that the indian ocean particularly its northern part is largely perturbed by anthropogenic pb inputs 206 pb 207 pb and 208 pb 207 pb of the indian sector southern ocean are still lower than natural pb showing this region was also affected by anthropogenic pb anomalously low or high 206 pb 207 pb and 208 pb 207 pb were observed in the thermocline and shallow waters of the southern indian ocean and the arabian sea which are ascribed to water mass distribution e g subantarctic mode water and evolving pb isotope ratios of this region as dominant anthropogenic pb sources change 206 pb 207 pb and 208 pb 207 pb in the bay of bengal are higher than those in the arabian sea which might be the result of the anthropogenic pb inputs from different provenance or seawater exchanging pb isotopes with natural particles derived from rivers and or sediments at the basin boundaries

a biomarker perspective on dust productivity and sea surface temperature in the pacific sector of the southern ocean abstract in this study we present a new multiproxy data set of terrigenous input marine productivity and sea surface temperature sst from 52 surface sediment samples collected along e w transects in the pacific sector of the southern ocean allochthonous terrigenous input was characterized by the distribution of plant wax n alkanes and soil derived branched glycerol dialkyl glycerol tetraethers brgdgts 230th normalized burial of both compound groups were highest close to the potential sources in australia and new zealand and are strongly related to lithogenic contents 232th indicating common sources and transport detection of both long chain n alkanes and brgdgts at the most remote sites in the open ocean strongly suggests a primarily eolian transport mechanism to at least 110 w i e by prevailing westerly winds two independent organic sst proxies were used the u 37 k based on alkenones and the tex86 based on isoprenoid gdgts both u 37 k and tex86 indices show robust relationships with temperature over a temperature range between 0 5 and 20 c likely implying different seasonal and regional imprints on the temperature signal alkenone based temperature estimates best reflect modern summer sst in the study area when using the polar calibration of sikes et al 1997 in contrast tex86 derived temperatures may reflect a subsurface signal rather than surface 230th normalized burial of alkenones is highest close to the subtropical front and is positively related to the deposition of lithogenic material throughout the study area in contrast highest isogdgt burial south of the antarctic polar front may be largely controlled by diatom blooms and thus high opal fluxes during austral summer

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

aeolian input of bioavailable iron to the ocean 1 atmospheric deposition of mineral dust supplies much of the essential nutrient iron to the ocean presumably only the readily soluble fraction is available for biological uptake previous ocean models assumed this fraction was constant here the variable solubility of fe in aerosols and precipitation is parameterized with a two step mechanism the development of a sulfate coating followed by the dissolution of iron hydr oxide on the dust aerosols the predicted soluble fe fraction increases with transport time from the source region and with the corresponding decrease in dust concentration the soluble fraction is 1 percent near sources but often 10 40 percent farther away producing a significant increase in soluble fe deposition in remote ocean regions our results may require more rapid biological and physicochemical scavenging of fe than used in current ocean models we further suggest that increasing so2 emission alone could have caused significant fe fertilization in the modern northern hemisphere oceans

coherent composition of glacial dust on opposite sides of the east antarctic plateau inferred from the deep epica ice cores 1 the dust provenance identification through isotopic and geochemical tracers focused mostly on ice cores drilled in the pacific indian sector of antarctica where a common provenance of dust from southern south america during glacial ages was demonstrated conversely in other areas of the east antarctic plateau as dronning maud land provenance was deduced indirectly from back trajectory analyses and soluble chemistry records in this work we present the first comparison of major elemental composition of dust archived in two ice cores from opposite sides of antarctica in the framework of the epica project mineral particles extracted from the edc and edml cores date back to glacial mis 2 4 and 6 over the last 200 kyr results reveal a coherent geochemical dust composition at both locations providing experimental evidence of a common provenance over the wide area of east antarctica during glacials and key analytical constrains for atmospheric general circulation models

glacial interglacial dust and export production records from the southern indian ocean abstract we present 230th normalized dust and export production fluxes for two contrasted marine sediment cores spanning the antarctic polar front close to the kerguelen plateau in the southern indian ocean covering the last glacial cycle we report glacial lithogenic fluxes comparable to the south atlantic and higher than in the south pacific sectors of the southern ocean structural and temporal discrepancies with dust reconstructions from antarctic ice cores and the atlantic and pacific sectors of the subantarctic zone saz point towards southern africa and or the kerguelen plateau as an additional source of lithogenic material to the southern indian ocean during the last ice age in the saz export production proxies respond to iron fe fertilization with total organic carbon toc fluxes as high as those previously reported from the atlantic sector of the southern ocean however the correlation between export production and dust proxies is weaker than in the other sectors and shows a muted response of export production during peak glacials we hypothesize that this muted response may be related to macronutrient co limitation imposed on phytoplankton growth possibly induced by a northward displacement of wind driven upwelling and or the polar frontal system during peak glacials the antarctic zone az record depicts the typical pattern of enhanced export production during interglacials and comparatively low productivity during glacials suggesting a decrease in the supply of macronutrients to the az surface during ice ages compared to warm periods as previously proposed however a muted response of opal fluxes during marine isotope stage mis 5e argues for a southward migration of the frontal system during warmer mis 5e possibly causing silicic acid co limitation at this site these results illustrate the important role of fe fertilization and changes in wind driven upwelling intensities in modulating the strength and efficiency of the biological carbon pump in the southern ocean but also highlight the potential role of frontal movements in explaining export production variability at sites located close to the antarctic circumpolar current acc fronts overall our new datasets provide new insights on the regional differences in dust and export production patterns that need to be considered in order to evaluate the efficiency of carbon sequestration in the different sectors of the southern ocean during ice ages

change in atmospheric mineral aerosols in response to climate last glacial period preindustrial modern and doubled carbon dioxide climates desert dust simulations generated by the national center for atmospheric research s community climate system model for the current climate are shown to be consistent with present day satellite and deposition data the response of the dust cycle to last glacial maximum preindustrial modern and doubled carbon dioxide climates is analyzed only natural non land use related dust sources are included in this simulation similar to some previous studies dust production mainly responds to changes in the source areas from vegetation changes not from winds or soil moisture changes alone this model simulates a 92 33 and 60 change in dust loading for the last glacial maximum preindustrial and doubled carbon dioxide climate respectively when impacts of carbon dioxide fertilization on vegetation are included in the model terrestrial sediment records from the last glacial maximum compiled here indicate a large underestimate of deposition in continental regions probably due to the lack of simulation of glaciogenic dust sources in order to include the glaciogenic dust sources as a first approximation we designate the location of these sources and infer the size of the sources using an inversion method that best matches the available data the inclusion of these inferred glaciogenic dust sources increases our dust flux in the last glacial maximum from 2 1 to 3 3 times current deposition

patagonian origin of glacial dust deposited in east antarctica vostok and dome c during glacial stages 2 4 and 6 abstract the source area of continental dust deposited at both vostok and dome c sites east antarctica during the glacial stages stage 2 18 ka last glacial maximum stage 4 60 ka and stage 6 160 ka of the last two climatic cycles has remained constant the isotopic composition 87 sr 86 sr and 143 nd 144 nd of the ice core dust has been compared with the isotopic composition of the potential source areas antarctica new zealand southern africa australia and south america this comparison reveals the southern south american provenance of the dust for all three glacial periods as has already been shown for the lgm 1 we show that the patagonian loess and the marine shelf sediments from the argentine continental shelf which was variably emerged during glacial periods display different isotopic compositions and that the composition of the patagonian loess best matches the signature of the ice core dust the identification of the patagonian region as the source of the windblown dust deposited over east antarctica during all the latest glacial periods permits a better understanding of paleo atmospheric circulations of the last climatic cycles and a better constraint on the parametrization of dust sources for paleoatmospheric general circulation models

a geochemical approach to reconstruct modern dust fluxes and sources to the south pacific abstract we present the first comprehensive dust provenance and lithogenic flux data set extracted from surface sediments distributed across the polar and subpolar south pacific the dataset comprises 230th normalized lithogenic fluxes combined with rare earth elements strontium neodymium and lead isotope data to determine lithogenic fluxes spatial distribution and sources of dust

south pole glacial climate reconstruction from multi borehole laser particulate stratigraphy the icecube neutrino observatory and its prototype amanda were built in south pole ice using powerful hot water drills to cleanly bore 100 holes to depths up to 2500 m the construction of these particle physics detectors provided a unique opportunity to examine the deep ice sheet using a variety of novel techniques we made high resolution particulate profiles with a laser dust logger in eight of the boreholes during detector commissioning between 2004 and 2010 the south pole laser logs are among the most clearly resolved measurements of antarctic dust strata during the last glacial period and can be used to reconstruct paleoclimate records in exceptional detail here we use manual and algorithmic matching to synthesize our south pole measurements with ice core and logging data from dome c east antarctica we derive impurity concentration precision chronology annual layer thickness local spatial variability and identify several widespread volcanic ash depositions useful for dating we also examine the interval around similar to 74 ka recently isolated with radiometric dating to bracket the toba sumatra supereruption

quasi static eocene oligocene climate in patagonia promotes slow faunal evolution and mid cenozoic global cooling abstract new local regional climatic data were compared with floral and faunal records from central patagonia to investigate how faunas evolve in the context of local and global climates oxygen isotope compositions of mammal fossils between c 43 and 21 ma suggest a nearly constant mean annual temperature of 16 3 c consistent with leaf physiognomic and sea surface studies that imply temperatures of 16 18 c carbon isotopes in tooth enamel track atmospheric 13 c but with a positive deviation at 27 2 ma and a strong negative deviation at 21 ma combined with paleosol characteristics and reconstructed leaf area indices rlais these trends suggest aridification from 45 ma c 1200 mm yr to 43 ma c 450 mm yr quasi constant map until at least 31 ma and an increase to 800 mm yr by 21 ma comparable map through most of the sequence is consistent with relatively constant floral compositions rlai and leaf physiognomy abundance of palms reflects relatively dry adapted lineages and greater drought tolerance under higher p co2 pedogenic carbonate isotopes imply low p co2 430 300 ppmv at the initiation of the eocene oligocene climatic transition arid conditions in patagonia during the late eocene through oligocene provided dust to the southern ocean enhancing productivity of silicifiers drawdown of atmospheric co 2 and protracted global cooling as the antarctic circumpolar current formed and earth cooled wind speeds increased across patagonia providing more dust in a positive climate feedback high tooth crowns hypsodonty and ever growing teeth hypselodonty in notoungulates evolved slowly and progressively over 20 ma after initiation of relatively dry environments through natural selection in response to dust ingestion a ratchet evolutionary model may explain protracted evolution of hypsodonty in which small variations in climate or dust delivery in an otherwise static environment drive small morphological shifts that accumulate slowly over geologic time

dirtmap the geological record of dust atmospheric dust is an important feedback in the climate system potentially affecting the radiative balance and chemical composition of the atmosphere and providing nutrients to terrestrial and marine ecosystems yet the potential impact of dust on the climate system both in the anthropogenically disturbed future and the naturally varying past remains to be quantified the geologic record of dust provides the opportunity to test earth system models designed to simulate dust records of dust can be obtained from ice cores marine sediments and terrestrial loess deposits although rarely unequivocal these records document a variety of processes source transport and deposition in the dust cycle stored in each archive as changes in clay mineralogy isotopes grain size and concentration of terrigenous materials although the extraction of information from each type of archive is slightly different the basic controls on these dust indicators are the same changes in the dust flux and particle size might be controlled by a combination of a source area extent b dust emission efficiency wind speed and atmospheric transport c atmospheric residence time of dust and or d relative contributions of dry settling and rainout of dust similarly changes in mineralogy reflect a source area mineralogy and weathering and b shifts in atmospheric transport the combination of these geological data with process based forward modelling schemes in global earth system models provides an excellent means of achieving a comprehensive picture of the global pattern of dust accumulation rates their controlling mechanisms and how those mechanisms may vary regionally the dust indicators and records of terrestrial and marine palaeoenvironments dirtmap data base has been established to provide a global palaeoenvironmental data set that can be used to validate earth system model simulations of the dust cycle over the past 150 000 years

comparing the epica and vostok dust records during the last 220 000 years stratigraphical correlation and provenance in glacial periods a new aeolian dust record from the first 2200 m of the epica dome c ice core 75 06 s 123 21 e covering about 220 000 years of climatic history is compared to the vostok 78 28 s 106 48 e ice core nature 399 1999 429 the two dust profiles are very similar and several common dust events allow to establish stratigraphical links the late quaternary period is characterized at both sites and likely overall east antarctic plateau by high dust input during glacial periods in the epica dome c ice core the dust flux rises by a factor of 25 20 and 12 in glacial stages 2 4 and 6 with respect to interglacial periods holocene and stage 5 5 the magnitude and pattern of changes are comparable in the vostok ice core in this study the geographical origin of ice core dust icd in cold periods has been investigated at both sites through 87sr 86sr versus 143nd 144nd isotopic tracers following the previous studies of grousset et al earth planet sci lett 111 1992 175 and basile et al earth planet sci lett 146 1997 573 the new data and the existing ones allow to define the isotopic fields for dust at the two antarctic sites that are almost identical and restricted into the 0 708 87sr 86sr 0 711 and 5 end 0 5 ranges this suggests a common geographical provenance for dust at vostok and dome c and for all the glacial periods of the late pleistocene to decipher the icd provenance more than 50 samples of loess and aeolian deposits sands and fluvioglacial sediments from the potential source areas psas of the southern hemisphere have been collected however the methodology has been refined with respect to former studies first the isotopic fractionation that can occur in function of grain size has been taken into account and the psa s signature has been defined in the 5 m size range within which fine grained dust reaching antarctica is found moreover a possible contribution from carbonates on the samples from psas has also been also considered south africa and australia can be excluded as dominant sources but a partial overlap arises among southern south america new zealand and the antarctic dry valleys isotopic fields these latter two documented for the first time a possible contribution from all these three sources cannot be excluded but complementary arguments suggest the dominant contribution to east antarctic dust in glacial times deriving from the southern south american region of patagonia and the pampas this study shows a first order uniformity in the dust flux and geographical provenance to the east antarctica plateau during glacial periods

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

an evaluation of australia as a major source of dust abstract since australia is the driest inhabited continent it is a natural laboratory to study on a large scale dust its composition its sources transport and geochemical composition this is necessary as there has been a lack of appreciation of the diversity of the australian regolith characterized by a great array of ages and compositions this is particularly true of studies that examined the geochemistry of australian dusts and links with potential deposition sites such as in antarctica and comparison with south america hence the first part of this paper provides an overview of the surficial geology of australia with emphasis on regions from where dust can become deflated a review follows on the investigations of significant dust transport and events in australia the second part of the paper provides a review of the sites of potential deflation of dust it includes the study of different geomorphological sites of dust deflation with a discussion on how dust particles can accumulate in regions linked to large playa lakes that are under the influence of groundwater below them this is an important mode of dust deflation a process of which had insufficiently been detailed before the processes involving evaporative pumping are explained and several illustrations are provided to document those processes and location of dust deposits another region of importance to dust deflation consists of extensive alluvial plains and these are also documented with an area in the upper reaches of the darling river being now documented more fully finally the inter dunal corridors in large dune fields are also mentioned as a source of dust as previous studies already show this second part ends with the description of the two main potential source areas psa of dust in australia and these are the kati thanda lake eyre region of central australia and the darling riverine plain in the upper reaches of the darling river these two regions are important for their geochemical fingerprints for transcontinental studies and supported by satellite imagery that identify dust plumes originating from these regions the third part of the paper examines the geochemical composition of australian psas by paying particular attention to neodymium strontium and lead isotopic ratios from both continents we also suggest the possibility of combining nd and pb isotopes as a way of fingerprinting geochemically between different australian regions and for comparison with other continental psas this part also reviews previous studies that aimed at geochemically fingerprinting the australian regolith by referring also how these studies were applied to reconstruct past environmental conditions

coupled evolution of stable carbon isotopes between the southern ocean and the atmosphere over the last 260 ka abstract the oceanic thermocline circulation provides a route of communication between the surface and deep ocean and could have played an important role in the global carbon cycle but studies on reconstructing past thermocline water properties are limited here we explore the potential use of left coiling globorotalia truncatulinoides as a recorder of thermocline conditions by measuring the stable oxygen and carbon isotopic compositions of this species from 28 surface sediments in the southwest pacific near new zealand our data show that g truncatulinoides sinistral calcify mainly in the range of subsurface thermocline depths in this study region between 100 and 850 m with their carbon isotopes largely corresponding to the surrounding seawater values to understand the controlling factors of the thermocline 13c evolution in the south pacific a 260 ka downcore 13c record on this species 13cg trunc from core site odp1123 is presented and compared with other 13c records the convergence of 13c from thermocline upper and lower circumpolar deep waters ucdw lcdw during glacial terminations indicates that the deep ocean is the predominant source of increased atmospheric pco2 and the 13c anomalies in the upper ocean and atmosphere during the deglacials this is evident in both the south pacific and south atlantic a quantitative calculation of predicted surface ocean 13c based on thermodynamic air sea equilibrium implies this process has a significant control on the temporal thermocline water 13c variation over the last glacial interglacial g i cycle the lower deglacial 13cg trunc values in the south atlantic compared to the pacific further suggest a stronger upwelling in the atlantic sector of the southern ocean indicating that this was a major ventilation route with an important stock of light 13c from the deep waters of this region this study demonstrates the deep water influence via upwelling and atmospheric carbon isotope imprint via air sea exchange on thermocline water 13c evolution it also provides important evidence for the rapid exchange of carbon between the southern ocean and atmosphere over multiple g i cycles

atmospheric decadal variability from high resolution dome c ice core records of aerosol constituents beyond the last interglacial along the epica dome c ice core we measured concentrations of different water soluble aerosol constituents and deduced total depositional flux records here we present high resolution sodium calcium ammonium and nitrate data covering the last 173 000 years the first three of these species are passive tracers and reveal source and long range transport changes whereas nitrate is deposited reversibly however it can be used to check isotope derived accumulation rate estimates a prerequisite to calculate total depositional fluxes during the last two transitions from glacial to interglacial periods changes in the total depositional flux differ strongly for different aerosol species the largest changes are observed in the terrestrial aerosol proxy non sea salt calcium only moderate changes occur in the marine sea salt indicator sodium while ammonium a proxy for marine bioproductivity remains rather constant in agreement with previous studies we find that only considerable glacial interglacial changes at both the terrestrial and the marine sea salt aerosol source can explain the observed pronounced changes the unprecedented high resolution of our data allows for the first time the examination of decadal variability back to the penultimate glacial period on the one hand we find occasional fast shifts occurring within a few years here we present such an event in the calcium record from the penultimate glacial period on the other hand we examine variation coefficients and pairwise correlation coefficients both determined in 200 year windows they generally reveal only moderate changes during glacial periods slightly lower variation coefficients are found concurrent with slightly higher correlation coefficients which points to a more uniform and stronger coupled atmospheric long range transport of the different aerosol species to the east antarctic plateau and less influence of cyclonic activities during cold periods the opposite is observed for interglacial periods with probably even reinforced importance of cyclonic influences during the last interglacial period the marine isotope stage 5 5 this period reveals no evidence for abrupt climatic changes in any of the species however the marine sea salt aerosol indicator sodium shows a distinct minimum followed by a pronounced increase this pattern is explained by significantly reduced sea ice production in the indian southern ocean sector which is believed to be the dominant source of sodium deposited in dome c during warm periods

dissolved manganese in the atlantic sector of the southern ocean the first comprehensive dataset 492 samples of dissolved mn in the southern ocean shows extremely low values of 0 04 up to 0 64 nm in the surface waters and a subsurface maximum with an average concentration of 0 31 nm n 20 s d 0 08 nm the low mn in surface waters correlates well with the nutrients po4 and no3 and moderately well with si oh 4 and fluorescence furthermore elevated concentrations of mn in the surface layer coincide with elevated fe and light transmission and decreased export th 234 u 238 deficiency and fluorescence it appears that mn is a factor of importance in partly explaining the hnlc conditions in the southern ocean in conjunction with significant controls by the combination of fe limitation and light limitation no input of mn from the continental margins was observed this is ascribed to the protruding continental ice sheet that covers the shelf and shuts down the usual biological production microbial breakdown and sedimentary geochemical cycling the low concentrations of mn in the deep ocean basins 0 07 0 23 nm were quite uniform but some elevations were observed the highest deep concentrations of mn were observed at the bouvet triple junction region and coincided with high concentrations of fe and are deemed to be from hydrothermal input the deep basins on both sides of the ridge were affected by this input in the deep weddell basin the input of weddell sea bottom water appears to be the source of the slightly elevated concentrations of mn in this water layer c 2010 elsevier ltd all rights reserved

ephemeral lakes and desert dust sources 1 the processes that determine which areas are strong sources of mineral aerosols are not well known in this study we consider the role of ephemeral lakes in modulating emissions of atmospheric mineral aerosols we focus on two ephemeral lake regions that have been identified as source regions the zone of chotts in tunisia and algeria and etosha pan in namibia comparisons of satellite retrieved inundation data and the toms absorbing aerosol index suggest that during some periods of inundation desert dust loadings are reduced there is some indication that after flooded areas have dried there is increased dust loading however the role of the inundated ephemeral lake compared with nearby regions in modulating desert dust sources is unclear in addition problems with interpreting the toms ai make conclusions difficult more research is required to understand the small scale sources of atmospheric desert dust in dry unvegetated topographic lows index terms 0305 atmospheric composition and structure aerosols and particles 0345 4801 0315 atmospheric composition and structure biosphere atmosphere interactions 1615 global change biogeochemical processes 4805 1655 global change water cycles 1836 3360 meteorology and atmospheric dynamics remote sensing citation mahowald n m r g bryant j del corral and l steinberger ephemeral lakes and desert dust sources geophys res lett 30 2 1074 doi 10 1029 2002gl016041 2003

aeolian dust in the talos dome ice core east antarctica pacific ross sea sector victoria land versus remote sources over the last two climate cycles a new ice core taldice drilled at talos dome east antarctica ross sea sector preserves a ca 250 ka long record of palaeoclimate and atmospheric history we investigate dust variability and provenance at the site during glacial periods and the holocene through the sr nd isotopic composition of ice core dust and potential source areas psa we provide new isotopic data on dust sources from victoria land such as regoliths glacial drifts aeolian sands and beach deposits some of these sources are located at high altitude and are known to have been ice free throughout the pleistocene the major features of the taldice dust record are very similar to those from central east antarctica during glacial times south america was the dominant dust supplier for talos dome as well as for the entire east antarctic plateau conversely during the holocene the principal input of mineral dust at talos dome probably derives from proximal sources which are the ice free areas of northern victoria land located at similar altitude with respect to the drilling site atmospheric mobilisation of dust from these neighbouring areas and transport inland to talos dome can be ultimately associated with advection of maritime air masses from the pacific ross sea region copyright 2010 john wiley sons ltd supporting information can be found in the online version of this article

ground satellite observations and atmospheric modeling of dust storms originating in the high puna altiplano deserts south america implications for the interpretation of paleo climatic archives 1 this study provides a detailed description of the sources transport dispersion and deposition of two major dust events originating from the high altitude subtropical puna altiplano plateau 15 26 s 65 69 w in south america a long and severe drought provided the right conditions for the onset of both events in july 2009 and 2010 dust was transported se and deposited over the pampas region and was observed to continue to the atlantic ocean dust monitoring stations located downwind recorded both events and samples were characterized through chemical and textural analysis through a combination of meteorological data and satellite observations calipso and modis detectors we estimate the emission flux for the 2010 event this estimate was used to constrain the hybrid single particle lagrangian integrated trajectory hysplit transport model and simulate the dust event both satellite imagery and model results agree in the location and extension of the dust cloud calipso detected dust between 6000 and 8500 m a s l which remained at this height during most of its trajectory the dust cloud mixed with a strong convective system in the region and the associated precipitation brought down significant amounts of dust to the ground dust particle size analysis for both events indicates that near the sources dust samples show median modes of 12 4 14 1 m similar to modes observed 1300 km away chemical composition of sediments from potential dust sources shows distinct signatures within the puna altiplano plateau the puna sector being clearly different from the altiplano area in addition both sources are markedly different from the patagonian chemical fingerprint these results have important implications to improve the interpretation of paleo environmental archives preserved on the argentine loess antarctic ice cores and southern ocean marine sediments

holocene dynamics of the southern westerly winds over the indian ocean inferred from a peat dust deposition record abstract the southern westerly winds sww play a major role in climate variability in southern hemisphere mid and high latitudes regulating rainfall ocean circulation and the southern ocean carbon sink despite their importance little is known about millennial scale changes in the sww and how they have influenced the climate system in the past and interacted with the earth s surface elements such as dust nutrients and carbon here we present a dust record from a 6 6 kyr old peat core in amsterdam island ams situated at the northern edge of the sww 37 s in the southern indian ocean mineral dust flux was used to track atmospheric dust production long distance transport and subsequent deposition dust provenance was determined from rare earth element ree and nd isotopic signatures end in the peat core compared with a reference dataset of southern hemisphere dust sources using a multi proxy mixing model the end and ree ratios show a relatively uniform mixture of ca 40 local 15 southern african and 45 southern south american dust sources since 6 6 cal kyr bp however from 1910 ad onwards there is a doubling in the contribution from southern africa 32 two mineral dust flux minima occur at 6 2 4 9 cal kyr bp and 3 9 2 7 cal kyr bp interpreted as periods with equatorward shifted and or strengthened sww at the northern edge of the wind belt conversely periods of higher dust flux at 6 6 6 2 cal kyr bp 4 9 3 9 cal kyr bp and 1 4 cal kyr bp onwards are interpreted as poleward shifted and or weakened sww these interpretations are based on the findings that higher lower wind speeds lead to enhanced less removal of distal dust on the way to ams by wet deposition and turbulence published holocene sww records at the northern edge of the wind belt 33 41 s covering south america southern africa and australia show much variability over the last 6 6 kyr we suggest this reflects complex regional climate variability in the different sh longitudinal sectors indicating that sww are not zonally homogeneous at the northern edge of the wind belt the recent shift in dust provenance is not accompanied by enhanced total dust deposition at ams we therefore suggest that human impact e g land use changes and drier climate conditions in southern africa have led to enhanced dust mobilization

tracking eolian dust with helium and thorium impacts of grain size and provenance reconstructions of the deposition rate of windblown mineral dust in ocean sediments offer an important means of tracking past climate changes and of assessing the radiative and biogeochemical impacts of dust in past climates dust flux estimates in ocean sediments have commonly been based on the operationally defined lithogenic fraction of sediment samples more recently dust fluxes have been estimated from measurements of helium and thorium as rare isotopes of these elements he 3 and th 230 allow estimates of sediment flux and the dominant isotopes he 4 and th 232 are uniquely associated with the lithogenic fraction of marine sediments in order to improve the fidelity of dust flux reconstructions based on he and th we present a survey of he and th concentrations in sediments from dust source areas in east asia australia and south america our data show systematic relationships between he and th concentrations and grain size with he concentrations decreasing and th concentrations increasing with decreasing grain size we find consistent he and th concentrations in the fine fraction 5 m of samples from east asia australia and central south america puna central west argentina with th concentrations averaging 14 g g and he concentrations averaging 2 cc stp g we recommend use of these values for estimating dust fluxes in sediments where dust is dominantly fine grained and suggest that previous studies may have systematically overestimated th based dust fluxes by 30 source areas in patagonia appear to have lower he and th contents than other regions as fine fraction concentrations average 0 8 cc stp g and 9 g g for 4he and 232th respectively the impact of grain size on lithogenic he and th concentrations should be taken into account in sediments proximal to dust sources where dust grain size may vary considerably our data also have important implications for the hosts of he in long traveled dust and for the 3he 4he ratio used for terrigenous he in studies of extraterrestrial he in sediments and ice we also investigate the use of he th ratios as a provenance tracer our results suggest differences in fine fraction he th ratios between east asia australia central south america and patagonia with ratios showing a positive relationship with the geological age of source rocks he th ratios may thus provide useful provenance information for example allowing separation of patagonian sources from puna central west argentina or australian dust sources he th ratios in open ocean marine sediments are similar to ratios in the fine fraction of upwind dust source areas he th ratios in mid latitude south atlantic sediments suggest that dust in this region primarily derives from the puna central west argentina region 23 32 s rather than patagonia 38 s in the equatorial pacific he th ratios are much lower than in extratropical pacific sediments or potential source areas measured as a part of this study east asia south america australia for reasons that are at present unclear complicating their use as provenance tracers in this region

the glaciogenic origin of the pleistocene calcareous dust in argentina on the basis of field mineralogical textural and geochemical analyses calcareous dust occurs in argentina as layers and pockets closely associated with pleistocene deposits and periglacial features from southernmost patagonia to at least the mendoza precordillera and has been traditionally interpreted as a soil horizon resulting from postdepositional pedogenesis during interglacials detailed field and microscopic observations and sedimentological and geochemical analyses of more than 100 samples collected from lower to upper pleistocene deposits between 51 s and 33 s and from near sea level to 2800 m asl allow us to interpret the dust as synchronous with the host sediment all observations and analyses lead us to conclude that 1 the cryogenic morphology and the chemical signatures of the calcite component show that the dust is glaciogenic 2 the dust was carried by southeasterly antarctic winds and 3 it was deposited over most of southern and central argentina field observations geomorphic evidence and radiocarbon dates suggest that the dust was deposited during several pleistocene glacial episodes