terrigenous sediment supply in the scotia sea southern ocean response to late quaternary ice dynamics in patagonia and on the antarctic peninsula geochemical and mineralogical compositions of modern and late quaternary marine sediments from the scotia sea trace sources and transport paths of terrigenous sediment we discuss downcore variations of compositional data of two sediment cores from the northern and southern scotia sea that correlate with fluctuations in magnetic susceptibility sediments were derived from very different sources at both localities as revealed by contrasting clay mineral assemblages however a common feature is the input of more basic and undifferentiated crustal material with the potential of high magnetic susceptibility during glacial periods indicated by variable quartz feldspar ratios and major trace and rare earth elements terrigenous sediments mainly originate from nearby terrestrial sources or are introduced through interbasinal sediment transfer from adjacent seas the observed temporal compositional variations have to be attributed to changes in the relative detrital contributions from the diverse source areas ice mass extensions in southern patagonia on the antarctic peninsula and adjacent islands likely control the supply of glaciogenic detritus to the open ocean during times of glacial expansion diluting the sediment input of interbasinal origin current transport is mainly responsible for sediment dispersal to the pelagic scotia sea and may amplify the glaciological source signals during glacial climate periods because of a stronger wind forcing of the antarctic circumpolar current

expansion of ice marginal lakes at the vatnajokull ice cap iceland from 1999 to 2009 abstract outlet glaciers from the vatnajokull ice cap in iceland europe s largest ice cap have been retreating since the end of the little ice age only interrupted by short intervals of advances the net mass balance has been negative since 1995 and ice marginal lakes in front of the outlets have been expanding since then the switch from land based glacier termini to lake terminating glaciers is an eye catching environmental change the heat capacity of the ice marginal lakes and the change into calving glacier fronts accelerates ice loss from vatnajokull landsat 7etm satellite imagery from 1999 to 2009 reveals high resolution snapshots of the lake development during the last decade ice marginal lakes are growing at many outlet glaciers draining the southern sector of vatnajokull this is most pronounced at the large brei amerkurjokull glacier where the jokulsarlon lake expanded from 15 km 2 in 2000 to more than 21 km 2 in 2009 the lakes act as traps for sediment that was earlier transported across outwash plains toward the atlantic coast hence the glacier retreat and sediment trapping enhance coastline retreat and river incision in the outwash plains similar changes although at a much larger scale occurred in many past glaciated regions during the last glacial termination thus the lakes in front of vatnajokull provide important modern analogues for processes that likely impacted global climate in the past

strengthening of north american dust sources during the late pliocene 2 7 ma here we present orbitally resolved records of terrestrial higher plant leaf wax input to the north atlantic over the last 3 5 ma based on the accumulation of long chain n alkanes and n alkanl 1 ols at iodp site u1313 these lipids are a major component of dust even in remote ocean areas and have a predominantly aeolian origin in distal marine sediments our results demonstrate that around 2 7 million years ago ma coinciding with the intensification of the northern hemisphere glaciation nhg the aeolian input of terrestrial material to the north atlantic increased drastically since then during every glacial the aeolian input of higher plant material was up to 30 times higher than during interglacials the close correspondence between aeolian input to the north atlantic and other dust records indicates a globally uniform response of dust sources to quaternary climate variability although the amplitude of variation differs among areas we argue that the increased aeolian input at site u1313 during glacials is predominantly related to the episodic appearance of continental ice sheets in north america and the associated strengthening of glaciogenic dust sources evolutional spectral analyses of the n alkane records were therefore used to determine the dominant astronomical forcing in north american ice sheet advances these results demonstrate that during the early pleistocene north american ice sheet dynamics responded predominantly to variations in obliquity 41 ka which argues against previous suggestions of precession related variations in northern hemisphere ice sheets during the early pleistocene

millennial scale sea surface temperature and patagonian ice sheet changes off southernmost chile 53 s over the past 60 kyr 1 glacial millennial scale paleoceanographic changes in the southeast pacific and the adjacent southern ocean are poorly known due to the scarcity of well dated and high resolution sediment records here we present new surface water records from sediment core md07 3128 recovered at 53 s off the pacific entrance of the strait of magellan the alkenone derived sea surface temperature sst record reveals a very strong warming of ca 8 c over the last termination and substantial millennial scale variability in the glacial section largely consistent with our planktonic foraminifera oxygen isotope 18o record of neogloboquadrina pachyderma sin the timing and structure of the termination and some of the millennial scale sst fluctuations are very similar to those observed in the well dated sst record from odp site 1233 41 s and the temperature record from drowning maud land antarctic ice core supporting the hemispheric wide antarctic timing of sst changes however differences in our new sst record are also found including a long term warming trend over marine isotope stage mis 3 followed by a cooling toward the last glacial maximum lgm we suggest that these differences reflect regional cooling related to the proximal location of the southern patagonian ice sheet and related meltwater supply at least during the lgm consistent with the fact that no longer sst cooling trend is observed in odp site 1233 or any sst chilean record this proximal ice sheet location is documented by generally higher contents of ice rafted debris ird and tetra unsaturated alkenones and a slight trend toward lighter planktonic 18o during late mis 3 and mis 2

rock magnetic proxies of wind intensity and dust since 51 200 cal bp from lacustrine sediments of laguna potrok aike southeastern patagonia the sedimentary archive from laguna potrok aike is the only continuous record reaching back to the last glacial period in continental southeastern patagonia located in the path of the southern hemisphere westerly winds and in the source region of dust deposited in antarctica during glacial periods southern patagonia is a vantage point to reconstruct past changes in aeolian activity here we use high resolution rock magnetic and physical grain size data from site 2 of the international continental scientific drilling program icdp potrok aike maar lake sediment archive drilling project pasado in order to develop magnetic proxies of dust and wind intensity at 52 s since 51 200 cal bp rock magnetic analysis indicates the magnetic mineral assemblage is dominated by detrital magnetite based on the estimated flux of magnetite to the lake and comparison with distal dust records from the southern ocean and antarctica klf is interpreted as a dust indicator in the dust source of southern patagonia at the millennial time scale when ferrimagnetic grain size and coercivity influence are minimal comparison to physical grain size data indicates that the median destructive field of isothermal remanent magnetization mdfirm mostly reflects medium to coarse magnetite bearing silts typically transported by winds for short term suspension comparison with wind intensity proxies from the southern hemisphere during the last glacial period and with regional records from patagonia since the last deglaciation including marine lacustrine and peat bog sediments as well as speleothems reveals similar variability with mdfirm up to the centennial time scale mdfirm is interpreted as a wind intensity proxy independent of moisture changes for southeastern patagonia with stronger winds capable of transporting coarser magnetite bearing silts to the lake

changes in environment over the last 800 000 years from chemical analysis of the epica dome c ice core the epica ice core from dome c extends 3259 m in depth and encompasses 800 ka of datable and sequential ice numerous chemical species have been measured along the length of the cores here we concentrate on interpreting the main low resolution patterns of major ions we extend the published record for non sea salt calcium sea salt sodium and non sea salt sulfate flux to 800 ka the non sea salt calcium record confirms that terrestrial dust originating from south america closely mirrored antarctic climate both at orbital and millennial timescales a major cause of the main trends is most likely climate in southern south america which could be sensitive to subtle changes in atmospheric circulation sea salt sodium also follows temperature but with a threshold at low temperature we re examine the use of sodium as a sea ice proxy concluding that it is probably reflecting extent with high salt concentrations reflecting larger ice extents with this interpretation the sodium flux record indicates low ice extent operating as an amplifier in warm interglacials non sea salt sulfate flux is almost constant along the core confirming the lack of change in marine productivity for sulfur producing organisms in the areas of the southern ocean contributing to the flux at dome c for the first time we also present long records of reversible species such as nitrate and chloride and show that the pattern of post depositional losses described for shallower ice is maintained in older ice it appears possible to use these concentrations to constrain snow accumulation rates in interglacial ice at this site and the results suggest a possible correction to accumulation rates in one early interglacial taken together the chemistry records offer a number of constraints on the way the earth system combined to give the major climate fluctuations of the late quaternary period

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

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

glacial influence on the geochemistry of riverine iron fluxes to the gulf of alaska and effects of deglaciation riverine iron fe derived from glacial weathering is a critical micronutrient source to ecosystems of the gulf of alaska goa here we demonstrate that the source and chemical nature of riverine fe input to the goa could change dramatically due to the widespread watershed deglaciation that is underway we examine fe size partitioning speciation and isotopic composition in tributaries of the copper river which exemplify a long term goa watershed evolution from one strongly influenced by glacial weathering to a boreal forested watershed iron fluxes from glacierized tributaries bear high suspended sediment and colloidal fe loads of mixed valence silicate species with low concentrations of dissolved fe and dissolved organic carbon doc iron isotopic composition is indicative of mechanical weathering as the fe source conversely fe fluxes from boreal forested systems have higher dissolved fe concentrations corresponding to higher doc concentrations iron colloids and suspended sediment consist of fe hydr oxides and organic complexes these watersheds have an iron isotopic composition indicative of an internal chemical processing source we predict that as the goa watershed evolves due to deglaciation so will the source flux and chemical nature of riverine fe loads which could have significant ramifications for alaskan marine and freshwater ecosystems

palaeoclimatological and chronological implications of the vostok core dust record the2 083 m vostok ice core recovered by the soviet antarctic expeditions has provided much information of climatic and environmental interest for a period covering a full glacial inter glacial cycle1 6 here we present and discuss the dust record obtained down to 2 202 m the final depth to which this core was extended in 1986 first we document the fact that major changes in aeolian deposits as recorded in the vostok core appear to be of global significance and confirm the existence of a link between high latitude aeolian deposits and the earth s orbital parameters7 8 second we propose atmospheric dust as a strati graphic marker to compare timing with other records of palaeocli mate and use the magnetic susceptibility profile measured along the rc11 120 indian ocean core9 for this purpose assuming that major dust events correspond to common aeolian inputs this approach indicates that the vostok and marine records were roughly in phase at the previous glacial interglacial transition

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

dust transport from patagonia to antarctica a new stratigraphic approach from the scotia sea and its implications for the last glacial cycle abstract we studied two deep sea cores from the scotia sea to reconstruct past atmospheric circulation in the southern hemisphere and to resolve a long standing debate on the interpretation of magnetic susceptibility ms records in southern ocean so sediment high sedimentation sites md07 3134 0 2 1 2 m kyr and md07 3133 0 3 2 1 m kyr cover the last 92 5 kyr and 36 kyr respectively both exhibit a one to one coupling of the ms and ca2 signal to the non sea salt nss ca2 signal of the edml ice core clearly identifying atmospheric circulation as means of distribution comparison of additional proxies also excludes major influence by volcanic sources sea ice icebergs or oceanic current transport the close resemblance of the dust proxies over the last glacial cycle in turn allows for the establishment of an age model of unprecedented resolution and precision for so deep sea sediment because atmospheric transport involves no major leads or lags this is of particular importance because ms is routinely measured on deep sea cores in the so but the sediments usually lack biogenic carbonate and therefore had only limited stratigraphic control so far southern south america ssa is the likely source of eolian material because site md07 3133 located closer to the continent has slightly higher ms values than site md07 3134 and also the ms record of patagonian site salsa shows comparable variability patagonia was the dust source for both the scotia sea and east antarctica dust fluxes were several times higher during glacial times when atmospheric circulation was either stronger or shifted in latitude sea level was lowered shelf surfaces were exposed and environmental conditions in ssa were dominated by glaciers and extended outwash plains hence ms records of so deep sea sediment are reliable tracers of atmospheric circulation allowing for chronologically constrained reconstructions of the circum antarctic paleoclimate history

preferential dust sources a geomorphological classification designed for use in global dust cycle models received 11 april 2011 revised 28 september 2011 accepted 4 october 2011 published 24 december 2011 1 we present a simple theoretical land surface classification that can be used to determine the location and temporal behavior of preferential sources of terrestrial dust emissions the classification also provides information about the likely nature of the sediments their erodibility and the likelihood that they will generate emissions under given conditions the scheme is based on the dual notions of geomorphic type and connectivity between geomorphic units we demonstrate that the scheme can be used to map potential modern day dust sources in the chihuahuan desert the lake eyre basin and the taklamakan through comparison with observed dust emissions we show that the scheme provides a reasonable prediction of areas of emission in the chihuahuan desert and in the lake eyre basin the classification is also applied to point source data from the western sahara to enable comparison of the relative importance of different land surfaces for dust emissions we indicate how the scheme could be used to provide an improved characterization of preferential dust sources in global dust cycle models

minimal change in antarctic circumpolar current flow speed between the last glacial and holocene relatively little is known about the dynamics of the antarctic circumpolar current during the last glacial period estimates of current speeds over the past 20 000 years based on sediment grain size suggest that average flow speeds during the last glacial were comparable to modern speeds but not in the areas with overlying winter sea ice

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

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

south pole paleowind from automated synthesis of ice core records 1 we develop a fully automated reconstruction of south pole surface roughness as a measure of past wind intensity using dynamic warping feature recognition and internal consistency checks to reduce subjectivity and analysis time we synchronized millimeter resolution optical profiles of deep south pole glacial dust together with ice core data between the ages 26 and 90 thousand years b p the images were captured using a laser dust logger in six boreholes of the icecube neutrino detector array a massive construction project in the ice at south pole and an unusual opportunity for glaciology and paleoclimate research south pole surface roughness anticorrelated with curves of antarctic pco2 and temperature which we propose were connected through secular migrations of the southern hemisphere westerlies this new paleoclimate signal may be direct evidence of atmospheric reorganization during the glacial helping to deconvolve the thermodynamics and biogeochemistry of climate change we also found that local intensity of atmospheric circulation roughly tracked the quantity of wind borne particulates deposited in antarctic ice during the glacial period although the largest dust increases were likely furnished by the source regions

aeolian sequence and the archaeological record in the fuegian steppe argentina abstract a 20 m thick sequence of aeolian deposits and palaeosols deposited above neogene marine sediments adjacent to the shallow saline ephemeral lake arturo in interior tierra del fuego is described a deposit of archaeological stone artifacts and bones the lake arturo 1 archaeological site is located in a deflation hollow near the top of the aeolian sequence the sequence of nine aeolian deposits including eight palaeosols and capped by the contemporary soil provides evidence of environmental changes which have occurred during the holocene in the cold fuegian steppe beginning as early as the late glacial early holocene transition a chronostratigraphy is provided by guanaco lama guanicoe and canidae bones embedded within palaeosols and organic matter content radiocarbon dated from 9951 59 bp 11 304 cal bp at the base of the sequence to 434 43 bp 471 cal bp near the top a tephra layer between palaeosols 4 and 5 is interpreted from its geochemical fingerprint as the product of one of the mid holocene eruptions of mt burney located in the southern patagonian andes it is suggested that the accumulation of the aeolian sediments occurred throughout most of the holocene as a result of both local acquisition of fine particles derived from the weathering and erosion of the basal neogene marine sediments and deflation from the intermittently dry lake bed as well as deposition of material transported by wind from more distant sources the orientation of the aeolian deposits suggests a more northwesterly wind direction instead of the present westerlies weakly developed a horizons capping each of the sediment units suggest that the landscape was sensitive to environmental change from more arid conditions when the aeolian deposits accumulated to brief periods of landscape stability when topsoil development occurred evidence of human occupation in lake arturo 1 is confined to the upper part of the sequence ca 500 years bp and is interpreted as a place for primary butchering and raw material acquisition

rock magnetic signature of precipitation and extreme runoff events in south eastern patagonia since 51 200 cal bp from the sediments of laguna potrok aike a 106 m long sediment sequence from the maar lake laguna potrok aike in southern patagonia was recovered in the framework of the international continental scientific drilling program icdp potrok aike maar lake sediment archive drilling project pasado about half of the sedimentary sequence is composed of mass movement deposits mmds and the event corrected record reaches back to 51 200 cal bp here we present a high resolution rock magnetic study revealing two sedimentary facies associated with mmds and characterized by two different types of spurious gyroremanent magnetization grm acquired during static alternating field demagnetization the first rock magnetic signature is detected in mmds composed of reworked sand and tephra material the signature consists of grm acquired during demagnetization of the natural remanent magnetization nrm and other rock magnetic properties typical of iron sulfides such as greigite we interpret these intervals as authigenic formation of iron sulfides in suboxic conditions within the mmd the second rock magnetic signature consists of a series of 10 short intervals located on the top of mmds characterized by grm acquisition during demagnetization of the isothermal remanent magnetization irm based on geological limnological stratigraphic and climatic evidence these layers are interpreted as reflecting pedogenic hematite and or goethite brought to the lake by runoff events related to precipitation and permafrost melt the pedogenic iron minerals mobilized from the catchment most likely settled out of suspension on top of mmds after a rapid remobilization event the series of runoff events corresponds to periods of increased lacustrine productivity in laguna potrok aike and are coeval within the limit of the chronology to warm periods of the last glacial as recorded in antarctica the deglaciation in the mid latitudes of the southern hemisphere and enhanced precipitation during the early holocene in southeastern patagonia

microsedimentological characterization using image analysis and μ xrf as indicators of sedimentary processes and climate changes during lateglacial at laguna potrok aike santa cruz argentina palaeoclimatic and paleoenvironmental high latitude records in the southern hemisphere are scarce compared to the northern counterpart however understanding global evolution of environmental systems during sudden climate changes is inseparable from an equivalent knowledge of both hemispheres in this context a high resolution study of lacustrine sediments from laguna potrok aike santa cruz province patagonia argentina was conducted for the lateglacial period using concurrent x ray fluorescence xrf and scanning electron microscope analyses peaks of ca si and mn and occurrences of the green alga phacotus lenticularis have been interpreted as variations in ventilation of the water column from 13 6 to 11 1 ka cal bp during this interval mild climate conditions during the younger dryas are characterized by relatively weak westerlies favouring the formation of a stratified water body as indicated by preserved manganese and ca si peaks and high total organic carbon toc values in this environment water in the epilimnion can reach sufficiently high temperature to allow p lenticularis to grow colder conditions are marked by peaks in ca without p lenticularis and occur during the antarctic cold reversal acr in this lateglacial interval micropumices were also detected in large amount image analysis of thin sections allowed the counting and size measurement of detrital particles and micropumices separately micropumices significantly influence the iron and titanium content hence preventing to use them as proxies of detrital input in this interval

elevated dust deposition in tierra del fuego chile resulting from neoglacial darwin cordillera glacier fluctuations atmospheric mineral dust is intrinsically linked with climate although dust flux variability on glacial interglacial timescales is well documented holocene dust records remain scarce to fill this gap we conducted elemental isotopic and sedimentological analyses on a peat core from the karukinka natural park in tierra del fuego an 8000 year old mineral dust record was extracted indicating three periods of elevated dust deposition i 8 1 7 4 cal ka bp ii 4 2 cal ka bp and iii 2 4 1 4 cal ka bp the two oldest peaks are related to volcanic eruptions of the hudson and monte burney volcanoes respectively the most recent dust peak however has a rare earth element and neodymium isotopic composition that resembles the geochemical signature of outwash plain sediments from the darwin cordillera since the timing of this dust peak corresponds to a period of glacier retreat between neoglacial advances iii and iv we infer that holocene aeolian dust fluxes in southern patagonia are mostly driven by glacial sediment availability our results underline the important role of glaciers in producing aeolian dust in high latitude regions and they imply that the current retreat of glaciers worldwide may result in elevated atmospheric dust loads

impact of antarctic climate during the late quaternary records from zub lake sedimentary archives from schirmacher hills east antarctica abstract the antarctic continental margin is marked with ice free areas which are host to numerous freshwater lakes these lacustrine systems are rich in sedimentary deposits which archive in them the regional and general climatic variations these lakes respond to the seasonal variations in climate over glacial interglacial timescales and can be inferred from the sedimentary proxies in this study a 79 cm long radiocarbon dated sediment core retrieved from a peri glacial lake is analysed for elementary corg norg isotopic 13com 15nom and particle size sand silt clay the radiocarbon dated sections 0 65 cm extends up to 43 kyr bp the time series of sedimentary organic matter om proxies corg 3 5 3 c natomic ratio 11 3 and 13com 14 4 indicate that the om in this lake sedimentary record is an admixture of terrestrial and lacustrine biomass distinctly higher lower values during the holocene lgm suggests presence of terrestrial and aquatic aquatic biomass indicating ice free ice cover and warm cold holocene glacial conditions which would result in an increased decreased lake productivity and fluvial wind input of sand and clay silt higher sand content 30 24 and 15 kyr bp silt content 24 kyr bp corg and norg 24 kyr bp within the last glacial stage lgs indicates intermittent warming period in coherence with the antarctic isotope maximum aim the transition in values corg norg c n ratio 13com sand content starting at 16 6 kyr bp closely following antarctic deglaciation to reach holocene optimum values at 11 3 kyr bp documents the influence of antarctic climate on regional areas

links between patagonian ice sheet fluctuations and antarctic dust variability during the last glacial period mis 4 2 abstract antarctic and greenland ice core records reveal large fluctuations of dust input on both orbital and millennial time scales with potential global climate implications at least during glacial periods the antarctic dust fluctuations appear to be largely controlled by environmental changes in southern south america we compare dust flux records from two antarctic ice cores to variations in the composition of the terrigenous supply at odp site 1233 located off southern chile and known to record fluctuations in the extent of the northern part of the patagonian ice sheet npis during the last glacial period marine isotope stage mis 4 to 2 within age uncertainties millennial scale glacial advances retreats of the npis correlate to antarctic dust maxima minima in turn npis fluctuations were closely related to offshore sea surface temperature sst changes this pattern suggests a causal link involving changes in temperature in rock flour availability in latitudinal extensions of the westerly winds and in foehn winds in the southern pampas and patagonia we further suggest that the long term trend of dust accumulation is partly linked to the sea level related changes in the size if the patagonian source area due to the particular morphology of the argentine shelf we suggest that sea level drops at the beginning of mis 4 and mis 2 were important for long term dust increases while changes in the patagonian dust source regions primarily control the early dust decrease during the mis 4 3 transition and termination 1

southern patagonian glacial chronology for the last glacial period and implications for southern ocean climate the magellan region of southern south america is in a unique setting at 50 s on the equatorial side of the antarctic frontal zone to record in detail terrestrial glacial to interglacial events a 10be chronology shows growth and millennial fluctuations of a patagonian ice sheet between 25 and 17 6 17 0 cal ka in the strait of magellan the maximum ice margin position is dated to 24 6 0 9 ka and other moraine ages are 18 5 1 8 and 17 6 0 2 ka mean 1 standard deviation in bahia inutil dated moraine ages are 20 4 1 2 and 17 3 0 8 ka the chronology of the local last glacial maximum lgm reveals a record of atmospheric cooling that was broadly in phase with changes in southern ocean conditions such as sea ice fluctuations and surface water characteristics published modeling results indicate that a decline in temperature of 6 c and slight drying over southernmost patagonia could simulate the growth and sustained presence of an ice sheet to the mapped lgm limit the terrestrial record in southern patagonia and marine records in adjacent oceans indicate mean northward movement of the antarctic frontal zone which caused the last southern south american ice age the antarctic frontal zone at present lies only 3 5 to the south some significant changes in the magellan region occurred in step with north atlantic region and the northern hemisphere for example the overall time span of the last glaciation and the timing of maximum ice extent were similar between the hemispheres despite maximum local summer insolation intensity in southern south america other characteristics of the southern patagonian glacial history differ from the north atlantic region specifically an out of phase relationship during deglaciation which is more similar to that of southern ocean and antarctic records

late pleistocene dust deposition in the patagonian steppe extending and refining the paleoenvironmental and tephrochronological record from laguna potrok aike back to 55 ka abstract paleoenvironmental records extending well into the last glacial period are scarce in the steppe regions of southern south america here we present a continuous record for the past 55 ka from the maar lake laguna potrok aike 51 58 s 70 23 w southern patagonia argentina previous studies on a sedimentary core from a lake level terrace near the northern margin of the lake covered parts of oxygen isotope stage ois 3 59 29 ka whereas a second core from the centre of the basin comprised the last 16 ka tephrostratigraphical constraints and osl ages from a third core located below the lake level terrace provide the crucial piece to close the gap between the previous coring sites high resolution xrf and magnetic susceptibility as well as grain size data indicate a positive hydrological balance alongside with relatively high aeolian activity during the glacial which is contemporaneous with increased dust fluxes in antarctica this is therefore the first evidence for contemporaneity of aeolian deposition in both the target area antarctica and in the major source area of patagonia during the holocene climatic conditions driving sediment deposition seem to have been more variable and less dominated by wind compared to glacial times the identification of a minor lake level lowering at approximately 4 cal ka bp allows to refine earlier paleoenvironmental reconstructions for the holocene within error margins the osl ages are consistent with published radiocarbon dated records offering hence a valuable tool for further studies of the sediments from laguna potrok aike the new chronology confirms the age of three tephra layers up to now only found in laguna potrok aike sediments and ascribed to ois 3

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

southern ocean sea ice extent productivity and iron flux over the past eight glacial cycles sea ice and dust flux increased greatly in the southern ocean during the last glacial period palaeorecords provide contradictory evidence about marine productivity in this region but beyond one glacial cycle data were sparse here we present continuous chemical proxy data spanning the last eight glacial cycles 740 000 years from the dome c antarctic ice core these data constrain winter sea ice extent in the indian ocean southern ocean biogenic productivity and patagonian climatic conditions we found that maximum sea ice extent is closely tied to antarctic temperature on multi millennial timescales but less so on shorter timescales biological dimethylsulphide emissions south of the polar front seem to have changed little with climate suggesting that sulphur compounds were not active in climate regulation we observe large glacial interglacial contrasts in iron deposition which we infer reflects strongly changing patagonian conditions during glacial terminations changes in patagonia apparently preceded sea ice reduction indicating that multiple mechanisms may be responsible for different phases of co2 increase during glacial terminations we observe no changes in internal climatic feedbacks that could have caused the change in amplitude of antarctic temperature variations observed 440 000 years ago

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

aeolian dust in east antarctica epica dome c and vostok provenance during glacial ages over the last 800 kyr aeolian mineral dust archived in antarctic ice cores represents a key proxy for quaternary climate evolution the longest and most detailed dust and climate sequences from polar ice are provided today by the vostok and by the epica dome c edc ice cores here we investigate the geographic provenance of dust windborne to east antarctica during early and middle pleistocene glacial ages using strontium and neodymium isotopes as tracers the isotopic signature of antarctic dust points towards a dominant south american origin during marine isotopic stage mis 8 10 12 and back to mis 16 and 20 as deduced from edc core data provide evidence for a persistent overall westerly circulation pattern allowing efficient transfer of dust from south america to the interior of antarctica over the last 800 kyr some small but significant dissimilarity between old and recent glacial ages suggests a slightly reduced patagonian contribution during ancient glaciations

evidence for rapid ice flow and proglacial lake evolution around the central strait of magellan region southernmost patagonia this paper presents a detailed palaeoglaciological reconstruction of ice sheet dynamics in the seno skyring seno otway and strait of magellan region of the former patagonian ice sheet with a particular focus on previously hypothesised zones of rapid ice flow and the evolution of proglacial lakes geomorphological mapping from a combination of satellite imagery and oblique and vertical aerial photographs reveals a variety of glacial landforms that are grouped into several discrete flow sets and associated ice margin positions the most distinct features are represented by flow sets of highly elongate streamlined glacial lineations on both sides of the strait of magellan based on the shape and dimensions of the flow sets and their abrupt lateral margins a transverse and longitudinal variation in glacial lineation length and elongation ratio and the reported presence of a potentially deformable bed and thrust moraines the flow sets are interpreted as zones of rapid ice flow within the otway and magellan lobes we hypothesise that this provides evidence for contemporaneous surge like advances within the lobes which may explain the asymmetry in the lobate margin positions on either side of the strait the mechanisms that initiated rapid flow are unclear but are likely to have been influenced by internal factors such as a change in thermal hydrological conditions at the bed the topography of the region suggests ice dammed lakes would have formed as the ice lobes retreated the westernmost of the former lakes lake skyring is delimited by a series of palaeo shorelines surrounding the present day lake laguna blanca and we reconstruct lake evolution based on manipulation of a digital elevation model the size and orientation of meltwater channels and a large outwash plain indicate that lake skyring drained eastwards towards the strait of magellan probably quite rapidly we conclude that the potential for quasi independent surge like behaviour within adjacent lobes raises the possibility that during climate driven ice expansion some advances in this region may have been partly controlled by secondary internal feedback mechanisms

the mis 3 maximum of the torres del paine and ultima esperanza ice lobes in patagonia and the pacing of southern mountain glaciation abstract the timing structure and termination of the last southern mountain glaciation and its forcing remains unclear most studies have focused on the global last glacial maximum lgm 26 5 19 ka time period which is just part of the extensive time frame within the last glacial period including marine isotope stages 3 and 4 understanding the glacial fluctuations throughout the glacial period is a prerequisite for uncovering the cause and climate mechanism driving southern glaciation and the interhemispheric linkages of climate change here we present an extensive n 65 cosmogenic 10be glacier chronology derived from moraine belts marking the pre global lgm extent of the former patagonian ice sheet in southernmost south america our results show the mountain ice sheet reached its maximum extent at 48 0 1 8 ka during the local lgm but attained just half this extent at 21 5 1 8 ka during the global lgm this finding supported by nearby glacier chronologies indicates that at orbital time scales the southern mid latitude glaciers fluctuated out of phase with northern hemisphere ice sheets at millennial time scales our data suggest that patagonian and new zealand glaciers advanced in unison with cold antarctic stadials and reductions in southern ocean sea surface temperatures this implies a southern middle latitudes wide millennial rhythm of climate change throughout the last glacial period linked to the north atlantic by the bipolar seesaw we suggest that winter insolation acting alongside other drivers such as the strength and or position of the southern westerlies controlled the extents of major southern mountain glaciers such as those in southernmost south america

dust provenance in antarctic ice during glacial periods from where in southern south america 1 the origin of dust deposited in east antarctica is not fully understood yet this study demonstrates that contrary to nd sr isotopes are strongly fractionated in the finest sized material representing potential dust sources in south america analysis of nd isotopes suggests that argentine loess southern ocean sediments and antarctic dust may all have a related origin or can represent comparable mechanisms of eolian sediment transport and deposition this analysis also concludes that the patagonian signature can explain a high proportion of the isotopic composition of dust trapped in antarctic ice during glacial periods the puna altiplano plateau emerges as the second possible important sediment contributor explaining the crustal like signature found in east antarctic dust and should be considered as a potential source area when quaternary paleoclimate is reconstructed from argentine loess antarctic dust and south atlantic sediment records

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

dust composition changes from taylor glacier east antarctica during the last glacial interglacial transition a multi proxy approach abstract mineral dust is transported in the atmosphere and deposited in oceans ice sheets and the terrestrial biosphere temporal changes in locations of dust source areas and transport pathways have implications for global climate and biogeochemical cycles the chemical and physical characterization of the dust record preserved in ice cores is useful for identifying of dust source regions dust transport dominant wind direction and storm trajectories here we present a 50 000 year geochemical characterization of mineral dust entrapped in a horizontal ice core from the taylor glacier in east antarctica strontium sr and neodymium nd isotopes grain size distribution trace and rare earth element ree concentrations and inorganic ion cl and na concentrations were measured in 38 samples corresponding to a time interval from 46 kyr before present bp to present the sr and nd isotope compositions of insoluble dust in the taylor glacier ice shows distinct changes between the last glacial period lgp in this study ranging from 46 7 15 3 kyr bp the early holocene in this study ranging from 14 5 8 7 kyr bp and zero age samples the 87sr 86sr isotopic composition of dust in the taylor glacier ice ranged from 0 708 to 0 711 during the lgp while the variability during the early holocene is higher ranging from 0 707 to 0 714 the end composition ranges from 0 1 to 3 9 during the lgp and is more variable from 1 9 to 8 2 during the early holocene the increased isotopic variability during the early holocene suggests a shift in dust provenance coinciding with the major climate transition from the lgp to the holocene the isotopic composition and multiple physical and chemical constraints support previous work attributing southern south america ssa as the main dust source to east antarctica during the lgp and a combination of both local ross sea sector dust sources and ssa after the transition into the holocene this study provides the first high time resolution data showing variations in dust provenance to east antarctic ice during a major climate regime shift and we provide evidence of changes in the atmospheric transport pathways of dust following the last deglaciation

a uniform isotopic and chemical signature of dust exported from patagonia rock sources and occurrence in southern environments patagonia is considered to be the most important source of dust from south america that is deposited in surrounding areas and we present here a systematic sr and nd isotopic study of sediment currently being exported eolian and suspended riverine sediments from patagonia have a homogeneous chemical and isotopic composition that results from the mixing of by products from explosive andean volcanism derived from the extensive jurassic silicic province of chon aike and pyroclastic materials from the basic to intermediate southern andean quaternary arc which are easily denudated and dispersed the main andean uplift and the glaciations that began in the late tertiary account for the extensive distribution of these sediments in the extra andean region the present geochemical signature of patagonian sediments was produced during the pleistocene along with the onset of the southern andean explosive arc volcanism previously published compositions of sediments from other southern south american source regions assumed to be representative of patagonia are distinct from our data considering the alleged importance of patagonia as a dust source for different depositional environments in southern latitudes it is surprising to verify that the chemical and isotopic signatures of patagonian sourced sediments are different from those of sediments from the southern ocean the pampean region or the antarctic ice sediments from these areas have a crustal like geochemical signature reflecting a mixed origin with sediment from other southern south american sources whereas patagonian sediments likely represent the basic to intermediate end member composition

a silicate weathering mechanism linking increases in marine 87sr 86sr with global glaciation the 87sr 86sr ratio of sea water is generally regarded as a proxy for the rate of chemical weathering of the continents interpretation of the 87sr 86sr record in marine limestones requires an understanding of how changes in this quantity are linked to climate and tectonic events a connection between the strontium isotope record and the extent of global glaciation has been proposed1 8 but without a well established mechanism glaciation may influence marine 87sr 86sr by changing global riverine sr fluxes that is rock weathering rates and or 87sr 86sr ratios that is relative mineral weathering rates here we investigate how the 87sr 86sr release from silicate weathering is affected by glaciation using the sr isotope systematics of granitoid soils on alpine glacial moraines in the wind river range wyoming we observe a negative correlation between the 87sr 86sr ratio of exchangeable sr in soils and the soil age indicating that the 87sr 86sr ratio of sr released in the early stages of weathering is significantly higher than in later stages we estimate that this mechanism can increase global riverine 87sr 86sr by an average of 0 0002 during periods of glacial interglacial cycling when superimposed on long term trends controlled by tectonic processes2 7 9 10 this shift can account for the correlation between the rate of change of marine 87sr 86sr and the intensity of glaciation over at least the past 10 myr

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

glacial reduction of amoc strength and long term transition in weathering inputs into the southern ocean since the mid miocene evidence from radiogenic nd and hf isotopes combined seawater radiogenic hafnium hf and neodymium nd isotope compositions were extracted from bulk sediment leachates and foraminifera of site 1088 odp leg 177 2082 m water depth on the agulhas ridge the new data provide a continuous reconstruction of long and short term changes in ocean circulation and continental weathering inputs since the mid miocene due to its intermediate water depth the sediments of this core sensitively recorded changes in admixture of north atlantic deep water nadw to the antarctic circumpolar current acc as a function of the strength of the atlantic meridional overturning circulation amoc nd isotope compositions end range from 7 to 11 with glacial values generally 1 to 3 units more radiogenic than during the interglacials of the quaternary the data reveal episodes of significantly increased amoc strength during late miocene and pliocene warm periods whereas peak radiogenic end values mark a strongly diminished amoc during the major intensification of northern hemisphere glaciation near 2 8 ma and in the pleistocene after 1 5 ma in contrast the hf isotope compositions ehf show an essentially continuous evolution from highly radiogenic values of up to 11 during the miocene to less radiogenic present day values 2 to 4 during the late quaternary the data document a long term transition in dominant weathering inputs where inputs from the south america are replaced by those from southern africa moreover radiogenic peaks provide evidence for the supply of radiogenic hf originating from patagonian rocks to the atlantic sector of the southern ocean via dust inputs

antarctic timing of surface water changes off chile and patagonian ice sheet response marine sediments from the chilean continental margin are used to infer millennial scale changes in southeast pacific surface ocean water properties and patagonian ice sheet extent since the last glacial period our data show a clear antarctic timing of sea surface temperature changes which appear systematically linked to meridional displacements in sea ice westerly winds and the circumpolar current system proxy data for ice sheet changes show a similar pattern as oceanographic variations offshore but reveal a variable glacier response time of up to 1000 years which may explain some of the current discrepancies among terrestrial records in southern south america

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

coal derived rates of atmospheric dust deposition during the permian despite widespread evidence for atmospheric dust deposition prior to the quaternary quantitative rate data remains sparse as dust influences both climate and biological productivity the absence of quantitative dust data limits the comprehensiveness of models of pre quaternary climate and biogeochemical cycles here we propose that inorganic matter contained in coal primarily records atmospheric dust deposition to test this we use the average concentration of inorganic matter in permian coal to map global patterns and deposition rates of atmospheric dust over pangea the dust accumulation rate is calculated assuming permian peat carbon accumulation rates in temperate climates were similar to holocene rates and accounting for the loss of carbon during coalification coal derived rates vary from 0 02 to 25 g m 2 year 1 values that fall within the present day global range a well constrained east west pattern of dust deposition corresponding to expected palaeoclimate gradients extends across gondwana with maximum dust deposition rates occurring close to arid regions a similar pattern is partially defined over the northern hemisphere patterns are consistent with the presence of two large global dust plumes centred on the tropics the spatial patterns of dust deposition were also compared to dust cycle simulations for the permian made with the community climate system model version 3 ccsm3 key differences between the simulations and the coal data are the lack of evidence for an antarctic dust source higher than expected dust deposition over n and s china and greater dust deposition rates over western gondwana this new coal based dust accumulation rate data expands the pre neogene quantitative record of atmospheric dust and can help to inform and validate models of global circulation and biogeochemical cycles over the past 350 myr

strontium and neodymium isotopic signatures indicate the provenance and depositional process of loams intercalated in coastal dune sand western japan abstract isotopic analyses of strontium and neodymium suggest that layers of loam intercalated in dune sand on the japan sea coast at tottori western japan consist of a mixture of asian dust from china and locally derived sediment an outcrop exposure shows a succession of late pleistocene dune sand a lower loam layer daisen kurayoshi pumice dkp 50 55 ka or older an upper loam aira tn tuff ca 30 ka and holocene dune sand in ascending order bulk samples of the loam layers show an upward increase in 87 sr 86 sr suggesting that the contribution of asian dust increases upward the sr isotopic values also suggest a greater contribution of asian dust in the silt fraction than in the bulk sample asian dust transported by westerly jet from the taklamakan or gobi desert is the main constituent of the upper part of the lower loam of which isotopic values of silicate portion is isotopically identical to those of desert sand in china 87 sr 86 sr 0 717 0 719 e nd 9 5 to 9 4 in contrast the sr and nd isotopic values of dkp 87 sr 86 sr 0 705 e nd 2 6 to 0 6 are close to those of the volcanic rocks of mt daisen which is regarded as the source of the tephra the isotopic signature suggests that asian dust also have contributed to the upper part of the upper loam layer the upward increase of 87 sr 86 sr within each of the loam layers suggests that the contribution of asian dust increased as the proportion of reworked deposits from the underlying layer dune sand or dkp decreased by burial in contrast 87 sr 86 sr in dkp shows little vertical change suggesting very rapid deposition without entrainment of the underlying lower loam layer

compositions of dust and sea salts in the dome c and dome fuji ice cores from last glacial maximum to early holocene based on ice sublimation and single particle measurements we analyzed the chemical compositions of dust and sea salt particles in the epica dome c edc ice core during 26 7 kyr bp using an ice sublimation technique and compared the results with existing

pleistocene glacitectonic landforms and sediments around central magellan strait southernmost chile evidence for fast outlet glaciers with cold based margins abstract proglacial and subglacial glacitectonic sediments and landforms around the margins of the strait of magellan southernmost chile record the advance and retreat of outlet glaciers of the patagonian ice cap during the last glacial cycle the spatial arrangement of glacitectonic landforms in the area is inferred to have resulted from the advance of ice lobes with cold based margins and wet based interiors as the ice advanced subglacial basins were excavated beneath the glacier margins and the eroded material was pushed up into thrust moraines probably because frozen bed conditions formed a thermal dam against the free drainage of subglacial meltwater these ice marginal glacitectonic landforms were then overridden and streamlined into drumlins and flutes as thicker wet based ice passed over the area evidence for permafrost near sea level in patagonia during the last glaciation suggests that mean annual temperatures were several degrees lower than indicated by recent modelling studies the results indicate that future modelling experiments should incorporate more realistic basal boundary conditions particularly the presence of a weak deforming layer at the glacier bed to improve climatic reconstructions of southern south america

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

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

authigenic detrital and diagenetic minerals in the laguna potrok aike sediment sequence the 100 m long laguna potrok aike sediment sequence yielded a record spanning the last glacial period to the holocene this paper presents and discusses two aspects of the mineralogy of the lake the first aspect is based on a semi quantitative x ray diffraction analysis of bulk and clay mineralogical assemblages minor mineralogical changes are observed throughout the glacial section suggesting relatively uniform sediment sources the transition into the holocene is characterized by increasing fluxes of endogenic calcite thought to relate to lower lake levels the second aspect is based on analysis of uranium series disequilibria in diagenetic vivianite from the glacial section u series ages were expected to yield minimum ages for the host sediment unfortunately very little authigenic u is present in vivianite grains the low primary productivity of the lake and thus low organic carbon fluxes might have prevented the development of strong redox gradients at the water sediment interface and thus reduced diagenetic u uptake into the sediment one vivianite sample at a 56 9 m composite depth yielded enough authigenic uranium to calculate a 230th age of 29 4 5 9 ka 2 this age is younger than the one indicated by the radiocarbon chronology it is thus concluded that a relatively late diagenetic evolution of the u th system characterizes the recovered vivianite minerals the authigenic u displays a very high excess in 234u over 238u with an activity ratio of 4 58 0 58 2 it suggests that it originates from the transfer of highly fractionated u from surrounding detrital minerals through very low u content pore waters

high resolution paleomagnetic secular variations and relative paleointensity since the late pleistocene in southern south america abstract paleomagnetic inclination declination and relative paleointensity were reconstructed from the sediments of laguna potrok aike in the framework of the international continental scientific drilling program icdp potrok aike maar lake sediment archive drilling project pasado here we present the u channel based full vector paleomagnetic field reconstruction since 51 2 ka cal bp the relative paleointensity proxy rpi was built by normalising the natural remanent magnetisation with the anhysteretic remanent magnetisation using the average ratio at 4 demagnetisation steps part of the chrm interval nrm arm 10 40 mt a grain size influence on the rpi was removed using a correction based on the linear relationship between the rpi and the median destructive field of the natural remanent magnetisation mdf nrm the new record is compared with other lacustrine and marine records and stacks from the mid to high latitudes of the southern hemisphere revealing consistent millennial scale variability the identification of the laschamp and possibly the mono lake geomagnetic excursions and a direction swing possibly associated to the hilina pali excursion at 20 ka cal bp nonetheless a global scale comparison with other high resolution records located on the opposite side of the earth and with various dipole field references hint at a different behaviour of the geomagnetic field around southern south america at 46 ka cal bp

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

the mineral dust aerosol cycle during the last glacial maximum the canadian centre for climate modelling and analysis general circulation model gcm is used to investigate the factors influencing the mineral dust distribution at the time of the last glacial maximum lgm simulated deposition rates are used in conjunction with existing paleoclimate data to infer likely characteristics of the mineral dust conditions at that time and identify contributions to the pattern of enhanced dustiness of the lgm relative to the present indicated by ice core and loess data maximal consistency between the gcm the climate long range investigation mapping and prediction climap data set and the ice core data requires approximately a 15 to 30 fold increase in dust production globally during the last glacial maximum relative to the preindustrial holocene in particular regional 10 to 50 fold and 20 fold lgm increases are indicated in eastern asia and south america respectively these implied source enhancements are quite insensitive to the details of the dust model analysis of the contributing factors suggests an increase in fine particle availability in the source regions

the southern glacial maximum 65 000 years ago and its unfinished termination abstract glacial maxima and their terminations provide key insights into inter hemispheric climate dynamics and the coupling of atmosphere surface and deep ocean hydrology and cryosphere which is fundamental for evaluating the robustness of earth s climate in view of ongoing climate change the last glacial maximum lgm 26 19 ka ago is widely seen as the global cold peak during the last glacial cycle and its transition to the holocene interglacial dubbed termination 1 t1 as the most dramatic climate reorganization during this interval climate records show that over the last 800 ka ice ages peaked and terminated on average every 100 ka 100 ka world however the mechanisms pacing glacial interglacial transitions remain controversial and in particular the hemispheric manifestations and underlying orbital to regional driving forces of glacial maxima and subsequent terminations remain poorly understood here we show evidence for a full glacial maximum in the southern hemisphere 65 1 2 7 ka ago and its unfinished termination our 10 be chronology combined with a model simulation demonstrates that new zealand s glaciers reached their maximum position of the last glacial cycle during marine isotope stage 4 mis 4 southern ocean and greenhouse gas records indicate coeval peak glacial conditions making the case for the southern glacial maximum about halfway through the last glacial cycle and only 15 ka after the last warm period mis 5a we present the hypothesis that subsequently driven by boreal summer insolation forcing a termination began but remained unfinished possibly because the northern ice sheets were only moderately large and could not supply enough meltwater to the north atlantic through heinrich stadial 6 to drive a full termination yet the unfinished termination left behind substantial ice on the northern continents about 50 of the full lgm ice volume and after another 45 ka of cooling and ice sheet growth the earth was at inter hemispheric last glacial maximum configuration when similar orbital forcing hit maximum size northern ice sheets and ushered in t1 and thus the ongoing interglacial this argument highlights the critical role of full glacial conditions in both hemispheres for terminations and implies that the southern hemisphere climate could transition from interglacial to full glacial conditions in about 15 000 years while the northern hemisphere and its continental ice sheets required half a glacial cycle

postglacial fluctuations of cordillera darwin glaciers southernmost patagonia reconstructed from almirantazgo fjord sediments abstract most outlet glaciers of the cordillera darwin icefield cdi patagonia 54 s are currently transitioning from calving to land based conditions whether this situation is unique to the modern climate or also occurred during the holocene is entirely unknown here we investigate the holocene fluctuations of outlet glaciers from the northern flank of the cdi using a multi proxy sedimentological and geochemical analysis of a 13 5 m long sediment core from almirantazgo fjord our results demonstrate that sedimentation in almirantazgo fjord started prior to 14 300 cal yr bp with glacier proximal deposits occurring until 13 500 cal yr bp after 12 300 cal yr bp most glaciers had retreated to land locked locations and by 9800 cal yr bp almirantazgo fjord was a predominantly marine fjord environment with oceanographic conditions resembling the present day setting our sediment record shows that during the first part of the holocene cdi glaciers were almost entirely land based with a possible re advance at 7300 5700 cal yr bp this is in clear contrast with the neoglaciation during which cdi glaciers rapidly re advanced and shrank back several times mostly in phase with the eastern outlet glaciers of the southern patagonian icefield spi two significant meltwater events indicative of rapid glacier retreat were identified at 3250 2700 and 2000 1200 cal yr bp based on an increase in grain size mode and related inorganic geochemical parameters this interpretation is additionally supported by concomitant decreases in organic carbon of marine origin and in cl counts salinity reflecting higher terrestrial input to the fjord and freshening of the fjord waters overall our record suggests that cdi outlet glaciers advanced in phase with eastern spi glaciers during the neoglaciation and retreated far enough into their valleys twice to form large outwash plains our results also highlight the potential of fjord sediments to reconstruct glacier variability at high resolution on multi millennial timescales

the deuterium excess records of epica dome c and dronning maud land ice cores east antarctica new high resolution deuterium excess d data from the two epica ice cores drilled in dronning maud land edml and dome c edc are presented here the main moisture sources for precipitation at edc and edml are located in the indian ocean and atlantic ocean respectively the more southward moisture origin for edml is reflected in a lower present day d value compared to edc the edml and edc isotopic records 18o and d show the main climate features common to the east antarctic plateau and similar millennial scale climate variability during the last glacial period however quite large 18o and d differences are observed during mis5 5 and the glacial inception with a long term behaviour a possibility for this long term difference could be related to uncertainties in past accumulation rate which are used in the glaciological models regional climate anomalies between the two sites during mis5 5 could also be consistent with the observed edml edc 18o and d gradient anomalies simulations performed with the general circulation model echam4 for different time slices provide a temporal temperature isotope slope for the edml region in fair agreement to the modern spatial slope tsite and tsource records are extracted from both ice cores using a modelling approach after corrections for past 18o seawater and elevation changes a limited impact of d on antarctic temperature reconstruction at both edml and edc has been found with a higher impact only at glacial inception the aim antarctic isotope maximum events in both ice cores are visible also after the source correction suggesting that these are real climate features of the glacial period the different shape of the aim events between edc and edml as well as some climate features in the early holocene points to a slightly different climate evolution at regional scale a comparison of our temperature reconstruction profiles with the aerosol fluxes show a strong coupling of the nssca fluxes with antarctic temperatures during glacial period and a tighter coupling of 18o and tsite with ssna flux at edml compared to edc during the glacial period and mis5 5

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

synchronous volcanic eruptions and abrupt climate change 17 7 ka plausibly linked by stratospheric ozone depletion glacial state greenhouse gas concentrations and southern hemisphere climate conditions persisted until 17 7 ka when a nearly synchronous acceleration in deglaciation was recorded in paleoclimate proxies in large parts of the southern hemisphere with many changes ascribed to a sudden poleward shift in the southern hemisphere westerlies and subsequent climate impacts we used high resolution chemical measurements in the west antarctic ice sheet divide byrd and other ice cores to document a unique 192 y series of halogen rich volcanic eruptions exactly at the start of accelerated deglaciation with tephra identifying the nearby mount takahe volcano as the source extensive fallout from these massive eruptions has been found 2 800 km from mount takahe sulfur isotope anomalies and marked decreases in ice core bromine consistent with increased surface uv radiation indicate that the eruptions led to stratospheric ozone depletion rather than a highly improbable coincidence circulation and climate changes extending from the antarctic peninsula to the subtropics similar to those associated with modern stratospheric ozone depletion over antarctica plausibly link the mount takahe eruptions to the onset of accelerated southern hemisphere deglaciation 17 7 ka

the timing and cause of glacial advances in the southern mid latitudes during the last glacial cycle based on a synthesis of exposure ages from patagonia and new zealand abstract glacier advances in the southern mid latitudes during the last glacial cycle ca 110 10 ka were controlled by changes in temperature and precipitation linked to several important ocean climate systems as such the timing of glacial advance and retreat can yield important insights into the mechanisms of southern hemisphere climate change this is particularly important given that several recent studies have demonstrated significant glacial advances prior to the global last glacial maximum glgm in patagonia and new zealand the cause of which are uncertain the recent increase in chronological studies in these regions offers the opportunity to compare regional trends in glacial activity here we compile the first consistent 10be exposure dating chronologies for patagonia and new zealand to highlight the broad pattern of mid latitude glacial activity over the last glacial cycle our results show that advances or still stands culminated at 26 27 ka 18 19 ka and 13 14 ka in both patagonia and new zealand and were broadly synchronous but with an offset between regions of up to 900 years that cannot be explained by age calculation or physically plausible erosion differences furthermore there is evidence in both regions for glacial advances culminating from at least 45 ka during the latter half of marine isotope stage mis 3 glacial activity prior to the glgm differed from the large northern hemisphere ice sheets likely due to favourable southern hemisphere conditions during late mis 3 summer insolation reached a minimum seasonality was reduced winter duration was increasing and sea ice had expanded significantly inducing stratification of the ocean and triggering northward migration of oceanic fronts and the southern westerly winds glacial advances in patagonia and new zealand during the glgm were probably primed by underlying orbital parameters however the precise timing is likely to have been intrinsically linked to migration of the coupled ocean atmosphere system which may account for the small offset between patagonia and new zealand due to differences in oceanic frontal migration during deglaciation advances or still stands occurred in both regions during the southern antarctic cold reversal ca 14 5 12 9 ka rather than the northern younger dryas ca 12 9 11 7 ka our findings suggest that major rearrangements of the southern hemisphere climate system occurred at various times during the last glacial cycle with associated impacts on the position and intensity of the southern westerly winds and oceanic fronts as well as wind driven upwelling and degassing of the deep southern ocean thus reconstructing the timing of glacial advance retreat using our compilation is a powerful way to understand the mechanisms of past interhemispheric climate change

identification of multiple natural and anthropogenic sources of dust in snow from zhongshan station to dome a east antarctica the stable oxygen isotope composition major ions and isotopic compositions of strontium sr neodymium nd and lead pb in insoluble dust from recent surface snow samples along the transect from the zhongshan and progress stations located on the amery ice shelf east antarctica to dome a summit antarctica were analysed no previous isotopic fingerprinting studies have been conducted for this transect these data were used to document the dust provenances in antarctica along the transect up to the highest site dome a for the first time the insoluble dust in snow samples along the coast displays an overall crust line isotopic signature that is characterised by highly radiogenic 87 sr 86 sr values and less radiogenic 143 nd 144 nd values these signatures are comparable with those of samples collected near the ice free areas of the zhongshan and progress stations spatial differences are statistically significant along the transect and the sr nd and pb isotope components in insoluble dust from two continuous snow samples at dome a exhibit marked differences indicating that additional dust reaches the east antarctic plateau the isotopic characteristics of insoluble dust from this transect indicate that the long distance natural dust and anthropogenic pollutants in these samples primarily originate from australia

tonalites in crustal evolution tonalites including trondhjemite as a variety played three roles through geological time in the generation of earth s crust before about 2 9 ga ago they were produced largely by simple partial melting of metabasalt to give the dominant part of archaean grey gneiss terranes these terranes are notably bimodal andesitic rocks are rare tonalites played a crucial role in the generation of this protocontinental and oldest crust 3 7 2 9 ga ago in that they were the only low density high sio 2 rocks produced directly from basaltic crust in the enormous event giving the greenstone granite terranes mostly 2 8 2 6 ga ago tonalites formed in lesser but still important proportions by partial melting of metabasalt in the lower regions of down buckled greenstone belts and by remobilization of older grey gneisses tectonism in the archaean 3 9 2 5 ga ago perhaps was controlled by small cell convection mckenzie weiss 1975 little or no ophiolite or eclogite formed and only minor andesite plate tectonics of modern type involving large rigid plates commenced in the early proterozoic uniformitarianism thus goes back one half of the age of the earth tonalites compose about 5 10 of crust generated in proterozoic and phanerozoic time at convergent oceanic continental margins they occur here as minor to prominent members of the compositionally continuous continental margin batholiths a simple model of generation of these batholiths is offered mantle derived mafic magma pools in the lower crust above a subduction zone reacts with and incorporates wall rock components bowen 1922 and breaches its roof rocks as an initial diapir this mantle magma also develops a gradient of partial melting in its wall rocks this wall rock melt accretes in the collapsed chamber and moves up the conduit broached by the initial diapir the higher less siliceous fractions of melting first the lower more siliceous and further removed fractions of melting last the process gives in the optimum case a mafic to siliceous sequence of diorite or quartz diorite through tonalite or quartz monzodiorite to granodiorite and granite the model implies that great masses of cumulate phases and refractory wall rock form the roots of continentalmargin batholiths and that migmatites overlie that residuum and underlie the batholiths

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

meteoric cosmogenic beryllium 10 adsorbed to river sediment and soil applications for earth surface dynamics abstract rainfall scavenges meteoric cosmogenic 10be from the atmosphere 10be falls to the earth s surface where it binds tightly to sediment particles in non acidic soils over the life span of those soils as such meteoric 10be has the potential to be an excellent geochemical tracer of erosion and stability of surfaces in a diverse range of natural settings meteoric 10be has great potential as a recorder of first order erosion rates and soil residence times even though this tracer was first developed in the late 1980s and showed great promise as a geomorphic tool it was sidelined in the past two decades with the rise of the sister nuclide in situ 10be which is produced at a known rate inside quartz minerals since these early days substantial progress has been made in several areas that now shed new light on the applicability of the meteoric variety of this cosmogenic nuclide here we revisit the potential of this tracer and we summarize the progress 1 the atmospheric production and fallout is now described by numeric models and agrees with present day measurements and paleo archives such as from rain and ice cores 2 short term fluctuations in solar modulation of cosmic rays or in the delivery of 10be are averaged out over the time scale soils accumulate 3 in many cases the delivery of 10be is not dependent on the amount of precipitation 4 we explore where 10be is retained in soils and sediment 5 we suggest a law to account for the strong grain size dependence that controls adsorption and the measured nuclide concentrations and 6 we present a set of algebraic expressions that allows calculation of both soil or sediment ages and erosion rates from the inventory of meteoric 10be distributed through a vertical soil column the mathematical description is greatly simplified if the accumulation of 10be is at a steady state with its export through erosion in this case a surface sample allows for the calculation of an erosion rate explored further this approach allows calculation of catchment wide erosion rates from river sediment similar to the approach using 10be produced in situ in contrast to the in situ 10be approach however these analyses can be performed on any sample of fine grained material even where no quartz minerals are present therefore this technique may serve as a tool to date sediment where no other chronometer is available to track particle sources and to measure earth surface process rates in soil suspended river sediment and fine grained sedimentary deposits

regional mid pleistocene glaciation in central patagonia abstract southern south america contains a glacial geomorphological record that spans the past million years and has the potential to provide palaeoclimate information for several glacial periods in earth s history in central patagonia two major outlet glaciers of the former patagonian ice sheet carved deep basins 50 km wide and extending over 100 km into the andean plain east of the mountain front a succession of nested glacial moraines offers the possibility of determining when the ice lobes advanced and whether such advances occurred synchronously the existing chronology which was obtained using different methods in each valley indicates the penultimate moraines differ in age by a full glacial cycle here we test this hypothesis further using a uniform methodology that combines cosmogenic nuclide ages from moraine boulders moraine cobbles and outwash cobbles 10 be concentrations in eighteen outwash cobbles from the moreno outwash terrace in the lago buenos aires valley yield surface exposure ages of 169 269 ka we find 10 be inheritance is low and therefore use the oldest surface cobbles to date the deposit at 260 270 ka which is indistinguishable from the age obtained in the neighbouring lago pueyrredon valley this suggests a regionally significant glaciation during marine isotope stage 8 and broad interhemispheric synchrony of glacial maxima during the mid to late pleistocene finally we find the dated outwash terrace is 70 100 ka older than the associated moraines on the basis of geomorphological observations we suggest this difference can be explained by exhumation of moraine boulders

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

cenozoic microfossils in northern finland local reworking or distant wind transport abstract allochthonous cenozoic microfossils have been reported from late pleistocene lake and mire host sediments across an area of 30 000 km2 in northern finland two main groups of microfossils are recognised palaeogene marine diatoms silicoflagellates and ebridians that include taxa from around the time of the palaeocene eocene thermal maximum and pliocene to early pleistocene freshwater diatoms the presence of these microfossils has been regarded as evidence that eocene marine and late neogene freshwater sediments formerly existed on the shield surface both groups have been referred to frequently in reconstructions of the sea level tectonic and erosion history of the northern fennoscandian shield the questions raised by the presence of allochthonous cenozoic microfossils in northern finland are however strongly resonant of the debate over the biota origin and age of the pliocene sirius group in antarctica where competing hypotheses have been put forward of local deposition and reworking versus distant wind transport of marine diatoms from the continental shelf this review explores alternative origins for the allochthonous cenozoic microfossils in northern finland local reworking of palaeogene marine sediments during pleistocene glaciation is unlikely as no source rocks of palaeogene age are known from the shield surface or from surrounding sedimentary basins in the baltic and white sea moreover at all sites except akanvaara the marine diatom taxa cover wide age ranges and occur only as minor components in diatom assemblages that are dominated by quaternary freshwater taxa local reworking of pliocene pleistocene freshwater diatoms is however compatible with the widespread survival of pre pleistocene deep weathering although no in situ or unmixed ice rafted pliocene pleistocene lacustrine sediment has yet been found an alternative origin for the marine palaeogene microfossils by distant wind transport is proposed in this hypothesis palaeogene diatomites on the barents sea shelf were exposed to deep glacial and fluvioglacial erosion during the pliocene and early pleistocene and in low sea level stages of the middle and late pleistocene intense wind action acting on comminuted mudstones on outwash plains carried dust including microfossils into northern fennoscandia to be deposited by rain out in lakes and wetlands this material may have been later further recycled by glacial and meltwater transport and more localised wind action processes that also may help to account for the distribution of eemian marine diatoms well beyond eemian shorelines the distant wind transport hypothesis implies that the presence of marine palaeogene diatoms on the shield surface in northern finland cannot be regarded as vestiges of former marine sediments and so do not constrain the tectonic and geomorphic history of the northern fennoscandian shield in the cenozoic

icesat measurements of sea ice freeboard and estimates of sea ice thickness in the weddell sea 1 sea ice freeboard heights in the weddell sea of antarctica are derived from the ice cloud and land elevation satellite icesat laser altimeter measurements which have a unique range precision to flat surfaces of 2 cm within 70 m footprints spaced at 172 m along track although elevations of flat surfaces can be obtained to an accuracy of 10 cm 1s per footprint direct determination of freeboard heights is precluded by errors in knowledge of the geoid and temporal variability of the ocean surface therefore freeboards are determined relative to an ocean reference level detected over areas of open water and very thin ice within the sea ice pack using an along track filtering method the open water thin ice selections show good agreement in the combined analysis of icesat segments and envisat synthetic aperture radar sar imagery the average residual between the icesat measured ocean level and the egm96 geoid is 1 4 m estimates of snow depth on the sea ice from amsr e passive microwave data along with nominal densities of snow water and sea ice are used to estimate sea ice thickness four periods of icesat data in may june fall and october november late winter of 2004 and 2005 between longitudes 298e and 360e are analyzed in the fall the mean freeboards are 0 28 m in 2004 and 0 29 m in 2005 and the mean thicknesses are 1 33 m in 2004 and 1 52 m in 2005 in late winter the freeboards grew to 0 37 m in 2004 and 0 35 in 2005 and the thicknesses grew to 2 23 m in 2004 and 2 31 m in 2005 the interannual differences in freeboard are small and the larger interannual change in estimated thickness mainly represents differences in the snow depth estimates seasonal changes in the spatial patterns of freeboard and thickness over the 4 months correlate with the expected circulation of sea ice in the weddell sea as indicated by sea ice velocity fields

middle pleistocene glaciation in patagonia dated by cosmogenic nuclide measurements on outwash gravels the well preserved glacial record in argentine patagonia offers a 1 ma archive of terrestrial climate extremes in southern south america these glacial deposits remain largely undated beyond the range of radiocarbon dating at ca 40 ka dating old glacial deposits several 105 a by cosmogenic surface exposure methods is problematic because of the uncertainty in moraine degradation and boulder erosion rates here we show that cobbles on outwash terraces can reliably date old glacial deposits in the lago pueyrredon valley 47 5 s argentina favorable environmental conditions e g aridity and strong winds have enabled continuous surface exposure of cobbles and preservation of outwash terraces the data demonstrate that nuclide inheritance is negligible and we therefore use the oldest surface cobbles to date the deposit 10be concentrations in outwash cobbles reveal a major glacial advance at ca 260 ka concurrent with marine isotope stage 8 mis 8 and dust peaks in antarctic ice cores a 10be concentration depth profile in the outwash terrace supports the age and suggests a low terrace erosion rate of ca 0 5 mm ka 1 we compare these data to exposure ages obtained from associated moraines and find that surface boulders underestimate the age of the glaciation by 100 ka thus the oldest boulders in this area do not date closely moraine deposition the 10be concentration in moraine cobbles help to constrain moraine degradation rates these data together with constraints from measured 26al 10be ratios suggest that all moraine boulders were likely exhumed after original deposition we determine the local last glacial maximum lgm occurred at 27 25 ka consistent with the maximum lgm in other parts of patagonia

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

causes of dust size variability in central east antarctica dome b atmospheric transport from expanded south american sources during marine isotope stage 2 abstract we here investigate the spatial and temporal variability of eolian dust particle sorting recorded in the dome b 77 05 s 94 55 e ice core central east antarctica during marine isotope stage mis 2 we address the question whether such changes reflect variable transport pathways from a unique source area or rather a variable apportionment from diverse southern hemisphere sources transported at different elevation in the troposphere the sr nd radiogenic isotope composition of glacial dust samples as well as single particle raman mineralogy support the hypothesis of a single dust provenance both for coarse and fine mode dust events at dome b the southern south american provenance of glacial dust in antarctica deduced from these results indicate a dust composition coherent with a mixture of volcanic material and minerals derived from metamorphic and plutonic rocks additionally dome b glacial samples contain aragonite particles along with diatom valves of marine benthic epiphytic species and freshwater species living today in the northern antarctic peninsula and southern south america these data suggest contribution from the exposed patagonian continental shelf and glacial outwash plains of southern patagonia at the time when sea level reached its minimum our results confirm that dust sorting is controlled by the relative intensity of the two main patterns of tropospheric dust transport onto the inner plateau i e fast low level advection and long range high altitude transport including air subsidence over antarctica

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

controls on deglacial changes in biogenic fluxes in the north pacific ocean the subarctic north pacific ocean holds a large co2 reservoir that is currently isolated from the atmosphere by a low salinity layer it has recently been hypothesized that the reorganization of these high co2 waters may have played a crucial role in the degassing of carbon dioxide to the atmosphere during the last deglaciation this reorganization would leave some imprint on paleo productivity records here we present 230th normalized biogenic fluxes from an intermediate depth sediment core in the northwest pacific rc10 196 54 7 n 177 1 e 1007 m and place them within the context of a synthesis of previously published biogenic flux data from 49 deep sea cores north of 20 n ranging from 420 to 3968 m water depth the 230th normalized opal carbonate and organic carbon fluxes from rc10 196 peak approximately 13 000 calendar years bp during the bolling allerod b a period our data synthesis suggests that biogenic fluxes were in general lowest during the last glacial period increased somewhat in the northwest pacific during heinrich event 1 and reached a maximum across the entire north pacific during the b a period we evaluate several mechanisms as possible drivers of deglacial change in biogenic fluxes in the north pacific including changes in preservation sediment focusing sea ice extent iron inputs stratification and circulation shifts initiated in the north atlantic and north pacific our analysis suggests that while micronutrient sources likely contributed to some of the observed changes the heterogeneity in timing of glaciogenic retreat and sea level make these mechanisms unlikely causes of region wide contemporaneous peaks in export production we argue that paleoobservations are most consistent with ventilation increases in both the north pacific during h1 and north atlantic during b a being the primary drivers of increases in biogenic flux during the deglaciation as respectively they were likely to bring nutrients to the surface via increased vertical mixing and shoaling of the global thermocline

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