characteristics of the antarctic surface mass balance 1958 2002 using a regional atmospheric climate model temporal and spatial characteristics of the antarctic specific surface mass balance ssmb are presented including its components solid precipitation sublimation deposition and melt for this purpose we use the output of a regional atmospheric climate model racmo2 ant horizontal resolution of 55 km for the period 1958 2002 racmo2 ant uses european centre for medium range weather forecasts ecmwf 40 year re analysis era 40 fields as forcing at the lateral boundaries racmo2 ant underestimates ssmb in the high interior of east and west antarctica and overestimates ssmb on the steep coastal slopes otherwise the modeled spatial pattern of ssmb is in good qualitative agreement with recent compilations of in situ observations large scale patterns like the precipitation shadow effect of the antarctic peninsula are well reproduced and mesoscale ssmb patterns such as the strong precipitation gradients on law dome are well represented in the model the integrated ssmb over the grounded ice sheet is 153mmw e a 1 for the period 1958 2002 which agrees within 5 with the latest measurement compilations sublimation and melt remove 7 and

integration of ice core marine and terrestrial records for the australian last glacial maximum and termination a contribution from the oz intimate group the degree to which southern hemisphere climatic changes during the end of the last glacial period and early holocene 30 8 ka were influenced or initiated by events occurring in the high latitudes of the northern hemisphere is a complex issue there is conflicting evidence for the degree of hemispheric teleconnection and an unresolved debate as to the principle forcing mechanism s the available hypotheses are difficult to test robustly however because the few detailed palaeoclimatic records in the southern hemisphere are widely dispersed and lack duplication here we present climatic and environmental reconstructions from across australia a key region of the southern hemisphere because of the range of environments it covers and the potentially important role regional atmospheric and oceanic controls play in global climate change we identify a general scheme of events for the end of the last glacial period and early holocene but a detailed reconstruction proved problematic significant progress in climate quantification and geochronological control is now urgently required to robustly investigate change through this period copyright c 2006 john wiley sons ltd

timing of millennial scale climate change at siple dome west antarctica during the last glacial period using atmospheric methane and the isotopic composition of o2 as correlation tools we place the dd record of ice from the siple dome west antarctica ice core on a precise common chronology with the gisp2 greenland ice core for the period from 9 to 57 ka the onset of major millennial warming events in siple dome preceded major abrupt warmings in greenland and the pattern of millennial change at siple dome was broadly similar though not identical to that previously observed for the byrd ice core also in west antarctica the addition of siple dome to the database of well dated antarctic paleoclimate records supports the case for a coherent regional pattern of millennial scale climate change in antarctica during much of the last ice age and glacial interglacial transition

10 be in ice at vostok antarctica during the last climatic cycle we have previously reported accelerator mass spectrometer measurements of the cosmogenic isotope 10be half life 1 5 myr in an 906 m ice core recovered at dome c antarctica1 in addition to an enhanced concentration during a period of reduced solar activity maunder minimum ad 1645 1715 2 we found substantially increased concentrations during that part of the core corresponding to the last ice age both effects have been confirmed and extended in greenland ice cores3 4 the recovery of a 2 083 m ice core at vostok antarctica5 together with an extended oxygen isotope chronology reported elsewhere in this issue6 permits an extension of 10be studies over the whole of the last climatic cycle 125 kyr we report here such measurements which show an excellent correlation with the oxygen isotope and thus presumably climate record over the whole of this period the results imply that precipitation rates in the antarctic during the last interglacial were similar to those of the holocene but were roughly halved during the last glaciation

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

the seafloor geomorphology of the windmill islands wilkes land east antarctica evidence of law dome ice margin dynamics abstract a high resolution multibeam sonar dataset covering an area of ca 33 km 2 was collected in the vicinity of the windmill islands 67 s 110 e wilkes land east antarctica the new data permit visualisation of the nearshore seafloor morphology in unprecedented detail providing invaluable insight into the ice sheet history of the region a range of geomorphic features are evident including prominent parallel northwest trending linear fault sets affecting mesoproterozoic metamorphic basement which appear to control the regional coastal physiography the fault systems probably formed during fragmentation of eastern gondwana during the mesozoic networks of sub glacial meltwater channels preserved on bedrock platforms and ridges indicate grounding of a thick ice sheet over the continental shelf during previous glaciations west trending subtle glacial lineations and streamlined landforms record evidence of the westward expansion of the grounded law dome ice sheet margin probably during the late pleistocene the direction of these features coincides with glacial striae on onshore crystalline bedrock outcrops perhaps the most striking glacial geomorphological features are sets of arcuate ridges confined mostly within glacially excavated u shaped troughs formed by erosion of the northwest trending bedrock fault sets these ridge sets are interpreted as push moraines or grounding zone features formed during episodic retreat of highly channelised topographically controlled ice streams following ice surging of the law dome margin this event was possibly triggered in response to local environmental forcing during the mid late holocene minor post glacial marine sedimentation is preserved in several small 1 km 2 isolated basins with shallow seaward sills

sea ice and wind variability during the holocene in east antarctica insight on middle high latitude coupling abstract micropaleontological and biomarker data from two high accumulation marine sites from the coastal and continental shelf zone ccsz off east antarctica adelie land at 140 e and eastern prydz bay at 77 e are used to reconstruct holocene changes in sea ice and wind stress at the basin wide scale these data demonstrate congruent increase in sea ice concentration persistence and wind stress related sea surface turbulence in the two regions since 7 cal ka bp with a particularly strong signal since 4 5 3 5 cal ka bp comparison of these high latitude records with sea ice and turbulence records from the southern mid latitudes highlights distinctive climatic evolutions according to the different latitudinal bands sea ice persistence and turbulence increase in east antarctica ccsz are opposite to sea surface warming and sea ice retreat recorded after 4 5 3 5 cal ka bp in the east atlantic and indian sector between 55 and 45 s at the same period paleodata suggest sst cooling in all major coastal upwelling systems of the southern hemisphere caused by the northward transport of subpolar surface waters as a response to southern westerlies reinforcement we therefore propose as suggested for the northern hemisphere that holocene changes in the latitudinal insolation gradient primarily forced by obliquity and precession and amplified by sea ice and glacial ice expansions in the antarctic realm are responsible for the observed contrasted latitudinal patterns of southern latitudes

late quaternary reef growth and sea level in the maldives indian ocean abstract based on rotary drilling and radiometric and u series dating we present the first comprehensive data on holocene reef anatomy and sea level rise as well as nature and age of underlying pleistocene limestone in the maldives holocene reefs in rasdhoo atoll central maldives are composed of four facies including 1 robust branching coral facies 2 coralline algal facies 3 domal coral facies and 4 detrital sand and rubble facies branching coral and coralline algal facies predominate the marginal reefs and domal corals and detrital facies preferentially occur in a lagoon reef in addition microbialite crusts are found in lower core sections of marginal reefs microbialites formed during the early holocene in reef cavities holocene reef thickness ranges from 14 5 m to 22 m reef growth started as early as 8 5 kyr bp marginal reefs accreted in the keep up mode with rates of 15 m kyr rate of sea level rise significantly slowed down from 7 6 kyr bp and subsequently gradually rose with rates

collapse of the luzon volcanic arc during onset of arc continent collision evidence from a miocene pliocene unconformity eastern taiwan a regional miocene pliocene unconformity in the coastal range of eastern taiwan provides information about vertical motions that affected the colliding volcanic arc during initiation of arc continent collision the unconformity separates precollisional volcanic and volcaniclastic rocks of the miocene luzon arc and forearc basin from an overlying thick sequence of syncollisional pliocene pleistocene sedimentary rocks derived from the metasedimentary accretionary wedge of taiwan the duration of time represented by the unconformity averages 1 2 m y and locally ranges up to 4 m y the basal unit of the younger syncollisional sequence consists of bathyal mega slump folded mudstone pebbly mudstone and thin bedded turbidites sharp stratigraphic juxtaposition of these deep marine deposits directly above shallow marine limestone and epiclastic rocks upper part of the older arc sequence requires extremely rapid subsidence during initiation of the collisional basin the coastal range unconformity is interpreted to represent a period of latest miocene nondeposition and or erosion in the luzon arc that was related to initial subduction of the eurasian continental margin along the manila trench this period was followed in pliocene time by very rapid subsidence or collapse of the arc platform to 1 2 km water depth there are two dissimilar mechanisms of basin subsidence that may have controlled initiation of the collisional basin 1 extension rifting and crustal thinning in the luzon arc massif to form a series of small rift or pull apart subbasins or 2 flexural subsidence of oceanic lithosphere in a foreland style basin due to crustal loading in the expanding accretionary wedge of proto taiwan although data are insufficient to provide a unique solution the flexural subsidence model is supported by systematic younging of the initial subsidence event from west to east which may record eastward migration of an outer flexural bulge notable differences between the unconformity and paleogeography of the early collisional basin and analogous present day basins in the offshore region to the south suggest that arc continent collision and basin development in eastern taiwan have experienced secular change since late pliocene time

spatial covariance of water isotope records in a global network of ice cores spanning twentieth century climate change 1 estimating the spatial extent of past climate changes has been an ongoing challenge for paleoclimatology for such estimates to be made with confidence it is important to establish an understanding of the spatial coherence of proxy records during an interval of known climate change we use water stable isotopes from high resolution ice cores and twentieth century observations of sea level pressures and sea surface temperatures to assess the covariance among isotopic records and its link to organized patterns of climate variability covarying signals in the cores are identified using empirical orthogonal function analysis results from regression analysis show that the leading signals are consistent with key climate patterns including the northern atlantic oscillation and southern annular mode and variability in tropical pacific sea surface temperatures associated with the el nino southern oscillation patterns that have recently been identified in instrumental data such as positive tropical pacific sst anomalies associated with the negative phase of the sam are evident in the ice cores these explanations for the variance of stable isotopes are consistent with recent studies using isotope enabled general circulation models and provide a physical basis for interpreting the observed isotopic signals while there is also a global change signal that is evident when analyzing the records collectively there are some limitations in reconstructing global temperatures due to the geographic coverage of the available records and the current lack of modeling studies to explain the observed global scale changes still water stable isotope ratios preserved in ice cores provide a sufficiently rich sampling of large scale climate variability that they can be more widely used in physically based paleoclimate reconstructions covering the last millennium and other periods

multiproxy summer and winter surface air temperature field reconstructions for southern south america covering the past centuries we statistically reconstruct austral summer winter surface air temperature fields back to ad 900 1706 using 22 20 annually resolved predictors from natural and human archives from southern south america ssa this represents the first regional scale climate field reconstruction for parts of the southern hemisphere at this high temporal resolution we apply three different recon struction techniques multivariate principal component regression composite plus scaling and regularized expectation maximization there is generally good

site information and initial results from deep ice drilling on law dome antarctica the aim of deep ice drilling on law dome antarctica has been to exploit the special characteristics of law dome summit i e low temperature and high accumulation near an ice divide to obtain a high resolution ice core for climatic environmental studies of the holocene and the last glacial maximum lgm drilling was completed in february 1993 when basal ice containing small fragments of rock was reached at a depth of 1196 m accurate ice dating obtained by counting annual layers revealed by fine detail 18 o peroxide and electrical conductivity measurements is continuous down to 399 m corresponding to a date of ad 1304 sulphate concentration measurements made around depths where conductivity tracing indicates volcanic fallout allow confirmation of the dating for agung in 1963 and tambora in 1815 or estimates of the eruption date from the ice dating for the kuwae vanuatu eruption 1457 the lower part of the core is dated by extrapolating the layer counting using a simple model of the ice flow at the lgm ice fabric measurements show a large decrease 250 to 14 mm 2 in crystal size and a narrow maximum in c axis verticality the main zone of strong single pole fabrics however is located higher up in a broad zone around 900 m oxygen isotope 18 o measurements show holocene ice down to 1113 m the lgm at 1133 m and warm 18 o about the same as holocene ice near the base of the ice sheet the lgm holocene 18 o shift of 7 0 only 1 larger than for vostok indicates that law dome remained an independent ice cap and was not overridden by the inland ice sheet in the glacial

response of a late miocene mediterranean reef platform to high frequency eustasy the upper miocene reef complex of mallorca a third order depositional sequence shows how carbonate deposition responds to high frequency sea level cycles this reef complex displays a fractal architecture of hierarchically stacked high frequency units from fourth to seventh order the building blocks are sigmoidal units bounded by unconformities not parasequences these sigmodds are stacked in sets of sigmoids the sets are stacked in cosets and these in turn are stacked in sets of cosets all these accretionary units have characteristics of depositional sequences but differ from the model developed by exxon and from other carbonate sequence stratigraphy models these departures result from changes in carbonate production in relation to sea level fluctuations which determined the changes in accommodation in the absence of significant subsidence all these high frequency sequences are composed of four systems tracts 1 a lowstand systems tract formed during the early rise of a sea level cycle and composed of progradational reef to open shelf facies thinning toward the basin 2 an aggrading systems tract formed during sea level rise and composed of thick lagoon to open shelf deposits without landward shift of facies 3 a highstand systems tract formed during the high part of a sea level cycle and composed of progradational reef to open shelf facies thinning toward the basin with lagoon beds thin or absent and 4 an offlapping systems tract formed during sea level fall and composed of thin downlapping reef facies passing into a condensed open shelf section which correlates with an erosion surface on the platform top two bounding surfaces can be recognized by lithofacies changes between these systems tracts the erosion surface on top of the offlapping systems tract and the downlap surface at its base both surfaces merge basinward into a condensed section the sequence boundary which corresponds to the lowest point of the sea level cycle is the erosion surface landward and within the correlative condensed section basinward

holocene subsurface temperature variability in the eastern antarctic continental margin 1 we reconstructed subsurface 45 200 m water depth temperature variability in the eastern antarctic continental margin during the late holocene using an archaeal lipid based temperature proxy tex86l our results reveal that subsurface temperature changes were probably positively coupled to the variability of warmer nutrient rich modified circumpolar deep water mcdw deep water of the antarctic circumpolar current intrusion onto the continental shelf the tex86lrecord in combination with previously published climatic records indicates that this coupling was probably related to the thermohaline circulation seasonal variability in sea ice extent sea temperature and wind associated with high frequency climate dynamics at low latitudes such as internal el nino southern oscillation enso this in turn suggests a linkage between centennial enso like variability at low latitudes and intrusion variability of mcdw into the eastern antarctic continental shelf which might have further impact on ice sheet evolution

seismic stratigraphy and depositional signatures of the maldive carbonate system indian ocean abstract as documented by industrial seismic reflection profiles and well data the cenozoic stratigraphic evolution of the maldive carbonate system shows three distinct intervals characterized by their own specific depositional signatures late palaeocene volcanics generated by the reunion hotspot filled deeper pull apart structures and created a flat topography that promoted the onset of the maldive carbonate system in the early eocene some of the initial structural depressions remained as deep internal seaways surrounded by reefal margins until the late oligocene the eocene early oligocene stratigraphic signature is essentially aggradational and corresponds to a transgressive cycle associated with a second order sea level rise in the mid oligocene a major sea level fall exposed the neritic carbonate system and restricted sedimentation to the former deep internal basins during the next transgression a neritic carbonate system re established itself on the newly flooded platform and was finally drowned near the oligocene miocene boundary the main effect of this second order transgressive cycle was the transformation of the central troughs into one single deep basin in the neogene the palaeo maldive inner sea when a reef framework was established in the early miocene near the present location of the platform edge systematic bank margin progradation toward the central inner sea basin became enhanced this neogene progradational phase is explained as the response to a long term sea level fall associated with a second order regressive cycle finally the late pliocene pleistocene depositional signature is mainly aggradational and corresponds to the regional modification from flat topped carbonate banks to atoll physiographies the antecedent karst theory suggests that increased karstification was triggered by high frequency eustatic and climatic changes in the last 3 0 ma

deduction of surface accumulation history from ice core age depth data ice core data are the only source of ice response on timescales of hundreds to thousands of years which is necessary to describe polar ice sheet flows and their interaction with changing climatic conditions ice properties such as a grain growth relation require knowledge of each ice particle s history since first deposited at the surface and not simply the present core state this study is an analysis of 11 present ice cores using their age depth data and present accumulation to infer their past accumulation and mean strain rate and in turn the strain at each level of the core these are the ingredients necessary to determine the particle paths and associated evolution of properties the conventional assumptions of a purely vertical velocity distribution with a uniform compressive strain rate in the core are made but unlike an earlier analysis which allowed independent surface accumulation and strain rate histories it is now assumed that the strain rate is proportional to the accumulation determination of the past accumulation and proportionality factor is accomplished by correlation with the present age depth data and while good correlations are obtained a consistent solution other close correlations can yield quite different accumulation histories and corresponding proportional strain rate histories

calibrating the ice core paleothermometer using seasonality high resolution oxygen isotope measurements on the dome summit south dss ice core from law dome antarctica provide a seasonal profile that is sufficiently stable and undistorted by biases in accumulation to permit comparison with measured temperature seasonality this comparison yields an isotope temperature relation with a gradient d dt of 0 44 0 02 c and provides a new method for exploring the isotope temperature relationship at high accumulation sites if applied to the observed isotope record from the dss core which extends through the last glacial and beyond this calibration suggests that at its coldest the last glaciation was 13 c colder than present at this site after correcting for elevation change this finding compares with a temperature difference of 8 c computed by using the local spatially derived calibration

modelled stress distributions at the dome summit south borehole law dome east antarctica a comparison of anisotropic ice flow relations in this study we compare the anisotropic flow relations for polycrystalline ice of azuma and goto azuma 1996 thorsteinsson 2002 placidi and others 2010 and budd and others 2013 observations from the dome summit south dss ice coring site at law dome east antarctica are used to model the vertical distribution of deviatoric stress components at the borehole site the flow relations in which the anisotropic rheology is parameterized by a scalar function so that the strain rate and deviatoric stress tensor components are collinear provide simple shear and vertical compression deviatoric stress profiles that are most consistent with laboratory observations of tertiary creep in combined stress configurations those flow relations where 1 the anisotropy is derived from the magnitude of applied stresses resolved onto the basal planes of individual grains and 2 the macroscopic deformation is obtained via homogenization of individual grain responses provide stress estimates less consistent with laboratory observations this is most evident in combined simple shear and vertical compression flow regimes where shear is dominant our results highlight the difficulties associated with developing flow relations which incorporate a physically based description of microdeformation processes in particular this requires that all relevant microdeformation recrystallization and recovery processes are adequately parameterized

monsoon induced partial carbonate platform drowning maldives indian ocean multibeam maps and high resolution seismic images from the maldives reveal that a late miocene to early pliocene partial drowning of the platform was linked to strong sea bottom currents in the upper miocene to holocene currents shaped the drowned banks the current moats along the bank edges and the submarine dune fields bottom currents in the maldives are driven by the monsoon it is proposed that the onset and the intensification of the monsoon during the neogene provoked platform drowning through injection of nutrients into surface waters since the late miocene topographically triggered nutrient upwelling and vigorous currents switched the maldives atolls into an aggradational to backstepping mode which is a growth pattern usually attributed to episodes of rising sea level

antarctic temperatures over the past two centuries from ice cores 1 we present a reconstruction of antarctic mean surface temperatures over the past two centuries based on water stable isotope records from high resolution precisely dated ice cores both instrumental and reconstructed temperatures indicate large interannual to decadal scale variability with the dominant pattern being anti phase anomalies between the main antarctic continent and the antarctic peninsula region comparative analysis of the instrumental southern hemisphere sh mean temperature record and the reconstruction suggests that at longer timescales temperatures over the antarctic continent vary in phase with the sh mean our reconstruction suggests that antarctic temperatures have increased by about 0 2 c since the late nineteenth century the variability and the long term trends are strongly modulated by the sh annular mode in the atmospheric circulation

features of meteorological events preserved in a high resolution law dome east antarctica snow pit snow pitandshallow firn corerecordsofoxygenisotoperatios d 18 o and traceionspeciesweregeneratedatahigh accumulationsiteonlaw dome eastantarctica concordancebetweenaccumulationeventsidentifiedin recordsupto 7 7kmapartconfirms that the observed glaciochemical variations are the result of regional rather than local sur face effects this allows calibration of the snow pit records with measured meteorological parameters netaccumulationperiodsthatcomprisethesnow pitrecordareidentifiedusing hourly snow accumulation measurements from a co located automatic weather station aws particular focus isgiventothreenetaccumulationperiods preservedduringaustral summer 1999 2000 that correspond to the top 0 5m of the snow pit local meteorological conditions recorded during the summer accumulation periods by the aws are combined with regional and synoptic scale meteorology derived from casey station 110km away and advancedvery high resolution radiometer satellite imagery to identify potential source regions forchemical signals preserved in summer snowat law dome

antarctic and global climate history viewed from ice cores a growing network of ice cores reveals the past 800 000 years of antarctic climate and atmospheric composition the data show tight links among greenhouse gases aerosols and global climate on many timescales demonstrate connections between antarctica and distant locations and reveal the extraordinary differences between the composition of our present atmosphere and its natural range of variability as revealed in the ice core record further coring in extremely challenging locations is now being planned with the goal of finding older ice and resolving the mechanisms underlying the shift of glacial cycles from 40 000 year to 100 000 year cycles about a million years ago one of the great mysteries of climate science a discussion of past antarctic and global climate history as seen from antarctic ice cores with an outlook on future goals and drilling priorities

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

giant pockmarks in a carbonate platform maldives indian ocean abstract circular structures and depressions in carbonate platforms are known to represent karst chimneys or sinkholes which form as a response to rock solution this formation mechanism is plausible for shallow water carbonates which lie in the reach of meteoric diagenesis or fresh water lenses circular structures which occur in deeper waters however need an alternative interpretation such an example of sea floor depressions in more than 300 m deep waters occurs in the inner sea of the maldives carbonate platform in the indian ocean the structures were mapped with multibeam and parasound multi channel seismics were used to link the depressions with structures at depth the circular depressions have diameters of up to 3000 m and depths of up to 180 m the craters are interpreted as pockmarks formed through the venting of gas and fluids gas and fluid lenses below the pockmarks are reflected by bright spots in the seismic sections as well as a reduction of the instantaneous frequency these areas at depth are linked to chimneys connected to faults and drowned oligocene carbonate banks a model is presented that relates the different forms and sizes of the structures to distinct development stages of sea floor deformation to one process early stages of gas and fluid migration into the shallow part of the sedimentary succession induce formation of dome shaped bodies initial gas and fluid escape to the sea floor is reflected by the formation of sand volcanoes and aligned small pockmarks active pockmarks are the deepest and have the shape of truncated cones in cross section mature pockmarks are characterized by erosion of the flanks of the structure by bottom currents late stage pockmarks are bowl shaped in cross section and are to different degrees filled by drift sediments packages of strata revealing high reflection amplitudes and high interval velocities interpreted as microbially mediated carbonate precipitates underlie some of the pockmarks the pockmarks in the maldives show that circular structures other than solution related features can be abundant in carbonate platform deposits and that such structures may be more abundant in the geological record of carbonate platforms as previously thought pockmarks in the maldives indicate that the archipelago is an example of a hydrocarbon system which consists of an isolated oceanic carbonate platform overlying a volcanic basement and lacustrine source rocks

variable relationship between accumulation and temperature in west antarctica for the past 31 000 years the antarctic contribution to sea level is a balance between ice loss along the margin and accumulation in the interior accumulation records for the past few decades are noisy and show inconsistent relationships with temperature we investigate the relationship between accumulation and temperature for the past 31 ka using high resolution records from the west antarctic ice sheet wais divide ice core in west antarctica although the glacial interglacial increases result in high correlation and moderate sensitivity for the full record the relationship shows considerable variability through time with high correlation and high sensitivity for the 0 8 ka period but no correlation for the 8 15 ka period this contrasts with a general circulation model simulation which shows homogeneous sensitivities between temperature and accumulation across the entire time period these results suggest that variations in atmospheric circulation are an important driver of antarctic accumulation but they are not adequately captured in model simulations model based projections of future antarctic accumulation and its impact on sea level should be treated with caution

a millennial proxy record of enso and eastern australian rainfall from the law dome ice core east antarctica enso causes climate extremes across and beyond the pacific basin however evidence of enso at high southern latitudes is generally restricted to the south pacific and west antarctica here the authors report astatisticallysignificantlinkbetweenensoandseasaltdepositionduringsummerfromthelawdome ld ice core in east antarctica enso related atmospheric anomaliesfrom the central western equatorialpacific cwep propagate to the south pacific and the circumpolar high latitudes these anomalies modulate high latitude zonal winds with el nino la nina conditions causing reduced enhanced zonal wind speeds and subsequent reduced enhanced summer sea salt deposition at ld over the last 1010 yr the ld summer sea salt ldsss recordhasexhibitedtwobelow average elnino like epochs 1000 1260 adand1920 2009 ad and a longer above average la nina like epoch from 1260 to 1860 ad spectral analysis shows the below average epochs are associated with enhanced enso like variability around 2 5 yr while the above average epoch is associated more with variability around 6 7 yr the ldsss record is also significantly correlated with annual rainfall in eastern mainland australia while the correlation displays decadal scale variability similar to changes in the interdecadal pacific oscillation ipo the ldsss record suggests rainfall in the modern instrumental era 1910 2009 ad is below the long term average in addition recent rainfall declines in some regions of eastern and southeastern australia appear to be mirrored by a downward trend in the ldsss record suggesting current rainfall regimes are unusual though not unknown over the last millennium

global ocean response to orbital forcing in the holocene 1 global upper ocean evolution in the holocene is studied in two coupled ocean atmosphere models under orbital forcing conditions at 3 6 8 and 11 ka the annual mean sea surface temperature sst changes in the early to mid holocene are found to be forced mainly by the annual mean insolation forcing with an overall symmetric response of colder equator 1 c in the arctic this sst change is consistent with a synthesis of mid holocene paleo sst records in contrast the temperature response in the thermocline is dominated by an antisymmetric pattern with a cooling warming in the northern southern hemisphere midlatitudes the thermocline response is determined predominantly by surface water subduction and ultimately the insolation forcing in local late winter

imaging tertiary carbonate system the maldives indian ocean insights into carbonate sequence interpretation seismic imaging of carbonate systems is often more complicated than their siliciclastic counterparts carbonates sediments typically get cemented very early and their seismic velocities are normally faster than those of siliciclastic sediments this reduces the resolution of carbonates in comparison to the clastics when using identical acquisition design carbonates are also easily dissoved which may lead to karsting a phenomenon unique to carbonate rocks karst surfaces commonly form highly irregular topography that causes energy dispersion and makes it difficult to image the sediments or rocks below it

high precision dating of volcanic events a d 1301 1995 using ice cores from law dome antarctica a record of volcanic activity over the period a d 1301 1995 has been extracted from three law dome ice cores east antarctica the record dating is unambiguous at the annual level from a d 1807 to 1995 and has an uncertainty of 1 year at a d 1301 signals from 20 eruptions are preserved in the record including those of two unknown eruptions with acid deposition beginning in a d 1810 8 and a d 1685 8 the beginning of the ice core signal from the a d 1815 tambora eruption is observed in the austral summer of a d 1816 1817 the mean observed stratospheric transport and deposition time to law dome from the eruption site is 1 5 years 0 6 years from 11 well dated eruptions the largest eruption observed in the law dome record has its maximum in a d 1460 with volcanic sulfate deposition beginning in the austral winter of a d 1459 this event is also observed in other ice core records and is attributed to the volcano kuwae with an eruption date in the range a d 1455 9 1459 9 if all sources of error are considered this is at least three years later than the date previously ascribed by dendrochronological and historical studies

holocene productivity changes off adelie land east antarctica 1 this study presents the first high resolution multiproxy investigation of primary productivity pp during the holocene from the antarctic continental margins micropaleontological and geochemical data from the sediment core md03 2601 associated to sea ice model outputs give unprecedented insights into the biological pump of the antarctic coastal area off adelie land in response to climatic changes plurimillennial and millennial changes of pp are observed in the study area in response to changes in nutrient availability stratification and growing season duration which are linked to sea ice upwelling wind and glacier dynamics the precessional cycle seems to be responsible in the pp long term variations while forcing factors involved at the millennial timescale remain more enigmatic our results emphasize enhanced biological pump during warmer and windier holocene phases because of a longer growing season and greater nutrient input antarctic coastal and continental shelf zones may therefore represent a more intense carbon sink in the future

holocene glacier and deep water dynamics adelie land region east antarctica abstract this study presents a high resolution multi proxy investigation of sediment core md03 2601 and documents major glacier oscillations and deep water activity during the holocene in the adelie land region east antarctica a comparison with surface ocean conditions reveals synchronous changes of glaciers sea ice and deep water formation at milankovitch and sub milankovitch time scales we report 1 a deglaciation of the adelie land continental shelf from 11 to 8 5 cal ka bp which occurred in two phases of effective glacier grounding line retreat at 10 6 and 9 cal ka bp associated with active deep water formation 2 a rapid glacier and sea ice readvance centred around 7 7 cal ka bp and 3 five rapid expansions of the glacier sea ice systems during the mid to late holocene associated to a long term increase of deep water formation at milankovich time scales we show that the precessionnal component of insolation at high and low latitudes explains the major trend of the glacier sea ice ocean system throughout the holocene in the adelie land region in addition the orbitally forced seasonality seems to control the coastal deep water formation via the sea ice ocean coupling which could lead to opposite patterns between north and south high latitudes during the mid to late holocene at sub milankovitch time scales there are eight events of glacier sea ice retreat and expansion that occurred during atmospheric cooling events over east antarctica comparisons of our results with other peri antarctic records and model simulations from high southern latitudes may suggest that our interpretation on glacier sea ice ocean interactions and their holocene evolutions reflect a more global antarctic holocene pattern

a 700 year record of atmospheric circulation developed from the law dome ice core east antarctica 1 a 700 year high resolution multivariate ice core record from dome summit south dss 66 46 s 112 48 e 1370 m law dome is used to investigate sea level pressure slp variability in the region of east antarctica empirical orthogonal function eof analysis reveals that the first eof ldeof1 of the combined glaciochemical oxygen isotope ratio and accumulation rate record from dss represents most of the variability in sea salt seen in the record ldeof1 is positively correlated at least 95 confidence level to instrumental june mean slp across most of east antarctica over the last 700 years ldeof1 levels at law dome were the highest during the nineteenth century suggesting an increase in intensification of winter circulation during this period the law dome dss oxygen isotope ratio series also indicates that the nineteenth century had the coldest winters of any century in the record in contrast ldeof1 levels were the lowest at law dome during the eighteenth century suggesting a significant shift in the patterns and or intensity of east antarctic atmospheric circulation between the eighteenth and the nineteenth centuries the ldeof1 sea salt record is characterized by significant decadal scale variability with a strong 25 year periodic structure

iron in ice cores from law dome a record of atmospheric iron deposition for maritime east antarctica during the holocene and last glacial maximum total dissolvable iron tdfe was measured in sections of ice cores recovered from law dome on the coast of wilkes land east antarctica these samples include ice dating from the last glacial maximum lgm the last deglaciation and the early and mid holocene as well as samples from the anthropocene that have been dated with seasonal to annual resolution combining our tdfe concentration data with estimates of the ice accumulation rate we estimate the atmospheric iron deposition for law dome and the adjacent southern ocean during these periods our results indicate that the atmospheric iron deposition flux to this region during the lgm 8 mol fe m 2 yr 1 was an order of magnitude higher than the average holocene deposition flux 0 8 mol fe m 2 yr 1 this holocene flux estimate is significantly higher than recent estimates of atmospheric iron deposition based on the analysis of iron in samples of the dome c epica ice core implying that there are significant meridional gradients in eolian iron flux to the antarctic region our data also suggest that there have been significant variations in atmospheric iron deposition to law dome and adjacent ocean waters over seasonal to decadal timescales during the past century analysis of ice samples dating from calendar years 1927 to 1928 indicates an anomalously high flux of tdfe to the law dome region amounting to around half the maximum lgm flux possibly as a result of severe drought conditions on the australian continent given that chronic iron deficiency is thought to limit phytoplankton production in much of the ocean around antarctica such large secular variations in atmospheric iron supply are likely to have had profound impacts on year to year primary production and ecosystem structure in antarctic waters

firn air δ15n in modern polar sites and glacial interglacial ice a model data mismatch during glacial periods in antarctica the phase lag between atmospheric composition air bubbles and temperature water isotopes can be quantified from ice cores provided that the age difference between entrapped air and the surrounding air can be correctly estimated this difference depends on the lock in depth lid when air no longer mixes with the atmosphere the lid can be estimated from firnification models or from the air isotopic composition 15n and 40ar both methods give consistent results for greenland and one coastal site in antarctica byrd new firn measurements in greenland northgrip and antarctica berkner island bas depot dome c confirm that firnification models correctly reproduce the present lid over a large range of surface conditions however a systematic mismatch is observed for the last glacial maximum lgm in east antarctic sites vostok dome c dome f questioning the model s validity here we use new 15n measurements from two coastal antarctic sites kohnen station and law dome providing depth estimates again distinct from firnification model calculations we show that this discrepancy can be resolved by revising the estimate of past accumulation rates 15n measurements can therefore help to constrain past accumulation rate and improve ice core dating

unglaciated areas in east antarctica during the last glacial marine isotope stage 3 new evidence from rauer group abstract limited information on the east antarctic ice sheet eais geometry during marine isotope stage 3 mis 3 60 25 ka restricts our understanding of its behaviour during periods of climate and sea level change ice sheet models forced by global parameters suggest an expanded eais compared to the holocene during mis 3 but field evidence from east antarctic coastal areas contradicts such modelling and suggests that the ice sheet margins were no more advanced than at present here we present a new lake sediment record and cosmogenic exposure results from bedrock which confirm that rauer group eastern prydz bay was ice free for much of mis 3 we also refine the likely duration of the last glacial maximum lgm glaciation in the region lacustrine and marine sediments from rauer group indicate the penultimate period of ice retreat predates 50 ka the lacustrine record indicates a change from warmer wetter conditions to cooler drier conditions after ca 35 ka substantive ice sheet re advance however may not have occurred until much closer to 20 ka contemporary coastal areas were still connected to the sea during mis 3 restricting the possible extent of grounded ice in prydz bay on the continental shelf in contrast relative sea levels rsl deduced from field evidence indicate an extra ice load averaging several hundred metres thicker ice across the bay between 45 and 32 ka thus ice must either have been thicker immediately inland with a steeper ice profile or there were additional ice domes on the shallow banks of the outer continental shelf further work is required to reconcile the differences between empirical evidence of past ice sheet histories and the history predicted by ice sheet models from far field temperature and sea level records

antarctic ice rises and rumples their properties and significance for ice sheet dynamics and evolution locally grounded features in ice shelves called ice rises and rumples play a key role buttressing discharge from the antarctic ice sheet and regulating its contribution to sea level ice rises typically rise several hundreds of meters above the surrounding ice shelf shelf flow is diverted around them on the other hand shelf ice flows across ice rumples which typically rise only a few tens of meters above the ice shelf ice rises contain rich histories of deglaciation and climate that extend back over timescales ranging from a few millennia to beyond the last glacial maximum numerical model results have shown that the buttressing effects of ice rises and rumples are significant but details of processes and how they evolve remain poorly understood fundamental information about the conditions and processes that cause transitions between floating ice shelves ice rises and ice rumples is needed in order to assess their impact on ice sheet behavior targeted high resolution observational data are needed to evaluate and improve prognostic numerical models and parameterizations of the effects of small scale pinning points on grounding zone dynamics

the maldives a giant isolated carbonate platform dominated by bottom currents abstract the maldives a 900 km north south trending paired chain of atolls that surround a ca 100 km wide central basin the inner sea represent a giant isolated carbonate platform in the indian ocean new reflection seismic multibeam and acoustic doppler current profiler data show that its development exhibits a distinct change from sea level to mainly bottom current controlled sedimentation at the end of the middle miocene the post middle miocene intra basinal fill consists of 9 mega units that have been formed and shaped by strong bottom currents entering the inner sea between the inter atoll passages at the end of the middle miocene the maldives represent a rimmed platform with the inner sea forming an empty bucket a connection to the indian ocean existed only in the northeastern part of the platform namely the kardiva channel probably concomitant with the onset of the indian monsoon the current pattern around the maldives changed significantly resulting in the formation of channels in the rimmed platform margin the latter process was encouraged by local drowning of large platform parts and additionally by bottom current forced submarine erosion that widened the channels to passages disintegrating the platform into separated atolls of different sizes the reworked material was dumped into the inner sea where it formed large contourite fans along slope bottom currents entering the inner sea from the north further redistributed the material leading to a southward shift of these sedimentary bodies in this way the inner sea was filled from west to east mega units 1 5 starting with mega unit 6 the opening of a southern gateway introduced a prominent northward flow of bottom waters in the inner sea it leads to the deposition of giant elongated drifts at the eastern flank of the basin filling it from east to west because the current swept away most of the material around the atolls the system was not able to prograde and the steady subsidence was compensated by aggradation accordingly a fundamental characteristic of a current controlled carbonate system is that aggradation occurs irrespective of platform sediment export or differently worded the rate of change in accommodation is always positive and greater than the rate of sediment supply adcp measurements in the winter monsoon season show two water masses in the inner sea one at the surface 0 150 m and a second below it that reaches its sea floor by the use of the grain size distribution of odp leg 716 located in the inner sea as proxy for the flow intensity of the bottom water we recognized an inverse proportional relationship to the monsoon strength from late upper miocene to present some of the current controlled deposits form sigmoidal prograding clinoforms preferably at the edges of the atolls adjacent to the passages where the velocity of the current entering the inner sea is high the anatomy of these prograding wedges is similar to sea level controlled clinoforms described for large isolated carbonate platforms in the sequence stratigraphic concept however our results document that they are not influenced by sea level fluctuations because of the high current velocities involved in their deposition they predominately consist of coarse sand sized carbonate fragments exhibiting large pore space and high permeability therefore these drift deposits comprise a possible exploration target

recent southern indian ocean climate variability inferred from a law dome ice core new insights for the interpretation of coastal antarctic isotopic records stable isotopes in water have been measured along a very high accumulation ice core from law dome on the east antarctic coast these enable a detailed comparison of the isotopic records over sixty years 1934 1992 with local antarctic station data and remote meteorological observations atmospheric reanalyses and sea surface temperature estimates on a seasonal to inter annual time scale using both observations and isotopic atmospheric general circulation model gcm results we quantify the relationships between stable isotopes 18o d and deuterium excess d d 8 18o with site and source temperature at seasonal and decadal time scales showing the large imprint of source conditions on law dome isotopes these calibrations provide new insights for the quantitative interpretation of temporal isotopic fluctuations from coastal antarctic ice cores an abrupt change in the local meridional atmospheric circulation is clearly identified from law dome deuterium excess during the 1970s and analysed using gcm simulations

relative timing of deglacial climate events in antarctica and greenland the last deglaciation was marked by large hemispheric millennial scale climate variations the bolling allerod and younger dryas periods in the north and the antarctic cold reversal in the south a chronology from the high accumulation law dome east antarctic ice core constrains the relative timing of these two events and provides strong evidence that the cooling at the start of the antarctic cold reversal did not follow the abrupt warming during the northern bolling transition around 14 500 years ago this result suggests that southern changes are not a direct response to abrupt changes in north atlantic thermohaline circulation as is assumed in the conventional picture of a hemispheric temperature seesaw

bayesian glaciological modelling to quantify uncertainties in ice core chronologies abstract valuable information about the environment and climate of the past is preserved in ice cores which are drilled through ice sheets in polar and alpine regions a pivotal part of interpreting the information held within the cores is to build ice core chronologies i e to relate time to depth existing dating methods can be categorised as follows 1 layer counting using the seasonality in signals 2 glaciological modelling describing processes such as snow accumulation and plastic deformation of ice 3 comparison with other dated records or 4 any combination of these conventionally implementation of these approaches does not use statistical methods in order to quantify dating uncertainties in this paper we develop the approach of category 2 further first the sources of uncertainty involved in glaciological models are formalised feeding these into a statistical framework that we call bayesian glaciological modelling bgm allows us to demonstrate the effect that uncertainty in the glaciological model has on the chronology bgm may also include additional information to constrain the resulting chronology for example from layer counting or other dated records such as traces from volcanic eruptions our case study involves applying bgm to date an antarctic ice core a dyer plateau core working through this example allows us to emphasise the importance of properly assessing uncertain elements in order to arrive at accurate chronologies including valid dating uncertainties valid dating uncertainties in turn facilitate the interpretation of environmental and climatic conditions at the location of the ice core as well as the comparison and development of ice core chronologies from different locations

climatic and glaciological information inferred from air content measurements of a law dome east antarctica ice core the total air content v of ice has been measured along the dome summit south dss core from law dome east antarctica the main features of this record are the very well preserved sub annual fluctuations of v down to at least 900 m depth and the significant increase of the v values during the last deglaciation the sub annual variations reflect changes in close off porosity and we interpret the v seasonal peaks as tracers of depth hoar layers for the longer time scale the large v fluctuations observed are interpreted in terms of elevation and or close off porosity changes under different assumptions we analyze the possible influence of a different global pressure field and or a change in seasonal temperature and precipitation cycles during the last glacial period our estimates of surface elevation changes derived from the v data are then compared with independent reconstructions of past elevations

a diatom inferred record of lake variability during the last 900 years in lutzow holm bay east antarctica decadal centennial scale climate variability in coastal antarctica remains poorly understood due to the limited number of highly resolved well dated records we present a 900 year decadal scale reconstruction based on sedimentary diatoms from lake abi in lutzow holm bay east antarctica hydrological change is inferred from diatom ecological preferences in conjunction with an existing regional training set and implies that lake water specific conductivity depth and nitrogen availability are the key drivers of diatom assemblage change lake abi underwent a series of subtle environmental changes related to these environmental variables possibly driven by changes in catchment snow melt and the duration of seasonal ice cover ordination is used to trace the major patterns of change in the diatom community with notable shifts identified between 470 and 400 and at 350 cal a bp where present ce 1950 the frequency of environmental variability at lake abi is broadly consistent with a record of the interdecadal pacific oscillation during the last millennium but contrasts with the apparent climate stability elsewhere in eastern antarctica further research is required to constrain the limnological and ecological responses of lakes in coastal antarctica to obtain more rigorous palaeoclimate reconstructions from these sites of immense potential

holocene accumulation and ice flow near the west antarctic ice sheet divide ice core site the west antarctic ice sheet divide core wdc provided a high resolution climate record from near the ross amundsen divide in central west antarctica in addition radar detected internal layers in the vicinity of the wdc site have been dated directly from the ice core to provide spatial variations in the age structure of the region using these two data sets together we first infer a high resolution holocene accumulation rate history from 9 2 thousand years of the ice core timescale and then confirm that this climate history is consistent with internal layers upstream of the core site even though the wdc was drilled only 24 kilometers from the modern ice divide advection of ice from upstream must be taken into account we evaluate histories of accumulation rate by using a flowband model to generate internal layers that we compare to observed layers results show that the centennially averaged accumulation rate was over 20 percent lower than modern at 9 2 thousand years before present b p increased by 40 percent from 9 2 to 2 3 thousand years b p and decreased by at least 10 percent over the past 2 thousand years b p to the modern values these holocene accumulation rate changes in central west antarctica are larger than changes inferred from east antarctic ice core records despite significant changes in accumulation rate throughout the holocene the regional accumulation pattern has likely remained similar to today and the ice divide position has likely remained on average within 5 kilometers of its modern position continent scale ice sheet models used for reconstructions of west antarctic ice volume should incorporate this accumulation history

high resolution ice core stable isotopic records from antarctica towards interannual climate reconstruction ice core records are a key resource for reconstructing antarctic climate however a number of physical processes preclude the simple interpretation of ice core properties such as oxygen isotopic ratios in terms of climate variables like temperature or sea level pressure we show that well dated sub annually resolved stable isotopic records from the united states international trans antarctic scientific expedition us itase traverses and other sources have a high correlation with local seasonal temperature variation however this temporal relationship cannot be simply extended to quantitative interannual resolution reconstructions of site temperature we suggest that a consistent and important target for ice core calibrations is a composite of annual mean temperature records from antarctic weather stations which covaries strongly with the dominant mode from principal component analysis of temperature variability in the antarctic significant correlations with this temperature index are found with individual ice core records with a composite of the ice cores and through a multiple linear regression model with the ice cores as predictors these results imply that isotopic signals like the instrumental temperature mode itself have a strong response to large scale atmospheric circulation variability which in the antarctic region is dominated by the southern annular mode

evidence for an early holocene climatic optimum in the antarctic deep ice core record in the interpretation of the antarctic deep ice core data little attention has been given to the holocene part of the records as far as translation of the stable isotope content in terms of temperature is concerned this can be understood because expected temperature changes may be obscured by isotopic noise of various origins and because no 14c dating has yet been available for this type of sequence in this article we focus on the dome c and vostok cores and on a new 850 m long ice core drilled out at komsomolskaia by the soviet antarctic expeditions these three sites are located in east antarctica on the antarctic plateau in a region essentially undisturbed by ice flow conditions so that their detailed intercomparison may allow us to identify the climatically significant isotopic signal our results compare well with the proximal records of southern hemisphere high latitudes and support the existence of a warmer climatic optimum between 10 and 6 ka y bp maximum temperatures are reached just at the end of the last deglaciation which confirms previous observations at high latitudes in contrast with later dates for the atlantic and hypsithermal optima in europe and north america

evidence for substantial accumulation rate variability in antarctica during the holocene through synchronization of co 2 in the taylor dome dome c and dml ice cores high resolution records of atmospheric co2 concentration during the holocene are obtained from the dome concordia and dronning maud land antarctica ice cores these records confirm that the co2 concentration varied between 260 and 280 ppmv in the holocene as measured in the taylor dome ice core however there are differences in the co2 records most likely caused by mismatches in timescales matching the taylor dome timescale to the dome c timescale by synchronization of co2 indicates that the accumulation rate at taylor dome increased through the holocene by a factor two and bears little resemblance to the stable isotope record used as a proxy for temperature this result shows that different locations experienced substantially different accumulation changes and casts doubt on the often used assumption that accumulation rate scales with the saturation vapor pressure as a function of temperature at least for coastal locations d 2004 elsevier b v all rights reserved

evidence for two intervals of enhanced 10 be deposition in antarctic ice during the last glacial period we have previously reported concentration profiles of cosmic ray produced cosmogenic 10be in deep ice cores from dome c and vostok antarctica1 2 in both these cores we found a concentration of 10be approximately two times larger in ice from the late glacial period than in the holocene ice we interpreted this as probably resulting from a lower precipitation rate on the antarctic plateau during glacial periods compared to interglacial periods in the vostok profile there was one sample corresponding to 60 000 yr bp which gave an unusually large 10be concentration not correlated with any obvious climatic event we suggested that this sample might be reflecting increased 10be production as for example during a period of reduced solar modulation2 we have now measured a much more detailed concentration profile for 10be in the vostok core the results confirm a 10be peak lasting 1 000 2 000 years at 60 000 yr bp and show another similar peak at 35 000 yr bp we have also observed the latter peak in the dome c core we discuss possible sources for these peaks and their potential as stratigraphic markers

glacial interglacial changes in ocean surface conditions in the southern hemisphere the stable isotope signatures of oxygen and hydrogen in the water of preserved ice and snow are both widely used to infer local temperatures of past environments a derived quantity based on these two signatures the deuterium excess 1 provides additional palaeoclimatic information2 3 4 as this parameter depends on the meteorological and oceanic characteristics of the water s source regions in particular their temperature2 3 and relative humidity4 published studies mainly focus on records from the past 40 000 years here we present a deuterium excess history obtained from ice cores from vostok east antarctica spanning the full glacial interglacial cycle of the past 150 000 years the deuterium excess record shows a strong anticorrelation with the earth s orbital obliquity 41 000 year periodicity and values are markedly higher during the cold stage 5d following the last interglacial than during the other cold stages we interpret the relationship with obliquity as resulting from changes in the latitudinal insolation gradient affecting ocean surface conditions and thus the delivery of moisture to the polar region we argue that the high 5d values relative to other cold stages are driven by relatively less moisture delivered from high latitudes and more from low latitudes the deuterium excess in antarctic precipitation thus provides long term spatially integrated information on ocean surface conditions and ocean atmosphere circulations in the southern hemisphere

identification of antarctic ablation areas using a regional atmospheric climate model the occurrence of antarctic ablation areas in dronning maud land the lambert glacier basin victoria land the transantarctic mountains and the antarctic peninsula is realistically predicted by the regional atmospheric climate model racmo2 ant with snowdrift related processes calculated offline antarctic ablation areas are characterized by a low solid precipitation flux in combination with strong sublimation snowdrift erosion and or melt the strong interaction between atmospheric circulation and topography plays a decisive role in the precipitation distribution and hence that of ablation areas three types of antarctic ablation areas can be distinguished all occurring in dry regions type 1 is the erosion driven ablation area caused by 1 d and or 2 d divergence in the katabatic wind field at high elevations 2000 3200 m asl type 2 is the sublimation driven ablation area this type occurs at lower elevations

exposure ages from mountain dipsticks in mac robertson land east antarctica indicate little change in ice sheet thickness since the last glacial maximum past changes in east antarctic ice sheet eais volume are poorly known and diffi cult to measure yet are critical for predicting the response of the ice sheet to modern climate change in particular it is important to identify the sources of sea level rise since the last glacial maximum lgm and ascertain the present day stability of the world s largest ice sheet we present altitudinal transects of 10 be and 26 al exposure ages across the framnes mountains in mac robertson land that allow the magnitude and timing of eais retreat to be quantifi ed our data show that the coastal eais thinned by at most 350 m in this region during the past 13 k y this reduction in ice sheet volume occurred over a 5 k y period and the present icesheet profi le was attained ca 7 ka in contrast to the west antarctic ice sheet which continues to retreat today combined with regional offshore and terrestrial geologic evidence our data suggest that the reduction in eais volume since the lgm was smaller than that indicated by contemporary ice sheet models and added little meltwater to the global oceans stability of the ice margin since the middle holocene provides support for the hypothesis that eais volume changes are controlled by growth and decay of northern hemisphere ice sheets and associated global sea level changes

glacio isostasy and glacial ice load at law dome wilkes land east antarctica abstract the holocene sea level high stand or marine limit in wilkes land east antarctica reached 30 m above present sea level at a few dispersed sites the most detailed marine limit data have been recorded for the windmill islands and budd coast at the margin of the law dome ice cap a dome of the east antarctic ice sheet eais relative sea level lowering of 30 m and the associated emergence of the windmill islands have occurred since 6900 14c corr yr b p numerical modeling of the earth s rheology is used to determine the glacio isostatic component of the observed relative sea level lowering glaciological evidence suggests that most of eais thickening occurred around its margin with expansion onto the continental shelf consequently a regional ice history for the last glacial maximum lgm was applied in the glacio isostatic modeling to test whether the observed relative sea level lowering was primarily produced by regional ice sheet changes the results of the modeling indicate that the postglacial 13 000 to 8000 14c yr b p removal of an ice load of between 770 and 1000 m from around the margin of the law dome and adjacent eais have produced the observed relative sea level lowering such an additional ice load would have been associated with a 40 to 65 km expansion of the law dome to near the continental shelf break together with a few hundred meters of ice thickening on the adjoining coastal slope of the eais up to 2000 m elevation whereas the observed changes in relative sea level are shown to be strongly influenced by regional ice sheet changes the glacio isostatic response at the windmill islands results from a combination of regional and to a lesser extent antarctic wide effects the correspondence between the holocene relative sea level lowering interpreted at the margin of the law dome and the lowering interpreted along the remainder of the wilkes land and oates land coasts 105 160 e suggests that a similar ice load of up to 1000 m existed along the eais margin between wilkes land and oates land

a 150 000 year climatic record from antarctic ice during much of the quaternary the earth s climate has undergone drastic changes most notably successive glacial and interglacial episodes the past 150 kyr includes such a climatic cycle the last interglacial the last glacial and the present holocene interglacial a new climatic time series for this period has been obtained using 18 o data from an antarctic ice core

ice core age dating and paleothermometer calibration based on isotope and temperature profiles from deep boreholes at vostok station east antarctica an interpretation of the deuterium profile measured along the vostok east antarctica ice core down to 2755 m has been attempted on the basis of the borehole temperature analysis an inverse problem is solved to infer a local geophysical metronome the orbital signal in the surface temperature oscillations expressed as a sum of harmonics of milankovich periods by correlating the smoothed isotopic temperature record to the metronome a chronostratigraphy of the vostok ice core is derived with an accuracy of 3 0 4 5 kyr the developed timescale predicts an age of 241 kyr at a depth of 2760 m the ratio 13d 13t i between deuterium content and cloud temperature fluctuations at the top of the inversion layer is examined by fitting simulated and measured borehole temperature profiles the conventional estimate of the deuterium temperature slope corresponding to the present day spatial ratio 9 per mil oc is confirmed in general however the mismatch between modeled and measured borehole temperatures decreases noticeably if we allow surface temperature responsible for the thermal state of the ice sheet to undergo more intensive precession oscillations than those of the inversion temperature traced by isotope record with this assumption we obtain the long term temporal deuterium temperature slope to be 5 8 6 5 per mil oc which implies that the glacial interglacial temperature increase over central antarctica was about 15oc in the surface temperature and 10oc in the inversion temperature past variations of the accumulation rate and the corresponding changes in the ice sheet surface elevation are simultaneously simulated

a revised 1000 year atmospheric δ13c co2 record from law dome and south pole antarctica 1 we present new measurements of 13c of co2 extracted from a high resolution ice core from law dome east antarctica together with firn measurements performed at law dome and south pole covering the last 150 years our analysis is motivated by the need to better understand the role and feedback of the carbon c cycle in climate change by advances in measurement methods and by apparent anomalies when comparing ice core and firn air 13c records from law dome and south pole we demonstrate improved consistency between law dome ice south pole firn and the cape grim tasmania atmospheric 13c data providing evidence that our new record reliably extends direct atmospheric measurements back in time we also show a revised version of early 13c measurements covering the last 1000 years with a mean preindustrial level of 6 50 finally we use a kalman filter double deconvolution to infer net natural co2 fluxes between atmosphere ocean and land which cause small 13c deviations from the predominant anthropogenically induced 13c decrease the main features found from the previous 13c record are confirmed including the ocean as the dominant cause for the 1940 a d co2 leveling our new record provides a solid basis for future investigation of the causes of decadal to centennial variations of the preindustrial atmospheric co2 concentration those causes are of potential significance for predicting future co2 levels and when attempting atmospheric verification of recent and future global carbon emission mitigation measures through coupled climate carbon cycle models