a late glacial high resolution site and source temperature record derived from the epica dome c isotope records east antarctica the timing and synchronisation of greenland and antarctic climate events that occurred during the last glacial period are still under debate as is the magnitude of temperature change associated with these events here we present detailed records of local and moisture source temperature changes spanning the period 27 45 kyr bp from water stable isotope measurements deltad and delta 18 o in the recently drilled epica dome c ice core east antarctic plateau using a simple isotopic model site deltat site and source deltat source temperatures are extracted from the initial 50 yr high resolution isotopic records taking into account the changes in seawater isotopic composition the deuterium isotope variability is very similar to the less precise deltad record from the vostok ice core and the site temperature inversion leads to a temperature profile similar to the classical palaeothermometry method due to compensations between source and ocean water corrections the reconstructed deltat site and deltat source profiles show different trends during the glacial the former shows a decreasing trend from the warm al event 38 kyr bp toward the last glacial maximum while the latter shows increasing values from 41 to 28 kyr bp the low frequency deuterium excess fluctuations are strongly influenced by obliquity fluctuations controlling the low to high latitude temperature gradients and show a remarkable similarity with a high resolution southeast atlantic sea surface temperature record a comparison of the temperature profiles site and source and temperature gradient deltat source deltat site with the non sea salt calcium and sodium records suggests a secondary influence of atmospheric transport changes on aerosol variations

change in climate ocean and ice sheet conditions in the ross embayment antarctica at 6 ka evidence from the ross embayment antarctica suggests an abrupt cooling and a concomitant increase in sea ice cover at about 6000 sp 6 ka stable isotope delta d concentrations in the taylor dome ice core at the western edge of the ross embayment decline rapidly after 6 ka and continue to decline through the late holocene methanesulfonic acid concentrations at taylor dome show opposite trends to delta d sediment cores from the western ross sea show a percentage minimum for the sea ice diatom fragilariopsis curta between 9 and 6 ka when taylor dome delta d values are highest followed by an increase through the late holocene radiocarbon dates from raised beach deposits indicate that the retreat of ice shelves in the ross embayment ceased atabout 6 ka coincident with the environmental changes inferred from the sediment and ice core records the similarity in timing suggests an important role for climate in controlling the evolution of ice shelf margins following the end of the last 9 glaciation

an 15 000 year record of el nino driven alluviation in southwestern ecuador debris flows have deposited inorganic laminae in an alpine lake that is 75 kilometers east of the pacific ocean in ecuador these storm induced events were dated by radiocarbon and the age of laminae that are less than 200 years old matches the historic record of el nino events from about 15 000 to about 7000 calendar years before the present the periodicity of clastic deposition is greater than or equal to 15 years thereafter there is a progressive increase in frequency to periodicities of 2 to 8 5 years this is the modern el nino periodicity which was established about 5000 calendar years before the present this may reflect the onset of a steeper zonal sea surface temperature gradient which was driven by enhanced trade winds

regional imprints of millennial variability during the mis 3 period around antarctica the climate of the last glacial marine isotopic stage 3 mis3 period is characterized by strong millennialscale variability with a succession of dansgaardeoeschger events first identified in greenland ice cores and associated with variations of the atlantic meridional overturning circulation amoc these abrupt events have a smooth and lagged counterpart in water stable isotopes from antarctic ice cores in this study we aim at depicting and understanding the circum antarctic expression of this millennial scale variability to illustrate the mechanisms potentially at work in the response of the southern high latitudes to an abrupt decrease of the amoc we first present results from experiments performed with the ipsl cm4 atmosphere ocean coupled model under glacial boundary conditions when the amoc is perturbed by imposing an additional freshwater flux in the north atlantic our model produces the classical bipolar seesaw mechanism generally invoked to explain the warming of the southern ocean antarctic region however this mechanism can be locally offset by faster atmospheric teleconnections originating from the tropics even though the precise location of this fast response is not coherent among different climate models our model results are confronted with a synthesis of antarctic records of ice core stable isotope and sea salt sodium including new data obtained on the taldice ice core the ipslcm4 produces a dipole like pattern around antarctica with warming in the atlantic indian sectors contrasting with an unexpected cooling in the east pacific sector the latter signal is not detected in our data synthesis both ice core data and simulations are consistent in depicting a more rapid response of the atlantic sector compared to the indian sector this feature can be explained by the gradual impact of ocean transport on which faster atmospheric teleconnections are superimposed detailed investigations of the sequence of events between different proxies are conducted in three ice cores earlier shifts in deuterium excess and significant changes in sea salt sodium fluxes in the most coastal sites taldice and edml compared to edc suggest reorganizations in local moisture sources possibly linked with sea ice cover this study demonstrates the added value of circum antarctic ice core records to characterize the patterns and mechanisms of glacial climate variability

new mis 19 epica dome c high resolution deuterium data hints for a problematic preservation of climate variability at sub millennial scale in the oldest ice marine isotope stage 19 mis 19 is the oldest interglacial period archived in the epica dome c ice core 780 ky bp and the closest orbital analogue to the holocene albeit with a different obliquity amplitude and phase with precession new detailed deuterium measurements have been conducted with a depth resolution of 11 cm corresponding time resolution of 130 years they confirm our earlier low resolution profile 55 cm showing a relatively smooth shape over the mis 20 to mis 18 time period with a lack of sub millennial climate variability first thought to be due to this low resolution the mis 19 high resolution profile actually reveals a strong isotopic diffusion process leading to a diffusion length of at least 40 cm erasing sub millennial climate variability we suggest that this diffusion is caused by water veins associated with large ice crystals at temperatures above 10 c temperature conditions in which the mis 19 ice has spent more than 200 ky this result has implications for the selection of the future oldest ice drilling site

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

holocene glacial and climate history of prince gustav channel northeastern antarctic peninsula the antarctic peninsula is one of the most rapidly warming regions on earth as evidenced by a recent increase in the intensity and duration of summer melting the recession of glaciers and the retreat and collapse of ice shelves despite this only a limited number of well dated near shore marine and lake sediment based palaeoenvironmental records exist from this region so our understanding of the longer term context of this rapid climate change is limited here we provide new well dated constraints on the deglaciation history and changes in sea ice and climate based on analyses of sedimentological proxies diatoms and fossil pigments in a sediment core collected from an isolation basin on beak island in prince gustav channel ne antarctic peninsula 63 36 s 57 20 w twenty two radiocarbon dates provided a chronology for the core including a minimum modelled age for deglaciation of 10 602 cal yr bp following the onset of marine sedimentation conditions remained cold and perennial sea ice persisted in this part of prince gustav channel until c 9372 cal yr bp this was followed by a seasonally open marine environment until at least 6988 cal yr bp corresponding with the early retreat and disintegration of the ice shelf in southern prince gustav channel following isolation of the basin from 6988 cal yr bp a relatively cold climate persisted until 3169 cal yr bp a mid late holocene climate optimum occurred between 3169 and 2120 cal yr bp inferred from multiple indicators of increased biological production this postdates the onset of the mid late holocene climate optimum in the south shetland islands 4380 cal yr bp and the south orkney islands 3800 cal yr bp suggesting that cooler climate systems of the weddell sea gyre to the east of the peninsula may have buffered the onset of warming climate deterioration is inferred from c 2120 cal yr bp until 543 cal yr bp this was followed by warming superimposed on this warming trend the instrumental record of recent warming at nearby hope bay is mirrored by a recent increase in the lake s primary production and a shift in the diatom communities in the uppermost 3 cm of sediments suggesting that this is amongst the first records to show an ecological response to recent rapid temperature increase these new constraints on glaciological and climate events in prince gustav channel are reviewed in the context of wider changes in the antarctic region

common millennial scale variability of antarctic and southern ocean temperatures during the past 5000 years reconstructed from the epica dome c ice core measurements of the two water stable isotopes dd and d18o along epica european project for ice coring in antarctica dome c ice core are combined with simple isotopic modelling distillation models to reconstruct the variability of both the site temperature east antarctica and the moisture source temperature nowadays probably the subantarctic indian ocean we discuss the difference between the reconstructed site and source temperature pro les with respect to the initial isotopic data we show that i the early holocene optimum appears rst in antarctica and 800 years later in the southern ocean and ii during the last 5000 years the site and source temperatures co vary at the centennial timescale an 833 year periodicity is observed only on deuterium and site temperature and therefore probably of local origin

early mid holocene climatic variations in tasmania australia multi proxy records in a stalagmite from lynds cave mass spectrometric uranium series dating and c o isotopic analysis of a stalagmite from lynds cave northern tasmania australia provide a high resolution record of regional climate change between 5100 and 9200 yr before present bp combined delta 18 o delta 13 c growth rate initial u 234 u 238 and physical property color transparency and porosity records allow recognition of seven climatic stages stage i 9080 yr bp a relatively dry period at the beginning of stalagmite growth evidenced by elevated u 234 u 238 stage ii 9080 8600 yr bp a period of unstable climate characterized by high frequency variability in temperature and bio productivity stage 111 8600 8000 yr bp a period of stable and moderate precipitation and stable and high bio productivity with a continuously rising temperature stage iv 8000 7400 yr bp the warmest period with high evaporation and low effective precipitation rainfall less evaporation stage v 7400 7000 yr bp the wettest period with highest stalagmite growth and enhanced but unstable bio productivity stage vi 7000 6600 yr bp a period with a significantly reduced precipitation and bio productivity without noticeable change in temperature stage vii 6600 5100 yr bp a period of lowest temperature and precipitation marking a significant climatic deterioration overall the records suggest that the warmest climate occurred between 8000 and 7400 yr bp followed by a wettest period between 7400 and 7000 yr bp these are broadly correlated with the so called mid holocene optimum previously proposed using pollen and lake level records however the timing and resolution of the speleothem record from lynds cave are significantly higher than in both the pollen and lake level records this allows us to correlate the abrupt change in physical property delta 18 o delta 13 c growth rate and initial u 234 u 238 of the stalagmite at similar to8000 yr bp with a global climatic event at early mid holocene transition c 2001 elsevier science b v all rights reserved

estimates of late holocene soil production and erosion in the snowy mountains australia soil production in actively uplifting or high precipitation alpine landscapes is potentially rapid however these same landscapes are also susceptible to erosion and can be sensitive to changes in climate and anthropogenic activity which can upset the balance between soil production and erosion the snowy mountains southeastern australia are a tectonically stable low relief moderate precipitation mountain environment the alpine area is extensively blanketed by soil that has been subjected to more intensive episodes of erosion during past periods of anthropogenic disturbance and under cold climate conditions of the late quaternary in this study rates of soil development and hillslope erosion were investigated using radiocarbon dating fallout radionuclides and sediment cores collected from lakes and reservoirs estimated holocene soil development rates were 20 220 t km y erosion rates determined from the radionuclides cs and pb were equivocal due to the inherent spatial variability of radionuclide inventories relative to apparent erosion rates estimated average erosion rates over the past 100 years determined from pb inventories were 60 t km y 95 ci 10 90 inventories of cs observed at the same site implied that more recent erosion rates over the past 60 years was below the detection limits of the sampling method applied here i e 70 t km y the upper estimate of 90 t km y is comparable to the mean erosion rate estimated using the radionuclide method for uncultivated sites in australia and is significantly lower than that measured at sites were vegetation cover was disturbed by livestock grazing prior to its exclusion from the alpine area in the 1940s ce low erosion and high soil production rates relative to the lowland soils are likely related to extensive vegetation cover which in this context protects soils against erosion and contributes to the formation of organic alpine soils that rapidly accumulate organic matter by comparison to other soil types

salt dome controlled sulfide precipitation of paleoproterozoic fe cu sulfide deposits eastern liaoning northeastern china the lower portion of the paleoproterozoic northern liaohe group liaoning northeast china comprises metavolcanics tuff dominated and metasediments mostly arkoses and dolostones that host stratiform strata bound fe cu sulfides and ca ba sulfates the ore bearing sequence consists of in ascending order pyroclastic rocks terrigenous clastics and carbonates all of which have been metamorphosed to greenschist amphibolite grade extensive albite rich breccias are present at the base of the succession and as pipes crosscutting a variety of lithologic units in the lieryu formation the geometry geochemistry and associated structures of these albite rich rocks suggest that they are metamorphosed salt domes the sulfide sulfate fe cu ores occur in a transitional zone between tuffs and dolomitic carbonates with those in the upper cycle being economically more important the sulfides were precipitated at two sites around venting centers as breccias lenses and veins and as stratiform pyrite chalcopyrite associated with anhydrite that is distal to the salt domes within each mining district the proximal ores are associated with brecciated albite and tourmaline rich rocks the sulfides in the proximal ores have delta 34 s values of 8 9 to 12 7 per mil whereas the distal ores have delta 34 s values of 2 6 to 8 8 per mil for the sulfides and 7 9 to 19 0 per mil for the anhydrite suggesting a sulfate dominated sulfur source with the pyrite delta 34 s variations arising mainly from decreasing temperatures away from the centers of the deposits the origin of the deposits is best described by a model in which sulfate carbonate rocks were deposited in peripheral sinks during salt diapirism the salt domes then acted as focuses for subsequent hydrothermal venting and were the centers of sulfide mineralization the sulfides precipitated during interaction of the reduced metal bearing hydrothermal fluids with the in situ sulfates that were the major source of the sulfur

spatial distribution of 17o excess in surface snow along a traverse from zhongshan station to dome a east antarctica the influence of temperature on the triple isotopic composition of oxygen in water is still an open question and limits the interpretation of water isotopic profiles in antarctic ice cores the main limitation arises from the lack of 17o excess measurements in surface snow and especially for remote regions characterized by low temperature and accumulation rate in this study we present new 17o excess measurements of surface snow along an east antarctic traverse from the coastal zhongshan station to the highest point of the antarctic ice sheet at dome a the 17o excess data significantly decrease inland with a latitudinal gradient of 1 33 0 41 per meg degree an altitudinal gradient of view the mathml source and a temperature gradient of view the mathml source theoretical calculations performed using a rayleigh model attribute this inland decrease to kinetic isotopic fractionation occurring during condensation from vapor to ice under supersaturation conditions at low temperatures however large heterogeneity of 17o excess in antarctic precipitation cannot only be explained by temperature at condensation and or influences of relative humidity in the moisture source region

a review of the australian new zealand sector of the southern ocean over the last 30ka aus intimate project the australia new zealand region of the southern ocean is influenced by several of the major global water masses of the oceans and is the prime entry point for cold deep waters into the pacific basin during the last glacial there was increased sea ice extent around antarctica as far north as 55 s as well as increased iceberg presence inferred from ice rafted debris evidence from microfossil assemblages suggests that sea surface temperatures sst were up to 7 c cooler consistent with recent estimates of cooling for new zealand derived from glacier modelling and other terrestrial proxies the subtropical front stf subantarctic front saf and polar front pf had migrated north except where the position of the fronts were controlled bathymetrically despite the potential for iron fertilisation by increased dust input into the ocean during the glacial there is limited evidence for higher total biological productivity in the pacific sector of the southern ocean the altered oceanic circulation during the glacial also decreased nutrients in the surface waters and affected the outgassing of co 2 this contributed to an increased storage of co 2 in the deep waters and lowering of the carbonate lysocline during the deglaciation sea ice retreat and sst increased rapidly at 18 ka roughly synchronous with the reinvigoration of deep water circulation in the southern ocean and the release of co 2 stored in the deep waters the gradient in carbon isotopes 13 o benthic between antarctic intermediate water aaiw and lower circumpolar deep water lcdw was greatest at the start of the deglaciation suggesting that the aaiw ventilation preceded lcdw ventilation or there was a significant change in air sea fractionation of 13 o benthic there was a slight enrichment in 18 o planktic decrease in ssts and a reduction in intermediate and deep water circulation between 14 and 12 5 ka bp during the antarctic cold reversal acr coincident with glacier advances in the new zealand southern alps and other terrestrial records of cooling following the acr there was a second more minor release of deep water co 2 most likely related to reinvigoration of north atlantic deep water nadw from 10 ka onwards the modern intermediate and deep water circulation was established air temperatures and ssts reached a maximum in the early holocene with the stf located at its most southerly position and there was a widespread retreat of antarctic ice sheets to their modern position a decline to modern sst and air temperatures in the mid to late holocene followed while millennial cycles overprinted on the sst and 18 o planktic records may be the result of subtle changes in the position and strength of the westerly winds during the holocene

early holocene laurentide ice sheet deglaciation causes cooling in the high latitude southern hemisphere through oceanic teleconnection the impact of the early holocene laurentide ice sheet lis deglaciation on the climate at southern hemisphere high latitudes is studied in three transient simulations performed with a global climate model of the coupled atmosphere ocean vegetation system considering the lis deglaciation we quantify separately the impacts of the background meltwater fluxes and the changes in topography and surface albedo in our model the meltwater input into the north atlantic results in a substantial weakening of the atlantic meridional overturning circulation associated with absence of deep convection in the labrador sea northward ocean heat transport by the atlantic ocean is reduced by 28 this weakened ocean circulation leads to cooler north atlantic deep water nadw upwelling of this cool nadw in the southern ocean results in reduced surface temperatures by 1 degrees c to 2 degrees c here between 9 and 7 ka compared to an experiment without lis deglaciation poleward of the polar front zone this advective teleconnection between the southern and northern hemispheres overwhelms the effect of the classical bipolar seesaw mechanism these results provide an explanation for the relatively cold climatic conditions between 9 and 7 ka reconstructed in several proxy records from southern hemisphere high latitudes such as antarctic ice cores

major factors controlling holocene δ13corg changes in a seasonal sea ice environment adelie land east antarctica 1 in an effort to investigate the controlling factors behind holocene 13corg changes in east antarctica we report high resolution down core records of bulk organic matter carbon isotopic ratios 13corg diatom census counts total organic carbon and biogenic silica content taken from one core recovered in the adelie trough a good correspondence between the 13corg record and records of small large and pennate centric ratios in many of the core segments indicates that diatom species composition affected holocene 13corg variations possibly via diatom shape and size effects variations in the surface water co2 concentration and in the isotopic composition of the source during the holocene cannot be ruled out although they cannot explain rapid and large amplitude 13corg changes within the limit of our investigation our results argue against active carbon acquisition through a carbon concentration mechanism as evidenced in low latitude upwelling systems the bulk organic matter thus represents a mixing of diatom taxa having different fractionation affinity to aqueous co2 our results confirm previous evidence which demonstrates that 13corg down core records should be used with great caution to reconstruct past co2 content in surface waters

otolith δ18o record of mid holocene sea surface temperatures in peru peruvian sea catfish galeichthys peruvianus sagittal otoliths preserve a record of modern and mid holocene sea surface temperatures ssts oxygen isotope profiles in otoliths excavated from ostra 6010 90 years before the present yr b p 8 degrees 55 s indicate that summer ssts were approximately 3 degrees c warmer than those of the present siches otoliths 6450 110 yr b p 4 degrees 40 s recorded mean annual temperatures approximately 3 degrees to 4 degrees c warmer than were measured under modern conditions trophic level and population diversity and equitability data from these faunal assemblages and other peruvian archaeological sites support the isotope interpretations and suggest that upwelling of the peru chile current intensified after approximately 5000 yr b p

abrupt early to mid holocene climatic transition registered at the equator and the poles paleoclimatic records from equatorial east africa antarctica and greenland reveal that atmospheric circulation changed abruptly at the early to mid holocene transition to full postglacial conditions a climatic reorganization occurred at all three sites between 8200 and 7800 years ago that lasted 200 years or less and appears to have been related to abrupt transitions in both marine and terrestrial records around the world

holocene climate evolution in the high latitude southern hemisphere simulated by a coupled atmosphere sea ice ocean vegetation model the holocene climate is simulated in a 9000 yr long transient experiment performed with the ecbilt clio vecode coupled atmosphere sea ice ocean vegetation model this experiment is forced with annually varying orbital parameters and atmospheric concentrations of co2 and ch4 the objective is to study the impact of these long term forcings on the surface temperature evolution during different seasons in the high latitude southern hemisphere we find in summer a thermal optimum in the mid holocene 6 3 ka bp with temperatures locally 3 degrees c above the preindustrial mean in autumn the temperatures experienced a long term increase particularly during the first few thousand years the opposite trend was simulated for winter and spring with a relatively warm southern ocean at 9 ka bp in inter up to 3 5 degrees c above the preindustrial mean and a warm continent in spring 3 degrees c followed by a gradual cooling towards the present these long term temperature trends can be explained by a combination of 1 a delayed response to orbital forcing with temperatures lagging insolation by i to months owing to the thermal inertia of the system and 2 the long memory of the southern ocean this long memory is related to the storage of the warm late winter spring anomaly below the shallower summer mixed layer until next winter sea ice plays an important role as an amplifying factor through the ice albedo and ice insulation feedbacks our experiments can help to improve our understanding of the holocene signal in proxies for instance the results suggest that in contrast to recent propositions teleconnections to the northern hemisphere appear not necessarily to explain the history of southern hemisphere temperature changes during the holocene

orbital controls on the el nino southern oscillation and the tropical climate the global synchroneity of glacial interglacial events is one of the major problems in understanding the link between milankovitch forcing and the climate of the late quaternary in this study we isolate a part of the climate system the tropical pacific and test its sensitivity to changes in solar forcing associated with changes in the earth s orbital parameters we use a simplified coupled ocean atmosphere model that is run for the past 150 000 years and forced with milankovitch changes in the solar insolation this system responds primarily to the precessional cycle in solar forcing and is capable of generating a mean response to the changes in the seasonal distribution of solar radiation even while the annual mean insolation is roughly constant the mean response to the precessional forcing is due to an interaction between an altered seasonal cycle and the el nifio southern oscillation enso changes in the enso behavior result in a mean tropical climate change the hypothesis is advanced that such a change in the tropical climate can generate a globally synchronous climate response to milankovitch forcing

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

the grip deuterium excess record abstract ice cores from greenland and antarctica are ideal archives for retrieving long time series of deuterium excess d d 8 18 o a parameter influenced by conditions prevailing in the oceanic regions which provide moisture for polar snow the central greenland grip deuterium excess record has recently been interpreted in terms of oceanic source temperatures both for the holocene and for the last glacial period this approach being less straightforward for the latter period because of changes in the precipitation seasonality between glacial and interglacial periods this article examines why a conventional or sea surface temperature interpretation of the grip excess record seems inconsistent with inferred site and source temperature changes in addition the grip excess record is extended back into the penultimate glacial period and we assess its geographic significance through a comparison with existing dye 3 and north grip data we examine why low d 18o slopes observed during glacial times are associated with low deuterium excess values similarities between the greenland grip and antarctic vostok excess records are discussed in terms of potential links with insolation and insolation gradient changes finally the isotope records in specific do events are examined in light of intruiging differences between the isotope ratios d or 18o and the excess records that may result from a feedback mechanism linked with freshwater oceanic input

holocene periodicity in north atlantic climate and deep ocean flow south of iceland climate fluctuations during the past millennium are relatively well documented1 on a longer timescale there is growing evidence of millennial scale variability of holocene climate at periodicities of 2 500 and 950 years possibly caused by changes in solar flux 2 3 and 1 500 years maybe related to an internal oscillation of the climate system 4 5 6 but the involvement of deep water masses in these holocene climate changes has yet to be established here we use sediment grain size data from the iceland basin to reconstruct past changes in the speed of deep water flow the study site is under the influence of iceland scotland overflow water isow the flow of which is an important component of the thermohaline circulation that modulates european climate flow changes coincide with some known climate events the little ice age and the mediaeval warm period and extend over the entire holocene epoch with aquasi periodicity of 1 500 years the grain size data indicate afaster isow flow when the climate of northern europe is warmer however a second mode of operation is observed in the early holocene when warm climate intervals are associated with slower isow flow at that time the melting remnant of land based glacial age ice may have provided a sufficient source of fresh water to the ocean to reduce isow flow south of iceland

the medieval climate anomaly in antarctica abstract the medieval climate anomaly mca is a well recognized climate perturbation in many parts of the world with a core period of 1000 1200 ce here we are mapping the mca across the antarctic region based on the analysis of published palaeotemperature proxy data from 60 sites in addition to the conventionally used ice core data we are integrating temperature proxy records from marine and terrestrial sediment cores as well as radiocarbon ages of glacier moraines and elephant seal colonies a generally warm mca compared to the subsequent little ice age lia was found for the subantarctic islands south of the antarctic convergence the antarctic peninsula victoria land and central west antarctica a somewhat less clear mca warm signal was detected for the majority of east antarctica mca cooling occurred in the ross ice shelf region and probably in the weddell sea and on filchner ronne ice shelf spatial distribution of mca cooling and warming follows modern dipole patterns as reflected by areas of opposing temperature trends main drivers of the multi centennial scale climate variability appear to be the southern annular mode sam and el nino southern oscillation enso which are linked to solar activity changes by nonlinear dynamics

geometry internal architecture and evolution of buried volcanic mounds in the northern south china sea abstract high resolution seismic and borehole data were used to characterize a volcanic mound in the northern south china sea including its internal architecture lithological characteristics and evolutionary history on seismic profiles the mound shows a convex geometry similar to an isolated carbonate buildup it was therefore previously seen as a carbonate buildup and a significant hydrocarbon target until an industrial well by7 1 proved its volcanic nature ten seismic facies are identified to analyze the internal architecture of the mound under the constraint of borehole data petrologic analysis based on cuttings and thin sections reveals that the mound is composed of volcanic tuffs siliciclastics carbonates and basalt layers depositions and architecture of the mound are interpreted as a result of an interplay between tephra accumulation during volcanic eruptions wave induced re deposition of volcaniclastics when the volcanic mound emerged above sea level and subsequent siliciclastic carbonate deposition when the volcanic mound was flooded during the phases of volcanic quiescence furthermore the correlation of seismic and well data allows us to reconstruct the entire evolutionary history of the mound from its formation to its demise and final burial this work presents a detailed description of the mound architecture and its genesis and thus provides an analogue for detailed interpretations of similar structures encountered during petroleum explorations in the south china sea or elsewhere

sea ice seasonality during the holocene adelie land east antarctica abstract thin sections of laminated cores from different antarctic coastal areas have demonstrated the potential of diatom species to document climate change at the seasonal scale here we present the relative abundances of four diatom species and species groups fragilariopsis curta group as a proxy for yearly sea ice cover f kerguelensis as a proxy for summer sea surface temperature chaetoceros hyalochaete resting spores as a proxy for spring sea ice melting and the thalassiosira antarctica group as a proxy for autumn sea ice formation in core md03 2601 retrieved off adelie land on the antarctic continental shelf these abundances were compared to surface temperatures and sea ice cover modelled over the last 9000 years both the marine records and the simulated climate demonstrated a cooler early holocene 9000 7700 years bp a warmer mid holocene 7700 4000 years bp and a colder late holocene 4000 1000 years bp yearly sea ice cover followed an inverse pattern to temperatures with less sea ice during the mid holocene hypsithermal than during the late holocene neoglacial however diatom census counts and model output indicate that sea ice spring melting happened earlier in the season as expected but that autumn sea ice formation also occurred earlier in the season during the hypsithermal than during the colder neoglacial thereby following seasonal changes in local insolation

sea ice diatom contributions to holocene nutrient utilization in east antarctica combined high resolution holocene 30sidiat and 13cdiat paleorecords are presented from theseasonal ice zone east antarctica both data sets re ect periods of increased nutrient utilization by diatomsduring the hypsithermal period circa 7800 to 3500 calendar years cal years b p coincident with a higherabundance of open water diatom species fragilariopsis kerguelensis increased biogenic silica productivity bsi and higher regional summer temperatures the neoglacial period after circa 3500 cal years b p isre ected by an increase in sea ice indicative species fragilariopsis curta and fragilariopsis cylindrus upto50 along with a decrease in bsi and 13cdiat 18 to 23 however over this period 30sidiatdata show an increasing trend to some of the highest values in the holocene record average of 0 43 competing hypotheses are discussed to account for the decoupling trend in utilization proxies including ironfertilization species dependent fractionation effects and diatom habitats based on mass balance calculations we highlight that diatom species derived from the semi enclosed sea ice environment may have a confoundingeffect upon 30sidowncorecompositions of the seasonal sea ice zone a diatom composition with approximately28 of biogenic silica derived from the sea ice environment diat si can account for the increased averagecompo sition of 30sidiatduring the neoglacial these data highlight the signi cant role sea ice diatoms can playwith relation to their export in sediment records which has implications on productivity reconstructions fromthe seasonal ice zone

late holocene climatic variability south of the alps as recorded by lake level fluctuations at lake ledro trentino italy a lake level record for the late holocene at lake ledro trentino northeastern italy is presented it is based on the sediment and pollen analysis of a 1 75 m high stratigraphic section observed on the southern shore site ledro i and a 3 2 m long sediment core taken from a littoral mire on the southeastern shore site ledro ii the chronology is derived from 15 radiocarbon dates and pollen stratigraphy the late holocene composite record established from these two sediment sequences gives evidence of centennial scale fluctuations with highstands at c 3400 2600 1700 1200 and 400 cal bp in agreement with various palaeohydro logical records established in central and northern italy as well as north of the alps in addition high lake level conditions at c 2000 cal bp may be the equivalent of stronger river discharge observed at the same time in central italy s rivers in agreement with the lake level record of accesa tuscany the ledro record also suggests a relatively complex palaeohydrological pattern for the period around 4000 cal bp on a millennial scale sediment hiatuses observed in the lower part of the ledro i sediment sequence indicate that except for a high stand occurring just after 7500 cal bp lower lake levels generally prevailed rather before c 4000 cal bp than afterwards finally the lake level data obtained at lake ledro indicate that the relative continuity of settlements in humid areas of northern italy during the bronze age in contrast to their general abandonment north of the alps between c 3450 and 3150 cal bp does not reflect different regional patterns of climatic and palaeohy drological conditions in contrast the rise in lake level dated to c 3400 cal bp at ledro appears to coincide with a worldwide climate reversal observed in both the hemispheres while palaeoenvironmental and archaeological data collected at lake ledro may suggest as a working hypothesis a relative emancipation of proto historic societies from climatic conditions

the cold event 8200 years ago documented in oxygen isotope records of precipitation in europe and greenland stable oxygen isotope ratios of ostracod valves in late glacial and holocene sediments of core as 92 5 from deep lake ammersee southern germany reflect variations of mean oxygen isotope ratios in past atmospheric precipitation the record reconfirms the strong similarity of climate evolution in europe and greenland during the last deglaciation for the first time in europe we find a 200 year long negative 18o excursion which is contemporaneous with the strongest negative 18o excursion in the greenland ice around 8 2 ky before present the 8 2 ky isotopic event on both sides of the north atlantic ocean is interpreted as a cold period most probably induced by a perturbation of the north atlantic thermohaline circulation we discuss two possible triggering mechanisms 1 weak forcing as proposed by alley et al and 2 forcing by a strong and sudden freshwater pulse from the collapse of the hudson ice dome

holocene long and short term climate changes off adelie land east antarctica diatom data from a marine sediment core give insight on holocene changes in sea surface conditions and climate at high southern latitudes off adelie land east antarctica the early to mid holocene was warmer than the late holocene with a transition at 4000 calendar years b p sea ice was less present and spring summer growing season was greater during the warm period relative to the cold one thus limiting sea ice diatom production and favoring more open ocean diatom to develop the long term holocene climatic evolution in east antarctica is explained by a combination of a delayed response to local seasonal insolation changes coupled to the long memory of the southern ocean abrupt variations of the diatom relative abundances indicating rapid climate changes are superimposed to the holocene long term trends spectral analyses calculate robust frequencies at 1600 a where a is years 1250 a 1050 a 570 a 310 a 230 a 150 125 a 110 a 90 a and 66 a such periods are very close to solar activity cyclicities except for the periods at 310 a and 1250 a which are close to internal climate variability cyclicities wavelet analyses estimate the same periods but indicate nonstationary cyclicities rapid climate changes at high southern latitudes may therefore be explained by a combination of external solar and internal thermohaline circulation forcings

a tentative chronology for the epica dome concordia ice core a tentative age scale edc1 for the last 45 kyr is established for the new 788 m epica dome c ice core using a simple ice flow model the age of volcanic eruptions the end of the younger dryas event and the estimated depth and age of elevated 10be about 41 kyr ago were used to calibrate the model parameters the uncertainty of edc1 is estimated to 10 yr for 0 to 700 yr bp up to 200 yr back to 10 kyr bp and up to 2 kyr back to 41 kyr bp the age of the air in the bubbles is calculated with a firn densification model in the holocene the air is about 2000 yr younger than the ice and about 5500 yr during the last glacial maximum

late quaternary deglacial history across the larsen b embayment antarctica abstract we measured meteoric 10 be variation throughout a marine sediment core from the larsen b embayment lbe of the antarctic peninsula and collected in situ 10 be and 14 c exposure ages on terrestrial glacial deposits from the northern and southern margins of the lbe we use these data to reconstruct last glacial maximum lgm to present deglaciation and ice shelf change in the lbe core sedimentary facies and meteoric 10 be data show a monotonic progression from subglacial deposits to sub ice shelf deposits to open marine conditions indicating that its collapse in 2002 was unprecedented since the lgm exposure age data from the southern lbe indicate 40 m of ice surface lowering between 14 and 6 ka then little change between 6 ka and the 2002 collapse exposure age data from the northern lbe show a bimodal distribution in which clusters of apparent exposure ages in the ranges 4 9 5 1 ka and 1 0 2 0 ka coexist near 50 m elevation based on these results other published terrestrial and marine deglaciation ages and a compilation of sea bed imagery we suggest a north to south progression of deglaciation in the northeast antarctic peninsula in response to holocene atmospheric and oceanic warming we argue that local topography and ice configuration inherited from the lgm in addition to climate change are important in controlling the deglaciation history in this region

formal subdivision of the holocene series epoch a discussion paper by a working group of intimate integration of ice core marine and terrestrial records and the subcommission on quaternary stratigraphy international commission on stratigraphy this discussion paper by a working group of intimate integration of ice core marine and terrestrial records and the subcommision on quaternary stratigraphy sqs of the international commission on stratigraphy ics considers the prospects for a formal subdivision of the holocene series epoch although previous attempts to subdivide the holocene have proved inconclusive recent developments in quaternary stratigraphy notably the definition of the pleistocene holocene boundary and the emergence of formal subdivisions of the pleistocene series epoch mean that it may be timely to revisit this matter the quaternary literature reveals a widespread but variable informal usage of a tripartite division of the holocene early middle or mid and late and we argue that this de facto subdivision should now be formalized to ensure consistency in stratigraphic terminology we propose an early middle holocene boundary at 8200 a bp and a middle late holocene boundary at 4200 a bp each of which is linked to a global stratotype section and point gssp should the proposal find a broad measure of support from the quaternary community a submission will be made to the international union of geological sciences iugs via the sqs and the ics for formal ratification of this subdivision of the holocene series epoch copyright 2012 john wiley sons ltd

stable isotopes in surface snow along a traverse route from zhongshan station to dome a east antarctica samples of surface snow were collected for stable isotope analysis along the traverse route from zhongshan to dome a east antarctica from dec 28th 2007 to feb 8th 2008 the local relationship between d and surface temperature is established to be 6 4 0 2 per c very similar to the average for east antarctic the deuterium excess shows a pattern of high values over antarctica particularly at dome a we compare our data with an atmospheric general circulation model which includes stable water isotopes echam5 wiso the model simulation captures the right levels of d but overestimates 18o this study provides support for the ongoing deep ice core project at dome a

rapid deglaciation of marguerite bay western antarctic peninsula in the early holocene glacial geological evidence of rapid ice stream retreat is important for the potential insight it can bring to understanding of contemporary rapid ice sheet change here we report new chronological constraints on the deglacial history of the marguerite trough ice stream which formerly drained part of the western margin of the antarctic peninsula this ice stream has been previously identified on geomorphological grounds as an example of an outlet that underwent rapid retreat following the last glacial maximum but the precise timing of this retreat has not been conclusively determined we obtained cosmogenic surface exposure dates on erratic boulders that record the thinning history of ice flowing into the ice stream these dates show that the ice stream underwent 270 m of thinning very rapidly at 9 6 ka bp the timing of ice stream thinning agrees closely with previously published data on ice shelf retreat the age of the first post glacial beaches and minimum constraining ages for the onset of lacustrine sedimentation and post glacial sedimentation in inner shelf fjords we compare the timing of retreat to the similarly sized anvers trough ice stream further north and find that retreat in marguerite bay was more rapid and earlier than in the anvers trough we argue that the intrusion of circumpolar deep water is the most likely forcing mechanism for retreat in marguerite bay a key finding of this study is that rapid retreat occurred in deep water with reverse continent dipping slope but also in relatively shallow water with a positive slope this may have implications for understanding of oceanographically forced ice sheet change in other parts of west antarctica

holocene antarctic climate variability from ice and marine sediment cores insights on ocean atmosphere interaction abstract holocene climate variability in the southeast atlantic sector of the southern ocean and antarctic is assessed and quantified through integration of available marine sediment core and antarctic ice core data we use summer sea surface temperature ssst and sea ice presence sip reconstructions from two marine sediment cores recovered north 50 s and south 53 2 s of the present day antarctic polar front apf as well as an atmospheric temperature and sea ice proxy from the epica ice core from dronning maud land edml we find reasonably good agreement in the timing of climate evolution in the analyzed series almost all records show a gradual glacial to holocene climate transition interrupted by the antarctic cold reversal around 13 000 cal yr bp and early holocene climatic optimum hco at about 11 000 cal yr bp during the early hco the seasonal ice cover retreats to south of 53 s it then readvances in the course of the mid to late holocene the maximum winter sea ice edge position during the recent 10 000 years varied mainly within 51 53 s with sporadic growth to north of 50 s a position similar to that during the last glacial the onset of the neoglacial period after ca 4000 yr bp is associated with a steepening of the ssst gradient between the marine core sites strengthening of the westerlies and cooling in the inland ice sheet the agreement in timing between elevated ssst during the early hco and decreased deuterium excess in edml and other ice cores from different locations in the east antarctic suggests that the retreat of sea ice during the early hco and weakening of the apf was a general feature of the east antarctic climate during that time

coherent high and low latitude climate variability during the holocene warm period a faunal record of sea surface temperature sst variations off west africa documents a series of abrupt millennial scale cooling events which punctuated the holocene warm period these events evidently resulted from increased southward advection of cooler temperate or subpolar waters to this subtropical location or from enhanced regional upwelling the most recent of these events was the little ice age which occurred between 1300 to 1850 a d when subtropical ssts were reduced by 3 to 4 c these events were synchronous with holocene changes in subpolar north atlantic ssts documenting a strong in phase link between millennial scale variations in high and low latitude climate during the holocene

is the recently reported 65 to 70 year surface temperature oscillation the result of climatic noise in a recent paper schlesinger and ramankutty 1994 we reported finding a 65 to 70 year oscillation in each of the four records of observed global mean surface temperature we also found that the oscillation does not exist everywhere over the earth but rather only over the north atlantic ocean and its bordering continental regions of north america europe and northern africa we proposed three possible causes for our finding 1 random radiative forcing of the climate system that is climatic noise 2 oscillatory forcing external to the climate system such as by a variation in solar irradiance and 3 an oscillation internal to the climate system perhaps not unlike that of the el nino southern oscillation but with a longer timescale in this paper we critically examine the first hypothesis our analysis shows that this hypothesis can be rejected at a very high level of statistical confidence

global characterization of the holocene thermal maximum we analyze the global variations in the timing and magnitude of the holocene thermal maximum htm and their dependence on various forcings in transient simulations covering the last 9000 years 9 ka performed with a global atmosphere ocean vegetation model in these experiments we consider the influence of variations in orbital parameters and atmospheric greenhouse gases and the early holocene deglaciation of the laurentide ice sheet lis considering the lis deglaciation we quantify separately the impacts of the background melt water fluxes and the changes in topography and surface albedo in the analysis we focus on the intensity of the maximum temperature deviation relative to the preindustrial level its timing in the holocene and the seasonal expression in the model the warmest htm conditions are found at high latitudes in both hemispheres reaching 5 c above the preindustrial level while the smallest htm signal is seen over tropical oceans less than 0 5 c this latitudinal contrast is mostly related to the nature of the orbitally forced insolation forcing which is also largest at high latitudes and further enhanced by the polar amplification the holocene timing of the htm is earliest before 8 ka bp in regions not affected by the remnant lis particularly nw north america e asia n africa n south america the middle east ne siberia and australia compared to the early holocene insolation maximum the htm was delayed by 2 3 ka over ne north america and regions directly downwind from the lis a similar delay is simulated over the southern ocean while an intermediate lag of about 1 ka is found over most other continents and oceans the seasonal timing of the htm over continents generally occurs in the same month as the maximum insolation anomaly whereas over oceans the htm is delayed by 2 3 months exceptions are the oceans covered by sea ice and north africa were additional feedbacks results in a different seasonal timing the simulated timing and magnitude of the htm are generally consistent with global proxy evidence with some notable exceptions in the mediterranean region sw north america and eastern eurasia 2012 elsevier ltd

an oceanic cold reversal during the last deglaciation a detailed deuterium excess profile measured along the dome c epica european project for ice coring in antarctica core reveals the timing and strength of the sea surface temperature changes at the source regions for dome c precipitation we infer that an oceanic cold reversal took place in the southern indian ocean 800 years after the antarctic cold reversal the temperature gradient between the oceanic moisture source and antarctica is similar to the dome c sodium profile during the deglaciation illustrating the strong link between this gradient and the strength of the atmospheric circulation

enso sam interactions during the middle and late holocene a new chronology of large magnitude rainfall events derived from the continuous high resolution lake tutira storm sediment record covers the last 6800 years and provides the first insight into changes in el nino southern oscillation enso teleconnections to the higher southern latitudes to be obtained from new zealand synthesis with independent paleoclimate records from the tropical pacific and antarctica also reveals a millennial scale waxing and waning of the teleconnections that were not visible in the narrow historical window previously used to view interactions between enso and the southern annular mode sam consistent with modern enso behaviour we find teleconnections to the southwest pacific varied throughout the middle and late holocene depending on the strength and phase of enso and the phase of the sam we suggest that precession driven changes in the seasonal cycle of solar radiation exert a first order control on the interaction between the two climate modes consequently their present

simulation of an abrupt change in saharan vegetation in the mid holocene climate variability during the present inter glacial the holocene has been rather smooth in compar ison with the last glacial nevertheless there were some rather abrupt climate changes one of these changes the desertication of the saharan and arabian region some 4 6 thousand years ago was presumably quite important for human society it could have been the stimulus leading to the foundation of civilizations along the nile euphrat and tigris rivers here we argue that saharan and arabian de sertication was triggered by subtle variations in the earth s orbit which were strongly amplied by atmosphere vegeta tion feedbacks in the subtropics the timing of this tran sition however was mainly governed by a global interplay between atmosphere ocean sea ice and vegetation

the 8 2 kyr bp event simulated by a global atmosphere sea ice ocean model seven freshwater perturbation experiments were performed with a global atmosphere sea ice ocean model to study the mechanism behind the 8 2 kyr bp holocene cooling event these experiments differed in initial state and duration of the applied freshwater pulse while the amount of freshwater was kept constant 4 67x10 14 m 3 one of the scenarios with freshwater added to the labrador sea at a rate of 0 75 sv during 20 years resulted in weakening of the north atlantic thermohaline circulation during 320 years and surface cooling varying from 1 to 5 degreesc over adjacent continents this result is consistent with proxy data suggesting that a meltwater induced weakening of the thermohaline circulation caused the event moreover our results indicate that the time scale of the meltwater release and the initial state are important as both have a strong effect on the magnitude and duration of the produced model response

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

centennial scale holocene climate variability revealed by a high resolution speleothem δ18o record from sw ireland evaluating the significance of holocene submillennial 18 o variability in the greenland ice cores is crucial for understanding how natural climate oscillations may modulate future anthropogenic warming a high resolution oxygen isotope record from a speleothem in southwestern ireland provides evidence for centennial scale 18 o variations that correlate with subtle 18 o changes in the greenland ice cores indicating regionally coherent variability in the early holocene evidence for previously undetected early holocene cooling events is presented but mid to late holocene ice rafting in the north atlantic appears to have had little impact on 18 o at this ocean margin site

southward migration of the intertropical convergence zone through the holocene titanium and iron concentration data from the anoxic cariaco basin off the venezuelan coast can be used to infer variations in the hydrological cycle over northern south america during the past 14 000 years with subdecadal resolution following a dry younger dryas a period of increased precipitation and riverine discharge occurred during the holocene thermal maximum since approximately 5400 years ago a trend toward drier conditions is evident from the data with high amplitude fluctuations and precipitation minima during the time interval 3800 to 2800 years ago and during the little ice age these regional changes in precipitation are best explained by shifts in the mean latitude of the atlantic intertropical convergence zone itcz potentially driven by pacific based climate variability the cariaco basin record exhibits strong correlations with climate records from distant regions including the high latitude northern hemisphere providing evidence for global teleconnections among regional climates

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

water isotopes as tools to document oceanic sources of precipitation the isotopic composition of precipitation in deuterium oxygen 18 and oxygen 17 depends on the climatic conditions prevailing in the oceanic regions where it originates mainly the sea surface temperature and the relative humidity of air this dependency applies to present day precipitation but also to past records which are extracted for example from polar ice cores in turn coisotopic measurements of deuterium and oxygen 18 offer the possibility to retrieve information about the oceanic origin of modern precipitation as well as about past changes in sea surface temperature and relative humidity of air this interpretation of isotopic measurements has largely relied on simple rayleigh type isotopic models and is complemented by lagrangian back trajectory analysis of moisture sources it is now complemented by isotopic general circulation models igcm in which the origin of precipitation can be tagged we shortly review published results documenting this link between the oceanic sources of precipitation and their isotopic composition we then present experiments performed with two different igcms the giss model ii and the lmdz model we focus our study on marine water vapor and its contribution to precipitation over antarctica and over the andean region of south america we show how igcm experiments allow us to relate climatic conditions prevailing in the oceanic source of precipitation to its isotopic composition such experiments support at least qualitatively the current interpretation of ice core isotopic data in terms of changes in sea surface temperature additionally we discuss recent studies clearly showing the added value of oxygen 17 measurements key points link between the isotopic content of precipitation and its oceanic origin application of this method to polar ice cores andean precipitation potential of combining deuterium excess and oxygen 17 excess 2013 american geophysical union all rights reserved

magnitude of isotope temperature scaling for interpretation of central antarctic ice cores 1 the conventional interpretation of ice core deuterium and oxygen 18 isotope profiles based on the use of present day observations spatial slope underestimates glacialinterglacial surface temperature changes in central greenland by up to a factor of two this likely results from changes in the seasonality of the precipitation due to the particular location of the greenland ice sheet next to the highly variable northern polar front in this regard the situation is much simpler for central antarctica and this should be reflected in the temperature interpretation of ice core isotopic records with this in mind we closely examine all relevant information focusing on the east antarctic plateau where both model and empirical isotope temperature estimates are available we point to the fact that correctly accounting for the influence of ocean isotopic change is important when interpreting deuterium profiles from ice cores in this region the evidence presently available indicates that unlike for greenland the present day spatial slope can probably be taken as a surrogate of the temporal slope to interpret glacial interglacial isotopic changes at sites such as vostok and epica dome c corresponding temperature changes are within 10 to 30 of those obtained from the conventional interpretation based on the use of the spatial slope index terms 1040 geochemistry isotopic composition chemistry 1827 hydrology glaciology 1863 3344 meteorology and atmospheric dynamics paleoclimatology 9310 information related to geographic region antarctica keywords water isotopes temperature estimate antarctica deuterium oxygen 18

uncertainties in elevation changes and their impact on antarctic temperature records since the end of the last glacial period abstract this study presents a sensitivity analysis considering the influence of elevation changes associated with both ice thickness and land height changes on water stable isotope temperature proxies from antarctic ice cores we compare results from three different ice sheet models and three different earth viscosity models at a 10 ice core sites as expected the ice thinning signal at west antarctic sites is the largest contributor to elevation induced temperature changes the signal predicted by the ice models considered produced 100 200 of the total glacial to interglacial signal in d indicating that the deglacial ice thinning is overestimated by an amount approaching an order of magnitude at some locations this indicates that the total volume loss in these models is considerably overestimated furthermore the predicted rate of this change is not supported by the isotope data and so again most likely reflects inaccuracies in the adopted ice models estimates of contemporary ice mass changes inferred from satellite gravity data corrected using any of these models with therefore be biased as a result the isostatic signal acts to reduce the total elevation change at most sites and has a relatively small magnitude a few to 20 of that due to the ice thickness change so is secondary at most sites and for most of the time however our results indicate that it could be the dominant control on elevation at some west antarctic sites during the holocene resulting in a secular cooling signal of 10 20 in d none of the models capture the holocene isotopic depletion trend present at several sites in east antarctica

holocene deglacial history of the northeast antarctic peninsula a review and new chronological constraints the northeast antarctic peninsula neap region is currently showing signs of significant environmental change evidenced by acceleration of glacial retreat and collapse of both larsen a and b ice shelves within the past 15 years however data on the past extent of the eastern margin of the antarctic peninsula ice sheet apis and its holocene retreat history are sparse and hence we cannot yet put the recent changes into a long term context in order to investigate the timing of deglaciation we present 16 new cosmogenic 10be surface exposure ages from sites on northern james ross island cape lachman johnson mesa and terrapin hill and seymour island the majority of the ages cluster around 6e10 ka with three significantly older 25e31 ka we combine these ages with existing terrestrial and marine radiocarbon deglaciation ages and a compilation of existing swath bathymetry data to quantify the temporal and spatial character of the regional glacial history ice had begun to retreat from the outer shelf by 18 3 ka reaching seymour island by w8 ka northern james ross island began to deglaciate around the time of the early holocene climatic optimum c 11e9 5 ka deglaciation continued and a transition from grounded to floating ice in prince gustav channel occurred around 8 ka separating the james ross island ice cap from the apis this occurred shortly before prince gustav channel ice shelf began to disintegrate at 6 2 ka our results suggest there may be a bathymetric control on the spatial pattern of deglaciation in the neap

holocene climate variability in antarctica based on 11 ice core isotopic records a comparison is made of the holocene records obtained from water isotope measurements along 11 ice cores from coastal and central sites in east antarctica vostok dome b plateau remote komsomolskaia dome c taylor dome dominion range d47 km105 and law dome and west antarctica byrd with temporal resolution from 20 to 50 yr the long term trends possibly reflect local ice sheet elevation fluctuations superimposed on common climatic fluctuations all the records confirm the widespread antarctic early holocene optimum between 11 500 and 9000 yr in the ross sea sector a secondary optimum is identified between 7000 and 5000 yr whereas all eastern antarctic sites show a late optimum between 6000 and 3000 yr superimposed on the long time trend all the records exhibit 9 aperiodic millennial scale oscillations climatic optima show a reduced pacing between warm events typically 800 yr whereas cooler periods are associated with less frequent warm events pacing 1200 yr

offset timing of climate oscillations during the last two glacial interglacial transitions connected with large scale freshwater perturbation multidecadal to centennial planktic 18o and mg ca records were generated at ocean drilling program site 976 odp976 in the alboran sea the site is in the flow path of atlantic inflow waters entering the mediterranean and captured north atlantic signals through the surface inflow and the atmosphere the records reveal similar climatic oscillations during the last two glacial to interglacial transitions albeit with a different temporal pacing glacial termination 1 t1 was marked by heinrich event 1 h1 post h1 bolling allerod warming and younger dryas yd cooling during t2 the h11 18o anomaly was twice as high and lasted 30 longer than during h1 the post h11 warming marked the start of mis5e while the subsequent yd style cooling occurred during early mis5e the post h11 temperature increase at odp976 matched the sudden asian monsoon termination ii at 129 ka b p extending the 230th dated speleothem timescale to odp976 suggests glacial conditions in the northeast atlantic region were terminated abruptly and interglacial warmth was reached in less than a millennium the early mis5e cooling and freshening at odp976 coincided with similar changes at north atlantic sites suggesting this was a basin wide event by analogy with t1 we argue that this was a yd type event that was shifted into the early stages of the last interglacial period this scenario is consistent with evidence from northern north atlantic and nordic sea sites that the continuing disintegration of the large saalian stage mis6 ice sheet in eurasia delayed the advection of warm north atlantic waters and full strength convective overturn until later stages of mis5e

mechanisms of holocene palaeoenvironmental change in the antarctic peninsula region the antarctic peninsula is one of the three fastest warming regions on earth here we review holocene proxy records of marine and terrestrial palaeoclimate in the region and discuss possible forcing mechanisms underlying past change with a specific focus on past warm periods our aim is to critically evaluate the mechanisms by which palaeoclimate changes might have occurred in order to provide a longer term context for assessing the drivers of recent warming two warm events are well recorded in the holocene palaeoclimate record namely the early holocene warm period and the mid holocene hypsithermal mhh whereas there are fewer proxy data for the mediaeval warm period mwp and the recent rapid regional rrr warming we show that the early holocene warm period and mhh might be explained by relatively abrupt shifts in position of the southern westerlies superimposed on slower solar insolation changes a key finding of our synthesis is that the marine and terrestrial records in the ap appear to show markedly different behaviour during the mhh this might be partly explained by contrasts in the seasonal insolation forcing between these records circumpolar deep water cdw has been implicated in several of the prominent changes through the holocene but there are still differences in interpretation of the proxy record that make its influence difficult to assess further work is required to investigate contrasts between marine and terrestrial proxy records east west contrasts in palaeoclimate the history of cdw to retrieve a long onshore high resolution record of the holocene and determine the role of sea ice in driving or modulating palaeoclimate change along with further efforts to study the proxy record of the rrr and the mwp

holocene climatic changes in greenland different deuterium excess signals at greenland ice core project grip and northgrip 1 water stable isotope measurements d and 18o have been conducted on the holocene part of two deep greenland ice cores greenland ice core project grip and northgrip located 320 km apart these combined measurements provide the first two continuous greenland holocene deuterium excess profiles d d 8 18o a parameter strongly influenced by changes in moisture sources we discuss here temporal and regional fluctuations of the deuterium excess within central to north greenland with a mean temporal resolution of 4 years although grip and northgrip exhibit similar annual mean surface temperatures and 18o levels a significant offset of modern deuterium excess is observed between the two sites we attribute this offset to a different mix of modern moisture sources pointing to regional scale differences in moisture advection toward greenland the common long term deuterium excess holocene increasing trend is probably related to the increased relative contribution of low latitude moisture to greenland snowfall in response to the change in the earth obliquity as symmetrically observed in antarctica three abrupt declines punctuate the grip excess record 8 2 4 5 and 0 35 ka bp suggesting associated reorganizations of the northern high latitudes hydrological cycle the 8 2 ka bp event is characterized by 1 a rapid cooling followed by a progressive warming and 2 a deuterium excess cooling restricted to grip therefore totally different from rapid events during glacial times by contrast the northgrip deuterium excess record is more stable we propose that a slightly larger proportion of moisture supplied by local storm tracks to grip induces an isotopic compensation mechanism between simultaneous site and source temperature coolings resulting in a rather temperature insensitive 18o profile together with well marked deuterium excess amplitudes northgrip 18o seems less biased by isotopic processes and should provide a more reliable past temperature record

influence of summer sublimation on δd δ18o and δ17o in precipitation east antarctica and implications for climate reconstruction from ice cores

holocene sea surface temperature variability in the chilean fjord region here we provide three new holocene 11 0 cal ka bp alkenone derived sea surface temperature sst records from the southernmost chilean fjord region 50 53 s sst estimates may be biased towards summer temperature in this region as revealed by a large set of surface sediments the holocene records show consistently warmer than present day ssts except for the past 0 6 cal ka bp however they do not exhibit an early holocene temperature optimum as registered further north off chile and in antarctica this may have resulted from a combination of factors including decreased inflow of warmer open marine waters due to lower sea level stands enhanced advection of colder and fresher inner fjord waters and stronger westerly winds during the mid holocene pronounced short term variations of up to 2 5 c and a cooling centered at 5 cal ka bp which coincides with the first neoglacial glacier advance in the southern andes are recorded the latest holocene is characterized by two pronounced cold events centered at 0 6 and 0 25 cal ka bp i e during the little ice age these cold events have lower amplitudes in the offshore records suggesting an amplification of the sst signal in the inner fjords