drivers of holocene sea level change in the caribbean abstract we present a holocene relative sea level rsl database for the caribbean region 5 n to 25 n and 55 w to 90 w that consists of 499 sea level index points and 238 limiting dates the database was compiled from multiple sea level indicators mangrove peat microbial mats beach rock and acroporid and massive corals we subdivided the database into 20 regions to investigate the influence of tectonics and glacial isostatic adjustment on rsl we account for the local scale processes of sediment compaction and tidal range change using the stratigraphic position overburden thickness of index points and paleotidal modeling respectively we use a spatio temporal empirical hierarchical model to estimate rsl position and its rates of change in the caribbean over 1 ka time slices because of meltwater input the rates of rsl change were highest during the early holocene with a maximum of 10 9 0 6 m ka in suriname and guyana and minimum of 7 4 0 7 m ka in south florida from 12 to 8 ka following complete deglaciation of the laurentide ice sheet lis by 7 ka mid to late holocene rates slowed to

carbon isotopes in peat doc co2 and ch4 in a holocene peatland on dartmoor southwest england carbon gases with younger sup 14 c ages than those of the surrounding peat have been reported from continental boreal peatlands a fact which suggests that significant movement of co sub 2 ch sub 4 or doc dissolved organic carbon and export of c via subsurface processes are not accounted for in most estimates of contributions to the c cycle this paper tests the hypothesis that similar processes can occur in oceanic ombrotrophic mires where water and gas movement is theoretically minimal measurements of sup 14 c and delta sup 13 c in co sub 2 ch sub 4 and doc and of tritium are reported from depths to 250 cm at tor royal a raised mire in southwest england radiocarbon ages of gases are 1 460 to 500 yr younger than those of peat from the same depths and co sub 2 is consistently younger than ch sub 4 doc is 1 260 to 830 yr younger than the peat and significant amounts of tritium were found at all depths gas ages are mostly intermediate between the age of the peat and that of the doc which suggests that c is principally transported as doc however some gases are younger than their associated doc which implies that movement of dissolved gasesmore may also take place delta sup 13 c values in gases suggest that co sub 2 reduction is the major pathway for ch sub 4 production transport of c in deep peats is likely to be a significant component in the overall c budget of ombrotrophic oceanic peatlands and c export via discharge to ground or surface waters may be an important mechanism for gaseous c emissions less

constant holocene southern ocean 14c reservoir ages and ice shelf flow rates article i nfo southern ocean radiocarbon reservoir ages i e non zero radiocarbon ages in seawater are the highest in the world s surface ocean constraining these reservoir ages at present and in the past is important not only because unknown reservoir ages limit the interpretation of antarctic radiocarbon chronologies but also because reservoir ages provide information about ocean circulation as a recorder of past circulation and as an end member for major deep water masses in today s ocean in this study we use paired u th and 14 c ages of an unusual set of solitary coral samples trapped by fringing ice shelves in the ross sea to provide the first detailed study of holocene reservoir ages for the southern ocean our results indicate a relatively constant marine radiocarbon reservoir age of 1144 120 years for the past 6000 years these results are consistent with extrapolation of the relationship between 14 c and alkalinity seen elsewhere supporting the use of this empirical relationship in high latitudes the results also suggest constant deep ocean circulation and air sea exchange during the holocene and provide a good target for tuning ocean models of modern circulation combining the new ages for corals with their distance from the modern day ice shelf grounding line provides some of the first long term records of ice shelf velocities for any region and indicates constant flow of the mcmurdo ice shelf during the holocene at a rate similar to that observed today

holocene elephant seal distribution implies warmer than present climate in the ross sea we show that southern elephant seal mirounga leonina colonies existed proximate to the ross ice shelf during the holocene well south of their core sub antarctic breeding and molting grounds we propose that this was due to warming including a previously unrecognized period from 1 100 to 2 300 14c yr b p that decreased coastal sea ice and allowed penetration of warmer than present climate conditions into the ross embayment if as proposed in the literature the ice shelf survived this period it would have been exposed to environments substantially warmer than present

abandoned penguin rookeries as holocene paleoclimatic indicators in antarctica penguins are sensitive indicators of the antarctic climate and of the environmental parameters that limit their presence and distribution paleoenvironmental data obtained from the study of abandoned penguin rookeries pygoscelis adeliae along the victoria land coast in antarctica indicate 14c date of 11 13 ka for the oldest abandoned rookery and supply new information about the timing of glacier retreat in southern victoria land after the last glacial maximum the continuous presence of the adelie penguins is documented from 7 ka according to our data the limiting factors that control the presence of penguins along the coast of victoria land changed during the holocene whereas several colonies were occupied for very long periods other sites were used for more or less extended periods and then abandoned the greatest diffusion of rookeries occurred between 3 and 4 ka a period of particularly favorable environmental conditions that has never been repeated it was followed by a sudden decrease in the number of penguin rookeries shortly after 3 ka this event has been attributed to an increase of the sea ice extension and may have been correlated to a worldwide phase of climate change near the subboreal subatlantic boundary a minor phase of penguin reoccupation occurred locally in the eighth to fourteenth centuries a d because the presence and number of penguins reflect the state of health of the antarctic marine ecosystem it is important to evaluate the variations in their distribution in the past in the absence of human induced changes

past and future grounding line retreat of the west antarctic ice sheet the history of deglaciation of the west antarctic ice sheet wais gives clues about its future southward grounding line migration was dated past three locations in the ross sea embayment results indicate that most recession occurred during the middle to late holocene in the absence of substantial sea level or climate forcing current grounding line retreat may reflect ongoing ice recession that has been under way since the early holocene if so the wais could continue to retreat even in the absence of further external forcing

holocene depositional environments and surface level changes at lake fryxell antarctica we report on holocene surface level variations of lake fryxell antarctica as determined from multiproxy analyses of 18 sediment cores during this time accumulating sediments were predominantly aeolian sand with algal and carbonate laminae based on stratigraphy mineralogy and diatom assemblages we suggest some carbonate laminae were deposited when lake level dropped leading to concentration and subsequent precipitation of salts although lake level appears to have remained relatively stable throughout the holocene minor 4 5 m below present lowstands occurred at approximately 6400 4700 3800 and 1600 cal yr bp the stability of lake fryxell during the holocene contrasts with large scale variability at other dry valleys lakes eg lake vanda and with suggestions from chemical diffusion models of a near desiccation at 1200 cal yr bp the reason for the comparative stability of lake fryxell is uncertain but may be the result of basin morphology and the number aspect and proximity of meltwater sources

insights into the holocene environmental setting of terra nova bay region ross sea antarctica from oxygen isotope geochemistry of adelie penguin eggshells an oxygen isotope record of adelie penguin pygoscelis adeliae eggshells from terra nova bay victoria land antarctica has been reconstructed in order to provide insights into the palaeoenviroment of this region during the last 8000 years the 18o values measured in eggshell carbonate show a great variability over the course of the studied period with maximum values consistently around 27 5 adopting a metabolic enrichment relative to water source of 28 5 eggshell 18o values can be interpreted in terms of marine water uptake by the penguins the spread in 18o of eggshell carbonate at any given time toward more negative values reflects the existence of a low 18o water end member most plausibly snow or snowmelt samples younger than 2000 years are characterized by a general lack of very negative 18o values as also attested by other proxies this shift toward more positive isotopic values is likely to be related both to a decreasing contribution of snow or meltwater in the seawaters and con

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

characterization and quantification of inorganic constituents of tropical peats and organic rich deposits from tasek bera peninsular malaysia implications for coals abstract since the carboniferous tropical latitudes have been the site of formation of many economic coal deposits most of which have a restricted range of mineralogical composition as a result of their depositional environment climatic conditions and diagenesis mineralogical and microscopic investigations of tropical peats from tasek bera peninsular malaysia were performed in order to better understand some of these factors controlling the nature distribution and association of inorganic matter in peat forming environments distribution and nature of the inorganic fraction of peat deposits give insight into the weathering conditions and detrital input into the mire system because the inorganic composition of peat deposits is determined by plant communities height of water table and climate the results of the quantitative and qualitative analysis can be used to reconstruct palaeoclimatic conditions tasek bera is a peat accumulating basin in humid tropical malaysia with organic deposits of low to high ash yield and thus representative of many ancient peat forming environments clay minerals dominate the mineralogical composition of the peat and organic rich sediments while quartz and clays dominate the underlying siliciclastic deposits kaolinite is the most abundant clay mineral in the organic deposits with minor amounts of illite and vermiculite particle size analyses indicate that 50 of the inorganic detrital fraction is 75 of the ash constituents as a consequence the vegetational communities make an important contribution to the inorganic and overall ash composition of peats and coals the ash content of the often inundated peat consists on average of 10 opaline silica from diatoms and sponge spicules while the ash of the top deposits may have up to 50 biogenic silica hence al and si hydroxides and the opaline silica from diatoms and sponges represent a large repository of al and si which may form the basis of mineral transformation neoformation and alteration processes during coalification of the peat deposits as a result most coal deposits from paleotropical environments are anticipated to have little to no biogenic inorganic material but high amounts of secondary clays such as kaolinite detrital kaolinite resilisified kaolinite or desilisified gibbsite or illite and various amounts of detrital and authigenetic quartz

modern and holocene aeolian dust variability from talos dome northern victoria land to the interior of the antarctic ice sheet abstract high elevation sites from the inner part of the east antarctic plateau sample windborne dust representative of large portions of the southern hemisphere and are sensitive to long range atmospheric transport conditions to polar areas on the periphery of the ice sheet conversely the aeolian transport of particles from high elevation ice free areas can locally represent a relatively important additional input of dust to the atmosphere and the interplay of atmospheric dynamics dust transport and deposition is strictly related to the regional atmospheric circulation behaviour both at present day and in the past the understanding of the spatial extent where local sources can influence the mineral dust budget on the ice sheet is fundamental for understanding the atmospheric dust cycle in antarctica and for the interpretation of the dust history in marginal glaciological settings in this work we investigate the spatial variability of dust flux and provenance during modern pre industrial and holocene times along a transect connecting talos dome to the internal sites of the antarctic plateau and we extend the existing documentation of the isotopic sr nd fingerprint of dust sized sediments from victoria land source areas dust flux grain size and isotopic composition show a marked variability between talos dome mid point d4 and dome c vostok suggesting that local sources play an important role on the periphery of the ice sheet microscope observations reveal that background mineral aerosol in the taldice core is composed by a mixture of dust volcanic particles and micrometric sized fragments of diatoms these latter representing a small but pervasive component of antarctic sediments a set of samples from victoria land mostly consisting of regolith and glacial deposits from high elevation areas was collected specially for this work and the isotopic composition of the dust sized fraction of samples was analyzed results reveal a close relationship with the parent lithologies but direct comparison between source samples and firn ice core dust is problematical because of the ubiquitous volcanic contribution to the environmental particulate input in the talos dome area the frequency of events potentially suitable for peripheral dust transport to talos dome appears relatively high for present day conditions according to back trajectories calculations and the related air flow pattern well defined from a seasonal and spatial perspective also as expected from palaeo data these events appear extremely uncommon for internal sites

diatom evidence for late holocene climatic events in granite harbor antarctica downcore diatom data from a deep basin in granite harbor antarctica provide new high resolution information concerning changes in oceanographic and depositional processes that have occurred during approximately the last 1250 years the influence of global scale climatic change during the time of the medieval warm period and possibly the little ice age is revealed by long term changes in floral assemblages as recorded by changes in the relative concentration of nitzschia cylindrus the diatom data suggest that granite harbor experienced less annual ice and pack ice cover during both these periods possibly because of higher temperatures during the medieval warm period and stronger offshore winds during the little ice age the sedimentary record reveals several distinct short lived events in which nearly monospecific blooms of corethron criophilum and chaetoceros spp occurred possibly the result of strong stabilization of the upper water column and were most likely a response to regional rather than global conditions although short lived these events may play a significant role in the delivery of organic carbon and biogenic silica to the seafloor

assessing the link between coastal morphology wave energy and sea ice throughout the holocene from antarctic raised beaches post glacial rebound has preserved beaches across many ice free parts of the antarctic coastline these beaches typically contain gravel to boulder sized deposits and are built by high magnitude waves five new ages from the western antarctic peninsula were added to a compilation of 282 published ages from antarctic beaches a reduced compilation based solely on those ages that date beach formation is used to assess variations in beach formation throughout the holocene around antarctica we suggest the clustering of beach ages centered at 0 8 and 2 4 ka in the antarctic peninsula 1 5 3 6 and 6 0 ka in the ross sea and a broad peak from 2 7 to 6 3 ka in east antarctica indicates periods of heightened wave exposure leading to increased beach formation measurements of clast roundness from raised beaches show more rounded material is coincident with periods of heightened beach formation providing an independent means of assessing wave climate a comparison of periods of increased beach formation with available sea ice proxies suggests beach formation is synchronous with reduced sea ice conditions and thus higher wave climate as the presence or absence of sea ice determines open water conditions the factors that control sea ice directly influence antarctic coastal evolution

post glacial regional climate variability along the east antarctic coastal margin evidence from shallow marine and coastal terrestrial records we review the post glacial climate variability along the east antarctic coastline using terrestrial and shallow marine geological records and compare these reconstructions with data from elsewhere nearly all east antarctic records show a near synchronous early holocene climate optimum 11 5 9 ka bp coinciding with the deglaciation of currently ice free regions and the optimum recorded in antarctic ice and marine sediment cores shallow marine and coastal terrestrial climate anomalies appear to be out of phase after the early holocene warm period and show complex regional patterns but an overall trend of cooling in the terrestrial records a mid to late holocene warm period is present in many east antarctic lake and shallow coastal marine records although there are some differences in the regional timing of this warm period it typically occurs somewhere between 4 7 and 1 ka bp which overlaps with a similar optimum found in antarctic peninsula terrestrial records the differences in the timing of these sometimes abrupt warm events in different records and regions points to a number of mechanisms that we have yet to identify nearly all records show a neoglacial cooling from 2 ka bp onwards there is no evidence along the east antarctic coastline for an equivalent to the northern hemisphere medieval warm period and there is only weak circumstantial evidence in a few places for a cool event crudely equivalent in time to the northern hemisphere s little ice age there is a need for well dated high resolution climate records in coastal east antarctica and particularly in terre adelie dronning maud land and enderby land to fully understand the regional climate anomalies the disparity between marine and terrestrial records and to determine the significance of the heterogeneous temperature trends being measured in the antarctic today 2010 elsevier b v

adelie penguin dietary remains reveal holocene environmental changes in the western ross sea antarctica carbon and nitrogen stable isotope analyses were performed on modern and holocene adelie penguin guano samples collected from ornithogenic soils along the scott coast southern victoria land antarctica from cape irizar to dunlop island and at cape bird ross island guano samples also were sieved and sorted under stereomicroscope in order to select penguin dietary remains such as fish bones and otoliths carbon and nitrogen stable isotope composition coupled with the taxonomic identification of fish otoliths from scott coast holocene samples indicated a mainly fish based diet for this area with pleuragramma antarcticum as the most eaten prey throughout the investigated period from 390 cal bp to ca 7300 cal bp the isotopic values of ross island samples from modern to 3850 cal bp showed a krill consumption increase in the samples younger than 2000 cal bp with the maximum in modern samples scott coast and ross island holocene samples showed 13c and 15n trends similar to those previously published from terra nova bay northern victoria land whereas modern samples from ross island have similar 15n composition but different 13c values this 13c divergence started at ca 2000 bp and follows the abandonment of the scott coast colonies the 13c trend observed in ross island and terra nova bay samples and the abandonment of the scott coast colonies could suggest the stability and the persistence of the previous oceanographic conditions i e polynya for the terra nova bay area and the establishment of new conditions for water circulation in the southern ross sea since 2000 bp when persistent sea ice sealed the scott coast

contributions and unrealized potential contributions of cosmogenic nuclide exposure dating to glacier chronology 1990 2010 abstract this paper reviews the application of cosmogenic nuclide exposure dating to glacier chronology exposure dating of glacial landforms has made an outsize impact on this field because the technique filled an obvious need that had already been recognized by glacial geologists by now hundreds of studies have used cosmogenic nuclide exposure dating to date glacial deposits and in fact it is rare to find a study of glacial geology or glacier chronology or any paleoclimate synthesis that makes use of such studies that does not involve exposure dating these developments have resulted in major contributions to glacier chronology and paleoclimate in particular i reconstructing antarctic ice sheet change ii establishing the chronology of late pleistocene and holocene glacier change in mountain regions where it was previously unknown iii establishing the broad chronological outlines of mountain glaciations prior to the last glacial maximum and iv gaining insight into subglacial erosional processes through the observation that many glaciated surfaces preserve cosmogenic nuclide inventories from long past ice free periods as well as the present one an important potential future contribution will be the application of the large data set of exposure dated glacier chronologies to better understand global and regional climate dynamics during lateglacial and holocene millennial scale climate changes however this contribution cannot be realized without significant progress in two areas i understanding and accounting for geologic processes that cause apparent exposure ages on glacial landforms to differ from the true age of the landform and ii minimizing systematic uncertainties in exposure ages that stem from cosmogenic nuclide production rate estimates and scaling schemes at present there exists an enormous data set of exposure ages on glacial deposits but these data cannot be used to their full potential in paleoclimate syntheses due to an inadequate understanding of geologic scatter and production rate uncertainties the intent of this paper is to highlight this situation and suggest some strategies for realizing this potential

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

glacier surge after ice shelf collapse the possibility that the west antarctic ice sheet will collapse as a consequence of ice shelf disintegration has been debated for many years this matter is of concern because such an event would imply a sudden increase in sea level evidence is presented here showing drastic dynamic perturbations on former tributary glaciers that fed sections of the larsen ice shelf on the antarctic peninsula before its collapse in 1995 satellite images and airborne surveys allowed unambiguous identification of active surging phases of boydell sjogren edgeworth bombardier and drygalski glaciers this discovery calls for a reconsideration of former hypotheses about the stabilizing role of ice shelves

recent atmospheric warming and retreat of ice shelves on the antarctic peninsula in 1978 mercer1 discussed the probable effects of climate warming on the antarctic ice sheet predicting that one sign of a warming trend in this region would be the retreat of ice shelves on the antarctic peninsula analyses of 50 year meteorological records have since revealed atmospheric warming on the antarctic peninsula2 3 and a number of ice shelves have retreated4 8 here we present time series of observations of the areal extent of nine ice shelves on the antarctic peninsula showing that five northerly ones have retreated dramatically in the past fifty years while those further south show no clear trend comparison with airtemperature data shows that the pattern and magnitude of ice shelf retreat is consistent with the existence of an abrupt thermal limit on iceshelf viability the isotherm associated with this limit having been driven south by the atmospheric warming ice shelves therefore appear to be sensitive indicators of climate change

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

dynamics of penguin population size and food availability at prydz bay east antarctica during the last millennium a solar control abstract the paleoecology of the adelie penguin pygoscelis adeliae is controlled by multiple factors in this study we analyzed two millennial scale ornithogenic sediment cores rnl and rl from the vestfold hills east antarctica using the al normalized phosphorus content of the bulk sediment and carbon nitrogen fractions in penguin remains we reconstructed relative changes in the penguin population size of each sub colony and relative krill abundance in the summer prydz bay polynya both records are correlated to solar irradiance at the centennial scale the penguin population recorded in core rnl decreased from 1120 860 yr bp reached a peak from 860 630 yr bp remained at a low level from 630 320 yr bp and then increased with large fluctuations during the past 400 years these changes are all in phase with the trend of solar irradiance at the decadal scale penguin population minima correspond to solar minima from 490 400 yr bp sporer minimum 290 220 yr bp maunder minimum and from 160 120 yr bp dalton minimum whereas population maxima correspond to solar maxima from 1030 980 yr bp 350 290 yr bp 210 160 yr bp 120 70 yr bp the population recorded in core rl exhibited the same changes as in rnl during the last 480 years the reconstructed krill abundance also corresponds to these trends when data are available this correspondence demonstrates a food chain mechanism that is related to solar activity and light availability at the ocean surface which influence the intensity of photosynthesis and phytoplankton productivity and thus the abundance of krill and apex predators such as penguins our findings highlight the fact that despite the various climatic impacts on penguin populations their effects on the base of the food chain are usually the direct drive