a multi proxy lacustrine record of holocene climate change on northeastern baffin island arctic canada reconstructions of past environmental changes are critical for understanding the natural variability of earth s climate system and for providing a context for present and future global change radiocarbon dated lake sediments from lake cf3 northeastern baffin island arctic canada are used to reconstruct past environmental conditions over the last 11 200 years numerous proxies including chironomid inferred july air temperatures diatom inferred lakewater ph and sediment organic matter reveal a pronounced holocene thermal maximum as much as 5 c warmer than historic summer temperatures from 10 000 to 8500 cal yr b p following rapid cooling 8500 cal yr b p lake cf3 proxies indicate cooling through the late holocene at many sites in northeastern canada the holocene thermal maximum occurred later than at lake cf3 this late onset of holocene warmth is generally attributed to the impacts of the decaying laurentide ice sheet on early holocene temperatures in northeastern canada however the lacustrine proxies in lake cf3 apparently responded to insolation driven warmth despite the proximity of lake cf3 to the laurentide ice sheet and its meltwater the magnitude and timing of the holocene thermal maximum at lake cf3 indicate that temperatures and environmental conditions at this site are highly sensitive to changes in radiative forcing

eemian interglacial reconstructed from a greenland folded ice core efforts to extract a greenland ice core with a complete record of the eemian interglacial 130 000 to 115 000 years ago have until now been unsuccessful the response of the greenland ice sheet to the warmer than present climate of the eemian has thus remained unclear here we present the new north greenland eemian ice drilling neem ice core and show only a modest ice sheet response to the strong warming in the early eemian we reconstructed the eemian record from folded ice using globally homogeneous parameters known from dated greenland and antarctic ice core records on the basis of water stable isotopes neem surface temperatures after the onset of the eemian 126 000 years ago peaked at 8 4 degrees celsius above the mean of the past millennium followed by a gradual cooling that was probably driven by the decreasing summer insolation between 128 000 and 122 000 years ago the thickness of the northwest greenland ice sheet decreased by 400 250 metres reaching surface elevations 122 000 years ago of 130 300 metres lower than the present extensive surface melt occurred at the neem site during the eemian a phenomenon witnessed when melt layers formed again at neem during the exceptional heat of july 2012 with additional warming surface melt might become more common in the future

holocene thinning of the greenland ice sheet the nature of the response of the greenland ice sheet gis to climate change is a fundamental question in climate science but the details remain unclear during the holocene climate optimum 6 000 to 9 000 years ago for example many locations in the northern hemisphere showed unusual warmth yet changes in greenland appeared inconsistent vinther et al now standardize the previously disparate seeming ice core records of climate history on the gis during the holocene and find consistent evidence for a stronger climate optimum than was previously recognized together with elevation reduction and marginal ice sheet thinning the response of the greenland ice sheet gis to changes in climate remains uncertain during the holocene climatic optimum an unusually warm period from about 9 000 to 6 000 years ago changes in greenland appear inconsistent with the rest of the northern hemisphere here the greenland holocene temperature history and the evolution of gis surface elevation are extracted from four gis locations the results may resolve this disparity on entering an era of global warming the stability of the greenland ice sheet gis is an important concern1 especially in the light of new evidence of rapidly changing flow and melt conditions at the gis margins2 studying the response of the gis to past climatic change may help to advance our understanding of gis dynamics the previous interpretation of evidence from stable isotopes 18o in water from gis ice cores was that holocene climate variability on the gis differed spatially3 and that a consistent holocene climate optimum the unusually warm period from about 9 000 to 6 000 years ago found in many northern latitude palaeoclimate records4 did not exist here we extract both the greenland holocene temperature history and the evolution of gis surface elevation at four gis locations we achieve this by comparing 18o from gis ice cores3 5 with 18o from ice cores from small marginal icecaps contrary to the earlier interpretation of 18o evidence from ice cores3 6 our new temperature history reveals a pronounced holocene climatic optimum in greenland coinciding with maximum thinning near the gis margins our 18o based results are corroborated by the air content of ice cores a proxy for surface elevation7 state of the art ice sheet models are generally found to be underestimating the extent and changes in gis elevation and area our findings may help to improve the ability of models to reproduce the gis response to holocene climate

sea level rise due to polar ice sheet mass loss during past warm periods background although thermal expansion of seawater and melting of mountain glaciers have dominated global mean sea level gmsl rise over the last century mass loss from the greenland and antarctic ice sheets is expected to exceed other contributions to gmsl rise under future warming to better constrain polarice sheetresponse to warmer temperatures we draw on evidence from in terglacial periods in the geologic record that ex perienced warmer polar temperatures and higher gmsls than present coastal records of sea level from these previous warm periods dem onstrate geographic variability because of the influence of several geophysical processes that operate across a range of magnitudes and time scales inferring gmsl and ice volume changes from these reconstructions is nontrivial and generally requires the use of geophysical models advances interdisciplinary studies of geo logic archives have ushered in a new era of deciphering magnitudes rates and sources of sea level rise advances in our understanding of polar ice sheet response to warmer climates have been made through an increase in the number and geographic distribution of sea level reconstructions better ice sheet constraints and the recognition that several geophysical processes cause spatially complex patterns in sea level in particular accounting for glacial isostatic processes helps to decipher spatial variability in coastal sea level records and has reconciled a number of site specific sea level reconstructions for warm periods that have oc curred within the past several hundred thou sand years this enables us to infer that during recent interglacial periods small increases in

quaternary glacial and marine environmental history of northwest greenland a review and reappraisal new information on middle and late quaternary deposits of the thule region northwest greenland necessitates the revision of the chronostratigraphy of the area and allows fuller understanding of the marine environmental changes in ba n bay the stratigraphic record is interpreted as the product of three marine events saunders qarmat and nuna in decreasing age during which marine sedimentation occurred on coastal areas now land and three or four glacial events of decreasing age and ice cover agpat narsaarsuk and kap abernathy wolstenholme fjord to which the marine events were glacio isostatically related subarctic atlantic water reached this northern part of ba n bay during all three marine events but the warmest conditions warmer than the present occurred in the qarmat event correlated with the deep sea oxygen isotope stage 5e the question of late stage 5 events is considered the nuna event dates to latest stage 2 and the holocene whilst the saunders event is of uncertain age but at least stage 6 a number of glacial events with advances confined to the fjords are dated to stage 2 wolstenholme fjord and late stage 6 narsaarsuk and an intermediate advance kap abernathy is undated in the range of stage 2 5 extension of glaciation to the shelf edge is dated to stage 6 agpat event 1999 elsevier science ltd all rights reserved

interglacial and holocene temperature reconstructions based on midge remains in sediments of two lakes from baffin island nunavut arctic canada abstract midge remains insecta diptera chironomidae and chaoboridae from two upland lake basins on the cumberland peninsula of baffin island were analyzed and the results used in a transfer function to reconstruct paleotemperatures this upland region remained ice free throughout the last glacial cycle and the two lake basins retain sediments deposited during the previous interglacial period as well as during the holocene period but they did not accumulate sediment during most of the glacial period midge remains are abundant and well preserved at both sites midge inferred summer surface water temperatures and mean july air temperatures were estimated using an inference model built on modern samples spanning a geographic range extending from devon island canada to maine usa data from twenty nine new surface samples from baffin island were added to an existing inference model the new weighted averaging wa model for summer surface water temperature yields r 2 jack 0 88 and rmsep 2 22 c for summer water temperatures and r 2 jack 0 88 and rmsep 1 53 c for mean july air temperatures reconstructions at both sites indicate that summer temperatures during the last interglacial were higher than at any time in the holocene and 5 to 10 c higher than present peak holocene temperatures occurred in the first half of the period and have decreased since about the mid holocene

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

warm climate isotopic simulations what do we learn about interglacial signals in greenland ice cores measurements of last interglacial stable water isotopes in ice cores show that central greenland 18o increased by at least 3 compared to present day attempting to quantify the greenland interglacial temperature change from these ice core measurements rests on our ability to interpret the stable water isotope content of greenland snow current orbitally driven interglacial simulations do not show 18o or temperature rises of the correct magnitude leading to difficulty in using only these experiments to inform our understanding of higher interglacial 18o here analysis of greenhouse gas warmed simulations from two isotope enabled general circulation models in conjunction with a set of last interglacial sea surface observations indicates a possible explanation for the interglacial 18o rise a reduction in the winter time sea ice concentration around the northern half of greenland together with an increase in sea surface temperatures over the same region is found to be sufficient to drive a 3 interglacial enrichment in central greenland snow warm climate 18o and d in precipitation falling on greenland are shown to be strongly influenced by local sea surface condition changes local sea surface warming and a shrunken sea ice extent increase the proportion of water vapour from local isotopically enriched sources compared to that from distal isotopically depleted sources precipitation intermittency changes under warmer conditions leads to geographical variability in the 18o against temperature gradients across greenland little sea surface warming around the northern areas of greenland leads to low 18o against temperature gradients 0 1 0 3 per c whilst large sea surface warmings in these regions leads to higher gradients 0 3 0 7 per c these gradients imply a wide possible range of present day to interglacial temperature increases 4 to 10 c thus we find that uncertainty about local interglacial sea surface conditions rather than precipitation intermittency changes may lead to the largest uncertainties in interpreting temperature from greenland ice cores we find that interglacial sea surface change observational records are currently insufficient to enable discrimination between these different 18o against temperature gradients in conclusion further information on interglacial sea surface temperatures and sea ice changes around northern greenland should indicate whether 5 c during the last interglacial is sufficient to drive the observed ice core 18o increase or whether a larger temperature increases or ice sheet changes are also required to explain the ice core observations

revised estimates of greenland ice sheet thinning histories based on ice core records abstract ice core records were recently used to infer elevation changes of the greenland ice sheet throughout the holocene the inferred elevation changes show a significantly greater elevation reduction than those output from numerical models bringing into question the accuracy of the model based reconstructions and to some extent the estimated elevation histories a key component of the ice core analysis involved removing the influence of vertical surface motion on the 18 o signal measured from the agassiz and renland ice caps we re visit the original analysis with the intent to determine if the use of more accurate land uplift curves can account for some of the above noted discrepancy to improve on the original analysis we apply a geophysical model of glacial isostatic adjustment calibrated to sea level records from the queen elizabeth islands and greenland to calculate the influence of land height changes on the 18 o signal from the two ice cores this procedure is complicated by the fact that 18 o contained in agassiz ice is influenced by land height changes distant from the ice cap and so selecting a single location at which to compute the land height signal is not possible uncertainty in this selection is further complicated by the possible influence of innuitian ice during the early holocene 12 8 ka bp our results indicate that a more accurate treatment of the uplift correction leads to elevation histories that are in general shifted down relative to the original curves at grip ngrip dye 3 and camp century in addition compared to the original analysis the 1 uncertainty is considerably larger at grip and ngrip these changes reduce the data model discrepancy reported by vinther et al 2009 at grip ngrip dye 3 and camp century a more accurate treatment of isostasy and surface loading also acts to improve the data model fits such that the residuals at all four sites for the period 8 ka bp to present are significantly reduced compared to the original analysis prior to 8 ka bp the possible influence of innuitian ice on the inferred elevation histories prevents a meaningful comparison

age of the fjord stade moraines in the disko bugt region western greenland and the 9 3 and 8 2 ka cooling events abstract retreat of the western greenland ice sheet during the early holocene was interrupted by deposition of the fjord stade moraine system the fjord stade moraine system spans several hundred kilometers of western greenland s ice free fringe and represents an important period in the western greenland ice sheet s deglaciation history but the origin and timing of moraine deposition remain uncertain here we combine new and previously published 10 be and 14 c ages from disko bugt western greenland to constrain the timing of fjord stade moraine deposition at two locations 60 km apart at jakobshavn isfjord the northern of two study sites we show that jakobshavn isbrae advanced to deposit moraines ca 9 2 and 8 2 8 0 ka in southeastern disko bugt the ice sheet deposited moraines ca 9 4 9 0 and 8 5 8 1 ka our ice margin chronology indicates that the greenland ice sheet in two distant regions responded in unison to early holocene abrupt cooling 9 3 and 8 2 ka as recorded in central greenland ice cores although the timing of fjord stade moraine deposition was synchronous in jakobshavn isfjord and southeastern disko bugt within uncertainties we suggest that jakobshavn isbrae advanced while the southeastern disko bugt ice margin experienced stillstands during the 9 3 and 8 2 ka events based on regional geomorphology and the distribution of 10 be ages at each location the contrasting style of ice margin response was likely regulated by site specific ice flow characteristics jakobshavn isbrae s high ice flux results in an amplified ice margin response to a climate perturbation both warming and cooling whereas the comparatively low flux sector of the ice sheet in southeastern disko bugt experiences a more subdued response to climate perturbations our chronology indicates that the western greenland ice sheet advanced and retreated in concert with early holocene temperature variations and the 9 3 and 8 2 ka events although brief were of sufficient duration to elicit a significant response of the western greenland ice sheet

pronounced summer warming in northwest greenland during the holocene and last interglacial projections of future rates of mass loss from the greenland ice sheet are highly uncertain because its sensitivity to warming is unclear geologic reconstructions of quaternary interglacials can illustrate how the ice sheet responded during past warm periods providing insights into ice sheet behavior and important tests for data model comparisons however paleoclimate records from greenland are limited early holocene peak warmth has been quantified at only a few sites and terrestrial sedimentary records of prior interglacials are exceptionally rare due to glacial erosion during the last glacial period here we discuss findings from a lacustrine archive that records both the holocene and the last interglacial lig from greenland allowing for direct comparison between two interglacials sedimentary chironomid assemblages indicate peak july temperatures 4 0 to 7 0 c warmer than modern during the early holocene maximum in summer insolation chaoborus and chironomids in lig sediments indicate july temperatures at least 5 5 to 8 5 c warmer than modern these estimates indicate pronounced warming in northwest greenland during both interglacials this helps explain dramatic ice sheet thinning at camp century in northwest greenland during the early holocene and for the lig aligns with controversial estimates of eemian warming from ice core data retrieved in northern greenland converging geologic evidence for strong lig warming is challenging to reconcile with inferred greenland ice sheet extent during the lig and the two appear incompatible in many models of ice sheet evolution an increase in lig snowfall could help resolve this problem pointing to the need for hydroclimate reconstructions from the region

last interglacial arctic warmth confirms polar amplification of climate change the warmest millennia of at least the past 250 000 years occurred during the last interglaciation when global ice volumes were similar to or smaller than today and systematic variations in earth s orbital parameters aligned to produce a strong positive summer insolation anomaly throughout the northern hemisphere the average insolation during the key summer months m j j was ca 11 above present across the northern hemisphere between 130 000 and 127 000 years ago with a slightly greater anomaly 13 over the arctic greater summer insolation early penultimate deglaciation and intensification of the north atlantic drift combined to reduce arctic ocean sea ice allow expansion of boreal forest to the arctic ocean shore across vast regions reduce permafrost and melt almost all glaciers in the northern hemisphere insolation amplified by key boundary condition feedbacks collectively produced last interglacial summer temperature anomalies 4 5 c above present over most arctic lands significantly above the average northern hemisphere anomaly the last interglaciation demonstrates the strength of positive feedbacks on arctic warming and provides a potentially conservative analogue for anticipated future greenhouse warming

vegetation and climate of the last interglacial on baffin island arctic canada abstract sediment cores recovered from three mid arctic lakes on cumberland peninsula eastern baffin island arctic canada contained two units of unconformably superimposed organic sediment gyttja the upper of which represented sedimentation during the holocene radiocarbon ages on aquatic macrofossils from the lower gyttja suggested it to be 50 ka bp while luminescence ages from two cores constrained the age of this sediment to 90 and betula and alnus pollen grains than did overlying holocene sediments numerical comparisons of fossil pollen assemblages to a data set of 400 modern high latitude lake sediment samples revealed that the last interglacial vegetation of east central baffin island was low arctic in character comparable to present day southwest greenland from applications of both correspondence analysis regression and best modern analogue methodologies we infer july air temperatures of the last interglacial to have been 4 to 5 c warmer than present on eastern baffin island which was warmer than any interval within the holocene on these grounds we ascribe the lower lacustrine unit in these lakes to the climatic optimum of the last interglacial ca 117 to 130 ka bp marine isotopic stage 5e

understanding the climatic signal in the water stable isotope records from the neem shallow firn ice cores in northwest greenland 1 samples of precipitation and atmospheric water vapor were collected together with shallow firn ice cores as part of the new deep drilling project in northwest greenland the neem project these samples were analyzed for their isotope composition to understand the processes affecting the climatic signal archived in the water stable isotope records from the neem deep ice core the dominant moisture source for the snow deposited at the neem site may be originating as far south as 35 n from the western part of the atlantic ocean the surface atmospheric water vapor appears in isotopic equilibrium with the snow surface indicating a large water exchange between the atmosphere and snowpack the interannual variability of neem shallow firn ice cores stable isotope data covering the last 40 years shows an unexpectedly weak nao signal regional to global atmospheric models simulate a dominant summer precipitation in the neem area suggesting that the intermittency of modern winter precipitation is responsible for the lack of a strong nao imprint the interannual variability of neem isotope data however shows a strong correlation with interannual variations of baffin bay sea ice cover a relationship consistent with air mass trajectories neem deep ice core isotopic records may therefore provide detailed information on past baffin bay sea ice extent neem stable water isotope content increasing trend points to a local warming trend of 3 0 c over the last 40 years

quantitative interpretation of fossil pollen spectra dissimilarity coefficients and the method of modern analogs abstract dissimilarity coefficients measure the difference between multivariate samples and provide a quantitative aid to the identification of modern analogs for fossil pollen samples how eight coefficients responded to differences among modern pollen samples from eastern north america was tested these coefficients represent three different classes 1 unweighted coefficients that are most strongly influenced by large valued pollen types 2 equal weight coefficients that weight all pollen types equally but can be too sensitive to variations among rare types and 3 signal0to noise coefficients that are intermediate in their weighting of pollen types the studies with modern pollen allowed definition of critical values for each coefficient which when not exceeded indicate that two pollen samples originate from the same vegetation region dissimilarity coefficients were used to compare modern and fossil pollen samples and modern samples so similar to fossil samples were found that most of three late quaternary pollen diagrams could be reconstructed by substituting modern samples for fossil samples when the coefficients indicated that the fossil spectra had no modern analogs then the reconstructed diagrams did not match all aspects of the originals no modern analogs existed for samples from before 9300 yr b p at kirchner marsh minnesota and from before 11 000 yr b p at wintergreen lake michigan but modern analogs existed for almost all holocene samples from these two sites and brandreth bog new york

temperature trends during the present and last interglacial periods a multi model data comparison though primarily driven by insolation changes associated with well known variations in earth s astronomical parameters the response of the climate system during interglacials includes a diversity of feedbacks involving the atmosphere ocean sea ice vegetation and land ice a thorough multi model data comparison is essential to assess the ability of climate models to resolve interglacial temperature trends and to help in understanding the recorded climatic signal and the underlying climate dynamics we present the first multi model data comparison of transient millennial scale temperature changes through two intervals of the present interglacial pig 8 1 2 ka and the last interglacial lig 123 116 2 ka periods we include temperature trends simulated by 9 different climate models alkenone based temperature reconstructions from 117 globally distributed locations about 45 of them within the lig and 12 ice core based temperature trends from greenland and antarctica 50 of them within the lig the definitions of these specific interglacial intervals enable a consistent inter comparison of the two intervals because both are characterised by minor changes in atmospheric greenhouse gas concentrations and more importantly by insolation trends that show clear similarities our analysis shows that in general the reconstructed pig and lig northern hemisphere mid to high latitude cooling compares well with multi model mean temperature trends for the warmest months and that these cooling trends reflect a linear response to the warmest month insolation decrease over the interglacial intervals the most notable exception is the strong lig cooling trend reconstructed from greenland ice cores that is not simulated by any of the models a striking model data mismatch is found for both the pig and the lig over large parts of the mid to high latitudes of the southern hemisphere where the data depicts negative temperature trends that are not in agreement with near zero trends in the simulations in this area the positive local summer insolation trend is counteracted in climate models by an enhancement of the southern ocean summer sea ice cover and or an increase in southern ocean upwelling if the general picture emerging from reconstructions is realistic then the model data mismatch in mid and high southern hemisphere latitudes implies that none of the models is able to resolve the correct balance of these feedbacks or alternatively that interglacial southern hemisphere temperature trends are driven by mechanisms which are not included in the transient simulations such as changes in the antarctic ice sheet or meltwater induced changes in the overturning circulation

numerical simulations of the foehn in the rhine valley on 24 october 1999 map iop 10 abstract this paper presents numerical simulations of the map iop 10 foehn case 24 october 1999 for the lower alpine rhine valley which was one of the two target areas selected for foehn observations the simulations have been performed with a modified version of the fifth generation pennsylvania state university ncar mesoscale model mm5 most importantly the horizontal diffusion of temperature and the mixing ratios of water vapor and cloud water is computed truly horizontally rather than along the model surfaces as is the case in the original mm5 in the rhine valley the foehn case under consideration was characterized by a complex and rapidly changing flow field in the early morning the foehn was restricted to the upper parts of the valley while a cold air pool was present in the lower parts and around the exit toward lake constance during the following hours the cold air pool was gradually eroded and the foehn reached lake constance around noon only 3 h later a shallow cold front passing f

multiple generations of interglacial lake sediment preserved beneath the laurentide ice sheet it is generally assumed that regions glaciated by continental ice sheets offer little promise for long paleoenvironmental records due to erosional processes associated with glaciation we show that beneath portions of the northeastern laurentide ice sheet characterized by cold based glaciation sediment sequences representing multiple interglaciations have been pre served within extant lake basins radiocarbon and optically stimulated luminescence dating confi rm the antiquity of the sediments thereby extending the terrestrial paleoenvironmental record of the canadian arctic by hundreds of thousands of years the lake sediment record presented here corroborates numerous recent cosmogenic exposure dating studies indicating complex patterns of erosion beneath polar ice sheets it also demonstrates that the presence of intact interglacial sediments does not demand unglaciated refugia similarly ancient sedi ments may be preserved in many regions formerly covered by pleistocene ice sheets

a model of greenland ice sheet deglaciation constrained by observations of relative sea level and ice extent an ice sheet model was constrained to reconstruct the evolution of the greenland ice sheet gris from the last glacial maximum lgm to present to improve our understanding of its response to climate change the study involved applying a glaciological model in series with a glacial isostatic adjustment and relative sea level rsl model the model reconstruction builds upon the work of simpson et al 2009 through four main extensions 1 a larger constraint database consisting of rsl and ice extent data model improvements to the 2 climate and 3 sea level forcing components 4 accounting for uncertainties in non greenland ice the research was conducted primarily to address data model misfits and to quantify inherent model uncertainties with the earth structure and non greenland ice our new model termed huy3 fits the majority of observations and is characterised by a number of defining features during the lgm the ice sheet had an excess of 4 7 m ice equivalent sea level iesl which reached a maximum volume of 5 1 m iesl at 16 5 cal ka bp modelled retreat of ice from the continental shelf progressed at different rates and timings in different sectors southwest and southeast greenland began to retreat from the continental shelf by 16 to 14 cal ka bp thus responding in part to the bolling allerod warm event c 14 5 cal ka bp subsequently ice at the southern tip of greenland readvanced during the younger dryas cold event in northern greenland the ice retreated rapidly from the continental shelf upon the climatic recovery out of the younger dryas to present day conditions upon entering the holocene 11 7 cal ka bp the ice sheet soon became land based during the holocene thermal maximum htm 9 5 cal ka bp air temperatures across greenland were marginally higher than those at present and the gris margin retreated inland of its present day southwest position by 40 60 km at 4 cal ka bp which produced a deficit volume of 0 16 m iesl relative to present in response to the htm warmth our optimal model reconstruction lost mass at a maximum centennial rate of c 103 4 gt yr our results suggest that remaining data model discrepancies are affiliated with missing physics and sub grid processes of the glaciological model uncertainties in the climate forcing lateral earth structure and non greenland ice particularly the north american component finally applying the huy3 greenland reconstruction with our optimal earth model we generate present day uplift rates across greenland due to past changes in the ocean and ice loads with explicit error bars due to uncertainties in the earth structure present day uplift rates due to past changes are spatially variable and range from 3 5 to 7 mm a including earth model uncertainty

calibrating a glaciological model of the greenland ice sheet from the last glacial maximum to present day using field observations of relative sea level and ice extent we constrain a three dimensional thermomechanical model of greenland ice sheet gris evolution from the last glacial maximum lgm 21 ka bp to the present day using primarily observations of relative sea level rsl as well as field data on past ice extent our new model huy2 fits a majority of the observations and is characterised by a number of key features i the ice sheet had an excess volume relative to present of 4 1 m ice equivalent sea level at the lgm which increased to reach a maximum value of 4 6 m at 16 5 ka bp ii retreat from the continental shelf was not continuous around the entire margin as there was a younger dryas readvance in some areas the final episode of marine retreat was rapid and relatively late c 12 ka bp leaving the ice sheet land based by 10 ka bp iii in response to the holocene thermal maximum htm the ice margin retreated behind its present day position by up to 80 km in the southwest 20 km in the south and 80 km in a small area of the northeast as a result of this retreat the modelled ice sheet reaches a minimum extent between 5 and 4 ka bp which corresponds to a deficit volume relative to present of 0 17 m ice equivalent sea level our results suggest that remaining discrepancies between the model and the observations are likely associated with non greenland ice load differences between modelled and observed present day ice elevation around the margin lateral variations in earth structure and or the pattern of ice margin retreat

3d reconstruction of fabric and metamorphic domains in a slice of continental crust involved in the alpine subduction system the example of mt mucrone sesia lanzo zone western alps geological mapping multiscale structural analysis and estimations of the degree of fabric evolution and of reaction progress allow the construction of a 3d quantitative model of structural and metamorphic gradients in a portion of continental crust deeply involved in the alpine subduction system and mainly structured under eclogite facies conditions before the continental collision the investigated and modelled rocks outcrop in the surroundings of mt mucrone in the central sesia lanzo zone the geomodeller software allowed a quantitative 3d estimation of domains characterized by homogeneous fabric evolution and metamorphic reaction progress dfe and drp respectively for two of the seven structural and metamorphic imprints detected in this area the d2 eclogitic and d5 greenschist stages which are the most pervasive at km scale such a 3d modelling clarifies mutual relationships between fabric and metamorphic gradients and indicates that i dfe and drp are closely related regardless of the rock type ii the syn deformational thermal regime can influence the degree of metamorphic transformation if dfe remains below the 60 threshold iii the phase transitions can not be properly implemented in quantitative geodynamic modelling without considering the heterogeneity of reaction progress and fabric evolution

temporal and spatial structure of multi millennial temperature changes at high latitudes during the last interglacial the last interglacial lig 129e116 thousand of years bp ka represents a test bed for climate model feedbacks in warmer than present high latitude regions however mainly because aligning different palaeoclimatic archives and from different parts of the world is not trivial a spatio temporal picture of lig temperature changes is difficult to obtain here we have selected 47 polar ice core and sub polar marine sediment records and developed a strategy to align them onto the recent aicc2012 ice core chronology we provide the first compilation of high latitude temperature changes across the lig associated with a coherent temporal framework built between ice core and marine sediment records our new data synthesis highlights non synchronous maximum temperature changes between the two hemispheres with the southern ocean and antarctica records showing an early warming compared to north atlantic records we also observe warmer than present day conditions that occur for a longer time period in southern high latitudes than in northern high latitudes finally the amplitude of temperature changes at high northern latitudes is larger compared to high southern latitude temperature changes recorded at the onset and the demise of the lig we have also compiled four data based time slices with temperature anomalies compared to present day conditions at 115 ka 120 ka 125 ka and 130 ka and quantitatively estimated temperature uncertainties that include relative dating errors this provides an improved benchmark for performing more robust model data comparison the surface temperature simulated by two general circulation models ccsm3 and hadcm3 for 130 ka and 125 ka is compared to the corresponding time slice data synthesis this comparison shows that the models predict warmer than present conditions earlier than documented in the north atlantic while neither model is able to produce the reconstructed early southern ocean and antarctic warming our results highlight the importance of producing a sequence of time slices rather than one single time slice averaging the lig climate conditions

sr nd pb isotope evidence for ice sheet presence on southern greenland during the last interglacial to ascertain the response of the southern greenland ice sheet gis to a boreal summer climate warmer than at present we explored whether southern greenland was deglaciated during the last interglacial lig using the sr nd pb isotope ratios of silt sized sediment discharged from southern greenland our isotope data indicate that no single southern greenland geologic terrane was completely deglaciated during the lig similar to the holocene differences in sediment sources during the lig relative to the early holocene denote however greater southern gis retreat during the lig these results allow the evaluation of a suite of gis models and are consistent with a gis contribution of 1 6 to 2 2 meters to the 4 meter lig sea level highstand requiring a significant sea level contribution from the antarctic ice sheet