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The temperature of the earth is one of the most important climate parameters. Proxy records of past climate changes, in particular temperature, are a fundamental tool for exploring internal climate processes and natural climate forcings. Despite the excellent information provided by ice core records in Antarctica, the temperature variability of the past 2000 years is difficult to evaluate from the low accumulation sites in the Antarctic continent interior. Here we present the results from the Aurora Basin North (ABN) ice core (71° S, 111° E, 2690 m a.s.l.) in the lower part of the East Antarctic plateau where accumulation is substantially higher than other ice core drilling sites on the plateau, and provide unprecedented insight in East Antarctic past temperature variability. We reconstructed the temperature of the last 2000 years using two independent methods: the widely used water stable isotopes (δ18O), and by inverse modelling of borehole temperature and past temperature gradients estimated from the inert gas stable isotopes (δ40Ar and δ15N). This second reconstruction is based on three independent measurement types: borehole temperature, firn thickness, and firn temperature gradient. The δ18O temperature reconstruction supports stable temperature conditions within 1 °C over the past 2000 years, in agreement with other ice core δ18O records in the region. However, the gas and borehole temperature reconstruction suggest that surface conditions 2 °C cooler than average prevailed in the 1000–1400 CE period, and support a 20th century warming of 1 °C. These changes are remarkably consistent with reconstructed Southern Annular Mode (SAM) variability, as it shows colder temperatures during the positive phase of the SAM in the beginning of the last millennium, with rapidly increasing temperature as the SAM changes to the negative phase. The transition to a negative SAM phase after 1400 CE is however not accompanied by a warming in West Antarctica, which suggests an influence of Pacific South American modes, inducing a cooling in West Antarctica while ABN is warming after this time. A precipitation hiatus during cold periods could explain why water isotope temperature reconstruction underestimates the temperature changes. Both reconstructions arguably record climate in their own way, with a focus on atmospheric and hydrologic cycles for water isotopes, as opposed to surface temperature for gases isotopes and borehole. This study demonstrates the importance of using a variety of sources for comprehensive paleoclimate reconstructions.

Oxygen-17 excess (Δ17O) in carbonate minerals can provide valuable insights into past continental and marine environments, long-term trends in the temperature and oxygen-isotope composition of ancient oceans, isotopic disequilibrium effects in biogenic and abiotic carbonates, and cryptic diagenesis. Triple oxygen isotope analyses of carbonates and/or CO2 using isotope-ratio mass spectrometers (IRMS) remain challenging, however, because of isobaric interference between 16O13C16O and 16O12C17O. Using spectroscopic methods, the abundance of each CO2 isotopologue may be directly quantified, potentially providing simple, non-destructive measurements of δ13C, δ18O and Δ17O on small samples of CO2.Here we report new data characterizing the application of VCOF-CRDS (V-shaped Cavity Optical Feedback - Cavity Ring Down Spectroscopy [1]) to the analysis of small samples (

The water isotope composition of snow precipitations, archived in the Antarctic ice sheet every year, is an important proxy of climatic conditions. This signal depends on several parameters such as local temperature, altitude, moisture source areas and air mass pathways.However, especially in areas where snow accumulation is very low (as on the East Antarctic Plateau), the isotopic composition is affected by additional spatial variability induced by the interactions between the atmosphere and snow surface, and the pristine signal may be modified through isotopic exchanges, sublimation processes and mechanical mixing originated from wind action.Here, we present the isotopic composition (δD and δ18O) and the second-order parameter d-excess of surface snow and snowpit samples collected during the Italian-French campaign in Antarctica (2019-2020). The sampling sites cover the area from Dumont D'Urville to Concordia Station and from Concordia Station towards the South Pole (EAIIST – East Antarctic International Ice Sheet Traverse). These data, compared with a previous dataset of Antarctic surface snow isotopic composition (Masson-Delmotte et al. 2008), are analyzed to determine the variability of the spatial relationship between precipitation isotopic composition and local temperature in relation to geographical parameters (latitude, distance from the coast and elevation). The interpretation of these factors determining the isotope signature is the base to better define the amount of the effects caused by subsequent interaction between atmosphere and surface snow, and by the wind action.Understanding the spatial variability of this proxy, which strongly decreases the signal-to-noise ratio, could permit to improve the use of the “isotopic thermometer” to quantify past changes in temperature based on the stable isotopic record of deep ice cores.

We present an age model for the 651 m deep ice core from Skytrain Ice Rise, situated inland of the Ronne Ice Shelf, Antarctica. The top 2000 years have previously been dated using age markers interpolated through annual layer counting. Below this, we align the Skytrain core to the AICC2012 age model using tie points in the ice and air phase, and we apply the Paleochrono program to obtain the best fit to the tie points and glaciological constraints. In the gas phase, ties are made using methane and, in critical sections, δ18Oair; in the ice phase ties are through 10Be across the Laschamps event and through ice chemistry related to long-range dust transport and deposition. This strategy provides a good outcome to about 108 ka (∼ 605 m). Beyond that there are signs of flow disturbance, with a section of ice probably repeated. Nonetheless values of CH4 and δ18Oair confirm that part of the last interglacial (LIG), from about 117–126 ka (617–627 m), is present and in chronological order. Below this there are clear signs of stratigraphic disturbance, with rapid oscillation of values in both the ice and gas phase at the base of the LIG section, below 628 m. Based on methane values, the warmest part of the LIG and the coldest part of the penultimate glacial are missing from our record. Ice below 631 m appears to be of age > 150 ka., Climate of the Past, 19 (4), ISSN:1814-9324, ISSN:1814-9332

The current global warming driven by human activities has been accentuated in Polar Regions due to the polar amplification, resulting in large releases of ice that have impacts on circulation and sea level at the global scale. In the Arctic, the temperature has increased at three times the global rate, and lead to significant melt of the Greenland ice sheet and sea ice decline. Yet, for Antarctica, the impact of warming is still poorly constrained given the lack of instrumental data and the large decadal climate variability. Using a compilation of 78 ice core records, we provide a high-resolution reconstruction of past temperatures over the last 1000 years for seven regions of Antarctica and direct evidence of Antarctic polar amplification at regional and continental scales. We also show that both the natural and forced variability are not captured by pseudo-proxy experiments using the CMIP5 and 6 ensembles. This that the feedback loops causing the polar amplification are not properly taken into account, leading to an underestimation of the magnitude of anthropogenic warming and its consequences in Antarctica., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

International audience; High-precision triple oxygen isotope data on 40 water samples (5–10 923 m in depth) collected at the Challenger Deep of the Mariana Trench are reported in this study. The analyses at Laboratoire des Sciences du Climat et l’Environnement yield mean isotope values δ18O = −0.084 ± 0.224‰, δ17O = −0.061 ± 0.117‰, and 17O-excess = −17 ± 5 per meg, with standard deviations reported at 1σ. The range of δ18O (from −0.480 to 0.544‰) falls within records of the Global Seawater Oxygen-18 Database at the Mariana Trench. The average 17O-excess value at the Mariana Trench is more negative than the average 17O-excess value of −5 ± 4 (1σ) per meg in the only prior data set including deep ocean samples. The slope (λ) of the three-isotope plot of Mariana Trench water is 0.521 ± 0.003 (1σ), lower than λ of 0.528 ± 0.001 (1σ) for ocean water in the prior study. The new data set matches the prediction of the ocean isotope mass balance model, suggesting that it may represent a more appropriate ocean endmember for triple oxygen isotope thermometry. The 17O-excess of ocean water with respect to Vienna Standard Mean Ocean Water (VSMOW) is recognized to be a necessary correction in quantifying gross oxygen productivity of euphotic regions and relative humidity of moisture source regions.

Stable isotopes of hydrogen, carbon and oxygen are used to investigate numerous physical and chemical processes in the water and inorganic carbon cycles. Measuring and comparing natural isotopic variations requires reliable primary reference materials and consistent data treatment. However, these reference materials have changed over time, while advances in technology have led to better constrained isotopic compositions of the reference materials. In this Technical Review, we provide an overview of the historical evolution of such materials, and explain their relationships across time and isotopic scales. Recommendations are provided for the measurement and reporting of isotopic compositions against the consensual VPDB and VSMOW scales in light of the newest carbonate and water reference materials distributed by the International Atomic Energy Agency. Stable isotope fractionation factors and their temperature dependence in processes specific to the water cycle (2H, 18O, 17O) and the CO2–water–carbonate system (13C, 18O) are described, including for carbonate clumped isotope thermometry. Propagation of errors is also addressed for a consistent reporting of real uncertainties of isotopic measurements and calculations. Lastly, current gaps in knowledge on the behaviour of stable isotopes in the water cycle and the CO2–water–carbonate system are highlighted for future studies. The use of isotopes has provided key insights into the Earth system, but their use can be fraught with experimental and theoretical pitfalls. This Technical Review explains the use of and fractionation factors associated with hydrogen, carbon and oxygen isotopes in water cycle and CO2–carbonate–water system studies.

The EPICA Dome C (EDC) ice core provides the longest continuous climatic record, covering the last 800 000 years (800 kyr). A unique opportunity to investigate decadal to millennial variability during past glacial and interglacial periods is provided by the high-resolution water isotopic record (δ18O and δD) available for the EDC ice core. We present here a continuous compilation of the EDC water isotopic record at a sample resolution of 11 cm, which consists of 27 000 δ18O measurements and 7920 δD measurements (covering, respectively, 94 % and 27 % of the whole EDC record), including published and new measurements (2900 for both δ18O and δD) for the last 800 kyr. Here, we demonstrate that repeated water isotope measurements of the same EDC samples from different depth intervals obtained using different analytical methods are comparable within analytical uncertainty. We thus combine all available EDC water isotope measurements to generate a high-resolution (11 cm) dataset for the past 800 kyr. A frequency decomposition of the most complete δ18O record and a simple assessment of the possible influence of diffusion on the measured profile shows that the variability at the multi-decadal to multi-centennial timescale is higher during glacial than during interglacial periods and higher during early interglacial isotopic maxima than during the Holocene. This analysis shows as well that during interglacial periods characterized by a temperature optimum at the beginning, the multi-centennial variability is strongest over this temperature optimum.

The isotopic compositions of oxygen (δ18O) and hydrogen (δ2H) are widely used to locate the geo- graphical origin of biological remains or manufactured products. In this paper, we analyse the distributions of δ18O and δ2H in tap waters sampled across France, and in precipitation interpolated with the Online Isotopes in Precipitation Calculator and modelled with the isotope-enabled ECHAM6-wiso model. Our aim is to provide isoscapes usable in archaeology and forensics and evaluate whether the modelled data could be surrogates for measured ones. The δ18O and δ2H in the 396 tap waters sampled varied spatially within a range of 10‰ and 77‰, respectively. Their consistent distributions followed rules summarized by the effects of altitude and dis- tance from the coast. Their variations along the year were small. Therefore, the database provides a solid ref- erence for δ18O and δ2H of the water supply system at the regional scale. The areas with the most uncommon oxygen and hydrogen isotopic compositions (Atlantic coast south of Brittany and the highest elevations in the Alps) are the most accurately traceable areas in provenancing studies. The isotopic compositions of modelled precipitation have the same spatial distributions but different absolute values from those of tap waters. There- fore, our results favour the use of statistical isoscapes rather than general circulation model-based isoscapes in provenancing studies.

Stable water isotopes are a tracer of hydrological processes and a paleoclimate proxy from ice core records. The interpretation of the latter relies on fractionation processes throughout the hydrological cycle, from the evaporation over the ocean, during each precipitation event, and during post-deposition processes, in particular due to the exchanges between the snow and the moisture in the atmosphere. Thanks to new developments in infrared spectroscopy, it is now possible to monitor not only the snow isotopic composition but also the vapour continuously, and thus document exchanges between the snow and the vapour. On the East Antarctic Plateau, records of water vapour isotopic composition in Kohnen and Dome C during summer have revealed significant diurnal variability which can be used to address the exchange between surface snow and atmospheric water vapour as well as the stability of the atmospheric boundary layer. In this study, we present the first vapour monitoring on a transect across East Antarctica for a period of 3 months from November 2019 to February 2020 during the EAIIST traverse, covering more than 3600 km. In parallel, we also monitored the vapour isotopic composition at two stations: Dumont D’Urville (DDU), the starting point, and Dome C, half way through. Efforts on the calibration on each monitoring station, as well as cross-calibration of the different instruments offer a unique opportunity to compare both the spatial and temporal (diurnal variability or at the scale of several days) gradients of humidity, temperature and water vapour isotopic composition in East Antarctica during the summer season. With the use of the Modele Atmospherique Régional (MAR), we compare the variability measured in water vapour isotopic composition, temperature and humidity with the different systems (fixed or mobile location). Although further comparisons with the surface snow isotopic composition are required to quantify the impact of the snow-atmosphere exchanges on the local surface mass balance, these three simultaneous measurements of the vapour isotopic composition show the potential of using water stables isotopes to evaluate hydrological processes in East Antarctica.

In the search for very old ice, finding the age of the ice is a key parameter necessary for its interpretation. Most ice core dating methods are based on chronological markers that require the ice to be in stratigraphic order. However, the oldest ice is likely to be found at the bottom of ice sheets, where the stratigraphy is disturbed, or in ablation areas, where the classical methods cannot be used. Absolute dating techniques have recently been developed to provide new constraints on the age of old ice. In particular, 81Kr measurements provide strong dating constraints for the old ice cores. Still, these measurements are limited in deep ice cores because of the large sample size required (5-6 kg). In addition to 81Kr dating, we discuss here the analytical performances of a new technique for 40Ar dating, which allows us to provide a reliable age with 80g of ice rather than 800g, as previously published. Finally, we present two applications for the 81Kr and 40Ar dating on the bottom of the TALDICE and Dome C ice cores.

The recent development of optical spectroscopy enabled the development of the use of water isotopes in climate, environment and hydrological studies. An increasing number of studies also includes the most recent parameter 17O-excess as an indicator for kinetic fractionation effects in the water cycle. However, for some applications such as ice core science, the 17O-excess signal to be measured is very small, of the order of 10 – 20 ppm and it is a big analytical challenge to obtain the requested precision.Here, we present results of performance of the new express mode and the standard mode developed for d18O, dD and now also 17O-excess for a Picarro analyzer. In the standard mode, there is a new injection of water vapor lasting 4.5 minutes every 10 minutes. To get rid of memory effect, the first injections are discarded or a correction is applied which depends on the difference in water isotopic composition between the measured sample and the previous one. For each new sample measured with the express mode, the sequence begins with 6 injections of water vapor in the cavity of 40 secondes each to get rid of the memory effect. It is followed by injections of water vapor lasting 2 minutes every 4 minutes. The advantage of the express mode is to avoid the memory correction and to decrease the measurement time. It thus permits to run more replicates which is important to improve the accuracy of the measurements, especially 17O-excess. We present here results of several series of samples and standards of different water isotopic composition (d18O ranging from -54 to 0 ‰) ran three times with both the standard and the express modes and compare the performances of the two modes.

The growth and decay of marine ice sheets act as important controls on regional and global climate and sea level. The Wilkes Subglacial Basin ice sheet appears to have undergone thinning and ice discharge events during recent decades, but its past dynamics are still under debate. The aim of our study is to investigate ice margin retreat of the Wilkes Subglacial Basin ice sheet during late Pleistocene interglacials with the help of new high-resolution records from the TALDICE ice core. Here we present a multiproxy approach associated with modelling sensitivity experiments.The novel high-resolution δ18O signal reveals that interglacial periods MIS 7.5 and 9.3 are characterized by a unique double-peak feature, previously observed for MIS 5.5 (Masson-Delmotte et al., 2011), that is not seen in other Antarctic ice cores. A comparison with our GRISLI modelling results indicates that the Talos Dome site has probably undergone elevation variations of 100-400 m during past interglacials, with a major ice thickness variation during MIS 9.3, likely connected to a relevant margin retreat of the Wilkes Subglacial Basin ice sheet. To validate this elevation change hypothesis, the modelling outputs are compared to the ice-rafted debris record (IBRD) and the neodymium isotope signal from the U1361A sediment core (Wilson et al., 2018), which show that during MIS 5.5 and especially MIS 9.3, the Wilkes Subglacial Basin ice sheet has been subjected to ice discharge events.Overall, our results indicate that the interglacial double-peak δ18O signal could reflect decreases in Talos Dome site elevation during the late stages of interglacials due to Wilkes Subglacial Basin retreat events. These changes coincided with warmer Southern Ocean temperatures and elevated global mean sea level, confirming the sensitivity of the Wilkes Subglacial Basin ice sheet to ocean warming and its potential role in sea-level change.

The EPICA Dome C (EDC) ice core has been drilled from 1996 to 2004. Its study revealed a unique 800 ka long continuous climatic record including 9 deglaciations. Ice cores contain numerous proxies in the ice and in the air trapped in bubbles (chronological constraints, greenhouse gases concentration, local temperature proxies, mid to low latitude climate proxies).Here, we focus on the link between the high and low latitudes during the glacial/interglacial transitions provided by the isotopic composition of water and oxygen archived in both ice and gas matrix. On one hand, the water isotopic composition brings information on past temperatures and water cycle re-organizations: dD records past temperature, whereas the combination of d18O with dD or d17O provide information on the past water cycle organization through d-excess and 17O-excess linked to climatic conditions of the evaporative regions. On the other hand, the elemental composition of oxygen expressed in the O2/N2 ratio provides key information for orbital dating over the last 800 ka in complement with the isotopic composition of atmospheric oxygen (d18O of O2 or d18Oatm) which is related as well to the low latitude water cycle.In this study, we present new high resolution records of water isotopes of many proxies (d18O, d-excess and 17O-excess) as well as high resolution measurements of O2/N2 and d18Oatm over the last 9 deglaciations on the EDC ice core. We detail the coherent low to mid-latitude orbital patterns obtained using our multiproxy approach with a focus on Termination II, Termination V and the 800 – 500 ka. deglaciations. We look at the similar patterns between terminations and between the different proxies presented.

International audience; Optical feedback is an efficient way to narrow and stabilise semi-conductor lasers. As a step forward for ultra-stable, yet highly tunable sources, we developed a new prototype of a three-mirror V-shaped optical cavity (VCOF). It is made of a precisely machined Zerodur spacer, that holds 3 optical contacted mirrors forming a high finesse V-shaped cavity. This arrangement allows the resonant light to be sent back to the seeding laser, triggering a drastic narrowing of the emission linewidth well below the cavity mode width without the need for high-bandwidth active electronic lock of the laser on the cavity. Low expansion material and precise temperature control of the reference cavity leads to a source with Hz level frequency drift and 70 Hz-level emission linewidth at 215 THz. We discuss the benefits of this new prototype compared to its predecessor for high-sensitivity cavity ring down spectroscopy (CRDS). To serve this purpose, the frequency stabilised laser was characterised on short, mid and long time scales, using a high finesse etalon, a self referenced optical frequency comb and a long term saturated CRDS absorption Lamb dip measurement on water.

This chapter summarises the environmental changes that accompanied the rapid growth of the Northern Hemisphere ice sheets c. 35–30 cal ka BP and their maximum extent c. 29–19 cal ka BP, with a special focus on the European continent and its surrounding margins.

This chapter describes the millennial-scale climatic variability in the atmosphere of Greenland during the Last Glacial Cycle (MIS 5e–MIS 1, 116–14.7 cal ka BP), that is, the Dansgaard–Oeschger (D–O) cycles, and the associated global changes in greenhouse gas atmospheric concentrations, particularly CO2 and CH4, and atmospheric circulation (Ca2+ concentration and d-excess). This chapter highlights the contrasting regional impact of the D–O cycles on the North Atlantic Sea surface temperatures and the vegetation and climate across Europe, as well as the synchronicity between changes in Greenland temperature and the hydrological cycle in the tropics and midlatitudes of the Northern Hemisphere. By contrast, the shape and phasing of millennial-scale events between Greenland and Antarctica differ between the two regions. The mechanisms underlying such a variability are still under debate.

Water isotope ratios of ice cores are a key source of information on past temperatures. Through fractionation within the hydrological cycle, temperature is imprinted in the water isotopic composition of snowfalls. However, this signal of climatic interest is modified after deposition when snow remains at the surface exposed to the atmosphere. Comparing time series of surface snow isotopic composition at Dome C with satellite observations of surface snow metamorphism, we found that long summer periods without precipitation favor surface snow metamorphism altering the surface snow isotopic composition. Using excess parameters (combining D,17O, and 18O fractions) allow the identification of this alteration caused by sublimation and condensation of surface hoar. The combined measurement of all three isotopic compositions could help identifying ice core sections influenced by snow metamorphism in sites with very low snow accumulation., Plain Language Summary: Water isotopes in ice core records are often used to reconstruct past climate temperature variations. Classically, the temperature signal is thought to be imprinted in water isotopes of precipitation, and then archived in the ice core as it falls, and in cold areas of Antarctica, piles up for very long period. Here, we show that the surface snow isotopic composition varies in between precipitation events, suggesting that there might be more than one contribution to the isotopic signal in ice core records. This is particularly important for low accumulation sites, where the snow at the surface remains exposed for very long time periods. The combined use of several isotopic ratios in surface snow helps us disentangle the processes that create this signal., Key Points: During summer without precipitation, intense snow metamorphism shows a strong water isotopic signature. During summer without precipitation, intense snow metamorphism shows a strong water isotopic signature. The d‐excess and 17O‐excess of the snow is a proxy of snow metamorphism for low accumulation regions., FP7 Ideas: European Research Council (FP7 Ideas) http://dx.doi.org/10.13039/100011199, Foundation Prince Albert of Monaco, Alexander von Humboldt‐Stiftung (Humboldt‐Stiftung) http://dx.doi.org/10.13039/100005156, DFG project CLIMAIC, https://doi.pangaea.de/10.1594/PANGAEA.934273

Dumont d'Urville station, located on the East coast of Antarctica in Adelie Land, is in one of the windiest coastal region on Earth, due to katabatic winds downslope from the East Antarctic ice sheet. In summer, the season of interest in this study, coastal weather is characterized by well-marked diel cycles in temperature and wind patterns. Our study aims at exploring the added value of water vapor stable isotopes in coastal Adelie Land to provide new information on the local atmospheric water cycle and climate. An important application is the interpretation of water isotopic profiles in snow and ice cores recently drilled in Adelie Land. We present the first continuous measurements of δ 18 O and d-excess in water vapor over Adelie Land. During our measurements period (26/12/2016 to 03/02/2017), we observed clear diel cycles in terms of temperature, humidity and isotopic composition. The cycles in isotopic composition are particularly large given the muted variations in temperature when compared to other Antarctic sites where similar monitoring have been performed. Based on data analyses and simulations obtained with the regional MAR model on the coastal Adelie Land, we suggest that the driver for δ 18 O and d-excess diel variability in summer at Dumont d'Urville is the variation of the strength of the wind coming from the continent: the periods with strong wind are associated with the arrival of relatively dry air with water vapor associated with low δ 18 O and high d-excess from the Antarctic plateau. Finally, in addition to the interpretation of snow and ice core isotopic profiles in the coastal regions, our study has implications for the evaluation of atmospheric models equipped with water isotopes.

Data availability and temporal resolution make it challenging to unravel the anatomy (duration and temporal phasing) of the Last Glacial abrupt climate changes. Here, we address these limitations by investigating the anatomy of abrupt changes using sub-decadal-scale records from Greenland ice cores. We highlight the absence of a systematic pattern in the anatomy of abrupt changes as recorded in different ice parameters. This diversity in the sequence of changes seen in ice-core data is also observed in climate parameters derived from numerical simulations which exhibit self-sustained abrupt variability arising from internal atmosphere-ice-ocean interactions. Our analysis of two ice cores shows that the diversity of abrupt warming transitions represents variability inherent to the climate system and not archive-specific noise. Our results hint that during these abrupt events, it may not be possible to infer statistically-robust leads and lags between the different components of the climate system because of their tight coupling., Palaeodata resolution and dating limit the study of the sequence of changes across Earth during past abrupt warmings. Here, the authors show tight decadal-scale coupling between Greenland climate, North Atlantic sea ice and atmospheric circulation during these past events using two highly resolved ice-core records.

Since 2018, under the impetus of the IGE (Grenoble) and the LSCE (Saclay) and the common interest of the "Carottes de Glace France" consortium, an analytical platform dedicated to glacier archives was created to meet the growing analytical needs requested by projects involving French partners (Ice Memory, EAIIST, BE-OI ...) and international collaborations with a ten-year vision. Within this framework 5 modules have been developed between the IGE and the LSCE. 3 modules are installed at the IGE, including a CHEMISTRY module which includes a large number of instruments coupled to the CFA (Continuous Flow Analysis) system, allowing high-resolution multi tracer analysis on a single ice stick (water isotopes, dust, conductivity, colorimetry, black carbon, trace metals and gas) as well as several auto-samplers for discrete analyses (major ions, organic species, trace metals, sugars ...). The GAS module is shared between continuous analyses on the CFA system (laser spectrometry CH4/CO) and discrete analyses (Gas chromatography CH4/CO2). The ISOTOPY module allows the analysis of nitrogen (N), sulfur (S) and oxygen (O) isotopes. At the LSCE, the WATER ISOTOPY module allows continuous (Picarro coupled to a CFA line equipped with conductivity cells and auto-sampler) or discrete (Picarro or mass spectrometer) analyses for δD, δ18O and δ17O in water. The AIR ISOTOPY module completes the platform for analyses by mass spectrometry of δ15N of N2, the triple isotopic composition of O2 and noble gases isotopes (36/38/40 Ar; 82/84/86 Kr; 129-132 Xe). An overview of the capacity and performance of the platform will be presented.

Stable water isotopes are effective hydrological tracers due to fractionation processes throughout the water cycle, and thus, the stable isotopes from ice cores can serve as valuable proxies for past changes in the climate and local environment of polar regions. Proper interpretation of these isotopes requires to understand the influence of each potential fractionating process, such as initial evaporation over the ocean and precipitation events, but also the effects of post-depositional exchange between snow and moisture in the atmosphere. Thanks to new developments in infrared spectroscopy, it is now possible to continuously monitor the isotopic composition of atmospheric water vapor in coordination with discrete snow sampling. This allows us to readily document the isotopic and mass exchanges between snow and vapor as well as the stability of the atmospheric boundary layer, as has recently been shown on the East Antarctic Plateau at Kohnen (Ritter et al., TC, 2016) and Dome C (Casado et al., ACP, 2016) stations where substantial diurnal isotopic variations have been recorded.In this study, we present the first vapor monitoring of an East Antarctic transect that covered more than 3600 km over a period of 3 months from November 2019 to February 2020 as part of the EAIIST mission. The isotopic record therefore describes the evolution from typical coastal values to highly depleted values deep inside the continent on the high-altitude plateau. In parallel, we also monitored the vapor isotopic composition at two stations: the coastal starting point of Dumont D’Urville (DDU) and the plateau halfway point of Dome C. Two automatic weather stations (at Paleo and Megadunes sites) were also installed in a previously unexplored region of the East Antarctic plateau that was covered by this transect. This suite of cross-calibrated vapor isotope observations and weather stations, coupled with Modele Atmospherique Régional (MAR) climate modeling, offers a unique opportunity to compare the spatial and temporal gradients of humidity, temperature, and water vapor isotopic composition in East Antarctica during the summer season, and to estimate how the water vapour isotope measurements at Dome C and DDU are representative of the conditions in East Antarctica. The quantitative agreement between the EAIIST record and those recorded at DDU and Dome C stations at the times the raid was nearby, gives confidence in the quality of the results acquired on this traverse. Although further comparisons with the surface snow isotopic composition are required to quantify the impact of the snow-atmosphere exchanges on the local surface mass balance, these initial results of vapor isotopic composition show the potential of using water stables isotopes to evaluate hydrological processes in East Antarctica and better reconstruct past climate changes through ice cores.

Atmospheric abundance of oxygen (O2) has been co-evolved with different aspects of the Earth system since appearance of oxygenic photosynthesis by cyanobacteria around 2.4 109 years before present (Ga). Therefore, much attention has been paid to understand the changes in O2 and the underlying mechanisms over the Earth’s history. The pioneering work by Stolper et al. (2016) revealed the long-term decreasing trend of O2 mixing ratios over the last 800,000 years using the ice-core composite record of molar ratios of O2 and nitrogen (δ(O2/N2)), implying a slight imbalance between sources and sinks. Over geological time scale, O2 is mainly controlled by burial and oxidation of organic carbon and pyrite, but also by oxidation of volcanic gases and sedimentary rocks. Nevertheless, the O2 cycle of the late Pleistocene has not been well understood, partly due to the lack of knowledge about the individual sources and sinks. Since then, Kölling et al. (2019) proposed a simple model to estimate the O2 release/uptake fluxes due to the pyrite burial/oxidation that predicts up to ~70% of the O2 decrease of the last 800,000 years could be explained by pyrite burial/oxidation.Building on this, we present here our preliminary, tentative attempt for reconstruction of the net organic carbon burial flux over the last 800,000 years by combining available information (including new δ(O2/N2) data) and assuming constant O2 fluxes associated with volcanic outgassing and rock weathering. The long-term organic carbon burial flux trend obtained with our new calculations is similar to the global ocean δ13C records but also to simulations using a conceptual carbon cycle model (Paillard, 2017). These results partly support the geomorphological hypothesis that the major sea-level drops during the earlier period of the last 800,000 years lead to enhanced organic carbon burial, and that significant changes in the net organic carbon happen around Marine Isotopic Stage (MIS) 13. In addition, we present the long-term decreasing trend of the global biosphere productivity, or gross photosynthetic O2 flux, reconstructed from new measurements of triple-isotope composition of atmospheric O2 trapped in ice cores. As the largest O2 flux, the observed decrease in gross photosynthesis requires to be compensated by parallel reduction of global ecosystem respiration.

On December 19-21, 2018, an atmospheric river hit the French-Italian Concordia station, located at Dome C, East Antarctic Plateau, 3 269 m above sea level. It induced an extreme surface warming (+ 15°C in 3 days), combined with high specific humidity (multiplied by 3 in 3 days) and a strong isotopic anomaly in water vapor (+ 15 ‰ for δ18O). The isotopic composition of water vapor monitored during the event may be explained by (1) the isotopic signature of long-range water transport, and by (2) local moisture uptake during the event. In this study we quantify the influence of each of these processes.To estimate the isotopic composition of water vapor advected by long-range transport, we perform back-trajectories with the FLEXible PARTicle dispersion model FLEXPART. We retrieve meteorological conditions along different trajectories between the moisture uptake area and Concordia, and use them to compute isotopic fractionation during transport with the mixed cloud isotope model MCIM. While intermediate conditions along the trajectory do not seem to have a major impact on the final isotopic composition (less than 0.1 ‰), the latter appears sensitive to surface conditions (temperature, pressure and relative humidity) in the moisture uptake area (±5.1 ‰). As the event is characterized by the presence of liquid water clouds above Concordia, we show additional sensitivity tests exploring the impact of mixed phase clouds on the water vapor isotopic composition.Finally, we perform a water vapor mass budget in the boundary layer using observations and simulations from the regional atmospheric model MAR, ran with and without drifting snow. The presence of mixed-phase clouds during the event induced a significant increase in downward longwave radiative fluxes, which led to high turbulent mixing in the boundary layer and to heavy drifting snow (white-out conditions). Using MAR simulations, we show that a significant part of the atmospheric water vapor originates from sublimation of drifting snow particles removed from the snowpack. Consequently, the isotopic signal monitored in water vapor during this atmospheric river event reflects both long-range moisture advection and interactions between the boundary layer and the snowpack. Only specific meteorological conditions driven by the atmospheric river, and their associated intense poleward moisture transport, can explain these strong interactions.

In the search for very old ice, finding the age of the ice is a key parameter necessary for its interpretation. Most ice core dating method are based on chronological markers that require the ice to be in stratigraphic order. However, the oldest ice is likely to be found at the bottom of ice sheets, where the stratigraphy is disturbed, or in ablation areas, where the classical methods cannot be used. Absolute dating techniques have recently been developed to provide new constraints on the age of old ice, but their development in the context of ice cores is limited by the large sample size required. Here, we discuss the analytical performances of a new technique for 40Ar dating, which allows us to provide a reliable age with 80g of ice rather than 800g, as previously published. We present an application to the dating of the bottom of the TALDICE and Dome C ice cores. This method represents a significant advance for its application to the very precious ice at the bottom of ice cores.

The Southern Ocean (SO) is a key region for ocean-atmosphere CO2 exchanges, as it witnesses significant changes in physical and biological pump dynamics. While numerous studies have highlighted the central role of reinvigorated SO upwelling behind rapid increases in atmospheric CO2 during glacial terminations, a very few studies have yet focused on the impact of the Biological Carbon Pump and more specifically of the Carbonate Counter Pump (CCP) that, contrary to the Soft Tissue Pump, participates to increase the concentration of dissolved CO2 in oceanic surface waters and thus, in the atmosphere.Amongst the last 9 interglacials, Marine Isotope Stage (MIS) 11 (~ 400 ka) is the longest interglacial of the past 800,000 years, characterised by a ~30 ka-long plateau with atmospheric CO2 hovering around 280 ppm. Reconstructions of past global biosphere productivity based on Δ17O of O2 measurements on air bubbles trapped in ice cores, show that MIS 11 registers the strongest global biosphere productivity (~ 20% higher) compared to the other 8 interglacials (Brandon et al., 2020; Yang et al., EGU21) Meanwhile, marine sedimentary records suggest strong carbonate production and export. Studying the detailed variations of the CCP during this specific period can therefore be useful to better understand its relationship with biospheric productivity changes and to better constraint its impacts on atmospheric CO2.As calcifying organisms, coccolithophores and planktonic foraminifera represent the major producers of CaCO3 in pelagic environments and are therefore useful tools to reconstruct past variations in the CCP strength. Here, we calibrate CaXRF and CaCO3 signals from marine core MD04-2718 located in the Indian sector of the SO (48°53 S; 65°57 E) in terms of coccolith and planktonic carbonate production and export signals over the last 800 ka, with a focus on the interval MIS 12 to MIS 10. We compare our results with published micropaleontological and geochemical records from the subantarctic zone (SAZ) in order to reconstruct past changes in CCP efficiency and circulation at the SO scale and understand their relationships with atmospheric CO2 patterns.We show an increase in CCP efficiency during interglacial periods, with an exceptional high carbonate export production during MIS 11. We demonstrate that enhanced CCP efficiency at the beginning of MIS 11 is likely the consequence of both higher SST conditions and nutrient contents in the upper water column of the SAZ, that increase coccolithophore and planktonic foraminifera productions, thanks to the southward migration of SO fronts and the reinvigoration of southern upwelling. While the sharp increase in atmospheric CO2 during Termination V seems correlated with the reinvigoration of the SO upwelling, enhanced CCP at the beginning of MIS 11 might have greatly reduced the efficiency of the biological pump, impacting the CO2 flux from the ocean to the atmosphere. The strong global biological productivity registered during this interval might have permitted to sustain the 30 ka-long plateau of atmospheric CO2 that characterize this time interval.

The EPICA Dome C (EDC) ice core has been drilled from 1996 to 2004. Its study revealed a unique 800 ka long continuous climatic record including 9 deglaciations. Ice cores contain numerous proxies in the ice and in the air trapped in bubbles (chronological constraints, greenhouse gases concentration, local temperature proxies, mid to low latitude climate proxies). Here, we focus on information provided by the isotopic (and elemental) composition of water and oxygen archived in both ice and gas matrix. On one hand, the water isotopic composition brings information on past temperatures and water cycle re-organizations: d18O or dD records past temperature, whereas the combination of d18O with dD or d17O provide information on the past water cycle organization through d-excess and 17O-excess linked to climatic conditions of the evaporative regions. On the other hand, the elemental composition of oxygen expressed in the O2/N2 ratio provides key information for orbital dating over the last 800 ka in complement with the isotopic composition of atmospheric oxygen (d18O of O2 or d18Oatm) which is related as well to the low latitude water cycle.In this study, we present new high resolution records of water isotopes (d18O, d-excess and 17O-excess) as well as high resolution measurements of O2/N2 and d18Oatm over the last 9 deglaciations on the EDC ice core. We first use the high resolution records of O2/N2 and d18Oatm to improve absolute dating constrain over the glacial terminations and discuss the link between orbital forcing and climate variations recorded in the EDC ice core. In a second part, we use d-excess, 17O-excess and d18Oatm to constrain the relative chronology of high vs low latitude climatic events at sub-millennial scale over past deglaciations.

The primary production, or oxygenic photosynthesis of the global biosphere, is one of the main source and sink of atmospheric oxygen (O2) and carbon dioxide (CO2), respectively. There has been a growing number of evidence that global gross primary productivity (GPP) varies in response to climate change. It is therefore important to understand the climate- and/or environment controls of the global biosphere primary productivity for better predicting the future evolution of biosphere carbon uptake. The triple-isotope composition of O2 (Δ17O of O2) trapped in polar ice cores allows us to trace the past changes of global biosphere primary productivity as far back as 800,000 years before present (800 ka). Previously available Δ17O of O2 records over the last ca. 450 ka show relatively low and high global biosphere productivity over the last five glacial and interglacial intervals respectively, with a unique pattern over Termination V (TV) - Marine Isotopic Stage (MIS) 11, as biosphere productivity at the end of TV is ~ 20 % higher than the four younger ones (Blunier et al., 2012; Brandon et al., 2020). However, questions remain on (1) whether the concomitant changes of global biosphere productivity and CO2 were the pervasive feature of glacial periods over the last 800 ka, and (2) whether the global biosphere productivity during the “lukewarm” interglacials before the Mid-Brunhes Event (MBE) were lower than those after the MBE.Here, we present an extended composite record of Δ17O of O2 covering the last 800 ka, based on new Δ17O of O2 results from the EPICA Dome C and reconstruct the evolution of global biosphere productivity over that time interval using the independent box models of Landais et al. (2007) and Blunier et al. (2012). We find that the glacial productivity minima occurred nearly synchronously with the glacial CO2 minima at mid-glacial stage; interestingly millennia before the sea level reaches their minima. Following the mid-glacial minima, we also show slight productivity increases at the full-glacial stages, before deglacial productivity rises. Comparison of reconstructed interglacial productivity demonstrates a slightly higher productivity over the post-MBE (MISs 1, 5, 7, 9, and 11) than pre-MBE ones (MISs 13, 15, 17, and 19). However, the mean difference between post- and pre-MBE interglacials largely depends on the box model used for productivity reconstruction.

High precision measurements of triple isotopic composition of oxygen in the air trapped in ice cores is a useful tool to infer the global gross biosphere productivity in the past. The isotopic composition of oxygen is influenced by many physical, chemical and biological processes during consumption and production of oxygen by the oceanic and terrestrial biosphere. For an accurate quantification of the past biosphere productivity, it is thus important to determine the different fractionation processes occurring in the biosphere during respiration and photosynthesis processes.We present here quantification of fractionation coefficients associated with δ180 and the D170 of 02 during respiration and photosynthesis within the terrestrial biosphere. The experimental set-up relies on closed biological chambers in which all the environmental parameters are controlled and measured. Triple isotopic composition of oxygen is regularly measured through sampling of small aliquots at a low frequency (4 h to 4 days). Seven 2-month long experiments were performed in order to check the reproducibility of our set-up and quantify uncertainty on the determination of the fractionation coefficients.In order to improve our set-up for future experiments using different plants, we also present perspectives for a continuous measurement of the isotopic composition of oxygen using optical spectroscopy (Optical Feedback Cavity Enhanced Absorption Spectroscopy (OF-CEAS) technique). This instrument is currently being characterized and we will present its current performances.Triple isotopic composition of oxygen in the atmospheric dioxygen to reconstruct the dynamic of global biosphere productivity in the past from measurements in biological chambers.

The growth and decay of marine ice sheets act as important controls on regional and global climate, in particular, the behavior of the ice sheets is a key uncertainty in predicting sea-level rise during and beyond this century. The East Antarctic Ice Sheet (EAIS), which contains deep subglacial basins with reverse-sloping, is considered to be susceptible to ice loss caused by marine ice sheet instability. Sediment core offshore Wilkes Subglacial Basin reveals oscillations in the provenance of detrital sediment that have been interpreted to reflect an erosion of Wilkes Basin during interglacial periods MIS 5, MIS 7, and MIS 9 greater than Holocene period (Wilson et al., 2018). The aim of our study is to investigate past climate and environmental changes in the coastal area of the East Antarctic Ice Sheet during MIS 7.5 and 9.3 with the help of a new high-resolution water isotopes record of the TALDICE ice core.Here we present new δ18O and δD high resolution (5 cm) records covering the oldest portion of the TALDICE ice core. MIS 7.5 and 9.3 isotopic signal reveals a unique feature, already observed for MIS 5.5, that has not been spotted in other Antarctic ice cores (Masson-Delmotte et al., 2011). Interglacial periods at TALDICE are characterized by a first peak, observed in correspondence to the culmination of the deglaciation event as for all Antarctic cores, followed by a less pronounced isotopic peak (for MIS 5.5 and 9.3) or a plateau (for MIS 7.5) prior to the glacial inception. Several factors might drive this peculiar behavior of the water stable isotopes record, as an increase in temperatures due to a drop in surface elevation or changes in moisture sources.The new δ18O and δD high-resolution records for the TALDICE ice core reveal a unique pattern that characterizes interglacial periods at Talos Dome. Taking into account the coastal position of the core and its vicinity to the Wilkes Subglacial Basin we intend to investigate the possible decrease in surface elevation, through the application of the GRISLI ice sheet model (Quiquet et al., 2018), and changes in moisture sources, traceable from the d-excess record.

Past climatic and environmental changes can be reconstructed thanks to paleoclimatic archives such as ice cores, marine sediment cores, lake sediment cores, speleothems, tree rings, corals, etc. The dating of these natural archives is crucial for deciphering the temporal sequence of events during past climate changes. It is also essential to estimate the absolute and relative errors of such estimated chronologies. This task is, however, complex since it involves the combination of different dating approaches on different paleoclimatic sites and often different types of archives. Here we present Paleochrono, a new probabilistic model to derive a common and probalistically optimal chronology for several paleoclimatic sites with potentially different types of archives. Paleochrono is based on the inversion of an archiving model: a varying deposition rate (also named sedimentation or accumulation rate) and also, for ice cores, a lock-in-depth of air bubbles (since air is not trapped at surface) and a thinning function (since ice undergoes flow). The model integrates several types of chronological information: prior knowledge of the archiving process, independently dated horizons, depth intervals of known duration, undated stratigraphic links between records, and, for ice cores, Δdepth observations (depth differences between synchronous events recorded in the bubbles and ice, respectively). The optimization is formulated as a least-squares problem, assuming that all densities of probabilities are near-Gaussian and that the model is almost linear in the vicinity of the best solution. Paleochrono is the successor of IceChrono, which was dealing only with ice-core records. Paleochrono performs better than IceChrono in terms of computational efficiency, ease of use, and accuracy. We demonstrate the ability of Paleochrono in a new AICC2012-Hulu dating experiment, which combines the AICC2012 dating experiment, based on records from five polar ice cores, with data from two U/Th-dated speleothems from Hulu Cave (China). We analyse the performance of Paleochrono in terms of computing time and memory usage in various dating experiments. Paleochrono is freely available under the MIT open source license.

Succession of cold glacials and warm interglacials during the Quaternary results from large global climate responses to variable orbital configurations, accompanied by fluctuating greenhouse gas concentrations. Despite the influences of sea ice and atmospheric and ocean circulations in the Southern Ocean on atmospheric CO2 concentrations and climate, past changes in this region remain poorly documented. Here, we present the 800 ka deuterium excess record from the East Antarctica EPICA Dome C ice core, tracking sea surface temperature in evaporative regions of the Indian sector of the Southern Ocean from which moisture precipitated in East Antarctica is derived. We find that low obliquity leads to surface warming in evaporative moisture source regions during each glacial inception, although this relative temperature increase is counterbalanced by global cooling during glacial maxima. Links between the two regions during interglacials depends on the existence of a temperature maximum at the interglacial onset. In its absence, temperature maxima in the evaporative moisture source regions and in East Antarctica were synchronous. For the other interglacials, temperature maxima in the source areas lag early local temperature maxima by several thousand years, probably because of a change in the position of the evaporative source areas. Interglacial temperature coupling between East Antarctica and the Southern Ocean was set by the position of moisture source regions, according to an 800,000-year-long deuterium-excess ice-core record from East Antarctica.

We report high resolution measurements of the stable isotope ratios of ancient ice (δ18O, δD) from the North Greenland Eemian deep ice core (NEEM, 77.45° N, 51.06° E). The record covers the period 8–130 ky b2k (y before 2000) with a temporal resolution of ≈0.5 and 7 y at the top and the bottom of the core respectively and contains important climate events such as the 8.2 ky event, the last glacial termination and a series of glacial stadials and interstadials. At its bottom part the record contains ice from the Eemian interglacial. Isotope ratios are calibrated on the SMOW/SLAP scale and reported on the GICC05 (Greenland Ice Core Chronology 2005) and AICC2012 (Antarctic Ice Core Chronology 2012) time scales interpolated accordingly. We also provide estimates for measurement precision and accuracy for both δ18O and δD., Measurement(s) isotope analysis • water ice core Technology Type(s) cavity ring-down spectroscopy Factor Type(s) δ18O • δD Sample Characteristic - Location Greenland Ice Sheet Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.14216441

Using new and previously published CO2 data from the EPICA Dome C ice core (EDC), we reconstruct a new high-resolution record of atmospheric CO2 during Marine Isotope Stage (MIS) 6 (190 to 135 ka) the penultimate glacial period. Similar to the last glacial cycle, where high-resolution data already exists, our record shows that during longer North Atlantic (NA) stadials, millennial CO2 variations during MIS 6 are clearly coincident with the bipolar seesaw signal in the Antarctic temperature record. However, during one short stadial in the NA, atmospheric CO2 variation is small ( ∼5 ppm) and the relationship between temperature variations in EDC and atmospheric CO2 is unclear. The magnitude of CO2 increase during Carbon Dioxide Maxima (CDM) is closely related to the NA stadial duration in both MIS 6 and MIS 3 (60–27 ka). This observation implies that during the last two glacials the overall bipolar seesaw coupling of climate and atmospheric CO2 operated similarly. In addition, similar to the last glacial period, CDM during the earliest MIS 6 show different lags with respect to the corresponding abrupt CH4 rises, the latter reflecting rapid warming in the Northern Hemisphere (NH). During MIS 6i at around 181.5± 0.3 ka, CDM 6i lags the abrupt warming in the NH by only 240± 320 years. However, during CDM 6iv ( 171.1± 0.2 ka) and CDM 6iii ( 175.4± 0.4 ka) the lag is much longer: 1290± 540 years on average. We speculate that the size of this lag may be related to a larger expansion of carbon-rich, southern-sourced waters into the Northern Hemisphere in MIS 6, providing a larger carbon reservoir that requires more time to be depleted.