Sub-millennial climate variability from high-resolution water isotopes in the EPICA Dome C ice core

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.publishedVersio

Étude à haute résolution des cycles hydrologiques et climatiques à partir d'une carotte de glace d'Antarctique avec un focus sur les déglaciations

Ice cores from the polar ice caps are valuable climate archives that have allowed us to document the past climate and environment. The EPICA Dome C (EDC) core in Antarctica was drilled to a depth of 3,189 m, which corresponds to an age of 800,000 years. This core located on the Antarctic Plateau is currently the longest continuous glacial archive providing high resolution stable isotope records of water and gas trapped in the ice to document past climate.This thesis focuses on the study of high frequency variability from high resolution sample measurements on the EDC core. In particular, we focus on the variability of the atmospheric hydrological cycle and climate during deglaciation.This thesis has consisted of extensive analytical work. First, from high resolution (11 cm) measurements of water isotopic composition on the EDC core, we concluded that the multi-centennial variability is lower during warm periods, called interglacials, than during cold periods, called glaciations. In addition, this data set allowed us to quantify the evolution of the diffusion length along the EDC core and to study how the diffusion in the ice attenuates the climate signal for the deepest part of the core.In a second step, I made measurements of δ15N of N2, δ18O of O2, δO2/N2 in the air trapped in the ice at a time resolution of 200-300 years over the different deglaciations. These data allow us to better date the ice core and study the evolution of the low-latitude hydrological cycle (δ18O of O2). I combined these data with other 17O - exess measurements that I made every 55 cm (50-300 year resolution) and d-excess data over the same time periods. The d-excess and the 17O - exess are tracers of the climatic conditions of the evaporation sources. By synthesizing these deglaciation data, we have described the sequences of events during orbital forcing-driven warming. In particular, we have highlighted a millennial variability that occurs during deglaciations at temperate latitudes but does not affect the Antarctic climate. There is thus a decoupling between the evolution of the Antarctic climate and the climate of the lowest latitudes during deglaciations.Finally, our analytical results on deglaciations have been compared to general circulation model outputs (PMIP project).Les carottes de glace provenant des calottes polaires constituent de précieuses archives climatiques qui nous ont permis de documenter le climat et l'environnement passé. La carotte d'EPICA Dôme C (EDC) en Antarctique a été forée jusque 3 189 m de profondeur, ce qui correspond à un âge de 800 000 ans. Cette carotte située sur le plateau Antarctique est actuellement la plus longue archive glaciaire continue permettant d'obtenir des enregistrements à haute résolution d'isotopes stables de l'eau et de gaz piégé dans la glace pour documenter le climat passé.Cette thèse se concentre sur l'étude de la variabilité à haute fréquence à partir de mesures d'échantillons à haute résolution sur la carottes EDC. Nous nous concentrons plus particulièrement sur la variabilité du cycle hydrologique atmosphérique et du climat pendant les déglaciations.Cette thèse a constitué en un important travail analytique. Dans un premier temps, à partir de mesures à haute résolution (11 cm) de la composition isotopique de l'eau sur la carotte EDC, nous avons conclu que la variabilité multi-centennale est plus faible pendant les périodes chaudes, dites interglaciaires, que pendant les périodes froides, dites glaciaires. De plus, cette série de données nous a permis de quantifier l'évolution de la longueur de diffusion tout au long de la carotte EDC et d'étudier comment la diffusion dans la glace atténue le signal climatique pour la partie la plus profonde de la carotte.Dans un second temps, j'ai effectué des mesures de δ15N de N2, δ18O de O2, δO2/N2 dans l'air piégé dans la glace à une résolution temporelle de 200 à 300 ans sur les différentes déglaciations. Ces données permettent de mieux dater la carotte de glace et d'étudier l'évolution du cycle hydrologique des basses latitudes (δ18O de O2). J'ai combiné ces données avec d'autres mesures de 17O − exess que j'ai effectuées tous les 55 cm (résolution de 50 à 300 ans) et des données de d-excess sur les mêmes périodes. Le d-excess et le 17O − exess sont des traceurs des conditions climatiques des sources d'évaporation. En synthétisant ces données sur les déglaciations, nous avons décrit les séquences d'évènements lors des réchauffements dus au forçage orbital. Nous avons en particulier mis en évidence une variabilité millénaire qui a lieu pendant les déglaciations aux latitudes tempérées mais qui n'affecte pas le climat Antarctique. Il y a donc un découplage entre l'évolution du climat Antarctique et le climat des plus basses latitudes pendant les déglaciations.Enfin, nos résultats analytiques sur les déglaciations ont été comparés à des sorties de modèles de circulation générale (projet PMIP)

High resolution climate and water cycle records in Antarctic ice cores with a focus on deglaciations

Les carottes de glace provenant des calottes polaires constituent de précieuses archives climatiques qui nous ont permis de documenter le climat et l'environnement passé. La carotte d'EPICA Dôme C (EDC) en Antarctique a été forée jusque 3 189 m de profondeur, ce qui correspond à un âge de 800 000 ans. Cette carotte située sur le plateau Antarctique est actuellement la plus longue archive glaciaire continue permettant d'obtenir des enregistrements à haute résolution d'isotopes stables de l'eau et de gaz piégé dans la glace pour documenter le climat passé.Cette thèse se concentre sur l'étude de la variabilité à haute fréquence à partir de mesures d'échantillons à haute résolution sur la carottes EDC. Nous nous concentrons plus particulièrement sur la variabilité du cycle hydrologique atmosphérique et du climat pendant les déglaciations.Cette thèse a constitué en un important travail analytique. Dans un premier temps, à partir de mesures à haute résolution (11 cm) de la composition isotopique de l'eau sur la carotte EDC, nous avons conclu que la variabilité multi-centennale est plus faible pendant les périodes chaudes, dites interglaciaires, que pendant les périodes froides, dites glaciaires. De plus, cette série de données nous a permis de quantifier l'évolution de la longueur de diffusion tout au long de la carotte EDC et d'étudier comment la diffusion dans la glace atténue le signal climatique pour la partie la plus profonde de la carotte.Dans un second temps, j'ai effectué des mesures de δ15N de N2, δ18O de O2, δO2/N2 dans l'air piégé dans la glace à une résolution temporelle de 200 à 300 ans sur les différentes déglaciations. Ces données permettent de mieux dater la carotte de glace et d'étudier l'évolution du cycle hydrologique des basses latitudes (δ18O de O2). J'ai combiné ces données avec d'autres mesures de 17O − exess que j'ai effectuées tous les 55 cm (résolution de 50 à 300 ans) et des données de d-excess sur les mêmes périodes. Le d-excess et le 17O − exess sont des traceurs des conditions climatiques des sources d'évaporation. En synthétisant ces données sur les déglaciations, nous avons décrit les séquences d'évènements lors des réchauffements dus au forçage orbital. Nous avons en particulier mis en évidence une variabilité millénaire qui a lieu pendant les déglaciations aux latitudes tempérées mais qui n'affecte pas le climat Antarctique. Il y a donc un découplage entre l'évolution du climat Antarctique et le climat des plus basses latitudes pendant les déglaciations.Enfin, nos résultats analytiques sur les déglaciations ont été comparés à des sorties de modèles de circulation générale (projet PMIP).Ice cores from the polar ice caps are valuable climate archives that have allowed us to document the past climate and environment. The EPICA Dome C (EDC) core in Antarctica was drilled to a depth of 3,189 m, which corresponds to an age of 800,000 years. This core located on the Antarctic Plateau is currently the longest continuous glacial archive providing high resolution stable isotope records of water and gas trapped in the ice to document past climate.This thesis focuses on the study of high frequency variability from high resolution sample measurements on the EDC core. In particular, we focus on the variability of the atmospheric hydrological cycle and climate during deglaciation.This thesis has consisted of extensive analytical work. First, from high resolution (11 cm) measurements of water isotopic composition on the EDC core, we concluded that the multi-centennial variability is lower during warm periods, called interglacials, than during cold periods, called glaciations. In addition, this data set allowed us to quantify the evolution of the diffusion length along the EDC core and to study how the diffusion in the ice attenuates the climate signal for the deepest part of the core.In a second step, I made measurements of δ15N of N2, δ18O of O2, δO2/N2 in the air trapped in the ice at a time resolution of 200-300 years over the different deglaciations. These data allow us to better date the ice core and study the evolution of the low-latitude hydrological cycle (δ18O of O2). I combined these data with other 17O - exess measurements that I made every 55 cm (50-300 year resolution) and d-excess data over the same time periods. The d-excess and the 17O - exess are tracers of the climatic conditions of the evaporation sources. By synthesizing these deglaciation data, we have described the sequences of events during orbital forcing-driven warming. In particular, we have highlighted a millennial variability that occurs during deglaciations at temperate latitudes but does not affect the Antarctic climate. There is thus a decoupling between the evolution of the Antarctic climate and the climate of the lowest latitudes during deglaciations.Finally, our analytical results on deglaciations have been compared to general circulation model outputs (PMIP project)

δO2/N2 and δ18O of O2 from EPICA Dome C ice core (Antarctica) (0-800 ka)

We present the full compilation of δO2/N2 and δ18O of O2 data measured in the gas phase on the EPICA Dome C ice core from 1420 m to the bottom (3191 m), hence covering the last 800 kyr. The EPICA Dome C ice core has been drilled in Antarctica (-75.1°S; 123.395°E; 3233 m elevation) between 1996 and 2004 and measurements were performed from 2001 to 2022. Some of the data were already presented in previous published studies (Dreyfus et al., 2007, 2008; Landais et al., 2012; Bazin et al., 2016; Extier et al., 2018) but corrections were performed in the present data file. The new highly-resolved datasets have been measured over five glacial terminations (TII, III, IV, V and VI) by Grisart (2023) using a dual inlet Delta 219 V plus (Thermo Electron Corporation) mass spectrometer at the LSCE. They are combined to previous published data to obtain the final compilation of the δ18O of O2 and δO2/N2 records covering the last 800 kyr

Oxygen-18 isotope ratios from the EPICA Dome C ice core at 11 cm resolution

Abstract: We present here a high resolution (0.11 m) dataset of the isotopic composition of the ice (δ¹⁸O) from the EPICA Dome-C ice core. The dataset covers the depth range 7.81-3189.89 m (0.05-802.427 ka). Analysis is performed in Copenhagen with a CO~2~ equilibration Mass Spectrometry system (Finnegan MAT 251). Samples of 5 ml are equilibrated with CO~2~ for 6 hours under vibrations, thereafter injected to the mass spectrometer where the ¹⁸O/¹⁶O ratio is obtained on masses 46 and 44. All measurements reported on the SMOW-SLAP scale using a 2-point linear calibration (standards used: Crete: -33.61 ‰ and DC02: -54.11 ‰ . The combined uncertainty of the record is 0.07 ‰. We interpolate the dataset on the AICC2012 chronology

Sub-millennial climate variability from high-resolution water isotopes in the EPICA Dome C ice core

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Sub-millennial climate variability from high-resolution water isotopes in the EPICA Dome C ice core

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 27000 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 800kyr. 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 multidecadal 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