Polar boreholes provide unique records of the climate over the last 800,000 years. By analysing the ice and air bubbles, it is possible to reconstruct variations in local temperature and atmospheric composition. These boreholes have documented large-scale climatic changes, such as the glacial-interglacial transitions that affect the entire Earth system at intervals ranging from 40,000 to 120,000 years. Precise dating of these boreholes is crucial to understanding the correlations between external forcings (solar energy received at the Earth’s surface), climate responses and internal feedbacks (greenhouse gas concentration, dynamics of ice caps and oceanic and atmospheric circulation, etc.). This study presents the new AICC20231 reference dating for the EPICA2 Dome C borehole, reaching a depth of 3200 m in East Antarctica and constituting the oldest continuous record to date, covering 800,000 years.
From the time they are deposited on the surface until they are buried at depth, the ice strata become thinner. The first 100 metres of the EPICA Dome C borehole contain 1,000 years of climatic record, while the last 100 metres contain almost 100,000 years. However, the dating of the deep section is not very accurate (uncertainty of 8,000 years) because the data used to date the borehole is poorly resolved.
To improve the dating, the study incorporates numerous new measurements taken in the air bubbles from the EPICA Dome C borehole, stratigraphic links between several boreholes in Antarctica and Greenland and a model of the evolution of the snow cover. The uncertainty has been reduced to an average of 900 years, reaching 4,000 years in the deepest part of the borehole.
1Antarctic Ice Core Chronology 2023
2European Project for Ice Coring in Antarctica
Bouchet, M., Landais, A., Grisart, A., Parrenin, F., Prié, F., Jacob, R., Fourré, E., Capron, E., Raynaud, D., Lipenkov, V. Y., Loutre, M.-F., Extier, T., Svensson, A., Legrain, E., Martinerie, P., Leuenberger, M., Jiang, W., Ritterbusch, F., Lu, Z.-T., and Yang, G.-M.: The AICC2023 chronological framework and associated timescale for the EPICA Dome C ice core, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-1081 , 2023.