Two thousand years of temperature variability on the lower East Antarctic Plateau inferred from the analysis of stable isotopes of water and inert gases in the Aurora Basin North ice core

• Main Author: Servettaz, Aymeric
• Other Authors: Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Université Paris-Saclay, Amaëlle Landais, Anaïs Orsi
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2021
• Subjects: Antarctica; Climate; Temperature; Stable isotopes; Ice core; Antarctique; Climat; Température; Isotopes stables; Carotte de glace; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Antarc*; Antarctic; Antarctique*; ice core; Wilkes Land
• Online Access: https://theses.hal.science/tel-03228029; https://theses.hal.science/tel-03228029/document; https://theses.hal.science/tel-03228029/file/99453_SERVETTAZ_2021_archivage.pdf

Antarctica is a major component in Earth’s climate system, as the equator to pole temperature gradient controls the characteristics of the general circulation of the atmosphere. Antarctica is also very useful to understand climate variability, as past climate information preserved in the ice may help extend the short observational records. However, the ice core drilling locations are unevenly spread across the glaciated continent, and the temperature reconstructions from the high elevation East Antarctic plateau suffer from poor temporal resolution, because low snow accumulation hampers our interpretation of water isotopes. Here, we present new temperature reconstructions from the Aurora Basin North (ABN, 77°S, 111°E, 2700 masl) ice core. First, we use the regional atmospheric model MAR to characterize the recent climate at ABN, and show that precipitation events are intermittent, and occur under temperature 2°C warmer than average. The large precipitation events are marked in the snow isotopes with δ18O values on par with summer levels, even during the winter, as attested by snow measurements and the isotope-enabled atmospheric model ECHAM5-wiso. Precipitations are consistently associated with a blocking on the Wilkes Land coast, North-East of ABN, and the blockings are more likely to occur during negative phases of the Southern Annular Mode (SAM), the main mode of variability in the southern hemisphere climate. Consequently, SAM positive phases are marked by cold temperatures at ABN, but not necessarily low δ18O, as precipitations may be weakened. The temperature reconstructed from the δ18O in the 300-m-deep, 2000-year ice core drilled at ABN supports stable conditions, with a temperature remaining within a ± 1°C range. We present a second temperature reconstruction from the same core, based on the inversion of borehole temperature and past firn temperature gradients, estimated with the stable isotope composition of Ar and N2 gases trapped in bubbles. This second temperature reconstruction, representative of ...