Preprints
https://doi.org/10.5194/cp-2022-91
https://doi.org/10.5194/cp-2022-91
 
20 Dec 2022
20 Dec 2022
Status: this preprint is currently under review for the journal CP.

A 2000-year temperature reconstruction on the East Antarctic plateau, from argon-nitrogen and water stable isotopes in the Aurora Basin North ice core

Aymeric P. M. Servettaz1,2, Anaïs J. Orsi1,3, Mark A. J. Curran4,5, Andrew D. Moy4,5, Amaelle Landais1, Joseph R. McConnell6, Trevor J. Popp7, Emmanuel Le Meur8, Xavier Faïn8, and Jérôme Chappelaz8 Aymeric P. M. Servettaz et al.
  • 1Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA‐CNRS‐UVSQ, Université Paris‐Saclay, Gif‐sur‐Yvette, 91190, France
  • 2Biogeochemistry Research Center, Japan Agency for Marine-Earth Science and Technology, Yokosuka, 237-0061, Japan
  • 3Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, V6T 1Z4, British Columbia, Canada
  • 4Australian Antarctic Division, Kingston, 7050, Tasmania, Australia
  • 5Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, 7000, Tasmania, Australia
  • 6Division of Hydrologic Sciences, Desert Research Institute, Reno, 89512, Nevada, USA
  • 7Niels Bohr Institute, University of Copenhagen, Copenhagen, 2200, Denmark
  • 8University Grenoble Alpes, CNRS, IRD, Grenoble INP, IGE, 38000 Grenoble, France

Abstract. 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.

Aymeric P. M. Servettaz et al.

Status: open (until 22 Feb 2023)

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Aymeric P. M. Servettaz et al.

Aymeric P. M. Servettaz et al.

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Short summary
The temperature of the past 2000 years is still poorly known in vast parts of the East Antarctic plateau. In this study, we present temperature reconstructions based on water and gases stables isotopes from the Aurora Basin North ice core. Spatial and temporal significance of each proxy differs, and we can identify some cold periods in the snow temperature, consistent with Southern Annular Mode variability, which could not be determined with water isotopes only.