Challenges associated with the climatic interpretation of water stable isotope records from a highly resolved firn core from Adélie Land, coastal Antarctica

Sentia Goursaud (1, 2) , Valérie Masson-Delmotte (2, 3) , Vincent Favier (1) , Susanne Preunkert (1) , Michel Legrand (1) , Bénédicte Minster (2, 3) , Martin Werner (4)

1 IGE - Institut des Géosciences de l’Environnement
2 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
3 GLACCIOS - Glaces et Continents, Climats et Isotopes Stables
4 Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research

A new 21.3 m firn core was drilled in 2015 at a coastal Antarctic high-accumulation site in Adélie Land (66.78 • S; 139.56 • E, 602 m a.s.l.), named Terre Adélie 192A (TA192A). The mean isotopic values (−19.3 ‰ ± 3.1 ‰ for δ 18 O and 5.4 ‰±2.2 ‰ for deuterium excess) are consistent with other coastal Antarctic values. No significant isotope-temperature relationship can be evidenced at any timescale. This rules out a simple interpretation in terms of local temperature. An observed asymmetry in the δ 18 O seasonal cycle may be explained by the precipitation of air masses coming from the eastern and western sectors in autumn and winter, recorded in the d-excess signal showing outstanding values in aus-tral spring versus autumn. Significant positive trends are observed in the annual d-excess record and local sea ice extent (135-145 • E) over the period 1998-2014. However, process studies focusing on resulting isotopic compositions and particularly the deuterium excess-δ 18 O relationship , evidenced as a potential fingerprint of moisture origins, as well as the collection of more isotopic measurements in Adélie Land are needed for an accurate interpretation of our signals.

Domaines: Océan, Atmosphère; Interfaces continentales, environnement

Sentia Goursaud, Valérie Masson-Delmotte, Vincent Favier, Susanne Preunkert, Michel Legrand, et al.. Challenges associated with the climatic interpretation of water stable isotope records from a highly resolved firn core from Adélie Land, coastal Antarctica. The Cryosphere, 2019, 13, pp.1297 - 1324. ⟨10.5194/tc-13-1297-2019⟩. ⟨hal-02864992⟩