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

• Published in: The Cryosphere
• Main Authors: Goursaud, Sentia, Masson-Delmotte, Valérie, Favier, Vincent, Preunkert, Suzanne, Legrand, Michel, Minster, Bénédicte, Werner, Martin
• Format: Text
• Language: English
• Published: 2019
• Subjects: Antarctic; Austral; Terre Adélie; Terre-Adélie; Antarc*; Antarctica; Sea ice
• Online Access: https://doi.org/10.5194/tc-13-1297-2019; https://tc.copernicus.org/articles/13/1297/2019/

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 ( <math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">19.3</mn><mspace width="0.125em" linebreak="nobreak"/><mi mathvariant="normal">‰</mi><mo>±</mo><mn mathvariant="normal">3.1</mn></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="70pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="8c7cb92ef210551f462adaf6959f644a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-13-1297-2019-ie00001.svg" width="70pt" height="10pt" src="tc-13-1297-2019-ie00001.png"/></svg:svg> ‰ 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 austral 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.