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

Goursaud, Sentia; Masson-Delmotte, Valérie; Favier, Vincent; Preunkert, Suzanne; Legrand, Michel; Minster, Bénédicte; Werner, Martin

A new 21.3 m firn core was drilled in 2015 at a coastal Antarctic high-accumulation site in Adélie Land (66.78inline-formula S; 139.56inline-formula E, 602 m a.s.l.), named Terre Adélie 192A (TA192A).

The mean isotopic values (inline-formula M3inlinescrollmathml - normal 19.3 0.125emnobreak normal ‰ ± normal 3.1 70pt10ptsvg-formulamathimg8c7cb92ef210551f462adaf6959f644a tc-13-1297-2019-ie00001.svg70pt10pttc-13-1297-2019-ie00001.png  ‰ for inline-formulaδ18O and inline-formula5.4 ‰±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 inline-formulaδ18O 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 inline-formulad-excess signal showing outstanding values in austral spring versus autumn. Significant positive trends are observed in the annual inline-formulad-excess record and local sea ice extent (135–145inline-formula E) over the period 1998–2014.

However, process studies focusing on resulting isotopic compositions and particularly the deuterium excess–inline-formulaδ18O 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.

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Goursaud, Sentia / Masson-Delmotte, Valérie / Favier, Vincent / et al: Challenges associated with the climatic interpretation of water stable isotope records from a highly resolved firn core from Adélie Land, coastal Antarctica. 2019. Copernicus Publications.

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