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

Abstract

A new 21.3m firn core was drilled in 2015 at a coastal Antarctic high-accumulation site in Adelie Land (66.78 S; 139.56 E, 602ma.s.l.), named Terre Adelie 192A (TA192A). The mean isotopic values (19:33:1for 18O and 5:42:2for 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 18O 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-18O relationship, evidenced as a potential fingerprint of moisture origins, as well as the collection of more isotopic measurements in Adelie Land are needed for an accurate interpretation of our signals.