Multiproxy analyses for a network of firn cores covering the last 40 years from coastal Adélie Land

Water stable isotopes signals recorded in snow, firn and ice cores were successfully used to investigate past temperatures on glacial/interglacial scales (Jouzel and Masson-Delmotte 2010, Dansgaard, 1964). However, as evidenced by Goursaud et al. (2018) in coastal Adélie Land, many uncertainties hampered the interpretation of water isotope records at sub-annual to decadal resolution as a proxy of past temperature variations only (Goursaud et al. 2018). Condensation, sublimation and/or redistribution of snow triggered by strong katabatic winds as well as precipitation intermittencies, origin of moist air masses bringing precipitation and diffusion within firn lessen the representativity of a single isotopic profile to reconstruct past temperature in this region (Grazioli et al. 2017, Khale et al. 2018, Picard et al. 2019, Casado et al. 2020, Hirsch et al. 2023). In order to mitigate the non-representativity of a single isotopic profile, a solution consists in averaging several records to increase signal to noise ratios. However, to do so, it is necessary to provide a good correspondence between the different cores of interest.

In this study, we make good use of water stable isotopes and major chemistry records from 9 firn core (20 to 40m deep) drilled at 3 sites (so called D47, Stop5 and Stop0) during the ASUMA campaign. These sites display a high mean accumulation rate of about 250 mm.weq/year and a wide range of environmental conditions with elevation ranging from 1550m to 2460m, distance from coast ranging from 103km to 423km and different katabatic winds influence. In particular, we use the Paleochrono probabilistic model with water stable isotopes signal and major chemistry records coupled with beta-gamma and RADAR data to obtain the best correspondence between the different cores. We then quantify to what extent the stacking of several cores enable to increase the signal to noise ratio at the different sites and can provide a faithful record to document variations of the temperature and/or atmospheric water cycle over the last decades in this region.