PhD Opportunity at Laboratoire des Sciences du Climat et de l'Environnement, Paris, France

We are looking for a student willing to undertake a doctoral research project in ice core interpretation. The fully funded PhD position will analyse snow and ice samples from Antarctica to understand how the climatic signal is archived in the water isotopic composition. Applicants require a background in the field of Earth Sciences, strong skills in appropriate programming languages such as python or matlab and interest in analytical work. The successful candidate will undertake research on (1) recent snow profiles to study how the signal has been archived over the last 20 years, and (2) sections of the EPICA Dome C ice core to evaluate the high resolution variability over the last deglaciation.

Water isotopes in ice core records from Antarctica are a favoured proxy to study past temperature changes. The interpretation of water isotopes, based on empirical laws, enabled to reconstruct past temperature changes over the last 800 000 years (EPICA, 2004) thanks to extremely cold conditions, as well as low amount of snowfall which provided favourable conditions for very old ice to accumulate. These low precipitation amounts also leave snow layers exposed to the atmosphere for longer period, during which wind and sublimation/condensation can occur. This can lead to an alternation of the isotopic signal, in particular for high frequency variability stored in the isotopic composition (interannual to decadal) (Casado et al., 2018, 2020, 2021). In order to study the climatic signal archived in the water isotopes at high resolution, it is necessary to take into account the impact of these surface processes on the isotopic signal.

The site of Dome C (French-Italian station Concordia), where the EPICA Dome C 800 000-year old ice core has been drilled, is one of these low accumulation sites. To interpret the signal stored in the Dome C ice core, it is crucial to evaluate the impact of the surface processes, due to the large contribution of exchanges between the snow and the atmosphere to the local surface mass balance compared to the precipitation amount. This is why for almost 10 years, samples of precipitation, surface snow, and summer monitoring of the vapour isotopic composition have been set up at the Concordia station. These measurements, coupled with an array of 32 vertical profiles in the firn (1.5m deep, encompassing roughly 20 years of snow accumulation) should provide the tools to evaluate the impact on the isotopic signal of the exchanges between the snow and the atmosphere, the redistribution of snow by the wind, and snow metamorphism.

The goal of this thesis is to determine the transfer function which links the temperature signal to the isotopic composition stored in (i) precipitation, (ii) surface snow, and (iii) ice cores. These results will be used to
improve the precision of past temperature reconstruction at high resolution over the last 2000 years at first. Then, we will extend these results to climate variability stored in the isotopic signal in glacial period, when accumulation was even lower than presently, and, as a result, the contribution of precipitation to the surface mass balance even less favourable to the preservation of the climatic signal.

The proposed strategy relies on data acquired over the continuum from vapour to precipitation to surface snow to buried snow at Dome C. Most of the samples are already available and should be measured during the thesis. The analysis of the data will use statistical and modelling tools that the applicant will have to modify to suit the interpretation of the results. The applicant will use an ice core proxy system model which already exist, and in which he will have to add parametrisations for the exchanges between the snow and the atmosphere. The selected applicant should have strong skills in Physics and/or Earth Science, some background in coding (matlab/R/python), and interest for paleoclimate. They will benefit from technical support for the various analysis of the samples, and of the results.

This project targets a student interested by paleoclimate studies with strong basis in Physics and/or Geosciences. Strong teamwork skills will be required with collaborations outside of LSCE in France or abroad. A proficient English level is needed (French optional). This is a 3-year appointment offering a competitive salary along with benefits, supported by grants from the CEA.

Applications (cover letter and CV) and informal inquires should be sent to Dr. Mathieu Casado (This email address is being protected from spambots. You need JavaScript enabled to view it.). All applications are welcome!

Closing date: 30 April 2023, 5pm UTC (Zoom interviews will start the first week of May)