M/F PhD student in geosciences : Evolution of Himalayan glaciers during the Holocene based on cosmogenic dating and glacier modelling

Job Description

Thesis Subject

Our understanding of the evolution of Himalayan glaciers during the Holocene (the last 11,700 years) primarily relies on the dating of moraines and glaciological modeling forced by climate model outputs (Owen et al., 2005, 2009; Murari et al., 2014; Saha et al., 2019a). To date, we have a few hundred cosmogenic ages collected from the margins of around sixty glaciers in the Himalayas (see, for example, Saha et al., 2019b; Hornsey et al., 2022; Jomelli et al., 2022, 2024).
In parallel, glaciological studies conducted in recent years across the entire mountain range reveal strong spatial variability in surface mass balance (SMB), which depends on the glaciers' varying sensitivity to temperature and precipitation changes (e.g., Sakai and Fujita, 2012), combined with the non-negligible influence of geomorphological variables such as the average elevation of the catchment area, the presence of rock debris, or the type of terminus (e.g., Brun et al., 2019). However, this spatial variability in SMB is still poorly accounted for in paleo studies.
Furthermore, our knowledge of Holocene climate at high altitudes remains very limited (Jomelli et al., 2022). Monsoon proxies located at low altitudes show no direct links with glacier evolution and rarely align with climate model outputs. These models also exhibit biases due to the omission of certain physical processes, and their spatial resolution is often too coarse to be functional at the glacier scale (Braconnot et al., 2019; Cretat et al., 2020).
During this PhD, the candidate will study the relationships between high-altitude climate, geomorphological context, and glacier evolution during the Holocene in the southern Himalayan range (India, Nepal, Bhutan), relying on glacial chronologies and climate model outputs. The work will be divided into two consecutive phases:
The first phase, following familiarization with the data, will involve proposing—by climatically homogeneous region—an evolution of glaciers based on glacier types and geomorphological context throughout the Holocene. The student will use existing data as well as their own. In this initial phase, the candidate will aim to document the maximum glacier extent by region, glacier type, and their context, and then describe their evolution up to the most recent centuries.
The second, more advanced phase will focus on investigating the climatic causes and associated external forcings. This will initially involve large-scale analysis using General Circulation Model (GCM) outputs, followed by forcing a glaciological model through parameter perturbation experiments. The student will benefit from outputs of the IPSL model and sensitivity tests developed as part of the CIME project.
It is expected that the results will be published in the form of two or three articles, depending on the project's progress (the first on the spatiotemporal variability of glaciers, the second on the specificity of debris-covered glaciers, and the last on climate-glacier relationships at both local and large scales), as well as participation in one or two international conferences, such as the EGU General Assembly.

Your Work Environment

The thesis will rely on a multidisciplinary approach combining geochemical analyses, statistical methods, and glacio-climatic modeling. The main objectives are:
• Document the extent of glaciers over time using moraine dating and reconstruct the evolution of the glacier fronts of the studied glaciers using a statistical model.
• Identify and quantify the influence of geomorphological factors (elevation, slope, aspect, debris cover) on the long-term evolution of glaciers.
• Compare the long-term evolution of glaciers based on their degree of sensitivity to climate.
• Calibrate the OGGM glaciological model for present-day conditions and simulate the recent behavior of selected studied glaciers.
• Simulate glacier behavior throughout the Holocene using available climate model outputs.
• Conduct sensitivity tests using perturbed synthetic climates.
• Identify and rank the internal and external forcings influencing the evolution of these glaciers.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

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