Thesis on the study of sea ice through space observations (M/F)

Job Description

Thesis Subject

Understanding the dynamics of Antarctic sea ice and its interactions through high-resolution space-based observations

Antarctic sea ice plays a vital role in the climate due to its influence on albedo, ocean circulation, heat and carbon absorption, and the stability of ice shelves. Over the past decade, Antarctic sea ice has declined, reversing previous trends and aligning more closely with climate projections (Himmich et al., 2024). Yet the state of Antarctic sea ice and its key processes remain poorly characterised. Field observations reveal striking contrasts with the Arctic: heavy snowfall, interactions with icebergs and ice shelves, and ocean waves. As a result, climate models poorly simulate key Antarctic sea ice phenomena, such as seasonal cycling, thickness distribution, coastal ice, or polynyas. This limits our ability to predict or explain short-term events and long-term trends.
The SWOT mission (launched in October 2022) can help fill this gap. Its KaRIn SAR product resolves surface topography at 500 m per day, distinguishing between floes and channels, and recovering freeboard compatible with CryoSat-2 (Kacimi et al., 2025; Jestin et al., 2025), thus providing an unprecedented means of documenting changes in Antarctic sea ice thickness, floes and channels at fine spatio-temporal scales, in interaction with other elements of the Earth system.
This motivates the main question of this thesis: how can SWOT document the state of Antarctic sea ice and advance our understanding of how it works?
We have two main objectives:
1. Generate a one-year SWOT product (2024) including classification, concentration, freeboard and thickness of sea ice.

2. Analyse sea ice dynamics in the Amery Ice Shelf and Prydz Bay area.
Objective 1 assesses SWOT's ability to retrieve the state of Antarctic sea ice relative to existing products. Objective 2 explores SWOT's ability to describe small-scale sea ice processes.
The Amery Ice Shelf-Prydz Bay marine region was chosen because of the diversity of sea ice types and processes: fixed coastal ice, polynyas, drifting sea ice influenced by waves. Important climatic processes also occur in the region. Prydz Bay is one of four Antarctic sites of dense water formation, associated with two large polynyas, and is characterised by extensive fixed coastal ice anchored by grounded icebergs. The Amery Ice Shelf, the third largest in Antarctica, drains a large area of East Antarctica, which is essential to its stability. Finally, numerous in situ observations are available in the region.

Originality, strengths, impacts, risks
The project draws on LEGOS's solid expertise in sea ice remote sensing and LOCEAN's expertise in Antarctic sea ice physics, combining different approaches to observe and understand Antarctic sea ice processes. This thesis uniquely combines high-resolution SWOT observations with process-based regional analyses, such as small-scale interactions with icebergs, waves or coastal ice shelf break-up. This work will also provide the first SWOT algorithm for Antarctic sea ice characteristics, including classification, concentration, freeboard and thickness. The high spatial resolution and process-based focus of SWOT observations will provide information previously unattainable by other satellite missions. Key risks include uncertainty in snow depth, which affects the conversion of freeboard to thickness, and potential gaps in SWOT coverage. These will be addressed using multiple datasets, sensitivity analyses, and careful processing.
Conclusion and outlook
This thesis will produce the first SWOT product on Antarctic sea ice and assess its ability to capture small-scale processes, including interactions between waves and ice, between icebergs and sea ice, coastal ice and polynya dynamics. The resulting products will benefit both the sea ice and climate communities and address issues related to simulations of the future of Antarctic sea ice.

Your Work Environment

At LEGOS on a computer workstation

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.

CNRS

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