Lucie Germain

UMR CRBE

PhD student / Oct 2024 to Oct 2027

Impact of permafrost thaw on iron speciation and methane dynamics

My PhD research focuses on assessing the impact of permafrost thaw on iron speciation and its influence on methane dynamics in the Arctic. Climate warming is driving the degradation of permafrost, which contains large amounts of organic carbon. Iron–carbon interactions in soils play a key role in preserving this organic carbon by limiting its microbial degradation and its release as greenhouse gases. However, permafrost thaw also alters the hydrological connectivity between soils and surface waters, thereby modifying soil pH and redox conditions. The central question is therefore how these changes affect iron speciation and, consequently, its ability to stabilise organic carbon.

Ulysse Chabroux

ENS - PSL

PhD student / Sept 2025 to August 2028

Dynamics and stoichiometry of soil organic matter in thawing permafrost: an experimental approach

By the end of the century, permafrost will have almost entirely disappeared. Sub‑Arctic peatlands will experience a warmer and wetter climate, profoundly altering the soil–vegetation–water‑table system. This PhD project aims to investigate the future of peatlands affected by permafrost thaw through a combination of in situ and mesocosm experiments.

At the Stordalen peatland in Sweden, organic matter labelled with ¹³C and ¹⁵N will be incubated along a gradient of permafrost degradation. Tracking this labelled material will make it possible to understand the fate of fresh organic matter and to trace the forms of nitrogen produced and transported as a function of permafrost‑thaw stage.

Peat monoliths collected from the same peatland will also be incubated in different climate‑controlled chambers simulating either current or future Arctic conditions, with or without nitrogen fertilisation. This experimental setup will allow us to test the combined effects of nitrogen enrichment and the increasing mismatch between light and temperature regimes that sub‑Arctic peatlands are expected to experience in the coming decades.

Aliénor Allain

UMR CRBE

Postdoctoral researcher / Oct 2024 to Oct 2026

Characterisation and quantification of organic matter and nutrients in Arctic permafrost soils

My work involves the geochemical characterisation of both dissolved and solid phases in Arctic permafrost soils, with the aim of identifying the environmental and geochemical factors that control the spatial variability of organic‑matter and nutrient stocks.

Baptiste Emery

UMR GET

PhD student / Oct 2025 to Oct 2028

Carbon and metals in peat‑pond ice and the bioavailability of organic matter

In Arctic regions, rising temperatures are causing permafrost thaw and the formation of new water bodies. Elements previously stored in ice and frozen soils—such as nutrients (C, N, P, etc.) and metals—are then transferred into these aquatic systems. Once released, these elements can be taken up by organisms and contribute to greenhouse‑gas emissions. The objective of this PhD is to investigate their behaviour and their different phases within hydrosystems, in order to better understand the role of metal–organic‑matter associations, which may inhibit heterotrophic consumption.

This work includes field sampling in a Swedish peatland (Abisko) and freeze–thaw experiments designed to simulate natural cycles disrupted by climate change. The ice of small peat ponds remains poorly studied and may play a significant role in controlling the behaviour of these elements and the bioavailability of organic matter.

César Ciebiera

UMR GEOPS

PhD student / Oct 2025 to Oct 2028

Understanding the development of ice‑rich permafrost thaw in Canada

This PhD aims to improve our understanding of the ongoing development of permafrost thaw, from its initiation to the quantification of its progression. Two sites in Canada where ice‑rich permafrost is currently degrading will be studied: one in western Yukon and one in northern Manitoba. Summer field campaigns will provide essential data to constrain the spatio‑temporal dynamics of permafrost thaw, identify the key environmental and climatic parameters controlling thaw processes, and characterise the cryolithology of the permafrost.

The use of drones, geophysical methods, and long‑term on‑site instruments (temperature sensors, time‑lapse cameras, etc.) represents an innovative approach in these extreme environments. This work will contribute to a better understanding of the vulnerability and resilience of boreal ecosystems to surface disturbances.