{"id":27210,"date":"2025-03-25T15:39:01","date_gmt":"2025-03-25T14:39:01","guid":{"rendered":"https:\/\/www.cerege.fr\/?page_id=27210"},"modified":"2025-04-08T16:56:01","modified_gmt":"2025-04-08T14:56:01","slug":"focus-joanna-charton","status":"publish","type":"page","link":"https:\/\/www.cerege.fr\/en\/accueil-cerege\/focus-joanna-charton\/","title":{"rendered":"FOCUS Joanna CHARTON"},"content":{"rendered":"
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FOCUS | Joanna Charton<\/h1>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Postdoctoral researcher in glacial geomorphology and geochemistry at the Lamont-Doherty Earth Observatory<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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A former doctoral student at CEREGE, she specialises in the study of past palaeo-glaciers to better understand their evolution and their interaction with climate in the past, present and future. Her atypical career path, which began with literary studies, has led her to explore the natural archives of glacial environments, from the Alps to Kerguelen, via the Great Caucasus and now Greenland.<\/b><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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An unusual career path: nothing predestined her to study glaciers!\u00a0<\/h2>

My relationship with climate science and glacial geomorphology - if I may say so - has not really been a direct one. A few years ago, I discovered the work of Claude Lorius, who played a major role in the discovery of fossil air bubbles trapped in Antarctic ice cores. Although it may sound clich\u00e9, this discovery deeply inspired me and motivated me to work in this field. From that moment on, I knew that I wanted, in my own small way, to contribute to tracing the history of glaciers and climate. My only problem at the time - and it was a big one - was that I was studying for a double degree in History and Geography at Panth\u00e9on Sorbonne (Paris I), with only a literary baccalaur\u00e9at and a hypokh\u00e2gne in my pocket. In short, a literary background that put aside the fundamental scientific disciplines early on in my school career.<\/p>

Determined to change my career path, I contacted Vincent Jomelli<\/a>CNRS researcher at CEREGE specialising in glacial geomorphology, and landed my first research placement studying Greenland's palaeo-glaciers. These initial investigations piqued my interest and led me to delve deeper into the question of cosmogenic dating. In this vein, I was soon co-supervised by Irene Schimmelpfennig<\/a>a CNRS research fellow at CEREGE, for the geochemistry part. Thanks to their invaluable help, as well as to my hard work and determination, I was able to join the amU Master STPE<\/a>I then obtained a ministerial grant to carry out a thesis at the CEREGE. CEREGE's Climate team<\/a> under their supervision. My time at CEREGE was therefore decisive in my academic career, and taught me a great deal at both analytical and scientific levels.<\/p>

Why study glaciers of the past?<\/h2>

The main aim of my research is to retrace the evolution of glaciers over time scales of hundreds and thousands of years in order to understand their past history and their relationship with the climate, in an environment that was not influenced by human activity. Understanding this evolution is vital today, particularly for assessing the current retreat of glaciers and the link with climate change. Studying the interactions between glaciers and climate provides us with valuable keys to understanding current changes and anticipating future developments.<\/p>

So, to explore glaciers in the past, we are interested in the traces left in the landscape by their passage: the glacial geological archive. Glaciers are powerful erosive agents: as they flow, they tear off pieces of rock from their beds and carry them away. When they retreat, these rocks are left behind in the landscape in the form of rocky debris known as moraines, or isolated, scattered blocks known as erratic boulders. Our role as geomorphologists is to decipher this landscape in order to understand the geomorphological processes behind these formations over time.<\/p>

Boulders transported by glaciers can then be dated using the cosmogenic isotopes produced in the rock. The concentration of cosmogenic isotopes is proportional to the time the rock is exposed to cosmic radiation after deglaciation. So, by measuring the concentration of cosmogenic isotopes on the surface of rocks, we can obtain information about when the glacier began to retreat.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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Franco-South African team on a field mission in the French Alps at the St Sorlin glacier site<\/em><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Valley of the Shkhara glacier, Georgia (\u00a9Vincent Jomelli)<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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Sampling glacier rock deposits in the French Alps<\/em> (\u00a9Thibaut Vergoz<\/a>)<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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Field and laboratory work in glacial geomorphology<\/h2>

To measure the concentration of cosmogenic isotopes, you first have to go out into the field to collect surface rock samples from glacial morphologies (such as moraine blocks, erratic blocks and boulders). During my thesis at CEREGE, the COVID-19 pandemic prevented me from taking part in a mission to the Kerguelen Archipelago. However, I did have the opportunity to do some fieldwork in the French Alps (see for example Charton et al,<\/em> 2021<\/a>) and to carry out four missions in the Greater Caucasus, mainly in Russia and Georgia, as part of the International \"Deglaciation in the Greater Caucasus\" project<\/a>led by the CNRS (PI: Vincent Jomelli). With peaks over 5,000 metres high, the Greater Caucasus is a sparsely urbanised mountainous region, making it an ideal terrain for geomorphologists. As well as the scientific analysis of the evolution of glaciers in these vast territories, this is a human experience: we often stay with local people or in tents at the foot of the glaciers, where we interact with local communities and meet shepherds on horseback. On the margins of the glaciers we study, we take kilos of rock samples, which we then take back to France in our suitcases. Once the samples arrive at CEREGE, they are crushed and then completely dissolved in acids in LN's dedicated laboratories.2<\/sub>C (Laboratoire National des Nucl\u00e9ides Cosmog\u00e9niques) to extract the cosmogenic isotope of our choice. The concentration of cosmogenic nuclides is then measured on the accelerator mass spectrometer and by the ASTER team<\/a>.<\/p>

The Kerguelen Archipelago: a checkpoint in the Southern Ocean\u00a0<\/h2>

My thesis research focused mainly on reconstructing the chronology of glaciers in the Kerguelen Archipelago (49\u00b0S, 69\u00b0E) and understanding the associated palaeoclimates over the last 40,000 years using cosmogenic nuclides. This research is part of the ANR MARGO projects<\/a>Les Envahisseurs (LabEx Dynamite) and LEFE Glacepreker. Located in the southern Indian Ocean, this French territory is a unique observatory for studying the evolution of glaciers, as it is one of the few areas to contain numerous glacial morphologies dating back to ancient times. Interestingly, the archipelago is also home to the Amp\u00e8re glacier, France's largest glacier. The results of my research, presented at my thesis defence on 7 May 2024, highlighted several original points:<\/p>