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Emmanuelle Pucéat - Geochemist

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Emmanuelle Pucéat

Research fields of interest

My research interests concern the mechanisms governing the long-term evolution (> 1myr) of the Earth climate during ancient periods (Jurassic and Cretaceous).

In order to understand these processes, I have been using both geochemical proxies and climate models. The Cretaceous and Jurassic periods are of particular interest because they are punctuated by episodes of volcanism, of enhanced organic matter burial, of carbonate calcification crises and of fluctuations in seawater temperature. Understanding how these events are related to climate changes would help to better understand the processes governing the Earth climate. More specifically, the mid-Cretaceous period encountered one of the warmest intervals of the past 300 million years, with atmospheric CO2 concentrations possibly up to 10 times the modern one. If this period cannot be used as an analogue to predict the consequences of modern global warming, because of a markedly different continent-ocean configuration which affects the global climate system, it provides us with an example of an extreme greenhouse climate. Studying how this extreme greenhouse climate has been established, how the earth leaved this state, and how the climate system responds to perturbations in a warm interval is important to improve our knowledge of the climate system behavior.

To study the evolution of the climate system, I have been using both proxies of marine paleotemperatures (δ18O of both biogenic apatite forming fish teeth, or of bivalves) and proxies of past ocean circulation (neodymium isotope composition of seawater, inferred from fish remains, Fe-Mn oxydes, and carbonates leached from bulk rocks). Indeed, as oceanic circulation is part of the climate system it is essential for our understanding of climate change to track possible changes in oceanic circulation pattern during the main climate transitions depicted from paleotemperature proxies. In order to go a step beyond identification of the main thermal and oceanic circulation changes, I have also used climate models to test the scenarios inferred from geochemical proxies and get a more comprehensive view of the mechanisms driving the observed changes. I have either performed simulations myself using a climate model of intermediate complexity (CLIMBER-2) or collaborated with modellers when more complex models were required (like FOAM). One of the aims in coupling geochemical proxies of both marine paleotemperatures and oceanic circulation with climate model simulations is to better understand the role of modifications in the continent-ocean configuration and of opening or closing of ocean gateways on multi-million years time scale.

I am now begun to additionally work with proxies of continental weathering, as some changes in oceanic circulation linked to modifications of oceanic gateway and basin configuration are also associated to creation of topographic reliefs. Creation of relief is able to impact climate through atmospheric CO2 drawdown liked to enhanced silicate weathering. More specifically, I have begun to try applying the combined Lu-Hf and Sm-Nd system in clays to depict changes in continental weathering at a local scale for the Late Cretaceous period.


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