PhD Defense

Description of the past climatic variability at millenial and orbital timescales is essential to put the ongoing climate change in its context. Studying the sequence of events and relationships between hydrological cycle, biosphere, environment and climate permits to constrain the mechanisms and forcings at play. Such studies are the core of my research activity based on the measurements and modeling of isotopic proxies in the air (δ15N of N2, δ18O of O2, δ40Ar of Ar) and in the water (δ17O, δ18O, δD de H2O) of polar ice cores.

In this synthesis, I will begin with the study of the rapid climatic variability (millenial timescale) from ice cores: what amplitude of the temperature change for these events ? What are the links between the millenial variability and the background climatic state (ice sheets volume, orbital configuration) ? What is the sequence of events between Greenland and Antarctica ? How is initiated the rapid variability of the last glacial period ? Then, I will show how water isotopes and especially the new tracer δ17O permits to better constrain the links between climate and hydrological cycle : what retroactions between climate and hydrological cycle occur on large climatic transitions ? How climatic changes in the high latitudes and in the low latitudes (evaporative regions) are related ? Finally, I will show how the use of oxygen isotopes permits to obtain global information on the terrestrial biosphere repartition as well as on the evolution of global productivity with time.