Insights into past climate variability can help constrain the climate system’s response to external forcing and future projections. Paleoclimate data offer empirical estimates of large-scale, pre-human climate changes across various timescales, including glacial-interglacial transitions occurring every ~100,000 years over the past million years. Such data can estimate ice cap melting rates and investigate “tipping point” events with rapid and significant climate shifts
Among paleo archives, deep polar ice cores are unique, providing records of ancient atmospheric composition, snowfall, and temperature. My PhD focused on the EPICA Dome C (EDC) drilling site in East Antarctica, the oldest continuous ice core record, documenting climate change across timescales up to 800,000 years.
While water isotopes are typically used to infer past temperatures from ice cores, we demonstrate that δ¹⁵N of N2 in air bubbles can also be a valuable indicator, reflecting the depth of bubble enclosure influenced by surface temperature and snow accumulation. A new δ¹⁵N of N2 record over the last 800,000 years clarifies the timing between atmospheric CO₂ and Antarctic climate changes during deglaciations. Additionally, I developed a refined timescale for five deep ice cores, known as the Antarctic Ice Core Chronology (AICC) 2023, reducing EDC age scale uncertainty from 1,700 to 900 years. This chronology better aligns with other paleo archives and improves the identification of climatic event sequences, like changes in insolation, greenhouse gases, sea level, and temperatures.
Our preliminary study suggests atmospheric CO₂ led sea level in six of the last seven deglaciations. Further research is needed to understand the causal relationships between external forcing and climate response. My work combined glaciological and statistical modeling with analysis of EDC air samples and other paleo records, advancing climate reconstructions, reducing dating uncertainties, and refining chronological frameworks for better understanding of Earth’s climate system during glacial-interglacial transitions.
04/10/2024 – PhD defense of Marie Bouchet directed by Amaëlle Landais and Frédéric Parrenin