Antarctic Circumpolar Current and ice sheet interactions

The Antarctic Circumpolar Current (ACC), flowing around the Antarctic continent, is the widest and most powerful ocean current on Earth. In addition to connect the three major ocean basins and to be a principal actor in the global thermohaline circulation and the regulation of marine ecosystems, the ACC plays a crucial role on the ocean-atmosphere CO2 exchange and the stability of the Antarctic ice sheet (AIS), which have a direct incidence on atmospheric greenhouse gases (GHG) and sea level, respectively. Despite its importance on the Earth´s climate system, the lack of long-term observations still prevents a robust assessment of the ACC evolution within the next decades, centuries and beyond. In this context, it is critical to improve our understanding of the ACC functioning and its interactions with the different Earth’s climatic compartments during past warm geological times when temperatures and CO2 concentrations were either similar to present-days or close to those predicted by the Intergovernmental Panel on Climate Change 2019 and discussed during the COP21 in Paris, 2015. The overarching objective of ACCION project is to study marine sediment sections from an international Ocean Drilling Program (ODP) site retrieved off the French Kerguelen Islands, on the main ACC pathway. Here we aim to scrutinise the evolution of the ACC since its onset, i.e. over the last 30 million years (Ma), with a special focus on the mid-Miocene and mid-Pliocene periods, corresponding to the modern and projected climatic conditions in terms of temperature and atmospheric GHG concentrations. We also aim to face changes in the ACC activities with the AIS extension in a way that we will better understand how the ACC affects the Antarctic ice cap and hence past sea level. Unquestionably, our results will provide crucial boundary conditions to climate models and considerably refine projections.