To accurately project the consequences of anthropogenic carbon cycle perturbations, it is vital to first understand the fluctuations and variability of the natural sinks and sources of the Earth’s carbon cycle. This requires accurate reconstruction of the oceanic carbonate chemistry because changes in the carbon storage in the deep ocean are the key to explain the glacial/interglacial atmospheric CO2 variations observed in ice core records. Herein, we propose to quantify the processes that led to the ca. 100ppmv increase in atmospheric pCO2 over the glacial/interglacial transition. Processes in the Southern Ocean, where most of the deep water is ventilated, are suspected to play a central role in this regard. It is believed that the sluggish glacial ocean could store more carbon, and that increased stratification reduced carbon leakage from the Southern Ocean back to the atmosphere. During the deglaciation, this deep ocean carbon “capacitor” becomes reconnected with the atmosphere and leads to rapid CO2 outgassing. To date, all of this remains hypothetical, and not proven by direct reconstructions of the glacial/interglacial carbonate chemistry evolution. The overarching goal of our proposal is to analyse two independent carbonate chemistry proxies on benthic and planktonic foraminiferal tests from sediment cores recording the last G/IG transition in order to quantify natural CO2 outgassing and contribute to a better understanding of natural carbon storage and release.
The effect of human activities are particularly visible in the so-called “Critical Zone” of the Earth surface, which is the thin veneer between rocks and the sky, and which forms the basis for the habitability of our planet and for the development of civilisation. Within this Critical Zone, water and soils are two resources that are essential for mankind. However, these resources are under great threat because of the global climate and land use changes. With this project, we will lead an ambitious study of the sediments of the largest Chinese rivers. China is drained by many very large river basins flowing eastward and covering a large range of climatic conditions from North to South. These rivers collect the material exported by the Critical Zone (water, organic carbon, and particles formed in soils) over large areas. We aim to test the ability of the sediment transported by rivers to provide integrated information on the environmental status of the regions drained by these rivers. Although large river products somehow “average out” over the area of the drainage basin the effects of different settings such as soils, floodplains, or dams, they provide fundamental, first-order information and reflect what is transported from continental surfaces to estuaries and coastal oceans.