Unraveling tipping dynamics of marine biogeochemistry from past climate transitions

CO2 emissions are the primary driver of anthropogenic climate change, and it is thus vital to enhance our understanding of the global carbon cycle, its changes, internal processes, and feedbacks with Earth’s climate system. Climate change further threatens to push the Earth system across multiple tipping points, which could have significant, but yet unconstrained impacts on the carbon cycle. BGCTip will address these challenges by investigating the potentially cascading interactions of climate and ocean tipping points with marine biogeochemical systems that drive CO2-uptake. By leveraging the extensive information of Earth’s past abrupt climatic events of the last glacial cycle, BGCTip aims to decipher the triggers and feedback mechanisms that govern the complex relationship between climate and the carbon cycle. This will be achieved through a novel combination of methods that link proxy reconstructions with biogeochemical isotope modeling. An intermediate complexity Earth system model will be used and further developed capable of transiently simulating these past climate transitions. New isotope proxies (δ15N, δ30Si, δ138Ba, and δ60Ni), that trace various aspects of marine biogeochemistry, will be implemented in the model. For the first time, these new biogeochemical proxies will be employed together with ocean circulation proxies in a coherent model framework constrained by global compilations of proxy reconstructions. This will provide a comprehensive understanding of the impacts of past climate tipping on the biological pump and oceanic carbon uptake. Exploiting these paleo-constraints, the impact of tipping points will then be systematically assessed across the full range of available future climate scenarios.