Humans are a dominant component of the Earth System. Yet the study of human and natural systems are typically carried out separately. The BIGSEA project aims to develop fundamentally new approaches for quantifying the interactions between human and natural components of the Earth System. Based in Barcelona, BIGSEA will build a unique integrated understanding of the coupled relationships between ocean chemistry, phytoplankton, animals, fishing activity and society, within an Earth System model framework. The work will be advanced through data analysis, the development of new theory and the application of numerical models. Three PhD fellowships and three postdoctoral fellowships are available for highly motivated candidates with excellent track records and strong quantitative skills.