Background

The scientific rationale can be summarized as follows:



• The most recent global models of ocean carbon cycling include representations of ecosystem processes, which are now seen as vital to a better understanding of basin-scale sources and sinks of CO2, and of the feedbacks from climate change to atmospheric CO2. Yet these representations are currently primitive (especially in terms of the characterization of marine plankton functional types, PFTs) and many potential biogeophysical and biogeochemical feedbacks have not been incorporated.
  
  

• Major advances in observational and experimental ocean biogeochemistry have taken place during recent years, leading to a greatly improved understanding of marine ecosystems at a local scale. Yet understanding of the basin- and global-scale controls on ocean ecosystem function is lagging, because biological process understanding has generally not been integrated into the broader context of ocean circulation and external nutrient supplies.
  
  

• The control of atmospheric CO2 content on glacial-interglacial time scales has emerged as a key Earth system issue, potentially involving orbital forcing of sea ice and SSTs, climate effects on the distribution of PFTs, changes in the supply of Fe and Si to marine ecosystems, and the natural control of the atmospheric sulphur cycle. Improved understanding of this question will require a multidisciplinary approach utilizing linked physical-biological models and a broad spectrum of paleo-data, including bio-markers and other sedimentary proxies for ecosystem composition and productivity.