OC3 scientific goals

Stable carbon isotopes (δ13C) are routinely measured on shells of fossil benthic (deep dwelling) and planktonic (near surface) foraminifera and have been used for a long time as a proxy to infer both carbon cycling as well as deep ocean circulation in the past. A large number of data has therefore been measured. However, δ13C is determined by air-sea gas exchange as well as by biological processes, which has made unequivocal interpretations difficult. Moreover, a global assessment of how reliably different species of foraminifera represent the water column has not been undertaken. These difficulties may have led to many measurements being unpublished and unreported. Fortunately, in recent years, process based models including δ13C have been developed and a new global dataset of water column δ13C measurements has been compiled.

Here we propose a project to synthesize δ13C data from both benthic and planktonic foraminifera including unpublished and unreported data. Coretop data will be carefully compared to the water column measurements and errors and biases will be documented. Planktonic δ13C data will be calibrated using species specific equations. Downcore data will reveal changes in ocean circulation and carbon cycling and will be useful for comparison with other paleo data (e.g. from ice cores or speleothems) and transient model simulations. Focus of the downcore compilation will be on the last glacial cycle and in particular on the last deglaciation.

Specific science questions addressed are:

How did the deep ocean circulation change during the last deglaciation?

How did ocean carbon cycling and storage change during the last deglaciation?

How did deglacial changes in ocean circulation and carbon cycle affect climate and atmospheric CO2?


poster OC3 agu15