Calculating surface water pCO(2) from foraminiferal organic delta C-13

The delta(13)C Of organic matter bound within the crystal lattice of foraminiferal calcite tests may provide a potential tracer of the isotopic composition of the surface water primary photosynthate. Using delta(13)C of the organic matter extracted from the crystal lattice and the calcite test, it is theoretically possible to estimate the paleo-surface water pCO(2). We have tailored this technique initially for the subpolar planktonic foraminifera species Globigerina bulloides. Initial surface water pCO(2) estimates from deepsea core BOFS 5K (50 degrees 41.3'N, 21 degrees 51,9'W, water depth 3547 m) indicate that the northeast Atlantic Ocean may have been a greater sink for CO2 during the last glacial than during the Holocene. Greatly reduced benthic foraminifera abundances, especially phytodetritus feeders, in BOFS 5K during the last glacial indicates low surface productivity. This rules out a productivity-driven CO2 sink. The enhanced glacial CO2 sink must, therefore, have results from a southwards shift of the centre of deep water formation.