GLACIAL NORTHEAST ATLANTIC SURFACE-WATER P(CO2) - PRODUCTIVITY AND DEEP-WATER FORMATION

The carbon isotopic composition of bound organic material within the c rystal lattice of planktonic foraminiferal calcite is a valuable proxy for the isotopic composition of primary photosynthate in surface wate rs. This proxy can be used to estimate P-CO2 in the surface waters of the northeast Atlantic during the last glacial period, if combined wit h data on the carbon isotopic composition of foraminiferal calcite. Ou r first estimates of surface water p(CO2) at the location of Biogeoche mical Ocean Flux Studies Core 5K (50 degrees 41.3'N, 21 degrees 51.9'W ) indicate that this region was probably a more important sink for CO2 during the glacial than during the Holocene. This increased sink coul d not have been caused by local high primary productivity, because gla cial primary productivity as estimated from benthic foraminiferal data was extremely low at 5K. We thus conclude that the enhanced sink at t hese latitudes resulted from increased convection of surface water to intermediate or greater depths, i.e. from the southward shift of an im portant centre of deep-intermediate water formation, as confirmed by c omputer simulation. (C) 1997 Elsevier Science B.V.