Cadmium/calcium and carbon isotope reconstructions of the glacial northeast Atlantic Ocean

Abstract

The δ 13 C and Cd measurements from benthic foraminifera from Biogeochemical Ocean Flux Study (BOFS) northeast Atlantic Ocean sediment cores are presented. The δ 13 C values in glacial foraminifera are consistent with those from elsewhere in the North Atlantic Ocean. For intermediate water (1000–2000 m water depth), δ 13 C values were higher at the last glacial maximum than in present North Atlantic Deep Water (NADW), whereas for deep water (>2000 m) they were lower during the glacial maximum. The Cd concentrations of glacial northeast Atlantic intermediate water were lower than those of present NADW. However, deepwater Cd concentrations increased to values between NADW and present Pacific Deep Water (PDW). The δ 13 C and Cd data are consistent and show that the northeast Atlantic Ocean was strongly stratified with 13 C enriched, low Cd intermediate water overlying 13 C depleted, high Cd deep water. The glacial water column comprised two different water masses: deep water, similar in character to present Antarctic Bottom Water (AABW), and intermediate water, different in character from both AABW and NADW, and any present intermediate‐depth North Atlantic water. The characteristics of glacial intermediate water were, however, similar to present near‐surface waters in the North Atlantic, which suggests rapid ventilation of the glacial ocean to depths of up to 2000 m by cold, nutrient‐depleted young surface waters.