Glacial-to-deglacial reservoir and ventilation ages on the southwest Iberian continental margin

Abstract

Detailed assessments of past changes in surface and deep ocean reservoir ages are required to obtain robust 14C-based chronologies of planktic foraminifera and provide insights into ocean circulation changes and the C cycle. Here, we use plateau tuning on foraminiferal 14C data from a sediment core retrieved from the ‘Shackleton Sites’, a benchmark region for paleoceanographic studies, to i) develop a high-resolution record of surface water reservoir ages, ii) estimate “raw” apparent ventilation ages at two bottom water depths (3150 and 2650 mwd), and iii) establish robust age control for the last 23 ka. Our results provide new insights into the rapid changes in surface and deep-ocean reservoir ages that occurred over the last glacial maximum and last deglaciation. Marine reservoir ages contrast with previous estimates, especially for the cold spell Heinrich Stadial 1, and primarily reflect short-term changes in local hydrography. Variations in ventilation age indicate the influence of 14C-depleted, southern-source deep waters and a marked deepening of the settling depth of the highly ventilated Mediterranean Outflow Water during some millennial-scale intervals, much farther than previously assumed.