Evidence from the North Eastern Atlantic basin for variability of the Meridional Overturning Circulation through the last deglaciation

• Published in: Earth and Planetary Science Letters
• Main Authors: Gherardi, J. M., Labeyrie, L., McManus, J. F., Francois, R., Skinner, L. C., Cortijo, E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2005
• Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems; Rockall Plateau; Fennoscandian; Labrador Sea; North Atlantic
• Online Access: http://eprints.esc.cam.ac.uk/1651/; http://eprints.esc.cam.ac.uk/1651/1/GherardiEPSL240,3-4%282005%29.pdf; https://doi.org/10.1016/j.epsl.2005.09.061

A first study from the subtropical western Atlantic, using 231Pa/230Th ratios as a kinematic proxy for deep water circulation, provided compelling evidence for a strong link between climate and the rate of Meridional Overturning Circulation (MOC) over the last deglaciation. However, these results warrant confirmation from additional locations and water depths because the interpretation of the sedimentary 231Pa/230Th ratio in terms of circulation vigor can be biased by variations in particle flux and composition. We have measured 231Pa/230Th in a core from the Iberian margin, in the Northeastern Atlantic basin, and have compared these new results to the data from the western Atlantic basin. We find that the reduction in the circulation during H1 and YD and the subsequent increases first recognized in the sediment deposited on Bermuda Rise are also evident in the eastern basin, in a totally different sedimentary regime, confirming that sedimentary 231Pa/230Th ratios record basin-wide changes in deep water circulation. However, some differences between the eastern and western records are also recognized, providing preliminary evidence to differentiate between renewal rates in the two North Atlantic basins and between shallower and deeper overturning. Our results suggest the possible existence of two sources of Glacial North Atlantic Intermediate Deep Water (GNAIW), one in the south Labrador Sea and another west of Rockall Plateau. Both sources contributed to the meridional overturning but the two had different sensitivity to meltwater from the Laurentide and the Fennoscandian ice sheets during the deglaciation. These results indicate that additional information on the geometry and strength of the ventilation of the deep Atlantic can be obtained by contrasting the evolution of sediment 231Pa/230Th in different sections of the Atlantic Ocean.