Deep ocean 14C ventilation age reconstructions from the Arctic Mediterranean reassessed

• Published in: Earth and planetary science letters Vol. 518; pp. 67 - 75
• Main Authors: Ezat, Mohamed M., Rasmussen, Tine L., Skinner, Luke C., Zamelczyk, Katarzyna
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.07.2019; Elsevier
• Subjects: Arctic Ocean; Fram Strait; Geofag: 450; Geosciences: 450; last glacial climate; Matematikk og Naturvitenskap: 400; Mathematics and natural science: 400; Nordic Seas; ocean circulation; radiocarbon; VDP; last glacial climate; Arctic Ocean; radiocarbon; Nordic Seas; Fram Strait; ocean circulation
• ISSN: 0012-821X; 1385-013X; 1385-013X
• DOI: 10.1016/j.epsl.2019.04.027

The present-day ocean ventilation in the Arctic Mediterranean (Nordic Seas and Arctic Ocean), via transformation of northward inflowing warm Atlantic surface water into cold deep water, affects regional climate, atmospheric circulation and carbon storage in the deep ocean. Here we study the glacial evolution of the Arctic Mediterranean circulation and its influence on glacial climate using radiocarbon reservoir-age reconstructions on deep-sea cores from the Fram Strait that cover the late glacial period (33,000–20,000 yr ago; 33–20 ka). Our results show high Benthic-Planktic 14C age differences of ∼1500 14C years 33–26.5 ka suggesting significant water column stratification between ∼100–2600 m water depth, and reduction and/or shoaling of deep-water formation. This phase was followed by break-up of the stratification during the Last Glacial Maximum (LGM; 26–20 ka), with Benthic-Planktic 14C age differences of ∼250 14C years, likely due to enhanced upwelling. These ocean circulation changes potentially contributed to the final intensification phase of glaciation via positive cryosphere-atmosphere-ocean circulation-carbon cycle feedbacks. Our data also do not support ‘extreme aging’ of >6000 14C years in the deep Arctic Mediterranean, and appear to rule out the proposed outflow of very old Arctic Ocean water to the Nordic Seas during the LGM and to the subpolar North Atlantic Ocean during the deglacial period. •Strong ocean stratification in the Fram Strait during the late glacial (33–26 ka).•Breakup of ocean stratification during the LGM (26–20 ka) due to enhanced upwelling.•No extreme aging of >6000 yr in the Arctic Mediterranean as previously suggested.