edu.ucar.opensky::articles:21121 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T02:22:30.722908 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7w66p9v Asynchronous warming and δ18O evolution of deep Atlantic water masses during the last deglaciation 2017-10-02T00:00:00Z publication https://n2t.org/ark:/85065/d7w66p9v https://doi.org/10.1073/pnas.1704512114 Zhang, J. author Liu, Z. author Brady, Esther C. author Oppo, D. W. author Clark, P. U. author Jahn, A. author Marcott, S. A. author Lindsay, Keith author UCAR/NCAR - Library publisher The large-scale reorganization of deep ocean circulation in the Atlantic involving changes in North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) played a critical role in regulating hemispheric and global climate during the last deglaciation. However, changes in the relative contributions of NADW and AABW and their properties are poorly constrained by marine records, including delta O-18 of benthic foraminiferal calcite (delta O-18(c)) . Here, we use an isotope-enabled ocean general circulation model with realistic geometry and forcing conditions to simulate the deglacial water mass and delta O-18 evolution. Model results suggest that, in response to North Atlantic freshwater forcing during the early phase of the last deglaciation, NADW nearly collapses, while AABW mildly weakens. Rather than reflecting changes in NADW or AABW properties caused by freshwater input as suggested previously, the observed phasing difference of deep delta O-18(c) likely reflects early warming of the deep northern North Atlantic by similar to 1.4 degrees C, while deep Southern Ocean temperature remains largely unchanged. We propose a thermodynamic mechanism to explain the early warming in the North Atlantic, featuring a strong middepth warming and enhanced downward heat flux via vertical mixing. Our results emphasize that the way that ocean circulation affects heat, a dynamic tracer, is considerably different from how it affects passive tracers, like delta O-18, and call for caution when inferring water mass changes from delta O-18(c) records while assuming uniform changes in deep temperatures. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright 2017 Author(s). Published under license by the National Academy of Sciences. None eng geoscientificInformation