Asynchronous warming and δ18O evolution of deep Atlantic water masses during the last deglaciation Zhang, Jiaxu Liu, Zhengyu Brady, Esther C. Oppo, Delia W. Clark, Peter U. Jahn, Alexandra Marcott, Shaun A. Lindsay, Keith 2017-10-16T18:21:42Z 2017-08-21
dc.description Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 114 (2017): 11075-11080, doi: 10.1073/pnas.1704512114. en_US
dc.description.abstract 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 δ18O of benthic foraminiferal calcite (δ18Oc). Here we use an isotope-enabled ocean general circulation model with realistic geometry and forcing conditions to simulate the deglacial water mass and δ18O 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 due to freshwater input as suggested previously, the observed phasing difference of deep δ18Oc likely reflects early warming of the deep northern North Atlantic by ~1.4°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 mid-depth warming and enhanced downward heat flux via vertical mixing. Our results emphasize that the way ocean circulation affects heat, a dynamic tracer, is considerably different than how it affects passive tracers like δ18O, and call for caution when inferring water mass changes from δ18Oc records while assuming uniform changes in deep temperatures. en_US
dc.description.sponsorship This work is supported by the U.S. NSF P2C2 projects (1401778 and 1401802) and OCE projects (1600080 and 1566432), China NSFC 41630527, and the Wisconsin Alumni Research Foundation en_US
dc.language.iso en_US en_US
dc.subject Atlantic water masses en_US
dc.subject Last deglaciation en_US
dc.subject Oxygen isotopes en_US
dc.subject Deep ocean warming en_US
dc.title Asynchronous warming and δ18O evolution of deep Atlantic water masses during the last deglaciation en_US
dc.type Preprint en_US
dspace.entity.type Publication
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