Scientific Researches | Gu Sifan publishes research results on the mechanism of the δ13C decrease in the mid-depth Atlantic during the last deglaciation Earth and Planetary Science Letters
Author:Sifan GU Redactor:Jie Wen Date:2021/07/24

Recently, Gu Sifan, the tenure-tracked assistant professor of Shanghai Jiao Tong University’s School of Oceanography (SJTU-SOO), published research paper titled "Remineralization dominating the δ13C decrease in the mid-depth Atlantic during the last deglaciation" as the first author and co-correspondence in the authoritative international geoscience journal Earth and Planetary Science Letters. 

The paper was completed by Assistant Professor Gu Sifan at SJTU-SOO in collaboration with Professor Liu Zhengyu at the Ohio State University, Scientist Delia Oppo at the Woods Hole Oceanographic Institute, Professor Jean Lynch-Stieglitz at Georgia Tech, and Academician Wu Lixin at Ocean University of China. 

δ13C records from the mid-depth Atlantic show a pronounced decrease during the Heinrich Stadial 1 (HS1), a deglacial episode of dramatically weakened Atlantic Meridional Ocean Circulation (AMOC). Proposed explanations for this mid-depth decrease include a greater fraction of δ13C-depleted southern sourced water (SSW), a δ13C decrease in the North Atlantic Deep Water (NADW) end-member, and accumulation of the respired organic carbon. However, the relative importance of these proposed mechanisms cannot be quantitatively constrained from current available observations alone. Therefore, the individual contributions to the deglacial Atlantic mid-depth δ13C change from these mechanisms are examined in a transient simulation with carbon isotopes and idealized tracers. The results suggest that although the fraction of the low-δ13C SSW increases in response to a weaker AMOC during HS1, the water mass mixture change only plays a minor role in the mid-depth Atlantic δ13Cdecrease. Instead, increased remineralization due to the AMOC-induced mid-depth ocean ventilation decrease is the dominant cause. In this study, the deep end-members, which are assigned to deep water regions used in previous paleoceanography studies, is differentiated from the surface end-members, which are from the near-surface water defined from the physical origin of deep water masses. The decomposition of the deep NADW end-member suggests that it includes additional remineralized material accumulated when sinking from the surface (surface NADW end-member). Therefore, the surface end-members should be used in diagnosing mechanisms of δ13C changes. Furthermore, remineralization in the surface end-member is more critical than the remineralization along the transport pathway from the near-surface formation region to the deep ocean, especially during the early deglaciation.

 


Sifan Gu received the bachelor’s degree in Atmospheric Science at Peking University in 2012, and Ph.D. degree in Atmospheric and Oceanic Sciences at University of Wisconsin Madison in 2018. She worked as a Postdoctoral Research Associate (2018-2020) at Ocean University of China. She joined SJTU-SOO in June 2020 as a tenure-traced Assistant Professor. Her research interest lies in: paleoceanography and isotope modeling, and Atlantic Meridional Overturning Circulation under different climate conditions. 

Link to the paper:
https://doi.org/10.1016/j.epsl.2021.117106

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