The North Atlantic subpolar ocean dynamics during the past 21,000 years

IF 1.9 4区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Gagan Mandal , Amali I. Hettiarachchi , Shail V. Ekka
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Abstract

Numerous studies have suggested that the North Atlantic subpolar gyre (SPG), Atlantic Meridional Overturning Circulation (AMOC), and Arctic sea ice impact the polar and global climate. Here, we use a fully linked atmosphere-ocean-sea ice Earth system model to investigate the North Atlantic subpolar ocean dynamics over the last 21 thousand years before the present (ka). We found that the SPG strength, net ocean surface heat flux, and mixed layer depth in the North Atlantic deep convection sites declined during the Heinrich 1 (H1; ∼19–17 ka) and Younger Dryas (YD; ∼12.9–11.3 ka) cold events. Consequently, the deep convection and AMOC strength declined, reducing the northward meridional heat transport and causing the expansion of Atlantic sea ice coverage. We also found that the North Atlantic subpolar net ocean surface heat flux varied coherently with AMOC strength throughout the past 21 ka. Subsequently, we observed a sea ice-capping mechanism wherein an increase (decrease) in Atlantic sea ice coverage during H1/YD (Bølling-Allerød (BA; ∼17–14.35 ka)) reduces (increases) net ocean surface heat flux and deep convection, thereby influencing the AMOC strength. Meanwhile, the SPG and AMOC strengths have been in-phase throughout the past 21 ka, except during the abrupt termination and input of freshwater flux during the BA and Meltwater Pulse 1 A (∼14.4–13.9 ka) events, respectively. In conclusion, our study suggests that a sudden shift in freshwater discharge into the subpolar North Atlantic may disturb the polar ocean dynamics.

过去 21,000 年北大西洋次极地海洋动力学
大量研究表明,北大西洋副极地涡旋(SPG)、大西洋经向翻转环流(AMOC)和北极海冰影响着极地和全球气候。在此,我们利用大气-海洋-海冰完全关联的地球系统模式研究了距今 21000 年(ka)前北大西洋副极地海洋的动态变化。我们发现,在海因里希 1 期(H1;19-17 ka)和少干纪(YD;12.9-11.3 ka)寒冷事件期间,北大西洋深对流点的 SPG 强度、净海洋表面热通量和混合层深度下降。因此,深层对流和 AMOC 强度下降,减少了向北的经向热输送,导致大西洋海冰覆盖面积扩大。我们还发现,在过去的 21 ka 年中,北大西洋次极地海洋表面净热流量随 AMOC 强度的变化而变化。随后,我们观测到了海冰封盖机制,即H1/YD(Bølling-Allerød (BA; ∼17-14.35 ka))期间大西洋海冰覆盖面积的增加(减少)减少(增加)了净海洋表面热通量和深对流,从而影响了AMOC强度。同时,在过去的 21 ka 中,除了 BA 和融水脉冲 1 A(∼14.4-13.9 ka)事件期间淡水通量的突然终止和输入外,SPG 和 AMOC 的强度一直是同相位的。总之,我们的研究表明,北大西洋副极地淡水排放的突然转变可能会扰乱极地海洋动力学。
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来源期刊
Dynamics of Atmospheres and Oceans
Dynamics of Atmospheres and Oceans 地学-地球化学与地球物理
CiteScore
3.10
自引率
5.90%
发文量
43
审稿时长
>12 weeks
期刊介绍: Dynamics of Atmospheres and Oceans is an international journal for research related to the dynamical and physical processes governing atmospheres, oceans and climate. Authors are invited to submit articles, short contributions or scholarly reviews in the following areas: •Dynamic meteorology •Physical oceanography •Geophysical fluid dynamics •Climate variability and climate change •Atmosphere-ocean-biosphere-cryosphere interactions •Prediction and predictability •Scale interactions Papers of theoretical, computational, experimental and observational investigations are invited, particularly those that explore the fundamental nature - or bring together the interdisciplinary and multidisciplinary aspects - of dynamical and physical processes at all scales. Papers that explore air-sea interactions and the coupling between atmospheres, oceans, and other components of the climate system are particularly welcome.
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