Preprints
https://doi.org/10.5194/cp-2024-23
https://doi.org/10.5194/cp-2024-23
02 Apr 2024
 | 02 Apr 2024
Status: a revised version of this preprint is currently under review for the journal CP.

Shoaled glacial AMOC despite vigorous tidal Dissipation: Vertical Stratification matters

Yugeng Chen, Pengyang Song, Xianyao Chen, and Gerrit Lohmann

Abstract. During the Last Glacial Maximum (LGM), tidal dissipation was about threefold higher than today, which could have led to a considerable increase in vertical mixing. This would enhance the glacial Atlantic Meridional Overturning Circulation (AMOC), contradicting the shoaled AMOC as indicated by paleo proxies. Here, we conduct ocean model simulations to investigate the impact of background climate conditions and tidal mixing on the AMOC during LGM. We successfully reproduce the stratified ocean characteristic of the LGM by accurately simulating the elevated salinity of the deep sea and the rapid temperature decrease in the ocean's upper layers. Our findings indicate that show that the shoaled glacial AMOC is mainly due to strong glacial ocean stratification, irrespective of enhanced tidal dissipation. However, glacial tidal dissipation plays a critical role in the intensification of the AABW during the LGM. Given the critical role of AMOC in (de-)glacial climate evolution, our results highlight the complex interactions of ocean stratification and tidal dissipation that have been neglected so far.

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Yugeng Chen, Pengyang Song, Xianyao Chen, and Gerrit Lohmann

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Yugeng Chen, Pengyang Song, Xianyao Chen, and Gerrit Lohmann
Yugeng Chen, Pengyang Song, Xianyao Chen, and Gerrit Lohmann

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Short summary
Our study explores the LGM ocean circulation, specifically the AMOC. Despite stronger tidal forces during the LGM, we found that the AMOC remained shallow due to the ocean’s increased stratification. This contradicts previous beliefs that stronger tides would deepen the AMOC. Our findings are significant for understanding past climate changes and could inform future climate models. We used ocean model simulations to analyze the impact of tidal forces and stratification on the AMOC.