Transient overturning changes cause an upper-ocean nutrient decline in a warming climate
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1.
California Institute of Technology
Abstract
Models and proxy data suggest multi-centennial nutrient reorganization and biological productivity changes under sustained climate warming. These changes have traditionally been attributed to processes in the Southern Ocean. Here we instead show that transient overturning circulation adjustments, associated with changes in the Atlantic Meridional Overturning Circulation (AMOC), dominate the global nutrient reorganization on centennial timescales. Following an AMOC weakening, a typical feature of a warming climate, a transient overturning circulation develops in the Indo-Pacific basins, characterized by enhanced southward transport in the deep ocean. Coupled with the vertical nutrient structure, these transient overturning changes produce a net transport of nutrients from the Indo-Pacific into the Southern Ocean. Meanwhile, isopycnal surfaces deepen and bring nutrient-depleted waters to greater depths, causing nutrient concentrations to decline in much of the global upper ocean. Given the close link between nutrients and carbon, our findings suggest that transient overturning circulation changes across different basins can critically affect the marine carbon cycle.
Copyright and License
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Acknowledgement
Without implying their endorsement, we are grateful for helpful discussions with Daniel Sigman, Jess Adkins, Keith Moore, Frankie Pavia, and Ariane Verdy. J.Y. acknowledges support from NSF China (42330403, 42076056). A.F.T. was supported by NSF OCE-2023259, the Resnick Sustainability Institute, and the David and Lucille Packard Foundation.
Data Availability
The CESM2 model output was downloaded from the Earth System Grid Federation node (https://esgf-node.llnl.gov/search/cmip6/). The climatological Si data used in creating Fig. 1 were downloaded from GLODAPv2 (https://glodap.info/). Source data for Figs. 2–4 are provided in this paper. Model outputs from the MITgcm experiments are made publicly available from the online open access repository, Figshare, with https://doi.org/10.6084/m9.figshare.26787751. Source data are provided in this paper.
Code Availability
The code for reproducing the ocean-biogeochemical experiments in this study is made publicly available from the online open-access repository, Figshare, with https://doi.org/10.6084/m9.figshare.26129629.
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Additional details
- National Science Foundation
- OCE-2023259
- Resnick Sustainability Institute
- David and Lucile Packard Foundation
- Accepted
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2024-08-29Accepted
- Available
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2024-09-04Published online
- Publication Status
- Published