Most state-of-art models project a reduced equatorial Pacific east-west temperature gradient and a weakened Walker circulation under global warming. However, the causes of this robust projection remain elusive. Here, we devise a series of slab ocean model experiments to diagnostically decompose the global warming response into the contributions from the direct carbon dioxide (CO2) forcing, sea ice changes, and regional ocean heat uptake. The CO2forcing dominates the Walker circulation slowdown through enhancing the tropical tropospheric stability. Antarctic sea ice changes and local ocean heat release are the dominant drivers for reduced zonal temperature gradient over the equatorial Pacific, while the Southern Ocean heat uptake opposes this change. Corroborating our model experiments, multimodel analysis shows that the models with greater Southern Ocean heat uptake exhibit less reduction in the temperature gradient and less weakening of the Walker circulation. Therefore, constraining the tropical Pacific projection requires a better insight into Southern Ocean processes.
This study develops a new regional model of the Southern Ocean including an improved representation of the iron biogeochemistry and ecosystem component, nesting within a biogeochemical ocean state estimate, and benchmarking with a suite of observations. The regional domain focuses on the Udintsev Fracture Zone (UFZ) in the central Pacific sector of the Southern Ocean. The UFZ is characterized by the deep gap between the Pacific‐Antarctic Ridge and the East Pacific Rise, which is one of the key “choke points” of the Antarctic Circumpolar Current where major Southern Ocean fronts are constrained within close proximity to this topographic feature. It is also a region of elevated mesoscale eddy activity, especially downstream of the UFZ. The model reproduces observed partial pressure of carbon dioxide in the surface water (pCO2) remarkably well from seasonal to interannual timescales relative to prior studies (
- Award ID(s):
- 1744755
- NSF-PAR ID:
- 10445791
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Advances in Modeling Earth Systems
- Volume:
- 14
- Issue:
- 6
- ISSN:
- 1942-2466
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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