Sensitivity of North Atlantic subpolar gyre and overturning to stratification-dependent mixing: response to global warming
International audience We use a reduced complexity climate model with a three-dimensional ocean component and realistic topography to investigate the effect of stratification-dependent mixing on the sensitivity of the North Atlantic subpolar gyre (SPG), and the Atlantic meridional overturning circul...
Published in: | Climate Dynamics |
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Main Authors: | , , |
Other Authors: | , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
HAL CCSD
2010
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Subjects: | |
Online Access: | https://hal.science/hal-00760275 https://doi.org/10.1007/S00382-008-0521-4 |
Summary: | International audience We use a reduced complexity climate model with a three-dimensional ocean component and realistic topography to investigate the effect of stratification-dependent mixing on the sensitivity of the North Atlantic subpolar gyre (SPG), and the Atlantic meridional overturning circulation (AMOC), to idealized CO 2 increase and peaking scenarios. The vertical diffusivity of the ocean interior is parameterized as κ ˜ N -α, where N is the local buoyancy frequency. For all parameter values 0 ≤ α ≤ 3, we find the SPG, and subsequently the AMOC, to weaken in response to increasing CO 2 concentrations. The weakening is significantly stronger for α ≥ αcr ≈ 1.5. Depending on the value of α, two separate model states develop. These states remain different after the CO 2 concentration is stabilized, and in some cases even after the CO 2 concentration has been decreased again to the pre-industrial level. This behaviour is explained by a positive feedback between stratification and mixing anomalies in the Nordic Seas, causing a persistent weakening of the SPG. |
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