Glacial ocean overturning intensified by tidal mixing in a global circulation model

Due to lower sea levels during the Last Glacial Maximum (LGM), tidal energy dissipation was shifted from the shallow margins into the deep ocean. Here using a high‐resolution tide model, we estimate that global energy fluxes below 200 m depth were almost quadrupled during the LGM. Applying the energ...

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Bibliographic Details
Published in:Geophysical research letters 2015-05, Vol.42 (10), p.4014-4022
Main Authors: Schmittner, A., Green, J. A. M., Wilmes, S.-B.
Format: Article
Language:English
Subjects:
Abyssal circulation
Abyssal zone
Amplification
Boundary conditions
Circulation
Climate
Climate models
Computer simulation
Depth
Diffusion coefficients
Diffusivity
Dissipation
Energy consumption
Energy dissipation
Energy exchange
Fluxes
Global climate
Global warming
High resolution
Last Glacial Maximum
Marine
Meridional overturning circulation
Ocean circulation
Ocean currents
Oceans
Paleoclimate
Parameterization
Parametrization
Sea level
Tidal dissipation
Tidal energy
Tidal mixing
Tidal power
Tides
Water circulation
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Summary:Due to lower sea levels during the Last Glacial Maximum (LGM), tidal energy dissipation was shifted from the shallow margins into the deep ocean. Here using a high‐resolution tide model, we estimate that global energy fluxes below 200 m depth were almost quadrupled during the LGM. Applying the energy fluxes to a consistent tidal mixing parameterization of a global climate model results in a large intensification of mixing. Global mean vertical diffusivity increases by more than a factor of 3, and consequently, the simulated meridional overturning circulation accelerates by ~21–46%. In the model, these effects are at least as important as those from changes in surface boundary conditions. Our findings contrast with the prevailing view that the abyssal LGM circulation was more sluggish. We conclude that changes in tidal mixing are an important mechanism that may have strongly increased the glacial deep ocean circulation and should no longer be neglected in paleoclimate simulations. Key Points Lower LGM sea level caused more deep ocean tidal energy dissipation As a result, deep ocean mixing increases strongly in a global climate model This accelerates the meridional overturning circulation by 21–46%
ISSN:0094-8276
1944-8007
DOI:10.1002/2015GL063561