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| Titel |
Stratification-dependent Mixing May Increase Sensitivity of a Wind-driven Atlantic Overturning to Surface Freshwater Flux |
| VerfasserIn |
B. Marzeion, A. Levermann |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250022966
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| Zusammenfassung |
| Stratification-dependent mixing is employed in a coupled climate model of intermediate
complexity with a 3-dimensional ocean component. The vertical diffusivity in the ocean is
calculated as κ ~ N-α, where N is the local buoyancy frequency. The sensitivity of the
Atlantic meridional overturning circulation (AMOC) to freshwater forcing is tested for
exponents of 0 ≤ α ≤ 2 by first slowly increasing, then decreasing the freshwater forcing
over the North Atlantic, keeping the model close to equilibrium.
The fresh anomaly imposed at the surface between 20∘N and 50∘N in the Atlantic reaches
the deep ocean by vertical diffusion, and by AMOC advection via the northern convection
sites. Higher values of α lead to enhanced stratification and thereby reduced vertical mixing
in the subtropical forcing region. Consequently, the freshwater anomaly reaches the northern
deep water formation regions less diluted, and reduces the AMOC more strongly compared to
lower values of α. |
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