Eddy saturation and frictional control of the Antarctic Circumpolar Current

The Antarctic Circumpolar Current is the strongest current in the ocean and has a pivotal impact on ocean stratification, heat content, and carbon content. The circumpolar volume transport is relatively insensitive to surface wind forcing in models that resolve turbulent ocean eddies, a process term...

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Bibliographic Details
Published in:Geophysical research letters 2017-01, Vol.44 (1), p.286-292
Main Authors: Marshall, David P., Ambaum, Maarten H. P., Maddison, James R., Munday, David R., Novak, Lenka
Format: Article
Language:English
Subjects:
Antarctic Circumpolar Current
Atmospheric models
bottom drag
Bottom friction
Carbon content
Carbon dioxide
Carbon dioxide atmospheric concentrations
Density stratification
Drag
Eddies
Eddy currents
eddy saturation
Energy budget
Energy dissipation
Energy exchange
Enthalpy
Friction
Heat
Heat content
Induction heating
Ingredients
Loads (forces)
Marine
Momentum
Momentum budget
Ocean currents
ocean eddies
Ocean models
ocean stratification
Oceanic eddies
Oceans
Physics
Polar environments
Saturation
Stratification
Stress
Stresses
Surface wind
Transport
Transportation models
Turbulence
Volume transport
Wave generation
Wind
Wind stress
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Summary:The Antarctic Circumpolar Current is the strongest current in the ocean and has a pivotal impact on ocean stratification, heat content, and carbon content. The circumpolar volume transport is relatively insensitive to surface wind forcing in models that resolve turbulent ocean eddies, a process termed “eddy saturation.” Here a simple model is presented that explains the physics of eddy saturation with three ingredients: a momentum budget, a relation between the eddy form stress and eddy energy, and an eddy energy budget. The model explains both the insensitivity of circumpolar volume transport to surface wind stress and the increase of eddy energy with wind stress. The model further predicts that circumpolar transport increases with increased bottom friction, a counterintuitive result that is confirmed in eddy‐permitting calculations. These results suggest an unexpected and important impact of eddy energy dissipation, through bottom drag or lee wave generation, on ocean stratification, ocean heat content, and potentially atmospheric CO2. Key Points The physics of eddy saturation is explained from first principles Enhanced bottom drag increases eddy energy dissipation and hence circumpolar volume transport Eddy energy dissipation may have an important impact on ocean heat tcontent and atmospheric CO2
ISSN:0094-8276
1944-8007
DOI:10.1002/2016GL071702