The MIT Ocean Model

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The MIT Ocean Model

• Description
• Novel formulation
• Parameterizations
• Applications
• Process studies
• Global circulation
• Development
• Parameterizations
• Numerical

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Description I

• Grid-point model
• Arakawa C grid
• Z coordinate
• Hydrostatic ? Non-hydrostatic
• Process studies
• Global circulation
• Highly portable
• Very efficient

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Description II

• Implicit free surface
• Equal ?t in external mode momentum eqns
• Allows natural fresh-water flux
• Non-linear equation of state
• Parameterizations
• Gent-McWilliams (Geostrophic eddies)
• KPP (BL scheme)
• Convective adjustment

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Applications

• Data assimilation (MIT, JPL, Scripps)
• constrained estimates of circulation
• bio-geochemical cycles (MIT, Goddard)
• Process studies
• lab. Experiments, Labrador Sea, Internal waves
• Climate (MIT, JPL, ETH)
• ocean only, coupled
• Coastal (U. Conn.)

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Key Numerical Innovations

• Finite Volume
• allows shaved cell representation of topography
• Hydrostatic ? Non-hydrostatic
• applicable to a wide range of dynamical scales
• Coriolis term (CD scheme)
• allows C grid solution at low resolution

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Finite Volume Shaved cells
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Hydraulic Control in Overflows

• E.g. Denmark Straight overflow

Legg WHOI
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Breaking Internal Waves
Legg Wunsch WHOI/MIT
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CD scheme
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General CirculationBasic Setup

• 2.8 x 2.8 x 15 levels (128x64 points)
• Forced with observed surface fluxes
• stress, heat, fresh-water
• restoring to Levitus SST (36 W m-2)
• monthly data
• Realistic topography
• Gent-McWilliams eddy parameterization

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ETOPO51/12º x 1/12º
Model2.8º x 2.8º
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Heat Transport (PW)
Fresh Water Transport (Sv)
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Global Overturning ?(y,z)
CI 5 Sv
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Atlantic ?(y,z)
CI 5 Sv
Indo-Pacific ?(y,z)
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Drift from Levitus
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Ongoing Developments I

• Formulation
• Curvilinear coordinates (horizontal)
• Move pole over Greenland ? avoid converging
  meridians in Arctic Ocean
• Place more resolution in boundary currents
• Cubed sphere ? more uniform resolution
• Hybrid vertical coordinate
• More adiabatic
• BBL parameterization
• Semi-implicit time-stepping

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Ongoing Developments II

• Parameterizations
• Eddy parameterizations
• Visbeck et al.
• T.E.M. ? Potential Vorticity flux
• Bottom Boundary Layer
• Killworth
• Ganadesikan
• Internal Wave Breaking
• Polzin

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Related Ongoing Work

• Passive Tracer experiments (Follows)
• Carbon cycle modeling
• Geo-thermal heating (Scott, Marotzke)
• Response to fresh-water forcing (Stone)
• Coupling
• to MIT Intermediate Atmosphere (Marshall)
• to ECHAM (Sheinin)