Crossing the Southern Ocean: How the parameterization of poleward heat transport may differ from that of the real world

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Speaker: 
Matthew Hecht
Affiliation: 
LANL, USA
Seminar Date: 
22. October 2018 - 12:30 - 13:10
Location: 
Lecture room, Ground Floor, NERSC

As the only major ocean basin that allows for circumpolar flow, with no continental boundaries against which zonal pressure gradients may be established, the Southern Ocean has been singled out as a region in which transient mesoscale eddies are especially important. When effects of bathymetry on the flow are considered, however, transient eddies alone need not generate the entire poleward heat transport that compensates the equatorward heat transport forced by the prevailing westerly winds. Instead, topographically fixed meanders can deliver much of this poleward component of the heat transport.

In a simplified channel model that is strongly eddying, we find that standing meanders dominate the poleward heat transport. In contrast, when an eddy parameterization is used in a lower resolution configuration of the model, the meander transport drops and the eddy parameterization itself makes up for the weak heat transport of the meander. Analysis of a global ocean model indicates that these findings are not limited to the idealized problem. If the underlying problem is a tendency of the eddy parameterization to smooth out and weaken an otherwise strong and deeply penetrating jet, we suspect this impact to be problematic in other regions as well.

A recommendation from this work is that minimization of impact on meander transport should be one criterion in the evaluation of candidate schemes.