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| Titel |
Cross-shelf transport and dispersion due to baroclinic instabilities |
| VerfasserIn |
Kristen Thyng, Robert Hetland |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093606
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| Publikation (Nr.) |
 EGU/EGU2014-8503.pdf |
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| Zusammenfassung |
| The dominant forcing mechanisms for the circulation in the northwestern Gulf of Mexico are
largely determined by location relative to the shelf break. On the inner shelf, the flow is
mostly controlled by the wind and on the outer shelf is affected by the mesoscale loop-current
eddies. However, in the summer, baroclinic instabilities can develop along the boundary
of the mid-shelf river plume front, leading to large eddies (~50 km length scale)
that can reach across the entire shelf and strongly affect the local flow field. These
instabilities advect fresher water toward the shelf edge and pull denser water back
toward the coast. The details of how the flow crosses between these two regimes is of
interest because it controls the flux of river-borne biogeochemical properties to
the deep ocean, as well as for the potential onshore transport of oil from offshore
spills.
We approach this problem using a high resolution numerical model of the
Texas-Louisiana shelf run using the Regional Ocean Modeling System (ROMS) and a
Lagrangian particle tracking model (TRACMASS). By initializing drifters at the
sources of fresh water (the Atchafalaya and Mississippi rivers) in the numerical
model, we are able to explicitly track its trajectory through the numerical domain in
time. These trajectories can then be used to characterize the cross-shelf transport
and lateral dispersion due to the instabilities caused by the presence of the fresher
water. We expect the transport and dispersion to be enhanced when compared with
these quantities at other times of the year when the instabilities are not present, as
well as with other regions of the shelf break that are farther from the plume edge
area.
Additionally, an idealized numerical model of a shelf break with both horizontal
and vertical density gradients has been run through relevant parameter spaces to
examine the range of baroclinic instabilities. Drifters are run in these simulations
for comparison of transport and dispersion with that seen in the realistic model. |
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