U.S. Minerals Management
Services
Numerical
modeling of currents near
the continental slope of the Gulf of Mexico
Project
Summary
With recent
technological developments, the oil industry is now capable of drilling
in deeper water for oil and gas extraction at costs that are commercially
viable. Mineral resources under the continental slope and rise of
the Gulf of Mexico are now within practical reach of offshore drilling
operations, and the oil industry is likely to apply for more leases
and operating licenses in these areas. There is thus an emerging
critical need to determine the environmental impacts of oil and
gas extraction operations over the slope and rise of the Gulf of
Mexico. As part of its response to this need, the U. S. Minerals
Management Service awarded AEF a four year contract to perform process-oriented
research directed towards furthering the basic scientific understanding
of the currents that occur near the continental slope, rise, and
shelf in the Gulf of Mexico. AEF designed
a scientific strategy to elucidate the fundamental dynamical effects
of flow-topography interaction, specifically Loop Current Eddy interactions
with topography and interactions of currents with submarine canyons,
on slope, rise, and shelf circulation and the larger-scale deep-water
circulation of the Gulf of Mexico. Physical processes responsible
for water mass exchange between the shelf and the deeper regions
of the Gulf of Mexico are of particular interest. The primary goal
of the research is the development of a correct physical understanding
of the processes of flow-topography interaction that would then
provide a foundation for improving the predictive capabilities of
numerical models of Gulf of Mexico circulation. The specific scientific
focus is cross- and near-shelf circulation driven by interactions
between canyon and slope bathymetry and currents including Loop
Current Eddies, other eddy features, topographic Rossby waves, and
mean and time varying along slope currents. Verification of the
processes represented in our models will be guided, as appropriate,
by rigorous comparison with available data.
Our numerical
modeling program employs two models. All experiments requiring faithful
representation of either complete primitive equation physics or
realistic representation of the basin scale Gulf of Mexico circulation
employ our primitive equation model. The model is configured with
a highly accurate and innovation movable nested-mesh grid system
that is uniquely suited to better represent the essential smaller-scale
processes during Loop current eddy interactions with topography
and current interactions with canyons while preserving the dynamical
context of the larger-scale Gulf of Mexico circulation. When appropriate,
idealized experiments are performed in the simpler computational,
conceptual, and diagnostic framework provided by our multi-layer
intermediate equation model. The relationship between the two models
is synergistic: the nested-grid model is the primary tool, and the
intermediate equation model provides a superior level of diagnostics
which enable a more thorough understanding of the nested-grid model
results. Although our focus during the term of this research program
is on improving the understanding of the basic dynamics governing
flow-topography interaction, the movable nested-mesh model will
evolve towards a state-of-the-art ocean forecast system for the
Gulf of Mexico circulation by the end of our program.
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