ACCESS NUMBER: 30128 

STUDY TITLE: Modeling and Data Analysis of Circulation Processes in the Gulf of 

Mexico 

REPORT TITLE: Modeling and Data Analysis of Circulation Processes in the Gulf of 

Mexico, Final Report 

CONTRACT NUMBER: 1435-01-99-CT-31028 

SPONSORING OCS REGION: Gulf of Mexico 

APPLICABLE PLANNING AREA(S): Eastern, Central and Western Gulf of Mexico 

FISCAL YEARS OF PROJECT FUNDING: 2000, 2001, 2002, 2003 

COMPLETION DATE OF REPORT: November 2003 

COSTS: FY 2000: $40,400; FY 2001: $262,600; FY 2002: $127,100; FY 2003: 

$439,377; FY 2004: $70,000; CUMULATIVE PROJECT COSTS: $939,543 

PROJECT MANAGER: P. Hamilton 

AFFILIATION: Science Applications International Corporation 

ADDRESS: 615 Oberlin Rd., Suite 100; Raleigh, NC 27605 

PRINCIPAL INVESTIGATORS: L. Y. Oey, Peter Hamilton, H. C. Lee 

KEY WORDS: Gulf of Mexico, Florida Straits, Yucatan Channel, numerical model, 

Princeton Ocean Model (POM), data analysis, data assimilation, currents, deep 

currents, continental slope, topography, topographic Rossby waves, Loop Current, Loop 

Current eddies, boundary eddies, deep currents, kinetic energy, ray tracing. 

BACKGROUND: This study was conducted to utilize a sophisticated numerical 

circulation model (POM), extract indicators of Gulf ocean dynamic patterns from the 

model results and compare these patterns to those identified in existing observational 

data bases. This study contributed to sequential development of a verified circulation 

model that may eventually support evaluation of physical oceanographic conditions and 

processes as they relate to oil and gas exploration and production, in particularly in the 

deeper portions of the northern Gulf of Mexico. At a qualitative level, several numerical 

models are able to reproduce major circulation patterns in the Gulf. The present effort 

was to compare not only this incarnation of the POM, but also quantitatively evaluate 

how well it reproduced details of the known current patterns. The project report presents 

results of the numerical modeling activities, the quantitative expression of the modeled 

flow patterns and a rigorous comparison with comparable analysis and presentation of 

existing field measurements. 

OBJECTIVES: The objectives of this study were to describe and understand circulation 

processes in the Gulf of Mexico through coordinated modeling and data analysis. The 
ACCESS NUMBER: 30128 

main focus was on two topics: topographic Rossby waves (TRWs) and slope eddies 

with particular emphasis on their occurrence in deepwater regions over the northern 

continental slope and rise in the Gulf of Mexico. 

DESCRIPTION: The study area for this project nominally included the entire Gulf of 

Mexico from the Yucatan Channel, over the entire Gulf and to the Florida Straits. 

Process evaluation and comparison was primarily that occurring deepwater portion of 

the northern Gulf of Mexico (water depth > 1000 m). Most observational programs used 

for comparison with model results were supported by the MMS over the past twenty 

years. These included Year 1-5 of the Physical Oceanography Program, the DeSoto 

Canyon Study and the Deewater Currents in the Northern Gulf of Mexico. The model 

used to simulate ocean patterns was a version of the Princeton Ocean Model (POM) as 

modified by L. Y. Oye, one of the study PIs. 

SIGNIFICANT CONCLUSIONS: Methods for initializing and optimizing a proven 

numerical circulation model produced strong similarities between the simulated and 

measured conditions. While some discrepancies between model and observations, 

many patterns were consistent and indicate that many of the processes governing 

feature generation and evolution are incorporated in the model dynamics and 

energetics. 

STUDY RESULTS: Based on the results of a high-resolution model, the analysis 

concentrated more precisely on regions in the Gulf where TRW’s are likely to occur, 

their possible generation site(s) and mechanism(s), and also propagation paths. It was 

found that TRW’s in the 20 to 100-day periods are excited by small-scale peripheral 

eddies or meanders around the LC or propagating Loop Current Eddies (LCE’s). The 

TRW’s propagated westward and the energy was predominantly confined seaward of 

the 3,000 m isobath in the central and western Gulf. It was also concluded that the 

deep Gulf circulation was cyclonic, and that the deep (horizontal) shear in part 

accounted (together with sloping topography) for the seaward confinement of the TRW 

rays 

This study evaluated whether this model can generate the observed spatial and 

temporal evolution of the slope eddy field over the north-central Gulf of Mexico. 

Selected field surveys measurements (LATEX C and GulfCet I) in conjunction with 

satellite altimetry and sea surface temperatures were used to initialize the model while 

similar and independent later observations were used to evaluate how successfully the 

model reproduced observed conditions. The use of basin-wide SSH and SST remotely 

sensed observations allowed the large scale (e.g. LC and LCE) circulation patterns to 

be integrated in the model initialization. Between initialization and verification, the 

model ‘predicted’ growth the of eddy energy in this initial field. The growth agreed with 

the observed increase of the kinetic energy of the geostrophic flow between initialization 

and verification intervals. Stability analysis indicated that the growth was caused by 

mixed barotropic and baroclinic instabilities. The success of this use of hydrographic 

surveys in a model assimilation scheme was a first step along the path that will allow 

the incorporation of in-situ, ocean observing systems into real-time model predictions. 
ACCESS NUMBER: 30128 

STUDY PRODUCT(S): Oey, L.-Y., P. Hamilton, H. C.-Lee. 2003. Modeling and Data 

Analyses of Circulation Processes in the Gulf of Mexico. Final Report. U.S. Dept. of the 

Interior, Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA. 

OCS Study MMS 2003-074, 129 pp.

Oey, L.-Y. and H.-C. Lee, 2002: Deep eddy energy and topographic Rossby waves in 

the Gulf of Mexico, J. Phys. Oceanogr., 32: 3499-3527. 

Ezer, T., L.-Y. Oey, W. Sturges and H.-C. Lee, 2003: The variability of currents in the 

Yucatan Channel: analysis of results from a numerical ocean model, J. Geophys. Res.

10.1029/2002JC001509. 

Oey, L.-Y., H.-C. Lee and W. J. Schmitz Jr., 2003a: Effects of Winds and Caribbean 

Eddies on the Frequency of Loop Current Eddy Shedding: A Numerical Model Study, J. 

Geophys. Res., in press. (This manuscript is available from 

http://www.aos.princeton.edu/WWWPUBLIC/PROFS/ under "Publications.") 

Wang, D.-P., L.-Y. Oey, T. Ezer and P. Hamilton, 2003: Nearsurface currents in DeSoto 

Canyon. J. Phys. Oceanogr., 33: 313-326.