Gulf Of Mexico Region Research Articles

A Simulation Tool for Hurricane Evacuation Planning

Atlantic hurricanes and severe tropical storms are a serious threat for the communities in the Gulf of Mexico region. Such storms are violent and destructive. In response to these dangers, coastal evacuation may be ordered. This paper describes the development of a simulation model to analyze the movement of vehicles through I-65, a major US Interstate highway that runs north off the coastal City of Mobile, Alabama, towards the State of Tennessee, during a massive evacuation originated by a disastrous event such a hurricane. The constructed simulation platform consists of a primary and two secondary models. The primary model is based on the entry of vehicles from the 20 on-ramps to I-65. The two secondary models assist the primary model with related traffic events such as car breakdowns and accidents, traffic control measures, interarrival signaling, and unforeseen emergency incidents, among others. Statistical testing was performed on the data generated by the simulation model to indentify variation in relevant traffic variables affecting the timely flow of vehicles travelling north. The performed statistical analysis focused on the closing of alternative on-ramps throughout the Interstate.

Contrasting marine policies in the United States, Mexico, Cuba and the European Union: Searching for an integrated strategy for the Gulf of Mexico region

The three nations surrounding the Gulf of Mexico (GoM) are experiencing rapidly expanding populations and economic development. Problems associated with governing a transboundary body of water such as the GoM are becoming increasingly evident. Despite various attempts within each nation to establish more integrated ocean and coastal governance mechanisms within their own jurisdictions, there has been very little cooperation between the U.S., Mexico and Cuba in developing coordinated maritime policies for the GoM Region. After providing an overview of current marine policy initiatives in the three nations, a brief analysis of recent efforts by the European Union is presented. The paper contends that this European initiative may provide guidance for future integrated management policies in the GoM, but notes that progress depends on reducing legal and political obstacles to international collaboration in the Region.

Light absorbing carbon emissions from commercial shipping

Extensive measurements of the emission of light absorbing carbon aerosol (LAC) from commercial shipping are presented. Vessel emissions were sampled using a photoacoustic spectrometer in the Gulf of Mexico region. The highest emitters (per unit fuel burnt) are tug boats, thus making significant contributions to local air quality in ports. Emission of LAC from cargo and non cargo vessels in this study appears to be independent of engine load. Shipping fuel consumption data (2001) was used to calculate a global LAC contribution of 133(±27) Ggyr−1, or ∼1.7% of global LAC. This small fraction could have disproportionate effects on both air quality near port areas and climate in the Arctic if direct emissions of LAC occur in that region due to opening Arctic sea routes. The global contribution of this LAC burden was investigated using the MOZART model. Increases of 20–50 ng m−3 LAC (relative increases up to 40%) due to shipping occur in the tropical Atlantic, Indonesia, central America and the southern regions of South America and Africa.

Optimization of Ozonated Water Treatment of Wild-Caught and Mechanically Peeled Shrimp Meat

ABSTRACT Ozone is a USFDA and USDA approved food contact sanitizing agent and has been used in the seafood industry in both gaseous and dissolved forms to destroy bacteria. The wild harvest shrimp industry is the most economically important fishery in the U.S. Gulf of Mexico region, and in Louisiana the majority of the harvest is mechanically peeled and frozen. Dissolved ozone was measured in processing water at product application to study the optimization of ozonated water treatment for reducing microbial contamination of peeled shrimp meat. Shrimp samples were either sprayed or soaked in water with 1, 2, and 3 ppm dissolved ozone. Treatment times of 20, 40, and 60 seconds were investigated for all applications and concentrations. Similar volumes of water were applied for all treatments, and soaking showed greater bacterial reduction than spray treatments for all time and concentration combinations studied. Soaking in 3 ppm dissolved ozone for 40 s and 60 s showed the greatest reduction of total aerobic bacteria, and 60 s at 3 ppm resulted in the greatest reduction of Pseudomonas bacteria. Ozonated water treatment did not produce oxidation in the shrimp samples. The optimal treatment of soaking shrimp in 3 ppm dissolved ozone for 60 s will be used for further investigations of refrigerated shelf life extension and Listeria monocytogenes destruction in peeled shrimp meat.

What Drives the Seasonal Onset and Decay of the Western Hemisphere Warm Pool?

Abstract The annual heat budget of the Western Hemisphere warm pool (WHWP) is explored using the output of an ocean general circulation model (OGCM) simulation. According to the analysis, the WHWP cannot be considered as a monolithic whole with a single set of dominating processes that explain its behavior. The three regions considered, namely the eastern north Pacific (ENP), the Gulf of Mexico (GoM), and the Caribbean Sea (CBN), are each unique in terms of the atmospheric and oceanic processes that dominate the corresponding heat budgets. In the ENP region, clear-sky shortwave radiation flux is responsible for the growth of the warm pool in boreal spring, while increased cloud cover in boreal summer and associated reduction in solar radiation play a crucial role for the ENP warm pool’s demise. Ocean upwelling in the Costa Rica Dome connected to surrounding areas by horizontal advection offers a persistent yearlong cooling mechanism. Over the Atlantic, the clear-sky radiation flux that increases monotonically from December to May and decreases later is largely responsible for the onset and decay of the Atlantic-side warm pool in boreal summer and fall. The CBN region is affected by upwelling and horizontal advective cooling within and away from the coastal upwelling zone off northern South America during the onset and peak phases, thus slowing down the warm pool’s development, but no evidence was found that advective heat flux divergence is important in the GoM region. Turbulent mixing is also an important cooling mechanism in the annual cycle of the WHWP, and the vertical shear at the warm pool base helps to sustain the turbulent mixing. Common to all three WHWP regions is the reduction of wind speed at the peak phase, suggestive of a convection–evaporation feedback known to be important in the Indo-Pacific warm pool dynamics.

Cost of Site Clearance and Verification Operations in the Gulf of Mexico

The cost of site clearance and verification operations in the Gulf of Mexico is examined based on nearly 300 jobs performed by B&J Martin, Inc. from 1997 to 2001. A description of the activities and regulatory requirements involved in site clearance verification establishes the manner in which service cost is determined. Descriptive statistics are provided and relations are derived that estimate the time and cost of clearance and verification based on various descriptor variables. The expected size and potential value of the site clearance verification market in the Gulf of Mexico is also estimated. A major conclusion of the analysis is that the cost of site clearance verification is a time-variant site-dependent function which cannot be predicted prior to performing the service. The analysis represents the first empirical study to construct clearance and verification cost functions for the Gulf of Mexico region.

Decommissioning Cost Functions in the Gulf of Mexico

The cost to decommission offshore structures in the Gulf of Mexico is examined based on 60 projects managed by Twachtman, Synder, & Byrd, Inc., over the years 1991–2001. Cost functions are established for each stage of decommissioning, including well plugging and abandonment, structure preparation, pipeline abandonment, structure removal, and site clearance and verification. The component cost of decommissioning is analyzed statistically, and regression models are empirically derived using various descriptor variables. A candid discussion of the limitations of analysis is also presented. This paper represents the first empirical study to construct decommissioning cost functions for the Gulf of Mexico region based on actual job data.

Export pathways for river discharged fresh water in the northern Gulf of Mexico

A numerical simulation of the Gulf of Mexico (GoM) using the Navy Coastal Ocean Model (NCOM) is used to identify the pathways by which fresh water discharged by major rivers in the northern Gulf is exported away from the region. The NCOM, a new primitive equation ocean model with a hybrid sigma/geopotential level vertical coordinate, is described along with its application to the GoM region. Trajectories from surface drifters are analyzed to show evidence of the seasonally shifting alongshore and cross‐shelf transport in the region. The model results are used to determine the preferred locations and times of year for cross‐shelf and along‐shelf export of low‐salinity water from the northern GoM. The annual cycle of local wind stress plays an important role in shifting the export pathway of the fresh water discharged from the major rivers (primarily the Mississippi River) toward the east in the spring/summer, where it can be transported offshore by the currents associated with deep ocean mesoscale eddies, and toward the west in the fall/winter, where it is transported southward along the Mexican coastline as a coastally trapped current.

Technical Assessment of Using Dispersants On Marine Oil Spills in The U.S. Gulf of Mexico and California

ABSTRACT This paper describes two comprehensive technical assessments of potential dispersant use in the Gulf of Mexico Region (GOMR) and Pacific Outer Continental Shelf Region (POCSR). The assessments considered both operational and environmental issues. Spill scenarios currently used for spill response planning or environmental impact assessments were analyzed. Dispersibility of oils and “time-windows” (TWs) for dispersant operations were assessed for GOMR- and POSCR-produced crude oils, as well as for oils imported into California. The TWs were estimated by oil fate modeling. It was found that most of the GOMR-produced oils for which data were available are light and dispersible when fresh. By contrast, only a few of the POCSR produced oils appear to be dispersible. The situation for oils imported into California is more favorable, as over 50% of crude oil volume imported annually is comprised of oils with adequate TWs. Logistic capacities of various dispersant application platforms were analyzed. Net environmental benefit (NEB) of dispersants was determined by analyzing a number of spill scenarios. Impact and NEB were estimated using models of oil fate, trajectory and environmental impact, combined with resource vulnerability databases. In the NEB-GOMR analysis, dispersants offered a clear net environmental benefit in every scenario. The NEB-POCSR analysis yielded similar conclusions, even though the study involved more complex scenarios.

Late glacial–Holocene atmospheric circulation and precipitation in the northeast United States inferred from modern calibrated stable oxygen and carbon isotopes

As global climate changes because of anthropogenic influences, it has become critical to better understand past climate and its various forcing mechanisms as a baseline for future comparison. To this end, we present a continental isotopic record from an 11.2-m-long wetland piston core sampled at 10‐50 yr resolution; the core was taken in the heavily populated, economically vibrant northeastern United States (adjacent to Fayetteville Green Lake) and spans 14,600‐3200 cal. yr B.P. We use a historically based correlation between d 18 Ocalcite obtained from individual varves in a box core from Fayetteville Green Lake and winter atmospheric circulation over the northeast United States to examine the way in which changes in winter circulation have influenced d 18 O in precipitation from 14,600 to 3200 cal. yr B.P. Our correlation analysis suggests that in periods during which the circumpolar westerlies are expanded, storms track more frequently from the Gulf of Mexico region, delivering precipitation with relatively high d 18 O values to the study site. By contrast, contracted westerlies result in more frequent low-d 18 Oprecipitation cross-continental storms. By using this relationship we model winter-vortex latitudes over the northeast United States for the prehistoric oxygen isotope record, focusing on millennial-scale

Potential genotoxicity of wastewater‐contaminated pore waters with comparison to sediment toxicity and macrobenthic community composition

The objectives of this survey were to determine the genotoxic potential of sediment pore waters above and below 10 wastewater outfalls and to compare the results to sediment chemical quality guidelines, acute toxicity, and macrobenthic community composition. The focus of the study was on genotoxicity since its occurrence in environmental media below wastewater discharges in the Gulf of Mexico region has not been reported in the scientific literature. Pore waters from 43 sediment samples were assayed using a microbial mutagenicity assay before and after activation with a rat liver microsome mix (S-9). A combination of either direct or activated responses was observed for 40% of the pore waters. Direct, activated, and both direct and activated responses were observed in 5, 26, and 9% of the total samples, respectively. Mutagenic effects were observed below 7 of the 10 outfall areas and in 4 of 6 control areas associated with 6 outfalls. The lowest pore water concentrations causing an activated mutagenic response were statistically similar above and below the outfalls. Mutagenicity occurred more frequently than acute toxicity to estuarine and freshwater invertebrates and there was no consistent relationship between its occurrence and the exceedance of sediment chemical quality guidelines. In contrast, there was some indication that mutagenic activity paralleled low benthic community diversity. © 2002 by Wiley Periodicals, Inc. Environ Toxicol 17: 63–73, 2002

Three new Procamallanus (Spirocamallanus) species from freshwater fishes in Mexico.

The following 3 new species of Procamallanus (Spirocamallanus) are described from the intestines of freshwater fishes in Mexico, all belonging to the morphological group characterized by the presence of wide caudal alae, 3 pairs of subventral preanal papillae, and unequal spicules in the male: Procamallanus (Spirocamallanus) jaliscensis n. sp. (type host: Agonostomus monticola) and Procamallanus (Spirocamallanus) gobiomori n. sp. (hosts: Gobiomorus maculatus [type host], Gobiomorus polylepis and Eleotris picta) from 2 rivers in Jalisco State, western Mexico, and Procamallanus (Spirocamallanus) mexicanus n. sp. (type host: Cichlasoma geddesi) from Xalapa District, Veracruz State (Gulf of Mexico region), southeastern Mexico. Procamallanus jaliscensis is characterized by the length of the spicules (606-900 microm and 282-354 microm), number (15-16) of spiral ridges in the buccal capsule, and the digit-like protrusion with 1 terminal cuticular spike on the female tail; P. mexicanus by the length of the spicules (456-480 microm and 231-233 microm), number (10-12) of spiral ridges in the capsule, and the shape of the female tail (conical with a suddenly narrowed distal part, without any terminal spikes); and P. gobiomori by the length of spicules (318-348 microm and 156-192 microm), number (8-10) of spiral ridges and by the digit-like protrusion with 2 terminal cuticular spikes on the female tail.

A statistical comparison of wind speed, wave height, and wave period derived from satellite altimeters and ocean buoys in the Gulf of Mexico region

The capability of spaceborne altimeters to provide precise measurement of significant wave height and wind speed has been demonstrated repeatedly. It is shown in this paper that in addition to the significant wave height and wind speed, the wave period can be calculated from the semiempirical functions established from earlier wave research. The calculated characteristic wave period using the altimeter‐derived wind speed and wave height are found to be in excellent agreement with the peak wave period and average wave period from the ocean buoy measurements in the Gulf of Mexico. Also, with the long time series of collocated data set, it is possible to compare altimeter output of wind and wave parameters with ocean buoy measurements taking into consideration the spatial lags between the buoy locations and the altimeter footprints, and the temporal lags between the two sensor systems. It is found that when the spatial lags are less than 10 km, the RMS difference of the significant wave height is approximately 0.1 m, which is the digitization resolution of the output from both altimeter and ocean buoy. For the wind speed, the RMS difference approaches 1.2 m/s in the Gulf of Mexico using the empirical algorithms. The wind speed agreement is significantly improved to 0.8 m/s when the tilting effect on the altimeter cross section is accounted for. In contrast to the spatial lags, temporal lags of up to 1 hour do not appear to produce significant difference in the statistics of comparison based on this study.

Preliminary Evaluation of the Use of Phosphogypsum for Reef Substrate in the Gulf of Mexico

Phosphogypsum (PG), a solid by-product of phosphoric acid production in the fertilizer industry, contains radionuclides and trace metals in concentrations which are potentially hazardous to human health and to the environment. Due to the presence of these contaminants and to the lack of safe alternative uses for PG, the industry has necessarily resorted to on-site stockpiling as the primary disposal method. Thirty-three such stockpiles, totaling millions of tons of PG, are currently extant in the Gulf of Mexico region. The environmental and economic liabilities associated with PG stockpiling has prompted continuing research into alternative beneficial uses of this solid waste which will be protective of the public health. To investigate the efficacy of PG in the construction of artificial reefs, we conducted two preliminary studies which demonstrate that cement-consolidated PG may provide a suitable and safe substrate for artificial reef construction. The first, performed in the laboratory, examined the possibility of bioaccumulation of radium and six heavy metals over time when three levels (copepods, grass shrimp, and fishes) of an aquatic food chain experience both trophic and environmental exposure to PG. Other than higher radium levels in the experimental grass shrimp, little possible effect of PG exposure could be discerned. In all cases where increased metals concentrations were indicated within the experimental groups, roughly equivalent increases in metal concentrations also occurred in the control groups. The second, performed under natural conditions in four ¼-acre estuarine ponds, evaluated the effects of PG exposure on the community structures of marine meiofauna, macroinvertebrates, and fishes. Abundances of copepod species either were slightly increased in ponds with PG or were inconsistently affected. Diversity indices for macroinvertebrates and fishes showed modest but inconsistent variation among experimental and control ponds. Thus, no differences in community structure attributable to the presence of PG could be detected among benthic invertebrates, natant invertebrates, or fishes.

Effects of flooding, salinity and herbivory on coastal plant communities, Louisiana, United States.

Flooding and salinity stress are predicted to increase in coastal Louisiana as relative sea level rise (RSLR) continues in the Gulf of Mexico region. Although wetland plant species are adapted to these stressors, questions persist as to how marshes may respond to changed abiotic variables caused by RSLR, and how herbivory by native and non-native mammals may affect this response. The effects of altered flooding and salinity on coastal marsh communities were examined in two field experiments that simultaneously manipulated herbivore pressure. Marsh sods subjected to increased or decreased flooding (by lowering or raising sods, respectively), and increased or decreased salinity (by reciprocally transplanting sods between a brackish and fresh marsh), were monitored inside and outside mammalian herbivore exclosures for three growing seasons. Increased flooding stress reduced species numbers and biomass; alleviating flooding stress did not significantly alter species numbers while community biomass increased. Increased salinity reduced species numbers and biomass, more so if herbivores were present. Decreasing salinity had an unexpected effect: herbivores selectively consumed plants transplanted from the higher-salinity site. In plots protected from herbivory, decreased salinity had little effect on species numbers or biomass, but community composition changed. Overall, herbivore pressure further reduced species richness and biomass under conditions of increased flooding and increased salinity, supporting other findings that coastal marsh species can tolerate increasingly stressful conditions unless another factor, e.g., herbivory, is also present. Also, species dropped out of more stressful treatments much faster than they were added when stresses were alleviated, likely due to restrictions on dispersal. The rate at which plant communities will shift as a result of changed abiotic variables will determine if marshes remain viable when subjected to RSLR.

Stygofauna of Oman, 1 A new freshwater stygobiontCyathura(Isopoda, Anthuridae), from interstitia of coarse wadi sediments in Oman

A well-characterized new species of Cyathura (Stygocyathura) is described from the underflow of a wadi in Oman where a large population is present. Sixteen species have been attributed to this entirely stygobiont subgenus; they are either from the Caribbean - Gulf of Mexico region, or from the western Pacific, whereas a single species has been recorded from the realm of the Indian Ocean: C. (S.) milloti Chappuis, Delamare & Paulian from Reunion Island. The new species could be remotely related to C. (S.) milloti.

Characterizing dissolved oxygen conditions in estuarine environments

Dissolved oxygen concentration, which is often measured in estuaries to quantify the results of and stresses associated with eutrophication, can be highly variable with time of day and tidal stage. To assess how well dissolved oxygen conditions are characterized by typical monitoring programs, we conducted Monte Carlo sampling from 16 semi-continuous, 31-day dissolved oxygen records collected from estuaries along the Atlantic and Gulf coasts to mimic three sampling strategies: (1) systematic point-in-time sampling, (2) random point-in-time sampling, and (3) short-term continuous records. These strategies were evaluated for their accuracy in estimating mean oxygen concentration, minimum oxygen concentration, and percent of time below a threshold value of 2 ppm. Mean dissolved oxygen concentration was most accurately estimated in both estuarine regions by random point-in-time sampling, but this strategy required more than ten samplings per month for the estimate to be within 0.5 ppm on 50% of the simulations. Short-term continuous sampling (24-48 h) correctly identified estuaries in the Gulf of Mexico region where dissolved oxygen concentrations of less than 2 ppm were experienced greater than 20% of the time. However, large tidal variations in Atlantic coast estuaries showed this measure to be inaccurate in these estuarine environments. None of the sampling strategies correctly identified month-long oxygen minima within 0.5 ppm for more than 50% of the simulations. This inability to characterize correctly dissolved oxygen conditions could add significant uncertainty to risk assessments, waste load allocation models, and other water quality evaluations that are the basis for developing wastewater treatment strategies and requirements. Perhaps more importantly, the inaccuracy with which conventional sampling procedures characterize minimum dissolved oxygen values suggests that the extent of hypoxia in estuarine waters in being substantially underestimated.

Studies of North American continental‐scale hydrology using Eta model forecast products

In this study, the forecast products of the National Meteorological Center's Eta model during the period August 1993 to March 1994 are critically examined to gain insight into the quality of the first guess fields used in the model's four‐dimensional data assimilation and the usefulness of the forecast products in diagnostic studies involving unmeasured hydrological variables. We find that the Eta model 12–36 hour forecasts produce patterns of monthly precipitation that are a reasonably good approximation of the monthly observed precipitation fields for the period under consideration. The diurnal cycle of the water vapor fluxes and their seasonal changes obtained from the model forecasts are also in good agreement with observations. During the warm months the stationary component of the forecast fluxes includes a good representation of the low‐level jet (LLJ) that is an important means for the transport of moisture from the Gulf of Mexico into the Great Plains. The LLJ decays during autumn, when it is replaced by the transient component of the fluxes as the means of transport of water vapor from the Gulf of Mexico region into the United States. Finally, evaporation estimates were derived from the convergence of the fluxes of the forecast fields and model and observed values of precipitation. All estimates agree within 0.5 mm d−1 and showed a reasonable seasonal cycle, with maximum evaporation during the warm season and a minimum evaporation during February.

A Study of Satellite-derived Moisture with Emphasis on the Gulf of Mexico

Visible-Infrared Spin Scan Radiometer (VISSR) Atmospheric Sounder (VAS) moisture retrievals are compared to the National Meteorological Center Regional Analysis and Forecast System (RAFS) 12-h forecast and to 1200 UTC rawinsondes over the U.S. and the Gulf of Mexico on a daily basis for nearly 1.5 years. The principal objective is to determine what information the current moisture retrievals add to that available from the RAFS and surface data. The data are examined from the climatological perspective, that is, total precipitable water over the seasons for three geographical regions, and also for synoptic applications, that is, vertical and horizontal resolution. VAS retrievals are found to be systematically too moist at higher values. The variance of the VAS soundings more closely agrees with the rawinsonde at locations around the Gulf of Mexico than the RAFS. An examination of a case (6 June 1989) over the Gulf of Mexico region comparing three layers of VAS-derived moisture to the RAFS forecast shows the former capable of outperforming the latter in both the horizontal and, to some extent, the vertical frame of reference.

Contrasting characteristics attributed to migration observed in petroleums reservoired in clastic and carbonate sequences in the Gulf of Mexico region

Abstract Systematic differences among two subsets of petroleums selected geographically and by reservoir type were attributed to lithologically-characteristic migration phenomena. Most oils in offshore Louisiana Tertiary clastic reservoirs are deficient in light ends, evidently because of evaporative fractionation. Residual oils are enriched in cycloalkanes and aromatic hydrocarbons. Spuriously low evident maturities based upon concepts of paraffinicity are observed. Numerous oils are both fractionated and biodegraded. Mesozoic carbonate-sealed reservoirs at the margins of the basin generally contain pristine oils with intact light ends. However, many oils appear to be depleted in preferentially water soluble compounds: benzene, toluene, light cycloalkanes and phenanthrene, evidently due to aqueous fractionation during intraformational migration.