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Gulf of Mexico

Contributed by: George A. Maul Publication year: 2019

The Gulf of Mexico is a subtropical semi-enclosed sea bordering the western North Atlantic Ocean. It is the northern-most basin of the Intra-Americas Sea. It connects to the Caribbean Sea on the south through the Yucat´an Channel and with the North Atlantic Ocean on the east through the Straits of Florida. To the north, it is bounded by the United States of America, to the west and south by Texas and Mexico, and on the east and southeast by Florida and Cuba, respectively. The Gulf of Mexico Basin lies wholly within the boundaries of the North American tectonic plate. See also: BASIN; INTRA-AMERICAS SEA; PLATE TECTONICS.

Marine geology

The continental shelves surrounding the gulf are very broad along the eastern (Florida), northern (Texas, Louisiana, Mississippi, Alabama), and southern (Campeche) area, averaging 125–186 mi (200–300 km) wide (see illustration). Characterized as a passive continental margin, the continental shelves along the western and southwestern (Mexico) and southeastern (Cuba) boundaries of the gulf are narrow, often being less than 12 mi (20 km) wide. Between the continental shelves and the Sigsbee Abyssal Plain are three steep continental slopes: the Florida Escarpment off west Florida, the Campeche Escarpment off Yucat´an, and the Sigsbee Escarpment south of Texas and Louisiana. Two major submarine canyons crease the gulf’s shelf areas: the De Soto Canyon near the Florida-Alabama border, and the Campeche Canyon west of the Yucat´an Peninsula. Tides in the gulf are primarily diurnal with a range of less than 1 m (3 ft). See also: CONTINENTAL MARGIN; ESCARPMENT; HOLOCENE; MARINE GEOLOGY.

Meteorology

The Gulf of Mexico is a transition zone between the tropical wind system (easterlies) and the westerly frontal-passage-dominated weather (in winter particularly) to the north, punctuated with intense tropical storms in summer∕autumn called the West Indian Hurricane. The gulf is a net evaporation basin, where evaporation exceeds precipitation plus river-runoff. Much of the atmospheric moisture supplied to the North American heartland during spring and summer has its origin over the gulf, and thus it is a vital element in the North American Monsoon. Compared with the United States’ rivers, the Mexican rivers are short, but they still provide approximately 20% of the freshwater input to the gulf because of extensive orographic rainfall from the trade winds that dominate the southern flank of the basin. See also: HURRICANE; MONSOON METEOROLOGY; STORM SURGE; TROPICAL METEOROLOGY. AccessScience from McGraw-Hill Education Page 2 of 4 www.accessscience.com

WIDTH:EBottom topography and physiographic provinces in the Gulf of Mexico. Contours in meters.

Ocean currents

The Gulf Stream System dominates the oceanic circulation in the Gulf of Mexico. The Yucat´an Current, flowing northward into the eastern Gulf of Mexico, is the first recognizable western boundary current in the Gulf Stream System. North of the Yucat´an Peninsula, the flow penetrates into the eastern gulf (where it is called the Gulf Loop Current) at varying latitudes with a distinctive chronology, loops around clockwise, and finally exits through the Straits of Florida, where it is called the Florida Current. This intense current reaches to more than 1000 m (3300 ft) depth, and transports 3 × 10,7 m,3∕s (1.1 × 10,9 ft,3∕s) of water, an amount 1800 times that of the Mississippi River. See also: GULF STREAM; MEDITERRANEAN SEA; OCEAN CIRCULATION.

The Gulf Loop Current is known to reach the Mississippi Delta, where it entrains river-water that is transported as far as Cape Hatteras. After reaching its maximum northerly position, a cycle that averages eleven months, an AccessScience from McGraw-Hill Education Page 3 of 4 www.accessscience.com

anticyclonic eddy, approximately 186 mi (300 km) in diameter, separates from the Loop Current and drifts westward. The main flow then reforms between the Yucatan Channel and the Florida Keys, and the process starts again. Deep-water, at the sill of the Yucatan Channel 2000 m (6600 ft) below the sea surface, flows southward from the gulf into the Caribbean Sea. See also: OCEAN CIRCULATION; SEAWATER.

Biogeography

Surrounding the Gulf of Mexico are many population centers that exploit the numerous estuaries, lagoons, and oil and gas fields. Tropical coral reefs off Yucat´an, Cuba, and Florida, and the Flower Garden Banks off Texas, provide important fishery and recreational activities. There are extensive wetlands along most coastal boundaries with ecological connections to many seagrass beds nearshore and coastal mangrove forests of Mexico, Cuba, and Florida. This biogeographic confluence creates one of the most productive marine areas on Earth, providing the food web for commercially important species such as lobster, demersal (bottom-dwelling) fish, and shrimp. This same ecology supports large populations of sea turtles and marine mammals. Coastal and nearshore waters also have large phytoplankton populations; for example, the “red tide” is often found off west Florida. The juxtaposition of these enormous marine resources and human activities has led to a distinctive anthropogenic impact on the health of the marine ecosystem. See also: BIOGEOGRAPHY; ESTUARINE OCEANOGRAPHY; FOOD WEB; MANGROVE; MARINE ECOLOGY; REEF; WETLANDS.

Marine petro-energy

The gulf is not only a major source of offshore petroleum, but also the most heavily trafficked corridor for marine transportation by tankers in North America. Despite all the petro-industry in and around the gulf, natural seeps account for 95% of petroleum input into gulf waters (approximately 140,000 tonnes per year). However, the catastrophic and deadly Deepwater Horizon accident in 2010 caused approximately 600,000–750,000 tonnes (4.4–5.4 million barrels or 700–860 × 10,3 m,3 or 185–227 million gallons) to flow into the gulf. The fate of all this petroleum is uncertain. Wind-driven surface currents advected some of the crude oil northward, some of it sank to the seafloor, some of it evaporated at the sea surface, some dissolved or underwent biodegradation, and some of it was collected by surface containment vessels. However, the fate of much of it remains unknown because of lack of information on subsurface currents and biological processes and rates at depth. George A. Maul

Keywords

Semi-enclosed sea; Gulf Stream system; Intra-Americas Sea; marine petro-energy AccessScience from McGraw-Hill Education Page 4 of 4 www.accessscience.com

Bibliography

R. A. Larson et al., High-resolution investigation of event driven sedimentation: Northeastern Gulf of Mexico, Anthropocene, 24:40–50, 2018 DOI: http://doi.org/10.1016/j.ancene.2018.11.002

F. Xie et al., Passive continental margin basins and the controls on the formation of evaporites: A case study of the Gulf of Mexico Basin, Carbonates Evaporites, 34(2):405–418, 2019 DOI: http://doi.org/10.1007/s13146-017-0404-z

Additional Readings

J. W. Snedden and W. E. Galloway, The Gulf of Mexico Sedimentary Basin: Depositional Evolution and Petroleum Applications, Cambridge University Press, 2019

NASA Earth Observatory

NOAA Tides and Currents

Naval Research Laboratory Real-Time Global Ocean Analysis and Modeling: Global NLOM Nowcast∕ Forecast