Loop Current

A parent to the Florida Current, the Loop Current is a warm ocean current that flows northward between Cuba and the Yucatán Peninsula, moves north into the Gulf of Mexico, loops east and south before exiting to the east through the Florida Straits and joining the Gulf Stream. The Loop Current is an extension of the western boundary current of the North Atlantic subtropical gyre.[1] Serving as the dominant circulation feature in the Eastern Gulf of Mexico, the Loop Currents transports between 23 and 27 sverdrups[2] and reaches maximum flow speeds of from 1.5 to 1.8 meters/second.[3]

A related feature is an area of warm water with an "eddy" or "Loop Current ring" that separates from the Loop Current, somewhat randomly every 3 to 17 months.[4] Swirling at 1.8 to 2 meters/second, these rings drift to the west at speeds of 2 to 5 kilometers/day and have a lifespan of up to a year before they bump into the coast of Texas or Mexico.[5] These eddies are composed of warm Caribbean waters and possess physical properties that isolate the masses from surrounding Gulf Common Waters. The rings can measure 200 to 400 kilometers in diameter and extend down to a depth of 1000 meters.[6]

Loop current2
A map of the Loop Current

Effect on tropical cyclones

Around 1970, it was believed that the Loop Current exhibited an annual cycle in which the Loop feature extended farther to the north during the summer. Further study over the past few decades, however, has shown that the extension to the north (and the shedding of eddies) does not have a significant annual cycle, but does vacillate in the north-south and east-west directions on an inter-annual basis.[7]

The Loop Current and its eddies may be detected by measuring sea surface level. Sea surface level of both the eddies and the Loop on September 21, 2005 was up to 60 cm (24 in) higher than surrounding water, indicating a deep area of warm water beneath them.[8] On that day, Hurricane Rita passed over the Loop current and intensified into a Category 5 storm with the help of the warm water.

In the Gulf of Mexico, the deepest areas of warm water are associated with the Loop Current and the rings of current that have separated from the Loop Current are commonly called Loop Current eddies. The warm waters of the Loop Current and its associated eddies provide more energy to hurricanes and allow them to intensify.

As hurricanes pass over warm areas of the Gulf of Mexico, they convert the ocean's heat into storm energy. As this energy is removed from the seas, a wake of colder water can be detected along the hurricane's path. This is because heat is withdrawn from the ocean mixed layer in a number of ways. For instance, sensible and latent heat are lost directly to the tropical cyclone across the air-sea interface. Also, the horizontal divergence of wind-driven mixed layer currents results in the upwelling of colder thermocline water. Finally, the turbulent entrainment of colder thermocline waters caused by wind stirring also results in the cooling of the surface waters.[9] These are the reasons that the depth of the ocean mixed layer is more important in hurricane deepening than sea surface temperature. A thin veneer of warm surface waters will be more susceptible to hurricane induced cooling than waters with a larger mixed layer and deeper thermocline. Furthermore, models suggest that cyclones are more likely to reach a larger fraction of their maximum potential intensity over warm oceanic features where the 26 °C isotherm extends beyond 100 meters.[10][11]

An example of how deep warm water, including the Loop Current, can allow a hurricane to strengthen, if other conditions are also favorable, is Hurricane Camille, which made landfall on the Mississippi Gulf Coast in August 1969. Camille formed in the deep warm waters of the Caribbean, which enabled it to rapidly intensify into a category 3 hurricane in one day. It rounded the western tip of Cuba, and its path took it directly over the Loop Current, all the way north towards the coast, during which time the rapid intensification continued. Camille became a category 5 hurricane, with an intensity rarely seen, and extremely high winds that were maintained until landfall (190 mph (310 km/h) sustained winds were estimated to have occurred in a very small area to the right of the eye).

In 1980, Hurricane Allen strengthened to a category 5 hurricane while moving over the Loop Current, but it weakened before landfall in Texas.

In 2005, Hurricane Katrina and Hurricane Rita both greatly increased in strength when they passed over the warmer waters of the Loop Current. Hurricane Wilma of 2005 was expected to make its Florida landfall as a category 2 hurricane, but after encountering the southeastern portion of the Loop Current, it reached the Florida coast as a category 3 instead.[12]

While not as infamous as Katrina, Hurricane Opal most definitively illustrates the deepening abilities of a warm core ring. After crossing the Yucatan peninsula, Opal reentered the Gulf of Mexico and passed over an eddy shed by the Loop Current. Within a fourteen-hour period, sea surface pressure dropped from 965 to 916 hectaPasals, surface winds increased from 35 to 60 meters/second, and the storm condensed from a radius of 40 kilometers to 25 kilometers. Prior to the storm, the 20 °C isotherm was located at a depth between 175 and 200 meters, but was found 50 meters shallower after the storm had passed. While the majority of this hurricane induced cooling of the mixed layer was attributed to upwelling (due to Ekman divergence), another 2000 to 3000 watts/meter squared were estimated to be lost through heat flux at the air-water interface of the storm's core. Furthermore, buoy-derived sea surface temperature readings recorded temperature dropping 2° to 3 °C as Opal passed over Gulf Common Waters, but only 0.5° to 1 °C as the storm encountered the more massive ocean mixed layer associated with the warm core eddy.[13]

In 2008, Hurricane Gustav transited the Loop Current, but due to the current's temperature (then only in the high 80's-degrees-F) and truncated size (extending only halfway from Cuba to Louisiana, with cooler water in-between its tip and the Louisiana coast) the storm remained a category 3 hurricane instead of increasing strength as it passed over the current.[14][15]

Hurricane Ivan rode the Loop Current twice in 2004.


Hurricane strengthening and weakening is the product of extensive thermodynamic interactions between the atmosphere and the ocean. Generally speaking, the evolution of a hurricane's intensity is determined by three factors. First, the initial intensity of a tropical cyclone is a predominant factor and its strength will be reflected throughout the storm's life. Second, the thermodynamic state of the atmosphere through which the cyclone moves will affects its ability to strengthen, as strong horizontal winds will disperse internal circulation and prevent the vertical stacking of energy within the storm. The third component affecting hurricane intensity is the heat exchange between the upper layer of ocean waters and the core of the storm.[16] For this reason, a major focus of hurricane research has been sea surface temperature prior to a storm. However, recent studies have revealed that surface temperature is less important in hurricane deepening than the depth of the ocean mixed layer. In fact, a hurricane's sea level pressure has been shown to be more closely correlated with the 26 °C isotherm depth (and oceanic heat content) than the sea surface temperature.[17] Storms passing over the Loop Current or warm core eddies have access to more tepid water, and therefore the higher energy content of the heated molecules.

Once Hurricane Rita left the Loop Current and passed over cooler water, it declined in strength, but the main factor in this weakening was an eyewall replacement cycle (ERC) occurring at that time. The ERC and other atmospheric factors are why Rita did not reintensify when subsequently passing over the eddy vortex.

Also of note: tropical depressions, tropical storms, and hurricanes gain strength from, but are not steered by, the temperature of the water. They are steered by the atmosphere, and the atmospheric level involved in steering a hurricane is different at different intensities (i.e., it relates to the minimum pressure of the hurricane).

Sea level and sea temperature

Sea level is relatively easy to measure accurately using radars from satellites. Sea temperature below the surface is not as easy to measure widely, but can be inferred from the sea level since warmer water expands and thus (all other factors, such as water depth, being equal) a vertical column of water will rise slightly higher when warmed. Thus sea level is often used as a proxy for deep sea temperatures.

NOAA's National Data Buoy Center maintains a large number of data buoys in the Gulf of Mexico, some of which measure sea temperature one meter below the surface.


The Loop Current and Loop Current Eddies affect biological communities within the Gulf of Mexico. In general, however, it is not the warm-core Loop Current and eddies themselves that affect these communities. Instead, it is the smaller cold-core features known as Frontal Eddies that form around the boundary of the Loop Current and Loop Current Eddies, which affect biological communities in the Gulf.

Loop Current Frontal Eddies are cold-core, counter-clockwise rotating (cyclonic) eddies that form on or near the boundary of the Loop Current. LCFEs range from about 80 km to 120 km in diameter.[18] These cold features are smaller than the warm-core eddies shed from the Loop Current.

Multiple studies have shown differences in biological communities inside versus outside of the various features in the Gulf of Mexico. Higher standing stocks of zooplankton and micronekton were found in cold-core features than in both the Loop Current and the Loop Current Eddies.[19] However, no difference in the abundance of euphausiids, planktonic shrimp-like marine crustaceans, was found between areas of upwelling and warm-core eddies,[20] but in 2004 the hyperiid abundance was found to be lower within Loop Current Eddies as opposed to outside.[21] Concurrently, it was found that nutrient (nitrate) levels were low above 100 meters within warm-core eddies, while nitrate levels were high within cold features.[22][23] Low standing stock of chlorophyll, primary production, and zooplankton biomass was found to be low in LCEs.[24]

Low chlorophyll concentrations and primary production are likely a result of low nutrients levels, as many planktonic species require nitrate and other nutrients to survive. In turn, low primary production could be one cause of heterotrophic (organism-eating, as opposed to photosynthetic) species abundances being low inside the Loop Current and Loop Current Eddies. Alternatively, temperature may play a role for low abundances of both communities: Atlantic Blue Fin Tuna have developed behavioral patterns of avoiding the high temperatures associated with warm-core features, such as the Loop Current and Loop Current Eddies, in the Gulf of Mexico.[25] It is possible, also, that planktonic species likewise avoid the higher temperatures in these features.

See also


  1. ^ Perez-Brunius, Paula; Candela, Julio; Garcia-Carrillo, Paula; Furey, Heather; Bower, Amy; Hamilton, Peter; and Leben, Robert. (March 2018). "Dominant Circulation Patterns of the Deep Gulf of Mexico." Journal of Physical Oceanography. American Meteorological Society. 48(3):511. https://doi.org/10.1175/JPO-D-17-0140.1 AMS website Retrieved 27 August 2018.
  2. ^ Johns, W; Townsend, T.; Fratantoni, D.; Wilson, W. (2002). "On the Atlantic Inflow to the Caribbean Sea". Deep-Sea Research Part I: Oceanographic Research Papers. 49 (2): 211–243. Bibcode:2002DSRI...49..211J. doi:10.1016/s0967-0637(01)00041-3.
  3. ^ Gordon, A (1967). "Circulation of the Caribbean Sea". Journal of Geophysical Research. 72 (24): 6207–6223. Bibcode:1967JGR....72.6207G. CiteSeerX doi:10.1029/jz072i024p06207.
  4. ^ Sturges, W; Leben, R (2000). "Frequency of Ring Separations from the Loop Current in the Gulf of Mexico: A Revised Estimate". Journal of Physical Oceanography. 30 (7): 1814–1819. Bibcode:2000JPO....30.1814S. doi:10.1175/1520-0485(2000)030<1814:forsft>2.0.co;2.
  5. ^ Oey, L; Ezer, T.; Lee, H. (2005). Rings and Related Circulation in the Gulf of Mexico: A Review of Numerical Models and Future Challenges. Geophysical Monograph Series. 161. pp. 31–56. Bibcode:2005GMS...161...31O. CiteSeerX doi:10.1029/161gm04. ISBN 9781118666166.
  6. ^ Mooers, C (1998). Intra-Americas Circulation. The Sea, The Global Coastal Ocean, Regional Studies and Syntheses. John Wiley and Sons. pp. 183–208.
  7. ^ Oey, L; Ezer, T.; Lee, H. (2005). Rings and Related Circulation in the Gulf of Mexico: A Review of Numerical Models and Future Challenges. Geophysical Monograph Series. 161. pp. 31–56. Bibcode:2005GMS...161...31O. CiteSeerX doi:10.1029/161gm04. ISBN 9781118666166.
  8. ^ "CU-Boulder Researchers Chart Hurricane Rita Through Gulf Of Mexico accessed 8 Jan. 2012". Archived from the original on 2013-05-27. Retrieved 2012-01-08.
  9. ^ Jaimes, B; Shay, L. (2009). "Mixed Layer Cooling in Mesoscale Oceanic Eddies during Hurricanes Katrina and Rita". Monthly Weather Review. 137 (12): 4188–4207. Bibcode:2009MWRv..137.4188J. doi:10.1175/2009mwr2849.1.
  10. ^ DeMaria, M; Kaplan, J. (1994). "Sea Surface Temperatures and the Maximum Intensity of Atlantic Tropical Cyclones". Journal of Climate. 7 (9): 1324–1334. Bibcode:1994JCli....7.1324D. doi:10.1175/1520-0442(1994)007<1324:sstatm>2.0.co;2.
  11. ^ Shay, L; Goni, G.; Black, P. (2000). "Effects of a Warm Oceanic Feature on Hurricane Opal". Monthly Weather Review. 128 (5): 1366–1383. Bibcode:2000MWRv..128.1366S. doi:10.1175/1520-0493(2000)128<1366:eoawof>2.0.co;2.
  12. ^ http://www.weather.gov/storms/wilma/wilma_trak_lg.jpg
  13. ^ Shay, L; Goni, G.; Black, P. (2000). "Effects of a Warm Oceanic Feature on Hurricane Opal". Monthly Weather Review. 128 (5): 1366–1383. Bibcode:2000MWRv..128.1366S. doi:10.1175/1520-0493(2000)128<1366:eoawof>2.0.co;2.
  14. ^ "Gustav headed for current that fuels big storms". 2008-08-29. Retrieved 2008-09-01.
  15. ^ "Loop Current could generate a powerful Hurricane Gustav". 2008-08-30. Archived from the original on 2008-08-31. Retrieved 2008-09-01.
  16. ^ Emanuel, K (1999). "Thermodynamic Control of Hurricane Intensity". Nature. 401 (6754): 665–669. Bibcode:1999Natur.401..665E. doi:10.1038/44326.
  17. ^ Jaimes, B; Shay, L. (2009). "Mixed Layer Cooling in Mesoscale Oceanic Eddies during Hurricanes Katrina and Rita". Monthly Weather Review. 137 (12): 4188–4207. Bibcode:2009MWRv..137.4188J. doi:10.1175/2009mwr2849.1.
  18. ^ Le Hénaff, M., Kourafalou, V.H., Dussurget, R., Lumpkin, R. (In-press), Cyclonic activity in the eastern Gulf of Mexico: Characterization from along-track altimetry and in situ drifter trajectories, Progress in Oceanography, doi:10.1016/j.pocean.2013.08.002
  19. ^ Zimmerman, R. A.; Biggs, D. C. (1999). "Patterns of distribution of sound-scattering zooplankton in warm- and cold-core eddies in the Gulf of Mexico, from a narrowband acoustic Doppler current profiler survey". J. Geophys. Res. Oceans. 104 (C3): 5251–5262. Bibcode:1999JGR...104.5251Z. doi:10.1029/1998JC900072.
  20. ^ Gasca, R.; Castellanos, I.; Biggs, D. C. (2001). "Euphausiids (Crustacea, Euphausiacea) and summer mesoscale features in the Gulf of Mexico". Bull. Mar. Sci. 68: 397–408.
  21. ^ Gasca, R (2004). "Distribution and abundance of hyperiid amphipods in relation to summer mesoscale features in the southern Gulf of Mexico". J. Plankton Res. 26 (9): 993–1003. doi:10.1093/plankt/fbh091.
  22. ^ Biggs, D. C.; Vastano, A. C.; Ossinger, A.; Gil-Zurita, A.; Pérez-Franco, A. (1988). "Multidisciplinary study of warm and cold-core rings in the Gulf of Mexico". Mem. Soc. Cienc. Nat. La Salle, Venezuela. 48: 12–31.
  23. ^ Biggs, D. C. (1992). "Nutrients, plankton, and productivity in a warm-core ring in the western Gulf of Mexico". J. Geophys. Res. Oceans. 97 (C2): 2143–2154. Bibcode:1992JGR....97.2143B. doi:10.1029/90JC02020.
  24. ^ Biggs, D. C. (1992). "Nutrients, plankton, and productivity in a warm-core ring in the western Gulf of Mexico". J. Geophys. Res. Oceans. 97 (C2): 2143–2154. Bibcode:1992JGR....97.2143B. doi:10.1029/90JC02020.
  25. ^ Teo, S. L. H.; Boustany, A. M.; Block, B. A. (2007). "Oceanographic preferences of Atlantic bluefin tuna, Thunnus thynnus, on their Gulf of Mexico breeding grounds". Mar. Biol. 152 (5): 1105–1119. doi:10.1007/s00227-007-0758-1.

External links

Cold core ring

Cold-core rings are a type of oceanic eddy, which are characterized as unstable, time-dependent swirling ‘cells’ that separate from their respective ocean current and move into water bodies with different physical, chemical, and biological characteristics. Their size can range from 1 mm to over 10,000 km in diameter with depths over 5 km. Cold-core rings are the product of warm water currents wrapping around a colder water mass as it breaks away from its respective current. The direction an eddy swirls can be categorized as either cyclonic or anticyclonic depending on the hemisphere. A counterclockwise movement of water in the Northern hemispheres is cyclonic, but the same counterclockwise movement is anticyclonic in the Southern hemisphere (Yasuda, 2000). Although eddies have large amounts of kinetic energy, their rotation is relatively quick to diminish in relation to the amount of viscous friction in water. They typically last for a few weeks to a year. The nature of eddies are such that the center of the eddy, the outer swirling ring, and the surrounding waters are well stratified and all maintain their distinct properties throughout the eddy’s short time-scale.

DP cell

A DP cell is a device that measures the differential pressure between two inputs.Example:

To measure the pressure difference between a container (or vessel) and the surrounding atmosphere, you may connect 'Hi' port of the DP-cell to a fitting that enters the vessel, using suitable tubing. The 'Lo' port, you leave open to the atmosphere (open air, or possibly through a buffer or desiccant chamber). The DP-cell will indicate the relative difference between the pressure of the vessel (container) and the atmospheric pressure.

This signal is often wired to an indicator that reads out locally, or remotely in a control room, and/or as a control (or feedback) signal to a valve, pump, or other control element to maintain a set pressure, or limit a maximum pressure.

Typically, the signal is 4-20 mA DC loop current, where, usually, 4mA represents the minimum differential pressure and 20mA represents the maximum differential pressure.

. Alternatively, the signal may be a variable voltage, or digital information stream.

Electrical resistance and conductance

The electrical resistance of an object is a measure of its opposition to the flow of electric current. The inverse quantity is electrical conductance, and is the ease with which an electric current passes. Electrical resistance shares some conceptual parallels with the notion of mechanical friction. The SI unit of electrical resistance is the ohm (Ω), while electrical conductance is measured in siemens (S).

The resistance of an object depends in large part on the material it is made of—objects made of electrical insulators like rubber tend to have very high resistance and low conductivity, while objects made of electrical conductors like metals tend to have very low resistance and high conductivity. This material dependence is quantified by resistivity or conductivity. However, resistance and conductance are extensive rather than bulk properties, meaning that they also depend on the size and shape of an object. For example, a wire's resistance is higher if it is long and thin, and lower if it is short and thick. All objects show some resistance, except for superconductors, which have a resistance of zero.

The resistance (R) of an object is defined as the ratio of voltage across it (V) to current through it (I), while the conductance (G) is the inverse:

For a wide variety of materials and conditions, V and I are directly proportional to each other, and therefore R and G are constants (although they will depend on the size and shape of the object, the material it is made of, and other factors like temperature or strain). This proportionality is called Ohm's law, and materials that satisfy it are called ohmic materials.

In other cases, such as a transformer, diode or battery, V and I are not directly proportional. The ratio V over I is sometimes still useful, and is referred to as a "chordal resistance" or "static resistance", since it corresponds to the inverse slope of a chord between the origin and an I–V curve. In other situations, the derivative may be most useful; this is called the "differential resistance".

Florida Current

The Florida Current is a thermal ocean current that flows from the Straits of Florida around the Florida Peninsula and along the southeastern coast of the United States before joining the Gulf Stream Current near Cape Hatteras. Its contributing currents are the Loop Current and the Antilles Current. The current was discovered by Spanish explorer Juan Ponce de León in 1513.

The Florida Current results from the movement of water pushed from the Atlantic into the Caribbean Sea by the rotation of the Earth (which exerts a greater force at the equator). The water piles up along Central America and flows northward through the Yucatán Channel into the Gulf of Mexico. The water is heated in the Gulf and forced out through the Florida Straits, between the Florida Keys and Cuba and flows northward along the east coast of the United States. The Florida Current is often referred to imprecisely as the Gulf Stream. In fact, the Florida Current joins the Gulf Stream off the east coast of Florida.

Flow control valve

A flow control valve regulates the flow or pressure of a fluid. Control valves normally respond to signals generated by independent devices such as flow meters or temperature gauges.

Ground loop (electricity)

In an electrical system, a ground loop or earth loop occurs when two points of a circuit both intended to be at ground reference potential have a potential between them. This can be caused, for example, in a signal circuit referenced to ground, if enough current is flowing in the ground to cause two points to be at different potentials.

Ground loops are a major cause of noise, hum, and interference in audio, video, and computer systems. Wiring practices that protect against ground loops include ensuring that all vulnerable signal circuits are referenced to one point as ground. The use of differential connections can provide rejections of ground-induced interference. Removal of safety ground connections to equipment in an effort to eliminate ground loops also eliminates the protection the safety ground connection is intended to provide.

Gulf of Mexico

The Gulf of Mexico (Spanish: Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. The U.S. states of Texas, Louisiana, Mississippi, Alabama, and Florida border the Gulf on the north, which are often referred to as the "Third Coast", in comparison with the U.S. Atlantic and Pacific coasts.

The Gulf of Mexico formed approximately 300 million years ago as a result of plate tectonics. The Gulf of Mexico basin is roughly oval and is approximately 810 nautical miles (1,500 km; 930 mi) wide and floored by sedimentary rocks and recent sediments. It is connected to part of the Atlantic Ocean through the Florida Straits between the U.S. and Cuba, and with the Caribbean Sea (with which it forms the American Mediterranean Sea) via the Yucatán Channel between Mexico and Cuba. With the narrow connection to the Atlantic, the Gulf experiences very small tidal ranges. The size of the Gulf basin is approximately 1.6 million km2 (615,000 sq mi). Almost half of the basin is shallow continental shelf waters. The basin contains a volume of roughly 2,500 quadrillion liters (550 quadrillion Imperial gallons, 660 quadrillion US gallons, 2.5 million km3 or 600,000 cu mi). The Gulf of Mexico is one of the most important offshore petroleum production regions in the world, comprising one-sixth of the United States' total production.

Highway Addressable Remote Transducer Protocol

The HART Communication Protocol (Highway Addressable Remote Transducer) is a hybrid analog+digital industrial automation open protocol. Its most notable advantage is that it can communicate over legacy 4–20 mA analog instrumentation current loops, sharing the pair of wires used by the analog-only host systems. HART is widely used in process and instrumentation systems ranging from small automation applications up to highly sophisticated industrial applications.

According to Emerson, due to the huge installation base of 4–20 mA systems throughout the world, the HART Protocol is one of the most popular industrial protocols today. HART protocol has made a good transition protocol for users who wished to use the legacy 4–20 mA signals, but wanted to implement a "smart" protocol.

The protocol was developed by Rosemount Inc., built off the Bell 202 early communications standard in the mid-1980s as a proprietary digital communication protocol for their smart field instruments. Soon it evolved into HART and in 1986 it was made an open protocol. Since then, the capabilities of the protocol have been enhanced by successive revisions to the specification.

Hurricane Weather Research and Forecasting Model

The Hurricane Weather Research and Forecasting (HWRF) model is a specialized version of the weather research and forecasting model and is used to forecast the track and intensity of tropical cyclones. The model was developed by the National Oceanic and Atmospheric Administration (NOAA), the U.S. Naval Research Laboratory, the University of Rhode Island, and Florida State University. It became operational in 2007.The HWRF computer model is the operational backbone for hurricane track and intensity forecasts by the National Hurricane Center (NHC). The model will use data from satellite observations, buoys, and reconnaissance aircraft, making it able to access more meteorological data than any other hurricane model before it. The model will eventually run q at an even higher resolution which will allow smaller scale features to become more discernible.

Mary Glackin, acting director of NOAA's National Weather Service, says that "It is vital that we understand all the factors of hurricane forecasting throughout the life of a storm and HWRF will provide an unprecedented level of detail. Over the next several years, this model promises to improve forecasts for tropical cyclone intensity, wave and storm surge, and hurricane-related inland flooding." She also says that the HWRF "will be one of the most dynamic tools available" for forecasters.Development of the HWRF model began in 2002. In 2007, the HWRF model became operational. While the HWRF model will eventually replace the GFDL model, the GFDL model will continue to be run in 2007. The GFDL model has continued to be run operationally through 2012.

Loop start

Loop start is a telecommunications supervisory protocol between a central office or private branch exchange (PBX) and a subscriber telephone or other terminal for the purpose of starting and terminating a telephone call. It is the simplest of the telephone signaling systems, and uses the presence or absence of loop current to indicate the off-hook and on-hook loop states, respectively. It is used primarily for subscriber line signaling. An extension of the protocol that adds disconnect supervision is often called kewlstart.

Mesh analysis

Mesh analysis (or the mesh current method) is a method that is used to solve planar circuits for the currents (and indirectly the voltages) at any place in the electrical circuit. Planar circuits are circuits that can be drawn on a plane surface with no wires crossing each other. A more general technique, called loop analysis (with the corresponding network variables called loop currents) can be applied to any circuit, planar or not. Mesh analysis and loop analysis both make use of Kirchhoff’s voltage law to arrive at a set of equations guaranteed to be solvable if the circuit has a solution. Mesh analysis is usually easier to use when the circuit is planar, compared to loop analysis.

Meteorological history of Hurricane Gustav

The meteorological history of Hurricane Gustav spanned eleven days, from August 25 to September 4, 2008. The tropical disturbance which eventually spawned Hurricane Gustav gathered on August 16, southwest of the Cape Verde islands, but was slow to develop as it trekked west across the Atlantic. Upon reaching the warm waters of Caribbean Sea it began to organize and became a tropical depression on August 25. It quickly strengthened to a tropical storm, and then a hurricane, before making landfall on Haiti's southwest peninsula. Gustav was severely disrupted by Hispaniola's mountains and stalled, disorganized, in the Gulf of Gonâve between August 26 and 27.

Deep convection reformed the storm's center southwest of Haiti, near Jamaica's east coast. Under the influence of a mid-level ridge that extended from the Gulf of Mexico to the western Atlantic Ocean, Gustav picked up a westward motion. It was briefly disrupted by Jamaica as it passed over the mountainous island but rapidly strengthened when it moved over open water once again. Reaching Category 4 strength about 24 hours after having been upgraded to a hurricane, Gustav brushed the Isle of Youth and made landfall on Cuba's western's peninsula.

Disrupted by mountains once again, Gustav never regained its former strength. Briefly traveling over a warm eddy of the Gulf Stream's loop current it encountered moderate wind shear and cooling sea surface temperatures. Fluctuations in its internal structure and visible appearance did not counter the storm's general weakening trend, and Hurricane Gustav made its final landfall as a Category 2 hurricane near Cocodrie, Louisiana on September 1. Moving inland, the storm quickly weakened but persisted as a significant tropical depression until it was adsorbed by a frontal boundary on September 5.

Meteorological history of Hurricane Katrina

Hurricane Katrina was an extremely destructive Category 5 hurricane that affected the majority of the Gulf Coast. Its damaging trek began on August 23, 2005, when it originated as Tropical Depression Twelve near the Bahamas. The next day, the tropical depression strengthened to a tropical storm, and was named Katrina; it proceeded to make landfall on the southern tip of the U.S. state of Florida as a minimal hurricane.

In passing across Florida, Katrina did not attain any more strength but did manage to maintain hurricane status. After passing over Florida, the warm waters of the Gulf of Mexico allowed it to rapidly intensify to the sixth-strongest Atlantic hurricane in recorded history. Afterward, Katrina made landfall as a Category 3 storm near Buras-Triumph, Louisiana, and once more near the Mississippi/Louisiana border. Katrina progressed northward through the central United States and finally dissipated near the Great Lakes on August 31, when it was absorbed by a cold front.

Paul G. Gaffney II

Vice Admiral Paul Golden Gaffney II, USN (Ret.), (born May 30, 1946) was the seventh president of Monmouth University in West Long Branch, New Jersey, from 2003 to 2013, becoming president emeritus August 1, 2013.

Gaffney graduated from the United States Naval Academy in 1968. Upon graduation, he was selected for immediate graduate education and received a master's degree in Ocean Engineering from The Catholic University of America in Washington, D.C. He completed a year as a student and advanced research fellow at the Naval War College, graduating with highest distinction. He completed an M.B.A. at Jacksonville University. The University of South Carolina, Jacksonville University, and The Catholic University of America have awarded him honorary doctorates.

He was president of the National Defense University from 2000 to 2003. Admiral Gaffney was the Chief of Naval Research with responsibility for science and technology investment for the Navy and Marine Corps from 1996-2000 and Commander of Naval Oceanography and Meteorology, 1994-1997. In July 2001 he was appointed by the President to the United States Commission on Ocean Policy, and served through the full term of the Commission until 2004. In August 2009, Gaffney was named the chair of the Ocean Research Advisory Panel (ORAP), a panel created by statute to advise federal agencies regarding ocean science and management matters. In 2012 he co-chaired the Decadal Review of the US Ocean Exploration Program. In October 2014, he was appointed as the first chair of new Ocean Exploration Advisory Board (OAEB), serving until 2017. Since 2015, he has been a member of the National Academies of Science, Engineering and Medicine's Gulf of Mexico Research Program Advisory Board.Gaffney's naval career spanned over three decades including duty at sea, overseas, and ashore in executive and command positions. He served in Japan, Vietnam, Spain, and Indonesia. While a military officer, his career focused on oceanography.

He is the eponym of Gaffney Ridge, an undersea ridge in the South China Sea, 220 miles west of the Philippines (located at Latitude 13° 23' 00" N and Longitude 118° 32' 00" E). Gaffney also became the namesake of a supercomputer at the newest Department of Defense Supercomputing Resource Center at the John C. Stennis Space Center, in Hancock County, Miss., when he was honored by the Naval Meteorology and Oceanography Command (NMOC) on January 25, 2019.Gaffney is the recipient of a number of military decorations, the Naval War College's J. William Middendorf Prize for Strategic Research, the Outstanding Public Service Award from the Virginia Research and Technology Consortium, and the Potomac Institute for Policy Studies Navigator Award. He has served on several boards of higher education and was a member of the Ocean Studies Board of the United States National Research Council. He is a director of Diamond Offshore Drilling Inc., and currently serves as a Fellow of the Urban Coast Institute at Monmouth University, and on the leadership council of the Joint Ocean Commission Initiative. In 2010, he was elected to the National Academy of Engineering for technical leadership in naval research and development and its impact on U.S. defense, ocean policy, and the Arctic. He chaired a National Academies’ Transportation Research Board study on domestic transportation of energy fluids (2015-2017) and chaired a National Academies consensus study on the Gulf of Mexico Loop Current. He is a Trustee of the Ocean Exploration Trust.Gaffney retired from Monmouth University in August 2013. His contributions to the success of Monmouth University and its athletic programs during his tenure were noted in a February 2016 retrospective.Following his retirement from Monmouth University, Gaffney has remained active in academia, and was the guest speaker at the hooding ceremony for master's and doctoral graduates of the Arnold School of Public Health at the University of South Carolina in May 2014. On June 13, 2015, Gaffney was honored by the Aquarium of the Pacific with a 2015 Ocean Conservation Award." On May 7, 2016, Gaffney was the recipient of the Ellis Island Medal of Honor sponsored by the National Ethnic Coalition of Organizations. At a Jan. 25, 2019 ceremony Gaffney was one of three honorees inducted into the first class of the Naval Meteorology and Oceanography Hall of Fame. Gaffney was lauded as the first naval oceanographer to attain the rank of vice admiral who "attained the visionary goal of making Naval Oceanography a true world-class supercomputing facility and delivered three oceanographic survey ships into the operational fleet—USNS Pathfinder (T-AGS-60), USNS Sumner (T-AGS-61) and USNS Bowditch (T-AGS-62)."

Shutdown of thermohaline circulation

A shutdown or slowdown of the thermohaline circulation is a hypothesized effect of global warming on a major ocean circulation.

Data from NASA in 2010 suggested that the Atlantic Meridional Overturning Circulation (AMOC) had not slowed down, but may have actually sped up slightly since 1993. A 2015 study suggested that the AMOC has weakened by 15-20% in 200 years.

Supervision (telephony)

In telecommunication, supervision is the monitoring of a telecommunication circuit for telephony to convey to an operator, user, or a switching system, information about the operational state of the circuit. The typical operational states of trunks and lines are the idle and busy states, seizure, and disconnect. The states are indicated by various electrical signals and electrical conditions depending of the type of circuit, the type of terminating equipment, and the type of intended service.

Answer and disconnect supervision are functions of line signaling that convey circuit seizure and disconnect. Answer supervision indicates that a call has been answered. Disconnect supervision provides a signal that the call has been disconnected.

For example, the called party may indicate to the telephone exchange that the call is being disconnected by the called party by allowing loop current to flow in the line, or the called party indicates to the exchange that the call is being answered.

Timeline of the Deepwater Horizon oil spill (July 2010)

Following is a timeline of the Deepwater Horizon oil spill for July 2010 .

Volume and extent of the Deepwater Horizon oil spill

The Deepwater Horizon oil spill was discovered on the afternoon of 22 April 2010 when a large oil slick began to spread at the former rig site. According to the Flow Rate Technical Group, the leak amounted to about 4.9 million barrels (210 million US gal; 780,000 m3) of oil, exceeding the 1989 Exxon Valdez oil spill as the largest ever to originate in U.S.-controlled waters and the 1979 Ixtoc I oil spill as the largest spill in the Gulf of Mexico. BP has challenged this calculation saying that it is overestimated as it includes over 810,000 barrels (34 million US gal; 129,000 m3) of oil which was collected before it could enter the Gulf waters.

Wave base

The wave base, in physical oceanography, is the maximum depth at which a water wave's passage causes significant water motion. For water depths deeper than the wave base, bottom sediments and the seafloor are no longer stirred by the wave motion above.

Ocean zones
Sea level


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