A warm core ring is a type of

mesoscale eddy In fluid dynamics, an eddy is the swirling of a fluid and the reverse current created when the fluid is in a turbulent flow regime. The moving fluid creates a space devoid of downstream-flowing fluid on the downstream side of the object. Fluid beh ...

which forms and breaks off from an

ocean current An ocean current is a continuous, directed movement of sea water generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences. Depth contours, s ...

, such as the

Gulf Stream The Gulf Stream, together with its northern extension the North Atlantic Current, North Atlantic Drift, is a warm and swift Atlantic Ocean, Atlantic ocean current that originates in the Gulf of Mexico and flows through the Straits of Florida a ...

or the

Kuroshio Current The , also known as the Black or or the is a north-flowing, warm ocean current on the west side of the North Pacific Ocean basin. It was named for the deep blue appearance of its waters. Similar to the Gulf Stream in the North Atlantic, the Ku ...

. The ring is an independent circulatory system of warm water that can persist for several months before losing its distinctive identity. Warm core rings also form in certain powerful ocean currents, such as the Kuroshio and the Gulf Stream. Warm core rings can be detected using infrared satellites or sea height anomalies resulting from and are easily identifiable against the surrounding colder waters. In addition, warm core rings are also distinguished by their low levels of biological activity. This type of system is thought to have helped develop several hurricanes, most notably

Hurricane Katrina Hurricane Katrina was a destructive Category 5 Atlantic hurricane that caused over 1,800 fatalities and $125 billion in damage in late August 2005, especially in the city of New Orleans and the surrounding areas. It was at the time the cost ...

, into significantly stronger storms due to the abundance of warmer ocean water reaching down to a significant depth, which in turn fuels and intensifies the hurricane. Warm core rings are also known for affecting wildlife, having the capacity to bring wildlife from typically warm waters to areas typically dominated by cold waters.

Formation and Movement

Formation

In general, warm core rings form as a meander of a strong oceanic current. They generally form when a strong meander on an oceanic current creates a "loop" by closing in on the meander, resulting in an independent system. SST Gulf stream

Movement

Rings will drift to the west-southwest at 3–5 km/day for several months up to a year. The rings always rotate clockwise due to the direction of the Gulf Stream and can reach rotational velocities of up to 1 m/s. Usually warm core rings cannot move onto the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

because they reach deeper than the seafloor on the shelf by over 1000 meters, though they can approach the shelf.

Dissipation

Warm core rings are often reabsorbed by the Gulf Stream, but they can break apart on their own as well if they move onto the continental shelf.

Detection and Tracking

Warm core rings are easily observed in the Gulf of Mexico or elsewhere through the use of infrared imagery by

weather satellite A weather satellite or meteorological satellite is a type of Earth observation satellite that is primarily used to monitor the weather and climate of the Earth. Satellites can be polar orbiting (covering the entire Earth asynchronously), or ge ...

s. Since the ocean water temperature of the ring is significantly higher than the surrounding waters, these rings show up easily in infrared images. This, coupled with models of ring movement, allow well-developed tracking of the rings. Because warm core rings include warm water to a significant depth, infrared satellites can differentiate the temperature, unlike cold core rings, which cannot be easily detected due to the rapid warming of waters in a cold core ring. Warm core rings are also detected by sea surface height anomalies. Since warm water takes up more space as it expands than cold water, the large amount of warm water causes an upwelling in sea height which can be detected by buoys.

Adverse Effects

Intensification of Hurricanes

Warm core rings have been linked to the intensification of several hurricanes passing over their location. Because high

sea surface temperature Sea surface temperature (SST), or ocean surface temperature, is the ocean temperature close to the surface. The exact meaning of ''surface'' varies according to the measurement method used, but it is between and below the sea surface. Air mass ...

as well as warmer water at greater depth is the primary intensifier of a

hurricane A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...

, warm core rings account for tremendous strengthening of these storms. Notably,

Hurricane Opal Hurricane Opal was a large and powerful Category 4 hurricane that caused severe and extensive damage along the northern Gulf Coast of the United States in October 1995. The fifteenth named storm, ninth hurricane and strongest tropical cyclon ...

passed over a ring and had sudden increases of wind speed from 110 miles per hour to 135 miles per hour shortly before landfall, a trend also seen in

Hurricane Allen Hurricane Allen was a rare and extremely powerful Cape Verde hurricane that affected the Caribbean, eastern and northern Mexico, and southern Texas in August 1980. The first named storm and second tropical cyclone of the 1980 Atlantic hurricane ...

and

Hurricane Camille Hurricane Camille was the second most intense tropical cyclone on record to strike the United States, behind the 1935 Labor Day hurricane. The most intense storm of the 1969 Atlantic hurricane season, Camille originated as a tropical depression ...

. There is evidence that

and

Hurricane Rita Hurricane Rita was the most intense tropical cyclone on record in the Gulf of Mexico and the fourth-most intense Atlantic hurricane ever recorded. Part of the record-breaking 2005 Atlantic hurricane season, which included three of the top ten L ...

, both notable storms which reached Category 5 intensity, as well as

Hurricane Ivan Hurricane Ivan was a large, long-lived, Cape Verde hurricane that caused widespread damage in the Caribbean and United States. The cyclone was the ninth named storm, the sixth hurricane and the fourth major hurricane of the active 2004 Atlan ...

, were also strengthened by warm core rings.

Effects on Wildlife

Warm core rings typically include far less biological specimens than the surrounding ocean. When the rings approach continental shelves, coastal currents are affected, which can cause organisms to drift onto the shelf that ordinarily would not be there. In fact, there are human accounts of sea turtles and tropical fish which normally live in much warmer waters coming near the coastal shelf due to the deep, warm waters of a warm core ring.

Damages to Offshore Drilling

Due to currents around warm core rings of up to nearly 5 miles per hour, warm core rings can damage offshore oil platforms and increase the risk of accidents.

Larval Transport

Many fish species’ life cycle involves two distinct habitats. The adults live in warmer temperate waters south of Cape Hatteras, NC while the juveniles are found in estuaries of cooler waters north of Cape Hatteras.Able, K.W. and M.P. Fahay (1998). The first year in the life of estuarine fishes in the Middle Atlantic Bight. New Brunswick: Rutgers University Press.Hare, J.A. and R.K. Cowen (1996). Transport mechanisms of larval and pelagic juvenile bluefish (Pomatomus saltatrix) from South Atlantic Bight spawning grounds to Middle Atlantic Bight nursery habitats. Limnology and Oceanography 41(6): 1264-1280. Warm Core Rings play an important role in the transport of

larvae A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

between the two habitats. Species like the

bluefish The bluefish (''Pomatomus saltatrix'') is the only extant species of the family Pomatomidae. It is a marine pelagic fish found around the world in temperate and subtropical waters, except for the northern Pacific Ocean. Bluefish are known as ta ...

(Pomatomus saltatrix) and pearly razorfish (Xyrichtys novacula) spawn near the western edge of the

just south of Cape Hatteras. Because of the convergence of the Gulf Stream from the south and cooler coastal water current from the north, most water around Cape Hatteras flows into the Gulf Stream. The larvae released near this convergence is swept into the Gulf Stream and flows north. Since the larvae are

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

ic, they don't swim into the center of the Gulf Stream but stay near the western edge.Hare, J.A. and R.K. Cowen (1991). Expatriation of Xyrichtys novacula (Pisces: Labridae) larvae: Evidence of rapid cross-slope exchange.

Journal of Marine Research The ''Journal of Marine Research'' is an American journal, first published by Yale University in 1937, that covers peer-reviewed scientific articles and is still published today. The academic journal publishes articles Article often refers to: ...

49: 801-823.Cowen, R.K., J.A. Hare, and M.P. Fahay (1993). Beyond hydrography: Can physical processes explain larval fish assemblages within the Middle Atlantic Bight? Bulletin of Marine Science. 53: 567-587. This is beneficial for when warm core rings form. Warm core rings are formed when the crest of a meander breaks off from the Gulf Stream. Any larvae in the crest of the meanders are then entrapped in the warm core ring. Once the warm core ring breaks way, it takes a southwesterly path towards the coast. The interaction between warm core rings and the

creates a weakening of the ring and enables the larvae to escape and continue their journey to nearby

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...

. The warm core rings formed along the northeastern states can last between 4 and 5 months.Auer, S.J. (1987). Five-year climatological survey of the Gulf Stream system and its associated rings. Journal of Geophysical Research 92: 11709-11726. During this time the larvae grow so that by the time they reach the estuaries, they are able to swim away from the warm core ring into the estuaries.

References

Weather events Ocean currents