Summary
Zonation is apparent on many coral reefs and coral growth
form reflects environmental gradients in several factors,
particularly light availability, wave energy, emersion,
and sedimentation patterns.
Bibliography
Chappell, J., 1980. Coral morphology, diversity and reef growth.
Nature, 286, 249–252.
Hopley, D., 2008. Geomorphology of coral reefs with special reference
to the Great Barrier Reef, In Hutchings, P., Kingsford, M., and
Hoegh-Guldberg, O. (eds.), The Great Barrier Reef: biology, environment and management. Australia: CSIRO Publishing, pp. 5–16.
Cross-references
Corals: Environmental Controls on Growth
Eco-Morphodynamics
Geister Classification of Reefs
Geomorphic Zonation
Microatoll
Reef Front Wave Energy
Sediment Durability
EL NIN ˜ O, LA NIN ˜ A, AND ENSO
Joshua S. Feingold
Nova Southeastern University, Dania Beach,
Florida, USA
Synonyms
La Niña is also called Anti-El Niño and El Viejo
Definition
El Niño (The Christ child) is a seasonal current that typically transports warm sea surface water from the Pacific
coast of Central America to the equatorial Eastern Pacific.
Also, it refers to the migration of Central Pacific equatorial
warm water to the east, and the warm phase of the Southern Oscillation.
La Niña (The little girl) is the cool phase of the Southern
Oscillation.
El Niño-Southern Oscillation (ENSO) is the coupled
ocean–atmospheric shifts in high pressure centers from
the equatorial Western Pacific to the equatorial Eastern
Pacific.
Introduction
El Niño, La Niña, and El Niño-Southern Oscillation
(ENSO) are related but distinct phenomena. The El Niño
current is a seasonal, warm current that typically originates
near Central America and flows into sea surface waters off
Ecuador and Peru. This current typically appears in late
December or early January, and its association with Christmas and the Epiphany led to it being called El Niño (The
Christ Child). Central Pacific equatorial warm water that
migrates to the east also produces warming of the Eastern
Pacific, and has been called El Niño. The term El Niño is
also used to denote the warm phase of ENSO, with La Niña
referring to the cool phase (Philander, 1990). ENSO results
from a wide scale shift in pressure centers related to feedback cycles within the coupled ocean–atmosphere climate
system of the tropical Pacific, potentially influenced by
external forcing (Enfield, 1989). During the ENSO warm
phase, high atmospheric pressure, typically located in the
West Pacific (near Darwin, Australia), shifts to the Central
Pacific (near Tahiti), reducing westerly trade wind velocities, and consequently reducing the flow of the South Equatorial Current. Tropical heat that is normally pumped to the
west by this current is retained in the Eastern Pacific. Under
extreme warm phase ENSO conditions, wind fields reverse
and easterly winds move warm surface water into the Eastern Pacific. Kelvin Waves are also associated with Eastern
Pacific warming, as they pump subsurface warm water to
the east along the equator. Persistence of high pressure in
the Central Pacific indicates El Niño conditions, and especially high pressures in the Western Pacific associated with
colder Eastern Pacific sea-surface water are indicators of La
Niña. The cool phase of ENSO (La Niña) can follow the
warm phase as global pressure shifts relax towards normal
and occasionally overshoot, resulting in anomalously cool
conditions in the eastern tropical Pacific (Enfield, 2001).
Links between ENSO and global climate perturbations
have been documented (Holland, 2009), and related impacts
to adjacent regions (teleconnections) affect coral ecosystems in the western Caribbean Sea (Coffroth et al., 1990),
Indian Ocean (Wilkinson et al., 1999), Indonesia (Brown
and Suharsono, 1990), French Polynesia (Hoegh-Guldberg,
1999), and even coral reefs worldwide (Wilkinson, 2000).
ENSO events have occurred every 3.8 Æ 1.8 (mean Æ s.d.)
years, and strong and very strong events every 9.9
Æ 4.2 years (Enfield and Cid, 1991). No two ENSO events
are alike. Their strength is related to the intensity and duration of sea-surface temperature (SST) anomalies (differences between measured temperatures and long-term
means). Two very strong events occurred in 1982–1983
and 1997–1998. The event in 1982–1983 was called the
strongest of the twentieth century (Kerr, 1983), at least until
the 1997–1998 event which was comparable in magnitude
(Enfield, 2001). Conditions are now (August 2009) favorable for the development of another ENSO in 2009–2010
(NOAA, 2009).
The strength of the event is generally proportional to
the amount of impact to coral. Weak to moderate ENSO
events have had little effect, whereas the severe events of
1982–1983 and 1997–1998 resulted in coral mortality
ranging from 15 to 99% at locations in the tropical Eastern
Pacific (Glynn, 2001).
ENSO effects on corals
ENSO effects on corals were first well documented during
the 1982–1983 event, and even more thorough investigations were performed during the 1997–1998 event
EL NIN ˜ O, LA NIN ˜ A, AND ENSO
365
Zonation is apparent on many coral reefs and coral growth
form reflects environmental gradients in several factors,
particularly light availability, wave energy, emersion,
and sedimentation patterns.
Bibliography
Chappell, J., 1980. Coral morphology, diversity and reef growth.
Nature, 286, 249–252.
Hopley, D., 2008. Geomorphology of coral reefs with special reference
to the Great Barrier Reef, In Hutchings, P., Kingsford, M., and
Hoegh-Guldberg, O. (eds.), The Great Barrier Reef: biology, environment and management. Australia: CSIRO Publishing, pp. 5–16.
Cross-references
Corals: Environmental Controls on Growth
Eco-Morphodynamics
Geister Classification of Reefs
Geomorphic Zonation
Microatoll
Reef Front Wave Energy
Sediment Durability
EL NIN ˜ O, LA NIN ˜ A, AND ENSO
Joshua S. Feingold
Nova Southeastern University, Dania Beach,
Florida, USA
Synonyms
La Niña is also called Anti-El Niño and El Viejo
Definition
El Niño (The Christ child) is a seasonal current that typically transports warm sea surface water from the Pacific
coast of Central America to the equatorial Eastern Pacific.
Also, it refers to the migration of Central Pacific equatorial
warm water to the east, and the warm phase of the Southern Oscillation.
La Niña (The little girl) is the cool phase of the Southern
Oscillation.
El Niño-Southern Oscillation (ENSO) is the coupled
ocean–atmospheric shifts in high pressure centers from
the equatorial Western Pacific to the equatorial Eastern
Pacific.
Introduction
El Niño, La Niña, and El Niño-Southern Oscillation
(ENSO) are related but distinct phenomena. The El Niño
current is a seasonal, warm current that typically originates
near Central America and flows into sea surface waters off
Ecuador and Peru. This current typically appears in late
December or early January, and its association with Christmas and the Epiphany led to it being called El Niño (The
Christ Child). Central Pacific equatorial warm water that
migrates to the east also produces warming of the Eastern
Pacific, and has been called El Niño. The term El Niño is
also used to denote the warm phase of ENSO, with La Niña
referring to the cool phase (Philander, 1990). ENSO results
from a wide scale shift in pressure centers related to feedback cycles within the coupled ocean–atmosphere climate
system of the tropical Pacific, potentially influenced by
external forcing (Enfield, 1989). During the ENSO warm
phase, high atmospheric pressure, typically located in the
West Pacific (near Darwin, Australia), shifts to the Central
Pacific (near Tahiti), reducing westerly trade wind velocities, and consequently reducing the flow of the South Equatorial Current. Tropical heat that is normally pumped to the
west by this current is retained in the Eastern Pacific. Under
extreme warm phase ENSO conditions, wind fields reverse
and easterly winds move warm surface water into the Eastern Pacific. Kelvin Waves are also associated with Eastern
Pacific warming, as they pump subsurface warm water to
the east along the equator. Persistence of high pressure in
the Central Pacific indicates El Niño conditions, and especially high pressures in the Western Pacific associated with
colder Eastern Pacific sea-surface water are indicators of La
Niña. The cool phase of ENSO (La Niña) can follow the
warm phase as global pressure shifts relax towards normal
and occasionally overshoot, resulting in anomalously cool
conditions in the eastern tropical Pacific (Enfield, 2001).
Links between ENSO and global climate perturbations
have been documented (Holland, 2009), and related impacts
to adjacent regions (teleconnections) affect coral ecosystems in the western Caribbean Sea (Coffroth et al., 1990),
Indian Ocean (Wilkinson et al., 1999), Indonesia (Brown
and Suharsono, 1990), French Polynesia (Hoegh-Guldberg,
1999), and even coral reefs worldwide (Wilkinson, 2000).
ENSO events have occurred every 3.8 Æ 1.8 (mean Æ s.d.)
years, and strong and very strong events every 9.9
Æ 4.2 years (Enfield and Cid, 1991). No two ENSO events
are alike. Their strength is related to the intensity and duration of sea-surface temperature (SST) anomalies (differences between measured temperatures and long-term
means). Two very strong events occurred in 1982–1983
and 1997–1998. The event in 1982–1983 was called the
strongest of the twentieth century (Kerr, 1983), at least until
the 1997–1998 event which was comparable in magnitude
(Enfield, 2001). Conditions are now (August 2009) favorable for the development of another ENSO in 2009–2010
(NOAA, 2009).
The strength of the event is generally proportional to
the amount of impact to coral. Weak to moderate ENSO
events have had little effect, whereas the severe events of
1982–1983 and 1997–1998 resulted in coral mortality
ranging from 15 to 99% at locations in the tropical Eastern
Pacific (Glynn, 2001).
ENSO effects on corals
ENSO effects on corals were first well documented during
the 1982–1983 event, and even more thorough investigations were performed during the 1997–1998 event
EL NIN ˜ O, LA NIN ˜ A, AND ENSO
365