El Niño and the 2014-2017? Global Coral Bleaching Event

As of May 12, 2016, NOAA's National Centers for Environmental Prediction has issued an El Niño Advisory/La Niña Watch. Sea surface temperature (SST) anomalies continued decreasing across most of the equatorial Pacific this month. A transition to a brief period of ENSO-neutral conditions is likely during early Northern Hemisphere summer, with an increasing chance (about 75%) of La Niña conditions developing in summer and persisting through fall and winter 2016-17, as seen in the figure on the left.


This next figure on the left shows forecasts, made by a set of dynamic and statistical models, published on May 19, 2016, for sea surface temperature (SST) in the Niño 3.4 region for nine overlapping 3-month periods. This figure also indicates a likely transition to ENSO-neutral conditions during Northern Hemisphere summer, followed by a La Niña as of early fall 2016. We will continue to provide updates as the ENSO forecast changes.


Most Recent Bleaching Observations in Press

2016 May 30 Coral death toll climbs on Great Barrier Reef (Link to the source article)
2016 May 27 Update on coral bleaching and mortality in the Great Barrier Reef (Link to the source article)
2016 May 13 Update on coral bleaching in the Great Barrier Reef (Link to the source article)
2016 May 13 Updated Map of observed bleaching for the Great Barrier Reef (Link to the source article)
2016 May 6 Update on coral bleaching in the Great Barrier Reef (Link to the source article)
2016 April 20 Press release: Only 7% of Great Barrier Reef has avoided coral bleaching (Link to the source article)
2016 April 20 Map of reef survey results accompanying Great Barrier Reef press release (Link to the source article)
2016 April 20 Statement on Great Barrier Reef coral bleaching surveys (Link to the source article)
2016 April 12 Dead Kiribati reefs mark potential arrival at "dangerous" climate change threshold (Link to the source article)
2016 April 12 Updated Map of observed bleaching for the Great Barrier Reef (Link to the source article)
2016 April 12 Update on coral bleaching in the far northern Great Barrier Reef (Link to the source article)
2016 April 11 ABC-TV News interview with Mark Eakin about Great Barrier Reef bleaching (Link to the source video)
2016 April 9 Climate-Related Coral Bleaching and Death - A Global Update (Link to the source article)
2016 April 6 Intense bleaching thermal stress continues devastating reefs of Kiribati (Link to the source article)
2016 April 5 National Coral Bleaching Taskforce unleashes an armada of experts (Link to the source article)
2016 April 1 Map of observed bleaching for the Great Barrier Reef (Link to the source article)
2016 April 1 Update on coral bleaching in the far northern Great Barrier Reef (Link to the source article)
2016 April 1 El Niño continues devastating reefs worldwide, including the Great Barrier Reef (Link to the source article)
2016 March 29 Appeal for underwater photographers and videographers to document bleaching (Link to the source video)
2016 March 29 Coral Bleaching Taskforce documents most severe bleaching on record (Link to the source article)
2016 March 21 Scientist witnesses severe coral bleaching at Lizard Island (Link to the source article)
2016 March 20 Coral mortality rises in remote far northern Great Barrier Reef (Link to the source article)
2016 March 14 Australian National Coral Taskforce puts plan into effect as bleaching intensifies (Link to the source article)
2016 March 14 Coral Bleaching Intensifies in the Far Northern Great Barrier Reef (Link to the source article)
2016 March 8 Marine Reserve in Reunion Alerts of Coral Bleaching (Link to the source article)
2016 March 1 Widespread Low Level Coral Bleaching on the Great Barrier Reef (Link to the source article)
2016 February 25 New Caledonia Mass Bleaching (Link to the source article)
2016 February 23 El Niño Prolongs Longest Global Coral Bleaching Event  
2015 October 8 NOAA Declares Third Ever Global Coral Bleaching Event  
2015 September 11 Record Ocean Temperatures Causing Coral Bleaching Across Hawaii  
2015 July 6 Coral Bleaching Threat Increasing in Western Atlantic and Pacific Oceans  

Coral Reef Watch's Analysis of Current Thermal Condition and Four-Month Outlook

NOAA Coral Reef Watch's most recent Coral Bleaching Alert Area is below. This figure shows the regions currently experiencing high levels of thermal stress that cause coral bleaching.

NOAA Coral Reef Watch's most recent Four-Month Coral Bleaching Thermal Stress Outlook is below. This figure shows the distribution of the lowest thermal stress levels predicted by at least 60% of the model ensemble members. In other words, there is a 60% chance that the displayed thermal stress levels will occur.  

CRW's daily 5-km satellite coral bleaching thermal stress monitoring products and Four-Month Coral Bleaching Outlook indicate that the coral bleaching thermal stress in the eastern Pacific Ocean remains high. The Costa Rica Pacific 5-km Regional Virtual Station remains at Alert Level 2 and the Panama Pacific West station remains at Alert Level 1, although heat stress in these areas is expected to dissipate shortly. Thermal stress surrounding the Clipperton Island (France) station continues to increase, and Alert Level 1 bleaching is expected in the next few weeks. El Salvador is also expected to reach Alert Level 1 bleaching conditions in late May-early June.

In the central equatorial Pacific Ocean, reefs in the Northern Line Islands (Kiribati), Southern Line Islands, and the Marquesas Islands are again at Alert Level 2 bleaching conditions associated with significant bleaching and widespread mortality. The Northern Cook Islands also just reached Alert Level 1. The Phoenix Islands (Kiribati) remain at Alert Level 2, with no end in sight. As noted in multiple articles above and by numerous news outlets worldwide, in Kiribati, persistent elevated ocean temperatures (as high as 31.4-degrees Celsius) since June 2015 have killed most of the corals in the region. Photos taken by scientists surveying the reef damage, especially around the island of Kiritimati, where more than 80% coral mortality has been documented, are gruesome. The ongoing high bleaching thermal stress in Kiribati is tied to the very strong El Niño that has only begun to dissipate, but whose effects will last for many months in the southern hemisphere. It is estimated that only 5% of Kiribati's reefs will survive this bleaching thermal stress event.

It also is important to note that waters in Southeast Asia and the Coral Triangle continue to heat up. Many different CRW 5-km Regional Virtual Stations are monitoring Bleaching Warning stress presently, especially to the east of Sumatra, throughout the Java Sea (south of Malaysia), and into southern and western Indonesia, including the Banda and Molucca Seas. One Regional Virtual Station, West Nusa Tenggara, has been at Alert Level 1 since late February. The bleaching thermal stress in much of the Southeast Asia and Coral Triangle region is expected to elevate quickly to Alert Level 1 and 2 conditions in the weeks ahead. We will continue to monitor the developing stress in these regions and provide updates.

While bleaching thermal stress has now left Australia's Great Barrier Reef (GBR), as reported in multiple articles above and by news sources around the world, high ocean temperatures these last few months did significant damage to the GBR. Australia's National Coral Bleaching Task Force (of which NOAA CRW is a partner) reported that of the 911 coral reefs it surveyed by air along the full 2,300 km of the Great Barrier Reef (GBR), 93% of the reefs exhibited signs of bleaching. Of those reefs that bleached, 316 - nearly all of which are in the remote, usually protected northern GBR - displayed severe bleaching (i.e., 60-100% of corals were bleached on the reef). Divers surveying the northern GBR have also documented 50% coral mortality. The Great Barrier Reef Marine Park Authority now considers this to be the worst bleaching event in the history of the GBR.

Along the western coast of Australia, Scott to Ashmore Reefs is expected to remain at Alert Level 2 conditions for much of May, before the thermal stress dissipates completely. The other 5-km Regional Virtual Stations in the area range from No Stress to Bleaching Watch only.

Thermal stress also continues to develop across much of the Indian Ocean. Australia's Pulu Keeling remains under Alert Level 2, associated with significant bleaching and widespread mortality. Northern Mauritius, which has been at Alert Level 2 for weeks now, is expected to maintain this high level of bleaching thermal stress for an additional few weeks, while Somalia and Kenya continue at Alert Level 1. Many other 5-km Regional Virtual Stations in the Western Indian Ocean are also experiencing stress at Bleaching Watch and Bleaching Warning levels. Historical patterns from past El Niño and CRW's Four-Month Coral Bleaching Outlook both indicate thermal stress should intensify across the Indian Ocean over the next two months, then follow with thermal stress in the Coral Triangle and Southeast Asia by mid-2016. Bleaching has already been reported from western India and Aldabra Atoll.

The Main Hawaiian Islands (MHI), which observed record levels of bleaching in 2014 and static Alert Level 2 conditions (associated with significant, widespread coral bleaching and mortality) in October and November 2015, remain at a level of No Stress now. The Northwestern Hawaiian Islands (NWHI), which sustained high, prolonged levels of bleaching thermal stress in 2014 and some subsequent coral death, also remain under No Stress conditions. CRW continues to collect data from field partners, including Hawaii's Eyes of the Reef (EOR) volunteer community reef monitoring program concerning the extent and severity of the bleaching and coral death observed in the MHI and NWHI in 2015.

In the Atlantic Ocean, substantial bleaching was observed by local coral reef managers and monitoring networks in the Florida Keys in 2014; bleaching and coral disease were again documented in August and September 2015 in the Florida Keys (including the National Marine Sanctuary) and Southeast Florida. Waters in the region finally cooled in late November, placing the Florida Keys and Southeast Florida Virtual Stations under a level of No Stress.

The 2015 bleaching season ended in the Caribbean as well, with almost all Caribbean 5-km Regional Virtual Stations displaying a level of No Stress. Only the Panama Atlantic West Regional Virtual Station remains under a Bleaching Watch, which is predicted to downgrade to a level of No Stress in 1-2 weeks time.

Of note, the bleaching of Caribbean corals at a number of locations (e.g., Cuba, the Turks and Caicos, the Bahamas, Haiti, the Dominican Republic, and Mexico) in 2015, as reported by partner organizations with divers working on affected reefs, including the XL Catlin Seaview Survey and Reef Check, led to NOAA's declaration of the third ever global coral bleaching event on record (after the 1998 and 2010 global events). As of the end of 2015, the global event was expected to have impacted approximately 38% of the world's coral reefs and killed over 12,000 square kilometers of reefs. This has put at risk the lives and livelihoods of millions of people, who rely on coral reefs for sustenance, income, and coastal protection. U.S. coral reefs, in particular, were hit quite hard by this event; predictions indicate that as of the end of 2015, almost 95% of U.S. coral reefs were exposed to the prolonged high temperatures that cause coral bleaching.

Click here to read the NOAA press release of October 8, 2015 announcing the third ever documented global coral bleaching event!

As noted in the NOAA press release, a large concern remains as to impacts of the strong El Niño, which climate models indicate will cause coral bleaching again in the Indian and southeastern Pacific Oceans in the next few months. This may cause bleaching to spread globally again in 2016, as can be seen in CRW's extended bleaching outlooks for the period May-August 2016.

Please continue to visit the CRW website for more information on the developing coral bleaching conditions globally and to view the current Four-Month Coral Bleaching Outlook.

Click here to access the most recent Pacific Climate Update from NOAA CRW.

For more information about the Top 10 Things Resource Managers and Other Coral Reef Stakeholders Can Do Before, During, and After a Bleaching Event, please visit: http://www.coris.noaa.gov/activities/projects/bleach_events/.

1997-1999 ENSO and Patterns of Coral Bleaching

With the current (2015) El Niño continuing to develop and intensify in the Northern Hemisphere, the following is a brief overview of the pattern and timing of thermal stress that resulted in widespread severe coral bleaching during 1997-1999. Past reports have estimated that over 15% of the world's coral reefs were effectively lost during the 1997-1999 period (Wilkinson 2000). At that time, NOAA Coral Reef Watch observed widespread, prolonged high temperatures that caused coral bleaching. This was associated with what has been argued to be the largest El Niño on record (1997-1998) followed immediately by a strong La Niña (1998-1999). In general, many areas that are untouched by warming during an El Niño are influenced by warming during a La Niña (see Eakin et al. 2009).

In short, several areas of the tropical oceans experienced thermal stress sufficient for coral bleaching with impacts covering a 14-month period (May 1997-June 1998). Reefs in the central Pacific and eastern tropical Pacific were exposed to thermal stress early after the onset of the El Niño. Thermal stress moved to the Great Barrier Reef and across the islands of the south Pacific during February-April 1998 and the Indian Ocean during March-June 1998. In the Gulf of Mexico and the Caribbean, the worst of the El Niño impacts with the highest thermal exposure culminated in July-October 1998. The mid-1998 onset of La Niña conditions resulted in thermal stress in the northwestern Pacific Ocean from July-October 1998.

The following discussion uses the NOAA Coral Reef Watch SST Anomaly and Bleaching Alert Area products to illustrate the events. The Bleaching Alert Area shows patterns of areas with accumulated thermal stress sufficient to cause coral bleaching. The patterns are a bit different, and more coral-focused, than those visible in the SST Anomaly data. More on these products can be found at: http://coralreefwatch.noaa.gov/satellite/index.php.


The classical El Niño warming pattern formed by May 1997, with initiation of SST warming from the central tropical Pacific eastward to the South American coastline. Prolonged thermal stress with the potential to cause bleaching was seen along the equator, from Howland and Baker Islands east to the Galapagos and the Ecuadorian coastline, during the remainder of 1997. During this time, warming also proceeded northward along the South American coast to Panama. Additionally, warming was seen reaching northeast to Mexico, and some warming was seen along the Central American Coastline. Limited warming was seen in the Caribbean.  



By early 1998, the classic El Niño pattern was fully developed, with broader areas of high temperature in the eastern Tropical Pacific and extending up the Central American coast past Costa Rica, including all of the eastern Tropical Pacific islands; high temperatures in these regions began to dissipate in June. Bleaching levels of warming were seen along the Great Barrier Reef in February-March. Warming also began in the eastern to central Indian Ocean south of the equator, spreading to the eastern Indian Ocean by March, and dissipating after May.  


In May and June, bleaching levels of warming were also seen across the Indian Ocean north of the equator and into Southeast Asia.
With the rapid onset of La Niña conditions in July 1998, warming was observed in the western Pacific Ocean, north of the equator. August-September saw warming in the South China Sea, Philippines, and the Ryukyu Islands, which spread southeastward through Palau and Micronesia, finally dissipating in November.  

Fig. 4.9. Significantly (at 5% level) warmer (red) or cooler (blue) annual maximum SST difference: a El Niño year t, b El Niño year t+1, c La Niña year t, and d La Niña year t+1. Average values calculated for 20 El Niño events and 20 La Niña events, and tested for significant differences from 20 ENSO-neutral years. The groups of years were identified from the Troup (1965) SOI updated by the Australian Bureau of Meteorology.

Bleaching warming in the Western Atlantic/Gulf of Mexico/Caribbean is most commonly seen in the year after the onset of an El Niño (see figure on left from Eakin et al. 2009).

The bleaching warming started to develop in July 1998 and peaked in the Gulf of Mexico in August and in the Caribbean Sea in October.  


By 1999, the worst of the thermal stress was over, from a coral bleaching perspective, but only after major losses of coral reefs worldwide in 1998. Some warming was seen along the Great Barrier Reef in early 1999 but was much weaker than the prior year. Conditions were rather quiescent until August, when warming of the western North Pacific led to low bleaching levels of thermal stress that reached down to the Mariana Islands. Warming was again seen in the Caribbean in August-September 1999 but to a lesser extent than in 1998.


Eakin CM, Lough JM, and Heron SF (2009) Climate Variability and Change: Monitoring Data and Evidence for Increased Coral Bleaching Stress. In Coral Bleaching, vanOppen MJH and Lough JM eds. Ecological Studies 205: 41-67, Springer-Verlag Berlin Heidelberg.

Wilkinson CR (2000) Status of Coral Reefs of the World: 2000. Global Coral Reef Monitoring Network and Australian Institute of Marine Science, Townsville, Australia 363pp.

For more information, please contact coralreefwatch@noaa.gov


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