In 2014, NOAA Coral Reef Watch wrote in Reef Encounter about the prospect for a 2014-15 El Niño (Eakin et al. 2014). While that El Niño never fully formed, it did help set off the current, ongoing multi-year global coral bleaching event. A subsequent 2015-16 strong El Niño formed, spreading and worsening the bleaching, such that multiple coral reef areas around the world have now experienced bleaching two or even three years in a row. As of May 2017, the ongoing global coral bleaching event continues to be the longest, most widespread, and most damaging on record. It has affected more reefs than any previous global bleaching event and has been worse in some locales (e.g., Great Barrier Reef, Kiribati, Jarvis Island). Heat stress during this event also has caused mass bleaching in several reefs that never bleached before (e.g., northernmost Great Barrier Reef).
NOAA Coral Reef Watch's most recent Coral Bleaching Alert Area is below. This figure shows the regions currently experiencing high levels of heat stress that can cause coral bleaching.
NOAA Coral Reef Watch's most recent Four-Month Coral Bleaching Heat Stress Outlook is below. This figure shows the distribution of the lowest heat stress levels predicted by at least 60% of the model ensemble members. In other words, there is a 60% chance that the displayed heat stress levels will occur.
NOAA Coral Reef Watch's Coral Bleaching Alert Area below shows the maximum heat stress during the ongoing 2014-17 global coral bleaching event. Regions that have experienced the high levels of heat stress that can cause coral bleaching, from January 2014 to March 2017, are displayed. Alert Level 2 heat stress indicates widespread coral bleaching and significant mortality. Alert Level 1 heat stress indicates significant coral bleaching. Lower levels of stress may have caused some bleaching as well. More than 70% of coral reefs around the world have experienced the heat stress that can cause bleaching and/or mortality since the start of this almost three-year long global event.
NOAA Coral Reef Watch's (CRW) daily 5km satellite coral bleaching heat stress monitoring products indicate that in the eastern Pacific Ocean, cooler waters have arrived and all of CRW's 5km Regional Virtual Stations are experiencing low or no heat stress conducive to coral bleaching. However, CRW's Four-Month Coral Bleaching Heat Stress Outlook indicates the return of bleaching heat stress to the eastern Pacific in the next 2-3 months. Alert Level 1 heat stress (typically associated with significant coral bleaching) is expected again at Clipperton Island, France in the next 5-8 weeks and at the 5km Regional Virtual Stations at Costa Rica Pacific, Panama Pacific West, and Panama Pacific East within the next 9-12 weeks.
In the central equatorial Pacific, the majority of CRW's 5km Regional Virtual Stations have decreased to a Bleaching Watch or No Stress status. Alert Level 2 heat stress (associated with widespread coral bleaching and significant mortality) continues in the Samoas (where bleaching of both shallow and deeper corals has now been confirmed) but is expected to dissipate shortly.
The Main Hawaiian Islands (MHI), which observed record levels of bleaching in 2014 and static Alert Level 2 bleaching heat stress in October and November 2015, remain at a level of No Stress. No Stress conditions are also present in the Northwestern Hawaiian Islands (NWHI), which sustained high, prolonged levels of bleaching heat stress in 2014 and some subsequent coral death. CRW continues to collect data from field partners, including Hawai'i'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.
CRW's other 5km Regional Virtual Stations in Micronesia are all at a level of Bleaching Watch or No Stress, after multiple regions, including the Republic of the Marshall Islands and the Eastern Federated States of Micronesia (FSM), registered Alert Level 2 bleaching heat stress for many weeks in early 2017. Note however that Alert Level 1 bleaching conditions are expected again in the Marshall Islands and Nauru in the next 9-12 weeks.
In Micronesia's Phoenix Islands, in particular, as noted in multiple articles below and by numerous news outlets worldwide, in Kiribati, persistent elevated ocean temperatures (as high as 31.4-degrees Celsius) in 2015-2016 killed most of the corals in the region. Photos taken by scientists surveying the reef damage, especially around Kiritimati (Christmas Island), where more than 80% coral mortality has been documented, are gruesome. The high bleaching heat stress in Kiribati was tied to the very strong El Niño that dissipated in late 2016 but whose effects lasted for multiple additional months in the southern hemisphere. It is estimated that only 1-5% of Kiribati's reefs will survive and recover from this severe bleaching heat stress event.
Severe heat stress (Alert Levels 1 and 2) persisted for many weeks in East Asia in summer 2016, with significant coral bleaching being reported in multiple reef areas, including Hainan Island, China, Northern Vietnam, and Dongsha, Taiwan. Now, as Northern Hemisphere summer 2017 approaches, Alert Level 1 heat stress is expected again in Southern Vietnam in the next 1-4 weeks and in Northern Vietnam and the Parcel Islands, China in 5-8 weeks' time. CRW continues communicating with local coral reef managers and research partners to try and assess the extent of the damage to the region's coral reefs from the ongoing global bleaching event.
Coral bleaching heat stress is diminishing finally throughout the Coral Triangle, with all of CRW's 5km Regional Virtual Stations
at a status of Bleaching Watch or Bleaching Warning. CRW's Four-Month Bleaching Outlook predicts the return of Alert Level 1 bleaching
stress to Papua New Guinea, however, in the next 9-12 weeks.
As reported in multiple articles below and by news sources around the world, sustained, high ocean temperatures in early 2016 (especially in March) did significant damage to Australia's Great Barrier Reef (GBR). Per the Australian National Coral Bleaching Taskforce, the Australian Research Council Centre of Excellence for Coral Reef Studies, and the Great Barrier Reef Marine Park Authority, the event turned out to be the worst bleaching in the GBR's history. This was especially true in the northernmost portion of the GBR, which experienced massive die-offs of coral. A NOAA CRW co-authored Nature cover story on the 2016 GBR bleaching was published on March 15, 2017. Click here for additional information.
After multiple weeks of severe (Alert Levels 1 and 2) heat stress along much of the GBR, especially the central GBR, in March 2017, cooler waters finally arrived in the region in mid-April. All of CRW's 5km Regional Virtual Stations for the GBR region have returned to a level of No Stress. As reported on in multiple media articles below, reports from the Great Barrier Reef Marine Park Authority, the Australian National Coral Bleaching Taskforce, the Australian Marine Conservation Society, multiple coral reef dive operators, and other local partners indicate that the GBR is currently in its unprecedented, second consecutive year of mass bleaching, especially in the central portions of the Reef. CRW's near-real-time satellite monitoring and modeled predictions of environmental stress associated with the ongoing global coral bleaching event have been instrumental in helping local management and research partners plan effectual in-water and aerial surveys of the GBR, in both 2016 and again this year.
As of mid-May 2017, cooler waters have arrived along the western coast of Australia as well, in the Indian Ocean. All of CRW's 5km Regional Virtual Stations along Australia's
west coast are at a level of Bleaching Watch or No Stress.
Bleaching heat stress developed again in early March 2017 in the Western Indian Ocean, perpetuating the ongoing global coral bleaching event.
As of mid-April 2017, all of the 5km Regional Virtual Stations for the Western Indian Ocean region
had returned to a level of Bleaching Watch or No Stress.
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. In mid-July 2016, a Bleaching Warning was issued for both the Florida Keys and Southeast Florida 5km Regional Virtual Stations. However, significant bleaching heat stress (Bleaching Alert Levels 1 and 2) did not impact Florida this season, providing much needed relief to corals and other reef organisms that are still recovering from severe back-to-back bleaching events.
A strong bleaching season in 2015 impacted coral reefs throughout the Caribbean. Bleaching of Caribbean corals at a number of reef 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 global coral bleaching event on record (after the 1998 and 2010 global events). In early November 2016, high levels of bleaching heat stress returned to the eastern and southern portions of the Caribbean basin; these bleaching conditions remained until late December 2016. Now in May 2017, Alert Level 1 heat stress is expected again at the 5km Regional Virtual Stations at Costa Rica Atlantic in the next 1-4 weeks, at Columbia Atlantic, Panama Atlantic East, Panama Atlantic West, and Nicaragua in the next 5-8 weeks, and in Honduras in the next 9-12 weeks.
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/.
Click here to access a presentation, given by the NOAA CRW Coordinator on March 17, 2017, as part of the Virginia Institute of Marine Science Spring Seminar Series, on the ongoing global coral bleaching event.
Climatic Background Conditions
In June 2014 the US National Oceanic and Atmospheric Administration's (NOAA) National Centers for Environmental Prediction (NCEP) issued an El Niño Watch, indicating a greater than 70% chance that a weak-to-moderate El Niño would develop by late 2014. While the ocean warmed for several months, the atmosphere never fully engaged in formation of this event, and the warming dissipated without an El Niño being declared. However, warming resumed early in 2015 - this time with full engagement of the atmosphere. In March 2015, NOAA issued an El Niño Advisory, indicating that El Niño conditions had finally been observed and were expected to continue. Starting in 2013 and coincident with these events, an unusually warm patch of water appeared in the eastern North Pacific. Nicknamed "The Blob", it was most likely caused by a record-strength anomalously strong high-pressure ridge in the atmosphere over the region (Bond et al. 2015). This anomaly increased already warm ocean temperatures impacting marine life in much of the eastern North Pacific until late 2015 when the strengthening El Niño caused it to dissipate.
As of April 2016 and this writing, with NOAA's El Niño Advisory still in effect, the warming in the central to eastern tropical Pacific had begun to dissipate, following the usual chronology of an El Niño. Importantly for some reefs, such as in Micronesia and Palau, a La Niña Watch was in effect as the forecast estimated a >70% chance of a La Niña forming later this year.
2014: Initiation of the Global Bleaching Event
The current global coral bleaching event began in June 2014, with mass bleaching being first observed in Guam and the Commonwealth of the Northern Mariana Islands (CNMI, Heron et al. 2016a). This region is not normally linked to warming during an El Niño (Figure 1). However, the warming around Guam and the CNMI started a chain of large-scale warming events that propagated throughout the world's oceans and included the record-strength El Niño that peaked in late 2015. Elevated ocean temperatures lasted in Guam and the CNMI until October 2014. Regions of anomalously warm water then expanded until they merged with the southwestward extension of "The Blob", encompassing parts of the Hawaiian archipelago, where the most severe bleaching was seen at Lisianski Atoll in the Papaha̅naumokua̅kea Marine National Monument in September-October 2014. Thermal stress and bleaching also extended into the Main Hawaiian Islands where major bleaching was seen along windward Oahu, especially Ka̅ne´ohe Bay (Bahr et al. 2015). This was only the second widespread bleaching ever seen in the main islands of Hawai´i (Jokiel and Brown 2004). Also in September 2014, severe bleaching was documented in the Atlantic Ocean, in both southeastern Florida and the Florida Keys. In November, sustained high water temperatures in the Republic of the Marshall Islands resulted in their most severe bleaching ever reported (Fellenius 2014). NOAA Coral Reef Watch's 5-km Degree Heating Week values (Liu et al. 2014) exceeded 8 °C-weeks (categorized as Alert Level 2 thermal stress, associated with widespread coral bleaching and significant mortality) in many of these areas.
Figure 1. Coral Reef Watch Maximum Bleaching Alert Area map for September 2014. Marked are four areas exhibiting bleaching in the latter half of 2014. Alert Level 2 is associated with widespread coral bleaching and significant mortality.
January-June 2015: Bleaching Spreads
With the onset of austral summer, ocean temperatures started to rise and bleaching was reported in the Southern Hemisphere (Figure 2). Moderate levels of thermal stress and bleaching were reported in eastern Papua New Guinea (PNG) and the Solomon Islands early in 2015, and subsequently in northern Fiji. The Samoas, especially American Samoa, reported the worst bleaching ever seen (Figure 3). Mass bleaching also spread into the Indian Ocean in the first half of 2015; moderate levels of thermal stress and bleaching were reported in the Chagos Archipelago, the Maldives, western Indonesia, and the southern Red Sea. Note that the pattern of bleaching in the South Pacific and Indian Ocean is most commonly seen during the second year of an El Niño, as in 1998 and 2010. However, most of the bleaching in the first half of 2015 occurred before the 2015-16 El Niño conditions developed, raising the suspicion that this bleaching was associated with either the aborted 2014-15 El Niño or an oceanographic precursor of the 2015-16 record-strength El Niño.
Initiation of the 2015-16 El Niño in mid-2015 resulted in high thermal stress in the eastern tropical Pacific, with observations of bleaching in Panamá, and expected but unconfirmed bleaching in the northern Galápagos Islands (Figure 4). Mid-2015 also brought thermal stress to Kiribati, especially the Line Islands (Figure 4).
Figure 2. Coral Reef Watch Maximum Bleaching Alert Area map for January-June 2015. Marked are six areas exhibiting bleaching in the first half of 2015.
Figure 3. Photo composite of before, during, and after bleaching at Airport Reef, Tutuila, American Samoa (image courtesy of R. Vevers, XL Catlin Seaview Survey).
July-December 2015: Global Bleaching
With the 2015-16 El Niño in full swing, thermal stress intensified in the central to eastern Pacific (Figure 4). Reports from the Phoenix and Line Islands of Kiribati indicated bleaching and mortality of corals were well underway. Thermal stress reached the highest levels ever recorded and killed at least 80% of the corals there (K. Cobb, pers. comm.). A warm water mass, most likely related to warm El Niño waters off the Americas, spread to the Hawaiian archipelago from the southeast, resulting in widespread bleaching in the main islands of Hawai´i, with the most severe bleaching seen along shores of Hawai´i Island and Maui Nui. This was the worst bleaching seen in the main Hawaiian Islands and their first documented instance of back-to-back bleaching.
Unlike 2014, thermal stress and bleaching were widespread in the northern Caribbean, along with some bleaching in other parts of the basin. Bleaching of varying severity was reported in Florida, Cuba (northern and southern coasts), the Bahamas, Turks & Caicos, the Cayman Islands, parts of the Dominican Republic, Haiti, and Bonaire. Southeastern Florida and the Florida Keys not only saw a second year of bleaching, but southeastern Florida saw a severe outbreak of a white disease resulting in high levels of mortality.
As of October 2015, with widespread bleaching in each of the Indian, Pacific, and Atlantic basins, NOAA declared that the third documented global coral bleaching event was underway. This followed confirmed global bleaching in 1998 (Wilkinson 2000) and 2010 (Heron et al. 2016b). Of note, this actually may have been the fourth global event, as widespread, possibly global bleaching was seen in 1983 in association with the 1982-83 El Niño (Coffroth et al. 1990).
The El Niño continued to strengthen over the rest of 2015 and peaked in November-December 2015, becoming one of the strongest ever. By the end of 2015 32% of global coral reefs had been exposed to thermal stress of 4 °C-weeks or more and almost all of the world's reefs had exceeded their normal warm-season temperatures.
Figure 4. Coral Reef Watch Maximum Bleaching Alert Area map for 2015. Marked are five areas exhibiting bleaching in the latter half of 2015.
January-May 2016: Global Bleaching Continues
With the El Niño still at its peak strength and with the onset of the austral summer, thermal stress and bleaching returned to the Southern Hemisphere. As of this writing, bleaching has been reported from as far west as Tanzania to as far east as French Polynesia (Figure 5), with severe bleaching in the Far Northern Great Barrier Reef, New Caledonia, and Fiji. Bleaching in the GBR has been the worst ever documented, affecting over 93% of the reefs with severe bleaching in 95% of the reefs in the northern 1/3 of the GBR, formerly the healthiest part of the GBR (De´ath et al. 2012). Far worse is the bleaching in Kiribati. Surveys in March and April 2016 revealed over 80% of corals dead and 15% bleached, leaving few untouched (J. Baum, pers. comm. and in Harvey 2015).
Figure 5. Coral Reef Watch Maximum Bleaching Alert Area map for January-May 2016. Includes list of marked areas with reports of severe bleaching.
An important question now for Micronesia, Palau, and some other parts of the western Pacific Ocean, is whether a strong La Niña will follow this El Niño, as occurred in 1998. It is still too soon to tell. In April 2016, NOAA issued a 70% chance of a moderate La Niña for later this year, but based on past model performance, predictions of El Niño and La Niña issued before June are not highly reliable. NOAA Coral Reef Watch's Four-Month Outlook for May-August indicates that more bleaching is likely in the northern Indian Ocean, parts of the Coral Triangle and Southeast Asia, and the central to eastern tropical Pacific (Figure 6). Also, CRW's extended-range outlook and past El Niño patterns indicate bleaching will likely return to the Caribbean again this year. While still beyond the range of the seasonal models, bleaching has been seen in the Southern Hemisphere in the year after an El Niño, leaving open the possibility of this event continuing into 2017.
Figure 6. Map of areas where 60% or more of the model ensemble members are predicting thermal stress at each of NOAA Coral Reef Watch's bleaching thermal stress alert levels through August 2016 (as of 3 May 2016).
Unfortunately, two international programs that previously documented coral bleaching events are no longer serving this purpose. ReefBase has not added new bleaching observations since 2012 and few records in the database document the 2010 global bleaching. Also, since the retirement of its former global coordinator, Clive Wilkinson, the Global Coral Reef Monitoring Network (GCRMN) has not actively maintained observations and reporting of bleaching worldwide. Fortunately, some regional GCRMN networks are still in place or are rebuilding, while other regional and global programs, like Reef Check, continue to coordinate coral reef monitoring.
To ensure documentation of the ongoing global coral bleaching event is as complete as possible, NOAA Coral Reef Watch continues collating data and information about and reporting on the global extent of this event. We are happy to work with any local or regional partners who plan to report on this event. Please continue any monitoring you are conducting and either report to your existing regional efforts or send them directly to us at Coral Reef Watch. Of note, we need both bleaching and non-bleaching observations to document the spatial extent and timing of the event, and for us to validate our satellite- and climate model-based products. Contributing data ensures that your site data are considered in global analyses; helps users understand how to better utilize the tools for your reefs; gives context to how bleaching patterns at your sites compare with global and regional patterns; and provides access to the latest global bleaching data analyses to communicate climate impacts to decision makers. All contributors will have the opportunity to co-author peer-reviewed publication(s) on global and/or regional bleaching that we are planning.
The content on this web page was initially drafted based on the article, "Global Coral Bleaching 2014-2017: Status and an Appeal for Observations",
published in Reef Encounter in April 2016.
Bond NA, Cronin MF, Freeland J, and Mantua N (2015) Causes and impacts of the 2014 warm anomaly in the NE Pacific. Geophysical Research Letters 42(9): 3414-3420.
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Fellenius K (2014) Republic of the Marshall Islands Coral Bleaching Report. University of Hawai´i Sea Grant, Coastal Management Extension. Dec 31, 2014.
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Heron, S.F., Johnston L., Liu G., Geiger E.F., Maynard J.A., De La Cour J.L., Johnson S., Okano R., Benavente D., Burgess T.F.R., Iguel J., Perez D., Skirving W.J., Strong A.E., Tirak K., Eakin C.M. (2016a) Validation of Reef-scale Thermal Stress Satellite Products for Coral Bleaching Monitoring. Remote Sens. 8(1): 59, doi: 10.3390/rs8010059.
Heron, SF, Eakin CM, vanHooidonk R, Maynard JA (2016b) Coral Reefs. In Laffoley D and Baxter J (eds.) Explaining ocean warming: causes, scale, effects and consequences, International Union for the Conservation of Nature. In press.
Jokiel PL, Brown EK (2004) Global warming, regional trends and inshore environmental conditions influence coral bleaching in Hawai´i. Global Change Biology 10: 1627-1641.
Liu, G, Heron SF, Eakin CM, Muller-Karger FE, Vega-Rodriguez M, Guild LS, De La Cour JL, Geiger EF, Skirving WJ, Burgess TFR, Strong AE, Harris A, Maturi E, Ignatov A, Sapper J, Li J, Lynds S (2014) Reef-scale Thermal Stress Monitoring of Coral Ecosystems: New 5-km Global Products from NOAA Coral Reef Watch. Remote Sens. 6(11): 11579-11606, doi:10.3390/rs61111579.
Wilkinson, C (2000) Status of Coral Reefs of the World: 2000. Australian Institute of Marine Science, Townsville, Australia.
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