Current ENSO forecast and 1997-1999 ENSO and Patterns of Coral Bleaching

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-level or no heat stress conducive to coral bleaching. However, CRW's Four-Month Coral Bleaching Heat Stress Outlook indicates the return of severe 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 the 5km Regional Virtual Stations at Panama Pacific West and Panama Pacific East in the next 5-8 weeks, and at Costa Rica Pacific and El Salvador within the next 9-12 weeks. Alert Level 2 heat stress (associated with widespread coral bleaching and significant mortality) is expected again at the 5km Regional Virtual Station at Clipperton Island, France in the next 9-12 weeks.

In the central equatorial Pacific, all of CRW's 5km Regional Virtual Stations have decreased to Bleaching Watch or No Stress status. This includes the Samoas, which suffered multiple weeks of Alert Level 2 heat stress over the last few months, with confirmed reports of bleaching of both shallow and deeper corals.

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; however, Alert Level 1 heat stress is expected in the NWHI in the next 9-12 weeks. 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 coral bleaching and mortality in the MHI and NWHI since the start of the Third Global Coral Bleaching Event.

CRW's other 5km Regional Virtual Stations in Micronesia are all at a level of Bleaching Watch or Bleaching Warning again, 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 that Alert Level 1 bleaching conditions are expected in the Western FSM and Palau in the next 1-4 weeks; in the Northern Mariana Islands, Guam (which has been hit by severe bleaching four years in a row already), the Eastern FSM, the Marshall Islands, and Nauru in the next 5-8 weeks; and in Wake Atoll 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, Dongsha, Taiwan, and in the Ryukyu Islands, Japan - where extensive (over 90%) bleaching was observed in the region's largest coral reef (Sekiseishoko Reef) as of July 2016, resulting in 70% mortality. Now, as Northern Hemisphere summer 2017 approaches, Alert Level 1 heat stress is expected again in Southern Taiwan, Dongsha, Taiwan, and the Hainan Islands, China in the next 5-8 weeks; and in the Southern Ryukyu Islands, Japan, Northern Taiwan, Hong Kong, China, the Parcel Islands, China, and Northern Vietnam in 9-12 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 Third Global Coral Bleaching Event.

In Southeast Asia, only the 5km Regional Virtual Station at Northern Myanmar remains at Alert Level 1 heat stress, although that bleaching heat stress is expected to dissipate shortly. The rest of the region is at a level of either Bleaching Watch or No Stress.

Coral bleaching heat stress had been diminishing well throughout the Coral Triangle; however, CRW's five 5km Regional Virtual Stations for the Philippines show Alert Level 1 bleaching stress is expected to return to the Eastern, Central, and Southern coral reef areas in the next 1-4 weeks; and to the Northern and Western reef areas in 5-8 weeks' time. CRW's Four-Month Bleaching Outlook also predicts the return of prolonged Alert Level 1 bleaching stress to Papua New Guinea in the next 1-4 weeks and to the Solomon Islands in the next 5-8 weeks. Short-lived Alert Level 1 heat stress also is expected in North Sulawesi, West Papua, and Maluku, Indonesia in the next 5-8 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 (the Reef's unprecedented, second consecutive year of confirmed mass bleaching), cooler waters finally arrived in the region in mid-April. All of CRW's 5km Regional Virtual Stations for the GBR region returned to a level of No Stress. CRW's near-real-time satellite monitoring and modeled predictions of environmental stress associated with the Third Global Coral Bleaching Event have been critical in helping local management and research partners plan effectual in-water and aerial surveys of the GBR, in both 2016 and 2017.

As of mid-May 2017, cooler waters had 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. However, since moderate bleaching was confirmed in only one area of the Indian Ocean in April 2017 - in Southwestern Madagascar - not basin-wide, this provided the first hint that the the Third Global Coral Bleaching Event might be coming to an end. 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 southeastern Florida and the Florida Keys in August and September 2014. Then in September and October 2015, moderate to severe coral bleaching (and disease) and low to moderate mortality were observed along the Florida Reef Tract (including in the National Marine Sanctuary) for the second year in a row. 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 develop in Florida in 2016, providing much needed relief to corals and other reef organisms that were still recovering from severe back-to-back bleaching. As of early June 2017, the Florida Keys and Southeast Florida 5km Regional Virtual Stations remain at a level of No Stress. However, Alert Level 1 heat stress is expected at both Florida Regional Virtual Stations in the next 9-12 weeks.

In the Gulf of Mexico, heat stress in the Flower Garden Banks, Texas and Yucatan Peninsula dissipated in early November 2016.

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. As of early June 2017, Alert Level 1 heat stress has returned to Panama Atlantic West; is expected again at the 5km Regional Virtual Stations at Costa Rica Atlantic, Columbia Atlantic, and Panama Atlantic East in the next 1-4 weeks, with further elevation to Alert Level 2 bleaching stress thereafter; and is expected in Nicaragua and Honduras in the next 5-8 weeks and in Belize and Quintana Roo, Mexico in 9-12 weeks' time.

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 Third Global Coral Bleaching Event.

Official Bleaching Announcements and Select Media Stories

Progression of the Third Global Coral Bleaching Event (Initial Information: 2014-May 2016)

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.

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).

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.

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).

Documenting the 2014-2017 Global Bleaching Event

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 Third 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 assist us further by continuing to report coral bleaching and disease observations to your existing regional efforts, along with a brief email to coralreefwatch@noaa.gov, or submit your reports directly to us at Coral Reef Watch. We still 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.

Acknowledgements

NOAA Coral Reef Watch work is supported primarily by the NOAA Coral Reef Conservation Program and the NOAA National Environmental Satellite, Data, and Information Service's Center for Satellite Applications and Research.

References

Bahr, KD, Jokiel PL, and Rodgers KS (2015) The 2014 coral bleaching and freshwater flood events in Ka̅ne´ohe Bay, Hawai´i. PeerJ 3: e1136, doi:10.7717/peerj.1136.

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.

Coffroth MA, Lasker HR, and Oliver JK (1990) Coral Mortality Outside of the Eastern Pacific During 1982-1983: Relationship to El Niño. In Glynn PW (ed.) Global Ecological Consequences of the 1982-83 El Niño-Southern Oscillation. Elsevier Oceanography Series 52:141-182.

De´ath G, Fabricius KE, Sweatman H, and Puotinen M (2012) The 27-year decline of coral cover on the Great Barrier Reef and its causes. Proceedings of the National Academy of Sciences, www.pnas.org/cgi/doi/10.1073/pnas.1208909109.

Eakin, CM, Rauenzahn JL, Liu G, Heron SF, Skirving WJ, Geiger EF, and Strong AE (2014) Will 2014-2015 be the Next Big El Niño? If so, What Might it Mean for Coral Reefs? Reef Encounter 29(5): 30-35.

Fellenius K (2014) Republic of the Marshall Islands Coral Bleaching Report. University of Hawai´i Sea Grant, Coastal Management Extension. Dec 31, 2014.

Harvey, C (2015) Why dead coral reefs could mark the beginning of 'dangerous' climate change. The Washington Post, April 12, 2015. https://www.washingtonpost.com/news/energy-environment/wp/2016/04/12/why-dead-coral-reefs-stir-fears-of-dangerous-climate-change/.

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, Maynard JA, van Hooidonk R (2016b) Impacts and effects of ocean warming on coral reefs. In: Laffoley, D., & Baxter, J.M. (editors). 2016. Explaining ocean warming: Causes, scale, effects and consequences. Full report. Gland, Switzerland: IUCN. pp. 177-197. doi:http://dx.doi.org/10.2305/IUCN.CH.2016.08.en.

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.

For more information, please contact coralreefwatch@noaa.gov