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 continues to diminish.

In the central equatorial Pacific, bleaching thermal stress continues to build. Alert Level 2 bleaching stress (associated with widespread coral bleaching and significant mortality) is expected in the Northern Cook Islands, Southern Cook Islands, the Samoas, Wallis & Futuna, Northern Tonga, and Southern Tonga in the next 1-4 weeks. Alert Level 1 bleaching conditions (associated with significant bleaching) are expected in Tuvalu, the Tuamotu Archipelago, Society Archipelago, and the Austral Islands, and should elevate to Alert Level 2 in the next 5-8 weeks.

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 Bleaching Watch after a short period of Alert Level 1 thermal stress. A Bleaching Watch also remains in effect for the Northwestern Hawaiian Islands (NWHI), which sustained high, prolonged levels of bleaching thermal 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 5-km Regional Virtual Stations in Micronesia are all at a level of Bleaching Watch or No Stress, after multiple regions, including the Marshall Islands and Eastern FSM, registered Alert Level 2 bleaching thermal stress for many weeks. Note that while the Eastern FSM has downgraded to a Bleaching Watch, it is expected to increase again to Alert Level 1 in the next 9-12 weeks.

Of note, cooler waters have finally reached the Phoenix Islands (Kiribati). 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) since June 2015 have 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 ongoing high bleaching thermal stress in Kiribati is tied to the very strong El Niño that has now dissipated, but whose effects will last for many months in the southern hemisphere. It is estimated that only 1-5% of Kiribati's reefs will survive this bleaching thermal stress event.

The severe thermal stress in East Asia also has dissipated, after Alert Levels 1 and 2 bleaching persisted in multiple areas for many weeks. This included Hainan Island, China, Northern Vietnam, and Dongsha, Taiwan. CRW is communicating with local coral reef managers and research partners to try and assess the extent of the damage to the region's coral reefs.

In Southeast Asia, while waters have cooled, Alert Level 1 bleaching thermal stress is expected to return to Southern Java and Lampung and Banten in the upcoming 9-12 weeks.

Bleaching thermal stress continues to increase in parts of the Coral Triangle. Alert Level 1 conditions associated with significant coral bleaching are expected in the next few weeks in Papua New Guinea and the Solomon Islands. Alert Level 1 bleaching stress is also expected in West Nusa Tenggara, East Nusa Tenggara, West Timor, and Timor-Leste in the next 9-12 weeks. We advise our local partners to continue monitoring the development of bleaching stress in these regions over the next few months.

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 Australia's National Coral Bleaching Task Force, 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 Bleaching Warning is expected to be issued for the northern, central, and southern portions of the GBR in the next 1-4 weeks, but thermal stress in those areas is not expected to elevate to Alert Level 1 and cause bleaching. Alert Level 1 bleaching conditions are expected in the Northern Coral Sea Islands in the next 5-8 weeks, however.

Additionally, Alert Level 1 bleaching stress is expected in the next few months along the northwestern coast of Australia, including at Pulu Keeling, Beagle Gulf, Scott to Ashmore Reefs, North Western Australia, and Rowley Shoals. Alert Level 1 bleaching conditions are also expected along the central portion of Australia's west coast in the next 9-12 weeks, as warm waters continue south.

The high levels of bleaching thermal stress that were sustained in the eastern Indian Ocean and the Middle East in October and early November have now dissipated.

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 5-km Regional Virtual Stations. However, it now looks as though significant bleaching thermal stress (Bleaching Alert Levels 1 and 2) will not impact Florida this season, hopefully providing much needed relief to corals and other reef organisms that are still recovering from severe back-to-back bleaching events.

In the Gulf of Mexico, thermal 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. In fact, 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 global coral bleaching event on record (after the 1998 and 2010 global events). In early November 2016, high levels of bleaching thermal stress returned to the eastern and southern portions of the Caribbean basin. As of December 8, 2016, Alert Levels 1 and 2 thermal stress remained around Venezuela, La Guajira, Colombia, and Aruba, Curacao, and Bonaire, but is expected to dissipate shortly.

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

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.

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).

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 that documentation of the ongoing bleaching event is as complete as possible, Coral Reef Watch plans to collate and report on the global extent of this event. We would be 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.

Additionally, film-makers at Exposure Labs are developing a documentary on this bleaching event. They are in need of assistance capturing pictures and video of the bleaching in as many places as possible. They have issued an appeal for underwater photographers and videographers to help them in this project.

The content on this web page page is based on the article, "Global Coral Bleaching 2014-2017: Status and an Appeal for Observations", published in Reef Encounter in April 2016.

1997-1999 ENSO and Patterns of Coral Bleaching