[Coral-List] NOAA CRW Coral Bleaching Analysis and Outlook Message (Aug 2010)

Coral Reef Watch coralreefwatch at noaa.gov
Thu Aug 12 17:40:14 EDT 2010

*Analysis of Current Coral Bleaching Thermal Stress and Seasonal 
Guidance Through November 2010 *
(August 2010)


The Coral Reef Watch (CRW) satellite coral bleaching monitoring shows 
sea surface temperatures (SSTs) have been above average throughout the 
Caribbean and Gulf of Mexico, and are already above the bleaching 
threshold in some areas. The CRW Coral Bleaching Thermal Stress Outlook 
indicates that there is a high potential for thermal stress capable of 
causing coral bleaching in the Caribbean in 2010. The intensity of the 
stress is likely to increase until mid-October.

According to the CRW HotSpot, there is currently bleaching-level thermal 
stress around a large region in the northwestern Pacific, with the 
highest stress currently centered on the Philippines. Note that clouds 
have covered these areas for a prolonged time period, so satellite data 
have not been updated regularly at many locations in this region. This 
may be causing the CRW products to overestimate the thermal stress. The 
outlook shows that the thermal stress in the northeastern Philippines is 
expected to linger into September. The potential of high thermal stress 
is predicted to spread east into Guam, the Commonwealth of the Northern 
Mariana Islands, the Federated States of Micronesia, and the surrounding 
areas. Dissipation of this thermal stress may begin in mid- to 

The southern hemisphere and the entire Indian Ocean basin are expected 
to remain free from significant bleaching thermal stress through 
November 2010.

(See full alert message with figures at 

*Caribbean Analysis and Outlook: *

/Current conditions:/

The CRW satellite monitoring shows that the development of thermal 
stress has already started in the Caribbean, bearing a similar signature 
to the thermal stress observed at the same time period in 2005, the year 
of a record mass coral bleaching event. SSTs in most of the Caribbean 
region and tropical Atlantic Ocean have been significantly above the 
normal for most of 2010. Temperatures in the Gulf of Mexico and Florida 
Keys increased dramatically in early May, rising nearly 2°C over several 
days at some locations. Warming in Florida followed an extreme cold 
outbreak in January 2010 that resulted in significant coral mortality.. 
Two tropical storms (Alex in June and Bonnie in July) and other tropical 
depressions have temporarily relieved some thermal stress in the 
northern Caribbean, Gulf of Mexico, and Florida Keys. However, the 
thermal stress has quickly bounced back in these areas. Bleaching 
recently has been reported from parts of Puerto Rico. Degree Heating 
Weeks currently show low to medium levels of thermal stress built up in 
the northern Bahamas and the central Lesser Antilles island arc, 
centered east of Dominica and Guadeloupe. DHWs around 4, high enough to 
cause significant bleaching, have been observed on the Caribbean coast 
of Panama and Costa Rica.

/Bleaching outlook: /

The CRW Coral Bleaching Thermal Stress Outlook continues to indicate a 
high potential for thermal stress capable of causing significant coral 
bleaching in the Caribbean in 2010. The region potentially at greatest 
risk fills the region east from Nicaragua past the island of Hispaniola 
to Puerto Rico and the Lesser Antilles, and south along the Caribbean 
coasts of Panama and South America. The intensity of the potential 
thermal stress is predicted to increase until mid-October. The Caribbean 
typically experiences elevated temperature during the second year of an 
El Niño event, with the 2009-2010 El Niño ending in May 2010. The region 
described here as having the highest potential to experience 
bleaching-levels of thermal stress is the same region that has been 
anomalously warm for most of 2010.

/Comparison to the 2005 mass bleaching event: /

In 2005, a record breaking mass coral bleaching event in the Caribbean 
along with the most active hurricane season on record in the Atlantic 
Ocean followed a similar pre-bleaching season SST anomaly pattern. This 
preheating increases the likelihood that temperatures will exceed 
bleaching thresholds during the following bleaching season, indicating 
high potential for thermal stress above levels required for significant 
coral bleaching.

In 2005, the active hurricane season cooled waters in the Florida Keys 
and Gulf of Mexico greatly reducing the coral bleaching stress. However, 
the lack of tropical cyclones around the Lesser Antilles contributed to 
consistently warm temperatures in the epicenter of the 2005 mass coral 
bleaching event. This year, two tropical storms (Alex in June and Bonnie 
July) and other tropical depressions have temporarily relieved some 
thermal stress in the northern Caribbean, Gulf of Mexico, and Florida 
Keys. However, the thermal stress has quickly bounced back in these 
areas. Given the record-breaking mass coral bleaching in 2005 and the 
similarity in the pattern of the thermal stress between this year and 
2005, the development of this year’s thermal stress in the Caribbean 
needs to be monitored closely.

*Northwestern Pacific Analysis and Outlook: *

/Current conditions: /

The thermal stress that caused bleaching in Southeast Asia has abated, 
but stress has moved into the central and northern Philippines. 
Temperatures across much of the western tropical Pacific are above 
normal at the moment, especially along the west coast of the Philippines 
where bleaching has been reported. However, the Alert Level 2 areas seen 
in the Gulf of Thailand and the eastern South China Sea may be over 
estimated, as three months of persistent cloud cover have prevented 
updates to the satellite SST data since May 2010 at some locations.

/Bleaching outlook: /

The high temperatures that have caused mass coral bleaching in the 
Philippines may persist in the northern-most Philippines into September. 
As the summer continues in the northern hemisphere, our outlook shows 
that temperatures in the northwestern Pacific will increase during the 
next few months. The outlook indicates that there is a high potential of 
thermal stress capable of causing bleaching in Guam, CNMI (Commonwealth 
of the Northern Mariana Islands), FSM (Federated States of Micronesia), 
and the surrounding areas until late October and early November.

*Indian Ocean 2010 Bleaching Season Retrospective: *

With the 2009-2010 El Niño, the Indian Ocean experienced significant 
coral bleaching thermal stress since the beginning of this year in a 
spatial pattern similar to that seen in 1998. Most of the northern 
Indian Ocean and Southeast Asia regions have been experiencing intensive 
thermal stress. Significant bleaching has been reported in the Maldives, 
both sides of the Thai Peninsula (Andaman Sea and Gulf of Thailand), 
Malaysia, Singapore, Cambodia, parts of Indonesia, and the Anilao region 
of the Philippines. Bleaching was observed in southwestern and 
northeastern Madagascar earlier this year.

The thermal stress has now dissipated in the Indian Ocean and most of 
Southeast Asia. Many areas in this region have been experiencing 
persistent cloud cover since early May, which should be favorable for 
corals’ recovery from the mass bleaching.

The CRW bleaching outlook has been predicting well the overall high 
thermal stress in the Indian Ocean since the beginning of 2010, 
indicating an active bleaching season. However, our outlook issued 
earlier this year under-predicted the high thermal stress observed in 
the Bay of Bengal and over-predicted the thermal stress in the region 
off Sumatra where low levels of thermal stress were observed. This is 
most likely caused by the relatively low skill level of the LIM model 
(the SST prediction model of the CRW outlook system) in the Bay of 
Bengal and off Sumatra. Further evaluation and testing of a new scheme 
to refine the LIM are underway to improve the skill in this region.

[Note: The Bleaching Outlook discussed below is an experimental product 
and should be used as an indicator of potential general patterns rather 
than a precise predictor of thermal stress at any location. Actual 
conditions may vary due to model uncertainty, subsequent changes in 
climatic conditions, extreme localized variability, or weather patterns.]

Current HotSpot and Degree Heating Week charts and data formatted for 
HDF and Google Earth can be found at:

Time series graphics for index sites can be found at:

You can sign up for automated bleaching alerts at:

Please report bleaching events (or non-events) at:

NOAA Coral Reef Watch
coralreefwatch at noaa.gov

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