NOAA Coral Bleaching Outlook System Indicates Potential for High Level Coral Bleaching in the Caribbean and Parts of the Equatorial Pacific

Scientists from NOAA’s Coral Reef Watch Program are forecasting a significant potential for higher than normal thermal stress in the Caribbean, especially in the Lesser Antilles, through October 2009. Continued high water temperatures can lead to a high probability of significant coral bleaching and infectious coral disease outbreaks.  The forecast is based on the July NOAA Coral Reef Watch outlook.

Scientists are concerned that bleaching may reach the same levels or exceed those recorded in 2005, the worst coral bleaching and disease year in Caribbean history. There is also some potential for high stress in the central Gulf of Mexico and a region stretching from the Lesser Antilles, including the US Virgin Islands, across to Puerto Rico, and across to the southern coast of Hispaniola and the Caribbean coast of Nicaragua.

Other areas of concern for coral bleaching this year are the central Pacific region including the equatorial Line Islands and Kiribati.  Some thermal stress may also develop between the Northern Mariana Islands and Japan.

An important caveat is that the model used for this outlook is not yet calling for El Niño development, whereas NOAA’s operational Climate Forecast System is now calling for development of an El Niño during 2009-10. If El Niño continues to strengthen, this could increase the bleaching risk in the central to eastern Pacific and Caribbean.

Just like any climate forecast, local conditions and weather events can influence actual temperatures. However, we are quite concerned that high temperatures may threaten the health of coral reefs in the Caribbean this year.

The Thermal Stress Outlook is based on sea surface temperature (SST) forecasts generated by the Linear Inverse Model (LIM) from the NOAA Earth System Research Laboratory. This system is the first to use sea surface temperature forecast models to provide seasonal outlooks of bleaching around the world.

In the Pacific, the area of concern includes the equatorial Line Islands and Kiribati. This area is especially subject to stress if El Niño development continues.  There is a potential for some thermal stress to develop between the Northern Mariana Islands and Japan. There is also some indication of thermal stress along the Pacific coast of Mexico. However, the model is only generating small areas in the Pacific with a potential for abnormally high temperatures. Care should be taken that areas of warming in open areas of the Pacific are likely to move from the locations seen in the current forecast models. This region is also subject to intensification during El Niño conditions.

The NOAA Coral Reef Watch forecast comes on the heels of NOAA’s National Climatic Data Center reporting in June that the world’s ocean surface temperature was the warmest on record, breaking the previous high mark set in 2005, the last year of record-setting global coral bleaching incidents. Updates can be found here. Divers who see bleaching can report it at ReefBase.

In its inaugural year the forecast system did well in predicting the general patterns of mild Caribbean stress in 2008 and high thermal stress in the western Pacific in 2008-9, especially earlier in the season. The guidance issued in early December provided valuable guidance on the potential for bleaching 2-4 months in advance. The general pattern of warming in the outlook corresponded well with large-scale patterns of actual thermal stress. However, strong monsoonal activity along northeastern Australia cooled waters on the Great Barrier Reef (GBR) reducing thermal stress there. This was a fortunate difference between the forecast and actual conditions that protected these valuable reef resources.