A new NOAA coral bleaching prediction system indicates that there will be some bleaching in the Caribbean later this year, but bleaching will probably not be severe. There is a potential for widespread bleaching in the Northwestern Hawaiian Islands but this is less certain than the Caribbean forecast because of variable winds in this area. Some bleaching is also expected around Papua-New Guinea, the Philippines, and Japan but little bleaching potential elsewhere during the northern hemisphere summer. The following figure shows the Global 4-month Coral Bleaching Outlook for the northern hemisphere summer/fall of 2008 (through October).
In a normal year, the model will forecast no potential for bleaching. When sea surface temperature forecasts exceed bleaching thresholds and continue long enough to cause bleaching, the outlook products display the bleaching potential during the upcoming warm season. Actual conditions may vary due to subsequent changes in climatic conditions or weather patterns.
Caribbean Bleaching Outlook:
The forecast system indicates that there is a potential for bleaching across the Caribbean basin in 2008, but it is not likely to be severe. The strongest warming forecast by the SST model is in the northern Gulf of Mexico that might impact the Flower Garden Banks. Note that if this system had been operating in 2005, it would have predicted severe bleaching (see forecast system discussion below). The following figure shows the current outlook for this year’s Caribbean bleaching season (through October).
Pacific Bleaching Outlook:
The most significant concern for bleaching this season is in the Northwestern Hawaiian Islands (NWHI). The current outlook suggests severe bleaching is possible in the westernmost islands. This comes with important caveats. Warm anomalies in the North Pacific are not geographically constrained in the way they are in the Caribbean. We are not confident that this warming will remain over the NWHI. A slight move to the north or west that could result from a change in the track of the trade winds could completely eliminate the potential for bleaching.
There is also a potential for some bleaching elsewhere in the North Pacific that may influence reefs from Papua-New Guinea, through along the eastern Philippines, up through Japan. Bleaching is likely to be mild, similar to that expected in the Caribbean this year.
The following figure shows the Global 4-month Coral Bleaching Outlook for the northern hemisphere summer/fall of 2008 (through October).
About the Forecast System:
The new forecast system uses NOAA experimental sea surface temperature (SST) forecasts (Linear inverse Modeling) to develop maps of potential coral bleaching severity during the upcoming bleaching season (August to October for the northern hemisphere and January-March for the southern hemisphere). While NOAA’s Coral Reef Watch Program has been using satellite SST data to alert managers and scientists around the world of the risk of coral bleaching, this forecast system now includes longer-range SST forecasts.
The new system was developed by scientists in NOAA’s Coral Reef Watch in Silver Spring, MD and NOAA Earth Science Research Laboratory's Physical Science Division in Boulder, Colo., with funding from the NOAA Climate Program Office’s Sectoral Applications Research Program and NOAA’s Coral Reef Conservation Program.
The outlook is based on a composite of forecasts for all weeks included in the time period indicated in the outlook figure. An animation through this period is also available. Because of the nature of the forecast system, events of similar magnitude are often underpredicted at longer forecast lead-times. Their purpose is not to provide exact predictions at any particular reef locations, but to provide general patterns of bleaching potential.
The forecast system has been run in hindcast mode for years 2001-2007. The figures below shows a hindcast of the July 2005 outlook for the July-October 2005 period and the record-setting thermal stress levels observed during the 2005 Caribbean bleaching event.
Hindcast Caribbean 4-month Coral Bleaching Outlook for the summer/fall of 2005.
Observed maximum Degree Heating Week thermal stress accumulations during the record setting 2005 Caribbean bleaching event.
