50-km Bleaching Alert Area
Current coral bleaching alert area
Regional crw_optw_bleachingalertarea chart Regional crw_optw_bleachingalertarea chart Regional crw_optw_bleachingalertarea chart Regional crw_optw_bleachingalertarea chart Regional crw_optw_bleachingalertarea chart Regional crw_optw_bleachingalertarea chart Regional crw_optw_bleachingalertarea chart Regional crw_optw_bleachingalertarea chart Regional crw_optw_bleachingalertarea chart Regional crw_optw_bleachingalertarea chart Regional crw_optw_bleachingalertarea chart Regional crw_optw_bleachingalertarea chart Regional crw_optw_bleachingalertarea chart Regional crw_optw_bleachingalertarea chart
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Current images: Global | E.Hem. | W.Hem. | Pacific | Caribbean | Coral Triangle


Data Formats Available

images Image Archives
Regional imagery and image archives.
Google Earth Google Earth
All of our satellite data products are available on Google Earth.
Virtual Stations 50-km Virtual Stations
Imagery, graphs, ASCII data, and e-mail alerts for reef pixels around the world.
animations Animations
Data animations and downloadable animated GIF files from NOAA/NESDIS' Office of Satellite and Product Operations (OSPO).
HDF data HDF data files
Raw data in Hierarchical Data Format (HDF), with free NOAA viewing software.


The NOAA Coral Reef Watch (CRW) twice-weekly 50-km satellite Bleaching Alert Area product presented here outlines the areas where coral bleaching thermal stress currently reaches various bleaching stress levels, based on our satellite sea surface temperature (SST) monitoring. The coral bleaching thermal stress levels are defined in the table below and are based on the current values of the NOAA CRW operational 50-km Coral Bleaching HotSpot and Degree Heating Week (DHW) products.

Stress Level
    Definition
    Potential Bleaching Intensity
No Stress
Bleaching Watch
Bleaching Warning
Bleaching Alert Level 1
Bleaching Alert Level 2
    HotSpot <= 0
0 < HotSpot < 1
1 <= HotSpot and 0 < DHW < 4
1 <= HotSpot and 4 <= DHW < 8
1 <= HotSpot and 8 <= DHW
    No Bleaching
 
Possible Bleaching
Bleaching Likely
Mortality Likely

Please note that locations with a current status of Bleaching Watch or No Stress recently may have been exposed to thermal stress. Although these two levels classify the current thermal stress condition, they do not take into account the recent stress history that is measured by the 50-km DHW product. When the instantaneous thermal stress during the current twice-weekly time period drops to a Bleaching Watch or No Stress level from a previously higher level, this product does not present any information on accumulated thermal stress during the past 12 weeks up to the previous twice-weekly period. Hence, a coral reef that is at Alert Level 2 one week may drop to Bleaching Watch or No Stress the following week. Please refer to CRW's 50-km DHW product for information on the accumulated thermal stress during the past 12 weeks.

This product is updated twice-weekly on every Monday morning and Thursday morning, U.S. Eastern Time. CRW's methodology web page and Liu et al. 2013 provide detailed information about CRW products.

NOAA CRW has been providing near-real-time global 50-km (0.5 by 0.5-degree spatial resolution precisely) satellite monitoring of thermal stress that causes mass coral bleaching to the U.S. and international coral reef communities since 1997. Our operational 50-km monitoring products, including Coral Bleaching HotSpot and DHW, derived from our operational nighttime SST measured by POES AVHRR, have been very successful in detecting and monitoring the thermal stress that causes coral bleaching.


Additional description in the 50-km products tutorial.
Technical details on the methodology page and in Liu et al. 2013.