Using Satelites to Predict Coral Bleaching

Coral reefs around the world are under threat from a wide variety of issues including  – overfishing, dredging, and rising sea temperatures. Satellites are being deployed to track and monitor many of these risks


Coral Bleaching Before and Afterr - in 2016

Pictures from the Great Barrier Reef – before and after a coral bleaching event


Coral bleaching is one of the global threats to reefs – with 75% of corals under threat from bleaching over just three years (2014 to 2017).  Coral bleaching, as the name implies, is when the coral loses its colour, but more importantly, it is when the coral dies, which in turn destroys the reef.

As coral reefs support 25% of marine species and over 500 million people depend on them for food or work – when they die it is devastating for plants, animals, and people globally.

Causes of coral bleaching:  When sea temperature rises, by as little as 1 degree C,  this causes corals stress. The zooxanthellae, which live inside the coral and give them their unique colours are then forced out of the coral, removing their colour – the “bleaching” effect. If Temperatures remain high the zooxanthellae will not be able to return to the coral and the coral will die. 

The US National Ocean and Atmospheric Administration (NOAA) provides a service to monitor corals at risk of bleaching using satellites – with a daily, weekly,  and monthly outlook – predicting as far as 4 months ahead of time.

The chart below shows a 4-month outlook, animated with a weekly interval. 

Animatation fo Alerts for Coral Bleaching


This data enables governments, reef managers, and the public to take action to help protect these reefs when they are most vulnerable.

Such actions that can be taken to protect coral before during and after a bleaching event, include:  

  • Before and during
    • Restricting activities on or near the reef, including
      • Fishing and construction on or around the reefs
    • Provide artificial shade to cool reefs
    • Removal coral predators 
  • After 
    • Transplant new corals after the bleaching event
    • Continue to restrict activities while the coral is weak

These threat predictions are made possible by satellites which are constantly monitoring reefs around the world, it would not be possible to place local sensors around the world’s oceans. The cost of simply deploying the local sensors would be prohibitive and the ongoing costs of collecting the data from millions of locations and maintaining the network of local sensors further emphasize how this type of analysis is only possible via satellites. 

The NOAA has two “missions” (satellite systems) that collect data from for this purpose, as well as working with international partners. The NOAA’s satellites are:

  • Geostationary Operational Environmental Satellite (GOES)
  • NOAA-20’s Visible Infrared Imaging Radiometer Suite (VIIRS)



The GOES-R Series is a four-satellite program (GOES-R/S/T/U)  and will be in service until  2036. These satellites can provide the following capabilities as well as monitoring the temperature of the sea:  

  • Improved hurricane track and intensity forecasts
  • Improve  tornado warning lead time
  • Improved detection of fog and low cloud
  • Improved air quality warnings and alerts
  • Better fire detection and intensity estimation
  • Improved solar flare warnings (to minimise disruptions)
  • Early warning of ground lightning strike hazards


NOAA-20, which launched in 2017 and will run until 2024 and focuses on the following areas:

  • Cross-track Infrared Sounder (CrIS) –  This will produce high-resolution, three-dimensional temperature, pressure, and moisture profiles.
  • Advanced Technology Microwave Sounder (ATMS) –  This provides sounding observations needed to retrieve atmospheric temperature and moisture profiles for weather forecasting
  • Ozone Mapping and Profiler Suite (OMPS) – monitoring the total ozone and ozone profile. 
  • Clouds and the Earth’s Radiant Energy System (CERES) – senses radiation emitted from the earth and solar-reflected and Earth-emitted radiation from the top of the atmosphere to the Earth’s surface.
  • Visible Infrared Imaging Radiometer Suite (VIIRS) –  visible and infrared observations of the earth (land, sea, and atmosphere)