Coral reefs get bleached when water is too warm, which forces out the tiny algae that normally live in coral, helping it to thrive and giving it its vivid color, NASA said in a statement. Without these algae, coral can whiten and eventually die.
"Australia's Great Barrier Reef is the largest and most complex system of reefs in the world, and like so many of the coral reefs in the world's oceans, it's in trouble," said oceanographer Gene Carl Feldman of NASA's Goddard Space Flight Center outside Washington.
NASA's Terra and Aqua satellites offer data about ocean surface temperature and color, available online within three hours of the satellites' pass. Color is linked to the concentration of chlorophyll in ocean plants, and shows changes in the ocean's biological productivity.
Researcher Scarla Weeks at the University of Queensland, Australia, use the satellite data to observe changes in sea surface temperatures andalong the Great Barrier Reef .
"The Great Barrier Reef is an icon, and we just want to know what we can do to save it," said Weeks in the statement. "Sea surface temperatures over the last five months are actuallynow than they were in 2002 when we witnessed the worst bleaching incident to date."