After suffering through the most severe bleaching event ever recorded last year, the Great Barrier Reef is once again being savaged by a marine heat wave.
After just one day of aerial surveys, the Great Barrier Reef Marine Park Authority, which oversees the region, has already confirmed that warm waters are causing another mass bleaching. Climate change is compounding the reef's woes as warming waters put corals in a precarious position to survive.
Scientists surveyed a 200-mile stretch of the northern end of the reef earlier this week. The full extent of the bleaching will take weeks to tease out as the reef covers an area roughly the size of Germany. But the early returns are bad news for one of the world's natural wonders.
The region was home to some of the worst bleaching last year, and coral have been weakened by months on end of continued heat. Waters in the region have rapidly warmed over the past two months and are currently up to 5.4°F above normal.
"We are seeing a decrease in the stress tolerance of these corals," Neal Cantin, a reef scientist with the Australian Institute of Marine Science, said. "This is the first time the Great Barrier Reef has not had a few years between bleaching events to recover. Many coral species appear to be more susceptible to bleaching after more than 12 months of sustained above-average ocean temperatures."
Greenpeace has also been documenting the reef's plight starting on the northern end. Its underwater surveys have revealed equally disturbing images of a reef in distress.
"I've been photographing this area of the reef for several years now and what we're seeing is unprecedented," Brett Monroe Garner, a marine biologist working with Greenpeace, said. "In these photos nearly 100 percent of the corals are bleaching, and who knows how many will recover. Algae is already beginning to overgrow many of the corals."
Bleaching happens when waters get too warm for the algae that live inside coral. The heat causes them to die off or be expelled, leaving behind ghostly white coral skeletons.
It's that process that hit 93 percent of the Great Barrier Reef last year, causing nearly a quarter of the coral to die off. For scientists who have studied the reef for years, that development brought them to tears because it foretold what the future holds for the reef unless carbon pollution is cut. If oceans warm 2.7°F, it will essentially be a death sentence for most coral.
Last year's bleaching event shows climate change is taking its toll. Scientists working with the World Weather Attribution team revealed that climate change made the warm waters that caused the bleaching last year up to 175 times more likely. The Great Barrier Reef bleaching was the most widely publicized aspect of a global coral bleaching event that spread to every ocean basin for three years and counting.
Bleaching warnings and alerts over the past 90 days. Credit: Coral Reef Watch