The world’s oceans are sweltering. Over the last century, marine heat waves have become more common and are lasting longer. Two recent heat waves have had a devastating effect on corals in the Great Barrier Reef, off the coast of Australia. But corals might not be as doomed as scientists once thought.
A marine heat wave isn’t just any bout of hot water in the ocean. Scientists define it as lasting at least five consecutive days. The water also must be unusually warm for that ocean region or season. These temperature extremes can be killers for marine species such as corals, kelp and oysters. They also can wreak havoc on fisheries and aquaculture.
In a new study, researchers wanted to know whether the frequency of these heat waves has changed. They searched for such events in data on sea-surface temperatures dating as far back as 1900. They also looked in satellite data that have been collected since 1982.
Those data suggest that the number of days each year that some part of the ocean experiences a heat wave has increased by 54 percent between 1925 and 2016. Over that time, heat waves also have become 34 percent more common — and last about 17 percent longer. Researchers shared their new findings April 10 in Nature Communications.