Not just land heat waves: Oceans are in hot water too
WASHINGTON — Even the oceans are breaking temperature records in this summer of heat waves.
Off the San Diego coast, scientists earlier this month recorded all-time high seawater temperatures since daily measurements began in 1916.
“Just like we have heat waves on land, we also have heat waves in the ocean,” said Art Miller of the Scripps Institution of Oceanography.
From 1982 to 2016, the number of “marine heat waves” roughly doubled, and likely will become more common and intense as the planet warms, a study released last week found. Prolonged periods of extreme heat in the oceans can damage kelp forests and coral reefs, and harm fish and other marine life.
“This trend will only further accelerate with global warming,” said Thomas Frolicher, a climate scientist at the University of Bern in Switzerland, who led the research.
His team defined marine heat waves as extreme events in which sea-surface temperatures exceeded the 99th percentile of measurements for a given location. Because oceans both absorb and release heat more slowly than air, most marine heat waves last for at least several days — and some for several weeks, said Frolicher. Many sea creatures have evolved to survive within a fairly narrow band of temperatures compared to creatures on land, and even incremental warming can be disruptive.
Some free-swimming sea animals like bat rays or lobsters may shift their routines. But stationary organisms like coral reefs and kelp forests “are in real peril,” said Michael Burrows, an ecologist at the Scottish Marine Institute, who was not part of the research.
In 2016 and 2017, persistent high ocean temperatures off eastern Australia killed off as much as half of the shallow water corals of the Great Barrier Reef — with significant consequences for other creatures dependent upon the reef.
“One in every four fish in the ocean lives in or around coral reefs,” said Ove HoeghGuldberg, a marine biologist at the University of Queensland. “So much of the ocean’s biodiversity depends upon a fairly small amount of the ocean floor.”
The latest study in Nature relied on satellite data and other records. Warm ocean temperatures disrupted the food supply for many species, including marine mammals.