Oct 17, 2019

Marine heat waves, like the one behind Hawaii’s sweltering summer, poised to be ‘new normal’

Honolulu, HI
Melanie Yamaguchi
Hawaii News Now
Sea Surface Temperatures September 15, 2019
Sea Surface Temperatures September 15, 2019

 Five years ago, a vast stretch of warm water emerged across the North Pacific Ocean, extending from Alaska to California to Hawaii.

This marine heat wave, dubbed “The Blob,” was largely responsible for causing a mass coral bleaching event that ravaged nearly half of Hawaii’s coral reefs.


Now, a new expanse of unusually warm water is building in roughly the same area and has quickly become the second-largest marine heat wave in the last 40 years of recorded data.

The new version of “The Blob” is not only being blamed for driving record heat in Hawaii this summer, but it’s already sparked what scientists fear is the start of another mass coral bleaching event.


“Since 1985, we’ve seen two of these extreme events, 2015 and 2019, where temperatures were not just a little bit warmer but several degrees warmer than anything we’ve seen in the historical satellite record,” said Jeff Polovina, a former division chief at NOAA Fisheries.

“It could be that we’re looking at some rare summer events. But the alternative is that due to climate change, there’s been changes in the ocean and the atmosphere in the mid-latitudes that will result in more of these heat waves. And the kind of summer we had this year, we’ll see more frequently going forward. It could be the new normal.”


But Gove said while marine heat waves are natural, they’re being superimposed on the “backdrop” of climate change, which is already driving up ocean temperatures.

“Climate change is ratcheting up the level of ocean temperatures of where we’re at every single year,” Gove said. “It’s increasing ocean temperatures through time. So when a marine heat wave comes now, it’s way more intense than it was 100 years ago.”


Coral bleaching occurs when corals are stressed from higher temperatures and will expel their symbiotic algae ― which provide a source of nutrients for the coral ― outside their tissues, causing the corals to turn stark white. Once that happens, coral are at considerable risk of death.

Up until the 1990s, coral bleaching was virtually unheard of ― especially in Hawaii.


If coral bleaching kills off reefs, you lose important habitats for fish and other marine organisms ― and that could significantly impact fisheries, an important industry for Hawaii’s economy.


Disappearing reefs could also put coastal communities at greater risk.

Reefs act as a buffer during wave events and high tides. And they’re more important than ever as sea levels rise. But if reefs aren’t around, erosion and near-shore flooding could be much worse.