Marine heat waves, like the one behind Hawaii’s sweltering summer, poised to be ‘new normal’
HONOLULU, Hawaii (HawaiiNewsNow) - 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.
“The 2014-2015 ‘Blob’ as everyone’s come to call it, was a huge wake-up call for ocean heat waves,” said Jamison Gove, oceanographer for the National Oceanic and Atmospheric Administration.
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.
And it’s put a spotlight on an emerging field of climate change research.
“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.”
The impacts of not only more frequent but more intense ocean heat waves could be wide-reaching, not only driving up temperatures in the islands, but devastating coral reefs, worsening coastal erosion and potentially crippling Hawaii fisheries.
Among the dire predictions: In just 20 years, Hawaii could start to see mass coral bleaching events happening every single year, putting the island reefs that so much marine life relies on at risk of all but disappearing.
“Climate change is like you’re on this escalator and it just keeps increasing ocean temperatures through time with every passing year,” Gove said. “Even if we had the same marine heat wave as we did 100 years ago, it’s way more intense now because of climate change.”
Marine heat waves aren’t a new phenomenon. They’re simply characterized by a period of abnormally warmer water, just as warmer temperatures on land are also possible.
During a marine heat wave, weaker winds stick around for an extended period of time. That means warm water at the surface isn’t mixing with cooler waters at lower depths.
Instead, the warm water sits at the surface and just keeps heating up.
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.”
A recent report by the United Nations Intergovernmental Panel on Climate Change ― arguably the most comprehensive to date on how climate change will affect the world’s oceans ― says the frequency of marine heat waves has “very likely” doubled since 1982.
By 2081, the report continues, the frequency could jump by 20 to 50 times.
Erik Franklin, assistant research professor at the Hawaii Institute of Marine Biology at the University of Hawaii at Manoa, said the fact that Hawaii has seen two major marine heat waves unprecedented in modern records in just the last five years is raising red flags.
“The frequency of these heat waves and the frequency and magnitude of these events that we’re experiencing over the past few years in Hawaii, we weren’t predicting these to happen for say another 10 or 20 years, so the fact that they’re happening sooner is even more of a concern,” Franklin said.
“It appears that the phenomenon is happening faster than we were predicting.”
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.
“We were fortunate in that we were one of the last areas that experienced a mass coral bleaching events. Previously they had been observed at reefs all around the world, and the first really truly global event happened in 1998 during a very strong El Niño,” Franklin said. “And so that was the first point in which we started to, as a coral reef community, observe these things on a global scale.”
The fact that coral bleaching is now happening globally ― and not just in one geographic region ― must mean there’s a global factor driving the effect, he said.
The threat to corals has widespread ramifications because reefs serve as important ecosystems and also protect shorelines. And warming waters are just one of the threats corals are facing.
Gove, of NOAA, added that ocean acidification ― which happens as the world’s oceans take in more carbon dioxide from the air ― is also hampering the ability of shellfish and corals to grow.
Gove said ocean acidification will exacerbate the effects of coral bleaching because corals are less resilient. He likens it to human health.
"If you and I are working really hard, long hours, getting terrible sleep, we're not eating well, our immune system is compromised, and then something like we're exposed to the flu or pneumonia, we're much more likely to get sick and have the impacts of pneumonia or flu be really severe," Gove said.
It’s the same with corals.
“If corals are experiencing this sort of chronic stress when something like the coral bleaching event comes in, it’s way more vulnerable to the impacts of that coral bleaching event than it would be otherwise,” Gove said.
Scientists say the impacts of marine heat waves won’t stop at the shoreline.
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.
“People like to fish for, catch and eat a lot of the organisms on the reef,” said Franklin, of UH.
“From our simulations, there are predictions that there will be diminished fishery capacity and productivity with the loss of coral reefs from near-shore habitats.”
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.
“Without coral reefs, waves that would break onto reefs would now be coming right up on the shoreline, on the beaches, or areas that would affect shoreline property owners on roads that are on the coast,” Franklin said.
All of these impacts have a dollar impact. Franklin said even tourism could take a hit as beaches disappear and visitors flock elsewhere.
So when could Hawaii start to see more intense marine heat waves?
The science isn’t clear, but models show major changes happening throughout this century.
“The trend we’re on right now is globally we have this gradual increase in temperatures everywhere, Hawaii included,” Franklin said.
That means average temperatures aren’t just going up, but so are the extremes. And those extremes will start becoming more common.
If all this feels overwhelming, Gove said there are actually things everybody can do to decrease the risk of the worst impacts of climate change taking hold.
“I think that we do need to make really dramatic changes in our carbon footprint, both individually as well as globally," he said.
“But what we do on a day-to-day basis definitely influences reef ecosystems ― things like wastewater pollution, fishing pressure, agricultural runoff ― all of these things influence ecosystem health, and we all play a role in that.”
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