As always the economic implications are staggering. We could destroy an entire industry.
This is new science and terrain. Finding causes and solutions is a long way off, unfortunately.
The blob': how marine heatwaves are causing unprecedented climate chaos
Then emaciated and dehydrated sea lion pups began showing up, stranded and on the brink of death
A surge in dead whales was reported in the same region, and that was followed by the largest ever toxic algal bloom seen along the Californian coast. Mixed among all that, there were population booms of several marine species that normally aren’t seen surging in the same year.
Plague, famine, pestilence and death was sweeping the northern Pacific ocean between 2014 and 2015.
This chaos was caused by a single massive heatwave, unlike anything ever seen before. But it was not the sort of heatwave we are used to thinking about, where the air gets thick with warmth. This occurred in the ocean, where the effects are normally hidden from view.
Nicknamed “the blob”, it was arguably the biggest marine heatwave ever seen. It may have been the worst but wide-scale disruption from marine heatwaves is increasingly being seen all around the globe, with regions such as Australia seemingly being hit with more than their fair share.
It might seem strange given their huge impact but the concept of a marine heatwave is new to science. The term was only coined in 2011. Since then a growing body of work documenting their cause and impact has developed.
According to Emanuele Di Lorenzo from the Georgia Institute of Technology, that emerging field of study could not only reveal a hitherto underestimated source of climate-related chaos, it could change our very understanding of the climate.
The eye of the storm
On the other side of the Pacific from “the blob”, Australia has been buffeted by a string of extreme marine heatwaves. This year at least three parts of the coast have been devastated by extreme water temperatures.Australia, it seems, could be smack in the middle of this global chaos. According to work published in 2014, both the south-east and south-west coasts are among the world’s fastest warming ocean waters.
“They have been identified as global warming hot spots,” says Eric Oliver, an oceanographer at the University of Tasmania. “The seas there are warming fast and so we might expect there to be an increased likelihood or increased intensity of the events that happen there.
“Certainly attention is being focused on ocean changes on the south-east and south-west of Australia.”
A field born in the death of a forest
It was in the study of a marine heatwave in southwest Australia that the term was coined just five years ago. In a report that still used the term “marine heatwave” in scare quotes, scientists from the West Australian department of fisheries found the heatwave off the state’s coast was “a major temperature anomaly superimposed on the underlying long-term ocean-warming trend”.That year, the researchers found, Western Australia had an unprecedented surge of hot water along its coast. Surface temperatures were up to 5C higher than the usual seasonal temperature. The pool of warm water stretched more than 1,500km from Ningaloo to the southern tip of the continent at Cape Leeuwin, and it extended more than 200km offshore. Unlike a terrestrial heatwave that will normally last a couple of weeks at most, this persisted for more than 10 weeks.
But five years later the full impact of that marine heatwave have are beginning to be more fully understood.
Thomas Wernberg, an ecologist from the University of Western Australia, examined the impact on the gigantic kelp forests that line the western and southern coast of Australia, publishing his results in the prestigious journal Science.
“It got so hot that the kelp forests died,” Wernberg says. For hundreds of kilometres, magnificent kelp forests that line the coast and support one of the world’s most biodiverse marine environments simply died in the heat
But it wasn’t just their death that was the problem. While heatwaves on land can kill and destroy large sections of terrestrial forests – usually by allowing fires to spread – those trees normally grow back. What was disturbing about this marine heatwave was that many of the vast underwater forests never came back. The warming climate created changes that meant the kelp didn’t recover. About 100km of kelp forests just disappeared, probably forever.
“At the same time, there was a range extension of tropical and subtropical fish that love eating seaweed. So that basically means that, even when the temperatures came down, the kelp couldn’t recover – there was a range extension of the herbivorous fishes that were eating the kelp.”
In the place of the kelp forest, Wernberg found coral was starting to emerge. It was as if the heatwave in 2011 bulldozed the area, making way for a shift in the ecosystem that climate change was already trying to impose.
“It is probably too early to say if this will eventually lead to new coral reefs,” Wernberg says. “However, this is how I imagine the process would start.”
Wernberg estimated those kelp forests were directly responsible for sustaining rock lobster and abalone fisheries, as well as a tourist industry, together worth $10bn. If they were lost, it would be a serious problem for Australia, not to mention for the animals that rely on them.
Wernberg says the kelp forests in Western Australia were likely to keep contracting. “I think the next big heatwave is just going to push what we see in the north ultimately further down and then it just depends on how bad that heatwave is, whether we go all the way down to Perth or whether we just go another 10km,” he told the Guardian when the study first came out...
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