Marine heat waves are spreading around the world
In recent decades, the oceans have warmed. Marine heat waves, once rare events, have become more common.
One particularly intense event known as "the Blob' lasted years and devastated plankton populations, starving millions of fish and seabirds and damaging commercial fishing.
Recently, high temperatures have persisted. In January 2024, the share of the ocean surface experiencing a heat wave topped 40%.
Unusual heat waves have occurred in all of the major ocean basins around the planet in recent years. And some of these events have become so intense that scientists have coined a new term: super marine heat waves.
"The marine ecosystems where the super marine heat waves occur have never experienced such a high sea surface temperature in the past,' Boyin Huang, an oceanographer at the National Oceanic and Atmospheric Administration, said in an email.
The seas off the coasts of the United Kingdom and Ireland experienced an unusually intense marine heat wave, one of the longest on record, starting in April, and the temperature rise happened much earlier in the year than usual. Australia and its iconic coral reefs were recently struck by heat waves on two coasts.
Scientists define marine heat waves in different ways. But it's clear that as the planet's climate changes, the oceans are being fundamentally altered as they absorb excess heat trapped in the atmosphere from greenhouse gases, which are emitted when fossil fuels are burned.
Hotter oceans are causing drastic changes to marine life, sea levels and weather patterns.
Some of the most visible casualties of ocean warming have been coral reefs. When ocean temperatures rise too much, corals can bleach and die. About 84% of reefs worldwide experienced bleaching-level heat stress at some point between January 2023 and March 2025, according to a recent report.
Last year, the warmest on record, sea levels rose faster than scientists expected. Research showed that most of that rise in sea levels came from ocean water expanding as it warms, which is known as thermal expansion, not from melting glaciers and ice sheets, which in past years were the biggest contributors to rising seas.
In a photo from the National Park Service, a humpback whale named Festus that was found dead just outside the mouth of Glacier Bay, Alaska, June 2016. A report on this whale revealed numerous health conditions, including poor nutrition and elevated levels of harmful algal toxins. |
Craig Murdoch / National Park Service, NOAA permit #18786 / via The New York Times
Excess heat in the oceans can also affect weather patterns, making hurricanes more likely to rapidly intensify and become more destructive. In the southwest Pacific, last year's ocean heat contributed to a record-breaking streak of tropical cyclones hitting the Philippines.
"If we understand how global warming is affecting extreme events, that is essential information to try to anticipate what's going on, what's next,' said Marta Marcos, a physicist at the University of the Balearic Islands in Spain.
Marcos was the lead author of a recent study published in Proceedings of the National Academy of Sciences that found that climate change has been responsible for the overwhelming majority of marine heat waves in recent decades.
The losses
Some of the earliest research on mass die-offs associated with marine heat waves, before there was a name for them, came from the Mediterranean, which has been warming three to five times faster than the ocean at large. Joaquim Garrabou, a marine conservation ecologist at the Institut de Ciencies del Mar in Barcelona, Spain, started studying these events after witnessing a die-off of sponges and coral in 1999.
He and other scientists believed that with climate change, these die-offs would reoccur. "The reality is moving even faster than what we thought,' he said. "Having these mass mortality events is the new normal, instead of something infrequent, which it should be.'
In 2012, a marine heat wave in the Gulf of Maine highlighted the risk these events pose to fisheries. The Northern shrimp population went from an estimated 27.25 billion in 2010 to 2.8 billion two years later, according to modeling by the Atlantic States Marine Fisheries Commission.
"This disappearance of the shrimp was just shocking,' said Anne Richards, a retired research fisheries biologist who worked at NOAA's Northeast Fisheries Science Center at the time.
In a photo from Jemina Stuart-Smith, University of Tasmania, a red handfish is collected in the waters off the coast of Tasmania. In a heatwave that began in 2023, researchers in Tasmania transferred 25 red handfish to an aquarium until the temperatures fell. |
Jemina Stuart-Smith, University of Tasmania / via The New York Times
Her research pointed to a significant culprit: Longfin squid drawn north by warmer water were eating the shrimp.
The fishery has not yet reopened. By 2023, the Northern shrimp population was estimated to have dropped to around 200 million.
Commercial fishing has always been difficult, but now, "climate change is taking that to another level,' said Kathy Mills, a senior scientist at the Gulf of Maine Research Institute.
Complicating matters is the fact that much of the research on marine heat waves comes from just a few countries, including Australia, the United States, China, Canada, Spain and the United Kingdom.
"There are lots of regions around the world where monitoring isn't as good as other places, and so we don't really know what's happening,' said Dan Smale, a community ecologist at the United Kingdom's Marine Biological Association.
Rising ocean temperatures can also set off a domino effect through the marine food web, starting at the bottom with plankton.
In a photo from the Coastal Observation and Seabird Survey Team, emaciated Cassin's auklets found during a single survey on an Oregon beach, on Jan. 8, 2015. During the ocean heat event in the North Pacific known as 'the Blob,' hundreds of thousands of birds died of starvation. |
Coastal Observation and Seabird Survey Team / via The New York Times
Since the end of most commercial whaling in the 1970s and '80s, humpback whales in the North Pacific had been recovering, reaching a peak population of about 33,000 in 2012.
But then came the heat event known as "the Blob' that blanketed much of region from 2014 to 2017. The heat wave diminished wind and waves, limiting the nutrients that typically get churned up to the sea surface. Fewer nutrients meant fewer phytoplankton, fewer zooplankton, fewer fish and fewer of everything else that eats them.
How 'the blob' took a toll
After the Blob dissipated, researchers learned that the effects of a severe marine heat wave could endure long after the event itself has passed.
Ted Cheeseman, a doctoral candidate at Southern Cross University, had co-founded Happywhale, a database of tens of thousands of marine mammals built on photos submitted by researchers and whale watchers around the world. Cheeseman found a sharp drop in humpback whale sightings by 2021.
The decrease was so significant, at first he thought the Happywhale team was doing the math wrong. The team members spent several years checking and last year published a study that concluded the humpback whale population in the North Pacific had fallen by 20% from 2012 to 2021. They attributed the decline to the loss of food like krill during and after the Blob.
With "an estimate of 7,000 whales having disappeared and not showing up anywhere else,' Cheeseman said, "there's really no other explanation.'
Looking ahead
Eventually, parts of the ocean might enter a constant state of marine heat wave, at least by today's common definition. Some scientists see today's shorter-term spikes as practice for this future.
Alistair Hobday, a biological oceanographer at Australia's Commonwealth Scientific and Industrial Research Organisation, has been conducting public briefings with marine heat wave forecasts months ahead of time.
People are tuning in — and responding.
In a photo from Jemina Stuart-Smith, University of Tasmania, a red handfish in the waters off the coast of Tasmania. |
Jemina Stuart-Smith, University of Tasmania / via The New York Times
The critically endangered red handfish lives off the coast of Tasmania, crawling along the seafloor on fins shaped like hands. These unusual fish have only been found within two small patches of rocky reef and sea grass meadow.
In late 2023, Hobday's forecast predicted potentially deadly marine heat waves. Researchers from the University of Tasmania's Institute for Marine and Antarctic Studies, with support from the Australian Department of Climate Change, took a drastic step. They transferred 25 red handfish to an aquarium until the temperatures fell.
Jemina Stuart-Smith, an ecologist at the University of Tasmania, described those weeks as the most stressful time of her life. "If it all went wrong,' she said, "you're talking about the potential extinction of an entire species.'
After three months, 18 fish were returned to the ocean. Three had died, and four were enrolled in a captive breeding program.
Scientists recognize that temporary fixes can only do so much in the face of long-term warming.
"It's kind of putting a Band-Aid on a broken leg,' said Kathryn Smith, a marine ecologist and postdoctoral researcher at the Marine Biological Association.
But those studying today's extreme events still hope their work gives people some visibility into the future of the world's oceans, Hobday said. "Clever people, if you tell them about the future,' he said, "can think of all kinds of things to do differently.'
This article originally appeared in The New York Times © 2025 The New York Times Company
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Japan Times
4 days ago
- Japan Times
Marine heat waves are spreading around the world
In recent decades, the oceans have warmed. Marine heat waves, once rare events, have become more common. One particularly intense event known as "the Blob' lasted years and devastated plankton populations, starving millions of fish and seabirds and damaging commercial fishing. Recently, high temperatures have persisted. In January 2024, the share of the ocean surface experiencing a heat wave topped 40%. Unusual heat waves have occurred in all of the major ocean basins around the planet in recent years. And some of these events have become so intense that scientists have coined a new term: super marine heat waves. "The marine ecosystems where the super marine heat waves occur have never experienced such a high sea surface temperature in the past,' Boyin Huang, an oceanographer at the National Oceanic and Atmospheric Administration, said in an email. The seas off the coasts of the United Kingdom and Ireland experienced an unusually intense marine heat wave, one of the longest on record, starting in April, and the temperature rise happened much earlier in the year than usual. Australia and its iconic coral reefs were recently struck by heat waves on two coasts. Scientists define marine heat waves in different ways. But it's clear that as the planet's climate changes, the oceans are being fundamentally altered as they absorb excess heat trapped in the atmosphere from greenhouse gases, which are emitted when fossil fuels are burned. Hotter oceans are causing drastic changes to marine life, sea levels and weather patterns. Some of the most visible casualties of ocean warming have been coral reefs. When ocean temperatures rise too much, corals can bleach and die. About 84% of reefs worldwide experienced bleaching-level heat stress at some point between January 2023 and March 2025, according to a recent report. Last year, the warmest on record, sea levels rose faster than scientists expected. Research showed that most of that rise in sea levels came from ocean water expanding as it warms, which is known as thermal expansion, not from melting glaciers and ice sheets, which in past years were the biggest contributors to rising seas. In a photo from the National Park Service, a humpback whale named Festus that was found dead just outside the mouth of Glacier Bay, Alaska, June 2016. A report on this whale revealed numerous health conditions, including poor nutrition and elevated levels of harmful algal toxins. | Craig Murdoch / National Park Service, NOAA permit #18786 / via The New York Times Excess heat in the oceans can also affect weather patterns, making hurricanes more likely to rapidly intensify and become more destructive. In the southwest Pacific, last year's ocean heat contributed to a record-breaking streak of tropical cyclones hitting the Philippines. "If we understand how global warming is affecting extreme events, that is essential information to try to anticipate what's going on, what's next,' said Marta Marcos, a physicist at the University of the Balearic Islands in Spain. Marcos was the lead author of a recent study published in Proceedings of the National Academy of Sciences that found that climate change has been responsible for the overwhelming majority of marine heat waves in recent decades. The losses Some of the earliest research on mass die-offs associated with marine heat waves, before there was a name for them, came from the Mediterranean, which has been warming three to five times faster than the ocean at large. Joaquim Garrabou, a marine conservation ecologist at the Institut de Ciencies del Mar in Barcelona, Spain, started studying these events after witnessing a die-off of sponges and coral in 1999. He and other scientists believed that with climate change, these die-offs would reoccur. "The reality is moving even faster than what we thought,' he said. "Having these mass mortality events is the new normal, instead of something infrequent, which it should be.' In 2012, a marine heat wave in the Gulf of Maine highlighted the risk these events pose to fisheries. The Northern shrimp population went from an estimated 27.25 billion in 2010 to 2.8 billion two years later, according to modeling by the Atlantic States Marine Fisheries Commission. "This disappearance of the shrimp was just shocking,' said Anne Richards, a retired research fisheries biologist who worked at NOAA's Northeast Fisheries Science Center at the time. In a photo from Jemina Stuart-Smith, University of Tasmania, a red handfish is collected in the waters off the coast of Tasmania. In a heatwave that began in 2023, researchers in Tasmania transferred 25 red handfish to an aquarium until the temperatures fell. | Jemina Stuart-Smith, University of Tasmania / via The New York Times Her research pointed to a significant culprit: Longfin squid drawn north by warmer water were eating the shrimp. The fishery has not yet reopened. By 2023, the Northern shrimp population was estimated to have dropped to around 200 million. Commercial fishing has always been difficult, but now, "climate change is taking that to another level,' said Kathy Mills, a senior scientist at the Gulf of Maine Research Institute. Complicating matters is the fact that much of the research on marine heat waves comes from just a few countries, including Australia, the United States, China, Canada, Spain and the United Kingdom. "There are lots of regions around the world where monitoring isn't as good as other places, and so we don't really know what's happening,' said Dan Smale, a community ecologist at the United Kingdom's Marine Biological Association. Rising ocean temperatures can also set off a domino effect through the marine food web, starting at the bottom with plankton. In a photo from the Coastal Observation and Seabird Survey Team, emaciated Cassin's auklets found during a single survey on an Oregon beach, on Jan. 8, 2015. During the ocean heat event in the North Pacific known as 'the Blob,' hundreds of thousands of birds died of starvation. | Coastal Observation and Seabird Survey Team / via The New York Times Since the end of most commercial whaling in the 1970s and '80s, humpback whales in the North Pacific had been recovering, reaching a peak population of about 33,000 in 2012. But then came the heat event known as "the Blob' that blanketed much of region from 2014 to 2017. The heat wave diminished wind and waves, limiting the nutrients that typically get churned up to the sea surface. Fewer nutrients meant fewer phytoplankton, fewer zooplankton, fewer fish and fewer of everything else that eats them. How 'the blob' took a toll After the Blob dissipated, researchers learned that the effects of a severe marine heat wave could endure long after the event itself has passed. Ted Cheeseman, a doctoral candidate at Southern Cross University, had co-founded Happywhale, a database of tens of thousands of marine mammals built on photos submitted by researchers and whale watchers around the world. Cheeseman found a sharp drop in humpback whale sightings by 2021. The decrease was so significant, at first he thought the Happywhale team was doing the math wrong. The team members spent several years checking and last year published a study that concluded the humpback whale population in the North Pacific had fallen by 20% from 2012 to 2021. They attributed the decline to the loss of food like krill during and after the Blob. With "an estimate of 7,000 whales having disappeared and not showing up anywhere else,' Cheeseman said, "there's really no other explanation.' Looking ahead Eventually, parts of the ocean might enter a constant state of marine heat wave, at least by today's common definition. Some scientists see today's shorter-term spikes as practice for this future. Alistair Hobday, a biological oceanographer at Australia's Commonwealth Scientific and Industrial Research Organisation, has been conducting public briefings with marine heat wave forecasts months ahead of time. People are tuning in — and responding. In a photo from Jemina Stuart-Smith, University of Tasmania, a red handfish in the waters off the coast of Tasmania. | Jemina Stuart-Smith, University of Tasmania / via The New York Times The critically endangered red handfish lives off the coast of Tasmania, crawling along the seafloor on fins shaped like hands. These unusual fish have only been found within two small patches of rocky reef and sea grass meadow. In late 2023, Hobday's forecast predicted potentially deadly marine heat waves. Researchers from the University of Tasmania's Institute for Marine and Antarctic Studies, with support from the Australian Department of Climate Change, took a drastic step. They transferred 25 red handfish to an aquarium until the temperatures fell. Jemina Stuart-Smith, an ecologist at the University of Tasmania, described those weeks as the most stressful time of her life. "If it all went wrong,' she said, "you're talking about the potential extinction of an entire species.' After three months, 18 fish were returned to the ocean. Three had died, and four were enrolled in a captive breeding program. Scientists recognize that temporary fixes can only do so much in the face of long-term warming. "It's kind of putting a Band-Aid on a broken leg,' said Kathryn Smith, a marine ecologist and postdoctoral researcher at the Marine Biological Association. But those studying today's extreme events still hope their work gives people some visibility into the future of the world's oceans, Hobday said. "Clever people, if you tell them about the future,' he said, "can think of all kinds of things to do differently.' This article originally appeared in The New York Times © 2025 The New York Times Company
Japan Times
13-06-2025
- Japan Times
Natural disasters may be shaping babies' brains
Climate disasters are known for damaging homes, disrupting power and displacing residents. But even after the lights come back on and people return to their homes, their effects can linger — including in the brains of children born afterwards, a new study suggests. Climate stressors, and the effect they have on pregnant people, appear to affect the brain development of their babies, according to the study published in PLOS One on Wednesday, which relied on brain imaging conducted years after 2012's Superstorm Sandy hit the New York City metro area. The study evaluated a sample of 34 children, 11 whose parents were pregnant during Superstorm Sandy. By the time of assessment, the kids were roughly eight years old. Those who had been exposed to Sandy in utero had a significant enlargement in a part of the brain known as the basal ganglia. Parts of the basal ganglia were as much as 6% larger than in unexposed children, a change that could have negative implications for the children's behavior. The parents living through the disruptions from a storm that displaced more than 23,000 people and suspended electric services in the area for days to weeks may have affected their offspring's neurodevelopment, the researchers say. The findings signal how new generations of children may be marked by climate crises that occur before they were born, and speak to a need to better evaluate and educate pregnant people about climate risks, the researchers say. They contribute to a growing consensus about pregnant people's vulnerability to climate change, with extreme heat, air pollution and natural disasters posing risks like preterm births. "This is something which people who are going to get pregnant should know and be prepared,' says Yoko Nomura, an author of the PLOS One research and a professor at Queens College at the City University of New York. "Society as a whole has to have a strategy to protect those pregnant people.' Non-climate-related stress can affect pregnancies and influence fetal brain development. But studies typically haven't examined how natural disasters may work in the same way. Project Ice Storm, a project examining the aftermath of a devastating 1998 storm in Canada, found that stress had an effect on everything from kids' temperament to their IQ. Superstorm Sandy, which hit New York and New Jersey in October 2012, devastated coastal areas, leading to around 120 deaths and billions in damages. Queens College, in Flushing, New York, served as a shelter. Nomura, who was already on the faculty there at the time, observed how distressed storm evacuees in the on-campus gym were. Many of them were pregnant, and facing stressors like losing power and being displaced from their homes. That inspired Nomura to look into how the experience might affect their unborn babies. While the team hasn't yet determined how the changes they observed in the basal ganglia may affect participating children in the day-to-day, that part of the brain is involved in functions including emotional regulation. Other studies have linked the basal ganglia to conditions like depression and autism. Demonstrators, including mothers and babies, take part in a protest in London in October 2019. | Reuters "We do think that those changes we're seeing could lead to negative outcomes for the children's behavior,' says Donato DeIngeniis, the study's lead author and a doctoral student in clinical neuropsychology at the CUNY Graduate Center. For a subset of seven children whose parents had been exposed to Sandy and separately, over the course of their parent's pregnancy, extreme heat, the brain differences were more pronounced. Researchers observed that one portion of the basal ganglia was enlarged while another was reduced. "That might mean one area is impaired, which might lead the other to have to work harder to compensate,' DeIngeniis says, which is common in the brain in instances of brain damage or injury. The cohort of children examined in the study is small, reflecting the cost of brain imaging and the fact that the study's recruitment was interrupted by the COVID-19 crisis. Even after recruitment resumed in 2021, participants were reluctant to visit for in-person imaging. Burcin Ikiz, chair of the Neuro Climate Working Group, part of Columbia University's Global Consortium on Climate and Health Education, calls the study "small but mighty.' It's increasingly important to understand how different climate stressors may together affect human health, she says. For instance, children in New Delhi are experiencing both air pollution and extreme heat. "And this is one of the first studies — that's why it's a trailblazing study — that looks at these joint things,' she says. But she added that additional work still needs to be done to address limitations of the study such as the small sample size, and to examine the effect of heat with more depth. While the researchers used statistical methods to ensure the accuracy of their findings, it's still possible that other factors could explain the differences seen in the kids' brains, like genetic variability or socioeconomic status. The research team is now in the process of conducting a similar, larger study, with around 80 participants so far. But rather than wait to release those results, Nomura says the team felt it was important to release earlier findings more quickly to raise awareness among the public.
Nikkei Asia
07-06-2025
- Nikkei Asia
North Korea internet hit by a major outage, analyst says
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