As the world's climate changes, ocean warming is accelerating and sea levels are rising more quickly, warns a new report by the U.N. Intergovernmental Panel on Climate Change.
The report is a synthesis of the most up-to-date climate science on oceans and ice, and it lays out a stark reality: Ocean surface temperatures have been warming steadily since 1970, and for the past 25 years or so, they've been warming twice as fast.
Sea levels are also rising increasingly quickly "due to increasing rates of ice loss from the Greenland and Antarctic ice sheets," the report states.
"For me, it's the complete picture that's kind of surprising and, frankly, concerning," says Ko Barrett, vice-chair of the U.N. panel and the deputy assistant administrator for research at the National Oceanic and Atmospheric Administration in the U.S. "This is, in some ways, a report about water. Water is the lifeblood of the planet."
The report also discusses a relatively new phenomenon in the oceans: marine heat waves.
"It's sort of remarkable that prior to 2012 [or] 2013, nobody had thought about heat waves in the ocean," says Andrew Pershing, chief scientific officer at the Gulf of Maine Research Institute in Portland, Maine. "And then, in 2012 we had a huge event here in the Northwest Atlantic, and the Gulf of Maine was right at the center of it. It was a real surprise."
The abnormally hot water affected animals that live off the coast of Maine, including lobster and other creatures that are crucial to the local fishing economy. What's more, it quickly became clear that the state wasn't alone.
"Subsequently, these kind of heat wave events have kind of popped up all over the ocean," Pershing says. "We've actually had three major heat waves in the Gulf of Maine — 2012, 2016 and 2018 — and now we're looking at repeat heat waves in the northern Pacific; Australia's had some repeat heat waves. So it's really becoming a part of the conversation in oceanography."
"It's kind of an emerging issue," Barrett says. "The report finds that these heat waves have doubled in frequency since the 1980s and are increasing in intensity."
That's a big deal for coastal communities whose economies rely on fish and other seafood. Marine heat waves in recent years drove a cascade of changes in marine life off the coast of the Pacific Northwest, which in turn led to disastrous seasons for commercial fishermen.
"We had two federally declared fishery disaster seasons in 2016 and 2017," says Noah Oppenheim, executive director of the Pacific Coast Federation of Fishermen's Associations. "The disaster seasons that we've experienced lately put a lot of fishermen right on the brink."
Abnormally hot water supported blooms of algae that polluted the Dungeness crab fishery on the West Coast, shutting it down for months. Meanwhile, the so-called blob of hot water off the coast was associated with drought on land, which decimated salmon runs, raised the risk of wildfires and strained water resources inland.
"Certainly, this is a phenomena we should be placing higher attention on because I think there are connections between marine heat waves and, say, weather as it impacts even the interior of continents," Barrett says.
Rising water temperatures in the Gulf of Mexico have also affected weather in that region. When sea surface temperatures are unusually high, it helps fuel larger, wetter tropical storms. For example, Hurricane Harvey and Tropical Depression Imelda came inland and dropped incredible amounts of rain on Texas in the past two years.
The U.N. panel's report suggests multiple actions that local, state and national leaders can take to slow ocean warming and rising, and to adapt to its impacts. First and foremost, the authors reinforce what has been known for decades: Greenhouse gas emissions from burning fossil fuels are the main driver of changes in the world's oceans, and the global economy must undergo a dramatic transformation to reduce those emissions.
The report notes that the oceans are getting more acidic, which could lead to mass extinction of marine organisms, especially animals with shells, such as oysters and clams.
However, the report also notes that if greenhouse gas emissions are immediately and dramatically curtailed, some impacts of ocean acidification could be avoided this century.
Some marine impacts of climate change will unfold in the coming years no matter what. Accelerating sea level rise, for example, will threaten billions of people and present an existential threat to millions who live in Indigenous coastal communities that are flood-prone and rely on fishing.
"Even if we cut carbon emissions right now, we are still looking at 20 to 30 years of change," Pershing explains. "That means, no matter what we do, we have to figure out how are we going to adapt to these changes."
NOEL KING, HOST:
The U.N. has released a new climate science report on oceans. Here's are the headlines. Ice is melting everywhere and sea level rise is accelerating. The oceans are getting hotter faster. This is killing sea animals and disrupting fisheries. And there's also a relatively new problem - heat waves in the oceans.
NPR's Rebecca Hersher has the story.
REBECCA HERSHER, BYLINE: The report is a synthesis of everything we know about climate change in the oceans so everyone's on the same page about what's happening. And what's happening, in the most basic terms, is that the oceans are getting a lot hotter. The rate of ocean warming has doubled since 1993. And marine heat waves are getting more frequent and intense. Haven't heard of marine heat waves? That's because they're new.
Andrew Pershing is the chief scientific officer at the Gulf of Maine Research Institute.
ANDREW PERSHING: It's sort of remarkable that prior to 2012, 2013, nobody kind of thought about heat waves in the ocean. And then in 2012, we had a huge event here in the Northwest Atlantic. And the Gulf of Maine was right at the center of it.
HERSHER: Just like a heat wave on land, the water near Maine got abnormally hot that year. Scientists had never seen anything like it. And it was happening in other places, too.
PERSHING: It was a real surprise. And then subsequently, these kind of heat wave events have popped up all over the ocean. So we've actually had three major heat waves in the Gulf of Maine - 2012, 2016 and 2018 - and repeat heat waves in the North Pacific. Australia's had some repeat heat waves. So it's really becoming a part of the conversation in oceanography.
HERSHER: Because they're so new, scientists still aren't able to predict ocean heat waves or say much about how long they'll last once they start. In fact, right now, there's a marine heat wave off the west coast of the U.S. where there's an area of abnormally hot water known as the blob.
HILLARY SCANNELL: How hot is it? So right now, it is up to 4 degrees Celsius above what we would normally expect.
HERSHER: Hillary Scannell studies marine heat waves at the University of Washington. Four degrees Celsius is about 7 degrees Fahrenheit hotter than usual - a big enough difference where you'd notice it if you touched the water.
SCANNELL: This patch of warm water is very unusual because it is so extreme and intense.
HERSHER: Which is bad news for the animals that live in that water. Noah Oppenheim is the executive director of the Pacific Coast Federation of Fishermen's Associations. He's also a former marine researcher.
NOAH OPPENHEIM: The impacts to the ocean sort of cascade up through the food web starting with plankton and into the krill, which form the prey base for animals as small as sardines all the way up to salmon and then whales.
HERSHER: That cascade comes up in the new report. As oceans get hotter and marine heat waves get more intense, it knocks everything in the ocean out of equilibrium. That's already happened in the Pacific Northwest in recent years. Blobs of hot water there caused blooms of toxic algae, which meant the region's Dungeness crab fishery was closed for months. Salmon was also decimated.
The federal government declared fishery disasters in 2016 and 2017. It's one of the many economic challenges that come with warmer oceans in addition to the costs of dealing with sea level rise. And hotter oceans also affect the weather far from the coasts, contributing to droughts and driving bigger, wetter storms. Cutting greenhouse gas emissions dramatically will help with all of these effects but slowly.
OPPENHEIM: Even if we cut carbon emissions right now, we are still looking at 20 or 30 years of change. And so that means no matter what we do, we have to figure out how are we going to adapt to these changes?
HERSHER: Which will mean remaking the global economy, rebuilding infrastructure and rethinking how we manage coastal communities.
Rebecca Hersher, NPR News.
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