Global ocean heat sets record for 12 straight months, alarming scientists

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Last year around this time, scientists watched in disbelief as the world’s oceans reached record levels of heat and wondered what could have triggered it. The jump in sea surface temperatures It was more dramatic than anything seen before..

Scientists explored a link to El Niño, the weather pattern known to warm the Pacific Ocean, and possible warming influences from decreased pollution from shipping ships and a major volcanic eruption. But nothing explains the influx of heat, which continued for months and spread heat waves across almost all ocean surfaces.

Now, the record-breaking streak of ocean heat is entering its second year. Scientists say it could represent a major change in Earth’s systems that cannot be reversed on any human time scale.

That’s because what they’ve seen in the oceans so far “doesn’t add up,” Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies, told the Washington Post.

“It could imply that global warming is already fundamentally altering the functioning of the climate system, much sooner than scientists had anticipated,” he wrote in a column in Nature magazine.

Ocean temperatures jump ‘off the charts’

The warming has spread away from a stretch of the Pacific influenced by El Niño.

Across much of the Atlantic basin, for example, surface temperatures have been 1 to 2 degrees Celsius (1.8 to 3.6 degrees Fahrenheit) above the 1971-2000 baseline. The anomaly is 3 degrees Celsius (5.4 degrees Fahrenheit) or higher in some waters off South Africa, Japan and the Netherlands, according to satellite data from the National Oceanic and Atmospheric Administration.

Ocean heat waves coincide with The warmest conditions ever observed in the atmosphere., also. Last year, the average global air temperature rose more than humans have ever known, perhaps bringing the planet to its hottest point in more than 100,000 years. Climate scientists predict 2024 could be even warmer.

But seeing such dramatic warming across all of Earth’s oceans is even more alarming, given that it takes much more energy to heat water than air, said Celeste Saulo, secretary general of the World Meteorological Organization.

“The time scale of the oceans is not as fast as that of the atmosphere,” Saulo said at a news conference. “Once a change is established, I would say it is almost irreversible on time scales from centenary to millennium.”

In its annual State of the Climate report released Tuesday, the organization said many climate indicators last year “gave ominous new meaning to the phrase ‘off the charts.’” That included the unprecedented melting of glaciers, Loss of sea ice in Antarctica and sea levels will rise as marine heat waves spread across more than 90 percent of ocean surfaces sometime during 2023.

The most exceptional heat affected the eastern North Atlantic, the Gulf of Mexico and the Caribbean, the North Pacific and large areas of the Southern Ocean, the WMO said. Since April, global average sea surface temperatures have hit records every month, with records in July, August and September “by a particularly wide margin,” the organization said.

Profound, yet unpredictable, impacts

Warming of the world’s oceans is already having devastating consequences for coral reefs. Fatal heat levels hit a largely pristine section of Australia’s Great Barrier Reef this month, a repeat of the Coral bleaching and mortality around Florida. last year.

Other impacts will take longer to detect.

However, there are concerns that warming and melting are causing the collapse of a key Atlantic Ocean current system. The tipping point at which this could occur is unknown.. It would have massive impacts on underwater ecosystems and weather patterns.

And cascading impacts on marine life are likely.

In the Gulf of Maine, where waters have warmed much faster than the world’s oceans overall, researchers have already seen important species like cod and herring struggling to find cold waters within their normal geographic range. Many fish grow faster at younger ages, but then plateau as they reach smaller sizes, a sign that they aren’t getting enough food or that the heat is stressing their bodies, said Katherine Mills, senior scientist at the Gulf Research Institute. of Maine. .

The temperatures observed over the past year are so extreme relative to past conditions that it is becoming increasingly difficult to reliably predict what the consequences might be, Mills said. Existing data on ecosystem changes are becoming too outdated, too fast, she said.

“In general, we expect that in the ocean there will be variability in temperatures,” Mills said. “What this has done is send that variability into a range that we haven’t encountered before.”

“I think it’s a real wake-up call,” he added.

Scientists don’t know if or when extreme ocean warming will slow. So far, none of his theories about what drives him have answered all the questions.

Some of the warming is likely related to a decrease in air pollution from liners, allowing more sunlight to reach ocean surfaces. And the eruption of the underwater Hunga Tonga-Hunga Ha’apai volcano near the island nation Tonga in 2022 sent large amounts of water vapor, a planet-warming greenhouse gas, into the atmosphere. But neither factor explains the drastic increase in ocean heat.

Ocean temperatures rose last spring at the end of what had been three consecutive years of a La Niña global weather pattern, which is the opposite of El Niño and known to suppress global warming. The change from La Niña to which became a historically strong El Niñoknown to increase planetary temperatures, could explain much of the increase in ocean heat, said Boyin Huang, a NOAA oceanographer focused on ocean temperature analysis.

Therefore, ocean temperatures are likely to moderate later this year and La Niña conditions are forecast to return.

But it remains to be seen whether a shift from El Niño to La Niña would be enough to significantly counteract warming or the power of greenhouse gases. That could become clearer in late summer, if ocean temperatures continue to set records, Huang said.

If record heat persists even under La Niña conditions, Schmidt wrote, “the world will be in uncharted territory,” with far more uncertainty about its future climate than scientists had previously known.

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