Crucial Atlantic Ocean Current System Is Faltering, Research Suggests

A slowdown in the network, which influences weather far and wide, could spell trouble. “We’re poking a beast,” one expert said. “But we don’t really know the reaction we’ll cause.”,

breaking

Surveying the damage from the Dixie Fire in Greenville, Calif., on Thursday.Credit…Josh Edelson/Agence France-Presse — Getty Images

After the Dixie Fire destroyed the Gold Rush town of Greenville, Calif., local officials said they were hopeful that improving weather conditions on Friday would help firefighters prevent the blaze from dealing further damage.

At a community meeting on Thursday night, a meteorologist told residents of threatened towns several hours north of Sacramento that winds were expected to decrease and that the wildfire smoke would keep temperatures on the ground cooler. He said there was no sign of the strong weather systems that had plagued this week.

But nobody was resting easy after seeing the destruction that shifting winds had brought to Greenville, a town of about 1,000 people.

“It looks like a bomb went off,” said Ryan Meacher, 37, whose father’s house in Greenville was one of many that burned down. “There is nothing left.”

Mr. Meacher lives in Grass Valley, which is itself being threatened by the River Fire, and said it was heartbreaking to think about what was lost in Greenville — the library where he would pick up books and VHS tapes, the pizza place next door with an arcade.

Also destroyed was a charter school where Kjessie Essue’s husband works and the Cy Hall Memorial Museum, which covered the history of Indian Valley and which her parents spent hundreds of hours building.

Ms. Essue, 38, lives in nearby Taylorsville and evacuated south on Thursday with her Nigerian Dwarf goats, her husband, her three young children and her parents, who do not know whether their Greenville home still stands.

She said it seemed liked a movie as they packed up, with an alarm blaring and wild winds sending a smoke plume with a black center toward the area.

“Greenville is a wasteland,” she said. “It’s surreal.”

Sheriff Todd Johns of Plumas County said at the community meeting that there were no reported injuries but that the authorities were still looking for four people who were unaccounted for. He estimated that the blaze, now the sixth-largest in recorded California history, had destroyed more than 100 homes in the area.

“My heart is crushed by what has occurred there, and to the folks who have lost residences and businesses,” said Sheriff Johns, a lifelong Greenville resident.

The Dixie Fire is 35 percent contained and has burned more than 420,000 acres across four counties. Officials said that the blaze seemed to have spared Chester, burning around both sides of the town off Lake Alomar, but that other communities — Westwood, Chester Mills — closer to Greenville remained under threat.

On Sunday, the authorities had lifted a mandatory evacuation order for Greenville after several days of favorable weather. But then the wind changed directions three times in two days, explosively spreading the Dixie Fire.

“We’re seeing truly frightening fire behavior, and I don’t know how to overstate that,” said Chris Carlton, supervisor for the Plumas National Forest. “We have a lot of veteran firefighters who have served for 20, 30 years and have never seen behavior like this.”

Gov. Gavin Newsom declared a state of emergency for three counties on Thursday, noting that “strong winds, high temperatures, drought conditions, and dry fuels have further increased the spread” of the Antelope Fire in Siskiyou County, on the Oregon border, and the River Fire in Nevada and Placer Counties, northeast of Sacramento.

The River Fire, which has grown to 2,600 acres since starting on Wednesday, has destroyed 76 structures and injured three people, including a firefighter. It is 15 percent contained but threatens 3,400 more structures, with 24,000 people living within five miles of the blaze, according to the New York Times fire tracker.

Dozens of wildfires are actively burning across the Western United States, charring large swaths of land in recent days, according to a New York Times analysis of government and satellite data. Some are threatening thousands of people who live and work just a few miles away.

As the fire season gets underway, The Times built an interactive map to track the latest wildfires as they spread across Western states. Check back regularly for updates.

Miami, where the Gulf Stream passes relatively close to the coastline.Credit…Wilfredo Lee/Associated Press

The water in the Atlantic is constantly circulating in a complex pattern that influences weather on several continents. And climate scientists have been asking a crucial question: Whether this vast system, which includes the Gulf Stream, is slowing down because of climate change.

If it were to change significantly, the consequences could be dire, potentially including faster sea level rise along parts of the United States East Coast and Europe, stronger hurricanes barreling into the Southeastern United States, reduced rainfall across parts of Africa and changes in tropical monsoon systems.

Now, scientists have detected the early warning signs that this critical ocean system is at risk, according to a new analysis published Thursday in the scientific journal Nature Climate Change.

“I showed that this gradual slowing down of the circulation system is associated with a loss of stability,” said Niklas Boers, a researcher at the Potsdam Institute for Climate Impact Research in Germany, “and the approaching of a tipping point at which it would abruptly transition to a much slower state.”

Alex Hall, the director of the Center for Climate Science at the University of California, Los Angeles, who was not involved in the study, said that although the findings did not signal to him that any collapse of that ocean system might be imminent, the analysis offered a crucial reminder of the risks of interfering with currents.

“We’re poking a beast,” he said. “But we don’t really know the reaction we’ll cause.”

Studying ocean systems is difficult for many reasons. One challenge is that there’s only one Earth, said Andrew Pershing, director of climate science at Climate Central, an organization of scientists and journalists focused on climate change. Consequently, researchers can’t easily compare two oceans — one ocean dealing with the effects global warming caused by increased carbon dioxide in the atmosphere, and another ocean that hasn’t had to contend with that problem.

Dr. Pershing praised the analytical workarounds that the scientists came up with in order to study the ocean-spanning tangle of currents, which are known as Atlantic Meridional Overturning Circulation, or AMOC. By parsing more than a century of ocean temperature and salinity data, Dr. Boers showed significant changes in multiple indirect measures of AMOC’s strength.

“The work is fascinating,” he said.

Dr. Pershing said that analysis supported the idea that the AMOC has gotten weaker over the course of the 20th century. It’s a critical area to study because AMOC epitomizes the idea of climatic “tipping points” — hard-to-predict thresholds in Earth’s climate system that, once crossed, have rapid, cascading effects far beyond the corner of the globe where they occur.

“The big challenge is, what do we do with that information?” he said of the new study.

Susan Lozier, a physical oceanographer and dean at the College of Sciences at Georgia Tech, said that there was no doubt that climate change is affecting oceans. There is wide consensus in her field that sea levels are rising and oceans are warming, she said.

She also called Dr. Boers’ study “interesting,” but said she wasn’t convinced that the findings showed that circulation in that ocean system is slowing. “There are lots of things to worry about with the ocean,” she said, such as the more definitive concerns involving sea-level rise.

around the world

Residents helped crews putting out a fire spreading on Tuesday in the town of Oren, in southern Turkey.Credit…Agence France-Presse — Getty Images

As southern Europe grapples with one of its worst heat waves in decades, deadly forest fires have engulfed stretches of the region, bringing a newly reopened tourism industry to a halt and forcing mass evacuations.

Here is a collection of images from recent days.

For more than a week, raging fires have pushed residents from their homes in villages on the Greek mainland and islands and across neighboring Turkey, and forced tourists to abandon beachside destinations across the region.

In Greece overnight Thursday, thousands more people fled their homes and hundreds were evacuated by sea. Seven European Union nations were sending firefighting support on Friday, including planes from France, Sweden, Croatia and Switzerland as conditions were expected to worsen with forecasts of stronger winds in the coming days.

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