VOA科学技术2023--Study: Heat Spreading Ocean Currents Could Collapse by Midcentury（在线收听）

Study: Heat Spreading Ocean Currents Could Collapse by Midcentury

A new study has predicted that a system of ocean currents that transports warm water northward could collapse in the next 70 years.

Climate scientists have warned that such collapse could cause sea level rise in the U.S. and extreme weather in Europe.

The currents spread, or circulate, water in the Atlantic Ocean, the U.S. National Oceanic and Atmospheric Administration (NOAA) explains. The currents carry warm water north and cold water south.

Two years ago, the United Nations Intergovernmental Panel on Climate Change said it was unlikely that ocean currents would cause disastrous conditions in the next 80 years or so.

However, the new study recently published in Nature Communications suggests that the huge ocean current system might collapse sooner than some scientists believe.

Altogether, the currents studied by the scientists are known as the Atlantic meridional overturning circulation, or AMOC. It circulates water throughout the Atlantic Ocean. The circulation is very lengthy, taking an estimated 1,000 years to complete. But NOAA says the circulation has been slowing since the mid-1990s.

The Atlantic current called the Gulf Stream is part of this huge current system, NOAA says.

Scientists in the United States and Germany have warned that a further slowdown or complete halt to the circulation process could create more extreme weather in the Northern Hemisphere. It could also cause sea-level rise on the U.S. East Coast and drought in southern Africa. But predictions about the possible timing remain unclear.

In the new study, Danish researchers Peter and Susanne Ditlevsen examined sea surface temperatures in the North Atlantic between 1870 and 2020. Under current conditions, they have suggested the circulation system could collapse as soon as 2025 or as late as 2095.

Their prediction is different from a prediction made by the United Nations' Intergovernmental Panel on Climate Change (IPCC) in 2021. The IPCC said the collapse was not likely to happen before 2100.

Julio Friedmann is chief scientist at New York City-based Carbon Direct, a carbon management company. He said in a statement he thinks the latest study makes clear that "action must be swift and profound" to reduce major climate risks.

Stefan Rahmstorf co-wrote a 2018 study on ocean currents in the Atlantic. He also published his comments about the Danish-led study on the website RealClimate. Rahmstorf noted that the timing of a collapse of Atlantic Ocean currents remains "highly uncertain."

He added that he finds the IPCC's estimate conservative. "Increasingly, the evidence points to the risk being far greater than 10 percent during this century," Rahmstorf wrote. He added that the problem is likely to remain "...rather worrying for the next few decades."

Words in This Story

drought – n. a long period of time during which there is very little or no rain

swift – adj. happening or moving quickly

profound – adj. very great or intense

uncertain – adj. not sure about something

decade – n. a period of ten years