科学家称北极冬天录得历史最高温

New weather information shows the Arctic just had its warmest winter on record.

The same information also shows that sea ice hit record lows for this time of year. That means there is plenty of open water in the Arctic Ocean, where ocean water normally freezes into thick pieces of ice.

Scientists told the Associated Press what is happening now has never happened before. They say it is part of a vicious cycle, a series of cause and effect events, in Earth's atmosphere.

The scientists believe that climate change could be fueling these changes. They say slowly rising temperatures in the atmosphere are likely influencing strong icy, storms in Europe and the northeastern United States.

"It's just crazy, crazy stuff," said Mark Serreze, director of the National Snow and Ice Data Center in Boulder, Colorado.

Serreze has been studying the Arctic since 1982. "These heat waves, I've never seen anything like this," he said.

Unusual temperatures across the Arctic

This past winter has been so warm that the land weather station closest to the North Pole, at the top of Greenland, spent more than 60 hours above freezing last month. Before this year, scientists had only seen temperatures there briefly rise above freezing in February only two times before.

On February 24, 2018, the temperature at the top of Greenland reached six degrees Celsius, setting a record for that date.

The warmer weather reached other parts of the Arctic Circle. In Barrow, Alaska, the temperature in February was 10 degrees warmer than normal. All winter long, the average temperatures were 7.8 degrees Celsius higher than normal.

At over 30 different Arctic weather stations, 15 of them were at least 5.6 degrees Celsius above normal for the winter. That information comes from climate scientist Brian Brettschneider of the International Arctic Research Center at the University of Alaska Fairbanks.

Weather scientists consider December, January, and February to be winter. Arctic weather stations averaged 4.9 degrees Celsius higher than normal for the season that just ended. The air above the Chukchi and Bering seas near Alaska averaged about 11 degrees Celsius higher than normal for February, the data center reported.

Less ice and a vicious cycle

In February, Arctic sea ice covered 13.9 million square kilometers. This is about 160,000 square kilometers less than the record low last year, the ice data center said. Sea ice coverage in February also was 1.4 million square kilometers below the 30-year average. That represents an area nearly two times the size of the state of Texas.

Sea ice is frozen ocean water that forms, grows and melts on the ocean. Near Greenland, warm air moved north over part of the Atlantic Ocean that usually has sea ice. Something similar was also happening in the Pacific Ocean, creating open water on normally frozen parts of the Bering Sea, said data center scientist Walt Meier. To be happening on opposite sides of the Arctic at the same time is unusual, he added.

While some natural weather systems were involved, climate change is the most important influence, Meier said. "When you have warmer temperatures, you are going to melt more ice and it's going to grow more slowly."

In the winter, sea ice "acts as a lid to keep the warmth of the water at bay." But when there is less sea ice, more heat goes into the air, Brettschneider said. "You end up with a vicious cycle of warm air preventing sea ice formation and lack of sea ice allowing warmth to escape into the air."

I'm Jonathan Evans.

Seth Borenstein wrote this story for the Associated Press. Phil Dierking adapted his report for VOA Learning English. George Grow was the editor.

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