WASHINGTON — A growing body of evidence demonstrates a link between the melting of Arctic sea ice and worsening summer heat waves and other extreme weather in the United States and elsewhere in the world, leading scientists said Thursday.

“The Arctic is not like Vegas. What happens in the Arctic does not stay in the Arctic,” said Howard Epstein, a University of Virginia environmental scientist who’s part of a team that produced the Arctic Report Card for the federal National Oceanic and Atmospheric Administration (NOAA).

The report card, released Thursday, said that while this year’s melting of Arctic sea ice didn’t reach the record levels of 2012, the ice was thin and was at the sixth-lowest minimum since observations began in 1979.

“We cannot expect to be smashing records every year; there are going to be ups and downs. But those up and downs are going to be superimposed on the trend of a warming Arctic,” said Martin Jeffries, a University of Alaska, Fairbanks, professor who’s the adviser to the U.S. Arctic Research Commission.

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The decades-long decline in Arctic sea ice is among the most visible signs of global warming. NOAA’s Arctic Report Card came days after a study in the journal Nature Climate Change linked the sea-ice melt to extreme summer weather in North America and Europe.

Experts from China and the U.S. wrote in the journal that rising temperatures over the melting Arctic were changing the character of the Northern Hemisphere jet stream, the fast-flowing air current that circles the globe.

Scientists are strongly debating those conclusions. But Jeffries, who edited the NOAA Arctic Report Card, said they reflected a growing body of evidence.

“We can say the statistical relationships are there,” Jeffries said.

Alaska experienced record-breaking heat this summer, though it followed a cold spring in which the first green buds didn’t appear in the Alaskan Interior until May 26. That’s the latest since observations began in 1972, according to the NOAA report.

The report also found a substantial increase in the number and severity of Arctic wildfires. More than half the wildfires reported since 1950 on the North Slope of Alaska happened during the past decade.