Scientists are seeing surprising melting in Earth's polar regions at times they don't expect, like winter, and in places they don't expect, like eastern Antarctica.

New studies and reports issued this week at a major Earth sciences conference paint one of the bleakest pictures yet of dramatic warming in the Arctic and Antarctica. Alaskan scientists described to the Associated Press never-before-seen melting and odd winter problems, including permafrost that never refroze this past winter and wildlife die-offs.

The National Oceanic and Atmospheric Administration on Wednesday released its annual Arctic report card, detailing the second warmest year on record in the Arctic and problems, including record low winter sea ice in parts of the region, increased toxic algal blooms, which are normally a warm-water phenomenon, and weather changes attributable to what's happening in the far North.

"The Arctic is experiencing the most unprecedented transition in human history," report lead author Emily Osborne, chief of Arctic research for NOAA, said this week.

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What's happening is a big deal, said University of Colorado environmental science programme director Waleed Abdalati, Nasa's former chief scientist who was not part of the NOAA report. "It's a new Arctic. We've gone from white to blue," said Abdalati, adding that he normally wouldn't use the word "scary" but that it applies.

And that means other problems.

"Continued warming of the Arctic atmosphere and ocean are driving broad change in the environmental system in predicted, and, also, unexpected ways," the NOAA report said.

One of the most noticeable problems was a record low sea ice in winter in the Bering Sea in 2017 and 2018, scientists said.

In February the Bering Sea "lost an area of ice the area of Idaho", said Dartmouth College engineering professor Donald Perovich, a report card co-author.

This is a problem because the oldest and thickest sea ice is down 95 per cent from 30 years ago. In 1985, about one-sixth of Arctic sea ice was thick multi-year ice, now it is maybe one-hundredth, Perovich said.

University of Alaska Fairbanks marine mammal biologist Gay Sheffield not only studies the record low ice, but she lives it daily in Nome, far north on the Bering Sea.

"I left Nome and we had open water in December," Sheffield said at the American Geophysical Union conference in Washington. "It's very much impacting us. Having this area ice-free is having this massive environmental change." Sheffield said there has been a "multi-species die-off" of ocean life. She said that includes the first spring mass die-off of seals along the Bering Strait.

Ornithologist George Divoky who has been studying the black guillemots of Cooper Island for 45 years, noticed something different this year. In the past, 225 nesting pairs of the seabirds would arrive at his island. This past winter it was down to 85 pairs but only 50 laid eggs and only 25 had successful hatches. He blamed the lack of winter sea ice.

"It looked like a ghost town," Divoky said.

With overall melting, especially in the summer, herds of caribou and wild reindeer have dropped about 55 per cent - from 4.7 million to 2.1 million animals - because of the warming and the flies and parasites it brings, said report card co-author Howard Epstein of the University of Virginia.

University of Alaska Fairbanks researcher Vladimir Romanovsky said he was alarmed by what happened to the permafrost - ground that stays frozen years on end.

This past year, Romanovsky found 25 spots that used to freeze in January, then February, but never froze this year.

Because of warming, the Arctic was "seeing concentrations of algal toxins moving northward", infecting birds, mammals and shellfish to become a public health and economic problem, said report card co-author Karen Frey.

And the warmer Arctic and melting sea ice has been connected to shifts in the jet stream that have brought extreme winter storms in the east in the past year, Osborne said.

But it's not just the Arctic. Nasa's newest space-based radar, Icesat 2, in its first couple of months has already found that the Dotson ice shelf in Antarctica has lost more than 120m in thickness since 2003, said radar scientist Ben Smith of the University of Washington.

Another study released this week by Nasa found unusual melting in parts of East Antarctica, which scientists had generally thought was stable.

Four glaciers at Vincennes Bay lost about 3m of ice thickness since 2008, said Nasa scientists Catherine Walker and Alex Gardner.

Loss of ice sheets in Antarctica could lead to a large rise in sea level.

"We're starting to see change that's related to the ocean," Gardner said. "Believe it or not, this is the first time we're seeing it in this place."

- AP