Ice is melting in unprecedented ways as summer approaches in the Arctic. In recent days, observations have revealed a record-challenging melt event over the Greenland ice sheet, while the extent of ice over the Arctic Ocean has never been this low in mid-June during the age of weather satellites.

Greenland saw temperatures soar to 40 degrees above normal Wednesday, while open water exists in places north of Alaska where it seldom, if ever, has in recent times.

It's "another series of extreme events consistent with the long-term trend of a warming, changing Arctic," said Zachary Labe, a climate researcher at the University of California-Irvine.

Greenland ice sheet

Data from the National Snow and Ice Data Center show the Greenland ice sheet this week appears to have witnessed its biggest melt event on record so early in the season (although a few other years showed similar mid-June melting).

"The melting is big and early," said Jason Box, an ice climatologist at the Geological Survey of Denmark and Greenland.

Box said temperatures over the western Greenland ice sheet have been abnormally high, and snow has been well below normal.

Marco Tedesco, an ice researcher at Columbia University, added that it's been unusually warm in east and central Greenland as well.

"This has triggered widespread melting that has reached about 45 percent of the ice sheet," he wrote in an e-mail.

Normally, melting this widespread over the ice sheet doesn't occur until midsummer, if even then.

Weather satellites have monitored sea ice in the Arctic since 1979, and the current ice coverage is the lowest on record for mid-June.

The ice extent has been especially depleted in the part of the Arctic Ocean adjacent to the Pacific Ocean. "It's pretty remarkable how much open water is in that area," said Labe.

Labe said high pressure over the Arctic has helped to pull sea ice way from the northern Alaska coast.

Sea ice loss over the Chukchi and Beaufort seas situated along Alaska's northern coast has been "unprecedented," said Rick Thoman, a climatologist based in Fairbanks.

Implications in the U.S.

The extreme conditions in the Arctic have far-reaching implications.

The bulging zones of high pressure in the Arctic, which have facilitated the unusual warmth and intensified melting, are displacing the cold air normally contained in that region into the mid-latitudes — like a refrigerator door left open.

Much of the central and eastern United States have seen cooler than normal conditions in the past week.

The jet stream, the high-altitude current separating cold air and warm air, has taken unusually erratic meanders.

Jennifer Francis, one of the leading researchers who has published studies connecting Arctic change and mid-latitude weather, has suggested that conditions in the Arctic may have played a role in the extreme jet stream pattern that spurred the tornado swarm and record flooding in the central U.S. during the last two weeks of May.

"We can't say that the rapid Arctic warming is causing this particular pattern, but it certainly is consistent with that," Francis said.