Will Alaskans see a rerun of a warm winter?
Winter used to rush quickly into the nation's northernmost town once the autumn equinox had passed and the days started getting short. No more.
Now October in Barrow has become a season of what is, by Arctic standards, mild fall weather. Ocean waters that in the past developed solid ice covers are now open in October, air temperatures since 2001 have been well above long-term averages for the month and Barrow, at least in fall, is settling into a pattern with autumn conditions more similar to those in high-latitude but open-water areas of Scandinavia.
Barrow has developed an "Arctic maritime" climate unlike anything that had persisted in the weather records there, said Rick Thoman, climate science and services manager for the National Weather Service in Alaska.
"It's a new climate for Barrow," he said.
So far, this autumn is fitting right into the new normal for the town. Temperatures since late last week have hit daily records or come close, and deep freeze has yet to arrive.
"There's open water. There's not even any ice out on the horizon right now," said Bryan Thomas, station chief at the National Oceanic and Atmospheric Administration's Barrow Observatory.
There is some thin "grease ice" forming on the lagoon, but for now that is melting away, Thomas said. "It's getting cold at night. It's just not getting cold enough," he said.
Three record-high daily temperatures were posted last week, and Barrow's warming autumn trend has been linked directly to low sea ice. All indications are that the spiral will continue.
This year's seasonal minimum ice extent tied 2007 for the second-lowest in the satellite record, according to the National Snow and Ice Data Center in Boulder, Colorado.
The quality of that ice is deteriorating, too. Preliminary analysis shows that only 3.1 percent of the ice that remained at this year's minimum was four years old or older, the center said. In the mid-1980s, a third of the summer minimum ice was old enough to have survived at least four melt seasons.
Another snow-sparse winter for Alaska?
All of Alaska is also expected to have a warmer-than-average October and late-fall/early winter, according to the National Weather Service's Climate Prediction Center.
After that, however, the winter picture is mixed for much of the state. The Climate Prediction Center forecasts high probabilities for warmer-than-average temperatures in parts of northern and western Alaska, but the rest of Alaska appears to be setting up for a more normal winter.
Thoman said the coming months will not be a rerun of last year, when forces combined to create a record-warm winter across the Arctic and the second warmest winter on record for Alaska.
"Last year all the dice were loaded to be warm," he said. "This year, maybe all the dice aren't loaded."
Last winter was warmed by a record El Nino cycle, a condition in which waters in the Equatorial Pacific are hotter than normal usual and trade winds blow that heat east to the Americas.
Warmth was helped along by the mass of persistently warm North Pacific water that appeared in late 2013 — the so-called "Blob." And the multi-year Pacific Decadal Oscillation pattern was in a positive — or warm — phase last winter.
Going into this winter, some warming factors do remain, Thoman said.
Loss of sea ice will continue to affect the North Slope, and the Blob is back to influence southern Alaska, he said. That warm-water Blob actually never went away, though for a while it sank deeper into the ocean and was not as apparent on the surface, he said.
Persistence of the shape-shifting Blob has been remarkable, said Nick Bond, the Washington state climatologist and University of Washington research meteorologist who bestowed the name.
The mass of warm water was intensified over the summer because a ridge of high pressure over the northeast Pacific created clear skies that allowed solar heat to beat down on the upper ocean, he said.
"The Blob has kind of a new lease on life," he said. Some spots got up to 3 degrees Celsius (5.4 degrees Fahrenheit) warmer than normal, he said.
For the Pacific Northwest and parts of coastal southern Alaska — regions affected by regular air flow from the ocean to land — the Blob "continues to kind of load the dice, stack the deck" for the coming winter, Bond said.