October in Nome warmest in over a century; scientists predict late freeze up, ice loss and early spring break up
Sea ice is a physical ocean feature that helps to regulate the planet’s weather.
Sea ice is melting and not coming back. The new ice that forms in the Arctic lately does not replace the thick old ice that has melted. The old ice that took hundreds of years to form has taken with it the kind of cold weather that northern peoples expect. The loss of sea ice has removed the natural air conditioner from the local climate and affected temperatures around the globe.
This year, the fall season in the Nome region has gotten underway with the warmest October in 112 years. The high temperature of 61°F on Sept. 30 was not only a record for the date, but the warmest so late in the season.
Regulating weather is just one function of sea ice. It additionally provides habitat for tiny organisms, marine mammals and birds. Sea ice affects migration of birds and mammals, and influences the distribution of fish. Durable ice provides transportation to gather winter foods from the sea.
The Bering Sea and Chukchi Sea regions around Alaska had unprecedentedly low sea ice last winter, according to Rick Thoman, climate scientist with the Alaska Center for Climate Assessment and Policy.
“It was an extreme event that made people wonder, ‘What is in store for next winter?” he said.
“The year 2018 is in a league by itself.”
Thoman came to Nome to exchange knowledge about local weather with indigenous groups in small Bering Sea coastal communities.
People in the Arctic have observed climate for thousands of years as they determine where and when they may safely and productively hunt for food.
While in Nome, Thoman spoke on Nov. 1 at a session of Strait Science, an ongoing program of informational presentations sponsored by UAF Northwest Campus and the Alaska Sea Grant marine advisory program.
Thoman spoke of the upcoming winter and what it means for western Alaska sea ice. He began with an overview of what has been happening to sea ice in the recent past. “In our great grandparents’ time there was nothing remotely like this,” Thoman declared concerning rapidly disappearing sea ice. “The ice in the Bering Sea was effectively gone in the first week of May 2018, two weeks earlier than the previous year, which was the earliest in the satellite era [of observation].”
By contrast, in 1999, the ice went in the second week of June. The year 2001 was an extra low ice year, but compared to 2017 still had a lot of ice, according to Thoman.
“So, in the past 18 years since 2001, we have lost about four weeks. The rate of change is really the most shocking thing,” Thoman said. “People think of environmental change as very gradual. We know that is not the case. Some things are changing very rapidly—sea ice extent and melt out dates are very good examples.”
Very rapidly was when a third of the Bering Sea ice melted in about eight days, when the temperature zoomed to 45°F in the mid-February. The Chukchi Sea had open water above the Bering Strait. Satellite data show that this year the Chukchi had summer sea ice extent greater in area than in 2017, until September when melt caught up and the ice area got a little below 2017.
The Chukchi Sea had a very late freeze-up last winter, with the southern Chukchi having unstable ice all winter long, according to Thoman.
The Bering Sea had the lowest ice cover in 160 years of estimates of what late winter ice was.
“Almost every day of winter was lowest ice extent of any of the last 40 winters,” Thoman said. “With no ice to start, what we had melted out early.”
For indigenous peoples, who for thousands of years have depended on the northern oceans for food, sea ice —and not the calendar — marks the beginning and end of seasons for hunting, fishing and gathering food and other resources.Winter starts not on Dec. 21, but when the ice comes and becomes firm for hunting and travel.
The early ice loss in both the Chukchi and Bering seas has influenced what has happened in the ocean during the summer. Research has shown impacts to fisheries tied to lack of sea ice last year.
The Bering Sea has been considerably warmer than average, 7° F or more than average for open water, especially outside bays and inlets. “The entire North Pacific is warmer than normal now,” according to Thoman. “In the North Pacific, there is a complete lack of cooler than average water.”
“That is stunning! We are at the core of that,” Thoman said. “We are very much warmer than the same time last year. This summer saw surface temperatures of 64° F off Unalakleet.”
The Bering Sea lost its cold bottom water that has acted as a thermal barrier to southern fish moving into the northern Bering Sea, an obvious impact of low sea ice, Thoman said. The cold pool, another name for the thermal barrier, impacts the distribution of walleye pollock and Pacific cod. The cold pool ecologically separates the Bering Sea into north and south. The thermal separation is what makes the northern Bering Sea more arctic than the Pacific Ocean and makes the southern Bering Sea a specific regime from the northern Bering Sea.
Forecasters expect an El Niño this winter. El Niño means that equatorial Pacific ocean temperatures warm up south and east of Hawaii by 1/2° C or 1.5°F. How can minor changes 1,000 miles south of Hawaii possibly impact Alaska weather?
“The sea surface temperatures aren’t impacting our weather at all,” said Thoman. “What slight changes in mid-Pacific temperatures are doing are changing where those giant tropical thunderstorms form, which in turn changes where the jet stream coming off Asia and off the Pacific sets up, so it’s through the big tropical thunderstorms affect the jet stream That’s how it affects our weather.
“So, you hear El Niño is coming. You think you’re going to have a warm, crappy winter. In South Central Alaska, that’s usually the case. What happens is during El Niño, the jet stream on average extends farther east across the Pacific, so the storm track ends up more in the Gulf of Alaska and less in the Bering Sea.
“Does it mean no storms in the Bering Sea? It can mean more than average in the Gulf and typically less than average in the Bering Sea. Some El Niño in western Alaska do end up being warm. Some do not. That depends on where the storm track sets up. If it is far enough to the east, then western Alaska gets a cold northerly flow to the back side of those lows. That would help the sea ice grow. If the storm track goes a little farther west, over Kodiak, recur back westward at least into the south Bering Sea,” Thoman explained.
“That’s how western Alaska and the Seward Peninsula area can be warm during El Niño so it is a very mixed bag for our part of the world—warm or cold, not a sure thing.”
The outlook for early winter from the Climate Prediction Center is no surprise, according to Thoman, “given the obscenely warm surface temperature and lack of ice giving a very strong tilt for significantly warmer temperatures on average for early winter season for our part of the world— in round numbers, 65 percent chance of significantly warmer than average temperatures with only 5 percent chance of significantly below average temperatures. These are really strongly driven by what we are seeing with the ice and the ocean temperatures,” Thoman continued.
“Precipitation comes with the storm track favored in the Gulf of Alaska. It is no surprise to see the CPC forecast a better than three-sided coin flip chance for above normal precipitation across southern Alaska. CPC opted to go for ‘We don’t know’ for western Alaska.
“If I were doing this, I would have gone for at least wet weak tilt. Why? Because we’ve got very warm water, we’ve got more evaporation. If storms come along that can tap into that, there’s a potential for more precipitation.
“I would have extended this slight tilt much farther northwest. They didn’t ask my opinion. I gave it. They opted not to take it,” Thoman said.
“For the midwinter season—December, January, and February—really not much change. For most of Alaska, including western Alaska, again a strong tilt for increased chances of warmer than average temperatures. For western Alaska, there is uncertainty. El Niño could be warm or could be cool, but the low sea ice expected is the driver to push these odds up for warmer temperatures. As for precipitation: no change. Same basic pattern, storm track into the Gulf of Alaska. Western Alaska, we don’t know. Maybe by mid-winter I might have given it a weak tilt towards wet,” Thoman said.
What does this mean for sea ice?
“Oceans are excessively warm; at this point a late freeze up is guaranteed everywhere, no great forecast there. El Niño, that may increase our late winter ice extent beyond what it would be otherwise. Sea ice extent is likely to be higher than last year. Given how extremely low last year was, lower than the 30-year average, that should not be a bold forecast, but it does make me nervous to see ocean temperatures so, so warm. It would be hard, not impossible, but hard to imagine that given where we’re at with the warm water, that we could exceed the 30-year average for ice extent. I suppose if we had nothing but north winds all winter long, it would happen, but I would not predict that. One thing, with at least some north wind, the shore-fast ice will be more stable than we had last year. Last year, some places had no shore-fast ice and were unable to do normal activities on the ice. When I was here in March, talking to people in Unalakleet, they weren’t able to do much crabbing because the shore-fast ice simply did not stay in place long enough. I think it will be better than that this year.
“The sea, I think is a certainty, to be thinner ice and poorer quality than we would like, especially outside protected areas. At this point I don’t think it matters what the weather does. Freeze up is coming so late, we’re going to run out of time to thicken up ice, and to get the ice we’d like for many activities. I just don’t think there will be enough time, even if we are in a cool pattern for a month or two. So if we have got less ice and thinner and more mobile, I think we’ll have an early breakup. We’ve got two thumbs on those scales. Even if we have a coolish spring pattern, with the ice being thinner than average, which I think it has to be, with the late, late freeze-up, we are very likely to have a very early ice loss in our region. So that’s the deal.”
Thoman will give the same presentation, “ Standing at The Brink: The Coming Winter and What It Means for Alaska’s Sea Ice” on Tuesday, Nov. 13 at 10 a.m. Check the ACCAP website at https://accap.uaf.edu/.