Arctic Sea Ice

Arctic storm part 3: detachment

Yes, ladies and gentlemen, the Arctic summer storm is still there. After approximately 48 hours (which is long for an Arctic summer storm) it has weakened some compared to yesterday or the day before, but as far as I can see sea level pressure in the centre of the storm is still around 970 mb, which is low.

And so we're still seeing significant changes on the Uni Bremen sea ice concentration maps. Here's the animation from August 3rd to 7th:

That large patch of sea ice in the East Siberian Sea is almost entirely detached from the main ice pack. This is something I for one have never seen before, and I wouldn't be surprised if it's unprecedented in the satellite era. We have speculated a lot about this in previous melting seasons, but now the moment seems to have finally arrived. The fact that the ice pack can get divided like this, is yet another sign that the ice is exceptionally thin, as thin ice gets pushed around more easily and melts quicker, leaving open space between thicker, slower moving ice floes.

I've also updated the animation of DMI sea level pressure maps that shows the development and position of the storm:

Arctic storm part 2: the color purple

A new day with new information. Here's an animation of Uni Bremen sea ice concentration maps from August 3rd-6th:

We see some more flash melting from the 5th to the 6th on the edge of the ice pack in the Beaufort Sea region, although technically I think this is more compaction than real melting. We also see some of the early flash melting flashing back, or 'unflashing', in the East Siberian Sea. It looks like that large swath of ice there has almost detached itself from the main ice pack.

On this animation of DMI sea level pressure maps we can see how the cyclone developed from the 3rd to the 6th. The purple in the centre of the storm shows how low sea level pressure was and still is (lowest I've seen in yesterday's reports was 963 mb):

Arctic storm part 1: in progress

This is what I meant when I said 'flash melting' yesterday:

Now it's there on the Uni Bremen sea ice concentration map, the next day, poof, it's gone. Mind you, not all of it is gone, the sensor is thrown off a bit due to that crazy cyclone downstairs, but it ain't exactly good for the ice if you catch my drift.

Here's the culprit:

Cyclone warning!

I have postponed this post until I was sure that what follows is going to happen.

Remember the term 'flash melting'? That's when from one day to the next large swathes of ice disappear on the University of Bremen sea ice concentration maps. We witnessed one such instance last year when a relatively large and intense low-pressure area moved in from Alaska over the ice in the Beaufort and Chukchi Sea regions (see blog post). It lasted about a day or two and then quickly faded, but the effects were spectacular.

Well, it looks like we have something bigger coming up this year. This is the ECMWF weather forecast for the coming four days (click for a bigger version):

Not only does this low-pressure area, or cyclone, look bigger, more intense and longer-lasting than the one from last year, the ice also seems to be in a weaker state than ever, as evidenced by the fact that 2012 trend lines on both sea ice area and sea ice extent graphs track lower than previous record years, despite weather that until recently would completely stall the decline.

There are many things that cyclones do to cause flash melting:

Storm impacts

The 'Arctic Hurricane' that slammed into Alaska and Siberia a couple of days ago caused wide- spread damage and presumably cost one person his life. Luckily the storm didn't top the 1974 record storm, but still. As the Associated Press reported: Emergency responders called the storm an epic event that displaced residents, flooded the shoreline, ripped up roofs and knocked out power in many villages.

Jeff Masters from Weather Underground has more details:

The most powerful storm to affect the Bering Sea coast of Alaska since 1974 is slowly winding down today, after pounding Alaska's west coast and Eastern Siberia with hurricane-force winds, a destructive storm surge more than 8 feet high, waves up to 40 feet high, and heavy snow. The highest wind gust recorded during the storm, 89 mph, was at Wales at the western tip of the Seward Peninsula, which forms the U.S. side of the Bering Strait.

A storm surge of 8.6 feet hit Nome, Alaska near 9 pm EST last night, pushed inland by sustained winds that reached 45 mph, gusting to 61 mph. Large waves on top of the surge encrusted with sea ice battered the coast, causing extensive damage and coastal flooding. Significant wave heights at the Bering Sea buoy north of the Aleutian Islands reached 40 feet during the peak of the storm. The last time Nome, Alaska saw a storm this strong was November 11 - 12 1974, when the city experienced sustained winds of 46 mph with gusts to 69 mph, a pressure that bottomed out at 969 mb, and a storm surge of 13 feet. The center of yesterday's storm moved ashore over eastern Siberia near 12 UTC with a central pressure of 945 mb, and later bottomed out with a pressure of 943 mb. The storm's central pressure had risen to 958 mb this morning, with the center of the storm now located north of Siberia over the Arctic.

I'm sure we'll hear what the erosional effects on the coasts have been, but right now I'm primarily interested in the effects on the sea ice. It appears they were quite substantial. I've made an animation of sea ice concentration maps from Uni Bremen (who have switched from the defunct AMSR-E sensor to the SSMIS instrument aboard the DMSP satellites) from the past week:

Arctic hurricane slams Alaska

Of course I'd like to know what this storm will do to the ice and coasts, but first and foremost I hope that no one gets hurt.

From CNN via Desdemona Despair:

November 9 (CNN) – A winter storm of hurricane strength was slamming Alaska early Wednesday with winds of up to 100 mph, high seas and blizzard conditions.

The National Weather Service called the storm moving into the state off the Bering Sea "a powerful and extremely dangerous storm of record or near-record magnitude."

Early Wednesday, Twitter reports said wind speeds in Nome in northwestern Alaska had reached 100 mph. That would be the equivalent of a category 2 hurricane if it occurred in the tropics. Twitter postings reported structural damage in Nome, including the roof blown off a building. Landline phones were down, according to a Twitter post.

"These things get named hurricanes down south and get a category. It's that magnitude," said Jeff Osiensky, regional warning coordination meteorologist with the National Weather Service, told the Anchorage Daily News. The storm's scope was also hurricane-like, he said, covering 750 to 1,000 miles in breadth.

Chip Leeper, incident commander with the Nome government, told CNN that people in low-lying areas and on along the town's sea wall had been advised to seek shelter elsewhere.

National Weather Service meteorologist Steven Kearney told CNN that Nome could endure sea levels up to 8 feet above normal as well as 10-foot waves.

Other coastal and island villages were preparing evacuations if surf became too high.

Inland, the storm was expected to produce blizzard or near-blizzard conditions across western Alaska, the weather service said. Snow accumulations of up to 14 inches were possible. A Twitter poster reported winds gusts of 50 mph in the inland village of Aniak early Wednesday.

CNN also has regular updates now that the storm has reached Alaska.

An interesting quote from the Weather Channel:

Offshore, waves have been reported as high as 40 feet, and dangerous heavy freezing spray will affect the Bering and Chukchi Seas. Waves of 15 to 25 feet are expected to crash along portions of the coastline.

The current lack of sea ice in the Bering Sea will allow this storm to maximize its impact. Ice typically acts as a natural barrier that mitigates the effects of destructive wave action and coastal flooding along the shoreline.

This image was on Jeff Masters' blog: Predicted storm surge for today's storm, as forecast by the Ocean Prediction Center's Extratropical Storm Surge Model. Image credit: NOAA Environmental Visualization Lab.: