Fabled Northwest Passage begins to re-freeze

By: Dr. Jeff Masters , 2:29 PM GMT on October 12, 2007

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This summer's dramatic loss of Arctic sea ice peaked on September 15, and the polar ice cap is finally beginning to re-freeze, according to a press release issued by the National Snow and Ice Data Center on October 1. Extent of the September polar sea ice fell 39%, compared to the 1979-2000 average. To put this loss in perspective, in one year we lost as much ice as we lost during the previous 28 years. Summertime Arctic sea ice is now at 50% of what it was in the 1950s (Figure 1). One may look at at graph and wonder, but what about sea ice loss in other seasons? It hasn't been nearly so severe. True, but it is the summer ice we care most about, since summer is when the thick, multi-year ice melts, which can then precondition the Arctic for much greater ice loss in future years. As sea ice melts in response to rising temperatures, more of the dark ocean is exposed, allowing it to absorb more of the sun's energy. This further increases air temperatures, ocean temperatures, and ice melt in a process know as the "ice-albedo feedback" (albedo means how much sunlight a surface reflects). There is an excellent chance that the summer of 2007 will be remembered as the "tipping point" for Arctic sea ice, when an irreversible ice-albedo feedback process firmly established itself.



Figure 1. Arctic sea ice extent since 1900, as estimated from satellite and ship reports compiled by Walsh and Chapman (2001). Image credit: University of Illinois cryosphere group.

Northwest Passage opens for the first time in recorded history
Long before the Panama and Suez Canals made commercial trading between the Atlantic and Pacific Oceans economically feasible, ships made the long and perilous trip around the African and South America continents. Explorers, traders, and world leaders looking for faster and less dangerous shipping routes to far-away areas of the world have long eyed two routes through the ice-choked Arctic Ocean--the fabled Northwest Passage, through the cold Arctic waters north of Canada, and the Northeast Passage, extending along the northern coast of Russia. The first recorded attempt to find and sail the Northwest Passage was in 1497, and ended in failure. The thick ice choking the waterways thwarted all attempts at passage for the next four centuries. Finally, in 1905, Roald Amundsen completed the first successful navigation of the Northwest Passage. It took his ship two-and-a-half years to navigate through narrow passages of open water, and his ship spent two cold, dark winters locked in the ice during the feat. More recently, icebreakers and ice-strengthened ships have on occasion battered their way through the ice-blocked route.



Figure 2. The Northwest Passage shipping route (red line) and Northeast Passage (green line) superimposed on an ice coverage map from August 22, 2007. The Northwest Passage was ice-free and navigable for 36 days between August 14 and September 18, 2007. The Northeast Passage was blocked by a narrow strip of ice most of the summer. Image credit: National Snow and Ice Data Center.

Times are changing. In 2001, the Bering Strait, a key portion of both the Northwest and Northeast Passages, was completely ice free. This was followed in 2005 by record-breaking sea-ice melt in the Arctic, leading to the first ever recorded opening of the Northeast Passage. The fabled Northwest Passage remained closed in 2005. Arctic ice recovered a bit in 2006, and both passages remained closed. But the unprecedented melting during the summer of 2007 saw the Northwest Passage become ice-free and navigable along its entire length without the need for an icebreaker as of August 14, 2007. Remarkably, the Northwest Passage remained ice-free for 36 days, finally refreezing over a small section on September 19. The Northeast Passage was blocked by a narrow strip of ice all summer. However, this strip of ice thinned to just 30% coverage on September 25 and 26, making the Northeast Passage passable for ordinary ships on those days.

When is the last time the Northwest Passage was open?
We can be sure the Northwest Passage was never open from 1900 on, as we have detailed ice edge records from ships. It is very unlikely the Passage was open between 1497 and 1900, since this was a cold period in the northern latitudes known as "The Little Ice Age". Ships periodically attempted the Passage and were foiled during this period, and the native Inuit people have no historical tales of the Passage being navigable at any time in the past.

A good candidate for the last previous opening of the Northwest Passage was the period 5,000-7,000 years ago, when the Earth's orbital variations brought more sunlight to the Arctic in summer than at present. Prior to that, the Passage was probably open during the last inter-glacial period, 120,000 years ago. Temperatures then were 2-3 degrees Centigrade higher than present-day temperatures, and sea levels were 4-6 meters higher.

Final thoughts
If we have reached the tipping point for Arctic ice, what are the implications? I'll discuss this more in a future blog. Sea ice is very complicated, and it is not a sure thing that we have reached the tipping point. For more on the complexities of sea ice, read wunderblogger Dr. Ricky Rood's latest blog.

NASA has posted a beautiful satellite image of the Arctic ice cap at the September 15 2007 minimum, showing the open water of the Northwest Passage.

I thank Edalin Michael of the University of Michigan's School of Natural Resources and Robert Grumbine of NOAA's Sea Ice Group for their contributions to this blog.

References
Walsh, J.E and W.L.Chapman, 2001, "Twentieth-century sea ice variations from observational data", Annals of Glaciology, 33, Number 1, January 2001 , pp. 444-448.

Jeff Masters

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397. beell
7:11 PM GMT on October 12, 2007
299. nrtiwlnvragn 6:04 PM GMT on October 12, 2007
Marine Weather Discussion

Weak high press ridge over the northern gulf of mexico with light n to ne winds over most area. The models differ some on the movement of the low pres currently over the nw caribbean. Overall the gfs differs the most then the other models...a it brings the low across the yucatan peninsula into the eastern bay of campeche mon night and into the central portion of the sw gulf mon afternoon and se of the mouth of the mississippi tue and into the florida panhandle wed. The other models are a little more similar bringing the low across the yucatan peninsula into the bay of campeche mon but keep it in the sw gulf through wed. Either way in the sort term winds should increase across the eastern gulf will increase with the low to the s and ridge to the n tighten the gradient.
Member Since: September 11, 2007 Posts: 145 Comments: 16924
393. stormybil
7:01 PM GMT on October 12, 2007
is td 15 thats a naked spin moving to the sw now
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380. tampabayfish
7:04 PM GMT on October 12, 2007
You know when the tropics are slow when....

377. jphurricane2006 7:04 PM GMT on October 12, 2007
I will bring the marshmallows lol

we can all make smores

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375. NotAnotherHURRICANE
6:59 PM GMT on October 12, 2007
Hello All -
It's been around 11 months that I don't get on this. How's the tropics? Looks like Florida might get speared another year. I LOVE IT!!!
Guys, quick question how do you post an image on the left side of the comment you leave?
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374. tampabayfish
7:00 PM GMT on October 12, 2007
Agreed weatherg8r... Quite different when I walked out the door this morning.... I think there is also a large shiny barrel in my future tonight, going away party...outside!
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373. moonlightcowboy
6:59 PM GMT on October 12, 2007
You Tube has a 10 minute limit regardless of file type and, or type of account. I'd like to post a podcast file...very interesting, on topic, and extremely funny!
Member Since: July 9, 2006 Posts: 184 Comments: 29610
372. weatherg8r
6:58 PM GMT on October 12, 2007
362. tampabayfish 6:55 PM GMT on October 12, 2007
NE... Its game time, beer thirty, Beckett gonna pitch a gem, Brady for 400 and 4 TD's... Oh its gonna be a good weekend!

beer is in the cooler,just waiting for me,gotta get this rain out of here first.


I agree...except our weather is so nice...as I have probably mentioned to EVERYONE today...might even be able to have a fire and look at stars tonight...first time in a while with NO clouds!
370. Floodman
6:57 PM GMT on October 12, 2007
366. tampabayfish 6:57 PM GMT on October 12, 2007
Wow Flood... That has changed since the last time I checked. May be an interesting week ahead.



All that having been said, the week could be a wash...who knows?
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369. LakeShadow
6:56 PM GMT on October 12, 2007
yeah floodman...also over bonedog...
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366. tampabayfish
6:56 PM GMT on October 12, 2007
Wow Flood... That has changed since the last time I checked. May be an interesting week ahead.
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364. weatherg8r
6:55 PM GMT on October 12, 2007
358. weatherboyfsu 6:53 PM GMT on October 12, 2007
Whoaaaaaaa.....Where did weatherg8r come from?

Hello WeatherG8R......



I have been reading the blog for a long time only posting recently...Don't get me in trouble and banned! :)
363. Floodman
6:52 PM GMT on October 12, 2007
Have a look at Vorticity; very interesting feature on the coast of the Yucatan
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362. tampabayfish
6:54 PM GMT on October 12, 2007
NE... Its game time, beer thirty, Beckett gonna pitch a gem, Brady for 400 and 4 TD's... Oh its gonna be a good weekend!
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361. NEwxguy
6:54 PM GMT on October 12, 2007
tgif,sure wish the day would move quicker
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360. tampabayfish
6:51 PM GMT on October 12, 2007
A couple of the models (GFDL,GFS?) from a few days ago seemed to have nailed the loop over the Yucatan, heading back towards the W Carib
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359. LakeShadow
6:52 PM GMT on October 12, 2007
It appears to be likely...(do I sound like the magic 8 ball?)

outlook not so good
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357. beell
6:49 PM GMT on October 12, 2007
mlc, no problem. nailed may imply a higher level of precision than future reality.
Member Since: September 11, 2007 Posts: 145 Comments: 16924
356. catwomen
6:43 PM GMT on October 12, 2007
I'm wondering what the 5pm report will say about td 15? and any other disturbance in the Atlantic. I would like to say thank you for all the good info I get on here.
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355. weatherg8r
6:51 PM GMT on October 12, 2007
Good afternoon JP
354. Floodman
6:50 PM GMT on October 12, 2007
352. weatherboyfsu 6:50 PM GMT on October 12, 2007
Looks like 94L might make it back out into the caribbean.....What do you guys think?



It appears to be likely...(do I sound like the magic 8 ball?)
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353. tampabayfish
6:50 PM GMT on October 12, 2007
352. weatherboyfsu 6:50 PM GMT on October 12, 2007
Looks like 94L might make it back out into the caribbean.....What do you guys think?


Seems to be working itself that way, slowly...
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352. weatherboyfsu
6:49 PM GMT on October 12, 2007
Looks like 94L might make it back out into the caribbean.....What do you guys think?
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350. tampabayfish
6:48 PM GMT on October 12, 2007
I'm seeing the low centered at the Belize/Guat. border near Honduras Bay.... Anyone?
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349. weatherboyfsu
6:48 PM GMT on October 12, 2007
Is the coast clear?
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348. Floodman
6:46 PM GMT on October 12, 2007
I smelled troll very briefly there...
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347. moonlightcowboy
6:46 PM GMT on October 12, 2007
lol, beell, no. It's an audio file from a podcast, that I'd like to link to and post here. Having trouble though.

--btw, haven't had a chance "due to the man" to get back with you on WUmail, but I think your post in the blog probably nailed it. We'll see.
Member Since: July 9, 2006 Posts: 184 Comments: 29610

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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