Flushing out the Fjord

I wrote a blog post on Jakobshavn Isbræ last year when a 7 square kilometer (2.7 square mile) section of the glacier broke up. Here's some basic information from Wikipedia on one of the most important Greenland glaciers, with an image of the glacier on August 5th last year (the glacier is on the bottom right, with the fjord in front of it filled with icebergs):

Jakobshavn Isbræ drains 6.5% of the Greenland ice sheet and produces around 10% of all Greenland icebergs. Some 35 billion tonnes of icebergs calve off and pass out of the fjord every year. Icebergs breaking from the glacier are often so large (up to a kilometer in height) that they are too tall to float down the fjord and lie stuck on the bottom of its shallower areas, sometimes for years, until they are broken up by the force of the glacier and icebergs further up the fjord.

Well, it appears that something convinced those icebergs to get a move on, because in just a few weeks time the Illulisat Isfjord has been flushed clean. On February 26th (day 57) resident Arctic expert Lodger informed us in Open Thread 6 that some of those icebergs had left the fjord. I didn't think much of it at the time (couldn't be bothered really, as images were too cloudy). On March 1st (day 60) everything seemed to be just hunky dory again, with gaps neatly frozen over, but apparently this was just a prelude to the Great Flushing.  I've made a reconstruction with a handful of satellite images that were clear enough to be used from day 52 (Feb. 21st) to day 102 (April12th). Check out the Royal Flush between days 82 and 83:

The reason I decided to have another look at Jakobshavn was a post from April 10th I read on the NASA Operation IceBridge blog, written by Kathryn Hansen, called Mission Mop up:

After hitting some clouds as expected from the morning's weather brief, we headed back north and reflew the center flow line of Jakobshavn -- always spectacular -- before flying over Illulisat Isfjord, which was surprisingly free of ice. The reason for the ice-free conditions was unknown to scientists onboard. There could have been fewer calving events, warmer water, or wind patterns that pushed ice out of the area.

"Half of the Illulisat Isfjord was open water with several fishing boats in the area, something I have never seen before," said Michael Studinger, the mission's project scientist.

A camera mounted on the belly of the aircraft captured this image of a fishing boat (top) in the Illulisat flord, which was mostly open water with a few visible patches of ice. Credit: NASA/DMS team

 

Me? I think 'twas the wind.

Here's an animation of the full MODIS images of the region (r02c02). We can clearly see the ice floes in Disko and Baffin Bay retreat northwards full-speed around the time of the Royal Flush:

Comments

[Glacierchange.wordpress.com]

Can you zoom in more to distinguish the sea ice in fjord from the icebergs? Though some icebergs do get stuck for a time, most do not remain in the fjord for years in my experience there.

[Werther]

Great info on Sermeq Kujalleq! I’m not sure it’s the wind though, that’s clearing the fjord. Last two weeks the atmospheric flow has been steady from the northwest. It may also be upwelling, while the fjord is deep, and even meltwater being pushed out from under the glacier. That sounds contradictionary in winter. But the deep gorge under the ice (-1600 m!) must contain pressurized water. I wonder wether the glacier may have ‘sunk’ since last summer. On MODIS last days, in the striking light it stands out as a blueish depression surrounded by the icesheet.I may be wrong, but it looks 'deeper' than it used to.
Still it is interesting to see the Fjord clearing, after two months of being iced over, and 2m temps remaining deep freeze.

[Neven]

Mauri, I hadn't considered this. And it's true, if you check out Day 77 in the animation it looks as if the fjord already flushed out (it's a bit cloudy though), so it could be that that was sea ice mainly, after which the waters froze up again and the Fjord re-flushed.

Unfortunately I can't zoom in much more to distinguish the two. My idea that it was icebergs being flushed out was based on that big ice jam of last year. Where did they go?

Thanks for the interesting thoughts, Werther!

What do you think of all this, Mauri?

[Glacierchange.wordpress.com]

I updated the Jakobshavn post and put two Landsat images from April 2010 and April 2011 in. The icebergs are definitely more visible in the better quality 2010 image. The snowline is also higher in 2010 though this can reflect very short term weather events at this time of the year.

[Andrew Xnn]

Agree that it's probably the wind and or weather patterns responsible for the flushing. However, also suspect that the tides are a factor, especially with grounded bergs.

Also, don't know how relevant, but believe the moon was at one of it nearest approaches within the past month.

[Andrew Xnn]

Here is a link about the super moon of March 19, 2011:

http://news.nationalgeographic.com/news/2011/03/110319-supermoon-full-moon-earth-science-space-biggest-closest-brightest/

[Efredri]

Using the false-color 'Bands 3-6-7' makes it a bit easier to separate ice and clouds. It's only available from Terra, not Aqua.

[crandles]

Had thought there wasn't much melting out let alone flushing recently but now there seems more signs of some flushing.

http://lance-modis.eosdis.nasa.gov/imagery/subsets/?subset=Arctic_r02c02.2011263.terra.250m

There would be some haze just in the wrong place.

[Chris Biscan]

ftp://ftp-projects.zmaw.de/../../seaice/near_real_time/Arc_latest_yesterday.png

the final from the hamburg site is out.

so there data is ok.