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Messages - mspelto

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1
Greenland and Arctic Circle / Re: Nunatakassap Sermia / North West Greenland
« on: September 06, 2015, 12:38:30 PM »
You are an expert, just a different expertise, and that is knowing from seeing the changes.  There are annual changes of GIS margins documented by various groups note Twila Moon-Joughin UW and Howat OSU group.  The annual shifts not that important overall, decadal shifts key and any dramatic irreversible changes of course.  For this glacier most of the change occurred by 2011.

http://blogs.agu.org/fromaglaciersperspective/2012/08/19/alison-gletscher-nw-greenland-rapid-retreat/

2
It was the rapid rift extension illustrated between 6/6 and 6/17 that set this up.  No surprise.  The rift development behind the front is now poorer than typical it seems to me.

3
What I find impressive is the lack of movement of the icebergs between the two, indicating the first was near freezeup.

4
Antarctica / Re: Larsen "B" will be gone in a decade: NASA
« on: May 26, 2015, 02:38:19 AM »
In this case it is not just the cracks, but those circular depression indicates points of collapse where the thickness is just not sufficient to support the ice shelf.

5
Antarctica / Re: Discussion of the Antarctic Peninsula
« on: May 26, 2015, 02:35:55 AM »
AbruptSLR:  The basal crevasses have been the focus of research for sometime by the British Antarctic Survey, and this is the threat for rift development.  These can develop without surface melting, of which there is little on Larsen C.  I do not think the breakup of this ice shelf is imminent, but it is beginning to develop instability features.  http://blogs.agu.org/fromaglaciersperspective/2012/12/01/jones-ice-shelf-loss-antarctica/

6
On Feb. 12th there is some rifting near the calving front, these rifts are structural weaknesses that indicate calving is imminent.  Melange movement ahead of calving generally reflects changes in sub glacial water output.  The amount of calving here is not impressive except for it being February as you have all noted.  Given that the velocity of JI is faster than in the past, that alone makes such an event more likely.

7
Greenland and Arctic Circle / Re: Ice caps / All Greenland
« on: August 20, 2014, 04:03:49 PM »
The glacier arm that advanced on the Disko Island, seems to have a looped moraine, this suggests a possible surge.  The image is not good quality. 

8
A Team and Espen excellent work examining the changes in the calving front.  The northern branch cannot be done this summer, the current calving front is too high and the crevassing-rifting behind the front to extreme to be stable.  This area of visible instability does not seem to extend far behind the front at this point.

9
Supraglacial lakes most often do reflect surface topographic lows that are generated by the topography of the glacier bed, there is a distance lag that depends on thickness and velocity.  So the bedrock feature is not immediately below the surface expression.  In the case of melt ponds they can also be self-reinforcing by accentuating melt, this is the case where surface velocity is quite low.  Most melt lakes do not drain rapidly, though that mechanism gets most of the press. 
 http://www.the-cryosphere.net/8/107/2014/tc-8-107-2014.html is one example that looks at this.

10
This glacier is not the largest in Northern Hemisphere, just has the widest calving face.  It also lacks deep water extending far beneath the glacier.  The crack noted I am not convinced is real-could be an artifact, if it is it appears to be a surficial stream not crevasse or rift. http://glacierchange.wordpress.com/2010/09/04/humboldt-glacier-retreat-greenland/

11
May 9th
June 1

Lack of surficial transverse crevassing is unusual before a large calving event.  Basal crevassing maybe key. Notice the longitudinal feature that marks the main boundary of southern arm.

Jakobshavn overall assessment

12
It is evident in spring 2014 that there is no rift that is substantial enough to predict an imminent large calving event. 

13
CHW is not to date an important part of the acceleration puzzle for the GIS, it takes a long time to warm the ice.  This type of acceleration would also tend to impact areas inland more than near the terminus, yet acceleration has been most pronounced at the terminus.  There is limited acceleration away from the large outlet glaciers, yet CHW would impact all locations.

14
It is not a new calving front, but it does represent a steepening of the slope, enhanced crevasse and serac activity.  This is close enough to the front to potentially not be stable without retreat to it. We generally do not see such a narrow embayment develop on this glacier, so if it does retreat to that point the lateral extent will be greater.

15
Nice new images sets from this spring I had looked at the March but not the April Landsat.  The supraglacial lakes form in same geographic location mainly because of the bed of the glacier induces changes in the surface of the glacier.  Depending on the speed of movement and ablation rate, the lake could persists or not.  The lakes form because of the surface features, but do not necessarily disappear as they move beyond that feature. Lampkin (2011) is a paper that best describes the bed-surface relationship and lag. http://onlinelibrary.wiley.com/doi/10.1029/2010JF001725/abstract

16
Zachariae does have a substantial flux, what makes you think much of Storstrommen is afloat?

17
Just published a piece on the Storstrømmen and L. Bistrup Brae area, any further suggestions welcome. http://glacierchange.wordpress.com/2013/08/25/storstrommen-susceptible-to-rapid-retreat/.

18
Lots of calving off the front of ZIS as the large rift noted early this summer has peeled off as of July 23.

19

Zachariae Ice Stream June 17 2013 note all the late 2012 icebergs yellow dots, terminus position which has retreated since July 2012 and the rift that promises to release more icebergs as soon as the ice has cleared.

20
Greenland and Arctic Circle / Re: NEGIS outlet
« on: June 27, 2013, 05:01:47 PM »

Zachariae from June 17 2013 indicating with yellow dots all of the new icebergs from late 2012 and the new ice front.

21
Greenland and Arctic Circle / Re: Jøkelbugt/North East Greenland
« on: June 18, 2013, 01:34:23 PM »
New post on 79 Glacier with imagery from this week. <a href="http://glacierchange.wordpress.com/2013/06/18/nioghalvfjerdsbrae-79-glacier-northeast-greenland/">79 Glacier</a>.

22
Greenland and Arctic Circle / Re: Jøkelbugt/North East Greenland
« on: June 13, 2013, 04:33:28 PM »
I prefer to get the imagery, more choices at
http://ocean.dmi.dk/arctic/modis.uk.php
Looking at Landsat images of this area today.

23
The placemarks in Google Earth do not appear to be in any collective folder.   Create a new folder and drag them all in, then when you close the folder the placemarks should disappear if they are int folder.  Then save the folder and post.

24
 I do not see this 1 km, change, nor do I see the icebergs that should have been generated by such a change.  What am I missing? :-\

25
Greenland and Arctic Circle / Re: Canadian glaciers face 'big losses'
« on: March 11, 2013, 11:48:31 PM »
This is and you can see this occurring for example on Dexterity Ice Cap.

http://glacierchange.wordpress.com/2013/03/10/dexterity-ice-cap-baffin-island/

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