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Author Topic: Jakobshavn Isbræ / Ilulissat Isfjord / West Greenland  (Read 558498 times)

Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #150 on: October 03, 2013, 02:11:59 PM »
An update on retreat, as you can see from this animation spanning from Sept 2011 to Sept 2013, the retreat of Jakobshavn continued this year, an estimated 1 km from 2012 to 2013 alone:
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Lennart van der Linde

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #151 on: October 03, 2013, 03:47:04 PM »
So that makes the retreat about 19 km over the past 12 years. About 1.5 km/yr on average.

How long can this continue? Do we expect acceleration or slow-down?

I haven't checked IPCC AR5 on this yet, but maybe other people here know?

Lennart van der Linde

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #152 on: October 03, 2013, 04:13:18 PM »
A start is this article from 2010:
http://www.cejournal.net/?p=4225

Because the fjord enters deep into the interior, the glacier is vulnerable to continuing and faster retreat. Maybe the only reason that this will be kept somewhat in check is that the fjord is relatively small, as someone in the comments on the article mentions, referring to the paper by Pfeffer et al 2008.

The map in the article (from a presentation by Konrad Steffen) may be outdated, since Bamber et al published a new map earlier this year (see their figure 3a):
http://www.the-cryosphere.net/7/499/2013/tc-7-499-2013.pdf

The main difference seems to be that the fjord of Humboldt glacier may not extent into the interior as far as is suggested by the earlier map.

Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #153 on: October 03, 2013, 04:33:27 PM »
So that makes the retreat about 19 km over the past 12 years. About 1.5 km/yr on average.

How long can this continue? Do we expect acceleration or slow-down?

I haven't checked IPCC AR5 on this yet, but maybe other people here know?

The southern part (the animated) of Jakobshavn seems to be most busy.
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Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #154 on: October 23, 2013, 10:25:36 AM »
Jacobshavn retreated 3 km in 2013.
Jakobshavn southern calving front retreated ~ 3 km this season, as can be seen in this animation.
And very little action is seen at the northern front.
« Last Edit: October 23, 2013, 12:37:01 PM by Espen »
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Neven

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #155 on: October 23, 2013, 11:03:21 AM »
Wow, that's quite a bit of retreat, I'd say. Thanks for keeping an eye on this, Espen.
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Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #156 on: October 26, 2013, 09:45:07 AM »
New updated front map 1851 - 2013:

Please click on image to enlarge for better details!
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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #157 on: October 26, 2013, 03:55:53 PM »
Espen....

Is this one of the fastest glaciers in Greenland?

Other than general trends in AGW, what could be contributing to this rapid increase in speed and retreat?

We know that the southern third of Greenland is suffering from unprecedented surface melt with much of that melt flowing via moulins to the bedrock below with some of it reducing friction between the glacier and the bedrock. This could explain it I suppose. I've read things that suggest most of this melt water does not escape to the sea but instead collects under the ice sheet (warming it, softening it etc.) Given the topography of Greenland, (link below) it seems that the Ilulissat Icefjord is very nearly a water path to these inland lakes. Could this be a factor? Could the melt water from surface melt be collecting in these inland lakes? Could they be raising the level of the water? With  the  pressure of the ice above, could this be driving pulses of melt water into this type of fjord?

http://upload.wikimedia.org/wikipedia/commons/8/8b/Topographic_map_of_Greenland_bedrock.jpg


Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #158 on: October 27, 2013, 08:56:57 PM »
We have seen some big movements at Jakobshavn over a number of years now, but what about the future?
Will the calving front move further inland?
My guess is yes, and that prediction is based on what we have already learned / seen.
To prove this I use a Landsat image from October 1972, where there ice-movement lines are clearly seen, it more or less resembles a superhighway system from above, with one highway heading north with little potential for much further extension, but the southern branch got the potential moving much further in both a southern and a south-eastern direction.
It is interesting to see  "Cap Ice" was already "designed" back in 1972, what is behind this resistance may be hidden rocks / island.
What are your thoughts?

Please click on image for enlargement and better details!
« Last Edit: October 28, 2013, 07:57:16 AM by Espen »
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Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #159 on: October 28, 2013, 10:59:34 AM »
I have have just updated the retreat prediction map, for Jakobshavn.

Please click on image to enlarge and for better details!
« Last Edit: October 28, 2013, 02:41:50 PM by Espen »
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DaddyBFree

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #160 on: October 29, 2013, 06:29:34 PM »
Great updates Espen!
The next 40 years have been set up to be quite interesting.  Reminds me of the "Chinese curse" "May you live in interesting times," popularized/modernized by Terry Pratchett and others.

Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #161 on: October 29, 2013, 08:57:38 PM »
Thanx DaddyBFree,

Yes it is interesting, that a first generation Landsat image from 1972 (Landsat program was launched in 1972), and almost within few meters tells where Jakobshavn is planning to retreat over the next 41 years (2013), so based on that I have enough confidence to predict where Jakobshavn is heading over the next many years, with a little correction, seen in GREY area around the Green area on the above image, that is where new but not so strong movement lines are found in more recent sat-images.
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ggelsrinc

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #162 on: October 30, 2013, 06:14:14 AM »
Bedrock map of Jakobshavn :
I did put an arrow where I guess the front of the glacier is, or is it where the sea is viewed !?

You can click on the image to enlarge it !

Laurent, that image you posted speaks volumes about the past geologic history of that area. The main direction of eventual glacial retreat is written in stone and not surface details, it will eventually follow that easily recognized path of least resistance, it only takes time.

I can see all kinds of past details of other places represented in that image. Will you carefully explain in detail, beyond what you already did, how such exaggerated topographical images can be easily obtained?

In my mind's eye, your image shows me details of past glaciation and retreat; notice the peaks lined up on the right! That carved out image on the left is very typical of multiple coastal glacial feeds, IMO.

I can see major problems for the people living in that area of mining interests around anywhere mother nature was the bulldozer for a season for over millions of years. It's only logical that heavy metals will collect in areas where forces remove lighter materials. This is a tangent that I don't want to discuss on this thread, but I think such areas as Greenland, like the Arctic and Antarctic should be placed under the jurisdiction of all our world's nations and people.

Focusing back on Jakobshavn Isbræ, I don't think there is any doubt the "glacier" (part of the GIS ice sheet flow) will continue it's present path, but will eventually follow that line marked in stone shown on your posted image. The ice has only temporarily met a line of resistance and parted because that is how calving is presently fed with material. I see Jakobshavn Isbræ removing the material from the north and heading east, even before the material from the south is removed.

I don't consider flows from ice sheets, glaciers in the normal sense.

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #163 on: October 30, 2013, 08:01:56 AM »
I'm looking fonrward to Sentinel-1a SAR-satellite that will be launched in 2014 - with it monthly tracking of the calving fronts in Greenland will be possible in all weather conditions + the data will available to anyone.

Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #164 on: October 30, 2013, 10:26:44 AM »
Thanks to NASA and Laurent.
Here is a modified bedrock image from Jakobshavn.

Please click on image to enlarge and for better details!
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sidd

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #165 on: November 19, 2013, 07:08:27 AM »
here is Joughin sounding the alarm,free access


The Cryosphere Discuss., 7, 5461–5473, 2013
www.the-cryosphere-discuss.net/7/5461/2013/
doi:10.5194/tcd-7-5461-2013

From the abstract:

" At a point a few kilometres inland from the terminus, the mean annual speed for 2012 is nearly three times as large as that in the mid 1990s, while the peak summer speeds are more than a factor of 4 greater. These speeds were achieved as the glacier terminus retreated to the bottom of an overdeepened basin with a depth of ∼ 1300 m below sea level. "

But scarier, from the paper, suggests that Pffefer's  upper bound estimates from 2008 are already here:

"If, as the glacier recedes up the trough, it is able to maintain the peak speeds year round, then a sustained speedup by a factor of 4 of 5 is conceivable based on recent behavior, which is about half of the ad hoc tenfold upper limit on speed proposed by Pfeffer et al. (2008). Nevertheless, these speeds would occur in a trough roughly twice as deep as prior to the speedup. Hence, a tenfold increase in ice flux may be possible for Jakobshavn Isbræ if the trough does not narrow substantially with distance upstream. Equivalently, while the increase in terminus speed and the glaciers overall maximum speed may remain under a factor of five, as the terminus retreats farther inland where the speeds now are comparatively slow, the relative speedup is much greater (e.g., if the terminus retreated to M26 with a speed of 16 000 m yr−1 , this would represent a twelve-fold speedup). Thinning by hundreds of meters to a terminus near flotation, however, yields something closer to a ten-fold flux increase."

sidd

Lennart van der Linde

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #166 on: November 19, 2013, 04:18:58 PM »
sidd, as I replied on RealClimate:

Thanks for the reference to the draft paper by Joughin & Smith. I'm trying to understand how exactly this compares to Pfeffer et al 2008:
http://www3.geosc.psu.edu/~jfk4/Geosci_500/Discussion%20papers/Last%20week%202/Science%202008%20Pfeffer.pdf

Pfeffer et al say:
"Average (present day to 2100) outlet glacier speeds required to meet 2- and 5-m SLR targets range from 26.8 km/year to 125 km/year, depending on the scenario considered [table 2 and supporting online material (SOM)]. These velocities must be achieved immediately on all outlets considered and held at that level until 2100."

So about an average speed of 27 km/yr is needed from now until 2100 for all GIS outlet glaciers, in combination with a 10x higher surface melt rate, to get a GIS-contribution to global SLR of 2 meters this century.

It seems Joughin & Smith argue in their last sentence this seems unlikely to be possible. However, Pfeffer et al also show a scenario of 2 meter total SLR by 2100 in which GIS contributes about 54 cm. In this scenario:
"Greenland SMB was accelerated at present-day rates of change, but dynamic discharge was calculated by accelerating outlet glacier velocities by an order of magnitude in the first decade."

This implies that over the 21st century all GIS outlet glaciers should reach an average speed of about 12 km/yr in this scenario, if I understand correctly. Marine outlet glaciers could then reach a higher average speed and land outlet glaciers a lower average, but it's not obvious from Joughin & Smith that such average speeds could be sustained for nine decades, I think.

Jim Hansen for one seems to think Pfeffer et al may under-estimate in particular the potential AIS contribution, so all this is not to say that 2 meter of total SLR by 2100 would be impossible.

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #167 on: February 04, 2014, 01:12:18 AM »
Glacier that sunk the Titanic speeds toward disaster!   :D

http://www.egu.eu/news/100/greenlands-fastest-glacier-reaches-record-speeds/
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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #168 on: February 04, 2014, 01:52:39 AM »
Good article: "We are now seeing summer speeds more than 4 times what they were in the 1990s on a glacier which at that time was believed to be one of the fastest, if not the fastest, glacier in Greenland..."

"In the summer of 2012 the glacier reached a record speed of more than 17 kilometres per year, or over 46 metres per day. These flow rates are unprecedented: they appear to be the fastest ever recorded for any glacier..."

"We know that from 2000 to 2010 this glacier alone increased sea level by about 1 mm. With the additional speed it likely will contribute a bit more than this over the next decade"

"The researchers believe Jakobshavn Isbræ is in an unstable state, meaning it will continue to retreat further inland in the future."
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sidd

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #169 on: February 04, 2014, 01:57:16 AM »
looks like the final version of the Joughin paper i posted above.I have issues with this statement


"While the high spot above the basin may slow flow, the terminus would still be grounded on a bed at least 900 m below sea level, likely yielding speeds well above balance that would maintain strong, although potentially diminished, thinning"

Bassis(2013) DOI: 10.1038/NGEO1887 points out that glacier is unconditionally unstable at approx 1000m against calving

Fig 1b)

htto://membrane.com/sidd/bassis-1b.png

sidd

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #170 on: February 04, 2014, 07:31:45 AM »
Phillips(2013)
doi:10.1002/jgrf.20079

is interesting. Sermeq Avannarleq is close to this region, and the authors tie expansion of melt zone to warming of ice by meltwater that increases leads to flow parameter in Glen's law. In short, once you see surface melt, ice underneath is flowing faster.

"The corresponding increase in the temperature-dependent flow law parameter (A) is a factor of 3.2 and 1.8, respectively. This doubling or tripling of the flow law parameter can have significant thermomechanical consequences on ice velocity."

The quote is in reference to an idealized test case, but they do see that:

(CHW is cryohydrologic warming)

"The base case CHW simulations reproduce the observed increase in inland ice velocity between 2001 and 2007 reasonably well. The no CHW and surface CHW simulations significantly underestimate observed ice surface velocities in both epochs. The higher ice velocities in the base case CHW simulations are attributable to both decreased basal ice viscosities associated with increased basal ice temperatures and an increase in the extent of basal sliding permitted by temperate bed conditions. Only the temperate bed extent predicted by the base case CHW simulation is consistent with independent observations of basal sliding. Based on our sensitivity analysis of CHW, we evaluate alternative explanations for an increase in inland ice velocity and suggest CHW is the most
plausible mechanism."

now consider that equilibrium line altitude and melt zone rose above saddle at 67 N year an a half ago.

sidd

Lennart van der Linde

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #171 on: February 04, 2014, 01:39:28 PM »
Also see the maps and reference to the final Griggs, Bamber et al paper on ASIB (thanks to Tenney Naumer for catching this):
http://neven1.typepad.com/blog/2012/12/looking-for-winter-weirdness-4.html?cid=6a0133f03a1e37970b017c3524438c970b#comment-6a0133f03a1e37970b017c3524438c970b

A-team's bedrock map is clearer than the original in the paper.

Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #172 on: February 17, 2014, 08:48:31 PM »
Jakobshavn,waiting for your next move:
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Yuha

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #173 on: February 17, 2014, 09:11:57 PM »
Jakobshavn,waiting for your next move:


The first calving of the season happened already:

Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #174 on: February 17, 2014, 09:27:45 PM »
Yuha,

You are right, something definitely moved ;)
« Last Edit: February 17, 2014, 09:41:40 PM by Espen »
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Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #175 on: February 18, 2014, 09:50:40 PM »
First 2014 Landsat image from the Ice Cube maker at Jakobshavn, and as Yuha pointed out, the thing is moving:

!!There might be a problem with the February 9 2014 image!!


Please click on image to enlarge and start animation ;)
« Last Edit: February 18, 2014, 10:42:56 PM by Espen »
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icefest

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #176 on: February 28, 2014, 08:44:58 AM »
Thanks for the enimation Espen,

I'm looking forward to this melt season. (with trepidation)



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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #177 on: February 28, 2014, 01:09:35 PM »
Sequence of Landsat 8 images from Feb 9 and 25. More calving has taken place. I estimate the progress of the south branch about 22x21 pixels (left and up). That translates to 456 meters, or about 28 meter per day.
Accuracy should improve when the light gets better (sun elevation is 5.8 and 11.4 degrees ).

(click for that animation)

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #178 on: February 28, 2014, 04:56:43 PM »
Wipneus,

If a 1997-1998 like El Nino event happens in 2014-2015 (see the discussion on this probability in the "Consequence" folder), and if such a Super El Nino sufficiently disrupts the Thwaites, and/or Pine Island, Ice Shelf (Shelves); then conditions could be created therefore to set-up calving events for either Thwaites, and/Pine Island, Glacier(s) comparable, or worse, than Jakobshavn is exhibiting.  That is a truly chilling prospect, and if so your Landsat 8 sequences for the Amundsen Sea Embayment glaciers, in the next austral summer, would be greatly appreciated.

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sidd

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #179 on: February 28, 2014, 08:21:00 PM »
detail of Jacobshawn bedrock, overhead view in attached image

more bedrock images at

http://membrane.com/sidd/greenland-2013/
i will add more detail and ice surface elevation to those pages this weekend


sidd

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #180 on: March 03, 2014, 10:48:35 PM »
added surface elevation, Jacobshawn,Petermann detail

http://membrane.com/sidd/greenland-2013/

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #181 on: March 03, 2014, 10:56:48 PM »
Great comparison, Wipneus.
Though I must say the shadow cast by the 100-120 m high calving front plays a delusive role.

Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #182 on: April 09, 2014, 04:41:32 PM »
A new calving front seems to be developing in the northern part of the eastern branch, marked with a red circle, 2014 is likely to be a very interesting glacier year!

Please click on image to enlarge!
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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #183 on: April 10, 2014, 07:21:30 PM »
As mentioned above the "New Front" development is seen on this NASA image from yesterday
Or is it "only" a ice slide due to the elevation? :
« Last Edit: April 10, 2014, 07:26:32 PM by Espen »
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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #184 on: April 19, 2014, 12:32:58 PM »
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.

mspelto

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #185 on: April 19, 2014, 12:38:31 PM »
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.

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #186 on: April 19, 2014, 01:59:22 PM »
As mentioned above the "New Front" development is seen on this NASA image from yesterday

The IceBridge P-3 is heading back to Jakobshavn as we speak.
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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #187 on: April 19, 2014, 03:11:19 PM »
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.

Since this enhanced crevasse and serac activity is occurring beyond the existing calving front, should we expect this kind of activity to expand as the calving front retreats?

Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #188 on: April 19, 2014, 03:25:30 PM »
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.

Since this enhanced crevasse and serac activity is occurring beyond the existing calving front, should we expect this kind of activity to expand as the calving front retreats?

I would guess it is more likely on the northern "shore" than the southern because of the elevation?
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Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #189 on: April 19, 2014, 03:57:23 PM »
Just followed the today's flight. It looks like they are following the future retreat route? 
« Last Edit: April 19, 2014, 04:07:36 PM by Espen »
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sidd

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #190 on: April 20, 2014, 11:43:09 PM »
Comparison of surface and bedrock. Looks how the surface contours have concave kinks where the cross the bedrock canyons.

For other comparisons and some previous work by Csatho, please see

http://membrane.com/sidd/greenland-2013/walkback.html

sidd

Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #191 on: April 22, 2014, 05:13:12 AM »
The ice slide at the northern "shore" is developing, watch the encircled area (red):

Please click on image to start animation!
Have a ice day!

sidd

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #192 on: April 26, 2014, 04:45:18 AM »
And what lies beneath from Hughes(2014) doi:10.5194/tcd-8-2043-2014 (open access)
"Gogineni Gorge"  fig14 attached
I like it

That is a nice paper, but the Byrd comparison is probably better discussed in one of the Antarctica threads.

sidd

Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #193 on: April 26, 2014, 09:34:05 AM »
Sidd,

There seems to be a threshold just behind the present calving front?

And what is the date of the calving front on that image?
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Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #194 on: April 26, 2014, 11:34:26 AM »
From the same paper : Quantifying the Jakobshavn Effect:
Jakobshavn Isbrae, Greenland, compared
to Byrd Glacier, Antarctica
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sidd

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #195 on: April 26, 2014, 08:08:57 PM »
The grounding line seems to be from 2012 as in the other grafs ?

andy_t_roo

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #196 on: April 27, 2014, 08:31:56 AM »
Would you be able to plot the ice thickness at which it would be possible to float at? That could be the limiting factor, as long as the deep area just past the current front remains grounded by the arrival of new ice vs melting then it is fine, but if the Ice thins enough to float, and water manages to infiltrate to the base, then all bets would be off. 

Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #197 on: May 02, 2014, 08:54:09 PM »
Another slice of Jakobshavn since April 23 2014 (Landsat image from May 2 2014 only partial)

Please click on image to start animation:
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Espen

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #198 on: May 07, 2014, 09:15:02 PM »
Update May 7 2014:
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Yuha

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Re: Jakobshavn Isbræ / Sermeq Kujalleq / Ilulissat Icefjord
« Reply #199 on: May 07, 2014, 11:13:42 PM »
Espen's Landsat animation shows that there has been a "spring cleaning" of the fjord recently.

The first image below shows the start of the event on April 21. Most of the fjord was empty but there was a lot of ice dammed behind a blockage. By May 2 (second image) the fjord had been filled and there was a large plume of icebergs in Disko Bay. The event is still not over as can be seen in the images from the last two days.