Jakobshavn Isbræ / Ilulissat Isfjord / West Greenland

[sidd]

Would you be able to plot the ice thickness at which it would be possible to float at?

the number you want is 1.1*bedrock depth
but you might want to look at Volume above Flotation, (VAF)  = total ice thickness - 1.1*bedrock depth

I think someone has done VAF for Jacobshawn, but i can't recall the reference off the top of my head.

sidd

[Bernard]

http://www.hotel-arctic.gl/files/webcam/webcamshot.jpg has been showing a lot of ice chunks flowing out for a couple of days. Any calving event associated in the past days, or just seasonal flushing?

[Anne]

Bernard, this webcam is a favourite of mine and I check it out most days. The current flow of ice doesn't seem unusual to me: watching the ice is one of the reasons people stay at the hotel. Sometimes there are icebergs and sometimes just bergy bits and growlers. They shift quite quickly so if you want other people to see what you're looking at it's worth posting the image.

But I'm hardly expert and stand to be corrected.

[Anne]

Many apologies! You did post the image.
Still doesn't strike me as exceptional.

[Espen]

Due to a heavy cloud cover above Jakobshavn over a prolonged period, reporting is at a low pace.
But there are indications of a major calving at the southern branch including its northern shore, I base this on a very "cloudy" image from Landsat (May 25) combined with data from ASAR images.
As soon as reasonable images are received, they will be reported.

[jimbenison]

I think Espen is right. Either low clouds are creating artifacts here or a huge chunk of ice has fallen into the sea.

https://earthdata.nasa.gov/labs/worldview/?switch=arctic&products=baselayers,!MODIS_Aqua_CorrectedReflectance_TrueColor,MODIS_Terra_CorrectedReflectance_TrueColor~overlays,arctic_coastlines_3413&time=2014-05-27&map=-419200,-2393216,10880,-2168960

It would be great to get a higher resolution pic.

[Anne]

There's always Hotel Arctic webcam at Ilulissat, which may be north of where you're looking. It's not showing anything exceptional right now.
http://www.hotel-arctic.gl/om_hotel_arctic/webcam/

[Espen]

There's always Hotel Arctic webcam at Ilulissat, which may be north of where you're looking. It's not showing anything exceptional right now.
http://www.hotel-arctic.gl/om_hotel_arctic/webcam/

That is way away from where the action is (only about 45 km).

[jimbenison]

There's always Hotel Arctic webcam at Ilulissat, which may be north of where you're looking. It's not showing anything exceptional right now.
http://www.hotel-arctic.gl/om_hotel_arctic/webcam/

That is way away from where the action is (only about 45 km).

It is far away, but large calving events can push energy all the way out the fiord and move those big bergs. Viewing a time lapse is more informative than a still.

http://www.lookr.com/lookout/1310041325-Ilulissat

[Espen]

WOW! This is far more than I expected (May 25), the retreat and calving must have been of record size, not only the southern branch expanded but so did the northern.

Just puzzled to where all that ice went? My estimate is 5 - 6 km² of glacier ice went down the drain!

Please click on the image to start animation!

[Rubikscube]

Holy Moly, that's huge. Looks like the entire northern slope on the southern branch just fell into the ocean.

[Neven]

Pretty big, indeed. Thanks for keeping an eye on this, Espen. I'll put a blog post on the ASIB in a couple of days.

[Yuha]

Just puzzled to where all that ice went? My estimate is 5 - 6 km² of glacier ice went down the drain!

5 - 6 km² seems about right. Furthermore, the glacier is flowing pretty fast. If there had been no calving between May 7 and June 1, the calving front of the southern branch would have moved nearly 1 km forward, now it's about 1 km back. Thus the actual ice lost in the calving(s) is more like 10 km².

[nukefix]

Jakobshavn is one of the "supersites" for the ESA S-1 satellite which means that it will be imaged with a Synthetic Aperture Radar twice in every 12-day period. As the data will be freely available this will allow continuous monitoring of this key ice stream throughout the year regardless of ambient light or cloud coverage.

Here's an example what will be possible (Kangerdluqssuaq-trakcked with an earlier SAR-satellite):

http://www.esa.int/images/glacier-ERS2-March-May_H.gif

[Bernard]

@nukefix any idea when such Sentinel-1 images will be available?
I did not find any indication at http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-1/Oceans_and_ice

BTW looking at this Kangerdluqssuaq animation it's amazing how the speed of the ice seems to be the same on each side of the calving front ...

[nukefix]

@nukefix any idea when such Sentinel-1 images will be available?

The satellite in in commissioning-phase that should take until late September or so. See mission status for updates:

https://sentinel.esa.int/web/sentinel/missions/sentinel-1/mission-status

Some limited imagery is already available at https://senthub.esa.int/ but the search interface is cumbersome to say the least.

[Espen]

To answer some questions asked by Steve Bloom at the Sea Ice Blog:

The furthest retreat I have observed was in September / October 2013, after that Jakobshavn expanded into 2014 and started calving again in March / April as can be seen on the animation below:

Please click on image to start animation!

[RaenorShine]

RobertScribbler's blog has picked this up from here also (I've cross posted this from the ASIB)

http://robertscribbler.wordpress.com/2014/06/06/ten-cubic-kilometers-of-ice-lost-from-jakobshavn-glacier-in-less-than-one-month/#comments

Ten Cubic Kilometers of Ice Lost From Jakobshavn Glacier in Less than One Month
How large is a cubic kilometer? Think of something the size of a mountain. Now multiply that by ten and you end up with a veritable mountain range. Think of it. An entire mountain range of ice. That’s a good rough comparison to the volume of ice lost from just a single Greenland glacier over the course of a mere 26 days from May 7 to June 1 of 2014.

For according to reports from expert sea ice observer Espen over at the scientist and ice researcher camp that is Neven’s Arctic Ice Blog, about 7.5 square kilometers over an ice face about 1,300 meters tall (when including the above and below sea level ice front) shoved off from the great Jakobshavn Ibrae glacier during the past month. It was a period of time well before peak Greenland warming and one that featured a collapse of ice into the heating ocean even larger than the epic event caught on film during the seminal documentary Chasing Ice.

[Yuha]

(Cross post from ASIB)

Probably the currently most accurate map of the bed topography of Jacobshavn is on page 15 in this paper:

http://www.nature.com/ngeo/journal/v7/n6/extref/ngeo2167-s1.pdf

It's a supplement to a recent paper by Morlighem et al in Nature Geoscience (doi:10.1038/ngeo2167). The main paper is behind a paywall but the supplement is free. It covers many other Greenland glaciers too.

[jimbenison]

A couple of years ago I stumbled across a paper that showed the bedrock topography of this glacier near the calving front of the south branch in great detail. I have been looking for it for the last week and cannot find it for the life of me. Epsen's image from Sep 27 2013 shows a couple of important features related to it thanks to the lighting angle.

Notice that just upstream of the calving front in the main south ice stream a couple of longitudinal bumps are visible. One is toward the north side and one is almost dead center. These are pinning points with relatively shallow bedrock that pushes the ice higher in these areas. Inland from there the glacier bed gets deeper. The really deep (-1500 meters) portion of the bed is actually a few kilometers upstream of where this branch makes a 45 degree turn due east.

If I can find the paper I will post it. The relationship between surface features on the ice stream and the bedrock topography are pointed out very clearly. It would be extremely handy here.

[icefest]

@jimbenison

Was it this image:

From here: http://www.igsoc.org/annals/55/67/t67A001.pdf

[sidd]

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

that the best i know

[jimbenison]

@icefest

That's not the one. This is a little better (see figure 1), but it still does not even hold a candle to the level of detail in the one I saw.

http://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/52825/1/Herzfeld_etal_2012_AnnGlac.pdf

I looked through dozens of papers today trying to find it. My best guess is that it's now behind a paywall.

[icefest]

Hmm, is this any better?
https://www.cresis.ku.edu/sites/default/files/Research/Sensors/jakobshavn.jpg
It looks like some variation of the CReSIS data seems to have the highest resolution.

[Espen]

Believe it or not Jakobshavn continues its massive calvings:

Please click on image to start animation!

[Neven]

Holy crêpe!

[Espen]

Here a triple day animation May 7, June 1 and June 8 2014:

[Shared Humanity]

If you look at the glacier moving around the bend, it's also moving fast.

[Shared Humanity]

Espen.....I want to confirm what I think I am seeing. You have been watching glaciers for a long time.

On that last animation it looks as if the huge bed of ice (northeast?) of Jakobshavn sped up towards the fjord when the calving removed its pinning or dam effect. Could this part of the ice sheet come into play? Now that Jakobshavn has retreated past this point, has this entire portion of the ice sheet become unstable?

[Espen]

Shared Humanity, yes it looks like the whole plateau is on the move, I don't really know what is happening, but there must be a lot of stress and re-stress in area as a whole, and there is more to come over next few days, that can be seen when analyzing the images.

[Neven]

How much km2 are we talking now? Is this picked up anywhere? NASA?

[Espen]

The series of calvings over the last moth are several times bigger than Manhattan NV.

[Shared Humanity]

Espen.....You may want to look at this just published research. I've copied the link from a post by Lynn Shwadchuck on another Greenland thread. They have just completed a detailed topography map using an  entirely different technique. (mass conservation?)

http://www.nature.com/ngeo/journal/v7/n6/extref/ngeo2167-s1.pdf

The topography detail on each glacier is amazing. The new topography map suggests that this entire ice sheet that is on the move is grounded below sea level!

Please look at page 15 and tell me I'm seeing this wrong!

[Espen]

How much km2 are we talking now? Is this picked up anywhere? NASA?

My prelim calculation is a total of 10,6 km2 ( May 7  - June 8 ) (excluding expansion)

Or 14,7 times the size of Manhattan NV.

[LRC1962]

Very sad that Robert Scribbler and here seem to be the only places on the WWW that seem to have caught onto the story. No search engine as of yet can find anything else about this particular calving.

[Shared Humanity]

Very sad that Robert Scribbler and here seem to be the only places on the WWW that seem to have caught onto the story. No search engine as of yet can find anything else about this particular calving.

That's because we have Espen keeping an eye on things. Take a look at the link  that shows detailed topography on 20  separate Greenland glaciers. I think Jakobshavn is going to be a huge story this year!

[mspelto]

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

[LRC1962]

Complain to CBC not sure if it will help. Could be melt working through from last year, but also the SSTA around that area has been very high lately, could it not also be a case ocean water working its way underneath and only impacting now? And since it would be traveling either level or even slightly downhill, could get far farther inland then if it had to go uphill.

[Espen]

Be aware! We have have not reached the maximum retreat point of September 2013 yet, at some points yes but not depth wise :

Please click on image to start animation!

[Neven]

Be aware! We have have not reached the maximum retreat point of September 2013 yet, at some points yes but not depth wise :

Please click on image to start animation!

Thanks, Espen. I don't keep an eye on this, and so I didn't know about the retreat point.

[Espen]

Be aware! We have have not reached the maximum retreat point of September 2013 yet, at some points yes but not depth wise :

Please click on image to start animation!

Thanks, Espen. I don't keep an eye on this, and so I didn't know about the retreat point.

But I am pretty sure we will pass that point later this season, maybe even within days?

[Neven]

Well, let us know, and I'll post a follow-up on the ASIB.

[Bernard]

Espen I suppose in your last animation the date 2013 June 8 has to be read 2014 June 8? 

[Espen]

Bernard, yes that is June 8 2014, very early in the morning

It is now corrected!

[Espen]

Although we probably had some of the largest calvings ever seen at Jakobshavn, we did not reach the retreat point Jakobshavn saw in September 2013.
Since September 2013 Jakobshavn grew, but that growth is now almost gone, so if Jakobshavn follow the plan, large calvings usually come in the summer season, we can expect Jakobshavn to retreat beyond the point reached in September 2013.
To illustrate where we are today I have made the graphic below, with the latest Landsat-8 image of Jakobshavn with the retreat line seen in September 2013 (red line).   

[Shared Humanity]

Shared Humanity, yes it looks like the whole plateau is on the move, I don't really know what is happening, but there must be a lot of stress and re-stress in area as a whole, and there is more to come over next few days, that can be seen when analyzing the images.

If I look at your animation again and compare it to the increasingly accurate topography map from recent completed research published here.......

http://www.nature.com/ngeo/journal/v7/n6/extref/ngeo2167-s1.pdf

........the retreating calving face of Jakobshavn is exposing a large section of ice sheet to the north of the Fjord. As can be seen, this portion of the ice is grounded below sea level and is already moving fast. Could we see significant calving from this ice sheet?

Because this ice sheet is grounded below sea level, will it also suffer significant melt by the sea on the bottom of this ice. The grounding is much shallower than the Fjord (perhaps only 200 meters). Would this shallower grounding serve to slow or protect this sheet from bottom melt?

I guess my concern is that, with the retreat of the Jakobshavn, we've essentially doubled the potential calving into the Fjord, perhaps more as this ice sheet calving face is considerably wider.

[Rubikscube]

Many thanks for all the nice topography maps everyone. I kind of share your concern SH, perhaps first and foremost because of the developments we have seen in the Northern branch during recent years, a branch which also seems to have a quite limited depth. My assumption after seeing the newst maps, is that it wouldn't be a very big surprise to see a third branch slowly emerge.


However, what really frighten me is this.


Hopefully, and probably, it is going take several decades before Jakobshavn splits into multiple branches that each are capable of penetrating several hundred kilometers into the Greenland ice sheet, but the fact that all these canyons exist would suggest pretty strongly that there have been numerous fast moving glacial outlets right in the middle of Greenland during previous meltdowns. It strikes me though, that most of this vast network of canoyns is excluded from more detailed topography maps of Jakobshavn and doesn't seems to be a videly discussed issue. Is it just too far into the future?

[Espen]

Thanks guys, for the topography graphics, although I find Jakobshavn interesting, I think it is far more interesting and especially far more serious what is happening at Zachariae Isstrøm.
I know Zachariae Isstrøm is not a media and blogger darling like Jakobshavn, Petermann and to some degree Helheim, very little image/film documentation could be one of the reasons, but the indifference frustrates me?
 

[jimbenison]

Looks like NASA has picked up on the recent calving.

http://earthobservatory.nasa.gov/IOTD/view.php?id=83837&eocn=home&eoci=iotd_readmore

I tend to agree with Espen on Zachariae. Jakobshavn is relatively narrow and may be already flowing about as fast as it can. It's like a firehose. Zachariae is very wide, it's deep, and it's waking up.

[Neven]

Looks like NASA has picked up on the recent calving.

http://earthobservatory.nasa.gov/IOTD/view.php?id=83837&eocn=home&eoci=iotd_readmore

And they link to the ASIB at the end of the article! Well done, Espen!