Jakobshavn Isbræ / Ilulissat Isfjord / West Greenland

[Shared Humanity]

April 1st to present every 15 days.

You really need to slow this down...a lot. A person is barely able to follow the calving front, let alone observe the behavior of the main glacier or the ice to the northeast of the now open water which is always calving.

An animation that allows about 10% of the visual information available in the images to be reviewed.

[oren]

April 1st to present every 15 days.

Let me rephrase SH's post:

Thanks for the animation, it gives a better perspective of the changes in the last two months. A piece of advice, it would be better to slow it a bit and make a longer pause on the last frame, I recommend using EZGIF's GIF Maker to set the delay of each frame, which anyone can do, not just the OP.

[Shared Humanity]

Thank you for the translation. My comment was rude.

[nukefix]

Large cracks visible on S-1 acquisition today - more calvings imminent. Also the radar-shadow in the main trunk looks exceptionally high indicating tall calving front.

[NotaDenier]

LOL. Thanks for translating Oren. I think whatever crappy gif maker I used reduced the resolution too.

Crack is getting wider.

[Espen]

Jakobshavn Isbræ :
A large calving will soon happen again - watch the very deep crevasses near the calving front - it could well be beyond the retreat record set on August 15 - 16 2015.

!This animation is a combination of Landsat 8 and Sentinel 2 Data!

Please click on image to enlarge and animate!

[johnm33]

Given it's position and durability I suspect the crack is caused by a rising giant pushing up through the overburden of lighter glacial ice fed into by the main flow from the sides. So when it goes it should be like a logjam bursting.

[nukefix]

John the fjord is filled with ice until the bottom since the grounding-line is very near or at the calving front.

[A-Team]

we know from drilling and a zillion overflghts of ice-penetrating radar the glacier is packed top to bottom with solid ice its entire length.

True. Except during melt season large pulses of fresh meltwater can quickly drain down moulins and fissures to channel conduits at bedrock bottom and out the fjord, churning warm seawater below the calving front while lubricating glacial advance.

Jakobshavn Isbræ - A large calving is underway June 15 2021 beyond the record retreat line of August 15 2015 (not shown) as the speed (not calculated) may be approaching the maximum ever recorded 55 m/day (corporate billboard obscures critical sub-stream).

How can this be, given that it is ruled out by high confidence community consensus peer-reviewed theoretical models of Jakobshavn Isbræ that, while never really tested, accurately describe its future behavior to the end of time.

Low tech tools such as commonsense, satellite pictures and advancing climate change markers are thus misinterpreted to the extent they contradict the model, confusing what the glacier is actually doing with what it should be doing. 

Even with melt season having two full months to go before reaching the previous peak -- and despite the fjord completely losing its retarding melange -- we can be sure that the current aberration is just that, an exception proving the model rules.

https://tc.copernicus.org/articles/15/407/2021/ I Joghin et al 2021
https://tc.copernicus.org/articles/14/211/2020/  I Joghin et al 2020
https://tc.copernicus.org/articles/12/2087/2018/  I Joghin et al 2018
https://tinyurl.com/ejxyfwtw I Joghin et al 2017
https://tc.copernicus.org/articles/8/209/2014/  I Joghin et al 2014
https://tinyurl.com/9tsca4v I Joghin et al 2012
https://tinyurl.com/7xwwfrzm I Joghin et al 2010
https://tinyurl.com/7dfwr8ry I Joghin et al 2008
https://tinyurl.com/yp9nyt79  I Joghin et al 2004

[Tor Bejnar]

Some A-Team snark is good news 
(It means they're back)

[SteveMDFP]

True. Except during melt season large pulses of fresh meltwater can quickly drain down moulins and fissures to...

To echo Tor, it's a great pleasure and relief to see A-Team contributing on the forum. 

[Espen]

Thanks to A-Team for his contribution:

"A large calving is underway June 15 2021 beyond the record retreat line of August 15 2015 (not shown)"

As mentioned somewhere above , there is no High Resolution data / images from August 15 2015, at that time only Landsat 8 existed, Sentinel entered the scene in 2017, Nasa World View indicates there is a further retreat on Aug 15 than Aug 16 2015,  but I chose not using that as documentation because of the low quality of the images.
And to support A-Teams argument, the glacier is only doing what it supposed to do, that is moving and subsequently calving.

[Jim Hunt]

Welcome back A-Team 

[nukefix]

As mentioned somewhere above , there is no High Resolution data / images from August 15 2015, at that time only Landsat 8 existed, Sentinel entered the scene in 2017, Nasa World View indicates there is a further retreat on Aug 15 than Aug 16 2015,  but I chose not using that as documentation because of the low quality of the images.

Actually there is S-1 data in 2015 but I'm not sure if any were acquired in August. TerraSAR-X data certainly exists but it is harder to obtain. This plot is from Joughin's 2018 paper:

[NotaDenier]

I’ve been told the calving front is 5km wide and looking at the pictures it appear the glacier would need to retreat around 12 km to reach the (what I’ve been told) 115 degree bend. Would someone smarter than me verify those numbers?

Note: I am not suggesting this would happen this year, or in the next 20, I’m just curious on the distance.

What I picture happening eventually is the glacier retreating far enough up stream that ice falls into the ice canyon from the sides and flows out to the sea allowing a much larger calving front. Though a negative feedback would be the fjord getting jammed up by the rapid calving of ice.

[Espen]

Nukefix wrote: Actually there is S-1 data in 2015 but I'm not sure if any were acquired in August.
No there is no S-1 HR data available between Aug. 7 and Aug. 19 2015.

[Espen]

 (corporate billboard obscures critical sub-stream)

Instead of peer-review, pay-per-view could be an option?

[Espen]

I am still wondering where this came from:
Jakobshavn Isbræ - A large calving is underway June 15 2021 beyond the record retreat line of August 15 2015 (not shown) as the speed (not calculated) may be approaching the maximum ever recorded 55 m/day (corporate billboard obscures critical sub-stream).
I never composed this!

[oren]

I believe A-Team (welcome!) composed a future headline to contrast what the glacier will (most probably) be doing with what the conservative scientific consensus expects.

[gerontocrat]

What with no NSIDC to worry about, I have time to post about acouple of thoughts that have been niggling me about Jakobshavn Isbræ /  Ilulissat Isfjord.

A post a day or two ago questioned whther the melange in the fjord of the glacier front could slow things down.

Baffin Bay melts out earlier than it did in the 1980's, 1990's and 2000's, though this is not so in the 2010's. However, 2020 and 2021 show early melt. (see 1st attachment).  More importantly, the melt always starts up the West coast. By May 1st this year, the seas around Jakobshavn Isbræ /  Ilulissat Isfjord were open water with above zero temperatures (attachment 2). By now, land temperatures at low altitudes are well above freezing.

It would seem to me that melting in the fjord must start earlier and be stronger than in previous years.

On the other hand, Greenland is losing mass, in that area to well inland by more than 5 tons per m² since 2002. (3rd image attached). 5 tons a m² is 5 million tons a km2. I don't know what is the area that composes the catchment area of the glacier. But it must mean that there is a lot less weight for gravity to work on. Is there any studies on how this effects the rate of glacier flow? (There is a recent study on how loss of elevation through mass loss may increase surface melt - lower elevation = higher temperature.)

[NotaDenier]

On the other hand, Greenland is losing mass, in that area to well inland by more than 5 tons per m² since 2002. (3rd image attached). 5 tons a m² is 5 million tons a km2. I don't know what is the area that composes the catchment area of the glacier. But it must mean that there is a lot less weight for gravity to work on. Is there any studies on how this effects the rate of glacier flow? (There is a recent study on how loss of elevation through mass loss may increase surface melt - lower elevation = higher temperature.)

Per this website a ton of ice is 1.3 x 1.3 x 1.3 meters a side.

https://www.answers.com/Q/How_big_is_a_ton_of_ice

So math, if you make that same ton of ice a 1 meter by 1 meter it’s depth would be 2.197 meters.  Someone please correct me if I’m wrong.

So the entire side of Greenland in your picture has slumped/melted 11 meters in the last 20 years? With reported ice cliff heights at Jakob over 100 meters I’m not sure 11 meters makes a difference?

https://en.m.wikipedia.org/wiki/Jakobshavn_Glacier

Per Wikipedia the glacier got taller by around 30 meters over the last 5 years.

There is also an explanation for why the glacier slowed down after 2015.

https://www.nbcnews.com/mach/science/key-greenland-glacier-growing-again-after-shrinking-years-nasa-study-ncna987116

https://www.nature.com/articles/s41561-019-0329-3/

Abstract
Jakobshavn Isbrae has been the single largest source of mass loss from the Greenland Ice Sheet over the last 20 years. During that time, it has been retreating, accelerating and thinning. Here we use airborne altimetry and satellite imagery to show that since 2016 Jakobshavn has been re-advancing, slowing and thickening. We link these changes to concurrent cooling of ocean waters in Disko Bay that spill over into Ilulissat Icefjord. Ocean temperatures in the bay’s upper 250 m have cooled to levels not seen since the mid 1980s. Observations and modelling trace the origins of this cooling to anomalous wintertime heat loss in the boundary current that circulates around the southern half of Greenland. Longer time series of ocean temperature, subglacial discharge and glacier variability strongly suggest that ocean-induced melting at the front has continued to influence glacier dynamics after the disintegration of its floating tongue in 2003. We conclude that projections of Jakobshavn’s future contribution to sea-level rise that are based on glacier geometry are insufficient, and that accounting for external forcing is indispensable.

[nukefix]

So the entire side of Greenland in your picture has slumped/melted 11 meters in the last 20 years? With reported ice cliff heights at Jakob over 100 meters I’m not sure 11 meters makes a difference?

No, it depends on where you are. The resolution of GRACE & GRACE-FO is around 300km so you need other sensors to pinpoint the mass-loss, for example altimeters:

https://earth.esa.int/eogateway/news/systematic-swath-elevation-and-monthly-dems-over-the-greenland-ice-sheet-margin-from-cryosat

[gerontocrat]

Jakobshavn - glacier & drainage basin.

I guess the 30 metres height increase refers to the glacier itself. I found one reference to say the entire catchment area is 110,000 km2 (can I find a map? - no), which on average has lost at least 5 million tons of mass per km2. So that is at a guess 550 GT less ice today than in 2002 wanting to flow to the sea.

An article from May 2019 (link in italics below) confirms that the drainage basin as a whole is losing ice depite the growth in the glacier itself. And this year it's all bets off?

http://www.esa.int/Applications/Observing_the_Earth/Jakobshavn_Isbrae_Glacier_bucks_the_trend

10 or 11 metres elevation loss doesn't sound a lot, maybe. It seems if the air is fairly dry, "the lapse rate" i.e. temperature drop per 100 metres is about 1^o Centigrade, so 10 metres say 0.1 ^o Centigrade. That can make all the difference, so the climate scientists tell us.

ps:-

The resolution of GRACE & GRACE-FO is arounf 300km so you need other sensors to pinpoint the mass-loss, for example altimeters:

The data from GFZ (the German end of the GRACE-FO project) for Feb-21 gives a total mass loss since 2002 in Basin 6 ( the middle of the western half of Greenland ) as 1,997 GT with a 1-sigma value of 10.5 GT. I am not sure if they are combining GRACE-FO data with Cryosat-2*** to greatly improve resolution in the data by basin on their website, and it is that data that I use.

***https://www.mdpi.com/2072-4292/11/2/144

[oren]

Per this website a ton of ice is 1.3 x 1.3 x 1.3 meters a side.

https://www.answers.com/Q/How_big_is_a_ton_of_ice

So math, if you make that same ton of ice a 1 meter by 1 meter it’s depth would be 2.197 meters.  Someone please correct me if I’m wrong.

This is horribly wrong, sorry.
Never take advice from people using inches, feet and yards. The reply itself has wrong math, 3 feet 3 inches is not 1.3 yards. In any case, density of ice is 0.9168 g/cm3, and a 1x1x1.09m block pf ice weighs 1 ton. So mass loss of 5 ton/m2 means a slump of ~5.5m.

Edit: that answer gave 1.3 cubic yards, but in any case always best to seek metric system answers.

[AbruptSLR]

Jakobshavn - glacier & drainage basin.

...
I found one reference to say the entire catchment area is 110,000 km2 (can I find a map? - no), which on average has lost at least 5 million tons of mass per km2.
...

Attached is a figure from AR5 that shows the catchment area for Jakobshavn.

[gerontocrat]

Jakobshavn - glacier & drainage basin.

...
I found one reference to say the entire catchment area is 110,000 km2 (can I find a map? - no), which on average has lost at least 5 million tons of mass per km2.
...

Attached is a figure from AR5 that shows the catchment area for Jakobshavn.

Well, that map (& Oren's correction of the arithmetic) clobbers my speculation on mass loss. The drainage basin extends well into the high interior, where all the GRACE data says that mass is increasing.

But I will stick with my other bit - the melange in front of the glacier front is year by year more vulnerable to melt.

[nukefix]

GRACE's resolution is too low, radar altimeters see more detail in where the surface is lowering:

http://products.esa-icesheets-cci.org/products/downloadlist/SEC/

[Espen]

Jakobshavn Isbræ - The suspicious days mid August 2015 - Judge for yourself!

Please click on image to enlarge and animate!

[Alphabet Hotel]

Extreme zoom on the calving front, June 12, 2021

2.5 MB PNG

[Espen]

Jakobshavn Isbræ - Due to the weather at the location - Sentinel 1 data is used combined with Landsat 8 data .

Please click on image to enlarge and animate!

[nukefix]

Big calving appears to have taken place in the Northern side before the 18th.

edit: On comparison with Espen's June 14th image, the situation appears to be quite static. Still waiting for next calving...

[nukefix]

..same in 3D.

[Tor Bejnar]

The North Branch of the Jakobshavn Glacier's large calving about June 6 (+/- 1 day).  Anyway, a GIF made from 5 (not evenly spaced) dates in June 2021 from Sentinel Playground showing the calving: June 2, 5, 7, 10 and 17.  The calving caused much movement of mélange, compared to before and afterwards. (Why you don't want to be in a boat near a large calving...)  Also of interest is the ebb and flow at the bottom of the images between North Branch and South (east) Branch derived mélange.  And the amount the North Branch has advanced since the calving... [click to enlarge & run, apparently.]

[NotaDenier]

Slight changes on south branch.

[NotaDenier]

After around a month another calving.

[Espen]

Heavy calving activities at Jakobshavn, and the retreat position is very close to where it was on August 15 2015, but due to bad weather it is difficult to show.

[nukefix]

Radar to the rescue! Unfortunately the north branch is on the next S-1 slice but this is where the records are set. I let some coastline in for easier alignment with optical data.

[Espen]

Jakobshavn Isbræ - Heavy calving, but not there yet.

Please click oin image to enlarge and animate!

[Tor Bejnar]

If it would just calve but not advance at all we'd get to a new record fast!  But no, the glacier insists on sending new ice to replace the old.
 

[NotaDenier]

July 2nd vs 8th

[Espen]

If it would just calve but not advance at all we'd get to a new record fast!  But no, the glacier insists on sending new ice to replace the old.
 

It is called Natural Replenish Service or NRS?

[NotaDenier]

Was there a slump on the north side of the south ice stream? Looks different…

[Alphabet Hotel]

July 02, 08, 10, 12, 15, 17, 18

A lot to look at here

6.5 MB animated GIF, click to animate

[Stephan]

Thank you, very interestng.
How damn fast is this icestream? It looks more like an ice-highway...

[oren]

I seem to recall up to 40 meters per day. A highway indeed.

[Stephan]

This is almost three centimeters per minute. You could really watch it flow...

[oren]

Some actual data, from A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity by Ian Joughin et al.



Figure 2(a) Terminus position (T: black circles) and position 1 km upstream of annual minimum terminus extent (Tmax−1 km: brown dots). Terminus positions are given as distances measured relative to the seaward origin of our reference profile (see Fig. 1), and the arrows show the direction of retreat and advance. Two points in 2014 were excluded in determining Tmax−1 km (see text). The blue squares indicate when rigid mélange was present in front of the terminus at the locations indicated by the blue boxes in Fig. 1. (b) Elevations of the points M6 (red) and M9 (gold) extracted from all available DEMs along with the inferred flotation height, hfT (grey), at the terminus. (c) Surface speeds through time extracted from a TerraSAR-X/TanDEM-X velocity time series, with a few points from summer 2019 derived using COSMO-SkyMed data. See Fig. 1 for the locations of points M6–M26. The black circles indicate the speed at Tmax−1 km. Because this minimum position is updated annually, unlike the static points, there are discontinuities at each year boundary since the sampling point location changes (e.g. brown points in the top plot). The average summer (1 June to 30 September) speeds are shown as red bars for the five summers when the terminus was most retreated (2012–2016). A linear fit (r2=0.91, p=0.013) to these summer averages is shown with a black line that extrapolates the trend through 2019.

40 m/d is 14.6 km/year, so max speed was actually higher than 40 m/d in 2012 and even summer average speed was higher than that.
One can also see that max retreat (temporary) was reached in 2015.

[Espen]

Jakobshavn Isbræ: There is a very good chance we have a new record retreat on July 25 2021. As soon I have reliable high resolution data it will be published on this site!

Please click on image to enlarge and animate!

It is not there yet!

[Tor Bejnar]

I'm confused:  you write "It's not there yet," yet the frame labeled 2021 clearly has the south branch glacial snout further inland (along at least most of the terminus) than the frame labeled 2015 does.

[FredBear]

The more modern image also has the snow line on the surrounding land retreating north and south of Jakobshavn Isbræ - melt has been quietly continuing.