Petermann Gletscher / Petermann Fjord / North West Greenland

[Hunter]

Might have a pic for you later on, flew over Petermann about 2 hours ago.

[Hunter]

Credit NASA

[Hunter]

Credit NASA

preliminary data plot not for scientific use.

Last pic is the Kee Bird as it sits today.
https://en.wikipedia.org/wiki/Kee_Bird

[Tealight]

Scientists just found a strange and worrying crack in one of Greenland’s biggest glaciers https://www.washingtonpost.com/news/energy-environment/wp/2017/04/14/scientists-just-found-a-strange-and-worrying-crack-in-one-of-greenlands-biggest-glaciers

This crack was already known in December last year. I posted an image of it in Reply #438 on: December 01, 2016, 09:39:09 PM »
S1B_20161201_Petermann.jpg (1840.12 kB, 2260x1624 - viewed 79 times.)

[oren]

Hunter, thanks for the amazing images.

[Neven]

This crack was already known in December last year. I posted an image of it in Reply #438 on: December 01, 2016, 09:39:09 PM »
S1B_20161201_Petermann.jpg (1840.12 kB, 2260x1624 - viewed 79 times.)

I remember that, and I believe Andreas Muenchow has also mentioned it, if memory serves me well.

[Cate]

Hunter, thanks for the amazing photos and the link re the Kee Bird---very informative.

[Adam Ash]

'A sensor in 3,000-foot-deep waters had found that in the warm, salty Atlantic layer, temperatures were even warmer than just a year earlier, in 2015. Those waters are likely flowing toward Petermann glacier’s grounding line and helping to melt the shelf from below.'

http://www.washingtonpost.com/sf/business/2016/12/30/with-enough-evidence-even-skepticism-will-thaw/?utm_term=.62144c2fdb37

Great views of the Petermann and Jakobshavn canyons in the video on this page too
The canyon feeding Petermann gives a direct connect to all of inland Greenland.  Huge, and its already melting into a groove...
https://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=4097
Video at:  'The Earth layer alone with transparency at gamma 1.0.'

[AndrewB]

WaPo: NASA just snapped the first photos of a mysterious crack in one of Greenland’s largest glaciers

https://www.washingtonpost.com/news/energy-environment/wp/2017/04/15/nasa-just-snapped-the-first-photos-of-a-new-crack-in-one-of-greenlands-largest-glaciers/?utm_term=.e72ad91835e0

[Xela]

This crack was already known in December last year. I posted an image of it in Reply #438 on: December 01, 2016, 09:39:09 PM »
S1B_20161201_Petermann.jpg (1840.12 kB, 2260x1624 - viewed 79 times.)

I remember that, and I believe Andreas Muenchow has also mentioned it, if memory serves me well.

According to Andreas Muenchow https://twitter.com/AndreasMuenchow/status/852491527796523008 and Stef Lhermitte https://twitter.com/StefLhermitte/status/852873863427969024 it seems like it's a new crack.

More here: https://twitter.com/Petermann_Ice

[Cate]

NASA blog today on the new crack in Petermann.

https://earthobservatory.nasa.gov/blogs/earthmatters/2017/04/24/petermann-glaciers-new-crack/

More details here:

https://earthobservatory.nasa.gov/IOTD/view.php?id=90043

[Tor Bejnar]

I've been thinking about that new crevasse (rift, crack) that appears to 'start' at the longitudinal trough (river bed, "feature") that runs down the middle of Petermann Glacier. (screen shot from the 2nd link above) 

... Brunt points out that the rift currently appears to end at a feature running down the center of the glacier. “That’s pretty typical,” she said, citing similar occurrences on ice shelves in Antarctica. ...

I'm surprised this is "typical"! Why would ice shelves have a mid-glacial river bed at which rifts start or end? (I'm confused, unless she's referring to chevron cracks that form semi-parallel relatively short cracks when a somewhat brittle material [like a glacier or ice shelf or cheese or clay] is stretched.) 

I wonder if there might be a longitudinal weakness (crack) that runs under the mid-glacier river bed, with the left side of the glacier moving slightly faster than the right side, providing a triple-point.  (Pure speculation!)


I will want to watch this new rift, and see if it connects with other known cracks or the sides of the glacier.

I'm of course also watching what appears to be a completed rift around the right end of the glacier (see my previously post (March 14, 2017), above).

[Tealight]

For a change here are some non-cracking news.

The terminus of Petermann Glacier is mostly blown snow free and left behind blue ice. It looks like several melt lakes survived the winter and appear in a deeper blue. I would really like to know how deep they are and how thick the ice cover is.

[DrTskoul]

Neat!!

[sidd]

Very nice pictures.  Are they draining off the edge as in the Bell paper ? doi:10.1038/nature22048

I commented on that paper here :

https://forum.arctic-sea-ice.net/index.php/topic,622.msg111095.html#msg111095

Ifso that is a stabilizer.

sidd

[Tealight]

Very nice pictures.  Are they draining off the edge as in the Bell paper ? doi:10.1038/nature22048
...

Most of the lakes are on the part that is about to calve and probably don't have and any effect on stability.

I've been thinking about that new crevasse (rift, crack) that appears to 'start' at the longitudinal trough (river bed, "feature") that runs down the middle of Petermann Glacier. (screen shot from the 2nd link above) 

... Brunt points out that the rift currently appears to end at a feature running down the center of the glacier. “That’s pretty typical,” she said, citing similar occurrences on ice shelves in Antarctica. ...

I'm surprised this is "typical"! Why would ice shelves have a mid-glacial river bed at which rifts start or end? (I'm confused, unless she's referring to chevron cracks that form semi-parallel relatively short cracks when a somewhat brittle material [like a glacier or ice shelf or cheese or clay] is stretched.) 

I'm not sure there is something as typical rifts/cracks. If something is typical then a glacier flows fasted in the middle, where the ocean is deepest and the lowest friction occurs. Because of the higher speed, the centre of the glacier detaches (cracks) from the main glacier before the sides do. But Petermann Gletscher is squeezed through a small fjord and the edges constantly grind along the rock. If the ice gets struck then cracks develop from the sides.

By the way the centre crack already cut through the main drainage channel. Not good for any rafting fan.

[TerryM]

Tor
You might want to explore
https://icyseas.org/




I thing you will find many of your questions about the underside of Petermann answered.


Terry

[Thomas Barlow]

Any thoughts on the state of the Petermann Glacier right now, May 27, in relation to open Nares and Lincoln Sea, and warmer SSTs ? And likely near future?

[Thomas Barlow]

http://glacierhub.org/2017/05/18/dont-step-on-the-crack-at-petermann-glacier/

[oren]

Any thoughts on the state of the Petermann Glacier right now, May 27, in relation to open Nares and Lincoln Sea, and warmer SSTs ? And likely near future?

I'm not sure if Petermann is affected by the opening of Nares or not. But in any case it will be interesting to note when the sea ice clears from inside the fjord, and compare it to previous years.

[Thomas Barlow]

What's interesting in the long-term, is that the Petermann valley appears to be an almost totally sub-sea-level valley, and maybe the only one that goes all the way to the ancient inland sea of Greenland !
https://arstechnica.com/science/2014/05/greenland-may-lose-more-ice-than-expected/

[johnm33]

We're in a period of peak tides, with a couple of days to go, the break up in Lincoln can only let in more N Atlantic water which flows far into the fjord. I don't expect anything major in the next few days, but we'll see,

[TerryM]

We're in a period of peak tides, with a couple of days to go, the break up in Lincoln can only let in more N Atlantic water which flows far into the fjord. I don't expect anything major in the next few days, but we'll see,

I don't see the connection between the break up of Lincoln Sea ice & more water flow into Petermann Fjord. What am I missing?
Terry

[Thomas Barlow]

Accumulated (melting - mass loss or gain) Anomaly since Sept. 1 2016:
http://polarportal.dk/en/groenlands-indlandsis/nbsp/isens-overflade/

[Thomas Barlow]

We're in a period of peak tides, with a couple of days to go, the break up in Lincoln can only let in more N Atlantic water which flows far into the fjord. I don't expect anything major in the next few days, but we'll see,

I don't see the connection between the break up of Lincoln Sea ice & more water flow into Petermann Fjord. What am I missing?
Terry

Maybe the almost consistent warmer air and SST anomalies going for months now, in the Nares, links then all? And this has led to the early Lincoln break-up, which will probably just accelerate now, and expand. And the SSTAs will infiltrate the bay, and, by summer, the glacier terminus, as air temp. anomalies settle over the glacier itself.

The reason I went looking for glaciers in the area was because of what was happening in the Nares and Lincoln right now. I thought a while back, I wonder if the event goes beyond just the channel and the 'sea'? Turns out there is probably a correlation.

[TerryM]

We're in a period of peak tides, with a couple of days to go, the break up in Lincoln can only let in more N Atlantic water which flows far into the fjord. I don't expect anything major in the next few days, but we'll see,

I don't see the connection between the break up of Lincoln Sea ice & more water flow into Petermann Fjord. What am I missing?
Terry

Maybe the almost consistent warmer air and SST anomalies going for months now, in the Nares, links then all? And this has led to the early Lincoln break-up, which will probably just accelerate now, and expand. And the SSTAs will infiltrate the bay, and, by summer, the glacier terminus, as air temp. anomalies settle over the glacier itself.

The reason I went looking for glaciers in the area was because of what was happening in the Nares and Lincoln right now. I thought a while back, I wonder if the event goes beyond just the channel and the 'sea'? Turns out there is probably a correlation.

Petermann's sill is located in the Lincoln Sea, but ice cover there has no effect because of stratification. I have noticed large MYI bergs caught in the Hall Basin Gyre that bumped hard against solid FYI in the fjord which may have put sudden pressure on the glacial tongue, but these didn't result in calving.
As far as warming the air over the glacier you have to remember that cold air follows a glacier down hill and blows any SST warmed air away from the glacier.


http://muenchow.cms.udel.edu/papers/29-4_munchow.pdf


Fig. 1 shows the location of the sill.


As far as I know neither SST nor ice cover has any connection to calving of marine terminating glaciers. The deeper, warmer waters undercutting the tongue eventually lead to calving. 


Terry

[Thomas Barlow]

The reason I went looking for glaciers in the area was because of what was happening in the Nares and Lincoln right now. I thought a while back, I wonder if the event goes beyond just the channel and the 'sea'? Turns out there is probably a correlation.

Petermann's sill is located in the Lincoln Sea...
As far as warming the air over the glacier you have to remember that cold air follows a glacier down hill and blows any SST warmed air away from the glacier.

As far as I know neither SST nor ice cover has any connection to calving of marine terminating glaciers. The deeper, warmer waters undercutting the tongue eventually lead to calving. 
Terry

I see. Thanks.
I'm not sure what the relationship of the 'sill', deep in the Lincoln Sea to Petermann's can be? That seems to refer to ancient geology? Where the ancient geological terminus of a much bigger multi-glacier complex may have been?
That warmer SSTs could flow into the fjord seems plausible. Or just getting warmed on the spot by the regional effect of lowered albedo (ever since the sun hit this spot in mid-March), causing warmer air temps than usual. The regional effects of such a huge area of dark water seem probable.

It does seem to me that the air would be in a constant flow down the valley, day and night, unlike a valley outside the Arctic circle (where it alternates wind direction, day and night, due to difference in warming and cooling rates of land and sea-surface, but I'm not sure how that would work on a glacier.) It seems that the wind would be constantly flowing down the valley, day and night, as you suggested?

As in the above image of accumulated melting anomalies (presumably meaning surface air temp. anomalies as well - by correlation), it seems that the glacier has warmer than usual air temps., and that must be because of a regional effect, most likely connected to the low albedo in the Nares, and now the Lincoln. Just guessing. Maybe not?

I think the top image here could have a melting effect on the Fjord sea-ice, compared to the lower one from (roughly) the same date in 2016 for example ? The earlier in the season the sea-ice in the fjord melts (which I think it will - it is more than a month ahead in the Nares right now), surely that will have an effect on the terminus of the glacier itself? Maybe my understanding of glaciers and fjords is too limited.

[TerryM]

TomB


Interesting discussion, but I'm off to a monthly dinner. If you ever stand at the foot of a glacier you'll face a very chilling wind (breeze is too soft a word) coming from the ice. There are two names for this wind, both which escape me for the moment. (one is specific to Greenland)


The sill is the lowest obstruction that water has to clear before it can get to the calving front. Because of stratification the depth of the sill regulates the temperature of the water that attacks the calving front. Lower sill, warmer water. Afraid this may not even be clear - but I really have to run.


Give my link above a read - its up to date and the author drops by here!


Have Fun
Terry

[oren]

TB, there is a sill between the fjord and Nares Strait. The fjord is actually deeper.
As for effects of early Nares clearing on local glaciers, I would first look at Humboldt glacier, draining into Kane Basin, as it is far wider and its calving front much closer to the area of action. http://forum.arctic-sea-ice.net/index.php/topic,800.0.html
Petermann is much more stable than other Greenland glaciers, despite several massive calvings in the last few years.
In general I agree with the statement posted up-thread that marine-terminating glaciers are not affected by sea ice cover nearby, and are mostly affected by deeper water temps and currents. I personally believe Zachariae Isstrom is a rare exception, where the calving area is covered by sea ice year-round except some years in August, and the sea ice and iceberg melange is compressed against rocks further ahead, potentially slowing the glacier somewhat. Not albedo, but a small buttressing effect. Even this is just my personal layman opinion, with lots of caveats and unsupported by science. Other potential effects might be more waves and storms when sea ice is absent, but this requires a larger body of water, not a narrow fjord.
Note in the Nares albedo plays a much smaller role than usual as there is an almost-constant southbound current, carrying any accumulated heat out of the Arctic proper. Perhaps if the sea ice were to clear inside the Petermann fjord itself much earlier than usual, then accumulated heat might have some small effect on the glacier. But remember that the thickness of the floating part of the glacier is around 200 meters, and the calving is usually along cracks developing behind the front. Hard to affect by sea surface temps.
Hope this mess is somewhat helpful...

[Thomas Barlow]

Hi Terry and Oren.
Thanks, that makes sense.
The warmer Atlantic water is percolating in over the sill and all the way into the grounding line of Petermann's with water that is at or above 0C.
So I could see how that is more constant temp., and not affected by the surface water, as you pointed out.
---> http://www.pressherald.com/2016/12/30/greenlands-thaw-melts-a-climate-change-skeptic/

“Flow of Atlantic waters into Nares Strait and into Petermann Fjord thus originates from the Lincoln Sea in the north where deep ocean temperatures at sill depth frequently exceed 0.3°C (de Steur et al., 2013). This water is warm relative to the −2.2°C pressure-dependent in situ freezing point at the base of the ice shelf …This observed heat flux is three times larger than the 1.1 × 1011 J s–1 required to melt the ~12 Gt yr–1 of ice that crosses the grounding line: for the ice shelf at its historical minimum extent of ~70 km long and 15 km wide, this is equivalent to an aerial average melt rate of 9.7 m yr–1”
http://muenchow.cms.udel.edu/papers/29-4_munchow.pdf

I guess my question to Andreas Münchow would be, has this Atlantic water flowing into the Petermann fjord become warmer because of global warming (of N. Atlantic), or has it always just eaten away at the grounding line, with enough new ice being created above, on the surface of the glacier to more than make up for the loss, increase/sustain overall mass (eg, pre-1970)?
In other words, is the main degrading of these glaciers from recently increased warmth in Atlantic waters (which seems to be suggested in the paper, but I'm not clear on it), or is potential glacier weakening coming from there being less new ice being created above? Or both equally bad?

However, I think, if the SSTs are warmer than usual in the region, the air temps will be warmer than usual, and the melting anomaly (since Aug. 2016) I posted above (Polar Portal), in the Petersonn valley, must be related to this SST anomaly? How else could a valley be warmer (melting more) than usual? Where could that warm air come from?

Can meltwater cut into a glacier causing rifts, sinkholes, and cracks? So if a weakness shows at, or near, the grounding line (or elsewhere), could that crack not be hugely exacerbated by increased meltwater on the surface of the glacier? (I think the warmer SSTs - and even lower albedo - on the Nares and Lincoln could cause the air to be warmer than usual. Can that air rise into the valley? (and the Nares has been open all winter).
I can't think what explains the extra melt anomaly in that valley, especially since it seems to face NW. Perhaps, during the day, with warmer, open water, the sun's heat is captured by the dark surface, but the albedo on the glacier would warm the air above the glacier during the day. That could cause warm, sea-level air, to rise up the valley because warm air above glacier has to rise, leaving a vacuum that must be filled (similar effects occur in valleys outside of Arctic circle, and reverse at night - wind direction changes).

If that melting anomaly goes away (it seems more at Petermann's than Humbolt right now), then that is different. (I agree you would expect to see the same in Humbolt. Humbolt may not show as much melt anomaly because it is a much wider valley? So gets a decent melt most of the time?) But as long as there is more melting than usual in Petermann's, how is that happening, other than warmer air, and is there more of a chance of cracks opening due to warmer air?

It could be that Petermann's is faster moving than Humbolt, and could pile down faster if something loosens, and it has a bigger surface melt anomaly over 10 months now.
Speed --> http://tinyurl.com/yd5cacay
(from : http://climatechangepsychology.blogspot.com/2010/11/nyt-restless-ice-greenlands-glaciers.html)

With all the cracks showing, you guys were talking about, and the melt anomaly in Petersonn's, and the warmer SSTs, and months of winter open water, perhaps something is different this year for this glacier. Worth watching the melt-anomaly this summer maybe.

Anyway, glad to hear the thickness of the glacier could be so thick, and the melt season shorter in that valley, that maybe it will not be too affected.

Thanks for all the info.

[johnm33]

Terry "I don't see the connection" It's easier to know what you think than how you arrived there so I had to think again.
 I was surprised that atlantic waters were making their way through to Nares, and how it was tidally driven, curiously enough in the paper you linked to above.

 The tidal surge of atlantic waters arrives in the north atlantic rather like a wave on a beach, that is there's actual movement of water, from there it follows the path of least resistance. If there's solid ice north of Greenland all the way to Nares even though the atlantic waters are moving at depth, perhaps because, the tidal surge, which is quite small, is supressed and pushed further north, either way it has to displace the water present and force it's way through it. The atlantic water is energetically inclined to continue moving east and from 60⁰N has been directly approaching the axis of rotation, thus prone to generate powerful vortices which will rotate more freely in more open water. In fact it's easier to imagine that it's the pull of high tide in Kane basin that draws the atlantic water into Lincoln/ Nares, where even though it comes from the north it hugs the left coast, indicating it's still turbulent. Once the current punches through, and it's just a little easier to punch through with no solid ice cover,  a residual current becomes established and thus the current builds through the new/full moon tidal peaks.   
Tidal flow, Baffin/Kane need work, gives some indication of times either side of Greenland though.

M2 arctic tides, shows atlantic waters eastward impetus, against the 'natural' E-W movement.

john

[TerryM]

Katabatic winds was of course the name that escaped me last evening, and piteraq winds in Greenland. - Getting old does have it's disadvantages, I can still get there, it just requires more time.


John22
Don't understand your "hugs the left coast", Coriolis effect forces arctic currents to the right, therefor hugging the right coast. In Nares Strait the southerly current flows by Ellesmere while the northerly current hugs Greenland. (except when gyres mess things up.)


TomB
Does knowing that the keel of PII2012 was as deep as the Cheops Pyramid was tall help?


Oren
The sill near the end of Petermann fjord is indeed deeper than the sill out in the Lincoln Sea, so it's the Lincoln Sea sill that determines the temperature and salinity of the water chewing away at Petermann Glacier. I agree that buttressing may slow glacial flow, but don't believe it has a measurable effect on Petermann.


Can I again do a quick plug for:


https://icyseas.org/


This is Andreas Muenchow's blog. He posts here from time to time, is passionate about sharing his extensive knowledge, and has risked much by insisting that the public has the right to know what their tax dollars have helped discover. The blog covers Petermann, Nares Strait & so much more. If I've messed up on this thread it's because I didn't understand what Andreas was saying & if his explanation differs from mine you can rest assured that his is correct.


Terry

[oren]

The sill near the end of Petermann fjord is indeed deeper than the sill out in the Lincoln Sea, so it's the Lincoln Sea sill that determines the temperature and salinity of the water chewing away at Petermann Glacier. I agree that buttressing may slow glacial flow, but don't believe it has a measurable effect on Petermann.

Can I again do a quick plug for:
https://icyseas.org/

Terry you're correct on all fronts, also thanks for reminding me of the admirable Andreas M's blog

[johnm33]

"hugs the left coast" Petermann remains entrenched on the left, and the atlantic waters penetrate to it's grounding line. That implies that the atlantic waters remain 'energetic'.

[Thomas Barlow]

TomB
Does knowing that the keel of PII2012 was as deep as the Cheops Pyramid was tall help?

Interesting.
The problem with that graphic from the news article on Meunchow that I posted above is that it is squished.
The real cross-section would probably look more like this below (or much longer).
So it all depends if those cracks at the grounding line are actually that evident, or if it is just a symbol for much smaller cracks. If the former, then it's bad, especially if anomalous heat in the valley, and melt-fissures are exacerbated.
The floating ice seems vulnerable since it probably does float on the warmer waters.
So now you have warm Atlantic water eating at the grounding line, and presumably rising under the glacier, but added to that, anomalously warm Nares surface water seeping in much more than usual. So the floating ice is more vulnerable this year, and if it recedes, opens up more dark surface water, and I think, warmer air in the valley. Compounding.
It would nice to get a real cross-section, I guess the grounding line does not look as vulnerable as being suggested by some media? Unless there is a lot of seeping surface melt-water at that point.

(PS. I have camped on a glacier, just not one this big)

[TerryM]

"hugs the left coast" Petermann remains entrenched on the left, and the atlantic waters penetrate to it's grounding line. That implies that the atlantic waters remain 'energetic'.

I'm afraid I don't understand what you are saying.


If it's that Petermann Glacier is west of the predominant southerly flow in Nares and is therefore "entrenched on the left" that is of course correct. Petermann Fjord meets Nares Strait at the Hall Basin Gyre and a portion of the WAW (Warm Atlantic Water) that has crossed the sill in the Lincoln Sea crosses the deaper sill near the end of Petermann Fjord, then erodes the base of Petermann Glacier.


When you say 'energetic', are you referring to temperature, mobility or?


The fresh, cold water exiting from beneath Petermann Glacier is ~ 1/2 the flow of the Thames River. In general it exits the fjord flowing above and to the north side of the fjord - again hugging it's right side.


TomB
Going upthread to #403, page 9 and reading forward may help. Over a ~30 period the glacier is thinned from ~600M to ~200M, it's WAW that is responsible & that water is far beneath, and not mixed with surface water. The ice tongue is for the most part floating on fresh, cold water that has exited beneath the glacier mixed with WAW that has been chilled and freshened by it's contact with glacial ice.


Terry

[Andreas T]

Terry, can you point me to a sea floor map of Nares Strait? You say the sill which determines the inflow of denser but warmer Arctic Intermediate Water is in Lincoln Sea?
A brief search brought up this https://books.google.co.uk/books?id=X0PDBca_EqEC&pg=PA137&lpg=PA137&dq=nares+strait+bathymetry&source=bl&ots=o76j8_33Q0&sig=4EQi56TjLDGnFWRtV_TcViR3Kh4&hl=en&sa=X&ved=0ahUKEwjjruTj2pXUAhWrKsAKHUZTAZMQ6AEIOzAC#v=onepage&q=nares%20strait%20bathymetry&f=false
is there a clearer source?

[johnm33]

Terry, as you pointed out water coming from the north should keep right, and deep water from the arctic does, penetrating and clearing the fjords on Ellesmere, the atlantic water behaves differently.
 The last graphic by Thomas Barlow makes me think that even the 2ft. tides hereabouts are going to displace vast quantities of water from beneath the glacier, when low, and when the tide turns the glacier itself acts as a huge vacuum pump, sucking in atlantic waters. IIRC this didn't happen years ago when the ice north of Greenland was thick. If the water was more or less neutral it would not penetrate so deeply, I suspect there would just be just a turnover of waters near to Nares which it seems is what happens with arctic waters. Because it gets to the grounding line implies it has plenty of kinetic energy, it 'wants' to be further east, or at least move eastward, and i suspect it 'wants' to be further from the axis of rotation, thus in it's forced journey around northern Greenland and beneath the glacier it will generate powerful vortices, it may even have had a hand in the breakup of ice by the coast today.   To put it another way if this water was in the vicinity of say the Faroes it would be more stable, far enough away from the axis of rotation and moving east at a comfortable speed. I hope that makes sense.
I was looking at full/new moon times for 2015 to compare to fig.7 above it seems there's a 5-7 day delay to temp./salinity peaks.

[oren]

Andreas, search google for Nares Strait bathymetry. There a paywalled paper from 1986, and there's also this paper by Andreas Muenchow which has a hard-to-read bathymetric map http://muenchow.cms.udel.edu/papers/Nares2011Warming.pdf

[TerryM]

Terry, can you point me to a sea floor map of Nares Strait? You say the sill which determines the inflow of denser but warmer Arctic Intermediate Water is in Lincoln Sea?
A brief search brought up this https://books.google.co.uk/books?id=X0PDBca_EqEC&pg=PA137&lpg=PA137&dq=nares+strait+bathymetry&source=bl&ots=o76j8_33Q0&sig=4EQi56TjLDGnFWRtV_TcViR3Kh4&hl=en&sa=X&ved=0ahUKEwjjruTj2pXUAhWrKsAKHUZTAZMQ6AEIOzAC#v=onepage&q=nares%20strait%20bathymetry&f=false
is there a clearer source?

This isn't the best I've seen, but may be adequate for your needs.


https://icyseas.org/2012/09/02/petermann-ice-island-2012-breaking-up/


Terry

[Andreas T]

I find this 7,2,1 bands image intriguing, usually darker blues indicate water present on the surface. I find it hard to believe that melt onset is earlier on Petermann than anywhere around. Could it be that this is ice swept bare of snow by katabatic wind? My other option would be föhn but why would that be so much stronger at Petermann?
note that the calving front shows up clearly: bluer on the glacier, lighter on the sea ice.

PS  the same feature can be seen last year but there seems to have been more snow generally at the time.

[bairgon]

I had noticed that the brown colour in the valley to the west of the glacier had increased recently. Perhaps the winds are coming from the Strait and blowing south on that valley as well as the glacier, and melting the snow/ice.

[P-maker]

Andreas & bairgon

Katabatic wind is a good candidate for the agent shaping the observed patterns. Perhaps enhanced by a weak Föhn effect. I suggest that bare ice at those latitudes this time of the year is a result of sublimation and NOT melt.

It is often the case in Greenland, that the strongest Katabatic winds occur less than 10 km from the ice edge. You will see some snow accumulation on the sea ice just in front of the glacier snout, and then a wind scoured ice surface further out to the north of the glacier and on the lower part of the glacier itself.

[johnm33]

If the current of atlantic water is powerful enough, and it still has a couple of days to run, it may just break in to the fjords north of Petermann, and generate some upwelling there too.
http://membrane.com/sidd/greenland-2013/
https://go.nasa.gov/2smqvT3
and if not now almost certainly after the next tidal max.

[Tor Bejnar]

Remember that no Nares Strait ice bridge formed during the 2006-7 winter, so as unusual as this year's ice-bridge-free winter/spring is, it it not unprecedented.  (No, it is not a 10-year cycle.)

[ghoti]

There's a new IcySeas blog post up about temperatures rising under the Petermann Glacier.

https://icyseas.org/2017/06/16/is-petermann-gletscher-breaking-apart-this-summer/

[nukefix]

Petermann "wakes up" in July, at least in the past two years. Image source: Enveo Cryoportal

[Thomas Barlow]

I hope some of this is just cloud. I think that is a crack on the left?

[bairgon]

Yep, that does look like a crack on the left?

Yes, looks like it has been developing over the last few days. Animation from 16th June below - it was cloudy before then.

[Espen]

What you are seing is probably a string of melt ponds: