Messages

1

Antarctica / Re: The Ross Ice Shelf Thread

« on: September 25, 2019, 09:21:51 PM »

New and very important crack on the east side - expect major calving relatively soon!

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Antarctica / Re: The Amery Ice Shelf Thread

« on: September 25, 2019, 09:11:07 PM »

Big claving at Amery!

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Antarctica / Re: What's new in Antarctica ?

« on: February 19, 2019, 10:59:28 PM »

Also a very interesting region to watch is around the southern part of the Wilkins Ice Shelf (and its neighbours). The cracks in the picture (Beethoven Peninsula at bottom) will eventually help to break up Wilkins Ice Shelf completely within the next years.

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Antarctica / Re: The Ross Ice Shelf Thread

« on: February 19, 2019, 10:50:53 PM »

Just a comment to Stephans post above: My impression is that it is a piece of old fast ice that broke off, not a real ice berg. But note as well that the major crack directly below the date has expanded several kilometers to the west this year. However, I still expect the next major calving to occur along the even bigger crack behind within the next few years.

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Antarctica / Re: What's new in Antarctica ?

« on: February 19, 2019, 10:45:12 PM »

I just want to draw some attention to a future calving in East Antarctica. I don't know the name of the ice shelf but it's the one directly west of Roi Baudouin Ice Shelf. Big calvings in this area seem to be rather rare.

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Antarctica / Re: PIG has calved

« on: February 19, 2019, 10:34:34 PM »

There seem to be some cracks which will be very important and interesting to watch in the future that nobody seems to have noticed so far. I tried to highlight them together with the bigger known ones. To be clear: I'm talking about the small ones that are the most retreated. Probably you have to watch the original Sentinel pic yourself in order to see them properly.

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Antarctica / Re: PIG has calved

« on: October 06, 2018, 08:51:19 PM »

Action! That's a serious one!

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Antarctica / Re: Rift in Filchner-Ronne Ice Shelf

« on: September 22, 2018, 01:27:43 PM »

My understanding is also that the rift will propagate parallel to the front but there are also some cracks perpendicular to the front which will split the developing ice berg into parts. As Grygory suggests, and similarly to Larsen C, there are areas in the ice shelf where two ice streams merged (suture zones) which can prevent rift propagation for some time because the ice lost the nicely ordered structure there. Further inhibiting rift propagation at the Ronne ice shelf is bottom accumulation stemming from refreezing supercooled water originating somewhere at greater depth near the grounding line. That can close newly formed rifts again.  However, now we have the left hand side of the ice berg essentially dangling freely and it can move back and forth with the tides etc. It is a huge lever and and should be able to open the rift much faster than before. That was also the case at Larsen C and was the reasoning behind my previous comment about a calving event rather soon. "Soon" in this context may still mean several month to probably a couple of years...

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Antarctica / Re: Rift in Larsen C

« on: September 22, 2018, 11:53:40 AM »

Well, we can look at the first Sentinel pictures of the year to try to answer this question. It looks like not much happened. The cracks in that opened when the berg was still attached are still there and the old cracks to the northeast didn't really open up. But one can see three small new cracks along the innermost old one... The effects of the repeated collisions between the berg and the shelf seem to be mostly limited to the (shelf) ice edge where ice was piled up.

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Greenland and Arctic Circle / Re: Greenland 2018 melt season

« on: September 07, 2018, 12:39:19 PM »

I wonder what the mass balance measurements will tell us, especially from the Q-transect (hopefully in the Arctic Report Card). I have been in South Greenland this summer and it was wet. Still, I noted that on a cold and very foggy/rainy day about 10-15 cm of snow melted off a snow patch. In the evening there was even some fresh snow/sleet falling and the next day was cold as well but became sunnier. The snowline moved back up to about 2000m that day. My guess is now that all this humidity might have melted a lot of snow/ice in the lower elevations of the south but may have accumulated significantly higher up. Therefore I expect a steep mass balance gradient.

I don't really know what is a normal melt rate but during a stay at the same location a few years ago roughly one meter melted in 1,5 weeks during sunny and warm weather. 

11

Greenland and Arctic Circle / Re: Canadian glaciers face 'big losses'

« on: September 07, 2018, 12:24:56 PM »

The prediction is that there will be more snow in winter but it will (on average) melt earlier in a warmer climate. Both effects combine to warm up permafrost. The runoff of fresh water may also influence oceanic currents.

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Antarctica / Re: Rift in Larsen C

« on: September 07, 2018, 12:20:40 PM »

Nice animation from Adrian Luckman:
https://adrianluckman.wordpress.com/2018/09/05/iceberg-a68-escapes-into-the-weddell-gyre/

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Antarctica / Re: Antarctic images

« on: September 07, 2018, 12:18:08 PM »

Good spotting Grygory! I haven't noticed this but I watched another crack further to the east expand maybe two years ago. The long one will connect to this and a calving might occur rather soon.

14

Antarctica / Re: Halley base shut down and new crack in Brunt shelf

« on: January 13, 2018, 08:31:47 PM »

I'm still wondering how things will unfold at Brunt. Currently my best guess is that the chasm will connect to the Halloween crack somewhere behind the Mc Donald ice rise. Still 10 km to go though. The Halloween crack still seems to terminate on the wrong side of the ice rise and I guess a second parallel crack will form just next to it close to the ice rise to eventually relase the big ice berg. The result could be a complete disintegration of the Brunt ice shelf because the ice closer to the coast seems to be much weaker and the connection to the Mc Donald ice rise would be narrow and unstable (in case the chasm terminates downstream of the ice rise). I even wonder whether the Stancom-Wills ice tongue could react to this and start to bend over because of the pressure of the ocean current. In an extreme scenario it may even break off. Any other ideas?

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Antarctica / Re: Halley base shut down and new crack in Brunt shelf

« on: January 13, 2018, 08:19:32 PM »

Yes. This seems to be the normal behavior. Wait until mid February or March, then the iceberg will start to move again. Usually rather fast at first until the sea ice becomes thick enough to slow things down.

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Antarctica / Re: PIG has calved

« on: December 26, 2017, 03:57:38 PM »

The picture in Susan's entry shows several more cracks. They can also be seen from time to time in Aqua (Modis) pictures but not in such detail. I marked some of them.

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Antarctica / Re: PIG has calved

« on: September 23, 2017, 02:36:34 PM »

Polarview has it as well now. Interesting crack across the berg. Must have been quite some pressure on the western tip!

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Antarctica / Re: PIG has calved

« on: September 23, 2017, 11:08:13 AM »

I also don't think that the SW tributary did already loose a lot of buttressing. I'm rather more worried about the front of it breaking away. I imagine PIG speeding up as a consequence and the western shear zone slipping through the new opening (where currently the half-calved berg sits). This should rapidly weaken the western shelf of PIG even more and eventually it won't be able to keep up pressure on PIG which in turn will retreat at least until the end of the bay somewhere around the position where the grounding line is plotted in the Modis pictures. From there I expect slower retreat in a different style, similar to Jakobshavn.

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Antarctica / Re: PIG has calved

« on: September 22, 2017, 08:24:33 PM »

Action at PIG!

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Arctic sea ice / Re: Arctic Image of the Day

« on: August 17, 2017, 09:47:35 PM »

By the way: The moraine may still be from the little ice age. There was no other one around and it looked like the glacier was shearing off the hill side. So retreat may have a significant delay but potential for large increases...

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Arctic sea ice / Re: Arctic Image of the Day

« on: August 17, 2017, 08:32:58 PM »

I always thought this glacier near Kangerlussuaq is boring and ugly. Not anymore! Quite impressive moraines from which the glacier is starting to retreat. From what I can tell, the north arm will retreat sooner and faster because it appears to be thinner.

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Antarctica / Re: Rift in Larsen C

« on: July 09, 2017, 12:32:01 PM »

The rifts you mention were probably initiated during the last major calving there in 2005. They probably have a lot to do with pressure from Bawden ice rise and I assume that the calving event will include these rifts as well. Probably not good for the complete northern and central part of the ice shelf...

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Antarctica / Re: Thwaites Glacier Discussion

« on: March 29, 2017, 09:10:55 PM »

Yes, the tongue is the same. And it lost a few icebergs since 2012. But the big one marked as new iceberg in your September 2012 picture was already gone by December (it might actually still be visible in the top left corner under the cloud). The detailed pictures can be found at:
http://nsidc.org/data/iceshelves_images/cgi-bin/modis_iceshelf_archive.pl

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Antarctica / Re: Thwaites Glacier Discussion

« on: March 25, 2017, 11:00:03 AM »

I would call it a calving event. The berg that calved in 2012 which is labeled as new iceberg in the picture has moved away long ago and is currently floating in the Ross sea, roughly along a line from the Sulzberger Ice Shelf to Cape Adare. What is breaking off now is a part of the remaining Thwaites Ice Tongue. It may have been grounded or possibly still is, but it's breaking apart rapidly.  The sea is getting deeper towards the land and we have to expect a rapid breakup of the complete remaining ice tongue. The Eastern Thwaites Ice Shelf will follow soon. It is still grounded at the tip but cracks are developing all over the place. Probably less than three more years to go...

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Antarctica / Re: Shackleton ice shelf

« on: February 04, 2017, 10:29:29 PM »

Dear Patrick,

the map is correct. Now you just have to go to the NSIDC webpage that you linked and look at the different ice shelfs.

http://nsidc.org/data/iceshelves_images/index_modis.html

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Antarctica / Re: Halley base shut down and new crack in Brunt shelf

« on: February 04, 2017, 03:33:00 PM »

Does anyone understand the new crack? I don't! The old one ("chasm") looks reasonable and will one day calve the complete western corner but the new crack starts in the middle of the ice shelf and bends from almost parallel to the flow direction to a more perpendicular direction. It doesn't appear to be directly caused by the faster flowing Riiser ice tongue since it is on the wrong side of the shelf. It also appears to trend to the wrong side of the ice rumples. Not sure if it will lead to a calving event anytime soon but it doesn't look good for the Brunt ice shelf. If the front goes, the rest will probably follow soon since it looks that cracks originating near the grounding line heal over time and stabilize the shelf.

27

Antarctica / Re: Shackleton ice shelf

« on: February 04, 2017, 03:17:30 PM »

There is a mix of ice shelfs here: Only the first picture shows the Shackelton Ice Shelf, the others show the West Ice Shelf where a large ice berg is finally breaking apart after staying put for at least 25 years.

28

Antarctica / Re: Melt water in Antarctica

« on: February 04, 2017, 03:11:44 PM »

I'm rather sure that the plume is some kind of ice. At the Amery Ice Shelf warm water enters from the east side, goes down to the grounding line and exits on the west side. The ice at the grounding line is extremely thick, 2 or 3km and the pressure melting point at this depth is a bit below the melting point at the surface. So, if the warm water loses all its energy to melt at depth, it will be below the freezing point at the surface when it exits from the cavity. The summer sunshine rapidly melts the ice again. The ice can also freeze to the bottom of the ice shelf and heal cracks which explains why the cracks are mostly on the east side of the ice shelf. We can observe the same feature ot the west side of the Ronne Ice Shelf.