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Messages - Andreas T

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Antarctica / Re: Thwaites Glacier Discussion
« on: September 28, 2019, 09:47:11 PM »


The water depth is known relatively well and available on the bedmap2 from the British Antarctic Survey.

The whole ice field is over a roughly 300-400m deep part.This is about half the depth of the surrounding areas. I attached an image of the bedrock overlayed with a coastline mask. The mask is maybe from 2012 when the bedmap2 was created and doesn't have the newest glacier front positions.
Oren, it is worth looking through the thread for information on this.
The reason the broken off ice tongue has been stuck for so many years is the relatively shallow dept there. This does not stop more recently calved bergs from leaving the area and meting out further north. B22 does not melt in situ because the upper 300m of water are cold, warmer more salty water is found beneath that layer. Therefore this water reaches the grounding line of Thwaites via a deeper channel east of the stranded tongue. For calved ice to obstruct this water it would have to pile up much higher than the glacier surface. I can't see how it would do that.

Arctic background / Re: MOSAiC project
« on: August 18, 2019, 10:59:51 PM »
I think it is worth mentioning again, there was a transpolar drift by just two norwegian scientists over the 2014/2015 winter. The weekly reports are a fascinating read here:

thanks for sharing this Espen, but could you let us know where (which website) the Nasa image comes from, I was unable to find it?

Antarctica / Re: Thwaites Glacier Discussion
« on: March 20, 2019, 07:57:50 AM »
This is from the Thor cruise blog and shows some detailed bathymetry off the Twaites ice tongue and some pretty impressive sea floor coring sites
The ice position in this  looks like the last clear world view image on Feb 17. The ice edge probably stayed in that position enabling the NBP to reach all the places shown in the track. On the Mar 2. icebergs started to come off the mix of begs and sea ice and 3rd  and 4th this loosening spread further towards the actual calving front of the glacier. The icebergs set loose by this spread into the water crisscrossed by the NBP in the trackmap posted above (without dates which is a bit disappointing) I dont think any ship would want to be among this stuff when they would have to dodge multiple icebergs and thick sea ice shifting rapidly.
A clear out of the bergs has happened fairly recently so her comment was probably a general statement for an audience with isn't expected to know much about this topic.

Antarctica / Re: Thwaites Glacier Discussion
« on: March 16, 2019, 06:32:59 PM »
from the same report come this photo which shows some pretty thick icefloes. That freeboard looks like 2m in places. I guess it is some of the ice which has been sitting between the icebergs of the Thwaites ice cube maker for years. a large part of that freeboard will of course be snow (multiyear firn I guess) of lower density so not a guide to below waterline thickness

Arctic background / Re: Antarctic Expeditions
« on: March 16, 2019, 06:24:47 PM »
The Nathaniel B Palmer is on its way back now it seems but there is another report on the blog
another report with some more detail is here

Antarctica / Re: Thwaites Glacier Discussion
« on: March 15, 2019, 08:37:05 PM »
This is from the Thor cruise blog and shows some detailed bathymetry off the Twaites ice tongue and some pretty impressive sea floor coring sites

Arctic background / Re: Antarctic Expeditions
« on: March 09, 2019, 03:02:50 PM »
A new post is up  on
which has short clips on the ice edge of Thwaites Glacier Ice shelf (thats what the caption says) It would be nice to have more detail on the location of these images but nice to see what the white bits we see in the satellite images look close up.
Tasha Snow also has a new post up, interesting background to the research going on
The NBP has moved on to the PIG according to sailwx by the way

Arctic background / Re: Antarctic Expeditions
« on: March 05, 2019, 10:47:09 PM »
A new entry on the THOR cruise news about their trip to Rothera with many nice photos:

Antarctica / Re: Antarctic Icebergs
« on: March 03, 2019, 09:52:26 PM »
on the other side of the Wedell sea there is an ice berg drifting towards the Brunt ice shelf. Maybe another "Pooh stick" (as in the Milne books) to watch.

Antarctica / Re: Thwaites Glacier Discussion
« on: March 03, 2019, 08:05:27 PM »
this observation is confirmed by the ice velocities for the thwaites ice tongue posted further upthread
The reason lies in the shallower depth below the ice surface both upstream and downstream of the grounding line shown in the bathymetry posted by tealight



The water depth is known relatively well and available on the bedmap2 from the British Antarctic Survey.

The whole ice field is over a roughly 300-400m deep part.This is about half the depth of the surrounding areas. I attached an image of the bedrock overlayed with a coastline mask. The mask is maybe from 2012 when the bedmap2 was created and doesn't have the newest glacier front positions.

Antarctica / Re: Thwaites Glacier Discussion
« on: February 28, 2019, 04:00:18 PM »
This (marked by X) is where the Nathaniel B Palmer is today according to sailwx, S 74°54' W 107°18'. It probably be a while before we hear details of the research there, but the blog posts have a lot of information.
North marked for orientation.

Arctic background / Re: Antarctic Expeditions
« on: February 26, 2019, 02:06:17 AM »
The N B Palmer is back off Pine island Glacier according to sailwx.
a post from the 24th is probably about activities before the detour to Rothera.

but contains a lot of interesting information about the research.

Arctic background / Re: Antarctic Expeditions
« on: February 22, 2019, 08:30:19 PM »
Thanks for that info, they are heading west again now.

Antarctica / Re: The Ross Ice Shelf Thread
« on: February 21, 2019, 10:49:57 PM »
Marine Ice Cliff Instability is a process which could affect grounded ice as far as I know. This would mean that a floating ice shelf (like Ross) may be affected by Marine Ice Shelf Instability but not MICI if its edge retreats to thicker parts of the shelf, which at the present is not happening.
I also think it is not the keel (below water) but the height above water (freeboard) which is critical. Iceshelves with a ice thickness of more than 300m are calving as tabular icebergs in Antarctica and in Greenland.

Arctic background / Re: Antarctic Expeditions
« on: February 21, 2019, 12:11:34 PM »
Tasha Snow writes  about water temperature measurements, it obviously will take some time until those come out but getting access  below the ice with the AUV is really promising.
Since then the Nathaniel B Palmer has gone to Rothera station it seems from sailwx

Arctic background / Re: Antarctic Expeditions
« on: February 18, 2019, 10:15:12 PM »
here is a blog by one of the scientists on the way to Thwaites glacier:

The Polarstern has left Punta Arenas and is heading for the Wedell sea

Antarctica / Re: PIG has calved
« on: February 17, 2019, 11:03:04 PM »
Here are some pictures of research in Pine island bay happening now. I had not realised that there are parts which get free of snow in the summer.

I assume these were taken on the Lindsay islands mentioned in an earlier post

Antarctica / Re: Halley base shut down and new crack in Brunt shelf
« on: February 14, 2019, 07:47:19 PM »
This paper looks interesting and has not been linked to before it seems:
one small quote:
However, the DEM surface topography (and ICESat data) shows large variations in the distribution of
the incorporated icebergs (Fig. 5), and the ice shelf draft upstream of the MIR (Fig. 6) which can be used to
determine if grounding will be maintained. For example, there are currently portions of the ice shelf, due to pass
over MIR 4-12 years from 2017 that may have insufficient draft to ground, with no keels extending below -200
m. At this time the ice shelf might be more prone to reduced, or loss of, contact (Fig. 6b).

Antarctica / Re: Thwaites Glacier Discussion
« on: February 10, 2019, 03:08:33 AM »
Sorry for being pedantic but to avoid confusion, the large iceberg is named B22A by the US National Ice Centre

Antarctica / Re: PIG has calved
« on: February 04, 2019, 05:44:49 PM »
CPOM does an automated version of what you are doing with Sentinel 1 images 6 days apart:
The most recent pair of 23.1. - 29.1 shows a speed of just over 12m / day, only slightly below your result.

Antarctica / Re: Thwaites Glacier Discussion
« on: February 04, 2019, 01:22:54 PM »
I have found some more information on thickness of Thwaites ice tongue, although it does not tell me more because it again is the tongue after separation of B22A (I am guessing this from the shape, no date is given).
It is very low resolution because it comes from a small picture in a slide show type PDF
but it shows that data is around, I am guessing that this comes from the 1km elevation model

Antarctica / Re: Thwaites Glacier Discussion
« on: February 03, 2019, 09:38:28 PM »

from an earlier post by ASLR
I found the attached radar soundings which give an idea of the (initial) thickness of B22A. The line RS is along the ice tongue from which B22A broke off a few years before.

How much bottom melting has occurred since then is hard to know but we know that it is the deeper water which is melting the glacier and that melting rates become smaller as ice shelves thin towards the seaward end.

Stephan, I think there is slight pivoting of B22A but no westward (i.e. down in the worlview image) movement. But the key point is that it is now clear that it is not held in place by sea ice, since that has now cracked across its width on the landward side.
For comparison the movement since march 2012 when it arrived in its present vicinity as seen on worldview

Antarctica / Re: Thwaites Glacier Discussion
« on: February 02, 2019, 02:37:04 PM »
thank you very much, Tealight.
This is really helpful, I guess that means B22A would need to move north or north east if it becomes mobile, westwards its path is blocked. The small amount of movement since it arrived in its present position is probably due to some bottom melting. I guess there is ice thickness data for B22A somewhere? I hope it isn't too cheeky to ask, instead of searching for it myself, but if somebody has done the work already, or can tell me where to look?

Antarctica / Re: Thwaites Glacier Discussion
« on: February 01, 2019, 06:48:22 PM »
Looking through past years i noticed there has been a swathe of grounded icebergs in the past which seemed to follow the same line as some of the present sea ice.
To have a better comparison I have overlayed an image of 21 feb 2008 in a purple tint over 22 jan 2019
This shows that the stranded icebergs were mostly further west than the curved piece of sea ice. In the same location there are still icebergs which don't move when other bits of ice move around them.
We will probably see soon how much the mobility of the large chunk of sea ice is constrained by frozen in icebergs.

So, my hunch was a bit off, but I thought it might be worth sharing because it tells us something about water depth in that area.

Antarctica / Re: PIG has calved
« on: January 28, 2019, 07:24:07 PM »
Looking at the coastline marked on worldview, suggests that bedrock is below the waterline in this area. I think the ice is floating at that point so when ever a crack opens it fills with seawater and possibly meltwater from below. You see dark areas where cracks open in Luckman's animation. Information where the grounding line is for the ice is probably further up the thread.

Antarctica / Re: Thwaites Glacier Discussion
« on: January 27, 2019, 09:32:40 PM »
I thought the broken off glacier tongue was grounded on an underwater ridge (moraine of the glacier during ice age?)
but the animated comparison with 2017 I posted above shows movement of the entire huge iceberg northward. I doubt that the sea ice could hold the glacier in place over so many summers if it was otherwise free to move. The "fetch" of something this size when driven by wind or water must be huge.
Maybe we will find out soon if this area between the berg and land disintegrates this austral summer.

Antarctica / Re: Thwaites Glacier Discussion
« on: January 26, 2019, 03:51:16 PM »
Instead of trawling through ASLR's posts over many many pages of the PIG thread which has loads of relevant information I just googled Pelto Thwaites glaicier and hey presto:
which show 3000m /a speeds published in 2001

Antarctica / Re: Thwaites Glacier Discussion
« on: January 26, 2019, 03:26:00 PM »
good point, I should have included a scale!,B02,B03&maxcc=52&gain=0.3&gamma=1.3&time=2018-07-01%7C2019-01-10&atmFilter=&showDates=false
shows a 10km bar in the right hand bottom corner which is about as long as the longest red lines
doing this more acurately is a bit pointless because the Sentinel-2 images don't go any further back.
If wipneus could dig out some Landsats....
There are charts with colour coded glacier speed in the PIG thread I think

Antarctica / Re: Thwaites Glacier Discussion
« on: January 26, 2019, 02:45:32 PM »
for a more detailed view I have been waiting for a clear image on Sentinel but now I just used the one from 10.1.
This isn't as up to date as the images posted above but I think it shows the stresses of faster glacier movement in the centre and slower movement on both sides.
comparison is between 25.1.2017 and 10.1.2019
orientation is different from worldview!

Antarctica / Re: Thwaites Glacier Discussion
« on: January 25, 2019, 08:07:02 PM »
I have been watching this too for a while, it will be interesting to see how much of this area will become mobile this year.
It is worth scrolling back to 2002 on worldview to see how this looked before the Thwaites ice tongue broke off. Images are available back to March 2000 when this was clearly sea ice with a few icebergs frozen in. The grounding of the ice tongue in front of it then made it immobile. In 2013 much of the iceberg "rubble" cleared out in the eastern part of the area marked by Stephan. But now it is opening further to the west

Antarctica / Re: PIG has calved
« on: January 19, 2019, 10:17:28 PM »
Pine Island Bay and Pine  Island Glacier were named after a ship involved in the mapping of this area in 1946.
The ship in turn was named after an island off the coast of Florida, a more likely place to find pine trees I guess ;)

Arctic sea ice / Re: Latest PIOMAS update (October)
« on: October 13, 2018, 05:54:25 PM »
apologies if this should be in another thread, but i only just found that CPOM has updated their cryosat based volume graph. Maybe this can serve as supporting information for the discussion about the recent volume trend.

Arctic background / Re: 2018 north pole expeditions
« on: August 30, 2018, 10:55:53 PM »
Interesting post from the oden with good pictures, i particularly like the aereal view of the floe, where all the activity takes place.

Helen Czerski writes about the work to get as much measurements as possible before open leads start to freeze

They had a visit from a walrus, which surprises me, I thought they need shallower water to feed than what is found in the central arctic?

Arctic sea ice / Re: Arctic Image of the Day
« on: August 29, 2018, 09:13:37 PM »
I find the reaction of a lot of people here bewildering.
I like to think this forum is about facts and science. If I make a statement about the xyz ice shelf I should make sure I know what the xyz iceshelf actually is. I certainly do such fact checking because I would hate to make such a mistake.
It did not take me long to find the information I posted above. Maintaining high standards on this forum is certainly worth the effort in my opinion. (of course there are people who think diferently )
JD  and treform have apologized and that is ok, I hope they take more care in the future. Being incentivized to make the extra effort to reduce the risk of making mistakes is a good thing, right? That is not a personal issue, and should not be about hurt feelings.
Can you really not tell the difference between that and mistake about who said what???

Arctic sea ice / Re: Arctic Image of the Day
« on: August 27, 2018, 10:40:22 PM »
..... But nobody of you seems to care, if that claim is actually true.
I read that forum for the last few years because I was used to get factually correct information from here. But if you have to verify for each post, if the claims or "facts" presented are actually true, than I have no reason to waste my time here distinguishing between actual facts and fake news.

I remember a slogan from the early eighties in german: es gibt nichts Gutes ausser man tut es! There is no good thing unless someone does it (makes it happen)
It is a often thankless chore to bother with fact checking and contradicting false, I think mostly erroneous claims on this forum. But unless someone does it, you can't (sadly I agree) rely on correct information on this forum. The claims of disintegrating ice shelfs come up everytime sea ice breaks off the north coast of Ellesmere.
Diablobanquisa's questioning was at least a pointer to this being a dubious claim, Jim showed an image of an ice shelf which certainly was not disintegrated (without explaining what part is old ice, it is the stuff which has ridges parallel to the coast) and I did provide information which I hoped refuted the claim of "obliteration"
I think the "peer review process" on this forum worked reasonably well.
But each of those mentioned put in an effort and spent time they could have spent on something else.
I personally feel encouraged to do this by your comment, deconstruct, because I agree that this forum should be better than other ones, but you could have worded it in a more constructive way, if i may say.

Arctic sea ice / Re: Arctic Image of the Day
« on: August 26, 2018, 04:02:24 PM »
comparing the recent image with this one from 2008 shows the ice which is called  "Ward Hunt iceshelf" by the canadian government undisintegrated.
Can you point out where you see an "obliterated ice shelf"?

Arctic background / Re: Research Icebreaker Polarstern
« on: August 26, 2018, 03:39:18 PM »
the most recent entry (in german) has only vague information and undated photos.

Arctic background / Re: Research Icebreaker Polarstern
« on: August 24, 2018, 05:30:34 PM »
reports from polarstern indicate that they were just in the right place at the right time to benefit from the opening water north of Greenland.
Having been as far as nearly 37 deg west, which probably counts as the Lincoln sea they are making their way back out east it seems. It would be great to see what ice conditions are like as they make it through some of the stuff which now seems to drift south again towards Morris Jessup.

If my french is sufficient to get this right, they have decided to turn south. They  say the wind is against them and the safety margins are getting narrow for getting to the pole and making it out without being picked up by some ship.

Arctic sea ice / Re: "Stupid" Questions :o
« on: June 15, 2018, 06:15:45 PM »
Have a look on sentinel playground where you can see much higher resolution images,B02,B03&maxcc=99&gain=0.4&gamma=1.0&time=2015-01-01%7C2018-06-14&atmFilter=&showDates=false&showImage
I have noticed before that Foxe basin in the summer has a turquoise colour in many places which suggests  sediment stirred up along the shallow island coasts. That may explain darker, dirty ice?
I looked for images of freezing which may explain the rounded floes but it gets dark before refreeze it seems

Arctic sea ice / Re: The 2018 melting season
« on: April 25, 2018, 06:31:47 PM »
Neven is impressed by some research that shows melt ponds are the devil.

The argument is that if you have ponds of water forming on top of the ice, they can gather up a lot of heat and melt the ice from the top during the early summer (until the ice cracks and the ponds drain). That means more total solar heat absorbed over the summer, and conditions the remaining ice to melt faster.

And how do you make melt ponds? By shining the sun on the snow to melt it, but not breaking up the ice too early with a storm.

So that's why high pressure on the arctic, from the end of April to early June, seems bad.
repeating some stuff from previous discussions because this keeps coming up:
It is worth looking at the mechanisms by which ponds accelerate melt, rather than just repeat the shorthand "meltponds absorb"
The ponds are darker in colour because much of the light passes through the clear water in the pond and the fairly translucent ice floe into the ocean below and doesn't come back out again.
Absorption therefore takes place mostly in the ice (especially if there are algae present) and in the ocean, not so much in the water in the pond.
Snow reflects sunlight so the best way to melt it is to blow warm air over it (especially if its also moist) rain would be best.
This comes with low pressure rather than high pressure which at the lower sun angle in April looses more outgoing radiation through clear sky than it gains.

I guess the greater speed of the glacier at the centre seen in the position of the calving front as well as  in the movement of features in the two close ups I posted causes stresses which contribute to the formation of the fairly regular pattern of lateral cracks

sentinel 2 images are available again so here is a detail of the southern corner, some calving has happened over the winter in the south more cracks  appear as the glacier is flowing into the sea.

Consequences / Re: Ice-free Arctic
« on: March 08, 2018, 05:06:56 PM »
The difference is that CO2 stays in the atmosphere longer than particulates. So if we stop adding CO2 into the atmosphere it stays nearly what it is now for longer, whereas particulates concentration and their dimming of the atmosphere starts to drop much more quickly.

Policy and solutions / Re: Cars, cars and more cars. And trucks, and....
« on: January 20, 2018, 07:15:57 PM »
People in general imagine that, reality is a bit different.
I once had a heated discussion with a friend. He was upset after seeing someone smoking at a gas station. Everyone would agree, it's stupid. But when I tried to explain that during summer the air/fuel ratio would be off and it's at least a bit safer then. Then he was mad at me. :)

I asked him how many times have you turned off your (open flame) propane fridge in your motor home while refuelling?
Has the gas station ever exploded or caught fire?
Why is that?
Adding an image depicting the flammable air/fuel ratio in closed containers for gasoline and ethanol. In the open air during summer it's almost impossible to ignite gasoline fumes. Only in Hollywood.
But of course gas stations are not in closed containers and even if some part of it would have air which is saturated in fuel vapour at summer air temperature it will be diluted to a flammable mixture by air currents at least in the transition from saturated vapour to surrounding fresh air.
Maybe your friend was exasperated by your lack of logic?

Policy and solutions / Re: Renewable Energy
« on: January 20, 2018, 06:11:34 PM »
This press release gives some "real world" numbers for combining photovoltaic panels with agriculture. The spacing of the panels clearly is wider which, together with the height to allow for large farm machinery to pass underneath, means more steel goes into the support structure.
The output graph shows that allignment is facing south westerly (mentioned in the text) but also is offset by the local time in the south west corner of Germany being over half an hour later than CET.

Arctic sea ice / Re: What the Buoys are telling
« on: October 04, 2017, 07:36:47 PM »
This recent image serves as a reminder that snow is drifting quite a lot on the ice which must make it quite difficult to quantify what effect snowfall has. Thicker than average drifts alternating with thin patches.
The sentinel image from the 28th shows that floes are still moving and rotating, I would expect wind direction to have been quite uniform when those drifts were formed. Snow blowing onto the sea surface could have helped starting ice cover to form.

Arctic sea ice / Re: Fram Export
« on: September 25, 2017, 09:02:42 PM »
as a heads up about some interesting research in this area, here is a link to a press release by the AWI
During the past weeks, sea-ice thickness measurements were the main topic of the TIFAX (Thick Ice Feeding Arctic Export) campaign, which involved research aircraft using laser scanners and a towed electromagnetic probe. In the area surveyed, which lies to the north of the Fram Strait between Greenland and Svalbard, the sea-ice thickness was ca. 1.7 metres, roughly 50 centimetres more than was recorded in 2016. This is most likely due in part to a higher percentage of several-year-old ice in the area. Nevertheless, the measured thickness is ca. 30 per cent lower than between 2001 and 2004. As Marcel Nicolaus summarises, “Despite the warm winter, the sea ice wasn’t unusually thin. Our explanation is that the small and thin ice coverage from the previous summer – the second-smallest area ever recorded – grew faster and thicker than in other years, since thin ice grows faster than thick ice.”

Arctic sea ice / Re: What the Buoys are telling
« on: September 24, 2017, 09:20:32 PM »
As the periods of sufficient sunlight to power the buoy bare getting shorter, we will soon have to say goodbye to OBuoy14 for 6 months. At the moment frost blooms are forming on the ice, which shows that the gaps between ice floes have frozen over. Air temperatures are only -5C which probably means that larger expanses of open water are not freezing yet.
Lets hope the frost starting to form on the camera is not covering up the lens too soon.
The sentinel shot is from the 22nd but probably gives a fair impression of the amount of ice surrounding the buoy location at pressent.

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