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Messages - Tealight

Pages: [1] 2
1
Arctic sea ice / Re: "Stupid" Questions :o
« on: October 17, 2019, 11:43:31 AM »
you can clearly see the effect of refraction  in the photo.
The sun should be a round disk in that photo it is an oblong shape suggesting light bending from refraction.

I agree the photo shows just a refraction. If the sun would be above the horizon the ice would also be very bright, but it is dark. You must keep in mind that at 87N you are only surrounded by extremly flat and highly reflective sea ice. No mountains, trees or buildings to block sunlight. If direct sunshine hits the ice at 82N at an angle of 1-2 degrees it gets reflected and travels a few hundred kilometer further through the atmosphere. Clouds can then reflect this reflection back again towards the surface.

I so happen to have webcam footage from McMurdo Station in Antarctica from the 9th August when the sun was equally 4 degrees below the horizon and the phenomena looks the same to me.

2
Arctic sea ice / Re: AMSR2 Snow & Ice Volume/Thickness
« on: September 02, 2019, 06:54:43 PM »
Volume and thickness are the same league as 2012 and 2016, but the minimum might have already happened.

Full size images and August animation at:
https://cryospherecomputing.tk/SIT

3
Glaciers / Re: Barnes Ice Cap / Penney Ice Cap
« on: August 25, 2019, 01:19:07 AM »
Here is a high resolution Sentinel 2 animation of the retreat in the northern part. From Aug 2016 to Aug 2019 retreat ranges from about 50m on land to 130m in the lake. Or 16.6m/yr and 43.3m/yr.

Assuming a 33m/yr melt rate for the widest part it would take 750 years for the ice cap to melt away.

4
Arctic sea ice / Re: AMSR2 Snow & Ice Volume/Thickness
« on: August 02, 2019, 10:03:48 AM »
Volume and thickness were record low until the second half of the month and then lost slightly out to 2012 and 2016.

Full size images and June animation at:
https://cryospherecomputing.tk/SIT

5
Arctic sea ice / Re: AMSR2 Snow & Ice Volume/Thickness
« on: July 02, 2019, 08:41:19 PM »
Volume and thickness crashed to lowest during the second half of June. In the first half melt was apparently below average. The gif shows the Beaufort gyre in action transporting ice into the melt zone.

One should keep in mind that the product doesn't try to calculate actual ice thickness, but average thickness per ice covered gridcell. If you have an even 50/50 split of water and ice than the gridcell thickness is just 50% of the ice floes.

Full size images and June animation at:
https://cryospherecomputing.tk/SIT

6
Arctic sea ice / Re: Albedo-Warming Potential
« on: June 17, 2019, 06:26:31 PM »
Did you submit to the SIPN? The site seems abandoned, no way to know the participants of course...

I did submit my forecast. The June Report is scheduled to be released on the 21 June 2019. It seems like the whole ARCUS (Arctic Research Consortium of the United States) website was taken offline, not just SIPN.

7
Two years ago I spotted quite big icebergs in the lake, but just like you didn't find a name.

old thread:
https://forum.arctic-sea-ice.net/index.php/topic,2149.0.html

8
Tealight, bear in mind that in some years in August the sea ice disappears from the inner bay, and all the icebergs are swept away. I think this happens every couple of years, but haven't done the stats. This is discussed somewhere upthread. My pet theory was that the massive iceberg jam stuck in sea ice could delay calving processes and even possibly slow the glacier down slightly. Never tested it though.

Oren, you are talking about recently calved icebergs. I was talking about icebergs that have already been swept away from the glacier. About 100km further south the icebergs are piling up like Tetris blocks. They just don't magically vanish  once a latitude line is full. There is still around 1800km2 (30*60) of space for new icebergs, but maybe 600km2 has already been tightly piling up.

9
Arctic sea ice / Re: Albedo-Warming Potential
« on: June 08, 2019, 01:07:52 AM »
The recent warm temperatures over the central Arctic did not result in a significant albedo drop. I suspect the peak sunshine intensity this far north is just too low to force widespread meltponding. Without imported heat from the south it just stays an iceblock. It's like trying to melt some metal in a common household oven. You can heat it for a few days, but you never melt the surface unlike a few minutes in a furnace.

The absence of importet heat means 2016 won the battle for first place and in a few days begins the dominance of 2012 until the end of the melting season.

10
Arctic sea ice / Re: Updating the ASIG
« on: June 04, 2019, 01:13:32 AM »
There also seems to be a problem with DMI no longer updating the Greenland maps and graphs they had on their website. Polarportal has the same images, but their addresses are dynamic (ie each date has its own file name) and so I can't hotlink to them. I wish I knew how to write scripts...

I haven't used googlesites in a while, but I know how to write html image references with a variable url. The following solution works with a generic html file (copy everything into a text file, rename ending to html and open in a browser)
You can try putting it into an HTML box in google sites and maybe it will work.

Code: [Select]
<html>
<img id="Greenland">

<script>
var today = new Date();
yesterday = new Date(today - 68400000); //set off time in milliseconds
var dd = String(yesterday.getUTCDate()).padStart(2, '0');
var mm = String(yesterday.getUTCMonth() + 1).padStart(2, '0'); //January is 0!
var yyyy = yesterday.getFullYear();

yesterdaystring = yyyy+mm+dd;

var imageid = "http://polarportal.dk/fileadmin/polarportal/surface/SMB_map_LA_day_EN_"+yesterdaystring+".png";
document.getElementById("Greenland").src = imageid;
</script>

</html>

Edit: changed getDate() to getUTCDate() for same execution worldwide

11
Arctic sea ice / Re: AMSR2 Snow & Ice Volume/Thickness
« on: June 02, 2019, 01:01:30 AM »
Volume continued below the mean, but thickness went up at the end of the month. It looks like the Beaufort gyre compacted sea ice against eastern Siberia and Hudson Bay ice was compacted against the southern coast.

Full size images and May animation at:
https://cryospherecomputing.tk/SIT

12
Arctic sea ice / Re: What's new in the Arctic ?
« on: May 31, 2019, 12:33:55 AM »
I made a quick and lightweight sea ice comparison page for the entire NSIDC data set. At the moment it's just for the 1st of the month, but soon I add the 15th of the month as well.

https://cryospherecomputing.tk/PastSIC

13
Antarctica / Re: Antarctic Icebergs
« on: May 28, 2019, 10:11:01 PM »
A68A rotation continues in the same spot. Animation beween 3rd May and 28th May.

14
Greenland and Arctic Circle / Re: Greenland 2019 Melt Season
« on: May 22, 2019, 11:43:21 PM »
Even if we have slightly more melt than precipitation right now. Most losses are happening in June and July. On the attached gif I compared the 10th July 2012 with today. It almost looks like we have no melt right now.

15
Antarctica / Re: Sea Ice Extent around Antarctica
« on: May 12, 2019, 06:03:23 PM »
Hi Rich, the current low sea ice extent is caused mostly by the Weddel Sea (see picture below). The Ross Sea is around average. I would say the cause is the current weather pattern. The circumpolar winds are very weak and plenty of mid latitude warmth reaches further south. Somewhere I read that the Antarctic Circumpolar Current is gradually moving south over the last few years, but I can't remember the source.

16
Arctic sea ice / Re: Albedo-Warming Potential
« on: May 05, 2019, 11:18:23 PM »
Thanks everyone. I can confirm it feels good to beat major international organisations like NASA, MetOffice and ecmwf.

Tealight, you derive AWP using sea ice area and then use this as a basis to calculate the energy available to reduce sea ice thickness ? How do you translate reduced thickness into resulting sea ice area and extent? A sea might have remaining ice piled up in one area  or spread out giving a higher extent value due to varying winds and currents?

Technically I keep track of two sea ice concentration values. One to calculate the melt (using SIC from previous years) and another calculated from thickness. The second one is the final model output. The additional thickness step makes the model more robust against flashes of low SIC like short term melt ponds.

For the Antarctic I used the following formula to get the best results:
SIC(%) = (Thickness(m)^1.3) / 0.0155

Thickness(m)   SIC value (%)
1.4   100
1.25   86
1   65
0.75   44
0.5   26
0.25   11
0   0

anything over 1.4m stays at 100% SIC.

17
Arctic sea ice / Re: Albedo-Warming Potential
« on: May 05, 2019, 08:27:26 PM »
Very popular here are the sea ice minimum and maximum polls guessing the correct sea ice extent in millions of square kilometer. A more scientific oriented version of it is the Sea Ice Prediction Network: https://www.arcus.org/sipn
This year was the second time they made a trial run to forecast the Antarctic summer minimum and I participated (as Nico Sun) with a forecast model derived from this Albedo-Warming Potential model. The underlying physics are the same. The major difference is that instead of accumulating an energy value in a grid cell, this energy is used to calculate the sea ice thickness loss. Additionally I added an outgoing infrared radiation variable to get an actual energy balance.

With the post season report released I can proudly claim victory not only in overall area values, but also on a regional scale with the lowest error over the entire 3 month forecasting period. This is in part thanks to the real world usefulness of the AWP model and in part due to the submission deadline of 1st December. Some other team's can only run their models at the beginning of every month and had to use October data for their model initialization. I attached the two most relevant figures, but recommend to read the whole report.

Full 2018-2019 post season report
http://www.climate.be/users/fmasson/SIPN-South_2018-2019_postseason.pdf

General SIPN south website
http://acecrc.org.au/sipn-south/


Sea Ice Loss Formula of the forecast model:

Ed = MJ_inlat,day x (1 - SIC) - MJ_out
z = Ed / Efusion

Ed = Melt energy per day
MJ_in = incoming solar radiation per m2
MJ_out = outgoing infrared emmision per m2
SIC = sea ice concentration
z = thickness loss in m
Efusion = Enthalpy of fusion per m3

18
Antarctica / Re: What's new in Antarctica ?
« on: May 04, 2019, 06:29:14 PM »
I made some Glacier size comparison charts featuring Greenland & Antarctic Glaciers. I hope it better visualizes how much ice is exposed to ocean water than a Bedrock map. The charts shows the dimensions of the glacier front. Where the x-axis is the glacier width and the y-axis is the glacier height.

https://cryospherecomputing.tk/Glacier-size

(same post as what's new in Greenland)

19
Greenland and Arctic Circle / Re: What's new in Greenland?
« on: May 04, 2019, 06:28:40 PM »
I made some glacier size comparison charts featuring Greenland & Antarctic Glaciers. I hope it better visualizes how much ice is exposed to ocean water than a Bedrock map. The charts shows the dimensions of the glacier front. Where the x-axis is the glacier width and the y-axis is the glacier height.

https://cryospherecomputing.tk/Glacier-size

20
Arctic sea ice / Re: AMSR2 Snow & Ice Volume/Thickness
« on: May 03, 2019, 11:29:48 AM »
Another month of low overall gain, but above average thickness.

Full size images and April animation at:
https://cryospherecomputing.tk/SIT

21
Arctic sea ice / Re: Albedo-Warming Potential
« on: May 01, 2019, 01:05:08 AM »
Just in time before the May melt ponds start I created the regional anomaly charts. Just like last year almost all of the early accumulated AWP anomaly comes from the Bering Sea, but this year none of the regions is in the negative.

https://cryospherecomputing.tk/NRTawp

22
Arctic sea ice / Re: Albedo-Warming Potential
« on: April 27, 2019, 07:04:48 PM »
Before working on all region graphs I created another section for the High Arctic. This one should be more useful for determining the record low in September. It only includes the following regions: Kara Sea, Laptev Sea, East Siberian Sea, Chukchi Sea, Beaufort Sea, Canadian Archipelago, Central Arctic.

For the high Arctic 2012 still holds the record high followed by 2016 in second and 2007/2011 tied in third. The far higher average ice cover also significantly increases the gap to a completly ice-free state. On one hand the 2010s just reach 40% of the ice-free conditions compared to 61% for the whole Arctic. But on the other hand the 2010s absorb 32% more than the 1980s. For the whole Arctic it's just 15% more. So the last ten years really impacted the high latitudes more than the lower ones.

https://cryospherecomputing.tk/awp

Note: Before doing this recalculation I increased the ice albedo from 80% to 85% relative to ocean albedo. This is more in line with the values I measured from satellite images. The result is slighly lower absolute values, but hardly any change to anomaly values. The near-real time data will be updated tomorrow.

23
Antarctica / Re: What's new in Antarctica ?
« on: April 23, 2019, 01:49:47 AM »
The Antarctic Bedrock data was over 10 times harder to align than Greenland. There are hardly any landmarks, just plain white and with fast ice or ice shelfs you don't even know where the land begins. I had to use huge area images to align islands and then cut it down to individual glaciers. The bedrock resolution is just 1km/px as opposed to 0.15km/px for Greenland data.

https://cryospherecomputing.tk/Bedrock-Antarctica

24
Greenland and Arctic Circle / Re: What's new in Greenland?
« on: April 22, 2019, 12:08:53 PM »
Did anybody say their favorite glacier isn't featured? No? Well here is all of Greenland Bedrock anyway.

https://cryospherecomputing.tk/Bedrock

25
Arctic sea ice / Re: Albedo-Warming Potential
« on: April 20, 2019, 05:33:12 PM »
Two images to show the current massive regional differences. First a Peak Watt map showing maximum solar intensity at noon. It might be important to get the initial punch to turn snow into a melt pond. The high Arctic never receives this intensity and relies entirely on imported warmth.

For daily averaged energy values the Sea of Okhotsk, closely followed by Bering Sea currently absorbs over ten times more energy than the central Arctic.

Arctic mean: 6.1 MJ/m2

Sea of Okhotsk   18.711
Bering Sea   16.264
Hudson Bay   4.977
Baffin Bay   9.695
East Greenland Sea   8.159
Barents Sea   8.567
Kara Sea   2.753
Laptev Sea   2.387
East Siberian Sea   2.462
Chukchi Sea   3.255
Beaufort Sea   2.598
Canadian Archipelago   2.75
Central Arctic   1.601

26
Greenland and Arctic Circle / Re: What's new in Greenland?
« on: April 20, 2019, 02:50:03 PM »
Just awesome Tealight!

May i suggest using a bigger font and a visual separation (thin line perhaps) between the glaciers and centring of the pics. Would make it even more beautiful imho.

Technically all pictures are centered (if you span the browser over two monitors) The Petermann Glacier has a different aspect ratio and the image overlay code needs a point zero which is set for the widest images. So all image overlays have to begin at the same position.

I try to add a visual separation, but the font is already quite big imo. After loading the webpage from the web and not locally I noticed it has a loading time. With 20MB it's already a decent size. Thus I probably create a separate page for Antarctic Glaciers.

Tealight...you should get an award for this work.

For this? It's just using some web templates, downloading other peoples work and aligning two images in a paint program. All in all two afternoons of work.

27
Greenland and Arctic Circle / Re: What's new in Greenland?
« on: April 20, 2019, 11:37:05 AM »
New Bedrock overlay page for all of Greenlands major glaciers.

https://cryospherecomputing.tk/Bedrock

28
Greenland and Arctic Circle / Re: Bedrock overlay poll
« on: April 20, 2019, 11:34:33 AM »
Thanks everyone for voting. As I suspected both options have a use case. The problem with combining them was that the template for the image overlay slider and the template for the range slider both had "slider" in the name and interferred with another. I solved it by setting the opacity with a number input field and a button.

The test pages are now removed and the overlays have an offical page:
https://cryospherecomputing.tk/Bedrock

29
Greenland and Arctic Circle / Bedrock overlay poll
« on: April 14, 2019, 03:40:48 AM »
I've often seen users asking about a glaciers bedrock elevation to estimate future retreat. Then some veteran users post a bedrock map, but it's still difficult to compare it to current satellite images. Therefore I want to build a bedrock overlay webpage for all major glaciers. However I'm not sure which of the two presentation styles is better.

You can vote for both options if you have no major preference.

Horizontal overlay
https://cryospherecomputing.tk/Test1

Full image Opacity
https://cryospherecomputing.tk/Test2

30
Arctic sea ice / Re: Albedo-Warming Potential
« on: April 11, 2019, 12:11:44 AM »
Some feedback - not sure if you are aware but images don’t seem to load on mobile. When I hold down on the empty space and ask to open image though, it does show up on the next tab.

I still have to upload daily updated images to google drive and insert a shared link into the website. (I don't know yet how put them on the github server)

Oren had the exact same problems and it had something to do with his googleaccount. Can you try opening the webpage in incognito mode?

31
Arctic sea ice / Re: "Stupid" Questions :o
« on: April 10, 2019, 02:25:57 AM »
With the high (relative) levels of melting in the Arctic recently, the flooding that occurred in the NE USA, and the jet stream in that area..... I was wondering whether the water in the clouds came from the melting in the Arctic region, traveled South, then dropped it on the US?

It seems plausible in my head, but is that what happened?

The water generally comes from the warm & wet south, especially in spring. However without cold air from the Arctic the moisture wouldn't come down as heavily and cause flooding. The cold & dense air causes the warm & less dense air to rise, kind of like a mountain. As the warm air rises it cools, can't hold the moisture anymore and develops thick clouds & rain. On earth.nullschool.net I have often seen constant weather front change in the north eastern USA and south eastern Canada. A few days of warm & wet Atlantic air followed by cold air from the Arctic.

Good overview on wikipedia:
https://en.wikipedia.org/wiki/Cold_front

32
Arctic sea ice / Re: Albedo-Warming Potential
« on: April 07, 2019, 10:37:28 PM »
Thanks for the patience and support everybody.

Here is the AWP NRT link:
https://cryospherecomputing.tk/NRTawp

By the way I added a website icon which should be displayed next to the page name in the tab. Right now it's some melting sea ice in Beaufort Sea (2016) at super low resolution. Maybe I make a logo in the future.

33
Arctic sea ice / Re: Albedo-Warming Potential
« on: April 07, 2019, 12:11:26 AM »
The new near-real-time Albedo-Warming Potential script is programmed. If it updates tomorrow as intended I post the website link. The regional data has to wait until I structure the regional data from the previous 40 years.

34
Arctic sea ice / Re: Latest PIOMAS update (April 2019)
« on: April 04, 2019, 01:21:33 AM »
question to the specialists, theoretically i can calculate but there may be hidden traps for a layman, hence i thought to ask:

how much thicker must the ice be to keep the same volume while loosing > 1'000'000km2 in the 2 other dimensions. i assume extent and area won't produce the same result and since i'm not privy with the calculations, i ask that question.

trigger for the question is that each time after a month of steep losses i wonder how it can be that volume could keep level or even increase, is it realistic that the reminder at the same time would grow that much in thickness ?

after all the real area of thickness increase is relatively small, since i think that if the ice is melting at the periphery, there must be some significant range in the midle between the pole and the periphery where ice is melting, just not to zero, keeping thickness and another part where thickness is growing only a little, hence there is not much area left where ice would grow so much to compensate for all the losses.

so much my logics which may be wrong (apparently) and i want to know why i'm apparently erring.

In simple terms the ice that melts at the edge must be replaced by new ice in the centre. The major problem here is that everyone is only publishing average thickness values for the entire Arctic. The ice that was in Bering Sea and Guld of St Lawrence was probably just 10-20cm thick. So 20cm*1million km2 divided by 10 million km2 for the central Arctic gives you a thickness increase of only 2cm.

PIOMAS is really bad at getting the ice edge right, most of all soutwest Greenland which is pretty much never frozen. It's one of the reason why I developed the high resolution "AMSR2 Snow & Ice Volume". It's not as good for the very thick central Arctic, but much better for thin ice and defining an ice edge.

https://cryospherecomputing.tk/SIT

35
Arctic sea ice / Re: Albedo-Warming Potential
« on: April 03, 2019, 01:45:58 AM »
Stumbled on to it while looking at your AMSR2 tab and I have to say it is absolutely beautiful in its presentation.

Please keep up the amazing work and cannot wait for the near real time data additions!

Thanks Viggy, it really means a lot to me. The presentation takes up about 75% of the time, but is also the most important part.

36
Arctic sea ice / Re: Albedo-Warming Potential
« on: April 03, 2019, 01:19:03 AM »
BAM! Two years have gone by without an update.

I finally have the processsing power and coding skills to take the AWP model to where I intended it to be. Instead of only calculating the anomaly of potentially absorbed solar radiation. I now calculate the raw accumulated values, the anomaly and a percentage of the current year to the maximum possible (complete Ice-free conditions). From the 1980s to 2010s this percentage has gone up from roughly 52% to 62%. Generally from August onwards the Arctic is 75% icefree and from September onwards the Arctic is 90% icefree.

Everything is now much better presented with interactive graphs and sliders to compare individual years. The regional data is already calculated, but needs even more work for proper presentation. Near-real time data for 2019 is in the works too.

Fancy new webpage:
https://cryospherecomputing.tk/awp

Still too short documentation of AWP model:
https://cryospherecomputing.tk/doc.


37
Arctic sea ice / Re: AMSR2 Snow & Ice Volume/Thickness
« on: April 02, 2019, 11:16:09 AM »
Only a moderate thickness increase and a complete volume stall in the second half of March, probably caused by the Bering Sea and Gulf of St Lawrence melt out.

Full size images and March animation at:
https://cryospherecomputing.tk/SIT

38
Arctic sea ice / Re: What's new in the Arctic ?
« on: March 28, 2019, 02:17:41 PM »
New Sea Ice comparison tool showing the number of Ice Free Days in a year and the anomaly compared to the long term baseline of 1979-2018.

https://cryospherecomputing.tk/IceFreeDays

39
All hail HTML, CSS, Javascript and the W3.CSS template creators.

I managed to combine a beautiful slider with an image slideshow. Now I have the tools to easily compare years against each other. The images are updated in the same place to a new year for easy comparison instead of putting all images into a huge grid like on my old website.

These news are posted here due to the first content using this are the Snow Covered Days maps.

https://cryospherecomputing.tk/Snow-Cover

40
Arctic sea ice / Re: The 2019 melting season
« on: March 12, 2019, 02:37:40 AM »
A short off topic announcement & question. (It will help you following sea ice melt in the future)

I'm trying to get off googlesites to get more presentation freedom and created a webpage with github pages and a proper address saluting to the glorios pacific atoll of Tokelau.  :D

https://cryospherecomputing.tk/

Currently it's just a generic template with links to the images on googledrive thrown into. None of the buttons should do anything. Does anybody have problems accessing the website or seeing any of the images?

Attached is an image of all Tokelau islands (stuck next to each other) and how the website should look like on a 1080p monitor.

41
Greenland and Arctic Circle / Re: What's new in Greenland?
« on: March 10, 2019, 06:47:44 PM »
As many of you know the DMI moved all their Greenland data products to the Polar Portal website (http://polarportal.dk/en/greenland/surface-conditions/)

I emailed them about the missing accumulated SMB map and their reply was that it isn't as popular as the anomaly map and therefore unlikely to make it over to PolarPortal. I find it dissapointing, but to brighten up my day I found their monthly raw data is freely available for research purposes. (currently Jan 1980 to Aug 2017)

So I think I produce the accumulated SMB maps myself all the way back to 1980 and create some long term SMB graphs (whole year Sep-Aug) and only the melt season (Jun-Aug). Is there anything you would like to see that's possible to create with monthly surface mass balance data?

42
Arctic sea ice / Re: AMSR2 Snow & Ice Volume/Thickness
« on: March 07, 2019, 02:12:18 PM »
Only moderate increases in the AMSR2 Snow & Ice Volume. The St. Lawrence and Sea of Okhotsk ice
is too thin affect the overal numbers much.

Full size images and February animation at:
https://cryospherecomputing.tk/SIT

43
Arctic sea ice / Re: Guess the date of the max
« on: February 21, 2019, 11:49:06 PM »
Anyway I am going for the 15th March as recommended by my ouija board. After all, this is a science-oriented forum.

The 11th - 15th March category is almost completly empty in your graph. The average is just there because other years are earlier and later.

I voted 1-5th of March, but I feel it might be even earlier. Currently we have very high extent in the southern most regions of Sea of Okhotsk and around Newfoundland which melt early. The only region with significant growth potential is the Bering Sea.

44
Arctic sea ice / Re: PIOMAS vs CryoSat
« on: February 12, 2019, 10:58:59 AM »
Well this region has been very cold this winter, but we can only guess if this has translated into extra thickness. From Lebedev ice growth formula we know that sea ice over 2m grows very slowly no matter how cold the air is.

All I know for sure is that my AMSR2 thickness is high as well, but it is definitely affected by snow.

45
Antarctica / Re: Thwaites Glacier Discussion
« on: February 01, 2019, 09:14:44 PM »
New melting and breaking off at Thwaites Glacier. Today I analysed the outer ice field which continues Thwaites Ice tongue to the northwest. I compared the EOSDIS data from Jan 12 and Jan 30, 2019. I marked lost fast sea ice positions in pale magenta and newly formed cracks in orange. I wonder whether this outer ice field, which now has almost completely lost its connection to the Thwaites Ice tongue, will survive this fading austral summer.
See attached picture.

What you have marked as "Thwaites Ice tongue" has been named iceberg B22A for several years., since it is not connected to the main glacier anymore.

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.

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

https://www.bas.ac.uk/project/bedmap-2/#data

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.




46
Permafrost / Re: Snow Cover changes on regional scale
« on: January 29, 2019, 03:40:48 AM »
Question for you, Tealight. Would you be able to reproduce the US graphs with two curves for each 10-year period? (i.e., 1999-2008, and 2009-2018?). Or 11-years, whatever the split is. Curious to see how the curves shift when we compare longer averages vs. individual years and I would think that would be most informative re: ongoing trends.

Sure I can show 10 year averages, but you have to be careful in not selcting a very specific range which happended to be very high or low. We only have 21 years of data so I chose the middle period (2004-2013) as a control period.

2004-2013 compared to 1999-2008 and 2009-2018
Rockies: pretty consistently between the other two averages
Mid-West: mostly between other two except early December significantly higher
North-east: same as the other two averages
South: similar noise to other two averages

47
Slow and steady growth of the side crack continued, now growing directly towards the centre crack and about halfway there. I'd bet they connect by the start of summer.

48
Antarctica / Re: Rift in Larsen C
« on: January 21, 2019, 09:51:18 PM »
A nice view of A-68A today showing the rifts in a lot more detail than usual. A small part even broke off since the last picture posted here in December.

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Antarctica / Re: What's new in Antarctica ?
« on: January 18, 2019, 07:58:39 PM »
I'm failing in finding an article that tells me how this is happening. I would like to know the physics behind this because in freezing temperatures at a high albedo (fresh)water should not just melt, right?

Melting snow and ice below freezing is nothing extraordinary at molecular level.

Melting snow and ice is all about breaking bonds between water molecules. At 0°C and standard atmospheric pressure the individual molecules move or vibrate so much around that existing bonds break and not enough new bonds can form. Temperature is just a description of the average movement of the molecules. Some move faster and some move slower than the average. During noon the slopes of the Amery ice shelf get to around -5°C so not very far off from 0°C. Depending on the slope angle the surface also get's blasted with 700-1000W/m2 (during noon)  of electromagnetic radiation from the sun which further increases the movement of molecules.

Albedo is just an average of reflected vs absorbed energy for all molecules in an area. A single molecule doesn't have an albedo value. Either it get's hit and absorbs the photon's energy (followed by a quick re-release of the energy with a lower energy photon) or the photon misses the molecule.

On a macro level snow can get down to an albedo of 50%, meaning it absorbs 300-500W/m2 while only losing maybe 100-200W/m2 to the below freezing air.


50
Antarctica / Re: Antarctic Icebergs
« on: January 17, 2019, 11:46:51 AM »
Looking at    http://www.arctic.io/explorer/   top right drop down  Antarctica-true color

B22 broke clear from Thwaites between 2002.02.13 and 2002.03.13 and joined the ice peninsular (which often formed) by about 2012.03.20.
Another major calving from the Thwaites tongue occurred in the dark before 2012.09.01 and headed north east of B22 towards the open sea. It drifted westwards, then back towards the coast, onwards towards the northern Ross Sea, where it was breaking up on 2018.03.14 (long153.9, lat 67.8 )
This shows that Thwaites is fairly free to calve even if B22A does not move (and the ice tongue that B22A joined at the base is more often present than not.) but some of the other 'bergs are trapped to the west of Thwaites.

If you only look at ice edge glacier definitions it is true that Thwaites could calve freely the last few years. Especially the sub-region of Thwaites Ice Tongue where several other icebergs came from. I meant more the whole Thwaites area. Haynes Glacier is really just a sub glacier of Thwaites. Even the Crosson ice shelf is connected to Thwaites over Pope/Smith glacier.

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