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Author Topic: What's new in Antarctica ?  (Read 132444 times)

johnm33

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charles_oil

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Re: What's new in Antarctica ?
« Reply #301 on: November 10, 2017, 11:23:58 AM »
Is "New Base" on the map where they plan to get to next ?

FredBear

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Re: What's new in Antarctica ?
« Reply #302 on: November 10, 2017, 12:02:41 PM »
"New Base" is where they parked Halley VI last year    .    .   .   then twitched about the Halloween crack to the east ('above' in the images). Halloween crack seems to show up on (ant)arctic io for 2017.11.04.
« Last Edit: November 10, 2017, 12:17:50 PM by FredBear »

Susan Anderson

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Re: What's new in Antarctica ?
« Reply #303 on: November 10, 2017, 09:54:13 PM »
Thanks for explaining FredBaer, I'll try that.

Moving on ...
I've been wanting to post this but was trying to figure out how to make the image smaller using html without success. The simple image editor on the older Macs is gone, and I want to post this without further delay, so I'll come back and fix it later, meanwhile, people can click on it to see the whole thing.

Being a true amateur, I flounder around a bit. I don't know how helpful this might be to anyone, but it just popped up recently via Wunderground comments:
Hot News from the Antarctic Underground NASA Jet Propulsion Lab https://www.jpl.nasa.gov/news/news.php?release=2017-291


Quote
Study Bolsters Theory of Heat Source Under West Antarctica

A new NASA study adds evidence that a geothermal heat source called a mantle plume lies deep below Antarctica's Marie Byrd Land, explaining some of the melting that creates lakes and rivers under the ice sheet. Although the heat source isn't a new or increasing threat to the West Antarctic ice sheet, it may help explain why the ice sheet collapsed rapidly in an earlier era of rapid climate change, and why it is so unstable today.


charles_oil

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Re: What's new in Antarctica ?
« Reply #304 on: November 11, 2017, 02:23:32 PM »
Thanks Fred - seems odd they saw and marked the tracks from the earlier VI location -  wonder where next !

Shared Humanity

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Re: What's new in Antarctica ?
« Reply #305 on: November 11, 2017, 03:26:18 PM »
Thanks for link Susan.

solartim27

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Grygory

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Re: What's new in Antarctica ?
« Reply #307 on: November 16, 2017, 09:08:20 PM »
What do you think about this photo (Ross Ice shelf)? - Is a new iceberg created?
http://www.polarview.aq/images/105_S1jpgfull/S1B_EW_GRDM_1SDH_20171115T112359_75CF_S_1.final.jpg
Sorry if this is not the topic

sidd

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Re: What's new in Antarctica ?
« Reply #308 on: December 12, 2017, 01:05:06 AM »
Reese et al on vulnerable spots for ice shelf thinning:

doi: 10.1038/s41558-017-0020-x

This is a theoretical study using finite element analysis, so awaits validation by observation. They find that there are certain spots on ice shelves, that when thinned, induce flow acceleration of grounded ice hundreds of kilometers away. They characterize the vulnerability by a "response ratio " . This is " the ratio between the total changes in annual mass flux across all grounding lines to the magnitude of locally applied thinning"

I attach fig 1d showing the Amundsen Sea region. Black is a ratio of 100%

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Susan Anderson

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Re: What's new in Antarctica ?
« Reply #309 on: December 21, 2017, 06:29:02 AM »
Very beautiful short flick here, I suspended my usual attitudes and questions and just enjoyed it. Lovely music, and I recommend putting it on full screen (source: my weekly Earth Observatory Newsletter which has all sorts of other goodies in it: https://earthobservatory.nasa.gov/ )



There are some interesting and odd things on the youtube collection as well.
« Last Edit: December 21, 2017, 06:35:03 AM by Susan Anderson »

sidd

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Re: What's new in Antarctica ?
« Reply #310 on: December 23, 2017, 12:05:18 AM »
Campbell et al. have an unsettling result about the Ross shelf. Apparently it will continue thinning this century even absent ocean warming. This is an analysis using surface heights from GLAS and IceSAT and but all they say about the ice model is that it is a "well-tested numerical model of ice shelf flow that simulates both mass and momentum balance responses to various forcings on the ice shelf."

I wonder which one it is.

doi: 10.1002/2017GL075794

sidd

sidd

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Re: What's new in Antarctica ?
« Reply #311 on: December 23, 2017, 08:22:16 AM »
In the light of Mercer's warning i look at 0C in antarctica around the solstice in december. So i did today. PIG/Thwaites and Amery-Holmes seem around freezing.

Amery has been worrying me for a long time.

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Susan Anderson

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Re: What's new in Antarctica ?
« Reply #312 on: December 25, 2017, 09:15:35 PM »
I'm curious as to what is happening with east Antarctica. As I often do, I've been looking at Nullschool - https://earth.nullschool.net/#current/wind/surface/level/overlay=temp/orthographic=328.21,-93.13,569 - and there appears to be quite a bit of warming in the area I think is in the area of Davis Sea and Enderby Land http://nsidc.org/arcticseaicenews/files/2014/07/antarctica_locator_map_nbv_20170213-1002x1024.png

Is that unusual or is it because summer is really getting starting at the south pole?

sidd

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Re: What's new in Antarctica ?
« Reply #313 on: January 04, 2018, 09:13:43 AM »
This post could easily belong on many threads, but i post here because it is a new and beautiful result from WAIS divide ice core. Bereiter et al. have produced a record of mean ocean temperature since the last deglaciation from isotope fractions of noble gases. The timespan is  from 24 kyr. to 7.5 kyr and from 4 Kyr to present. The unfortunate data gap is due to sample rejection. Over most of the data the time resolution is 250 yr.

In the quotes below MOT is mean ocean temperature, LGM is last glacial maximum

"It is interesting to note that since the LGM about the same amount of energy has gone into MOT as into melting grounded ice (Fig. 3b). This is not contradicting the understanding that most of the current anthropogenic warming has been taken up by the ocean ..."

"The warming from 12,750 yr bp to 12,050 yr bp (referred to as YD1) within the Younger Dryas represents the strongest global ocean warming phase within our record. The MOT change rate is 2.5 ± 0.53 mK yr −1 and the corresponding energy uptake (13.8 ± 2.9) × 1e21  J/yr. This unprecedented natural MOT warming rate is comparable to the strong warming since 1997 estimated in ref. 1, but clearly surpasses the estimate therein for the multidecadal trend from 1971 to 2005 ..."

I attach fig 2 because the data shows the pretty agreement between all the different isotope ratio estimates.  I also attach panel a) from fig 3 showing ocean heat uptake. The dashed vertical lines in Fig 3a are the same as in Fig 2 althoug the timescale is from 22 kyr to 7.5 kyr BP (before present, where "present" is taken to mean 1950)

doi: 10.1038/nature25152

sidd

« Last Edit: January 04, 2018, 09:20:14 AM by sidd »

AbruptSLR

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Re: What's new in Antarctica ?
« Reply #314 on: January 09, 2018, 05:33:15 PM »
For your edification:

Zhao, L., Moore, J. C., Sun, B., Tang, X., and Guo, X.: Where is the 1-million-year-old ice at Dome A?, The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-269, in review, 2018.

https://www.the-cryosphere-discuss.net/tc-2017-269/

Abstract. Ice fabric influences the rheology of ice, and hence the age/depth profile at ice core drilling sites. We use the depth varying anisotropic fabric suggested by the recent polarimetric measurements around Dome A along with prescribed fabrics ranging from isotropic through girdle to single maximum in a three-dimensional, thermo-mechanically coupled full-Stokes model of a 70 × 70 km2 domain around Kunlun station. This model allows to simulate the near basal ice temperature and age, and ice flow around the location of the Chinese deep ice coring site. Ice fabrics and geothermal heat flux strongly affect the vertical advection and basal temperature which in consequence controls the age profile. Constraining modeled age-depth profiles with dated radar isochrones to 2/3 ice depth, the surface vertical velocity, and also the spatial variability of a radar isochrones dated to 153.3 kyr BP, limits the age of the deep ice at Kunlun to 649–831 kyr, a much smaller range than inferred previously. The simple interpretation of the polarmetric radar fabric data that we use produces best fits with a geothermal heat flux of 55 mWm−2. A heat flux of 50 mWm−2 is too low to fit the deeper radar layers, and a heat flux of 60 mWm−2 leads to unrealistic surface velocities. The modeled basal temperature at Kunlun reaches the pressure melting point with a basal melting rate of 2.2–2.7 mm yr−1. Using the spatial distribution of basal temperatures and the best fit fabric suggests that within 400 m of Kunlun station, 1 million-year old ice may be found 200 m above the bed, and there are large regions where even older ice is well above the bedrock within 1–2 km of the Kunlun station.
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Tealight

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Re: What's new in Antarctica ?
« Reply #315 on: January 14, 2018, 02:12:59 AM »
Edit: The small part was actually sea ice and not part of the ice shelf anymore. The part just hasn't broken off so early in the melting season before or sometimes didn't become ice-free at all.


Nasa Worldview Link: https://go.nasa.gov/2FCpa1R
« Last Edit: February 07, 2018, 09:27:27 PM by Tealight »

Susan Anderson

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Re: What's new in Antarctica ?
« Reply #316 on: January 14, 2018, 09:56:44 PM »
Fascinating, if scary. Combined with what is going on with PIG (https://forum.arctic-sea-ice.net/index.php/topic,429.msg138777.html#new), a southern "summer" to remember.

Gray-Wolf

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Re: What's new in Antarctica ?
« Reply #317 on: January 15, 2018, 12:00:58 PM »
I've been monitoring a huge crack that runs from roosevelt into the centre of the shelf. I spoke with McMurdo back in 09' and they were then putting sensors along the feature to monitor development. This calve opens up the Roosevelt Island end of that fissure
https://worldview.earthdata.nasa.gov/?p=antarctic&l=VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Coastlines&t=2017-12-14&z=3&v=-429312,-1278080,-79616,-1115008
and so may lead to further stresses as the ocean accesses the base there ( if the grounding line is not already there?).
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FredBear

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Re: What's new in Antarctica ?
« Reply #318 on: January 15, 2018, 04:20:41 PM »
Gray-Wolf: There is also the 'loose tooth' berg half way along the Ross shelf (is it the 'ice' in current nsidc Antarctic maps - I cannot see any sea ice there?), and some fraying of the shelf at the Mt. Erebus end too. The "coastline" marking shows how much the shelf has advanced since (?). Recently nsidc sea ice extent has been trying to catch up (down!) with last year too. Jan 14 2018 view:-

https://worldview.earthdata.nasa.gov/?p=antarctic&l=VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Coastlines&t=2018-01-14&z=3&v=-689065.3881177683,-1434110.2019443244,-339369.38811776834,-1236560.9422758163

solartim27

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Re: What's new in Antarctica ?
« Reply #319 on: January 16, 2018, 04:56:49 PM »
A nice series of pictures and videos from the Swiss Polar Institutes circumnavigation expedition in early 2017.
https://interactive.aljazeera.com/aje/2017/antarctica-voyage/index.html#11
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Yuha

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Re: What's new in Antarctica ?
« Reply #320 on: January 16, 2018, 08:38:38 PM »
A nice series of pictures and videos from the Swiss Polar Institutes circumnavigation expedition in early 2017.
https://interactive.aljazeera.com/aje/2017/antarctica-voyage/index.html#11

Fascinating, well worth the time to watch it through. Some highlights:
  • Rotten ice under Mertz glacier
  • A brittle star catching a living fish, which has never been observed before.

Susan Anderson

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Re: What's new in Antarctica ?
« Reply #321 on: January 16, 2018, 09:16:00 PM »
A nice series of pictures and videos from the Swiss Polar Institutes circumnavigation expedition in early 2017.
https://interactive.aljazeera.com/aje/2017/antarctica-voyage/index.html#11

Fascinating, well worth the time to watch it through. Some highlights:

  • Rotten ice under Mertz glacier
  • A brittle star catching a living fish, which has never been observed before.

Indeed, amazing ... takes a while, do view all of it!

solartim27

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Re: What's new in Antarctica ?
« Reply #322 on: January 19, 2018, 04:03:23 PM »
Just a background article on a core drilling expedition on the Ross sea, JOIDES

http://blogs.discovermagazine.com/crux/2018/01/18/antarctica-melted-joides/

Quote
Over the next couple months, their ship, the International Ocean Discovery Program’s JOIDES Resolution, will drill at least five core samples reaching thousands of feet below the Ross Sea. These cores will let scientists read layers in the rock record like pages of a book, unraveling climate and ice conditions stretching back tens of millions of years.

Twitter account:  https://mobile.twitter.com/TheJR

Expedition blog:  http://joidesresolution.org/first-core-on-deck-2/
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solartim27

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Re: What's new in Antarctica ?
« Reply #323 on: January 19, 2018, 05:23:56 PM »
A nice satellite shot of the USCG icebreaker Polar Star heading to Mcmurdo station
From: https://mobile.twitter.com/peter_neff/status/953857709450805249
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solartim27

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Re: What's new in Antarctica ?
« Reply #324 on: January 19, 2018, 05:31:04 PM »
Another nice Landsat 8 pic of meltwater
From:  https://mobile.twitter.com/StefLhermitte/status/952996849128017923
And:  https://mobile.twitter.com/AntarcticReport/status/954329004105900032
Quote
More mid-summer surface water, this time on King Baudouin Ice Shelf, Dronning Maud Land, East #Antarctica. Landsat 8 satellite image includes "englacial" lakes, i.e. sandwiched between surface of the ice shelf and its base floating on the ocean beneath @NASA_Landsat @USGSLandsat
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Susan Anderson

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Re: What's new in Antarctica ?
« Reply #325 on: January 19, 2018, 09:59:21 PM »
@Solartim27

That looks a bit like Larsen B just before it broke up.
https://earthobservatory.nasa.gov/Features/WorldOfChange/larsenb.php

charles_oil

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Re: What's new in Antarctica ?
« Reply #326 on: January 28, 2018, 07:39:42 PM »

Interesting short video on CNN about robots being used in a year-long study under the Antarctic ice.


https://edition.cnn.com/2018/01/27/world/antarctica-ice-robots/index.html



Scientists with the University of Washington in conjunction with Paul G. Allen Philanthropies are sending robots to Antarctica for as long as a year in what will be the longest mission ever undertaken in the region.
The aim: to gain more extensive data about the rate of ice loss and thus more accurately predict future sea-level rise.
Navigation algorithms enable the Seaglider robots to maneuver autonomously.
The autonomous underwater gliders move by changing their buoyancy, rising to the surface to transmit data, and that comes with a risk -- some may sink and be lost for good as they move under the Antarctic ice sheets.

It's a small price to pay when talking about the fate of the world, according to a spokesman for Microsoft co-founder and investor Paul Allen, who has funded the mission.

Jim Hunt

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The 2041 SPEC trek to the South Pole
« Reply #327 on: February 02, 2018, 12:45:53 PM »
Slightly belated news that on January 15th the father and son team of Robert and Barney Swan reached the South Pole after a 56 day trek powered entirely by renewable energy:

https://www.2041.com/blog/father-and-son-at-the-pole-day-56-of-spec/

Shell were one of the expedition's sponsors:

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Susan Anderson

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Re: What's new in Antarctica ?
« Reply #328 on: February 03, 2018, 07:07:06 PM »
Warmth being pushed south toward Antarctica at speed today (roughly, Feb = August north of equator).
https://earth.nullschool.net/#current/wind/surface/level/overlay=temp/orthographic=-53.48,-77.19,317
---
Thanks for posting that, Jim.

solartim27

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Re: What's new in Antarctica ?
« Reply #329 on: February 06, 2018, 07:15:20 PM »
I'm not sure how useful this may be, but it looks interesting,  and it's free.
http://www.npolar.no/en/news/2018/02-06-relansering-av-Quantarctica.html
Quote
Version 3 of the Quantarctica mapping tool is released today.
Quantarctica is a free package of scientific and geographic datasets for Antarctica. Version 3 now includes data from ten different scientific themes, increased from just two in version 2.

An international team of scientific editors was also recruited to Quantarctica's Editorial Board, and helped review and evaluate datasets to represent their fields in Quantarctica.



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sidd

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Re: What's new in Antarctica ?
« Reply #330 on: February 11, 2018, 06:27:35 AM »
Nice paper by Snow et al. on changes in bottom water after a caving event in Adelie Land. After the calving Deep Shelf Water freshened resulting in not just fresher, but warmer Bottom Water. This is one of the few results from in situ measurements at the bottom of the world, covering a period from 1994 to 2015.

I attach Fig3a and fig S1. The y axis on the former is density, and Fig S1 shows the process that warms and freshens Bottom Water.

sidd

ivica

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Re: What's new in Antarctica ?
« Reply #331 on: February 22, 2018, 11:34:41 AM »

https://www.nasa.gov/feature/jpl/new-study-brings-antarctic-ice-loss-into-sharper-focus

Quote
“We’re entering a new age,” said the study’s lead author, cryospheric researcher Alex Gardner of NASA’s Jet Propulsion Laboratory in Pasadena, California. “When I began working on this project three years ago, there was a single map of ice sheet flow that was made using data collected over 10 years, and it was revolutionary when it was published back in 2011. Now we can map ice flow over nearly the entire continent, every year. With these new data, we can begin to unravel the mechanisms by which the ice flow is speeding up or slowing down in response to changing environmental conditions.”



Earth Research Findings, Feb. 20, 2018

sidd

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Re: What's new in Antarctica ?
« Reply #332 on: February 22, 2018, 09:09:32 PM »
The Gardner paper is nice. From the table 1) i see that basins 20,21,22 (include thwaites) are showing increases in mass loss of the order of 5-7%. If I were to buy into Hansen's exponential increas picture, thats a doubling time of 10-15 yrs. We shall see.

sidd

sidd

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Re: What's new in Antarctica ?
« Reply #333 on: February 24, 2018, 10:06:00 PM »
edit: My last post is erroneous:  The mass loss in Table 1 is for the periods 2008-2015, 7 years. So the increase is 5-7% over seven years, say 1% a year, for  doubling time of 70 years

sidd

FredBear

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Re: What's new in Antarctica ?
« Reply #334 on: March 02, 2018, 01:25:46 PM »
Quite a chunk of 1 y.old sea ice is breaking away in the S.E. corner of the Weddell Sea in the last few days. There seems to be off-shore winds blowing new sea ice away from the continent in many places.
The off-shore ice in front of Thwaites has also been fracturing & moving out a little since late February.

sidd

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Re: What's new in Antarctica ?
« Reply #335 on: March 03, 2018, 02:56:45 AM »
Nias et al. have a new bedrock fit to PIG:

doi: 10.1002/2017GL076493

Apparenty a modelled rise near the grounding line may not exist, and affects features a very long way upstream.

"Subtle variation in the geometry near the grounding line can trigger a response in the ice sheet that is felt hundreds of kilometers upstream."

sidd

Hyperion

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Re: What's new in Antarctica ?
« Reply #336 on: March 16, 2018, 08:43:57 AM »
Hot core fully eyewalled up tropical cyclones raging around the coast of Antarctica.
Policy: The diversion of NZ aluminum production to build giant space-mirrors to melt the icecaps and destroy the foolish greed-worshiping cities of man. Thereby returning man to the sea, which he should never have left in the first place.
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Grygory

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Re: What's new in Antarctica ?
« Reply #337 on: March 20, 2018, 11:08:24 AM »
New crack in Ross ice Shelf?- I am wrong?
https://postimg.org/image/wckqa96zv/

sidd

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Re: What's new in Antarctica ?
« Reply #338 on: April 02, 2018, 10:25:15 PM »
This paper has been posted in another thread, but i include it here: Konrad et al., "Net retreat of Antarctic glacier grounding lines"

doi: 10.1038/s41561-018-0082-z

Apparently PIG has slowed, but Thwaites retreats faster:

"At Thwaites Glacier, the average rate of grounding-line retreat has increased from 340  ±​ 280 m yr −1
between 1996 and 2011-12 to 420  ±​ 240 m ..."

"Retreat at Pine Island Glacier appears to have stagnated at 40 m yr −1  ±​ 30 m yr −1 during the CryoSat-2 period, after it migrated inland at a rate of around 1,000 m yr −1 between 1992 and 2011"

"This leads us to conclude that the main trunk’s grounding line has stabilized, potentially due to the absence of warm sub-shelf water 36 that drove retreat until 2011."

Elsewhere, retreat proceeds apace:

" ... high local rates of retreat of ~1,200 m/yr in our results on Haynes, Smith and Kohler glaciers are comparable to peak rates of 1,800 to 2,000 m/yr detected by InSAR between 1992 and 2014 [12,15] . In the Bellingshausen Sea, slower rates of retreat recorded over the last 40 years [13] are similar to those we have derived: at Ferrigno Ice Stream, rates of retreat remain in the range of 50 to 200 m/yr ; at Lidke Glacier, Berg Ice Stream and Venable and Abbot ice shelves, our rates of retreat are in the range of 10 to 40 m/yr in accordance with the multi-decadal range of 10 to 90 m/yr (ref.  13 ); and at the Cosgrove Ice Shelf, we detect no significant retreat, in agreement with previously observed rates between −​40 m/yr and +​11 m/yr (ref.  13 ). In East Antarctica, Totten Glacier is the only location where grounding-line retreat has been documented, and our result of 154 m/yr  ±​ 24 m/yr retreat in its fast-flowing section is consistent with the maximum rate of 176 m/yr recorded between 1996 and 2013 [14] ."

I attach fig 1.

sidd



Tealight

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Re: What's new in Antarctica ?
« Reply #339 on: April 03, 2018, 12:57:03 AM »
I found some great high quality videos of helicopter flights over the McMurdo Dry Valleys. No satellite can ever reach this detail.

First video is from Scott Base to Mt JJ Thomson:


You can also try to follow the flight path on worldview on a second screen:
https://go.nasa.gov/2uCmXBO

miki

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Re: What's new in Antarctica ?
« Reply #340 on: April 03, 2018, 05:17:15 PM »
Antarctica's Underwater Ice Is Retreating 5 Times Faster Than It Should Be

https://www.livescience.com/62203-antarctica-underwater-ice-loss.html

"In the new study, Hannes and his colleagues at the Centre for Polar Observation and Modelling (CPOM) at the University of Leeds used a combination of satellite imagery and buoyancy equations to map out the invisible retreat of underwater ice across roughly 10,000 miles (16,000 kilometers) of Antarctica's coastlines — roughly one-third of the continent's total perimeter."

*****************************

Antarctica 'gives ground to the ocean'

http://www.bbc.com/news/science-environment-43627673

"Scientists now have their best view yet of where Antarctica is giving up ground to the ocean as some its biggest glaciers are eaten away from below by warm water."

*****************************

Net retreat of Antarctic glacier grounding lines

Hannes Konrad1,2*, Andrew Shepherd1, Lin Gilbert3, Anna E. Hogg1, Malcolm McMillan1, Alan Muir3 and Thomas Slater1

https://www.nature.com/articles/s41561-018-0082-z.epdf

Grounding lines are a key indicator of ice-sheet instability, because changes in their position reflect imbalance with the surround-ing ocean and affect the flow of inland ice. Although the grounding lines of several Antarctic glaciers have retreated rapidly due to ocean-driven melting, records are too scarce to assess the scale of the imbalance. Here, we combine satellite altimeter observations of ice-elevation change and measurements of ice geometry to track grounding-line movement around the entire continent, tripling the coverage of previous surveys. Between 2010 and 2016, 22%, 3% and 10% of surveyed grounding lines in West Antarctica, East Antarctica and at the Antarctic Peninsula retreated at rates faster than 25 m yr−1 (the typical pace since the Last Glacial Maximum) and the continent has lost 1,463 km2 ±  791 km2 of grounded-ice area. Although by far the fastest rates of retreat occurred in the Amundsen Sea sector, we show that the Pine Island Glacier grounding line has stabilized, probably as a consequence of abated ocean forcing. On average, Antarctica’s fast-flowing ice streams retreat by 110 metres per metre of ice thinning.

RoxTheGeologist

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Re: What's new in Antarctica ?
« Reply #341 on: April 09, 2018, 03:25:27 PM »

Antarctic snow fall has since an increase since 2000 - interesting as they measure 200 years of yearly snowfails.

http://www.bbc.com/news/science-environment-43691671

Daniel B.

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Re: What's new in Antarctica ?
« Reply #342 on: April 09, 2018, 04:48:20 PM »
Results from the New Zealand team's bore hole through the Ross shelf show ice growth.

https://news.nationalgeographic.com/2018/02/ross-ice-shelf-bore-antarctica-freezing/

sidd

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Re: What's new in Antarctica ?
« Reply #343 on: April 09, 2018, 08:03:16 PM »
The paper by Thomas et al. on antarctic snowfall is at

https://www.clim-past.net/13/1491/2017/cp-13-1491-2017.html

They find snowfall has been increasing since 1800. But there is a caveat at the end of the paper:

"However, the combined regional representation of these records is less than 30 % of the total Antarctic continent and includes single ice core sites with only limited regional representation in SMB. Our findings suggest that small changes in the high-accumulation AP, or the low-accumulation but geographically much larger EAP region, could change the sign and significance of the total Antarctic SMB trend dramatically."

Open access.

sidd

Shared Humanity

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Re: What's new in Antarctica ?
« Reply #344 on: April 10, 2018, 02:29:19 AM »
In other words, we're not sure.

sidd

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Re: What's new in Antarctica ?
« Reply #345 on: April 20, 2018, 02:51:33 AM »
The freshwater cap idea has been round for a while but here are observations and a (simple) model:
The idea is that more light meltwater enhances stratification and suppresses formation of dense saline shelf water. This allows warm circumpolar deep water to creep in and melt the ice faster.

https://phys.org/news/2018-04-reveals-antarctic-contributing-sea-climate.html

paper is

doi: 10.1126/sciadv.aap9467

open access. read all about it.

sidd

oren

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Re: What's new in Antarctica ?
« Reply #346 on: April 21, 2018, 08:24:54 AM »
The freshwater cap idea has been round for a while but here are observations and a (simple) model:
The idea is that more light meltwater enhances stratification and suppresses formation of dense saline shelf water. This allows warm circumpolar deep water to creep in and melt the ice faster.

https://phys.org/news/2018-04-reveals-antarctic-contributing-sea-climate.html

paper is

doi: 10.1126/sciadv.aap9467

open access. read all about it.

sidd
Thanks. Interesting paper, strongly grounded in observations.

bluesky

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Re: What's new in Antarctica ?
« Reply #347 on: April 21, 2018, 11:03:19 PM »
The freshwater cap idea has been round for a while but here are observations and a (simple) model:
The idea is that more light meltwater enhances stratification and suppresses formation of dense saline shelf water. This allows warm circumpolar deep water to creep in and melt the ice faster.

https://phys.org/news/2018-04-reveals-antarctic-contributing-sea-climate.html

paper is

doi: 10.1126/sciadv.aap9467

open access. read all about it.

sidd
Thanks. Interesting paper, strongly grounded in observations.

Here is the link to the full paper in Sciences Advances, for whatever reason the link on phys.org is out of order
http://advances.sciencemag.org/content/4/4/eaap9467.full

"On warm continental shelves, as those on the Sabrina Coast and in the Amundsen Sea, MCDW drives rapid ice shelf basal melt. The large volume of glacial meltwater prevents DSW (Dense Shelf Water)  formation in polynyas downstream of the meltwater outflow. MCDW (Modified Circumpolar Deep Water) remains in the bottom layer throughout the year in the polynya and further downstream, where it can access the ice shelf cavities. On cold continental shelves, the ice shelf cavities are filled by cold shelf waters, and basal melt rates are low. Glacial meltwater input is not sufficient to suppress winter convection in polynyas downstream of the meltwater outflow, as seen at Cape Darnley Polynya, allowing formation of DSW, the precursor to Antarctic Bottom Water. "


Further explanation on MCDW and Antarctica sea water circulation in EGU blog:
https://blogs.egu.eu/divisions/cr/tag/modified-circumpolar-deep-water/





ivica

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Re: What's new in Antarctica ?
« Reply #348 on: May 12, 2018, 11:51:40 PM »
http://m.esa.int/Our_Activities/Observing_the_Earth/CryoSat/New_view_of_Antarctica_in_3D

"Thanks to ESA’s CryoSat mission, a new map of Antarctica provides the most accurate 3D view ever of the continent’s vast ice sheet and floating ice shelves.

This latest digital elevation model, which is available for download, is a result of research published recently in The Cryosphere. The model replaces the version published in March 2017."


Ice height: Released 11/05/2018 2:30 pm, CPOM

"Using around 250 million measurements taken by ESA’s CryoSat mission between 2010 and 2016, scientists at the UK Centre for Polar Observation and Modelling have created the most comprehensive picture to date of the height of the Antarctic ice sheet. This is about five million more than were used in the 2017 version, giving a snapshot of the height of the ice across 95% of the continent."

Juan C. García

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Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.