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Antarctica 2017

Re: Antarctica 2017

Unread postby jedrider » Thu 18 May 2017, 18:01:45

dohboi wrote:And now there's a story in the Guardian, for the trifecta!

https://www.theguardian.com/science/201 ... eseatchers

Climate change is turning Antarctica green, say researchers

In the past 50 years the quantity and rate of plant growth has shot up, says study, suggesting further warming could lead to rapid ecosystem changes


Ah, future home of mankind. It's starting to look habitable.
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Re: Antarctica 2017

Unread postby dohboi » Fri 19 May 2017, 21:51:56

Yup

future real estate prospects loom...

and now rolling stone is picking up the antarctic story...but the topic still doesn't rate a sticky on our humble site, for some reason...

http://www.rollingstone.com/politics/fe ... er-w481260
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Re: Antarctica 2017

Unread postby Plantagenet » Fri 19 May 2017, 22:12:59

dohboi wrote:and now rolling stone is picking up the antarctic story...

http://www.rollingstone.com/politics/fe ... er-w481260


Lots of different scenarios have been proposed for "DOOM" over the years

Now, according to Rolling Stone, we've got a "DoomsDay Glacier".

The newly funded NSF study of Thwaites Glacier should get us some more data in a couple more years to better evaluate just how dangerous this threat will turn out to be and how quickly it will eventuate..

IMHO Its going to turn out to be very very dangerous.

Cheers!

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Re: Antarctica 2017

Unread postby dohboi » Sat 20 May 2017, 01:56:28

Thanks, P.

And the hits just keep comin'

“Decoding Antarctica's response to a warming world”

http://www.bbc.com/news/science-environment-39975709

In the iceberg-infested waters of the Amundsen Sea Embayment (ASE), it obtained the very first cores to be drilled from just in front of some of the mightiest glaciers on Earth.

Chief among these are Pine Island Glacier and Thwaites Glacier, colossal streams of ice that drain the White Continent and which are now spilling mass into the ocean at an alarming rate.

There's concern that deep, warm water is undercutting the glaciers, possibly tipping them into an unstoppable retreat. And that has global implications for significant sea-level rise.
...
The goal was to retrieve seafloor sediments that would reveal the behaviour of the West Antarctic Ice Sheet (WAIS) in previous warm phases. To read the future in the past.

"If you find ice-rafted debris (stones dropped by icebergs), for example, you can be sure there was ice on land and that the ice had advanced to the coast," explained Claus-Dieter Hillenbrand from the British Antarctic Survey (BAS).

"But also new developments - especially what's known as geochemical provenance - have emerged in the last 10 years that mean it's even possible now to compare this material with rocks on land to pin down the actual sources in the hinterland
.

thnx to aslr at neven's forum for this
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Re: Antarctica 2017

Unread postby dohboi » Sun 21 May 2017, 09:20:53

CNN has picked up on Antarctic greening, too

http://edition.cnn.com/2017/05/19/europ ... index.html
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Re: Antarctica 2017

Unread postby Revi » Fri 26 May 2017, 06:59:31

The Rolling Stone article is really interesting. The short story is that there is a continental shelf that's holding back the warm water, and it's getting in now and melting underneath the glacier. It is 6000 feet deep and goes down to bedrock, under sea level. Once it melts it will start to fall into the ocean. The tallest cliffs of ice are 300 feet tall, so that 6000 will have to crumble down to 300, and it's going to take a while and continuous crashing of the ice mass will continue until we have raised sea levels by hundreds of feet. Maybe by the end of the century. Great...

http://www.rollingstone.com/politics/fe ... er-w481260
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Re: Antarctica 2017

Unread postby Newfie » Sat 03 Jun 2017, 08:15:46

Larsen C is set to have a large break off, likely leading general disintegration.

http://www.abc.net.au/news/science/2017 ... ng/8585418
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Re: Antarctica 2017

Unread postby dohboi » Sun 04 Jun 2017, 23:19:51

Yup

It's a comin'

Ibon, how's that sale of your Florida property goin'?
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Re: Antarctica 2017

Unread postby Revi » Mon 05 Jun 2017, 08:31:35

Image

Here's the latest image I found of what's going on with Larsen C. It's making a break for the coast!
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Re: Antarctica 2017

Unread postby Plantagenet » Mon 05 Jun 2017, 16:55:45

Revi wrote:The Rolling Stone article is really interesting. The short story is that there is a continental shelf that's holding back the warm water, and it's getting in now and melting underneath the glacier. It is 6000 feet deep and goes down to bedrock, under sea level. Once it melts it will start to fall into the ocean. The tallest cliffs of ice are 300 feet tall, so that 6000 will have to crumble down to 300, and it's going to take a while and continuous crashing of the ice mass will continue until we have raised sea levels by hundreds of feet. Maybe by the end of the century. Great...

http://www.rollingstone.com/politics/fe ... er-w481260


Its even worse than that.

Once the ocean water gets into the deep basin under the glacier, the edge of the glacier will become buoyant. This encourages rapid calving and collapse of the ice margin. This means you can get really rapid ice retreat without melting occurring right at the glacier---the glacier becomes unstable. The glacier retreats rapidly and generates armadas of ice bergs that float away and melt elsewhere----. Destroying a glacier by calving bergs from its margins can occur much more rapidly then by melting it all in situ.

Image
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Re: Antarctica 2017

Unread postby dohboi » Wed 07 Jun 2017, 21:32:53

Nicely put.

The other dynamic that Richard Alley and others have discussed is the physical fact of the limits to stability of tall ice cliffs: once they get more than 100 meter tall (including above and below the water line), the cliffs are inherently unstable and will keep on collapsing back--in most cases to ever higher, even less stable cliffs--till the entire glacier is rubble on its way to the sea to melt. This can happen remarkably rapidly. Few fully appreciate the consequences of this physical fact about ice cliff behavior, it seems.
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Re: Antarctica 2017

Unread postby Revi » Mon 12 Jun 2017, 12:42:04

I read that in the Rolling Stone article. That's the scary part. 300 feet is the height of the highest ice walls, and the Thwaites glacier is 6000 feet tall and goes down to bedrock, below sea level, with at least 1800 above sea level! Endless collapse!

http://www.rollingstone.com/politics/features/the-doomsday-glacier-w481260
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Re: Antarctica 2017

Unread postby dohboi » Thu 15 Jun 2017, 13:44:33

Get ready for a lot of future hydrofracture events in the WAIS:

Scientists stunned by Antarctic rainfall and a melt area bigger than Texas

https://www.washingtonpost.com/news/ene ... 6054dc4fdf

Scientists have documented a recent, massive melt event on the surface of highly vulnerable West Antarctica that, they fear, could be a harbinger of future events as the planet continues to warm.

In the Antarctic summer of 2016, the surface of the Ross Ice Shelf, the largest floating ice platform on Earth, developed a sheet of meltwater that lasted for as long as 15 days in some places. The total area affected by melt was 300,000 square miles, or larger than the state of Texas...


(Thanks to ASLR at ASIF for text and link...I'm still not clear on why the Arctic gets a sticky thread but not the Antarctic... [smilie=bduh.gif] [smilie=dontknow.gif]
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Re: Antarctica 2017

Unread postby rockdoc123 » Mon 26 Jun 2017, 17:02:59

new paper pointing out the potential for Lambert-Amery system to stabilize

Pittard M.L., B.K. Galton-Fenzi, C.S. Watson, and J.L Roberts (2017), Future sea level change from Antarctica's Lambert-Amery glacial system, Geophys. Res. Lett., 44, doi:10.1002/2017GL073486

Future global mean sea level (GMSL) change is dependent on the complex response of the Antarctic Ice Sheet to ongoing changes and feedbacks in the climate system. The Lambert-Amery glacial system has been observed to be stable over the recent period yet is potentially at risk of rapid grounding line retreat and ice discharge given a significant volume of its ice is grounded below sea level, making its future contribution to GMSL uncertain. Using a regional ice sheet model of the Lambert-Amery system, we find that under a range of future warming and extreme scenarios, the simulated grounding line remains stable and does not trigger rapid mass loss from grounding line retreat. This allows for increased future accumulation to exceed the mass loss from ice dynamical changes. We suggest the Lambert-Amery glacial system will remain stable, or gain ice mass and mitigate a portion of potential future sea level rise over the next 500 years, with a range of +3.6 to -117.5 mm GMSL-equivalent.
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Re: Antarctica 2017

Unread postby Plantagenet » Mon 26 Jun 2017, 17:38:51

rockdoc123 wrote:new paper pointing out the potential for Lambert-Amery system to stabilize

Pittard M.L., B.K. Galton-Fenzi, C.S. Watson, and J.L Roberts (2017), Future sea level change from Antarctica's Lambert-Amery glacial system, Geophys. Res. Lett., 44, doi:10.1002/2017GL073486

Future global mean sea level (GMSL) change is dependent on the complex response of the Antarctic Ice Sheet to ongoing changes and feedbacks in the climate system. The Lambert-Amery glacial system has been observed to be stable over the recent period yet is potentially at risk of rapid grounding line retreat and ice discharge given a significant volume of its ice is grounded below sea level, making its future contribution to GMSL uncertain. Using a regional ice sheet model of the Lambert-Amery system, we find that under a range of future warming and extreme scenarios, the simulated grounding line remains stable and does not trigger rapid mass loss from grounding line retreat. This allows for increased future accumulation to exceed the mass loss from ice dynamical changes. We suggest the Lambert-Amery glacial system will remain stable, or gain ice mass and mitigate a portion of potential future sea level rise over the next 500 years, with a range of +3.6 to -117.5 mm GMSL-equivalent.


Lets do the math, shall we?

If this model is correct, then the Lambert-Amery system will remain stable and perhaps even gain some mass equivalent to roughly 3.6 to 117.5 mm over the next 500 years. Lets call it 60 +/- 57 mm or so.

Averaged over 500 years that is roughly equivalent to 0.12 +/- 0.11 mm per year.

Meanwhile, Sea Level is already going up by ca. 3.5 mm year and the rate is steadily accelerating ---- so the effect of this postulated mass gain at the Lambert Avery glacier system is negligible, if it happens at all.

CHEERS!

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Re: Antarctica 2017

Unread postby rockdoc123 » Mon 26 Jun 2017, 18:15:02

Meanwhile, Sea Level is already going up by ca. 3.5 mm year and the rate is steadily accelerating ---- so the effect of this postulated mass gain at the Lambert Avery glacier system is negligible, if it happens at all.


Currently total losses from Antarctica are ~ -90 GT/yr which is 0.26 mm/yr. Using your own calculations that is 1/2 balanced by the potential gain at Lambert Avery. Given that this is not the only ice sheet where the grounding line could remain stable using the same model this is indeed significant from the perspective of Antarctica.

a major point here is that just because ice sheets have a large volume grounded below sea level you can't assume that grounding lines will not remain stable or re-stabilize. This was a point made in earlier threads where taking into account isostatic adjustments due to ice removal can result in changes to the grounding line configuration.
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Re: Antarctica 2017

Unread postby dohboi » Mon 26 Jun 2017, 20:21:47

https://robertscribbler.com/2017/06/26/ ... ar-future/

A Delaware-Sized Iceberg is About to Enter the Southern Ocean — Loss of Larsen C Ice Shelf Possible in Near Future

A rift in West Antarctica’s Larsen C Ice Shelf is about to expel a 1,000 foot tall, Delaware-sized iceberg into the Southern Ocean. The crack began to form in 2011. But over the past year, it has expanded rapidly. Now this massive, newly-forming iceberg hangs by just a thin 13 kilometer wide thread.

...rift progression has occurred in large leaps as pressure on the shelf reached various breaking points. New additions to the rift have often been in jumps of 20 kilometers or more of rift length in numerous instances over the past year. With just 13 kilometers of connecting ice remaining, the entire state-sized iceberg could now break off at any time.

According to Project Midas, late June observations show the crack continuing to widen at the rate of about 2 meters per day. So the larger section of the newly-forming berg is progressing toward the Southern Ocean at a rather rapid rate. And this movement is increasing strain on the small remaining ice bridge to the larger Larsen C Shelf.

Once the massive berg breaks off, researchers are concerned that it could precipitate a larger collapse of the Larsen C Ice Shelf itself. Such an event would be the third ice shelf loss along the Antarctic Peninsula during recent decades. A series of ice shelf collapses precipitated by warming oceans and atmospheres induced primarily by fossil fuel burning...
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Re: Antarctica 2017

Unread postby chilyb » Tue 27 Jun 2017, 09:57:34

rockdoc123 wrote:
Meanwhile, Sea Level is already going up by ca. 3.5 mm year and the rate is steadily accelerating ---- so the effect of this postulated mass gain at the Lambert Avery glacier system is negligible, if it happens at all.


Currently total losses from Antarctica are ~ -90 GT/yr which is 0.26 mm/yr. Using your own calculations that is 1/2 balanced by the potential gain at Lambert Avery. Given that this is not the only ice sheet where the grounding line could remain stable using the same model this is indeed significant from the perspective of Antarctica.

a major point here is that just because ice sheets have a large volume grounded below sea level you can't assume that grounding lines will not remain stable or re-stabilize. This was a point made in earlier threads where taking into account isostatic adjustments due to ice removal can result in changes to the grounding line configuration.


Hi rockdoc123,

curious as to what you think about Jan Lenaerts' ice sheet mass loss plot shown here on his twitter feed.

https://twitter.com/lenaertsjan/status/ ... 5248164864

Antarctic ice sheets are losing mass "in between mid and upper RCP8.5 scenario"

Lenaerts also specifically comments that "Here I plot mass balance (MB -ve -> mass loss). MB = SMB - ice discharge. Ice discharge is increasing more rapidly."

Jan Lenaerts is an assistant professor of atmospheric and ocean sciences at the University of Colorado.

http://www.colorado.edu/lab/icesheetcli ... n-lenaerts

Just thought you should be aware of this, if you were not already!
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Re: Antarctica 2017

Unread postby rockdoc123 » Tue 27 Jun 2017, 11:12:19

The graph shown doesn't reference any particular publication as a source for this information so pretty hard to make comment.
As I've mentioned before there a number of studies conducted over the past number of years regarding mass balance in Antarctica. The range in most accepted values runs from -50 GT/yr to -120 GT/yr. Most recent papers seem to be hovering in the -70 GT/yr to -100 GT/yr (which is why I used -90 GT/yr). Mass balance calculations are subject to the particular GIA model used which is one of the reasons for the range in values.

As to the suggestion that ice flow is increasing it is important to understand this is local and not observed everywhere in Antarctica. A very recent paper points to that.

Petlicki, M. et al, 2017. Recent deceleration of the Ice Elevation Change of Ecology Glacier (King George Island, Antarctica). Remote Sensing, 9, 520. doi:10.3390/rs9060520

Abstract: Glacier change studies in the Antarctic Peninsula region, despite their importance for global sea level rise, are commonly restricted to the investigation of frontal position changes. Here we present a long term (37 years; 1979–2016) study of ice elevation changes of the Ecology Glacier, King George Island (62◦110S, 58◦290W). The glacier covers an area of 5.21 km2 and is located close to the H. Arctowski Polish Antarctic Station, and therefore has been an object of various multidisciplinary studies with subject ranging from glaciology, meteorology to glacial microbiology. Hence, it is of great interest to assess its current state and put it in a broader context of recent glacial change. In order to achieve that goal, we conducted an analysis of archival cartographic material and combined it with field measurements of proglacial lagoon hydrography and state-of-art geodetic surveying of the glacier surface with terrestrial laser scanning and satellite imagery. Overall mass loss was largest in the beginning of 2000s, and the rate of elevation change substantially decreased between 2012–2016, with little ice front retreat and no significant surface lowering. Ice elevation change rate for the common ablation area over all analyzed periods (1979–2001–2012–2016) has decreased from −1.7 ± 0.4 m/year in 1979–2001 and −1.5 ± 0.5 m/year in 2001–2012 to −0.5 ± 0.6 m/year in 2012–2016. This reduction of ice mass loss is likely related to decreasing summer temperatures in this region of the Antarctic Peninsula
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Re: Antarctica 2017

Unread postby dohboi » Wed 28 Jun 2017, 13:38:15

Antarctic ice shelf crack is moving at record speeds, poised to cleave off massive iceberg any minute

http://mashable.com/2017/06/28/antarcti ... -shelf.amp

The soon-to-be-iceberg part of [the] Larsen C Ice Shelf has tripled in speed to more than ten meters per day between 24th and 27th June 2017...the highest speed ever recorded on this ice shelf...this is a notable departure from previous observations...
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