[vtsnowedin]

I have to ask how they came to the conclusion that the melting only started three years ago. They have no previous measurements showing when it was solid and few if any temperature readings of the water under it now or decades ago. When did the first human set foot on top of the portion of this glacier that is grounded ice shelf?

[dohboi]

From the abstract to the paper:

Using a constellation of satellites, we detect the evolution of ice velocity, ice thinning, and grounding line retreat of Thwaites Glacier from 1992 to 2017

http://advances.sciencemag.org/content/5/1/eaau3433

[vtsnowedin]

From the abstract to the paper:

Using a constellation of satellites, we detect the evolution of ice velocity, ice thinning, and grounding line retreat of Thwaites Glacier from 1992 to 2017

http://advances.sciencemag.org/content/5/1/eaau3433

Sounds good but they throw in a few provisos.

There has been no adequate interferometric synthetic aperture radar (InSAR) data after 2011 to observe the grounding line retreat (13, 14).

[dohboi]

It is my understanding that the grounding line is different than the development of the explosively growing cavity within the glacier.

If you have a different view, perhaps you could elucidate.

[Newfie]

Here’s a good short NASA paper about the Jacobshaven glacier in Greenland. It’s a very large Northern glacier but very small Compared to the Antarctic glaciers which are really more entire ice fields.

Other research has shown the same phenomenon in Greenland glaciers, the ice front is eroded from underneath by relatively warm water. Remember that water has it highest density at about 2°. Then it rises in the water colum, that’s why ice floats. So the water under the ice is warmer. They also now know melt water from the surface bores through the ice sheet and races out the fjords under the glacier, warmish water under the ice errodes the ice.

[vtsnowedin]

It is my understanding that the grounding line is different than the development of the explosively growing cavity within the glacier.

If you have a different view, perhaps you could elucidate.

Why use the word explosively instead of rapidly? There are no explosions going on.
While we have had satellites orbiting over the poles for some thirty years ones with the capability to measure ice thickness are a relatively new development and that data can't be made up after the fact. So they know where the calving face of the glacier has been for thirty years but not if there were any voids under the grounded portion of the glacier or how big they might have been.
The fact that the advancement rate of the land based portion of the glacier is troubling enough and I'd be interested in what is happening at the top of the glacier in the way of snow fall and replacement ice but using frantic superlatives about ice melting when it reaches the sea is much more about future research funding then science.

[onlooker]

Well we know this "The thesis that Hansen has put forward for several years is that Ice Sheet collapse is a non-linear process: that with the inclusion of amplifying climate feedbacks it is likely to follow an exponential rate of acceleration - a doubling rate. It might be a 10 year doubling time, or less. This will lead to extensive sea level rise, perhaps in the order of 5 metres this century."
I trust everyone on this forum knows the impeccable credentials of Dr. Hansen

https://takvera.blogspot.com/2012/12/is ... ntial.html

[Newfie]

VT,

What’s being discussed is the evolution of understanding, not anything completly new.

The Jacokhaven refreafnis well documented and shocking in rapidity.

Unfortunately there are other ice fields on the other side of the Antarctic peninsula that have lost their floating front. Because it was floating it did not contribute to SLR. But that buffer is now gone, and the fast ice was acting as a break in hose ice fields, which are now accelerating.

There are additional ice fields in the same position, set to loose their putter edge which is akin to taking the breaks off.

The nasty feed back is that once these grounded fields accelerate their flow they WILL be contributing to SLR. And that SKR will put additional pressure on the remaining locked ice fields to either melt behind their locking shelf or raise over it.

So while “explosive” is not a technically correct word one should understand that there are significant positive feedback looks that will accelerate the ice loss and SLR. No one knows how fast it willl happen, however it MAY happen with shocking rapidity. If you do a risk analysis assessment the it would become clear, this is a very high consequence with a 100% probability of occurring, only the time frame is in doubt.

[dohboi]

vt, that was not my word, but the word from the article, apparently used by the authors.

Compared to how things generally move there--literally 'glacially'!!--one could say that size of a hole developing in just three years is pretty explosive growth.

(Ah, but I forgot that you are on of the 'metaphorically challenged'!! Good luck with that! )

[jawagord]

Antarctica is 14,000,000 square kilometres of ice averaging 1.5+ kilometres thick, the hole in the Thwaites glacier is supposedly 2/3 size of Manhattan or 40 square kilometres. Do the math folks, doomsday sea level rise isn’t happening in your lifetime or your children’s or your grand children’s. Look at the map, Antarctica is the size of the US+Mexico, can you even identify Manhattan or Thwaites in all that expanse?

https://www.nasa.gov/mission_pages/iceb ... ca-US.html

[dohboi]

Arguments from incredulity are...well...not really arguments, just hand waving. Go wave your hands elsewhere, please

https://www.logicallyfallacious.com/too ... ncredulity

[jawagord]

Arguments from incredulity are...well...not really arguments, just hand waving. Go wave your hands elsewhere, please

https://www.logicallyfallacious.com/too ... ncredulity

Your reference links are always good for a laugh. From now on I won’t call climate change ‘junk science’ i’ll rename it as referenced by the link in your post, ‘Crackpot Science”!

Exception: We can't possibly entertain every crackpot with crackpot ideas. People with little credibility or those pushing fringe ideas need to provide more compelling evidence to get the attention of others.

[Whitefang]

Antarctica is 14,000,000 square kilometres of ice averaging 1.5+ kilometres thick, the hole in the Thwaites glacier is supposedly 2/3 size of Manhattan or 40 square kilometres. Do the math folks, doomsday sea level rise isn’t happening in your lifetime or your children’s or your grand children’s. Look at the map, Antarctica is the size of the US+Mexico, can you even identify Manhattan or Thwaites in all that expanse?

https://www.nasa.gov/mission_pages/iceb ... ca-US.html

Twaites is a bit more in extent as Manhattan is....

https://en.wikipedia.org/wiki/Thwaites_Glacier

Thwaites Glacier (75°30′S 106°45′W) is an unusually broad and fast Antarctic glacier flowing into Pine Island Bay, part of the Amundsen Sea, east of Mount Murphy, on the Walgreen Coast of Marie Byrd Land.[1] Its surface speeds exceed 2 km/yr near its grounding line, and its fastest flowing grounded ice is centred between 50 and 100 km east of Mount Murphy. It was named by ACAN[2] after Fredrik T. Thwaites, a glacial geologist, geomorphologist and professor emeritus at the University of Wisconsin–Madison.[3] Thwaites Glacier drains into West Antarctica’s Amundsen Sea and is closely watched for its potential to raise sea levels.[4]
Along with Pine Island Glacier, Thwaites Glacier has been described as part of the "weak underbelly" of the West Antarctic Ice Sheet, due to its apparent vulnerability to significant retreat. This hypothesis is based on both theoretical studies of the stability of marine ice sheets and recent observations of large changes on both of these glaciers. In recent years, the flow of both of these glaciers has accelerated, their surfaces lowered, and the grounding lines retreated.

Together with PIG it holds back a large part of the WAIS, that is enough to cause 2 to 3 meters of SLR.
Together with the GIS, totals about 10 meters SLR that can happen in a short period, stil decades though, but instant on a geological timescale. I think you mistook a part of Twaites Glacier crumbling into the ocean.
oops, sorry, the hole in end of Twaites measures bit less than Manhattan, I see the rest of Twaites and recent devellopments have been discussed already, so nothing new on this post, next time better

[Keith_McClary]

From now on I won’t call climate change ‘junk science’ i’ll rename it as referenced by the link in your post, ‘Crackpot Science”!

Exception: We can't possibly entertain every crackpot with crackpot ideas. People with little credibility or those pushing fringe ideas need to provide more compelling evidence to get the attention of others.

The only serious scientific alternatives to AGW are solar variations and cosmic rays, but they aren't terribly compelling because they don't correlate well with observations and aren't based on a convincing physical mechanism.
https://en.wikipedia.org/wiki/Attributi ... nsus_views
Maybe you know alternative theories that Wikipedia has suppressed.

[Whitefang]

Paul B on Antarctica needing a dentist:

https://paulbeckwith.net/

NERC has an article on Twaites, cool pics.

https://nerc.ukri.org/

https://nerc.ukri.org/press/releases/2018/32-northpole/


Lets hope they still manage to get stranded, lodged in by the sea ice next september

Six berths on the 120m-long icebreaker have been confirmed for UK researchers, who will work alongside up to 600 international scientists and crew from 17 countries as part of this major international effort to better understand the fastest changing environment on the planet.
This year-long study will see the RV Polarstern move with the current in the ice across the central Arctic Ocean from September 2019 to September 2020.
Spearheaded by Germany's Alfred Wegener Institute (AWI), the €120 million Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) mission aims to answer some of the biggest scientific questions about the Arctic, including investigating why the region is warming twice as fast as the global average.
This is among the first missions of its kind since the 1890s, when Norwegian explorer Fridtjof Nansen attempted to reach the North Pole by drifting in a ship locked in ice. Nansen had to abandon his ship when he realised he had gone off track, but the ship itself made it across the ice cap intact and the expedition resulted in breakthrough scientific discoveries about the Arctic and weather patterns.
More than a hundred years later, the MOSAiC research aims to deliver a step change in our understanding of the Arctic climate system and how it affects global climate models. NERC has partnered with the Department for Business, Energy & Industrial Strategy (BEIS), who have provided funding for ship berth fees on the MOSAiC expedition.
NERC has now awarded grants worth £1·8 million to six research proposals that will each utilise a two-month berth on the German research vessel.

Cannot find the info on Twaites, Maybe old and into the archive

https://nerc.ukri.org/research/funded/p ... /thwaites/

Considerable uncertainty remains in projections of future ice loss from West Antarctica. Since the 1990s, satellites have shown accelerating ice loss driven by ocean change in five neighbouring glacier catchments, including Thwaites Glacier, that drain more than one third of the West Antarctic Ice Sheet (WAIS). The rate of ice loss there doubled in six years and now accounts for about 10% of global sea-level rise. The most rapid ice loss is currently from Pine Island Glacier, which has been the focus of the NERC Ice Sheet Stability Programme and National Science Foundation (NSF)-funded science. Recent studies indicate the greatest risk for future rapid sea-level rise now arises from Thwaites Glacier.
NERC and the NSF are co-funding a research programme which aims to substantially improve both decadal and longer-term (century-to multi-century) projections of ice loss and sea-level rise originating from Thwaites Glacier in West Antarctica.

Ok, so this hole in the wall is one of their latest findings, the grant they are working on, 20 million up to 2022.

[Tanada]

Here’s a good short NASA paper about the Jacobshaven glacier in Greenland. It’s a very large Northern glacier but very small Compared to the Antarctic glaciers which are really more entire ice fields.

Other research has shown the same phenomenon in Greenland glaciers, the ice front is eroded from underneath by relatively warm water. Remember that water has it highest density at about 2°. Then it rises in the water colum, that’s why ice floats. So the water under the ice is warmer. They also now know melt water from the surface bores through the ice sheet and races out the fjords under the glacier, warmish water under the ice errodes the ice.

Newfie, you start with 'Here's a good paper' but you forgot to include the link so the interested can read it for ourselves.

[dohboi]

Some Arctic ground no longer freezing—even in winter

https://www.nationalgeographic.com/envi ... -expected/

Extract: "On January 16, 2019, a new global study published in Nature Communications confirmed that permafrost is thawing quickly across much of the world. Between 2007 and 2016, permafrost temperature increased by 0.29 ± 0.12 °C globally. The greatest warming was seen in parts of Siberia, up to 0.93 °C. Significant warming was also seen in Antarctica, and less in mountain regions. In much of the Arctic ground temperature increased because of rising average air temperatures, while increased snow thickness in some areas also contributed to warming the ground underneath."
&

Biskaborn et al. (2019), "Permafrost is warming at a global scale", Nature Communications 10, No. 264, https://doi.org/10.1038/s41467-018-08240-4

https://www.nature.com/articles/s41467-018-08240-4#Fig6

[Cid_Yama]

In a paper published this month by the American Geophysical Union, researchers say sharp rises in levels of methane – which is a powerful greenhouse gas – have strengthened over the past four years. Urgent action is now required to halt further increases in methane in the atmosphere, to avoid triggering enhanced global warming and temperature rises well beyond 2C.

“What we are now witnessing is extremely worrying,” said one of the paper’s lead authors, Professor Euan Nisbet of Royal Holloway, University of London. “It is particularly alarming because we are still not sure why atmospheric methane levels are rising across the planet.”

Natural chemicals in the atmosphere – which help to break down methane – may be changing because of temperature rises, causing it to lose its ability to deal with the gas.

Our world could therefore be losing its power to cleanse pollutants because it is heating up, a climate feedback in which warming allows more greenhouse gases to linger in the atmosphere and so trigger even more warming.

link

[dohboi]

Yeah, it looks like the long predicted depletion of OH radicals in the atmosphere may finally be underway in real time, with very dire consequences likely soon to follow.

Can they measure levels of OH in the atmosphere directly, or is it too much of a trace gas and too volatile?

Can it be generated by artificial means?

[dohboi]

And...more feedcbacks pushing us in the wrong direction:

Arctic Bogs Hold Another Global Warming Risk That Could Spiral Out of Control

Increasing spring rains in the Arctic could double the increase in methane emissions from the region by hastening the rate of thawing in permafrost, new research suggests.

...

"Our results emphasize that these permafrost regions are sensitive to the thermal effects of rain, and because we're anticipating that these environments are going to get wetter in the future, we could be seeing increases in methane emissions that we weren't expecting," said the study's lead author, Rebecca Neumann, a civil and environmental engineering professor at the University of Washington. The study appears in the journal Geophysical Research Letters.

...
In the new study, Neumann and colleagues tracked rainfall, soil temperature and methane emissions at a thawing permafrost bog approximately 20 miles southwest of Fairbanks, Alaska, from 2014 through 2016.

In 2016, a year marked by early spring rain, the team saw soil temperatures at the edge of the bog begin to increase 20 days earlier than usual. Methane emissions across the bog were 30 percent higher than in the two previous years which did not have early spring rains.

The study projects that as the temperature and precipitation in the region continue to increase, the rate of increase in methane emissions from the region may be roughly twice that of current estimates that don't account for rainfall.

and more:
https://insideclimatenews.org/news/1902 ... dback-loop