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Runaway Global Warming - Has Arrived pt 15

Re: Abrupt Climate Change

Unread postby vox_mundi » Thu 08 Nov 2018, 11:51:46

Amazon Forests Failing To Keep Up With Climate Change

A team of more than 100 scientists has assessed the impact of global warming on thousands of tree species across the Amazon to discover the winners and losers from 30 years of climate change. Their analysis found the effects of climate change are altering the rainforest's composition of tree species but not quickly enough to keep up with the changing environment.

The team, led by University of Leeds in collaboration with more than 30 institutions around the world, used long-term records from more than a hundred plots as part of the Amazon Forest Inventory Network (RAINFOR) to track the lives of individual trees across the Amazon region. Their results found that since the 1980s, the effects of global environmental change - stronger droughts, increased temperatures and higher levels of carbon dioxide in the atmosphere - has slowly impacted specific tree species' growth and mortality

In particular, the study found the most moisture-loving tree species are dying more frequently than other species and those suited to drier climates were unable to replace them. ... The species most vulnerable to droughts are doubly at risk, as they are typically the ones restricted to fewer locations in the heart of the Amazon, which make them more likely to be extinct if this process continues.


Climate Change Causing More Severe Wildfires, Larger Insect Outbreaks In Temperate Forests

A warmer, drier climate is expected is increase the likelihood of larger-scale forest disturbances such as wildfires, insect outbreaks, disease and drought, according to a new study co-authored by a Portland State University professor.

The study, published Oct. 19 in the journal Nature Communications, sought to provide a more complete snapshot of disturbances in the world's temperate forests by quantifying the size, shape and prevalence of disturbances and understanding their drivers.

The study found that while many temperate forests are dominated by small-scale disturbance events -- driven largely by windstorms and cooler, wetter conditions -- there was also a strong link between high disturbance activity and warmer and drier-than-average climate conditions. Andrés Holz, a co-author and geography professor in PSU's College of Liberal Arts and Sciences, said this suggests that with a warming climate, disturbances are expected to become larger and more severe in some temperate forests including the western U.S.

"Under the warmer conditions we have been seeing, it is likely that we're going to see a higher probability of areas that tend to have very big disturbances," he said.


New Research Questions the Rate of Climate Change

Climate change may be occurring even faster than first thought.

That is according to a ground-breaking new study by Dr Clayton Magill from the Lyell Centre at Heriot-Watt University.

Scientists measured the vast migration of sea bed materials such as clay and sand, a process that occurs over thousands of years.

The research found that constant movement resulted in the erosion of ancient fossils trapped within the ocean floor and that these fossils release their harmful carbon dioxide, which is a strong greenhouse gas. Researchers previously thought that the rate of erosion on these fossils was significantly slower – hence climate change was slower.
... “We don’t know how much carbon is trapped in the ocean but now we’ve proven the process, it could pose catastrophic threat to earth’s climate.”

Our results suggest differential lateral transfer dynamics can influence apparent lead–lag patterns among proxies with differing grain-size associations.

Open Source: Clayton R. Magill et al. Transient hydrodynamic effects influence organic carbon signatures in marine sediments, Nature Communications (2018)

Abstract
Ocean dynamics served an important role during past dramatic climate changes via impacts on deep-ocean carbon storage. Such changes are recorded in sedimentary proxies of hydrographic change on continental margins, which lie at the ocean–atmosphere–earth interface. However, interpretations of these records are challenging, given complex interplays among processes delivering particulate material to and from ocean margins. Here we report radiocarbon (14C) signatures measured for organic carbon in differing grain-size sediment fractions and foraminifera in a sediment core retrieved from the southwest Iberian margin, spanning the last ~25,000 yr. Variable differences of 0–5000 yr in radiocarbon age are apparent between organic carbon in differing grain-sizes and foraminifera of the same sediment layer. The magnitude of 14C differences co-varies with key paleoceanographic indices (e.g., proximal bottom-current density gradients), which we interpret as evidence of Atlantic–Mediterranean seawater exchange influencing grain-size specific carbon accumulation and translocation. These findings underscore an important link between regional hydrodynamics and interpretations of down-core sedimentary proxies.
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Re: Abrupt Climate Change

Unread postby Plantagenet » Sat 02 Feb 2019, 01:25:23

The enormous void discovered at the base of the Thwaites Glacier in Antarctica seems to have mostly formed during the last three years

NYT: climate/thwaites-glacier-antarctica-cavity

If the void continues to expand, there is a fair chance the Thwaites Glacier will begin to collapse into the void, triggering rapid ice retreat back up into the West Antarctic Ice Sheet along with significantly more sea level rise then IPCC has been predicting.

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Re: Thwaites Glacier

Unread postby jawagord » Sat 02 Feb 2019, 19:03:35

There’s always a Thwaites glacier study going on, melting faster or melting slower, take your pick. There is nothing we can do about it, except observe a natural process that has been going on for millions of years. Doomers will need a really big bag of popcorn, even the accelerated melt scenario’s are 100+ years.

Thwaites Glacier and the surrounding coastal region alone could raise sea levels by half a meter (1.6 feet) within 100 years.
https://nsidc.org/nsidc-highlights/2019 ... laboration

A new NASA study finds that Thwaites' ice loss will continue, but not quite as rapidly as previous studies have estimated. The new study, published in the journal Geophysical Research Letters, finds that numerical models used in previous studies have overestimated how rapidly ocean water is able to melt the glacier from below, leading them to overestimate the glacier's total ice loss over the next 50 years by about 7 percent.The glacier has the potential to add several inches to global sea levels.


https://phys.org/news/2017-06-thwaites- ... ickly.html
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Re: Abrupt Climate Change

Unread postby Tanada » Sat 02 Feb 2019, 19:21:05

What people are failing to grasp is water terminating glaciers are only stable when they are resting on submerged land. When they pull back from the ridge/sill that keeps them stable they begin shedding icebergs at a greatly accelerated rate, limited mostly by how quickly the new bergs can float away from the new face and let the warmer sea water reach and erode it further. Sure, its not like firing a rocket, but you only have to look at what is taking place in Alaska and Greenland where water terminating glaciers are in rapid ret5reat to understand what is on the cusp of happening in Antarctica as well. Thwaites and Pine Island glaciers are both stable on sills ATM, but once they retreat off of them it is literally scores of miles of very deep basin filled with ice behind the sill.

Ice is mechanically weak in air, at a height of about 250-300 feet above sea level it becomes unstable and sheers off into bergs. Sitting on the sill stabilizes the base, take away that stability and the dynamics change, radically and rapidly.
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Re: Abrupt Climate Change

Unread postby vtsnowedin » Sat 02 Feb 2019, 19:27:44

What? Are you telling me that otherwise ethical scientists would phrase the results of their research in the most flamboyant terms in hopes of securing continued funding for next years expedition complete with a couple of nubile young grad students?
I've never heard of such a thing. :lol:
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Re: Thwaites Glacier

Unread postby Plantagenet » Sat 02 Feb 2019, 20:24:00

jawagord wrote:Thwaites glacier study ..... observe a natural process that has been going on for millions of years.


Actually, the huge cavity just studied under the Thwaites Glacier using submersibles is thought to have mostly formed within the last three years as warm ocean water begins to penetrate under the Thwaites Glacier. The basic concept involved here is that the warm ocean water is rapidly melting the base of the glacier.

If it took "millions of years" to form, then I wouldn't have posted about it here in this topic about "Abrupt Climate Change."

Get it now?

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Re: Thwaites Glacier

Unread postby jawagord » Sat 02 Feb 2019, 22:47:11

Plantagenet wrote:
jawagord wrote:Thwaites glacier study ..... observe a natural process that has been going on for millions of years.


Actually, the huge cavity just studied under the Thwaites Glacier using submersibles is thought to have mostly formed within the last three years as warm ocean water begins to penetrate under the Thwaites Glacier. The basic concept involved here is that the warm ocean water is rapidly melting the base of the glacier.

If it took "millions of years" to form, then I wouldn't have posted about it here in this topic about "Abrupt Climate Change."

Get it now?

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Finding a possible “hole” under the ice is not abrupt climate change, it’s a natural process that’s been occurring for millions of years to glacial ice that is in contact with sea water. We only recently have the technology to observe it or in this case infer it from plane and sat radar, which makes it an interesting discovery for the scientists and another scare story for the NYT.
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Re: Abrupt Climate Change

Unread postby onlooker » Sat 02 Feb 2019, 23:20:20

It IS abrupt if
The cavity is about two-thirds the area of Manhattan and nearly 1,000 feet tall, according to a study released Wednesday by NASA’s Jet Propulsion Laboratory. The hulking chamber is large enough to have contained about 14 billion tons of ice — most of which the researchers say melted in three years.

As per the previous linked article. Then of course also what Tanada stated makes this more than just some distant threat. It is well documented that ice loss and consequent SLR can proceed at some point exponentially
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Re: Abrupt Climate Change

Unread postby jedrider » Sat 02 Feb 2019, 23:44:30

Climate Change could proceed in a number of 'shocks', i.e. really big changes all at once. It will be a sight to behold what the reaction is to these events. Geologic Gradualism has been giving way to geologic catastrophism. I'm just speculating, of course.
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Re: Abrupt Climate Change

Unread postby vtsnowedin » Sun 03 Feb 2019, 04:30:55

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?
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Re: Abrupt Climate Change

Unread postby dohboi » Sun 03 Feb 2019, 04:59:19

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
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Re: Abrupt Climate Change

Unread postby vtsnowedin » Sun 03 Feb 2019, 05:25:37

dohboi wrote: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).
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Re: Abrupt Climate Change

Unread postby dohboi » Sun 03 Feb 2019, 05:33:04

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.
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Re: Abrupt Climate Change Pt. 2

Unread postby Newfie » Sun 03 Feb 2019, 09:55:25

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.
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Re: Abrupt Climate Change Pt. 2

Unread postby vtsnowedin » Sun 03 Feb 2019, 10:00:40

dohboi wrote: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.
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Re: Abrupt Climate Change Pt. 2

Unread postby onlooker » Sun 03 Feb 2019, 10:09:47

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

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Re: Abrupt Climate Change Pt. 2

Unread postby Newfie » Sun 03 Feb 2019, 10:59:47

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.
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Re: Abrupt Climate Change Pt. 2

Unread postby dohboi » Sun 03 Feb 2019, 11:04:03

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! :lol: :lol: :lol: )
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Re: Abrupt Climate Change Pt. 2

Unread postby jawagord » Sun 03 Feb 2019, 13:30:24

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
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Re: Abrupt Climate Change Pt. 2

Unread postby dohboi » Sun 03 Feb 2019, 21:44:58

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

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