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Less Doom from the Antarctic?

by Nomad Mon May 25th, 2009 at 03:18:16 AM EST

An interesting article was published in Science last week, concerning the estimated melt from the Antarctic ice sheet, due to the effects of higher temperatures:

From the abstract:

Reassessment of the Potential Sea-Level Rise from a Collapse of the West Antarctic Ice Sheet -- Bamber et al. 324 (5929): 901 -- Science

Theory has suggested that the West Antarctic Ice Sheet may be inherently unstable. Recent observations lend weight to this hypothesis. We reassess the potential contribution to eustatic and regional sea level from a rapid collapse of the ice sheet and find that previous assessments have substantially overestimated its likely primary contribution. We obtain a value for the global, eustatic sea-level rise contribution of about 3.3 meters, with important regional variations.

Emphasis mine; the rest of the article is only available for people with a subscription. But the main point: the estimated 5 - 6 meters of catastrophic sea-level rise has become a little more nuanced.

promoted by whataboutbob


The collapse and melting off the West Antarctic Ice Sheet (WAIS), would result in the largest contribution of global sea-level rise - with dramatic consequences for coastal areas. There have been found indications that the ice sheet has significantly calved back previously in geological times. For instance, it's suspected to have occurred during an interglacial period 400.000 years ago, another period when the earth was not experiencing an ice-age. On a side note, there are indications that this interglacial period is the most similar, in terms of planetary movements, to the interglacial the earth has been experiencing the past 10.000 years. This period could then give the best comparison how today's climate is (or isn't) different.

Previous estimates of the contribution of the WAIS to sea-level rise were calculated using data that since then have been improved:

BBC NEWS | Science & Environment | Ice sheet melt threat reassessed

But Professor Bamber said that no-one had revisited the calculation, despite new data sets becoming available, and scientists developing a better understanding of the dynamics in the vast ice sheets.

The original estimates were based on "very basic ice thickness data", he explained.

"Ice thickness data gives you information about the depth of the bedrock underneath the ice sheet.

"Over the past 30 years, we have acquired much more ice thickness data over the whole of Antarctica, particularly over West Antarctica.

"We also have much better surface topography. Those two data sets are critical in determining two things."

In other words, more precision in determining the volume of the ice sheet, and better detail for determining its integrity. It now seems that the integrity of the WAIS could be more robust than was previously assumed.

The new study brings two important observations:
1)    the volume of ice released from a collapse of the WAIS is almost half of what was previously predicted (although still catastrophic in the long run)
2)    the period of time in which the collapse will occur could well take longer than was previously estimated (in other words, we don't really know what the rate will be)

The crucial hang-up remains:

BBC NEWS | Science & Environment | Ice sheet melt threat reassessed

Responding to Professor Bamber's paper in Science, British Antarctic Survey science leader Dr David Vaughan described the findings as "quite sound".

"But for me, the most crucial question is not solely about the total amount of ice in West Antarctica, because that might take several centuries to be lost to the ocean," he told BBC News.

"The crucial question is how much ice could be lost in 100-200 years; that's the sea level rise we have to understand and plan for.

While I'm at it, there may have been a few more messages that might not have reached a large audience. For instance:

I list those things on purpose, because I suspect that for many these events do not easily fit in the concept of an increasingly warmer climate. What they are, is this: little wiggles and minor variations on the bigger climate curve. Do they matter; who can say? (I sure won't try.)

But the point is that these messages are not in line with the expectations of many who've been mostly hearing about those articles that predict imminent (or even not-so imminent) catastrophes. What's more, I won't be surprised either that at some point they will be seized by people who prefer to maintain business-as-usual. When people use climate change on Mars as an argument, or a few cold winters, then certainly these will suffice...

Display:
the estimated 5 - 6 meters of catastrophic sea-level rise has become a little more nuanced.

Is 3.3 metres of sea level rise still not pretty catastrophic?

The brainless should not be in banking. — Willem Buitler

by Migeru (migeru at eurotrib dot com) on Sat May 23rd, 2009 at 09:51:31 AM EST
And that is from the West Antarctic Ice Sheet.  What is the likelihood that it will melt without the Greenland Ice Sheet also melting?

When I was involved in advocating for seismic safety in public schools in California, back in the late '80s, I sought a map that would show those areas within Los Angeles Unified that were vulnerable to liquefaction.  The only map I could find that showed these data dated from before the construction of the Interstate Freeway System, 1959 IIRC.  My geologist contact at the Office of the State Architect deplored the situation, but coule offer no help.  My estimate then and now is that these professionals risked their jobs if they became too forth -coming on such a topic.  It was seen as being bad for the real estate business.

When I introduced a resolution to improve seismic standards at the State PTA meeting, opponents from San Diego made a quick counter argument and called a snap vote that defeated the proposal before I could even get to a microphone to speak.  As I had voted for the resolution, I could not call for a reconsideration.  Fortunately, the President of our local association had, or claimed she had, voted against it and called for a re-vote.  After my sobering presentation it passed and became the State PTA's official position.  It was, after the Northridge and Oakland quakes, eventually made law.

Never underestimate the resistance to bad news.  Only "renagades" and outsiders can deliver such news.  Doing so from within the system can be career suicide.  

"It is not necessary to have hope in order to persevere."

by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Sat May 23rd, 2009 at 12:13:11 PM EST
[ Parent ]
It will depend on the rate whether it will be catastrophic. And of those rates I can't seem to find very decisive estimates.
by Nomad on Sat May 23rd, 2009 at 05:36:29 PM EST
[ Parent ]
Expected sea level rise is still a shady area. I'm wondering about the 'important regional variations', perhaps there is some connection with an article from last year that was (as far as I know) the first to emphasise how long it would take for the sea level rise from Greenland and the Antarctic to spread (see Cascio here and here).

Otherwise: Berlin is going to be 32 degrees tomorrow. Doom!

by nanne (zwaerdenmaecker@gmail.com) on Mon May 25th, 2009 at 06:15:58 AM EST
[ Parent ]
due to rise of Antarctica, from what I gather by looking at one of the pictures in Science...

Patrice Ayme Patriceayme.com Patriceayme.wordpress.com http://tyranosopher.blogspot.com/
by Patrice Ayme on Tue May 26th, 2009 at 07:43:04 PM EST
[ Parent ]
shows it's actually 3.8 meters, according to them (they restrict themselves to "negative" slope, a useless, somewhat lunatic restriction).

Moreover I dont't like their emotional tone, which takes for granted it would take millennia for the WAIS to go, whereas the real problem is whether it would take 45 minutes, like in the Hollywood movies (as happened with some shelves).

PA

Patrice Ayme Patriceayme.com Patriceayme.wordpress.com http://tyranosopher.blogspot.com/

by Patrice Ayme on Sat May 23rd, 2009 at 07:48:29 PM EST
[ Parent ]
have a full subscription to SCIENCE, and we read, and re-read the article in our bath,last week, and macerated its strange reasoning in my head. But the pictures of this cover story were great.

BTW, the article is ominous about the fate of West Antarctica:"INHERENTLY UNSTABLE" (first sentence of the article!).

Then I looked at the pretty pictures, and looked again, and looked on the side, where East Antarctica, most of Antartica, is found. How interesting.

There I saw a positively enormous area where the icecap bottom is LOWER than 200 METERS BELOW SEA LEVEL.Yes 200 meters below! Imagine the disaster when warm water is going to slip below that...

Thus, if anything, I found the conclusions scarier than ever. I want to see an article incorporating all what can blow up in a flash of steam in EASTERN ANTARCTICA. Now. Methinks it's got to be of the order of twenty meters of seal level rise, just looking at it.

So thank you science, thank you lord, and let's be real nomads, and run for the hills!

A bad emotion reinforced by a little bit of the wrong knowledge often spells disaster.

PA

Patrice Ayme Patriceayme.com Patriceayme.wordpress.com http://tyranosopher.blogspot.com/

by Patrice Ayme on Sat May 23rd, 2009 at 04:43:38 PM EST
So let's not get all emotionally charged, don't run for the hills just yet, and start building a durable planet instead.
by Nomad on Sat May 23rd, 2009 at 05:20:35 PM EST
[ Parent ]


The Fates are kind.
by Gaianne on Thu May 28th, 2009 at 06:57:22 PM EST
[ Parent ]
If you are young or middle aged and planning for retirement by the sea, it might be prudent to look for something, say, 8-10 meters above sea level.  And while nonlinear processes could result in melting faster than current projections, it is unlikely that any process, other than a large meteor impact, could bring about a rise of even a meter in  a couple of years.  But one wouldn't want to try to sell one's retirement home when water is lapping at the front step. To me a one meter+ rise is quite conceivable, and perhaps likely, over a forty year period.  

"It is not necessary to have hope in order to persevere."
by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Sat May 23rd, 2009 at 05:51:02 PM EST
[ Parent ]
The problem has nothing to do with one particular parameter of the possible, for example sea rise.  When all forms of ecosystems are now subject to irreversible damage, it's the totality of the effects which must be considered.  Who cares if the sea rises 1 or 3 or 5 meters if the basic foodstuffs are damaged by this civilization, if the destruction of genetic diversity leaves us hanging by our primordial toes, if the destruction of coral reefs is a symptom that even a higher sea has nothing to harvest, then it doesn't matter where you live.

"Life shrinks or expands in proportion to one's courage." - Ana´s Nin
by Crazy Horse on Sat May 23rd, 2009 at 06:12:01 PM EST
[ Parent ]


Patrice Ayme Patriceayme.com Patriceayme.wordpress.com http://tyranosopher.blogspot.com/
by Patrice Ayme on Sat May 23rd, 2009 at 08:02:01 PM EST
[ Parent ]
Certainly true.  The comment about selling your retirement home was a bit facetious.  Even with a +4C rise in temperatures we are likely to have other problems as bad as sea level rise.  Most basically, we could have a significant reduction in the carrying capacity of the earth.  

"It is not necessary to have hope in order to persevere."
by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Sat May 23rd, 2009 at 08:05:58 PM EST
[ Parent ]
such as me, thinks that one meter is certain, but as much as 25 meters is possible by 2100 (more importantly, so does NASA's Hansen). Too many highly non linear guns in the face (methane, albedo). The planet is going to try to trsnsfer heat to the poles with even more enthusiasm, so melting is going to accelerate.
PA

Patrice Ayme Patriceayme.com Patriceayme.wordpress.com http://tyranosopher.blogspot.com/
by Patrice Ayme on Sat May 23rd, 2009 at 07:58:29 PM EST
[ Parent ]
ARGeezer:
To me a one meter+ rise is quite conceivable, and perhaps likely, over a forty year period.

And Patrice seems to suggest he is as pessimistic about this. What are your reasons/thoughts behind this?

I ask because there are at least two groups that I know which do not think this is likely. The first the AR4 from the IPCC, the second the Dutch water boards. My uncle used to work for the latter, and the consensus remains that for 2100 the Netherlands will not face a 1 meter rise of sea level.

Granted, I'm one of the first to say that in climate change we don't know what we don't know, and a lot uncertainty remains, but on what is this pessimism based?

by Nomad on Sun May 24th, 2009 at 08:13:07 AM EST
[ Parent ]
radiative output (6% in some wavelenghts, it is claimed!)
Sun has got to be worshipping coal and Pluto.
Absent this solar silliness (demonstrated by fewer sunspots in a century), I gave the reasons  above for a considerable sea rise.

Moreover, upon warming I see a reason for the EAST Antarctic basins to melt. They front the sea at the polar circle (i.e., way far from the pole).

I will put all this together in a post on patriceayme.wordpress.com... But I can't believe the sun... Will not save us, because if the CO2 keeps on going up, the oceans will turn into diluted lemon juice...
PA

Patrice Ayme Patriceayme.com Patriceayme.wordpress.com http://tyranosopher.blogspot.com/

by Patrice Ayme on Sun May 24th, 2009 at 10:47:43 AM EST
[ Parent ]
but on what is this pessimism based?

In my case, I am pessimistic that we, as a species, will be able to act with sufficient alacrity to avert ambient temperature increases of 2-4C, or possibly more.  The collective reporting I have seen on the Greenland and West Antarctic Ice Sheets, combined with what I have read about the probable rapid rate of melting of the North American Ice Sheet at the beginning of our current epoch, leads me to doubt that extrapolations of melt rates for these ice sheets will follow current linear models.  

I fear current models assume that the ice sheets will melt in place and perhaps the rate of calving of icebergs into the ocean will increase at about the rate of increase we have recently observed.  Were you able to inform me otherwise I would be relieved.  I am concerned that recent reports of melt water toward the center of these ice sheets creating channels to bedrock will increase and will increase the rate of motion in second order or higher ways.

I think it is more likely that we will document accelerating  processes at work within a decade or so than that we will confirm existing models.  I have no way of knowing how fast melting will occur, but a one meter rise seems much more likely to me than a 10cm rise by mid-century.  I am also concerned that responsible and competent authorities are not creating models that are based on accelerating melt rates and ice movement and using them to evaluate which model best fits observation.  If they are and if they have published results, I have missed the report.

We have all deplored the extent to which Bush era science was subjected to political censorship.  But I do not think that this problem has vanished with the change of one administration in one country.  Nor do I think that current estimates err on the side of pessimism.  To me the question is how much less optimistic should we be.  

"It is not necessary to have hope in order to persevere."

by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Sun May 24th, 2009 at 01:03:24 PM EST
[ Parent ]
who is saying what. Sun seems confused too. I gave above new reasoning for 25 meter rise. But if the sun slows down seriously, that's out of the window, we will know soon. I will put things in an essay, to kill time before my next publication of Qur'an selects...
;-)!

Patrice Ayme Patriceayme.com Patriceayme.wordpress.com http://tyranosopher.blogspot.com/
by Patrice Ayme on Mon May 25th, 2009 at 02:28:18 AM EST
[ Parent ]
I'm pessimistic because I suspect that the ice shelves are being modelled as more stable and warming-resistant than they really are. A while ago I wrote:
A lot of the climate models seem to have modelled the ice sheets as ice cubes when they behave more like a drop of honey. Ice cubes are very poor heat conductors, insulate their own interior, and only melt on the surface. A drop of honey gets less viscous and flows more easily as it warms up. But I am not an expert on climate modelling.
ARGeezer:replied with
Lately I have been reading articles in Science News and elsewhere about glacial lakes melting holes through very thick glaciers and disappearing through said holes. It appears that this additional water further lubricates the interface between the ice and the rock below, increasing the rate of glacier flow.
I was recalling an article we had discussed in the Salon a couple of years back where some climate scientists suggested that the "ice cube" model used in climate simulations led to melting times of the order of 1,000 years whereas the actual dynamics of the ice shelf might lead it to disintegrate on much shorter timescales.

Then I have seen footage of how meltwater pours into deep crevasses in the Antarctiva ice sheet, going directly to the bedrock where it lubricates the interface between the ice and the rock. I am not convinced large chunks of the Antactica ice cap couldn't simply slide into the sea as a result of this lubrication.

The brainless should not be in banking. — Willem Buitler

by Migeru (migeru at eurotrib dot com) on Mon May 25th, 2009 at 06:32:49 AM EST
[ Parent ]
of the geologist, I think that's too pessimist. For now. Don't understand me wrong, if global temperatures creep up another 2 degrees, we are in deep serious - which is why business-as-usual GHG emissions cannot hold.

A few responses up, nanne actually links to one of the articles that illustrate the point, namely:

  1. as far as has been determined, current global temperature is still cooler than the Holocene climatic optimum - particularly in the northern hemisphere.

  2. the last interglacial period (prior to this one) did have 4 - 6 meters higher sea level - but temperatures were an estimated 2 degrees higher. See here and here for examples I've found quickly.

Looking at temperature correlations, we may be seeing calving reaching a new equilibrium and grow constant but on the condition that temperatures stablise.
by Nomad on Mon May 25th, 2009 at 09:52:25 AM EST
[ Parent ]
Nomad:
Don't understand me wrong, if global temperatures creep up another 2 degrees, we are in deep serious - which is why business-as-usual GHG emissions cannot hold.
On that note:



The brainless should not be in banking. — Willem Buitler

by Migeru (migeru at eurotrib dot com) on Tue May 26th, 2009 at 04:12:27 AM EST
[ Parent ]
are still something else: bottom is below sea level. Way below. my hunch is that if ocean temps get above a threshold, the WAIS will disintegrate instantaneously.

Patrice Ayme Patriceayme.com Patriceayme.wordpress.com http://tyranosopher.blogspot.com/
by Patrice Ayme on Tue May 26th, 2009 at 07:46:59 PM EST
[ Parent ]


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