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Author Topic: AbruptSLR by P.Sinclair  (Read 5766 times)

Pmt111500

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AbruptSLR by P.Sinclair
« on: January 26, 2015, 03:14:57 PM »
P.Sinclair summarizes recent studies on glaciers worldwide so posting this here: http://climatecrocks.com/2015/01/26/new-research-suggests-sea-level-could-rise-faster-sooner/

this starts to sound like a scenario I'd believe in, whether this starts in 2025 or 2090 is still a bit open question but I'll believe it's coming, is irriversible when it starts and thus guessing the engineer children of todays engineer/builder children should have a profitable and recurring career in building harbours for what ever stuff still gets shipped around the world by then. Glad that gardening here in the north will become easier with less need for frost protection, though slightly scared of some of the southern pests that'll likely be a menace on the corn fields of Finland by then...

Pmt111500

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Re: AbruptSLR by P.Sinclair
« Reply #1 on: January 28, 2015, 05:01:14 AM »
Ok, now I see this topic has already been talked about by none other than our resident 'AbruptSLR' here, can't keep up with all the posts...  The article in question is of course Pollard&al., Sinclair connects the study to newer findings about Pliocene climate in a more accessible way, I think (linking to ArsTechnica article.

The abstract of Pollard&al
 http://www.sciencedirect.com/science/article/pii/S0012821X14007961
The article for those with enough math/physics abilities:
 http://ac.els-cdn.com/S0012821X14007961/1-s2.0-S0012821X14007961-main.pdf?_tid=8b35131c-a6a1-11e4-a0ad-00000aab0f6b&acdnat=1422417528_3104c0863825d7c5469418f0936bf45a

Gray-Wolf

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Re: AbruptSLR by P.Sinclair
« Reply #2 on: January 28, 2015, 10:37:38 AM »
Right from the 'get go' my concerns over the melt across Antarctica ( East and West) has been centred on the partial catastrophic collapse of key sectors of the continent . I just do not see mother N. giving us an orderly retreat of the ice the way the graphs show it. rather I see the slow 'drip,drip' model running in the background ( with some variation in rates) but included in the plot are 'surges' where we are surprised by a period of rapid increase following collapse of this or that sector of Antarctica?

With melt behind Ross already impacting up to a mile up in the trans Antarctic range how long before we see uncharacteristic calving on the front edge of Ross?
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AbruptSLR

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Re: AbruptSLR by P.Sinclair
« Reply #3 on: January 28, 2015, 06:33:32 PM »
The linked book cites a number of examples of punctuated SLR contributions from Antarctica in the paleo-record:

Antarctic Palaeoenvironments and Earth-Surface Processes
 edited by M.J. Hambrey, P.F. Barker, P.J. Barrett, V. Bowman, B. Davies, J.L. Smellie, M. Tranter, (2013), ISBN-13: 978-1862393639 ISBN-10: 186239363X

http://www.amazon.com/SP381-Palaeoenvironments-Earth-Surface-Geological-Publication/dp/186239363X

Abstract: "The volume highlights developments in our understanding of the palaeogeographical, palaeobiological, palaeoclimatic and cryospheric evolution of Antarctica. It focuses on the sedimentary record from the Devonian to the Quaternary Period. It features tectonic evolution and stratigraphy, as well as processes taking place adjacent to, beneath and beyond the ice-sheet margin, including the continental shelf.

The contributions in this volume include several invited review papers, as well as original research papers arising from the International Symposium on Antarctic Earth Sciences in Edinburgh, in July 2011. These papers demonstrate a remarkable diversity of Earth science interests in the Antarctic. Following international trends, there is particular emphasis on the Cenozoic Era, reflecting the increasing emphasis on the documentation and understanding of the past record of ice-sheet fluctuations. Furthermore, Antarctic Earth history is providing us with important information about potential future trends, as the impact of global warming is increasingly felt on the continent and its ocean."
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dorlomin

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Re: AbruptSLR by P.Sinclair
« Reply #4 on: January 28, 2015, 08:05:49 PM »
Where is the "abrupt"?

This is just strengthening the know position that ties CO2 levels to sea level (roughly about 20m for 400ppm).

The big question is how quick. Abrupt for a geologist may be 1000 years for 20m, that will be forever for a policy marker or many voters.

2m per century will be slow for many of them.

And before people start talking about Meltwater pulse 1a.
There was 3 times as much ice on the continents then.
The ice sheets were much further south.
There had been several thousand years of warming before hand.

It tells us what could happen, but it is not a prediction of what will happen.
Take it for granted you are wrong.
Just try to work out what about and why.

AbruptSLR

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Re: AbruptSLR by P.Sinclair
« Reply #5 on: January 28, 2015, 08:55:08 PM »
First, the NRC 2013 abrupt climate change report makes it clear that these researchers consider AbruptSLR to be at least a 1m of SLR within an approximately 30-year period (for an averaged rate of SLR of 33 mm/yr over such a 30-year period). At higher rates of SLR the researchers believe that policy makers would not be able to respond quickly enough to prevent major infrastructure damage in the coastal areas.

Second, the following abstract from DeConto & Pollard (2014) confirms that under a RCP 8.5 scenario a SLR rate exceeding this limit is possible before 2100:
 
DeConto R, and Pollard D., (2014), "Antarctica's potential contribution to future sea-level rise", SCAR - COMNAP Symposium

http://www.scar2014.com/assets/SCAR_and_COMNAP_2014_Abstract_Document.pdf

Abstract: "A hybrid ice sheet-shelf model with freely migrating grounding lines is improved by accounting for 1) surface meltwater enhancement of ice shelf calving; and 2) the structural stability of thick (>800 m), marine-terminating (tidewater) grounding lines. When coupled to a high-resolution atmospheric model with imposed or simulated ocean temperatures, the new model is demonstrated to do a good job simulating past geologic intervals with high (albeit uncertain) sea levels including the Pliocene (3Ma; +20 ±10m) and the Last Interglacial (130-115ka; +4-9m).  When applied to future IPCC CMIP5 RCP greenhouse gas forcing scenarios with ocean temperatures provided by the NCAR CCSM4, the same model shows the potential for massive ice and freshwater discharge beginning in the second half of this century. In both RCP2.6 and 8.5 scenarios considerable retreat begins in the Pine Island Bay region of West Antarctica. In the more aggressive (and arguably more likely) RCP8.5 scenario, Pine Island Bay retreat is followed by more massive retreat of the entire WAIS, and eventual ice retreat into deep East Antarctic basins. During peak rates of retreat, freshwater discharge exceeds 1 Sv and exceeds 0.2 Sv for several centuries with potential to disrupt ocean circulation in addition to contributing between 2m and 9m sea level rise within the next 500 years. Here, we demonstrate that large portions of the Antarctic Ice Sheet (in West and East Antarctica) can retreat on relatively short (decadal to centennial) timescales, posing a serious threat to global populations."

Note the part of the abstract that says:

"… the same model shows the potential for massive ice and freshwater discharge beginning in the second half of this century.  …
During peak rates of retreat, freshwater discharge exceeds 1 Sv …"

And as 1 Sv = 86mm of SLR per year, this research indicates that the AIS might plausibly contribute over 0.86 meters per decade to SLR.
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Lennart van der Linde

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Re: AbruptSLR by P.Sinclair
« Reply #6 on: January 28, 2015, 09:40:23 PM »
And before people start talking about Meltwater pulse 1a.
There was 3 times as much ice on the continents then.
The ice sheets were much further south.
There had been several thousand years of warming before hand.

True, but that warming was maybe about 1 degree C per two millennia. Now we've had almost 1 degree in two centuries, and we may get another few degrees this century. So warming will be at least 10x faster than 14.000 years ago and could well be 50x faster, or even more, under BAU.

Also, back then average global temperature was maybe 2-3 degrees cooler than now, and we now still have a large area of Arctic sea ice and Northern Hemisphere snow cover, which will cause an albedo flip when melted, so this will strongly amplify global warming and melting of land ice.

And back then most melting ice was land based, according to Eric Rignot, while now a significant part of the vulnerable ice is marine based, so can collapse faster than the land ice back then.

This is not a prediction that we'll see 5 meter of SLR per century again in the coming centuries, but it is an argument why this certainly seems a serious risk, that we better not ignore.

dorlomin

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Re: AbruptSLR by P.Sinclair
« Reply #7 on: January 28, 2015, 11:35:48 PM »
DeConto R, and Pollard D., (2014), "Antarctica's potential contribution to future sea-level rise", SCAR - COMNAP Symposium
So your modus operandi is to pick a conclusion (hence your name) then skim abstracts to filter out the ones you agree with, and turn up online to whip up a bit of excitement.

Sort of the same as a climate change denier just on the other extreme.

And funnily enough, just like a denier, you are always right.
Take it for granted you are wrong.
Just try to work out what about and why.

Lennart van der Linde

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Re: AbruptSLR by P.Sinclair
« Reply #8 on: January 28, 2015, 11:54:10 PM »
just like a denier, you are always right.

A denier denies scientific findings. How's that the same as quoting scientific findings?

If someone quotes scientific findings he's not denying science.

If there's no consensus on some worrisome scientific findings, there's still a risk they may turn out right. Or are you saying there's no risk the findings of DeConto and Pollard will turn out right?

AbruptSLR

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Re: AbruptSLR by P.Sinclair
« Reply #9 on: January 29, 2015, 12:44:40 AM »
DeConto R, and Pollard D., (2014), "Antarctica's potential contribution to future sea-level rise", SCAR - COMNAP Symposium
So your modus operandi is to pick a conclusion (hence your name) then skim abstracts to filter out the ones you agree with, and turn up online to whip up a bit of excitement.

Sort of the same as a climate change denier just on the other extreme.

And funnily enough, just like a denier, you are always right.

dorlomin,

If you want to learn something about this topic then go to the Antarctic folder and scroll through some of the posts there, particularly in the "Potential Collapse Scenario for the WAIS" linked below:

http://forum.arctic-sea-ice.net/index.php/topic,31.0.html

The IPCC has steadily increased their SLR projections from AR3 to AR4 to AR5 and I am very confident that if there is an AR6 then it will contain SLR projections that are higher than AR5.

It is convenient for policy makers to fail to act because they say that the current uncertainties about future SLR are too high to make prudent decisions today; however, if such policy makers want to have any kind of favorable legacy with the next generation then I believe that they will need to face the reality of the risks of abrupt SLR sooner rather than later.

Best,
ASLR
« Last Edit: January 29, 2015, 12:58:23 AM by AbruptSLR »
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wili

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Re: AbruptSLR by P.Sinclair
« Reply #10 on: January 29, 2015, 03:43:45 AM »
Wasn't there a study recently that concluded that a significant portion of pulse 1a was from melt coming from the Antarctic Ice Sheet? Or am I mis-remembering again?

ETA: Ah, this is what I was thinking of: 

"The highest IBRD flux occurred 14,600 years ago, providing the first direct evidence for an Antarctic contribution to meltwater pulse 1A."

http://www.nature.com/nature/journal/v510/n7503/full/nature13397.html

And note the immediately following (and concluding) sentence:

"Climate model simulations with AIS freshwater forcing identify a positive feedback between poleward transport of Circumpolar Deep Water, subsurface warming and AIS melt, suggesting that small perturbations to the ice sheet can be substantially enhanced, providing a possible mechanism for rapid sea-level rise."
« Last Edit: January 29, 2015, 03:51:02 AM by wili »
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Re: AbruptSLR by P.Sinclair
« Reply #11 on: January 29, 2015, 07:53:16 PM »
wili,
There are lots of papers showing that abrupt sea level rise contributions came from Antarctic marine glaciers during Meltwater Plus – 1A), including the following physical evidence cited by Deschamps et al 2012:

Pierre Deschamps, Nicolas Durand, Edouard Bard, Bruno Hamelin, Gilbert Camoin, Alexander L. Thomas, Gideon M. Henderson, Jun'ichi Okuno & Yusuke Yokoyama, (2012), "Ice-sheet collapse and sea-level rise at the Bølling warming 14,600 years ago", Nature, Volume: 483, Pages: 559–564, doi:10.1038/nature10902

http://www.nature.com/nature/journal/v483/n7391/full/nature10902.html

Abstract: "Past sea-level records provide invaluable information about the response of ice sheets to climate forcing. Some such records suggest that the last deglaciation was punctuated by a dramatic period of sea-level rise, of about 20 metres, in less than 500 years. Controversy about the amplitude and timing of this meltwater pulse (MWP-1A) has, however, led to uncertainty about the source of the melt water and its temporal and causal relationships with the abrupt climate changes of the deglaciation. Here we show that MWP-1A started no earlier than 14,650 years ago and ended before 14,310 years ago, making it coeval with the Bølling warming. Our results, based on corals drilled offshore from Tahiti during Integrated Ocean Drilling Project Expedition 310, reveal that the increase in sea level at Tahiti was between 12 and 22 metres, with a most probable value between 14 and 18 metres, establishing a significant meltwater contribution from the Southern Hemisphere. This implies that the rate of eustatic sea-level rise exceeded 40 millimetres per year during MWP-1A."

Best,
ASLR
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: AbruptSLR by P.Sinclair
« Reply #12 on: January 29, 2015, 08:57:46 PM »
For those who think that the USA will not be impacted too much by ASLR because the US is a relatively rich country, please considered the attached American Society of Civil Engineers Infrastructure Report Card grades for Water, Environment & Transportation.  If today the US can only just maintain a D minus grade in many key coastal infrastructure categories; how is such a relatively rich country going to pay for all of the capital expenditures associated with ASLR? 

Control of many coastal infrastructure assets with good value will likely be transferred to concessioners controlled by the top 1% of the private wealthy in exchange for financing the flood protection and/or relocation/retreat efforts; while much of the remaining assets of lower value will be written off as a loss to the remaining 99% of the population.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson