Sea Level Rise and Social Cost of Carbon

[Lennart van der Linde]

Thanks for this article.

In the abstract of the paper they say:

For a mid-range climate-sensitivity scenario that incorporates dynamic ice sheet melting, the approach yields national estimates of the impacts of storm surge and SLR of $990 billion through 2100 (net of adaptation, cumulative undiscounted 2005$); GHG mitigation policy reduces the impacts of the mid-range climate-sensitivity estimates by $84 to $100 billion.

So these are only adaptation costs? Or also potential damage costs? In that case it would be interesting to know what assumptions they make about the timing of adaptation investments. And how much SLR do they take into account?

In any case the news article says it may still be an under-estimate:

The study's results, as eye-popping as they may be, likely represent an underestimate of the total economic impacts from sea level rise and storm surge events — because it does not include several key factors. For one, it doesn't incorporate storm surges from storms that are not tropical storms and hurricanes, such as nor'easters. Also absent is wave action, which tends to increase the damage from storm surge events. The study also doesn't factor in regional variations in sea level rise, with the Mid-Atlantic and Northeast projected to be a regional hotspot for sea level rise due to regional ocean currents and other factors. Damage to infrastructure, such as coastal roads and airports, and ecosystem damages are not included either.

[jai mitchell]

Published on Nov 25, 2014


Jeremy Jackson, senior scientist emeritus at the Smithsonian Institution and professor of oceanography Emeritus at the Scripps Institution of Oceanography, discusses how saving the oceans and ourselves will require fundamental changes in the ways we live and obtain food and energy for everything we do. Recorded Nov. 20, 2014, in Mayser Gymnasium.

cut ahead to where he talks about sea level rise at minute 27 in talk. 

https://www.youtube.com/watch?v=ljM2o6bIHSo&t=27m

[GeoffBeacon]

Jai

Thanks.

But

cut ahead to where he talks about sea level rise at minute 27 in talk.

Don't cut ahead if you've got an hour. An amazing talk.

[Lennart van der Linde]

Is that possible: 4m of SLR in a 'couple of years', when WAIS abruptly collapses/disintegrates?

What science is that statement by Jackson based on? Maybe 4m in a couple of decades, but years? How would that work?

[Laurent]

It took 4 weeks for Larsen B to collapse !?...
The size does not seem to matter, past a certain threshold in temps, patatra ?...

[Lennart van der Linde]

Yes, but is that science or just wild speculation? In that case, why not say 4m in a few weeks may be possible? Or in a few days? Why even do science at all, if it's that easy to infer the risk of ice sheet collapse from the observed collapse of an ice shelf? It seems too much like those reverse statements of pseudo-sceptics to me, unless there's some more reasoned and peer-reviewed argument behind Jackson's statement. Or at least a speculation by a glacialogist instead of an oceanographist.

[Laurent]

I do not infer anything, just recall a recent past that should remain in memory. A fast collapse is just something we should not exclude. Off course we have to study the pig ice shelf in 3D if we want to predict something.

[AbruptSLR]

Is that possible: 4m of SLR in a 'couple of years', when WAIS abruptly collapses/disintegrates?

What science is that statement by Jackson based on? Maybe 4m in a couple of decades, but years? How would that work?

Lennart,

First, I do not know what was the source of Jackson's statement that the WAIS could substantially collapse within 2-years after it reaches some undefined tipping point at some undefined date in the future.  That said, I imagine that this date in the future would probably be after 2070; which time I believe would be necessary to precondition the WAIS marine ice sheets by grounding line retreat, fracturing of the ice streams, etc. to allow an armada of icebergs to calve and float-out of the various WAIS basins in a manner similar to the Heinrich and Bond events discussed in the Paleo thread at the following link:
http://forum.arctic-sea-ice.net/index.php/topic,130.msg1757/topicseen.html#msg1757

In this regard, see the horizontal error bars in the first attached image from O'Leary et al 2013, illustrating that sea level rose over 5m, during the Eemian, in as much as a few thousand years or as little as a couple of years (again see the overlapping error bars)
Michael J. O’Leary, Paul J. Hearty,William G. Thompson, Maureen E. Raymo, Jerry X. Mitrovica and Jody M.Webster (2013), doi:10.1038/ngeo1890


http://www.nature.com/ngeo/journal/v6/n9/full/ngeo1890.html
http://www.nature.com/ngeo/journal/v6/n9/fig_tab/ngeo1890_F1.html


Similarly, the second image from Grant et al 2012 also shows the possibility that during the Eemian sea level may (or may not) have risen over 5m in a few years (or not):

Grant et al 2012 (doi:10.1038/nature11593)

Best,
ASLR

[jai mitchell]

This has been well documented here (by ASLR) but is worth repeating.

“All of our simulations show it will retreat at less than a millimeter of sea level rise per year for a couple of hundred years, and then, boom, it just starts to really go,” Joughin said.

Researchers did not model the more chaotic rapid collapse, but the remaining ice is expected to disappear within a few decades.

http://www.washington.edu/news/2014/05/12/west-antarctic-ice-sheet-collapse-is-under-way/

I believe that his analysis of a few years is certainly after 2100 and is predicated on losing the Ronne's significant buttressing ice shelf effect and the Thwaites glacier which both allow for an "unpinning" of the remaining western sheet.

The only mechanism I have seen is the Larsen B scenario where rapid surface warming/cooling produces hydrofracture events and, coupled with the above loss of pinning allows for rapid collapse of land based sheets.

This will almost certainly happen by 2300 under a RCP 8.5 scenario with globally averaged temperatures reaching somewhere around 14-16C above pre-industrial averages.

[AbruptSLR]

While I do not seem to have the time nor the energy to detail how it might be physically possible (however likely, or not likely) to produce an armada of icebergs from the WAIS in a few years, I would note that debris fields in Drakes Passage have shown that during Meltwater Pulse 1A (with different conditions than today) such iceberg armadas did exist and circled around the Southern Ocean.


See: Weber(2014) doi:10.1038/nature13397 on timing of iceberg-rafted Antarctic debris

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


See also: Research published in Nature Communications showing that current Southern Ocean waters are becoming more layered with cold water on top and warm water below; which promotes ice melting near the grounding lines of Antarctic marine glaciers, as occurred 14,000 years ago during the Meltwater Pulse 1A.  This clear indicates an increasing risk of multiple meters of SLR this century:

http://www.sciencecodex.com/changing_antarctic_waters_could_trigger_steep_rise_in_sea_levels-142713

Extract: "The research published in Nature Communications found that in the past, when ocean temperatures around Antarctica became more layered - with a warm layer of water below a cold surface layer - ice sheets and glaciers melted much faster than when the cool and warm layers mixed more easily.

This defined layering of temperatures is exactly what is happening now around the Antarctic.
"The reason for the layering is that global warming in parts of Antarctica is causing land-based ice to melt, adding massive amounts of freshwater to the ocean surface," said ARC Centre of Excellence for Climate System Science researcher Prof Matthew England an author of the paper.
"At the same time as the surface is cooling, the deeper ocean is warming, which has already accelerated the decline of glaciers on Pine Island and Totten. It appears global warming is replicating conditions that, in the past, triggered significant shifts in the stability of the Antarctic ice sheet.""

Returning to the main topic: jai pointed out that Joughin's lower bound estimate of it taking about a couple of hundred years to pre-condition the WAIS into a collapse mode; however, I could image that on a BAU pathway such conditions could be achieved by about 2090 (see the WAIS Collapse thread in the Antarctic folder).  For such a condition: (a) ice shelves for the PIG & Thwaites, and the FRIS & RIS could be subject to the melt-pond hydro-fracturing scenario that jai mentions, and (b) the thinning ice streams for all of the WAIS marine ice streams could result in upstream crevasses that could be subject to a similar hydro-fracturing mechanism as that being considered for the Jakobshavn Glacier (see the following post by A-team in the Greenland folder):


https://agu.confex.com/data/handout/agu/fm14/Paper_28053_handout_1869_0.pdf # Greenland # Saturated Crevasses along Shear Margins of Jakobshavn # A Ring # "temporal increase in lateral drag seems to indicate  long-­‐term stress loading of the shear margins as the ice  stream response to down stream mass perturbations at  the terminus. Differences in transects indicate that  regions where water-­‐filled crevasses are found the  magnitude of lateral drag is less and the rate of drag  increase is smaller than regions without water. Given  this, preliminary results suggest that water-­‐filled  crevasses are weakening the shear margins and likely  resulting in enhanced stress loading in other parts of  the shear margins that are devoid of water."

In the PIG/Thwaites thread in the Antarctic folder, I call this the Thwaites Effect (after the well documented Jakobshavn Effect), where a marine ice stream without an ice shelf can progressively calve potentially producing an armada of icebergs.

[Lennart van der Linde]

Rignot recently estimated 100-200 years for one third of WAIS to collapse into the ocean, so about 1m in one century at the fastest:
http://www.washingtonpost.com/national/health-science/research-casts-alarming-light-on-decline-of-west-antarctic-ice-sheets/2014/12/04/19efd3e4-7bbe-11e4-84d4-7c896b90abdc_story.html

Blanchon et al 2009 estimate 2-3m in as little as 50 years during the Eemian:
http://thinkprogress.org/climate/2009/04/15/203960/nature-sea-level-rise-global-warming-reefs/

Richard Alley speaks of 3m in centuries or decades (at 40m10s):
http://youtu.be/o4oMsfa_30Q?t=40m10s

Rohling et al 2013 estimate a maximum potential rate of 1 meter/decade in their figure 2a:
http://www.nature.com/srep/2013/131212/srep03461/fig_tab/srep03461_F2.html

Meltwater Pulse 1A was 4-6 meter/century, probably, but in different conditions, with more ice, but lower climate forcing.

So my view so far is that 4m in four decades is to some extent supported by some experts as the most extreme worst-case possibility. Jackson's 4m in a 'couple of years' I've not heard before, so I'll ask him what his argument is for that statement.

[jai mitchell]

Here is the reference doc looking at Antarctica's meltwater pulse 1A contribution.  Note the paleo grounding lines extending out beyond the current limits of the Ronne and Ross Ice Shelves.

http://www.nature.com/ncomms/2014/140929/ncomms6107/full/ncomms6107.html

Antarctic contribution to meltwater pulse 1A from reduced Southern Ocean overturning
doi:10.1038/ncomms6107
N. R. Golledge et. al.

During the last glacial termination, the upwelling strength of the southern polar limb of the Atlantic Meridional Overturning Circulation varied, changing the ventilation and stratification of the high-latitude Southern Ocean. During the same period, at least two phases of abrupt global sea-level rise—meltwater pulses—took place. Although the timing and magnitude of these events have become better constrained, a causal link between ocean stratification, the meltwater pulses and accelerated ice loss from Antarctica has not been proven. Here we simulate Antarctic ice sheet evolution over the last 25 kyr using a data-constrained ice-sheet model forced by changes in Southern Ocean temperature from an Earth system model. Results reveal several episodes of accelerated ice-sheet recession, the largest being coincident with meltwater pulse 1A. This resulted from reduced Southern Ocean overturning following Heinrich Event 1, when warmer subsurface water thermally eroded grounded marine-based ice and instigated a positive feedback that further accelerated ice-sheet retreat.

[Lennart van der Linde]

Yes, but do we know how fast SLR was during Meltwater Pulse 1A?

Deschamps et al give 14-18m over about 350 years, so that would be about 4-5 meter/century on average:
http://www.nature.com/nature/journal/v483/n7391/full/nature10902.html

If there were separate shorter pulses during MWP 1A, then the maximum rate of SLR was maybe even faster than 4-5 meter/century. So who knows, maybe even 4-5 meters in a few decades?

Golledge et al think Antarctica probably contributed about 3-4 meter of SLR in a few centuries to MWP 1A:
http://www.reportingclimatescience.com/news-stories/article/antarctic-changes-could-trigger-steep-sea-level-rise.html

For the possibility of a few meters in a few years I've not seen any indications so far.

[AbruptSLR]

Yes, but do we know how fast SLR was during Meltwater Pulse 1A?

Deschamps et al give 14-18m over about 350 years, so that would be about 4-5 meter/century on average:
http://www.nature.com/nature/journal/v483/n7391/full/nature10902.html

If there were separate shorter pulses during MWP 1A, then the maximum rate of SLR was maybe even faster than 4-5 meter/century. So who knows, maybe even 4-5 meters in a few decades?

Golledge et al think Antarctica probably contributed about 3-4 meter of SLR in a few centuries to MWP 1A:
http://www.reportingclimatescience.com/news-stories/article/antarctic-changes-could-trigger-steep-sea-level-rise.html

For the possibility of a few meters in a few years I've not seen any indications so far.

Lennart,

It is good that you are going to e-mail Jackson for his source because I doubt that you will find in a published reference with any statement that at some indefinite point in the future that the WAIS could collapse in a couple of years.  That said you should remain aware about the difference between a statement (by Jackson) that as an upper bound physical possibility that the WAIS could collapse in a couple of years is much different than getting a computer model to simulate and forecast such a possibility (including confidence levels); which is about the only thing besides an expert opinion poll that can be peer reviewed.  I suspect that the ACME projections, completed in about 10-years, will be the only reliable first approximation of such a possibility/probability; and it may well be several more decades after that before a model can make a meaningful projection of this risk (note that earthquakes, volcanoes, basal melting, changes in currents, winds and possible future rain events and interaction with Greenland events, etc. would need to be considered to establish an upper physical bound [which the IPCC does not address]).

Best,
ASLR

[jai mitchell]

I cannot recall specifically but I think that the model involved a grounding line retreat such that the PIG eventually meets the Ronne-Filchner sea with a seaway. oh looky I found a link to the resident master's analyses!

Yes, the idea is that significantly increased flowrates produce rapid collapse once a seaway is opened beneath the sheets.

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

In the accompanying figure from Vaughan et al. 2011, the researcher postulate that the indicated seaways opened in the WAIS during the Eemian period some 124,000 years ago.  Vaughan et al. proved that for an upper bound that the longest of these seaways formed within less than a thousand years (which is well within the timeframe of the Eemian peak proving that WAIS could have contributed at least 3.4 to 3.8 m to eustatic SLR in that period) .  I propose that by 2100 such seaways could be re-established in the WAIS via a combination of: (a) floatation of ice sheet sections that have thinned sufficiently for them to float; (b) the formation of a network of interconnected subglacial cavities paralleling the seaways identified by Vaughan et al., which (when interconnected) would allow tidally induced flushing of CDW to rapidly melt the basal ice around the expanding interconnected cavities; (c) accelerated caving of both glaciers and ice shelves due to such factors as increasing CDW temperatures, tidal action, periodic subglacial meltwater network lubrication of basal friction (see surge post topic), and increased wave action due to telecommunication from the Topical Pacific Ocean; (d) a melt-pond mechanism collapse of the Ross Ice shelf after 2050; and (e) a change in the currents in the Weddell Sea after 2050 leading to accelerated CDW advection forced retreat of the glaciers grounding lines in that region so that the grounding lines retreat past buttressing ridges that have been supporting those glaciers.

[jai mitchell]

More from SLRs thread

As my proposed WAIS collapse scenario has many similarities as to what may have happened during the Eemian, I provide the accompanying figure from Barnes et al 2010 showing the probable condition of the WAIS at the Eemian peak.  This condition is supported both on the fossil records of Bryozoans and on DNA of existing  family of Antarctic octopus the West Antarctic.  Furthermore, in 2011 based on marine sediments it was found that GIS could only have contributed 1.6-2.2m to Eemian sea level; while in 2012, based on GIS ice core (NEEM) findings, the high-end of this contribution was further limited indicating that the WAIS contributed at least 3.5 to 3.8m at that time.

[AbruptSLR]

jai,

Indeed, if you want to talk about non-peer reviewed scenarios, then the attached image from Reply #23 (from the linked Antarctic fold thread on the WAIS Collapse), shows a conceivable scenario of how the WAIS could be on the brink of total collapse by 2090, following a RCP 8.5 50% CL pathway.

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

However, I think that Lennart is looking for more of a peer-reviewed published reference; which according to RAND and the Robust Decision Making methodology is the wrong thing to be looking for, because by the time that you have that, you will be well past the tipping point.

Best,
ASLR

[wili]

"Rignot recently estimated 100-200 years for one third of WAIS to collapse into the ocean, so about 1m in one century at the fastest"

From that one source. So the max in one century would be considerably higher when you add in GIS, glaciers and expansion, twice as fast. And of course there are known and unknowns unknowns that could accelerate that further.

[Lennart van der Linde]

ASLR, Jai,

Let's just say I would like to know how people like Hansen, Pfeffer, Rignot, Alley, Rohling, Joughin, Vaughan, etc. think of Jeremy Jackson's statement. They all have peer-reviewed papers published, but they also make statements in lectures and popular articles, or via expert elicitations, that indicate their thinking beyond their scientific papers. I've referred to a few of those statements above.

I've sent Jackson an email and will let you know if and when he replies. It could also be he meant decades instead of years. It has happened to me that I said meters/year when I meant meters/century during a presentation.

[Lennart van der Linde]

wili,
You're right of course. That 1 meter of Rignot could make total SLR by 2100 near 2m, or even some more. And from 2100 to 2200 maybe 4, 5 or even 6-7 meter could be added, according to Kopp  et al 2014. But all that would imply 4m in a few decades as the most abrupt SLR considered plausible by the experts so far.

Who knows it can go even faster, but that's a speculation that Jackson did not present as such. So either he knows more than others, of he made a mistake, or he speculated without making that explicit, or he tried to alarm his audience by making the science sound even more alarming than it already is.

[AbruptSLR]

"Rignot recently estimated 100-200 years for one third of WAIS to collapse into the ocean, so about 1m in one century at the fastest"

From that one source. So the max in one century would be considerably higher when you add in GIS, glaciers and expansion, twice as fast. And of course there are known and unknowns unknowns that could accelerate that further.

I think that we should all recognize that in the following extract, Rignot does suggest that within 100 to 150-years 1/3 of the WAIS could be gone.  However, if one realizes that any such SLR contribution must accelerate non-linearly from about 0.3mm/year today to say 1,500 mm/year by the end of 100 to 150-years, then it may be conceivable that Jackson's statement might be approximately correct at the end of such a period of non-linear acceleration (obviously my projection of such a rate of SLR contribution being possible between 2090 and 2100 is contingent upon the effective climate sensitivity also increasing to something like 6 C by 2100):

http://www.washingtonpost.com/national/health-science/research-casts-alarming-light-on-decline-of-west-antarctic-ice-sheets/2014/12/04/19efd3e4-7bbe-11e4-84d4-7c896b90abdc_story.html

Extract: "So how fast could the loss of West Antarctica unfold? Velicogna’s co-author, Eric Rignot of UC-Irvine, suggested that in his view, within 100 to 200 years, one-third of West Antarctica could be gone.
Rignot noted that the scientific community “still balks at this” — particularly the 100-year projection — but said he thinks observational studies are showing that ice sheets can melt at a faster pace than model-based projections take into account."

[AbruptSLR]

The following quote by Rignot is from the 2014 Rolling Stone article:

"Thwaites glacier started to accelerate after 2006 and in 2011 we detected a huge retreat of the glacier grounding lines since 2000. Detailed reconstructions of the glacier bed further confirmed that no mountain or hill in the back of these glaciers could act as a barrier and hold them up; and 40 years of glacier flow evolution showed that the speed-up was a long story.
At the current rate, a large fraction of the basin will be gone in 200 years, but recent modelling studies indicate that the retreat rate will increase in the future.
Controlling climate warming may ultimately make a difference not only about how fast West Antarctic ice will melt to sea, but also whether other parts of Antarctica will take their turn. Several "candidates" are lined up, and we seem to have figured a way to push them out of equilibrium even before warming of air temperature is strong enough to melt snow and ice at the surface.
Unabated climate warming of several degrees over the next century is likely to speed up the collapse of West Antarctica, but it could also trigger irreversible retreat of marine-based sectors of East Antarctica. Whether we should do something about it is simply a matter of common sense. And the time to act is now; Antarctica is not waiting for us."

Obviously, until we know what the climate sensitivity and the radiative forcing will be, we are all (including experts like Rignot) just guessing how bad the rate of Antarctic contribution to SLR could be by the end of the next 100 to 200 years.

[jai mitchell]

Similar to the projections of declines in Sea Ice Extent,
Similar to the hesitancy to use PIOMAS volume data instead of Sea Ice Extent,


Is the reluctance to accept that current model projections neglect to include newly discovered and thoroughly unexpected causal mechanisms of transformation.  These mechanisms, due to their unknown origin and, in some cases, uncertain effects cannot be constrained within standard climate model projections. 

For instance:  What if recently observed Circumpolar Deep Water temperatures continue to increase at the "jaw dropping" rates observed recently, and that this trend is the primary force that caused the massive contribution to SLR by Antarctica under meltwater pulse 1A?

http://blogs.ei.columbia.edu/2010/12/14/deep-ocean-heat-is-melting-antarctic-ice/

Martinson said that heat stored in deep waters far from Antarctica is being pushed southward and becoming entrained in the Antarctic Circumpolar Current, a vast, wind-driven water mass that constantly circles the frozen continent. The evidence comes from 18 years of Antarctic voyages Martinson has made to measure water temperature, salinity and other qualities at different depths. He called the increases in ocean heat in the past few decades “jaw dropping.”

[Lennart van der Linde]

Could we ever reach 1500 mm/yr of SLR?

Bouman et al 2014 measured about 0.5 mm/yr SLR from WAIS from 2009-2012:
http://onlinelibrary.wiley.com/doi/10.1002/2014GL060637/abstract

Jeremy Jackson said in his lecture last month that when WAIS collapses, and this will happen, he said, then that would mean '4m of SLR in a couple of years'. So let's say that would mean 1000 mm/yr SLR from WAIS, for a few years.

Rignot, Alley, Joughin etc indicate a potential WAIS-collapse, once initiated, within a few decades. Let's say about 3m in three decades, or about 100 mm/yr, at or around the end of this century at the earliest.

About 100 mm/yr is also the highest rate of SLR thought plausible by Rohling et al.

For the Amundsen Sector of WAIS, which contains about 1.2m of SLR rapid collapse will start once its SLR-contribution is about 1 mm/yr, according to Rignot et al 2014 and Joughin et al 2014:
http://onlinelibrary.wiley.com/doi/10.1002/2014GL060140/full

And:
http://www.sciencemag.org/content/344/6185/735.abstract

So how could we go from the current 0.5 mm/yr SLR from WAIS to 100 or even 1000 mm/yr?

If we assume, inspired by Jim Hansen, that SLR from WAIS will be 0.5 mm/yr from 2005-2015 and would double every 10 years, then we would need eight doublings to reach 128 mm/yr from 2085-2095, and three more doublings to reach 1024 mm/yr from 2115-2125. One more doubling would give 2048 mm/yr from 2125-2135.

This in turn would imply 2.55m of SLR from WAIS by 2095, and almost another meter by 2100, so let's say 3.5m by 2100, with about 3m in the last three decades of this century. Then all the most vulnerable ice from WAIS would be pretty much gone and it would have fully collapsed.

Total SLR by 2100 would then be 4-5m, depending on the GIS-contribution. If this could not be reached by 2100, then maybe shortly thereafter.

So could total SLR ever speed up to more than say 100-200 mm/yr, not just mathematically, but also physically?

That would probably require EAIS to be about as vulnerable as WAIS, at least from about 2100 onwards. Or a little less vulnerable relative to its greater size: since it contains about 19m of marine based ice it can afford to lose less ice per year per basin to reach a comparable SLR-contribution to WAIS. But then this would still seem only enough to sustain SLR at this very high speed of 100-200 mm/yr.

Also Pfeffer and Hansen have pointed to likely kinematic constraints and a negative iceberg cooling effect, which could imply maximum SLR could be rate-limited, as Rohling calls it. So maybe about 100 mm/yr is about the maximum plausible SLR that could be sustained for more than a few decades even under very strong forcing?

At least it's hard to see how it could become even faster than the 100-200 mm/yr we find via assuming a 10-year doubling time for ice mass loss (or what we could call a Hansen thought experiment or extrapolation). The doubling time could also be 5 or 20 years, but sooner or later it would stop because the (vulnerable) ice would be gone.

So the question is: will ice loss grow exponentially and if so, how fast and far? And how abrupt can the ice loss become, whether it will grow exponentially or not?

In any case, Jackson's 4m in a few years, seems impossible to me, but maybe others see possibilities for it to become reality nevertheless.

[AbruptSLR]

Lennart,

As you are willing to consider contributions to SLR other than from the WAIS in Jackson's statement: I first provide the following quote from the Rolling Stone article about Jason Box's theory about why Greenland ice sheet is disappearing (and will continue to disappear at accelerating rates) faster than previously predicted:

http://www.rollingstone.com/feature/greenland-melting

Quote: "In early 2012, Box predicted there would be surface melting across the entirety of Greenland within a decade.  Again, many scientists dismissed this as alarmist claptrap. If anything, Box was too conservative – it happened a few months later.  He also believes that the climate community is underestimating how much sea levels could rise in the coming decades.  When I ask him if he thinks the high-end projections of six feet are too low, he doesn't hesitate: "Shit, yeah."
"Jason has one very important quality as a scientist," says Thomas Painter, a research scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.  "He is willing to say crazy stuff and push the boundaries of conventional wisdom.""

Next, regarding SLR contributions from the EAIS, it is important to remember that several of these catchment basins immediately adjoin the WAIS and it is probable that Jackson would have lumped them in with the WAIS statement that he made.  For example: the article at the following link makes clear the projected introduction of warm water into the Weddell sea could eventually trigger between 3 and 4 m of SLR contribution from the Recovery catchment basin (see the associated first attached image):

http://www.bbc.co.uk/news/science-environment-25173121

Finally, I provide the second attached image of the time history of ice velocities for the Hudson Strait Ice Stream during the LGM, which shows that when the associated ice shelf breaks off (ala the Larsen-B shelf collapse), the ice velocities can peak for a short period of years; which if coupled with a subsequent Thwaites (Jakobshavn) Effect, might (just conceivably) make Jackson's statement plausible, if say a SLR surge from Greenland (or a large seismic event in West Antarctica) were to simultaneously trigger a shelf collapse/Thwaites Effect for multiple WAIS marine glaciers and the Recovery Ice Stream.

Alvarez-Solas, J., Robinson, A., and Ritz, C. (2012),  “Can recent ice discharges following the Larsen-B ice-shelf collapse be used to infer the driving mechanisms of millennial-scale variations of the Laurentide ice sheet?”, The Cryosphere, 6, 687–693, 2012, www.the-cryosphere.net/6/687/2012/ doi:10.5194/tc-6-687-2012.

Best,
ASLR

[Gray-Wolf]

And what of the 'unexpected' ( i.e. that which was unthinkable only 20yrs ago?) I've been a keen observer of Ross for the past decade and more and have had cause to approach Bob Grumbine concerning a crevasse that he was deploying seismometers into to map any changes there. It , to me, appears to be the next major calve from Ross but is far larger than the last major calve. The crevasse runs from the Roosevelt island end of Ross to beyond the central section ( heading out toward the U.S. Base). Is this not the end of Ross that needs to go before we see West Antarctica again become an island? I recall some NASA images of melt up to a mile up the trans Antarctic range to the rear of Ross so are we not now seeing the start of the process of the breakup of Ross. We know that the warm waters are now at that end of Ross so should we also now be expecting the grounding line to be retreating back toward this huge crevasse?

Changes below the feed glaciers at this end of Ross, due to the upland melt, could alter the response once this section of 'buttress' has been removed ( radar images show a huge ruck in the ice from when the shelf finally held up the ice flow and it ran over itself)?

For me Ross is the issue as we have huge amounts of ice ready to 'float off'. Any changes in either the buttress or the back pressure from the feed glaciers could lead to shear failure at the base of the shelf and catastrophic float off of large sections.

But first we have the next major calve to wait for!

[wili]

LvdL wrote: "will ice loss grow exponentially and if so, how fast and far?"

Aren't there other possibilities besides linear and exponential rates of increased ice loss? Aren't there possibilities/probabilities of discontinuities--as our colleagues handle says: Abrupt SLR?

Isn't that what Alley and others are talking about happening when warm water starts to flow under the main ice sheet beneath the parts that are grounded below sea level?

[GeoffBeacon]

Earthquakes and climate change (https://forum.arctic-sea-ice.net/index.php/topic,283)

Any recent information that might be relevent here?

[Gray-Wolf]

This is my main concern Wili! At times i think it unhelpful to look at past warmings , and the changes they wrought, because the forcing this time is novel and incredibly fast?

When I look at loading's in nature a slow build up in pressure will not drive the same results as an instant forcing of that pressure? And if this is true of the ice then would we not see a domino kind of response as other areas are forced to fail by the speed of change?

The warm bottom waters have only recently made it around to Ross but I do not think it necessarily means Thwaites/PIG will have a head start in any collapse? Each outlet is different.

The ruck in the ice beneath Ross, does that act like a spring or has all the stresses now dissipated from the tension of the ice buried there? Could the 'normal' calving at the edge of Ross lead to an abnormal response now warm waters are eating away at the base of the sheet there? Has increased melt in the mountains to the rear lead to different dynamics in the feed glaciers to the rear of the shelf?

I do hope that everything is fine and we ought expect a slow 'drip,drip' type melt but Nature does seem to like the odd catastrophic collapse in systems?

[wili]

One thing that I find rather stunning when I step back a bit and consider the nature of the debate, is that what we are essentially discussing is ice melting. One would think that understanding how and at what pace ice melts would be the most elementary type of physics imaginable. Yet the uncertainties about how and at what rate these particular kinds of ice will melt in various potential scenarios quickly becomes mind-numbingly complex. (The same, of course, goes for the complexities of Arctic sea ice.)

Thanks to all for helping to unravel some of that complexity for my perhaps-too-easily-benumbed brain.

[Lennart van der Linde]

As for Jason Box, I will ask him what he thinks of Jackson's statement as well.

Response by Box:
"4m in a 'couple of years' is really far far outside of expectations. Let us see if that 3 mm per year doubles in the coming decade to 6 mm then I would say we are on track for more than 2 m by end of century."

I then asked him what he thinks the worst-case rate of SLR for after 2100 could be, but no reply yet.

[Lennart van der Linde]

One thing that I find rather stunning when I step back a bit and consider the nature of the debate, is that what we are essentially discussing is ice melting. One would think that understanding how and at what pace ice melts would be the most elementary type of physics imaginable. Yet the uncertainties about how and at what rate these particular kinds of ice will melt in various potential scenarios quickly becomes mind-numbingly complex. (The same, of course, goes for the complexities of Arctic sea ice.)

wili,
I guess the melting itself may not be so complex, but how the ice will move and how the heat will get to the ice seem to be the complex questions, that are especially hard to answer since the current situation is without natural precedent.

[wili]

Good points, LvdL.  "3m in three decades" That's plenty fast enough for me. I hope we can all agree that Hollywood-style instant super-tidal waves coming from ice sheet melt are not in the cards. Even 3-7m in less than a decade is beyond what I, at least, can wrap my head around (though that alone is not particularly probative one way or the other, of course).

Since this thread is about slr and cost, I am going to ask something that should probably really go in the 'stupid questions' thread:

If one of the main mechanisms for destabilization of the Antarctic ice sheets is the incursion of warm ocean water under the sheet, would it ultimately be cheaper to try to build structures that might impede or obstruct that flow in a few crucial places than to pay for the massive infrastructures that would be needed to protect coastlines around the world?

[Laurent]

Almost 7,000 UK properties to be sacrificed to rising seas
http://www.theguardian.com/environment/2014/dec/28/7000-uk-properties-sacrificed-rising-seas-coastal-erosion

[Lennart van der Linde]

If one of the main mechanisms for destabilization of the Antarctic ice sheets is the incursion of warm ocean water under the sheet, would it ultimately be cheaper to try to build structures that might impede or obstruct that flow in a few crucial places than to pay for the massive infrastructures that would be needed to protect coastlines around the world?

wili,
Some people have had similar ideas for melting or preserving Arctic ice by damming the Bering Strait:
http://www.adn.com/article/could-massive-dam-between-alaska-and-russia-save-arctic

I haven't heard of any similar ideas for Antarctica, but who knows it could help to slow the melting.

[jai mitchell]

I think Grey-Wolf is hitting on it quite clearly. 

Imagine Antarctica conditions in 2150 under RCP 8.5

If we are seeing surface warming above the Ross shelf (1 mile as Grey says) what will it look like if the average temperature is 20C warmer? (assuming Antarctic amplification of 1.3)  What kind of surface melt dynamics would we see? How high up?  what if, by this time, all of the shelves are gone and multiple under ice channels have opened up between the Ronne-Filchner to the Admusen and even over to the Ross seas.  These channels allowing direct current flow of Deep water to melt the ice with significantly higher temperature water at flowrates 100 times the current rates of intrusion?

This is a snapshot of what it will most likely look like, in this scenario what does Greenland look like?

What will be the average sea level rise by this time under these scenarios? 2 meters? 5 meters?

if only 2 meters by 2150, what is the effect of this sea level rise on lifting current grounding lines?

------------

I write these things to remind all that the radical environmental changes that will be incurred by RCP 8.5 over the next few hundred years is inconceivable within current models.  It is far too different than current conditions.

[AbruptSLR]

I would like to note that some issues associated with the potential collapse of the FRIS/RIS ice shelves can be found in the Antarctic folder at the following link (which discusses melt pond risks, calving risks and changes in warm ocean currents).

http://forum.arctic-sea-ice.net/index.php/topic,117.0.html

Furthermore, I would like to note that due to systemic pressures most scientists have to date focused on either the most likely future scenarios, and/or the scenarios that err on the side of least drama.  Even efforts such as Tad Pfeffer's efforts to define an upper limit to SLR (or 2m) based on ice flow kinematics were based on the assumption that the ice streams would remain grounded.  For Jackson to be correct (assuming that he did not misspeak) then it is clear that the only mechanism that could achieve such a rapid rate of SLR would be the formation of icebergs (as within 2 years there would not be sufficient time for the ice to melt) from the previously grounded ice streams.  While the near simultaneous formation of armadas of icebergs may not appear to be terribly likely; in my opinion such scenarios merit serious investigation as the consequence of such a scenario are so very high.

[jai mitchell]

Is the present the key to the future?

doi:10.1016/j.earscirev.2014.12.005

The empirical and conceptual relationships between Earth surface processes and global changes are very complex. The concept that “the present is the key of the future” implies that we know enough the present to be able to extend our knowledge forward to focus on the future. Field and remote observations on the present-day Earth surface processes represent the methodological instruments for the forecasting. At the end of the 1980s, the scientific community predicted a significant increase of global warming followed by changes in the trends of related surface processes. Some processes, such as the Arctic and Antarctic snow melting are now accelerating and even irreversible, thus these trends show that we are now in an ‘out of scale’ discontinuity moment. Present-day measures and observations could be scarcely significant and may add uncertainty in the prediction of future trends. The ‘out-of-scale’ trend raises a fundamental question regarding the present, since it may provide a new angle of thought for contemporary theoretical approaches. The need for reducing the uncertainty in the trends of future processes requires a deep rethinking of the current paradigms in order to consider also the ‘out of scale‘ trends.

http://www.sciencedirect.com/science/article/pii/S0012825214002256

[Laurent]

East Cost "nuisance" flooding already increasing
http://www.enn.com/environmental_policy/article/48133?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+EnvironmentalNewsNetwork+%28Environmental+News+Network%29

[AbruptSLR]

The following abstract from DeConto & Pollard (2014) confirms the disturbing message that I have been conveying by saying:

"… the same model shows the potential for massive ice and freshwater discharge beginning in the second half of this century.
 …
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.
…
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."
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."


Edit:

Lennart,

Maybe this explains (partially) what Jackson was talking about (surface meltwater entering crevasses of marine glaciers more than 800 m thick, such as Thwaites)?

Best,
ASLR

[AbruptSLR]

As a follow-up note to my last post:  Sea level rise due to melting glaciers is about ~ 0.01 Sv, and as glaciers currently contribute about 0.71mm/year to SLR; therefore the peak 1.0 Sv discharge that DeConto & Pollard 2014 cite is equal to a rate of SLR of about 0.071meters per year, or about 1/30th the rate that Jackson cited.

Edit: I fixed a math error

[sidd]

1) That 800 m thickness is related to an earlier paper (whose name escapes me, and for which i have not time now to search) giving the upper limit for marine fonted ice mass thickness as a kilometer.

2) 0.071 m/yr is 1 m in 15 yr, exceeding estimated peak rate at MWP1A of 1 m/20 yr, although of course the latter persisted for 500 yr ...

3) decadal to centennial scale sounds bad

4)second half of this century sounds bad too ...

O dear, Pollard and Diconto have got much more assuredly pessimistic since a few years ago. So has Rignot.

sidd

[Lennart van der Linde]

Sea level rise due to melting glaciers is about ~ 0.01 Sv, and as glaciers currently contribute about 0.71mm/year to SLR; therefore the peak 1.0 Sv discharge that DeConto & Pollard 2014 cite is equal to a rate of SLR of about 0.071meters per year, or about 1/30th the rate that Jackson cited.

ALSR,

Thanks, I'd not realized yet that 1 Sv of meltwater sustained for a year contributes about 86 mm to SLR. So add in thermal expansion and meltwater from GIS, and about 100 mm/yr of SLR would be possible as a peak rate, according to DeConto & Pollard. This is also the maximum rate of SLR thought plausible in Rohling et al 2013, based only on geological evidence. Sustained for a decade that would be 1 meter/decade. Still about an order of magnitude smaller than Jackson's remark, but plenty abrupt enough for human societies, it seems.

[Laurent]

NOAA establishes 'tipping points' for sea level rise related flooding
http://www.terradaily.com/reports/NOAA_establishes_tipping_points_for_sea_level_rise_related_flooding_999.html

[AbruptSLR]

The linked article indicates that before the end of the century super-typhoons could attain wind speed of 85 to 90 m/sec, which will of course increase storm surge on top of SLR.

Kazuhisa Tsuboki, Mayumi Yoshioka, Taro Shinoda, Masaya Kato, Sachie Kanada and Akio Kitoh, (2014), "Future increase of super-typhoon intensity associated with climate change", Geophysical Research Letters, DOI: 10.1002/2014GL061793


http://onlinelibrary.wiley.com/doi/10.1002/2014GL061793/abstract

Abstract "Increases of tropical cyclone intensity with global warming have been demonstrated by historical data studies and theory. This raises great concern regarding future changes in typhoon intensity. The present study addressed the problem to what extent super-typhoons will become intense in the global warming climate of the late twenty-first century. Very high-resolution downscale experiments using a cloud-resolving model without convective parameterizations were performed for the 30 most intense typhoons obtained from the 20-km-mesh global simulation of a warmer climate. Twelve super-typhoons occurred in the downscale experiments and the most intense super-typhoon attained a central pressure of 857 hPa and a wind speed of 88 m s−1. The maximum intensity of the super-typhoon was little affected by uncertainties that arise from experimental settings. This study indicates that the most intense future super-typhoon could attain wind speeds of 85–90 m s−1 and minimum central pressures of 860 hPa."

[Laurent]

US coastal cities face daily flooding by mid-century – NOAA - S
http://www.rtcc.org/2015/01/06/us-coastal-cities-face-daily-flooding-by-mid-century-noaa/

[Sigmetnow]

Although the term “nuisance floods” may connote minor flooding with little reason for concern, the impacts of repetitive floods should not be underestimated, the study’s lead author, William Sweet of the National Oceanic and Atmospheric Administration (NOAA), told reporters at the annual meeting of the American Geophysical Union on Thursday.

“It’s an emerging flooding crisis,” Sweet, an oceanographer with NOAA’s National Ocean Service, said.

http://mashable.com/2014/12/20/washington-dc-sea-level-rise/

[Lennart van der Linde]

As for Jason Box, I will ask him what he thinks of Jackson's statement as well.

Response by Box:
"4m in a 'couple of years' is really far far outside of expectations. Let us see if that 3 mm per year doubles in the coming decade to 6 mm then I would say we are on track for more than 2 m by end of century."

I then asked him what he thinks the worst-case rate of SLR for after 2100 could be, but no reply yet.

[tombond]

As for Jason Box, I will ask him what he thinks of Jackson's statement as well.

Response by Box:
"4m in a 'couple of years' is really far far outside of expectations. Let us see if that 3 mm per year doubles in the coming decade to 6 mm then I would say we are on track for more than 2 m by end of century."

Very realistic reply from Jason Box.  The key to the timing of abrupt sea level rise is the rate of acceleration in the land ice melt rate.  If ice melt rates and thus sea level rise doubles every decade (or less) then we could see a one metre sea level rise by mid century or just after.

This possibility should be central to all coastal infrastructure planning world wide.

 

[AbruptSLR]

As for Jason Box, I will ask him what he thinks of Jackson's statement as well.

Response by Box:
"4m in a 'couple of years' is really far far outside of expectations. Let us see if that 3 mm per year doubles in the coming decade to 6 mm then I would say we are on track for more than 2 m by end of century."

I then asked him what he thinks the worst-case rate of SLR for after 2100 could be, but no reply yet.

Lennart,

Thanks for the great follow-up on this matter.  While I fully agree with Jason Box's response, I will play a little bit of the devil's advocate by citing the following few ways that such an occurrence so far far outside of expectations "might" (or might not) actually happen:

1.  The Earth's magnetic dipole is currently on a pace to flip 180 degrees within the next 100-years.  Thus given the Byrd Subglacial Basin's exceptionally thin crust, it may be that sometime after 2050 the magma beneath the BSB may change (may become: less viscous, faster flowing, etc.) sufficiently to induce seismic/volcanic activity or extreme basal ice melting in the BSB by 2100.
2.  ECS may very well currently be 4.5 C, and if society stays on a BAU pathway the effective climate sensitivity could equal or exceed 6 C by 2100; which in turn could lead to excessive surface ice melting on the West Antarctic ice shelves and on the lower altitude perimeter of the WAIS itself; which could accelerate marine glacier calving rates well beyond that cited by Bassis & Jacobs 2013 (due to hydrostatic pressure within the Bassis & Jacobs postulated crevasses).
3.  I am concerned that the projected increased magnitude and frequencies of both El Nino and cyclonic events will increase advection of ocean water into increasingly deep subglacial marine cavities; which will also cause accelerated calving.

Obviously, other extreme scenarios are possible, but until we have more/better evidence, or better Earth System Models, a SLR contribution from the WAIS by 2100 of 1m to 2m would appear to be much more likely.

Best,
ASLR