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Author Topic: Challenging Misconceptions about the Potential Abrupt Collapse of the WAIS  (Read 30728 times)

AbruptSLR

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An important part of the scientific method is to challenge prevailing misconceptions in order to gain a deeper insight into the true nature of a situation.  Most of my other threads about the potential abrupt collapse of the WAIS force on explaining my proposed hazard analysis; with little emphasis (except for by my brief critique of Pfeffer et al assumed [or expert opinion] limits on ice mass loss rates from WAIS) on challenging prevailing misconceptions on this matter.  Therefore, I open this thread focused on challenging what I believe to be prevailing misconceptions, and I begin in this post by challenging some of the mis-beliefs about the probability of occurence of the various SRES, and RCP, radiative forcing scenarios:

The global economic system that is driving the creation of man-made radiative forcing components is also system with net positive feedbacks encouraging the creation of more radiative forcing components, because fossil fuels have been historically associated with energizing the modern capitalistic system; thus all probability density functions associated with estimating man-made radiative forcing component emission scenario from the current modern capitalistic system will have a low probability of low emission and with have a fat tail for higher emissions.  This can be illustrated in the first attached image by noting that the AR4 SRES B1 family of emissions were developed by the IPCC to simulate the "Low" scenarios required to keep global temperature from raising 2oC above the 2000 temperature levels (and were nominally adopted by V&R as input to their "Low" SLR projections) in-line with the UN Kyoto Protocol goals; however, at the  17th Conference of Parties, COP 17, to the United Nations Framework Convention on Climate Change, held in Durban, South Africa in 2011, representatives of the Parties agreed to replace the Kyoto Protocol goal of a 2 oC global temperature rise, with a new "legal framework" that will allow global temperatures to rise to nominally 4 oC, thus indicating the probability function of anthropogenic emissions represented by smooth distribution of the 2007 data (a prior), could be transformed by future Bayesian Learning analysis into a posterior with a more asymmetric distribution due to the possible elimination of the SRES B1 (Full Participation) family of emission scenarios, and the addition of new high-end scenarios due to such factors as higher climate sensitivity than assumed.
For the "Full Participation" projection probabilities to be correct, strong negative feedback would have been implemented (by either policy or technology/market forcing); however, observations from 2007 to the Durban COP17 meeting in December 2011, indicates to most reasonable observers that this family of SRES B1 probabilities (limiting temperature increase to less than 2oC) is at risk of not happening and a Bayesian Learning analysis may numerically verify this.  Currently, most observers realize that if strong negative policy feedback can be negotiated in the Durban legal framework to be negotiated by 2015 and possibly implemented by 2020, then the best family of probability that can be hoped for is similar to the SRES A1B "Developing Countries Delay" scenario, while if weak negative feedback occurs then probabilities similar to the SRES A1FI "Reference" scenario are more likely.  This can be understood by examining the second attached figure, for the results of representative Bayesian Learn climate change analysis where: (a) the top graphs for Data from the 1961-1998 show on the left panel two blue Priors together with a red curve of observations resulting in the Posterior in the panel on the right; and (b) the middle graphs for Data from 1970 to 1998 show on the left panel the same two Priors as in the top graphs together with more recent observations indicated by a red curve to the right of the red curve in the top graph; which result in the Posterior shown in the right middle panel with the new probability curve shifted to the right of the curve in the top left panel; and (c) the bottom graphs for Data from 1980 to 1998 show the same two Priors together with still more recent observations shown by the red curve in the bottom left panel, which after Bayesian Learning analysis results in the Posterior in the bottom right panel which is still further to the right of the Posterior shown in the middle right panel.  This sequence of Bayesian analyses for a representative system with strong net positive feedback indicates how only a few years (or decades) of observations can result in the collapse of hypothetical probabilities for families of projections such as SRES B2/A1B, or RCP 3/4.5, converging the probabilities towards those for the families of projections associated with SRES A1FI or RCP 8.5.  It is also important to note that if new, or stronger net positive feedbacks are identified, then after Bayesian Learning it is probable that the Posterior would shift toward higher projections than such previous Priors as those associated with SRES A1FI or RCP 8.5.

A similar progression of Bayesian Learning from future observations related the collapse of the WAIS could transform the current "fat-tailed" of my proposed PDF for the risk of abrupt SLR for California (see the third image) into a more peaked posterior PDF for high sea levels as we progressively get closer to 2100.
“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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This post focuses again challenging the widespread misconceptiong that the risk of abrupt ice mass loss from the WAIS is limited by the "...persistence and magnitude of subsequent discharge", as stated in the following abstract (for which I concur with the methodology, but I disagree with the assumptions and conclusions):

Upper bounds on twenty-first-century Antarctic ice loss assessed using a probabilistic framework by Christopher M. Little, Michael Oppenheimer & Nathan M. Urban
Nature Climate Change, (2013), doi:10.1038/nclimate1845, 17 March 2013
Climate adaptation and flood risk assessments have incorporated sea-level rise (SLR) projections developed using semi-empirical methods (SEMs) and expert-informed mass-balance scenarios. These techniques, which do not explicitly model ice dynamics, generate upper bounds on twenty-first century SLR that are up to three times higher than Intergovernmental Panel on Climate Change estimates7. However, the physical basis underlying these projections, and their likelihood of occurrence, remain unclear. Here, we develop mass-balance projections for the Antarctic ice sheet within a Bayesian probabilistic framework, integrating numerical model output and updating projections with an observational synthesis. Without abrupt, sustained, changes in ice discharge (collapse), we project a 95th percentile mass loss equivalent to ~13 cm SLR by 2100, lower than previous upper-bound projections. Substantially higher mass loss requires regional collapse, invoking dynamics that are likely to be inconsistent with the underlying assumptions of SEMs. In this probabilistic framework, the pronounced sensitivity of upper-bound SLR projections to the poorly known likelihood of collapse is lessened with constraints on the persistence and magnitude of subsequent discharge. More realistic, fully probabilistic, estimates of the ice-sheet contribution to SLR may thus be obtained by assimilating additional observations and numerical models."

I disagree that the risk of abrupt ice mass loss this century from the WAIS is limited by the "...persistence and magnitude of subsequent discharge", because:

(a) as stated in the "Surge" thread I believe that the Thwaites Glacier grounding line has already started the process of retreating down the negative slope into the BSB.
(b) as stated in the "Hazard Analysis for PIG/Thwaites from 2012 to the 2040-2060 Timeframe" thread that by about 2040 the Thwaites grounding line may have retreated about 100-km down the negative slope into the BSB and then intercepted a known dammed subglacial lake at that location, thus triggering an effect that I called the "Thwaites Effect" similiar to the "Jakobshavn Effect", so that the grounding line for the Thwaites Glacier may have retreated to the extent indicated by the "transparent orange" colored region shown in the "Hazard Analysis for PIG/Thwaites from 2012 to the 2040-2060 Timeframe" thread.
(c) The "Thwaites Effect" will likely induce ice mass loss discharge velocities exceeding any limits assumed by Little et al 2013 (or Pfeffer et al 2009, or the IPCC AR5 SOD), as indicated by the first accompanying composite image that compares ice surface elevation and bottom topology along the lengths of: (a) the two main trough arcs for Thwaites (shown in transparent orange in the "PIG/Thwaites 2012 to 2040-2060" thread), to (b) the first 35km of the trough for the Jakobshaven Glacier; together with the Jakobshavn basal drag, and ice driving stress; as well as two graphs giving the ice discharge velocities as functions of basal drag, driving stress and the ice viscosity parameter.  The comparison of the ice elevations and bottom topology between Thwaites and Jakobshavn indicates that if the first 100 km of Thwaites float (ie the groundling line retreats down the negative slope in the BSB by this distance) by 2040 (as I postulate), then the driving stress on Thwaites will at least equal the 400 kPa driving stress indicated for Jakobshavn by 2005.  As the ice viscosity parameter for activated portions of the Thwaites Glacier by 2040 will likely be in the 150 range, this implies that due to the "Thwaites Effect" the ice discharge velocities along the lengths of the next 200 km of Thwaites main arc troughs could well be in the 30 to 40 km/yr range for the time period from 2040 to about 2060 (and for the eastern arc until about 2075).  The second image from BedMap2 shows the current best estimates of the bottom topology for the Antarctic (see the "PIG/Thwaites 2012 to 2040-2060" thread for BedMap2 images focused on the Thwaites arc troughs).

As the conclusions regarding SLR contributions from ice mass loss from the WAIS in documents such as the IPCC AR5 SOD are based on deductive logic, invalidating the assumed limit of ice discharge (as I have indicated above), invalidates the conclusions of such documents.

“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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I would like to try to clarify a few points regarding my last post:
1.  The surface slope of Jakobshavn was about 20m/km when it's "Jakobshavn Effect" began; but the slope of the ice in the Thwaites Gateway is currently only 1 to 5 m/km, so no "Thwaites Effect" is currently possible.
2. During the period from now to 2040 I postulate that a relatively thick ice shelf will form in the Thwaites Gateway from the current groundling line (where there is a submerged/buried seamount pinning the Thwaites Glacier) to a point about 100km up-iceflow; and that this ice shelf will primarily be formed by subglacial cavity formation due to advection, and periodic surges sufficient to allow the ice shelf to thin sufficiently to float.
3.  This postulated relatively thick ice shelf is assumed to provide sufficient buttressing action to sustain a relatively high (about EL 1km) ice surface elevation  at a distance of about 100 to 120km up-iceflow.
4.  Thus by 2040 when it is postulated that the subglacial cavity intercepts the subglacial lake, it is postulated that the subsequent surge is sufficient to reduce the buttressing action of the ice shelf sufficient so that the local driving stress at this subglacial lake location (about 100km up-iceflow from the submerged mount) increase to the 400kPa level so that the "Thwaites Effect" is triggered as locally the ice slope would be on the order of 20 to 30 m/km, and at this point at least locally portions of the ice shelf would change into an ice melange.
5.  Finally, I believe that due to the extreme thickness of the ice (2 to 3 km thick) up-iceflow from this point, that the influence of the bottom topology on the "Thwaites Effect" will be less than that for the "Jakobshavn Effect", thus allowing the "Thwaites Effect" to continue for several hundred kilometers up-icestream.
“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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Due to my time constraints I expect to address my challenge of the misconceptions about "tipping points" and the WAIS over a series of posts.

On this topic, I would like to start by noting that Lenton et al 2008 combines a literature review with an expert elicitation in discussing “tipping elements,” of which WAIS is one. In it, Lenton et al 2008 estimate that West Antarctica could disintegrate with 5-8°C of local warming, which is associated with 3-5°C global warming. Lenton et al 2008 also noted that “rapid sea level rise (>1 m per century) is more likely to come from the WAIS than from the GIS [Greenland Ice Sheet]”. In addition, Lenton et al 2008 also discuss a technique for an early warning system to detect when tipping points have been reached.  Studies such a Lenton et al 2008 have encouraged decision makers to assume that there will be no tipping point for the WAIS until the mean global temperature increase exceeds about 4oC, and that they have room to manuever (ie stimulate the fossil fuel based economy) until the world gets to about 4 C warmer (regardless of whether the Arctic Sea Ice has disappeared or not); at which point they can then take "corrective actions" (including a legally binding IPCC agreement) before WAIS passes this assumed tipping point (after which corrective actions would not be effective).

There are many problems with such out-dated thinking including: (a) ocean heat uptake (particularly in the depth range of 700 to 2000m) is dramatically exceeding GCM projections (see the "Forcing" thread) and as this is currently dramatically increasing the ocean heat content, OHC, of the cicumpolar deep water, CDW, which inturn is driving the tipping point of the WAIS by forming subglacial cavities and by driving sub-ice-shelf ice melting (currently for FRIS and in a few decades for RIS); which shows that the correlations of mean global temperature increase to the tipping point for the WAIS by such people at Lenton et al 2008 are non-conservative (from a safety point of view), and that it is likely that (following our current radiative forcing pathway) by 2045 the WAIS will have crossed it's "tipping point" as even if anthropogenic forcing were to stop or even retreat at that point, the ocean's thermal inertial would continue to drive my postulated collapse mechanism's for the PIG/Thwaites drainage basins, and for the collapse of both the FRIS and the RIS (see multiple threads about my proposed collapse timeline between 2045 and 2100).

I need to go, but I will continue this topic in my next series of posts, as this misconception (about the timing of a tipping point for WAIS) is of fundamental importance.
“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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First, as a follow on to my previous post I provide the attached image related to OHC (which is more refined data that for the graphs that I posted in the "Forcing" thread on this topic).

For my next points:
(b) The possible 2045 tipping point date for the WAIS cited in my immediately previous posting was intended for my RCP 8.5 50% CL scenario.  If decision makers want a 95%CL (for higher safety) the tipping point date could be circa 2035; and if a 99% CL is desired the tipping point may be closer to 2025; as once the "Thwaites Effect" starts it will be impossible to stop; and once warm CDW water begin circulating under FRIS and RIS they are almost likely to collapse within 30 to 50 years.
(c) The GCM projections that prior assertions that a tipping point for the WAIS is not likely to occur until the mean global temperature increases about 4 C +/- 1 C, are: (i) currently not sufficiently accurate to be relied upon; (ii) do not replicate the recently documented relatively high levels of upwelling around Antartica (see my March 21, 2013 post in the "Paleo-evidence" thread); (iii) they do not model the 13 year El Nino hiatus effect that we are experiencing; (iv) they do not include either the influence of Black Carbon, or the likely albedo flip from Arctic Sea Ice area loss in the near future; and (v) they do not consider methane emissions from permafrost thawing.
(d) The current GCM projections and associated policymakers decisions focus on risks associated with changes in the weather (including droughts and floods from run-off) which are more related to fast-response feedback mechanisms (as opposed to the slower ocean heat content feedback mechanisms); and thus policymakers tend to think that any future cuts in GHG emmission will have a faster response to their decisions, than will the WAIS risk of collapsing.
(e)  While many advisors believe that the somewhat slow rate of methane emissions during the PETM provides adequate evidence that a tipping point related to the clathrate gun effect will not happen this century; this in not necessarily true as current radiative forcing is over 100 times that which occurred during the PETM, and the increase in heat content in deep ocean waters increases the risk of the clathrate gun effect for both the Arctic and the Antarctic.
“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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If I am correct that the likelihood of slowing anthropogenic radiative forcing sufficiently to eliminate the near-term risk of exceeding a tipping point for the potential collapse of the WAIS, then I recommend the following early warning measures be taken as soon as practicable to monitor the risk that the Thwaites Glacier is approaching a tipping point:
(a) Compare the differences between the Thwaites Glacier (TG) surface elevation as measured by satellite altimeters with the ice mass loss measured by the GRACE satellite as any differences by be due to the drainage of subglacial (basal) melt water; which could possibly be correlated to "surge" events for the TG.
(b) Set-up a high-resolution acoustic listening array on to try to detect the sound of ice fracturing as the ice streams accelerate.
(c) Set-up an active/seismic array similar to that used by the Oil Industry to provide accoustical images of the interior of the TG and how it changes with time.
(d) Set-up piezometers, or observation wells, to observe the pressure of the subglacial meltwater system.
(e) Develop better Ice Sheet models of TG and run them for some of the hazard analysis cases that I have postulated for TG.
(f) Develop more accurate projections for the timing of possible future sea ice area loss from the Amundsen Sea.
(g) As the value of networked information distribution increases with the square of the people connected to the network; set-up a WAIS monitoring website for the public and post information from: (i) the GRACE satellite monthly; (ii) Icebridge radar surveys of the TG gateway; (iii) any findings from the early warning system recommendations cited above; (iv) any ARGO, vessel, or installed array, measurements of CDW temperatures around the ASE; and (v) any early projections from refined TG ice sheet models and ASE hydrodynamic models.  This could provide "crowd sourcing" insights provided that this website included a forum for the public to post to.
“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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As the US military is very familar with hazard assessments, and as most navy/marine bases, and many army/air force bases, would be significantly impacted by passing a tipping point for WAIS collapse; I recommend that the US military contract with (engage with) both national laboratories and the NRC to conduct formal hazard assessments for the risk of WAIS collapse; including risks beyond those considered by the IPCC AR5 projections; and then make the results available to the public.

Separately, I recommend that hollywood consider making a movie similar to the "Day after Tomorrow" focused on the consequences of the potential collapse of the WAIS this century; as this would educate the public, which would make it easier for politicians to enact appropriate legislation to mitigate the risk of the WAIS collapsing.  This is important because human resistance to acknowledging the risks of such a potential collapse is a major barrier to taking action, and educating the public by means of a movie with the RIS and FRIS collapsing and the "Thwaites Effect" feeding an ice melange resulting in an armada of icebergs around Antarctica; and large ice fjords left in the WAIS as ice streams rapidly retreat toward the WAIS Divide; would be something that the public could understand on an intuitive level.  Such a movie could also show: (a) ocean passageways opening across the WAIS (shortening the shipping route say from  Argentina to Australia); (b) icebergs being harvested (by towing) for water supply to drought ridden areas; (c) major ports and harbors being flooded around the world; (d) failed geoengineering efforts to try to stop the collapse of the WAIS; (e) large earthquakes, tsunamis and volcanoes resulting from the rapid ice mass loss from the WAIS; (f) possible oil/gas recovery; and (g) the tilting of the earths axis of rotation due to the rapid ice mass loss.
« Last Edit: March 30, 2013, 01:13:39 AM by AbruptSLR »
“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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I now change topics to challenge misconceptions on Climate Sensitivity:

Previous studies (including IPCC studies) suggest that the climate sensitivity (or equilibrium global surface warming) to a doubling of atmospheric CO2, deltaT, is 3 oC as the best mean estimate for the moderately stable Holocene period from the Last Glacial Maximum (LGM) to the present, with a 2 to 4.5 oC as the 66% probability range, and a nonzero probabilities for much higher values, the latter implying a small but significant chance of high-impact climate changes that would be difficult to avoid. 

Determination of the sensitivity during the current warming phase requires an understanding of the current feedbacks, which, maybe: more numerous, more positive, and faster responding, than for either cooling, or stable, phases of the climate.  The newest class of climate models are called Earth System Models, ESMs [which have been developed too recently (2010) to be accepted as input to AR5 (2013)] incorporate many intermediate and slow respond sensitivity feedbacks; as well as changes in the CO2 (and other GHGs) sequestration capacity of the land and ocean (note in the past 50 years this sequestration has changed from about 60% to about 55%; and also changes in sources of GHG such as melting of the permafrost).  Nevertheless, initial results are starting to become available from these models, which are attempting to more fully consider, fast (such as: changes in atmospheric temperature, water vapor, cloud formation, solar irradiance and sea-ice/snow cover), intermediate and slow (such as slow changes in albedo waxing and waning of ice sheets and associated vegetation) feedback systems.  The first image is of a diagram comparing the (a) traditional for climate forcing framework, with (b) the new ESM climate forcing framework, from Previdi et al. 2011.

Roe and Armour's 2011 statement that: "Very high temperature responses, if they develop, are associated with the very longest time scales [e.g. Baker and Roe, 2009].", is not necessarily the case as it is possible that many of the feedback response rates that have been traditionally classified as "slow" due to being calibrated by paleoclimate investigations, may under the current anthropocene conditions act as "fast" feedback response rate functions.  It is critical to correctly account for the various feedbacks into an Earth's System Model analysis, as if it is true that some "Slow" feedbacks will act as "Fast" feedbacks then some researchers (Previdi et.al. 2011), believe that climate sensitivity may be about 6 oC, which would imply a climate feedback parameter of 0.6 W m-2C-1.  As it has been estimated (Hansen et al., 2010) that the global temperature has already increased above pre-industrial temperatures by about 0.8 oC, this may only leave a safe remaining global surface temperature increase of about 0.7 oC.  Considering that delta Q is currently estimated to be 0.85 +/- 0.15 Wm-2 and if the climate feedback parameter were to be 0.6 W m-2C-1 (corresponding to a climate sensitivity of 6oC) this implies that global temperatures would increase by another 1.4 oC without any further increase in radiative forcing.
Furthermore, Swedish climate sensitivity research (by Kent Salo 2011) published in Atmospheric Chemistry and Physics, the open-access journal of the European Geosciences Union; argue that climate sensitivity could be ‘greater than previously believed’ because in the initial phases of the current CO2-induced warming plant life has emitted larger amounts of precursor gases that lead to the formation of reflective or blocking  secondary organic aerosols (SOA) in the atmosphere, thereby acting as a negative climate feedback, and masking part of the ‘warming’ that’s occurring underneath.  Because of the increased production of organic aerosols the sensitivity of our Holocene climate system to a doubling of the atmospheric CO2 concentration can not simply be extrapolated  from the observed temperature rise, but would in fact be higher.  The Salo 2011 study shows the chemical processes involved in the formations of SOAs favor higher temperatures. But as the aerosol precursor gases are a by-product of plant growth, and ecosystems will change dramatically under continued climate change. So perhaps warming will increase just about at the point where our planet’s many positive climate feedbacks from the ecological carbon cycle will start to pick up.

Climate feedbacks depend on the timescale considered, the characteristics of the forcing (e.g. spatial pattern, spectral dependence, see the second image) and the climate state when the forcing is applied.  The following are examples of phenomena that were once modeled to have slow response rates in the GCM analyses, which in my hazard assessment should provide a SLR correction for the probability that they may actually have fast response rates:
•   Reduced albedo from Arctic Sea Ice during the Summer months;
•   Potential decrease in Secondary Organic Aerosols (SOA) effect, due to stress on plant growth.
•   Reduced albedo from: (a) loss of permafrost; (b) plants moving north; (c) increase in lake surface area; and (d) increase in wild fires.
•   Reduced land absorption of CO2 due to (counters to more farming and increased plant growth rate due to warmer weather and plants moving north): (a) release of CO2 from warmer tropical rain forest floor and Northern wetlands/permafrost; and (b) Amazon droughts;
•   Reduced ocean absorption of CO2 due to: (a) acidification of oceans killing marine life and making the partial pressure different; and (b) slowing of ocean currents;
•   Relative reduction of air pollution in Asia and Africa, over several decades, thus reducing this negative aerosol feedback effect that has been masking the influence of GHG emitted from at least 1990 until the point where the aerosol effect is decreased.
•   More rapid ice mass loss due to polar amplification, and GHG increase (note that methane will last longer in the Arctic before decomposing to CO2 compared to the rest of the world, due to the limited amount of OH radicals in the Arctic atmosphere).
•   Potential acceleration of Greenland Ice Sheet mass loss due to such factors as: (a) reduction of buttressing of marine terminating glaciers from reduced Arctic Sea Ice; and (b) well documented reductions in albedo;
•   Synergy between the aerosol SO2 and methane, increasing the GHG effectiveness of methane as compared to CO2, from 72 to 105 times, taken over a 20-year period.
•   Ratcheting to quasi-equilibrium states driven by oscillations such as: solar cycles, Arctic Oscillation Index/Arctic dipoles (inducing sea ice flushing from the Arctic through the Fram Straits); and ENSO cycles

The danger with acting as though we have plenty of time to reduce our emissions is that if this turns out not to be the case, we may find ourselves beyond the point where potentially catastrophic climate change is avoidable.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Bruce Steele

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ASLR, the deep oceans contain dissolved inorganic carbon but on the shelves ,above the saturation horizon, carbonates ( shell material ) build up on the seabed. In the Atlantic near Iceland " the aragonite saturation is at 1750 meters and rising 4 meters per year" Olafsson et al 2009    As the saturation horizon shoals it exposes large areas of shelf carbonates to dissolution. When seawater with high DIC( dissolved inorganic carbon) is upwelled to the surface heating and a release of pressure allows Co2 back into the atmosphere. In the North Pacific the saturation horizon is much shallower than the Atlantic and therefor there are less carbonate oozes than the Atlantic. In the North Pacific the saturation horizon is shoaling 1 to 2 meters per year.  The shelf carbonates left undisturbed can be( via plate tectonics) moved onto the continents and represent a very long lived carbon sink. Seabed carbonates buried deeper than 10 centimeters will not dissolve but the planet is fairly rapidly losing large areas which have functioned as long term carbon sinks. Although terrestrial sources of alkalinity will eventually rebalance pH levels  it will take about 100,000 years. The planet will be functioning    with one of it's long term carbon sinks not working like it has for millions of years. To sum it up changing pH creates problems for sea life and also problems with the carbon cycle.       
« Last Edit: March 31, 2013, 07:51:34 AM by Bruce Steele »

AbruptSLR

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Bruce,

Thanks for the insights.  In the long-term this this DIC trend will have major consequences for mankind. 

As Weitzman 2011 states:  "There is "essentially" unlimited liability here because global stakeholders cannot short the planet as a hedge against catastrophic climate change." 

Weitzman continues: "Disagreement abound concerning how to interpret the infinity symbol that appears in the formulation of the DT (dismal theory).  There is a natural tendency to scoff at economic models that yield infinite outcomes.  This reaction is presumably inspired by the idea that infinity is a ridiculous result, and that, therefore, an economic model that yields an infinity symbol as an outcome is fundamentally misspecified, and thus dismissable.  Critics cite examples to argue earnestly that expected disutility from climate change cannot actually be infinite, as if this were an indictment of the entire fat-tailed methodology.  I believe that, in the particular case of climate change, the infinity symbol is trying to tell use something important.  That is, the infinite limit in the DT is a formal mathematical way of saying that structural uncertainty in the form of fat tails is, at least in theory, capable of swamping the outcome of any BCA (benefit cost analysis) that disregards this uncertainty."
“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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In conversations that I have, a number of people tell that they do not need to be concerned with SLR as they will be dead before any significant damage/consequences occur due to SLR. 

To anybody under the age of 50, I would like to point out that:
(a) By my RCP 8.5 50% CL scenario, a mean global temperature increased (from 1990) of 2 oC, and a eustatic SLR rise of about 0.4m, are likely to have occurred by about 2045.
(b) Thus, storm surge for a design event will increase the effect of RSLR by about 50%, thus locally increasing RSLR to about 0.6m by 2045.
(c) For such a condition Grinsted (2013) calculated that a Katrina-level hurricane (over a one in a hundred year event) will occur about every two years somewhere along the Gulf and Atlantic Coast of the USA; which combined with 0.6m of RSLR would exceed the design conditions for any storm surge protection system in this area.
(d) Superstorm Sandy (about a Cat 1 event) was much less intense than Hurricane Katrina (about a Cat 3 event); and thus if a Katrina-level event were to strike the New York-New Jersey area circa 2045 (under my RCP 8.5 50% CL), the economic damage (the first image shows the inundation for a Cat 3 hurricane without RSLR, and the second image shows the inundation for a Cat 4 hurricane without RSLR striking this area) would be sufficient to impair US economy and thus impact all US citizens.
« Last Edit: March 31, 2013, 05:30:36 AM by AbruptSLR »
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AbruptSLR

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For convenience, I repost the first attached image from Grinsted 2013, giving Katrina level hurricanes per decade for a 2 oC mean global temperature rise.
In the second image (also from Grinsted 2013) red represents hurricane projections with one degree (C) global warming; blue represents no warming. The gap between these lines suggests that a warmer climate will produce more frequent hurricanes; the gap is widest at the top, meaning the biggest increase will be with the biggest storms.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Bruce Steele

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 There are thousands of acres of the Calif. Delta that are already 15 ft. below sea level. Sea level rise, spring tides and a good rain year could take it out way before 2045. We can engineer a solution to some degree of sea level rise but there will be competing interests here in Calif.   We also have earthquakes that we live with but water supplies to millions of Southern Californians is on  shaky ground.  Sea level rise will leave us few options, around here that means the environment will take a beating. 
« Last Edit: March 31, 2013, 07:36:04 AM by Bruce Steele »

AbruptSLR

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Bruce,

I could not agree with you more, and I would like to point out that California is currently proposing to spend $14 to $17 billion on means to protect the water supply in the Calif. Delta, but that the current criteria for these civil works do not adequately consider the risk of abrupt SLR.  Thus within a few decades California may be $17 billion poorer, have damage to the Calif. Delta from saltwater intrusion, and have its water supply compromised/degraded.  Obviously, either California should not invest the money, or design to a criteria where the investment will not be wasted.
“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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As an abrupt collapse of the WAIS would be a Black Swan Event, BSE, I provide the following about Taleb's insights about BSEs:

Taleb's Black Swan Event has a central and unique attribute, high impact. His claim is that almost all consequential events in history come from the unexpected—yet humans later convince themselves that these events are explainable in hindsight (bias).  Taleb argues that the proposition "we know", in many cases, is an illusion, albeit a necessary one; the human mind tends to think it knows, but it does not always have a solid basis for this delusion of "I know". Similarly, to those who might argue that the advancement of science has rendered the world well-known, Taleb argues that while science added knowledge, we always run the risk of experiencing the improbable, rare, and novel. We can be shocked by this knowledge and experience or we can be open to it.  As with the dictum of Socrates, "the only thing I know is that I do not know", is as true as ever.   Taleb also questions the authority of experts, asserting that the truth behind science is limited to certain areas and methods.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Bruce Steele

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ASLR,Forty years ago the Arctic melting out would have been a Black Swan but would it still be a Black Swan now that it is so much more likely?   The Antarctic circumpolar current will take into it's circulation heat which is currently warming intermediate waters worldwide. Lots.     If the ocean temperature is modeled to increase 3 degrees by 2100 WAIS melt might not seem so Black Swan either. Both Arctic summer melt out  and WAIS events will have high impacts for sure but they almost seem predictable, predictable in comparison with say an asteroid impact.  Unknown unknowns that have high impacts are Black Swans but when does predictability or probability make Black Swans White?   

AbruptSLR

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Bruce,

First what is a Black Swan for a turkey is not a Black Swan for his butcher.  If you say that all of these climate changes are very clear to yourself and other knowledgable people but a new Pew Research poll suggests public interest and intensity with the issue is waning, see:

http://www.people-press.org/2013/04/02/keystone-xl-pipeline-draws-broad-support/

Therefore, if the common people do not recognize climate change as a threat then nothing will be done about it, and even though thoughtful people can see the problem; it still qualifies as a Black Swan because politician respond to the majority of voters who do not see it as a problem (when it really is a problem).
“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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If it is desired to most quickly change the US public's misconceptions about the risks of climate change (and of the risk of abrupt collapse of the WAIS) then I believe that focusing on educating pastors would have the highest benefit/cost ratio as indicated by the following internet article, the majority of these pastors still doubt climate change (note CT is Christian Today):

"A majority of pastors continue to doubt man-made global warming, according to a report by LifeWay Research.

The survey found about 4 in 10 Protestant pastors "believe global warming is real and man made" — an increase from similar data collected in 2010, but down slightly from 2008. Pastors' views generally line up with popular opinion on the topic, LifeWay states. The percentage of Americans who said they believed global warming was the result of human activity reached all-time low in 2010, when just 34 percent agreed with the statement.

Younger pastors are the biggest skeptics. "Pastors age 65 or older put more stock in the validity of global warming over their younger counterparts," Lifeway said. "This group is more likely (32%) than pastors age 45-54 (20%) and 18-44 (19%) to strongly agree with the statement: 'I believe global warming is real and man made.'"

Not surprisingly, pastors' perspectives on global warming and sustainability efforts corresponded with their politics: Democrat pastors were more likely than Republican pastors to say that their churches had taken steps toward sustainability.

With mixed views on global warming, less than half of pastors report "their church has taken tangible steps to reduce their carbon footprint." Two-thirds of Protestant churches offer some sort of recycling program, which may be the result of municipal regulations or economics over environmental beliefs, LifeWay's Scott McConnell told the Baptist Press.

CT previously has reported on the topic of global warming, noting even in 1998 that churches were joining the national debate over climate change. In 2010, CT discussed how concerned Christians should be about caring for the environment."
“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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As many scientists (including Hansen et al) have already warned about the risks of abrupt SLR due to the potential collapse of the WAIS this century, but the public keeps building new developments in coastal areas at risk of inundation from combined SLR and increase storm surge, I provide the following re-post of an article by Dr. Peter Gleick, a scientist, innovator, and communicator on global water, environment, and climate issues. He co-founded and leads the Pacific Institute in Oakland:

"(Mis)Understanding Sea-Level Rise And Climate Impacts
By Climate Guest Blogger on Mar 6, 2013 at 4:28 pm
One of the most important and threatening risks of climate change is sea-level rise (SLR). The mechanisms are well understood, and the direction of changes in sea-level is highly certain – it is rising and the rate of rise will accelerate. There remain plenty of uncertainties (i.e., a range of possible outcomes) about the timing and rate of rise that have to do with how fast we continue to put greenhouse gases in the atmosphere, the responses of (especially) ice sheets in Greenland and Antarctica, and the sensitivity of the climate.
Even little changes can have big consequences. As we saw with Superstorm Sandy, where extremely severe weather was combined with a very high tide, on top of sea levels that have risen six to nine inches over the past century, even a little bit of sea-level rise around the world has the potential to cause hundreds of billions of dollars of damages and the displacement of millions of people.
The Pacific Institute, among many other organizations, has been working to understand and evaluate the nature of the threat of sea-level rise and the risks posed to coastal populations, property, and ecosystems. In 1990, a colleague and I published the first detailed mapping and economic assessment of the risks of sea-level rise to the San Francisco Bay Area, looking at populations at risk, the value of property in new flood zones, and the costs of building some kinds of coastal protection (“adaptation”) to protect higher valued assets. That early report can be found here.
Then, in 2009 and 2010, the Pacific Institute, with funding from the State of California, conducted a detailed, high-resolution mapping analysis of the entire coast from Oregon to Mexico. We analyzed a set of sea-level rise scenarios developed by the Scripps Institution of Oceanography and worked with the California Energy Commission, the Metropolitan Transportation Commission, the Ocean Protection Council, the National Oceanic and Atmospheric Administration, the US Geological Survey, FEMA, and others to evaluate the risks to people, property, transportation infrastructure, ecosystems, power plants, wastewater treatment plants, and more, should those scenarios of sea-level rise happen. The full peer-reviewed report, the high resolution maps, specialty maps, and all open source GIS data can be publicly downloaded here. (A peer-reviewed journal article was also published.) That analysis suggests coastal regions are highly vulnerable to even modest sea-level rises with hundreds of thousands of people and more than a hundred billion dollars of infrastructure already in zones at risk of future flooding.

I was reminded this week, however, of the difficulty some people have in understanding the nature of climate risks, when a climate skeptic who shall remain nameless started tweeting his misunderstandings to me without having read our studies (I know this because after I pointed out his errors, he asked me to send the studies to him). My internet-savvy sons have tried for years (only partly successfully) to teach me: DNFTT. But these tweets offer insights into what might be more general misconceptions, so let me address some of them for those who actually want to help the public understand the real risks of climate change.
Misunderstanding #1: Predication versus Scenario. There is a big difference between a prediction and a scenario. Scenarios are tools for examining how changes in some kind of conditions (such as greenhouse gas concentrations) might affect something else (such as climatic conditions or sea-level). They are stories of possible futures based on a range of assumptions. Almost all studies of climate impacts evaluate scenarios to examine possible future conditions, risks, and threats. Climatologist Gavin Schmidt sometimes uses the following:
•   Forecast: What you think will happen in the future (could be probabilistic), but with no conditionals. Used in weather forecasts, sales forecasts etc.
•   Prediction: A much broader category of scientific statement that implies a complete specification of the circumstances under which X would be expected.
•   Projection or Scenario: A conditional prediction about the future. i.e., if a certain set of circumstances come to pass, the climate will respond in the following way.
In the case of sea-level rise, climate modelers and oceanographers make projections of how sea-level would react to a range of assumptions about energy use and type, greenhouse gas emissions, and climate and ice sensitivities. These are not predictions. In the case of our reports, we evaluate the implications for coastal regions should these future sea-level rises occur. This is a risk and vulnerability assessment. In fact, for the estimates of sea-level rise in our study, we clearly note that changes could be both smaller or larger, and slower or faster than our evaluation. None of this is actually relevant to our estimate of the things currently at risk from a 1.4 meter rise.
Misunderstanding #2: Linear versus Exponential. There is sometimes confusion in some people’s minds about the difference between a linear trend and an exponential trend. In this case, data on actual changes in sea-level suggest that the recent rates of rise are between 3 and 3.5 millimeters per year. If sea-level changes are linear, then it is easy to project past trends forward: 100 years of rise would add between 0.3 and 0.35 meters. This is what my tweeter did, in an effort to say SLR is a smaller problem than the state-of-the-science 1.4-meter scenario we evaluated. Why the difference? Because climate change, and sea-level responses – are not linear; they are exponential. This means the sea level in the future will rise at an accelerating rate, leading to a much higher end point for any given year. Figure 1 shows this simple concept, but also shows that in the short term, it may be hard to distinguish between the two. A high-school student would get an F for assuming a linear rate for an exponential process. I know of no climate scientist who believes the climate will change in a linear fashion if there is continued exponential growth in greenhouse gas emissions.

Misunderstanding #3: Evaluating Average versus Extreme Risks. Climate scientists are a conservative lot (in the scientific sense, as shown in a recent journal article). As a result, assumptions and scenarios that are typically analyzed (including the ones we used, developed by the Scripps Oceanographic Institute) are in the middle of the range of what could plausibly occur. In particular, even the exponential rate that produces 1.4 meters of rise by around the end of the century includes no rapid acceleration of ice-sheet melt or ablation or other factors that could lead to even faster rates of increase or higher rises. There are some far more disturbing sea-level rise scenarios out there but we didn’t analyze them. Any criticism that the scenarios evaluated were too extreme could be equally balanced by criticism that they were not extreme enough. The most recent report on SLR scenarios for the U.S. offers a range from 0.2 meters to 2 meters by 2100 (see Figure 2).
Misunderstanding #4: Beware False Dichotomies and Ad Hominem Arguments. This skeptic opened his assault on the sea-level science discussion by arguing that I must not care about sea-level rise because my office was nearly at sea-level. First, a minute spent with Google Earth or a topo map would have shown that our offices are actually around +40 feet above mean sea-level – not in a vulnerable zone even with expected climate change over the next century (barring some more catastrophic scenario), and second, even if my office was in a vulnerable zone, it wouldn’t mean I didn’t care about the future risks of flooding. His ad hominem response was “OK I get it it [sic], the plan is to sit tight and laugh at others [sic] misfortunes.” I know, DNFTT.
Misunderstanding #5. Mitigation versus Adaptation versus Suffering: That same nasty tweet also reveals a deeper misunderstanding about the nature of responses to sea-level rise or any other climate impacts. We only have three options for sea-level rise: trying to reduce the rate of rise (mitigation), coastal defense or retreat (adaptation), and suffering the impacts. People and valuable property in zones threatened by sea-level rise will either suffer greater and greater damage, or will have to be protected with new costly infrastructure, moved away over time in advance of rising seas, or abandoned. These are issues discussed clearly in our studies. Moreover, our work at the Institute explicitly identifies vulnerable populations and strategies to protect them.
This particular climate skeptic lives nowhere near the coast. That could partly explain his lack of understanding or interest in the threats posed by sea-level rise to our extensive coastlines. But the risks facing his own community include growing heat stress and extreme temperatures, loss of inexpensive local hydropower generation, increased forest fire risks, greater air pollution, and, should sea-level rise get really bad, migration of lots of people to his community! More on these risks later.
Let’s put these errors and misunderstandings to rest and begin the necessary climate mitigation and adaptation responses, soon, or those exponential curves will begin to bite."

“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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In the immediately prior post, Peter Gleick states:

"In particular, even the exponential rate that produces 1.4 meters of rise by around the end of the century includes no rapid acceleration of ice-sheet melt or ablation or other factors that could lead to even faster rates of increase or higher rises. There are some far more disturbing sea-level rise scenarios out there but we didn’t analyze them. Any criticism that the scenarios evaluated were too extreme could be equally balanced by criticism that they were not extreme enough."

Indeed, I can, and do criticize Gleick's and other researcher's work that do not present the public with an evaluation of SLR scenarios that include rapid acceleration of ice-sheet melt.  The public receives woefully inadequate risk analyses even from the world's best researchers; in that most researchers do not even try to "connect the dots" for all the dissparate pearls of wisdom that the scientific community generates regarding the risk of abrupt sea level rise, ASLR.  Apparently, the scientific community trusts the policy makers to conduct their own risk evaluation for ASLR.  In a normal situation the public could at least believe that they could sue the policy makers if the policy does not at least adequately warn the public of the numerous risks of ASLR already identified by the scientific community without adequate quantification of total risks; however, with each new "Adaption" plan for climate change issued by relevant Federal agencies; those same Federal agencies are issuing disclaimers warning the public that they cannot be held responsible for the safety of the public regarding the consequences of climate change.
“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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The attached one-year surface temperature anomaly map from NOAA indicates that those who do not believe that both the Arctic and the Antarctic are warming faster than the rest of world, are wrong.
“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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Many individuals are confused by the SLR values released by authorities.  For example when Pfeffer et al 2008 presented the results of their analysis for the the "Low1, Low2 and High1" shown in the first attached image; many people believe that the High1 upper value of 2.008m of eustatic SLR by 2100, represents an upper physical boundary for rapid/dynamic ice mass loss from the GIS and AIS.  However, as indicated by the second attached image which compares Pfeffer et al's and Rohling et al's SLR projections vs RAND's PDF of rapid/dynamic SLR based on Pfeffer et al 2008 analysis.  This second figure makes it clear that users of the information need to realize that even without considering the risks of abrupt SLR, there is considerable risks of SLR above Pfeffer et al's 2008 High1 "upper bound" of 2.008m, as indicated by the RAND PDF, and Rohling et al; which indicate meaningful rapid/dynamic SLR risk upto about 2.5 m of eustatic SLR by 2100.
“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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As I seem to be slow in recovering from my jet lag, I think that I will make a few simple posts; such as to point out that another misconception that many decision makers are suffering from when trying to interpret (or mis-interpret) the guidance given to them by experts can be illustrated by the following two images.  The first image presents the widely circulated V&R 2009 empirical projections for SLR for SRES A1FI, A2 and B1 (as compared to the AR4 projections).  The second attached image shows how the California State modified these V&R 2009 SLR projections into High, Medium and Low ranges of SLR for 2070 and 2100; while in the "Collapse" thread I have introduced the concept of Scenario Based Engineering Hazard Assessments, SBEHA, to correct such out-dated SLR rise guidance, as noted in the second image, to at least: (a) Eliminate the Low (B1) range from design consideration, because on our current BAU radiative forcing path, this SRES B1 forcing can never be achieved (as it is too low); and (b) the designers need to consider the risk of abrupt SLR which the V&R 2009 projections do not include (which is why the ranges are called "High", "Medium" and "Low", because the experts (such as V&R) cannot provide actual confidence level, CL, percentages for SLR because their projections do not include any allowances for abrupt SLR, which is left to the designers to addresse).
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Many decision makers appear to assume that if they manage to control anthropogenic global warming by about 2045, that the extreme weather will rapidly (in a decade or two) stabilize (as the atmospheric thermal gradients stabilize), and that applying a resiliency approach to storm surge inundation will be adequate to address the extreme weather events in the meantime.  However, as resiliency approachs almost never accommodate storm surge events with return period beyond 1,000-years; if abrupt SLR occurs then this may well be a misconception as indicated by the attached image (from the ice2sea 2013 report) which indicates the influence of SLR on the inundation return period for the Thames River estuary.  This figure indicates that with a one meter SLR a current 1,000-year return period storm surge inundation event would occur ever 12-years; and as my PDF for my RCP 50% CL scenario indicates that a one-meter SLR could occur by 2070; it is possible that the Thames River Surge Barrier could be overwhelmed by 2070 if it were to rely solely on a resiliency approach; which could result in London being flooded.
“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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Regarding misconceptions about what SLR values to use I am reposting the following opinion article that focuses on the new ice2sea report on SLR values; will in general terms this whole topic can be summarized by the phrase: "Caveat Emptor" (Let the Buyer Beware):

Sea level rise: Drowning in numbers
In: NewScientist: Opinion; May 2013 by Michael Le Page
"IMAGINE your job is to protect London from surging seas. In one way it is easy: unlike most coastal cities, London has a formidable flood defence system in the form of the Thames Barrier, capable of protecting it from all but the highest storm surges.
But as the seas rise, the risk of the barrier being breached will increase steadily. With a 1-metre rise in local sea level, London will get flooded every 10 years. So when do you start building new flood defences, and how high do you make them?
The stakes are enormous. Building new defences will cost tens of billions and involve decades of planning and controversy before construction even begins. Get it wrong, and storm surges could kill thousands and displace millions. So all around the world, planners are clamouring to know how fast the seas will rise as the planet warms.
Until recently, scientists could not give them any reliable numbers. There were no computer models capable of simulating the melting of the world's ice sheets and glaciers.
The 2007 report of the Intergovernmental Panel on Climate Change (IPCC) handled this uncertainty really badly. It acknowledged that we don't know how fast all the ice will melt, but then gave some numbers anyway – between 18 and 59 centimetres of sea level rise by 2100 – based on highly dubious assumptions such as glaciers continuing to flow at the same rate and the Antarctic ice sheet growing larger. The numbers also assumed a maximum warming of 5.4 °C, even though the report's highest projection was 6.4 °C. Unsurprisingly, many people wrongly took 59 cm of sea level rise to be the worst case.
Now we have some more numbers. A European-funded project called ice2sea has developed computer models of glaciers and ice sheets. Earlier this month it announced that melting ice would contribute between 4 and 37 cm to global sea level by 2100. Adding this to the other causes of sea level rise – the main one being the expansion of the oceans as they warm – gives figures of between 16 and 69 cm by 2100.
Some media reports focused on the fact that this is less than some other recent estimates of at least a metre. "Seas will rise no more than 69 centimetres by 2100," proclaimed this magazine.
Others focused on the fact that even this relatively small rise could have devastating consequences. "Floods could overwhelm Thames Barrier by end of century," declared The Guardian in London.
How much trust can we put in these numbers, though? The whole point of the ice2sea programme was to "reduce the uncertainty", but its numbers come with some rather large caveats.
For starters, the modellers didn't have the computing power to look at a range of scenarios for how much carbon dioxide we will pump into the atmosphere. Instead, they looked at just one – a "mid-range" scenario predicted by the 2007 report to lead to warming of around 3 °C.
Yet actual emissions today are much closer to the worst-case scenario, which some recent studies predict could lead to warming of 6 °C or more. And far from falling, annual global emissions are rising ever faster. With hundreds more coal-fired power stations being built and new sources of fossil fuels like tar sands being exploited, there is good reason to think emissions will continue to soar for many decades to come.
What's more, to account for the fact that warming will not be uniform across the globe, the modellers had to produce regional projections of warming, snowfall and so on to feed into the ice models. But regional projections are highly unreliable, with different models often producing wildly varying results. The prime example is the Arctic, where the sea ice is disappearing much faster than anyone expected.
To understand why regional climate predictions are so much less reliable than global ones, think of the heat entering the atmosphere and oceans as water pouring into a bath. Predicting the average level of the bath is much easier that predicting the height of the waves sloshing around.
So the climate information being fed into these latest ice models could be way off the mark.
And even if it isn't, how do we know the models are right? Well, say the researchers, they can reproduce some of the observed responses to the actual 0.5 °C warming of the past few decades, such as the retreat of glaciers. But that doesn't prove they can predict the response to future warming of 3 or 6 °C. There are similar issues with global climate models.
This kind of research is vital. But when such a limited study is presented as the "best estimate" available, the danger is that it will be misinterpreted in the same way as the 2007 IPCC report. Its numbers do not encompass the worst-case scenario – far from it. They don't even represent the most likely scenario. The narrow range implies a degree of certainty that simply doesn't exist. Nobody should be basing life-and-death decisions such as how to protect Londoners on these numbers.
The ice2sea organisers must have been aware of this because they also asked a bunch of experts how bad they thought it could get. This exercise produced yet another set of numbers – there is less than a 1 in 20 chance that the melting of ice sheets will contribute more than 84 cm to sea level rise by 2100. But isn't the whole point of modelling this stuff to reduce our reliance on guesstimates?
The big picture is that there is no doubt that the planet will get hotter and that sea level will eventually rise many metres. We know this because the last time atmospheric CO2 levels were higher than 400 parts per million, sea level was between 5 and 40 metres higher. Even if emissions stopped tomorrow, there would still be huge sea level rises. The only question is how fast it will happen. The frightening truth is that we still don't know."
“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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I thought that I would just provide the following selected list of reasons as to why our current climate condition may lead to abrupt ice mass from the WAIS this century as compared past paleo-periods when the rate of ice mass loss was slower:

The current rate of GHG increase is several hundred times faster than during any earlier paleo-period.  Those who count on the thermal inertia of both the ocean and of the ice sheets to distribute the ice mass loss from the WAIS over several centuries may be unpleasantly surprised due to reasons including the following:

- Never in the past has an ozone hole appeared so abruptly over Antarctica; which appears likely to be maintained for the foreseeable future by the increase in GHG over Antarctica (including the recently observed high atmospheric methane concentration over Antarctica); which, is causing: (a) a positive trend of SAM; (b) higher circumpolar wind velocities and (c) more upwelling of warm CDW that is causing a faster rate of Antarctic ice melting than observed in past paleo-periods.

- The rate of increase of the volume of CDW and the rate of decrease of AABW is very high by paleo-standards and will be difficult to slow down even if governments restrict antropogenic GHG emissions.

- The rate of collapse of Arctic sea ice is high by paleo-standards; and the importance of polar amplification is becoming clearer with recent findings of both current and past positive feedback mechanisms.

- The sensitivity of the WAIS positive feedback resulting in accelerating ice mass loss is becoming clearer with regard to such mechanisms as: (a) geothermal basal heating; (b) basal heating from friction as the ice velocities accelerate; (c) ice-ocean interaction and advective melting of adjoining ice by warm ocean water; (d) subglacial hydrologic systems; and (e) increasing wind velocities that can blow snow into the ocean.

- The possible increase in snow fall in Antarctica with increasing global warming is not likely to offset increases in dynamic ice mass loss, over then next century.

Happy 4th of July to all,
ASLR
« Last Edit: July 13, 2013, 05:01:37 PM by AbruptSLR »
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AbruptSLR

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From Wikipedia:
"The phrase not even wrong is generally attributed to theoretical physicist Wolfgang Pauli, who was known for his colorful objections to incorrect or sloppy thinking.  … The phrase "not even wrong" is often used to describe pseudoscience or bad science and is considered derogatory."

I believe that this phrase is particularly appropriate to apply to relatively sophisticated denialist authors who specialize in the use of half-truths in a manner where what they write is "not even wrong", but which presents such a skewed, or confused, impression, as to represent bad science advice to policy makers.

One of the most visible purveyors of "bad science"advice is Judith Curry, as illustrated by her June 18th, 2013 post on ocean heat content, OHC, at:

http://judithcurry.com/2013/06/18/ocean-heat-content-discussion-thread/

Interested readers will need to read her post at the link above as it is too long to reproduce; but in her normal style the first 99% of what she presents is "not even wrong"; but then in the last 1% of her article she draws conclusions, such as the following quote, that represents bad policy advice:

"We need to understand how the ocean exchanges heat vertically, between the upper ocean and deep ocean, and whether mixing in the deep ocean is more efficient than currently thought.  Until we understand this, we won’t know to what extent this heat will remain sequestered in the deep ocean."

In her article she repeatedly cites three year (or more) old research emphasizing how complex and uncertain the ocean-atmospheric interactions are (which is true); and then based on this old research she implies that we should do nothing until we know whether the heat recently introduced into the oceans below 700m "… will remain sequestered in the deep ocean."  In this regard, in many different threads I have cited more recent (2012 and 2013) research that indicates that a large portion of this recently added deep ocean heat content telecommunicates to the Southern Ocean; where increased wind velocities are causing increased regional upwelling sufficient to directly accelerate the ice mass loss from both Antarctic ice shelves and ice sheets; and that it is likely that this acceleration is likely to continues at least for several decades into the future.

Judith Curry's rational are much like those of Wall Street's just before the financial collapse of 2007; where Wall Street thought that they did not need to take precautionary actions for the risks that they were exposing the world community to; only to be proven how wrong they were by the subsequent events.  Again I advise: "Let the buyer beware!" before accepting any such half-truths by relatively sophisticated denialist such as Judith Curry.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

sidd

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I submit that paying any attention to deniers and their apologists is a waste of time. We have bigger fish to fry. We need more and better detail on the risks, so that our projections become more accurate, fine grained and helpful to real life concerns.

Leave the liars to the dustbin of history. Ignore them and pass them by. We need not excoriate them, soon enough,  their own children will curse their names.

sidd

AbruptSLR

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Sidd,

While I generally agree with your post immediately above (and I will try to focus on citing more and better details defining risks of ASLR that we are facing); nevertheless, I am concerned that the complexity of this issue creates a playground for denialist to create confusion that offsets our new and better details of the risks of ASLR (particularly about the potential collapse of the WAIS); and slows decision makers from taking steps to address real life concerns.  Therefore, I think that some limited response to clarify such nonsense is warranted; in order to help those less familiar with the actual complex details to see the real risks.

In this regard, I keep wondering whether it would be useful to open a new thread on "Sea Level Budget", or not.  On the one hand, the complexities of the Sea Level Budget issue make this topic a playground for denialist to raise endless doubts (such as the endless debates about calibration of semi-empirical models); but on the other hand; without the framework of a Sea Level Budget approach; how can the average decision maker keep track of the impact of the new and better research being cited in this Antarctic folder?  For the moment I plan to focus on posting new and better details about the actual ASLR risks, with only occasional responses to the darkside.
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AbruptSLR

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The drainage basins around Antarctica shown in the attached image (after King et al, 2012) are based on the areas that would drain out of a given gateway given the current ice surface gradients. One misconception worth discussing is that most researchers report the potential maximum SLR contribution from each of these basins as if the current ice surface gradients will be maintained into the future; which is not the case.  For example it is frequently reported that the maximum SLR contribution from PIG and Thwaites Glacier are approximately: 9" and 18", respectively, and also many researchers project that ice mass loss from PIG may slow sufficiently in the next 5 to 10 years to limit the SLR contribution from PIG this century to an inch or two; however, as the Thwaites basin adjoins the PIG basin, should the Thwaites Glacier collapse as I have indicated may be possible; then it is possible that several inches of SLR of ice in the PIG basin could drain through the Thwaites Gateway.  Such interactive logistics increase the likelihood that higher levels of SLR will occur by the end of this century; above that commonly thought likely.
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sidd

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Agreed, if PIG goes, so does Thwaites, if Thwaites goes, as is more likely, PIG will go similarly sideways. EAIS has Amery and Totten, and Moscow U and such, reaching deep into the heart. 

AbruptSLR

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A very important component of systemic uncertainty regarding the risk of ASLR is human communications.  The following points present examples of how policymakers can formulate better decisions with regard to ASLR policy:
-   It is important to understand that the Global Circulation Model, GCM, RSLR projections all contain statements by the scientists citing the limitations of their projections in view of the complexity of the problem that they are modeling.  Thus the stated confidence levels of their model projections do not represent all of the uncertainty required by policymakers, planners, and civil engineers to make decisions regarding RSLR and affected marine/civil features.
-   Many policymakers/planners also have not yet understood the combined risk of RSLR together with short-term events (e.g. storm surge, ENSO, backwater flooding, etc.), which can significantly accelerate the consequences of the slower changing RSLR trend.
-   A common human mechanism for dealing with uncertainty is to think that if economic resources are scarce then it is appropriate to use a Frequentist approach to calculating risk of ABSLR (thus limiting projections of SLR to linear extensions of what has been observed).  While the Bayesianist approach is to recognize the risk associated with uncertainty and then to plan how best to address the risk, using as models plans that have already been successfully executed in numerous pervious cases where relative water elevations have increased such as: (a) areas where offshore, and nearshore, oil extraction have required infrastructure elevations have been raised up to several meters; (b) ravine areas where increased flood risk has required designated overflow areas where population and infrastructure contractually addresses the risk by such means as evacuation, insurance, and sacrifice; and (c) cases where innovative engineering has been applied to eliminate the hazard by such means as floatable, or jackable, structural designs.

In short I believe that there is more than sufficient evidence that there is a serious risk of ASLR this century; and that there are reasonable planning measures (especially adaptive engineering) that can be taken now; and that the largest obstruction to taking appropriate actions now are associated with miscommunication of the actual risks to the public at large.
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AbruptSLR

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Re: Challenging Misconceptions about the Potential Abrupt Collapse of the WAIS
« Reply #32 on: January 28, 2014, 05:05:31 PM »
For those who have the patience to work through the Bayesian math example at the linked website (or similar websites), you can better appreciate that most people (many scientists included), do not apply proper probability analysis when interpreting findings/observations.  While the cited example indicates that many doctors believed that there was upwards of a 90% chance that their patient had cancer when the patient only had a 15.5% probability based on the reported test; the same can be said about abrupt sea level rise, ie based on a set of observations many professionals assume that there is a higher probability that ASLR will not happen this century, while the actual probabilities are significantly higher than most professionals assume:

http://mathsontrial.blogspot.com/2011/09/bayes-theorem-examples.html


For a deeper understanding of probabilities see: "The Improbability Principle: Why Coincidences, Miracles, and Rare Events Happen Every Day", by David Hand, Locus Publishing Co., 2014; which indicates that the actual probabilities of assumed rare events (such as ASLR) are actually higher than generally assumed (including by many scientists), due to the application of such statistics as the "law of combinations" which is very relevant in complex systems such as the Earth's circulatory systems.
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AbruptSLR

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Re: Challenging Misconceptions about the Potential Abrupt Collapse of the WAIS
« Reply #33 on: January 28, 2014, 05:45:20 PM »
Many people mistakenly believe that US agencies such as FEMA [which are tasked with responding to natural disasters (including from flood events like Katrina and Sandy)] must consider the possible consequence of climate change in their planning.  However, this is a misconception as the linked article makes clear:

http://www.bloomberg.com/news/2014-01-27/fema-caught-between-climate-change-and-congress-.html

Obviously, FEMA has no plan to address the risk of ASLR, let alone to recognize these risks.
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AbruptSLR

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Re: Challenging Misconceptions about the Potential Abrupt Collapse of the WAIS
« Reply #34 on: January 30, 2014, 06:32:24 PM »
l thought that I would post this image from Richard Alley of the range of possible climate outcomes, with policymakers focusing on the best case and ignoring the worst case.  Also, I would like to note that with all of the new research that I post every day on positive feedback factors for ASLR, that the fat tail of the PDF, that Alley shows, is recognized as becoming fatter and fatter.  Maybe, policymakers should shift their focus to the right side of the PDF.
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AbruptSLR

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Re: Challenging Misconceptions about the Potential Abrupt Collapse of the WAIS
« Reply #35 on: February 18, 2014, 04:24:42 PM »
Many people (including many scientists) have the misconception that in a changing (non-stationary) climatic world they are entitled to begin their process-based projections of future SLR contribution from the WAIS based on past behavior.  Even many of those who focused on the era since the GRACE satellite (operational in 2002) has been able to directly measure ice loss from the WAIS have not correctly communicated the SLR risks, even for only say until 2030, from such considerations as:
(1) The GRACE measurements have all been taken during the era of negative PDO (i.e. the era of El Nino hiatus), and as it is likely that from now until 2030 the PDO index will be dominated by positive values; therefore, all of these GRACE measurements are biased, and non-conservative from a safety point of view.
(2) Most glacial models of the Thwaites, and Pine Island, Glaciers, assume that their ice shelves will provide significant buttressing action for at least the next one hundred year; while a simple extrapolation of the rate of calving from these ice shelves (see MacGregor et al 2012) indicates that the buttressing action of these ice shelves will likely be significantly diminished well before 2030.
(3) While the most recent GIS measurements from the ASE indicate that the reported GRACE ice mass loss measurements many be up to 25% too low; most scientists have deferred correcting their WAIS SLR contribution projections until more GIS measurements are taken.
(4) Since the GRACE era the ABSL has largely been more westward than its historic mean local (nearer to the ASE), thus as the ozone hole heals itself and as we enter a positive PDO cycle, we can expect the ABSL to reposition eastward so as to blow more warm-CDW, and more regional SLR, into the ASE, both of which will accelerate ice mass loss.
(5) Most regional circulation models have assumed mean climate sensitivity values of about 3 degrees C, when the most likely value is closer to 4.4 to 4.5 degrees C; which will warm the ocean and the atmosphere faster than previously expected.
(6) The volume and the temperature of the CDW has increased during the past negative PDO era, which will result in more active future ocean-ice interaction than during the past GRACE era.

If we wait until the coming positive PDO cycle ends around 2030, to take any corrective actions; the inertia of the WAIS ice mass loss by that time many be very difficult to deal with effectively.
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wili

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Re: Challenging Misconceptions about the Potential Abrupt Collapse of the WAIS
« Reply #36 on: February 18, 2014, 06:42:54 PM »
ASLR, here's something I thought might interest you, if you haven't seen it already:

http://www.skepticalscience.com/vision-prize-ipcc-underestimating-sea-level-rise.html

scientists are worried the IPCC is underestimating sea level rise

Quote
despite the much higher sea level rise estimates this time around, the survey participants are worried that the IPCC is still underestimating future sea level rise. 41 percent responded that it's likely or very likely that sea level rise will exceed the IPCC highest estimate, and 71 percent answering that it's at least as likely as not.

Conversely, only 5 percent responded that it's likely sea level rise will be less than the IPCC lowest estimate, and 83 percent called this scenario unlikely.

Quote
   
These results broadly agree with a recent survey carried out by scientists in Germany and the US. In this survey, 90 researchers who'd published sea level research in the last 5 years concluded that sea level rise by 2100 is likely to be between 0.7 and 1.2 meters if we continue on a business-as-usual greenhouse gas emissions path. Two-thirds of the experts responded that sea level could rise more than the upper end of the IPCC's projected range by 2100...

(Apologies if you already posted on this somewhere and I missed it.)
« Last Edit: February 18, 2014, 06:51:59 PM by wili »
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

AbruptSLR

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Re: Challenging Misconceptions about the Potential Abrupt Collapse of the WAIS
« Reply #37 on: February 18, 2014, 08:47:51 PM »
wili,

Thank you very much, I had missed that article, and I attach the main figure from the survey for those who are interested.

Best,
ASLR
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jai mitchell

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Re: Challenging Misconceptions about the Potential Abrupt Collapse of the WAIS
« Reply #38 on: February 19, 2014, 08:03:05 PM »
New Paper on the Subject

http://www.igsoc.org/journal/60/220/t13J183.pdf

Journal of Glaciology, Vol. 60, No. 220, 2014
doi: <a href="
http://www.igsoc.org/journal/60/220/t13J183.pdf">10.3189/2014JoG13J183</a>

Firn air depletion as a precursor of Antarctic ice-shelf collapse
MUNNEKE et. al

Here we build upon this notion of firn air depletion as a precursor of ice-shelf collapse, by using a firn model to show that pore space was depleted in the firn layer on former ice shelves, which enabled their collapse due to hydrofracturing. Two climate scenario runs with the same model indicate that during the 21st century most Antarctic Peninsula ice shelves, and some minor ice shelves elsewhere, are more likely to become susceptible to collapse following firn air depletion. If warming continues into the 22nd century, similar depletion will become widespread on ice shelves around East Antarctica. Our model further suggests that a projected increase in snowfall will protect the Ross and Filchner–Ronne Ice Shelves from hydrofracturing in the coming two centuries.

Haiku of Futures Passed
My "burning embers"
are not tri-color bar graphs
+3C today

AbruptSLR

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People seem to have difficulty interpreting recent statement about the likelihood of the initiation of a rapid collapse mode for the ASE marine glacier.  Perhaps the following will help to clarify this matter:

National Research Council, NRC, (2013), Abrupt Impacts of Climate Change Anticipating Surprises, The National Academies Press, Washington D.C.

Selected Extract from NRC 2013: "Because large uncertainties remain, the Committtee judges an abrupt change in the WAIS with this century to be plausible, with an unknown although probably low probability."


Subsequent to the NRC 2013 report, Rignot et al 2014 indicates that if grounding line retreat of Pine Island, Thwaites, Smith and Kohler glaciers continues at the same rate as the 1992 to 2011 average then this section of the WAIS would initiate rapid collapse by about 2200.

Rignot, E., Mouginot, J., Morlighem, M., Seroussi, H. and Scheuchl, B., (2014), "Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith and Kohler glaciers, West Antarctica from 1992 to 2011", Geophysical Research Letter, DOI: 10.1002/2014GL060140.

Rignot et al 2014 are well aware that ice mass loss from the ASE marine glaciers is currently accelerating, and that the probability of this ice mass loss rate remaining constant for the next 86 years is low.

Indeed, if one want to make a rough approximation of the time required to say double this rate, and one were to assume that the rate of grounding line retreat is proportional to ice mass loss, then one could use the following formula together with the data for location C in the two accompanying images from the following linked reference:

y = a + b(t-to) + ½ c(t-to)2
 

Williams, Simon D.P. and Moore, Philip and King, Matt A. and Whitehouse, Pippa L. (2014) "Revisiting GRACE Antarctic ice mass trends and accelerations considering autocorrelation", Earth and planetary science letters, 385 . pp. 12-21; DOI: 10.1016/j.epsl.2013.10.016

http://dro.dur.ac.uk/12460/1/12460.pdf

http://www.sciencedirect.com/science/article/pii/S0012821X13005797

Using values of b = 115.4 and c = 17, one can calculate that it should take approximately 13.6 years to double the rate of ice mass loss indicating that the ASE glaciers are likely to begin collapse well before the end of this century.
« Last Edit: June 10, 2014, 01:44:29 AM by AbruptSLR »
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AbruptSLR

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As rate of ice mass loss is a function of both thinning area and change in ice thickness (assuming a stationary calving face location); it is probable that the rate of change of ice mass loss from the ASE marine glaciers is greater than the rate of the grounding line retreat, I provide the two attached images (& captions below) regarding the hinge retreat rate, and ice thickness change rate, for the PIG, in order to better characterize the relationship between ice mass loss and grounding line retreat for the ASE marine glaciers:

Caption for first image: "(Panel A) 2011 Profile and historical hinge line locations [grey lines], and (Panel B) Annual Change in Thickness along the Profile and historical hinge line locations, of the Pine Island Glacier, from Park et al. (2011)"

Caption for second image: "(Panel A) Hinge Line Retreat (km2), and (Panel B) Annual Change in Thickness (m/yr), of the Hinge Line for the Pine Island Glacier, from Park et al. (2011)"
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LRC1962

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Came across this Sea level rise: New iceberg theory points to areas at risk of rapid disintegration. Not sure if you have referenced it in all your excellent postings.
On the flip side I found this NZ ARI playing Chicken-Little. Tried to find their paper to see what it says but can not find it at all. (Maybe pulled because bad PR?)
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AbruptSLR

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LRC1962,

While I have referred to Bassis & Jacobs a few times, it is always good to both have a link to a video and to remind people of the excellent work that Bassis is doing:
 
Bassis, J.N., and Jacobs, S., (2013), "Diverse calving patterns linked to glacier geometry", Nature Geoscience, 6, 833–836, doi:10.1038/ngeo1887.

http://www.nature.com/ngeo/journal/v6/n10/full/ngeo1887.html

Thanks for the Kiwi link, the article refers to a researcher proposal rather than to a published paper (see the following link):

http://nzari.aq/supporting-research/the-antarctic-science-challenge-for-new-zealand
http://nzari.aq/images/downloads/Antarctic_Futures_White_Paper.pdf

I believe that research proposal authors are very reasonable to state:

“Antarctic ice melt may result in sea levels rising by up to 5 m and as fast as 4 cm per year. Even with the most optimistic scenarios for stabilizing atmospheric carbon-dioxide concentrations, the world can no longer avoid 2°C of warming by 2100, meaning we are already committed to irreversible meltdown of Greenland and West Antarctica. The questions is when, how much and how fast.”
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AbruptSLR

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This discussion focuses on two misconceptions about the nature of Probability Density Functions, PDFs, for the collapse of the ASE marine glaciers.

First, many people do not realize that Rignot et al 2014 have more or less demonstrated that there is essentially a 100% probability that the ASE marine glaciers will have begun their main phase of collapse (which implies an associated abrupt contribution to SLR at that time) behavior by about the year 2200, assuming that the current rate of the grounding lines for these marine glaciers continue to retreat at their current rates.  Thus one can assume that these conservative Rignot et al 2014 projections at least double the  risk of initiating abrupt SLR contribution from the ASE marine glaciers by 2100 as compared to PDFs generated before these findings were released (which is essentially all extant PDFs).

Second, the risk of initiating abrupt SLR contribution from the ASE marine glaciers should be increased each future year that ice mass loss measurements from the ASE region indicate that the rate of the grounding line retreat is accelerating (on average), above the rate of retreat that Rignot et al 2014 assumed in their calculations.
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nukefix

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First, many people do not realize that Rignot et al 2014 have more or less demonstrated that there is essentially a 100% probability that the ASE marine glaciers will have begun their main phase of collapse (which implies an associated abrupt contribution to SLR at that time) behavior by about the year 2200, assuming that the current rate of the grounding lines for these marine glaciers continue to retreat at their current rates
Perhaps, but aren't the current rates of retreat depending on the ocean currents doing what they are doing now? I imagine that the predictability of ocean current behaviour is low to very low.

AbruptSLR

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nukefix,

While I cannot provide proof, I would not characterize the predictability of the ocean currents into the ASE as low to very low, and I would say that it is at has at least medium confidence that: (a) the CDW temperature will slowly increase (from the value that Rignot et al 2014 used) with global warming (particularly for RCP 8.5); (b) the CDW will increase (from the value that Rignot et al 2014 used) during periods of El Nino; and (c) that the westerly wind velocities (driving the extant high CDW currents) will remain high as the atmospheric GHG concentration over Antarctica continues to increase while the ozone hole slowly heals itself.

I believe the reason that Rignot et al 2014 only projected a continuation of current rate of grounding line retreat for the next 200 years is that it is currently too difficult to model the influence of such factors as: (a) basal melting on the ice shelves and possible collapse of the local ice shelves; (b) basal meltwater beneath the marine glaciers episodically bursting out into the ocean from beneath the marine glaciers; (c) the nature and influence of the ENSO cycle on the advection of warm CDW into the ASE; (d) synergy between both horizontal advection of CDW within the ASE between different glaciers (particularly between PIG and Thwaites), (e) synergy between the ice flow out of the marine glaciers (particularly the SW Tributary Glacier for the PIG possibly triggering the Thwaites ice flow); and (f) teleconnection of atmospheric energy from the Tropical Pacific into the WAIS region, resulting in: reduced local sea ice extent, higher local SSTA, and higher local surface temperatures on the glacier surfaces.

And as scientist only report what they can model, their inability to model factors that are likely to contribute to accelerating ice mass loss in this area, results in their erring on the side of least drama; however, this inability to model the acceleration will not protect society from the consequences of this acceleration if/when it occurs.

Best,
ASLR
« Last Edit: June 18, 2014, 03:54:22 PM by AbruptSLR »
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steve s

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nukefix,

ASLR did not mention one monster issue associated with the Thwaites -- the shape of the bed and the thickness of the overlying ice. Much more unstable than the PIG. Now that the Thwaites has retreated onto the bed downslope, it is unstable in a self-reinforcing pattern. Also, because of the shape of the shelf and overlying ice dome, unless there is an ice jam limiting the outflow rate, the outflows may accelerate for an appreciable period.

As I understand the situation, no energy inputs are needed for collapse, although energy inputs can influence the rate. Also, because the retreat to the downslope is new at the Thwaites, the downslope's contribution to the rate of collapse is not fully understood or factored in to the calculations. As Rignot has stated, his team's date estimates are upper bounds.

So, no. The currents are probably not important any longer. Also the next few years may be illuminating.

If I am off base in this assessment, I am sure ASLR will correct me.

Steve

AbruptSLR

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I believe that Joughin et al 2014 did not utilize any ocean input and showed that Thwaites would eventually collapse without it; however, to get the collapse within 200-years I believe that Rignot et al 2014 assumed that the ASE marine glacier's grounding lines would continue retreating at the same that they have been doing on average for something like the past 10-years (I am traveling and am away from my references), which would assumes the ocean's input during the hiatus period.

Furthermore, while I believe that the grounding line in the Thwaites Glacier gateway has retreated over 14km since 1992, I do not believe that this grounding line has yet retreated to the reverse slope leading down to the BSB.
« Last Edit: July 15, 2014, 12:38:42 AM by AbruptSLR »
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steve s

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From the abstract of Rignot, et.al., 27 May 2014:

"Upstream of the 2011 grounding line positions, we find no major bed obstacle that would prevent the glaciers from further retreat and draw down the entire basin."

AbruptSLR

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steve s,

Thanks for the quote, and as the attached image illustrates [from one of NASA's associated videos], what Rignot et al 2014 showed is that as the grounding line retreats the ice shelf thins and can float over the top of any potential pinning points (I have made this same point in my posts about a likely collapse scenario almost a year and a half ago, and I am sure that Rignot et al have been aware of this behavior for even longer [as soon as the improved bathymetry that they reference was available], but they had to get their model to demonstrate it, and then they had to get through the peer review process and get their findings published).

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