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Author Topic: Potential Collapse Scenario for the WAIS  (Read 175095 times)

AbruptSLR

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Potential Collapse Scenario for the WAIS
« on: February 21, 2013, 04:25:06 PM »
In the accompanying figure from Vaughan et al. 2011, the researcher postulate that the indicated seaways opened in the WAIS during the Eemian period some 124,000 years ago.  Vaughan et al. proved that for an upper bound that the longest of these seaways formed within less than a thousand years (which is well within the timeframe of the Eemian peak proving that WAIS could have contributed at least 3.4 to 3.8 m to eustatic SLR in that period) .  I propose that by 2100 such seaways could be re-established in the WAIS via a combination of: (a) floatation of ice sheet sections that have thinned sufficiently for them to float; (b) the formation of a network of interconnected subglacial cavities paralleling the seaways identified by Vaughan et al., which (when interconnected) would allow tidally induced flushing of CDW to rapidly melt the basal ice around the expanding interconnected cavities; (c) accelerated caving of both glaciers and ice shelves due to such factors as increasing CDW temperatures, tidal action, periodic subglacial meltwater network lubrication of basal friction (see surge post topic), and increased wave action due to telecommunication from the Topical Pacific Ocean; (d) a melt-pond mechanism collapse of the Ross Ice shelf after 2050; and (e) a change in the currents in the Weddell Sea after 2050 leading to accelerated CDW advection forced retreat of the glaciers grounding lines in that region so that the grounding lines retreat past buttressing ridges that have been supporting those glaciers.
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AbruptSLR

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Re: Potential Collapse Scenario for the WAIS
« Reply #1 on: February 21, 2013, 04:44:18 PM »
It should be noted that WAIS is that remaining marine ice sheet on earth, and that it is unique from all of the other previous marine ice sheets in that the WAIS can retreat from four different regions (the Bellingshausen Sea region, the Amundsen Sea region; the Ross Sea region and the Weddell Sea region) all converging on a common central subglacial basin area (roughly below the WAIS divide).  The accompanying figure from Bingham et al 2012 shows that the West Antarctic with WAIS removed has numerous subglacial troughs that can lead warm ocean water (driven by: advection, currents and tidal action) from all four seas directly into the heart of the WAIS subglacial basins (see the surge topic posts for a similar view of the West Antarctic with WAIS in-place).  In this figure the area for the Ferrigno Glacier is indicated by the black rectangle; which rests in a rift valley that leads directly into the back side of the trough that the PIG rests in thus leading any subglacial cavities extending beneath these two glaciers to interconnect in the future (leading to tidal driven water flushing through the interconnected cavities); and that the glaciers around the Weddell Sea, and the Thwaites Glacier also lead directly into a subglacial basin that would interconnect all of these subglacial cavities into a network similar to the seaways shown by Vaughan et al. 2011 (note that the glaciers around the Ross Ice Shelf as so thin that if they lose the buttress action of the Ross Ice Shelf after 2050 by a meltpond mechanism that more thinning would cause them to float without the need for advective melting via troughs).
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AbruptSLR

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Re: Potential Collapse Scenario for the WAIS
« Reply #2 on: February 21, 2013, 06:05:43 PM »
While there is a fair amount of signal noise in the historical record, the accompanying figure from Rohling et. al. 2007 indicates that the rate of SLR during the Eemian peak ranged from 2.5 to 4 m per century (mean of 3.5 cm/yr).   Specifically, from circa 124.2 to 123.8 kyr ago it is proposed that the collapse of portions of other marine ice sheets resulted in abrupt SLR, while from circa 123.8 to 123.7 kyr ago the current portion of the WAIS collapsed resulting in about 3.5m of eustatic SLR and about 5m of RSLR in the Coral Sea.  Also, note: during the Meltwater Pulse 1A, 14,600 years ago, a collapse of some prior portions (on the current continental shelf) of the WAIS may have contributed to an average of a 4 m per century SLR for 500 years.  As by Rohling's figure by 123.8 kyr ago the WAIS may have been in full active retreat (which promotes internal friction of the glacial ice that then drains to the bottom of the glaciers, which promotes reduction of the basal friction) and the current WAIS is not yet at that level of activation; nevertheless the radiative forcing of SRES A1FI that we are currently trending has much more forcing than what was occurring during the Eemian, and the thermal inertia of the oceans may not delay the anthropogenic induced warming of the CDW water as much as the GCM projections indicate as: (a) the Southern Ocean dominates the ocean heat uptake; and (b) the ocean water heat content between 700 to 2000m, which feeds the CDW temperature, is currently accelerating faster (due to upwelling) than any other portion of the ocean.
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AbruptSLR

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Re: Potential Collapse Scenario for the WAIS
« Reply #3 on: February 21, 2013, 09:57:15 PM »
The accompanying figure from Orsi et al. 2012 reports temperature measurements from a station at the WAIS Divide which indicates that for the 50-year period from 1957 to 2007 the surface temperature at the WAIS Divide increased at a mean rate of 0.231 C/decade; however for the 20-year period that mean rate of surface temperature was 0.804 C/decade.  This means that the WAIS is currently one of the fastest warming locations on Earth, which means that after 2050 surface melting of the ice sheet will be come more frequently a factor that affects both ice sheet (as is the case for GIS now) and ice shelf (as occurred in the Antarctic Peninsula for the Larsen B ice shelf) stability.  Futhermore, strong El Nino events can temporarily raise surface temperatures well above the decade trend line for periods of month, thus increasing the risk of high episodic ice mass loss during future strong El Nino events (which we have not had for over 10 years).
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Re: Potential Collapse Scenario for the WAIS
« Reply #4 on: February 22, 2013, 02:29:01 AM »
The accompany figure is from a Dec. 2011 AGU poster and shows measured Ross Ice Shelf retreat from 2005 to 2010 with the highest face retreat found near of the central zone with rates from 1 to 1.65 km/yr normal to the face.  Presumably with climate change this rate of calving will increase, but even if it does not the ice shelf face would retreat over 60 km by 2050 thus exposing the Ross Ice Shelf from abrupt collapse from a melt pond mechanism similar to that which occurred for the Larsen B ice shelf.  If so, it is likely that the glaciers buttressed by the Ross Ice Shelf would accelerate by about a factor of 5 times, which would thin the leading edges of these glaciers causing the grounding line to retreat rapidly as the leading edge lifts off of the seafloor.
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #5 on: February 22, 2013, 05:22:36 PM »
The accompanying figure from Hellmer et al. 2012 shows key model results from their state of the art regional circulation model.  This results indicate that due to projected changes in the sea ice by 2075 (using SRES A1B and scientifically conservative assumptions) will lead to a redirection of warm CDW below that Filchner-Ronne Ice Shelf which will gradual impinge upon the ice at the grounding lines of the adjoing glaciers, which has been projected to result in the relatively rapid retreats of these grounding lines due to the inherent instability of many of the glaciers in this area.  While the glaciers in the Weddell Sea region account for only approximately 10% of the WAIS ice mass loss potential, the formation of subglacial cavities beneath these glaciers (see discussion in the "surge" thread), may connect with nearby subglacial cavities from the Bellingshausen and Amundsen Sea regions before the end of this century, given that the world may continue along our current SRES A1FI path and given the fact that ice mass loss from the Bellingshausen and Amundsen Sea glaciers seem to be accelerating both earlier and faster than most researchers are stating publically at the moment.
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #6 on: February 22, 2013, 11:26:18 PM »
The accompanying figures show both direct measurement of the thickness of the Ross Ice Shelf (which is rapidly thinning) and of how in 2003 tides interacted with the velocity of the ice flow from the adjoining Whillian Ice Stream.  The subsequent reply will illustrate that as calving occurs for the Ross Ice Shelf tidal interaction will accelerate ice flow from the Siple Coast ice streams.
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #7 on: February 22, 2013, 11:32:13 PM »
The accompanying figure shows finite element model results of how the tidal cycle the horizontal ice flow within the Ross Ice Shelf.  As the Ross Ice Shelf face calves the areas of higher horizontal tidally influenced ice velocities will increasing interact with the adjoining Siple Coast ice streams which will accelerate the rate of ice mass loss from these ice streams.
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #8 on: February 23, 2013, 12:27:02 AM »
The accompanying figures from Vaughan et al. 2012 illustrate how sub-ice-shelf water flows (from either tides, currents, eddies or melt water advective processes) become channelized which then forms grooves on the underside of the ice shelves; and when the ice shelf flexes (see due to tides, barametric pressure changes from storms, or infragravity waves) the induced flexure stresses can lead to the production of crevasses; which inturn can lead to increased calving from the ice shelves.  It is probable that climate change will lead to increase storm activity around West Antarctica and that changes in sea level will induce flexure stresses within the ice shelves.
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #9 on: February 23, 2013, 01:14:33 AM »
The attached figure by Fogt et al 2011 indicates that trends for cyclones storm in both the Ross Sea, and Bellingshausen Sea, Basins has been of increased intensity (ie lower cental pressure) and increase storm frequency.  This will tend to increase calving from ice shelves/tongues in these areas.
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #10 on: February 23, 2013, 01:45:15 AM »
The accompanying figures indicate the present and potential future contributions to SLR from mountain glaciers and ice caps (GIC), the Antarctic Peninsula, GIS, EAIS, and WAIS.  In my proposed collapse scenario the SLR contributions from GIC and GIS play an important role in raising sea levels around Antarctica which contributes to the destabilization of marine ice sheets and marine glaciers.
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #11 on: February 23, 2013, 01:59:32 AM »
The accompanying figures of Envisat altimetry measurements of the trend in elevation changes (m/yr) thru June of 2012 (with detail of PIG for 2008 & 2009) for Antarctica, indicate that ice mass loss from marine ice sheets and glaciers is not only a growing concern for the WAIS but also for the EAIS (however the total ice mass loss for the EAIS for recent years as been masked by several years of unusually high snow fall, which could well only be natural variations).  These measurements indicate that ice mass loss from the WAIS is accelerating non-linearly as compared to previous years.
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #12 on: February 23, 2013, 02:09:58 AM »
The accompanying figure shows modeled cumulative precipitation in eq. meters of SLR for Antarctica for families of ECP (extended RCP scenarios).  These models indicate that precipitation will only increase linearly in the Antarctic until 2100, while as previously noted current ice mass loss trends from marine ice sheet and marine glaciers is already non-linear.  Therefore, it can be expected that ice mass loss from the Antarctic will become an increasing percentage of the total contribution to SLR through 2100.  Also note that some of the future precipitation the West Antarctic may fall as rain before the end of the century.
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #13 on: February 23, 2013, 02:33:36 AM »
Accompanying is GRACE satellite data of measured ice mass loss rates from 2002 to 2011 for different drainage basins in Antarctica, from Sasgen et al. 2012.  While this time frame is too short to filter out the influence of snowfall variability, the information clearly indicates the importance of ice-mass-loss from West Antarctica and inparticular from the Thwaites Drainage basin (which has the highest rate of ice mass loss).
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #14 on: February 23, 2013, 02:41:45 AM »
Accompanying is GRACE satellite data of measured the acceleration of ice mass loss from 2002 to 2011 for different drainage basins in Antarctica, from Sasgen et al. 2012.  While this time frame is too short to filter out the influence of snowfall variability, the information clearly indicates the importance of the acceleration of ice-mass-loss from West Antarctica and inparticular from the Thwaites Drainage basin (which has the highest measured rate of acceleration ice mass loss in Antarctica).  Note that this data does not include the probable surge of ice mass loss from WAIS and from Thwaites inparticular in 2012 discussed in the "Surge" thread.
 As stated previously these rates of accelerations are expected to increase non-linear with continued climate change.
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #15 on: February 23, 2013, 03:37:08 PM »
I forgot where this image came from, but it makes a useful comparison between the ice/ocean interaction for WAIS marine glaciers with ice shelves and GIS marine glaciers (for those who don't already know).  One particular point that I would like to make is that in the image's caption that author makes a clear distinction between the ice/ocean interaction for cold WAIS marine glaciers with ice shelves such as at the Ross Ice Shelf and the Filchner-Ronne Ice Shelf (where the majority of the Antarctic's Bottom Water is produced) and warm WAIS marine glaciers with ice shelves such as PIG.  For the cold WAIS ice shelf case that author shows that the dense, high-salinity shelf water that forms near the ice-shelf front during winter sea-ice growth (which is normally a source of Bottom Water) can get drawn under the cold ice shelf where it can melt the underside of the cold ice shelf thereby diluting the previously high-density shelf water, which would likely prevent much of this self water from sinking further in order to become Bottom Water.  It is noted that the amount of Antarctic Bottom Water has dropped dramatically in recent years; which could be an indication that the melting of the underside of the cold ice shelves is accelerating; which could contribute to accelerated calving of such cold ice shelves relative to prior projections.
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #16 on: February 23, 2013, 07:35:10 PM »
As my proposed WAIS collapse scenario has many similarities as to what may have happened during the Eemian, I provide the accompanying figure from Barnes et al 2010 showing the probable condition of the WAIS at the Eemian peak.  This condition is supported both on the fossil records of Bryozoans and on DNA of existing  family of Antarctic octopus the West Antarctic.  Furthermore, in 2011 based on marine sediments it was found that GIS could only have contributed 1.6-2.2m to Eemian sea level; while in 2012, based on GIS ice core (NEEM) findings, the high-end of this contribution was further limited indicating that the WAIS contributed at least 3.5 to 3.8m at that time.
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #17 on: February 23, 2013, 09:11:23 PM »
As previously cited, Vaughan et al. 2011 clearly identify sea passage ways for ocean water to travel from outlet marine glaciers (e.g. PIG, Thwaites, and Ferrigno, Glaciers) and ice streams (e.g. Bindschadler, Moller and Rutford ice streams) that are at risk of rapid grounding line retreat would convey warm ocean water to the interior basins of the WAIS, frequently through subglacial cavities such as observed for PIG and Thwaites (see the "Surge" thread).  Furthermore, Vaughan et al. 2011 state: "Progressive thinning of coastal ice resting on a bed below sea level will eventually allow it to float.  If such thinning connected two coastal seas, whether or not a float-ing ice shelf remained, seawater would pass freely beneath the ice and between the seas, forming an open seaway. Although the impact of such seaways on the oceanography of the Southern Ocean and Antarctic climate is likely to have been substantial, to date there has been little effort to investigate their importance. The only comparable seaway in existence today, that beneath George VI Ice Shelf on the Antarctic Peninsula, has a strong ocean current flowing through it, which influences considerably oceanography of the nearby continental shelf [Jenkins and Jacobs, 2008]."  This demonstrates that the formation of passage ways (with or without ice above the passage ways) through the WAIS can have strong currents that would accelerate ice sheet collapse. 
Also, the presence of identified subglacial water networks (see the "Surge" thread) can accelerate the collapse of ice sheets as indicated by Branecky et al. 2011 who states in regards to the Pine Island paleo-ice stream: "Paleo-ice thicknesses of less than 1.35 km result in water escape from basins and transport of significant subglacial water into the ocean. The retreat of the Pine Island paleo-ice stream was likely impacted by such discharge events because they have the potential to increase ice flow velocities by reducing bed resistance and change hydrologic flow regimes by affecting subglacial pressures."
Furthermore, the rapid collapse of the WAIS would result in large (multiple meters) of local GIA seafloor rebound resulting in significant tectonic/seismic activity that would have a positive feedback effect on the collapse of the WAIS, as would the basal ice melting from the basal heat generated by the upwell of magma beneath the seafloor crust (beneath the WAIS) causing the meters of GIA rebound (note that as stated previously the basal melting rate measured directly in a drillhole at the WAIS Divide is extraordinarily high, 1.5~cm a-1.
Also, finally for this post, the accompany figure illustrates the risk of the release of subglacial seafloor methane that could occur during a rapid retreat of the grounding lines of marine glaciers in both the WAIS and the EAIS; which would provide a positive feedback by accelerating the advective process by the methane bubbles generated at the face of the grounding line acting like an air-lift to force the syphon effect (this air-lift action would likely occur even if the methane bubbles release from the seafloor hydrates were absorbed by the surrounding seawater before the bubbles made it to the surface as the change in effect water density (averaging both bubbles and adjoining water) would provide momentum to the vertical advective syphon effect within the subglacial cavities.  Note also that methane releases from the seafloor in the Antarctic Peninsula have already been observed.
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AbruptSLR

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Re: Potential Collapse Scenario for the WAIS
« Reply #18 on: February 23, 2013, 11:24:51 PM »
The following briefly lists a: Timeline and Key External Events for SLR Contributions According My Scenario for a 50% CL RCP 8.5 Scenario (as stated in the "Forcing Thread" I believe the actual probabilities of occurrence for the RCP 8.5 Scenario to be many times higher than the IPCC publically acknowledges)  for the Collapse of the WAIS:

(1) 2020 - (a)Arctic Sea Ice Absent in September, (b) 1mm/yr SLR contribution from groundwater extraction; (c) Larsen C ice shelf has collapsed.
(2) 2030 Mean global temperature anomaly = 1.2 C
(3) 2040 Mean global temperature anomaly = 1.5 C: Himalayan Glaciers accelerate and some Himalayan Ice Dams rupture which releases the previously impounded water to the ocean.  Carbon dioxide and methane emissions from Northern Hemisphere permanfrost is in the 1.2 to 1.4 Gt/yr range (see accompanying figure)
(4) 2050 Mean global temperature anomaly = 2 C: Ice mass loss form Greenland Marine Terminating Glaciers accelerates.
(5) 2070 Mean global temperature anomaly = 3 C: Degradation of the amazon forest begins to accelerate.
(6) 2080 Mean global temperature anomaly = 3.4 C: ENSO amplitude begins to increase.
(7) 2090 Mean global temperature anomaly = 4.2 C
( 8 ) 2100 Mean global temperature anomaly = 4.9 C
« Last Edit: May 11, 2014, 10:35:31 PM by AbruptSLR »
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AbruptSLR

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Re: Potential Collapse Scenario for the WAIS
« Reply #19 on: February 23, 2013, 11:36:09 PM »
The accompanying figure from Vaughan et al. 2011 illustrates how much ice needs to be lost in order for the lower ice to float-up off of the bottom (James Hansen has emphasized that the Antarctic sheet ice does not all need to melt in order to for the sea level to rise, provided that this ice can float-off of the seafloor.
« Last Edit: February 24, 2013, 12:00:28 AM by AbruptSLR »
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Peter Ellis

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Re: Potential Collapse Scenario for the WAIS
« Reply #20 on: February 24, 2013, 12:29:15 AM »
Huh?

The point at which the remaining ice floats is the point at which sea level rise stops.  Melting floating ice does not change sea level.

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Re: Potential Collapse Scenario for the WAIS
« Reply #21 on: February 24, 2013, 12:33:16 AM »
I plan to gradually post a series of images superimposed on Vaughen et al 2011 plan and profile of their passageway alignments showing areas of my assumed areas of grounding line retreat and calving for cases based on a 50% Confidence Level, CL, and a 95% CL, RCP 8.5 scenarios for descrete periods from 2040 to 2100.  The attached image is the first of these images for the 50% CL RCP 8.5 case for 2040.  In this paricular scenario it is assumed that: (a) the "surge" observed for the Ferrigno and Thwaites Glaciers repeat in the future until subglacial cavities indicated occur by 2040; (b) Calving reduces the Ross Ice Shelf buttress action to 85% of the 2000 value and the enhanced tidal influence leads to sufficient thinning of the adjoining ice streams to result in floatation of the previously grounded ice in the indicated areas; and (c) the PIG grounding line retreats to the indicated areas in accordance with Gladstone et al. 2012.
The purpose of these images is to help clarify the points that I am trying to make.
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Re: Potential Collapse Scenario for the WAIS
« Reply #22 on: February 24, 2013, 12:57:52 AM »
The attached images is for the 50% CL RCP 8.5 case for 2060.  In this paricular scenario it is assumed that: (a) acceleration of advection (due to increased CDW temperature, and larger subglacial cavity size, and branching of the subglacial cavities beneath the Thwaites Glacier to follow the subglacial melt water network) and accelerated subglacial water flow from melt water flowing down through the glacier due to internal ice friction from more dynamic ice movement) for the Ferrigno and Thwaites Glaciers repeat in the future until subglacial cavities indicated occur by 2060; (b) Calving reduces the Ross Ice Shelf buttress to 65% of 2000 value and the melt pond mechanism then reduces the buttress action to 10% of 2000 value, causing the grounding line to retreat in the indicated areas; (c) the PIG grounding line retreats to the indicated areas in accordance with Gladstone et al. 2012 and (d) Sea ice continues to thin in the Weddell Sea and reduce in extent, and warm CDW enters the Filchner Trough, leading to the grounding line retreat indicated.
The purpose of these images is to help clarify the points that I am trying to make.
« Last Edit: February 24, 2013, 01:14:38 AM by AbruptSLR »
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Re: Potential Collapse Scenario for the WAIS
« Reply #23 on: February 24, 2013, 01:24:47 AM »
The attached images is for the 50% CL RCP 8.5 case for 2090.  In this paricular scenario it is assumed that: (a) acceleration of advection (due to increased CDW temperature, and larger subglacial cavity size, and branching of the subglacial cavities beneath the Thwaites Glacier to follow the subglacial melt water network) and accelerated subglacial water flow from melt water flowing down through the glacier due to internal ice friction from more dynamic ice movement) for the Ferrigno, PIG and Thwaites Glaciers repeat in the future until subglacial cavities indicated occur by 2090 with formation of interconnected basal passageways causing tidal induced water to surge through; (b) Continued thinning of the ice streams around the collapsed Ross Ice Shelf  leads to a progressive retreat of the grounding line due to floatation of the ice sheet edge and continued calving of the ice shelf, similar to the behavior observed for the Larsen B shelf after 2002 melt pond collapse and (c) Sea ice continues to degrade in the Weddell Sea and reduce in extent, and warm CDW volumes accelerate through the Filchner Trough,  and the formation of the interconnected basal passageways, and seaways, leads to a partial collapsed shown.
The purpose of these images is to help clarify the points that I am trying to make
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Re: Potential Collapse Scenario for the WAIS
« Reply #24 on: February 24, 2013, 01:51:31 AM »
My 95% CL RCP 8.5 scenario is modified from the official RCP 8.5 scenario primarily in that it envisions a significant release of nature methane into the environment together with an accelerated antropogenic methane release from increased use of hydrofracting and shale gas.  I plan to post more specifics later about this methane emissions assumption in the "Forcing" thread, but for now I provide the accompanying figure illustrating the temperature scenario that this 95% CL RCP WAIS collapse scenaro assumes.

Furthermore, as the effects of this assumed methane concentration pathway is not expected to become significant for WAIS ice mass loss until after 2040, the 95% CL RCP 8.5 2040 scenario is essentially identical to the 50% CL RCP 8.5 2040 scenario and thus this figure is not repeated here.
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Re: Potential Collapse Scenario for the WAIS
« Reply #25 on: February 24, 2013, 02:08:13 AM »
The attached images is for the 95% CL RCP 8.5 case for 2060.  In this paricular scenario it is assumed that: (a) acceleration of advection (due to increased CDW temperature, and larger subglacial cavity size, and branching of the subglacial cavities beneath the Thwaites Glacier to follow the subglacial melt water network) and accelerated subglacial water flow from melt water flowing down through the glacier due to internal ice friction from more dynamic ice movement) for the Ferrigno and Thwaites Glaciers repeat in the future until subglacial cavities indicated occur by 2060; (b) Continued thinning of the ice streams adjoining the Ross Ice Shelf leads to a progressive retreat of the grounding lines due to floatation of the ice sheet edge and continued calving of the ice shelf, similar to the melt pond behavior observed for the Larsen B shelf after 2002; (c) the PIG grounding line retreats to the indicated areas in accordance with Gladstone et al. 2012 and (d) Sea ice continues to thin in the Weddell Sea and reduce in extent, and warm CDW enters the Filchner Trough, leading to the grounding line retreat indicated.
The purpose of these images is to help clarify the points that I am trying to make and not to precisely project grounding line retreat patterns.
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Re: Potential Collapse Scenario for the WAIS
« Reply #26 on: February 24, 2013, 02:27:29 AM »
As the 95% RCP 8.5 2090 case is inbetween the 50% RCP 8.5 2090 and the 95% RCP 8.5 2100 cases it is not shown.  The accompanying images are for the 50% CL RCP 8.5 case for 2100.  In this paricular scenario it is assumed that by 2090 with formation of interconnected basal passageways causing tidal induced water to surge through leading to such rapid ice mass loss that seismic activity causes the all of the remaining susceptible ice to float by 2100. It is also noted that such a total collapse of the WAIS would active significant portions of the EAIS, as well accelerating ice mass loss from marine terminating glaciers in the GIS. The purpose of these images is to help clarify the points that I am trying to make.
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Lennart van der Linde

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Re: Potential Collapse Scenario for the WAIS
« Reply #27 on: February 25, 2013, 02:04:04 PM »
ASLR,
Thanks for all the info on WAIS you're posting here. It will take some time to digest it. For now, just a short remark on your reference above to Rohling et al (2007). If I've understood correctly Rohling has lowered his estimates for max rate of SLR (above current sea level) during the Eemian to about at least 0.7 meters/century. See Grant, Rohling et al (2012):
http://www.nature.com/nature/journal/v491/n7426/full/nature11593.html

"[R]ates of sea-level rise reached at least 1.2m per century during all major phases of ice-volume reduction, and were typically up to 0.7m per century (possibly higher, given the smoothing in our method) when sea-level exceeded 0m during the LIG".

Since the current/future GHG-forcing is/will probably be much higher than the Eemian insolation-forcing (averaged over the planet) a significantly higher max rate of SLR than this 0.7 m/century seems likely during the coming centuries.

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Re: Potential Collapse Scenario for the WAIS
« Reply #28 on: February 25, 2013, 03:17:21 PM »
Lennart,

Thank you for the very helpful update to Rohling, which I will review in more detail and comment on in a later post.  But for now I will agree that we cannot use any previous period (Eemian or otherwise) as a model for projecting our current case with the historically highest radiative forcing in millions of years.  Nevertheless, I will note here that the quote that you cite: "[R]ates of sea-level rise reached at least 1.2m per century during all major phases of ice-volume reduction, and were typically up to 0.7m per century (possibly higher, given the smoothing in our method) when sea-level exceeded 0m during the LIG"; only discusses minimum and average SLR rates during the LIG (for periods when sea-level was above our current levels) and not the maximum rates.  Saying the the rates of rise were at least 1.2m per century does not preclude higher values.
And while I believe that we need to model our own present case, still the past can be a guide as to what is possible, so please note that the attached information from Alvarez-Solas et al. 2012, that for at least 50 years the Hudson Strait Marine Glacier surged at a velocity of about 4,500 m/yr while the accompanying figure from Rignot 2008 indicates while in 2007 PIG was flowing at a rate of about 4,000 m/yr still in 2007 Thwaites was only flowing at about 2,500 m/yr; which indicates that there is plenty of opportunity for Thwaites to accelerate.
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Re: Potential Collapse Scenario for the WAIS
« Reply #29 on: February 25, 2013, 05:07:01 PM »
ASLR,

The 1.2 meters/century of Grant et al (2012) is for sea levels below present, the 0.7 m/century for up to 5 m above present. I understand the 0.7 m/century to be the max speed averaged over several centuries, so on shorter time scales the max speed could be higher. I do find their wording not entirely clear, however.

In correspondence with Rohling he told me that the 0.7 figure may well be increased again in follow-up work, although probably not as high as the earlier (2007) 1.6 figure. Also in that earlier paper the difference between 'average' and 'peak' rates is not fully clear to me.

Also Blanchon et al (2009) found indications for a rate of SLR of about 2.5 meters in about 50 years during the Eemian, but I don't know how much confidence other paleo-climatologists have in that estimate.

But let's assume that 1-2 meters/century did occur during the Eemian, or even the 3.5 meters/century from the earlier Rohling et al paper. How much faster could sea levels rise during this century and after?

Pfeffer et al (2008) estimate a max possible rise of about 2 meters by 2100:
http://www.sciencemag.org/content/321/5894/1340.full.pdf

That would imply a rate of SLR by about 2100 of probably circa 4 cm/yr, so if sustained about 4 m/century. The question is if this would be their estimated max potential rate of SLR, or if it could go even faster later in the next century.

Hansen and Sato (2012) seem to expect an 'iceberg cooling' negative feedback which would keep the max rate of SLR under about 5-6 meters/century (under BAU emissions). They criticize Pfeffer et al for (mainly) not sufficiently taking the instablity of WAIS into account.

Pfeffer et al assume an average outlet glacier velocity for PIG/Thwaites of about 14-15 km/yr from 2020-2100. How fast could we reach that speed and how much faster could those glaciers go?

And how about the assumption of Pfeffer et al for Greenland of an average outlet glacier velocity of about 27 km/yr from 2020-2100? How likely is that and how much faster could it go, if at all?

I'm very interested to hear your opinion on Pfeffer et al.

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Re: Potential Collapse Scenario for the WAIS
« Reply #30 on: February 25, 2013, 06:13:54 PM »
Lennart,

I very much appreciate you getting to the heart of the matter so directly (and framing the issue so well).  A full response to your questions may take me some days (or weeks) to unfold, but I will make the following brief points now (to be elaborated later): (a) on an expert opinion level I clearly side with Hansen and Sato 2012 and I do criticize Pfeffer et al 2008 for being dated and too narrow, but I do agree with Pfeffer that specific mechanisms need to be identified (which I have started in my other threads [see my latest post in the "surge" thread]); and (b) as I state in the "philosophy" thread ice believe that it will take several decades for computer ice models to fully capture the mechanisms that I am proposing and for now I suggest that a "Hazard Analysis" be conducted using something like Bayesian methodology.
To give approximate answers to your questions about Pfeffer et al 2008 I offer the following criticisms: (a) Pfeffer's high ice velocities are applied to too narrow of gateways: (i) as shown by Rignot 2008 the 2007 ice velocities of 2,500 m/yr is only applied over a narrow ice stream of 5 to 8 km; (b) I suspect that now that the subglacial cavity has extended to the lip of the BSB this this surge flow width may have expanded to 30 to 40 km before being currently pinned on the sides by the submarine mounts, but once the ice in this area thins so that it can float over the submarine mounts to the East (at El -650m) this throat should further widen to 50 to 60 km, and once the ice thins to float at El -450m this throat width widens to almost 100km. (b) Pfeffer disregards the branching that I propose will happen to the subglacial cavity once it reaches the bottom of the negative slope leading to the BSB, thus after 2040 local icebergs could calve off of multiple branches and float out of the 50 to 100 km wide throat; (c) Pfeffer ignores the activation of the Weddell Sea Coastal glaciers by the introduction of warm CDW beneath the Filchner-Ronne Ice Shelf circa 2060, and he ignores the risk of the activation of the Siple Coast glaciers/ice streams by the accelerated calving and probably ice melt pond mechanism (which in this tread I cite could begin circa 2050 to 2070; (d) Pfeffer ignores my proposed mechanism that the subglacial cavities may link together after 2070 leading to a very rapid surge of ice sheet disintergation from tidal water flow through the interconnected subglacial cavities; plus (e) as Hansen and Sato point out for SLR to rise all of the ice does not need to melt, it only needs to float so seismic activity associated with large ice mass loss circa 2070 to 2080 could cause accelerated floatation of multiple icebergs out form all four fronts (Amundsen Sea, Bellingshausen Sea, Weddell Sea, and Ross Sea) of the WAIS.  I believe that with these assumptions that limiting the ice average ice flow velocities to 4,500 to 6,000 m/yr is more than sufficient.  Furthermore, Pfeffer has ignored (failed to update) his case for GIS due to melt water from Albedo change including BC which caused ice mass loss for GIS of 700 Gt from January to Sept 2012 (while Pfeffer is only talking about ice flow/calving).  That is all for now, but please re-look as all the various mechanisms that I present in various different posts/threads.
« Last Edit: February 25, 2013, 10:43:45 PM by AbruptSLR »
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Re: Potential Collapse Scenario for the WAIS
« Reply #31 on: February 25, 2013, 08:13:00 PM »
Lennart,

In response to your first post about Rohling (both in 2007 & Grant et al 2012) I provide the two attached figures.  First from Grant et al 2012, in the timeframe of interest from over 125 kyr ago (when sea-level was higher than now) all that I can say is that several of the blue crosses appear to be between 6m to 8m higher than today indicating the potential for brief spikes of collapsed ice mass loss on the order of 50 to 100-years (in any event Grant's data does not rule out such spikes).  The second figure from Muhs et al 2012, shows that for California sea-level rapidly increased to just over 6m above today's sea level (which matches my graphs in the philosophical thread) and then was flat for a long prior.  Therefore, I suggest that one should be very careful when performing a "Hazard Analysis" of using averaged data that includes rapid rises together with long period of little or no rise (also Grant et al 2012 average over at least 1000 years which much to coarse to see a 50 to 100-yr spike).
« Last Edit: February 26, 2013, 02:05:39 AM by AbruptSLR »
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Re: Potential Collapse Scenario for the WAIS
« Reply #32 on: February 26, 2013, 12:41:30 AM »
Lennart,

I would like to supplement my earlier post about my criticism of Pfeffer's assumptions for the glaciers in the ASE to note that: (a) he did know about ice mass loss through advection through subglacial cavities and in my drawings of these cavities for the Thwaites Basin I show that this could be a very large area, and further I note that this subglacial ice melting would be accelerated by the geothermal heat coming up through the crust (which I presume to be commonly plugged from high volumes of release by a sediment plug at the base of the gateway to Thwaites).  Also I note that the Ross Ice Shelf (which is a cold ice shelf without warm CDW) loses a lot of thickness to sub-iceshelf melting which does not add to SLR because it is floating, but for any new Thwaites Ice Shelf formed above the BSB this would all contribute to SLR as all of this ice is now grounded; (b) Pfeffer takes a combined gateway cross-section for both PIG and Thwaites to be 120 sq km which is reasonable, but if we get a lot of subglacial advective ice melting within subglacial cavities in the BSB then ice may float out of this gateway.  Also, for those not familiar with Pfeffer et al 2008 I attach a pdf.
« Last Edit: February 26, 2013, 02:03:10 AM by AbruptSLR »
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Re: Potential Collapse Scenario for the WAIS
« Reply #33 on: February 26, 2013, 01:35:44 AM »
With regard to ice mass loss from the glaciers around the Filchner-Ronne Ice Shelf: The Alfred Wegener Institute is now studying the potential impact on sea levels of the risk of ice mass loss from the Weddell Sea sector of the WAIS, identified by Hellmer et al. 2012.   However, if the ice sheet flow toward the sea is as great as the ice loss projected for the shelf itself, the institute stated that global sea levels would rise by and additional 4.3 mm per year, before the end of the century.  It is noted here that Hellmer et al. 2012 examined scenarios less aggressive than those for both RCP 8.5 and for the SBEHA corrected RCP 8.5, which implies that the indicated ice mass loss could begin to accelerate closer to 2050 rather than the 2070 date cited by Hellmer et al. 2012.
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Re: Potential Collapse Scenario for the WAIS
« Reply #34 on: February 26, 2013, 01:49:47 AM »
For those not familar with the melt pond mechanism I provide the accompanying figure related to the collapse of the Larsen A & B Ice Shelf in 2002
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Re: Potential Collapse Scenario for the WAIS
« Reply #35 on: February 26, 2013, 12:17:28 PM »
ASLR,
Thanks for your views on Pfeffer et al (2008) and the reference to Muhs et al (2012). I don't have access to this last paper, but abstract and figures are here:
http://www.sciencedirect.com/science/article/pii/S0277379112000224

Spikes of very fast SLR over 50-100 yrs seem very hard to extract from the Eemian data, but I agree that they may very well have occurred.

I also support your risk hazard approach and find your overview of potential mechanisms that could contribute to collapse very useful.

Expert elicitation seems to be an important way of getting more insight into the potential risk of WAIS-collapse. Bamber & Aspinall (2013) gave some useful data from their survey amongst 13 experts (out of 26 invited) in 2010 and 2012:
http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1778.html

In their supplementary Table S1 (p.8 last column) they apparently show that the rate of SLR in 2100 from the ice sheets is estimated on average to be 5-7 mm/yr, with a 5% risk of more than circa 17 mm/yr, and a very small chance of almost 4 cm/yr in the most extreme scenario. That last scenario would seem to be about the same as the most extreme scenario by Pfeffer et al. On p.10 (bottom) of the supplementary info they also seem to give an even more extreme estimate for the max rate of (total) SLR in 2100 of almost 5 cm/yr, but I don't understand the technical details of these different estimates.

The 13 experts surveyed were (p.11 supplementary info):
Richard Alley, Richard Hindmarsh, Philippe Huybrechts, Ian Joughin, Shawn Marshall, Frank Pattyn, Jeff Ridley, Eric Rignot, Catherine Ritz, Robert Thomas, Michiel van den Broeke, Roderik van de Wal, David Vaughan.

I'm wondering what you make of these outcomes and what your own best guess for max rate of SLR around 2100 would be.

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Re: Potential Collapse Scenario for the WAIS
« Reply #36 on: February 26, 2013, 05:24:32 PM »
Lennart,

When I have time I will open a new thread on why the IPCC WG1 (not just Pfeffer) at the moment do not recognize the risk of abupt SLR this century (and I agree that timing is the primary question here).  But in general terms Bamber & Aspinall 2013 is the "tip of the iceberg" of a growing trend to at least formally recognize this risk of abrupt SLR from ice mass loss from ice sheets (IS), see the attached figure with a thin tail for the risk of abrupt SLR.  While B & A at least acknowledge the risk of abrupt SLR, ASLR, they are stuck in the officially recognized scenarios developed by the IPCC which limits its estimates of probabilities to what can be proven deductively by GCM projection give the RCP set of assumptions.  B&A's panel of experts all appear to accept this methodology while experts such as Hansen and Sato appear to try to look out side of the box using inductive reasoning to present the risk of 5m of SLR by 2100, which is to say that the fatten the tail of the IS ice mass lose curves presented by B&A to include factors such as ice from the WAIS thinning sufficiently to lift of the bottom and to float away much faster than Pfeffer and the IPCC WG1 are prepare to even acknowledge. 
Regarding my projections of SLR by 2100, they have been posted in the "philosophy" thread for many days now.  Again, I will open a new thread to try to clarify each out of the box hazard factor that will contribute layer by layer to fatten the trail of the probability curve for ASLR.
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Re: Potential Collapse Scenario for the WAIS
« Reply #37 on: February 26, 2013, 11:06:30 PM »
ASLR,

I wasn't sure how to read those graphs. Do I understand correctly that under RCP 8.5 you think almost 4 meters of (globally averaged) SLR around 2100 not only possible, but likely? And that between circa 2070 and 2090 you think about 2 meters not only possible, but likely? Or should I read this differently?

If so, and if that's a real risk, or even a probability, what adaptation options should we think of in that case, in your view?

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Re: Potential Collapse Scenario for the WAIS
« Reply #38 on: February 27, 2013, 12:03:31 AM »
Lennart,

The way that I mean for these graphs to be read, is that one would either design a new feature of infrastructure to what ever standard that has jurisdiction, or one would re-examine the design of an existing structure; and then one would use these graphs to determine ocean elevations for RSLR (for infrastructure in California) for a resiliency (or maximum credible) case similar to a maximum credible earthquake.  Note that the US Federal Emergency Management Agency, FEMA, requires a similar resiliency check case for the current risk of a 0.2% exceedance probability (one in 500-yr) inundation case.  I propose this MCE RSLR to be a similar resilency check case for future conditions at the end of the infrastructure features design life, rather than for the present case resiliency check.  I believe that what adaptive engineering provisions should be considered for such an MCE check case depends on the consequence of failure of the infrastructure feature and on its importance.  Note that the MCE check case would not include only the probability of a future sea level but also all storm and other short-term load combinations.
Examples of adaptive measures include: (a) design for a shorter service life; (b) design the feature to survive the short-term loading and be suitable for restoration; (c) retreat from the high risk area; (d) cover some risk with insurance; (e) design the feature to be upgradable as the RSLR goes up; or (f) be prepared to accept the loses.  Most militaries around the world are performing hazard analysis for abrupt climate change and they plan accordingly.  While it is more comfortable not to think about such possible hazard cases; it is still better to have resilient infrastructure as we enter our new age of climate change consequences.
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Re: Potential Collapse Scenario for the WAIS
« Reply #39 on: February 27, 2013, 12:36:45 PM »
ASLR,

Thanks again for all the info and insights you're posting here. Are you a publishing scientist in this field, or did your learn all this another way?

Just to be sure I repeat my question above: do I understand correctly that under RCP 8.5 you think almost 4 meters of (globally averaged) SLR around 2100 not only possible, but likely? And that between circa 2070 and 2090 you think about 2 meters not only possible, but likely? Or should I read this differently?

And in addition, what is your thought on the risks of SLR after 2100? For example, what do you think of these figures from Meehl et al (2012):
http://www.nature.com/nclimate/journal/v2/n8/fig_tab/nclimate1529_F3.html

At least they seem to take seriously a risk of about 10-12 meters of SLR by 2300, under BAU, which is more than any other explicit projections I've seen so far, such as from the Dutch Delta Committee. But the projection of Meehl et al is based on the semi-empirical method, not including possible non-linear responses of the ice sheets, so it may still be an under-estimate.

So I'm wondering how your collapse scenario would continue after 2200. Do you project one big surge around the end of this century, or beginning of the next, and a slower SLR afterwards? Or could the EAIS also contribute one or more follow-up surges in the coming centuries?

I ask this also in relation to Foster & Rohling (PNAS 2013):
http://www.pnas.org/content/early/2013/01/03/1216073110

They conclude that at 400 ppm CO2 there's circa 84% chance of at least 9 meters of SLR over the coming centuries/millennia and about 50% chance of circa 24 meters of SLR over this longer term. So even at 400 ppm, which we will reach soon, EAIS will probably start contributing significantly to SLR. It doesn't seem likely we will return below 400 ppm any time soon, although if we would really try it might still be possible.

Also Hansen & Sato 2011 (p.23) pointed to signs that Totten Glacier in EAIS is already starting to lose mass, based on Rignot et al 2008: "satellite gravity and radar interferometry data reveal that the Totten Glacier of East Antarctica, which fronts a large ice mass grounded below sea level, is already beginning to lose mass". Pfeffer et al did not take Totten Glacier into account.

For the record: I'm just a lay-man interested in and concerned about the risk of rapid and large SLR, among other climate risks, working for a local environmental ngo in The Hague, Netherlands, and trained in public administration/political science. I'm trying to understand the science as well as I can, but the technical details are often too hard to follow. So bear with me if I sometimes seem to ask for the obvious.

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Re: Potential Collapse Scenario for the WAIS
« Reply #40 on: February 27, 2013, 03:22:30 PM »
Lennart,

Thanks for the continued dialogue.  I will provide brief answers so that I can expand on the other threads in this forum.
First, I am an engineer (not a scientist), and I have published one paper on abupt SLR in a marine engineering conference proceeds that is not widely distributed.  I am to busy to prepare a peer reviewed paper by myself on this topic (so I am posting on this forum instead); however, if others want include this information in their own papers then well & good; or is they want my assistance with a peer reviewed paper in a scientific journal then they can e-mail me.  I learned all that I have put into this forum on the internet, since the Spring of 2011 (after Rignot's paper made the risks clear to me); and while researcher have done a great job of developing the facts that I have learned from the internet; it seems to me that the scientific community at large (with many promient exceptions) and the IPCC in particular have done a very poor job of communicating the actual risks (probability times consequences) to the public at large.
Second, I believe that if we continue on our current path then there is a "good" probability that we will see multiple meters (3m to 5m eustatically and upto 6.5m regionally) by 2100.  Also, I concur with Hansen et al's position that this WAIS ice mass loss contribution will be non-linear with the lion's share coming after 2050 (as clearly indicated numerically on my graphs in the philosophical discuss, and note that I put this graphes in the philosophical section because I believe that resiliency is more important than prescience, and that getting an MCE check case for abrupt SLR now is much more important than spending decades (which what it will take) to get highly accurate ice mechanisms that can project abrupt ice mass loss with GCM projections and I think that risk based hazard analyses run by hand now can make clear what magnitude of resiliency that we need to guard against multi-trillion dollar losses to our coastal cities using things such as storm surge barrier [which could have prevented well over half of the economic losses from Superstorm Sandy).
Third, in the scenario that I envision after the WAIS collapses by the end of this century or the beginning of the next century that SLR will slow-down  (as shown clearly in my graphs in the philosophical thread), for at least 50 to 100-yr (with EAIS and GIS still making significant but not abrupt contributions to SLR); then what happens after 2150 to 2200 depend very much on what anthopogenic forcing and/or what natural methane releases occur; but in general terms I see both EAIS and GIS as being more stable than the WAIS and that they will likely follow behaviors more like Meehl et al 2012 until 2500 (I believe it likely that nature methane releases will drive SLR for at least this long into the 9 to 12m range).
Fourth, I have never read anything yet published by Hansen and Sato that I disagree with, and I clearly see signs since Hansen and Sato's 2011 paper that indicate that the rapid dynamic ice mass loss from EAIS is accelerating and that this accelerating mass loss has been temporarily masked from the GRACE satellite results by some probably temporary heavy years of snow fall.  Also, when the WAIS collapses this will activate many EAIS glaciers adjoining WAIS (such as the Byrd Glacier); but while these EAIS will make significant contribution by the end of this century and times their after, I would call these contributions rapid dynamic contributions and not abrupt.
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Re: Potential Collapse Scenario for the WAIS
« Reply #41 on: February 27, 2013, 05:43:17 PM »
ASLR,

Very clear, and I agree on the importance of resilient adaptative measures based on your risk-based approach, and on the need for much clearer communication of those risks.

I also have a question on mitigation though: suppose we do work together globally and succeed in following not RCP 8.5, but one of the lower scenario's, to what extent would that reduce or eliminate the risk of ASLR, in your view/estimation? Or does that risk remain high enough even in the lower scenario's to require significant adaptive measures (since we're already about to cross 400 ppm and will probably not go below that level during this century, even in a very optimistic scenario)?

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Re: Potential Collapse Scenario for the WAIS
« Reply #42 on: February 27, 2013, 08:04:12 PM »
Lennart,

I estimate that if we can follow the RCP 4.5 50% CL path this will give SLR behavior similar to that shown in the graph in my Feb 25th 6:30am post on the "Philosophical" thread for the blue SBEHA Eustatic 5% curve (note that SBEHA means Scenario Based Engineering Hazard Analysis), which effectively does not have ASLR but does almost follows the semi-empirical projections (such as by Rahmstorf et al).  While it may be possible to follow RCP 4.5 with regard to anthropogenic GHG emissions, I am not very optimistic that we will be able to follow the radiative forcing for RCP 4.5 with regards to both Black Carbon and Natural Methane emissions (permafrost, ocean hydrates etc).
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Re: Potential Collapse Scenario for the WAIS
« Reply #43 on: February 27, 2013, 10:02:36 PM »
ASLR,

That would mean the worst-case scenario of the Delta Committee (2008) could actually be about our best-case scenario:
http://www.deltacommissie.com/doc/deltareport_full.pdf

That would be... alarming, right? How many knowledgeable people do you know, who share your views on this, apart from Hansen? How could these people work together to wake the rest of the scientific and wider community up? Any suggestions?

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Re: Potential Collapse Scenario for the WAIS
« Reply #44 on: February 27, 2013, 11:53:47 PM »
Lannert,

Your are correct that in my opinion by 2100 about the best that we can hope for is a eustatic SLR of about 1m which is at the upper bound of the accompanying figure including the 2008 Delta report finding.  The people that I know who think as I do, would not be interested in putting anything in writing until after the AR6 report is issued in 2020 to 2021 as they seem to what to have computer codes worked out, and do not want to rely on the hazard analysis approach.

Regarding a solution to this problem all that I can suggest is that the solution to the "Tyranny of the Commons" was to privatize the Commons, thus my only recommendation would be to legistate the use of Public Private Partnerships for flood control projects, and in the legislation make the private part legally responsible for the consequence of the possible failure of the infrastructure feature.  I believe that this topic is too complex to be addressed by the government (representing the people) alone, and until the private financial sector has direct legal liability then all parties (government, insurance, business) will continue to take advantage of the Commons without properly taking care of it.  Note that New York & New Jersey where bailed out by federal emergency aid and now they have little or no interest of taking anything but the easiest defensive measure (eg moving their generators from their basements to somewhere above the first floor) as they are expecting the federal government to bail them out again after a future Sandy event.  This is the "moral hazard" associated with most climate change related measures, that so long as they can "short or hedge" their risks/hazards at someone else's expense, why would they ever face the hard work that they need to face to solve this problem.
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Re: Potential Collapse Scenario for the WAIS
« Reply #45 on: February 28, 2013, 01:04:57 PM »
In addition to the last figure with several sea level rise estimates: the WBGU-estimate for 2300 was by no means a worst-case since their scenario assumed 3 degrees warming with 560 ppm CO2e. See pp.36-37 of:
http://www.wbgu.de/fileadmin/templates/dateien/veroeffentlichungen/sondergutachten/sn2006/wbgu_sn2006_en.pdf

For a BAU-scenario their high estimate of 5 meters in 2300 could maybe be doubled to about 10 meters.

AbruptSLR

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Re: Potential Collapse Scenario for the WAIS
« Reply #46 on: February 28, 2013, 02:28:08 PM »
Lennart,

Thanks for the input from 2006.  When developing projections (or hazard analyses) for the future, it is always good to look back to see where you came from.
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #47 on: March 08, 2013, 05:08:52 PM »
Regarding looking back from where we came from, while many of you will have already seen this first image, nevertheless some will not have, so I am posting the attached figure of historical global temperatures relative to peak Holocene temperature. (per Hansen and Sato, 2011).  This image illustrates that the peak temperature during the Eemain was only about 0.75 C above the peak temperature during the Holocene and I note here that the earth will returned to those temperatures levels during the Holocene peak by 2020 and to the Eemain peak temperatures by about 2035 if we keep following RCP 8.5 50% CL (see the second image)
« Last Edit: March 08, 2013, 05:45:45 PM by AbruptSLR »
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #48 on: March 11, 2013, 12:05:39 PM »
The following few selected extracts are taken from the attached fact sheet for the University of Washington's: 2012 Program on Climate Change, PCC, Summer Institute "Atmosphere-Ocean-Ice Shelf Interactions" Sunday, September 16, 2012 to Tuesday, September 18, 2012 Friday Harbor Labs, Friday Harbor, San Juan Island.  Note that all of the following observations related to the West Antarctic were made before the postulated "Surge" was observed, but they are all consistent with the initiation conditions assumed by the WAIS collapse scenario presented in many threads here:
(1) Christina Hulbe: "The Ross Sea sector of the West Antarctic Ice Sheet has the potential for rapid and significant change due to its marine character and fast-flowing ice streams. This makes modern change detection of particular interest and indeed, evidence for past ice flow variability is easy to find. The interest here is how changes observed today are to be interpreted: are modern changes a response to recent climate forcing, part of an ongoing response to warming after the last glacial maximum, or something else entirely? An example on the Ross Ice Shelf will be examined and used as a springboard for wider ranging speculation."
(2) Laurie Padman (padman@esr.org) and Scott Springer: "The now-standard paradigm of ice-shelf importance is that "ocean heat flux into the sub-ice-shelf cavity increases; ice shelf thins (and calves); buttressed glaciers accelerate; sea level rises". However, the ice shelves are not just middlemen, but actively participate in establishing the environment that determines their state. That is, feedbacks from the ice shelf to the ocean and sea ice are important to a full system model of ice shelves."
(3) Sarah G. Purkey & Gregory C. Johnson: "Complex processes that are difficult to model fully or parameterize well in coarse resolution numerical climate projections are numerous around Antarctica, including ice sheet dynamics, ocean circulation and water mass formation, and the incursion of relatively warm Circumpolar Deep Water (CDW) onto the shelf and under ice sheets. We discuss observations of changes in several of these processes. First we review warming and freshening of Antarctic Bottom Water (AABW) and estimate a rate of its contraction in recent decades from changes in water-mass inventories. We show that the contracting AABW is associated with a southward expansion of CDW in the Southern Ocean. We speculate that this expansion may allow increased intrusion of warmer northerly CDW across the slope onto the Antarctic continental shelves, in turn allowing basal ice sheet melt. We note that these processes, along with possible ice dynamic feedbacks discussed by previous speakers, have the potential to form a positive feed-back loop."
(4) Brian Rose, brose@atmos.washington.edu, and David Ferreira and John Marshall: "The coupled climate dynamics underlying large, rapid and potentially irreversible changes in ice cover are studied. A global atmosphere-ocean-sea ice general circulation model with idealized aquaplanet geometry is forced by gradual multi-kyr variations in solar luminosity. The model traverses a hysteresis loop between warm ice-free conditions and cold glacial conditions in response to ±5 W/m^2 variations in global, annual mean insolation. Comparison of several model configurations confirms the importance of polar ocean processes in setting the sensitivity and timescales of the transitions. A “sawtooth” character is found with faster warming and slower cooling, reflecting the opposing effects of surface heating and cooling on upper ocean buoyancy and thus effective heat capacity. The transition from glacial to warm, equable climate occurs in about 200 years."
“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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Re: Potential Collapse Scenario for the WAIS
« Reply #49 on: March 11, 2013, 10:30:41 PM »
ASLR, Purkey et al 2012 is available open source. Thanks to NOAA PMEL. Thanks for the tip.