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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1700 on: October 11, 2019, 05:57:44 PM »
As a follow-on to my last post, 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.  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:
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1701 on: October 11, 2019, 07:27:45 PM »
Consensus climate scientists have been slow to embrace the possibility that outbursts of subglacial meltwater may likely accelerate future grounding line retreat in the Thwaites Glacier gateway, largely because they do not yet fully understand the mechanism of such interactions.  For reasons to complex to go into in this post, there are multiple reasons to believe that lessons learned from current and paleo subglacial hydrology in the western Ross Sea reason can readily be applied to the Thwaites gateway region.  Thus, I provide the following linked reference about 'a meltwater drainage system beneath the ancestral East Antarctic ice sheet', which located in West Antarctica; which supports the position that '… ice stream dynamics in this region were sensitive to the underlying hydrological system.'  While this may not mean much to many readers, to me it supports the idea that the glacial ice in the trough through the Thwaites gateway is subject to being destabilized at a decadal-scale by outbursts of meltwater that pass through this very trough:

Simkins, L.M., Anderson, J.B., Greenwood, S.L., Gonnermann, H.M., Prothro, L.O., Halberstadt, A.R.W., Stearns, L.A., Pollard, D. and DeConto, R.M., 2017. Anatomy of a meltwater drainage system beneath the ancestral East Antarctic ice sheet. Nature Geoscience, 10(9), pp.691-697, doi: 10.1038/NGEO3012

https://www.nature.com/articles/ngeo3012

Abstract: "Subglacial hydrology is critical to understand the behaviour of ice sheets, yet active meltwater drainage beneath contemporary ice sheets is rarely accessible to direct observation. Using geophysical and sedimentological data from the deglaciated western Ross Sea, we identify a palaeo-subglacial hydrological system active beneath an area formerly covered by the East Antarctic ice sheet. A long channel network repeatedly delivered meltwater to an ice stream grounding line and was a persistent pathway for episodic meltwater drainage events. Embayments within grounding-line landforms coincide with the location of subglacial channels, marking reduced sedimentation and restricted landform growth. Consequently, channelized drainage at the grounding line influenced the degree to which these landforms could provide stability feedbacks to the ice stream. The channel network was connected to upstream subglacial lakes in an area of geologically recent rifting and volcanism, where elevated heat flux would have produced sufficient basal melting to fill the lakes over decades to several centuries; this timescale is consistent with our estimates of the frequency of drainage events at the retreating grounding line. Based on these data, we hypothesize that ice stream dynamics in this region were sensitive to the underlying hydrological system."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1702 on: October 11, 2019, 07:31:20 PM »
As a public service, I note that the Twenty-Sixth Annual WAIS Workshop is being held next week in California

Twenty-Sixth Annual WAIS Workshop
October 16-18, 2019
Camp Cedar Glen
Julian, California, U.S.A.

https://www.waisworkshop.org/workshop-2019


Extract: "For 2019, sessions topics will include:
•   Will the snowflakes save us? Near-surface science in West Antarctica using shallow geophysics, ice cores, firn studies, atmospheric reanalysis, meteorological observations, and modeling
•   Processes Beneath: Deep geophysics, direct-access experiments, microbiology, sediment coring, and modeling for quantifying critical processes from the basal interface to the core
•   The Great Glacier Conveyer - A John Nye & Wally Broecker Appreciation Session: Connecting paleo understanding with modern processes
•   From The Sea: Polar oceanography, tropical teleconnections, marine life, and ice front dynamics and their impact on a changing WAIS
•   The Leading Edge: New boundary conditions, new modeling techniques, Operation IceBridge, ICESat-2, GRACE, GRACE-FO, NISAR, and data science applications for West Antarctic science
•   Dynamics across the grounding line: Past, present, and future understanding of the ice stream-grounding zone-ice shelf transition seen from the ground, air, satellites, and models
•   Science Communication: Taking WAIS science beyond our room
•   Community Health: Avoiding, acknowledging, and approaching issues with field harassment"

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

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1703 on: October 12, 2019, 09:09:37 AM »
I have frequently recommended that climate scientists better discuss risk (probability times consequences) when presenting their findings.  The linked reference (about increasing damage from natural disasters due to climate change) is a very good example of how I believe more climate scientists should present their findings.  In particular, the associated attached image shows how, with time, increasing stress (i.e. radiative forcing) the pdf shifts to the right and the pdf becomes more right skewed with a fatter right tail; which dramatically increases the damage function:

Matteo Coronese, Francesco Lamperti, Klaus Keller, Francesca Chiaromonte, and Andrea Roventini (October 7, 2019), "Evidence for sharp increase in the economic damages of extreme natural disasters", PNAS https://doi.org/10.1073/pnas.1907826116

https://www.pnas.org/content/early/2019/10/01/1907826116

Significance
Observations indicate that climate change has driven an increase in the intensity of natural disasters. This, in turn, may drive an increase in economic damages. Whether these trends are real is an open and highly policy-relevant question. Based on decades of data, we provide robust evidence of mounting economic impacts, mostly driven by changes in the right tail of the damage distribution—that is, by major disasters. This points to a growing need for climate risk management.

Abstract
Climate change has increased the frequency and intensity of natural disasters. Does this translate into increased economic damages? To date, empirical assessments of damage trends have been inconclusive. Our study demonstrates a temporal increase in extreme damages, after controlling for a number of factors. We analyze event-level data using quantile regressions to capture patterns in the damage distribution (not just its mean) and find strong evidence of progressive rightward skewing and tail-fattening over time. While the effect of time on averages is hard to detect, effects on extreme damages are large, statistically significant, and growing with increasing percentiles. Our results are consistent with an upwardly curved, convex damage function, which is commonly assumed in climate-economics models. They are also robust to different specifications of control variables and time range considered and indicate that the risk of extreme damages has increased more in temperate areas than in tropical ones. We use simulations to show that underreporting bias in the data does not weaken our inferences; in fact, it may make them overly conservative.

Extract: "Inconclusive results in the literature might be due to the use of statistical techniques ill-suited to capture the evolution of the damage distribution. We hypothesize that relevant patterns may in fact correspond to changes in its right skew and tail. To investigate this, we use a different modeling and statistical strategy. First, we include control variables for socio-demographic factors as covariates in our models alongside time—this generalizes the Actual-to-Potential-Loss approach, allowing for multiple controls, and improves upon procedures that normalize damage values prior to modeling (Normalization). Second, and perhaps most importantly, we characterize the behavior of the damage distribution fitting quantile regressions over disaggregated, event-level data.

Our approach avoids 2 common pitfalls: 1) linear aggregation—i.e., summing damages associated to disasters occurring in a given year over a specified geographical area, which may lead to a substantial loss of information—and 2) the use of ordinary least squares (OLS)—i.e., mean regression, which captures only average trends in damages (changes in expected losses). With increasing evidence that natural disasters induce fat-tailed damage distributions and that fat tails can dramatically change policy implications in a variety of climate-economics models, analyzing quantiles can be an effective way to inspect extreme, low-probability events. In addition, OLS regression can be a rather blunt instrument to analyze skewed data. In contrast, quantile regressions do not rely on Gaussianity or even symmetry assumptions for the error distribution and have already been used to characterize the evolution of cyclone strength.

The Devil Is in the Tails: From Climate Stressors to Damages
We hypothesize that what changes over time is the right skew and tail behavior (as opposed to the average) of the damage distribution. This can be explained using the concept of damage function. Damage functions are widely used in the Integrated Assessment Modeling literature to link climate-related stressors (e.g., wind speed for tropical cyclones or storm surges) to damages.

Rightward Skewing and Tail Fattening: Economic Impacts Are Mounting
Turning from simulated to actual data, we find strong evidence of an accelerating rightward skewing and tail fattening of the damage distribution over time."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1704 on: October 12, 2019, 11:51:12 AM »
I have referenced Milillo et al. (2019) previously; however, as it tells part of a complex/heterogeneous story of the portion of the Thwaites Glacier gateway between the east side of the base of the Thwaites Eastern Ice Shelf (TEIS) and the west side of the base of the Thwaites Ice Tongue, I use it to kick-off a series of Replies using previously posted information in order try to emphasize how this dynamic area of the Thwaites Glacier gateway could lead to the initiation of an MICI-type of failure for the Thwaites Glacier beginning around 2035 to 2045. 

In this regard, the first attached image (Fig 1) shows this critical portion of the Thwaites gateway where:
1. Panel A/B shows the bed topology (blue with white contour lines) and areas of high basal ice melting (red zones) associated with the influx of warm CDW (yellow arrows).
2. Panel C shows DinSAR data and points A, B & F (near what I later call the Big Ear) and points C, D & E (to the east of what I later call the Little Ear).
3. Panel D shows the height above floatation.
4. Panel E shows change in ice surface elevation, dh, between decimal years 2013.5 and 2016.66.
5. Panel F shows ice flow velocities (with the highest velocities at the west side of the base of the Thwaites Ice Tongue).

The second image (Fig 2) zooms in on the points A, B & F (with high basal ice mass loss near the grounding line and high changes in the ice surface elevation) and points C, D & E (with high basal ice mass loss near the grounding line but with lower changes in the ice surface elevation)

The third image (Fig 3) shows the subglacial cavity in this area with Panel C focused on the Big Ear area (points A, B & F).

The fourth image from Tinto & Bell (2011) shows what I call the Big Ear and Little Ear areas prior to 2011 in relation to both the TEIS, the Thwaites Ice Tongue and the bed trough that extends from the ocean to the Byrd Subglacial Basin, where I suspect that ice-cliff failures may begin as early as 2035.

P. Milillo, E. Rignot, P. Rizzoli, B. Scheuchl, J. Mouginot, J. Bueso-Bello, and P. Prats-Iraola (2019), "Heterogeneous retreat and ice melt of Thwaites Glacier, West Antarctica", Sci Adv. 5(1): eaau3433, doi: 10.1126/sciadv.aau3433
PMCID: PMC6353628
PMID: 30729155

https://advances.sciencemag.org/content/5/1/eaau3433
&
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6353628/

Abstract: "The glaciers flowing into the Amundsen Sea Embayment, West Antarctica, have undergone acceleration and grounding line retreat over the past few decades that may yield an irreversible mass loss. Using a constellation of satellites, we detect the evolution of ice velocity, ice thinning, and grounding line retreat of Thwaites Glacier from 1992 to 2017. The results reveal a complex pattern of retreat and ice melt, with sectors retreating at 0.8 km/year and floating ice melting at 200 m/year, while others retreat at 0.3 km/year with ice melting 10 times slower. We interpret the results in terms of buoyancy/slope-driven seawater intrusion along preferential channels at tidal frequencies leading to more efficient melt in newly formed cavities. Such complexities in ice-ocean interaction are not currently represented in coupled ice sheet/ocean models."

Caption for the first image (Fig 1): "Thwaites Glacier, West Antarctica.
(A) Map of Antarctica with Thwaites Glacier (red box). (B) Shaded-relief bed topography (blue) with 50-m contour levels (white) (16), grounding lines color-coded from 1992 to 2017, and retreat rates for 1992–2011 (green circle) versus 2011–2017 (red circle) in kilometer per year. Thick yellow arrows indicate CDW pathways (32). White boxes indicate outline of figs. S1 and S2 (C) DInSAR data for 11 to 12 and 27 to 28 April 2016, with grounding lines in 2011, 2016, and 2017 showing vertical displacement, dz, in 17-mm increments color-coded from purple to green, yellow, red, and purple again. Points A to F are used in Fig. 2. (D) Height of the ice surface above flotation, hf, in meters. (E) Change in ice surface elevation, dh, between decimal years 2013.5 and 2016.66 color-coded from red (lowering) to blue (rising). (F) Ice surface speed in 2016–2017 color-coded from brown (low) to green, purple, and red (greater than 2.5 km/year), with contour levels of 200 m/year in dotted black."

Caption for the second image (Fig 2): "Changes in ice surface elevation, h, of Thwaites Glacier.
(A to F) from TDX data (blue dots) for the time period 2011–2017 over grounded ice (red domain, dh/dt) at locations A to F, with height above floatation, hf (red lines), and 1σ uncertainty (dashed red lines), converted into change in ice thickness, H, over floating ice (blue domain, dH/dt) in meters per year. Black triangles are TDX dates in (G) to (J). (G and H) Main trunk. (I and J) TEIS. Grounding line position is thin black for 2016–2017 and white dashed blue for 2011."

Caption for the third image (Fig 3): "Ice thickness change of Thwaites Glacier.
(A) Ice surface elevation from Airborne Topographic Mapper and ice bottom from MCoRDS radar depth sounder in 2011, 2014, and 2016, color-coded green, blue, and brown, respectively, along profiles T1-T2 and (B) T3-T4 with bed elevation (brown) from (16). Grounding line positions deduced from the MCoRDS data are marked with arrows, with the same color coding. (C) Change in TDX ice surface elevation, h, from June 2011 to 2017, with 50-m contour line in bed elevation and tick marks every 1 km."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1705 on: October 12, 2019, 06:08:18 PM »
As a follow-on to my last post, I present four images in this post and four images in the next post, in an attempt to get readers oriented in the area where I first expect ice cliff failures for Thwaites Glacier between two bed areas that I have labelled Big Ear and Little Ear in this series of images.

The first image comes from Kim et al. (2018), and shows two local areas of subglacial cavities that collapsed circa 2012.

https://www.mdpi.com/2072-4292/10/8/1236

With a hat tip to Sleepy, the second image shows the ears relative to the growth of the subglacial cavity at the base of the Thwaites Ice Tongue (near the Big Ear), circa 2017.

The third and fourth images show the alignment (plan & section, respectively) of A-B (circa 2017) that Rignot believes has low stability, and which transects the bed trough (see Tinto & Bell 2012), and this figure clearly shows that in the trough the height of any future local ice cliff above sea level would be well above El 100m and the water depth would be at least 800 m; indicating that ice-cliff failure mechanisms would occur in the future if/when this ice is no longer buttressed by the floating glacial ice.  Here, I remind readers that any icebergs calved into the trough (once the ice shelf & ice tongue are gone) can simply float-out to sea.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1706 on: October 12, 2019, 06:24:13 PM »
As a follow on to my last post, I present four images in an attempt to get readers oriented in the area where I first expect ice cliff failures for Thwaites Glacier between to bed areas that I have labelled Big Ear and Little Ear in this series of images.

The first image shows the locations of the Big & Little Ears relative to a collapse of the cavity (see Kim et al. 2018) that lead to a surge of the Thwaites Ice Tongue after January 2012.

The second image shows the location of Big & Little Ears on a Sentinel 1 image from May 23, 2019.  This image shows ice bergs already floating near the Little Ear location.

The third image shows the sources of CDW leading from the continental rise to the bases of the TEIS and the Thwaites Ice Tongue.

The fourth image shows the bathymetry of the Thwaites Gateway prior to 2013, which confirms that icebergs can readily float-out of the trough leading to the BSB once the TEIS and the Thwaites Ice Tongue have collapsed and are no longer pinned by the ridge that is seaward of the gateway.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1707 on: October 12, 2019, 09:54:32 PM »
To continue with my series of posts reminding readers why I believe that ice-cliff failure mechanisms will be activated in the trough passing through the Thwaites gateway near the base of the Thwaites Ice Tongue:

The first image illustrates how the increased circumpolar westerly winds (due to the Antarctic ozone hole) causes the coastal surface water to move offshore (due to the Coriolis effect), which causes increased upwelling of warm CDW (circumpolar deep water), so of which moves toward the continental shelf.

The second image (from a computer simulation) illustrates how this upwelled CDW is advected towards the grounding line of key Antarctic marine glaciers (including those in the Amundsen Sea Embayment, ASE), due to the presences of ice meltwater near the coastal seawater surface; which accelerates both basal ice melting of the associated ice shelves (including the Thwaites Eastern Ice Shelf, TEIS, and the Thwaites Ice Tongue) and grounding line retreat.  This figure also shows that around 2030 this mechanism will begin delivering warmer CDW to still shallower continental shelf water depths.  Which will stress the ASE ice shelves and grounding lines more than what has been occurring since about 1990 to about 2030.

The third image (from a computer simulation) shows how (under the right conditions, like an El Nino year) warm CDW can flow from the PIG westward along the coast to the Thwaites gateway, where it can accelerate the basal ice melting normally occurring due to tidally advected CDW into the Thwaites gateway.  As strong El Nino events happen every 15 years (with continued global warming), this mechanism may well accelerate basal ice mass loss from the TEIS & the Thwaites Ice Tongue circa 2015/16 +15 = 2030/31.

The fourth image shows how rapid the ice shelf/tongue mass loss has been in the ASE since the 1990's; and particularly shows how unstable the Thwaites Ice Tongue has been during this period of increase CDW advection to the Thwaites gateway.
« Last Edit: October 12, 2019, 10:00:10 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1708 on: October 12, 2019, 10:17:54 PM »
As a follow-on to my last post:

The first image shows the relationship between the ENSO cycle and the surface elevation of the ice shelves in the Amundsen Sea Sector; clearly increasing that these ice shelves float up on El Nino events and down on La Nina events; which causes flexure and cracking of the ice shelves (which weakens them and makes them more susceptible to the influence of warm CDW).

The second image shows how during the combination of an El Nino event and a positive SAM event tropical heat energy is advected from the Tropical Pacific directly to the coastal West Antarctica; where it can episodically accelerate local ice mass loss (along the coastal areas).

The third image shows how the Amundsen Bellingshausen Sea Low, ABSL (or ASL), can direct winds directly into the ASE, which also drags along ocean currents that advect more warm CDW into the ASE which accelerates local ice mass loss.

The fourth image shows the average potential temperature of the warm CDW (above freezing) typically being advected into the ASE, and the associate marine glacier ice flow velocities (because of the reduced buttressing from the degrading ice shelves and the retreating grounding lines).  Also, I note that relatively rapid ice flow velocities cause internal friction within the ice of the marine glaciers, which induces more basal meltwater beneath the marine glaciers (which further destabilize the marine glaciers).
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1709 on: October 12, 2019, 10:37:56 PM »
To continue my posts on why local ice-cliff failures may be initiated in the trough in the bed of the Thwaites gateway circa 2035:

The first image shows the ice flow velocities of the Thwaites Glacier and how those velocities change with distance from the calving front and with time & I note that both the internal ice friction and associated internal glacial ice melting has varied with distance from the calving front and with time.

The second image shows the typical phreatic water surface elevation within a marine glacier (here the Byrd Glacier) and how it varies in a similar fashion with the ice flow velocities with distance from the calving front.

The third image shows an idealized image of the subglacial meltwater conveyance system beneath the Thwaites Glacier and how this basal meltwater exists from beneath the glacier near the base of the Thwaites Ice Tongue & through the trough located near there.

The fourth image shows how when basal meltwater exists from beneath the calving front of a marine glacier it can cause mixing turbulence that can accelerate local ice mass loss.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1710 on: October 12, 2019, 10:49:53 PM »
To continue my series of posts on the instability of the Thwaites gateway:

The first image shows the location of four Thwaites subglacial lakes that drain between June 2013 and July 2014, just after the local collapse of the subglacial cavities in the Thwaites gateway.

The second image shows that the ice surface elevation above these four Thwaites subglacial lakes dropped as the lakes drained, & the associated outburst of meltwater contributed to the surge of the Thwaites Ice Tongue during this period.

The third image shows a photograph of base of the Thwaites Ice Tongue from January 2013, showing both the location of the calving front and the grounding line and how icebergs are floating away from the calving front during the 2012 to 2014 surge of the Thwaites Ice Tongue.

The fourth image shows the geothermal heat flux beneath the Thwaites Glacier which contributes to the volume of basal meltwater in the drainage system beneath the Thwaites:
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1711 on: October 12, 2019, 11:03:28 PM »
To continue my series of posts on the instability of the Thwaites gateway and associated ice shelf & ice tongue:

The first image shows how warm CDW passes through troughs in the continental shelf to the grounding line of a representative marine glacier (like in the ASE); where it both melts the ice at the grounding line and along the underside of the ice shelf causing a relatively freshwater current of water to exist from the calving front of the ice shelf/tongue.  This freshwater flow not only thins the thickness of the ice shelf/tongue but also causes grooves in the underside of the shelf/tongue which have accelerated ice melting.

The second image (from Bassis) shows how warm CDW beneath an ice shelf can 'burn' upwards through crevasses/channels in the underside of the ice shelf, thus reducing the stability of the ice shelf.

The third & fourth images show that so much ice meltwater has already been discharged from Antarctic ice shelves and marine glaciers that the surface waters of much of the Southern Ocean have become colder and fresher, both of which cause positive ice-climate feedback mechanisms.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1712 on: October 12, 2019, 11:19:15 PM »
I provide the following four images to illustrate additional reasons that the Thwaites Eastern Ice Shelf, TEIS, and Thwaites Ice Tongue may become unstable circa 2030/35 (whether they have thinned sufficiently to become unpinned from the submarine ridge pinning points, or not):

The first image shows how the melt-pond mechanism (also called hydrofracturing) caused the Larsen B ice shelf to collapse in less than a week, and I note that if ECS is much above 3C then similar meltwater ponds will likely form during the austral summer on the TEIS circa 2030/35; which could cause the TEIS to collapse abruptly in that timeframe.

The second image (from sidd) shows that the air space in the firn of Antarctic ice shelves are coming saturated with ice (including the TEIS); which means that hydrofracturing in the TEIS is becoming increasingly likely.

The third image shows the firn system in an ice shelf and how meltwater can displace the associate firn air; which increases the likelihood of hydrofracturing.

The fourth image shows the current susceptibility of the firn system on Antarctic ice shelves to become saturated with salty seawater as the ice shelves become thinner; thus increasing the risk of hydrofracturing of the ice shelf.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1713 on: October 12, 2019, 11:34:09 PM »
This post is the last of my recent series of posts on mechanisms that may likely lead to local ice-cliff failures occurring in the trough of the bed of the Thwaites gateway after the TEIS and the Thwaites Ice Tongue may have collapsed circa 2030/35:

The first image reminds us of the geometry of the bed topology and the subglacial cavity in the Thwaites gateway; which makes the Thwaites Glacier uniquely susceptible to an MICI-type of collapse in the coming decades.

The second image shows how snow fall primarily in the coastal areas of the West Antarctic; where it progressively increases the gravitational driving force on key marine glaciers in the ASE like the Thwaites Glacier.

The third image shows that the eastern shear margin of the Thwaites Glacier is linked to the SW Tributary Glacier.  Thus now that the calving front of the Pine Island Ice Shelf, PIIS, has retreated upstream of the ice shelf for the SW Tributary Glacier, we can expect that the associated acceleration of the ice velocities of the SW Tributary Glacier will reduce the buttressing of the eastern shear margin; which should accelerate the ice flow velocities of the Thwaites Glacier in coming decades.

The fourth image of a 'Domino Wave' reminds us that a cascade of tipping points associated with the stability of the Thwaites Glacier can accelerate rapidly once triggered.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1714 on: October 13, 2019, 06:58:59 PM »
The linked reference finds that simulating an armada of icebergs (from the WAIS) around the Southern Ocean substantially increases the positive feedback for most ice mass loss from the AIS:

Fabian Schloesser et al. (2019), "Antarctic iceberg impacts on future Southern Hemisphere climate", Nature Climate Change,  9, 672–677

DOI: https://doi.org/10.1038/s41558-019-0546-1

https://www.nature.com/articles/s41558-019-0546-1

Abstract: "Future iceberg and meltwater discharge from the Antarctic ice sheet (AIS) could substantially exceed present levels, with strong implications for future climate and sea levels. Recent climate model simulations on the impact of a rapid disintegration of the AIS on climate have applied idealized freshwater forcing scenarios rather than the more realistic iceberg forcing. Here we use a coupled climate–iceberg model to determine the climatic effects of combined iceberg latent heat of fusion and freshwater forcing. The iceberg forcing is derived from an ensemble of future simulations conducted using the Penn State ice-sheet model. In agreement with previous studies, the simulated AIS meltwater forcing causes a substantial delay in greenhouse warming in the Southern Hemisphere and activates a transient positive feedback between surface freshening, subsurface warming and ice-sheet/shelf melting, which can last for about 100 years and may contribute to an accelerated ice loss around Antarctica. However, accounting further for the oceanic heat loss due to iceberg melting considerably increases the surface cooling effect and reduces the subsurface temperature feedback amplitude. Our findings document the importance of considering realistic climate–ice sheet–iceberg coupling for future climate and sea-level projections."

May last series of posts provide some level of evidence that the Thwaites Glacier may initiate a MICI-type of collapse starting as early as 2035 to 2040; which might roughly match the information associated with the 5-year doubling time on Hansen et al (2016)'s attached plots.  However Schloesser et al. (2019), points out that analyses like Hansen et al.'s used meltwater hosing events (in both the Southern Ocean and/or the North Atlantic) instead of armadas of icebergs which have substantial latent heat of fusion; which both extends the timeline of cooling of the local SSTs and slows the rate of the positive ocean feedback to melt more ice from marine glaciers. 

That said, I note that one of Hansen's more significant warnings on this topic is that an episodic release of an armada of icebergs, into the Southern Ocean and/or the North Atlantic, would generate tremendously large storms (e.g. Cat 6 hurricanes and larger); which would likely act as multidecadal positive feedbacks for higher transient values of ECS due both to: a) heat energy advected by such mega-storms directly to the Arctic, thus providing a multidecadal increase in Arctic Amplification; and b) a likely multidecadal increase in Arctic rainfall, which would result in a transient increase in ECS due to such positive feedbacks as: melting of Arctic Sea Ice, degradation of permafrost, enhance ice mass loss from the GIS; and increased methane emissions from high latitude peatlands and degraded permafrost.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1715 on: October 14, 2019, 03:13:33 AM »
For readers who are uncertain of the timing, and direction, of when icebergs may float out from the bed trough near the 'Big Ear' (see Replies 1704 thru 1713) upstream of the base of the Thwaites Ice Tongue (TG), I provide the attached image that compares captures from the Sentinel 1 satellite in this area on May 23, 2019 and Oct 12, 2019 (less than 5 months apart).  This comparison shows new crevasses in the base of the TG just downstream of the 'Big Ear', and also the calving front at the western side of the TG base in moving towards the 'Big Ear'.  If this trend continues it seem probable that icebergs will be able to float in the northwest direction from the 'Big Ear' area of the bed trough prior to 2030.

Edit: If it is not clear from my prior posts, the new upstream crevasses in the Oct 12, 2019 occur as the glacial ice flows over the subglacial cavity (leading to the Big Ear) causing the surface elevation to drop abruptly, thus cracking the ice.  When the ice between these regularly spaced crevasses either thins enough, or reaches deep enough water, it will float; and when not confined it will float away as icebergs (see the third image in Reply #1710).
« Last Edit: October 14, 2019, 02:58:38 PM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1716 on: October 15, 2019, 10:08:27 AM »
As it may not be clear to some readers as to why the new upstream crevasses at the base of the Thwaites Ice Tongue might be at risk of creating icebergs that can float away, I note that:

1. The first attached image from Rignot et al. (2009) shows that the ice velocities exiting the Thwaites gateway at the base of the Thwaites Ice Tongue are particularly high.  So much so that when the ice tongue virtually collapsed in 2012, it was rapidly replaced by a new ice tongue that was about half as wide as the old ice tongue and was much more fractured than the old ice tongue (yet it maintains a fragile stability as its northerly end is pinned on the subsea ridge; which keeps the fragmented mass of icebergs in compression so they cannot readily float away).

2. I have previously posted the second image from Rignot et al. (2017) showing a second along the line AB that was near the centerline of the old ice tongue, but which now runs along the westerly edge of the new ice tongue, and passes upstream along the western edge of the 'Big Ear' subglacial cavity.  Thus the nearly 40 km-long ice tongue shown in this image use to be composed of less fractured glacial ice, but now consists of a relatively narrow field of confined floating icebergs; and even more importantly the figure shows a red line showing the hydrostatic bottom elevation calculated from the surface elevation which indicates whether the ice above the line can float if not restrained from floating as the over 2 km of ice upstream of the grounding line would do except that before 2017 it was restrained from floating by the weight of the adjoining upstream ice.  Thus, the new crevasses shown in the Oct 12, 2019 Sentinel-1 image define potential icebergs if their confinement is relieved as has occurred along their westerly edge as indicated by the area of new calving front indicated in the image in Reply #1715, and as this calving front (at the westerly side of the base of the Thwaites Ice Tongue) progresses in the southeasterly direction (both due to icebergs calving off this front and due to the 'Big Ear' subglacial cavity extending along the trough to the southwest) eventually the new Thwaites Ice Tongue will loss confinement and the icebergs currently confined in its mass will float away to the northwest (note the first 2009 image shows a subsea ridge to the northwest that might pin such icebergs, but the improved resolution of the third 2013 image shows that this subsea ridge to the northwest is not high enough to pin such future icebergs).

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Ken Feldman

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1717 on: October 15, 2019, 06:24:38 PM »
Skeptical Science has a good webpage about MICI here.

https://skepticalscience.com/new-light-antarctica-contribution-slr.html

It covers DeConto and Pollard's 2016 paper, the Edwards et. al 2019 response and discuss updates planned by DeConto and Pollard.

Quote
In that 2016 paper, DeConto and his co-author, Prof David Pollard of Penn State University, used an ice sheet model to ascertain how periods in the Earth’s history that were only slightly warmer than today managed to have sea levels that were many metres higher.
Simulating the Pliocene, around three million years ago, and the Last Interglacial, 130,000-115,000 years ago, DeConto and Pollard found that the high sea levels from those periods could only be recreated when MICI was included. DeConto explains:
“One key point is that including these brittle processes in ice sheet models is the best way we’ve found to reproduce the high sea levels we see in the geologic past.”
Turning their attention to the future, DeConto and Pollard ran model simulations calibrated on their findings for the past. They found that including MICI “greatly increases the pace of future sea level rise in high greenhouse gas emissions scenarios”, says DeConto.
The new paper revisits these estimates. It uses a statistical model, called an “emulator”, to replicate the model created by DeConto and Pollard. This allowed the researchers to expand the number of model simulations they ran to explore the full range of possible future outcomes – including those that do not include MICI – as well as calibrating the model with satellite data.
In simulations with MICI, the “most likely” model outcome under the high-emissions RCP8.5 scenario is a contribution from Antarctica of 45cm by 2100, says lead author Dr Tamsin Edwards, a climate scientist and lecturer at King’s College London. She tells Carbon Brief:
“This is much lower than the mean values in DeConto & Pollard – interpreted by many as the most likely values – which ranged from 64cm to 114 cm.”
But their findings also suggest that MICI was not necessary to produce the sea level rise seen in the Pliocene or the Last Interglacial. Without MICI, their most likely contribution from Antarctica is 15cm by 2100 under RCP8.5, with a “likely” range of 13-31cm. There is just a 5% likelihood of Antarctica contributing more than 39cm to sea levels by 2100, Edwards says:



Quote
DeConto and Pollard are also currently revisiting their 2016 results in a new paper. DeConto says he is not able to comment on it directly as it is undergoing peer review. However, he has presented some preliminary results at the Fall Meeting of the American Geophysical Union (AGU) in December.
An article published in the Atlantic shortly afterwards reported that DeConto and Pollard “have lowered some of their worst-case projections for the 21st century” after making improvements to their model. The results are likely to put Antarctica’s contribution to sea level rise in 2100 at “about a foot” (30cm), the article says, which is “much closer to projections made by other glaciologists”.


Ken Feldman

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1718 on: October 15, 2019, 06:27:47 PM »
Here is the article linked to from Skeptical Science (in my post above).

https://www.theatlantic.com/science/archive/2019/01/sea-level-rise-may-not-become-catastrophic-until-after-2100/579478/

Quote
A Terrifying Sea-Level Prediction Now Looks Far Less Likely
But experts warn that our overall picture of sea-level rise looks far scarier today than it did even five years ago.
Robinson Meyer
Jan 4, 2019

Quote
One of the scariest scenarios for near-term, disastrous sea-level rise may be off the table for now, according to a new study previewed at a recent scientific conference.

Two years ago, the glaciologists Robert DeConto and David Pollard rocked their field with a paper arguing that several massive glaciers in Antarctica were much more unstable than previously thought. Those key glaciers—which include Thwaites Glacier and Pine Island Glacier, both in the frigid continent’s west—could increase global sea levels by more than three feet by 2100, the paper warned. Such a rise could destroy the homes of more than 150 million people worldwide.

They are now revisiting those results. In new work, conducted with three other prominent glaciologists, DeConto and Pollard have lowered some of their worst-case projections for the 21st century. Antarctica may only contribute about a foot of sea-level rise by 2100, they now say. This finding, reached after the team improved their own ice model, is much closer to projections made by other glaciologists.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1719 on: October 15, 2019, 06:35:02 PM »
Tell that the people of Tuvalu, Kiribati, the Marshall Islands, or Florida.
Refugees welcome

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1720 on: October 15, 2019, 08:18:32 PM »
I don't see the need for alarmism, but Marine Ice Cliff Instability (MICI) of the West Antarctic Ice Sheet (WAIS) is serious catastrophic threat that would take tens of thousands of years of Antarctic snowfall to reverse.  Some respectable scientists feel that it is already inevitable.  I don't see it happening on the time scale that AbruptSLR is suggesting, but current models are too simplistic and based on insufficient data to give them much confidence.

One problem with AbrubtSLR's analysis is that a grounding line retreat in the "Trough" at the center of Thwaites Glacier is too narrow to lead to MICI all on it's own.  You would need at least a significant grounding line retreat on either the Eastern of Western sides of Thwaites, if not both, to open up the wide West Antarctic basin to a massive collapse.

This is what I see as a more realistic scenario.

1. Collapse or significant shortening of Thwaites Tongue, 0-5 years:  Significant shortening in this case is to anything less than half of its current length which would take it off the undersea ridge which gives it stability.

2.  Collapse of the Thwaites Eastern Ice Shelf (TEIS), 10 years:  Calving on both the Eastern and Western sides makes it unsustainable.

3.  Marine Ice Sheet Instability (MISI) or accelerated grounding line retreat on the Pine Island Glacier (PIG), 10-20 years:  Doesn't directly effect Thwaites, but it certainly seems likely to happen sooner.

4.  MISI or accelerated grounding line retreat on the Eastern side of Thwaites, 30+ years:  This is what the current models say, but they assume that TEIS will remain fixed in place.

5.  MISI or accelerated grounding line retreat on the Western side of Thwaites, (?):  I am personally not convinced that the West is inherently more stable than the East but I think better bathymetry will help decide the question.

I think in 5 years time we will have a lot more observations on Thwaites and published analysis.  I think the ice front picture will also be a little more clear which will help with better models.  I don't know if we will have anything like comprehensive models by then, but we can hope.

I spend a lot of time in Florida and the construction down there baffles me.  I don't think their current flood maps are accurate, since they still use flood assumptions from the 1970's.  Also, it shouldn't be called a "100 year flood" because who knows where they will be in 100 years.  It should be called the 1% flood.

I guess what I'm trying to say is that the idea that the scientific consensus is one foot of sea level rise by 2100 and therefore "there is nothing the see here, move along" I think is a mistake.  There is a lot to see here and we shouldn't just move along.
« Last Edit: October 15, 2019, 08:31:27 PM by baking »

Ken Feldman

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1721 on: October 15, 2019, 09:10:49 PM »
Do you think there might be a scenario between "nothing to see here" and "we're already doomed and there's nothing we can do about it?" 

The "consensus scientists" that many posters here sneer about seem to be operating as if there is a possibility that if we cut our carbon emissions, we may end up in a far more livable future than if we don't.  Based on what I've read, I tend to believe the scientists.

baking

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1722 on: October 15, 2019, 10:27:01 PM »
Do you think there might be a scenario between "nothing to see here" and "we're already doomed and there's nothing we can do about it?" 

The "consensus scientists" that many posters here sneer about seem to be operating as if there is a possibility that if we cut our carbon emissions, we may end up in a far more livable future than if we don't.  Based on what I've read, I tend to believe the scientists.

How about "if we cut our carbon emissions, we may end up in a far more livable future than if we don't, but we still might have 3 meters of higher sea level."?  On the whole, I am optimistic that we will find ways to reduce and even eliminate carbon emissions by (say) 2060, but I worry that there is a sea level tipping point that may have already been reached or is a few decades away from being reached, which probably amounts to the same thing.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1723 on: October 15, 2019, 11:23:10 PM »
Re: ice sheet melt: apocalypse or inconvenience ?

1) saving WAIS or GIS south dome will require dropping atmospheric CO2 from current values within decades. If we do not get atmospheric CO2 substantially (by 100 ppm or thereabouts)  by century end, kiss those two goodbye. Given we succeed in this effort, i am cautiously optimistic, recall those ice sheets advanced post holocene optimum until we really gunned the accelerator on fossil CO2 output.

2)Lets say we don't get CO2 concentration down. Then the question becomes how soon will those disappear. Worst case is several meters by century end, and several tens of meters by millennium end. An all bets are off if EAIS starts going.

sidd




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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1724 on: October 16, 2019, 05:55:36 AM »
Another way to look at it is that sea levels were 20-30 feet higher than today during the last interglacial, without anthropogenic global warming.  The major surface features of the earth are not that much different then they were 120,000 years ago, so that water had to come from somewhere.  I think the only logical conclusion has to be that there exists a tipping point for the WAIS and it was tipped in the last interglacial without human intervention.

Perhaps the earth could have escaped this current interglacial without hitting the tipping point.  Perhaps we still can.  Maybe we have accelerated it or maybe we have already hit it.  All are reasonable possibilities.  But denying the existence of the tipping point because you don't see it happening before 2100 seems shortsighted.

I think you can be an optimist about future carbon emissions and still be a pessimist about rising sea levels.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1725 on: October 16, 2019, 05:27:32 PM »
While many of my past posts in this thread have emphasized that ECS has a good chance to be considerably higher than the values cited in AR5; many of my other posts demonstrate that there is a good possibility that much of the WAIS may collapse in coming decades without any the need for either higher (than current consensus) values of ECS or even for more radiative forcing.  Still many of my other posts emphasize that the numerous transient positive ice-climate feedback mechanisms (e.g. slowing of the MOC, albedo flip, the bipolar seesaw mechanism, ocean-cloud feedbacks, etc.) can act to increase the effective equilibrium climate sensitivity (EffCS) for multidecadal periods; which raises the topic of this post.

If ECS is indeed currently above 5C as indicates by at least eight of the most sophisticated CMIP6 models, and if a collapse of the WAIS (beginning between 2030 & 2040) increases this value still higher for several (to multiple) decades, then it is possible that the North Hemisphere could tip into an equable climate, and stay in that pattern for at least centuries, for reason including:

1. The primary characteristic of an equable climate (as occurred during the Eocene) is that ocean heat energy is conveyed directly from the tropical oceans (particularly the Tropical Pacific) poleward (& particularly to the Arctic).  In this regard, Schneider et al. (2019) cites that the future risk of losing marine stratocumulus clouds (which currently produce a negative feedback) would would result in an abrupt increase in GMSTA.  While Schneider et al. (2019) showed that an increase of atmospheric carbon dioxide concentration to about 1,200ppm, would result in such a loss of marine stratocumulus cloud, I previously pointed out in Reply #652 (see also Replies: #633, #642 & #650), the risk of abruptly losing the marine stratocumulus clouds would also occur if the equatorial SST increases from about 27C to about 32C.  In this case the atmosphere for the North Hemisphere could be abruptly transitioned from modern to equable climate (or 'hot house') conditions.  Such a 5C SST increase in the equatorial oceans, could conceivable occur this century from a combination of: a) ice-climate feedbacks from the collapse of the WAIS & bipolar seesaw interaction with the Arctic & Greenland; b) a cascade of other tipping points (including methane feedbacks), c) a rapid decrease/redistribution of anthropogenic aerosol emissions and/or a high current value of ECS.

2.  The linked reference (Pistone et al 2019) calculates the radiative heating of a sea ice free Arctic Ocean during the sunlit part of the year and assuming constant cloudiness they '… calculate a global radiative heating of 0.71 W/m2 relative to the 1979 baseline state. This is equivalent to …' hastening global warming by an estimated 25 years.  If the Northern Hemisphere were to flip into an equable pattern this century, this would lead to a sea ice free Arctic Ocean during the sunlit part of the year (particularly due to rainfall on the Arctic Sea Ice); which (together with bipolar seesaw interaction between the GIS and the AIS) might well be sufficient to maintain an equable climate pattern even after the multidecadal pulse of planetary energy imbalance associated with glacial ice mass loss from the GIS & the AIS.

Kristina Pistone et al. (20 June 2019), "Radiative Heating of an Ice‐free Arctic Ocean", Geophysical Research Letters, https://doi.org/10.1029/2019GL082914

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL082914?af=R

&

3. The linked reference (Massoud et al 2019) indicates that using consensus science (CMIP5) analyses the frequency of Atmospheric Rivers (ARs) will increase in frequency by about 50% and in intensity by about 25% by 2100, without considering points 1. and 2. above.  As an AR rainfall event on the GIS would greatly accelerate the bipolar seesaw mechanism, these findings should be considered when evaluating future right-tail climate change risks this century:

E.C. Massoud et al. (12 October 2019), "Global Climate Model Ensemble Approaches for Future Projections of Atmospheric Rivers", Earth's Future, https://doi.org/10.1029/2019EF001249

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019EF001249?af=R

Abstract
Atmospheric rivers (ARs) are narrow jets of integrated water vapor transport that are important for the global water cycle, and also have large impacts on local weather and regional hydrology. Uniformly‐weighted multi‐model averages have been used to describe how ARs will change in the future, but this type of estimate does not consider skill or independence of the climate models of interest. Here, we utilize information from various model averaging approaches, such as Bayesian Model Averaging (BMA), to evaluate 21 global climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5). Model ensemble weighting strategies are based on model independence and atmospheric river performance skill relative to ERA‐Interim reanalysis data, and result in higher accuracy for the historic period, e.g. RMSE for AR frequency (in % of timesteps) of 0.69 for BMA vs 0.94 for the multi‐model ensemble mean. Model weighting strategies also result in lower uncertainties in the future estimates, e.g. only 20‐25% of the total uncertainties seen in the equal weighting strategy. These model averaging methods show, with high certainty, that globally the frequency of ARs are expected to have average relative increases of ~50% (and ~25% in AR intensity) by the end of the century.

Plain Language Summary

Atmospheric rivers (ARs) are storms of integrated water vapor transport that are important for the global water cycle, and also have large impacts on local weather and regional hydrology. An increase in the frequency of ARs is expected to occur by the end of the century throughout most of the globe. Usually, these types of assessments of future climate change rely on simple (i.e. equally‐weighted) multi‐model averages and do not consider the skill or independence of the climate models of interest. Here, we utilize information from various model averaging approaches to constrain a suite of 21 global climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5). The weighted model combinations are fit to reanalysis data (ERA‐Interim) and are useful because they provide higher skill as well as lower uncertainties compared to equal weighting. This work supports the claim that AR frequency will increase in the future by about ~50% (and intensity will increase by ~25%) globally by the end of the century.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1726 on: October 16, 2019, 07:21:50 PM »

It covers DeConto and Pollard's 2016 paper, the Edwards et. al 2019 response and discuss updates planned by DeConto and Pollard.



I do indeed consider Edwards et al. (2019) to be a representation of consensus climate science erring on the side of least drama; which is not to disrespect consensus climate scientists; but which is to say that in my opinion they are doing a poor job of communicating climate risk to both the public and to decision makers.

For example consensus climate science acknowledges that the probability density function (PDF) for climate sensitivity is right-skewed as shown in the first attached image; nevertheless, consensus climate scientists generally talk about the 'most likely' (or mode) value rather than the mean value which is considerably higher and which represents much more risk to our socio-economic system as discussed by the linked article and the second attached image; which assumes that the mode value for ECS is 3C instead of over 5C.


Title: "Climate Change Could End Human Civilisation as We Know It by 2050, Analysis Finds"

https://www.sciencealert.com/by-2050-climate-change-could-alter-human-civilisation-as-we-know-it

Extract: "The new report, co-written by a former executive in the fossil fuel industry, is a harrowing follow-up to the Breakthrough National Centre for Climate Restoration's 2018 paper, which found that climate models often underestimate the most extreme scenarios.

Endorsed by former Australian defence chief Admiral Chris Barrie, the message is simple: if we do not take climate action in the next 30 years, it is entirely plausible that our planet warms by 3°C and that human civilisation as we know it collapses.

Under this scenario, the authors explain, the world will be locked into a "hothouse Earth" scenario, where 35 percent of the global land area, and 55 percent of the global population, will be subject to more than 20 days a year of "lethal heat conditions, beyond the threshold of human survivability."

With a runaway event like this, climate change will not present as a normal distribution, but instead will be skewed by a fat tail – indicating a greater likelihood of warming that is well in excess of average climate models.
Under a business-as-usual scenario, the authors explain, warming is set to reach 2.4°C by 2050. If feedback cycles are taken into account, however, there may be another 0.6°C that current models do not assume.
"It should be noted," the paper adds, "that this is far from an extreme scenario: the low-probability, high-impact warming (five percent probability) can exceed 3.5–4°C by 2050.""

In this same vein of thought I note that Dr. Tasmin Edwards et al. (2019) demonstrated that when calibrating a MICI model to a left-tail set of assumptions from the paleorecord that it is possible to present less alarming MICI projections than if one were to calibrate an MICI model to either mean or right-tailed sets of assumptions from the paleorecord.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1727 on: October 16, 2019, 10:50:16 PM »
First, in the linked article Hausfather notes that 2019 most likely will have the second highest GMSTA on record, and per the first attached image the 'very likely' range for the 2019 GMSTA is from 1.12 to 1.21C; which is getting close to the 1.5C aspirational goal set by the IPCC.

Title: "State of the climate: Low sea ice and near-record warmth define 2019 to date"

https://www.carbonbrief.org/state-of-the-climate-low-sea-ice-and-near-record-warmth-define-2019-to-date

Extract: "This year is shaping up to be the second warmest on record for most surface temperature datasets, behind only the super-El Niño year of 2016. This is particularly noteworthy because 2019 has been characterised by a weak El Niño that has played little role in boosting temperatures."

Second, in the second attached image (of a Hausfather tweet), a given CH4 emission will raise the GMSTA by more than 100 times what the same emission of CO2 will do over a 10-year period.  Thus, assuming that we do not meaningfully change either CH4 or CO2 emission rates for the next 20-years; methane emissions will contribute more to potentially pushing the world over any possible Earth System tipping points that exist in the next couple of decades, than are carbon dioxide emissions (over the same period); and remember that the higher GMSTA gets the more likely we collectively are to crossing such a tipping point.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1728 on: October 17, 2019, 05:04:20 PM »
Many left-tail climate-change pdf focused people argue that as all climate models are wrong (see the linked Wikipedia article), they are entitled to advise decision makers using the least dramatic linear approximation for climate change projections.  However, it is my opinion that some models match reality sufficiently to be useful, while overly simplified models can be counterproductive.  Furthermore, I note that the 'scientific method' is not a given model, but rather is a process that progressively iterates towards developing new models that better match the complexities of reality with time.

Title: "All models are wrong"

https://en.wikipedia.org/wiki/All_models_are_wrong

Extract: ""All models are wrong" is a common aphorism in statistics; it is often expanded as "All models are wrong, but some are useful". It is usually considered to be applicable to not only statistical models, but to scientific models generally. The aphorism is generally attributed to the statistician George Box, although the underlying concept predates Box's writings.…
Although the aphorism seems to have originated with George Box, the underlying concept goes back decades, perhaps centuries.

In 1947, the mathematician John von Neumann said that "truth … is much too complicated to allow anything but approximations".
 
In 1942, the French philosopher-poet Paul Valéry said the following.
Ce qui est simple est toujours faux. Ce qui ne l’est pas est inutilisable.
What is simple is always wrong. What is not is unusable."

Furthermore, the developer of the holographic method (Dennis Gabor), once stated:

"The future cannot be predicted, but futures can be invented."

In this regard, I note that:

1. Left-tail climate-change focused people can serve to 'invent'/promote a 'hothouse' future by making decision makers believe that they have more time to curtail GHG emission than what is advisable to avoid triggering a cascade of climate change tipping points.

2. Right-tail climate-change focused people can serve to 'invent'/promote a 'sustainable' future by citing model projections that are sufficiently complex to effectively attribute cause and effect in the various interconnected Earth Systems responses; but which are simple enough to be useful to decision makers.

Regarding my second point about the usefulness of a right-tail climate-change focus when it promotes the development of models that are sufficiently complex to effectively attribute cause and effect in Earth System responses, I close this post by noting that just because many ice-climate feedback mechanisms flush ice meltwater into both the North Atlantic and the Southern Ocean thus decreasing the SSTA and thus limiting the increase in GMSTA with increasing radiative forcing, does not mean that we are all safer, but rather the opposite.  However, in order to recognize the threat from fresh-meltwater/iceberg hosing one must have climate models that are sufficiently sophisticated to correctly account for such somewhat complex mechanisms as: Ekman Transport, Meridional Overturning Circulation, Vertical Eddy Flux and Ocean Heat Uptake, etc.  In this regard, one of the reasons that CMIP5 projected values of ECS that will likely be lower than the ECS values to likely be projected by CMIP6 is that the CMIP5 models underestimated the influence of many of these ocean dynamics.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1729 on: October 17, 2019, 10:24:48 PM »
The linked reference suggests that consensus scientists likely avoid talking about known unknowns and unknown unknowns with the public in order to maintain the publics trust in their projections.  This behavior does not improve our safety regarding a potential collapse of the WAIS, unless somehow very wise decision makers are diligently working behind the scenes to evaluate the potential impacts of such right-tail risks (which I doubt).

Lauren C. Howe et al. Acknowledging uncertainty impacts public acceptance of climate scientists' predictions, Nature Climate Change (2019). DOI: 10.1038/s41558-019-0587-5

https://www.nature.com/articles/s41558-019-0587-5

Abstract: "Predictions about the effects of climate change cannot be made with complete certainty, so acknowledging uncertainty may increase trust in scientists and public acceptance of their messages. Here we show that this is true regarding expressions of uncertainty, unless they are also accompanied by acknowledgements of irreducible uncertainty. A representative national sample of Americans read predictions about effects of global warming on sea level that included either a worst-case scenario (high partially bounded uncertainty) or the best and worst cases (fully bounded uncertainty). Compared to a control condition, expressing fully bounded but not high partially bounded uncertainty increased trust in scientists and message acceptance. However, these effects were eliminated when fully bounded uncertainty was accompanied by an acknowledgement that the full effects of sea-level rise cannot be quantified because of unpredictable storm surges. Thus, expressions of fully bounded uncertainty alone may enhance confidence in scientists and their assertions but not when the full extent of inevitable uncertainty is acknowledged."

See also:

Title: "How uncertainty in scientific predictions can help and harm credibility"

https://phys.org/news/2019-10-uncertainty-scientific-credibility.html

Extract: "The more specific climate scientists are about the uncertainties of global warming, the more the American public trusts their predictions, according to new research by Stanford scholars.

But scientists may want to tread carefully when talking about their predictions, the researchers say, because that trust falters when scientists acknowledge that other unknown factors could come into play."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1730 on: October 17, 2019, 10:35:50 PM »
The linked 2014 article makes it clear that using the public's approach to dealing with uncertainty using delayed action is a bad idea.

Title: "Scientists unmask the climate uncertainty monster"

https://phys.org/news/2014-04-scientists-unmask-climate-uncertainty-monster.html

Extract: "Scientific uncertainty is a 'monster' that prevents understanding and delays mitigative action in response to climate change, according to The University of Western Australia's Winthrop Professor Stephan Lewandowsky and international colleagues, who suggest that uncertainty should make us more rather than less concerned about climate change.

In two companion papers published today in Climatic Change, the researchers investigated the mathematics of uncertainty in the climate system and showed that increased scientific uncertainty necessitates even greater action to mitigate climate change.

Professor Stephan Lewandowsky, who is also Chair in Cognitive Psychology and member of the Cabot Institute at the University of Bristol, said: "We can understand the implications of uncertainty, and in the case of the climate system, it is very clear that greater uncertainty will make things even worse. This means that we can never say that there is too much uncertainty for us to act. If you appeal to uncertainty to make a policy decision the legitimate conclusion is to increase the urgency of mitigation."

These new findings challenge the frequent public misinterpretation of uncertainty as a reason to delay action. Arguing against mitigation by appealing to uncertainty is therefore misplaced: any appeal to uncertainty should provoke a greater, rather than weaker, concern about climate change than in the absence of uncertainty."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1731 on: October 17, 2019, 11:35:44 PM »
I thought scientific uncertainty was covered by the Precautionary Principle, a tenet of Environmental Law.
There is a principle which is a bar against all information, which cannot fail to keep a man in everlasting ignorance. That principle is contempt prior to investigation. - Herbert Spencer

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1732 on: October 18, 2019, 10:02:33 AM »
...

One problem with AbrubtSLR's analysis is that a grounding line retreat in the "Trough" at the center of Thwaites Glacier is too narrow to lead to MICI all on it's own.  You would need at least a significant grounding line retreat on either the Eastern of Western sides of Thwaites, if not both, to open up the wide West Antarctic basin to a massive collapse.

...

I note that once potential ice-cliff failure mechanisms within the trough in the Thwaites gateway bed reaches the retrograde slope leading into the Byrd Subglacial Basin, that the most likely failure mechanism will be by slumping as described by Parizek et al. (2019); which would likely result in icebergs with much shallower drafts than those currently being formed in in Thwaites calving events; which would allow the Thwaites gateway to widen up to be 50-km wide; which would allow for the float-out of a large volume of ice mélange.

Byron R. Parizek et al. Ice-cliff failure via retrogressive slumping, Geology (2019). DOI: 10.1130/G45880.1

https://pubs.geoscienceworld.org/gsa/geology/article/569567/Icecliff-failure-via-retrogressive-slumping

Abstract
Retrogressive slumping could accelerate sea-level rise if ice-sheet retreat generates ice cliffs much taller than observed today. The tallest ice cliffs, which extend roughly 100 m above sea level, calve only after ice-flow processes thin the ice to near flotation. Above some ice-cliff height limit, the stress state in ice will satisfy the material-failure criterion, resulting in faster brittle failure. New terrestrial radar data from Helheim Glacier, Greenland, suggest that taller subaerial cliffs are prone to failure by slumping, unloading submarine ice to allow buoyancy-driven full-thickness calving. Full-Stokes diagnostic modeling shows that the threshold cliff height for slumping is likely slightly above 100 m in many cases, and roughly twice that (145–285 m) in mechanically competent ice under well-drained or low-melt conditions.

Also, see the following related abstract from the 2018 WAIS Workshop:

Title: "Across the Great Divide: The Flow-to-Fracture Transition and the Future of the West Antarctic Ice Sheet", by Richard B. Alley, Byron R. Parizek, Knut Christianson, Robert M. DeConto, David Pollard and Sridhar Anandakrishna

https://www.waisworkshop.org/sites/waisworkshop.org/files/webform/2018/abstracts/Alley_R.pdf

Abstract: "Physical understanding, modeling, and available data indicate that sufficient warming and retreat of Thwaites Glacier, West Antarctica will remove its ice shelf and generate a calving cliff taller than any extant calving fronts, and that beyond some threshold this will generate faster retreat than any now observed. Persistent ice shelves are restricted to cold environments. Ice-shelf removal has been observed in response to atmospheric warming, with an important role for meltwater wedging open crevasses, and in response to oceanic warming, by mechanisms that are not fully characterized. Some marine-terminating glaciers lacking ice shelves “calve” from cliffs that are grounded at sea level or in relatively shallow water, but more-vigorous flows advance until the ice is close to flotation before calving. For these vigorous flows, a calving event shifts the ice front to a position that is slightly too thick to float, and generates a stress imbalance that causes the ice front to flow faster and thin to flotation, followed by another calving event; the rate of retreat thus is controlled by ice flow even though the retreat is achieved by fracture. Taller cliffs generate higher stresses, however, favoring fracture over flow. Deformational processes are often written as power-law functions of stress, with ice deformation increasing as approximately the third power of stress, but subcritical crack growth as roughly the thirtieth power, accelerating to elastic-wave speeds with full failure. Physical understanding, models based on this understanding, and the limited available data agree that, above some threshold height, brittle processes will become rate-limiting, generating faster calving at a rate that is not well known but could be very fast. Subaerial slumping followed by basal-crevasse growth of the unloaded ice is the most-likely path to this rapid calving. This threshold height is probably not too much greater than the tallest modern cliffs, which are roughly 100 m."

For those who do not understand the implications of Alley et al. (2018)'s comment that ice deformation is a power-function of stress, I provide the first image that translates this underlying ice-cliff behavior into terms of calving rate (deformation) per year for various values of marine glacier freeboard (ice face height minus water depth) and relative water depth (which combine determine the primary stresses near the ice cliff face).

Edit: For what it is worth, the 2019 WAIS Workshop is ending today, and thus the associated abstracts should be available online within a few months.

Edit2: The last three images show a sequence of slumping.
« Last Edit: October 18, 2019, 04:37:26 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1733 on: October 18, 2019, 05:38:57 PM »
The accompanying four attached image provides one interpretation of how the influence of the November 2012 partial collapse of the subglacial cavity near the Little Ear and the subsequent growth of the size of the Big Ear subglacial cavity has change the gravitational load path between the buttressing action of the Thwaites Eastern Ice Shelf (TEIS), shown in yellow arrows, and the Thwaites Ice Tongue, shown in orange arrows, near the trough in the bed of the Thwaites gateway.  The first image shows the marked drop in the surface elevation of the ice near the Little Ear between Jan 2012 and Jan 2013 due to the Nov 2012 partial collapse of the subglacial cavity near the Little Ear.  The second image shows how this partial subglacial collapse provided a new load path from the gravitational load from the ice at the upstream end of the bed trough in the gateway to the buttressing action of the TEIS.  The third image reminds us of the subsequent growth of the subglacial cavity near the Big Ear, which likely resulted a reduction in the force on the load path to the ice tongue and an increase in the force on the load path to the middle of the TEIS as shown in the fourth image from May 23, 2019.  This conceptual sequence of events would also explain the significant calving of icebergs from the southwest corner of the TEIS (due to compression loading) and why the middle section of the TEIS appear to be shearing to the northeast past the pinning point at the downstream end of the TEIS (which is likely causing another iceberg calving event at the northeast region of the TEIS).

If correct, this sequence of events should: a) facilitate future calving of icebergs from the southwest corn of the ice tongue due to the reduced compressive force in this region; and b) accelerate the collapse of the TEIS by shearing the middle section of the TEIS into a northeastern direction past the TEIS pinning point.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1734 on: October 18, 2019, 08:16:11 PM »
...

One problem with AbrubtSLR's analysis is that a grounding line retreat in the "Trough" at the center of Thwaites Glacier is too narrow to lead to MICI all on it's own.  You would need at least a significant grounding line retreat on either the Eastern of Western sides of Thwaites, if not both, to open up the wide West Antarctic basin to a massive collapse.

...

I note that once potential ice-cliff failure mechanisms within the trough in the Thwaites gateway bed reaches the retrograde slope leading into the Byrd Subglacial Basin, that the most likely failure mechanism will be by slumping as described by Parizek et al. (2019); which would likely result in icebergs with much shallower drafts than those currently being formed in in Thwaites calving events; which would allow the Thwaites gateway to widen up to be 50-km wide; which would allow for the float-out of a large volume of ice mélange.


We can agree to disagree, but I think the widening needs to happen before the "slumping" or MICI begins.  There is just an enormous amount of ice sitting behind Thwaites that will fill up the "narrow" (20km at most) trough and prevent the sea from encroaching too far inland.  Basically ice is viscous and will clog up any opening that is too small to let it through easily.

On a related note, I am preparing some maps overlaying current Sentinel-1 images and published bathymetry and grounding line data for the Thwaites Glacier thread that I hope might clear up some of the confusion for us casual observers.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1735 on: October 19, 2019, 11:32:23 AM »
...
We can agree to disagree, but I think the widening needs to happen before the "slumping" or MICI begins.  There is just an enormous amount of ice sitting behind Thwaites that will fill up the "narrow" (20km at most) trough and prevent the sea from encroaching too far inland.  Basically ice is viscous and will clog up any opening that is too small to let it through easily.

On a related note, I am preparing some maps overlaying current Sentinel-1 images and published bathymetry and grounding line data for the Thwaites Glacier thread that I hope might clear up some of the confusion for us casual observers.

baking,

Thank you for creating the first attached image comparing grounding line information from Milillo et al. (2019) (see Reply #1704 for the reference) to the Sentinel-1 image for October 16, 2019; which I believes helps to clarify/support my concerns that the sustained growth and episodic abrupt partial collapse of the subglacial cavities near the Thwaites gateway, may eventually lead to both slumping and/or ice-cliff failures (possibly in less than 10-years) within the approximately 50-km wide threshold roughly between Stations 1021.7 and 1021.12 in the second attached image, for reasons including:
1. The compressive ice force arch from south of the Big Ear kicking northeast into the mid-section of the TEIS (which I showed previously in heavy yellow arrows, see Reply #1733) will likely reduce the compressive ice loading on the icebergs at the upstream base of the Thwaites Ice Tongue, thus allowing the local calving front at the southwest corner of the Thwaites Ice Tongue to retreat southward towards the growing subglacial cavity near the Big Ear.
2. An abrupt partial collapse of the subglacial cavity near Big Ear (sometime within the next 10-years) causes the remaining icebergs at the base of the Thwaites Ice Tongue to float away leaving an exposed ice cliff face extending over 145m above sea level, leading to local slumping and a rapid deterioration of the downstream end compressive ice force arch (south of the Big Ear) kicking into the mid-section of the TEIS.
3. The mélange from the slumping would have icebergs with drafts too shallow to become pinned to the subsea ridges as they float seaward; which would make room for still more slumping within the trough leading to the BSB; which would allow the Thwaites gateway to widen to the approximately 50-km width shown in the second image between Stations 1021.7 and 1021.12.

Best, ASLR
« Last Edit: October 19, 2019, 04:23:29 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1736 on: October 19, 2019, 04:44:47 PM »

baking,

Thank you for creating the first attached image comparing grounding line information from Milillo et al. (2019) (see Reply #1704 for the reference) to the Sentinel-1 image for October 16, 2019; …

baking,

If you want to be of more service to the ASIF readers then in addition to overlaying panel B from the attached image from Milillo et al (2019) on top of the Sentinel-1 image from Oct 16, 2019, you could also overlay the information from panels C, D, E & F.  Herein, I note that panel D shows a very abrupt change in the 'Height of the ice surface above flotation, hf, in meters' between the ice surface above the subglacial cavity at the Big Ear and the ice surface immediately upstream; which is where I postulate that an ice cliff will form with hf more than 145m if/when the local part of the subglacial cavity at the Big Ear collapse in less than ten years.

Best,
ASLR
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1737 on: October 21, 2019, 04:49:00 PM »
Attached is another status report on the progress being made to update the atmospheric component of the E3SM projections:

P. J. Rasch et al. (09 July 2019), "An Overview of the Atmospheric Component of the Energy Exascale Earth System Model", JAMES,
https://doi.org/10.1029/2019MS001629

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019MS001629

Abstract
The Energy Exascale Earth System Model Atmosphere Model version 1, the atmospheric component of the Department of Energy's Energy Exascale Earth System Model is described. The model began as a fork of the well‐known Community Atmosphere Model, but it has evolved in new ways, and coding, performance, resolution, physical processes (primarily cloud and aerosols formulations), testing and development procedures now differ significantly. Vertical resolution was increased (from 30 to 72 layers), and the model top extended to 60 km (~0.1 hPa). A simple ozone photochemistry predicts stratospheric ozone, and the model now supports increased and more realistic variability in the upper troposphere and stratosphere. An optional improved treatment of light‐absorbing particle deposition to snowpack and ice is available, and stronger connections with Earth system biogeochemistry can be used for some science problems. Satellite and ground‐based cloud and aerosol simulators were implemented to facilitate evaluation of clouds, aerosols, and aerosol‐cloud interactions. Higher horizontal and vertical resolution, increased complexity, and more predicted and transported variables have increased the model computational cost and changed the simulations considerably. These changes required development of alternate strategies for tuning and evaluation as it was not feasible to “brute force” tune the high‐resolution configurations, so short‐term hindcasts, perturbed parameter ensemble simulations, and regionally refined simulations provided guidance on tuning and parameterization sensitivity to higher resolution. A brief overview of the model and model climate is provided. Model fidelity has generally improved compared to its predecessors and the CMIP5 generation of climate models.

Plain Language Summary

This study provides an overview of a new computer model of the Earth's atmosphere that is used as one component of the Department of Energy's latest Earth system model. The model can be used to help understand past, present, and future changes in Earth's behavior as the system responds to changes in atmospheric composition (like pollution and greenhouse gases), land, and water use and to explore how the atmosphere interacts with other components of the Earth system (ocean, land, biology, etc.). Physical, chemical, and biogeochemical processes treated within the atmospheric model are described, and pointers to previous and recent work are listed to provide additional information. The model is compared to present‐day observations and evaluated for some important tests that provide information about what could happen to clouds and the environment as changes occur. Strengths and weaknesses of the model are listed, as well as opportunities for future work.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1738 on: October 21, 2019, 05:42:14 PM »
While the first linked reference Clerc et al. (2019), certainly sounds reassuring that an abrupt MICI-type of collapse of glacial ice in the Byrd Subglacial Basin is not likely, I note that the authors use a highly simplified model that does not necessarily match reality.  For instance, Clerc et al. (2019) indicate that currently that marine ice cliff subaerial heights do not exist above ~90m (~100m); however, Parizek et al. (2019) states: 'New terrestrial radar data from Helheim Glacier, Greenland, suggest that taller subaerial cliffs …' above ~100m exist today.  Also, in my past string of posts in this thread, I have indicated that it is conceivable/likely that a future partial collapse of the subglacial cavity near the 'Big Ear' in the 50km wide Thwaites gateway, could expose an subaerial ice cliff height on the order of 145m within hours if the downstream iceberg field/Thwaites Ice Tongue have substantially lost their ability to provide buttressing say over the next 10-years.

Fiona Clerc et al. (21 October 2019), "Marine Ice Cliff Instability Mitigated by Slow Removal of Ice Shelves", Geophysical Research Letters, https://doi.org/10.1029/2019GL084183

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL084183

Abstract

The accelerated calving of ice shelves buttressing the Antarctic Ice Sheet may form unstable ice cliffs. The marine ice‐cliff instability (MICI) hypothesis posits that cliffs taller than a critical height (~90‐m) will undergo structural collapse, initiating runaway retreat in ice‐sheet models. This critical height is based on inferences from pre‐existing, static ice cliffs. Here we show how critical height increases with the timescale of ice‐shelf collapse. We model failure mechanisms within an ice cliff deforming after removal of ice‐shelf buttressing stresses. If removal occurs rapidly, the cliff deforms primarily elastically and fails through tensile‐brittle fracture, even at relatively small cliff heights. As the ice‐shelf removal timescale increases, viscous relaxation dominates, and the critical height increases to ~540 m for timescales > days. A 90‐m critical height implies ice‐shelf removal in under an hour. Incorporation of ice‐shelf collapse timescales in prognostic ice‐sheet models will mitigate MICI, implying less ice‐mass loss.

Plain Language Summary

The seaward flow of ice from grounded ice sheets to the ocean is often resisted by the buttressing effect of floating ice shelves. These ice shelves risk collapsing as the climate warms, potentially exposing tall cliff faces. Some suggest ice cliffs taller than ~90 m could collapse under their own weight, exposing taller cliffs further to the interior of a thickening ice sheet, leading to runaway ice‐sheet retreat. This model, however, is based on studies of pre‐existing cliffs found at calving fronts. In this study, we consider the transient case, examining the processes by which an ice cliff forms as a buttressing ice shelf is removed. We show that the height at which a cliff collapses increases with the timescale of ice‐shelf removal. If the ice shelf is removed rapidly, deformation may be concentrated, forming vertical cracks and potentially leading to the collapse of small (e.g., 90‐m) cliffs. However, if we consider ice‐shelf collapse timescales longer than a few days (consistent with observations), deformation is distributed throughout the cliff, which flows viscously rather than collapsing. We expect including the effects of such ice‐shelf collapse timescales in future ice‐sheet models would mitigate runaway cliff collapse and reduce predicted ice‐sheet mass loss.

See also:

Title: "Antarctic ice cliffs may not contribute to sea-level rise as much as predicted"

http://news.mit.edu/2019/antarctic-ice-cliffs-not-contribute-sea-level-rise-1021

Extract: "Scientists have assumed that ice cliffs taller than 90 meters (about the height of the Statue of Liberty) would rapidly collapse under their own weight, contributing to more than 6 feet of sea-level rise by the end of the century — enough to completely flood Boston and other coastal cities. But now MIT researchers have found that this particular prediction may be overestimated.

In a paper published today in Geophysical Research Letters, the team reports that in order for a 90-meter ice cliff to collapse entirely, the ice shelves supporting the cliff would have to break apart extremely quickly, within a matter of hours — a rate of ice loss that has not been observed in the modern record.

“Ice shelves are about a kilometer thick, and some are the size of Texas,” says MIT graduate student Fiona Clerc. “To get into catastrophic failures of really tall ice cliffs, you would have to remove these ice shelves within hours, which seems unlikely no matter what the climate-change scenario.”

If a supporting ice shelf were to melt away over a longer period of days or weeks, rather than hours, the researchers found that the remaining ice cliff wouldn’t suddenly crack and collapse under its own weight, but instead would slowly flow out, like a mountain of cold honey that’s been released from a dam."

&

Byron R. Parizek et al. Ice-cliff failure via retrogressive slumping, Geology (2019). DOI: 10.1130/G45880.1

https://pubs.geoscienceworld.org/gsa/geology/article/569567/Icecliff-failure-via-retrogressive-slumping

Abstract
Retrogressive slumping could accelerate sea-level rise if ice-sheet retreat generates ice cliffs much taller than observed today. The tallest ice cliffs, which extend roughly 100 m above sea level, calve only after ice-flow processes thin the ice to near flotation. Above some ice-cliff height limit, the stress state in ice will satisfy the material-failure criterion, resulting in faster brittle failure. New terrestrial radar data from Helheim Glacier, Greenland, suggest that taller subaerial cliffs are prone to failure by slumping, unloading submarine ice to allow buoyancy-driven full-thickness calving. Full-Stokes diagnostic modeling shows that the threshold cliff height for slumping is likely slightly above 100 m in many cases, and roughly twice that (145–285 m) in mechanically competent ice under well-drained or low-melt conditions.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1739 on: October 21, 2019, 06:39:29 PM »
More troubling information about the potential net increase in carbon emissions from peatlands in a warming world, which current consensus climate change models underestimate:

Swindles, G.T. et al. (2019) Widespread drying of European peatlands in recent centuries, Nature Geoscience, doi.org/10.1038/s41561-019-0462-z

https://www.nature.com/articles/s41561-019-0462-z

Abstract: "Climate warming and human impacts are thought to be causing peatlands to dry, potentially converting them from sinks to sources of carbon. However, it is unclear whether the hydrological status of peatlands has moved beyond their natural envelope. Here we show that European peatlands have undergone substantial, widespread drying during the last ~300 years. We analyse testate amoeba-derived hydrological reconstructions from 31 peatlands across Britain, Ireland, Scandinavia and Continental Europe to examine changes in peatland surface wetness during the last 2,000 years. We find that 60% of our study sites were drier during the period 1800–2000 CE than they have been for the last 600 years, 40% of sites were drier than they have been for 1,000 years and 24% of sites were drier than they have been for 2,000 years. This marked recent transition in the hydrology of European peatlands is concurrent with compound pressures including climatic drying, warming and direct human impacts on peatlands, although these factors vary among regions and individual sites. Our results suggest that the wetness of many European peatlands may now be moving away from natural baselines. Our findings highlight the need for effective management and restoration of European peatlands."

&

Nichols, J.E. and Peteet, D.M. (2019) Rapid expansion of northern peatlands and doubled estimate of carbon storage, Nature Geoscience, doi.org/10.1038/s41561-019-0454-z

https://www.nature.com/articles/s41561-019-0454-z

Abstract: "Northern peatlands are an integral part of the global carbon cycle—a strong sink of atmospheric carbon dioxide and source of methane. Increasing anthropogenic carbon dioxide and methane in the atmosphere are thought to strongly impact these environments, and yet, peatlands are not routinely included in Earth system models. Here we present a quantification of the sink and stock of northern peat carbon from the last glacial period through the pre-industrial period. Additional data and new algorithms for reconstructing the history of peat carbon accumulation and the timing of peatland initiation increased the estimate of total northern peat carbon stocks from 545 Gt to 1,055 Gt of carbon. Further, the post-glacial increases in peatland initiation rate and carbon accumulation rate are more abrupt than previously reported. Peatlands have been a strong carbon sink throughout the Holocene, but the atmospheric partial pressure of carbon dioxide has been relatively stable over this period. While processes such as permafrost thaw and coral reef development probably contributed some additional carbon to the atmosphere, we suggest that deep ocean upwelling was the most important mechanism for balancing the peatland sink and maintaining the observed stability."

See also:

Title: "Europe’s carbon-rich peatlands show ‘widespread’ and ‘concerning’ drying trends"

https://www.carbonbrief.org/europes-carbon-rich-peatlands-show-widespread-and-concerning-drying-trends

Extract: "European peatlands could turn from carbon sinks to sources as a quarter have reached levels of dryness unsurpassed in a record stretching back 2,000 years, according to a new study.

This trend of “widespread” and “substantial” drying corresponds to recent climate change, both natural and human-caused, but may also be exacerbated by the peatlands being used for agriculture and fuel.

It comes as another study estimates that the amount of carbon stored in peatlands across northern regions could be as much as double previous, widely reported estimates.

The papers, both published in Nature Geoscience, indicate a need for efforts to conserve peatlands as sites of carbon storage at higher latitudes.

For his part, Nichols says that considering the threats facing peatlands, it is important for scientists to investigate the total volume of peat available across the world, in order to “put a number on how much there is to lose”:

“Peatlands are not usually part of global climate models. If we want to make realistic predictions of future climate, peatlands need to be a part of it.”"
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1740 on: October 21, 2019, 08:38:08 PM »
The abstract from the 2019 WAIS Workshop can be found at the following link, and I post one of these abstract below, to remind us all that hydrofracturing could cause the TEIS and/or the PIIS to collapse abruptly in the future:

https://drive.google.com/file/d/1o2-BqgOgPCEn7jY7IBpg_jugus0nwFCh/view


Title: "A poro-damage approach to simulating hydrofracture of glaciers and ice shelves" by Ravindra Duddu et al. (2019)

Abstract: "The dynamic ice mass loss from the Antarctic ice sheet into ocean is one of the greatest sources of uncertainty in predicting future sea level rise. The fracture and detachment of icebergs, that is, calving is an important control on the mass loss from the ice sheet, and is intricately linked to climate dynamics through processes such as hydrofracturing.  It has been hypothesized that hydrofracturing of ice shelves followed by ice cliff failure in Antarctica could contribute to rapid sea level rise over the coming centuries. Simulating hydrofracture propagation using process-based models can provide a better understanding of the conditions enabling full depth crevasse penetration and calving. To this end, we develop a new, nonlocal continuum poro-damage mechanics (CPDM) approach to simulate the propagation of water-filled surface crevasses in idealized rectangular glaciers based on creep-damage-mechanics and poro-mechanics. Using idealized simulations studies on rectangular glaciers in two-dimensions (plane strain conditions), we compare the penetration depths of isolated and closely-spaced water-filled surface crevasses predicted by the CPDM model with those from existing crevasse depth models. We find that the CPDM model is in good agreement with the linear elastic fracture mechanics (LEFM) models for an isolated surface crevasse and with the zero stress model (to a lesser extent) for closely-spaced surface crevasses, except when the glacier is near-floatation. We also examine crevasse propagation in relation to ice rheology, fracture process zone size, and basal boundary conditions using sharp crack and damage mechanics models. Based on these simulation studies, we argue that floating ice shelves are more vulnerable than grounded glaciers due to the combination of meltwater-induced hydrofracture and plate bending. To conclude, we discuss the limitations of the creep damage mechanics model and directions for future work, including modeling shear-dominated failure under compression using strain-energy-based damage models."
“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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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1741 on: October 21, 2019, 10:09:44 PM »
That Clerc paper is interesting. Given the absence of aerial cliffs over 100m, i find it difficult their stability analysis. Surely we ought to see at least a few cliffs over 100m ?

I find Parizek's picture more convincing.

sidd
 

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1742 on: October 21, 2019, 11:33:08 PM »
The linked reference indicates that the northern permafrost region already emits more carbon into the atmosphere than it absorbs:

Susan M. Natali et al. (2019), "Large loss of CO2 in winter observed across the northern permafrost region, "Nature Climate Change, DOI: https://doi.org/10.1038/s41558-019-0592-8

https://www.nature.com/articles/s41558-019-0592-8

Abstract: "Recent warming in the Arctic, which has been amplified during the winter, greatly enhances microbial decomposition of soil organic matter and subsequent release of carbon dioxide (CO2). However, the amount of CO2 released in winter is not known and has not been well represented by ecosystem models or empirically based estimates. Here we synthesize regional in situ observations of CO2 flux from Arctic and boreal soils to assess current and future winter carbon losses from the northern permafrost domain. We estimate a contemporary loss of 1,662 TgC per year from the permafrost region during the winter season (October–April). This loss is greater than the average growing season carbon uptake for this region estimated from process models (−1,032 TgC per year). Extending model predictions to warmer conditions up to 2100 indicates that winter CO2 emissions will increase 17% under a moderate mitigation scenario—Representative Concentration Pathway 4.5—and 41% under business-as-usual emissions scenario—Representative Concentration Pathway 8.5. Our results provide a baseline for winter CO2 emissions from northern terrestrial regions and indicate that enhanced soil CO2 loss due to winter warming may offset growing season carbon uptake under future climatic conditions."

See also:

Title: "Global impacts of thawing Arctic permafrost may be imminent"

https://www.sciencemag.org/news/2019/10/global-impacts-thawing-arctic-permafrost-may-be-imminent

Extract: "The Arctic permafrost, frozen soil that is chock full of carbon, is a ticking time bomb. When it thaws because of global warming, sometimes slumping into pits like on Herschel Island in Canada (above), scientists believe it is likely to release more carbon than it absorbs from new plant growth—adding to the atmosphere’s burden and accelerating climate change. But studies in the Arctic have been so limited that no one could say when that time would come.

It’s here now, according to research published today by a large team of scientists in Nature Climate Change. By pooling observations from more than 100 Arctic field sites, scientists from the Permafrost Carbon Network estimate that permafrost released an average of 1662 teragrams of carbon each winter from 2003 to 2017—double that of past estimates. Meanwhile, during the summer growing season, other surveys have found that the landscape absorbs only 1032 teragrams—leaving an average of more than 600 teragrams of carbon to escape to the atmosphere each year."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1743 on: October 22, 2019, 01:13:09 AM »
For those who do not care to click on the link in Reply #1740, I provide the following four abstracts form the 2019 WAIS Workshop:

Title: "Could increased melting from East Antarctic ice shelves trigger runaway melting beneath Filcher-Ronne Ice Shelf?" by Matthew Hoffman et al. (2019)

Abstract: "The Filchner-Ronne Ice Shelf (FRIS) presently experiences modest basal melt rates, but model studies have highlighted the potential for an order of magnitude increase in melt rates should relatively warm modified Circum-polar Deep Water (mCDW) reach beneath the ice shelves. Models and observations have indicated that redirection of a coastal current by changes in sea-ice cover and wind stress has the potential to transport mCDW beneath FRIS and initiate melt instability there. We investigate this FRIS melt instability using the Energy Exascale Earth System Model (E3SM) run in a global low-resolution configuration that includes ocean circulation beneath Antarctic ice shelves with fixed geometry and prognostic calculation of freshwater and heat fluxes from ice-shelf melting. We demonstrate the potential of an additional mechanism for FRIS melt instability by freshening and increasing stratification due to high meltwater fluxes from nearby ice shelves in East Antarctica. We see this behavior in partially-coupled simulations with only active ocean and sea-ice, as well as in fully-coupled simulations that also include active atmosphere and land components. Freshening from ice-shelf meltwater reduces ocean density on the continental shelf, shoaling isopycnals near the shelf break and allowing sustained flow of mCDW from offshore onto the continental shelf and into the cavity beneath Filcher Ice Shelf. However, when ice-shelf melting is disabled from neighboring ice shelves in East Antarctica, the melt instability at FRIS is avoided, identifying meltwater from these ice shelves as another potential contributing trigger for this instability. While E3SM indicates the possibility of such a domino effect in ice shelf-melting, we identify biases in the E3SM simulations that precondition the ocean for FRIS melt instability. Reducing these biases through increased regional resolution and improved ocean model tuning is the focus of ongoing work."

&

Title: "Vulnerability of Antarctica's ice shelves to meltwater-driven fracture", by Ching-Yao Lai et al. (2019)

Abstract: "Atmospheric warming threatens to accelerate the retreat of the Antarctic Ice Sheet by increasing surface melting and facilitating `hydrofracturing', where meltwater flows into and enlarges fractures on ice shelves. Hydrofracturing in turn could trigger ice-shelf collapse. The collapse of ice shelves that `buttress' the upstream ice sheet increases discharge from the ice sheet and accelerates sea-level rise. Despite progress in modelling hydrofracture, there is limited understanding of the extent to which ice-shelves are vulnerable to hydrofracturing, which is currently described simplistically in continent-scale ice-sheet models, hindering predictions ice-shelf collapse. Here we provide a new theoretical framework, based on Linear Elastic Fracture Mechanics, to predict fracture locations and for the first time quantify vulnerability to hydrofracture across Antarctica's ice shelves. To test theoretical predictions, we train a deep convolutional neural network (DCNN) to identify fractures in continent-wide satellite imagery, and demonstrate close agreement between the distribution of fracture and our model, without the need to tune any model parameters; 89% of 28000 locations identified by the DCNN as fractures across Antarctic ice-shelves lie in regions where our theory predicts fracture formation. We find that many regions regularly inundated with meltwater in the present climate are resilient to hydrofracturing. On the other hand, large regions that resist ice discharge (i.e., which provide significant buttressing to upstream grounded ice) are susceptible to hydrofracture if covered with meltwater. Our findings suggest that as the Antarctic atmosphere warms, increased meltwater production will generally only trigger hydrofracturing if water is formed in or flows into the vulnerable regions we identified. Our new theoretical framework could be included in ice-sheet models to improve predictions of Antarctica's response to atmospheric warming and impact on sea-level rise."

&

Title: "Sensitivity of submarine melting of 79N glacier to ocean forcing" by Philipp Anhaus et al. (2019)

The Nioghalvfjerdsbrae (79NG) is a floating ice tongue on Northeast Greenland draining a large part of the Greenland Ice Sheet. A CTD profile from a rift on the ice tongue close to the northern front shows that Atlantic Water (AW) is present in the cavity below, with maximum temperature of approximately 1C at 610 m depth. The AW present in the cavity thus has the potential to drive submarine melting along the ice base. Here, we simulate melt rates from the 79NG with a 1D numerical Ice Shelf Water (ISW) plume model. A melt water plume is initiated at the grounding line depth (600 m) and rises along the ice base as a result of buoyancy contrast to the underlying AW. Ice melts as the plume entrains the warm AW. Maximum simulated melt rates are 50 - 76 m/yr within 10 km of the grounding line. Melt rates drop rapidly to 6 m/yr within the first 10-20 km from the grounding line. Further downstream, melt rates are between 15 m/yr and 6 m/yr. The melt-rate sensitivity to variations in AW temperatures is assessed by forcing the model with AW temperatures between 0.1- 1.4 C, as identified from the 10 ECCOv4 ocean state estimate. The melt rates increase quadratically with rising AW temperature, and overall mean melting changes from 10 m/yr to 21 m/yr with the changes in ocean forcing. The corresponding freshwater flux ranges between 11-30 km3/yr (0.4 - 1.0 mSv). If the 79NG has gone from steady state to the warm AW forcing between 2012 and 2016 it accounts for approximately 9% of the recent freshwater discharge from the ice sheet. Our results show that submarine melting of the marine-terminating 79NG is sensitive to changes in ocean temperature."

&

Title: "Glacial Earthquakes and Precursory Seismicity Reveal Thwaites-Glacier Calving Behavior" by Paul Winberry et al. (2019)

Abstract: "We observe two large (~Ms 5) long-period (10-50 s) seismic-events that originate from the terminus of Thwaites Glacier, Antarctica. Serendipitous acquisition of radar satellite images display a calving event of Thwaites Glacier at this time and confirm that the seismic events were glacial earthquakes generated during the capsizing of icebergs. The glacial earthquakes were preceded by 6 days of discrete high frequency events with an increasing rate of occurrence, culminating in several hours of sustained tremor co-eval with the long period events. A series of optical satellite images collected during this precursory time-period show that the high frequency events and tremor are the result of accelerating growth of ancillary fractures prior to the culminating calving event. Although Thwaites Glacier is one of the largest sources of Antarctic ice-mass loss, the physics of the processes that control discharge into the ocean remains poorly resolved. This study indicates that seismic data have the potential to elucidate the processes by which Thwaites glacier discharges into the ocean, and improve our ability to constrain future sea-level rise."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1744 on: October 22, 2019, 10:59:02 AM »
That Clerc paper is interesting. Given the absence of aerial cliffs over 100m, i find it difficult their stability analysis. Surely we ought to see at least a few cliffs over 100m ?

I find Parizek's picture more convincing.

sidd
Unfortunately, the IPCC AR6 does not evaluate the findings of publications based on the skill of the analysis, only that the publication was peer reviewed; which of course means that the findings of AR6 are subject to manipulation by parties with vested interests against verifying the true risks of a MICI-type of collapse of parts of the WAIS.
« Last Edit: October 22, 2019, 11:23:52 AM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1745 on: October 22, 2019, 11:31:14 AM »
I have repeated noted that El Nino events drive more warm CDW into the Amundsen Sea Embayment where it temporarily accelerates basal ice mass loss from key ice shelves and accelerates the retreat of grounding lines.  In this regard, the linked reference provides more evidence that continued global warming will increase both the frequency and intensity of El Nino events; which is bad news for the stability of the PIIS, the TEIS and the Thwaites Ice Tongue, in the coming decades:

Bin Wang et al. (October 21, 2019), "Historical change of El Niño properties sheds light on future changes of extreme El Niño", PNAS,  https://doi.org/10.1073/pnas.1911130116

https://www.pnas.org/content/early/2019/10/15/1911130116

Significance
How the magnitude of El Niño will change is of great societal concern, yet it remains largely unknown. Here we show analysis of how changing El Niño properties, due to 20th century climate change, can shed light on changes to the intensity of El Niño in the future. Since the 1970s, El Niño has changed its origination from the eastern Pacific to the western Pacific, along with increased strong El Niño events due to a background warming in the western Pacific warm pool. This suggests the controlling factors that may lead to increased extreme El Niño events in the future. If the observed background changes continue under future anthropogenic forcing, more frequent extreme El Niño events will induce profound socioeconomic consequences.

Abstract
El Niño’s intensity change under anthropogenic warming is of great importance to society, yet current climate models’ projections remain largely uncertain. The current classification of El Niño does not distinguish the strong from the moderate El Niño events, making it difficult to project future change of El Niño’s intensity. Here we classify 33 El Niño events from 1901 to 2017 by cluster analysis of the onset and amplification processes, and the resultant 4 types of El Niño distinguish the strong from the moderate events and the onset from successive events. The 3 categories of El Niño onset exhibit distinct development mechanisms. We find El Niño onset regime has changed from eastern Pacific origin to western Pacific origin with more frequent occurrence of extreme events since the 1970s. This regime change is hypothesized to arise from a background warming in the western Pacific and the associated increased zonal and vertical sea-surface temperature (SST) gradients in the equatorial central Pacific, which reveals a controlling factor that could lead to increased extreme El Niño events in the future. The Coupled Model Intercomparison Project phase 5 (CMIP5) models’ projections demonstrate that both the frequency and intensity of the strong El Niño events will increase significantly if the projected central Pacific zonal SST gradients become enhanced. If the currently observed background changes continue under future anthropogenic forcing, more frequent strong El Niño events are anticipated. The models’ uncertainty in the projected equatorial zonal SST gradients, however, remains a major roadblock for faithful prediction of El Niño’s future changes.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Hefaistos

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1746 on: October 22, 2019, 02:44:38 PM »

Unfortunately, the IPCC AR6 does not evaluate the findings of publications based on the skill of the analysis, only that the publication was peer reviewed; which of course means that the findings of AR6 are subject to manipulation by parties with vested interests against verifying the true risks of a MICI-type of collapse of parts of the WAIS.

ASLR, I find your post troubling.
Interesting how you juxtapose 'skill of analysis' to 'peer reviewing'. Is there some systematic bias here, so that peer reviewing implicates a lack of skill of analysis? Or maybe this regards only MICI issues?
Also, would be very interesting if you could say some more on those 'vested interests', as you explicate that AR6 is 'subject to manipulation' here.

RoxTheGeologist

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1747 on: October 22, 2019, 06:01:34 PM »

What? Do they not give more weight to which journals publications papers are in? That's terrifying.

Peer review is not a perfect process. A biased editor can easily send a paper to review by like minded scientists or economists, particularly as it is hard to find editors for less well respected journals.

As far as I know the IPCC is a political creation, designed to put bias onto scientific results. It gives the opportunity for a nation to weigh a paper published in EPSL as highly as one published in less renowned journals. That's particularly true when it comes to counting the cost of climate change, and exactly how to measure financial risk. Even if everyone accepts that climate change is real and anthropogenic, there is still an argument to be muddied about whether it is better to pay now or pay later.

nanning

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1748 on: October 22, 2019, 06:25:46 PM »
You've said it very well Rox :)
"It is preoccupation with possessions, more than anything else, that prevents us from living freely and nobly" - Bertrand Russell
   Simple: minimize your possessions and be free and kind    It's just a mindset.       Refugees welcome

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1749 on: October 22, 2019, 08:43:20 PM »
..
ASLR, I find your post troubling.
Interesting how you juxtapose 'skill of analysis' to 'peer reviewing'. Is there some systematic bias here, so that peer reviewing implicates a lack of skill of analysis? Or maybe this regards only MICI issues?
Also, would be very interesting if you could say some more on those 'vested interests', as you explicate that AR6 is 'subject to manipulation' here.
While this can be made into a very complex topic as hinted at by RoxTheGeologist's reply, the primary points that I was thinking of include:

1. The dynamics of MISI models are currently poorly understood, and MICI models are only at the beginning of their refinement/calibration process; thus all of this uncertainty means that ice sheet models currently have a wide range of outputs and papers on these different ice sheet models can easily pass peer review by merely stating their input and assumptions that determine their various outputs, whether or not the outputs windup matching what actually occurs in the future.  Thus by 'skill of the analysis' I mean the future correction between the various model projections and what actually occurs (say this century).

2. By 'vested interests' I primarily mean the fossil fuel industry that heavy influence government policies and research funding; where such policies can encourage the conduct of numerous simplified models that do not include the complexity to correctly match MICI-types of required conditions (such as those currently occurring in the Thwaites gateway); and which err on the side of least drama but which easily pass peer review.  If a sufficient number of such overly simplified models are included in the AR6 review, this could/will bias their projections on such topics as sea level rise and ice-climate feedbacks.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson