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Author Topic: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)  (Read 43016 times)

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #450 on: January 12, 2019, 05:56:39 PM »
The linked reference indicates that as the Atlantic warm pool (AWP) continues to warm (& I note that a slowing of the AMOC acts to warm the AWP), enhance telecommunications from the AWP to the Pacific, increases the frequency of El Nino events; which increases ECS, and the telecommunication of heat energy from the Tropical Pacific to West Anarctica:

Park, JH., Li, T., Yeh, SW. et al. (2019), "Effect of recent Atlantic warming in strengthening Atlantic–Pacific teleconnection on interannual timescale via enhanced connection with the pacific meridional mode", Clim Dyn, https://doi.org/10.1007/s00382-018-4591-7

https://link.springer.com/article/10.1007%2Fs00382-018-4591-7

Abstract: "The Atlantic warm pool (AWP), which features the highest sea surface temperature (SST) in the western Hemisphere in boreal summer to early fall, has been known to have a significant influence on the climate in its surrounding regions. It is reported that the AWP has become warmer and warmer, so that AWP–SST during a couple of recent decades has been higher than any other period since the twentieth century. Under the increased mean AWP–SST, atmospheric responses to the anomalous AWP–SST are intensified, which corresponds to a higher possibility of deep convection formation. Through Rossby wave propagation induced by the deep convection, AWP signals are able to reach further west toward the central North Pacific. At this moment, anomalous northerly winds are introduced over the North Pacific, which advects negative moist static energy (MSE) into the subtropics and simultaneously contributes to a SST cooling by interacting with northerly mean trade winds. Owing to the Gill-type response to a negative heating anomaly associated with the anomalous SST cooling and the negative MSE, the anomalous northerly winds are further developed over the North Pacific. Such air–sea coupling persists throughout fall to winter, leading to Pacific meridional mode development in the following spring. Subsequently, the PMM acts to boost El Niño and Southern Oscillation events. Coupled model experiments were carried out to investigate the extent to which the mean AWP–SST warming strengthens the Atlantic–Pacific interbasin teleconnection on interannual timescales, and it is proven to support observational analysis."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #451 on: January 12, 2019, 06:43:31 PM »
I have previously speculated that when the Getz Ice Shelf eventually collapses, the associated regional changes in seawater temperatures and current flows could contribute to an acceleration of the degradation of the Ross Ice Shelf, RIS (see the Hazard Analysis for the FRIS/RIS in the 2012 to 2060 Timeframe).  In this regards, I provide the following linked reference that verifies the relationship of changes (climate change related) to the local winds that changed the local upwelling of warm CDW and consequent increasing in ice mass loss from the Getz Ice Shelf:

K. M. Assmann et al. (04 January 2019), "Warm Circumpolar Deep Water at the western Getz Ice Shelf Front, Antarctica", Geophysical Research Letters, https://doi.org/10.1029/2018GL081354

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL081354

Abstract
The Getz Ice Shelf is one of the largest sources of fresh water from ice shelf basal melt in Antarctica. We present new observations from three moorings west of Siple Island 2016‐18. All moorings show a persistent flow of modified Circumpolar Deep Water towards the western Getz Ice Shelf. Unmodified Circumpolar Deep Water with temperatures up to 1.5° C reaches the ice shelf front in frequent episodes. These represent the warmest water observed at any ice shelf front in the Amundsen Sea. Mean currents within the warm bottom layer of 18‐20 cm s−1 imply an advection time scale of 7 days from shelf break to ice shelf front. Zonal wind stress at the shelf break affects heat content at the ice shelf front on weekly to monthly time scales. Our two‐year mooring records also evince that upwelling over the shelf break controls thermocline depth on sub‐annual to annual time scales.

Plain Language Summary
The recent retreat of the West Antarctic Ice Sheet has been linked to changes in the transport of warm ocean water up to 1.5C to the floating ice shelves in the Amundsen Sea. One of these is the Getz Ice Shelf that produces one of the largest amounts of ice shelf melt water in Antarctica. To measure how much ocean heat is transported towards this ice shelf, we deployed a series of temperature, salinity and current sensors at its western end from 2016‐2018. We find a constant flow of warm water towards the ice shelf cavity. Comparing our ocean observations with wind data from the area we found that stronger easterly winds in the area make it harder for the warm water to reach the ice shelf front by depressing the warm bottom layer over the shelf break. Climate projections indicate that these easterlies will weaken in future, making it easier for the warm water to reach the ice shelf base. Gradients in the wind field over the shelf break control the thickness of the warm layer on longer time scales. This provides the missing ocean evidence for previous studies that have linked this wind mechanism to ice sheet changes.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #452 on: January 12, 2019, 06:55:05 PM »
The linked reference indicates that models of key Antarctic ice shelves currently underestimate observes ice melt rates, indicating that both more refined  local meshing needs to be employed as well as improved ice-ocean interaction, otherwise we are underestimating our associated risk levels:

D. N. Goldberg et al. (31 December 2018), "How Accurately Should We Model Ice Shelf Melt Rates?", Geophysical Research Letters, https://doi.org/10.1029/2018GL080383

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL080383

Abstract
Assessment of ocean‐forced ice sheet loss requires that ocean models be able to represent sub‐ice shelf melt rates. However, spatial accuracy of modeled melt is not well investigated, and neither is the level of accuracy required to assess ice sheet loss. Focusing on a fast‐thinning region of West Antarctica, we calculate spatially resolved ice‐shelf melt from satellite altimetry and compare against results from an ocean model with varying representations of cavity geometry and ocean physics. Then, we use an ice‐flow model to assess the impact of the results on grounded ice. We find that a number of factors influence model‐data agreement of melt rates, with bathymetry being the leading factor; but this agreement is only important in isolated regions under the ice shelves, such as shear margins and grounding lines. To improve ice sheet forecasts, both modeling and observations of ice‐ocean interactions must be improved in these critical regions.

Plain Language Summary
The Antarctic coastline is fringed by large floating ice shelves, often the size of cities or larger. They play a crucial role as a stopgap against acceleration of the ice sheet, and their loss could lead to considerable sea level rise. Many of these ice shelves are exposed to warm waters from farther north, leading to considerable melting underneath. Scientists use models of the ice sheet and the ocean in order to understand the link between warming oceans and sea levels, and how this might change in the future. In our study we focus on one of these fast‐thinning ice shelves and determine through satellite imagery that melting is not uniform across the ice shelf but is highly focused in certain areas due to ocean currents. Using state‐of‐the‐art ice and ocean models, we investigate what information will be needed in order to predict how the Antarctic Ice Sheet will respond to climate change. Our findings suggest that improved knowledge of ocean depth under ice shelves, as well as improved understanding of ocean flow just below the ice bottom, will be vital in determining the effects of climate change on ice shelves and ice sheets.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #453 on: January 12, 2019, 07:11:00 PM »
The linked reference indicates that projected increases of rainfall in Arctic permafrost regions will result in an increase in methane, that will "… increase near‐term global warming associated with permafrost thaw …", which is currently not considered in consensus science projections:

R. B. Neumann et al. (03 January 2019), "Warming effects of spring rainfall increase methane emissions from thawing permafrost", Geophysical Research Letters, https://doi.org/10.1029/2018GL081274

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL081274

Abstract
Methane emissions regulate the near‐term global warming potential of permafrost thaw, particularly where loss of ice‐rich permafrost converts forest and tundra into wetlands. Northern latitudes are expected to get warmer and wetter, and while there is consensus that warming will increase thaw and methane emissions, effects of increased precipitation are uncertain. At a thawing wetland complex in Interior Alaska, we found that interactions between rain and deep soil temperatures controlled methane emissions. In rainy years, recharge from the watershed rapidly altered wetland soil temperatures, warming the top ~80 cm of soil in spring and summer, and cooling it in autumn. When soils were warmed by spring rainfall, methane emissions increased by ~30%. The warm, deep soils early in the growing season likely supported both microbial and plant processes that enhanced emissions. Our study identifies an important and unconsidered role of rain in governing the radiative forcing of thawing permafrost landscapes.

Plain Language Summary
Because the world is getting warmer, permanently frozen ground around the arctic, known as permafrost, is thawing. When permafrost thaws, the ground collapses and sinks. Often a wetland forms within the collapsed area. Conversion of permanently frozen landscapes to wetlands changes the exchange of greenhouse gases between the land and atmosphere, which impacts global temperatures. Wetlands release methane into the atmosphere. Methane is a potent greenhouse gas. The ability of methane to warm the Earth is 32‐times stronger than that of carbon dioxide over a period of 100 years. In our study, we found that methane release from a thaw wetland in Interior Alaska was greater in rainy years when rain fell in spring. When spring rainwater entered the wetland, it rapidly warmed wetland soils. Rain has roughly the same temperature as the air, and during springtime in northern regions, the air is warmer than the ground. The microbial and plant processes that generate methane increase with temperature. Therefore, wetland soils, warmed by spring rainfall, supported more methane production and release. Northern regions are expected to receive more rainfall in the future. By warming soils and increasing methane release, this rainfall could increase near‐term global warming associated with permafrost thaw.
« Last Edit: January 12, 2019, 07:33:48 PM by AbruptSLR »
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #454 on: January 12, 2019, 07:25:15 PM »
The linked reference uses machine learning to demonstrate the consensus climate science underestimate the risk of carbon emissions that may occur from coastal temperate rainforests, with continued warming:

Gavin McNicol, Chuck Bulmer, David D'Amore, Paul Sanborn, Sari Saunders, Ian Giesbrecht, Santiago Gonzalez Arriola, Allison Bidlack, David Butman and Brian Buma (3 January 2019), "Large, climate-sensitive soil carbon stocks mapped with pedology-informed machine learning in the North Pacific coastal temperate rainforest", Environmental Research Letters, Volume 14, Number 1, https://doi.org/10.1088/1748-9326/aaed52

http://iopscience.iop.org/article/10.1088/1748-9326/aaed52/meta

Abstract
Accurate soil organic carbon (SOC) maps are needed to predict the terrestrial SOC feedback to climate change, one of the largest remaining uncertainties in Earth system modeling. Over the last decade, global scale models have produced varied predictions of the size and distribution of SOC stocks, ranging from 1000 to >3000 Pg of C within the top 1 m. Regional assessments may help validate or improve global maps because they can examine landscape controls on SOC stocks and offer a tractable means to retain regionally-specific information, such as soil taxonomy, during database creation and modeling. We compile a new transboundary SOC stock database for coastal watersheds of the North Pacific coastal temperate rainforest, using soil classification data to guide gap-filling and machine learning approaches to explore spatial controls on SOC and predict regional stocks. Precipitation and topographic attributes controlling soil wetness were found to be the dominant controls of SOC, underscoring the dependence of C accumulation on high soil moisture. The random forest model predicted stocks of 4.5 Pg C (to 1 m) for the study region, 22% of which was stored in organic soil layers. Calculated stocks of 228 ± 111 Mg C ha−1 fell within ranges of several past regional studies and indicate 11–33 Pg C may be stored across temperate rainforest soils globally. Predictions compared very favorably to regionalized estimates from two spatially-explicit global products (Pearson's correlation: ρ = 0.73 versus 0.34). Notably, SoilGrids 250 m was an outlier for estimates of total SOC, predicting 4-fold higher stocks (18 Pg C) and indicating bias in this global product for the soils of the temperate rainforest. In sum our study demonstrates that CTR ecosystems represent a moisture-dependent hotspot for SOC storage at mid-latitudes.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Lennart van der Linde

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #455 on: January 12, 2019, 10:58:41 PM »
There is not yet a compelling theory for the magnetic field or magnetic polar wander. There is almost certainly a coupling between the location of the spin axis and the magnetic poles, but the nature of this coupling is not understood, probably because the nature of the magnetic field is not well understood. There is a Nobel waiting for anyone who comes up with answers.

Could small changes in the position of the spin axis maybe cause changes in convection in the outer core, and could those in turn cause (small) changes in the position of the magnetic pole, as one factor amongst others?

Here someone says:
http://all-geo.org/highlyallochthonous/2008/03/where-the-earths-magnetic-field-comes-from/
“Earth’s rotation… has a strong influence on the patterns of convection in the outer core. Most significantly, it has a tendency to produce helical convection currents which align with the spin axis…”.

The geographical pole apparently moves partly due to convection in the Earth mantle:
https://phys.org/news/2018-09-scientists-id-earth-axis-drift.html
“Using observational and model-based data spanning the entire 20th century, NASA scientists have for the first time identified three broadly-categorized processes responsible for this drift—contemporary mass loss primarily in Greenland, glacial rebound, and mantle convection... Mantle convection is responsible for the movement of tectonic plates on Earth’s surface. It is basically the circulation of material in the mantle caused by heat from Earth’s core. Ivins describes it as similar to a pot of soup placed on the stove. As the pot, or mantle, heats, the pieces of the soup begin to rise and fall, essentially forming a vertical circulation pattern—just like the rocks moving through Earth’s mantle.”

Or is this hypothesis too farfetched?

sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #456 on: January 13, 2019, 06:49:39 AM »
Re: "Or is this hypothesis too farfetched?"

Can you put some numbers on the coupling between spin axis change and convection ? And then convection change and magnetic pole wander ?

 I have thought about this and i cannot.  This seems very difficult since mantle convection is very poorly understood ...

sidd

Lennart van der Linde

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #457 on: January 13, 2019, 09:15:24 AM »
I wish I could :)

Shared Humanity

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #458 on: January 13, 2019, 04:30:51 PM »
ASLR...

Thank you for the Plain Language Summaries on your posts.

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #459 on: January 14, 2019, 07:11:05 PM »
The two linked articles indicate that the Northwestern portion of the Ross Ice Shelf, RIS, is currently being destabilized by a previously unverified mechanism, i.e. local basal ice melting induced by '… seasonal masses of warm water near the ocean surface in front of the ice shelf.'  The attached image (which shows ice velocities from 2009) shows that a local weakening of buttressing action in the Northwestern portion of the RIS would likely lead to an acceleration of ice stream velocities for the important Byrd Glacier:

Title: "Antarctica's Largest Ice Shelf Could Be at Risk of Melting"

https://www.insidescience.org/news/antarcticas-largest-ice-shelf-could-be-risk-melting

Extract: "The ROSETTA-Ice researchers have built a computer model of the interconnected factors that control the Ross Ice Shelf, including seasonal conditions, ocean currents, and the structure of ice and bedrock on the adjacent continent. The model is based on data collected by the ROSETTA-Ice team using instruments mounted on aircraft and on undersea robots.

The findings suggest that a spot on the northwestern side of the ice shelf is melting in a way researchers have not seen before -- neither hydrofracture nor deep currents at the grounding line. Instead, the Ross's problem is seasonal masses of warm water near the ocean surface in front of the ice shelf.

The lost ice is currently being replaced by ice flowing down from the continent, so the shelf is not yet getting thinner. But it could easily start to thin as the climate continues to warm, and current projections don't take the processes the ROSETTA-Ice team observed into account, said Padman.
Most of the grounded glacier ice that is being held back by the Ross Ice Shelf is unlikely to melt anytime soon, in part because it is also held in place by the shape of underlying mountains and valleys, said Padman. But the melting corner of the Ross happens to be located right in front of a particularly vulnerable swathe of ice on the continent."

See also the associated presentation abstract:

Title: "C11A-04: Ice Shelf Vulnerability to Increased Seasonal Upper Ocean Warming" by Padman et al. (2018).

https://agu.confex.com/agu/fm18/meetingapp.cgi/Paper/446984

Abstract: "Ice shelf vulnerability to climate change is strongly controlled by the interactions between ice, ocean and atmosphere. Most studies of ice shelves have focused on changes in melt rates near the deep grounding lines, driven by deep intrusions of warm water. Increased melting at the grounding line leads to mass imbalance and grounding line retreat, with potentially long-lasting consequences for ice dynamics. However, mass loss from anywhere on the ice shelf can alter the back-stress acting on the grounded ice. For Ross Ice Shelf, basal melting near the grounding line is governed by deep circulation of cold, dense water that is formed by winter convection in polynyas near the ice front. Circulation of this dense water is primarily controlled by seafloor bathymetry and is resistant to change. In contrast, melt rates close to the ice front are known to vary on seasonal and interannual time scales, and ice-sheet models indicate that grounded ice flow into the ice shelf is sensitive to changes in ice thickness near the ice front.

We use data from new radar surveys of Ross Ice Shelf to measure multi-decadal averaged basal melt rates within a key region of the ice shelf near Ross Island. These rates are comparable to estimates from satellite altimetry, suggesting that ocean processes governing melt near the ice front have been stable for several decades. However, ocean models suggest that melt in this region is caused by warm surface waters in summer intruding beneath the ice shelf where ice draft is shallow. These results indicate that the common assumption of Ross Ice Shelf stability during the next century may be incorrect, if the summer upper ocean temperature in the western Ross Sea increases significantly in response to a longer period free of sea ice or a decrease in summertime cloudiness. Our findings emphasize the importance of processes beyond the grounding line and call for a rethinking of the vulnerability of ice shelves in large-scale models of future ice sheet behavior."
« Last Edit: January 16, 2019, 04:29:46 PM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #460 on: January 14, 2019, 07:55:42 PM »
As a supplement to my last post, I estimate that by 2050 that the calving face of RIS should have retreated at least 40km (using the current rate of retreat), and I postulate that this retreat of the ice shelf face will cause the Ross Gyre current (see the first attached image) to follow the retreating face until the gyre current is directed at the shallow bed trough leading to the base of the Byrd Glacier (see the second image).  Also, by 2050 I believe that that the AABW production will be sufficiently reduced (by both changing atmospheric patterns and the strengthening of the CDW volume & temperature) so that the cold AABW entrained in the Ross Gyre will not be able to adequately dilute the CDW entrained in the Ross Gyre (assuming also that the ice melt from the Getz Ice Shelf has slowed sufficiently to reduce the dilution of the CDW crossing the continental shelf with meltwater).  Therefore, I postulate that a warm tongue of CDW will make its way to the grounding line for the Byrd Glacier, which will help to trigger a positive feedback cycle that will alternate the circulation patterns in the Ross Sea Embayment so as to direct the warm tongue from the Byrd Glacier southward along the grounding lines of the Siple Coast ice streams (note that there is a pre-existing shallow trough leading from the Byrd Glacier to the Siple Coast; with the resulting cold ice melt water from the Siple Coast ice streams existing out through another shallow trough along the east side of the Ross Sea Embayment.  As the RIS is already thinner than the FRIS, and the CDW will be warmer by then, I postulate that a large portion of the RIS will be subject to a melt-pond collapse mechanism between 2060 & 2070; which, will reduce the buttressing of the RIS on the Siple Coast ice streams that the thinning ice streams will induce a grounding line treat pattern.
“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 #461 on: January 14, 2019, 11:25:03 PM »
The linked reference indicates that Antarctica is currently losing ice mass at a rate six times that during the 1980s; which should not surprise anyone following this thread:

Eric Rignot, Jérémie Mouginot, Bernd Scheuchl, Michiel van den Broeke, Melchior J. van Wessem, and Mathieu Morlighem (January 14, 2019), "Four decades of Antarctic Ice Sheet mass balance from 1979–2017", PNAS https://doi.org/10.1073/pnas.1812883116

https://www.pnas.org/content/early/2019/01/08/1812883116

Abstract: "We use updated drainage inventory, ice thickness, and ice velocity data to calculate the grounding line ice discharge of 176 basins draining the Antarctic Ice Sheet from 1979 to 2017. We compare the results with a surface mass balance model to deduce the ice sheet mass balance. The total mass loss increased from 40 ± 9 Gt/y in 1979–1990 to 50 ± 14 Gt/y in 1989–2000, 166 ± 18 Gt/y in 1999–2009, and 252 ± 26 Gt/y in 2009–2017. In 2009–2017, the mass loss was dominated by the Amundsen/Bellingshausen Sea sectors, in West Antarctica (159 ± 8 Gt/y), Wilkes Land, in East Antarctica (51 ± 13 Gt/y), and West and Northeast Peninsula (42 ± 5 Gt/y). The contribution to sea-level rise from Antarctica averaged 3.6 ± 0.5 mm per decade with a cumulative 14.0 ± 2.0 mm since 1979, including 6.9 ± 0.6 mm from West Antarctica, 4.4 ± 0.9 mm from East Antarctica, and 2.5 ± 0.4 mm from the Peninsula (i.e., East Antarctica is a major participant in the mass loss). During the entire period, the mass loss concentrated in areas closest to warm, salty, subsurface, circumpolar deep water (CDW), that is, consistent with enhanced polar westerlies pushing CDW toward Antarctica to melt its floating ice shelves, destabilize the glaciers, and raise sea level."

Significance Statement

We evaluate the state of the mass balance of the Antarctic Ice Sheet over the last four decades using a comprehensive, precise satellite record and output products from a regional atmospheric climate model to document its impact on sea-level rise. The mass loss is dominated by enhanced glacier flow in areas closest to warm, salty, subsurface circumpolar deep water, including East Antarctica, which has been a major contributor over the entire period. The same sectors are likely to dominate sea-level rise from Antarctica in decades to come as enhanced polar westerlies push more circumpolar deep water toward the glaciers.

See also the following related article:

Title: "Antarctica is losing ice six times faster than in 1980s"

https://www.axios.com/antarctica-ice-loss-has-grown-sixfold-in-past-4-decades-ad1ed0e1-ef89-4b80-9b14-242c847ac863.html

“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 #462 on: January 15, 2019, 01:40:30 AM »
The paper is open access. Nice work, has detail for every basin. I note that WAIS went from 56GT/y in 1999-2009 to 160 GT/yr in 2009-2017. Thats a tripling in 9 years, call it a doubling in 6. Not reassuring.

sidd

sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #463 on: January 15, 2019, 06:01:36 AM »
That Rignot latest table 1 includes decadal glacier discharge. I note that apart from the two biggies, that all "the glaciers next door" as a recent paper called them, Haynes, Crosson, Dotson, Getz are increasing discharge, to me clear signs of hot water lapping at their foundations.

6 yr doubling for WAIS mass waste, we will have half inch a year of SLR from WAIS alone by 2050.

A couple years ago I seem to recall either Joughin or Rignot remarking that mass waste models for WAIS blow up once you get to a few mm/yr SLR. Lets hope they got better.

sidd
« Last Edit: January 15, 2019, 07:27:23 AM by sidd »

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #464 on: January 15, 2019, 04:48:46 PM »
It appears that carbon pricing (& dividend) is facing trouble not only from the right, but now increasingly from the left.  It is hard for me to imagine that without strong carbon pricing measures, that the Green New Deal will make much headway against our current BAU pathway before 2040 (when I project that the WAIS will reach an irreversible tipping point towards collapse):

Title: "Carbon taxes are facing new troubles on the left"

https://www.axios.com/green-new-deal-carbon-tax-climate-change-85a5c503-fc5c-4610-89d5-8dff9be81a4f.html

Extract: "The bottom line: the biggest barrier to carbon pricing remains extremely widespread GOP resistance. But the idea is also fighting for air on the left."
“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 #465 on: January 15, 2019, 06:49:10 PM »
The fact that the Western Pacific warm pool has predominant influence on ECS, is bad news for those who believe in the ice-climate feedback mechanisms, as a slowing of the MOC (due to increasing ice mass loss) will directly increase the temperature of the Western Pacific, and thus will increase the frequency of El Nino events and the associated telecommunication of Tropical Pacific heat energy poleward:

Yue Dong, Cristian Proistosescu, Kyle Armour & David S. Battisti (Dec 19, 2018), "Attributing Historical and Future Evolution of Radiative Feedbacks to Regional Warming Patterns using a Green’s Function Approach: The Preeminence of the Western Pacific"

https://eartharxiv.org/tdrmx/

Abstract: "Global radiative feedbacks have been found to vary in global climate model (GCM) simulations. Atmospheric GCMS (AGCMs) driven with historical patterns of sea-surface temperatures (SST) and sea-ice concentrations produce radiative feedbacks that trend toward more negative values, implying low climate sensitivity, over recent decades.  Freely-evolving coupled GCMs driven by increasing CO₂ produce radiative feedbacks that trend toward more positive values, implying increasing climate sensitivity, in the future.  While this time-variation in feedbacks has been linked to evolving SST patterns, the role of particular regions has not been quantified.  Here, a Green's function is derived from a suite of simulations within an AGCM (NCAR's CAM4), allowing an attribution of global feedback changes to surface warming in each regions.

The results highlight the radiative response to surface warming in ascent regions of the western tropical Pacific as the dominant control on global radiative feedback changes.  Historical warming from the 1950s to 2000s preferentially occurred in the western Pacific, yielding a strong global outgoing radiative response at the TOA and producing a strongly negative global feedback.  Long-term warming in coupled GCMs occurs preferentially in tropical descent regions and in high latitudes, where surface warming yields small global TOA radiation changes, and thus a less-negative global feedback.  These results illuminate the importance of determining mechanism of warm pool warming for understanding how feedbacks have varied historically and will evolve in the future."
“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 #466 on: January 15, 2019, 07:04:22 PM »
The linked reference examines large-scale climate forcing associated with West Antarctic surface ice melting; which is one of the numerous positive feedbacks associated with the ice-climate mechanism:

Ryan C. Scott et al. (2019), "Meteorological Drivers and Large-Scale Climate Forcing of West Antarctic Surface Melt", Journal of Climate, https://doi.org/10.1175/JCLI-D-18-0233.1

https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-18-0233.1

Abstract: "Understanding the drivers of surface melting in West Antarctica is crucial for understanding future ice loss and global sea level rise. This study identifies atmospheric drivers of surface melt on West Antarctic ice shelves and ice sheet margins and relationships with tropical Pacific and high-latitude climate forcing using multidecadal reanalysis and satellite datasets. Physical drivers of ice melt are diagnosed by comparing satellite-observed melt patterns to anomalies of reanalysis near-surface air temperature, winds, and satellite-derived cloud cover, radiative fluxes, and sea ice concentration based on an Antarctic summer synoptic climatology spanning 1979–2017. Summer warming in West Antarctica is favored by Amundsen Sea (AS) blocking activity and a negative phase of the southern annular mode (SAM), which both correlate with El Niño conditions in the tropical Pacific Ocean. Extensive melt events on the Ross–Amundsen sector of the West Antarctic Ice Sheet (WAIS) are linked to persistent, intense AS blocking anticyclones, which force intrusions of marine air over the ice sheet. Surface melting is primarily driven by enhanced downwelling longwave radiation from clouds and a warm, moist atmosphere and by turbulent mixing of sensible heat to the surface by föhn winds. Since the late 1990s, concurrent with ocean-driven WAIS mass loss, summer surface melt occurrence has increased from the Amundsen Sea Embayment to the eastern Ross Ice Shelf. We link this change to increasing anticyclonic advection of marine air into West Antarctica, amplified by increasing air–sea fluxes associated with declining sea ice concentration in the coastal Ross–Amundsen Seas."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

rboyd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #467 on: January 15, 2019, 11:10:21 PM »
Extract: "The bottom line: the biggest barrier to carbon pricing remains extremely widespread GOP resistance. But the idea is also fighting for air on the left."

I think that the following quote from the article you linked to sums it up well:
"A carbon price should not be the centerpiece of legislation, it should be about spending and regulations to get the economy on an ambitious decarbonization pathway. ... Carbon prices and tax may have a role, but more to change market incentives and break up concentrations of wealth and income."

A carbon tax by itself will simply dump the cost predominantly on the poorer members of society. Fee + Flat Dividend helps redistribute, but it is not a silver bullet and requires extensive government spending (the military, infrastructure etc.) changes, together with regulations (e.g. applying the clean water act and the EPA to fracking etc., building codes ...). Probably could have worked in the 1990's, but we are already too far gone for such policies.

A true "WW2" type effort would ban over-consumption as an ethical issue given the need to fight climate change, just as happened in WW2 when things like private car production was banned. Ethics and shaming need to be employed, not just driving individuals and corporations cost-benefit analyses through pricing changes.

oren

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #468 on: January 16, 2019, 04:45:23 AM »
The two linked articles indicate that the Northwestern portion of the Ross Ice Shelf, RIS, is currently being destabilized by a previously unverified mechanism, i.e. local basal ice melting induced by '… seasonal masses of warm water near the ocean surface in from of the ice shelf.' 
Seeing that the Ross Sea ice extent has decreased sharply in summer in the last few years, I expect these seasonal masses of warm water near the ocean surface to be increasing. Bad news indeed.

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #469 on: January 16, 2019, 04:27:41 PM »
More paleo-evidence indicating that we may already have initiated conditions leading to a WAIS collapse at least as severe as that during the Eemian maximum (MIS-5e):

Paul Voosen. Antarctic ice melt 125,000 years ago offers warning, Science (2018). DOI: 10.1126/science.362.6421.1339

http://science.sciencemag.org/content/362/6421/1339

Abstract: "Some 125,000 years ago, during the last brief warm period between ice ages, Earth was flooded, with sea levels 6 to 9 meters higher than they are today. Temperatures during this time, called the Eemian, were barely higher than in today's greenhouse-warmed world. Scientists have now identified the source of all that water: a collapse of the West Antarctic Ice Sheet. Glaciologists worry about the present-day stability of this formidable ice mass. Its base lies below sea level, at risk of being undermined by warming ocean waters, and glaciers fringing it are retreating fast. The discovery, teased out of a sediment core and reported at a meeting of the American Geophysical Union in Washington, D.C., provides evidence that the ice sheet disappeared in the recent geological past under climate conditions similar to today's. The Eemian is not a perfect analog, as its sea levels were likely driven by slight changes in Earth's orbit and spin axis. But the work, if it holds up, could suggest the recent melt at the ice sheet is the start of a similar collapse, rather than a short-term variation."
“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 #470 on: January 16, 2019, 04:43:31 PM »
The two linked articles indicate that the Northwestern portion of the Ross Ice Shelf, RIS, is currently being destabilized by a previously unverified mechanism, i.e. local basal ice melting induced by '… seasonal masses of warm water near the ocean surface in from of the ice shelf.' 
Seeing that the Ross Sea ice extent has decreased sharply in summer in the last few years, I expect these seasonal masses of warm water near the ocean surface to be increasing. Bad news indeed.

The attached image shows that seasonal wind tend to blow sea ice seaward from the northeast edge of the RIS:
“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 #471 on: January 16, 2019, 06:23:23 PM »
The linked reference provides paleo-evidence that supports Hansen's interpretation of the ice-climate feedback mechanisms:

R.H. Levy et al. (2019), "Antarctic ice-sheet sensitivity to obliquity forcing
enhanced through ocean connections", Nature Geoscience, https://doi.org/10.1038/s41561-018-0284-4.

https://www.nature.com/articles/s41561-018-0284-4
&
https://www.nature.com/articles/s41561-018-0284-4.epdf?referrer_access_token=aCfwVc-RjgcGTd4MgHtGUNRgN0jAjWel9jnR3ZoTv0Ot_gu31-eQPxiztIuzStKFE6UdtLeqWzC_6QrFMHEaeupppjQfCG98e2wXxANtbC327DQWNypC7fIGTwbf37zfNbJuLl77xXlrAQ2hrla4hYmrO40qS9t3kY86lxyogxudK-e_txRwdssl87Qb6t3ioWYdHwuv5_PeCFAqfOE0lFWZ0IjRlZQMNgN4Ir-NxvIj62uPf18Ix08nKiMIBtHa&tracking_referrer=www.livescience.com

Abstract: "Deep sea geological records indicate that Antarctic ice-sheet growth and decay is strongly influenced by the Earth’s astronomical variations (known as Milankovitch cycles), and that the frequency of the glacial–interglacial cycles changes through time. Here we examine the emergence of a strong obliquity (axial tilt) control on Antarctic ice-sheet evolution during the Miocene by correlating the Antarctic margin geological records from 34 to 5 million years ago with a measure of obliquity sensitivity that compares the variance in deep sea sediment core oxygen-isotope data at obliquity timescales with variance of the calculated obliquity forcing. Our analysis reveals distinct phases of ice-sheet evolution and suggests the sensitivity to obliquity forcing increases when ice-sheet margins extend into marine environments. We propose that this occurs because obliquity-driven changes in the meridional temperature gradient affect the position and strength of the circum-Antarctic easterly flow and enhance (or reduce) ocean heat transport across the Antarctic continental margin. The influence of obliquity-driven changes in ocean dynamics is amplified when marine ice sheets are extensive, and sea ice is limited. Our reconstruction of the Antarctic ice-sheet history suggests that if sea-ice cover decreases in the coming decades, ocean-driven melting at the ice-sheet margin will be amplified."

See also:

Title: "Earth's Tilt May Exacerbate a Melting Antarctic"

https://www.livescience.com/64507-antarctica-ice-melt-earth-tilt.html

Extract: "At times of high tilt, the polar regions warm and the temperature differences between the equator and the poles become less extreme. This, in turn, alters wind and current patterns — which are largely driven by this temperature difference — ultimately increasing the flow of warm ocean water to Antarctica's edge.

This history spells trouble for Antarctica's future. In 2016, the level of carbon dioxide in Earth's atmosphere leapt past 400 ppm, permanently. The last time in Earth's geologic history that carbon dioxide was this high, there was no year-round sea ice in Antarctica, Levy said. If emissions continue as they are, the sea ice will falter, Levy said, "and we will jump back to a world that hasn't existed for millions of years."

"Antarctica's vulnerable marine-based ice sheets will feel the effect of our current relatively high tilt, and ocean warming at Antarctica's margins will be amplified," he said."
“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 #472 on: January 16, 2019, 06:29:00 PM »
For those who do not know what Marine Ice Sheet Instability, MISI, is, I provide the first linked article.

Title: "Marine Ice Sheet Instability “For Dummies”"

https://blogs.egu.eu/divisions/cr/2016/06/22/marine-ice-sheet-instability-for-dummies-2/

Extract: "The MISI hypothesis states that when the bedrock slopes down from the coast towards the interior of the marine ice sheet, which is the case in large parts of West Antarctica, the grounding line is not stable (in the absence of back forces provided by ice shelves, see next section for more details). To explain this concept, let us take the schematic example shown in Figure 4:
1.   The grounding line is initially located on a bedrock sill (Figure 4a). This position is stable: the ice flux at the grounding line, which is the amount of ice passing through the grounding line per unit time, matches the total upstream accumulation.
2.   A perturbation is applied at the grounding line, e.g. through the incursion of warm Circumpolar Deep Water (CDW, red arrow in Figure 4) below the ice shelf as observed in the Amundsen Sea Embayment.
3.   These warm waters lead to basal melting at the grounding line, ice-shelf thinning and glacier acceleration, resulting in an inland retreat of the grounding line.
4.   The grounding line is then located on a bedrock that slopes downward inland (Figure 4b), i.e. an unstable position where the ice column at the grounding line is thicker than previously (Figure 4a). The theory shows that ice flux at the grounding line is strongly dependent on ice thickness there (Weertman, 1974; Schoof, 2007), so a thicker ice leads to a higher ice flux.
5.   Then, the grounding line is forced to retreat since the ice flux at the grounding line is higher than the upstream accumulation.
6.   This is a positive feedback and the retreat only stops once a new stable position is reached (e.g. a bedrock high), where both ice flux at the grounding line and upstream accumulation match.

   In summary, the MISI hypothesis describes the condition where a marine ice sheet is unstable due to being grounded below sea level on land that is sloping downward from the coast to the interior of the ice sheet.
   This configuration leads to potential rapid retreat of the grounding line and speed up of ice flow from the interior of the continent into the oceans."
&
For those who do not know the difference between MISI and Marine Ice Cliff Instability, MICI, I provide the following linked article:

Title: "Marine ice sheet instability"

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

Extract: "Marine ice sheet instability (MISI) describes the potential for ice sheets grounded below sea level to rapidly destabilize in a runaway fashion.

A related process known as Marine Ice Cliff Instability (MICI) posits that due to the physical characteristics of ice, subaerial ice cliffs exceeding ~90 meters in height are likely to collapse under their own weight, and could lead to runaway ice sheet retreat in a fashion similar to MISI.  For an ice sheet grounded below sea level with an inland-sloping bed, ice cliff failure removes peripheral ice, which then exposes taller, more unstable ice cliffs, further perpetuating the cycle of ice front failure and retreat. Surface melt can further enhance MICI through ponding and hydrofracture."
“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 #473 on: January 16, 2019, 09:09:07 PM »
For what it is worth, the linked MIT Earth System Model updated using somewhat updated data (thru 2010) indicates that climate sensitivity is higher than previously projected:

Libardoni, A.G., C.E. Forest, A.P. Sokolov and E. Monier (2018): Estimates of climate system properties incorporating recent climate change. Advances in Statistical Climatology, Meteorology and Oceanography, 4(1/2),19-36 (doi:10.5194/ascmo-4-19-2018) (https://www.adv-stat-clim-meteorol-oceanogr.net/4/19/2018/)

https://www.adv-stat-clim-meteorol-oceanogr.net/4/19/2018/

Summary
We present new probabilistic estimates of model parameters in the MIT Earth System Model using more recent data and an updated method. Model output is compared to observed climate change to determine which sets of model parameters best simulate the past. In response to increasing surface temperatures and accelerated heat storage in the ocean, our estimates of climate sensitivity and ocean diffusivity are higher. Using a new interpolation algorithm results in smoother probability distributions.

Abstract
Historical time series of surface temperature and ocean heat content changes are commonly used metrics to diagnose climate change and estimate properties of the climate system. We show that recent trends, namely the slowing of surface temperature rise at the beginning of the 21st century and the acceleration of heat stored in the deep ocean, have a substantial impact on these estimates. Using the Massachusetts Institute of Technology Earth System Model (MESM), we vary three model parameters that influence the behavior of the climate system: effective climate sensitivity (ECS), the effective ocean diffusivity of heat anomalies by all mixing processes (Kv), and the net anthropogenic aerosol forcing scaling factor. Each model run is compared to observed changes in decadal mean surface temperature anomalies and the trend in global mean ocean heat content change to derive a joint probability distribution function for the model parameters. Marginal distributions for individual parameters are found by integrating over the other two parameters. To investigate how the inclusion of recent temperature changes affects our estimates, we systematically include additional data by choosing periods that end in 1990, 2000, and 2010. We find that estimates of ECS increase in response to rising global surface temperatures when data beyond 1990 are included, but due to the slowdown of surface temperature rise in the early 21st century, estimates when using data up to 2000 are greater than when data up to 2010 are used. We also show that estimates of Kv increase in response to the acceleration of heat stored in the ocean as data beyond 1990 are included. Further, we highlight how including spatial patterns of surface temperature change modifies the estimates. We show that including latitudinal structure in the climate change signal impacts properties with spatial dependence, namely the aerosol forcing pattern, more than properties defined for the global mean, climate sensitivity, and ocean diffusivity.
“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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While the Wall Street Journal (owned by Rupert Murdoch) is a questionable source, at least if a carbon fee & dividend is passed into US law, and it proves insufficient, then regulations and other climate change policies could be added as needed:

Title: "Former Fed chairmen and Nobel economists voice support for carbon tax"

https://www.axios.com/economists-back-carbon-dividend-to-tackle-climate-change--b84a96c6-6217-4e90-9ea0-93367c6b4832.html

Extract: "The increasing consensus among economists that the best thing to do with any money raised with a carbon tax is to return it to Americans is a significant policy marker as Washington debates to what degree, if at all, it will address Earth’s rising temperatures.

Details: All four of the still-living former Federal Reserve chairs, nearly 30 Nobel economists and all but one former chair of the White House’s Council of Economic Advisers have signed onto a statement laying out their support for a carbon-tax policy — one that has been gaining support from big oil companies, environmental groups and others across the political spectrum.
The plan includes a tax on carbon emissions that rises over time, with the proceeds sent back to Americans via quarterly dividend checks."

See also:

Title: "Economists’ Statement on Carbon Dividends"

https://www.wsj.com/articles/economists-statement-on-carbon-dividends-11547682910?mod=searchresults&page=1&pos=1

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