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Author Topic: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)  (Read 131877 times)

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1050 on: May 07, 2019, 08:30:02 PM »
The linked reference has relevance to my last post:

Slater, D., Straneo, F., Felikson, D., Little, C., Goelzer, H., Fettweis, X., and Holte, J.: Past and future response of Greenland's tidewater glaciers to submarine melting, The Cryosphere Discuss., https://doi.org/10.5194/tc-2019-98, in review, 2019.

https://www.the-cryosphere-discuss.net/tc-2019-98/

Abstract. The effect of the North Atlantic Ocean on the Greenland Ice Sheet through submarine melting of Greenland's tidewater glacier calving fronts is thought to be a key driver of widespread glacier retreat, dynamic mass loss and sea level contribution from the ice sheet. Despite its critical importance, problems of process complexity and scale hinder efforts to represent the influence of submarine melting in ice sheet-scale models. Here we propose parameterizing tidewater glacier terminus position as a simple linear function of submarine melting, with submarine melting in turn estimated as a function of subglacial runoff and ocean temperature. The relationship is tested, calibrated and validated using datasets of terminus position, runoff and ocean temperature covering the full ice sheet and surrounding ocean from the period 1960–present. We demonstrate a statistically significant link between multi-decadal tidewater glacier terminus position and submarine melting and show that the proposed parameterisation has predictive power when considering a population of glaciers. An illustrative 21st century projection is considered suggesting that tidewater glaciers in Greenland will undergo little further retreat in a low emissions RCP2.6 scenario. In contrast, a high emissions RCP8.5 scenario results in a median retreat of ∼6 km, with 35 % of glaciers experiencing retreat exceeding 10 km. Our study provides a long-term and ice sheet-wide assessment of the sensitivity of tidewater glaciers to submarine melting and proposes a practical and empirically validated means of incorporating ocean forcing into models of the Greenland ice sheet.

Edit, for fun I note that the linked reference does not consider ice-cliff failure mechanisms, but the attached images indicate that at least Jakobshavn & Helheim are primed to experience at least a spurt of ice-climate failures as their ice faces retreat down negative bed-slopes in the next decade or two:

The first attached image is from Espen, where: "Helheim (1.) is qualified to be on of the four super iceways of Greenland together with Jakobshavn (2.), Petermann / Humboldt (3.) and Zachariae (4.)"

The second image shows Jakobshavn bathymetry with the ice calving face thru 2017; which indicates that the ice face is retreating toward the negative bed-slope at location A15; and where the third image shows a profile of Jakobshavn where the negative bed-slope is at AA' distance 12km.

The fourth image shows that the calving ice face of the Helheim Glacier is also approaching a negative bed-slope.

Edit 2: Just a reminder that James Hanson warned in the 1980's that for modern society to be fully safe from significant negative climate impacts, the atmospheric carbon dioxide concentration should remain below 350ppm.
« Last Edit: May 08, 2019, 08:08:09 PM by AbruptSLR »
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Shared Humanity

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1051 on: May 07, 2019, 11:11:03 PM »
Christ AbruptSLR...I don't visit for a few hours and you dump a day's worth of reading on me!

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1052 on: May 08, 2019, 04:39:51 PM »
Christ AbruptSLR...I don't visit for a few hours and you dump a day's worth of reading on me!

Shared Humanity,

Please excuse my irregular posting (due to my irregular schedule); however, from my point of view theses posts are all re-posts of prior points that I have made before, that I have merely concentrated in one sequence for those who get lost in the noise of a blog.

Best regards,

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

Tor Bejnar

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1053 on: May 08, 2019, 05:14:11 PM »
I searched the ASIF Glossary for most of the acronyms AbruptSLR used in his recent posts, and if not found, gathered them (with definitions I knew or slewthed) into a single post.  If you are looking for a (scientific-related) acronym's meaning, first look in the first post of the Glossary (Neven adds Arctic-related terms regularly), then use the Search feature on that thread (upper right corner of webpage).  If not found, figure out what the acronym means (Abrupt's context may help, or search this thread for previous use) and post it into the Glossary. Obviously, if I got a definition wrong, please let me know so I can correct my post.

Edit:  if definitions are included within the post, I don't look further.  (For example, Abrupt's next post - an abstract - uses lots of acronyms, but all are defined.)
« Last Edit: May 08, 2019, 06:21:22 PM by Tor Bejnar »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1054 on: May 08, 2019, 06:05:09 PM »
I believe that current consensus climate science model projections under appreciate the impacts of the Antarctic ozone hole and in this regards, the linked reference discusses one way to improve climate model projections in order to better account for the impact of variations in the Antarctic ozone hole and Southern Hemisphere surface climate.

Zoe E. Gillett et al. (2019), "Evaluating the Relationship between Interannual Variations in the Antarctic Ozone Hole and Southern Hemisphere Surface Climate in Chemistry–Climate Models", Journal of Climate, https://doi.org/10.1175/JCLI-D-18-0273.1

https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-18-0273.1

Abstract
Studies have recently reported statistically significant relationships between observed year-to-year spring Antarctic ozone variability and the Southern Hemisphere annular mode and surface temperatures in spring–summer. This study investigates whether current chemistry–climate models (CCMs) can capture these relationships, in particular, the connection between November total column ozone (TCO) and Australian summer surface temperatures, where years with anomalously high TCO over the Antarctic polar cap tend to be followed by warmer summers. The interannual ozone–temperature teleconnection is examined over the historical period in the observations and simulations from the Whole Atmosphere Community Climate Model (WACCM) and nine other models participating in the Chemistry–Climate Model Initiative (CCMI). There is a systematic difference between the WACCM experiments forced with prescribed observed sea surface temperatures (SSTs) and those with an interactive ocean. Strong correlations between TCO and Australian temperatures are only obtained for the uncoupled experiment, suggesting that the SSTs could be important for driving both variations in Australian temperatures and the ozone hole, with no causal link between the two. Other CCMI models also tend to capture this relationship with more fidelity when driven by observed SSTs, although additional research and targeted modeling experiments are required to determine causality and further explore the role of model biases and observational uncertainty. The results indicate that CCMs can reproduce the relationship between spring ozone and summer Australian climate reported in observational studies, suggesting that incorporating ozone variability could improve seasonal predictions; however, more work is required to understand the difference between the coupled and uncoupled simulations.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1055 on: May 08, 2019, 09:44:37 PM »
The linked reference discusses how 'a recent shift toward an El Nino-like ocean state in the Tropical Pacific' "… is linked to the recent acceleration of global ocean warming":

Sang‐Chul Cha et al. (05 November 2018), "A Recent Shift Toward an El Niño‐Like Ocean State in the Tropical Pacific and the Resumption of Ocean Warming", Geophysical Research Letters, https://doi.org/10.1029/2018GL080651

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL080651

Abstract
Since approximately 2011, the tropical Pacific has been sharply shifting toward an opposite phase to that observed in the previous decade. This shift has coincided with a recent resumption of global warming after a hiatus in the 2000s. Based on a model‐data analysis using an ensemble empirical mode decomposition, we identified a distinct low‐frequency mode of the sea level in the tropical Pacific and showed its connection to global ocean warming and the suppression of global warming during the early 2000s, as well as the resumption of warming during recent years. Hindcast and model experiments conducted to illustrate the physical mechanism linking the decadal mode to the Pacific Decadal Oscillation‐related trade winds, which regulate the strength of the Equatorial Undercurrent and the surface temperature of the tropical Pacific Ocean, revealed an El Niño‐like state for the last several years.

Plain Language Summary

In contrast to previous decade, since roughly 2011, sea level in the western tropical Pacific has declined, while sea level in the central‐to‐eastern tropical Pacific has increased. This study focuses on a decadal shift in the tropical Pacific Ocean toward a low‐frequency El Niño‐like state, which coincides with a recent resumption of global warming after a hiatus in the 2000s. Here we identify whether the recent shift is a short‐term change associated with ENSO or longer‐term change and examine how the decadal shift in the Pacific is linked to the recent acceleration of global ocean warming. The model‐data analysis allows us to gain insight into the evolution of sea level and ocean circulation in the Pacific Ocean on decadal time scale, as well as the accuracy and reliability of observed decadal fluctuation. The decadal mode presented here could lead to a better understanding of how sea level and ocean circulation respond to the Pacific climate variability.
“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 #1056 on: May 08, 2019, 10:39:44 PM »
The linked reference provides a comparison between present-day conditions (CTR) and those characteristics of a super-interglacial epoch, the Marine Isotope Stage 31 (MIS31; early Pleistocene 1085–1055 ka), also see the attached image showing that MIS 31 occurred at the beginning of the 100-kyr cycles.  This work raises the probability that strong El Nino events may become more frequent with continued global warming:

Justino, F., Kucharski, F., Lindemann, D., Wilson, A., and Stordal, F.: A modified seasonal cycle during MIS31 super-interglacial favors stronger interannual ENSO and monsoon variability, Clim. Past, 15, 735-749, https://doi.org/10.5194/cp-15-735-2019, 2019.

https://www.clim-past.net/15/735/2019/

Abstract
It has long been recognized that the amplitude of the seasonal cycle can substantially modify climate features in distinct timescales. This study evaluates the impact of the enhanced seasonality characteristic of the Marine Isotope Stage 31 (MIS31) on the El Niño–Southern Oscillation (ENSO). Based upon coupled climate simulations driven by present-day (CTR) and MIS31 boundary conditions, we demonstrate that the CTR simulation shows a significant concentration of power in the 3–7-year band and on the multidecadal timescale between 15 and 30 years. However, the MIS31 simulation shows drastically modified temporal variability of the ENSO, with stronger power spectrum at interannual timescales but the absence of decadal periodicity. Increased meridional gradient of sea surface temperature (SST) and wind stress in the Northern Hemisphere subtropics are revealed to be the primary candidates responsible for changes in the equatorial variability. The oceanic response to the MIS31 ENSO extends to the extratropics, and fits nicely with SST anomalies delivered by paleoreconstructions. The implementation of the MIS31 conditions results in a distinct global monsoon system and its link to the ENSO in respect to current conditions. In particular, the Indian monsoon intensified but no correlation with ENSO is found in the MIS31 climate, diverging from conditions delivered by our current climate in which this monsoon is significantly correlated with the NIÑO34 index. This indicates that monsoonal precipitation for this interglacial is more closely connected to hemispherical features than to the tropical–extratropical climate interaction.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1057 on: May 09, 2019, 02:04:05 AM »
What studies in the next couple years that we could do would clarify the likelihood of this scenario (in the video) eventuating within a century?
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1058 on: May 09, 2019, 03:22:33 AM »
What studies in the next couple years that we could do would clarify the likelihood of this scenario (in the video) eventuating within a century?

You can review the program conducted this past austral summer in the ASE (Amundsen Sea Embayment) in Reply #824.  So if decision makers had more will power they could perform similar field and modeling work for the next two years.  Also, if DoD was so inclined they could introduce ice-cliff failure and hydrofracturing routines to E3SM within the next year so that we could check James Hansen's ice-climate feedback mechanism projections.

Unfortunately, I would be surprised if the Trump Administration would authorize any such accelerated work.

Edit, the following are reposts that I made in back 2013 in this folder (in the 'Recommendations and Summary wrt the WAIS Collapse Hazard', thread):

1) The following recommendations are from: Abrupt Climate Change a report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research, U.S. Geological Survey, Reston, VA. Lead Author: Konrad Steffen, University of Colorado:
Recommendations
•   Reduce uncertainties in estimates of mass balance. This includes continuing mass-balance measurements on small glaciers and completing the World Glacier Inventory.
•   Maintain climate networks on ice sheets to detect regional climate change and calibrate climate models.
•   Derive better measurements of glacier and ice-sheet topography and velocity through improved observation of glaciers and ice sheets. This includes utilizing existing satellite interferometric synthetic aperture radar (InSAR) data to measure ice velocity.
•   Use observations of the time-varying gravity field from satellites to estimate changes in ice sheet mass.
•   Survey changes in ice sheet topography using tools such as satellite radar (e.g., Envisat and Cryosat-2), laser (e.g., ICESat-1/2), and wide-swath altimeters.
•   Monitor the polar regions with numerous satellites at various wavelengths to detect change and to understand processes responsible for the accelerated ice loss of ice sheets, the disintegration of ice shelves, and the reduction of sea ice. It is the integrated satellite data evaluation that provides the tools and understanding to model the future response of cryospheric processes to climate change.
•   Utilize aircraft observations of surface elevation, ice thickness, and basal characteristics to ensure that such information is acquired at high spatial resolution along specific routes, such as glacier flow lines, and along transects close to the grounding lines.
•   Improve coverage of longer term (centennial to millennial) records of ice sheet and ocean history from geological observations.
•   Support field, theoretical, and computational investigations of physical processes beneath and along ice shelves and beneath glaciers, especially near to the grounding lines of the latter, with the goal of understanding recent increases in mass loss.
•   Develop ice-sheet models on a par with current models of the atmosphere and ocean. Particular effort is needed with respect to the modeling of ocean/ice-shelf interactions and physical processes, of surface mass balance from climatic information, and of all (rather than just some, as now) of the forces which drive the motion of the ice.

2) - Develop a sophisticated box model for the Thwaites Glacier (including the postulated subglacial cavity) to see how the grounding line retreats into the BSB.
- Run various ice sheet models with the initial starting conditions that have been presented here; particularly the conditions postulated for the Thwaites Glacier after 2060, including the basal melt rate measured at the WAIS-Divide bore hole.
- Run ice shelf models for both FRIS and RIS with CDW (with flow and temperature parameter calibrated to match the reduction of AABW in these respective areas) introduced beneath them in order to evaluate the rate of ice shelf thinning thru 2100.
- Try to hydraulically model the advective (horizontal) interaction between the PIG and Thwaites system to determine whether there is any synergistic advective action.
- Model the hydraulic action of the postulated interconnected sea passageways and side spurs, and their possible influences on local currents around a degraded WAIS (after 2070).
Possible Field Studies:
- Send a research vessel to the Northeast edge of the FRIS to see whether it is true that warm CDW is already entering the Filchner Trough, and monitor the water flow at outer edge of the RIS for indications of possible CDW fluxes.
- Conduct high-resolution ground penetrating radar examinations of the grounding line of the marine ice sheets for Basins A & B near the Southwest edge of the Filchner Ice Shelf, in order to see whether the grounding line has begun to retreat down the negative slope.
- Refine the ground penetrating survey of the ice in the Thwaites drainage basin, in order to more accurately locate, and delineate, the subglacial lakes in this area.
- Deploy a submersible ROV to survey the: (a) Thwaites Hollow/Subglacial cavity; and (b) the gateway to the Ferrigno Glacier to see if a subglacial cavity has formed there.

Edit 2:  With regard to current modeling efforts of the ocean - cryosphere interaction (i.e. the preponderance of ice-climate feedbacks), see Replies #781 & #990.
« Last Edit: May 09, 2019, 05:33:47 PM by AbruptSLR »
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Tor Bejnar

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1059 on: May 09, 2019, 04:02:56 AM »
Quote
a recent resumption of global warming after a hiatus in the 2000s
from a few posts up
Tamino says there was no global warming pause in the first decade of this century (for example, here) and regularly shows the math (or 'maths' if you're not American) to prove the statistical insignificance of what is called a pause.  Anybody who says there was was pause should pass their proof on to Tamino, I think.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1060 on: May 09, 2019, 05:48:42 AM »
I think anybody who claims a pause need their head examined.



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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1061 on: May 09, 2019, 08:16:40 AM »
As some has noted earlier in this thread, RCP2.6 is no longer attainable.
https://news.agu.org/press-release/new-studies-highlight-challenge-of-meeting-paris-agreement-climate-goals/
A short quote and snipping out the top image from the second study with Peters.
Quote
Stone, with the National Institute of Water and Atmospheric Research, said Peters’ study shows no one country can slip up in the goal to meet climate goals.

“It is hard to argue against their conclusion that we need to start seriously considering options such as the deployment of solar geoengineering, with all of the risks that entails, if the world is serious about achieving the Paris Agreement goals,” he said.



Glen Peters wrote a mini thread yesteday on this:
https://twitter.com/Peters_Glen/status/1126030557593382912
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1062 on: May 09, 2019, 06:49:11 PM »
The linked reference helps to quantify the contributions of sea ice melting and sea ice flux out of the Pacific sector (see the attached images) of the Arctic Ocean (PA), between 1979-2016.  This data is important as the PA is particularly sensitive to climate change, and thus can provide an early warning for any pending albedo flip contributing to accelerated Arctic Amplification in the coming decades:

Bi, H., Yang, Q., Liang, X., Zhang, L., Wang, Y., Liang, Y., and Huang, H.: Contributions of advection and melting processes to the decline in sea ice in the Pacific sector of the Arctic Ocean, The Cryosphere, 13, 1423-1439, https://doi.org/10.5194/tc-13-1423-2019, 2019.

https://www.the-cryosphere.net/13/1423/2019/
&
https://www.the-cryosphere.net/13/1423/2019/tc-13-1423-2019.pdf

Abstract
The Pacific sector of the Arctic Ocean (PA, hereafter) is a region sensitive to climate change. Given the alarming changes in sea ice cover during recent years, knowledge of sea ice loss with respect to ice advection and melting processes has become critical. With satellite-derived products from the National Snow and Ice Center (NSIDC), a 38-year record (1979–2016) of the loss in sea ice area in summer within the Pacific-Arctic (PA) sector due to the two processes is obtained. The average sea ice outflow from the PA to the Atlantic-Arctic (AA) Ocean during the summer season (June–September) reaches 0.173×106 km2, which corresponds to approximately 34 % of the mean annual export (October to September). Over the investigated period, a positive trend of 0.004×106 km2 yr−1 is also observed for the outflow field in summer. The mean estimate of sea ice retreat within the PA associated with summer melting is 1.66×106 km2, with a positive trend of 0.053×106 km2 yr−1. As a result, the increasing trends of ice retreat caused by outflow and melting together contribute to a stronger decrease in sea ice coverage within the PA (0.057×106 km2 yr−1) in summer. In percentage terms, the melting process accounts for 90.4 % of the sea ice retreat in the PA in summer, whereas the remaining 9.6 % is explained by the outflow process, on average. Moreover, our analysis suggests that the connections are relatively strong (R=0.63), moderate (R=−0.46 R=-0.46), and weak (R=−0.24 R=-0.24) between retreat of sea ice and the winds associated with the dipole anomaly (DA), North Atlantic Oscillation (NAO), and Arctic Oscillation (AO), respectively. The DA participates by impacting both the advection (R=0.74) and melting (R=0.55) processes, whereas the NAO affects the melting process (R=−0.46 R=-0.46).
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RoxTheGeologist

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1063 on: May 09, 2019, 07:42:31 PM »
Christ AbruptSLR...I don't visit for a few hours and you dump a day's worth of reading on me!

Keeping up with ASLR is a challenge all on its own :), but its well worth the effort and it has made me vastly more informed.

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1064 on: May 09, 2019, 09:30:43 PM »
Below is a link to an Oceanography magazine on 'Scientific Ocean Drilling: Looking to the Future', and I single out the linked article by Escutia et al. (2019) on Antarctic Ice Sheet stability (see the attached image):

March 2019, "Special Issue on Scientific Ocean Drilling: Looking to the Future", Oceanography, Volume 32, Number 1

https://tos.org/oceanography/issue/volume-32-issue-01
https://tos.org/oceanography/assets/docs/32-1_oceanography.pdf
&

Escutia, C., R.M. DeConto, R. Dunbar, L. De Santis, A. Shevenell, and T. Naish. 2019. Keeping an eye on Antarctic Ice Sheet stability. Oceanography 32(1):32–46, https://doi.org/10.5670/oceanog.2019.117.

https://tos.org/oceanography/article/keeping-an-eye-on-antarctic-ice-sheet-stability

Abstract: "Knowledge of how the Antarctic Ice Sheet (AIS) responded in the geologic past to warming climates will provide powerful insight into its poorly understood role in future global sea level change. Study of past natural climate changes allows us to determine the sensitivity of the AIS to higher-than-present atmospheric carbon dioxide (CO2) concentrations and global temperatures, thereby providing the opportunity to improve the skill and performance of ice sheet models used for Intergovernmental Panel on Climate Change (IPCC) future projections.
Antarctic and Southern Ocean (south of 60°S latitude) marine sediment records obtained over the last 50 years by seven scientific ocean drilling expeditions have revolutionized our understanding of Earth’s climate system and the evolution and dynamics of the Antarctic ice sheets through the Cenozoic (0–65 million years ago). These records document an ice-free subtropical Antarctica between ~52 and 40 million years ago when CO2 was ~1,000 ppm; the initiation of continental-scale Antarctic ice sheets ~34 million years ago as CO2 dropped below 800 ppm; evidence for a dynamic, largely terrestrial, ice sheet driving global sea level changes of up to 40 m amplitude between 34 and 15 million years ago; and colder periods of highly dynamic, marine-based ice sheets contributing up to 20 m of global sea level rise when CO2 levels were in the range of 500–300 ppm between ~14 and 3 million years ago.

Notwithstanding these discoveries, paleoenvironmental records obtained around Antarctica are still limited in their geographical coverage and do not provide a basis for comprehensive understanding of how different sectors of Antarctica respond to climate perturbations. Transects of drill cores spanning ice-proximal to ice-distal environments across the continental margin and at sensitive locations that have been identified by models and recent observations are needed to fully understand temporal and spatial ice volume changes that result from complex ice sheet-ocean-atmosphere interactions. These records are also critical for reconstructing equator-to-pole temperature gradients through time to better understand global climate change, interhemispheric long-distance transmission of changes through the atmosphere and ocean (teleconnections), and the amplification of climate signals in the polar regions.

Future Antarctic scientific ocean drilling will remain key to obtaining records of past Antarctic Ice Sheet dynamics that can be integrated into coupled ice sheet-climate models for improved projections of sea level change. Thus, keeping an eye on ice sheet stability is critical for improving the accuracy and precision of predictions of future changes in global and regional temperatures and sea level rise."

Edit:  The point of this post is that information from drilling in the Southern Ocean is critical for the improved calibration of WAIS and EAIS models.
« Last Edit: May 09, 2019, 09:40:14 PM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1065 on: May 09, 2019, 09:55:17 PM »
Researchers are making progress in understanding changes to the Earth's magnetic field, which hopefully will help us better understand the risk of the Earth's magnetic field flipping this century:

Title: "What does Earth's core have in common with salad dressing? Maybe this"

https://phys.org/news/2019-05-earth-core-common-salad.html

Extract: "A Yale-led team of scientists may have found a new factor to help explain the ebb and flow of Earth's magnetic field—and it's something familiar to anyone who has made a vinaigrette for their salad.

In a new study published May 6 in the Proceedings of the National Academy of Sciences, Yale associate professor Kanani K.M. Lee and her team found that molten iron alloys containing silicon and oxygen form two distinct liquids under conditions similar to those in the Earth's core. It is a process called immiscibility."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1066 on: May 10, 2019, 08:28:35 AM »
A short cross post (just because I really liked these two).
Stumbled over these two beautiful precipitation animations:
https://twitter.com/Climatologist49/status/1125790157284696065

Added below (optimized for size, sorry mac users).
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1067 on: May 10, 2019, 04:14:55 PM »
While the linked reference uses Totten Glacier as a case-study, their findings that: "Our study illustrates how circulation on the Antarctic slope regulates the ocean heat delivery to the continental shelf and ultimately to the ice shelves", are general and thus help to explain why the PIIS frequently has a major calving event in July (in the early austral winter), as I speculate will happen this (2019) year:

Alessandro Silvano et al. (03 May 2019),"Seasonality of warm water intrusions onto the continental shelf near the Totten Glacier", JGR Oceans, https://doi.org/10.1029/2018JC014634

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JC014634

Abstract
Warm Modified Circumpolar Deep Water (MCDW) from the Southern Ocean drives rapid basal melt of the Totten Ice Shelf on the Sabrina Coast (East Antarctica), affecting the mass balance of the grounded Totten Glacier. Recent observations show that MCDW intrudes onto the continental shelf through a depression at the shelf break. Here we investigate such intrusions by combining 1) new oceanographic and bathymetric observations collected for two consecutive years by profiling floats in the depression south of the shelf break, 2) oceanographic measurements collected by CTD‐instrumented seals on continental slope and 3) an ocean model. The depression provides a pathway for persistent inflow of warm (0‐1°C) MCDW to the inner shelf. In austral autumn and early winter MCDW intrusions were up to 0.5°C warmer and are ~75 m thicker than in spring and summer. The seasonality of the flow on the continental slope explains the seasonality of the intrusions. The MCDW layer on the continental slope is warmer and thicker to the east of the depression than to the west. In autumn and early winter a strong, top‐to‐bottom westward current (Antarctic Slope Current) transports the warmer and thicker MCDW layer along the slope and is diverted poleward at the eastern entrance of the depression. A bottom‐intensified eastward current (Antarctic Slope Undercurrent) develops in other months, allowing cooler and thinner intrusions to enter the depression from the west. Our study illustrates how circulation on the Antarctic slope regulates the ocean heat delivery to the continental shelf and ultimately to the ice shelves.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1068 on: May 10, 2019, 05:24:02 PM »
The linked reference indicates that many earlier CESM projections did not consider cloud radiative feedbacks with the ENSO cycles; however, it finds that when such feedbacks do indeed work synergistically with the ENSO.

Eleanor A. Middlemas et al. (8 May 2019), "Cloud radiative feedbacks and El Niño Southern Oscillation", Journal of Climate, https://doi.org/10.1175/JCLI-D-18-0842.1

https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-18-0842.1

Abstract
Cloud radiative feedbacks are disabled via “cloud-locking” in the Community Earth System Model, version 1.2, (CESM1.2) to result in a shift in El Niño Southern Oscillation (ENSO) periodicity from 2-7 years to decadal timescales. We hypothesize that cloud radiative feedbacks may impact the periodicity in three ways: by (1) modulating heat flux locally into the equatorial Pacific subsurface through negative shortwave cloud feedback on sea surface temperature anomalies (SSTA), (2) damping the persistence of subtropical Southeast Pacific SSTA such that the South Pacific Meridional Mode impacts the duration of ENSO events, or (3) controlling the meridional width of off-equatorial westerly winds, which impact the periodicity of ENSO by initiating longer Rossby waves. The result of cloud-locking in CESM1.2 contrasts that of another study which found that cloud-locking in a different global climate model led to decreased ENSO magnitude across all timescales due to a lack of positive longwave feedback on the anomalous Walker circulation. CESM1.2 contains this positive longwave feedback on the anomalous Walker circulation, but either its influence on the surface is decoupled from ocean dynamics or the feedback is only active on interannual timescales. The role of cloud radiative feedbacks in ENSO in other global climate models are additionally considered. In particular, it is shown that one cannot predict the role of cloud radiative feedbacks in ENSO through a multimodel diagnostic analysis. Instead, they must be directly altered.
“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 #1069 on: May 11, 2019, 12:38:28 AM »
As cited in Reply #147, the linked reference reminds us that the is an active volcanic heat source upstream of the PIIS; and I wonder how that subglacial volcano will respond if/when large amounts of ice mass loss occurs from the PIG and the Thwaites Glacier:

Brice Loose, et al. (2018), "Evidence of an active volcanic heat source beneath the Pine Island Glacier", Nature Communications, volume 9, Article number: 2431, https://doi.org/10.1038/s41467-018-04421-3

https://www.nature.com/articles/s41467-018-04421-3

Abstract: "Tectonic landforms reveal that the West Antarctic Ice Sheet (WAIS) lies atop a major volcanic rift system. However, identifying subglacial volcanism is challenging. Here we show geochemical evidence of a volcanic heat source upstream of the fast-melting Pine Island Ice Shelf, documented by seawater helium isotope ratios at the front of the Ice Shelf cavity. The localization of mantle helium to glacial meltwater reveals that volcanic heat induces melt beneath the grounded glacier and feeds the subglacial hydrological network crossing the grounding line. The observed transport of mantle helium out of the Ice Shelf cavity indicates that volcanic heat is supplied to the grounded glacier at a rate of ~ 2500 ± 1700 MW, which is ca. half as large as the active Grimsvötn volcano on Iceland. Our finding of a substantial volcanic heat source beneath a major WAIS glacier highlights the need to understand subglacial volcanism, its hydrologic interaction with the marine margins, and its potential role in the future stability of the WAIS.
« Last Edit: May 11, 2019, 01:20:12 AM by AbruptSLR »
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Stephan

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1070 on: May 11, 2019, 04:29:44 PM »
Usually volcanic activity is accompanied by seismic activity. Is there any direct evidence of an active volcanic system beneath the WAIS or are all information about this indirectly derived from isotope patterns or (it was posted somewhere here in this forum) higher bedrock temperatures/larger heat flux in the crust?

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1071 on: May 11, 2019, 05:06:28 PM »
Usually volcanic activity is accompanied by seismic activity. Is there any direct evidence of an active volcanic system beneath the WAIS or are all information about this indirectly derived from isotope patterns or (it was posted somewhere here in this forum) higher bedrock temperatures/larger heat flux in the crust?
The largest volcanic region on earth is 2 kilometers below West Antarctica.
Find about it on thread Antarctic Tectonics #104
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Tor Bejnar

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1072 on: May 11, 2019, 05:32:14 PM »
Antarctic Tectonics post #104
Quote
Scientists discover 91 volcanoes below Antarctic ice sheet
This is in addition to 47 already known about and eruption would melt more ice in region affected by climate change
Arctic ice is healthy for children and other living things.

Stephan

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1073 on: May 11, 2019, 06:11:38 PM »
Usually volcanic activity is accompanied by seismic activity. Is there any direct evidence of an active volcanic system beneath the WAIS or are all information about this indirectly derived from isotope patterns or (it was posted somewhere here in this forum) higher bedrock temperatures/larger heat flux in the crust?
The largest volcanic region on earth is 2 kilometers below West Antarctica.
Find about it on thread Antarctic Tectonics #104
Thank you!

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1074 on: May 11, 2019, 11:22:51 PM »
Some readers undoubtably think that because the 'Ice Apocalypse" thread is in the Antarctic folder, that this discussion is only related to Antarctic topics.  However, I clearly don't see it that way, as I post about cascades of ice-climate feedbacks throughout the entire gambit of Earth Systems (which includes feedback loops with non-ice related feedbacks).  So, in this vein of thinking, I provide a link to the following article on the rapidly disappearing multiyear (older than four years) Arctic sea ice.  The article points out that this older ice 'acts as an anchor' to partially protect younger sea ice from damage, and it will likely vanish as early as the mid-2030s.  Thus, at just the time that key ASE marine glaciers may be subject to MICI-type of ice mass loss; the Arctic sea ice may undergo a near concurrent albedo flip; which via the bipolar seesaw mechanism would work to reinforce each other leading to an 'Ice Apocalypse' occurring at a rate that society cannot adapt to:

Title: "The Last of the Arctic's Old Sea Ice Is on the Verge of Vanishing"

https://earther.gizmodo.com/the-last-of-the-arctics-old-sea-ice-is-on-the-verge-of-1834510753

Extract: "The severe toll of climate change at the top of the world is becoming clearer with each passing day. The latest sign comes courtesy of the National Snow and Ice Data Center (NSIDC), which released its monthly sea ice update on Thursday. It shows that just 1.2 percent of ice in the Arctic Ocean is older than four years. Just 35 years ago, ice that was four years old or older made up nearly a third of all Arctic sea ice.

Old sea ice is vital to holding Arctic icepack as a whole together. It acts as an anchor for younger ice and a buffer against the storms that pound the region. But as ocean and air temperatures have risen in the Arctic, its extent has shrunk dramatically.

Mark Serreze, NSIDC’s director, told Earther 5-10 years is a “more reasonable” timeframe for old ice finally melt away. Research shows the Arctic could see ice-free summers as early as the mid-2030s. "
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1075 on: May 12, 2019, 12:07:26 AM »
The linked article (& associated reference) discuss new findings that help to explain why the Earth warms so rapidly at the end of the late Pleistocene ice ages (see image).  They attribute part of this rapid warming to radiative forcing associated with carbon dioxide 'released into the ocean from geologic reservoirs located on the seafloor when the oceans began to warm.

During to the thermal inertia of the oceans, I would be surprised if such a feedback had much impact sooner than century timescales.  Nevertheless, ice-climate feedback mechanisms over this coming century might be sufficient to active such carbon dioxide hydrate related feedback mechanisms next century; which would be bad news for future generations:

Title: "Deep sea carbon reservoirs once superheated the Earth – could it happen again?"

https://theconversation.com/deep-sea-carbon-reservoirs-once-superheated-the-earth-could-it-happen-again-113518

Extract: "It is now clear from these studies that abrupt warming events are built into Earth’s climate system. They have occurred when disturbances in carbon storage at Earth’s surface released greenhouse gases into the atmosphere. One of the grand challenges for climate scientists like me is to determine where these releases came from before humans were present, and what triggered them. Importantly, we want to know if such an event could happen again.

In a recently published study, my colleagues Katie Harazin, Nadine Krupinski and I discovered that at the end of the last glacial era, about 20,000 years ago, carbon dioxide was released into the ocean from geologic reservoirs located on the seafloor when the oceans began to warm.

This finding is a potential game-changer. Naturally occurring reservoirs of carbon in the modern ocean could be disturbed again, with potentially serious effects to Earth’s oceans and climate.

Over the past two decades, ocean scientists have discovered that there are reservoirs of liquid and solid carbon dioxide accumulating at the bottom of the ocean, within the rocks and sediments on the margins of active hydrothermal vents. At these sites, volcanic magma from within the Earth meets superheated water, producing plumes of carbon dioxide-rich fluids that filter through crevices in the Earth’s crust, migrating upward towards the surface.

When a plume of this fluid meets cold seawater, the carbon dioxide can solidify into a form called hydrate. The hydrate forms a cap that traps carbon dioxide within the rocks and sediments and keeps it from entering the ocean. But at temperatures above roughly 48 degrees Fahrenheit (9 degrees Celsius), hydrate will melt, releasing buoyant liquid or gaseous carbon dioxide directly into the overlying water.

These discoveries are changing scientists’ understanding of the marine carbon system. Climate scientists have not included deep sea carbon reservoirs in current models that explore the potential impacts of future warming, because little is known about the size and distribution of these carbon sources.

Earth’s oceans are warming rapidly, and climate models project that they will warm fastest near the poles, where deep currents form that carry warming waters downward from the surface.

As these warm waters sink into the ocean’s interior, they transport excess heat towards sites where carbon dioxide reservoirs can form. Those warmer waters will eventually destabilize the hydrate seals that keep liquid carbon dioxide trapped.

Importantly, warm hydrothermal fluids are rising from below the carbon dioxide reservoir toward the surface. As the oceans continue to warm, the temperature difference between cold ocean waters and warmer hydrothermal fluids will decrease. This will cause the hydrate to thin, potentially to a point where it will no longer keep liquid carbon dioxide from escaping.

To date there has been no research to assess whether these ocean carbon dioxide reservoirs are vulnerable to rising ocean temperatures. But Earth’s pre-historic record clearly demonstrates that geologic reservoirs can be destabilized – and that when they are, it leads to rapid increases in atmospheric carbon dioxide and global warming. In my view, this represents an important unknown risk that cannot be ignored."
See also:

Lowell D Stott, Kathleen M Harazin and Nadine B Quintana Krupinski (15 February 2019), "Hydrothermal carbon release to the ocean and atmosphere from the eastern equatorial Pacific during the last glacial termination", Environmental Research Letters, Volume 14, Number 2

https://iopscience.iop.org/article/10.1088/1748-9326/aafe28/meta

Abstract: "Arguably among the most globally impactful climate changes in Earth's past million years are the glacial terminations that punctuated the Pleistocene epoch. With the acquisition and analysis of marine and continental records, including ice cores, it is now clear that the Earth's climate was responding profoundly to changes in greenhouse gases that accompanied those glacial terminations. But the ultimate forcing responsible for the greenhouse gas variability remains elusive. The oceans must play a central role in any hypothesis that attempt to explain the systematic variations in pCO2 because the Ocean is a giant carbon capacitor, regulating carbon entering and leaving the atmosphere. For a long time, geological processes that regulate fluxes of carbon to and from the oceans were thought to operate too slowly to account for any of the systematic variations in atmospheric pCO2 that accompanied glacial cycles during the Pleistocene. Here we investigate the role that Earth's hydrothermal systems had in affecting the flux of carbon to the ocean and ultimately, the atmosphere during the last glacial termination. We document late glacial and deglacial intervals of anomalously old 14C reservoir ages, large benthic-planktic foraminifera 14C age differences, and increased deposition of hydrothermal metals in marine sediments from the eastern equatorial Pacific (EEP) that indicate a significant release of hydrothermal fluids entered the ocean at the last glacial termination. The large 14C anomaly was accompanied by a ~4-fold increase in Zn/Ca in both benthic and planktic foraminifera that reflects an increase in dissolved [Zn] throughout the water column. Foraminiferal B/Ca and Li/Ca results from these sites document deglacial declines in [ ] throughout the water column; these were accompanied by carbonate dissolution at water depths that today lie well above the calcite lysocline. Taken together, these results are strong evidence for an increased flux of hydrothermally-derived carbon through the EEP upwelling system at the last glacial termination that would have exchanged with the atmosphere and affected both Δ14C and pCO2. These data do not quantify the amount of carbon released to the atmosphere through the EEP upwelling system but indicate that geologic forcing must be incorporated into models that attempt to simulate the cyclic nature of glacial/interglacial climate variability. Importantly, these results underscore the need to put better constraints on the flux of carbon from geologic reservoirs that affect the global carbon budget."
“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 #1076 on: May 12, 2019, 12:34:11 AM »
While Jeff Masters does a public service by posting about the Tapio Schneider lead research on the risk of losing marine stratocumulus clouds; he falls into the trap of associating such a potential future abrupt loss of marine stratocumulus clouds (which currently produce a negative feedback, so their potential future loss would result in an abrupt increase in GMSTA), to the atmospheric carbon dioxide concentration reaching about1,200ppm.  As I point out in Reply #652 (see also Replies: #633, #642 & #650), the risk of abruptly losing the marine stratocumulus clouds would actually 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) and c) a rapid decrease/redistribution of anthropogenic aerosol emissions:

Title: "Losing Marine Stratocumulus Clouds Could Create a Mega-Hothouse Climate"

https://www.wunderground.com/cat6/Losing-Marine-Stratocumulus-Clouds-Could-Create-Mega-Hothouse-Climate

Extract: "If humanity maintains its current business-as-usual emissions path for the next 100 years, the resulting 4°C (7°F) of warming may be enough to cause highly reflective stratocumulus clouds over the subtropical and tropical oceans to disintegrate, resulting in an additional 8°C (14°F) of warming, according to research published in February. The resultant “Hothouse Earth” climate, 12°C (22°F) warmer than pre-industrial levels, would be enough to melt all ice on the planet, raise sea levels by over 200 feet over a period of centuries, and produce heat waves too hot for humans to endure outdoors for over half of Earth’s population (as currently distributed.)

The paper, from a team of California Institute of Technology scientists led by Tapio Schneider, was called Possible climate transitions from breakup of stratocumulus decks under greenhouse warming."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Tom_Mazanec

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1077 on: May 12, 2019, 02:08:09 AM »
But do we have 100 years left to stop BAU, AbruptSLR? The longer we wait the harder it will be. We may not even have 100 months left until changing course would be massively disruptive to civilization.
SHARKS (CROSSED OUT) MONGEESE (SIC) WITH FRICKIN LASER BEAMS ATTACHED TO THEIR HEADS

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1078 on: May 12, 2019, 04:05:14 AM »
But do we have 100 years left to stop BAU, AbruptSLR? The longer we wait the harder it will be. We may not even have 100 months left until changing course would be massively disruptive to civilization.

Tom,
Climate change is complicated and no current climate model (not even E3SMv2) accounts for all of the actual feedback systems; for instance no model includes the hydrothermal carbon and carbon dioxide hydrate, feedback system discussed by Stott et al. (2019).  Furthermore, just because estimating how soon an 'Ice Apocalypse' might be initiated is of top priority (as I have sighted evidence that it is plausible that 'how soon' might be between 2030 and 2040); doesn't mean that we should ignore the questions of: (a) 'how fast' an 'Ice Apocalypse' might unfold; and (b) 'how far' might an 'Ice Apocalypse' triggered 'Hot House' event go.

For example, in my last post (Reply #1076) I noted that Schneider et al. (2019) pointed out that if the equatorial SST increases from about the 27C to about 32C, that marine stratocumulus clouds might abruptly disappear. Also, I noted that ice-climate feedbacks might cause this to occur well before the end of this century, which would likely tip the Northern Hemisphere into an equable atmospheric configuration where tropical heat was telecommunicated directly to the Arctic within months of the heating.  As tropical heat telecommunicated to the Arctic might rapidly warm the Arctic Bottom Water temperature, this could then be transported by the MOC to geothermal carbon and carbon dioxide hydrate caps much faster than currently assumed.

In summary, some decision makers (like Putin) don't seem to mind breaking some climate change eggs, so long as their country is not harmed as much as their competitors.  So such decision makers have little interest in getting off a BAU pathway in the next 100 months; however, they might (or might not) think twice about pushing the world into a 'Hot House' state by the end of this century, as even Russia would not benefit from the losses of others under such extreme climate change conditions.
Regards,
ASLR

Edit: I note that under the scenario that I outline above, it is plausible that the Earth could windup in a 'Hot House' condition if we stay on a BAU pathway for just then next ten years, due to the risk represented by cascading positive feedback mechanisms (including ice-climate feedback mechanisms).
« Last Edit: May 12, 2019, 04:37:22 AM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1079 on: May 12, 2019, 04:35:34 AM »
While both the linked references address the paleo-behavior of the West Antarctic Rift System (WARS), they both indicate that this tectonic system was/is more active than previously assumed.  So while their findings to not include specific projections about the plausible behavior of the WARS this century; nevertheless, they recommend further research to better define the potential risks from possible near-term future volcanic and seismic activity in this system (see the attached image showing the inferred boundaries of WARS):

Roi Granot & Jérôme Dyment (2018), "Late Cenozoic unification of East and West Antarctica",
Nature Communications, volume 9, Article number: 3189 https://doi.org/10.1038/s41467-018-05270-w

https://www.nature.com/articles/s41467-018-05270-w
&

Dennis L. Harry et al. (2018), "Geodynamic models of the West Antarctic Rift System: Implications for the mantle thermal state", Geosphere, 14 (6): 2407-2429, https://doi.org/10.1130/GES01594.1

https://pubs.geoscienceworld.org/gsa/geosphere/article/14/6/2407/565649/geodynamic-models-of-the-west-antarctic-rift

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

Sleepy

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1080 on: May 12, 2019, 07:40:44 AM »
Some readers undoubtably think that because the 'Ice Apocalypse" thread is in the Antarctic folder, that this discussion is only related to Antarctic topics.  However, I clearly don't see it that way, as I post about cascades of ice-climate feedbacks throughout the entire gambit of Earth Systems (which includes feedback loops with non-ice related feedbacks). <snip>
Yes, most things are beeing covered here, unfortunately that can also be problematic because many are not reading or responding to more than the last post. It certainly takes some effort but is a really nice repository. Thank you.
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Science is a jealous mistress and takes little account of a man's feelings.

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1081 on: May 12, 2019, 11:06:22 AM »
Antarctic Tectonics post #104
Quote
Scientists discover 91 volcanoes below Antarctic ice sheet
This is in addition to 47 already known about and eruption would melt more ice in region affected by climate change

We should also remember (see Reply #315) that abrupt ice mass loss from the gateway of the Thwaites Glacier circa 2040 might possibly trigger an eruption of Mt Takahe in the Byrd Subglacial Basin, BSB (see the attached image), which could accelerate ice mass loss in Antarctica just as happen about 17.7 kya as the linked article entitled: "Massive Antarctic volcanic eruptions linked to abrupt Southern hemisphere climate changes", cites that abrupt climate change was associated with a series of halogen rich eruptions from Mt Takahe in the BSB.  Who knows what lies in mankind's future if a potential collapse of the WAIS this century should trigger similar volcanic eruptions in West Antarctica:

https://phys.org/news/2017-09-massive-antarctic-volcanic-eruptions-linked.html

Extract: ""Detailed chemical measurements in Antarctic ice cores show that massive, halogen-rich eruptions from the West Antarctic Mt. Takahe volcano coincided exactly with the onset of the most rapid, widespread climate change in the Southern Hemisphere during the end of the last ice age and the start of increasing global greenhouse gas concentrations," according to McConnell, who leads DRI's ultra-trace chemical ice core analytical laboratory.

Climate changes that began ~17,700 years ago included a sudden poleward shift in westerly winds encircling Antarctica with corresponding changes in sea ice extent, ocean circulation, and ventilation of the deep ocean. Evidence of these changes is found in many parts of the Southern Hemisphere and in different paleoclimate archives, but what prompted these changes has remained largely unexplained.

"We know that rapid climate change at this time was primed by changes in solar insolation and the Northern Hemisphere ice sheets," explained McConnell. "Glacial and interglacial cycles are driven by the sun and Earth orbital parameters that impact solar insolation (intensity of the sun's rays) as well as by changes in the continental ice sheets and greenhouse gas concentrations."
"We postulate that these halogen-rich eruptions created a stratospheric ozone hole over Antarctica that, analogous to the modern ozone hole, led to large-scale changes in atmospheric circulation and hydroclimate throughout the Southern Hemisphere," he added. "Although the climate system already was primed for the switch, we argue that these changes initiated the shift from a largely glacial to a largely interglacial climate state. The probability that this was just a coincidence is negligible."

See also the subject reference:

Joseph R. McConnell el al., "Synchronous volcanic eruptions and abrupt climate change ∼17.7 ka plausibly linked by stratospheric ozone depletion," PNAS (2017). https://doi.org/10.1073/pnas.1705595114 

www.pnas.org/cgi/doi/10.1073/pnas.1705595114

Extract: "Glacial-state greenhouse gas concentrations and Southern Hemisphere climate conditions persisted until ∼17.7 ka, when a nearly synchronous acceleration in deglaciation was recorded in paleoclimate proxies in large parts of the Southern Hemisphere, with many changes ascribed to a sudden poleward shift in the Southern Hemisphere westerlies and subsequent climate impacts. We used high-resolution chemical measurements in the West Antarctic Ice Sheet Divide, Byrd, and other ice cores to document a unique, ∼192-y series of halogen-rich volcanic eruptions exactly at the start of accelerated deglaciation, with tephra identifying the nearby Mount Takahe volcano as the source. Extensive fallout from these massive eruptions has been found >2,800 km from Mount Takahe. Sulfur isotope anomalies and marked decreases in ice core bromine consistent with increased surface UV radiation indicate that the eruptions led to stratospheric ozone depletion. Rather than a highly improbable coincidence, circulation and climate changes extending from the Antarctic Peninsula to the subtropics—similar to those associated with modern stratospheric ozone depletion over Antarctica—plausibly link the Mount Takahe eruptions to the onset of accelerated Southern Hemisphere deglaciation ∼17.7 ka."

Extract: "Previous studies (e.g., ref. 42) suggested that rising insolation initiated melting of Northern Hemisphere (NH) ice sheets at 19 ka, which triggered a reduction in the strength of the Atlantic overturning circulation, and, through the bipolar seesaw, resulted in SH warming and CO2 release from the Southern Ocean, although the exact mechanisms driving the CO2 release are still debated. We postulate that the ∼192-y series of halogen-rich eruptions of Mount Takahe and the subsequent ozone hole (26) initiated a series of events analogous to the modern ozone hole that acted to accelerate deglaciation at 17.7 ka. First, stratospheric ozone depletion changed SH atmospheric circulation, resulting in a rapid increase and poleward shift in the westerlies (35) (SI Appendix, Fig. S7). Second, consequent widespread perturbations in SH hydrometeorology, including increased austral summer subtropical precipitation between ∼15°S and ∼35°S (Figs. 1F and 5), led to enhanced CH4 wetland emissions (43)."

Caption for the attached image: "Spatial extent of the glaciochemical anomaly. Evidence of the ∼192-y anomaly has been found >2,800 km from Mount Takahe in ice core (circles) chemical records (SI Appendix, Fig. S3) as well as radar surveys from much of West Antarctica. Also shown are area volcanoes (triangles). September/October horizontal wind vectors at 600 hPa based on 1981–2010 National Centers for Environmental Prediction reanalysis fields show transport patterns consistent with observations."

See also: "Antarctica: What Would Happen if All the Volcanoes Buried Beneath the Ice Erupted?"

http://www.newsweek.com/antarctica-subglacial-volcanoes-eruption-risk-sea-ice-659537

Extract: "Less well known is that Antarctica is also host to several active volcanoes, part of a huge “volcanic province” which extends for thousands of miles along the western edge of the continent. Although the volcanic province has been known and studied for decades, about 100 “new” volcanoes were recently discovered beneath the ice by scientists who used satellite data and ice-penetrating radar to search for hidden peaks.

These sub-ice volcanoes may be dormant. But what would happen if Antarctica’s volcanoes awoke?

We can get some idea by looking to the past. One of Antarctica’s volcanoes, Mount Takahe, is found close to the remote centre of the West Antarctic Ice Sheet. In a new study, scientists implicate Takahe in a series of eruptions rich in ozone-consuming halogens that occurred about 18,000 years ago. These eruptions, they claim, triggered an ancient ozone hole, warmed the southern hemisphere which caused glaciers to melt, and helped bring the last ice age to a close.

This sort of environmental impact is unusual. For it to happen again would require a series of eruptions, similarly enriched in halogens, from one or more volcanoes that are currently exposed above the ice. Such a scenario is unlikely although, as the Takahe study shows, not impossible. More likely is that one or more of the many subglacial volcanoes, some of which are known to be active, will erupt at some unknown time in the future.

Because of the enormous thickness of overlying ice, it is unlikely that volcanic gases would make it into the atmosphere. So an eruption wouldn’t have an impact like that postulated for Takahe. However, the volcanoes would melt huge caverns in the base of the ice and create enormous quantities of meltwater. Because the West Antarctic Ice Sheet is wet rather than frozen to its bed—imagine an ice cube on a kitchen work top—the meltwater would act as a lubricant and could cause the overlying ice to slip and move more rapidly.

Under-ice volcanoes are probably what triggered rapid flow of ancient ice streams into the vast Ross Ice Shelf, Antarctica’s largest ice shelf. Something similar might have occurred about 2,000 years ago with a small volcano in the Hudson Mountains that lie underneath the West Antarctica Ice Sheet—if it erupted again today it could cause the nearby Pine Island Glacier to speed up.

Most dramatically of all, a large series of eruptions could destabilise many more subglacial volcanoes. As volcanoes cool and crystallise, their magma chambers become pressurised and all that prevents the volcanic gases from escaping violently in an eruption is the weight of overlying rock or, in this case, several miles of ice. As that ice becomes much thinner, the pressure reduction may trigger eruptions. More eruptions and ice melting would mean even more meltwater being channelled under the ice streams.

Potentially a runaway effect may take place, with the thinning ice triggering more and more eruptions. Something similar occurred in Iceland, which saw an increase in volcanic eruptions when glaciers began to recede at the end of the last ice age."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1082 on: May 12, 2019, 11:47:43 AM »
But do we have 100 years left to stop BAU, AbruptSLR? The longer we wait the harder it will be. We may not even have 100 months left until changing course would be massively disruptive to civilization.

We may not have any time left to prevent a massive disruption of civilization. In fact, a proactive and intentional massive disruption might be just what we need to save ourselves from something worse.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1083 on: May 12, 2019, 02:01:43 PM »

At the risk of referring to a paper already discussed by AbruptSLR.....

A nice paper in Nature Communications - and open source to boot is
"Evidence of an active volcanic heat source beneath the Pine Island Glacier"

https://www.nature.coarticlesm//s41467-018-04421-3
and as a pdf - https://www.nature.com/articles/s41467-018-04421-3.pdf

Quote
The observed transport of mantle helium out of the Ice Shelf cavity indicates that volcanic heat is supplied to the grounded glacier at a rate of ~ 2500 ± 1700 MW, which is ca. half as large as the active Grimsvötn volcano on Iceland.

Discussion
The mantle 3He observed at the front of the Pine Island Ice Shelf, first in 2007 and again in 2014, reveals the presence of a volcanic heat source upstream of the Ice Shelf. The observation of this unique helium isotope signature, together with what is known of the bed forms and fluvial morphology of the Glacier suggests that this volcanic heat source lies within the Hudson Mountain range, and is driving a subglacial melt that subsequently crosses the ice shelf grounding line. Our calculations indicate that the volcanic heat source is comparable in magnitude to the active vent fields found along ocean spreading centers. The inferred heat supply is more than ten times the heat energy released by dormant (but not extinct) shield volcanoes on land.

These geochemical measurements provide an independent line of evidence of present day subglacial volcanism in Marie Byrd Land. They also support a growing list of studies revealing that regional volcanism is a recurring characteristic of the basal boundary beneath the WAIS. The present estimate of convective volcanic heat flux alone suggests a heat source of Q = 2500 MW, which is ~ 50% as large as the Grimsvötn volcano on Iceland, even before sensible and conductive heat flux have been accounted for.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1084 on: May 12, 2019, 02:14:52 PM »
The risk is unfortunately always there gc, earlier posted by Prokyarotes in this thread:
https://forum.arctic-sea-ice.net/index.php/topic,2205.msg170267.html#msg170267

Edit; bummer, made a quick search and ASLR actually posted it earlier:
https://forum.arctic-sea-ice.net/index.php/topic,2205.msg160628.html#msg160628
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1085 on: May 13, 2019, 03:24:52 AM »
As noted in Reply #243, the linked reference (see also the first attached image and associated caption below, and the second image that shows the basal meltwater drainage system beneath Thwaites) provides more evidence of high geothermal flux and associated basal melt water beneath the Thwaites Glacier, both of which will threaten its future stability, and they both work to refill the recently drained subglacial lakes beneath Thwaites:

Dustin M. Schroeder, Donald D. Blankenship, Duncan A. Young, and Enrica Quartini, (2014), "Evidence for elevated and spatially variable geothermal flux beneath the West Antarctic Ice Sheet", PNAS, doi: 10.1073/pnas.1405184111

http://www.pnas.org/content/early/2014/06/04/1405184111.abstract

http://www.pnas.org/content/suppl/2014/06/04/1405184111.DCSupplemental

Also see:
http://www.utexas.edu/news/2014/06/10/antarctic-glacier-melting/

Caption for first image: "This map shows the locations of geothermal flow underneath Thwaites Glacier in West Antarctica that were identified with airborne ice-penetrating radar. The dark magenta triangles show where geothermal flow exceeds 150 milliwatts per square meter, and the light magenta triangles show where flow exceeds 200 milliwatts per square meter. Letters C, D and E denote high melt areas: in the western-most tributary, C; adjacent to the Crary mountains, D; and in the upper portion of the central tributaries, E. Credit: University of Texas Institute Geophysics"
« Last Edit: May 13, 2019, 07:40:52 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1086 on: May 13, 2019, 06:17:32 PM »
I selected the two attached images from the 'Early Anthropocene' thread in the Science folder, to point that it appears likely that the Earth was headed towards a cooling cycle (as in headed towards a glacial period) before mankind started impacting both atmospheric carbon dioxide and methane concentrations.  Thus it is plausible that some of mankind's recent contributions to increasing GMSTA has been partially masked from the observed measurements by offsetting transient negative feedbacks associated with such a long-term/slow cooling trend.  Thus it is plausible that this is one more consideration (together with such masking factors as negative aerosol forcing) that may surprise consensus science projections if/when it turns out that the positive feedback mechanisms have been stronger than indicated by the masked GMSTA data.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1087 on: May 13, 2019, 06:54:49 PM »
This is in line with publications that show that global temperatures are over 100% caused by humans:
Quote

the IPCC’s implied best guess was that humans were responsible for around 110% of observed warming (ranging from 72% to 146%), with natural factors in isolation leading to a slight cooling over the past 50 years.

Similarly, the recent US fourth national climate assessment found that between 93% to 123% of observed 1951-2010 warming was due to human activities.

These conclusions have led to some confusion as to how more than 100% of observed warming could be attributable to human activity. A human contribution of greater than 100% is possible because natural climate change associated with volcanoes and solar activity would most likely have resulted in a slight cooling over the past 50 years, offsetting some of the warming associated with human activities.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1088 on: May 13, 2019, 07:36:21 PM »
Ralph Keeling believes that the annual 2019 atmospheric CO2 concentration will be about 3ppm higher than that for 2018; which represents an acceleration of the recent trendline.  If global society seriously expects to keep GMSTA well below 2C; it would be a good idea to be decelerating this trendline instead of accelerating it:

Title: "Earth's carbon dioxide level slips past another ominous milestone"

https://www.axios.com/carbon-dioxide-concentration-earth-all-time-high-2c5073f2-a4fb-445c-9613-8998dc8f58cb.html

Extract: "The new reading of 415.26 parts per million (ppm) on May 11 was the first daily baseline at Hawaii's Mauna Loa Observatory to eclipse 415 ppm.

"The increase from last year will probably be around three parts per million whereas the recent average has been 2.5 ppm," Keeling said."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1089 on: May 13, 2019, 11:57:13 PM »
The linked reference provides information that appears to refute the most significant claims of Edwards et al. (2019); and confirms that MICI-type of ice sheet collapse is a valid risk this century:

Ben Seiyon Lee, Murali Haran, Robert Fuller, David Pollard, Klaus Keller (24 March 2019), "A Fast Particle-Based Approach for Calibrating a 3-D Model of the Antarctic Ice Sheet", arXiv:1903.10032v1

https://arxiv.org/abs/1903.10032
https://arxiv.org/pdf/1903.10032.pdf

Abstract: "We consider the scientifically challenging and policy-relevant task of understanding the past and projecting the future dynamics of the Antarctic ice sheet. The Antarctic ice sheet has shown a highly nonlinear threshold response to past climate forcings. Triggering such a threshold response through anthropogenic greenhouse gas emissions would drive drastic and potentially fast sea level rise with important implications for coastal flood risks. Previous studies have combined information from ice sheet models and observations to calibrate model parameters. These studies have broken important new ground but have either adopted simple ice sheet models or have limited the number of parameters to allow for the use of more complex models. These limitations are largely due to the computational challenges posed by calibration as models become more computationally intensive or when the number of parameters increases. Here we propose a method to alleviate this problem: a fast sequential Monte Carlo method that takes advantage of the massive parallelization afforded by modern high performance computing systems. We use simulated examples to demonstrate how our sample-based approach provides accurate approximations to the posterior distributions of the calibrated parameters. The drastic reduction in computational times enables us to provide new insights into important scientific questions, for example, the impact of Pliocene era data and prior parameter information on sea level projections. These studies would be computationally prohibitive with other computational approaches for calibration such as Markov chain Monte Carlo or emulation-based methods. We also find considerable differences in the distributions of sea level projections when we account for a larger number of uncertain parameters."

Extract: "We chose these three parameters because they are considered to be important in modeling the long-term evolution of the Antarctic ice sheet (Edwards et al., 2019; DeConto and Pollard, 2016).

Calibration can be improved by considering an important source of uncertainty, the state of the Antarctic ice sheet during the Pliocene era …

This method includes the recent study of Edwards et al. (2019), who found that the important mechanism of marine ice cliff instability (MICI) is not necessary to capture past variations.  In this case, future sea level projections are considerably lower.  In contract, our new approach that accounts for more parametric uncertainties suggests that MICI may still be important and future sea level projections may be much higher, especially considering potential Pliocene windows."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1090 on: May 14, 2019, 12:27:16 AM »
The linked reference discusses a novel hypothesis associated the geothermal heat flux from beneath the GIS that is associated with the Iceland hot spot that passed under north-central Greenland 80 to 35 million years ago.  This hypothesis indicates that the geothermal heat flux across a broad swath of north‐central Greenland may (or may not) be higher than previously assumed by consensus climate science.  If we are unlucky, this potentially higher geothermal heat flux may help to destabilize portions of the north-central GIS this century:

R. B. Alley, D. Pollard, B. R. Parizek, S. Anandakrishnan, M. Pourpoint, N. T. Stevens, J. A. MacGregor, K. Christianson, A. Muto, N. Holschuh. Possible Role for Tectonics in the Evolving Stability of the Greenland Ice Sheet. Journal of Geophysical Research: Earth Surface, 2019; DOI: 10.1029/2018JF004714

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JF004714

Abstract

The history of the Greenland Ice Sheet has been influenced by the geodynamic response to ice sheet fluctuations, and this interaction may help explain past deglaciations under modest climate forcing. We hypothesize that when the Iceland hot spot passed beneath north‐central Greenland, it thinned the lithosphere and left anomalous heat likely with partially melted rock; however, it did not break through the crust to supply voluminous flood basalts. Subsequent Plio‐Pleistocene glacial‐interglacial cycles caused large and rapidly migrating stresses, driving dike formation and other processes that shifted melted rock toward the surface. The resulting increase in surface geothermal flux favored a thinner, faster‐responding ice sheet that was more prone to deglaciation. If this hypothesis of control through changes in geothermal flux is correct, then the long‐term (105 to 106 years) trend now is toward lower geothermal flux, but with higher‐frequency (≤104 to 105 years) oscillations linked to glacial‐interglacial cycles. Whether the geothermal flux is increasing or decreasing now is not known but is of societal relevance due to its possible impact on ice flow. We infer that projections of the future of the ice sheet and its effect on sea level must integrate geologic and geophysical data as well as glaciological, atmospheric, oceanic, and paleoclimatic information.

Plain Language Summary

The behavior of the Greenland Ice Sheet and its effect on future sea level depends on its geologic history as well as on greenhouse warming. The Iceland hot spot passed beneath Greenland millions of years ago, and left hot, possibly melted rock deep beneath the island. Since then, growth and shrinkage of the ice sheet have changed stresses in the rocks beneath. These stress changes may have shifted the melted rock upward, perhaps all the way to the base of the ice sheet, probably in pulses tied to times of rapid ice sheet change. This would have changed the heat flow from the Earth into the base of the ice, which affects how easily the ice sheet grows and shrinks. The future of the ice sheet depends primarily on how much the climate warms, but better understanding of the interactions between the ice and the rocks beneath will allow better predictions of ice sheet changes.

Extract: "Averaged over these glacial‐interglacial cycles, the geothermal flux at the surface rose to an early Pleistocene maximum and is now decreasing, although the geothermal flux remains notably elevated with locally very high values today. As discussed below, higher geothermal flux makes deglaciation easier, by increasing basal melting of the ice to generate lubricating water.

As discussed above, a broad swath across north‐central Greenland exhibits elevated geothermal flux, with locally greatly elevated flux. This is hypothesized to have given rise to anomalously thawed beds and lubricated ice, and thus an ice sheet that is thinner and more responsive than it otherwise would be (MacGregor et al., 2016; Rogozhina et al., 2016).

Most individual elements of this hypothesis have been articulated in previous studies, but the full exposition here may be novel.
1.   Passage of the Iceland hot spot beneath Greenland contributed to rifting and voluminous volcanism in the western and eastern Tertiary flood basalt provinces at and before the Paleocene‐Eocene Thermal Maximum ~56 Ma. This thinned the lithosphere in central Greenland, perhaps exploiting a preexisting geological boundary, but did not break through in central regions to erupt voluminous lavas there, instead leaving anomalously hot rock along the hot spot track, likely with partial melt.
2.   The extended Iceland hot spot continued to interact with Greenland long after the center of the hot spot moved to the east, interactions that may still continue, likely with flow from the hot spot channeling back along the hot spot track.
3.   The onset of glacial‐interglacial cycling, and subsequent increases in amplitude of GIS changes, generated large differential stresses in the lithosphere of Greenland, and also caused large variations in melt fraction left by the hot spot. Together, these shifted melted rock shallower, or all the way to the base of the ice.
4.   Because the extended hot spot had largely moved away from Greenland, however, and thus was no longer present to fully replenish melt extracted from the mantle, a rise in geothermal flux at the base of the ice sheet from melt migration should have been followed by a decline, although with higher‐frequency oscillations linked to glacial‐interglacial cycling interacting with remaining heat and melt.
5.   In turn, this may help explain why the Holocene experienced relatively little change in GIS but earlier interglacials caused near‐complete deglaciation.

We note that this hypothesis does not predict whether ice sheet stability should be increasing or decreasing over the decadal‐to‐millennial timescales of greatest present interest to society …"

See also:

Title: "Novel hypothesis goes underground to predict future of Greenland ice sheet"

https://www.sciencedaily.com/releases/2019/02/190202171847.htm

Extract: ""The hypothesis does not change the reality that if we make it hot, Greenland's ice melts, and no one will like that," Alley said. "It does not even really tell us whether geology just at this moment is making it harder or easier for the ice to melt. The ability of the ice to melt got easier in the past and is sort of bumpily getting harder, and we do not know where on the bumps we are.""
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1091 on: May 15, 2019, 11:02:52 PM »
In the linked article Rolf Schettenhelm focuses on IPCC SR15 to discuss the benefits of keeping GMSTA below 1.5C.  In this discussion Rolf notes that IPCC SR15 does not have terribly alarming SLR projections through 2100, until one comes to the caveat sections of IPCC SR15 (see extracts below).  In these caveats it is noted that on the millennial time-scale a 1.5C rise for GMSTA may be sufficient for several tens of meters of SLR contribution from the three ice sheets (GIS, WAIS & EAIS); and that under high-emission RCP scenarios (like RCP 8.5); this amount of ice mass loss from the WAIS and EAIS this century is highly dependent upon the model details.  Such IPCC caveats acknowledge a significant climate risk from SLR, that may be too late to reverse, if adequate climate action is not taken immediately:

Title: "Understanding Sea Level Rise 6: SLR benefits of keeping warming below 1.5 degrees (IPCC & Pattyn)"

http://www.bitsofscience.org/sea-level-rise-benefits-1-5-degrees-ipcc-7986/

Extract: "Also for the West-Antarctic ice sheet and large portions of the East-Antarctic ice sheet possible tipping points for complete melting are assessed. The precise position of associated thresholds is highly uncertain and dependent on future emissions. According to IPCC SR15 under the most favourable emissions scenario (concentration pathway RCP2.6) passing of Antarctic tipping points may still be prevented:

“The Antarctic ice sheet, in contrast, loses the mass gained by snowfall as outflow and subsequent melt to the ocean, either directly from the underside of floating ice shelves or indirectly by the melting of calved icebergs. The long-term existence of this ice sheet will also be affected by a potential instability (the marine ice sheet instability, MISI), which links outflow (or mass loss) from the ice sheet to water depth at the grounding line (i.e., the point at which grounded ice starts to float and becomes an ice shelf) so that retreat into deeper water (the bedrock underlying much of Antarctica slopes downwards towards the centre of the ice sheet) leads to further increases in outflow and promotes yet further retreat (Schoof, 2007). More recently, a variant on this mechanism was postulated in which an ice cliff forms at the grounding line and retreats rapidly though fracture and iceberg calving (DeConto and Pollard, 2016). There is a growing body of evidence (Golledge etal., 2015; DeConto and Pollard, 2016) that large-scale retreat may be avoided in emissions scenarios such as Representative Concentration Pathway (RCP) 2.6 but that higher-emissions RCP scenarios could lead to the loss of the West Antarctic ice sheet and sectors in East Antarctica, although the duration (centuries or millennia) and amount of mass loss during such a collapse is highly dependent on model details and no consensus exists yet.”

Nonetheless also for Antarctica it is supposed that tipping points for complete melting of major ice sheet sections can lie between 1.5 and 2 degrees global average temperature rise:
“The long-term committed future of Antarctica and the GMSL contribution at 2100 are complex and require further detailed process-based modelling; however, a threshold in this contribution may be located close to 1.5°C to 2°C of global warming.”

Summarising the above there is a real chance that tipping points for melting of both Greenland and Antarctica could lie between 1.5 and 2 degrees. It is difficult though to attach specific values for global average sea level rise to these tipping points:

“In summary, there is medium confidence that a threshold in the long-term GMSL contribution of both the Greenland and Antarctic ice sheets lies around 1.5°C to 2°C of global warming relative to pre-industrial; however, the GMSL associated with these two levels of global warming cannot be differentiated on the basis of the existing literature.”"
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1092 on: May 15, 2019, 11:25:54 PM »
With a hat-tip to vox_mundi, the linked article and associated reference, discusses a number of relatively recent paleo multi-century-scale abrupt deep-water warming events associated with a slowing of the MOC/AMOC.  Further it notes that one such abrupt multi-century-scale deep-water slowing event has been underway for the about the last century and that: 'If further weakening happens in the future, there may be unexpectedly broad implications not only on our atmospheric and ocean systems, but also on Earth's ecological systems and our society.'

Regarding Dr. Yasuhara's comment that such multi-century-scale MOC slowing event may broadly change our atmosphere; indicates to me that if the WAIS were to begin a MICI-type of collapse beginning around 2040; then we could see abrupt changes in the atmosphere, such as the significant telecommunication of energy associated with water evaporation from the tropical oceans moving rapidly poleward through the atmosphere.  This represents a significant climate risk to the stability of modern society.

Title: "Century-Scale Deep-Water Circulation Dynamics in the North Atlantic Ocean"

https://phys.org/news/2019-05-century-scale-deep-water-circulation-dynamics-north.html

Extract: "Dr. Yasuhara and his collaborators showed that subtropical North Atlantic intermediate-water temperature varied significantly during both of these time periods, based on trace element geochemistry of calcified shells of deep-sea microcrustacean Ostracoda in a sediment core. Their reconstructions reveal a series of multi-century-scale abrupt deep-water warming events likely caused by the reduction deep-water circulation. The authors also discovered that many of these weakening events of deep-water circulation can be widely recognized in the western North Atlantic.

Lead author of the study Dr. Yasuhara said "Holocene deep-water circulation was more dynamic than previously thought. There is increasing evidence that this circulation change in the North Atlantic affects climates of remote places including East Asia and also marine and terrestrial ecosystems. As recently discovered by scientists including my HKU colleagues Drs Benoit Thibodeau and Christelle Not, this global deep-water circulation has substantially weakened during the last century. If further weakening happens in the future, there may be unexpectedly broad implications not only on our atmospheric and ocean systems, but also on Earth's ecological systems and our society."

See also:

Moriaki Yasuhara et al. (2019), "North Atlantic intermediate water variability over the past 20,000 years", Geology, https://doi.org/10.1130/G46161.1

https://pubs.geoscienceworld.org/gsa/geology/article-abstract/570484/north-atlantic-intermediate-water-variability-over

Abstract: "North Atlantic intermediate-water temperature variations based on ostracod Mg/Ca ratios from Ocean Drilling Program (ODP) Hole 1055B document a series of multi-centennial-scale abrupt warming events throughout the last deglaciation and Holocene (up to ~3 °C). These events are coherent with abrupt climate reversals including Heinrich event 1, the Younger Dryas–Intra-Allerød cold period, and Holocene North Atlantic Deep Water (NADW) reduction periods. Deglacial–Holocene warm events were likely related to reduction in the strength of the upper NADW (Labrador Sea Water). We also found a long-term cooling trend in the ODP 1055 Mg/Ca record indicating continuous Labrador Sea Water strengthening throughout the Holocene. Our results help to better understand deglacial–Holocene upper NADW dynamics that remain poorly understood but can be important for regional and global climates."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1093 on: May 16, 2019, 03:53:55 AM »
Whether one agrees with Tamsin Edwards, or not, she is a lead author of the IPCC AR6, so it is worth watching the following 2018 video entitled: "How soon will the ice apocalypse come? (CCCR2018)", that she presented at the 2018 Cambridge Conference on Catastrophic Risk:


« Last Edit: May 16, 2019, 04:57:22 PM by AbruptSLR »
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kiwichick16

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1094 on: May 16, 2019, 07:58:44 AM »
all well and good .....just missed the bit about the rate of GHG emissions being 10x (???) greater than any historic record   

Rich

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1095 on: May 16, 2019, 11:17:33 AM »
Where one agrees with Tamsin Edwards, or not, she is a lead author of the IPCC AR6, so it is worth watching the following 2018 video entitled: "How soon will the ice apocalypse come? (CCCR2018)", that she presented at the 2018 Cambridge Conference on Catastrophic Risk:


[/qu wasote]

Thanks for sharing. I wasn't exactly impressed with her presentation.

She seemed quite nervous. The references to Meltwater Pulse 1A as providing any kind of upper bound seem spurious. She correctly points out that the ice lost during MWP1A no longer exists. Wee're contemplating the loss of a completely differently layer of Earth's ice today. There is no way for us to equate the sensitivities of the various layers and the next one may be more or less sensitive than the last.

She seemed to acknowledge and then dismiss the 6-9 meter higher sea levels of 100k years ago which Rignot speaks to. How are we ruling that out? Her presentation skates on that.

The thing I'm seeing. 20th century average slr ~ 1-1.5 mm / year. 1993 begins the satellite era and we bump up to 3mm / yr until 2010.

2011 - 2015 we have a 54 month period where slr increases 36mm !! That's 8mm / yr. 2016 we get an El Nino and no slr as heat is vented to the atmosphere. 2017 we get another 8 mm.

Where's the water coming from to support the recent more rapid increase in slr in the current decade? It seems the sample size isn't long enough to generate serious discussion. I'm on the lookout for the emergence of a potential hockey stick.

Rich

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1096 on: May 16, 2019, 12:50:41 PM »
Curious ..how does someone get appointed to become lead author of the AR6 section which covers sea level rise?

Who is making the hiring decision?

Sleepy

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1097 on: May 16, 2019, 03:26:37 PM »
I am.

Nah, expert nominations are presented by Governments, Observer Organizations and IPCC Bureau members. They are requested to submit their nominations via their focal points, for Sweden it's Markku Rummukainen so there's one for each country.

There's a full list of 'everything' at ipcc.ch, well documented for everyone.
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FishOutofWater

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1098 on: May 16, 2019, 04:40:48 PM »
She blogged about that story here:
https://blogs.plos.org/models/how-soon-will-the-ice-apocalypse-come/
It's much quicker to read it than watch a freaking video.

She's clearly very smart with a PhD in particle physics. She's clearly an expert at physical modelling. What she appears to lack is training in the earth or ocean sciences. Brilliant physicists who are modelling experts may not have the same appreciation for how the earth works as someone who has done a large amount of field study. At least, that's my personal experience.

bluice

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #1099 on: May 16, 2019, 05:09:41 PM »
I've learned a lot thanks to this topic, and my personal feeling is that future SLR is greatly underestimated due to uncertainties in the science behind it.

However most papers about marine ice sheet instabilities seem to be written by or referring to papers written by Pollard and DeConto. Is MISI/MICI type scenarios only a two man show and are their results approved or contested by other experts? I'm asking because I don't know and not to start a flame war :)
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