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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #4150 on: February 19, 2021, 03:51:30 PM »
While glaciovolcanism (defined as “the interactions of magma with ice in all its forms, including snow, firn and any meltwater”), may still be in its infancy; nevertheless, I provide the following links to relevant information (& two images about geomagnetism), and I note that there is more information in the 'Antarctic Tectonics' thread in the Antarctic folder; for those who are interested in learning more about this topic:

J.L. Smellie (2018), "Chapter 10 – Glaciovolcanism: A 21st Century Proxy for Palaeo-Ice",
Past Glacial Environments (Second Edition), Pages 335–375, https://doi.org/10.1016/B978-0-08-100524-8.00010-5

https://www.sciencedirect.com/science/article/pii/B9780081005248000105

Abstract: "Glaciovolcanism is a young science that has undergone a major transformation during the last 15 years. It is important for a variety of reasons but it is set to play a major role in deriving critical parameters of past ice sheets and thus greatly improve the accuracy of their reconstruction. Glaciovolcanic studies can deduce a wider range of parameters than any other methodology currently existing, including: establishing the presence of ice, its age, ice thickness, ice surface elevation, and basal thermal regime. These attributes can be acquired routinely for many glaciovolcanic sequences and, uniquely, several are quantifiable. Most glaciovolcanic terrains provide punctuated rather than continuous records of the coeval ice sheet, i.e., with numerous time gaps. Despite the gaps, glaciovolcanic studies of ice sheets have been completed successfully in the three major glaciovolcanic regions of the Earth: mainly Antarctica, but also Iceland and British Columbia (Canada). Future studies in these and other glaciovolcanic regions will considerably improve our knowledge of Earth’s water inventory and contribute to a better understanding of past ice dynamics and the impact of the cryosphere on global climate."

&

Title: "Antarctic Glaciovolcanism:

https://www2.le.ac.uk/departments/geology/people/smellie-jl/personal/ant-glaciovolc
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #4151 on: February 19, 2021, 03:52:32 PM »
The linked articles confirm that not only are the Earth's rotation poles wandering rapidly, but so are its magnetic poles:

Title: "Shifting Ice Caps - Magnetic Poles and Ice Caps move in Tandem"

https://planet-earth-2017.com/wandering-poles/

Extract: "“The rate of the magnetic pole’s movement has increased in the last  century compared with fairly steady movement in the previous four centuries”, said Joseph Stoner and the Oregon researchers."

See also:

Title: "Magnetic north pole drifting fast"

http://news.bbc.co.uk/2/hi/science/nature/4520982.stm

Extract: " The Earth's north magnetic pole is drifting away from North America so fast that it could end up in Siberia within 50 years, scientists have said."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #4152 on: February 19, 2021, 04:01:07 PM »
My guess is the polar wander caused by ice melt is just noise in the ancient signal.

RoxTheGeologist,

Thank you for your thoughtful comments, and you may well be correct that ice mass redistribution from an abrupt collapse of the WAIS to the oceans of the world, might not be a sufficient trigger to accelerate the current ongoing weakening of the global geomagnetic fields.  Nevertheless, have you considered the distinctive geomagnetic field lines in the Southern Hemisphere (shown in the last image of Reply #115) and the rather unique geology beneath the WAIS as indicated by the following information which comes from the 'Antarctic Tectonics' thread with the first two images in this post coming from:

http://www.largeigneousprovinces.org/apr13

"The links between large igneous provinces, and continental break-up: evidence reviewed from Antarctica" by: Bryan C Storey,  Alan P M Vaughan and Teal R Riley; April 2013
Gateway Antarctica, Private Bag 4800, University of Canterbury, Christchurch, New Zealand; bryan.storey@canterbury.ac.nz

The first attached image shows:  Middle Jurassic Gondwana reconstruction showing three large igneous provinces (after Storey & Kyle 1997); Ferrar, Karoo and Chon Aike, and the location of the Weddell Sea Triple Junction (WSTJ) after Elliot & Fleming 2000.  DML, Dronning Maud Land; FI, Falkland Islands

The second attached image shows:  Antarctic map showing the Transantarctic Mountains as the rift shoulder of the West Antarctic Rift System (WARS), the related Cenozoic alkaline magmatic province (WARS volcanoes), the outline of the Middle Jurassic Ferrar magmatic province and the outline of the mid Cretaceous alkaline magmatism in Marie Byrd Land.

The third image shows a map of Antarctica with the relief of the crust thickness below it's ice as indicated by seismic data. Abbreviations: DML, Dronning Maud Land; GSM, Gamburtsev Subglacial Mountains.  CREDIT: Baranov, A., Morelli, A., The Moho depth map of the Antarctica region, Tectonophysics (2013).

The fourth image shows the modeled internal structure of the lithosphere in West Antarctica, showing a major source of heat from the upper mantle.

Best regards,
ASLR
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #4153 on: February 19, 2021, 04:10:31 PM »
The linked reference, and associate article, indicate that '… a geomagnetic pulse under South America in 2016 shifted the magnetic field unexpectedly …'; which may have triggered '… a high-speed jet of liquid iron beneath Canada…'; which may have weakened the magnetic field beneath Canada, allowing the high-strength magnetic field beneath Siberia to accelerate the migration of the magnetic north pole towards Siberia since 2016.  Whether the acceleration in magnetic polar wander shown in the first attached image (from Nature 2019) is related to the high magnetic anomaly in the South Atlantic, see the second image (and Replies #113, #115 & #117), and thus possibly to Antarctic ice mass loss, is a matter worth investigating.

Title: "Earth's magnetic field is acting up and geologists don't know why"

https://www.nature.com/articles/d41586-019-00007-1?utm_source=twt_nnc&utm_medium=social&utm_campaign=naturenews&sf205680051=1

Extract: "First, that 2016 geomagnetic pulse beneath South America came at the worst possible time, just after the 2015 update to the World Magnetic Model.

… scientist are working to understand why the magnetic field is changing so dramatically. Geomagnetic pulses, like the one that happened in 2016, might be traces back to 'hydromagnetic' waves arising from deep in the core.  And the fast motion of the north magnetic pole could be linked to a high-speed jet of liquid iron beneath Canada."

See also:

Earth's Magnetic Field has Moved Unexpectedly and Scientists Aren't Sure Why

https://www.newsweek.com/earth-magnetic-field-baffle-scientists-north-pole-siberia-canada-world-1286507

Extract: "Earth’s north magnetic pole is moving fast and in an unexpected way, baffling scientists involved in tracking its motions

"The error is increasing all the time,” Arnaud Chulliat, a geomagnetist at the University of Colorado Boulder and the National Oceanic and Atmospheric Administration (NOAA), told Nature. He said finding out the WMM had become inaccurate placed scientists in an “interesting situation” with experts wondering just what was going on.

According to Nature, a geomagnetic pulse under South America in 2016 shifted the magnetic field unexpectedly. This was exacerbated by the movement of the north magnetic pole. “The fact that the pole is going fast makes this region more prone to large errors,” Chulliat is quoted as saying.

Researchers are now trying to work out why the magnetic field is changing so quickly. They are studying the geomagnetic pulses, like the one that disrupted the WMM in 2016, which could, Nature reports, be the result of “hydromagnetic” waves emanating from Earth’s core.

To fix the World Magnetic Model, he and his colleagues fed it three years of recent data, which included the 2016 geomagnetic pulse. The new version should remain accurate, he says, until the next regularly scheduled update in 2020."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #4154 on: February 19, 2021, 04:12:12 PM »
Whether the acceleration in magnetic polar wander shown in the first attached image (from Nature 2019) is related to the high magnetic anomaly in the South Atlantic, see the second image (and Replies #113, #115 & #117), and thus possibly to Antarctic ice mass loss, is a matter worth investigating.

Maybe this could contribute to an explanation:
http://advances.sciencemag.org/content/2/4/e1501693

“We analyze space geodetic and satellite gravimetric data for the period 2003–2015 to show that all of the main features of polar motion are explained by global-scale continent-ocean mass transport. The changes in terrestrial water storage (TWS) and global cryosphere together explain nearly the entire amplitude (83 ± 23%) and mean directional shift (within 5.9° ± 7.6°) of the observed motion. We also find that the TWS variability fully explains the decadal-like changes in polar motion observed during the study period, thus offering a clue to resolving the long-standing quest for determining the origins of decadal oscillations. This newly discovered link between polar motion and global-scale TWS variability has broad implications for the study of past and future climate.”

The Nature article doesn't seem to mention this possibility?
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #4155 on: February 19, 2021, 04:13:35 PM »
Re: the risk that ice sheet mass loss may be associated with this recent increase in the rate of drift [of the north magnetic pole]

This ice mass loss directly affects the rotation pole, not the magnetic pole. If they were locked together the drift would be the same for both, but they are not. A citation for a relation between the two poles would be helpful.
...

sidd

As I have stated previously:

Regarding correlating true polar wander (shifting of the Earth's rotational axis) and magnetic field reversals and mass redistribution around the Earth: I provide the first linked reference that provides paleo evidence that during periods of little polar wander there is reduced activity of magnetic pole flipping; while the second linked article makes it clear that polar wander is associated with all mass (ice, sea level, groundwater, isostatic rebound) redistribution.

Courtillot V & Besse J. (1987 Sep 4), "Magnetic field reversals, polar wander, and core-mantle coupling", Science vol 237, issue (4819), pp 1140-7, DOI:10.1126/science.237.4819.1140

http://science.sciencemag.org/content/237/4819/1140

Abstract: "True polar wander, the shifting of the entire mantle relative to the earth's spin axis, has been reanalyzed. Over the last 200 million years, true polar wander has been fast (approximately 5 centimeters per year) most of the time, except for a remarkable standstill from 170 to 110 million years ago. This standstill correlates with a decrease in the reversal frequency of the geomagnetic field and episodes of continental breakup. Conversely, true polar wander is high when reversal frequency increases. It is proposed that intermittent convection modulates the thickness of a thermal boundary layer at the base of the mantle and consequently the core-to-mantle heat flux. Emission of hot thermals from the boundary layer leads to increases in mantle convection and true polar wander. In conjunction, cold thermals released from a boundary layer at the top of the liquid core eventually lead to reversals. Changes in the locations of subduction zones may also affect true polar wander. Exceptional volcanism and mass extinctions at the Cretaceous-Tertiary and Permo-Triassic boundaries may be related to thermals released after two unusually long periods with no magnetic reversals. These environmental catastrophes may therefore be a consequence of thermal and chemical couplings in the earth's multilayer heat engine rather than have an extraterrestrial cause."

&

Title: "Climate Change Is Moving the North Pole"

https://news.nationalgeographic.com/2016/04/160408-climate-change-shifts-earth-poles-water-loss/

Extract: "As ice melts and aquifers are drained, Earth's distribution of mass is changing—and with it the position of the planet's spin axis."


Also, see the following reference which indicates that about 66% of the polar wander over the indicated period was due to rapid changes in ice mass loss:

Surendra Adhikari and Erik R. Ivins (08 Apr 2016), "Climate-driven polar motion: 2003–2015", Science Advances, Vol. 2, no. 4, e1501693, DOI: 10.1126/sciadv.1501693

http://advances.sciencemag.org/content/2/4/e1501693

Abstract: "Earth’s spin axis has been wandering along the Greenwich meridian since about 2000, representing a 75° eastward shift from its long-term drift direction. The past 115 years have seen unequivocal evidence for a quasi-decadal periodicity, and these motions persist throughout the recent record of pole position, in spite of the new drift direction. We analyze space geodetic and satellite gravimetric data for the period 2003–2015 to show that all of the main features of polar motion are explained by global-scale continent-ocean mass transport. The changes in terrestrial water storage (TWS) and global cryosphere together explain nearly the entire amplitude (83 ± 23%) and mean directional shift (within 5.9° ± 7.6°) of the observed motion. We also find that the TWS variability fully explains the decadal-like changes in polar motion observed during the study period, thus offering a clue to resolving the long-standing quest for determining the origins of decadal oscillations. This newly discovered link between polar motion and global-scale TWS variability has broad implications for the study of past and future climate."

Also here are some other background references:

1. Adam C. Maloof Galen P. Halverson Joseph L. Kirschvink Daniel P. Schrag Benjamin P. Weiss Paul F. Hoffman (2006), "Combined paleomagnetic, isotopic, and stratigraphic evidence for true polar wander from the Neoproterozoic Akademikerbreen Group, Svalbard, Norway",  GSA Bulletin, 118 (9-10): 1099-1124, DOI: https://doi.org/10.1130/B25892.1

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/118/9-10/1099/125331/combined-paleomagnetic-isotopic-and-stratigraphic?redirectedFrom=fulltext

Abstract: "We present new paleomagnetic data from three Middle Neoproterozoic carbonate units of East Svalbard, Norway. The paleomagnetic record is gleaned from 50 to 650 m of continuous, platformal carbonate sediment, is reproduced at three locations distributed over >100 km on a single craton, and scores a 5–6 (out of 7) on the Van der Voo (1990) reliability scale. Two >50° shifts in paleomagnetic direction are coincident with equally abrupt shifts in δ13C and transient changes in relative sea level. We explore four possible explanations for these coincidental changes: rapid plate tectonic rotation during depositional hiatus, magnetic excursions, nongeocentric axial-dipole fields, and true polar wander. We conclude that the observations are explained most readily by rapid shifts in paleogeography associated with a pair of true polar wander events. Future work in sediments of equivalent age from other basins can test directly the true polar wander hypothesis because this type of event would affect every continent in a predictable manner, depending on the continent's changing position relative to Earth's spin axis."

2. J. R. Creveling, J. X. Mitrovica, N.-H. Chan, K. Latychev & I. Matsuyama (08 November 2012), "Mechanisms for oscillatory true polar wander", Nature, volume 491, pages 244–248,
doi:10.1038/nature11571

http://www.nature.com/articles/nature11571

Abstract: "Palaeomagnetic studies of Palaeoproterozoic to Cretaceous rocks propose a suite of large and relatively rapid (tens of degrees over 10 to 100 million years) excursions of the rotation pole relative to the surface geography, or true polar wander (TPW). These excursions may be linked in an oscillatory, approximately coaxial succession about the centre of the contemporaneous supercontinent. Within the framework of a standard rotational theory, in which a delayed viscous adjustment of the rotational bulge acts to stabilize the rotation axis, geodynamic models for oscillatory TPW generally appeal to consecutive, opposite loading phases of comparable magnitude. Here we extend a nonlinear rotational stability theory to incorporate the stabilizing effect of TPW-induced elastic stresses in the lithosphere. We demonstrate that convectively driven inertia perturbations acting on a nearly prolate, non-hydrostatic Earth with an effective elastic lithospheric thickness of about 10 kilometres yield oscillatory TPW paths consistent with palaeomagnetic inferences. This estimate of elastic thickness can be reduced, even to zero, if the rotation axis is stabilized by long-term excess ellipticity in the plane of the TPW. We speculate that these sources of stabilization, acting on TPW driven by a time-varying mantle flow field, provide a mechanism for linking the distinct, oscillatory TPW events of the past few billion years."

To learn how much the North Pole has shifted in the recent decades due to rapid ice mass loss, see Chen, J..L., C.R. Wilson, J.C. Ries, B.D. Tapley, Rapid ice melting drives Earth's pole to the east, Geophys. Res. Lett., Vol. 40, 1-6, DOI: 10.1002/grl.50552, 2013; which can be found at the prime author's website at the University of Texas, where you can download a preprint (made available by the author):

http://www.csr.utexas.edu/personal/chen/publication.html

and here is a link directly to the preprint pdf:

ftp://ftp.csr.utexas.edu/pub/ggfc/papers/2013GL056164_preprint.pdf

Edit: Also, per Reply #166, RoxTheGeologist states:

"The first paper speculates that there is a causative mechanism that is due to changes in mantle/core boundary conditions, the dynamic convection changes in the mantle altering the shape of the earth and causing polar wander, and correlating with magnetic pole reversals from thermal changes at the core mantle boundary. The paper discussing convective changes backs up the fact that you get polar reversals when the convective pattern of the mantle changes. "
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #4156 on: February 19, 2021, 04:15:19 PM »
Re: magnetic pole movement

If magnetic pole wander is related to land ice mass loss, is there evidence from the Eemian or other interglacials ?

sidd

I imagine that it is better to think of relationship of ice sheet mass loss to magnetic polar wander is more a matter of changes in probability and dynamics (and/or chaos theory response) rather than a one to one correlation.  That said as I noted earlier the Laschamp events happened about 41,000 years ago during the last glacial maximum, LGM, so it would seem probably that the change in the ice sheets from the Eemian to the LGM may well have impacted these Laschamp events:

Title: "An extremely brief reversal of the geomagnetic field, climate variability and a super volcano"

https://phys.org/news/2012-10-extremely-reversal-geomagnetic-field-climate.html

Extract: "41,000 years ago, a complete and rapid reversal of the geomagnetic field occurred."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #4157 on: February 19, 2021, 04:17:15 PM »
Maybe this is a sign of a geomagnetic reversal this millennium?

Per the first linked article, in extreme cases, magnetic pole reversals took less than 100 years and per the second linked article true polar wander can trigger can ice sheet formation; thus it is logical that the abrupt loss of an ice sheet like the WAIS might possibly trigger a magnetic pole reversal this century (in an extreme case):

Title: "Shifting Magnetic North may be caught in 'tug of war' between Canada and Siberia"

https://www.theweathernetwork.com/ca/news/article/shifting-magnetic-north-pole-caught-in-tug-of-war-between-canada-siberia-blobs

Extract: "Based on the width of the sea-floor bands, in extreme cases, some pole reversals took less than 100 years. Some lasted only around 200 years before they flipped back.

&

Title: "'True polar wander' may have caused ice age"

https://www.sciencedaily.com/releases/2018/11/181119160239.htm

Extract: "Like any spinning object, Earth is subject to centrifugal force, which tugs on the planet's fluid interior. At the equator, where this force is strongest, Earth is more than 26 miles larger in diameter than at the poles. Gordon said true polar wander may occur when dense, highly viscous bumps of mantle build up at latitudes away from the equator."

If the mantle anomalies are massive enough, they can unbalance the planet, and the equator will gradually shift to bring the excess mass closer to the equator. The planet still spins once every 24 hours and true polar wander does not affect the tilt of the Earth's spin axis relative to the sun. The redistribution of mass to a new equator does change Earth's poles, the points on the planet's surface where the spin axis emerges.

Woodworth said the hot spot data from Hawaii provides some of the best evidence that true polar wander was what caused Earth's poles to start moving 12 million years ago. Islands chains like the Hawaiians are formed when a tectonic plate moves across a hot spot."

Edit, see also:

Daniel Woodworth, Richard G. Gordon. Paleolatitude of the Hawaiian Hot Spot Since 48 Ma: Evidence for a Mid-Cenozoic True Polar Stillstand Followed by Late Cenozoic True Polar Wander Coincident With Northern Hemisphere Glaciation. Geophysical Research Letters, 2018; DOI: 10.1029/2018GL080787

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL080787

Abstract
Paleospin axis locations since 48 Ma inferred from the distribution of equatorial sediment accumulation rates on the Pacific plate, together with paleomagnetic poles from magnetic anomaly skewness, indicate that the Hawaiian hot spot was nearly fixed in latitude from 48 to 12 Ma, but ≈3° north of its current latitude. From 48 to 12 Ma in the Pacific hot spot reference frame, which we take to be equivalent to the global hot spot reference frame, the spin axis was located near 87°N, 164°E, recording a stillstand in true polar wander. Global hot spots shifted coherently relative to the spin axis since ≈12 Ma, consistent with an episode of true polar wander, which may continue today. The motion of the spin axis away from the Hawaiian hot spot and toward Greenland since ≈12 Ma coincided with, and may have contributed to, the onset of northern hemisphere glaciation.

Plain Language Summary
The Earth has shifted relative to its spin axis over the past 12 million years (Ma). This shift, which geoscientists call true polar wander, caused the Earth's mantle beneath the tropical Pacific to move southward while causing Greenland to move northward. The latter motion may have contributed to the onset of the current ice age, which began ≈3 Ma before present. These conclusions follow our analysis of the history of motion of the Pacific tectonic plate relative to the spin axis, which is preserved in sediments and rocks on the Pacific seafloor. We also infer the motion of the Pacific plate relative to the solid Earth from the plate's history of motion relative to hot spots, such as Hawaii. Hot spots are sites of voluminous volcanism, thought to lie over rising plumes of hot rock from deep in the Earth's mantle. As the Pacific plate moves over the Hawaiian plume, it creates a line of extinct volcanoes that record the motion of the plate relative to the plume. Combining this information, we find that Hawaii and other global hot spots were nearly fixed in latitude from 48 to 12 Ma before present, which marks a 36‐Ma‐long time interval preceding the shift.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #4158 on: February 19, 2021, 04:18:45 PM »
The linked reference, and associate article, indicate that '… a geomagnetic pulse under South America in 2016 shifted the magnetic field unexpectedly …'; which may have triggered '… a high-speed jet of liquid iron beneath Canada…'; which may have weakened the magnetic field beneath Canada, allowing the high-strength magnetic field beneath Siberia to accelerate the migration of the magnetic north pole towards Siberia since 2016.  Whether the acceleration in magnetic polar wander shown in the first attached image (from Nature 2019) is related to the high magnetic anomaly in the South Atlantic, see the second image (and Replies #113, #115 & #117), and thus possibly to Antarctic ice mass loss, is a matter worth investigating.

Title: "Earth's magnetic field is acting up and geologists don't know why"

https://www.nature.com/articles/d41586-019-00007-1?utm_source=twt_nnc&utm_medium=social&utm_campaign=naturenews&sf205680051=1

Extract: "First, that 2016 geomagnetic pulse beneath South America came at the worst possible time, just after the 2015 update to the World Magnetic Model.

… scientist are working to understand why the magnetic field is changing so dramatically. Geomagnetic pulses, like the one that happened in 2016, might be traces back to 'hydromagnetic' waves arising from deep in the core.  And the fast motion of the north magnetic pole could be linked to a high-speed jet of liquid iron beneath Canada."

See also:

Earth's Magnetic Field has Moved Unexpectedly and Scientists Aren't Sure Why

https://www.newsweek.com/earth-magnetic-field-baffle-scientists-north-pole-siberia-canada-world-1286507

Extract: "Earth’s north magnetic pole is moving fast and in an unexpected way, baffling scientists involved in tracking its motions

"The error is increasing all the time,” Arnaud Chulliat, a geomagnetist at the University of Colorado Boulder and the National Oceanic and Atmospheric Administration (NOAA), told Nature. He said finding out the WMM had become inaccurate placed scientists in an “interesting situation” with experts wondering just what was going on.

According to Nature, a geomagnetic pulse under South America in 2016 shifted the magnetic field unexpectedly. This was exacerbated by the movement of the north magnetic pole. “The fact that the pole is going fast makes this region more prone to large errors,” Chulliat is quoted as saying.

Researchers are now trying to work out why the magnetic field is changing so quickly. They are studying the geomagnetic pulses, like the one that disrupted the WMM in 2016, which could, Nature reports, be the result of “hydromagnetic” waves emanating from Earth’s core.

To fix the World Magnetic Model, he and his colleagues fed it three years of recent data, which included the 2016 geomagnetic pulse. The new version should remain accurate, he says, until the next regularly scheduled update in 2020."

Per the linked website/video the South Atlantic Anomaly, in the Earth's magnetic field, is spreading towards Africa.  What will happen to this phenomenon if the WAIS collapses?

title: "Mysterious weak spot in the Earth's magnetic field is spreading: ESA"

https://www.msn.com/en-us/video/science/mysterious-weak-spot-in-the-earth-s-magnetic-field-is-spreading-esa/vi-BB14UBIk?ocid=msedgdhp

Extract: "A mysterious anomaly in the Earth's magnetic field that stretches from South America to Africa is spreading."
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sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4159 on: February 20, 2021, 08:00:10 AM »
Repetition is not argument. I read those articles when you first posted them, and some before you did, since i am interested in the matter also.

Your statement was "abrupt SLR were to trigger another geomagnetic reversal."

Oddly enuf, none of those articles posit a model linking increase in SLR to magnetic pole reversal. None of them even have correlations between SLR and pole reversal. In fact, the origin of the magnetic field of the earth is not well understood, much less the reversals.

Perhaps you have a theory of your own? Perhaps it has been peer reviewed and published ? I look forward to a citation.

sidd
« Last Edit: February 20, 2021, 08:21:37 AM by sidd »

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4160 on: February 20, 2021, 08:56:42 PM »
...

I note that if abrupt ice mass loss in coming decades were to trigger another geomagnetic reversal this century, then this would likely contribute to greater climate changes than currently projected by consensus climate science (CCS).

...

sidd,

First, my original quote above does include the word 'if', so there is no need for me to write a peer-reviewed article to present my thought process.

Second, that fact that the science of geomagnetic reversal is not fully developed does not relieve mankind from abrupt climate change risks associated with rapid geomagnetic reversal events like the Laschamp(s) Excursion/Event.

Third, interpreting the paleorecord involves a large number of uncertainties, such as: why does the attached image show that during the last ice age the center of the NH ice sheets were centered on the middle of Greenland rather than the North Polar, and does this suggest that there is a correlation between glacial ice mass and true polar wander?
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sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4161 on: February 20, 2021, 10:32:53 PM »
Re: "Third, interpreting the paleorecord involves a large number of uncertainties, such as: why does the attached image show that during the last ice age the center of the NH ice sheets were centered on the middle of Greenland rather than the North Polar, and does this suggest that there is a correlation between glacial ice mass and true polar wander?"

This is a bit garbled but i take it you are speaking here of the rotational poles and not the magnetic poles. But that is a different argument. It is well known that the rotational axis and poles move as the earth glaciates and deglaciates because of changes in the moment of inertia tensor arising from mass redistribution. But the rotational pole is not the magnetic pole. Or is your argument that magnetic field reversal is driven by rotational pole realignment ? There is actually some work on mantle geodynamics coupled to rotation, but nothing like a fully fledged theory of magnetic pole reversals with testable predictions. Unsurprising, since the fundamental nature of the geodynamo is still quite a mystery.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4162 on: February 21, 2021, 03:50:00 AM »
...

This is a bit garbled but i take it you are speaking here of the rotational poles and not the magnetic poles. But that is a different argument. It is well known that the rotational axis and poles move as the earth glaciates and deglaciates because of changes in the moment of inertia tensor arising from mass redistribution. But the rotational pole is not the magnetic pole. Or is your argument that magnetic field reversal is driven by rotational pole realignment ? There is actually some work on mantle geodynamics coupled to rotation, but nothing like a fully fledged theory of magnetic pole reversals with testable predictions. Unsurprising, since the fundamental nature of the geodynamo is still quite a mystery.

sidd

As pointed out by linked reference indicate that:

"Sufficiently rapid ocean level changes can disrupt the dynamo, resulting (in half of the cases) in a geomagnetic field reversal.

If no further correlation is found to exist between sudden sea-level changes and geomagnetic reversals, then we have a disturbing puzzle. It is difficult to see how a sufficiently large and sudden sea-level change could avoid severely affecting the Earth's field, unless the dynamo theory of the geomagnetic field is incorrect.
"

The linked reference also indicates that an abrupt SLR event would abruptly weaken the Earth's geomagnetic field; which, is typically the case when geomagnetic reversals occur.

Title: "Geomagnetic Reversals Driven by Abrupt Sea Level Changes" by Richard A. Muller and Donald E. Morris (1985).

https://www.osti.gov/servlets/purl/1004148

Abstract: "Changes in the moment of inertia of the earth, brought about by the redistribution of ocean water from the tropics to ice at high latitudes, couple energy from the spin of the earth into convection in the liquid core. This mechanism may help provide the driving energy for the earth's dynamo. Sufficiently rapid ocean level changes can disrupt the dynamo, resulting (in half of the cases) in a geomagnetic field reversal. The model can account for the previously mysterious correlation reported between geomagnetic reversals and mass extinctions."

Extract: "Note that a sudden rise in the sea level can have a similarly disruptive effect on the geomagnetic field. If the Antarctic ice shelf is truly unstable, as some speculate, then global warming (perhaps from C02 increases in the atmosphere) may trigger its slide from the continent into the sea. If that happens we will have the opportunity to test our theory directly by watching the slow-down of the earth's spin and the beginning of the turnoff of the geomagnetic field.

If no further correlation is found to exist between sudden sea-level changes and geomagnetic reversals, then we have a disturbing puzzle. It is difficult to see how a sufficiently large and sudden sea-level change could avoid severely affecting the Earth's field, unless the dynamo theory of the geomagnetic field is incorrect."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4163 on: February 21, 2021, 08:15:24 AM »
That is  a nice technical report from LBL from 1985,  unfortunately unpublished and without peer review, and i find only a few citations. But it does accurately line the energies and order of magnitudes under discussion.

They end with :

"If no further correlation is found to exist between sudden sea-level changes and geomagnetic reversals, then we have a  disturbing puzzle. It is difficult to see how a sufficiently large and sudden sea-level change could avoid severely affecting the Earth's field, unless the dynamo theory of the geomagnetic field is  incorrect."

Unfortunately that is the case, no correlation has been found between abrupt SLR changes and magnetic ield reversals. But i am not yet sure that their overall  picture of geodynamo coupled to rotaion is incorrect, it may yet be saved by a full stokes model including equations for phase change,heat and charge transfer (or current flow, if you prefer).  Full navier stokes + heat flow + phase change, as both of us know too well, is difficult enuf fot icesheets. Including charge and current into that mess for crust, mantle and core is beyond our reach at the moment.

We have come a long way from that report in 1985, and current understanding is that the magnetic field is driven by mantle convection; thus when plate tectonics dies, so does the magnetic field, as we see on Mars. But the mechanisms of coupling of charge, rotation, convection and resulting magnetic field is, alas, not at all understood.

There are later papers on putative couplings between moment of inertia of the earth-moon system and geodynamo, but no testable theory yet exists, even for a constant moment of inertia picture with just mantle plumes + charge transfer. Until we can do that, i do not think we can even begin to consider moment of imertia fluctuation driven by glacial cycle or other cause.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4164 on: February 21, 2021, 04:10:01 PM »
The linked reference, and associated article, indicate that current polar motion is primarily the result of three processes: ice mass loss, glacial rebound, and mantle convection (see that accompanying image).  Also, I note that abrupt ice mass loss from the WAIS this century would be accompanied by relatively rapid glacial rebound in West Antarctica; which would impact regional magma flow.

Surendra Adhikari et al. (15 November 2018), "What drives 20th century polar motion?", Earth and Planetary Science Letters, Volume 502, Pages 126-132, https://doi.org/10.1016/j.epsl.2018.08.059

https://www.sciencedirect.com/science/article/abs/pii/S0012821X18305314

Abstract
Astrometric and geodetic measurements show that the mean position of Earth's spin axis drifted through the solid crust toward Labrador, Canada at an average speed of 10.5±0.9 cm/yr during the 20th century. Understanding the origins of this secular polar motion (SPM) has significance for modeling the global climate, as it provides a link to ice mass balance and sea-level rise. A perplexing issue, however, is that while glacial isostatic adjustment (GIA) models satisfactorily explain the direction of SPM, the associated prediction of the amplitude is insufficient. Our Bayesian GIA analysis, with constraints from relative sea-level and vertical land motion data, reveals that this process only accounts for 33±18% of the observed SPM amplitude. This shortfall motivates a more broadly scoped reassessment of SPM drivers. To address this, we assemble a complete reconstruction of Earth's surface mass transport derived from recent advancements in modeling the global 20th century cryospheric, hydrologic, oceanic, and seismogenic mass exchange. The summed signals, nonetheless, cannot fully reconcile the observed SPM, even when considering the error statistics of each driver. We investigate an additional excitation source: changes in Earth's inertia tensor caused by mantle convection. Sophisticated models have recently been advanced in tectonic plate reconstructions, in conjunction with geoid and seismic tomographic models. Here we use these models to compute new estimates of SPM. While the convection-driven SPM has considerable uncertainty, the average direction of 283 recent models aligns with the residual SPM (within 2.7∘±14.8∘), significantly reducing the gap between observation and prediction. We assert that one key mechanism for driving 20th century SPM is long-term mass movement due to mantle convection.

See also:

Title: "Do you know why the Earth wobbles?"

https://www.geospatialworld.net/blogs/why-the-earth-wobbles/

Extract: "Using satellite data on how water moves around Earth, NASA scientists have been able to find out exactly how and why does the Earth wobble.

When the Earth rotates on its spin axis — an imaginary line that passes through the North and South Poles — it drifts and wobbles. These spin-axis movements are called “polar motion” in scientific parlance. NASA scientists have computed that the measurements for the 20th century show that the spin axis drifted about 4 inches (10 centimeters) per year. Over the course of a century, that becomes more than 11 yards (10 meters).

NASA scientists have broadly categorized three processes that are responsible for this drifting if the earth. The three processes are: contemporary mass loss primarily in Greenland, glacial rebound, and mantle convection."

Caption for the attached image: "The observed direction of polar motion, shown as a light blue line, compared with the sum (pink line) of the influence of Greenland ice loss (blue), postglacial rebound (yellow) and deep mantle convection (red). The contribution of mantle convection is highly uncertain. Image Courtesy: NASA/ JPL-Caltech"

Additionally, I note that the geographic poles are defined by the points on the surface of the Earth that are intersected by the axis of rotation, and data indicates that the geographical poles have not deviated by more than about 5° over the last 130 million years.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4165 on: February 22, 2021, 01:45:15 AM »
The linked article about Jerry Mitrovica's many scientific achievements including the one cited in the extract below; where he demonstrates that in order to explain the rotational behavior of the Earth, one needs to consider the impact of modern sea level rise on the braking effect of the magnetic coupling between the Earth's iron core and its rocky mantle.  To me this suggests that there could likely be a relationship between potential future abrupt sea level rise and the Earth's future geomagnetic behavior (including the possibility of a temporary reversal) over the next century.

Title: "The Plastic Earth"

https://harvardmagazine.com/2016/09/the-plastic-earth

Extract: "Last year, Mitrovica won the Geological Society of America’s Day Medal, which recognizes “outstanding distinction in the application of physics and chemistry to the solution of geologic problems.” The award was given in part for research that tackled a problem that had been unresolved for nearly 15 years: Munk’s enigma. Walter Munk, a renowned professor emeritus at the Scripps Institution of Oceanography, argued that if all the land-based ice that has supposedly been melting for the last century really has been melting, the water that was released from polar regions should have flowed toward lower latitudes and the equator—and this redistribution of mass should have slowed the rotation of the earth (much as spinning skaters slow as they extend their arms). But modern satellite observations suggested that the earth’s spin has not slowed as much as forecast. Although Munk wasn’t questioning estimates of sea-level rise per se, his enigma posed a serious challenge to earth scientists involved in studies of global warming.

The solution to the enigma required a reanalysis of a very different class of Earth rotation data. Specifically, ancient eclipse records extending back thousands of years from “Babylonian, Chinese, Arab, and Greek astronomers indicate that the earth’s rotation has slowed about four hours” in two and a half millennia, Mitrovica explains. Geophysicists have long attributed this slowing to two effects. First, tides crashing on shorelines apply a brake on Earth’s rotation—an effect known as tidal dissipation. The second is a remnant effect of the last ice age. “The earth 20,000 years ago was covered by ice at the poles” and that mass “squished the solid earth down, so that the earth’s shape was a little flattened. As those ice sheets melted—and continuing to the present day—the earth has gradually become more and more spherical,” and therefore less flattened—and fattened—at the equator. “As it comes back,” he says, linking the planet’s evolving geometry to figure skaters drawing their arms in—“it’s speeding up.” These two effects neatly added up to the four hours of slowdown evident in the eclipse record.

But Mitrovica and his colleagues realized that a very important process had been left out of this analysis. Magnetic coupling between the earth’s iron core and its rocky mantle has also been causing the rotation of the crust to slow. When Mitrovica’s team included this braking effect, the numbers no longer worked. They realized that the ice-age model scientists had been using in their calculations had been inaccurate. The model had to be revised so that all three effects—tidal dissipation, ice-age shape changes, and magnetic coupling—added up to the four hours of slowing.

How does that connect to Munk’s enigma, which asked why modern glacial meltwater had not measurably slowed the earth? The answer is a roundabout one. Modern satellite measurements allowed scientists to make an independent measurement of the earth’s rotation. When the satellite data were corrected for ice-age effects using the new model that fit the eclipse records, a small, unexplained slowdown was revealed. This discrepancy, Mitrovica says, was precisely the signal one would expect from the melting of glaciers during the past century. Munk’s enigma was solved—and another, albeit subtle, perturbation to the progressively warming Earth system was revealed. As Mitrovica explains, “Munk’s enigma reinforces my view that significant progress in understanding the real, long-term effects of climate change—past, present, and future—will sometimes require that we look downwards to embrace the complex, dynamic evolution of the solid earth.”"

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sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4166 on: February 22, 2021, 06:00:00 AM »
Yes, that is a very nice Mitrovica paper, but i should warn that his calculation for magnetic braking between core and mantle is not fully accepted. The difficulty are in the models of mantle plume used. There are some very nice longterm (1e9 year) studies of the coupled earth moon angular momentum that apply and also at the opposite end, short term effects like chandler wobble and even the ElNino-La Nina cycles yield  limits on coupling magnitudes between core, mantle and crust. I think there was a P/Swave deep seismic study couple years ago where they said wise things about coupling, but i have not the reference to hand.

Perhaps we should have a thread on magnetic pole reversals. It is quite fascinating and difficult, as most dynamic macroscopic magnetism usually is.

sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4167 on: February 22, 2021, 12:08:32 PM »
sidd:
Start one. I would do it, but the moderators don't like me doing that.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4168 on: February 22, 2021, 10:03:06 PM »
The Earth's geomagnetism is manifested in many different parameters like the risk of a possible Laschamps Excursion-type event in coming decades to a significant decrease in the South Atlantic Anomaly (see the linked article & image), and while consensus scientists suggest that we are safe in the coming decades the generally do not consider the impacts of a possibly abrupt sea level rise (largely from a possible collapse of the WAIS) in the coming decades.

Title: "The Herky-Jerky Weirdness of Earth’s Magnetic Field"

https://eos.org/features/the-herky-jerky-weirdness-of-earths-magnetic-field

Extract: "Dented, erratic, and wandering, our field is constantly changing its mind.

Most people don’t know that Earth’s magnetic field has a weak spot the size of the continental United States hovering over South America and the southern Atlantic Ocean.

A forecast from NASA scientist Weijia Kuang and University of Maryland, Baltimore County professor Andrew Tangborn shows that in addition to migrating westward, the anomaly is growing in size. Five years from now, the area below a field intensity of 24,000 nanoteslas (about half the normal magnetic strength) will grow by about 10% compared with 2019 values. The dent may also be splitting, Kuang said, or perhaps another weak spot is emerging independently and biting into it."
« Last Edit: February 22, 2021, 10:28:33 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4169 on: February 23, 2021, 10:29:24 AM »
The first linked reference indicates that '… a geomagnetic pulse under South America in 2016 shifted the magnetic field unexpectedly …'; which may have triggered '… a high-speed jet of liquid iron beneath Canada…'; which may have weakened the magnetic field beneath Canada, allowing the high-strength magnetic field beneath Siberia to accelerate the migration of the magnetic north pole towards Siberia since 2016.  Whether the acceleration in magnetic polar wander shown in the first attached image (from Nature 2019) is related to the high magnetic anomaly in the South Atlantic (see Reply #4167) and thus possibly to changes in terrestrial water storage cited in the second linked reference (see also the second and third attached images), is a matter worth investigating.

Title: "Earth's magnetic field is acting up and geologists don't know why"

https://www.nature.com/articles/d41586-019-00007-1?utm_source=twt_nnc&utm_medium=social&utm_campaign=naturenews&sf205680051=1

Extract: "First, that 2016 geomagnetic pulse beneath South America came at the worst possible time, just after the 2015 update to the World Magnetic Model.

… scientist are working to understand why the magnetic field is changing so dramatically. Geomagnetic pulses, like the one that happened in 2016, might be traces back to 'hydromagnetic' waves arising from deep in the core.  And the fast motion of the north magnetic pole could be linked to a high-speed jet of liquid iron beneath Canada."

&
Surendra Adhikari and Erik R. Ivins (08 Apr 2016), "Climate-driven polar motion: 2003–2015", Science Advances, Vol. 2, no. 4, e1501693, DOI: 10.1126/sciadv.1501693

https://advances.sciencemag.org/content/2/4/e1501693

Abstract
Earth’s spin axis has been wandering along the Greenwich meridian since about 2000, representing a 75° eastward shift from its long-term drift direction. The past 115 years have seen unequivocal evidence for a quasi-decadal periodicity, and these motions persist throughout the recent record of pole position, in spite of the new drift direction. We analyze space geodetic and satellite gravimetric data for the period 2003–2015 to show that all of the main features of polar motion are explained by global-scale continent-ocean mass transport. The changes in terrestrial water storage (TWS) and global cryosphere together explain nearly the entire amplitude (83 ± 23%) and mean directional shift (within 5.9° ± 7.6°) of the observed motion. We also find that the TWS variability fully explains the decadal-like changes in polar motion observed during the study period, thus offering a clue to resolving the long-standing quest for determining the origins of decadal oscillations. This newly discovered link between polar motion and global-scale TWS variability has broad implications for the study of past and future climate.


Caption for the second image: "Fig. 2 Climate-induced mass redistribution on Earth’s surface.
(A) Linear rate of change in mass (in WEH per year) during April 2002 to March 2015, derived from monthly GRACE observations and associated sea-level computations. Solutions are reproduced with different color scales for (B) the GIS, (C) the AIS, and (D) the oceans."

Caption for the third image: " Fig. 5 Origins of observed polar motion.
(A) Reconstruction and partition of polar motion during 2003–2015. Observed data have the 20th-century linear trends removed. Semimajor and semiminor axes of error ellipses are defined by the uncertainties in the magnitude and direction of the corresponding polar motion vector. For clarity, we do not show error ellipses for GICs, which have large uncertainties but very small amplitudes (see Materials and Methods) and AOM. (B) Observed (including the long-term linear trend) and reconstructed mean annual pole positions, in the excitation domain, with respect to the 2003–2015 mean position. Blue error band is associated with the reconstructed solution; red signifies additional errors that are related to uncertainty in the long-term linear trend."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4170 on: February 23, 2021, 09:11:20 PM »
Getz Glaciers On the Run
https://phys.org/news/2021-02-getz-glaciers.html



Using a 25-year record of satellite observations over the Getz region in West Antarctica, scientists have discovered that the pace at which glaciers flow towards the ocean is accelerating. This new research, which includes data from the Copernicus Sentinel-1 mission and ESA's CryoSat mission, will help determine if these glaciers could collapse in the next few decades and how this would affect future global sea-level rise.

Led by scientists at the University of Leeds in the UK, the new research shows that between 1994 and 2018, all 14 glaciers in Getz accelerated, on average, by almost 25%, with three glaciers accelerating by over 44%.

The results, published today in Nature Communications, also reported that the glaciers lost a total of 315 gigatonnes of ice, adding 0.9 mm to global mean sea level – equivalent to 126 million Olympic swimming pools of water.



... "Using a combination of observations and modeling, we show highly localized patterns of acceleration. For instance, we observe the greatest change in the central region of Getz, with one glacier flowing 391 meters a year faster in 2018 than in 1994. This is a substantial change as it is now flowing at a rate of 669 meters a year, a 59% increase in just two and a half decades," continued Heather.

The research, funded by the Natural Environment Research Council and ESA's Science for Society program, reports how the widely reported thinning and acceleration observed in the neighboring Amundsen Sea glaciers, now extends over 1000 km along the West Antarctic coastline into Getz.



Heather L. Selley et al. Widespread increase in dynamic imbalance in the Getz region of Antarctica from 1994 to 2018, Nature Communications (2021).
https://www.nature.com/articles/s41467-021-21321-1
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4171 on: February 24, 2021, 02:03:48 AM »
The linked article and associated linked reference indicates that even using using a MISI-based model the Thwaites Glacier could completely collapse within 60 to 70 years.  Needless to say, the study did not consider a possible cascade of freshwater hosing events nor the potential associated cascade of ice-climate feedbacks; possibly triggered by a collapse of the Thwaites Glacier.

Title: "New study models impact of calving on retreat of Thwaites Glacier"

https://phys.org/news/2019-12-impact-calving-retreat-thwaites-glacier.html

Extract: "The new study in the AGU journal Geophysical Research Letters modeled how much faster Thwaites, one of the region's largest and fastest-retreating glaciers, would retreat in the absence of its ice shelf—the part of the glacier that floats on top of the sea, supporting the thicker ice behind.

"We think that possibly in a few years or decades, we don't know yet, the remainder of the ice shelf in front of Thwaites might be gone," explained Hongju Yu, an assistant specialist at the University of California, Irvine and lead author of the new study.

If the ice shelf disappeared, it would no longer provide resistance to the glacier's flow, allowing the glacier to accelerate. The glacier would then begin losing mass mainly through increasing breakup of chunks of ice at its leading edge—a process called calving. The aim of the new study was to simulate how much Thwaites' retreat would accelerate through calving once the ice shelf disappears.

The researchers ran 20 different simulations combining the effects of two different calving mechanisms and ice front melting—melting that is concentrated at the glacier's edge rather than distributed over the entire ice shelf. Depending on the scenario, they found the volume of ice lost would increase between 5 percent and 160 percent compared to estimates based on ice shelf melt alone.

In the worst-case scenario, Thwaites could completely collapse within 60 to 70 years, according to the study's authors. Other scenarios predict the glacier to remain stable for an additional century. In each scenario, once Thwaites Glacier retreats past the ridge that anchors it to land, the retreat becomes unstoppable."

See also:

Hongju Yu et al. Impact of iceberg calving on the retreat of Thwaites Glacier, West Antarctica over the next century with different calving laws and ocean thermal forcing, Geophysical Research Letters (2019). DOI: 10.1029/2019GL084066

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL084066

Abstract
Thwaites Glacier, West Antarctica, has been a major contributor to global sea level rise over the past decades. Prior studies illustrated the critical role of ice shelf melt and iceberg calving based on cliff height in driving the retreat of Thwaites glacier. Here, we simulate its evolution with various calving laws and rates of frontal melt by the ocean in the absence of a buttressing ice shelf. Over the next century, we find that volume losses increase by 15–160% with a von Mises calving law compared to the case where the initial ice shelf is kept and the ice front is fixed at its current position, 10–20% with a buoyancy‐driven calving law, and 5–50% with frontal melt caused by ocean thermal forcing. Bed topography exerts the ultimate control on the evolution of Thwaites. In all simulations, once Thwaites Glacier retreats past the western subglacial ridge, the retreat becomes rapidly unstoppable.
« Last Edit: February 24, 2021, 02:36:17 AM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4172 on: February 24, 2021, 04:12:45 PM »

The linked article, supported by the associated linked reference, indicates that:

"An overlooked but powerful driver of cloud formation could accelerate the loss of polar sea ice.

Global iodine emissions have tripled over the past 70 years, and scientists predict that emissions will continue to accelerate as sea ice melts and surface ozone increases.

Researchers have observed in remote areas of Ireland, Greenland and Antarctica that iodine, which is released naturally from melting sea ice, algae and the ocean surface, may also be a significant driver of new particle formation.

Based on these results, an increase of molecular iodine could lead to more particles for water vapor to condense onto and spiral into a positive feedback loop.
"

This newly identified positive cloud aerosol feedback mechanism has not been included in any climate model (including in any CMIP6 model), but could markedly increase polar amplification, and consequently climate sensitivity (possibly even above the CMIP6 Wolf Pack estimates), in coming decades.

Title: "Cloud-Making Aerosol Could Devastate Polar Sea Ice"

https://www.quantamagazine.org/cloud-making-aerosol-could-devastate-polar-sea-ice-20210223/

Extract: "An overlooked but powerful driver of cloud formation could accelerate the loss of polar sea ice.

Now, while studying the atmospheric chemistry that produces clouds, researchers have uncovered an unexpectedly potent natural process that seeds their growth. They further suggest that, as the Earth continues to warm from rising levels of greenhouse gases, this process could be a major new mechanism for accelerating the loss of sea ice at the poles — one that no global climate model currently incorporates.

The full climate impact of this mechanism still needs to be assessed carefully, but tiny modifications in the behavior of aerosols, which are treated as an input in climate models, can have huge consequences, according to Andrew Gettelman, a senior scientist at the National Center for Atmospheric Research (NCAR) who helps run the organization’s climate models and who was not involved in the study. And one consequence “will definitely be to accelerate melting in the Arctic region,” said Jasper Kirkby, an experimental physicist at CERN who leads the Cosmics Leaving Outdoor Droplets (CLOUD) experiment and a coauthor of the new study.

Researchers have observed in remote areas of Ireland, Greenland and Antarctica that iodine, which is released naturally from melting sea ice, algae and the ocean surface, may also be a significant driver of new particle formation. But researchers still wondered how molecular iodine grows into a CCN, and how efficiently it does so, compared with other secondary aerosols. “Even though these particles were known to exist, we weren’t able to link a measured concentration in the atmosphere to a predicted formation of particles,” Kirkby said.

The findings are important for understanding the fundamental chemistry in the atmosphere that underlies cloud processes, Kirkby said, but also as a warning sign: Global iodine emissions have tripled over the past 70 years, and scientists predict that emissions will continue to accelerate as sea ice melts and surface ozone increases. Based on these results, an increase of molecular iodine could lead to more particles for water vapor to condense onto and spiral into a positive feedback loop. “The more the ice melts, the more sea surface is exposed, the more iodine is emitted, the more particles are made, the more clouds form, the faster it all goes,” Kirkby said.

Clouds generally cool the planet, as the white tops of the clouds reflect sunlight into space. But in polar regions, snowpack has a similar albedo, or reflectivity, as cloud tops, so an increase in clouds would reflect little additional sunlight. Instead, it would trap longwave radiation from the ground, creating a net warming effect.

In 2019, NCAR’s model projected a climate sensitivity well above IPCC’s average upper bound and 32% higher than its previous estimate — a warming of 5.3 degrees C (10.1 degrees F) if the global carbon dioxide is doubled — mostly as a result of the way that clouds and their interactions with aerosols are represented in their new model.

Brock remains hopeful that future research into new particle formation will help to chip away at the uncertainty in climate sensitivity. “I think we’re gaining an appreciation for the complexity of these new particle sources,” he said."

See also:

He, X.-C. et al. (05 Feb 2021), "Role of iodine oxoacids in atmospheric aerosol nucleation", Science, Vol. 371, Issue 6529, pp. 589-595, DOI: 10.1126/science.abe0298

https://science.sciencemag.org/content/371/6529/589

Abstract
Iodic acid (HIO3) is known to form aerosol particles in coastal marine regions, but predicted nucleation and growth rates are lacking. Using the CERN CLOUD (Cosmics Leaving Outdoor Droplets) chamber, we find that the nucleation rates of HIO3 particles are rapid, even exceeding sulfuric acid–ammonia rates under similar conditions. We also find that ion-induced nucleation involves IO3− and the sequential addition of HIO3 and that it proceeds at the kinetic limit below +10°C. In contrast, neutral nucleation involves the repeated sequential addition of iodous acid (HIO2) followed by HIO3, showing that HIO2 plays a key stabilizing role. Freshly formed particles are composed almost entirely of HIO3, which drives rapid particle growth at the kinetic limit. Our measurements indicate that iodine oxoacid particle formation can compete with sulfuric acid in pristine regions of the atmosphere.
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vox_mundi

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4173 on: February 24, 2021, 05:36:15 PM »
Possible Irreversible Changes to Sub-Systems Prior to Reaching Climate Change Tipping Points
https://phys.org/news/2021-02-irreversible-sub-systems-prior-climate.html

Recently a pair of researchers with the University of Copenhagen published a paper in the Proceedings of the National Academy of Sciences describing their work looking into the possibility of changes to the Atlantic Meridional Overturning Circulation (AMOC) and the circumstances that could lead to such changes. In their paper, Johannes Lohmann and Peter Ditlevsen noted that climate models show that irreversible changes to sub-systems such as the AMOC, one of Earth's global sub-systems, can occur prior to a tipping point if changes occur at a fast pace.

They further noted that fresh water pouring into the Atlantic Ocean due to melting ice could result in just such an irreversible change. More recently, an international team of climate scientists has published a Perspectives piece, also in PNAS, outlining the harm that could result if irreversible changes occur prior to tipping points, and also what models suggest will happen if the Earth does start to reach certain tipping points.

... Climate models suggest that under such scenarios, there is no turning back. Once a tipping point is reached, we cannot solve the problem by stopping carbon emissions. More recent research has suggested that there may be some pre-tipping points that could trigger climate changes on a smaller scale but which would still be irreversible. Fresh, cold water entering the North Atlantic, for example, could result in permanent changes to the AMOC. Notably, the AMOC is responsible for the mild temperatures in Europe.

In their paper, the authors of the Perspectives piece describe likely outcomes of different scenarios that could lead to pre-tipping point sub-system changes. They note, for example, that the world's oceans comprise sub-systems. In addition to rising water levels, the world's oceans are experiencing acidification due to carbon dioxide absorbed from the atmosphere. Acidification harms sea life. Additionally, prior research has shown that the upper part of the ocean absorbs heat from the atmosphere at a much higher rate than lower regions. The lower regions are only now beginning to feel the effects of warming, a long-term event that could change the entire underwater ecosystem—a change that would be irreversible.



Christoph Heinze et al. The quiet crossing of ocean tipping points, Proceedings of the National Academy of Sciences (2021)
https://www.pnas.org/content/118/9/e2008478118


Candidates for high-probability high-impact marine tipping elements that concern warming, deoxygenation, and ocean acidification as well as their impacts.
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Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

kassy

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4174 on: February 24, 2021, 06:47:41 PM »
A new global ice sheet reconstruction for the past 80 000 years
Abstract
The evolution of past global ice sheets is highly uncertain. One example is the missing ice problem during the Last Glacial Maximum (LGM, 26 000-19 000 years before present) – an apparent 8-28 m discrepancy between far-field sea level indicators and modelled sea level from ice sheet reconstructions. In the absence of ice sheet reconstructions, researchers often use marine δ18O proxy records to infer ice volume prior to the LGM. We present a global ice sheet reconstruction for the past 80 000 years, called PaleoMIST 1.0, constructed independently of far-field sea level and δ18O proxy records. Our reconstruction is compatible with LGM far-field sea-level records without requiring extra ice volume, thus solving the missing ice problem. However, for Marine Isotope Stage 3 (57 000-29 000 years before present) - a pre-LGM period - our reconstruction does not match proxy-based sea level reconstructions, indicating the relationship between marine δ18O and sea level may be more complex than assumed.

...

Recent work in the Hudson Bay region in North America5,6,7 shows that during part of MIS 3, ice-free conditions may have existed. Under this interpretation, the climatic conditions in this area were favorable to allow the growth of forests, with a climate that was potentially analogous to present8. This would indicate that not only was the Laurentide Ice Sheet reduced in size but it also had to be far enough removed from southern Hudson Bay to not strongly affect the climate there. Pico et al.9, through GIA modeling, provided additional support for a reduced extent Laurentide Ice Sheet to explain high relative MIS 3 sea-level indicators along the eastern coast of the United States. The dating methods used for inferring reduced ice sheet extent are near the limit of their reliability during mid-MIS 310. If regarded as minimum ages, then these deposits could be from an earlier ice-free period, such as the last interglacial.

Our reconstruction, called PaleoMIST 1.0 (Paleo Margins, Ice Sheets, and Topography), is created independently of indirect proxy records and far-field sea-level records. This allows us to investigate two of the most contentious problems when assessing past ice sheet configuration and sea level. First, our reconstruction can achieve the sea-level lowstand observed in many far-field locations at the LGM. Since our model adheres to ice physics, geological observations, and local relative sea-level change, we consider it to be a plausible depiction of the ice sheet configuration at the LGM. Therefore, the origin of the long-debated missing ice problem was likely from the starting assumptions on where ice was distributed and the Earth rheology model, while achieving the far-field sea-level lowstand is a nonunique problem. Second, the ice volume in our reconstruction is unable to match the pre-LGM δ18O values based on empirical relationships between ice volume (and therefore sea level) and δ18O but is consistent with some of the sea-level indicators and prior GIA studies6,9,11,12. From our results, we propose that these relationships of δ18O proxy records to sea level and ice volume are not valid.


https://www.nature.com/articles/s41467-021-21469-w
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4175 on: February 25, 2021, 04:05:00 PM »
Hopcroft et al. (2021) indicates that virtually all current climate models (including CMIP6 models) underestimate the amount of mixing between convective plumes and the environment in the upper troposphere relative to lower altitudes.  To my mind, increasing the convective mixing in the upper troposphere in CMIP 7 models could well lead to projections of both increased high-altitude cloud formation and increased advection of atmospheric tropical heat from the tropics to high latitudes (see the two attached images, and the linked article), with continued global warming.  If so, this would indicate that consensus climate science has underestimated two more positive feedback mechanisms.

Hopcroft, P.O., Paul J. Valdes and William Ingram (16 February 2021), "Using the mid‐Holocene ’greening’ of the Sahara to narrow acceptable ranges on climate model parameters", Geophysical Research Letters, https://doi.org/10.1029/2020GL092043

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL092043?af=R

Abstract
During the early to mid‐Holocene vegetation expanded to cover much of the present‐day Sahara. Although driven by a well‐understood difference in the orbital configuration, general circulation models have generally failed to simulate the required rainfall increase. One possible explanation is the presence of systematic biases in the representations of atmospheric convection which might also impact future projections. We employ a Bayesian method to learn from an ensemble of present day and mid‐Holocene simulations that vary parameters in the convection, boundary layer and cloud schemes. The model can reproduce the ’Green Sahara’ rainfall if mixing between convective plumes and the environment is increased in the upper troposphere relative to lower down. This does not appreciably impact the present day simulation, meaning that the palaeoclimate reconstructions are able to narrow constraints on suitable parameter ranges. This suggests that other uncertain components of climate models could be targeted in this way.

See also:

Title: " Convection, circulation, and deflection of air"

https://www.britannica.com/science/atmosphere/Convection-circulation-and-deflection-of-air

Extract: "The region of greatest solar heating at the surface in the humid tropics corresponds to areas of deep cumulonimbus convection. Cumulonimbus clouds routinely form in the tropics where rising parcels of air are warmer than the surrounding ambient atmosphere. They transport water vapour, sensible heat, and Earth’s rotational momentum to the upper portion of the troposphere. As a result of the vigorous convective mixing of the atmosphere, the tropopause in the lower latitudes is often very high, located some 17 to 18 km (10.5 to 11 miles) above the surface.

Since motion upward into the stratosphere is inhibited by very stable thermal layering, the air transported upward by convection diverges toward the poles in the upper troposphere. (This divergence aloft results in a wide strip of low atmospheric pressure at the surface in the tropics, occurring in an area called the equatorial trough). As the diverted air in the troposphere moves toward the poles, it tends to retain the angular momentum of the near-equatorial region, which is large as a result of Earth’s rotation. As a result, the poleward-moving air is deflected toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4176 on: February 25, 2021, 04:33:03 PM »
To me, the linked reference indicates that any climate risk assessment (particularly of complex climate issues with deep uncertainty) must account for climate scientists' values with regard to how they frame nature and uncertainty. 

Vazquez, M. et al. (18 February 2021), "Exploring Scientists’ Values by Analyzing How They Frame Nature and Uncertainty", Risk Analysis, https://doi.org/10.1111/risa.13701

https://onlinelibrary.wiley.com/doi/abs/10.1111/risa.13701?af=R

Abstract
Several scholars have proposed that values embedded in science are a central reason why more research does not necessarily resolve scientific controversies around complex environmental issues. In the Capital Regional District, British Columbia, Canada, scientists have positioned themselves for and against the construction of a wastewater treatment plant in a debate framed as purely technical. This study explores the link between the scientists’ positions in the debate and the way they, in their scientific publications, portray nature and environmental risks. We performed a qualitative content analysis of peer‐reviewed publications by scientists who have publicly taken opposing positions in the controversy. We found that scientists against treatment predominantly frame nature as tolerant, up to a limit, to disturbances and potential risks, and they seem to embrace a view of science as capable of reducing uncertainties. In contrast, scientists in favor of treatment predominantly portray nature as fragile, particularly toward human‐mobilized environmental risks and they commonly present scientific uncertainty as worrisome based on potentially harmful consequences. Our study suggests that value‐laden perspectives impact scientists’ positions even in a seemingly technical controversy.
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wdmn

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4177 on: February 25, 2021, 04:49:21 PM »
Our study suggests that value‐laden perspectives impact scientists’ positions even in a seemingly technical controversy.

If only so many professional philosophers weren't so obsessed with trying to be scientists, writing overly technical papers no one is interested in, scientists would have realized this a long, long time ago.

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4178 on: February 25, 2021, 05:02:46 PM »
I like the linked open access reference, so I provide the following with the open that it may offer one means of making climate change decision makers more sensitive to the needs of future generations; which, hopefully would help to improve the sustainability of future socioeconomic systems.

Hara, K., Kitakaji, Y., Sugino, H. et al. Effects of experiencing the role of imaginary future generations in decision-making: a case study of participatory deliberation in a Japanese town. Sustain Sci (2021). https://doi.org/10.1007/s11625-021-00918-x

https://rd.springer.com/article/10.1007%2Fs11625-021-00918-x

Abstract: "To ensure sustainability, overcoming intergenerational conflict is vital, and social systems supporting decision-making that takes into account the benefits to future generations is thus critically important. One promising approach in such social systems is introducing “imaginary future generations” who act as representatives for the benefits of future generation in actual, present-day decision-making situations. In this study, we explore the effects and implications of participants’ experiences as representatives of imaginary future generation. We conducted a citizens’ participatory debate on creating a vision and appropriate policies associated with public facilities and housing in a town in Japan, and examined how the thinking patterns and decisions of the participants shifted as a result of debating from the perspectives of both current and imaginary future generations. Based on analyses of a questionnaire and the keywords in answers to a worksheet provided to the participants, we demonstrate that through their experiences as representatives of imaginary future generations, a clear shift in perspective occurred, with increases in self-reflective viewpoint. We also found that the shared viewpoints of the current and future generations existed within the individuals. These findings hint at how we can develop institutions and social systems that facilitate sustainable decision-making."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4179 on: February 25, 2021, 09:50:23 PM »
The first reference (PDF available on Sci-Hub) and associated image, indicate that geomagnetic excursions (like the Laschamps Event) occur much more frequently and are associated with different dynamic mechanisms than geomagnetic reversals.  However, I note that excursions as strong as the Laschamps event (~ 42 kya) can cause substantial changes in atmospheric ozone concentration and circulation, driving synchronous global climate shifts that caused major environmental changes and extinction events.  Laj & Channell (2007) also found that such excursions tend to occur in pairs with the mores recent pair being the Laschamps-Mono Lake (~33kya) excursion pair.

Laj, C. and Channell, J. (2007), "Geomagnetic Excursions", DOI: 10.1016/B978-04452748-6.00095-X

Abstract
Geomagnetic excursions were generally treated with skepticism as recently as 20 years ago; however, as the global distribution of excursion records and quality of their age control have improved, excursions are being integrated into the polarity timescale, at least for the last few million years. The best-documented excursions comprise paired polarity reversals during paleointensity minima, defining polarity intervals of a few thousand years duration. The brevity of polarity excursions means that they are seldom recorded in sediments with sedimentation rates less than 5 cm ky− 1 or in sediments with nonideal magnetic properties. We review excursions identified in the Brunhes and Matuyama Chrons and the brief subchrons or excursions identified in the pre-Pliocene time and give a detailed description of the five most studied Brunhes-age excursions (Mono Lake, Laschamp, Blake, Iceland Basin, and Pringle Falls). The suggestion that a dipole component dominates the excursional fields during the Laschamp and Iceland Basin excursions (which are recorded at globally distributed sites) is reexamined and discussed. The short duration inferred for excursions, comparable with the diffusion time of the inner core, provides support to Gubbins' suggestion of a mechanistic difference between the excursion process and field reversals that bound long-lived polarity chrons and subchrons.

Korte et al. (2019), focuses on the most recent geomagnetic excursion pair (Laschamps-Mono Lake), and discusses the geodynamo processes that control such occurrences.

Korte, M. et al. (30 April 2019), "Robust Characteristics of the Laschamp and Mono Lake Geomagnetic Excursions: Results From Global Field Models", Front. Earth Sci., https://doi.org/10.3389/feart.2019.00086

https://www.frontiersin.org/articles/10.3389/feart.2019.00086/full

Abstract: "Data-based global paleomagnetic field models provide a more complete view of geomagnetic excursions than individual records. They allow the temporal and spatial field evolution to be mapped globally, and facilitate investigation of dipole and non-dipole field components. We have developed a suite of spherical harmonic (SH) field models that span 50–30 ka and include the Laschamp (~41 ka) and Mono Lake (~33 ka) excursions. Paleomagnetic field models depend heavily on the data used in their construction. Variations in paleomagnetic sediment records from the same region are in some cases inconsistent. To test the influence of data selection and reliance on age models, we have built a series of SH models based upon different data sets. A number of excursion characteristics are robust in all models, despite some differences in energy distribution among SH coefficients. Quantities, such as field morphology at the core-mantle boundary (CMB) or individual SH degree power variations should be interpreted with caution. All models suggest that the excursion process during the Laschamp is mainly governed by axial dipole decay and recovery, without a significant influence from the equatorial dipole or non-dipole fields. The axial dipole component reduces to almost zero, but does not reverse. This results in excursional field behavior seen globally, but non-uniformly at Earth's surface. The Mono Lake excursion may be a series of excursions occurring between 36 and 30 ka rather than a single excursion. In contrast to the Laschamp, these excursions appear driven by smaller decreases in axial dipole field strength during a time when the axial dipole power at the CMB is similar to the power in the non-dipole field. We suggest three phases for the 50 to 30 ka period: (1) a broadly stable phase dominated by the axial dipole (50–43 ka); (2) the Laschamp excursion, with the underlying excursion process lasting ~5 ka (43–38 ka) and the surface field expression lasting ~2 ka (42–40 ka); (3) a weak phase during which axial dipole and non-dipole power at the CMB are comparable, leading to more than one excursion between 36 and 30 ka."

Extract: "The geomagnetic main field varies on a broad temporal range. From years to decades, spherical harmonic (SH) core field models based on data from ground-based observatories and satellites provide an increasingly detailed view of the spatial and temporal evolution of the global geomagnetic field (e.g., Lesur et al., 2011; Hulot et al., 2015). Such models allow the geomagnetic field to be mapped at the core-mantle boundary (CMB), allowing investigation into core dynamics and the geodynamo process.
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kassy

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4180 on: February 25, 2021, 11:48:42 PM »
Our study suggests that value‐laden perspectives impact scientists’ positions even in a seemingly technical controversy.

If only so many professional philosophers weren't so obsessed with trying to be scientists, writing overly technical papers no one is interested in, scientists would have realized this a long, long time ago.
I totally doubt that on it´s own merit because why would they. After all they are mostly not thinking about those details but the ones they are supposed to work out.

Mostly you come into a field and work in it. So usually there is a common bias and a common believe that what you do is relevant. Now we can work out what our human contributions are the end of this century ignoring feedbacks but is that really useful?

Why not use simple first constraints. Work out the maximum temperature rise which allows us to keep the Arctic ice instead of way more uncertain end of century metrics?

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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4181 on: February 28, 2021, 01:16:24 AM »
Our study suggests that value‐laden perspectives impact scientists’ positions even in a seemingly technical controversy.

If only so many professional philosophers weren't so obsessed with trying to be scientists, writing overly technical papers no one is interested in, scientists would have realized this a long, long time ago.
I totally doubt that on it´s own merit because why would they. After all they are mostly not thinking about those details but the ones they are supposed to work out.

Mostly you come into a field and work in it. So usually there is a common bias and a common believe that what you do is relevant. Now we can work out what our human contributions are the end of this century ignoring feedbacks but is that really useful?

Why not use simple first constraints. Work out the maximum temperature rise which allows us to keep the Arctic ice instead of way more uncertain end of century metrics?

"Qu'on me donne six lignes écrites de la main du plus honnête homme, j'y trouverai de quoi le faire pendre."

"If you give me six lines written by the hand of the most honest of men, I will find something in them which will hang him." reportedly stated by Cardinal Richelieu.

Edit: My intent in offering this quote was to offer one reason why consensus climate scientists typically err on the side of least drama (to avoid having their careers hung out to dry by authorities). 

For instance, considering kassy's short written proposal to use simple constraints to determine the maximum GMSTA that would keep the mean Arctic sea ice extent from decreasing).  If we assume that kassy is one of the most honest members of mankind (but one who only thinks about of her scientific specialty), but that the authorities wanted to hold her accountable for being responsible for preventing an 'ice apocalypse' (so that they are no longer held accountable), they might ask her to guarantee (as engineers are asked to do for their designs) that a 'way more uncertain' cascade of tipping points events, such as the following will not occur:

1) That the SSTA pattern effect will not continue to increase climate sensitivity due to freshwater fluxes by 2040 slowing the MOC still further (its velocity is currently at a 1,600 year low point).
2) That a potential MICI-type of collapse of the Thwaites Glacier (without hydrofracturing) before 2040 does not trigger the upwelling of more relatively CDW along coastal locations westward of the ASE, as an armada of icebergs (from the Thwaites collapse) provides fresh meltwater all along those westward Antarctic coastlines as the coastal current advects these icebergs towards the iceberg ally in the Weddell Sea.
3) That the Beaufort Gyre does not flip and release a significant freshwater flux into the North Atlantic (thus slowing the AMOC) in the next decade, or two.
4) That key Greenland marine terminating glaciers (like Jakobshavn) do not release a significant freshwater flux into the North Atlantic (thus slowing the AMOC) in the next decade or two.
5) That decreases in anthropogenic aerosols in the coming decades will not drive positive cloud-aerosol feedback mechanisms to increase GMSTA even will GHG emissions may be decreasing (as occurred during 2020).
6) etc.
« Last Edit: February 28, 2021, 05:33:01 PM by AbruptSLR »
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kassy

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4182 on: February 28, 2021, 06:47:36 PM »
Since there is no time to waste i would propose the following:

1) Of all known problems we always expected Arctic Sea Ice to fail first so we should focus on that.
This makes sense because it interacts with AMOC, Greenland and Siberia (and arguably the atmosphere at large).

2) Then we look at historical constraints (paleo is mid thirties). It sort of depends on the time line but more arctic missions, better satellite replacement and dedicated super computers would all have helped.

3) But probably there would be some heated discussion and then you have to work outside of the system. Via some means we need to drive home the point that with all these connected systems we need to stay below the first trigger point.

The larger fight is the authority of the cardinal. He demands data while ignoring that pollution cost about 8 million deaths per year. Many western consumers don´t feel this and thus are happy to support this system. And it is hard to see the problem. We added more then 1% to the planet heat engine. Changing long term patterns are evident where i am (in the Netherlands) but much less in other places.

In a general way people just think someone will work it out because someone always did (green revolution, discovered CFCs just in time etc) but here we are running out of time.



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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4183 on: February 28, 2021, 07:51:03 PM »
Since there is no time to waste i would propose the following:

1) Of all known problems we always expected Arctic Sea Ice to fail first so we should focus on that.
This makes sense because it interacts with AMOC, Greenland and Siberia (and arguably the atmosphere at large).

...

Personally, I believe that the Thwaites Glacier has a 50% chance of initiating a MICI-type of collapse by 2035 +/-5yrs; while the attached CarbonBrief image indicates that following RCP 8.5 Arctic sea ice has a 50% chance of being seasonally ice-free by September 2040.

So it seems to me that assuming that no cascade of tipping points can be triggered before the Arctic sea ice is seasonally ice-free may well be erring on the side of least drama.
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kassy

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4184 on: February 28, 2021, 09:06:24 PM »
FWIW that ice collapse is always one of those things that was always so straight forward. You just need enough surface and bathymetry shows it will be there. Timing is a bit more complicated but they only way to stop it is to stop our planetary warming push.

Way way back in the nineties the Arctic ice was not really supposed to fail before 2040 and Antarctica would be a problem much later but there is quite a lot going on already.

I would say that this should be included but technically they should mostly manifest after ACI collapse (at least in theory at least the majority of them).
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4185 on: February 28, 2021, 10:02:58 PM »
FWIW that ice collapse is always one of those things that was always so straight forward. You just need enough surface and bathymetry shows it will be there. Timing is a bit more complicated but they only way to stop it is to stop our planetary warming push.

Way way back in the nineties the Arctic ice was not really supposed to fail before 2040 and Antarctica would be a problem much later but there is quite a lot going on already.

I would say that this should be included but technically they should mostly manifest after ACI collapse (at least in theory at least the majority of them).

While it is possible that the majority of scenarios leading to an 'ice apocalypse' are triggered by a collapse of Arctic Sea Ice (ASI); it is also possible that such ASI triggered scenarios do not represent as high of risk for global socio-economic collapse as do scenarios where abrupt glacial ice mass loss occurs for reasons including:

- Decision-makers believe that ASI loss is recoverable, so they do not mind overshooting Paris Climate targets like 1.5C or 2.0C; while a MICI-type of collapse of key marine glaciers would likely trigger an irreversible cascade of climate tipping points, including an abrupt slow down of the MOC.
- Due to heat already stored in the South Ocean, it is possible that stopping an future increase in GMSTA immediately, would only delay an MICI-type of collapse of Thwaites Glacier (say from 2035 to say 2045).
- Anthropogenic driven increases in climate sensitivity (say via the pattern effect [which would be greatly accelerated by an abrupt collapse of Thwaites Glacier circa 2035]) are significantly dependent on the rate of increase of GMSTA; so focusing on what the target level of GMSTA should be, may well be like missing the elephant in the room.

I could type more, but I have other things to attend to for a while.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4186 on: March 01, 2021, 01:47:48 AM »
I totally doubt that on it´s own merit because why would they. After all they are mostly not thinking about those details but the ones they are supposed to work out.

Mostly you come into a field and work in it. So usually there is a common bias and a common believe that what you do is relevant. Now we can work out what our human contributions are the end of this century ignoring feedbacks but is that really useful?

Why not use simple first constraints. Work out the maximum temperature rise which allows us to keep the Arctic ice instead of way more uncertain end of century metrics?

If there were a different relationship existing between philosophy departments and the various science departments, which allowed philosophers to work directly with scientists on live problems as well as doing their own "pure philosophy", then we could have both better philosophy and better science.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #4187 on: March 01, 2021, 03:58:13 PM »
While I believe that the linked reference supports my opinion that the Thwaites Glacier could most likely be subject to the initiation of an MICI-type of collapse circa 2035 +/- 5yrs, the CCS way that the paper is written could lead may readers to make a mistaken interpretation that any loss of the Thwaites Glacier would take multiple centuries.  In this regard, the first part of the Plain Language Summary notes that key parts of the AIS is losing ice mass at any accelerating rate (over the past few decades), but that the period of this accelerated ice mass loss is too short to make statistical inferences, so they examine episodic periods of rapid ice thinning of the southwestern Ross Sea during the early to mid-Holocene, because it is a longer period (even through this longer period lacks any anthropogenic forcing and lacked the presences of an ozone hole over Antarctica as is the present case).  The authors then conclude that during the longer paleo period that rapid ice loss took multiple centuries without directly associating this behavior to possible future ice mass loss in coming decades.

In defense of my interpretation, I provide the first attached image (see the top panel 'D') indicating that the base of the Thwaites Ice Tongue is only pinned to the seafloor by a surcharge of a few meters of ice above flotation, and that basal ice melting of these few meters of ice in this location could readily occur by 2035 +/- 5yrs; which could abruptly eliminate the associated buttressing action of the Thwaites Ice Tongue that is currently preventing a MICI-type of collapse of the ice in the region shown in the second image (see the red curved line in the top panel 'B').

Jones, R.S., et al (24 February 2021), "Ocean‐driven and topography‐controlled nonlinear glacier retreat during the Holocene: southwestern Ross Sea, Antarctica", Geophysical Research Letters,
https://doi.org/10.1029/2020GL091454

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL091454

Abstract
Recent ice sheet mass loss in Antarctica has been attributed to an influx of warm ocean waters, which drove grounding‐line retreat and ice thinning. Episodic retreat and rapid thinning also occurred in the southwestern Ross Sea during the Holocene, which today accommodates cold ocean waters. We applied finite‐element ice‐flow modeling to investigate the roles of ocean temperature and bed topography in the deglaciation of this region. First, our experiments demonstrate that bed topography controlled the spatial pattern of grounding‐line retreat. Topographic pinning points limited the rate of ice loss until retreat progressed beyond a bathymetric threshold. Second, ocean thermal forcing determined the timing of this ice loss. Enhanced ocean‐driven melt is required during the Early‐to‐Mid Holocene to replicate geological records of deglaciation, possibly indicating that warm ocean waters were once present in this region. On multi‐centennial timescales, ocean temperature drove, while bed topography controlled, nonlinear rates of ice mass loss.

Plain Language Summary
Parts of the Antarctic Ice Sheet are currently losing mass at an accelerating rate. The main cause is considered to be warming ocean waters, which melt the underside of floating ice shelves, initiating retreat and inland thinning of the ice sheet. Future ice loss will depend on when and where ocean warming occurs, and how the ice sheet responds. However, modern observations are too short to fully assess the effects of these processes. We use a state‐of‐the‐art numerical ice‐flow model to investigate the roles of ocean warming and bedrock geometry during a period of accelerated ice sheet thinning in recent geological past. We find that seafloor mounts and banks helped to slow down the rate of ice sheet retreat. Once the grounded ice became detached from these parts of the bedrock, retreat accelerated across areas of deeper water, causing rapid inland thinning of the ice sheet. Crucially, we also find that this period of past rapid thinning was initiated by an enhanced rate of ocean warming. This work highlights that key processes governing modern and future ice sheet mass loss – ocean warming and feedbacks associated with bedrock geometry – occurred in the past on timescales of centuries to millennia.
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