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Author Topic: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)  (Read 102313 times)

Tor Bejnar

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #400 on: December 24, 2018, 12:05:55 AM »
Thanks, ASLR, for introducing us (me) to "Markov blankets".  It helps explain why I still drive a Prius (even if it is 17 years old).  I like that these 'things' can be numericalized, but that is above my pay-grade.
Arctic ice is healthy for children and other living things.

Shared Humanity

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #401 on: December 24, 2018, 03:31:11 PM »
ASLR...you never cease to amaze me...I read much of what you post...learn every time I do but this piece is fascinating...

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #402 on: December 24, 2018, 04:24:16 PM »
ASLR...you never cease to amaze me...I read much of what you post...learn every time I do but this piece is fascinating...

Karl Friston may be providing conceptual tools, but each of us (including AI programmers) must do the hard work of applying these concepts to the reality of our lives, including the application of the concept of 'Embodied Cognition' which is closely associated with 'mindfulness' that is grounded by actual stimuli/input from outside our Markov Blankets (whether the Markov Blanket represented by our bodies, or otherwise).

Title: "Embodied Cognition Karl Friston"



« Last Edit: December 24, 2018, 06:01:06 PM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #403 on: December 24, 2018, 06:00:00 PM »
While the linked article reminds us that Greenland is not the only source of land ice mass loss to the ocean; we should also remember that ice mass loss/change from floating ice including sea ice and ice shelves (particularly in Antarctica) activates the ice-climate feedback mechanisms (separately than the matter of SLR):

Jason E Box et al. (2018), "Global sea-level contribution from Arctic land ice: 1971–2017", Environmental Research Letters, Vol 13, No. 12,

http://iopscience.iop.org/article/10.1088/1748-9326/aaf2ed

Abstract: "The Arctic Monitoring and Assessment Program (AMAP 2017) report identifies the Arctic as the largest regional source of land ice to global sea-level rise in the 2003–2014 period. Yet, this contextualization ignores the longer perspective from in situ records of glacier mass balance. Here, using 17 (>55 °N latitude) glacier and ice cap mass balance series in the 1971–2017 period, we develop a semi-empirical estimate of annual sea-level contribution from seven Arctic regions by scaling the in situ records to GRACE averages. We contend that our estimate represents the most accurate Arctic land ice mass balance assessment so far available before the 1992 start of satellite altimetry. We estimate the 1971–2017 eustatic sea-level contribution from land ice north of ~55 °N to be 23.0 ± 12.3 mm sea-level equivalent (SLE). In all regions, the cumulative sea-level rise curves exhibit an acceleration, starting especially after 1988. Greenland is the source of 46% of the Arctic sea-level rise contribution (10.6 ± 7.3 mm), followed by Alaska (5.7 ± 2.2 mm), Arctic Canada (3.2 ± 0.7 mm) and the Russian High Arctic (1.5 ± 0.4 mm). Our annual results exhibit co-variability over a 43 year overlap (1971–2013) with the alternative dataset of Marzeion et al (2015 Cryosphere 9 2399–404) (M15). However, we find a 1.36× lower sea-level contribution, in agreement with satellite gravimetry. The IPCC Fifth Assessment report identified constraining the pre-satellite era sea-level budget as a topic of low scientific understanding that we address and specify sea-level contributions coinciding with IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) 'present day' (2005–2015) and 'recent past' (1986–2005) reference periods. We assess an Arctic land ice loss of 8.3 mm SLE during the recent past and 12.4 mm SLE during the present day. The seven regional sea-level rise contribution time series of this study are available from AMAP.no."

See also:

Title: "Melting Arctic ice is now pouring 14,000 tons of water per second into the ocean, scientists find"

https://www.washingtonpost.com/energy-environment/2018/12/21/melting-arctic-ice-is-now-pouring-tons-water-per-second-into-ocean-scientists-find/?utm_term=.68f71445357d

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

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #404 on: December 27, 2018, 08:12:12 PM »
...

Karl Friston may be providing conceptual tools, but each of us (including AI programmers) must do the hard work of applying these concepts to the reality of our lives, including the application of the concept of 'Embodied Cognition' which is closely associated with 'mindfulness' that is grounded by actual stimuli/input from outside our Markov Blankets (whether the Markov Blanket represented by our bodies, or otherwise).

...

The reason that I mentioned AI development incorporating 'free energy', and 'active inference', concepts is because I suspect that more people (including those reading this thread) will not know how to apply such concepts into their daily activities without significant input from an AI agent.  Furthermore, I note that 'free energy' is the 'evidence lower bound' that is optimized by a large portion of today's machine learning algorithms (e.g. see the first linked reference on 'deep active inference'), and thus for 'wicked problems' like climate change quantum computing would likely need to be combined with deep learning (see the second linked reference on 'Bayesian Deep Learning on a Quantum Computer').

It's also worth noting that 'predictive coding' - a dominant paradigm in neuroscience - is a form of free energy minimization.  Moreover, free energy minimization (as predictive coding) approximates the backpropagation algorithm (see the second linked reference on, but in a biologically plausible fashion. In fact, most biologically plausible deep learning approaches use some form of prediction error signal, and are therefore functionally akin to predictive coding.  Which is to say that the notion of free energy minimization is somewhat commonplace in both neuroscience and machine learning, but that both quantum deep learning (QDL) and quantum reinforcement learning (QRL) will need to be applied to solve challenging problems (see the third and fourth linked references).

KAI UELTZHOFFER (2018), "DEEP ACTIVE INFERENCE", arXiv:1709.02341v5

https://arxiv.org/pdf/1709.02341.pdf

Abstract. "This work combines the free energy principle from cognitive neuroscience and the ensuing active inference dynamics with recent advances in variational inference on deep generative models and evolution strategies as efficient large-scale black-box optimization technique, to introduce the "deep active inference" agent. This agent tries to minimize a variational free energy bound on the average surprise of its sensations, which is motivated by a homeostatic argument. It does so by changing the parameters of its generative model, together with a variational density approximating the posterior distribution over latent variables, given its observations, and by acting on its environment to actively sample input that is likely under its generative model. The internal dynamics of the agent are implemented using deep neural networks, as used in machine learning, and recurrent dynamics, making the deep active inference agent a scalable and very flexible class of active inference agents. Using the mountaincar problem, we show how goal-directed behaviour can be implemented by defining sensible prior expectations on the latent states in the agent's model, that it will try to fulfil. Furthermore, we show that the deep active inference agent can learn a generative model of the environment, which can be sampled from to understand the agent's beliefs about the environment and its interaction with it."
&

Zhikuan Zhao, Alejandro Pozas-Kerstjens, Patrick Rebentrost, Peter Wittek (2018), "Bayesian Deep Learning on a Quantum Computer", arXiv:1806.11463

https://arxiv.org/abs/1806.11463

Abstract: "Bayesian methods in machine learning, such as Gaussian processes, have great advantages compared to other techniques. In particular, they provide estimates of the uncertainty associated with a prediction. Extending the Bayesian approach to deep architectures has remained a major challenge. Recent results connected deep feedforward neural networks with Gaussian processes, allowing training without backpropagation. This connection enables us to leverage a quantum algorithm designed for Gaussian processes and develop a new algorithm for Bayesian deep learning on quantum computers. The properties of the kernel matrix in the Gaussian process ensure the efficient execution of the core component of the protocol, quantum matrix inversion, providing an at least polynomial speedup over the classical algorithm. Furthermore, we demonstrate the execution of the algorithm on contemporary quantum computers and analyze its robustness with respect to realistic noise models."
&

Thomas Fösel, Petru Tighineanu, Talitha Weiss, Florian Marquardt. Reinforcement Learning with Neural Networks for Quantum Feedback. Physical Review X, 2018; 8 (3) DOI: 10.1103/PhysRevX.8.031084

https://journals.aps.org/prx/abstract/10.1103/PhysRevX.8.031084

Abstract: "Machine learning with artificial neural networks is revolutionizing science. The most advanced challenges require discovering answers autonomously. In the domain of reinforcement learning, control strategies are improved according to a reward function. The power of neural-network-based reinforcement learning has been highlighted by spectacular recent successes such as playing Go, but its benefits for physics are yet to be demonstrated. Here, we show how a network-based “agent” can discover complete quantum-error-correction strategies, protecting a collection of qubits against noise. These strategies require feedback adapted to measurement outcomes. Finding them from scratch without human guidance and tailored to different hardware resources is a formidable challenge due to the combinatorially large search space. To solve this challenge, we develop two ideas: two-stage learning with teacher and student networks and a reward quantifying the capability to recover the quantum information stored in a multiqubit system. Beyond its immediate impact on quantum computation, our work more generally demonstrates the promise of neural-network-based reinforcement learning in physics."


V. Dunjko, J. M. Taylor, H. J. Briegel (2018), "Advances in Quantum Reinforcement Learning", IEEE SMC, Banff, AB, pp. 282-287, DOI: 10.1109/SMC.2017.8122616

https://arxiv.org/abs/1811.08676

Abstract: "In recent times, there has been much interest in quantum enhancements of machine learning, specifically in the context of data mining and analysis. Reinforcement learning, an interactive form of learning, is, in turn, vital in artificial intelligence-type applications. Also in this case, quantum mechanics was shown to be useful, in certain instances. Here, we elucidate these results, and show that quantum enhancements can be achieved in a new setting: the setting of learning models which learn how to improve themselves -- that is, those that meta-learn. While not all learning models meta-learn, all non-trivial models have the potential of being "lifted", enhanced, to meta-learning models. Our results show that also such models can be quantum-enhanced to make even better learners. In parallel, we address one of the bottlenecks of current quantum reinforcement learning approaches: the need for so-called oracularized variants of task environments. Here we elaborate on a method which realizes these variants, with minimal changes in the setting, and with no corruption of the operative specification of the environments. This result may be important in near-term experimental demonstrations of quantum reinforcement learning.
&

Next, I note that while most forecasts indicate that general purpose commercial quantum computers are about 10-years +/- 5-years away, the next linked articles indicate the D-Wave system already offers a development platform that allows programmers to used classical algorithms together with their quantum annealing commercial computers.  Also, I note that while the D-Wave commercial quantum computers are currently not general purpose, that are currently working on another development platform that will allow programmers to address general purpose problems.

Title: "TechRepublic: D-Wave releases development kit for hybrid quantum-classical applications"

https://www.dwavesys.com/media-coverage/techrepublic-d-wave-releases-development-kit-hybrid-quantum-classical-applications
https://www.techrepublic.com/article/d-wave-releases-development-kit-for-hybrid-quantum-classical-applications/

Extract: "D-Wave Systems announced D-Wave Hybrid—an open-source platform for developing hybrid quantum-classical applications—on Monday, at the Quantum for Business conference in Mountain View, CA. The new development platform gives programmers the ability to more easily use classical and quantum computers in parallel, without requiring knowledge of quantum mechanics to get started."
&

Lastly, I provide the following linked to a Wikipedia article on quantum machine learning, that contains relevant, but somewhat dated information.

Title: "Quantum machine learning"

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

Extract: "Quantum machine learning is an emerging interdisciplinary research area at the intersection of quantum physics and machine learning. The most common use of the term refers to machine learning algorithms for the analysis of classical data executed on a quantum computer."

Edit: For what it is worth, I provide the first image that illustrates the Policy Network and Value Network (used in machine learning for AlphaGo), and the second image that uses the Prisoner's Dilemma as a very simple example of strategies used to address 'wicked problems' like trying to limit anthropogenic GHG emissions.
« Last Edit: December 27, 2018, 08:28:26 PM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #405 on: December 28, 2018, 12:23:49 AM »
Most assessments of the risk of ocean deoxygenation project that mankind has centuries to millennia before we will experience major impacts from this effect (see the two linked references); however, none of these protections consider the impacts of ice-climate feedbacks on the potential slowdown of the ocean's MOC.  Mankind would be in for a very significant jolt if a potential ice-climate feedback lead to an acceleration of the current trend for ocean deoxygenation:

D. Breitburg et al. (5 January, 2018), "Declining oxygen in the global ocean and coastal waters”, Science, Vol. 359, Issue 6371, eaam7240, DOI: 10.1126/science.aam7240.

http://science.sciencemag.org/content/359/6371/eaam7240

Structured Abstract

BACKGROUND
Oxygen concentrations in both the open ocean and coastal waters have been declining since at least the middle of the 20th century. This oxygen loss, or deoxygenation, is one of the most important changes occurring in an ocean increasingly modified by human activities that have raised temperatures, CO2 levels, and nutrient inputs and have altered the abundances and distributions of marine species. Oxygen is fundamental to biological and biogeochemical processes in the ocean. Its decline can cause major changes in ocean productivity, biodiversity, and biogeochemical cycles. Analyses of direct measurements at sites around the world indicate that oxygen-minimum zones in the open ocean have expanded by several million square kilometers and that hundreds of coastal sites now have oxygen concentrations low enough to limit the distribution and abundance of animal populations and alter the cycling of important nutrients.

ADVANCES
In the open ocean, global warming, which is primarily caused by increased greenhouse gas emissions, is considered the primary cause of ongoing deoxygenation. Numerical models project further oxygen declines during the 21st century, even with ambitious emission reductions. Rising global temperatures decrease oxygen solubility in water, increase the rate of oxygen consumption via respiration, and are predicted to reduce the introduction of oxygen from the atmosphere and surface waters into the ocean interior by increasing stratification and weakening ocean overturning circulation.

In estuaries and other coastal systems strongly influenced by their watershed, oxygen declines have been caused by increased loadings of nutrients (nitrogen and phosphorus) and organic matter, primarily from agriculture; sewage; and the combustion of fossil fuels. In many regions, further increases in nitrogen discharges to coastal waters are projected as human populations and agricultural production rise. Climate change exacerbates oxygen decline in coastal systems through similar mechanisms as those in the open ocean, as well as by increasing nutrient delivery from watersheds that will experience increased precipitation.

Expansion of low-oxygen zones can increase production of N2O, a potent greenhouse gas; reduce eukaryote biodiversity; alter the structure of food webs; and negatively affect food security and livelihoods. Both acidification and increasing temperature are mechanistically linked with the process of deoxygenation and combine with low-oxygen conditions to affect biogeochemical, physiological, and ecological processes. However, an important paradox to consider in predicting large-scale effects of future deoxygenation is that high levels of productivity in nutrient-enriched coastal systems and upwelling areas associated with oxygen-minimum zones also support some of the world’s most prolific fisheries.

OUTLOOK
Major advances have been made toward understanding patterns, drivers, and consequences of ocean deoxygenation, but there is a need to improve predictions at large spatial and temporal scales important to ecosystem services provided by the ocean. Improved numerical models of oceanographic processes that control oxygen depletion and the large-scale influence of altered biogeochemical cycles are needed to better predict the magnitude and spatial patterns of deoxygenation in the open ocean, as well as feedbacks to climate. Developing and verifying the next generation of these models will require increased in situ observations and improved mechanistic understanding on a variety of scales. Models useful for managing nutrient loads can simulate oxygen loss in coastal waters with some skill, but their ability to project future oxygen loss is often hampered by insufficient data and climate model projections on drivers at appropriate temporal and spatial scales. Predicting deoxygenation-induced changes in ecosystem services and human welfare requires scaling effects that are measured on individual organisms to populations, food webs, and fisheries stocks; considering combined effects of deoxygenation and other ocean stressors; and placing an increased research emphasis on developing nations. Reducing the impacts of other stressors may provide some protection to species negatively affected by low-oxygen conditions. Ultimately, though, limiting deoxygenation and its negative effects will necessitate a substantial global decrease in greenhouse gas emissions, as well as reductions in nutrient discharges to coastal waters.


See also:

Battaglia, G. and Joos, F.: Hazards of decreasing marine oxygen: the near-term and millennial-scale benefits of meeting the Paris climate targets, Earth Syst. Dynam., 9, 797-816, https://doi.org/10.5194/esd-9-797-2018, 2018.

https://www.earth-syst-dynam.net/9/797/2018/

Abstract: "Ocean deoxygenation is recognized as key ecosystem stressor of the future ocean and associated climate-related ocean risks are relevant for current policy decisions. In particular, benefits of reaching the ambitious 1.5 ∘C warming target mentioned by the Paris Agreement compared to higher temperature targets are of high interest. Here, we model oceanic oxygen, warming and their compound hazard in terms of metabolic conditions on multi-millennial timescales for a range of equilibrium temperature targets. Scenarios where radiative forcing is stabilized by 2300 are used in ensemble simulations with the Bern3D Earth System Model of Intermediate Complexity. Transiently, the global mean ocean oxygen concentration decreases by a few percent under low forcing and by 40 % under high forcing. Deoxygenation peaks about a thousand years after stabilization of radiative forcing and new steady-state conditions are established after AD 8000 in our model. Hypoxic waters expand over the next millennium and recovery is slow and remains incomplete under high forcing. Largest transient decreases in oxygen are projected for the deep sea. Distinct and near-linear relationships between the equilibrium temperature response and marine O2 loss emerge. These point to the effectiveness of the Paris climate target in reducing marine hazards and risks. Mitigation measures are projected to reduce peak decreases in oceanic oxygen inventory by 4.4 % ∘C−1 of avoided equilibrium warming. In the upper ocean, the decline of a metabolic index, quantified by the ratio of O2 supply to an organism's O2 demand, is reduced by 6.2 % ∘C−1 of avoided equilibrium warming. Definitions of peak hypoxia demonstrate strong sensitivity to additional warming. Volumes of water with less than 50 mmol O2 m−3, for instance, increase between 36 % and 76 % ∘C−1 of equilibrium temperature response. Our results show that millennial-scale responses should be considered in assessments of ocean deoxygenation and associated climate-related ocean risks. Peak hazards occur long after stabilization of radiative forcing and new steady-state conditions establish after AD 8000."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #406 on: December 28, 2018, 04:43:51 PM »
The linked 'explainer' by Zeke Hausfather provides more details about the SSP family of radiative forcing scenarios than my few extracts below can cover.  Even those the IPCC indicates that none of the SSP scenarios represents a projection (or best guess) of what is likely to happen; nevertheless, the majority of my recent posts have assumed that SSP5-Baseline scenario is a reasonable representation of our likely collective pathway until at least 2040.  However, as cited in my Reply #346 and reiterated in the first attached image and the extract below, SSP5-Baseline represents an optimistic assessment of such considerations as: population growth, methane emissions, unaccounted for GDP (such as for people living in deep poverty), and anthropogenic degradation of carbon sinks (e.g. deforestation). For example while the GDP projections shown in the second image indicate values that are slightly lower than those assumed by SSP5-Baseline, anthropogenic carbon emissions and GMSTA growth still match those shown in the third image for SSP5-Baseline through 2018.  Thus we would all do well to remember that SSP5-Baseline does not represent a worse case scenario with regards to either radiative forcing, ECS and/or GMSTA growth through at least 2060:

Title: "Explainer: How ‘Shared Socioeconomic Pathways’ explore future climate change"

https://www.carbonbrief.org/explainer-how-shared-socioeconomic-pathways-explore-future-climate-change

Over the past few years, an international team of climate scientists, economists and energy systems modellers have built a range of new “pathways” that examine how global society, demographics and economics might change over the next century. They are collectively known as the “Shared Socioeconomic Pathways” (SSPs).

The RCPs set pathways for greenhouse gas concentrations and, effectively, the amount of warming that could occur by the end of the century. Whereas the SSPs set the stage on which reductions in emissions will – or will not – be achieved.

SSP1 and SSP5 envision relatively optimistic trends for human development, with “substantial investments in education and health, rapid economic growth, and well-functioning institutions”. They differ in that SSP5 assumes this will be driven by an energy-intensive, fossil fuel-based economy, while in SSP1 there is an increasing shift toward sustainable practices.

Many of the SSPs end up being broadly similar in the narratives to the old SRES scenarios, used in the IPCC’s third and fourth assessment reports. For example, the sustainability-focused SSP1 is rather similar to SRES B1, while the more middle-of-the-road SSP2 is similar to SRES B2. The globally fragmented SSP3 is quite similar to SRES A2 and the high fossil-fuel reliant, high-growth SSP5 shares many elements with SRES A1F1.

Population levels are lowest in SSP1 and SSP5, peaking at 8.5 billion between 2050 and 2060, and declining to today’s level of around 7 billion by 2100. This is broadly consistent with the United Nation’s low fertility scenario.

Caption for the first image: "Global population (left) in billions and global gross domestic product (right) in trillion US dollars on a purchasing power parity (PPP) basis.

Caption for the third image: "CO2 emissions (left) in gigatonnes  (GtCO2) and global mean surface temperature change relative to pre-industrial levels (right) in degrees C across all models and SSPs for baseline no-climate-policy scenarios. The “marker” model for each SSP is shown by a thicker line, while all other model runs for that SSP have thin lines."

For the SSP data, see:

https://tntcat.iiasa.ac.at/SspDb/dsd?Action=htmlpage&page=welcome

Also, for a discuss of the SRES family of emissions scenarios see:

Title: "Special Report on Emissions Scenarios"

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

Extract: "The IPCC did not state that any of the SRES scenarios were more likely to occur than others, therefore none of the SRES scenarios represent a "best guess" of future emissions."

Edit: I should have noted that the IMF projections for GDP (see the second image) are not on a PPP basis as are the SSP5-Baseline shown in the first image.
« Last Edit: December 28, 2018, 05:34:05 PM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #407 on: December 28, 2018, 04:48:40 PM »
The linked reference indicates that with continued global warming ice caps are also prone to surges (abrupt accelerations) of ice mass loss:

Michael J. Willis et al (15 November 2018), "Massive destabilization of an Arctic ice cap", Earth and Planetary Science Letters, Volume 502, Pages 146-155; https://doi.org/10.1016/j.epsl.2018.08.049

https://www.sciencedirect.com/science/article/pii/S0012821X18305156?via%3Dihub

Abstract: "Ice caps that are mostly frozen at the bedrock-ice interface are thought to be stable and respond slowly to changes in climate. We use remote sensing to measure velocity and thickness changes that occur when the margin of the largely cold-based Vavilov Ice Cap in the Russian High Arctic advances over weak marine sediments. We show that cold-based to polythermal glacier systems with no previous history of surging may evolve with unexpected and unprecedented speed when their basal boundary conditions change, resulting in very large dynamic ice mass losses (an increase in annual mass loss by a factor of ∼100) over a few years. We question the future long-term stability of cold and polythermal polar ice caps, many of which terminate in marine waters as the climate becomes warmer and wetter in the polar regions."

See also:

Title: "New research shows the world’s ice is doing something not seen before"

https://www.theguardian.com/environment/climate-consensus-97-per-cent/2018/sep/26/new-research-shows-the-worlds-ice-is-doing-something-not-seen-before
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #408 on: December 28, 2018, 08:24:05 PM »
The linked reference confirms critical portions (related to accelerated marine glacier ice mass loss and slowed MOC) of the multifaceted ice-climate feedback mechanisms.  Other ice-climate feedback mechanisms not addressed by this reference include potential: a) increases in net positive cloud feedback, b) increases in net ice-albedo feedbacks, and c) increases in positive feedback from the bipolar seesaw mechanism:

Alessandro Silvano et al. (18 Apr 2018), "Freshening by glacial meltwater enhances melting of ice shelves and reduces formation of Antarctic Bottom Water", Science Advances, Vol. 4, no. 4, eaap9467, DOI: 10.1126/sciadv.aap9467

http://advances.sciencemag.org/content/4/4/eaap9467.full

Abstract: "Strong heat loss and brine release during sea ice formation in coastal polynyas act to cool and salinify waters on the Antarctic continental shelf. Polynya activity thus both limits the ocean heat flux to the Antarctic Ice Sheet and promotes formation of Dense Shelf Water (DSW), the precursor to Antarctic Bottom Water. However, despite the presence of strong polynyas, DSW is not formed on the Sabrina Coast in East Antarctica and in the Amundsen Sea in West Antarctica. Using a simple ocean model driven by observed forcing, we show that freshwater input from basal melt of ice shelves partially offsets the salt flux by sea ice formation in polynyas found in both regions, preventing full-depth convection and formation of DSW. In the absence of deep convection, warm water that reaches the continental shelf in the bottom layer does not lose much heat to the atmosphere and is thus available to drive the rapid basal melt observed at the Totten Ice Shelf on the Sabrina Coast and at the Dotson and Getz ice shelves in the Amundsen Sea. Our results suggest that increased glacial meltwater input in a warming climate will both reduce Antarctic Bottom Water formation and trigger increased mass loss from the Antarctic Ice Sheet, with consequences for the global overturning circulation and sea level rise."

See also:

Title: "Study Reveals Dangerous Antarctic Feedback Loop"

https://www.ecowatch.com/antarctic-climate-change-study-2562971817.html

Extract: "Hansen himself also commented, saying "this study provides a nice small-scale example of processes that we talk about in our paper," the Post reported.

"On the large-scale issue, it is too early to say how these feedback processes will play out, based on empirical evidence," Hansen told the Post by email. "If we stay on business-as-usual [greenhouse gas] emissions rates, so that global warming continues to increase, I expect that the freshwater injection rate will increase (mainly via ice faster ice shelf breakup and underwater melt) and sea ice area will increase. This experiment will be playing out over the next years and decades.""
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #409 on: December 28, 2018, 11:55:56 PM »
The linked reference confirms that: "Compared to the comprehensive models, the reduced-complexity models have a lower range of climate sensitivities …"; which is to say that more sophisticated climate models project higher values of ECS:

Patrik L Pfister and Thomas F Stocker (17 December 2018), "The realized warming fraction: a multi-model sensitivity study", Environmental Research Letters, Volume 13, Number 12, https://doi.org/10.1088/1748-9326/aaebae

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

Abstract: "The degree of physical-biogeochemical equilibration of the climate system determines for how long global warming will continue after anthropogenic CO2 emissions have ceased. The physical part of this equilibration process is quantified by the realized warming fraction (RWF), but RWF estimates differ strongly between different climate models. Here we analyze the RWF spread and its physical causes in three model ensembles: 1. an ensemble of comprehensive climate models, 2. an ensemble of reduced-complexity models, and 3. an observationally constrained parameter ensemble of the Bern3D-LPX reduced-complexity model. We show that RWF is generally lower in models with higher equilibrium climate sensitivity. The RWF uncertainty from applying different extrapolation methods for climate sensitivity is substantial, but smaller than the inter-model spread in the three ensembles. We decompose the inter-model spread of RWF using a diagnostic global energy balance model, to compare the spread contribution by the climate sensitivity to contributions by other physical quantities: the efficiency and efficacy of ocean heat uptake, and the effective radiative forcing. In the ensembles of the comprehensive climate models and the Bern3D-LPX model, the spread of the RWF is mostly determined by the spread of the climate sensitivity; for the reduced-complexity models, the spread contribution by the ocean heat uptake efficiency is dominant. Compared to the comprehensive models, the reduced-complexity models have a lower range of climate sensitivities and lower, more unitary ocean heat uptake efficacies, resulting in higher RWF. However, by tuning such models to higher climate sensitivities, they can also achieve RWF values in the lower range of comprehensive models, as demonstrated for Bern3D-LPX. This suggests that reduced-complexity models remain useful tools for future climate change projections, but should employ a range of climate sensitivity tunings to account for the uncertainty in both the long-term warming and the RWF."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #410 on: December 29, 2018, 12:10:17 AM »
The linked reference provides valuable information about how West Antarctic surface melting events can be facilitated by Foehn warming:

Xun Zou et al. (21 December 2018), "West Antarctic Surface Melt Event of January 2016 Facilitated by Foehn Warming", Quarterly Journal of the Royal Meteorological Society, https://doi.org/10.1002/qj.3460

https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/qj.3460

Abstract: "The Ross Ice Shelf (RIS) buttresses ice streams from the Antarctic continent and restrains the grounded ice sheet from flowing into the ocean, which is important for the stability of the ice sheet. In recent decades, West Antarctic ice shelves, including the RIS, have experienced more frequent surface melting during summer. We investigated the role of warm, descending foehn winds in a major melt event that occurred on the RIS in January 2016. Only a few summer melt events of this magnitude have been observed since 1979. Backward trajectories from the area of earliest melting were constructed using the Antarctic Mesoscale Prediction System (AMPS) to investigate the dominant mechanisms at the beginning of the melt event, mainly from 10 to 13 January. Analysis was conducted over two distinct areas. The foehn effect contributed around 2‐4 °C to the surface temperature increase over the coastal mountains of Marie Byrd Land (MBL) and around 1 °C over the much lower Edward VII Peninsula. Most of the foehn warming was caused by isentropic drawdown of air aloft. On 10 January, the second‐most important contributor for both mountain ranges was the thermodynamic mechanism. On 11 January, the second‐most important mechanism was the sensible and radiative heat flux. This study contributes to a better understanding of surface melt events over the RIS and benefits research associated with the stability of West Antarctic ice shelves."

Edit: Such surface melting events can increase the risk of hydrofracturing events for key West Antarctic ice shelves.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #411 on: December 29, 2018, 04:33:23 PM »
While we have seen that SSP5-Baseline is not a projection (see Reply #406), the linked studies use the Earth3 and the World3 models to make projections, and they both indicate a high risk of socio-economic collapse circa 2050, meaning that if the WAIS does cross a tipping point before 2040, the world will likely not be in any position to afford significant geoengineering by 2050:

Title: "Gloomy 1970s predictions about Earth's fate still hold true",  doi: 10.1038/d41586-018-07117-2

https://www.nature.com/articles/d41586-018-07117-2

Extract: "Four decades ago, the Club of Rome predicted looming economic collapse in its iconic report The Limits to Growth.  An update of the analysis sees much the same picture."
&

Title: "Transformation is feasible - How to achieve the Sustainable Development Goals within Planetary Boundaries"

https://www.stockholmresilience.org/publications/artiklar/2018-10-17-transformation-is-feasible---how-to-achieve-the-sustainable--development-goals-within-planetary-boundaries.html
&
https://www.stockholmresilience.org/download/18.51d83659166367a9a16353/1539675518425/Report_Achieving%20the%20Sustainable%20Development%20Goals_WEB.pdf

Extract: "There is high risk for pushing the Earth's life supporting systems beyond irreversible trigger-points by 2050, …"

Also, the first two attached images provide projections from the World3 model (see the linked pdf & the linked Wikipedia article) both showing model runs about 40-years after Limits to Growth was first published in the 1970's.  Both images show a normalized peak in population circa 2050.

Title: "40 years after Limits to Growth The World3 system dynamics model and its impacts"

http://www.wrforum.org/wp-content/uploads/2015/09/Limits-to-growth.pdf

&

https://en.wikipedia.org/wiki/World3

Extract: "At least one study, however, claims that "30 years of historical data compare favorably with key features of a business-as-usual scenario called the 'standard run' scenario" produced by the World3 model."

Edit: By early 2019 the world population will reach 7.7 Billion people.
« Last Edit: December 29, 2018, 04:41:23 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #412 on: December 30, 2018, 03:42:41 AM »
New evidence that the WAIS is unstable:

Title: "PP11A-05: Absence of the West Antarctic ice sheet during the last interglaciation" by Carlson et al (2018)

https://agu.confex.com/agu/fm18/meetingapp.cgi/Paper/421418

Abstract: "During the last interglaciation (LIG; ~129-116 ka), global mean sea level (GMSL) was >6 m above present. Based on evidence of only modest LIG Greenland ice-sheet retreat, Antarctic ice sheets may also have contributed to LIG GMSL, but direct data for a contribution is lacking. Here we investigate the LIG extent of the West Antarctic (WAIS) and Antarctic Peninsula (APIS) ice sheets using Sr-Nd-Pb isotopes of silt from ODP Site 1096 in the Bellingshausen Sea. Based on our shelf Sr-Nd-Pb provenance data and a stable-isotope age model, we document WAIS-APIS erosion of all radiogenically-discernable terranes from the latter part of marine isotope stage (MIS) 5 up through the Holocene, consistent with independent ice-margin chronologies showing ice presence on all of these terranes from MIS 2 through the Holocene. For the LIG/early MIS 5, we only find evidence of silt sourced from the erosion of the APIS and the mountain ranges that rim the northern modern WAIS, with an absence of silt from Pine Island glacier. Ice-sheet models link Pine Island glacier absence to full WAIS collapse into ice caps on mountains. Our record thus provides the first direct indication of a much smaller LIG WAIS, providing paleo-context for the susceptibility of the WAIS to collapse."

See also:

Title: "Discovery of recent Antarctic ice sheet collapse raises fears of a new global flood"

https://www.sciencemag.org/news/2018/12/discovery-recent-antarctic-ice-sheet-collapse-raises-fears-new-global-flood

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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #413 on: December 31, 2018, 01:26:10 AM »
The linked reference indicates that the Arctic Region's positive local lapse-rate feedback, predominately contributes to the observed Arctic Amplification.  That said, other feedbacks (such as ENSO warming of the North Pacific [see Reply #397], and ice-albedo) may contribute more to future Arctic Amplification as we approach (and then exceed) a GMSTA of 2C:

Stuecker, M. F., Bitz, C. M., Armour, K. C., Proistosescu, C., Kang, S. M., Xie, S.-P., … Jin, F.-F. (2018). Polar amplification dominated by local forcing and feedbacks. Nature Climate Change. doi:10.1038/s41558-018-0339-y

https://www.nature.com/articles/s41558-018-0339-y

Abstract: "The surface temperature response to greenhouse gas forcing displays a characteristic pattern of polar-amplified warming, particularly in the Northern Hemisphere. However, the causes of this polar amplification are still debated. Some studies highlight the importance of surface-albedo feedback, while others find larger contributions from longwave feedbacks, with changes in atmospheric and oceanic heat transport also thought to play a role. Here, we determine the causes of polar amplification using climate model simulations in which CO2 forcing is prescribed in distinct geographical regions, with the linear sum of climate responses to regional forcings replicating the response to global forcing. The degree of polar amplification depends strongly on the location of CO2 forcing. In particular, polar amplification is found to be dominated by forcing in the polar regions, specifically through positive local lapse-rate feedback, with ice-albedo and Planck feedbacks playing subsidiary roles. Extra-polar forcing is further shown to be conducive to polar warming, but given that it induces a largely uniform warming pattern through enhanced poleward heat transport, it contributes little to polar amplification. Therefore, understanding polar amplification requires primarily a better insight into local forcing and feedbacks rather than extra-polar processes."

See also:

Title: "It Looks Like a Weird Feature of The Arctic Atmosphere Is Making Climate Change Worse"

https://www.sciencealert.com/weird-carbon-dioxide-feature-in-arctic-amplifying-climate-change

Extract: ""This study is significant as it disproves previously suggested hypotheses of the cause of Polar Amplified warming, showing that local greenhouse gas concentrations, and Arctic climate feedbacks outweigh the impact of remote processes," says co-author Shayne McGregor, a climate scientist from Monash University in Australia.

Even compared to other local effects, the vertical atmospheric profile has an unequalled effect on Arctic amplification.

"Our computer simulations show that these changes in the vertical atmospheric temperature profile in the Arctic region outweigh other regional feedback factors, such as the often-cited ice-albedo feedback," says Stuecker."
« Last Edit: December 31, 2018, 04:42:19 PM by AbruptSLR »
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wili

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #414 on: December 31, 2018, 03:14:31 AM »
From the abstract:

"polar amplification is found to be dominated by forcing in the polar regions, specifically through positive local lapse-rate feedback"

Could you or someone explain a bit about what exactly lapse-rate feedback is, hopefully in terms that I and others can understand?

It sounds like it's pretty important, and it seems like a gap in my GW knowledge I'd like to fill.

Thanks ahead of time for any light you can throw on this.
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #415 on: December 31, 2018, 05:08:08 AM »
From the abstract:

"polar amplification is found to be dominated by forcing in the polar regions, specifically through positive local lapse-rate feedback"

Could you or someone explain a bit about what exactly lapse-rate feedback is, hopefully in terms that I and others can understand?

It sounds like it's pretty important, and it seems like a gap in my GW knowledge I'd like to fill.

Thanks ahead of time for any light you can throw on this.

Jargon that should be banished from publications intended for wider audience. I'm sure someone has corrections to the following, but "positive local lapse rate feedback" means the local greenhouse forcing is enhanced, whether this is because of locally increased water vapor, clouds, methane, winter/early spring peak of CO2 or even changes in air pressure (which affects the speed heat escapes to space), doesn't matter. It's an alternative way to say "local variations in positive atmospheruc feedbacks, without going into detail".

Lapse rate may be observed from temperature measurements from different heights for real atmosphere and a dry lapse rate calculation can be done to eliminate the effect of water vapor. This is, I understand, rather important measure for lateral atmospheric flow (that is, winds) predictions in meteorological models.

Lapse rate is itself calulated for assumed stable atmosphere and for the same moment in time for various layers, eliminating the effect of winds that take some more time to carry the heat elsewhere. Hope this helps, and isn't too inaccurate.
« Last Edit: December 31, 2018, 05:28:54 AM by Pmt111500 »
Amateur observations of Sea Ice since 2003.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #416 on: December 31, 2018, 05:36:40 AM »

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #417 on: December 31, 2018, 06:04:17 AM »
Re: lapse rate feedback

http://www.climate.be/textbook/chapter4_node7.html

sidd


The negative lapse rate feedback example for tropics there would probably be for the high troposphere/stratosphere methane in the real atmosphere, whereas the arctic positive one is from water vapor and ground level methane (+possibly CO2 in winter)
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #418 on: December 31, 2018, 06:07:20 AM »
Thanks, sidd.

So in the tropics, the lapse rate (basically the change in conditions, in this case temperature, as you move up through the atmosphere, iirc) involves a warmer upper troposphere, leading to more loss of radiation from the top of the atmosphere...so, a negative (damping) feedback on global warming.

But in the Arctic, less heat accumulates in the upper troposphere (because of lack of water vapor to conduct it up there??), so less heat is released to space, leading to a positive (exacerbating) feedback.

And this study found that this lapse rate feedback dominates others in the Arctic, as I understand it. Is that likely to change somewhat as water vapor levels increase in the region?
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #419 on: December 31, 2018, 05:01:52 PM »
Thanks, sidd.

So in the tropics, the lapse rate (basically the change in conditions, in this case temperature, as you move up through the atmosphere, iirc) involves a warmer upper troposphere, leading to more loss of radiation from the top of the atmosphere...so, a negative (damping) feedback on global warming.

But in the Arctic, less heat accumulates in the upper troposphere (because of lack of water vapor to conduct it up there??), so less heat is released to space, leading to a positive (exacerbating) feedback.

And this study found that this lapse rate feedback dominates others in the Arctic, as I understand it. Is that likely to change somewhat as water vapor levels increase in the region?

wili,

W.r.t. how the lapse rate feedback works, from the article that I linked:

https://www.sciencealert.com/weird-carbon-dioxide-feature-in-arctic-amplifying-climate-change

Extract: "This new study is changing our understanding of one important factor, called the vertical atmospheric temperature profile. It sounds complicated, but it just has to do with the distribution of carbon dioxide in the atmosphere.

In the Arctic, carbon dioxide has an opposite vertical distribution than in the tropics, and the recent research suggests this is what's causing the polar region such strife compared to the rest of the world.

In the tropics, where temperature and moisture is high, air can travel more easily through the atmosphere, rising to higher and higher altitudes. As carbon dioxide climbs further along with it, the upper atmosphere is warmed and the resulting energy can easily slip out into space.
But in the Arctic, something different happens. The temperature is colder and the air doesn't move as quickly to the upper atmospheres; its movement is more stable. This means that carbon dioxide heats up lower parts of the atmosphere more, so not quite as much energy can escape into space."

Regarding the future, you need to bear in mind that Stuecker et al (2018) are talking about observed Arctic Amplification, and you need to bear in mind that global warming is only now beginning to have a significant impact on the ENSO cycle (and in a few decades on summer Arctic Sea Ice extent and the associated flip in the ice-albedo feedback), and as cited in Reply #397:

"The linked reference indicates that the warming of the North Pacific subpolar waters is likely the most important feedback for driving enhanced Arctic Amplification with continued global warming, and the attached image demonstrates how the North Pacific subpolar water can be warmed directly by atmospheric telecommunication of energy from the Tropical Pacific.  If show this indicates that the CMIP5 projections likely underestimate ECS, and as ice-climate feedback would likely accelerate warming the Tropical Pacific, it is likely that CMIP6 projections will also underestimate ECS as these models do not consider ice-cliff failures or hydrofracturing:"

Summer Praetorius, Maria Rugenstein, Geeta Persad, Ken Caldeira. Global and Arctic climate sensitivity enhanced by changes in North Pacific heat flux. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-05337-8

https://www.nature.com/articles/s41467-018-05337-8

Thus by 2040 Arctic Amplification will likely be significantly higher that today due to increased water vapor migration from the North Pacific (associated with the increased telecommunication of Tropical Pacific energy due to increase El Nino frequencies), and decreased ice-albedo, as well as the lapse rate feedback cited by Stuecker et al (2018):
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #420 on: December 31, 2018, 08:47:25 PM »

..., whereas the arctic positive one is from water vapor and ground level methane (+possibly CO2 in winter)

Dry air has a density of about 1.29 g/L (gram per liter) at standard conditions for temperature and pressure (STP), while Methane has a density of 0.716 g/L at STP, so methane floats-up to the stratosphere (where is produces stratospheric ozone and water vapor) even in the Arctic.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #421 on: December 31, 2018, 09:11:27 PM »
The linked reference indicates that consensus climate science has been incorrectly adjusting paleo determined values of climate sensitivity (including land ice changes) for comparison with estimates of ECS based on climate models that do not consider land ice changes.  Their findings indicate that paleodata should estimate a value of ECS in the range of 5.6 +/- 1.3C.  While it is true that paleodata correctly considers land ice changes to be a long-term process, considering ice cliff, and hydrofracturing, failure mechanisms, land ice feedback mechanisms may well have significant impact on climate sensitivity within the coming decades.

Stap, L. B., Köhler, P., and Lohmann, G.: Including the efficacy of land ice changes in deriving climate sensitivity from paleodata, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2018-88, in review, 2018.

https://www.earth-syst-dynam-discuss.net/esd-2018-88/

Abstract. The influence of long-term processes in the climate system, such as land ice changes, has to be compensated for when comparing climate sensitivity derived from paleodata with equilibrium climate sensitivity (ECS) calculated by climate models, which is only generated by a CO2 change. Several recent studies found that the impact these long-term processes have on global temperature cannot be quantified directly through the global radiative forcing they induce. This renders the approach of deconvoluting paleotemperatures through a partitioning based on radiative forcings inaccurate. Here, we therefore implement an efficacy factor ε, that relates the impact of land ice changes on global temperature to that of CO2 changes, in our calculation of climate sensitivity from paleodata. We apply our new approach to a proxy-inferred paleoclimate dataset, and find an equivalent ECS of 5.6±1.3K per CO2 doubling. The substantial uncertainty herein is generated by the range in ε we use, which is based on a multi-model assemblage of simulated relative influences of land ice changes on the Last Glacial Maximum (LGM) temperature anomaly (46±14%). The low end of our ECS estimate, which concurs with estimates from other approaches, tallies with a large influence for land ice changes. To separately assess this influence, we analyse output of the PMIP3 climate model intercomparison project. From this data, we infer a functional intermodel relation between global and high-latitude temperature changes at the LGM with respect to the pre-industrial climate, and the temperature anomaly caused by a CO2 change. Applying this relation to our dataset, we find a considerable 64% influence for land ice changes on the LGM temperature anomaly. This is even higher than the range used before, and leads to an equivalent ECS of 3.8K per CO2 doubling. Together, our results suggest that land ice changes play a key role in the variability of Late Pleistocene temperatures.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #422 on: December 31, 2018, 09:32:02 PM »
Thanks, as always, aslr
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #423 on: January 01, 2019, 06:02:42 PM »
I have generally made relatively few posts about the dynamics between climate change and food production, as this matter seems to cut to the core of mankind's aspirational nature in the face of a very complex issue.  Here I use the word aspirational in the sense that 'the road to hell is paved with good intentions', in what James Hansen has called mankind's Faustian Bargain with the Earth's many biosystems (both wild and managed).

As this topic is so complex and politically charged, I will only make a few bullet points for the readers consideration and then I will provide some links to a few articles that err on the side of least drama on this topic as I could not find any references that directly face issues like the following bullet points in their various evaluations of our potential circumstances circa 2050 +/- 10-years.  Selected food production related issues relevant to this thread include:

1. Circa 2050 the median population projection per the UN is about 10 billion people, and meat consumption is projected to increase at an even faster rate (food demands between 2013 and 2050 are projected to increase by 50%).  BECCS and hydropower production both have a negative impact on food security, and also transportation and distribution for food will require make major demands on both energy (including fossil fuels) and infrastructure (ships, ports, road & rail etc), including due to climate change impacts on farm distributions.  I further not that currently world hunger is increasing, most likely due to the relatively mild impacts of climate change that we are already experiencing.
2. Abrupt climate change and ice-climate feedbacks associated with multiple meters of SLR in the coming decades, would have severe impacts on food production, virtually none of which are seriously addressed in any food security projections that I have ever seen.  Relevant topics include abrupt increases in: a. extreme weather events, b. shifts in rainfall and surface temperature patterns, c. coastal flooding (see the attached image from Hansen [2018]) of croplands and associated salinity intrusion into neighboring groundwater, etc.
3. Agriculture, forestry and land use already contribute on fifth of anthropogenic GHG emissions, and on a BAU pathway this percentage is likely to increase by 2050.  Furthermore, climate change is decreasing the nutritional value of crops and is increasing the risks of foodborne diseases and of transboundary pests.  Also, following a BAU pathway will increase climate change related human migration, which will increase regional and global conflicts.  Vegetation losses associated with abrupt climate change, will not only reduce the negative feedback from carbon sinks, but will increase carbon emissions from decaying plant matter.

Title: "Climate change will reshape the world’s agricultural trade"

http://theconversation.com/climate-change-will-reshape-the-worlds-agricultural-trade-102721

Extract: "Even the United States, which has opted out of the Paris Agreement, acknowledged at last year’s G7 summit that climate change was one of a number of threats to “our capacity to feed a growing population and need[ed] to be taken into serious consideration”.

However, the most recent UN report on food security and nutrition shows that world hunger is on the rise again and scientists believe this is due to climate change."
&

Title: "The future of food production amid global change"

http://news.mit.edu/2018/mit-joint-program-workshop-explores-future-food-production-amid-global-change-1120

Extract: "When it comes to impacting global change, agriculture cuts both ways. Subject to the vicissitudes of global climate change, population, and economic growth, the cultivation of crops and livestock alters atmospheric concentrations of planet-warming greenhouse gases and contributes to pollution of freshwater and coastal areas. Assessing the risks to and from the agriculture sector — and identifying opportunities for the sector to thrive amid global change — is both urgent and essential.

The Outlook shows significant increases in food production driven by population and economic growth as well as transformation of the value chain, with more rapid growth in livestock than crops.

Observing that 70 percent of today’s freshwater withdrawals are for irrigation, and that by 2050 about 17 percent of all water now used in agriculture will be at risk from reallocation to nonagricultural economic growth, population and urban growth, and environmental protection, Strzepek highlighted several trends that pose a growing threat to such withdrawals, including the adoption of clean energy generation through hydropower at the expense of water for irrigation.

“You can get a lot of energy at the expense of water and food security,” said Strzepek, who co-authored a study indicating that agriculture has the lowest marginal value of all economic sectors. “We’re seeing rapid growth and urbanization in Africa, and increased hydropower, which increases water demands. Where do we invest in the future? Water for agriculture? Water for energy? Where do we put our values?”

Joint Program Deputy Director C. Adam Schlosser explored the extent to which land-use and land-cover change impact the local, regional, and global climate by absorbing or redirecting energy received from the sun. He noted that at the regional level, changes in land use and land cover lead to corresponding changes in albedo (reflectivity), soil moisture, canopy, and plant characteristics, which can collectively amplify or offset global warming from key atmospheric greenhouse gases."

See also:

"Climate Change in a Nutshell: The Gathering Storm", 18 December 2018, by James Hansen

http://www.columbia.edu/~jeh1/mailings/2018/20181206_Nutshell.pdf

Extract: "In reality CO2 is not only continuing to increase, its rate of growth is increasing.  The reason is that global population and energy demands continue to increase, and about 85 percent of global energy is provided by fossil fuels.

A case has been made (Ice Melt, 2016) that the doubling time for ice sheet mass loss, assuming continued growth of fossil fuel emissions, may be as short as 10-20 years, based on evidence from the combination of paleoclimate data, modern observations, and ocean-atmosphere modeling.   In that case, multi-meter sea level rise would occur on a time scale of 50-150 years."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #424 on: January 02, 2019, 05:14:51 PM »
It is worth pointing out (reiterating) that a short-term surge (decadal) of ice mass loss (due to an acceleration of calving as the calving front retreats down a retrograde bedslope) from key South Greenland marine terminating glaciers (including both Jakobshavn and Kangerdlugssuaq Glaciers), would almost certainly accelerate ice mass loss from key Antarctic marine glaciers due to the bipolar seesaw mechanism:

Bevan, S. L., Luckman, A. J., Benn, D. I., Cowton, T., and Todd, J.: Warming of SE Greenland shelf waters in 2016 primes large glacier for runaway retreat, The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-260, in review, 2019.

https://www.the-cryosphere-discuss.net/tc-2018-260/

Abstract. Kangerdluqssuaq Glacier in south-east Greenland has now retreated further inland than at any time in the past 33 years and is fast approaching a region of retrograde bedslope, meaning that continued rapid retreat is likely. Here we show that the current retreat was driven by anomalously warm surface water on the continental shelf during 2016. The warm surface water likely penetrated the fjord and weakened the mixture of sea ice and icebergs known as mélange, which is normally rigid enough to inhibit calving in winter. As Kangerdlugssuaq Glacier continued to calve almost continuously throughout 2017 and 2018 it accelerated by 35% and thinned by 35m.

Caption for the first image: "Figure 7. Surface elevation profiles for advanced (red, 26/06/2016) and retreated (blue, 09/05/2018) front positions, corresponding to the same colour points plotted in Fig. 3c. The surface velocity profile is the result of feature tracking TanDEM-X data from 29/05/2014 to 09/06/2014"

Edit: The second image shows how close the calving face for the Jakobshavn Glacier is to entering a retrograde bedslope:

An, L., E. Rignot, S. Elieff, M. Morlighem, R. Millan, J. Mouginot, D. M. Holland, D. Holland, and J. Paden (2017), Bed elevation of Jakobshavn Isbræ, West Greenland, from high-resolution airborne gravity and other data, Geophys. Res. Lett., 44, 3728–3736, doi:10.1002/2017GL073245.

Caption for second image: "Figure 3. Profile A-A’ along the deepest bed of Jakobshavn Isbræ, West Greenland, showing the surface and bed elevations from the MC reconstruction (grey), the GBMF data in this study (black), Bamber et al. [2013] (dotted red), Joughin et al. [2014] (dotted purple), and CReSIS (dark blue) with corresponding error bars in shaded color (±1 sigma). The surface elevation is from year 2007 to 2008 (MC, B2013,C2009) and 2012 (GBMF). Red stars denote bathymetry data in the fjord. Colored triangles denote the positions of the glacier grounding lines at different epochs with the same color table as in Figure 1. Origin of distance is the 1996 grounding line position. Superimposed on that plot with a secondary vertical axis on the left-hand side is a comparison of the observed gravity anomaly (continuous blue) versus the calculated (dotted blue) gravity anomaly in mGal along profile A-A’."
« Last Edit: January 02, 2019, 10:06:30 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #425 on: January 02, 2019, 08:53:11 PM »
The linked reference indicates that the new generation (e.g. CMIP5) of ESMs include numerous feedback mechanisms that were not included in the past generation (e.g. CMIP5).  The uncertainties associated with these new feedbacks represent a risk to society (with continued warming).  Furthermore, I reiterate that CMIP6 does not include any feedback mechanisms associated with ice cliff, and hydrofracturing, failure mechanism; which means that society may very well be in for a rude awakening circa 2040 +/-5-years:

Heinze, C., Eyring, V., Friedlingstein, P., Jones, C., Balkanski, Y., Collins, W., Fichefet, T., Gao, S., Hall, A., Ivanova, D., Knorr, W., Knutti, R., Löw, A., Ponater, M., Schultz, M. G., Schulz, M., Siebesma, P., Teixeira, J., Tselioudis, G., and Vancoppenolle, M.: Climate feedbacks in the Earth system and prospects for their evaluation, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2018-84, in review, 2018.

https://www.earth-syst-dynam-discuss.net/esd-2018-84/

Abstract. Earth system models (ESMs) are key tools for providing climate projections under different scenarios of human-induced forcing. ESMs include a large number of additional processes and feedbacks such as biogeochemical cycles that traditional physical climate models do not consider. Yet, some processes such as cloud dynamics and ecosystem functional response still have fairly high uncertainties. In this article, we present an overview of climate feedbacks for Earth system components currently included in state-of-the-art ESMs and discuss the challenges to evaluate and quantify them. Uncertainties in feedback quantification arise from the interdependencies of biogeochemical matter fluxes and physical properties, the spatial and temporal heterogeneity of processes, and the lack of long-term continuous observational data to constrain them. We present an outlook for promising approaches that can help quantifying and constraining the large number of feedbacks in ESMs in the future. The target group for this article includes generalists with a background in natural sciences and an interest in climate change as well as experts working in interdisciplinary climate research (researchers, lecturers, and students). This study updates and significantly expands upon the last comprehensive overview of climate feedbacks in ESMs, which was produced 15 years ago (NRC, 2003).

Extract: "Within an Earth system context, many more climatically relevant feedbacks influence climate projections under given forcing scenarios than in previous generations of physical climate models. In addition to the classical physical climate feedbacks, biogeochemical feedbacks are also considered in more complex Earth system models."

Caption for image: "Table 1: Classification of specific feedbacks (left vertical column) with respect to general “archetypes” of feedbacks. Feedbacks can be summarised as thermodynamic and composition altering feedbacks. Aerosol feedbacks are among the most complex feedbacks.  The numbers in front of the specific feedbacks refer to the headers/sub-headers of the respective sections in the text."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #426 on: January 02, 2019, 09:33:36 PM »
For those who are interested in the details of the differences in the lapse rate feedbacks between the tropics and the poles, I provide the following linked reference:

Matthew Henry and Timothy M. Merlis (2018), "The Role of the Nonlinearity of the Stefan–Boltzmann Law on the Structure of Radiatively Forced Temperature Change", Journal of Climate, https://doi.org/10.1175/JCLI-D-17-0603.1

https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-17-0603.1

Abstract: "The Stefan–Boltzmann law governs the temperature dependence of the blackbody emission of radiation:  . A consequence of this nonlinearity is that a cold object needs a greater increase in temperature than a hot object in order to reach the same increase in radiation emitted. Therefore, this nonlinearity potentially has an impact on the structure of radiatively forced atmospheric temperature change in both the horizontal and vertical directions. For example, it has previously been argued to be a cause of polar amplification (PA) of surface air warming. Here, the role of this nonlinearity is investigated by 1) assessing the magnitude of its effect on PA compared to spatial variations in CO2’s radiative forcing for Earth’s atmosphere and 2) linearizing  in a gray radiation atmospheric general circulation model (GCM) with an interactive hydrological cycle. Estimates for Earth’s atmosphere show that the combination of the Planck feedback and forcing from CO2 would produce a tropically amplified warming if they were the only means of changing the Earth’s energy balance. Contrary to expectations, climate change simulations with linearized radiation do not have reduced polar amplification of surface air warming relative to the standard GCM configuration. However, simulations with linearized radiation consistently show less warming in the upper troposphere and more warming in the lower troposphere across latitudes. The lapse rate feedbacks from pure radiative and radiative–convective configurations of the model are used to show that the “cold-altitudes-warm-more” effect of the  nonlinearity carries across this model hierarchy"
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #427 on: January 02, 2019, 09:41:09 PM »
Thanks, as always, aslr!
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #428 on: January 03, 2019, 11:48:20 PM »
The linked reference confirms that current global methane budgets ignore contributions from ice sheets, yet the study indicates that the Greenland Ice Sheet emits methane in quantities comparable to that emitted by the world's river, and that potential future methane emissions from Antarctica may be several orders of magnitude larger than that:

Lamarche-Gagnon, G., Wadham, J. L., Sherwood Lollar, B., Arndt, S., Fietzek, P., Beaton, A. D., … Stibal, M. (2019). Greenland melt drives continuous export of methane from the ice-sheet bed. Nature. doi:10.1038/s41586-018-0800-0

Guillaume Lamarche-Gagnon et al. Greenland melt drives continuous export of methane from the ice-sheet bed, Nature (2018). DOI: 10.1038/s41586-018-0800-0

https://www.nature.com/articles/s41586-018-0800-0

Abstract: "Ice sheets are currently ignored in global methane budgets. Although ice sheets have been proposed to contain large reserves of methane that may contribute to a rise in atmospheric methane concentration if released during periods of rapid ice retreat, no data exist on the current methane footprint of ice sheets. Here we find that subglacially produced methane is rapidly driven to the ice margin by the efficient drainage system of a subglacial catchment of the Greenland ice sheet. We report the continuous export of methane-supersaturated waters (CH4(aq)) from the ice-sheet bed during the melt season. Pulses of high CH4(aq) concentration coincide with supraglacially forced subglacial flushing events, confirming a subglacial source and highlighting the influence of melt on methane export. Sustained methane fluxes over the melt season are indicative of subglacial methane reserves that exceed methane export, with an estimated 6.3 tonnes (discharge-weighted mean; range from 2.4 to 11 tonnes) of CH4(aq) transported laterally from the ice-sheet bed. Stable-isotope analyses reveal a microbial origin for methane, probably from a mixture of inorganic and ancient organic carbon buried beneath the ice. We show that subglacial hydrology is crucial for controlling methane fluxes from the ice sheet, with efficient drainage limiting the extent of methane oxidation to about 17 per cent of methane exported. Atmospheric evasion is the main methane sink once runoff reaches the ice margin, with estimated diffusive fluxes (4.4 to 28 millimoles of CH4 per square metre per day) rivalling that of major world rivers. Overall, our results indicate that ice sheets overlie extensive, biologically active methanogenic wetlands and that high rates of methane export to the atmosphere can occur via efficient subglacial drainage pathways. Our findings suggest that such environments have been previously underappreciated and should be considered in Earth’s methane budget."

Extract: "Our finding that subglacial environments in Greenland can generate high levels of methane emphasizes the need to directly measure methane reserves in subglacial systems containing high quantities of organic carbon, such as the thick sedimentary basins beneath the Antarctic Ice Sheet, where much larger amounts of methane, as hydrates, are expected to be present."

See also:

https://phys.org/news/2019-01-ice-sheets-tons-methane-atmosphere.html

Extract: "With Antarctica holding the largest ice mass on the planet, researchers say their findings make a case for turning the spotlight to the south. Mr Lamarche-Gagnon added: "Several orders of magnitude more methane has been hypothesized to be capped beneath the Antarctic Ice Sheet than beneath Arctic ice-masses. Like we did in Greenland, it's time to put more robust numbers on the theory." "

Edit: Also see Reply #31.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #429 on: January 03, 2019, 11:57:12 PM »
The linked reference explains that:

"The subduction and export of Subantarctic Mode Water (SAMW) supplies the upper limb of the overturning circulation and makes an important contribution to global heat, freshwater, carbon and nutrient budgets.  Upper ocean heat content has increased since 2006, helping to explain the so-called global warming hiatus between 1998 and 2014, with much of the ocean warming concentrated in extratropical latitudes of the Southern Hemisphere in close association with SAMW and Antarctic Intermediate Water (AAIW)."

This information helps readers to better understand the slow mode contribution to ECS that was clearly identified in the CMIP5 model projections by PH17 [Cristian Proistosescu and Peter J. Huybers (05 Jul 2017), "Slow climate mode reconciles historical and model-based estimates of climate sensitivity", Science Advances, Vol. 3, no. 7, e1602821, DOI: 10.1126/sciadv.1602821]

Gao et al (2018), "Recent wind-driven change in Subantarctic Mode Water and its impact on ocean heat storage", Nature Climate Change 8, 58-63, doi:10.1038/s41558-017-0022-8

http://www.nature.com/articles/s41558-017-0022-8

Abstract: "The subduction and export of Subantarctic Mode Water (SAMW) supplies the upper limb of the overturning circulation and makes an important contribution to global heat, freshwater, carbon and nutrient budgets. Upper ocean heat content has increased since 2006, helping to explain the so called global warming hiatus between 1998 and 2014, with much of the ocean warming concentrated in extratropical latitudes of the Southern Hemisphere in close association with SAMW and Antarctic Intermediate Water (AAIW). Here we use Argo observations to assess changes in the thickness, depth and heat content of the SAMW layer. Between 2005 and 2015, SAMW has thickened (3.6 ± 0.3 m yr−1), deepened (2.4 ± 0.2 m yr−1) and warmed (3.9 ± 0.3 W m−2). Wind forcing, rather than buoyancy forcing, is largely responsible for the observed trends in SAMW. Most (84%) of the increase in SAMW heat content is the result of changes in thickness; warming by buoyancy forcing (increased heat flux to the ocean) accounts for the remaining 16%. Projected increases in wind stress curl would drive further deepening of SAMW and increase in heat storage in the Southern Hemisphere oceans."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #430 on: January 03, 2019, 11:58:06 PM »
The linked reference provide evidence that the ocean's 'biological carbon pump' is likely a positive feedback on climate change.  This likely positive feedback is underestimated in current consensus science climate models:

F.Boscolo-Galazz et al. (30 August 2018), "Temperature dependency of metabolic rates in the upper ocean: A positive feedback to global climate change?", Global and Planetary Change, https://doi.org/10.1016/j.gloplacha.2018.08.017

https://www.sciencedirect.com/science/article/pii/S0921818118301905

Abstract: "The temperature of seawater can affect marine plankton in various ways, including by affecting rates of metabolic processes. This can change the way carbon and nutrients are fixed and recycled and hence the chemical and biological profile of the water column. A variety of feedbacks on global climate are possible, especially by altering patterns of uptake and return of carbon dioxide to the atmosphere. Here we summarize and synthesize recent studies in the field of ecology, oceanography and ocean carbon cycling pertaining to possible feedbacks involving metabolic processes. By altering the rates of cellular growth and respiration, temperature-dependency may affect nutrient uptake and food demand in plankton and ultimately the equilibrium of pelagic food webs, with cascade effects on the flux of organic carbon between the upper and inner ocean (the “biological carbon pump”) and the global carbon cycle. Insights from modern ecology can be applied to investigate how temperature-dependent changes in ocean biogeochemical cycling over thousands to millions of years may have shaped the long-term evolution of Earth's climate and life. Investigating temperature-dependency over geological time scales, including through globally warm and cold climate states, can help to identify processes that are relevant for a variety of future scenarios."

Extract: "- Heterotrophic respiration rates respond twice as fast as to ocean temperature changes than photosynthesis.

- This may alter the ratio of particulate organic carbon to export production in the ocean, with more carbon sequestered to the deep ocean when it is cooler.

- Temperature dependency of metabolic rates has potential for being a key internal feedback for Earth's climate"
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #431 on: January 04, 2019, 12:31:44 AM »
In the past, a negative AO in winter has been associated with the retention of thick ice in the Arctic Ocean and reduced export by drift into the Atlantic, favoring more extensive sea ice at the end of the summer melt season. Conversely, the first image provides an example of where it is postulated that the unusually positive AO index from 1989 to 1995 lead to the accelerated export of multi-year Arctic Sea Ice (see the second image).  Since 1995 the Arctic Sea Ice Volume has been more slowly trending downward (see the third image).  However, Proshutinsky et al (2015), see Reply #75, indicate that since 1997 the Beaufort Gyre (which is periodically associated with the export of Arctic Sea Ice) has been steadily accumulating freshwater and ocean heat content.  Therefore, it seem possible to me that the linked Meneghello et al. (2018) reference may offer an explanation for the Beaufort Gyre's unusual behavior since 1997, which may be due to the reduced roughness of the sea ice associated with the accelerated loss of multi-year sea ice from 1989 to 1995.  Furthermore, Meneghello et al. (2018) speculate that the Beaufort Gyre will become more volatile as the Arctic Sea Ice Extent decreases with continued global warming:

Gianluca Meneghello et al. (17 October 2018), "The Ice‐Ocean Governor: Ice‐Ocean Stress Feedback Limits Beaufort Gyre Spin‐Up", Geophysical Research Letters, https://doi.org/10.1029/2018GL080171

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL080171

Abstract
The Beaufort Gyre is a key circulation system of the Arctic Ocean and its main reservoir of freshwater. Freshwater storage and release affects Arctic sea ice cover, as well as North Atlantic and global climate. We describe a mechanism that is fundamental to the dynamics of the gyre, namely, the ice‐ocean stress governor. Wind blows over the ice, and the ice drags the ocean. But as the gyre spins up, currents catch the ice up and turn off the surface stress. This governor sets the basic properties of the gyre, such as its depth, freshwater content, and strength. Analytical and numerical modeling is employed to contrast the equilibration processes in an ice‐covered versus ice‐free gyre. We argue that as the Arctic warms, reduced sea ice extent and more mobile ice will result in a deeper and faster Beaufort Gyre, accumulating more freshwater that will be released by Ekman upwelling or baroclinic instability.

Plain Language Summary
The Beaufort Gyre, located north of Alaska and Canada, is a key circulation system of the Arctic Ocean. Changes in its depth and circulation influence the evolution of the Arctic sea ice cover, the North Atlantic circulation, and the global climate. The gyre is driven by persistent, ice‐mediated winds, accumulating surface freshwater toward the center, deepening the gyre, and spinning up its currents. We describe a mechanism, dubbed here the ice‐ocean governor, in which the interaction of surface currents with the ice regulates the depth of the Beaufort Gyre: The spinning up of the gyre reduces the relative speed between the ocean and the ice, and hence the freshwater accumulation. This competes with, and we argue is more important than, the release of freshwater by flow instability, which moves water from the center toward the periphery. In the current climate the depth and speed of the Beaufort Gyre are mainly set by the governor, but this may change in a warming world where reduced ice cover will render the ice‐ocean governor less effective. The resulting deeper, swifter gyre will likely exhibit more variability in its freshwater storage and flow speeds.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #432 on: January 04, 2019, 12:51:10 AM »
Just for fun I post:

A. The first image, which graphically shows the size of countries by the number of people that they have living less than 5m about sea level (which might happen by about 2080).

B. The second image, which indicates that in addition to global mean SLR, people living in coastal areas need to also consider: Regional eustatic SLR (including the fingerprint effect), Regional net land movements, Regional sea level variability, Tidal ranges, Storm surge and Storm tide; and

C. The third image, shows projected changes in Arctic surface temperatures per decade, with both rapid sea-ice loss and with periods of moderate or no sea-ice loss; with the differences being due to changes in albedo.
« Last Edit: January 04, 2019, 03:39:48 AM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #433 on: January 04, 2019, 05:13:37 PM »
The linked reference indicates that CMIP5 projections of ice mass loss from the Greenland Ice Sheet may be too low by a factor of two:

Edward Hanna et al, Recent changes in summer Greenland blocking captured by none of the CMIP5 models, The Cryosphere Discussions (2018). DOI: 10.5194/tc-2018-91

https://www.the-cryosphere.net/12/3287/2018/tc-12-3287-2018-discussion.html

Abstract: "Recent studies note a significant increase in high-pressure blocking over the Greenland region (Greenland Blocking Index, GBI) in summer since the 1990s. Such a general circulation change, indicated by a negative trend in the North Atlantic Oscillation (NAO) index, is generally highlighted as a major driver of recent surface melt records observed on the Greenland Ice Sheet (GrIS). Here we compare reanalysis-based GBI records with those from the Coupled Model Intercomparison Project 5 (CMIP5) suite of global climate models over 1950–2100. We find that the recent summer GBI increase lies well outside the range of modelled past reconstructions and future GBI projections (RCP4.5 and RCP8.5). The models consistently project a future decrease in GBI (linked to an increase in NAO), which highlights a likely key deficiency of current climate models if the recently observed circulation changes continue to persist. Given well-established connections between atmospheric pressure over the Greenland region and air temperature and precipitation extremes downstream, e.g. over northwest Europe, this brings into question the accuracy of simulated North Atlantic jet stream changes and resulting climatological anomalies over densely populated regions of northern Europe as well as of future projections of GrIS mass balance produced using global and regional climate models."

Extract: " The GCM-forced projections may also underestimate future GrIS surface mass balance decreases by a factor of 2, independently of the precise timing and amplitude of global warming, if the recent observed circulation changes continue to persist in summer (Delhasse et al., 2018). Model– observation discrepancies and thus model fidelity may, of course, be partly addressed in CMIP6 but clearly this is far from certain and meanwhile CMIP5 represents the current “state of the science”. Given the recent rapid changes in Arctic climate and Greenland Ice Sheet dynamics – which were not well predicted 15–20 years ago – it is therefore essential that future climate modelling efforts focus on improving their representation of blocking, as this is a key aspect of mid- to high-latitude cryosphere–climate dynamics and change."

See also:

Title: "Climate models fail to simulate recent air-pressure changes over Greenland"

https://phys.org/news/2018-10-climate-simulate-air-pressure-greenland.html

Extract: " Climatologists may be unable to accurately predict regional climate change over the North Atlantic because computer model simulations have failed to accurately include air pressure changes that have taken place in the Greenland region over the last three decades.

Researchers compared real data with simulation data over a 30 year period and found that the simulations on average showed slightly decreasing air pressure in the Greenland region, when in fact, the real data showed a significant increase in high air pressure—or so-called 'Greenland blocking' - during the summer months.

See also:

Title: "Climate change is more extensive and worse than once thought"

https://phys.org/news/2018-11-climate-extensive-worse-thought.html

Extract: "By nature, scientists said they are overly conservative.

In nearly every case, when scientists were off the mark on something, it was by underestimating a problem not overestimating, said Watson, the British climate scientist.

But there are ultimate worst cases. These are called tipping points, after which change accelerates and you can't go back. Ice sheet collapses. Massive changes in ocean circulation. Extinctions around the world.

"In the early 1990s we only had hints that we could drive the climate system over tipping points," said Jonathan Overpeck, environment dean at University of Michigan. "We now know we might actually be witnessing the start of a mass extinction that could lead to our wiping out as much as half the species on Earth." "

Also see:

Title: "What the past can tell us about the future of climate change"

https://pursuit.unimelb.edu.au/articles/what-the-past-can-tell-us-about-the-future-of-climate-change
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #434 on: January 04, 2019, 07:08:40 PM »
In prior posts in this thread, I have noted several NH decadal-scale positive feedback mechanisms that individually will contribute to a slowing of the AMOC, which in turn will serve to slow the entire MOC, and which via the bipolar seesaw mechanism will in turn accelerate ice mass loss from the AIS.  The first linked reference adds the conversion of the Barents Sea into an arm of the North Atlantic to the list of decadal-scale feedback mechanisms, of which I provide bullet point summaries for the more significant mechanisms below:

•   The Greenland Atmospheric Blocking pressure (see Reply #433) will likely double the projected surface mass loss from the GIS in coming decades.  I note that this accelerated surface mass loss will initially come primarily from episodic weather related high surface temperature events, but with continued warming will increasingly include ice mass loss from weather related rainfall events.

•   Several key Southern Greenland marine terminating glaciers will almost certainly experience accelerated rates of iceberg calving, as their calving face retreats along retrograde bedslopes (see Reply #424).

•   The current and projected increased frequency of El Nino events will increase the ocean surface temperature in the Northern Pacific Ocean (via atmospheric telecommunication), and then in non-El Nino periods [see Dai & Tan (2017), cited below] the increased water vapor from the North Pacific is advected into the Arctic Basin where it contributes directly to Arctic Amplification and the associated flux of freshwater into the Arctic Ocean.

•   The Beaufort Gyre has been stockpiling increasing quantities of freshwater since 1997, and as the Arctic Sea Ice Area progressively decreases, this stockpile of freshwater becoming increasingly unstable and subject to advection into the North Atlantic (see Reply #431).

Lind, S., Ingvaldsen, R. B., & Furevik, T. (2018). Arctic warming hotspot in the northern Barents Sea linked to declining sea-ice import. Nature Climate Change, 8(7), 634–639. doi:10.1038/s41558-018-0205-y

https://www.nature.com/articles/s41558-018-0205-y

Abstract: "The Arctic has warmed dramatically in recent decades, with greatest temperature increases observed in the northern Barents Sea. The warming signatures are not constrained to the atmosphere, but extend throughout the water column. Here, using a compilation of hydrographic observations from 1970 to 2016, we investigate the link between changing sea-ice import and this Arctic warming hotspot. A sharp increase in ocean temperature and salinity is apparent from the mid-2000s, which we show can be linked to a recent decline in sea-ice import and a corresponding loss in freshwater, leading to weakened ocean stratification, enhanced vertical mixing and increased upward fluxes of heat and salt that prevent sea-ice formation and increase ocean heat content. Thus, the northern Barents Sea may soon complete the transition from a cold and stratified Arctic to a warm and well-mixed Atlantic-dominated climate regime. Such a shift would have unknown consequences for the Barents Sea ecosystem, including ice-associated marine mammals and commercial fish stocks."

See also:

Title: "Barents Sea seems to have crossed a climate tipping point"

https://arstechnica.com/science/2018/06/barents-sea-seems-to-have-crossed-a-climate-tipping-point/

Extract: "Now, a team of Norwegian scientists is suggesting it has watched the climate reach a tipping point: the loss of Arctic sea ice has flipped the Barents Sea from acting as a buffer between the Atlantic and Arctic oceans to something closer to an arm of the Atlantic.

The loss of ice also means that the surface water in this area is exchanging heat with the atmosphere and absorbing more sunlight during the long Arctic summer days. These two have combined to heat the top 100m of water dramatically. If the mean of its temperature from 1970-1999 is taken as a baseline, the temperatures from 2010-2016 are nearly four standard deviations higher. 2016—the most recent year we have validated data for—was 6.3 standard deviations higher.

This has the effect of heating the intermediate water from above. Meanwhile, the warm Atlantic water will heat it from below. As a result, the cold intermediate water has essentially vanished from the Barents Sea, turning the area into a basin dominated by Atlantic water. The entire water column, from surface to the sea floor, has both warmed and gotten saltier, all starting in the late-2000s.

But the general gist of the study is considerably more ominous: not only have we discovered a climate tipping point, but we've spotted it after the system has probably already flipped into a new regime. It also provides some sense of what to expect from the future. Rather than seeing the entire planet experience a few dramatic changes, we're likely to see lots of regional tipping points that have more of a local effect. The future will be the sum of these events and their interactions, making it a bit harder to predict which changes we should be planning for."
&

Panxi Dai and Benkui Tan (2017), "The Nature of the Arctic Oscillation and Diversity of the Extreme Surface Weather Anomalies It Generates", Journal of Climate, https://doi.org/10.1175/JCLI-D-16-0467.1

https://journals.ametsoc.org/doi/10.1175/JCLI-D-16-0467.1

Abstract: "Through a cluster analysis of daily NCEP–NCAR reanalysis data, this study demonstrates that the Arctic Oscillation (AO), defined as the leading empirical orthogonal function (EOF) of 250-hPa geopotential height anomalies, is not a unique pattern but a continuum that can be well approximated by five discrete, representative AO-like patterns. These AO-like patterns grow simultaneously from disturbances in the North Pacific, the North Atlantic, and the Arctic, and both the feedback from the high-frequency eddies in the North Pacific and North Atlantic and propagation of the low-frequency wave trains from the North Pacific across North America into the North Atlantic play important roles in the pattern formation. Furthermore, it is shown that the structures and frequencies of occurrence of the five AO-like patterns are significantly modulated by El Niño–Southern Oscillation (ENSO). Warm (cold) ENSO enhances the negative (positive) AO phase, compared with ENSO neutral winters. Finally, the surface weather effects of these AO-like patterns and their implications for the AO-related weather prediction and the AO-North Atlantic Oscillation (NAO) relationship are discussed."

Readers should be aware that the caveats in AR5 relieves consensus scientists from any responsibility for accounts for the impacts of such regional and transient positive feedback mechanisms.

Edit: I forgot to note (reiterate) that the AMOC is currently in a natural slowing phase, and the decadal-scale freshwater inputs to the North Atlantic cited in this post, will serve to further decelerate the natural slowing of the AMOC (& the MOC), in the next few decades.

Edit2: For those who find this post too subtle, I am suggesting that a transient plus of freshwater into the North Atlantic (say from 2020 to say 2040) would likely accelerate the timing of the initiation of the collapse of the WAIS; which would likely then (via the bipolar seesaw mechanism) lead to an acceleration of Arctic Amplification (say from 2040 to say 2080); which would likely tip the world's ECS into Early Pliocene like conditions even if anthropogenic GHG emissions pathway follows say SSP1-Baseline.
« Last Edit: January 04, 2019, 08:31:51 PM by AbruptSLR »
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #435 on: January 04, 2019, 10:40:43 PM »
The linked reference provides further insights on the interaction (and timescales) between (of) Arctic sea ice loss and the bipolar seesaw mechanism:

Wei Liu et al, (26 December 2018), "Timescales and mechanisms of global climate impacts of Arctic sea ice loss mediated by the Atlantic meridional overturning circulation", Geophysical Research Letters, https://doi.org/10.1029/2018GL080602

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL080602

Abstract
We explore the global impacts of Arctic sea ice decline in climate model perturbation experiments focusing on the temporal evolution of induced changes. We find that climate response to a realistic reduction in sea ice cover varies dramatically between shorter decadal and longer multi‐decadal to centennial timescales. During the first two decades, when atmospheric processes dominate, sea ice decline induces a “bipolar seesaw” pattern in surface temperature with warming in the Northern and cooling in the Southern Hemisphere, leading to a northward displacement of the Intertropical Convergence Zone (ITCZ) and an expansion of Antarctic sea ice. In contrast, on multi‐decadal and longer timescales, the weakening of the Atlantic meridional overturning circulation, caused by upper‐ocean buoyancy anomalies spreading from the Arctic, mediates direct sea ice impacts and nearly reverses the original response pattern outside the Arctic. The Southern Hemisphere warms, a Warming Hole emerges in the North Atlantic, the ITCZ shifts southward, and Antarctic sea ice contracts.

Plain Language Summary
To understand how the recent Arctic sea ice decline may affect global climate, we conduct model experiments in which we modify the properties of Arctic sea ice, in order to simulate an Arctic sea ice loss similar to the observed. We find that climate response shows dramatically different patterns during different periods after the imposed sea ice decline. During the first one or two decades, Arctic sea ice decline allows more solar energy into the Northern Hemisphere (NH), altering the Earth's energy balance. As the NH warms while the Southern Hemisphere (SH) cools, the tropical rain belt moves northward and Antarctic sea ice expands. However, after several more decades to a century, the impacts from changes in the deep ocean become more important and eventually overwhelm the direct effects of sea ice loss on the atmosphere. The weakening of the Atlantic deep ocean circulation causes a cooling in the North Atlantic and a warming in the SH. Antarctic sea ice contracts and the tropical rain belt shifts back to it original position and further south.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #436 on: January 05, 2019, 12:24:54 AM »
The linked reference indicates interhemispheric synchronization between the AO and the AAO, may be one factor contributing to the bipolar seesaw mechanism.

Y. Tachibana et al. (28 November 2018), "Interhemispheric Synchronization Between the AO and the AAO", Geophysical Research Letters, https://doi.org/10.1029/2018GL081002

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL081002

Abstract
Teleconnections between lower and higher latitude regions are widely known in both the Northern and Southern Hemispheres. To broaden our view of these teleconnections, we searched a reanalysis data set for evidence of a teleconnection between the Arctic Oscillation (AO) and the Antarctic Oscillation (AAO), two widely separated circumpolar phenomena. Statistical analysis of the Japanese 55‐year reanalysis data set showed significant in‐phase synchronization between the AO and AAO, particularly in October and February, with a vertical structure extending from the troposphere to the stratosphere. This vertical structure may suggest a stratospheric control, and we did not find a significant signature indicating a tropical ocean control. We also observed decadal‐scale modulation of the synchronicity. Observational evidence implies that the stratospheric meridional circulation may be responsible for AO‐AAO synchronization.

Plain Language Summary
The Arctic Oscillation (AO) and the Antarctic Oscillation (AAO) are dominant atmospheric variability patterns in the Northern and Southern Hemispheres, respectively. Each is a pressure seesaw between the pole and the midlatitudes that remotely affects weather, climate, and environment around the world. We showed interhemispheric in‐phase synchronization between the AO and AAO in October and February, and we also found decadal‐scale variation of the synchronicity. Because the vertical structure of the AO‐AAO synchronization extends from the troposphere to the stratosphere, stratospheric variations may be responsible for the synchronization. This finding of AO‐AAO synchronization points the way to a better understanding of past, present, and future pole‐to‐pole climatic relationships and improvements in long‐term weather forecasts.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #437 on: January 05, 2019, 12:39:36 AM »
From the abstract:

"polar amplification is found to be dominated by forcing in the polar regions, specifically through positive local lapse-rate feedback"

Could you or someone explain a bit about what exactly lapse-rate feedback is, hopefully in terms that I and others can understand?

It sounds like it's pretty important, and it seems like a gap in my GW knowledge I'd like to fill.

Thanks ahead of time for any light you can throw on this.

Foehn winds warm by adiabatic compression resulting in a lapse rate of about 9.80C per Km. descent and will also give rise to cloudless skies on lee slopes. Over ice towards the edge of Antarctica this can warm enough to start the melt, leading to loss of albedo, increase of absorbtion of solar radiation, then melt pools and even expose underlying blue ice.

Sea ice to the lee (east) of the northern Antarctic Peninsula sometimes show a blue tint before it breaks up, and I suspect the blue melt over at the Amery Ice shelf is also largely caused by foehn winds. Many other places show a blue colouration from time to time in the summer.

The lapse rate of incoming winds to the continent will be lower as they contain water vapour, which precipitates out (giving up latent heat) as the air rises towards the centre. This can result in out-going air being warmer than the air blowing into the continent.

I am not certain this is the answer to your question??


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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #438 on: January 05, 2019, 12:47:01 AM »
To me, the linked reference provides direct evidence that the Middle to Late Pleistocene transitions from glacial to interglacial terminations were characterized by increase Arctic rainfall (at least in Siberia).  Furthermore, this implies to me that:

a) The increased Arctic rainfall would accelerated both local glacial ice mass loss and local permafrost degradation, and

b) The increased number of Arctic thermokarst lakes would increase the amount of associated methane emissions.

Both of these probable feedback mechanisms could serve to increase the positive ice-climate feedback in the coming decades:

Grigory Fedorov et al. (20 December 2018), "Middle to Late Pleistocene lake‐level fluctuations of Lake El'gygytgyn, far‐east Russian Arctic", Boreas, https://doi.org/10.1111/bor.12367

https://onlinelibrary.wiley.com/doi/abs/10.1111/bor.12367

Abstract: "Lake El'gygytgyn, located in central Chukotka, Russian Arctic, was the subject of an international drilling project that resulted in the recovery of the longest continuous palaeoclimatic and palaeoenvironmental record for the terrestrial Arctic covering the last 3.6 million years. Here, we present the reconstruction of the lake‐level fluctuations of Lake El'gygytgyn since Marine Isotope Stage (MIS) 7 based on lithological and palynological as well as chronological studies of shallow‐water sediment cores and subaerial lake terraces. Reconstructed lake levels show an abrupt rise during glacial–interglacial terminations (MIS 6/5 and MIS 2/1) and during the MIS 4/3 stadial–interstadial transition. The most prominent lowstands occurred during glacial periods associated with a permanent lake‐ice cover (namely MIS 6, MIS 4 and MIS 2). Major triggering mechanisms of the lake‐level fluctuations at Lake El'gygytgyn are predominantly changes in air temperature and precipitation. Regional summer temperatures control the volume of meltwater supply as well as the duration of the lake‐ice cover (permanent or seasonal). The duration of the lake‐ice cover, in turn, enables or hampers near‐shore sediment transport, thus leading to long‐term lake‐level oscillations on glacial–interglacial time scales by blocking or opening the lake outflow, respectively. During periods of seasonal ice cover the lake level was additionally influenced by changes in precipitation. The discovered mechanism of climatologically driven level fluctuations of Lake El'gygytgyn are probably valid for large hydrologically open lakes in the Arctic in general, thus helping to understand arctic palaeohydrology and providing missing information for climate modelling."
« Last Edit: January 05, 2019, 03:00:23 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #439 on: January 05, 2019, 01:01:07 AM »
Thanks, FB. I had heard about Foehn winds, but hadn't thought about how they might relate to lapse rate. Makes sense to me! Is this more of a factor in Antarctica than in most of the Arctic?
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #440 on: January 05, 2019, 03:17:44 PM »
Thanks, FB. I had heard about Foehn winds, but hadn't thought about how they might relate to lapse rate. Makes sense to me! Is this more of a factor in Antarctica than in most of the Arctic?

wili,

While the adiabatic lapse rate for Foehn wind that FB posted about is primarily a climate change issue in Antarctica (see Replies #19 and #410), it does impact regional climate in other areas as cited in the linked Wikipedia article:

Title: "Foehn wind"

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

Extract: "A föhn or foehn ... is a type of dry, warm, down-slope wind that occurs in the lee (downwind side) of a mountain range.

It is a rain shadow wind that results from the subsequent adiabatic warming of air that has dropped most of its moisture on windward slopes (see orographic lift). As a consequence of the different adiabatic lapse rates of moist and dry air, the air on the leeward slopes becomes warmer than equivalent elevations on the windward slopes. Föhn winds can raise temperatures by as much as 14 °C (25 °F) in just a matter of minutes. Central Europe enjoys a warmer climate due to the Föhn, as moist winds off the Mediterranean Sea blow over the Alps."

However, in Antarctica it can contribute to hydrofracturing (the meltpond mechanism) of ice shelves like the Larsen B shown in the attached image.  While hydrofracturing of ice shelves cannot occur in relatively thick portions of large ice shelves, still it can (and does) occur near the calving faces of key West Antarctic ice shelves like the Ross Ice Shelf; which could accelerate the collapse of the WAIS as demonstrated by Pollard, DeConto and Alley.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #441 on: January 05, 2019, 04:52:01 PM »
In this post I list three issues that I am not prepared to elaborate upon in separate individual posts:

1. As marine glaciers have collapsed numerous times in the past 35 million years, most of the key marine glaciers have previously dug troughs that should make them more susceptible to collapse in the near future, than during the Eemian/MIS 5.

2. The image shows an image from Skeptical Science showing the relative CO₂ velocity since 1850; which illustrates a sharp acceleration after 1950, and indicating that the current relative CO₂ velocity is several hundred times the velocity coming out of the last ice age.  First, due to the thermal inertia of the Earth's climate change systems, the sharp acceleration after 1950 can create a false sense of security that our current BAU pathway hasn't shown full, observable (as most of the observations have been collected after 1950) climate impact.  Second, our current high relative CO₂ velocity will not give terrestrial and oceanic biological ecologies adequate time to adapt; which will likely turn many associated carbon sinks into carbon sources. Finally, our current high relative CO₂ velocity makes it more likely that transient and phase related positive feedbacks (& forcings) will superimpose upon each other; which increases the risk that such a transient perturbation could push various Earth Systems beyond their tipping points.

3. While the IPCC reports cite a range of probably values for ECS, in reality only one value is applicable at any given time (noting that ECS can increase in value with increasing forcing).  Thus when policy makers, the public and/or the media focus on mean or mode values for ECS, they are eliminating your factor of safety against possible higher values of ECS.  This consideration has major significance for risk evaluations that use distributed values (PDFs) for ECS; which means that a worse case risk assessment for high values of ECS would indicate many times higher impacts on society that currently considered by the IPCC.
« Last Edit: January 05, 2019, 04:58:43 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #442 on: January 10, 2019, 05:11:30 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."
« Last Edit: January 10, 2019, 07:30:07 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #443 on: January 10, 2019, 11:23:28 PM »
The linked reference and associated image, indicate that observed Ocean Heat Content, OHC, has increased more rapidly than indicated by AR5.  Hopefully, AR6 will recognize that this trend is not good for mankind's future:

Lijing Cheng, John Abraham, Zeke Hausfather & Kevin E. Trenberth (11 Jan 2019), "How fast are the oceans warming?", Science, Vol. 363, Issue 6423, pp. 128-129, DOI: 10.1126/science.aav7619

http://science.sciencemag.org/content/363/6423/128

Abstract: "Climate change from human activities mainly results from the energy imbalance in Earth's climate system caused by rising concentrations of heat-trapping gases. About 93% of the energy imbalance accumulates in the ocean as increased ocean heat content (OHC). The ocean record of this imbalance is much less affected by internal variability and is thus better suited for detecting and attributing human influences than more commonly used surface temperature records. Recent observation-based estimates show rapid warming of Earth's oceans over the past few decades (see the figure). This warming has contributed to increases in rainfall intensity, rising sea levels, the destruction of coral reefs, declining ocean oxygen levels, and declines in ice sheets; glaciers; and ice caps in the polar regions. Recent estimates of observed warming resemble those seen in models, indicating that models reliably project changes in OHC."

Caption for image: "Past and future ocean heat content changes

Annual observational OHC changes are consistent with each other and consistent with the ensemble means of the CMIP5 models for historical simulations pre-2005 and projections from 2005–2017, giving confidence in future projections to 2100 (RCP2.6 and RCP8.5) (see the supplementary materials). The mean projected OHC changes and their 90% confidence intervals between 2081 and 2100 are shown in bars at the right. The inset depicts the detailed OHC changes after January 1990, using the monthly OHC changes updated to September 2018 [Cheng et al. (2)], along with the other annual observed values superposed."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #444 on: January 11, 2019, 06:57:53 PM »
In my last post about Cheng et al. (2019) I did not note that their findings indicate that observed Ocean Heat Content, OHC, is warming about 40% faster (see image) than predicted by AR5, which is in line with the recent findings of the corrected Resplandy et al (2018) findings:

Title: "Guest post: Observations and models agree that the oceans are warming faster"

https://www.carbonbrief.org/guest-post-observations-and-models-agree-that-the-oceans-are-warming-faster

Extract: "OHC records published in recent years show, on average, about 40% – with a range of 15% to 100% – more warming than the OHC records featured in AR5.
These three new records have been corrected for issues that were identified in data collected from XBTs. They also employ better statistical methods to account for limited coverage of data sampling for OHC, particularly prior to the Argo era.
A fourth new study by Prof Laure Resplandy of Princeton University and colleagues used a novel approach of estimating changes in OHC based on the amount of oxygen and CO2 being released by the oceans. Their data is not included in the chart above because they only provide estimates after 1991 due to a lack of measurements prior to that point.
However, their best estimate – after recent corrections to their methods – agrees quite well with other recent studies, despite their uncertainties being quite large."

Caption for image: "Rate of ocean heat content warming for the top 2000 meters of the ocean, from 1971-2010, in zetajoules (10^21 joules) per year. For each study the bar shows the 90% trend uncertainty, with the mean estimate shown by the black dot in the middle. For CMIP5 models, the bar spans the 90% range of models, with the black dot showing the multi-model mean."

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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #445 on: January 11, 2019, 07:28:42 PM »
The linked reference indicates that reductions in Arctic sea ice extent are increasing, but also the duration of the ice-free season is increasing.  Hopefully, AR6 projections will better model this positive feedback mechanism than AR5 projections:

Lebrun, M., Vancoppenolle, M., Madec, G., and Massonnet, F.: Arctic sea-ice-free season projected to extend into autumn, The Cryosphere, 13, 79-96, https://doi.org/10.5194/tc-13-79-2019, 2019.

https://www.the-cryosphere.net/13/79/2019/

Abstract
The recent Arctic sea ice reduction comes with an increase in the ice-free season duration, with comparable contributions of earlier ice retreat and later advance. CMIP5 models all project that the trend towards later advance should progressively exceed and ultimately double the trend towards earlier retreat, causing the ice-free season to shift into autumn. We show that such a shift is a basic feature of the thermodynamic response of seasonal ice to warming. The detailed analysis of an idealised thermodynamic ice–ocean model stresses the role of two seasonal amplifying feedbacks. The summer feedback generates a 1.6-day-later advance in response to a 1-day-earlier retreat. The underlying physics are the property of the upper ocean to absorb solar radiation more efficiently than it can release heat right before ice advance. The winter feedback is comparatively weak, prompting a 0.3-day-earlier retreat in response to a 1-day shift towards later advance. This is because a shorter growth season implies thinner ice, which subsequently melts away faster. However, the winter feedback is dampened by the relatively long ice growth period and by the inverse relationship between ice growth rate and thickness. At inter-annual timescales, the thermodynamic response of ice seasonality to warming is obscured by inter-annual variability. Nevertheless, in the long term, because all feedback mechanisms relate to basic and stable elements of the Arctic climate system, there is little inter-model uncertainty on the projected long-term shift into autumn of the ice-free season.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #446 on: January 11, 2019, 08:22:06 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 #447 on: January 11, 2019, 08:24:25 PM »
The linked reference indicates that reductions in Arctic sea ice extent are increasing, but also the duration of the ice-free season is increasing. 

I am gradually posting a sea by sea analysis from 1979 to 2018 on the 2018 Arctic Sea Ice Area and Extent thread. It includes looking at trends in ice-free days and in open water vs ice. The data or most seas is in line with that study in that the duration of the ice-free season is increasing.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #448 on: January 11, 2019, 09:19:35 PM »
Re: Polar wander, spin and magnetic

There is not yet a compelling theory for the magnetic field or magnetic polar wander. There is almost certainly a coupling between the location of the spin axis and the magnetic poles, but the nature of this coupling is not understood, probably because the nature of the magnetic field is not well understood. There is a Nobel waiting for anyone who comes up with answers.

sidd

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #449 on: January 12, 2019, 08:17:33 AM »
...
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?

Lennart,

Thanks for the 2016 reference, while the following linked 2018 article (& associated image) about the findings of the GRACE satellite findings about changes in freshwater over the past 14 years, shows that water changes in aquifers, ice, lakes, rivers, snow and soil are all having significant gravitational impacts on the Earth:

Title: "NASA finds 'human fingerprint' in many areas of water-supply change worldwide"

https://www.usatoday.com/story/tech/nation-now/2018/05/16/nasa-global-water-supply-study/616431002/

Extract: "The researchers analyzed 14 years of data from NASA’s twin Gravity Recovery and Climate Experiment satellites, which the space agency has dubbed GRACE. They studied areas with large increases or decreases in freshwater — including water stored in aquifers, ice, lakes, rivers, snow and soil — to determine the most likely causes of these changes.

Changes in two-thirds of the 34 hot spots from California to China may be linked to climate change or human activities, such as excessive groundwater pumping for farming, according to their new study."

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