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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2650 on: January 21, 2020, 05:33:43 PM »
While the linked article discusses several different aspects of the state of the climate in 2019, I note that in order to adjust the global mean surface temperature anomaly (GMSTA) values shown in the attached image from the 1981 to 2010 period to the 1880-1900 pre-industrial period one needs to add between 0.6 to 0.75C.  While many people like to focus on the mean GMSTA values, it is the right-tail probabilities where the risk exists (note that regarding the Copernicus data for 2019: 0.59C + 0.75C = 1.34C).

Title: "State of the climate: How the world warmed in 2019"

https://www.carbonbrief.org/state-of-the-climate-how-the-world-warmed-in-2019

Extract: "All of the official climate data for 2019 is now in. In this article, Carbon Brief explains why last year proved to be so remarkable across the planet’s oceans, atmosphere, cryosphere and surface temperature.

Temperatures are shown as anomalies relative to a 1981 to 2010 average; note that the 1981 to 2010 period is around 0.6 to 0.75C warmer than the 1880-1900 preindustrial period."

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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2651 on: January 21, 2020, 09:23:51 PM »
The linked article indicates that in 2019 natural gas emissions were "… growing relatively fast, and even accelerating.”:

Title: "CO2 Emissions Will Break Another Record in 2019"

https://www.scientificamerican.com/article/co2-emissions-will-break-another-record-in-2019/

Extract: "Natural gas has been the dominant driver of global carbon dioxide emissions since 2012, the report notes, despite being less carbon intensive than both coal and oil.
Worldwide, the report suggests that emissions from coal use will decline by 0.9% in 2019. Meanwhile, emissions from oil consumption will grow 0.9% and emissions from natural gas will grow by 2.6%.

“Now that we have got movement on coal, particularly in some countries, we also need to get movement on oil and natural gas,” Glen Peters, research director at the Center for International Climate Research in Norway and a co-author of the new report, said in an email to E&E News while in transit to the conference in Madrid. “It is a little worrying that natural gas is growing relatively fast, and even accelerating.”"

See also:

Lynch et al. (2020), "Demonstrating GWP*" a means of reporting warming-equivalent emissions that captures the contrasting impacts of short- and long-lived climate pollutants", Environ. Res. Lett., https://doi.org/10.1088/1748-9326ab6d7e

https://iopscience.iop.org/article/10.1088/1748-9326/ab6d7e/pdf
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2652 on: January 21, 2020, 09:44:32 PM »
Per the linked article, NOAA and NASA find that "… 2019 was 1.22°C (2.19°F) above the pre-industrial baseline temperature."

Title: "2019 in Review: Global Temperature Rankings"

https://medialibrary.climatecentral.org/resources/2019-in-review-global-temperature-rankings

Extract: "NOAA and NASA’s global temperature data is in, naming 2019 the 2nd hottest year on Earth since records began and making the 2010s the hottest decade on record.

While it’s important to note that a warming world will have year-to-year variations due to natural variability (so not every year will be warmer than the one before) 2019 was 1.22°C (2.19°F) above the pre-industrial baseline temperature."


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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2653 on: January 22, 2020, 12:28:26 AM »
While it is difficult to say with so little recent GMSTA data, but the attached plot by Hansen et al (2020) may indicate that in recent years GMSTA is beginning to accelerate above the past trend line (which I take to be the green line of the best linear fit since 1970):

http://www.columbia.edu/~jeh1/mailings/2020/20200115_Temperature2019.pdf
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2654 on: January 22, 2020, 02:06:01 AM »
Yes, we're starting to see the 11 year (132 month) running mean bend upwards. While major volcanic eruptions could cool the earth, otherwise it seems unlikely (as the UK MET office has published) that we will not pass 1.5C of warming (at least temporarily) within the next few years.

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2655 on: January 22, 2020, 03:54:04 AM »
Per the linked article, NOAA and NASA find that "… 2019 was 1.22°C (2.19°F) above the pre-industrial baseline temperature."

Title: "2019 in Review: Global Temperature Rankings"

https://medialibrary.climatecentral.org/resources/2019-in-review-global-temperature-rankings

...

Per the first linked article the WMO Secretary-General stated that GMSTA in 2019 relative to pre-industrial was only 1.1C; while the quoted NOAA-NASA article indicates that the average GMSTA above pre-industrial for the entitle 2010s decade was 1.2C and that for 2019 it was 1.22C.  It seems that the UN's WMO is erring on the side of least drama:

Title: "2019 second hottest year on record, UN confirms"

https://news.un.org/en/story/2020/01/1055392

Extract: "“The average global temperature has risen by about 1.1°C since the pre-industrial era and ocean heat content is at a record level,” said WMO Secretary-General Petteri Taalas.

WMO analysis showed the annual global temperature in 2019 was 1.1°C warmer than in the period from 1850-1900, or the pre-industrial era."
 
See also:

Title: "Thunberg says only ‘eight years left’ to avert 1.5°C warming"

https://www.climatechangenews.com/2020/01/21/thunberg-says-eight-years-left-avert-1-5c-warming/

Extract: "Thunberg said there was only eight years left at current levels of emissions to keep temperatures below 1.5°C. Average global temperatures are about 1.1°C above pre-industrial times, according to the United Nations. And the rise is causing more extreme weather, such as heatwaves, wildfires and rising sea levels."
« Last Edit: January 22, 2020, 04:06:06 PM by AbruptSLR »
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gerontocrat

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2656 on: January 22, 2020, 12:45:45 PM »

Quote from the WMO report for the IPCC -The Global Climate in 2015–2019

The average global temperature** for 2015–2019, which is currently estimated to be 1.1 ± 0.1 °C above pre-industrial (1850–1900) level, is therefore likely to be the warmest of any equivalent period on record. It is 0.20 ± 0.08 °C warmer than the average for 2011–2015

That's a rise of 0.2 celsius in 5 years. Does this suggest the temperature rise this decade may be more than the 0.17 degrees per decade from 1970 to 2010 ?
___________________________________________________
**Note the WMO assesses the temperature from 5 data sets.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2657 on: January 22, 2020, 05:00:42 PM »
The linked reference (pre-print pdf) uses pattern recognition methodology to extract more information from the DESM large ensemble, and the observed HadCRUT4 temperature record, in order to reduce the uncertainty of radiative forcing response versus unforced climate change components.  Hopefully, in the future this work can be extended to utilize nonlinear machine learning methods for better attribution of underlying Earth Systems mechanisms on climate sensitivity:

Wills RCJ, DS Battisti, KC Armour, T Schneider and C Deser (2020), "Identifying forced climate responses in climate model ensembles and observations using pattern recognition methods", Journal of Climate,

https://atmos.uw.edu/~rcwills/papers/2020_Wills_etal_Forced_Patterns.pdf
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2658 on: January 22, 2020, 05:02:05 PM »
@gerontocrat
Good observation.
In my opinion, YES that suggests that extrapolations and official estimates are not following the real accelleration curve.
(if I've understood your question)
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2659 on: January 22, 2020, 05:36:05 PM »
The linked reference (pre-print pdf) makes several comparisons between CMIP5 projections and CMIP6 projections; but here I want to highlight the differences in projected evolutions of SST patterns (the 'pattern effect') as indicated by the attached image and the reference statement:

"Inter-model spread in feedback changes is well explained by differences in the ratio of warm-pool warming to global-mean warming across CMIP5 models, but this correlation fails to explain differences across CMIP6 models, suggesting that stronger SST-pattern dependence of extratropical clouds may dominate feedback changes in CMIP6 models."

As CMIP5 models did not consider freshwater hosing, but CMIP6 models included some limited amounts of freshwater hosing, it is possible that some of the differences in projected SST-pattern dependence may be due to such freshwater hosing (via associate ice-climate feedback mechanisms).  If so, then it is probable that a potential collapse of the WAIS in coming decades may have a much stronger effect on SST-pattern evolution; which might cause the Tropical Pacific SST to warm more rapidly with continued radiative forcing than projected by either CMIP5 or CMIP6.  If so this would increase the risk of flipping into an equable atmospheric pattern in the Northern Hemisphere this century.

Dong Y, KC Armour, M Zelinka, C Proistosescu, D Battisti, C Zhou and T Andrews (2020), "Inter-model spread in the pattern effect and its contribution to climate sensitivity in CMIP5 and CMIP6 models", Journal of Climate

https://atmos.uw.edu/~david/Dong_etal_2020_submitted.pdf

Abstract: "The radiative feedbacks depend on the spatial patterns of sea-surface temperature (SST) and thus can change over time as SST patterns evolve – the so-called 'pattern effect'. This study investigates inter-model differences in the magnitude of the pattern effect and how these differences contribute to the spread in equilibrium climate sensitivity (ECS) with CMIP5 and CMIP6 models.  Although ECS is on average higher in CMIP6 than CMIP5, the model-mean feedback change over time is slightly smaller in CMIP6 than CMIP5 within simulations of abrupt CO2 quadrupling.  While ECS is on average 10% higher than that inferred from historical energy constraints in CMIP5, this difference is reduced to 5% on average in CMIP6, but still with a wide range across models.  The smaller feedback change in CMIP6 models are associated with smaller changes in the surface-albedo feedback, compensated by larger changes in extratropical cloud feedbacks.  For both ensembles, the total variance in ECS is dominated by the spread in radiative response on fast timescales, rather than the spread in feedback evolution.  Using Green's functions derived from two AGCMs shows that the spread in feedbacks on fast timescales is primarily determined by model physics, whereas the spread in feedback changes is primarily governed by the SST patterns.  Inter-model spread in feedback changes is well explained by differences in the ratio of warm-pool warming to global-mean warming across CMIP5 models, but this correlation fails to explain differences across CMIP6 models, suggesting that stronger SST-pattern dependence of extratropical clouds may dominate feedback changes in CMIP6 models."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2660 on: January 22, 2020, 09:44:41 PM »
While the linked reference provides evidence that as the "… observed weakening of the AMOC has therefore delayed global surface warming rather than enhancing it."  However, while a collapse of the WAIS in coming decades would slow the MOC, the attached image from Hansen et al (2016) concurs that this would also cool the global surface; nevertheless, this image also shows that such an event would rapidly increase the planetary energy imbalance; which might possibly serve to push our climate state to have an equable atmospheric pattern in the Northern Hemisphere this century.

L Caesar, S Rahmstorf and G Feulner (20 January 2020) "On the relationship between Atlantic meridional overturning circulation slowdown and global surface warming", Environmental Research Letters, Volume 15, Number 2, https://doi.org/10.1088/1748-9326/ab63e3

https://iopscience.iop.org/article/10.1088/1748-9326/ab63e3

Abstract
According to established understanding, deep-water formation in the North Atlantic and Southern Ocean keeps the deep ocean cold, counter-acting the downward mixing of heat from the warmer surface waters in the bulk of the world ocean. Therefore, periods of strong Atlantic meridional overturning circulation (AMOC) are expected to coincide with cooling of the deep ocean and warming of the surface waters. It has recently been proposed that this relation may have reversed due to global warming, and that during the past decades a strong AMOC coincides with warming of the deep ocean and relative cooling of the surface, by transporting increasingly warmer waters downward. Here we present multiple lines of evidence, including a statistical evaluation of the observed global mean temperature, ocean heat content, and different AMOC proxies, that lead to the opposite conclusion: even during the current ongoing global temperature rise a strong AMOC warms the surface. The observed weakening of the AMOC has therefore delayed global surface warming rather than enhancing it.

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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2661 on: January 22, 2020, 11:12:23 PM »
The linked reference (and associated article) indicates that emissions from Chinese aviation could quadruple by 2050:

Yu, J. et al. (2020) China's aircraft-related CO2 emissions: Decomposition analysis, decoupling status, and future trends, Energy Policy, doi.org/10.1016/j.enpol.2019.111215

https://www.sciencedirect.com/science/article/pii/S0301421519307979

Abstract:
In order to explore the decoupling relationship and its influence factors between the growth of China's civil aviation sector and carbon emissions, as well as to forecast future CO2 emissions, the extended log-mean Divisia index model (LMDI), Tapio decoupling model and an emission prediction model were applied in this study. The results show the following. (1) Total carbon emissions fluctuate on an overall upward trend, but the level of oil consumption per revenue tonne-kilometers (RTK) shows a steady downward trend. (2) Among the four main factors, the “transportation amount growth” factor contributed most to CO2 emissions increases; followed by transport structure adjustment effects and alternative fuel effects. The “energy consumption intensity” factor plays a major role in inhibiting CO2 emissions. (3) The decoupling state of civil aviation predominantly stayed in a weak decoupling prior to 1988, expansive coupling and expansive negative decoupling during 1988–2000, and expansive coupling post-2000, which implies that the government should take comprehensive measures to reduce CO2 emissions. (4) Based on eight scenarios, China's civil aviation sector is predicted to be responsible for 0.13 Gt of CO2 emissions by 2020. Between 2020 and 2050, CO2 emissions may increase by a factor 1.6 to 3.9.

See also:

Title: "Emissions from Chinese aviation ‘could quadruple by 2050’"

https://www.carbonbrief.org/emissions-from-chinese-aviation-could-quadruple-by-2050

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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2662 on: January 23, 2020, 12:00:31 AM »
The linked reference reminds readers that Antarctic ice sheets are instantaneously impacted as/when adjoining ice shelves thin/degrade:

G. Hilmar Gudmundsson et al. (20 November 2019), "Instantaneous Antarctic ice sheet mass loss driven by thinning ice shelves", Geophysical Research Letters, https://doi.org/10.1029/2019GL085027

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL085027

Abstract
Recent observations show that the rate at which the Antarctic ice sheet (AIS) is contributing to sea level rise is increasing. Increases in ice‐ocean heat exchange have the potential to induce substantial mass loss through the melting of its ice shelves. Lack of data and limitations in modeling, however, has made it challenging to quantify the importance of ocean‐induced changes in ice shelf thickness as a driver for ongoing mass loss. Here, we use a numerical ice sheet model in combination with satellite observations of ice shelf thinning from 1994 to 2017 to quantify instantaneous changes in ice flow across all AIS grounding lines, resulting from changes in ice shelf buttressing alone. Our process‐based predictions are in good agreement with observed spatial patterns of ice loss, providing support for the notion that a significant portion of the current ice loss of the AIS is ocean driven and caused by a reduction in ice shelf buttressing.

Plain Language Summary
The Antarctic ice sheet is currently losing mass, but the causes for the mass loss remain unclear. It has been suggested that the reduction in the thickness of the floating ice shelves that surround the ice sheet, for example, due to ocean warming or changes in ocean circulation, may be responsible for some of the observed ice loss. However, this hypothesis has remained untested. Here, we use a state‐of‐the art numerical ice flow model to calculate the direct mass loss due to observed changes in ice shelves between 1994 and 2017. We find that the magnitude and spatial variability of modelled changes of inland ice are in good agreement with observations, suggesting that a substantial portion of the recent ice loss from the grounded Antarctic ice sheet has been driven by changes in its thinning ice shelves. The process we consider (ice shelf buttressing) relates to changes in forces within the ice alone and is therefore effectively instantaneous (i.e., only limited by the speed of stress transition within the ice). Besides providing a possible explanation for a large part of the ongoing mass loss, this finding also shows that we are not protected against the impact of the Antarctic ice sheet on global sea levels by a long response time.

See also:

Title: "New study provides first evidence that thinning Antarctic ice shelves instantaneously result in more ice into the sea"

https://thwaitesglacier.org/news/prophet-instantaneous-Antarctic-ice-sheet-mass-loss

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jai mitchell

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2663 on: January 23, 2020, 02:10:29 AM »


"Inter-model spread in feedback changes is well explained by differences in the ratio of warm-pool warming to global-mean warming across CMIP5 models, but this correlation fails to explain differences across CMIP6 models, suggesting that stronger SST-pattern dependence of extratropical clouds may dominate feedback changes in CMIP6 models."

. . . for both ensembles, the total variance in ECS is dominated by the spread in radiative response on fast timescales, rather than the spread in feedback evolution.  Using Green's functions derived from two AGCMs shows that the spread in feedbacks on fast timescales is primarily determined by model physics, whereas the spread in feedback changes is primarily governed by the SST patterns.

 ;D
pats self on back. . .

Recent analysis of these higher ECS runs indicate midlatitude clouds as the primary driver with the southern hemisphere having the largest impact.  This indicates that the higher ECS values come in after significant warming by the ocean surface, hence the reduced TCR with the majority of warming happening much later in the century.
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2664 on: January 23, 2020, 06:05:28 PM »
The linked reference indicates that Arctic sea ice cannot quickly rebound from climate change induced reductions in extent/area, due to a positive feedback between the sea ice extent/area and the AMOC:

Paul R. Halloran et al. Natural drivers of multidecadal Arctic sea ice variability over the last millennium, Scientific Reports (2020). DOI: 10.1038/s41598-020-57472-2

https://www.nature.com/articles/s41598-020-57472-2

Abstract: "The climate varies due to human activity, natural climate cycles, and natural events external to the climate system. Understanding the different roles played by these drivers of variability is fundamental to predicting near-term climate change and changing extremes, and to attributing observed change to anthropogenic or natural factors. Natural drivers such as large explosive volcanic eruptions or multidecadal cycles in ocean circulation occur infrequently and are therefore poorly represented within the observational record. Here we turn to the first high-latitude annually-resolved and absolutely dated marine record spanning the last millennium, and the Paleoclimate Modelling Intercomparison Project (PMIP) Phase 3 Last Millennium climate model ensemble spanning the same time period, to examine the influence of natural climate drivers on Arctic sea ice. We show that bivalve oxygen isotope data are recording multidecadal Arctic sea ice variability and through the climate model ensemble demonstrate that external natural drivers explain up to third of this variability. Natural external forcing causes changes in sea-ice mediated export of freshwater into areas of active deep convection, affecting the strength of the Atlantic Meridional Overturning Circulation (AMOC) and thereby northward heat transport to the Arctic. This in turn leads to sustained anomalies in sea ice extent. The models capture these positive feedbacks, giving us improved confidence in their ability to simulate future sea ice in in a rapidly evolving Arctic."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2665 on: January 23, 2020, 06:23:48 PM »
The two linked articles indicate that the Doomsday Clock is now closer to midnight than it ever has been in its history, not only due to nuclear threats and climate change risks, but also due to disinformation campaigns:

Title: "Press Release—IT IS NOW 100 SECONDS TO MIDNIGHT"

https://thebulletin.org/2020/01/press-release-it-is-now-100-seconds-to-midnight/

Extract: " Doomsday Clock Now Closer to Midnight Than Ever in Its History; Bulletin of the Atomic Scientists Cite Worsening Nuclear Threat, Lack of Climate Action & Rise of “Cyber-Enabled Disinformation Campaigns” in Moving Clock Hand; Bulletin Joined by The Elders in Announcement Today."

&

Title: "Doomsday Clock is 100 seconds to midnight, the symbolic hour of the apocalypse"

https://www.washingtonpost.com/weather/2020/01/23/doomsday-clock/

Extract: "The Bulletin of the Atomic Scientists is moving the Doomsday Clock up to 100 seconds to midnight — a metaphor for the end of the world — in a recognition of growing threats from nuclear war, climate change and disinformation.

The clock had been at two minutes to midnight since 2018. Now, the looming dangers are captured in a smaller unit in a testament to the need for urgent action, the Bulletin said Thursday, as its president warned of influential leaders who “denigrate and discard the most effective methods for addressing complex threats.”"
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2666 on: January 23, 2020, 07:24:41 PM »
The linked reference discusses the possible use of paleo-information to improve our collective assessment of the risks of future collapse of Antarctic ice shelves:

Smith, J.A., Graham, A.G.C., Post, A.L. et al. The marine geological imprint of Antarctic ice shelves. Nat Commun 10, 5635 (2019). https://doi.org/10.1038/s41467-019-13496-5

https://www.nature.com/articles/s41467-019-13496-5

Abstract: "Reductions in the thickness and extent of Antarctic ice shelves are triggering increased discharge of marine-terminating glaciers. While the impacts of recent changes are well documented, their role in modulating past ice-sheet dynamics remains poorly constrained. This reflects two persistent issues; first, the effective discrimination of sediments and landforms solely attributable to sub-ice-shelf deposition, and second, challenges in dating these records. Recent progress in deciphering the geological imprint of Antarctic ice shelves is summarised, including advances in dating methods and proxies to reconstruct drivers of change. Finally, we identify several challenges to overcome to fully exploit the paleo record."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2667 on: January 23, 2020, 08:26:08 PM »
This post is just a reminder of the findings of the linked reference that using MISI theory and the assumed loss of the Thwaites ice shelf support:  "In all simulations, once Thwaites Glacier retreats past the western subglacial ridge, the retreat becomes rapidly unstoppable."

Also, the researchers found that in the worst MISI case examined Thwaites could collapse within 60 to 70 years:

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

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

Abstract: "Thwaites Glacier, West Antarctica, has been a major contributor to global sea level rise over the past decades. Prior studies illustrated the critical role of ice shelf melt and iceberg calving based on cliff height in driving the retreat of Thwaites glacier. Here, we simulate its evolution with various calving laws and rates of frontal melt by the ocean in the absence of a buttressing ice shelf. Over the next century, we find that volume losses increase by 15–160% with a von Mises calving law compared to the case where the initial ice shelf is kept and the ice front is fixed at its current position, 10–20% with a buoyancy‐driven calving law, and 5–50% with frontal melt caused by ocean thermal forcing. Bed topography exerts the ultimate control on the evolution of Thwaites. In all simulations, once Thwaites Glacier retreats past the western subglacial ridge, the retreat becomes rapidly unstoppable."

See also:

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

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

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

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

In the worst-case scenario, Thwaites could completely collapse within 60 to 70 years, according to the study's authors."
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AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2668 on: January 23, 2020, 08:35:05 PM »
With a hat tip to baking, the linked reference discusses the use of remote seismic observation of glacial earthquakes and precursory seismicity associated with Thwaites Glacier calving, can be used to improve forecasting of future ice mass loss from Thwaites:

J. Paul Winberry et al. (15 January 2020), "Glacial Earthquakes and Precursory Seismicity Associated with Thwaites‐Glacier Calving", Geophysical Research Letters, https://doi.org/10.1029/2019GL086178

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL086178

Abstract
We observe two (~MS 3) long‐period (10‐30 s) seismic events that originate from the terminus of Thwaites Glacier, Antarctica. Serendipitous acquisition of satellite images confirm that the seismic events were glacial earthquakes generated during the capsizing of icebergs. The glacial earthquakes were preceded by 6 days of discrete high frequency seismic events that can be observed at distances exceeding 250 km. The high frequency seismicity displays an increasing rate of occurrence, culminating in several hours of sustained tremor co‐eval with the long period events. A series of satellite images collected during this precursory time‐period show that the high frequency events and tremor are the result of accelerating growth of ancillary fractures prior to the culminating calving event. This study indicates that seismic data have the potential to elucidate the processes by which Thwaites Glacier discharges into the ocean, thus improving our ability to constrain future sea‐level rise.

Plain Language Summary
Thwaites Glacier is one of the largest sources of Antarctic ice‐mass loss, however, the physics of the processes that control its discharge into the ocean remains incomplete. The long‐term stability of glaciers, such as Thwaites, that discharge directly into the ocean is linked to the rate of calving, the process of iceberg production. Spaceborne observations are crucial to understanding the calving processes, however, the typical repeat time of a satellite imagery is much longer than the typical duration of a calving event (minutes to hours). Increasingly, the seismic signals generated during calving are being used to complement other observations. For larger calving events, seismic energy can be recorded by remote seismic observation (100s to 1000s of km away from a glacier). While these glacier earthquakes are now regularly used to study calving in Greenland, only a limited number of glacial earthquakes have been observed in Antarctica. We show that Thwaites Glacier has now begun generating glacial earthquakes similar to those observed in Greenland. Additionally, we show that enhanced rates of fracturing can be seismically observed before the event. Our observations open a new avenue for understanding the behavior of Antarctica's leading source of mass loss.
« Last Edit: January 23, 2020, 10:39:33 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2669 on: January 23, 2020, 09:44:39 PM »
While the linked article is a few months old, it still provides a useful reminder that a potential cascade of climate change tipping points '… aren’t a far-off catastrophe—we’re already living them. '

Title: "Our Planet May Be Barreling Toward a Tipping Point"

https://www.wired.com/story/climate-tipping-point/

Extract: "Today in the journal Nature, a group of researchers argues that we're closer to tipping nine climate demons than previously believed, and that we're already starting to see some associated effects. “We argue that the intervention time left to prevent tipping could already have shrunk towards zero, whereas the reaction time to achieve net zero emissions is 30 years at best,” they write. “Hence we might already have lost control of whether tipping happens.”

… these researchers have built a solid case that tipping points aren’t a far-off catastrophe—we’re already living them. “The evidence that it might actually be happening, that it might be true, is so high, that honestly this is just another very big reason why we need to get our act together and do everything that we could possibly do to fix the problem,” he says. “This is an article that just pulls together many, many good reasons why there is a real emergency, a real urgency here.”"
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2670 on: January 23, 2020, 10:06:24 PM »
I have little doubt that the US government will eventually implement some form of solar geoengineering program before 2050, no matter what the unintended consequences might be:

Title: "NOAA Gets Go-Ahead to Study Controversial Climate Plan B"

https://www.scientificamerican.com/article/noaa-gets-go-ahead-to-study-controversial-climate-plan-b/

Extract: "The top climate change scientist for NOAA said he has received $4 million from Congress and permission from his agency to study two emergency—and controversial—methods to cool the Earth if the U.S. and other nations fail to reduce global greenhouse gas emissions.

One is to inject sulfur dioxide or a similar aerosol into the stratosphere to help shade the Earth from more intense sunlight. It is patterned after a natural solution: volcanic eruptions, which have been found to cool the Earth by emitting huge clouds of sulfur dioxide.
The second approach would use an aerosol of sea salt particles to improve the ability of low-lying clouds over the ocean to act as shade.

At the moment, the government has no planned experiments and NOAA’s authority does not extend into the stratosphere. But there is a bill in Congress called the “Climate Intervention Research Act” that would broaden its jurisdiction.

“There could be more than $100 million attached to this, I’m told,” he explained."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2671 on: January 24, 2020, 05:29:09 PM »
"Extraordinary claims require extraordinary evidence” was a phrase made popular by Carl Sagan, and many people seem think that it is appropriate to apply this phrase to warnings about the risks of climate apocalypse.

However, to me the more extraordinary claims are those made by SSP1 (the most sustainable SSP considered) that the world will immediately become socio-economically more equable/enlightened as I currently see little evidence, let alone extraordinary evidence, to support such a claim; which if incorrect could lead to a climate apocalypse.

The first attached image shows that SSP1 assumes rapid reductions in global population growth and a more equable distribution of strong global GDP growth.  However, the linked June 17, 2019 article indicates that the UN projections (see the second attached image, and I note that by the end of January 2020 global population will be about 7.76 billion):

"The world’s population is expected to increase by 2 billion persons in the next 30 years, from 7.7 billion currently to 9.7 billion in 2050, according to a new United Nations report launched today."

Furthermore, the article states:

"Life expectancy at birth for the world, which increased from 64.2 years in 1990 to 72.6 years in 2019, is expected to increase further to 77.1 years in 2050. While considerable progress has been made in closing the longevity differential between countries, large gaps remain. In 2019, life expectancy at birth in the least developed countries lags 7.4 years behind the global average, due largely to persistently high levels of child and maternal mortality, as well as violence, conflict and the continuing impact of the HIV epidemic."

Finally, I note that counting on entrepreneurial innovation to solve climate change challenges, does not consider the creative destruction process inherent in capitalism; which takes many decades to complete.

https://www.un.org/development/desa/en/news/population/world-population-prospects-2019.html

See also:

https://population.un.org/wpp/Graphs/

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2672 on: January 24, 2020, 07:00:17 PM »
The linked reference and two related articles indicate that since 1997 the Beaufort Gyre (associated with the high pressure atmospheric condition shown in the first image) has accumulated an anomalously high amount of ocean heat content within the relatively fresh water accumulated in the gyre; which, could rapidly be released into the Arctic Ocean during sustained atmospheric conditions with a low pressure system over the Beaufort Gyre (see the second image).  Not only would such a relatively rapid release of relatively warm relatively fresh water from the Beaufort Gyre slow down the MOC (which would accelerated warming of the tropical sea surface temperatures) but would also likely result in a relatively abrupt reduction of Arctic sea ice as discussed in the second linked article from 2019.

Mary-Louise Timmermans John Toole and Richard Krishfield (29 Aug 2018), "Warming of the interior Arctic Ocean linked to sea ice losses at the basin margins", Science Advances, Vol. 4, no. 8, eaat6773, DOI: 10.1126/sciadv.aat6773

https://advances.sciencemag.org/content/4/8/eaat6773

Abstract
Arctic Ocean measurements reveal a near doubling of ocean heat content relative to the freezing temperature in the Beaufort Gyre halocline over the past three decades (1987–2017). This warming is linked to anomalous solar heating of surface waters in the northern Chukchi Sea, a main entryway for halocline waters to join the interior Beaufort Gyre. Summer solar heat absorption by the surface waters has increased fivefold over the same time period, chiefly because of reduced sea ice coverage. It is shown that the solar heating, considered together with subduction rates of surface water in this region, is sufficient to account for the observed halocline warming. Heat absorption at the basin margins and its subsequent accumulation in the ocean interior, therefore, have consequences for Beaufort Gyre sea ice beyond the summer season.

&

Title: "Signs of Big Change in the Arctic - A once-predictable system shifts out of balance"

https://www.whoi.edu/oceanus/feature/signs-of-big-changes-in-the-arctic/

Extract: "For at least half a century and probably longer, the climate in the Arctic has run like a clock. As reliably as a pendulum, it has oscillated every five to seven years between two distinct self-regulating phases that shift the region’s winds, ice, currents, and other conditions.

But in a new study, scientists say the system has been stuck in one phase since 1997. The monkey wrench that’s jamming the works, they suspect, may be warming temperatures that are accelerating the melting of the Greenland Ice Sheet.

When ice melts, it can no longer play the important role of reflecting sunlight. Instead, the melting gives the sun unfettered access to the open water, allowing the ocean to absorb more heat.

As that heat diffuses upward over time, it stalls the growth of the sea ice during the winter in the region, said Toole. “And, if the deeper, warmer water starts mixing more vigorously with the cold water above it, we will see even more sea ice thinning during the summer.”"

&

Title: "A ‘Ticking Time Bomb’ in the Arctic - Waters are warming beneath the ocean's sea ice"

https://www.whoi.edu/oceanus/feature/a-ticking-time-bomb-in-the-arctic/

Extract: "When it comes to the ocean, deeper usually means colder. But there are exceptions. In the Arctic Ocean, for example, a warm layer of water is trapped 150 feet under the ocean’s chunky ice floes by a ceiling of cold fresh water near the surface. The cold layer insulates the sea ice from the warmer waters below.

In a 2018 study, scientists have found that the amount of heat in the trapped warm layer in the Beaufort Gyre, a major Arctic Ocean circulation system north of Alaska, has doubled over the past 30 years. And, if the temperatures continue to spike, it could eventually spell trouble for the ice above.

“At some point, the heat from this layer is going to have to come up to the surface, and it’s going to impact the ice,” said John Toole, a scientist at Woods Hole Oceanographic Institution (WHOI) and co-author of the study. “It’s a ticking time bomb.”

The study is yet another case in point of why melting Arctic sea ice is a problem: When ice melts, it can no longer play the important role of reflecting sunlight. Instead, the melting gives the sun unfettered access to the open water, allowing the ocean to absorb more heat.

As that heat diffuses upward over time, it stalls the growth of the sea ice during the winter in the region, said Toole. “And, if the deeper, warmer water starts mixing more vigorously with the cold water above it, we will see even more sea ice thinning during the summer.”"

« Last Edit: January 24, 2020, 09:08:04 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2673 on: January 25, 2020, 03:21:15 PM »
This post is a follow-on to my last post (Reply #2672) about the Beaufort Gyre, as the following linked reference documents: "… an increase of more than 6,400 km3 of liquid freshwater content from 2003 to 2018, a 40% growth relative to the climatology of the 1970s. This fresh water volume is comparable to the fresh water volume released to the sub‐arctic seas during the Great Salinity Anomaly episode of the 1970s."

Furthermore, I remind readers that in addition to the risks (see Reply #2672) of slowing the MOC and an abrupt reduction in Arctic Sea Ice area/extent, a release of relatively warm relative fresh water from the Beaufort Gyre would also likely accelerate ice mass loss in Antarctica via the bipolar seesaw mechanism.

A. Proshutinsky et al (11 December 2019), "Analysis of the Beaufort Gyre Freshwater Content in 2003–2018", JGR Oceans, https://doi.org/10.1029/2019JC015281

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JC015281

Abstract
Hydrographic data collected from research cruises, bottom‐anchored moorings, drifting Ice‐Tethered Profilers, and satellite altimetry in the Beaufort Gyre region of the Arctic Ocean document an increase of more than 6,400 km3 of liquid freshwater content from 2003 to 2018: a 40% growth relative to the climatology of the 1970s. This fresh water accumulation is shown to result from persistent anticyclonic atmospheric wind forcing (1997–2018) accompanied by sea ice melt, a wind‐forced redirection of Mackenzie River discharge from predominantly eastward to westward flow, and a contribution of low salinity waters of Pacific Ocean origin via Bering Strait. Despite significant uncertainties in the different observations, this study has demonstrated the synergistic value of having multiple diverse datasets to obtain a more comprehensive understanding of Beaufort Gyre freshwater content variability. For example, Beaufort Gyre Observational System (BGOS) surveys clearly show the interannual increase in freshwater content, but without satellite or Ice‐Tethered Profiler measurements, it is not possible to resolve the seasonal cycle of freshwater content, which in fact is larger than the year‐to‐year variability, or the more subtle interannual variations.

Plain Language Abstract
The Beaufort Gyre centered in the Canada Basin of the Arctic Ocean is the major reservoir of fresh water in the Arctic. The primary focus of this study is on quantifying variability and trends in liquid (water) and solid (sea ice) freshwater content in this region. The Beaufort Gyre Exploration Program was initiated in 2003 to synthesize results of historical data analysis, design and conduct long‐term observations, and to provide information for numerical modeling under the umbrella of the FAMOS (Forum for Arctic Observing and Modeling Synthesis) project. The data collected from research cruises, moorings, Ice‐Tethered Profiler observations, and satellite altimetry document an increase of more than 6,400 km3 of liquid freshwater content from 2003 to 2018, a 40% growth relative to the climatology of the 1970s. This fresh water volume is comparable to the fresh water volume released to the sub‐arctic seas during the Great Salinity Anomaly episode of the 1970s. Thus, since the 2000s, the stage has been set for another possible release of fresh water to lower latitudes with accompanying climate impacts, including changes to sea ice conditions, ocean circulation, and ecosystems of the Sub‐Arctic similar to the influence of the Great Salinity Anomaly observed in the 1970s.

See also:

Title: "Great Salinity Anomaly"

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

Extract: "The Great Salinity Anomaly originally referred to a significant disturbance caused by a major pulse of freshwater input to the Nordic Seas in the late 1960s and early 1970s."

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2674 on: January 27, 2020, 12:42:26 AM »
For those who are serious about better understanding the connectivity be the Arctic Ocean (including the Beaufort Gyre which is currently accumulating increasing amount of heat content and freshwater; which might soon be released through the Arctic Ocean into the North Atlantic) and the North Atlantic (which is introducing increasing amounts of heat into the Arctic Ocean); I provide the first link to the titled session abstracts in the Ocean Sciences Meeting 2020 in San Diego this February.  Furthermore, I provide the second link to one of the session abstracts that indicates that a the eventual release of the excess accumulated warm freshwater from the Beaufort Gyre may well be sufficient to slow the MOC; which would constitute a significant ice-climate positive feedback accelerating further global warming:

Title: "HE11A - Arctic-North Atlantic Connectivity: Variability, Changes, and Impacts of Freshwater and Heat Exchange I"

https://agu.confex.com/agu/osm20/meetingapp.cgi/Session/92297

Session summary: "A two-way connectivity between the polar and subpolar basins realizing through salt and heat exchange between the Arctic Ocean and the subpolar North Atlantic is generally accepted. It is not fully understood yet at what time scales and to what extent the Arctic Ocean impacts the subpolar North Atlantic and how changes in the North Atlantic feedback to the Arctic Ocean. This problem is particularly important considering current rapid changes in the Arctic Ocean. Observations indicate a shift in the oceanic freshwater and heat content in the Arctic Ocean likely resulting in changes in oceanic fluxes to the subpolar seas. At the same time, recently observed changes in the subpolar seas, that are not obviously related to the Arctic export variations, may impact the heat input into the Arctic. Increasing Greenland runoff complicates the matter adding surplus freshwater into the subpolar North Atlantic. The goal of this session is to analyze present and future changes in the subpolar North Atlantic and their linkage to the Arctic Ocean fluxes as well as potential impact of the subpolar region on the Arctic Ocean via oceanic variability. This session solicits papers discussing observations and simulations of salt and heat transports between the Arctic Ocean and the North Atlantic; impacts of polar-subpolar fluxes on ocean circulation, convective mixing and water mass formation; biogeochemical impacts and marine ecosystem response to changing Arctic-North Atlantic fluxes; and identification and tracking of polar water, Greenland meltwater, and Atlantic water propagating in the polar and subpolar seas."

&

Title: "HE11A-04 - Impact of the Beaufort Gyre freshwater release on deepwater formation in the North Atlantic"

https://agu.confex.com/agu/osm20/meetingapp.cgi/Paper/656421

Abstract
The Beaufort Gyre (BG) is the largest liquid freshwater reservoir of the Arctic Ocean. Observations show a significant increase of its freshwater content over the past 15 years, with the increase reaching 40% of its climatology in 2017. If the freshwater is released into the North Atlantic, the magnitude would excess that of the Great Salinity Anomaly of the 1970s, raising the specter of slowing global ocean circulation. However, whether the BG freshwater can ultimately perturb the North Atlantic deepwater formation is highly uncertain. Here, we assess the impact of a potential BG freshwater release during the historical period, using an eddy-permitting ocean-sea ice model with passive tracers that explicitly track the BG volume and freshwater transport.

Our simulations suggest that more BG-sourced freshwater (36 mSv) reached the North Atlantic during a release phase (1983-1995) of the BG freshwater content than during an accumulation phase (1996-2008), when most BG-sourced water recirculated within the Arctic basin. 70% of this BG-sourced freshwater routed through Davis Strait, while 30% routed through Fram Strait. This BG-sourced freshwater was able to bring down the surface salinity by 0.35 psu in the western Labrador Sea towards the end of the release phase. Although the historical release was not able to induce obvious impact during the phase of harsh winters with very strong convection in the early 1990s, the current BG freshwater content anomaly has almost doubled its historical maximum and a future release may become large enough to dampen the deepwater formation once in conjunction with mild winters.

Edit:  I provide a second abstract from the session about how ocean heat content influx from the North Atlantic is already reducing Arctic Sea Ice extent and which is likely to cause more reductions of Arctic Sea Ice extent in the future:

Title: "HE11A-03 - How Atlantic heat makes Arctic sea ice retreat"

https://agu.confex.com/agu/osm20/meetingapp.cgi/Paper/646128

Abstract
How change comes to Arctic sea ice still remains mechanistically and prognostically unresolved. Here we provide observational and physically consistent evidence that sea ice variability and retreat north of Svalbard result from Atlantic water impinging directly on the oncoming transpolar sea-ice drift. We particularly show that the local halocline is largely maintained by local sea ice melt and that the winter sea-ice extent can be predicted from the upstream temperature of the Norwegian Atlantic Current one year in advance. The latter scaling also relates to trends; the long-term 1 ºC warming of Atlantic water over the last 40 years is reflected in 50.000 km2 sea-ice retreat north of Svalbard and into the Nansen Basin. Zooming out to the Arctic Ocean in general, and considering the projected future in a large-ensemble climate model simulation, we find that this “Atlantification” of the Arctic will progress throughout the 21st century but apparently restricted to the Eurasian Basin by the natural barrier of the Lomonosov Ridge.
« Last Edit: January 27, 2020, 12:51:43 AM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2675 on: January 27, 2020, 01:07:21 AM »
The linked reference provides evidence from models that indicate that AGW influence acceleration of wind speeds in the Greenland Sea would accelerate the 'Atlantification' of the Arctic Ocean, this represents another positive feedback mechanism due to the associated reduction in Arctic Sea Ice extent:

Morven Muilwijk  et al (07 August 2019), "Arctic Ocean Response to Greenland Sea Wind Anomalies in a Suite of Model Simulations", JGR Oceans, https://doi.org/10.1029/2019JC015101

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JC015101

Abstract
Multimodel Arctic Ocean “climate response function” experiments are analyzed in order to explore the effects of anomalous wind forcing over the Greenland Sea (GS) on poleward ocean heat transport, Atlantic Water (AW) pathways, and the extent of Arctic sea ice. Particular emphasis is placed on the sensitivity of the AW circulation to anomalously strong or weak GS winds in relation to natural variability, the latter manifested as part of the North Atlantic Oscillation. We find that anomalously strong (weak) GS wind forcing, comparable in strength to a strong positive (negative) North Atlantic Oscillation index, results in an intensification (weakening) of the poleward AW flow, extending from south of the North Atlantic Subpolar Gyre, through the Nordic Seas, and all the way into the Canadian Basin. Reconstructions made utilizing the calculated climate response functions explain ∼50% of the simulated AW flow variance; this is the proportion of variability that can be explained by GS wind forcing. In the Barents and Kara Seas, there is a clear relationship between the wind‐driven anomalous AW inflow and the sea ice extent. Most of the anomalous AW heat is lost to the atmosphere, and loss of sea ice in the Barents Sea results in even more heat loss to the atmosphere, and thus effective ocean cooling. Release of passive tracers in a subset of the suite of models reveals differences in circulation patterns and shows that the flow of AW in the Arctic Ocean is highly dependent on the wind stress in the Nordic Seas.

Plain Language Summary
The North Atlantic Current is an extension of the Gulf Stream, which brings warm Atlantic Water northward as the current flows through the Nordic Seas. Eventually, it enters the cold deep Arctic Ocean basins through the Barents Sea and Fram Strait. Nine different numerical ocean ice models have been analyzed and compared in order to investigate (1) their ability to simulate this northward flow of Atlantic Water, (2) its dependence on wind forcing, and (3) its impact on Arctic sea ice. Consistently, in all models, stronger winds in the Greenland Sea result in a stronger northward flow of warm Atlantic Water. The response on ocean circulation occurs from the North Atlantic, through the Nordic Seas and the Barents Sea, to the deep Canadian Basin. The flow of warm Atlantic Water within the Arctic Ocean is thus highly dependent on the wind stress in the Nordic Seas. There is particularly clear response in the Barents and Kara Seas where a wind‐driven anomalous warm inflow drives a smaller sea ice extent and thickness, and an increased heat transfer from the ocean to the atmosphere above. Weaker winds in the Greenland Sea produces weaker flow and hence a larger sea ice extent and thickness.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2676 on: January 27, 2020, 04:51:06 PM »
The attached image shows the 5-day Antarctic Surface Mass Balance, SMB, thru January 26 2020 (from the linked website); with the snowfall for 2019-2020 shown as a red dashed line.  This data shows that for 2019-2020 the snowfall has returned close to the 1981-2010 mean; thus highlighting the fact that surface ice melting has been atypically high during the 2019-2020 season (which is not good for ice sheet stability):

http://climato.be/cms/index.php?climato=the-2020-melt-season-over-antarctica-as-simulated-by-marv3-10
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2677 on: January 27, 2020, 05:12:30 PM »
As a public service the attached image shows Gavin Schmidt's comparison of CMIP3 model forecasts (using SRES A1B) vs observed GMSTA to include 2019.  I note that SRES A1B is a relatively high emissions scenario and that per GISTEMP we are now above the mean projected anomaly.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2678 on: January 27, 2020, 10:17:51 PM »
The linked article (& associated linked reference) indicates that tropical forests are losing their ability to absorb CO2, while boreal forests are currently increasing their ability to absorb CO2; but it is not clear to me how long these linear trends will continue:

Title: "Tropical forests losing ability to absorb CO2, study says"

https://www.carbonbrief.org/tropical-forests-losing-ability-to-absorb-co2-study-says

Extract: "The world’s tropical forests are losing their ability to remove CO2 from the atmosphere, while boreal forests are absorbing emissions at an increasingly fast rate, a study finds.

The new analysis uses a combination of remote-sensing data and modelling to create a detailed picture of carbon loss and gain across all of Earth’s biomes from 1992 to 2015.

Caption for image: "The contribution of boreal (black) and tropical (red) forests to the land carbon sink from 1992-2015. The shadow areas show margins of uncertainty. Source: Tagesson et al. (2020)"

See also:

Tagesson et al. (2020) Recent divergence in the contributions of tropical and boreal forests to the terrestrial carbon sink, Nature Ecology & Evolution,

https://www.nature.com/articles/s41559-019-1090-0

https://www.nature.com/articles/s41559-019-1090-0.epdf?referrer_access_token=XwQ79zKkT5GxB2aoleLik9RgN0jAjWel9jnR3ZoTv0OyGafLdLYZ0yrEX9r2SqIDZ77pHBkWlEd2UOk7KEwBqPrfB-jIgOZjkvGFf8NUvENeyxvS849AUxc4J0BdatgDB90-K25jAd-Sf3MLkbgKfaQdrCetK2QKnTO1uIw0BMQN91IxReHrQWZIyPHKgnzbo52VqlqepaUNcXL-XX2EjDNZ0GYmbVJjBb_CzNyh0jPxJ34wgjJXbh6Zv9PGH7fDuIix4w3jBJ52lj8P8FnZ_Q%3D%3D&tracking_referrer=www.carbonbrief.org

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2679 on: January 27, 2020, 11:37:08 PM »
The first attached image shows the locations of the two bore holes for the Thwaites-MELT project in 2020; while the second attached images indicates that as recently as November 2019 there had planned to be three bore holes.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2680 on: January 27, 2020, 11:57:30 PM »
While the linked reference (with a hat tip to Jim Hunt) indicates the rate of ice mass loss from the PIG has slowed since 2007; this is not surprising given that in 2007 the grounding line was retreating down a steep retrograde bed slope (see the attached associated image).  However, the PIG catchment basin shares a common boundary with the Thwaites Glacier; thus if Thwaites collapses, ice mass loss from the PIG will certainly accelerate:

Bamber, J.L., Dawson, G.J. Complex evolving patterns of mass loss from Antarctica’s largest glacier. Nat. Geosci. (2020). https://doi.org/10.1038/s41561-019-0527-z

https://doi.org/10.1038/s41561-019-0527-z

https://www.nature.com/articles/s41561-019-0527-z

Abstract: "Pine Island Glacier has contributed more to sea level rise over the past four decades than any other glacier in Antarctica. Model projections indicate that this will continue in the future but at conflicting rates. Some models suggest that mass loss could dramatically increase over the next few decades, resulting in a rapidly growing contribution to sea level and fast retreat of the grounding line, where the grounded ice meets the ocean. Other models indicate more moderate losses. Resolving this contrasting behaviour is important for sea level rise projections. Here, we use high-resolution satellite observations of elevation change since 2010 to show that thinning rates are now highest along the slow-flow margins of the glacier and that the present-day amplitude and pattern of elevation change is inconsistent with fast grounding-line migration and the associated rapid increase in mass loss over the next few decades. Instead, our results support model simulations that imply only modest changes in grounding-line location over that timescale. We demonstrate how the pattern of thinning is evolving in complex ways both in space and time and how rates in the fast-flowing central trunk have decreased by about a factor five since 2007."

The author's link below can be used to see the whole reference:

https://www.nature.com/articles/s41561-019-0527-z.epdf?author_access_token=bZJI5leN6hZ8TqRp0eZLS9RgN0jAjWel9jnR3ZoTv0M7fNB5emfAFhirntimuuT0grRSQohqvNz1TiXxZ8Hr1UsMw2GTex_ZcwVRJOg6AaJKjCYXCNmGu40JPal36DfeYMQuIWJer2sphU4omXssMQ%3D%3D
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2681 on: January 28, 2020, 12:19:55 AM »
Attached is Hausfather's comparison of modeled vs observed GMSTA through 2019.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2682 on: January 28, 2020, 05:02:20 PM »
I periodically get the impression that some people think that it is advisable to use up as much of our collective remaining carbon budget (whatever that may be), in order to give innovators more time to solve (frequently technologically) our climate change situation.  However, I would like to remind readers that carbon budgets are typically calculated using model projections that do not adequately simulation may key Earth System responses to more radiative forcing.  In this regard, I offer the following three thoughts about over relying on estimated carbon budgets:

1. The Beaufort Gyre has been atypically accumulating excess ocean heat content and freshwater since 1997 (in quantities already large enough to slow the MOC when released), most likely due to ice meltwater from the GIS.  Thus, if key southern Greenland marine terminating glaciers (such as Jakobshavn Glacier) were to calve an atypically large number of icebergs in say the next five years, such an increased release of GIS meltwater would likely allow the Beaufort Gyre to stably accumulate still more ocean heat content and more freshwater; which might then be abruptly released sometime in the 2025 to 2035 timeframe; which might then (through the bipolar seesaw mechanisms) trigger a collapse of the Thwaites Glacier in the 2035 to 2045 timeframe.  Furthermore, none of these mechanism/scenarios are considered in current climate models like CMIP6; even though the activation of such mechanisms/scenarios increases continuously with more anthropogenic radiative forcing.

2. Many climate feedback mechanisms (both fast and assumed slow response) are currently becoming (or may soon become) more net positive, with continued radiative forcing.  Thus, the climate sensitivity values assumed to calculate the remaining carbon budget are currently increasing, and may increase faster in the next few decades, with continued radiative forcing.

3. Future reductions in anthropogenic aerosols may temporarily increase radiative forcing in the next few decades more rapidly than assumed by the SSP scenarios.

« Last Edit: January 28, 2020, 05:48:02 PM by AbruptSLR »
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2683 on: January 28, 2020, 05:48:25 PM »
The linked video offers color commentary about the 'doomsday glacier' and the International Thwaites Glacier Collaboration efforts this year:

Title: "Antarctica melting: Journey to the 'doomsday glacier' - BBC News"



See also:

Title: "First look under Thwaites Glacier and Kamb Ice Stream"

https://schmidt.eas.gatech.edu/2019-field/firstlookunderthwaitesglacier/

Extract: "“We know that warmer ocean waters are eroding many of West Antarctica’s glaciers, but we’re particularly concerned about Thwaites,” he said. “This new data will provide a new perspective of the processes taking place, so we can predict future change with more certainty”"

&

Title: "Antarctica's doomsday glacier is melting. Can we save it in time?"

https://www.newscientist.com/article/mg24532650-900-antarcticas-doomsday-glacier-is-melting-can-we-save-it-in-time/

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2684 on: January 28, 2020, 09:12:00 PM »
Attached is an image that can help people better understand the different families/tiers of the SSP scenarios vs the RCP scenarios:
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2685 on: January 28, 2020, 09:56:16 PM »
Is there any obvious advantage in this new metric or are they just trying to muddy the waters?

Þetta minnismerki er til vitnis um að við vitum hvað er að gerast og hvað þarf að gera. Aðeins þú veist hvort við gerðum eitthvað.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2686 on: January 28, 2020, 10:41:38 PM »
Earth Systems do not care whether GHG emissions are anthropogenic or natural:

Bourtsoukidis, E., Pozzer, A., Sattler, T. et al. The Red Sea Deep Water is a potent source of atmospheric ethane and propane. Nat Commun 11, 447 (2020). doi.org/10.1038/s41467-020-14375-0 , www.nature.com/articles/s41467-020-14375-0

https://www.nature.com/articles/s41467-020-14375-0

Abstract: "Non-methane hydrocarbons (NMHCs) such as ethane and propane are significant atmospheric pollutants and precursors of tropospheric ozone, while the Middle East is a global emission hotspot due to  extensive oil and gas production. Here we compare in situ hydrocarbon measurements, performed around the Arabian Peninsula, with global model simulations that include current emission inventories (EDGAR) and state-of-the-art atmospheric circulation and chemistry mechanisms (EMAC model). While measurements of high mixing ratios over the Arabian Gulf are adequately simulated, strong underprediction by the model was found over the northern Red Sea. By examining the individual sources in the model and by utilizing air mass back-trajectory investigations and Positive Matrix Factorization (PMF) analysis, we deduce that Red Sea Deep Water (RSDW) is an unexpected, potent source of atmospheric NMHCs. This overlooked underwater source is comparable with total anthropogenic emissions from entire Middle Eastern countries, and significantly impacts the regional atmospheric chemistry."

See also:

Title: "Red Sea huge source of air pollution, greenhouse gases: study"

https://phys.org/news/2020-01-red-sea-huge-source-air.html

Extract: "Hydrocarbon gases bubbling from the bottom of the Red Sea are polluting the atmosphere at a rate equivalent to the emissions of some large fossil fuel exporting countries, researchers said Tuesday.

The gases seeping from the waters—which are ringed by the resorts and ports of several countries, including Egypt, Israel, Jordan and Saudi Arabia—then mix with emissions from industrial shipping and turned into noxious pollutants that are very harmful to human health."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2687 on: January 29, 2020, 12:12:29 AM »
Is there any obvious advantage in this new metric or are they just trying to muddy the waters?

The image comes from the linked reference.  I believe that the scientists are well meaning, but I suspect that all of this new data serves to increase confusion for many different parties:

Gidden, M. J., Riahi, K., Smith, S. J., Fujimori, S., Luderer, G., Kriegler, E., van Vuuren, D. P., van den Berg, M., Feng, L., Klein, D., Calvin, K., Doelman, J. C., Frank, S., Fricko, O., Harmsen, M., Hasegawa, T., Havlik, P., Hilaire, J., Hoesly, R., Horing, J., Popp, A., Stehfest, E., and Takahashi, K.: Global emissions pathways under different socioeconomic scenarios for use in CMIP6: a dataset of harmonized emissions trajectories through the end of the century, Geosci. Model Dev., 12, 1443–1475, https://doi.org/10.5194/gmd-12-1443-2019, 2019.

https://www.geosci-model-dev.net/12/1443/2019/

Abstract

We present a suite of nine scenarios of future emissions trajectories of anthropogenic sources, a key deliverable of the ScenarioMIP experiment within CMIP6. Integrated assessment model results for 14 different emissions species and 13 emissions sectors are provided for each scenario with consistent transitions from the historical data used in CMIP6 to future trajectories using automated harmonization before being downscaled to provide higher emissions source spatial detail. We find that the scenarios span a wide range of end-of-century radiative forcing values, thus making this set of scenarios ideal for exploring a variety of warming pathways. The set of scenarios is bounded on the low end by a 1.9 W m−2 scenario, ideal for analyzing a world with end-of-century temperatures well below 2 ∘C, and on the high end by a 8.5 W m−2 scenario, resulting in an increase in warming of nearly 5 ∘C over pre-industrial levels. Between these two extremes, scenarios are provided such that differences between forcing outcomes provide statistically significant regional temperature outcomes to maximize their usefulness for downstream experiments within CMIP6. A wide range of scenario data products are provided for the CMIP6 scientific community including global, regional, and gridded emissions datasets.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2688 on: January 29, 2020, 05:31:06 PM »
Don't forget that as of January 1, 2020 in order to meet a new UN mandate, marine shipping is required to use low sulfur fuels (which while reducing problems like acid rain also decreases negative forcing from anthropogenic aerosols); however, the linked article indicate that much of the marine shipping industry has switched to low sulfur fuels that have about 85% increased black carbon emissions.  Thus starting in 2020, the environment is likely to experience an abrupt decrease in negative radiative forcing and an abrupt increase in positive radiative forcing associated with maritime aerosol emissions:

Title: "Environmental groups sound alarm on new shipping ‘Frankenstein’ fuel"

https://www.rcinet.ca/en/2020/01/28/environmental-groups-sound-alarm-heavy-fuel-oil-shipping/

Extract: "A coalition of environmental groups is demanding answers from the oil refining and shipping industries after it emerged that new blends of marine fuels designed to reduce acid rain-causing sulphur emissions have instead increased emissions of “super pollutant” black carbon, a key climate change driver.

According to a German study presented to the International Maritime Organization, some of the new blends of low sulphur fuels developed and marketed by oil companies to comply with UN-mandated air pollution standards in the marine shipping that came into effect on Jan. 1 will actually lead to a surge in the emissions of black carbon.

The study submitted by Germany and Finland to the IMO’s upcoming meeting in February found that these new very low sulphur oil (VLSFO) blends contain high levels of aromatic compounds which, when combusted, could result in up to 85-per-cent increase in emissions of black carbon when compared with heavier fuel oil and distillate fuels used by the shipping industry.

Sian Prior, lead adviser to the Clean Arctic Alliance, a coalition of non-governmental organisations working for a ban on heavy fuel oil (HFO) from Arctic shipping, said the IMO needs to take immediate action.

The IMO has introduced the 0.5 per cent sulphur content cap in marine fuel with the aim of reducing harmful sulphur emissions from ships by 77 per cent by 2025.

This means that the shipping industry can no longer use heavy fuel oil, also known as bunker oil, the cheapest and the dirtiest marine fuel oil said, which normally contained up 3.5 per cent of sulphur, said Andrew Dumbrille, a World Wildlife Fund – Canada specialist in sustainable shipping.
The expectation was that the IMO’s low sulphur cap would encourage the shipping industry to transition to the less polluting distillate fuels, Dumbrille said.

But instead the shipping and the oil refining industries set about developing new blends of heavy fuel oil that contain less sulphur but are far more polluting than HFO when it comes to black carbon emissions, Dumbrille said."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2689 on: January 29, 2020, 06:19:51 PM »
Maybe it is my imagination, but it seems to me that more consensus climate scientists are seriously considering the implementation of geoengineering (including solar radiation-based geoengineering schemes, see the linked reference); without adequately evaluating the risks (including increased risk of war and the risks of abrupt climate change if say sulfur injections were to be terminated after a few decades of use due to global socio-economic disruption) of such assumptions:

Xu, Y., Lin, L., Tilmes, S., Dagon, K., Xia, L., Diao, C., Cheng, W., MacMartin, D., Wang, Z., Simpson, I., and Burnell, L.: Climate engineering to mitigate the projected 21st-century terrestrial drying of the Americas: Carbon Capture vs. Sulfur Injection?, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2020-2, in review, 2020.

https://www.earth-syst-dynam-discuss.net/esd-2020-2/
https://www.earth-syst-dynam-discuss.net/esd-2020-2/esd-2020-2.pdf

Abstract. To mitigate the projected global warming in the 21st century, it is well recognized that society needs to cut CO2 emission and other short-lived warming agents aggressively. However, to stabilize the climate at a warming level closer to the present day, such as the well below 2 °C aspiration in the Paris agreement, a net-zero carbon emission by 2050 is still insufficient. The recent IPCC special report calls for a massive scheme to extract CO2 directly from the atmosphere, in addition to the decarbonization, to reach negative net emission at the mid-century mark. Another ambitious proposal is the solar radiation-based geoengineering schemes, including injecting sulfur gas into the stratosphere. Despite being in the public debate for years, these two leading geoengineering schemes have not been carefully examined under a consistent numerical modeling framework.

Here we present a comprehensive analysis of climate impacts of these two geoengineering approaches using two recently available large-ensemble (> 10 members) model experiments conducted by a family of state-of-art Earth system models. The CO2-based mitigation simulation is designed to include both emissions cut and carbon capture. The solar radiation-based mitigation simulation is designed to inject the sulfur gas strategically at specified altitudes and latitudes and run a feedback control algorithm, to avoid common problems previously identified such as the over-cooling of the Tropics and large-scale precipitation shifts.

Our analysis focuses on the projected aridity conditions over the Americas in the 21st century, in detailed terms of the mitigation potential, the temporal evolution, the spatial distribution (within North and South America), the relative efficiency, and the physical mechanisms. We show that sulfur injection, in contrast to previous notions of leading to excessive terrestrial drying (in terms of precipitation reduction) while offsetting the global mean greenhouse gas (GHG) warming, will instead mitigate the projected drying tendency under RCP8.5. The surface energy balance change induced by Sulfur injection, in addition to the well-known response in temperature and precipitation, plays a crucial role in determining the overall terrestrial hydroclimate response. However, when normalized by the same amount of avoided global warming, in these simulations, sulfur injection is less effective in limiting the worsening trend of regional land aridity in the Americas, when compared with carbon capture. Temporally, the climate benefit of Sulfur injection will emerge more quickly, even when both schemes are hypothetically started in the same year of 2020. Spatially, both schemes are effective in curbing the drying trend over North America. However, for South America, the Sulfur Injection scheme is particularly more effective for the sub-Amazon region (South Brazil), while the Carbon Capture scheme is more effective for the Amazon region. We conclude that despite the apparent limitations (such as inability to address ocean acidification) and potential side effects (such as changes to the ozone layer), innovative means of Sulfur Injection should continue to be explored as a potential low-cost option in the climate solution toolbox, complementing other mitigation approaches such as emissions cut and carbon capture (Cao et al., 2017). Our results demonstrate the urgent need for multi-model comparison studies and detailed regional assessment in other parts of the world.
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2690 on: January 29, 2020, 08:01:45 PM »
Scientists Find Far Higher than Expected Rate of Underwater Glacial Melting


Tidewater glaciers, the massive rivers of ice that end in the ocean, may be melting underwater much faster than previously thought, according to a Rutgers co-authored study that used robotic kayaks.

...

“With the kayaks, we found a surprising signal of melting: Layers of concentrated meltwater intruding into the ocean that reveal the critical importance of a process typically neglected when modeling or estimating melt rates,” said lead author Rebecca Jackson, a physical oceanographer and assistant professor in the Department of Marine and Coastal Sciences in the School of Environmental and Biological Sciences at Rutgers University–New Brunswick. Jackson led the study when she was at Oregon State University.

...

Two kinds of underwater melting occur near glaciers. Where freshwater discharge drains at the base of a glacier (from upstream melt on the glacier’s surface), vigorous plumes result in discharge-driven melting. Away from these discharge outlets, the glacier melts directly into the ocean waters in a regime called ambient melting.

The study follows one published last year in the journal Science that measured glacier melt rates by pointing sonar at the LeConte Glacier from a distant ship. The researchers found melt rates far higher than expected but couldn’t explain why. The new study found for the first time that ambient melting is a significant part of the underwater mix.

Paper:


Meltwater Intrusions Reveal Mechanisms for Rapid Submarine Melt at a Tidewater Glacier

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL085335

Abstract
Submarine melting has been implicated as a driver of glacier retreat and sea level rise, but to date melting has been difficult to observe and quantify. As a result, melt rates have been estimated from parameterizations that are largely unconstrained by observations, particularly at the near‐vertical termini of tidewater glaciers. With standard coefficients, these melt parameterizations predict that ambient melting (the melt away from subglacial discharge outlets) is negligible compared to discharge‐driven melting for typical tidewater glaciers. Here, we present new data from LeConte Glacier, Alaska, that challenges this paradigm. Using autonomous kayaks, we observe ambient meltwater intrusions that are ubiquitous within 400 m of the terminus, and we provide the first characterization of their properties, structure, and distribution. Our results suggest that ambient melt rates are substantially higher (×100) than standard theory predicts and that ambient melting is a significant part of the total submarine melt flux. We explore modifications to the prevalent melt parameterization to provide a path forward for improved modeling of ocean‐glacier interactions.

Plain Language Summary
Tidewater glaciers discharge ice into the ocean through iceberg calving and submarine melting. Submarine melting has been implicated as a driver of glacier retreat and sea level rise, but melt rates have been difficult to directly observe and quantify. As a result, melt rates are typically estimated using a theory that has not been tested with observations at any tidewater glaciers. Two types of melting are expected at tidewater glaciers: Where subglacial discharge drains from outlets in the terminus, energetic upwelling plumes rise along the ice face, and theory predicts vigorous melting. Away from discharge outlets, weaker plumes form from ambient melting, and theory predicts that these ambient melt rates are effectively negligible compared to discharge‐driven melting. Here, we present new data from LeConte Glacier, Alaska, that challenges this paradigm. Using autonomous kayaks, we observe intrusions of meltwater—the product of ambient melt plumes—that are only found within 400 m of the terminus, and we provide the first characterization of their properties, structure, and distribution. Their ubiquity suggests that ambient melt rates are substantially higher than standard theory predicts and that ambient melting is a significant—but often neglected—part of the total submarine melt flux.

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2691 on: January 29, 2020, 08:22:56 PM »
The two linked Phys.org articles (& associated references) remind us that there are plenty of positive feedback mechanisms (for instance: the spread of earthworms into new environments and permafrost degradation) that CMIP7 models could simulate that CMIP6 models did not adequately account for:

Title: "Global worming: Earthworms add to climate change"

https://phys.org/news/2013-02-global-worming-earthworms-climate.html

Extract: "Earthworms are long revered for their beneficial role in soil fertility, but with the good comes the bad: they also increase greenhouse gas emissions from soils, according to a study published Feb. 3 in Nature Climate Change by a research team that includes a University of California, Davis, soil scientist.

They found that the presence of earthworms increased nitrous oxide emissions from soil by 42 percent and carbon dioxide emissions from soil by 33 percent. But they found no indications that earthworms affect soil organic carbon stocks—the carbon stored within the soil."

See also:

Lubbers, I., van Groenigen, K., Fonte, S. et al. Greenhouse-gas emissions from soils increased by earthworms. Nature Clim Change 3, 187–194 (2013). https://doi.org/10.1038/nclimate1692

https://www.nature.com/articles/nclimate1692?proof=true1

Abstract: "Earthworms play an essential part in determining the greenhouse-gas balance of soils worldwide, and their influence is expected to grow over the next decades. They are thought to stimulate carbon sequestration in soil aggregates, but also to increase emissions of the main greenhouse gases carbon dioxide and nitrous oxide. Hence, it remains highly controversial whether earthworms predominantly affect soils to act as a net source or sink of greenhouse gases. Here, we provide a quantitative review of the overall effect of earthworms on the soil greenhouse-gas balance. Our results suggest that although earthworms are largely beneficial to soil fertility, they increase net soil greenhouse-gas emissions."

&

Title: "Rising global temperatures turn northern permafrost region into significant carbon source"

https://phys.org/news/2020-01-global-temperatures-northern-permafrost-region.html

Extract: "Even more importantly, when modeling the carbon balance using the large collection of data, the scientists found that the CO2 released by permafrost soil in the winter could increase 41 percent by 2100 if human-caused greenhouse gas emissions continue at their current rate.

The study, published in Nature Climate Change this past October, is the most comprehensive study on this phenomenon to date. It highlights the need for more research on the permafrost region's net CO2 emissions, and it demonstrates the significant impact these emissions could have on the greenhouse effect and global warming.

"Climate and Earth system models often treat these winter permafrost CO2 emissions as insignificant or even non-existent," said Roser Matamala, a scientist in Argonne's Environmental Science division and a contributor to the study. "But this study, with its large volume of data extending over multiple seasons, shows that winter respiration is substantial and significant. The study should convince modelers that this flux of winter-time carbon to the atmosphere can no longer be overlooked. It is not small, and it needs to be taken into account.""

See also:

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

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

Abstract: "Recent warming in the Arctic, which has been amplified during the winter, greatly enhances microbial decomposition of soil organic matter and subsequent release of carbon dioxide (CO2). However, the amount of CO2 released in winter is not known and has not been well represented by ecosystem models or empirically based estimates. Here we synthesize regional in situ observations of CO2 flux from Arctic and boreal soils to assess current and future winter carbon losses from the northern permafrost domain. We estimate a contemporary loss of 1,662 TgC per year from the permafrost region during the winter season (October–April). This loss is greater than the average growing season carbon uptake for this region estimated from process models (−1,032 TgC per year). Extending model predictions to warmer conditions up to 2100 indicates that winter CO2 emissions will increase 17% under a moderate mitigation scenario—Representative Concentration Pathway 4.5—and 41% under business-as-usual emissions scenario—Representative Concentration Pathway 8.5. Our results provide a baseline for winter CO2 emissions from northern terrestrial regions and indicate that enhanced soil CO2 loss due to winter warming may offset growing season carbon uptake under future climatic conditions."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2692 on: January 29, 2020, 08:36:26 PM »
The linked article states that direct measurement of the ocean water at the grounding line (measured as part of the ITGC) indicate that the temperature of this water was 2C above freezing; and that the complete findings (from this part of this season's ITGC expedition) will be published in March, 2020:

Title: "Temperatures at a Florida-Size Glacier Alarm Scientists"

https://www.nytimes.com/2020/01/29/climate/thwaites-glacier-melting-antarctica.html

The researchers, working on the Thwaites Glacier, recorded water temperatures at the base of the ice of more than 2 degrees Celsius, or 3.8 degrees Fahrenheit, above the normal freezing point. Critically, the measurements were taken at the glacier’s grounding line, the area where it transitions from resting wholly on bedrock to spreading out on the sea as ice shelves.

It is unclear how fast the glacier is deteriorating: Studies have forecast its total collapse in a century and also in a few decades. The presence of warm water in the grounding line may support estimates at the faster range.

That is significant because the Thwaites, along with the Pine Island Glacier and a number of smaller glaciers, acts as a brake on part of the much larger West Antarctic Ice Sheet. Together, the two bigger glaciers are currently holding back ice that, if melted, would raise the world’s oceans by more than a meter, or about four feet, over centuries, an amount that would put many coastal cities underwater.

Drilling the hole — about 30 centimeters wide and 600 meters deep, or roughly one foot by 1,970 feet — and collecting the data took about 96 hours in subzero weather. The results of the study are expected to be published in March. The expedition was part of the International Thwaites Glacier Collaboration, a series of research projects aimed at understanding the glacier."
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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2693 on: January 29, 2020, 10:23:32 PM »
While many people like to closely track the changes in well-mixed greenhouse gases, WMGHGs, radiative forcing; the attached table (first image) from the linked EEA website shows that cumulative radiative forcing estimates for WMGHGs changed for AR4 (1970-2005) to AR5 (1970-2011) by a ratio of 2.83/2.63 = 1.076 while the same ratio for Total anthropogenic radiative forcing was 2.3/1.6 = 1.438; which emphasizes the importance of better understanding the impacts of all anthropogenic radiative forcing agents.  This is especially true given that the EEA calculates that CO2 equivalents (including cooling from aerosols) for 2017 was 454 ppm (see the second image); and that negative radiative forcing from anthropogenic aerosols could decrease rapidly in coming decades such as expected to be the case from maritime shipping beginning this year.

Title: "Atmospheric greenhouse gas concentrations"

https://www.eea.europa.eu/data-and-maps/indicators/atmospheric-greenhouse-gas-concentrations-6/assessment-1

Extract: "Considering all greenhouse gases, the total CO2 equivalent concentration reached a level of 454 ppm CO2 equivalents in 2017, which was an increase of 4 ppm compared with 2016 and 37 ppm more than in 2007."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

kassy

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2694 on: January 29, 2020, 11:19:35 PM »
So lets adapt russian roulette to the dotted line.

We take a single shot gun that is loaded or not and then pull the trigger.

Seems more stupid then the original version and we do that with the planet...
Þetta minnismerki er til vitnis um að við vitum hvað er að gerast og hvað þarf að gera. Aðeins þú veist hvort við gerðum eitthvað.

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2695 on: January 29, 2020, 11:43:33 PM »
The linked reference indicates that the inflow of Atlantic Water through the Fram Strait into the Arctic Ocean is accelerated by Arctic Sea Ice decline.  This represents a positive feedback on Arctic Amplification:

Qiang Wang et al. (24 January 2020), "Intensification of the Atlantic Water supply to the Arctic Ocean through Fram Strait induced by Arctic sea ice decline", Geophysical Research Letters, https://doi.org/10.1029/2019GL086682

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL086682

Abstract
Substantial changes have occurred in the Arctic Ocean in the last decades. Not only sea ice has retreated significantly, but also the ocean at mid‐depth showed a warming tendency. By using simulations we identified a mechanism that intensifies the upward trend in ocean heat supply to the Arctic Ocean through Fram Strait. The reduction in sea ice export through Fram Strait induced by Arctic sea ice decline increases the salinity in the Greenland Sea, which lowers the sea surface height and strengthens the cyclonic gyre circulation in the Nordic Seas. The Atlantic Water volume transport to the Nordic Seas and Arctic Ocean is consequently strengthened. This enhances the warming trend of the Arctic Atlantic Water layer, potentially contributing to the Arctic “Atlantification”. Therefore, the Nordic Seas can play the role of a switchyard to influence the heat budget of the Arctic Ocean.

Plain Language Summary
The Arctic sea ice decline is among the key indications of the climate change, which has strong impacts on the environment, human beings and biodiversity. In this paper we found that the Arctic sea ice decline at surface can even cause Arctic Ocean warming at mid‐depth by intensifying the upward trend of ocean heat supply to the Arctic Ocean through Fram Strait. The Nordic Seas play the role of a switchyard for the involved processes: The sea ice decline reduces the sea ice export through Fram Strait, which further increases the salinity in the Greenland Sea; Consequently, in the Nordic Seas the sea surface height decreases and the gyre circulation strengthens; These changes then increase the Atlantic Water inflow to the Nordic Seas and the Arctic Ocean, causing significant warming in the Atlantic Water layer of the Arctic Ocean. The changes in the ocean heat budget have strong implications on potential feedbacks to sea ice decline through basal melting in a future warming climate. The intensification of the Atlantic Water volume transport through Fram Strait can impact not only the Arctic heat budget, but also the nutrient budget and potentially the primary production.


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

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2696 on: January 30, 2020, 12:24:41 AM »
The linked reference confirms that surface ozone (from precursors interaction with sunlight) damages photosynthesis and reduces the ability of land ecosystems to assimilate carbon from the atmosphere.

Mitigation of ozone damage to the world's land ecosystems by source sector, Nature Climate Change (2020). DOI: 10.1038/s41558-019-0678-3 , https://nature.com/articles/s41558-019-0678-3

https://www.nature.com/articles/s41558-019-0678-3

Abstract: "Surface ozone damages photosynthesis and reduces the ability of land ecosystems to assimilate carbon from the atmosphere thereby further increasing global warming. Ozone is not emitted directly but formed in the atmosphere during complex chemical reactions of precursors, carbon monoxide, methane, non-methane volatile organic compounds and nitrogen oxides, in sunlight. These ozone precursors are emitted from a wide range of anthropogenic activities. Reductions in ozone precursor emissions are needed to mitigate ozone vegetation damage but it is unclear which are the most effective source sectors to target. Here, we apply a global Earth system model to compare the benefits to gross primary productivity of stringent 50% emission reductions in the seven largest anthropogenic ozone source sectors. Deep cuts in air pollutant emissions from road transportation and the energy sector are the most effective mitigation measures for ozone-induced gross primary productivity losses in Eastern China, Eastern United States, Europe and globally. Our results suggest that mitigation of ozone vegetation damage is a unique opportunity to contribute to negative carbon emissions, offering a natural climate solution that links fossil fuel emission abatement, air quality and climate. However, achieving these benefits requires ambitious mitigation pathways that tackle multiple source sectors."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

nanning

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2697 on: January 30, 2020, 09:32:20 AM »
Re: Reply #2693 "Atmospheric greenhouse gas concentrations"

Thank you AbruptSLR for that information regarding our calculation of CO2e. Of course aerosols should be included in that formula as a negative radiative forcing. We now only need the pre-industrial aerosol concentrations to calculate the actual CO₂ equivalent GHG concentrations.
"It is preoccupation with possessions, more than anything else, that prevents us from living freely and nobly" - Bertrand Russell
   Simple: minimize your possessions and be free and kind    It's just a mindset.       Refugees welcome

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2698 on: January 30, 2020, 05:28:55 PM »
The attached image reminds us that a high forcing scenario like RCP 8.5 can occur within a model using moderate forcing like SRES A1B if the model projects higher values of climate sensitivity.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #2699 on: January 30, 2020, 07:16:16 PM »
The attached image compares the Thwaites Ice Tongue on May 23 2019 (top view) to January 30 2020 (bottom view).  I provide this comparison because it shows not only that the ice tongue itself is breaking apart, but more so because the 'grounded' area at the base of the ice tongue is also breaking apart in real time; which, if this trend continues, in a few years could expose ice cliffs within the seafloor trough leading to the BSB with ice cliff heights (above the water line) over 100m; which could lead to a progressive ice cliff failure mechanism in this area:
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson