Support the Arctic Sea Ice Forum and Blog

Author Topic: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE  (Read 432029 times)

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3850 on: October 23, 2020, 10:59:24 AM »
While I have previous cited the linked open access reference, here I remind readers that Pollard et al (2018) confirms that ice mélange offers very little resistance to MICI-mechanisms in Antarctica and that if/when key Antarctic marine glaciers are subjected to mid-Pliocene type oceanic and atmospheric conditions that very rapid ice mass loss can occur in decades as indicated in the two attached images:

Pollard, D., R.M. DeConto and R.B. Alley (2018), "A continuum model (PSUMEL1) of ice mélange and its role during retreat of the Antarctic Ice Sheet", Geosci. Model Devel., 11, 5149-5172, https://doi.org/10.5194/gmd-11-5149-2018

https://gmd.copernicus.org/articles/11/5149/2018/

Abstract
Rapidly retreating thick ice fronts can generate large amounts of mélange (floating ice debris), which may affect episodes of rapid retreat of Antarctic marine ice. In modern Greenland fjords, mélange provides substantial back pressure on calving ice faces, which slows ice front calving rates. On the much larger scales of West Antarctica, it is unknown if mélange could clog seaways and provide enough back pressure to act as a negative feedback slowing retreat. Here we describe a new mélange model, using a continuum-mechanical formulation that is computationally feasible for long-term continental Antarctic applications. It is tested in an idealized rectangular channel and calibrated very basically using observed modern conditions in Jakobshavn fjord, West Greenland. The model is then applied to drastic retreat of Antarctic ice in response to warm mid-Pliocene climate. With mélange parameter values that yield reasonable modern Jakobshavn results, Antarctic marine ice still retreats drastically in the Pliocene simulations, with little slowdown despite the huge amounts of mélange generated. This holds both for the rapid early collapse of West Antarctica and for later retreat into major East Antarctic basins. If parameter values are changed to make the mélange much more resistive to flow, far outside the range for reasonable Jakobshavn results, West Antarctica still collapses and retreat is slowed or prevented only in a few East Antarctic basins.

Caption for first image: "Figure 6. Snapshots of mélange thickness (m, upper row) and speed (km yr−1 , middle row) in a simulation of Antarctic ice retreat, at selected times after a step-function transition from modern to warm mid-Pliocene climate. White regions are solid ice sheet or shelf, grey is ocean and the grounding line is shown by a black line. Mélange parameter values are as in the near-best-scoring run of the Jakobshavn ensemble shown in Fig. 3a (E = 106 , Hn(Hp) = 30(60), n = 5). Bottom row shows solid-ice extents from a corresponding simulation with no mélange. (a) 0 yr (modern). (b) 50 yr. (c) 200 yr. (d) 2000 yr. The first panel shows locations of features named in the text; EAIS: East Antarctic Ice Sheet; WAIS: West Antarctic Ice Sheet."

Caption for second image: "Figure 8. Time series in simulations of Antarctic retreat after a transition to warm mid-Pliocene climate with two different mélange parameter settings. Red curves: E = 101 , Hn(Hp) = 150(200), n = 5 (near-best scoring, as in Fig. 6). Green curves: E = 101 , Hn(Hp) = 150(200), n = 1 (much stiffer and thicker mélange, as in Fig. 7). (a) Equivalent global mean sea level rise (m), with black curve for a corresponding simulation with no mélange. (b) Total mélange volume (106 km3). (c) Total mélange area (106 km2), with thinner curves showing area where grounded. (d) Mélange thickness (m) averaged over all mélange grid cells adjacent to a solid ice face. (e) Total additional back force due to mélange summed over all Antarctic ice faces, compared to that due to ocean water pressure with no mélange (1015 N; see Appendix A)."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3851 on: October 23, 2020, 04:08:32 PM »
As a short follow-on to my last post about the influence of future mélanges on potentially limiting the rate of a MICI-type of collapse of the Thwaites Glacier in coming decades, I note that:

a) Before 2040 I expect that the integrity of both the grounded iceberg B22-A and the TEIS will have collapsed and would be easily pushed out of the Pine Island Embayment.

b) The attached image shows how a slumping ice cliff type of calving events result in relatively shallow draft icebergs that can readily float over the top of submerged seafloor ridges.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3852 on: October 24, 2020, 10:13:46 AM »
The linked reference finds that between 1960 and 2018 the ocean has become 5.3% more stratified primarily due to observed increases of the water temperature in the upper 200m.  This increasing stratification of the ocean will accelerate climate change (due to factors including: increased evaporation from the ocean surface and reduced absorption of carbon dioxide by the ocean).

Li, G., Cheng, L., Zhu, J. et al. Increasing ocean stratification over the past half-century. Nat. Clim. Chang. (2020). https://doi.org/10.1038/s41558-020-00918-2

https://www.nature.com/articles/s41558-020-00918-2

Abstract: "Seawater generally forms stratified layers with lighter waters near the surface and denser waters at greater depth. This stable configuration acts as a barrier to water mixing that impacts the efficiency of vertical exchanges of heat, carbon, oxygen and other constituents. Previous quantification of stratification change has been limited to simple differencing of surface and 200-m depth changes and has neglected the spatial complexity of ocean density change. Here, we quantify changes in ocean stratification down to depths of 2,000 m using the squared buoyancy frequency N2 and newly available ocean temperature/salinity observations. We find that stratification globally has increased by a substantial 5.3% [5.0%, 5.8%] in recent decades (1960–2018) (the confidence interval is 5–95%); a rate of 0.90% per decade. Most of the increase (~71%) occurred in the upper 200 m of the ocean and resulted largely (>90%) from temperature changes, although salinity changes play an important role locally."

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

Hefaistos

  • Grease ice
  • Posts: 725
    • View Profile
  • Liked: 76
  • Likes Given: 515
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3853 on: October 24, 2020, 12:02:35 PM »
The linked reference indicates that observation are just now entering the just entering the `detection window’ to determine whether the AMOC is slowing:

D. Lobelle et al. (17 October 2020), "Detectability of an AMOC decline in current and projected climate changes", Geophysical Research Letters, https://doi.org/10.1029/2020GL089974

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL089974?af=R

Abstract
Determining whether the Atlantic Meridional Overturning Circulation (AMOC)'s transport is in decline is challenging due to the short duration of continuous observations. To estimate how many years are needed to detect a decline, we conduct a simulation study using synthetic data that mimics an AMOC time series. The time series' characteristics are reproduced using the trend, variance, and autocorrelation coefficient of the AMOC strength at 26.5°,N from 20 Coupled Model Intercomparison Project Phase 5 (CMIP5) models under the RCP8.5 future scenario, and from RAPID observations (2004‐‐2018). Our results suggest that the 14‐year RAPID length has just entered the lower limits of the trend’s `detection window’ based on synthetic data generated using CMIP5 trends and variability (14‐‐42 years; median = 24 years), but twice the length is required for detectability based on RAPID variability (29‐‐67 years; median = 43 years). The annual RAPID trend is currently not statistically significant (‐0.11 Sv yr‐1, p>0.05).

Plain Language Summary
There are ongoing discussions in the scientific community about whether the Atlantic Meridional Overturning Circulation transport is slowing down. This is of interest due to the importance of this circulation in transporting heat from the tropics to the northern latitudes. A consensus about its decline is hard to reach due to the limited direct observational data available; with the longest continuous data being 14 years long from 2004 to 2018. We therefore conduct a simulation experiment to examine how many years of data are required to detect a decline in the circulation. We create simulations of the North Atlantic transport based on statistical properties from 20 general circulation models with future climate change projections (until 2100) and from the RAPID array observations (since 2004). Our results demonstrate that the length of data we currently have from observations has just entered the `detection window’ of 14—42 years (based on model simulations). However, the RAPID observations do not currently exhibit a statistically significant trend.

Thanks ASLR, interesting! Not least the conclusion, that the longest continuous observations available (14 years) from the annual RAPID time series do not exhibit a significant trend.

Regrettably, we'll have to wait until Summer 2021 for an update of the RAPID array data. An expedition was under sail in March this year, and had serviced around 1/3 of the stations, but was then abruptly recalled due to the Covid lockdowns. Latest data are from September 2018, and according to email from the researchers in that expedition, no new data will be published until the next expedition, due in December this year, has returned and data has been processed.

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3854 on: October 25, 2020, 05:24:21 PM »
The linked reference uses new paleo-findings to indicate that the risk of an abrupt remobilization of dormant carbon in the Siberian-Arctic permafrost is higher than previously assumed by consensus climate scientists.  This is particularly true if abrupt sea level rise floods coastal Arctic permafrost regions in coming decades:

Jannik Martens et al (16 Oct 2020), "Remobilization of dormant carbon from Siberian-Arctic permafrost during three past warming events", Science Advances, Vol. 6, no. 42, eabb6546, DOI: 10.1126/sciadv.abb6546

https://advances.sciencemag.org/content/6/42/eabb6546

Abstract
Carbon cycle models suggest that past warming events in the Arctic may have caused large-scale permafrost thaw and carbon remobilization, thus affecting atmospheric CO2 levels. However, observational records are sparse, preventing spatially extensive and time-continuous reconstructions of permafrost carbon release during the late Pleistocene and early Holocene. Using carbon isotopes and biomarkers, we demonstrate that the three most recent warming events recorded in Greenland ice cores—(i) Dansgaard-Oeschger event 3 (~28 ka B.P.), (ii) Bølling-Allerød (14.7 to 12.9 ka B.P.), and (iii) early Holocene (~11.7 ka B.P.)—caused massive remobilization and carbon degradation from permafrost across northeast Siberia. This amplified permafrost carbon release by one order of magnitude, particularly during the last deglaciation when global sea-level rise caused rapid flooding of the land area thereafter constituting the vast East Siberian Arctic Shelf. Demonstration of past warming-induced release of permafrost carbon provides a benchmark for the sensitivity of these large carbon pools to changing climate.

See also:

Title: "New Climate Warnings in Old Permafrost: 'It’s a Little Scary Because it’s Happening Under Our Feet.'"

https://insideclimatenews.org/news/16102020/permafrost-study-arctic-ocean-climate-change

Extract: "The study, published today in Science Advances, shows that only a few degrees of warming in the Arctic is enough "to abruptly activate large-scale permafrost thawing," suggesting a "sensitive trigger" for greenhouse gas emissions from thawing permafrost. The results also support climate models that have shown "large injections of CO2 into the atmosphere" when glaciers, and the frozen lands beneath them, melted.

"If we consider the magnitude and the speed of anthropogenic climate warming, by 1 degree Celsius (1.8 Fahrenheit) globally and 2 degrees Celsius (3.6 Fahrenheit) in the Arctic, during the past 150 years, and compare this with the first abrupt temperature increase of about 1 degree Celsius at the Bölling-Alleröd, it appears likely that large-scale permafrost thawing and carbon release is going to happen again," he said. "Our study indeed suggests that abrupt permafrost thawing represents a tipping point in the climate system.""
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3855 on: October 25, 2020, 05:34:02 PM »
The linked article indicates that methane emissions from fossil fuel hot spots has increased by about 32% so far this year.

Title: "The number of global methane hot spots has soared this year despite the economic slowdown"

https://www.washingtonpost.com/climate-environment/2020/10/14/number-global-methane-hot-spots-has-soared-this-year-despite-economic-slowdown/

Extract: "The worldwide number of methane hot spots has soared 32 percent so far this year despite the economic slowdown, according to satellite imagery analyzed by a private data firm.

Comparing the first eight months of 2019 to the same period in 2020, the Paris-based firm Kayrros said methane leaks from oil and gas industry hot spots climbed even higher in Algeria, Russia and Turkmenistan, growing by more than 40 percent. The largest contributors to rising methane releases were the United States, Russia, Algeria, Turkmenistan, Iran and Iraq, Kayrros said.

Methane accounts for a quarter of global warming emissions from human activities …"
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3856 on: October 26, 2020, 09:59:14 PM »
Hausfather provided the following Tweet and associated image today comparing the observed GMSTA with the mean of 36 different CMIP6 models.  While Hausfather, indicates that he believes that these 36 models are running a bit hot; if 2020 is near, or above, the 2016 GMSTA, then these CMIP6 projections could be spot-on:

"We now have historical CMIP6 model runs from 36 different models to do some initial comparisons to observations. Heres the CMIP6 mean and 2-sigma range. Its running bit hot, which is unsurprising given all thats been written about the high sensitivity in some of the new models."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3857 on: October 27, 2020, 09:39:28 PM »
This post is intended to help orient periodic readers to better understand the immediately following post.  In this regard:

The first image (from Millian 2017) shows a bathymetric map of the seafloor around the Thwaites Eastern Ice Shelf and the Thwaites Ice Tongue (with the yellow line showing a circa 2011 ice face), showing the seafloor trough lead directly from the base of the Thwaites Ice Tongue into the Byrd Subglacial Basin, BSB (which is the highest risk path for a potential MICI-type of collapse of the BSB in the coming decades).

The second image shows an image (from Kim et al. 2018) with ice velocities and grounding line locations prior to 2012, for their analysis of potential local collapses of the illustrated subglacial cavities (Little Ear and Big Ear); while the actual collapses that occurred in January of 2012 are shown in the third image.  Also, I note that since 2012 it is commonly assumed that the Thwaites Ice Tongue has lost its structural integrity.

The fourth image shows a 2013 image of crevasses at the base of the Thwaites Ice Tongue, with what I take to be a grounding line circa 1996; indicating that much of the ice at the base of the Thwaites Ice Tongue has been floating for years but is too confined to float away.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3858 on: October 27, 2020, 09:40:29 PM »
This post is a follow-on to my last post, with:

The first image showing the Thwaites Eastern Ice Shelf and Thwaites Ice Tongue on May 23, 2019, with yellow arrows showing my assumed primary compressive stress pathways in this region.  I show this first image as I believe that the thick yellow arrows leading from the Thwaites Eastern Ice Shelf to the region on the western side of the Big Ear subglacial cavity helps to explain (together with the buttressing action of the ice floating above the Big Ear) the over 140 m of ice height above floatation shown in panel D of the second image.

The third image (from Wang et al. 2019) shows various types of historical El Nino events between 1900 and 2017, with the black bars indicating Extreme El Nino events.  I note that these black bars indicate that since about 1970 Extreme El Nino events have been occurring about every 20-years; which suggests another Extreme El Nino event circa 2035-2036.

The fourth image shows non-MICI computer model perturbation runs from a TARSAN project study presented at the 2020 WAIS Workshop; with the top images showing 2011 ice velocities & differential ice velocities, respectively; while the bottom images show a possible future case where both the Thwaites Eastern Ice Shelf has become unpinned and concurrently the Thwaites Ice Tongue has floated away and no longer provides buttressing to the 140m high ice cliff on the upstream side of the Big Ear.  My primary concern is that an Extreme El Nino event circa 2035-36 could simultaneously unpin the Thwaites Eastern Ice Shelve and induce the ice over the Big Ear to float away; which (in my opinion) could abruptly expose a bare 140m high ice cliff and subject it to MICI-type of calving before the ice would have time to creep sufficient to ensure a MISI-type of glacier retreat into the Byrd Subglacial Basin.

&

Bin Wang et al. (November 5, 2019), "Historical change of El Niño properties sheds light on future changes of extreme El Niño", PNAS, 116 (45) 22512-22517; https://doi.org/10.1073/pnas.1911130116

https://www.pnas.org/content/116/45/22512

Abstract
El Niño’s intensity change under anthropogenic warming is of great importance to society, yet current climate models’ projections remain largely uncertain. The current classification of El Niño does not distinguish the strong from the moderate El Niño events, making it difficult to project future change of El Niño’s intensity. Here we classify 33 El Niño events from 1901 to 2017 by cluster analysis of the onset and amplification processes, and the resultant 4 types of El Niño distinguish the strong from the moderate events and the onset from successive events. The 3 categories of El Niño onset exhibit distinct development mechanisms. We find El Niño onset regime has changed from eastern Pacific origin to western Pacific origin with more frequent occurrence of extreme events since the 1970s. This regime change is hypothesized to arise from a background warming in the western Pacific and the associated increased zonal and vertical sea-surface temperature (SST) gradients in the equatorial central Pacific, which reveals a controlling factor that could lead to increased extreme El Niño events in the future. The Coupled Model Intercomparison Project phase 5 (CMIP5) models’ projections demonstrate that both the frequency and intensity of the strong El Niño events will increase significantly if the projected central Pacific zonal SST gradients become enhanced. If the currently observed background changes continue under future anthropogenic forcing, more frequent strong El Niño events are anticipated. The models’ uncertainty in the projected equatorial zonal SST gradients, however, remains a major roadblock for faithful prediction of El Niño’s future changes.

Caption for the third image: "Changing El Niño types from 1901 to 2017. The ONI bars represent the SSTA averaged in the NINO3.4 region (5°S–5°N, 120°W–170°W) and during the northern winter season from October to the next February (ONDJF). An El Niño event is defined by ONDJF ONI equal to or greater than 0.6 °C (the dashed line). The 33 El Niño events are shown in different color bars: SWB (black), MEP (blue), MCP (red), and successive (yellow), respectively. Gray bars mark the remaining warm neutral years."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3859 on: October 28, 2020, 02:17:14 AM »
The linked article presents new evidence that the increasing 'Atlantification' of the Arctic Ocean is beginning to release increasing quantities of methane from associated hydrates in the continental slope of the East Siberian coast.

Title: "'Sleeping giant' Arctic methane deposits starting to release, scientists find"

https://www.theguardian.com/science/2020/oct/27/sleeping-giant-arctic-methane-deposits-starting-to-release-scientists-find

Extract: "Scientists have found evidence that frozen methane deposits in the Arctic Ocean – known as the “sleeping giants of the carbon cycle” – have started to be released over a large area of the continental slope off the East Siberian coast, the Guardian can reveal.

High levels of the potent greenhouse gas have been detected down to a depth of 350 metres in the Laptev Sea near Russia, prompting concern among researchers that a new climate feedback loop may have been triggered that could accelerate the pace of global heating.

The slope sediments in the Arctic contain a huge quantity of frozen methane and other gases – known as hydrates. Methane has a warming effect 80 times stronger than carbon dioxide over 20 years. The United States Geological Survey has previously listed Arctic hydrate destabilisation as one of four most serious scenarios for abrupt climate change."

See also (& the associated image):

Website Title: "The ISSS-2020 Arctic Ocean Expedition"

https://www.aces.su.se/research/projects/the-isss-2020-arctic-ocean-expedition/

Extract: "The International Siberian Shelf Study (ISSS) Program is a Russian-Swedish led international collaboration that spans back about 15 years. The overarching aim of the ISSS Program is to investigate cryosphere-climate-carbon couplings on the extensive East Siberian Arctic Ocean Shelf.

The central focus of the ISSS-2020 expedition is one of the biggest open challenges in climate change science; understanding subsea and coastal permafrost thawing, hydrate collapse and the processes that result in releases of potent greenhouse gases such as methane, carbon dioxide and nitrous oxide.

The expedition will run from 26 Sept – 4 Nov 2020 and will depart from and return to the White Sea port of Archangelsk, the cruise track stretching across the entire Arctic rim of the Eurasian margin."
« Last Edit: October 28, 2020, 03:07:46 PM by AbruptSLR »
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3860 on: October 28, 2020, 03:02:53 PM »
The linked consensus climate science reference uses MISI ice sheet models and an ESM of intermediate complexity to estimate that changes in large-scale cryosphere elements will:

"Overall, we find a median additional global warming of 0.43 °C (interquartile range: 0.39−0.46 °C) at a CO2 concentration of 400 ppm. Most of this response (55%) is caused by albedo changes, but lapse rate together with water vapour (30%) and cloud feedbacks (15%) also contribute significantly."

I note that this research not only ignores MICI type risks, but also risks of large freshwater hosing events (like a reversal of the Beaufort Gyre) that would likely slow the MOC.

Wunderling, N., Willeit, M., Donges, J.F. et al. Global warming due to loss of large ice masses and Arctic summer sea ice. Nat Commun 11, 5177 (2020). https://doi.org/10.1038/s41467-020-18934-3

https://www.nature.com/articles/s41467-020-18934-3

Abstract: "Several large-scale cryosphere elements such as the Arctic summer sea ice, the mountain glaciers, the Greenland and West Antarctic Ice Sheet have changed substantially during the last century due to anthropogenic global warming. However, the impacts of their possible future disintegration on global mean temperature (GMT) and climate feedbacks have not yet been comprehensively evaluated. Here, we quantify this response using an Earth system model of intermediate complexity. Overall, we find a median additional global warming of 0.43 °C (interquartile range: 0.39−0.46 °C) at a CO2 concentration of 400 ppm. Most of this response (55%) is caused by albedo changes, but lapse rate together with water vapour (30%) and cloud feedbacks (15%) also contribute significantly. While a decay of the ice sheets would occur on centennial to millennial time scales, the Arctic might become ice-free during summer within the 21st century. Our findings imply an additional increase of the GMT on intermediate to long time scales."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3861 on: October 28, 2020, 03:53:03 PM »
The linked reference confirms that Atlantification of the Arctic Ocean not only reduces sea ice cover along the Russian continental shelves, but increasing in other regions of the Arctic Ocean.  This trend will not only increase Arctic Amplification beyond what is currently assumed by consensus climate science, but also increases the risk of potentially meaningful amount of methane emissions from hydrate decomposition in both Arctic continental shelf and slope regions.

Belter, H. J., Krumpen, T., von Albedyll, L., Alekseeva, T. A., Frolov, S. V., Hendricks, S., Herber, A., Polyakov, I., Raphael, I., Ricker, R., Serovetnikov, S. S., Webster, M., and Haas, C.: Interannual variability in Transpolar Drift ice thickness and potential impact of Atlantification, The Cryosphere Discuss., https://doi.org/10.5194/tc-2020-305, in review, 2020.

https://tc.copernicus.org/preprints/tc-2020-305/

Abstract. Changes in Arctic sea ice thickness are the result of complex interactions of the dynamic and variable ice cover with atmosphere and ocean. Most of the sea ice exits the Arctic Ocean through Fram Strait, which is why long-term measurements of ice thickness at the end of the Transpolar Drift provide insight into the integrated signals of thermodynamic and dynamic influences along the pathways of Arctic sea ice. We present an updated time series of extensive ice thickness surveys carried out at the end of the Transpolar Drift between 2001 and 2020. Overall, we see a more than 20 % thinning of modal ice thickness since 2001. A comparison with first preliminary results from the international Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) shows that the modal summer thickness of the MOSAiC floe and its wider vicinity are consistent with measurements from previous years. By combining this unique time series with the Lagrangian sea ice tracking tool, ICETrack, and a simple thermodynamic sea ice growth model, we link the observed interannual ice thickness variability north of Fram Strait to increased drift speeds along the Transpolar Drift and the consequential variations in sea ice age and number of freezing degree days. We also show that the increased influence of upward-directed ocean heat flux in the eastern marginal ice zones, termed Atlantification, is not only responsible for sea ice thinning in and around the Laptev Sea, but also that the induced thickness anomalies persist beyond the Russian shelves and are potentially still measurable at the end of the Transpolar Drift after more than a year. With a tendency towards an even faster Transpolar Drift, winter sea ice growth will have less time to compensate the impact of Atlantification on sea ice growth in the eastern marginal ice zone, which will increasingly be felt in other parts of the sea ice covered Arctic.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3862 on: October 28, 2020, 04:00:35 PM »
The linked reference indicates that the 2020 Larsen C Ice Shelf surface ice melt set a 40-year high record, and I note that many other Antarctic Peninsula ice shelves exhibited similar behavior.  To me this implies a trend that relatively surface temperatures are progressing southward; which will soon increase the risk of hydrofracturing of key ice shelves in West Antarctica.

Bevan, S., Luckman, A., Hendon, H., and Wang, G.: The 2020 Larsen C Ice Shelf surface melt is a 40-year record high, The Cryosphere, 14, 3551–3564, https://doi.org/10.5194/tc-14-3551-2020, 2020.

https://tc.copernicus.org/articles/14/3551/2020/

Abstract
Along with record-breaking summer air temperatures at an Antarctic Peninsula meteorological station in February 2020, the Larsen C ice shelf experienced an exceptionally long and extensive 2019/2020 melt season. We use a 40-year time series of passive and scatterometer satellite microwave data, which are sensitive to the presence of liquid water in the snow pack, to reveal that the extent and duration of melt observed on the ice shelf in the austral summer of 2019/2020 was the greatest on record. We find that unusual perturbations to Southern Hemisphere modes of atmospheric flow, including a persistently positive Indian Ocean Dipole in the spring and a very rare Southern Hemisphere sudden stratospheric warming in September 2019, preceded the exceptionally warm Antarctic Peninsula summer. It is likely that teleconnections between the tropics and southern high latitudes were able to bring sufficient heat via the atmosphere and ocean to the Antarctic Peninsula to drive the extreme Larsen C Ice Shelf melt. The record-breaking melt of 2019/2020 brought to an end the trend of decreasing melt that had begun in 1999/2000, will reinitiate earlier thinning of the ice shelf by depletion of the firn air content, and probably affected a much greater region than Larsen C Ice Shelf.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3863 on: October 28, 2020, 04:09:03 PM »
The linked reference indicates that projected GMSTA by CMIP5 models are 9 to 30% too low, due to model bias associated with trends in the Equatorial Pacific sea surface gradient; which confirms that CMIP5 estimates for climate sensitivity are too low.

Watanabe, M., Dufresne, J., Kosaka, Y. et al. Enhanced warming constrained by past trends in equatorial Pacific sea surface temperature gradient. Nat. Clim. Chang. (2020). https://doi.org/10.1038/s41558-020-00933-3

https://www.nature.com/articles/s41558-020-00933-3

Abstract
The equatorial Pacific zonal sea surface temperature (SST) gradient, known to be a pacemaker of global warming, has strengthened since the mid-twentieth century. However, the cause is controversial because a majority of Coupled Model Intercomparison Project Phase 5 (CMIP5) models suggest weakening of the zonal SST gradient from the past to the future. Reconciling this discrepancy is important for the climate change attribution and climate sensitivity assessment. Here we use the CMIP5 ensemble and large ensemble simulations by four climate models to show that the intensifying SST gradient observed during 1951–2010 could arise from internal climate variability. Models and members that simulate historical strengthening of the SST gradient commonly exhibit reversed future trends. Using these models as a constraint, the rate of global-mean temperature rise is amplified by 9–30%, with higher values occurring in low-emission scenarios, because internal variability has a greater impact when the externally forced response is smaller.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3864 on: October 28, 2020, 04:34:20 PM »
The linked reference concludes that:

"Simulations with reduced North Atlantic deep water formation, as a consequence of potentially increased continental runoff from ice-sheet melt and imposed changes in the hydrological cycle, more closely resemble the overturning circulation inferred from proxies. These circulation states also show bistable behavior, where the AMOC does not recover after North Atlantic freshwater hosing."

This raises the risk that a freshwater hosing event in the North Atlantic (such as due to a temporary reversal of the Beaufort Gyre) in the coming decades may mean that the resulting slowed AMOC might not recover its strength until long after (centuries) the freshwater hosing event has ended.  This is not good news.

Pöppelmeier, F., Scheen, J., Jeltsch-Thömmes, A., and Stocker, T. F.: Simulated stability of the AMOC during the Last Glacial Maximum under realistic boundary conditions, Clim. Past Discuss., https://doi.org/10.5194/cp-2020-135, in review, 2020.

https://cp.copernicus.org/preprints/cp-2020-135/

Abstract. The response of the Atlantic Meridional Overturning Circulation (AMOC) to freshwater perturbations critically depends on its mean-state. Large swaths of icebergs melting in the North Atlantic during the last deglaciation constituted such perturbations, and thus can provide important constraints on the stability of the AMOC. Yet, the mean AMOC state during the Last Glacial Maximum (LGM), preceding the rapid disintegration of the ice-sheets during the deglaciation, as well as its response to these perturbations remain debated. Here we investigate the evolution of the AMOC responding to freshwater perturbations under improved LGM boundary conditions in the Bern3D intermediate complexity model. Particularly, we consider the effect of an open versus a closed Bering Strait. The vigorous and deep AMOC under these glacial boundary conditions, consistent with previous simulations with different models, reacts more strongly to North Atlantic freshwater forcings than under pre-industrial conditions. This increased sensitivity is mostly related to the closed Bering Strait that cuts off the freshwater escape route through the Arctic into the Pacific, thus facilitating faster accumulation of freshwater in the North Atlantic halting deep water formation. Proxy reconstructions of the LGM AMOC instead indicate a weaker and possibly shallower AMOC than today, in conflict with the particularly strong and deep circulation states coherently simulated with ocean circulation models for the LGM. Simulations with reduced North Atlantic deep water formation, as a consequence of potentially increased continental runoff from ice-sheet melt and imposed changes in the hydrological cycle, more closely resemble the overturning circulation inferred from proxies. These circulation states also show bistable behavior, where the AMOC does not recover after North Atlantic freshwater hosing. However, no AMOC states are found here that either comprise an extreme shoaling or vigorous and concurrent shallow overturning as previously proposed based on paleoceanographic data.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3865 on: October 28, 2020, 05:00:42 PM »
The linked 2017 reference reminds us all that:

"Calculations indicate that sea level predictions in the near field of WAIS will depart significantly from elastic fingerprints in as little as a few decades. For example, when viscous effects are included, the peak sea level fall predicted in the vicinity of WAIS during a melt event will increase by about 20% and about 50%, relative to the elastic case, for events of duration 25 and 100 yr, respectively."

This research shows that an abrupt collapse of the BSB in the coming decades would decrease sea level several meters below the Ross Ice Shelf; which would likely cause this ice shelf to rapidly fracture/collapse; which would then accelerate ice mass loss from the WAIS.

Carling C. Hay et al. (2017), "Sea Level Fingerprints in a Region of Complex Earth Structure: The Case of WAIS", J. Climate, 30 (6): 1881–1892, https://doi.org/10.1175/JCLI-D-16-0388.1

https://journals.ametsoc.org/jcli/article/30/6/1881/94634/Sea-Level-Fingerprints-in-a-Region-of-Complex

Abstract
Sea level fingerprints associated with rapid melting of the West Antarctic Ice Sheet (WAIS) have generally been computed under the assumption of a purely elastic response of the solid Earth. The authors investigate the impact of viscous effects on these fingerprints by computing gravitationally self-consistent sea level changes that adopt a 3D viscoelastic Earth model in the Antarctic region consistent with available geological and geophysical constraints. In West Antarctica, the model is characterized by a thin (~65 km) elastic lithosphere and sublithospheric viscosities that span three orders of magnitude, reaching values as low as approximately 4 × 1018 Pa s beneath WAIS. Calculations indicate that sea level predictions in the near field of WAIS will depart significantly from elastic fingerprints in as little as a few decades. For example, when viscous effects are included, the peak sea level fall predicted in the vicinity of WAIS during a melt event will increase by about 20% and about 50%, relative to the elastic case, for events of duration 25 and 100 yr, respectively. The results have implications for studies of sea level change due to both ongoing mass loss from WAIS over the next century and future, large-scale collapse of WAIS on centennial-to-millennial time scales.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3866 on: October 29, 2020, 09:06:35 PM »
The linked reference indicates that conversion of Amazon rainforest into pasture increases the methane emissions from the soil due to methanogenesis from microorganisms.

Kroeger, M.E., Meredith, L.K., Meyer, K.M. et al. Rainforest-to-pasture conversion stimulates soil methanogenesis across the Brazilian Amazon. ISME J (2020). https://doi.org/10.1038/s41396-020-00804-x

https://www.nature.com/articles/s41396-020-00804-x

Abstract: "The Amazon rainforest is a biodiversity hotspot and large terrestrial carbon sink threatened by agricultural conversion. Rainforest-to-pasture conversion stimulates the release of methane, a potent greenhouse gas. The biotic methane cycle is driven by microorganisms; therefore, this study focused on active methane-cycling microorganisms and their functions across land-use types. We collected intact soil cores from three land use types (primary rainforest, pasture, and secondary rainforest) of two geographically distinct areas of the Brazilian Amazon (Santarém, Pará and Ariquemes, Rondônia) and performed DNA stable-isotope probing coupled with metagenomics to identify the active methanotrophs and methanogens. At both locations, we observed a significant change in the composition of the isotope-labeled methane-cycling microbial community across land use types, specifically an increase in the abundance and diversity of active methanogens in pastures. We conclude that a significant increase in the abundance and activity of methanogens in pasture soils could drive increased soil methane emissions. Furthermore, we found that secondary rainforests had decreased methanogenic activity similar to primary rainforests, and thus a potential to recover as methane sinks, making it conceivable for forest restoration to offset greenhouse gas emissions in the tropics. These findings are critical for informing land management practices and global tropical rainforest conservation."

See also:

Title: "Amazon Deforestation Stimulates Soil Microbes to Produce More Greenhouse Gases"

https://www.umass.edu/newsoffice/article/amazon-deforestation-stimulates-soil

Edit, see also:

Title: "3D view of Amazon captures effects of El Niño drought"

Extract: "Three-dimensional measurements of the central Brazilian Amazon rainforest have given NASA researchers a detailed window into the high number of branch falls and tree mortality that occur in response to drought conditions. They found that 65 percent more trees and large branches died due to an El Niño-driven drought in 2015-2016 than compared to an average year. Understanding the effects of prolonged drought gives scientists a better sense of what may happen to carbon stored in tropical forests if these events become more common in the future."

I note that if the MOC were to abruptly slow in coming decades due to a significant freshwater hosing event, this this could cause sustained (for more than a decade) El Nino-like conditions in the Tropical Pacific, leading to sustained (for more than a decade) drought conditions in the Amazon.

https://climate.nasa.gov/news/2747/3d-view-of-amazon-captures-effects-of-el-nino-drought/
« Last Edit: October 31, 2020, 06:10:13 PM by AbruptSLR »
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3867 on: October 31, 2020, 10:53:33 PM »
This is a reminder that per the linked reference about half of the Arctic warming since 1995 is due to ozone depleting compounds.

Polvani, L. M., Previdi, M., England, M. R., Chiodo, G. & Smith, K. L. Nature Clim. Change https://doi.org/10.1038/s41558-019-0677-4 (2020)

https://www.nature.com/articles/s41558-019-0677-4

Abstract: "The rapid warming of the Arctic, perhaps the most striking evidence of climate change, is believed to have arisen from increases in atmospheric concentrations of GHGs since the Industrial Revolution. While the dominant role of carbon dioxide is undisputed, another important set of anthropogenic GHGs was also being emitted over the second half of the twentieth century: ozone-depleting substances (ODS). These compounds, in addition to causing the ozone hole over Antarctica, have long been recognized3 as powerful GHGs. However, their contribution to Arctic warming has not been quantified. We do so here by analysing ensembles of climate model integrations specifically designed for this purpose, spanning the period 1955–2005 when atmospheric concentrations of ODS increased rapidly. We show that, when ODS are kept fixed, forced Arctic surface warming and forced sea-ice loss are only half as large as when ODS are allowed to increase. We also demonstrate that the large impact of ODS on the Arctic occurs primarily via direct radiative warming, not via ozone depletion. Our findings reveal a substantial contribution of ODS to recent Arctic warming, and highlight the importance of the Montreal Protocol as a major climate change-mitigation treaty."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Tor Bejnar

  • Young ice
  • Posts: 3720
    • View Profile
  • Liked: 653
  • Likes Given: 437
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3868 on: October 31, 2020, 11:33:45 PM »
This ozone paper's abstract is very interesting.  I have a couple questions...

I understand ozone depleting chemicals are being added to the atmosphere very slowly now (in contrast to before the Montreal Protocol).  Does that mean that this contribution to Arctic amplification, although static, will become more minor as time goes by as other GHGs continue to be emitted?

Is this paper solidly demonstrated? Or does it really need to be confirmed by other scientists?
Arctic ice is healthy for children and other living things.

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3869 on: November 01, 2020, 07:05:39 PM »
This ozone paper's abstract is very interesting.  I have a couple questions...

I understand ozone depleting chemicals are being added to the atmosphere very slowly now (in contrast to before the Montreal Protocol).  Does that mean that this contribution to Arctic amplification, although static, will become more minor as time goes by as other GHGs continue to be emitted?

Is this paper solidly demonstrated? Or does it really need to be confirmed by other scientists?

First, the reference considers the period from 1955 to 2005; while the Montreal Protocol entered into force in August 1989, so the conference considers the impact of ODS's both before and after the Montreal Protocol.  Also, ODS last longer in very cold atmospheres (like the Arctic, and Antarctic, atmospheres), as demonstrated that the Antarctic Ozone Hole is still very large and will take decades more to heal.  Also, many pre-Montreal Protocol refrigeration units were not disposed of properly and may leak in the coming decades.

Title: "Montreal Protocol"

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

Extract: "The Montreal Protocol entered into force on 26 August 1989, and has since undergone nine revisions, in 1990 (London), 1991 (Nairobi), 1992 (Copenhagen), 1993 (Bangkok), 1995 (Vienna), 1997 (Montreal), 1998 (Australia), 1999 (Beijing) and 2016 (Kigali)."

Second, the reference finds that: "... the large impact of ODS on the Arctic occurs primarily via direct radiative warming, not via ozone depletion."  Therefore, there is very little room to dispute these findings as the influence of direct radiative forcing is well understood in models.

Finally, once triggered, to accelerate nonlinearly, it may take a long time before numerous positive Arctic feedback mechanisms (like permafrost degradation) stop impacting global warming.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

kassy

  • Young ice
  • Posts: 2584
    • View Profile
  • Liked: 1204
  • Likes Given: 1062
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3870 on: November 01, 2020, 10:30:28 PM »
The environmental concern for CFCs follows from their long atmospheric lifetime (55 years for CFC-11 and 140 years for CFC-12, CCl2F2)9 which limits our ability to reduce their abundance in the atmosphere and associated future ozone loss.

...

Atmospheric measurements CFC-11 and CFC-12 reported in 1993 showed that their growth rates were decreasing as result of both voluntary and mandated reductions in emissions9. Many CFCs and selected chlorinated solvents have either leveled off (Figure 1) or decreased in concentration by 19949,10.

https://www.esrl.noaa.gov/gmd/hats/publictn/elkins/cfcs.html

https://www.esrl.noaa.gov/gmd/hats/about/cfc.html

The sad thing is that reductions from the Montreal protocol are a big part of actual realized emissions. Our big reductions in the west are basically that protocol and off shoring pollution.

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

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3871 on: November 02, 2020, 05:59:12 PM »
The linked reference indicates that a global warming of 2°C would lead to about 230 billion tons of carbon being released from the world's soil.  While some people believe that GMSTA (with a pre-industrial base) will never occur; however, if climate sensitivity (including freshwater hosing events) is higher than expected then we could cross this tipping point in coming decades.

Varney, R.M., Chadburn, S.E., Friedlingstein, P. et al. A spatial emergent constraint on the sensitivity of soil carbon turnover to global warming. Nat Commun 11, 5544 (2020). https://doi.org/10.1038/s41467-020-19208-8

https://www.nature.com/articles/s41467-020-19208-8

Abstract: "Carbon cycle feedbacks represent large uncertainties in climate change projections, and the response of soil carbon to climate change contributes the greatest uncertainty to this. Future changes in soil carbon depend on changes in litter and root inputs from plants and especially on reductions in the turnover time of soil carbon (τs) with warming. An approximation to the latter term for the top one metre of soil (ΔCs,τ) can be diagnosed from projections made with the CMIP6 and CMIP5 Earth System Models (ESMs), and is found to span a large range even at 2 °C of global warming (−196 ± 117 PgC). Here, we present a constraint on ΔCs,τ, which makes use of current heterotrophic respiration and the spatial variability of τs inferred from observations. This spatial emergent constraint allows us to halve the uncertainty in ΔCs,τ at 2 °C to −232 ± 52 PgC."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3872 on: November 03, 2020, 01:48:48 AM »
The linked reference (& associated linked article) explains how ECS could currently be above 5C, as indicated by several CMIP6 projections:

Bjordal, J., Storelvmo, T., Alterskjær, K. et al. Equilibrium climate sensitivity above 5 °C plausible due to state-dependent cloud feedback. Nat. Geosci. 13, 718–721 (2020). https://doi.org/10.1038/s41561-020-00649-1

https://www.nature.com/articles/s41561-020-00649-1

Abstract: "The equilibrium climate sensitivity of Earth is defined as the global mean surface air temperature increase that follows a doubling of atmospheric carbon dioxide. For decades, global climate models have predicted it as between approximately 2 and 4.5 °C. However, a large subset of models participating in the 6th Coupled Model Intercomparison Project predict values exceeding 5 °C. The difference has been attributed to the radiative effects of clouds, which are better captured in these models, but the underlying physical mechanism and thus how realistic such high climate sensitivities are remain unclear. Here we analyse Community Earth System Model simulations and find that, as the climate warms, the progressive reduction of ice content in clouds relative to liquid leads to increased reflectivity and a negative feedback that restrains climate warming, in particular over the Southern Ocean. However, once the clouds are predominantly liquid, this negative feedback vanishes. Thereafter, other positive cloud feedback mechanisms dominate, leading to a transition to a high-sensitivity climate state. Although the exact timing and magnitude of the transition may be model dependent, our findings suggest that the state dependence of the cloud-phase feedbacks is a crucial factor in the evolution of Earth’s climate sensitivity with warming."

See also:

Title: "Guest post: How declining ice in clouds makes high ‘climate sensitivity’ plausible"

https://www.carbonbrief.org/guest-post-how-declining-ice-in-clouds-makes-high-climate-sensitivity-plausible

Extract: "Simulations from the latest climate models have suggested that the Earth’s climate might be more sensitive to increasing atmospheric CO2 than previously thought."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3873 on: November 04, 2020, 12:33:13 AM »
The attached tweeted graphic shows that the Northeast Passage just closed, and that 2020 had the longest period for the Arctic Ocean being passable; which is a clear indication of Arctic Amplification.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3874 on: November 04, 2020, 03:37:34 PM »
The linked reference confirms that albedo effects due to increased phytoplankton growth in the Arctic Ocean is contributing to Arctic Amplification and that consensus climate months do not yet account for this positive feedback:

Vasileios Pefanis et al. (26 October 2020), "Amplified Arctic Surface Warming and Sea Ice Loss Due to Phytoplankton and Colored Dissolved Material", Geophysical Research Letters, https://doi.org/10.1029/2020GL088795

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020GL088795

Abstract: "Optically active water constituents attenuate solar radiation and hence affect the vertical distribution of energy in the upper ocean. To understand their implications, we operate an ocean biogeochemical model coupled to a general circulation model with sea ice. Incorporating the effect of phytoplankton and colored dissolved organic matter (CDOM) on light attenuation in the model increases the sea surface temperature in summer and decreases sea ice concentration in the Arctic Ocean. Locally, the sea ice season is reduced by up to one month. CDOM drives a significant part of these changes, suggesting that an increase of this material will amplify the observed Arctic surface warming through its direct thermal effect. Indirectly, changing advective processes in the Nordic Seas may further intensify this effect. Our results emphasize the phytoplankton and CDOM feedbacks on the Arctic ocean and sea ice system and underline the need to consider these effects in future modeling studies to enhance their plausibility."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3875 on: November 04, 2020, 03:47:29 PM »
The linked reference indicates that the flux of water vapor from the surface to the atmosphere is becoming an increasingly important component of the Greenland Ice Sheet mass balance that is currently being ignored by consensus climate science estimates/projections:

Kopec, B. G., Akers, P. D., Klein, E. S., and Welker, J. M.: Significant water vapor fluxes from the Greenland Ice Sheet detected through water vapor isotopic (δ18O, δD, deuterium excess) measurements, The Cryosphere Discuss., https://doi.org/10.5194/tc-2020-276, in review, 2020.

https://tc.copernicus.org/preprints/tc-2020-276/

Abstract. The summer of 2019 was marked by an extensive early onset of surface melt and record volume losses of the Greenland Ice Sheet (GrIS), which is part of a larger trend of increasing melt over time. Given the growing spatial extent of melt, the flux of water vapor from the ice to the atmosphere is becoming an increasingly important component of the GrIS mass balance that merits investigation and quantification. We examine the isotopic composition of water vapor from Thule Air Base, NW Greenland, particularly the deuterium excess (d-excess), to quantify the magnitude of GrIS vapor fluxes. To do this, we observe only water vapor transported off the ice sheet (i.e., when easterly winds occur) and during the active melt season. We find that the GrIS-derived water vapor d-excess values are controlled by two main factors: 1) the d-excess of the sublimating vapor, which is determined, in part, by the relative humidity and wind speed above the ice sheet, and 2) the proportion of sublimation- vs. marine-sourced moisture. Here, the GrIS melt extent serves as a proxy for the sublimation source and the North Atlantic Oscillation provides a measure of the meridional transport of marine moisture. We demonstrate that sublimation contributes ~20 % of the water vapor transported from the GrIS during the melt season. Sublimation is thus an important component of GrIS mass balance and the regional hydrologic cycle, and this flux will become more important in the coming years as further warming continues GrIS negative mass balance trends.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3876 on: November 05, 2020, 03:43:34 PM »
I thought that I would just remind readers that if the WAIS were to sustain a MICI-type of collapse in the coming decades this would constitute irreversible climate change that could not be reversed by geoengineering for millennia.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Gerntocratis#1

  • New ice
  • Posts: 23
    • View Profile
  • Liked: 9
  • Likes Given: 556
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3877 on: November 05, 2020, 04:13:52 PM »
I thought that I would just remind readers that if the WAIS were to sustain a MICI-type of collapse in the coming decades this would constitute irreversible climate change that could not be reversed by geoengineering for millennia.

What is the projected timeline for that scenario? Also, what kind of effect on climate would it have other than sea level rise?

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3878 on: November 05, 2020, 04:23:38 PM »
I thought that I would just remind readers that if the WAIS were to sustain a MICI-type of collapse in the coming decades this would constitute irreversible climate change that could not be reversed by geoengineering for millennia.

What is the projected timeline for that scenario? Also, what kind of effect on climate would it have other than sea level rise?

My projected timeframe is that the Byrd Subglacial Basin, BSB, could likely initiate an MICI-type of collapse between 2035 & 2040 and that the rest of the WAIS could collapse by about 2090.  Besides sea level rise, this would slow the MOC which would cause increased evaporation from the tropical oceans, which (in my opinion) might well flip the atmosphere into an equable pattern circa 2120.  Furthermore, I note that in this scenario there currently is not sufficient time to implement a geoengineering program sufficient to stop a MICI-type of collapse of the BSB in the 2035 to 2040 timeframe as the ocean heat content and circulation patterns in the Southern Ocean are already sufficient to trigger the proposed collapse (& geoengineering cannot change this fact).
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

gerontocrat

  • First-year ice
  • Posts: 9601
    • View Profile
  • Liked: 3803
  • Likes Given: 29
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3879 on: November 05, 2020, 05:23:02 PM »
The attached tweeted graphic shows that the Northeast Passage just closed, and that 2020 had the longest period for the Arctic Ocean being passable; which is a clear indication of Arctic Amplification.
I attach an open water graph for the entire Russian Side from the Barents to the ESS. It shows clearly the ever increasing open water for various periods of the year.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3880 on: November 06, 2020, 04:00:46 PM »
I thought that I would just remind readers that if the WAIS were to sustain a MICI-type of collapse in the coming decades this would constitute irreversible climate change that could not be reversed by geoengineering for millennia.

What is the projected timeline for that scenario? Also, what kind of effect on climate would it have other than sea level rise?

My projected timeframe is that the Byrd Subglacial Basin, BSB, could likely initiate an MICI-type of collapse between 2035 & 2040 and that the rest of the WAIS could collapse by about 2090.  Besides sea level rise, this would slow the MOC which would cause increased evaporation from the tropical oceans, which (in my opinion) might well flip the atmosphere into an equable pattern circa 2120.  Furthermore, I note that in this scenario there currently is not sufficient time to implement a geoengineering program sufficient to stop a MICI-type of collapse of the BSB in the 2035 to 2040 timeframe as the ocean heat content and circulation patterns in the Southern Ocean are already sufficient to trigger the proposed collapse (& geoengineering cannot change this fact).

In support of my opinion, the linked reference concludes that:

"Overall, we find that the interactions tend to destabilise the network. Furthermore, our analysis reveals the qualitative role of each of the five tipping elements showing that the polar ice sheets on Greenland and West Antarctica are oftentimes the initiators of tipping cascades, while the AMOC acts as a mediator, transmitting cascades."

The attached image of a domino wave illustrates the cascade effect that could be triggered by a significant freshwater hosing event such as a temporary reversal of the Beaufort Gyre and/or a MICI-type of collapse of the Byrd Subglacial Basin:

Nico Wunderling et al. (3 April 2020), "Interacting tipping elements increase risk of climate domino effects under global warming", Earth System Dynamics, https://doi.org/10.5194/esd-2020-18

https://esd.copernicus.org/preprints/esd-2020-18/esd-2020-18.pdf

Abstract. There exists a range of subsystems in the climate system exhibiting threshold behaviour which could be triggered under global warming within this century resulting in severe consequences for biosphere and human societies. While their individual tipping thresholds are fairly well understood, it is of yet unclear how their interactions might impact the overall stability of the Earth’s climate system. This cannot be studied yet with state-of-the-art Earth system models due to computational constraints as well as missing and uncertain process representations of some tipping elements.
Here, we explicitly study the effects of known physical interactions between the Greenland and West Antarctic Ice Sheet, the Atlantic Meridional Overturning Circulation, the El-Niño Southern Oscillation and the Amazon rainforest using a conceptual network approach. We analyse the risk of domino effects being triggered by each of the individual tipping elements under global warming in equilibrium experiments, propagating uncertainties in critical temperature thresholds and interaction strengths via a Monte-Carlo approach.
Overall, we find that the interactions tend to destabilise the network. Furthermore, our analysis reveals the qualitative role of each of the five tipping elements showing that the polar ice sheets on Greenland and West Antarctica are oftentimes the initiators of tipping cascades, while the AMOC acts as a mediator, transmitting cascades.
This implies that the ice sheets, which are already at risk of transgressing their temperature thresholds within the Paris range of 1.5 to 2 ◦ C, are of particular importance for the stability of the climate system as a whole.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3881 on: November 06, 2020, 11:15:53 PM »
The linked reference and associated, and attached image, shows that the Ocean Heat Uptake (OHU) of the Southern Ocean does not depend much on whether we follow RCP 2.6 or RCP 8.5 through 2100.

Xiaofan Ma et al. (06 Nov 2020), "Dependence of regional ocean heat uptake on anthropogenic warming scenarios", Science Advances, Vol. 6, no. 45, eabc0303, DOI: 10.1126/sciadv.abc0303

https://advances.sciencemag.org/content/6/45/eabc0303

Abstract
The North Atlantic and Southern Ocean exhibit enhanced ocean heat uptake (OHU) during recent decades while their future OHU changes are subject to great uncertainty. Here, we show that regional OHU patterns in these two basins are highly dependent on the trajectories of aerosols and greenhouse gases (GHGs) in future scenarios. During the 21st century, North Atlantic and Southern Ocean OHU exhibit similarly positive trends under a business-as-usual scenario but respectively positive and negative trends under a mitigation scenario. The opposite centurial OHU trends in the Southern Ocean can be attributed partially to distinct GHG trajectories under the two scenarios while the common positive centurial OHU trends in the North Atlantic are mainly due to aerosol effects. Under both scenarios, projected decline of anthropogenic aerosols potentially induces a weakening of the Atlantic Meridional Overturning Circulation and a divergence of meridional oceanic heat transport, which leads to enhanced OHU in the subpolar North Atlantic.

Caption: "Fig. 4 CESM1-CAM5 regional OHU time series under the RCP2.6 and RCP8.5 scenarios.
Top row: Annual mean OHU anomalies averaged over the North Atlantic (NA) (35°N to 70°N, 80°W to 10°W) during 2006–2100 under the (A) RCP2.6 and (B) RCP8.5 scenarios. Bottom row: As in the top row but for annual mean OHU anomalies averaged over the Southern Ocean (SO) (35°S to 70°S, 0° to 360°) (C and D). Thick black and blue curves indicate OHU anomalies in rcp and rcpFA simulations with CESM1-CAM5, which are calculated from the ensemble means of individual simulations. Thin black and blue curves denote OHU anomalies for three ensemble members in each of the rcp and rcpFA simulations. Orange lines denote the difference between the ensemble means of rcp and rcpFA simulations, which indicate aerosol effects. OHU anomalies are relative to the 2006–2025 mean and a 5-year running mean is applied. Notice the different scales in each panel."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3882 on: November 07, 2020, 05:33:48 PM »
The linked reference indicates that positive feedback factors have doubled the amount of Arctic sea ice loss resulting from riverine heat influx.

Increasing riverine heat influx triggers Arctic sea ice decline and oceanic and atmospheric warming, Science Advances (2020). DOI: 10.1126/sciadv.abc4699 , advances.sciencemag.org/content/6/45/eabc4699

https://advances.sciencemag.org/content/6/45/eabc4699

Abstract
Arctic river discharge increased over the last several decades, conveying heat and freshwater into the Arctic Ocean and likely affecting regional sea ice and the ocean heat budget. However, until now, there have been only limited assessments of riverine heat impacts. Here, we adopted a synthesis of a pan-Arctic sea ice–ocean model and a land surface model to quantify impacts of river heat on the Arctic sea ice and ocean heat budget. We show that river heat contributed up to 10% of the regional sea ice reduction over the Arctic shelves from 1980 to 2015. Particularly notable, this effect occurs as earlier sea ice breakup in late spring and early summer. The increasing ice-free area in the shelf seas results in a warmer ocean in summer, enhancing ocean–atmosphere energy exchange and atmospheric warming. Our findings suggest that a positive river heat–sea ice feedback nearly doubles the river heat effect.

Edit, to state the obvious: a) the more the Arctic sea ice extent is lost, the more likely the chance that the Beaufort Gyre might reverse due to a temporary reversal of the predominate wind; b) the more the volume of freshwater discharged into the Arctic Ocean from rivers, the larger the likely discharge of relatively freshwater into the North Atlantic from a coming reversal of the Beaufort Gyre; and c) both items 'a' and 'b' increase the likelihood of abrupt climate change in coming decades.
« Last Edit: November 08, 2020, 01:20:07 AM by AbruptSLR »
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3883 on: November 08, 2020, 04:25:54 PM »
A slight less evident implication of my post (Reply #3882) citing research demonstrating a positive feedback loop between Arctic sea ice loss and the influx of riverine discharge into the Arctic Ocean, is that the increase influx of fresh riverine water into the Arctic Ocean increases the thickness of the halocline layer (see the attached image); which reduces heat flux from the Atlantic layer to the Arctic atmosphere; which results in a masking of the true magnitude of Artic Amplification; as the coming temporary reversal of the Beaufort Gyre will abruptly increase the heat flux from the Atlantic layer into the Arctic atmosphere.  This is a meaningful masking mechanism for hiding the true value of ECS.

W.R.T. ECS (& GMSTA), other general masking mechanisms include:

(a) Temporary (observed at least from roughly 1998 to 2013) atmospheric conditions in the Tropical Pacific that not only temporarily increased the frequency of lower level cloud cover with negative feedback, but also above average La Nina-like conditions and generally negative PDO values; which, accelerated the sequestration of heat in the ocean, which was partially release during the 2015-16 El Nino and largely advected to the Southern Ocean.

(b) The temporary acceleration of anthropogenic aerosol emissions (largely associated with coal-fired power plants in both in China and elsewhere) that temporarily induced both negative forcing & negative feedback; which are now being rapidly reduced.

(c) A temporary acceleration of the absorption of carbon dioxide by land-based plants associated both with higher atmospheric carbon dioxide concentrations, and with global warming; which will soon be reverses as vegetative stress related to rapid climate change release temporarily sequestered carbon from vegetation into the atmosphere

(d) Decadal scale thermal inertia fluctuations associated the ocean, atmosphere and cryosphere.
 
(f) A probable underestimation of both natural and anthropogenic negative aerosol forcing and feedback.

(g) aerosol emissions, with high sulfur content, from shipping, and Canadian forests, have been masking the full impact of global warming (i.e. without these two negative feedback GMSTA would already be over 1.5C).
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3884 on: November 09, 2020, 03:33:25 PM »
The linked reference entitled 'Past climate inform our future' (see the first image) reminds me that after a one-time freshwater pulse as analyzed by Hansen et al. (2016); which as the second image may result in an initially high planetary energy imbalance that a more stable imbalance within a few decades; that there is a risk that a projected increase in high-latitude rainfall will thaw both permafrost regions and the Greenland Ice Sheet (which would maintain a slow MOC).  If so, this could push the atmosphere into an equable climate circa 2120.

Jessica E. Tierney et al. (06 Nov 2020), "Past climates inform our future", Science, Vol. 370, Issue 6517, eaay3701, DOI: 10.1126/science.aay3701

https://science.sciencemag.org/content/370/6517/eaay3701

Structured Abstract
BACKGROUND
Anthropogenic emissions are rapidly altering Earth’s climate, pushing it toward a warmer state for which there is no historical precedent. Although no perfect analog exists for such a disruption, Earth’s history includes past climate states — “paleoclimates” — that hold lessons for the future of our warming world. These periods in Earth’s past span a tremendous range of temperatures, precipitation patterns, cryospheric extent, and biospheric adaptations and are increasingly relevant for improving our understanding of how key elements of the climate system are affected by greenhouse gas levels. The rise of new geochemical and statistical methods, as well as improvements in paleoclimate modeling, allow for formal evaluation of climate models based on paleoclimate data. In particular, given that some of the newest generation of climate models have a high sensitivity to a doubling of atmospheric CO2, there is a renewed role for paleoclimates in constraining equilibrium climate sensitivity (ECS) and its dependence on climate background state.

ADVANCES
In the past decade, an increasing number of studies have used paleoclimate temperature and CO2 estimates to infer ECS in the deep past, in both warm and cold climate states. Recent studies support the paradigm that ECS is strongly state-dependent, rising with increased CO2 concentrations. Simulations of past warm climates such as the Eocene further highlight the role that cloud feedbacks play in contributing to high ECS under increased CO2 levels. Paleoclimates have provided critical constraints on the assessment of future ice sheet stability and concomitant sea level rise, including the viability of threshold processes like marine ice cliff instability. Beyond global-scale changes, analyses of past changes in the water cycle have advanced our understanding of dynamical drivers of hydroclimate, which is highly relevant for regional climate projections and societal impacts. New and expanding techniques, such as analyses of single shells of foraminifera, are yielding subseasonal climate information that can be used to study how intra- and interannual modes of variability are affected by external climate forcing. Studies of extraordinary, transient departures in paleoclimate from the background state such as the Paleocene-Eocene Thermal Maximum provide critical context for the current anthropogenic aberration, its impact on the Earth system, and the time scale of recovery.
A number of advances have eroded the “language barrier” between climate model and proxy data, facilitating more direct use of paleoclimate information to constrain model performance. It is increasingly common to incorporate geochemical tracers, such as water isotopes, directly into model simulations, and this practice has vastly improved model-proxy comparisons. The development of new statistical approaches rooted in Bayesian inference has led to a more thorough quantification of paleoclimate data uncertainties. In addition, techniques like data assimilation allow for a formal combination of proxy and model data into hybrid products. Such syntheses provide a full-field view of past climates and can put constraints on climate variables that we have no direct proxies for, such as cloud cover or wind speed.
OUTLOOK
A common concern with using paleoclimate information as model targets is that non-CO2 forcings, such as aerosols and trace greenhouse gases, are not well known, especially in the distant past. Although evidence thus far suggests that such forcings are secondary to CO2, future improvements in both geochemical proxies and modeling are on track to tackle this issue. New and rapidly evolving geochemical techniques have the potential to provide improved constraints on the terrestrial biosphere, aerosols, and trace gases; likewise, biogeochemical cycles can now be incorporated into paleoclimate model simulations. Beyond constraining forcings, it is critical that proxy information is transformed into quantitative estimates that account for uncertainties in the proxy system. Statistical tools have already been developed to achieve this, which should make it easier to create robust targets for model evaluation. With this increase in quantification of paleoclimate information, we suggest that modeling centers include simulation of past climates in their evaluation and statement of their model performance. This practice is likely to narrow uncertainties surrounding climate sensitivity, ice sheets, and the water cycle and thus improve future climate projections.

Caption for the first image: "Past climates provide context for future climate scenarios.
Both past (top) and future (bottom) climates are colored by their estimated change in global mean annual surface temperature relative to preindustrial conditions, ranging from blue (colder) to red (warmer). “Sustainability,” “Middle road,” and “High emissions” represent the estimated global temperature anomalies at year 2300 from the Shared Socioeconomic Pathways (SSPs) SSP1-2.6, SSP2-4.5, and SSP5-8.5, respectively. In both the past and future cases, warmer climates are associated with increases in CO2 (indicated by the arrow). Ma, millions of years ago."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3885 on: November 09, 2020, 04:33:33 PM »
I note that the Cordilleran Ice Sheet was about the size of the Greenland Ice Sheet, and the quoted post supports my concern that paleo-evidence implies that high latitude rainfall can rapidly melt both northern ice sheets and permafrost, and I not that such high latitude rainfall in the SH could readily promote hydrofracturing of both the FRIS and the RIS in coming decades.

The linked reference studies the paleo decay of the Cordilleran ice sheet and finds that it lost most of its ice mass earlier than consensus science previously thought, and it lost much of its ice mass over a relatively short period.  Personally, I am concerned about the impact of rainfall at increasingly high latitudes (with warming) on both the Greenland Ice Sheet, on Arctic permafrost, and on the WAIS:

B. Menounos et al (10 Nov 2017), "Cordilleran Ice Sheet mass loss preceded climate reversals near the Pleistocene Termination", Science, Vol. 358, Issue 6364, pp. 781-784, DOI: 10.1126/science.aan3001

http://science.sciencemag.org/content/358/6364/781

Abstract: "The Cordilleran Ice Sheet (CIS) once covered an area comparable to that of Greenland. Previous geologic evidence and numerical models indicate that the ice sheet covered much of westernmost Canada as late as 12.5 thousand years ago (ka). New data indicate that substantial areas throughout westernmost Canada were ice free prior to 12.5 ka and some as early as 14.0 ka, with implications for climate dynamics and the timing of meltwater discharge to the Pacific and Arctic oceans. Early Bølling-Allerød warmth halved the mass of the CIS in as little as 500 years, causing 2.5 to 3.0 meters of sea-level rise. Dozens of cirque and valley glaciers, along with the southern margin of the CIS, advanced into recently deglaciated regions during the Bølling-Allerød and Younger Dryas."

Disappearance of an ice sheet

The Cordilleran Ice Sheet is thought to have covered westernmost Canada until about 13,000 years ago, even though the warming and sea level rise of the last deglaciation had begun more than a thousand years earlier. This out-of-phase behavior has puzzled glaciologists because it is not clear what mechanisms could account for it. Menounos et al. report measurements of the ages of cirque and valley glaciers that show that much of western Canada was ice-free as early as 14,000 years ago—a finding that better agrees with the record of global ice volume (see the Perspective by Marcott and Shakun). Previous reconstructions seem not to have adequately reflected the complexity of ice sheet decay.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE (narrated video)
« Reply #3886 on: November 09, 2020, 04:40:25 PM »
The linked reference (& associated article and images) show that while the paleo marine portions of the Fennoscandian Ice Sheet and the Antarctic Ice Sheets made abrupt contributions to SLR during Melt Water Pulse 1a (MWP 1a) that the Younger Dryas event (circa 13kya to 11.5kya) may have been triggered by a MISI-type of collapse of part of the paleo Cordilleran Ice Sheet.  To me this added support to the idea that an abrupt collapse of major portions of the WAIS, and/or an abrupt freshwater hosing event from the Beaufort Gyre, could trigger rapid climate change this century:

T. Pico et al. Sea level fingerprinting of the Bering Strait flooding history detects the source of the Younger Dryas climate event, Science Advances (2020). DOI: 10.1126/sciadv.aay2935

https://advances.sciencemag.org/content/6/9/eaay2935

Abstract
During the Last Glacial Maximum, expansive continental ice sheets lowered globally averaged sea level ~130 m, exposing a land bridge at the Bering Strait. During the subsequent deglaciation, sea level rose rapidly and ultimately flooded the Bering Strait, linking the Arctic and Pacific Oceans. Observational records of the Bering Strait flooding have suggested two apparently contradictory scenarios for the timing of the reconnection. We reconcile these enigmatic datasets using gravitationally self-consistent sea-level simulations that vary the timing and geometry of ice retreat between the Laurentide and Cordilleran Ice Sheets to the southwest of the Bering Strait to fit observations of a two-phased flooding history. Assuming the datasets are robust, we demonstrate that their reconciliation requires a substantial melting of the Cordilleran and western Laurentide Ice Sheet from 13,000 to 11,500 years ago. This timing provides a freshwater source for the widely debated Younger Dryas cold episode (12,900 to 11,700 years ago).

Extract: "We refine the timing and geometry of relative sea level change in the Bering Strait during the last deglaciation by constructing an ice history within the CIS and western LIS that is consistent with available land dates. Our ice sheet reconstructions, which maintain fits to sea level records in the far-field (section S9), yield sea level predictions that reconcile disparate and previously enigmatic datasets recording the inundation history of the Bering Shelf. Our inferred ice-melting scenarios source substantial meltwater from the retreat between the CIS and LIS from 13 to 11.5 ka ago in the region west of 110°W, potentially initiated by marine retreat of the ice sheet (fig. S16). Part of the freshwater flux from this ice-mass loss (0.11 Sv over the period 13 to 11.5 ka ago) would have freshened the subpolar North Atlantic and may have been sufficient to suppress deepwater convection and thereby initiate Younger Dryas cooling (30–32). The end of the meltwater flux may have also had a role in terminating the anomalous Younger Dryas cooling and triggering the onset of early Holocene warmth."

Caption for the first image: "Fig. 3 Eustatic contributions of each ice sheet.
Cordilleran and western Laurentide Ice Sheet (CIS) in black, Laurentide Ice Sheet (east of 110°W; LIS) in gray, Fennoscandian Ice Sheet (FIS) in blue, and Antarctic Ice Sheet (AIS) in red, for both ICE-6G (solid) and an alternate ice model, GI-31 (dashed). The shaded gray rectangle highlights the interval of 13 to 11.5 ka. The Younger Dryas (YD; 12.9 to 11.7 ka) and Meltwater Pulse-1a (MWP-1a; 14.5 to 14 ka ago) are labeled. The inset compares total global eustatic histories for ICE-6G (gray) and GI-31 (pink), which differ by less than 2 m from 13 to 11.5 ka ago."

&

Supplementary Materials for Sea level fingerprinting of the Bering Strait flooding history detects the source of the Younger Dryas climate event T. Pico, J. X. Mitrovica, A. C. Mix

https://advances.sciencemag.org/content/suppl/2020/02/24/6.9.eaay2935.DC1
https://advances.sciencemag.org/content/advances/suppl/2020/02/24/6.9.eaay2935.DC1/aay2935_SM.pdf

Caption for the second image: "Fig. S17. Possible marine retreat of ice sheet. Modeled paleoelevation at 13 ka using GI-31 ice history. Contours show the margin and thickness of ice at 13 ka. Shaded regions show ice margin at 11.5 ka. Region with reverse bedrock slope (1m/km) is highlighted by black arrow. This region of ice may have been subject to a marine ice sheet instability, where water at the base of the ice sheet induces melting, causing a rapidly retreating grounding line to induce a large mass loss in this region"

&

Title: "Ancient flooding of Bering Strait shows us how ice sheets respond to climate change"

https://phys.org/news/2020-02-ancient-bering-strait-ice-sheets.html

Extract: "Despite the sea-level data from the Bering Strait, that hypothesis hasn't been universally accepted, Pico said, in part because the study places the melting of the "saddle"—the region where the two North American ice sheets meet—at a time significantly later than many believe it was.

"Most people assume that happened earlier because, even though sea level was rising quickly around the world, there was a period—called meltwater pulse 1A—when it rose especially fast," she said. "In that period, sea level rose by 15 to 20 meters in under 300 years. That would require a huge amount of ice melt, and many people have assumed the saddle melted during this time.

"But that assumed history doesn't fit the Bering Strait sea-level record," she continued. "When we use that flooding history as a sea-level record, it's not consistent with what everyone had assumed before.""

The quoted post (& associated images) cites paleo-evidence that one freshwater hosing event can trigger subsequent freshwater hosing events, that can accelerate climate change in a domino wave fashion (in the paleo case the MISI type of collapse of the Cordilleran Ice Sheet while in the future case this could be an MISI type of collapse of the Greenland Ice Sheet).
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3887 on: November 11, 2020, 05:37:35 PM »
The linked reference confirms that using consensus science climate assumptions, anthropogenic aerosol forcing has masked and delayed the formation of the North-Atlantic warming hole (NAWH), and now that anthropogenic aerosol emissions are already decreasing we can expect that the formation and growth of the NAWH will accelerate (beginning now); which will accelerate the slowdown of the MOC.

Guy Dagan et al. (04 November 2020), "Aerosol forcing masks and delays the formation of the North‐Atlantic warming hole by three decades", Geophysical Research Letters, https://doi.org/10.1029/2020GL090778

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL090778?af=R

Abstract
The North‐Atlantic warming hole (NAWH) is referred to as a reduced warming, or even cooling, of the North‐Atlantic during an anthropogenic‐driven global warming. A NAWH is predicted by climate models during the 21st century and its pattern is already emerging in observations. Despite the known key role of the North‐Atlantic surface temperatures in setting the Northern‐Hemisphere climate, the mechanisms behind the NAWH are still not fully understood. Using state‐of‐the‐art climate models, we show that anthropogenic aerosol forcing opposes the formation of the NAWH (by leading to a local warming) and delays its emergence by about 30 years. In agreement with previous studies, we also demonstrate that the relative warming of the North‐Atlantic under aerosol forcing is due to changes in ocean heat fluxes, rather than air‐sea fluxes. These results suggest that the predicted reduction in aerosol forcing during the 21st century may accelerate the formation of the NAWH.

Plain Language Summary
Anthropogenic aerosols are particles suspended in the atmosphere, which were released due to anthropogenic activity. These particles have a general cooling effect on the Earth due to their interactions with radiation and with clouds. Here we show that the surface temperature in the North‐Atlantic Ocean is predicted to increase due to aerosol forcing (despite the global cooling). This trend is the opposite of the surface temperature trend predicted due to increase in green‐house gases (global warming with a warming “hole” in the North‐Atlantic, trend known as the North‐Atlantic warming hole ‐ NAWH). Using state‐of‐the‐art climate models, we show that aerosol forcing delays the formation of the NAWH by about 30 years. This trend could have important climatic impacts due to the key role of the North‐Atlantic surface temperatures in setting the Northern‐hemisphere’s climate, and due to the predicted reduction in aerosol forcing in the next few decades.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3888 on: November 11, 2020, 05:49:35 PM »
I provide the linked review article about geothermal heat flow (GHF) in Antarctica without comment, except to note that the behavior of the ice near the base of the Thwaites Ice Tongue is very sensitive to the accumulation of basal ice meltwater that is related the GHF in the Byrd Subglacial Basin.

Burton-Johnson, A., Dziadek, R., and Martin, C.: Review article: Geothermal heat flow in Antarctica: current and future directions, The Cryosphere, 14, 3843–3873, https://doi.org/10.5194/tc-14-3843-2020, 2020.

https://tc.copernicus.org/articles/14/3843/2020/
https://tc.copernicus.org/articles/14/3843/2020/tc-14-3843-2020.pdf

Abstract:
"Antarctic geothermal heat flow (GHF) affects the temperature of the ice sheet, determining its ability to slide and internally deform, as well as the behaviour of the continental crust. However, GHF remains poorly constrained, with few and sparse local, borehole-derived estimates and large discrepancies in the magnitude and distribution of existing continent-scale estimates from geophysical models. We review the methods to estimate GHF, discussing the strengths and limitations of each approach; compile borehole and probe-derived estimates from measured temperature profiles; and recommend the following future directions. (1) Obtain more borehole-derived estimates from the subglacial bedrock and englacial temperature profiles. (2) Estimate GHF from inverse glaciological modelling, constrained by evidence for basal melting and englacial temperatures (e.g. using microwave emissivity). (3) Revise geophysically derived GHF estimates using a combination of Curie depth, seismic, and thermal isostasy models. (4) Integrate in these geophysical approaches a more accurate model of the structure and distribution of heat production elements within the crust and considering heterogeneities in the underlying mantle. (5) Continue international interdisciplinary communication and data access."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3889 on: November 11, 2020, 06:11:58 PM »
The linked reference finds that:

"Both two-box model inversions and variational 4D inversions suggest that ignoring the negative anomaly of OH during the El Niño years leads to a large overestimation of the increase in global CH4 emissions by up to 10 ± 3 Tg yr−1 to match the observed CH4 increase over these years. Not accounting for the increasing OH trends given by the CCMI models leads to an underestimation of the CH4 emission increase by 23 ± 9 Tg yr−1 from 1986 to 2010."

On balance this work indicates that the net observed methane emissions have been underestimated in recent decades.

Zhao, Y., Saunois, M., Bousquet, P., Lin, X., Berchet, A., Hegglin, M. I., Canadell, J. G., Jackson, R. B., Deushi, M., Jöckel, P., Kinnison, D., Kirner, O., Strode, S., Tilmes, S., Dlugokencky, E. J., and Zheng, B.: On the role of trend and variability in the hydroxyl radical (OH) in the global methane budget, Atmos. Chem. Phys., 20, 13011–13022, https://doi.org/10.5194/acp-20-13011-2020, 2020.

https://acp.copernicus.org/articles/20/13011/2020/

Abstract
Decadal trends and interannual variations in the hydroxyl radical (OH), while poorly constrained at present, are critical for understanding the observed evolution of atmospheric methane (CH4). Through analyzing the OH fields simulated by the model ensemble of the Chemistry–Climate Model Initiative (CCMI), we find (1) the negative OH anomalies during the El Niño years mainly corresponding to the enhanced carbon monoxide (CO) emissions from biomass burning and (2) a positive OH trend during 1980–2010 dominated by the elevated primary production and the reduced loss of OH due to decreasing CO after 2000. Both two-box model inversions and variational 4D inversions suggest that ignoring the negative anomaly of OH during the El Niño years leads to a large overestimation of the increase in global CH4 emissions by up to 10 ± 3 Tg yr−1 to match the observed CH4 increase over these years. Not accounting for the increasing OH trends given by the CCMI models leads to an underestimation of the CH4 emission increase by 23 ± 9 Tg yr−1 from 1986 to 2010. The variational-inversion-estimated CH4 emissions show that the tropical regions contribute most to the uncertainties related to OH. This study highlights the significant impact of climate and chemical feedbacks related to OH on the top-down estimates of the global CH4 budget.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3890 on: November 13, 2020, 06:21:04 PM »
Per Gavin Schmidt's projection of GMSTA projection using GISTEMPv4 LOTI data through the end of October 2020; 2020 is currently still projected to finish warmer than 2016.  While this situation may change as it appears likely that the 2020-2021 season will be a La Nina season; the fact that these two years are even close suggests that global warming is beginning to accelerate as compared to recent years.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3891 on: November 16, 2020, 04:04:46 PM »
The linked reference found that when tiny soot particles combine with ozone or sulfuric acid, the result can be changes in clouds—both low-lying and high altitude—that cause more heating.

Lohmann, U., Friebel, F., Kanji, Z.A. et al. Future warming exacerbated by aged-soot effect on cloud formation. Nat. Geosci. 13, 674–680 (2020). https://doi.org/10.1038/s41561-020-0631-0

https://www.nature.com/articles/s41561-020-0631-0

Abstract: "Clouds play a critical role in modulating the Earth’s radiation balance and climate. Anthropogenic aerosol particles that undergo aging processes, such as soot, aid cloud droplet and ice crystal formation and thus influence the microphysical structure of clouds.  However, the associated changes in cloud radiative properties and climate effects remain uncertain and are largely omitted in climate models. Here we present global climate simulations of past and future effects of both ozone-aged soot particles acting as cloud condensation nuclei and sulfuric acid-aged soot particles acting as ice-nucleating particles on the structure and radiative effects of clouds. Under pre-industrial conditions, soot aging led to an increase in thick, low-level clouds that reduced negative shortwave effective radiative forcing by 0.2 to 0.3 W m−2. In the simulations of a future, warmer climate under double pre-industrial atmospheric carbon dioxide concentrations, soot aging and compensating cloud adjustments led to a reduction in low-level clouds and enhanced high-altitude cirrus cloud thickness, which influenced the longwave radiative balance and exacerbated the global mean surface warming by 0.4 to 0.5 K. Our findings suggest that reducing emissions of soot particles is beneficial for future climate, in addition to air quality and human health."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3892 on: November 16, 2020, 04:56:02 PM »
The linked reference discusses both reasons why current Antarctic Sea Ice extends are currently relatively high; and why we might expect relatively rapid sea ice in the future due to changes in both wind patterns and ocean heat uptake/content:

Edward W. Doddridge et al. (2020), "Southern Ocean heat storage, reemergence, and winter sea ice decline induced by summertime winds", J. Climate 1–47, https://doi.org/10.1175/JCLI-D-20-0322.1

https://journals.ametsoc.org/jcli/article-abstract/doi/10.1175/JCLI-D-20-0322.1/355537/Southern-Ocean-heat-storage-reemergence-and-winter?redirectedFrom=fulltext

Abstract: "The observational record shows a substantial 40-year upward trend in summertime westerly winds over the Southern Ocean, as characterised by the Southern Annular Mode (SAM) index. Enhanced summertime westerly winds have been linked to cold summertime sea surface temperature (SST) anomalies. Previous studies have suggested that Ekman transport or upwelling is responsible for this seasonal cooling. Here, another process is presented in which enhanced vertical mixing, driven by summertime wind anomalies, moves heat downwards, cooling the sea surface and simultaneously warming the subsurface waters. The anomalously cold SSTs draw heat from the atmosphere into the ocean, leading to increased depth-integrated ocean heat content. The subsurface heat is returned to the surface mixed layer during the autumn and winter as the mixed layer deepens, leading to anomalously warm SSTs and potentially reducing sea ice cover. Observational analyses and numerical experiments support our proposed mechanism, showing that enhanced vertical mixing produces subsurface warming and cools the surface mixed layer. Nevertheless, the dominant driver of surface cooling remains uncertain; the relative importance of advective and mixing contributions to the surface cooling is model dependent. Modeling results suggest that sea ice volume is more sensitive to summertime winds than sea ice extent, implying that enhanced summertime westerly winds may lead to thinner sea ice in the following winter, if not lesser ice extent. Thus, strong summertime winds could precondition the sea ice cover for a rapid retreat in the following melt season."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

gerontocrat

  • First-year ice
  • Posts: 9601
    • View Profile
  • Liked: 3803
  • Likes Given: 29
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3893 on: November 16, 2020, 05:36:16 PM »
I quote below a couple of sentences from the paper quoted by AbruptSLR above.

I then suggest that the recent years' Antarctic sea ice data do not support the statements on winter and summer sea ice extent.

The linked reference discusses both reasons why current Antarctic Sea Ice extends are currently relatively high; and why we might expect relatively rapid sea ice in the future due to changes in both wind patterns and ocean heat uptake/content:

Edward W. Doddridge et al. (2020), "Southern Ocean heat storage, reemergence, and winter sea ice decline induced by summertime winds", J. Climate 1–47, https://doi.org/10.1175/JCLI-D-20-0322.1

https://journals.ametsoc.org/jcli/article-abstract/doi/10.1175/JCLI-D-20-0322.1/355537/Southern-Ocean-heat-storage-reemergence-and-winter?redirectedFrom=fulltext

Extracts

The subsurface heat is returned to the surface mixed layer during the autumn and winter as the mixed layer deepens, leading to anomalously warm SSTs and potentially reducing sea ice cover.
_____________________________
Thus, strong summertime winds could precondition the sea ice cover for a rapid retreat in the following melt season."

Sea ice maxima in recent years have increased (see September monthly average graph). This years maxima was 17th highest in the 42 year satellite record.

The February minimum has also increased in recent years  (see February monthly average graph). This year the melting season has been slow so far - - Extent loss from maximum on this date is 2.51 million km2, 0.42 million km2, (14%) less than the 10 year average of 2.93 million km2.

Basically the amazing 2016 collapse in sea ice extent has been followed by recovery.
There is no meaningful trend in sea ice extent maximum and minimum over the 42 year satellite record. However, maybe there is a meaningful upward trend in the scale of variation from year to year, i.e. increasing instability.

My speculation that belongs to me is that as yet science has little clue of what the effects of Global Heating up to the present (and in the future) will be on the Antarctic Sea Ice. Mind you, I doubt that the news will be good for (most) life on earth.


"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3894 on: November 16, 2020, 08:11:07 PM »
The linked reference helps to explain why CESM2 projects a higher climate sensitivity than CESM1.

CO2 Increase Experiments Using the CESM: Relationship to Climate J. T. Bacmeister et. al (14 October 2020), "Sensitivity and Comparison of CESM1 to CESM2", Journal of Advances in Modeling Earth Systems, Volume 12, Issue 11, https://doi.org/10.1029/2020MS002120

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020MS002120

Abstract
We examine the response of the Community Earth System Model Versions 1 and 2 (CESM1 and CESM2) to abrupt quadrupling of atmospheric CO2 concentrations (4xCO2) and to 1% annually increasing CO2 concentrations (1%CO2). Different estimates of equilibrium climate sensitivity (ECS) for CESM1 and CESM2 are presented. All estimates show that the sensitivity of CESM2 has increased by 1.5 K or more over that of CESM1. At the same time the transient climate response (TCR) of CESM1 and CESM2 derived from 1%CO2 experiments has not changed significantly—2.1 K in CESM1 and 2.0 K in CESM2. Increased initial forcing as well as stronger shortwave radiation feedbacks are responsible for the increase in ECS seen in CESM2. A decomposition of regional radiation feedbacks and their contribution to global feedbacks shows that the Southern Ocean plays a key role in the overall behavior of 4xCO2 experiments, accounting for about 50% of the total shortwave feedback in both CESM1 and CESM2. The Southern Ocean is also responsible for around half of the increase in shortwave feedback between CESM1 and CESM2, with a comparable contribution arising over tropical ocean. Experiments using a thermodynamic slab‐ocean model (SOM) yield estimates of ECS that are in remarkable agreement with those from fully coupled Earth system model (ESM) experiments for the same level of CO2 increase. Finally, we show that the similarity of TCR in CESM1 and CESM2 masks significant regional differences in warming that occur in the 1%CO2 experiments for each model.

Plain Language Summary
Computer models of the Earth's climate system are complex. Our best guess scenarios for how the climate system will change due to human activity over the next century are also complex. They include estimates of changing greenhouse gas (e.g., CO2) levels in the atmosphere, aerosol (e.g., smog and haze) emissions, and land use changes (e.g., deforestation and urbanization). To help understand this complex system, the climate modeling community has designed two simplified experiments: abrupt CO2 quadrupling (4xCO2) and 1% annual CO2 increase (1%CO2). In these experiments all human‐induced factors in the climate system are held constant (at preindustrial levels) except for CO2 in the atmosphere. Results of these experiments from different climate models can be compared to gain insight into the climate system. We look at two versions of the Community Earth System Model (CESM1 and CESM2). The warming simulated in the 4xCO2 experiment (climate sensitivity) has increased substantially in CESM2. This is related to changes in clouds over the Southern Ocean and tropics. At the same time warming in in the 1%CO2 experiment has not increased. This is related to differences in how CESM1 and CESM2 simulate northern oceans (Arctic, North Atlantic, and North Pacific).
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3895 on: November 17, 2020, 11:17:42 PM »
The linked reference indicates that Jakobshaven, Helheim and Kangerlussuaq marine terminating glaciers in Greenland will exceed current consensus climate science projections for SLR this century under RCP 8.5.  To me this is meaningful because SLR contribution from Greenland is amplified to induce higher than eustatic SLR in West Antarctica.  This implies that the risk of the Thwaites Eastern Ice Shelf becoming unpinned in coming decades is higher than assumed by consensus climate science; which could lead to a MICI-type of collapse of the ice in the Byrd Subglacial Basin in coming decades:

Centennial response of Greenland's three largest outlet glaciers, Nature Communications (2020). DOI: 10.1038/s41467-020-19580-5 , www.nature.com/articles/s41467-020-19580-5

https://www.nature.com/articles/s41467-020-19580-5

Abstract: "The Greenland Ice Sheet is the largest land ice contributor to sea level rise. This will continue in the future but at an uncertain rate and observational estimates are limited to the last few decades. Understanding the long-term glacier response to external forcing is key to improving projections. Here we use historical photographs to calculate ice loss from 1880–2012 for Jakobshavn, Helheim, and Kangerlussuaq glacier. We estimate ice loss corresponding to a sea level rise of 8.1 ± 1.1 millimetres from these three glaciers. Projections of mass loss for these glaciers, using the worst-case scenario, Representative Concentration Pathways 8.5, suggest a sea level contribution of 9.1–14.9 mm by 2100. RCP8.5 implies an additional global temperature increase of 3.7 °C by 2100, approximately four times larger than that which has taken place since 1880. We infer that projections forced by RCP8.5 underestimate glacier mass loss which could exceed this worst-case scenario."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

sidd

  • First-year ice
  • Posts: 5721
    • View Profile
  • Liked: 796
  • Likes Given: 0
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3896 on: November 18, 2020, 05:49:25 AM »
That's a nice paper. The list of authors includes a great number of the usual suspects. I did like the analysis in terms of bed topo discussion and the risks therein. I will have to reread carefully.

sidd

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3897 on: November 19, 2020, 12:43:28 AM »
The linked reference confirms the relatively high temperature sensitivity of soil carbon release to the atmosphere from northern permafrost soils.  This is not good news.

Shuai Ren et al. (12 November 2020), "Higher temperature sensitivity of soil C release to atmosphere from northern permafrost soils as indicated by a meta‐analysis", Global Biochemical Cycles, https://doi.org/10.1029/2020GB006688

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GB006688?af=R

Abstract: "The loss of carbon from soils to the atmosphere resulting from climate change is projected to be large, but these projections exhibit significant uncertainty, largely due to insufficient knowledge of the patterns and controls of the temperature sensitivity of soil microbial respiration. Here, we synthesized data from 52 soil incubation studies across the Northern Hemisphere to assess the spatial patterns of Q10 and its key drivers in different soil layers and geographic zones. The mean Q10 was 2.51 ± 1.13 across the northern ecosystems, but it exhibited significant variability. After averaged by ecosystem types, the highest mean Q10 value was observed in the northern permafrost soils, where the Q10 values were nearly 18% higher than those in non‐permafrost regions. The temperature sensitivity was larger in subsoil than in topsoil layers, particularly in permafrost subsoils. Besides, the dominant factors that correlate with Q10 values are the carbon input, described by satellite‐derived net primary productivity (NPP) in the topsoil, and the soil C:N ratio in the subsoil. Based on the main factors affecting Q10, we provide a gridded Q10 dataset for the mid‐high latitude areas, which further indicates that northern permafrost regions are more sensitive to climate warming than others. These results highlight the key role played by the permafrost in the temperature sensitivity of soil C release, and the necessity of including depth‐specific soil C release processes in models, if we are to make better predictions of the soil C dynamics in future climate change scenarios."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 19044
    • View Profile
  • Liked: 2106
  • Likes Given: 258
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3898 on: November 19, 2020, 12:53:04 AM »
This linked reference indicates that it is likely that increasing concentrations of atmospheric carbon dioxide will decrease rainfall in the Amazon rainforest.  This is not good news.

Gilvan Sampaio et al (2020), "CO2 fertilization effect can cause rainfall decrease as strong as large-scale deforestation in the Amazon", Biogeosciences Discuss., https://doi.org/10.5194/bg-2020-386

https://bg.copernicus.org/preprints/bg-2020-386/

Abstract. Climate in the Amazon region is particularly sensitive to surface processes and properties such as heat fluxes and vegetation coverage. Rainfall is a key expression of land surface-atmosphere interactions in the region due to its strong dependence on forest transpiration. While a large number of past studies have shown the impacts of large-scale deforestation on annual rainfall, studies on the isolated effects of elevated atmospheric CO2 concentration (eCO2) on canopy transpiration and rainfall are scarcer. Here for the first time we make a systematic comparison of the plant physiological effects of eCO2 and deforestation on Amazon rainfall. We use the CPTEC-Brazilian Atmospheric Model (BAM) with dynamic vegetation under a 1.5xCO2 and a 100 % substitution of the forest by pasture grassland, with all other conditions held similar between the two scenarios. We find that both scenarios result in equivalent average annual rainfall reductions (Physiology: −252 mm, −12 %; Deforestation: −292 mm, −13 %) that are well above observed Amazon rainfall interannual variability of 5.1 %. Rainfall decrease in the two scenarios are caused by a reduction of approximately 20 % of canopy transpiration, but for different reasons: eCO2-driven reduction of stomatal conductance in Physiology; decreased leaf area index of pasture (−66 %) and its dry-season lower surface vegetation coverage in Deforestation. Walker circulation is strengthened in the two scenarios (with enhanced convection over the Andes and a weak subsidence branch over east Amazon) but, again, through different mechanisms: enhanced west winds from the Pacific and reduced easterlies entering the basin in Physiology, and strongly increased easterlies in the Deforestation. Although our results for the Deforestation scenario are in agreement with previous observational and modelling studies, the lack of direct field-based ecosystem-level experimental evidence on the effect of eCO2 in moisture fluxes of tropical forests confers a considerable level of uncertainty to any projections on the physiological effect of eCO2 on Amazon rainfall. Furthermore, our results highlight the responsibilities of both Amazonian and non-Amazonian countries to mitigate potential future climatic change and its impacts in the region driven either by local deforestation or global CO2 emissions.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Tom_Mazanec

  • Young ice
  • Posts: 3912
  • Earth will survive AGW...but will Homo sapiens?
    • View Profile
    • Planet Mazanec
  • Liked: 641
  • Likes Given: 379
Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« Reply #3899 on: November 19, 2020, 01:47:42 PM »
Seas are rising faster than ever
https://www.sciencemag.org/news/2020/11/seas-are-rising-faster-ever
Quote
sk climate scientists how fast the world’s oceans are creeping upward, and many will say 3.2 millimeters per year—a figure enshrined in the last Intergovernmental Panel on Climate Change report, from 2014. But the number, based on satellite measurements taken since the early 1990s, is a long-term average. In fact, the global rate varied so much over that period that it was hard to say whether it was holding steady or accelerating.
It was accelerating, big time. Faster melting of Greenland’s ice has pushed the rate to 4.8 millimeters per year, according to a 10-year average compiled for Science by Benjamin Hamlington, an ocean scientist at NASA’s Jet Propulsion Laboratory (JPL) and head of the agency’s sea level change team. “The [Greenland] mass loss has clearly kicked into higher gear,” agrees Felix Landerer, a JPL sea level scientist. With the help of new data, new models of vertical land motion, and—this month—a new radar satellite, oceanographers are sharpening their picture of how fast, and where, the seas are gobbling up the land.
SHARKS (CROSSED OUT) MONGEESE (SIC) WITH FRICKIN LASER BEAMS ATTACHED TO THEIR HEADS