Ice Apocalypse - Multiple Meters Sea Level Rise

[AbruptSLR]

I concur with the linked article that climate scientists should make more use of empirical orthogonal functions (EOFs) when analyzing data to identify patterns and attribution.  Indeed, I recommend that this method be used more to identify/attribute ice-climate feedback patterns.

Title: "Why not use a clever mathematical trick?"

http://www.realclimate.org/index.php/archives/2020/03/why-not-use-a-clever-mathematical-trick/

Extract: "There is a clever mathematical trick for comparing different data sets, but it does not seem to be widely used. It is based on so-called empirical orthogonal functions (EOFs), which Edward Lorenz described in a Massachusetts Institute of Technology (MIT) scientific report from 1956. The EOFs are similar to principal component analysis (PCA).


The EOFs and PCAs provide patterns of spatio-temporal covariance structure. Usually these techniques are applied to datasets with many parallel variables to show coherent patterns of variability.
…
t is not that there is little use of EOFs (they are widely used), but the question is how the EOFs are used and how the results are interpreted. I learned that EOFs can be used in many different ways from Doug Nychka, when I visited University Corporation for Atmospheric Research (UCAR) in 2011.

The clever trick is to apply these techniques to data compiled from more than one source of data. When used this way, the technique is labelled “common EOFs” or “common PCA”.
…
Common EOFs are also particularly useful for quantifying local effects of global warming through a process known as empirical-statistical downscaling (ESD). It's pity that common EOFs aren't even mentioned in the recent textbook on ESD by Maraun and Widmann (2019)  (they are discussed in Benestad et al. (2008))."

[AbruptSLR]

I hope that attribution science keeps a close watch on all of the 'Climate Questions' cited in the linked article, so that it can provide us all with as early of a warning as practicable as to what is coming in the coming decades:

Title: "These Are the Biggest Climate Questions for the New Decade"

https://www.scientificamerican.com/article/these-are-the-biggest-climate-questions-for-the-new-decade/

Extract: "We asked climate researchers across a variety of disciplines about the biggest priorities and hottest topics for the 2020s. Here's what they said.

The Arctic is warming faster than anywhere else on Earth, with temperatures rising at least twice as fast as the global average. Many scientists believe that understanding the consequences of Arctic warming is essential for making accurate predictions about climate change around the world.
…
Accurately predicting the pace of future sea-level rise is one of the biggest priorities in climate science. And one of the biggest uncertainties about future sea-level rise is the behavior of the Greenland and Antarctic ice sheets, both of which are pouring billions of tons of ice into the ocean each year.
…
The past decade saw leaps and bounds in a field of climate research known as "attribution science" — the connection between climate change and extreme weather events.
…
Predicting how much the Earth will warm, given a certain level of greenhouse gas emissions, may seem like the simplest goal of climate modeling. But it's harder than it sounds.

Climate models don't always agree on the Earth's exact sensitivity to greenhouse gas emissions — although they do tend to fall within a certain range."

[AbruptSLR]

The Washington Post has reported today that the Trump Administration is likely to pursue federal aid for U.S. shale fracking companies; which is not good news in the fight against the climate crisis.

[Sciguy]

While the factory shutdowns in China may put a temporary slowdown on solar and wind projects, the damage to the oil and gas companies from the slowdown will result in more money being invested in renewables, not fossil fuel companies.

https://finance.yahoo.com/news/green-energy-10-trillion-revolution-000022946.html

Green Energy’s $10 Trillion Revolution Faces Oil Crash Test
Akshat Rathi
March 9, 2020

(Bloomberg) -- In 2014, when the price of oil last crashed, the world’s governments had no agreement in place to fight climate change. The following year leaders signed the Paris accord.

Green investments have soared since then. Some $1.2 trillion has been poured into renewable energy, and global electric vehicle sales reached 2 million last year. Bloomberg NEF expects as much as $10 trillion poured into clean energy by 2050.

So when this week Saudi Arabia and Russia joined in a price war that wreaked havoc on global markets already rattled by the coronavirus, it looked like the major oil-producing nations reasserting their supremacy in the short term. Instead, it may prove to be another step in a longer-term trend toward ending oil’s power to hold the world to ransom.

The price of a barrel of oil remains an important economic indicator. But the relentless push to move away from fossil fuels suggests that its geopolitical impact is likely to be softer than in the past, with the imperative to combat global warming assuming its place.

Oil’s fall to some $35 a barrel from $55 just last week has major implications for addressing climate change. Low prices incentivize more use of oil; it squeezes the budgets of oil companies, putting clean-energy projects in doubt; and some governments feel pressured to prop up struggling oil companies. All that drives up emissions, which is bad news for global warming.

However, if low prices are sustained this time, there might be big positives for fighting climate change.

Renewable energy is a more mature industry than five years ago. As it becomes a less risky investment, it has attracted big investors who are showering a lot of cash and building some projects that rival the capacity of conventional power plants. At the same time, oil exploration is becoming less viable economically, with an increased risk that even those projects that go ahead no longer yield good returns and with worries about stranded assets growing.

“Now it doesn’t make sense to reduce your investment in renewables if the oil price crashes,” said Mark Lewis, head of sustainability at BNP Paribas Asset Management. “It’s more logical to reduce your investment in oil.”

For governments worldwide, pressure for policy measures has mounted as the issue increasingly resonates, in part due to the kind of direct action and media campaigning espoused by Greta Thunberg.

Low oil prices offer one reason to heed that voter call, since it’s a good time to end fossil-fuel subsidies or to raise taxes on consumption of fossil fuels. Such a move can also help avoid the sorts of destabilizing anti-government protests seen in France, Iran and Ecuador when energy-price increases were proposed.

[AbruptSLR]

The linked pdf provides a convenient overview of many of the dynamical aspects of climate change.

Michael Ghil and Valerio Lucarini (2020), "The Physics of Climate Variability and Climate Change" by; arXiv:1910.00583v2

https://arxiv.org/pdf/1910.00583.pdf

Abstract: "The climate system is a forced, dissipative, nonlinear, complex and heterogeneous system that is out of thermodynamic equilibrium. The system exhibits natural variability on many scales of motion, in time as well as space, and it is subject to various external forcings, natural as well as anthropogenic. This paper reviews the observational evidence on climate phenomena and the governing equations of planetary-scale flow, as well as presenting the key concept of a hierarchy of models as used in the climate sciences. Recent advances in the application of dynamical systems theory, on the one hand, and of nonequilibrium statistical physics, on the other, are brought together for the first time and shown to complement each other in helping understand and predict the system’s behavior. These complementary points of view permit a self-consistent handling of subgrid-scale phenomena as stochastic processes, as well as a unified handling of natural climate variability and forced climate change, along with a treatment of the crucial issues of climate sensitivity, response, and predictability."

[AbruptSLR]

While the factory shutdowns in China may put a temporary slowdown on solar and wind projects, the damage to the oil and gas companies from the slowdown will result in more money being invested in renewables, not fossil fuel companies.

...

Even if western power companies do eventually decide to slow their investments in fossil fuels; the same economics do not apply to Russian and/or OPEC oil production as they have hundreds of years of oil&gas in the ground that is worthless to them unless they produce & sell those resources even at low prices.  Russia and Saudi Arabia have currently increased crude oil production primarily to damage the U.S. shale industry, and in the future they will not hesitate to repeat such actions if/when they feel threatened by renewable energy sources.

[Sciguy]

The last time the US Government had a major stimulus program (The American Recovery and Reinvestment Act of 2009), it worked out pretty well for the renewables industry.

https://solarindustrymag.com/what-the-american-recovery-act-did-for-clean-energy

What The American Recovery Act Did For Clean Energy
Posted by
SI Staff -
March 1, 2016

President Barack Obama’s American Recovery and Reinvestment Act of 2009 (ARRA), the largest single investment in clean energy in history, has provided more than $90 billion in strategic clean energy investments and tax incentives to promote job creation and the deployment of low-carbon technologies, as well as leveraged approximately $150 billion in private and other non-federal capital for clean energy investments, according to a new report released by the White House Council of Economic Advisors (CEA).

The report says clean energy investments made up over one-eighth of total ARRA spending and provided a meaningful boost to economic output.

Specifically, CEA says, these investments transformed America’s clean energy economy by doing the following:

    The act supported roughly 900,000 job-years in clean energy fields from 2009 to 2015.
    Through loan guarantees to support more than $40 billion of investments, as well as tax credits, the act spurred a major expansion of renewable energy generation through more than 100,000 projects across the country. Since 2008, solar electricity generation has increased over 30 times and wind generation has increased over three times.
    ARRA funding supported a plunge in technology costs for many clean energy technologies. Since 2008, the cost of utility-scale solar PV installations has fallen nearly 60%. Battery costs for electric vehicles fell from almost $1,000/kWh in 2008 to under $300/kWh in 2014.
    The act provided the seed funding needed to start the U.S. Department of Energy’s (DOE) Advanced Research Projects Agency-Energy (ARPA-E) program. The program has invested in 475 transformative energy technologies, and its projects have secured $1.25 billion in private-sector follow-on funding.
    ARRA funding for the Smart Grid Investment Program helped to support the installation of 16 million smart meters.
    According to a new report that will be released next week, the amount of battery storage increased by 500% from 2012 to 2015. As more renewable energy comes online, CEA expects the amount needed for storage to accelerate substantially. External analysts have projected that storage installations in the U.S. over the next four years will total nearly 10 times what is currently deployed. These estimates could be even higher due to the extensions of the renewable energy tax credits.

With Democrats in charge of the House of Represenatives, no major economic stimulus will pass without significant clean energy investments.

(The cynic in me thinks that no major economic stimulus will pass before the November elections).

[Sciguy]

While the factory shutdowns in China may put a temporary slowdown on solar and wind projects, the damage to the oil and gas companies from the slowdown will result in more money being invested in renewables, not fossil fuel companies.

...

Even if western power companies do eventually decide to slow their investments in fossil fuels; the same economics do not apply to Russian and/or OPEC oil production as they have hundreds of years of oil&gas in the ground that is worthless to them unless they produce & sell those resources even at low prices.  Russia and Saudi Arabia have currently increased crude oil production primarily to damage the U.S. shale industry, and in the future they will not hesitate to repeat such actions if/when they feel threatened by renewable energy sources.

It's not a question of eventually slowing their investments in fossil fuels, that's been happening for the past two years. 

https://www.forbes.com/sites/feliciajackson/2018/05/15/renewables-investment-nudges-out-fossil-fuel-and-nuclear/#a8012193752a

Renewables Investment Nudges Out Fossil Fuel And Nuclear
Felicia Jackson
May 15, 2018

The global clean energy transition is gaining pace as it becomes a mainstream investment option. According to the latest research from CERES on progress to a 'Clean Trillion' it is also one that far outstripped fossil fuels and nuclear in 2017.

In 2017 the clean energy industry reached a critical turning point. Growth and cost reductions across the sector have far outperformed expectations based on policy frameworks alone.  Dramatic reductions in cost, increases in scale, and technology improvements have fundamentally changed the dynamics of the clean energy market. Energy market dynamics have shifted in favor of clean energy technologies such as wind and solar, which increasingly out-compete new fossil fuel and nuclear power sources.

In 2017, global investment exceeded US$ 333 billion, compared to only US$ 144 billion invested in conventional fossil fuels and nuclear. As clean energy technology has matured and gained greater efficiencies, this investment has now increased its impact per dollar invested. There are now many regions where renewable energy is proving to be more competitive than nuclear power or fossil fuels.

The actions of Saudi Arabia and Russia are a desperate attempt to gain as much share of the declining market as they can as fossil fuels are phased out over the next few decades.

[AbruptSLR]

The linked reference indicates that the Amazon rainforest could collapse within the next 50-years.

Cooper, G.S., Willcock, S. & Dearing, J.A. Regime shifts occur disproportionately faster in larger ecosystems. Nat Commun 11, 1175 (2020). https://doi.org/10.1038/s41467-020-15029-x

https://www.nature.com/articles/s41467-020-15029-x

Abstract: "Regime shifts can abruptly affect hydrological, climatic and terrestrial systems, leading to degraded ecosystems and impoverished societies. While the frequency of regime shifts is predicted to increase, the fundamental relationships between the spatial-temporal scales of shifts and their underlying mechanisms are poorly understood. Here we analyse empirical data from terrestrial (n = 4), marine (n = 25) and freshwater (n = 13) environments and show positive sub-linear empirical relationships between the size and shift duration of systems. Each additional unit area of an ecosystem provides an increasingly smaller unit of time taken for that system to collapse, meaning that large systems tend to shift more slowly than small systems but disproportionately faster. We substantiate these findings with five computational models that reveal the importance of system structure in controlling shift duration. The findings imply that shifts in Earth ecosystems occur over ‘human’ timescales of years and decades, meaning the collapse of large vulnerable ecosystems, such as the Amazon rainforest and Caribbean coral reefs, may take only a few decades once triggered."

See also:

Title: "Amazon and other large ecosystems at risk of rapid collapse: study"

https://www.reuters.com/article/us-climate-change-collapse/amazon-and-other-large-ecosystems-at-risk-of-rapid-collapse-study-idUSKBN20X2MF

Extract: "Large ecosystems such as the Amazon rainforest and coral reefs could collapse faster than scientists had previously assumed, according to a study published on Tuesday."
…
Researchers crunched data on changes in dozens of ecosystems to conclude that Caribbean coral reefs could collapse in 15 years while the Amazon rainforest could die back within 50 years - although that finding was questioned by some experts."

[Sciguy]

From the report, "Global Trends in Renewable Energy Investment 2019" published by the UNEP and Bloomberg NEF:

https://wedocs.unep.org/bitstream/handle/20.500.11822/29752/GTR2019.pdf

KEY FINDINGS

    The   years   2010-2019   will   have   seen   $2.6   trillion   invested  in  renewable  energy  capacity  (excluding  large  hydro),  more  than  treble  the  amount  invested  in the previous decade. Solar is set to have attracted the  most  in  2010-2019,  at  $1.3  trillion,  with  wind  securing $1 trillion and biomass and waste-to-energy $115 billion.

The  decade  has  seen  a  spectacular  improvement  in  the  cost-competitiveness  of  renewables,  with  the  levelized  cost  of  electricity  for  solar  photovoltaics  2down  81%,  for  onshore  wind  down  46%  and  for  offshore  wind  down  44%.  One  or  other  renewables  technology  is  now  the  cheapest  option  for  new  generation in many countries around the world.

    Behind   these   cost   reductions   in   solar   and   wind   have  been  a  combination  of  economies  of  scale  in  manufacturing,  fierce  competition  along  the  supply  chain  –  intensified  by  the  introduction  of  auctions  in  many  countries  –  record-low  costs  of  finance,  and  improvements  in  the  efficiency  of  generating  equipment

   Global  investment  in  renewable  energy  capacity  in  2018  was  $272.9  billion,  the  fifth  successive  year  in  which  it  has  exceeded  $250  billion,  but  down  12%  compared  to  2017  –  due  in  large  part  to  a  policy  change that hit the financing of Chinese solar in the second half of the year.

    The  global  investment  figure  for  2018  was  achieved  despite  continuing  falls  in  the  capital  cost  of  solar  and  wind  projects.  Solar  kept  its  position  as  the  technology  attracting  the  most  capacity  investment,  at  $133.5  billion,  although  this  was  down  22%  on  2017. Wind secured $129.7 billion, up 3%.

    Investment  in  renewables  capacity  in  2018  was  about  three  times  global  investment  in  coal  and  gas-fired  generation   capacity   combined.  This   came   despite   further reductions last year in the average capital cost per MW of solar and wind projects.

There's a ton of information about current investments in renewables.  This report should be required reading to counter the vast amount of misinformation that fossil fuel industry shills post online.

[Sciguy]

This article, from early 2016, explains why Russia and Saudi Arabia are so desperate that they're willing to risk a global recession.

https://www.bloomberg.com/features/2016-ev-oil-crisis/

Here’s How Electric Cars Will Cause the Next Oil Crisis
A shift is under way that will lead to widespread adoption of EVs in the next decade.

By Tom Randall | Feb. 25, 2016

With all good technologies, there comes a time when buying the alternative no longer makes sense. Think smartphones in the past decade, color TVs in the 1970s, or even gasoline cars in the early 20th century. Predicting the timing of these shifts is difficult, but when it happens, the whole world changes.

It’s looking like the 2020s will be the decade of the electric car.

Battery prices fell 35 percent last year and are on a trajectory to make unsubsidized electric vehicles as affordable as their gasoline counterparts in the next six years, according to a new analysis of the electric-vehicle market by Bloomberg New Energy Finance (BNEF). That will be the start of a real mass-market liftoff for electric cars.

Yesterday, on the first episode of Bloomberg’s new animated series Sooner Than You Think, we calculated the effect of continued 60 percent growth. We found that electric vehicles could displace oil demand of 2 million barrels a day as early as 2023. That would create a glut of oil equivalent to what triggered the 2014 oil crisis.

“If you look at reports like what OPEC puts out, what Exxon puts out, they put adoption at like 2 percent,” said Salim Morsy, BNEF analyst and author of today’s EV report. “Whether the end number by 2040 is 25 percent or 50 percent, it frankly doesn’t matter as much as making the binary call that there will be mass adoption.”

One thing is certain: Whenever the oil crash comes, it will be only the beginning. Every year that follows will bring more electric cars to the road, and less demand for oil. Someone will be left holding the barrel.

[AbruptSLR]

This article, from early 2016, explains why Russia and Saudi Arabia are so desperate that they're willing to risk a global recession.

...

Ken,

As no one actually knows how much anthropogenic GHG emissions there will be in coming decades, I will agree to stop posting information on that topic if you do so also, in order not to swamp this thread with information on that topic; which is covered well in other threads of this forum.

Best,
ASLR

[Sciguy]

Many of the studies linked to in this section of the forum assume unrealistic levels of future ghg emissions. 

Many of the people on this forum seem to be unaware of the transitions going on in the energy and transportation sectors and how quickly "business as usual" can change.

For example, the linked article explains what exponential growth (which is currently underway for the adoption of renewable electricity and electrification of the transportation sector) means.

https://www.forbes.com/sites/walvanlierop/2020/01/24/how-soon-will-electric-vehicles-kill-the-gasoline-car/#549a43ff3482

How Soon Will Electric Vehicles Kill The Gasoline Car?
Wal van Lierop
Jan 24, 2020

When I talk about exponential growth in clean transportation—or say anything optimistic about climate change—the pessimists baulk. C’mon, they say, the overwhelming majority of our electricity comes from fossil fuels. Demand for oil is still growing. Electric vehicles (EVs) are a miniscule percentage of cars sold. What good can a few wealthy Tesla owners possibly do for the environment?

To pessimists, the EV revolution seems underwhelming. That’s because they underestimate the power of exponential growth.

What Exponential Growth Really Means

People say that innovations like the Internet, smartphone and social media grew “exponentially” because they radically changed our lives within a few years of appearing. But what do we mean by “exponential”? The late physics professor Al Bartlett used to demonstrate the shocking power of exponential growth very clearly.

Imagine a glass with one bacterium that divides into two bacteria every minute. In one hour, that doubling process fills the glass. If you started the process at 11 am, at what time would the glass be half full?

Many people assume 11:30 am. In reality, the glass is only half full at 11:59 am. At 11:58, it’s 25% full, and at 11:55, it’s only 3% full! 97% seems like business as usual, with no tipping point in sight. The progress seems unimpressive until the moment the bacteria become ubiquitous. The same is likely true of electric vehicles.

The article goes on to explain that we're at roughly 11:55 for adoption of EVs. 

Many of the studies linked on this section of the forum use the RCP8.5 climate scenario developed in 2005.  That scenario has been shown to be exceedingly unlikely.

https://www.bbc.com/news/science-environment-51281986

Climate change: Worst emissions scenario 'exceedingly unlikely'
By Matt McGrath Environment correspondent
29 January 2020

The worst-case scenario for emissions of CO2 this century is no longer plausible, say researchers.

Referred to as "business as usual", the scenario assumes a 500% increase in the use of coal, which is now considered unlikely.

Rather than being seen as something that only had a 3% chance of becoming reality, it became known as the "business-as-usual" scenario, by climate scientists and has been used in more than 2,000 research papers since.

"Obviously, a lot has changed since 2005 or so when the scenario was created. A lot of clean technology prices have fallen, by factors of five, while global coal use peaked in 2013. And it's been flat since then."

"So what originally was a sort of worst-case (scenario) with less than 10% chance of happening is today, exceedingly unlikely."

Very few scientists realised that RCP8.5 was originally a 90th percentile outcome, not a most likely or business-as-usual outcome. They assumed too much, when they should perhaps have checked, say the authors of the review.

[nanning]

Dear AbruptSLR,

Thank you for the introduction and links to:

"These Are the Biggest Climate Questions for the New Decade" (Scientific American)
     https://forum.arctic-sea-ice.net/index.php/topic,2205.msg253348.html#msg253348

"The Physics of Climate Variability and Climate Change" (pdf)
     https://forum.arctic-sea-ice.net/index.php/topic,2205.msg253361.html#msg253361

Especially the pdf I find very interesting.
Cheers.

[kassy]

This article, from early 2016, explains why Russia and Saudi Arabia are so desperate that they're willing to risk a global recession.

...

Ken,

As know one actually knows how much anthropogenic GHG emissions there will be in coming decades, I will agree to stop posting information on that topic if you do so also, in order not to swamp this thread with information on that topic; which is covered well in other threads of this forum.

Best,
ASLR

And we do read that there so there is no need to repeat them here Ken.

Also the only thing that matters for the earth system is CO2 and CH4 going down on a global level and we are far from that (and 100% EV does not equal 0 CO2 etc).

Then there is a whole discussion on time lines (planetary reality and the IPCCs idea of what will happen might not align).

Do you ever wonder how much of Antarctica would still melt if our CO2 output was magically 0 from tomorrow?

 

[Tom_Mazanec]

This article, from early 2016, explains why Russia and Saudi Arabia are so desperate that they're willing to risk a global recession.

...

Ken,

As know one actually knows how much anthropogenic GHG emissions there will be in coming decades, I will agree to stop posting information on that topic if you do so also, in order not to swamp this thread with information on that topic; which is covered well in other threads of this forum.

Best,
ASLR

And we do read that there so there is no need to repeat them here Ken.

Also the only thing that matters for the earth system is CO2 and CH4 going down on a global level and we are far from that (and 100% EV does not equal 0 CO2 etc).

Then there is a whole discussion on time lines (planetary reality and the IPCCs idea of what will happen might not align).

Do you ever wonder how much of Antarctica would still melt if our CO2 output was magically 0 from tomorrow?

No, kassy, I never wonder that since I know it ain’t gonna happen.
I do wonder if every last ton of Antarctica is going to melt in the real world.

[FrostKing70]

Low oil prices should reduce the growth rate of EV.   If the price war continues, as it appears likely to, at least in the United States I would expect more trucks and SUVs to sell. 

I read that the average age of a car in the US is 11.6 years.  If a large group of oil guzzling vehicles get sold concurrent with low oil prices, it will take a while for them to get out of the fleet.

Average age per:

https://www.statista.com/statistics/261877/average-age-of-passenger-cars-in-the-united-states/

[AbruptSLR]

Antarctic ice shelves have a variety of bathymetry/ice shelf/water column/etc. configurations and thus different Antarctic ice shelves have responded differently to the recent increase in the upwelling of warm CDW (Circumpolar Deep Water) associated with the recent increase in peak westerly wind velocities over the Southern Ocean.  While the PIIS, TEIS and the Thwaites Ice Tongue are examples of ice shelves that have already been significantly impacted by the westerly wind driven increase in upwelled CDW; the linked reference and associated article discuss the findings of field research on the Getz Ice Shelf, that indicates that the geometry of its ice face limits the transmission of the upwelled CDW beneath the ice shelf to the depth-varying (baroclinic) component, which is typically much smaller than the full upwelled flux of CDW.  However, the researchers warn that a projected increase of low-pressure atmospheric systems near such ice faces could increase the flux of warm beneath such ice shelves (as the Getz Ice Shelf) with continued global warming:

A. K. Wåhlin, N. Steiger, E. Darelius, K. M. Assmann, M. S. Glessmer, H. K. Ha, L. Herraiz-Borreguero, C. Heuzé, A. Jenkins, T. W. Kim, A. K. Mazur, J. Sommeria and S. Viboud (26 February 2020), “Ice front blocking of ocean heat transport to an Antarctic ice shelf”, Nature, DOI: 10.1038/s41586-020-2014-5

https://www.nature.com/articles/s41586-020-2014-5

Abstract: "Mass loss from the Antarctic Ice Sheet to the ocean has increased in recent decades, largely because the thinning of its floating ice shelves has allowed the outflow of grounded ice to accelerate. Enhanced basal melting of the ice shelves is thought to be the ultimate driver of change, motivating a recent focus on the processes that control ocean heat transport onto and across the seabed of the Antarctic continental shelf towards the ice. However, the shoreward heat flux typically far exceeds that required to match observed melt rates, suggesting that other critical controls exist. Here we show that the depth-independent (barotropic) component of the heat flow towards an ice shelf is blocked by the marked step shape of the ice front, and that only the depth-varying (baroclinic) component, which is typically much smaller, can enter the sub-ice cavity. Our results arise from direct observations of the Getz Ice Shelf system and laboratory experiments on a rotating platform. A similar blocking of the barotropic component may occur in other areas with comparable ice–bathymetry configurations, which may explain why changes in the density structure of the water column have been found to be a better indicator of basal melt rate variability than the heat transported onto the continental shelf. Representing the step topography of the ice front accurately in models is thus important for simulating ocean heat fluxes and induced melt rates."

See also:

Title: "Physics Shows Antarctic Glacier Ice Walls Are Vital Protection for the Climate"

https://scitechdaily.com/physics-shows-antarctic-glacier-ice-walls-are-vital-protection-for-the-climate/

Extract: "“What we found here is a crucial feedback process: the ice shelves are their own best protection against warm water intrusions. If the ice thins, more oceanic heat comes in and melts the ice shelf, which becomes even thinner etc. It is worrying, as the ice shelves are already thinning because of global air and ocean warming,” says Céline Heuzé, climate researcher at the Department of Earth Sciences of Gothenburg University."

“From the Getz glacier, we are receiving measurements of heat transport in the ocean that correspond with the melting ice being measured by satellites. This also means that the floating glaciers – the ice fronts in particular – are key areas that should be closely monitored. If the ice walls were to disappear, much greater levels of thermal energy would be released towards the ice on land.”

“Consequently, we no longer expect to see a direct link between increasing westerly winds and growing levels of melting ice. Instead, the increased water levels can be caused by the processes that pump up warmer, heavier water to the continental shelf, for example as low-pressure systems move closer to the continent.”

Researchers believe that the studies have provided them with significantly better tools to be able to predict future water levels and create more accurate climate prognoses."

[AbruptSLR]

The analysis at the linked website find that whether considering only long-lived GHG emissions or both long and short-lived GHG emissions from food; it is a good idea to become a vegetarian:

Title: "The carbon footprint of foods: are differences explained by the impacts of methane?"

https://ourworldindata.org/carbon-footprint-food-methane

Extract: "This data suggests that the most effective way to reduce the climate impact of your diet is to eat less meat overall, especially red meat and dairy
…
In this post I want to investigate whether these conclusions depend on the particular metric we rely on to quantify greenhouse gas (GHG) emissions. It could be argued that red meat and dairy have a much higher footprint because its emissions are dominated by methane – a greenhouse gas that is much more potent but has a shorter lifetime in the atmosphere than carbon dioxide. Methane emissions have so far driven a significant amount of warming – with estimates ranging from around 23% to 40% of the total – to date."

[AbruptSLR]

The linked article and WMO State of the Global Climate in 2019 report card indicates that climate change continued advance in 2019:

Title: "We've Officially Passed The Threshold of 1.1 Degree Celsius Warming"

https://www.sciencealert.com/the-last-five-years-were-the-warmest-ever-recorded-again

Extract: "Global average temperatures in 2019 were 1.1 degrees Celsius above pre-industrial levels. Only 2016 was hotter, but that year came at the end of an extreme El Niño, which typically has a warming influence on global temperatures."

See also:

Title: "WMO Statement on the State of the Global Climate in 2019"

https://library.wmo.int/index.php?lvl=notice_display&id=21700#.XmkbKHOSmUk
https://library.wmo.int/doc_num.php?explnum_id=10211

Caption: "Figure 14. Annual (blue) and cumulative (red) mass balance of reference glaciers with more than 30 years of ongoing glaciological measurements. Global mass balance is based on an average for 19 regions to minimize bias towards well-sampled regions. Annual mass changes are expressed in meter water equivalent (m w.e.) which corresponds to tonnes per square meter (1 000 kg m-2) (Source: World Glacier Monitoring Service (WGMS, 2020, updated)."

[AbruptSLR]

For those who want to read more about the International Thwaites Glacier Collaboration (ITGC) five-year program, I provide the following link to a relevant article:

Title: "Investigating Thwaites: the riskiest glacier on Earth"

http://geographical.co.uk/nature/polar/item/3606-investigating-thwaites-the-riskiest-glacier-on-earth

Extract: "Dubbed the riskiest glacier on Earth, an ongoing project to learn more about Thwaites is vital to ensure the accuracy of sea-level rise predictions"

[kassy]

Paleontologists discover solid evidence of formerly elusive abrupt sea-level jump

Meltwater pulses (MWPs) known as abrupt sea-level rise will inevitably affect cities especially those on coastal plains of low elevation. A recent study presented evidence of abrupt sea level change between 11,300-11,000 years ago in the Arctic Ocean, solving the puzzle of second largest meltwater pulse (labelled as ''MWP-1B'' next to the largest and already well understood MWP-1A).

...

The research study discovered a robust evidence of formerly elusive abrupt sea-level jump event during the climatic warming from the last ice age to the current climate state. The study presented evidence of abrupt sea level change between 11,300-11,000 years ago of 40m-80m in Svalbard, the Arctic Ocean. High time-resolution fossil records indicate a sudden temperature rise due to the incursion of warm Atlantic waters and consequent melting of the covering ice sheets. Because of the rebound of formerly suppressed lands underneath great ice load, the sedimentary environment changed from a bathyal setting (having deep-sea species shown in Image 1) to an upper-middle neritic setting (having shallow-marine species shown in Image 2) at the study sites. This is the first solid evidence of relative sea-level change of MWP-1B discovered in ice-proximal areas.

The research group used fossil Ostracoda preserved in two marine sediment cores as a model organism to quantitatively reconstruct the water depth changes in Svalbard in the past 14,000 years, as this small (usually <1 mm) aquatic crustacean is very sensitive to water conditions. Faunal turnovers also reveal temperature and salinity changes associated with the MWP-1B. All ostracode shells in the samples were picked and identified under the microscope, and then the faunal assemblage and species diversity were computed. More than 5,000 specimens and 50 species were recorded in two sediment cores from Storfjorden, Svalbard, where the environment is sensitive to both Arctic and North Atlantic influences.

...

https://www.sciencedaily.com/releases/2020/03/200310094223.htm

[kassy]

I guess this fits here too:

We climate scientists won’t know exactly how the crisis will unfold until it’s too late

...

This long period of stability seems to have ended already. Australia’s climate had been warming rapidly for many decades, and eventually the moment came when record-breaking extreme heat coupled with an exceptionally dry period created the conditions for a series of mega fires.

In all, the fires burned more than 20% of temperate broadleaf forests in New South Wales and Victoria, compared to less than 2% in a typical season. Many of the forests may never recover to their previous state. Other ecosystems may contain similar tipping points.

Predictive models are the lifeblood of climate science, and the foundation upon which political responses to the climate and ecological crisis are often based. But their ability to predict such large-scale disruptive events is severely limited.

For example, the massive scale of the recent Australian bushfires goes beyond what any model used by the Intergovernmental Panel on Climate Change (IPCC) has ever simulated – for the present or the future. In fact, one of us (Wolfgang) has published extensively on future wildfires, and his work found that fire activity in parts of south-eastern Australia would likely increase significantly by the late 21st century. In reality, much more widespread fires occurred some 70 years earlier than predicted.

This isn’t the only case where models used by climate scientists are inadequate. The IPCC’s estimates of how much CO₂ we can still emit to be on the safe side explicitly leave out many known large-scale disruptions or tipping points because of insufficient understanding or because models cannot capture them.

One such tipping event, the unravelling and eventual disappearance of the Amazon rainforest, may already be underway. A new study uses model-aided statistical analysis from past ecosystem collapses and comes to the conclusion that, once triggered, Amazon dieback could take as little as 50 years. Because we lack a full understanding of how exactly such a collapse might unfold, such models are not being included in future projections.

The IPCC’s recent report on the oceans and cryosphere (sea ice, glaciers and ice sheets) still doesn’t report the full possible range of sea level rise exacerbated by a possible collapse of the West Antarctic ice sheet. The IPCC’s range of 0.3 to 1.1 metres by 2100, dependent on emissions scenario, stays markedly below the worst-case scenario of 2.4 metres which resulted from an analysis of experts’ opinions. Zita Sebesvari, one of the report’s lead authors, has admitted that such a worst case scenario cannot be ruled out.

We know quite well that the climate we are about to create resembles that of millions of years ago, but we are mostly ignorant about how fast this will happen and what it means for humans and ecosystems. Yet scientists rarely point out the uncertainties in their predictions – in particular worst-case scenarios that are beyond the capability of models – and prefer to stick to the conservative but firm conclusions that can be drawn from well-established models.

To discuss highly uncertain but potentially catastrophic outcomes is often seen as political fearmongering. But basing the political response to the climate crisis on a series of safe-looking and – in their totality – apparently certain predictions is therefore painting a wholly inadequate picture of the potential risks that the climate and ecological crises pose to humanity and the biosphere.

...

https://theconversation.com/we-climate-scientists-wont-know-exactly-how-the-crisis-will-unfold-until-its-too-late-133400

[AbruptSLR]

To those who follow this thread, the linked article and associated reference come a no surprise:

Title: "Six-fold jump in polar ice loss lifts global oceans"

https://phys.org/news/2020-03-six-fold-polar-ice-loss-global.html

Extract: "Greenland and Antarctica are shedding six times more ice than during the 1990s, driving sea level rise that could see annual flooding by 2100 in regions home today to some 400 million people, scientists have warned."

See also:

Shepherd, A., Ivins, E., Rignot, E. et al. Mass balance of the Greenland Ice Sheet from 1992 to 2018. Nature 579, 233–239 (2020). https://doi.org/10.1038/s41586-019-1855-2

https://www.nature.com/articles/s41586-019-1855-2

Abstract: "The Greenland Ice Sheet has been a major contributor to global sea-level rise in recent decades, and it is expected to continue to be so3. Although increases in glacier flow and surface melting have been driven by oceanic and atmospheric warming, the magnitude and trajectory of the ice sheet’s mass imbalance remain uncertain. Here we compare and combine 26 individual satellite measurements of changes in the ice sheet’s volume, flow and gravitational potential to produce a reconciled estimate of its mass balance. The ice sheet was close to a state of balance in the 1990s, but annual losses have risen since then, peaking at 345 ± 66 billion tonnes per year in 2011. In all, Greenland lost 3,902 ± 342 billion tonnes of ice between 1992 and 2018, causing the mean sea level to rise by 10.8 ± 0.9 millimetres. Using three regional climate models, we show that the reduced surface mass balance has driven 1,964 ± 565 billion tonnes (50.3 per cent) of the ice loss owing to increased meltwater runoff. The remaining 1,938 ± 541 billion tonnes (49.7 per cent) of ice loss was due to increased glacier dynamical imbalance, which rose from 46 ± 37 billion tonnes per year in the 1990s to 87 ± 25 billion tonnes per year since then. The total rate of ice loss slowed to 222 ± 30 billion tonnes per year between 2013 and 2017, on average, as atmospheric circulation favoured cooler conditions and ocean temperatures fell at the terminus of Jakobshavn Isbræ. Cumulative ice losses from Greenland as a whole have been close to the rates predicted by the Intergovernmental Panel on Climate Change for their high-end climate warming scenario17, which forecast an additional 70 to 130 millimetres of global sea-level rise by 2100 compared with their central estimate."

[AbruptSLR]

Paleontologists discover solid evidence of formerly elusive abrupt sea-level jump

...

https://www.sciencedaily.com/releases/2020/03/200310094223.htm

For those who do not like to click on links, I provide the following reference that presents findings that kassy discussed.  Also, I note that much of the abrupt sea level rise contributions for the Meltwater pulses during the transition to the Holocene came from marine glaciers situated in various portions of the current Antarctic continental shelf.

Skye Yunshu Tian, Moriaki Yasuhara, Yuanyuan Hong, Huai-Hsuan M. Huang, Hokuto Iwatani, Wing-Tung Ruby Chiu, Briony Mamo, Hisayo Okahashi, Tine L. Rasmussen. Deglacial–Holocene Svalbard paleoceanography and evidence of meltwater pulse 1B. Quaternary Science Reviews, 2020; 233: 106237 DOI: 10.1016/j.quascirev.2020.106237

https://www.sciencedirect.com/science/article/abs/pii/S0277379119309485?via%3Dihub

Abstract
Better understanding of deglacial meltwater pulses (MWPs) is imperative for future predictions of human-induced warming and abrupt sea-level change because of their potential for catastrophic damage. However, our knowledge of the second largest meltwater pulse MWP-1B that occurred shortly after the start of the Holocene interglacial remains very limited. Here, we studied fossil ostracods as paleoenvironmental indicators of water depth, salinity, and temperature in two marine sediment cores from Storfjorden, Svalbard margin (the Arctic Ocean), to investigate near-field (i.e. areas located beneath continental ice sheets at the Last Glacial Maximum) evidence of MWP-1B. The depositional environment changed from a cold bathyal environment to a warmer bathyal environment at ∼11,300 yr BP indicating incursion of warm Atlantic water into the Nordic seas, and eventually to a cold neritic environment by ∼11,000 yr BP because of melting of the Svalbard-Barents Sea ice sheet and resultant isostatic rebound. This process corresponds to rapid relative sea-level fall of 40–80 m of MWP-1B from ∼11,300 to 11,000 yr BP.

[AbruptSLR]

The linked article discusses a new government-industries guide for UK pension funds as to how they might assess up-coming climate change risk, and they recommend including an analysis of at least one scenario assuming a "no transition, pathway to 4+^oC":

Title: "UK pension trustees presented with guide to climate-related risks"

https://www.ipe.com/news/uk-pension-trustees-presented-with-guide-to-climate-related-risks/10044243.article

Extract: "The Pensions Climate Risk Industry Group (PCRIG), as it was named, described the guide, as “structured sequentially based on the way a pension trustee board might typically approach decision-making”.
…
It recommends scenario analysis as “a helpful technique for trustees to assess their scheme’s resilience to different future outcomes”. Three scenarios are recommended: an orderly transition to a 2⁰C or lower scenario; an abrupt transition to a 2⁰C or lower scenario, and a “no transition, pathway to 4+⁰C scenario”.

[kassy]

I think the goal is to offer 3 scenarios of policy changes.
Option 3 offers lots of risk too. It is where they should prize in the loss of all beachfront property etc.

Bit more detail on:
https://www.gov.uk/government/consultations/aligning-your-pension-scheme-with-the-tcfd-recommendations/tcfd-for-trustees-of-pension-schemes-quick-start-guide

[AbruptSLR]

I think the goal is to offer 3 scenarios of policy changes.
...

If it is not clear in the cartoon, the figure with the hat is the decision maker and the figures without hats are consensus climate scientists.

[AbruptSLR]

While the PALeo constraints on SEA level rise (PALSEA) program will not be complete until the end of 2021; it is still worth remembering that the paleo-record contains numerous instances of extremely rapid sea level rise with durations ranging from decades to centuries.  It will be good to learn what PALSEA finally reports after 2021:

Title: "PALSEA - PALeo constraints on SEA level rise"

http://pastglobalchanges.org/science/wg/palsea/intro

Extract: "PALSEA is a continuation of PALSEA1, which operated from 2008 to 2012, and PALSEA2, which operated from 2013-2017.
This third phase of the group runs from 2019-2021.
…
Sea-level rise due to polar ice-sheet retreat in a warming world is one of the most important, and uncertain aspects associated with future climate change. The geologic record, features major, and sometimes rapid, changes in ice sheets and sea level that offers an excellent opportunity to assess the rates, magnitudes, and processes involved in ice-sheet and sea-level change, as well as their connection to climate forcings."

See also:

Title: "Ocean Circulation and Carbon Cycling"

http://pastglobalchanges.org/products/pages-magazine/12916

Edit: Also, I note that the image is from 2015 when GMSTA was about 0.9C but it is now officially over 1.1C.

[AbruptSLR]

As my schedule has become busier than previously, I will likely maker fewer posts than recent years.  Thus, I thought I would make a somewhat more philosophical post today by raising the question of what does the Paris Agreement mean when it set a goal of staying 'well below 2C'?

Furthermore, I raise the following sub-topics:

1. As I have previously noted the Paris Agreement probably would not have even adopted the 'well below 2C' goal if it had not been concerned about fat right-tailed risks, which raises the question of what right-screwed PDF did Paris assume and how much has the shape of that PDF changed since 2015?

2. What baseline did Paris assume and what baseline should have it used to measure 2C?

3. Evidently, Paris did not feel comfortable defining what it meant by 'well below' otherwise, it would have used a specific value, or a specific range, like 0.25C to 0.4C below 2C.  Possible reasons that Paris may not have felt comfortable include that 'well below' depends on:
a) Which socio-economic pathway we collectively choose to follow;
b) How much climate variability increases with increasing GMSTA and,
c) How much confidence did Paris have in the AR5 projections w.r.t. variables like: climate sensitivity, ice-climate feedbacks and initial boundary conditions.

4. What confidence range did Paris assume was appropriate when considering issues like:
a) Tipping points,
b) Reversibility and
c) Socio-economic fragility.

5. Much of the current progress in reduction in CO2 emissions has been achieved by substituting coal with natural gas; thus:
a) Do decision makers currently think that collectively we have made more progress in the fight against climate change than we actually have because we are discounting the methane emissions associated with the increased use of natural gas?
b) Will it become more difficult to reduce crude oil and natural gas consumption that it was to reduce coal consumption because of a lack of economically available substitutes?
c) If economic times become harder, will coal consumption increase again in future years?

6. If consensus climate scientists have underestimated the negative feedback associated with anthropogenic aerosol emissions; will future reductions in anthropogenic aerosol emissions drive GMSTA closer to 'well below 2C' even with declining GHG emissions?

[Hefaistos]

Antarctic bottom water is in a cooling trend for the last 5 years or so, not warming, according to this important paper:

"Stabilization of dense Antarctic water supply to the Atlantic Ocean overturning circulation"
by Abrahamsen et al, published recently in Nature.

https://www.nature.com/articles/s41558-019-0561-2

Abstract

The lower limb of the Atlantic overturning circulation is resupplied by the sinking of dense Antarctic Bottom Water (AABW) that forms via intense air–sea–ice interactions next to Antarctica, especially in the Weddell Sea. In the last three decades, AABW has warmed, freshened and declined in volume across the Atlantic Ocean and elsewhere, suggesting an ongoing major reorganization of oceanic overturning. However, the future contributions of AABW to the Atlantic overturning circulation are unclear. Here, using observations of AABW in the Scotia Sea, the most direct pathway from the Weddell Sea to the Atlantic Ocean, we show a recent cessation in the decline of the AABW supply to the Atlantic overturning circulation. The strongest decline was observed in the volume of the densest layers in the AABW throughflow from the early 1990s to 2014; since then, it has stabilized and partially recovered. We link these changes to variability in the densest classes of abyssal waters upstream. Our findings indicate that the previously observed decline in the supply of dense water to the Atlantic Ocean abyss may be stabilizing or reversing and thus call for a reassessment of Antarctic influences on overturning circulation, sea level, planetary-scale heat distribution and global climate.

Figure of researched area, and byline: "a, Map of the Scotia Sea, with the South and North Scotia Ridges marked by black lines. The SR1b section and the part of the A23 section in the Scotia Sea are marked in red. The parts of the A23 and SR4 sections in the Weddell Sea used here are marked in purple. Yellow arrows show schematic pathways of AABW from refs. 14,35,36. The bathymetry data are from the GEBCO_2014 Grid, v. 20150318.
b, Map showing the global extent (vertically integrated fraction) of AABW, based on the methods of Johnson10 using updated data from the World Ocean Atlas 201337,38,39,40, on a Lambert azimuthal equal-area projection. The area shown in a is outlined in blue."

[Hefaistos]

More on cooling trends in parts of the Ocean:
" Reduction in Ocean Heat Transport at 26°N since 2008 Cools the Eastern Subpolar Gyre of the North Atlantic Ocean" by Bryden et al, in American Meterological Society (AMS), january 2020

Abstract
"Northward ocean heat transport at 26°N in the Atlantic Ocean has been measured since 2004. The ocean heat transport is large—approximately 1.25 PW, and on interannual time scales it exhibits surprisingly large temporal variability. There has been a long-term reduction in ocean heat transport of 0.17 PW from 1.32 PW before 2009 to 1.15 PW after 2009 (2009–16) on an annual average basis associated with a 2.5-Sv (1 Sv ≡ 106 m3 s−1) drop in the Atlantic meridional overturning circulation (AMOC). The reduction in the AMOC has cooled and freshened the upper ocean north of 26°N over an area following the offshore edge of the Gulf Stream/North Atlantic Current from the Bahamas to Iceland. Cooling peaks south of Iceland where surface temperatures are as much as 2°C cooler in 2016 than they were in 2008. Heat uptake by the atmosphere appears to have been affected particularly along the path of the North Atlantic Current. For the reduction in ocean heat transport, changes in ocean heat content account for about one-quarter of the long-term reduction in ocean heat transport while reduced heat uptake by the atmosphere appears to account for the remainder of the change in ocean heat transport."

The paper reports a cooling of more than 2°C in just 8 years (2008-2016) for nearly the entire ocean region south of Iceland.
The cooling persists year-round and extends from the surface down to 800 m depth.
From 40°N to 70°N, and from 40°W to 0°W, average temperatures have plunged 0.6°C from 2008 to 2016 – also to depths of 800 m.

https://doi.org/10.1175/JCLI-D-19-0323.1
https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-19-0323.1

[AbruptSLR]

The linked reference indicates that most likely future Arctic sea ice losses will increase the frequency of Central Pacific El Nino events; which is particularly bad news for WAIS stability due to the like increase of Equatorial Pacific energy advected to West Antarctica via atmospheric Rossby Waves:

Hyerim Kim et al. (11 March 2020), "Arctic sea ice loss as a potential trigger for Central Pacific El Niño events", Geophysical Research Letters, https://doi.org/10.1029/2020GL087028

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL087028?af=R

Abstract
Little attention has been paid to the influence of Arctic sea ice loss on climate variability in the tropical Pacific. By analyzing observational datasets, we hypothesized that anomalous Arctic sea ice concentration variations have the potential to influence tropical Pacific sea surface temperature (SST) variability via atmosphere‐ocean coupled processes in the eastern subtropical North Pacific. To test this hypothesis, we conducted idealized model experiments with 15 ensembles in which historical SSTs for 1951‐2016 were restored in the Arctic only with different initial conditions. We found that a positive phase of North Pacific Oscillation–like atmospheric circulation, which is modulated by a sea ice reduction in the Pacific Arctic sector, triggers El Niño–like warming in the central tropical Pacific. This implies that connections between the Arctic and the tropics should be considered for further understanding of changes in El Niño and other tropical Pacific climate variability in a changing climate.

[AbruptSLR]

While the linked reference focuses on how SLR will influence estuarine hydrodynamics in populated areas; I note that the indicated changes in parameters including: tidal range and tidal bores will also serve to reduce the stability of key Antarctic marine glaciers and key Greenland marine terminating glaciers:

Danial Khojasteh et al. (16 March 2020), "Sea level rise and estuarine tidal dynamics: A review", Earth-Science Reviews, 103166, https://doi.org/10.1016/j.earscirev.2020.103166

https://www.sciencedirect.com/science/article/abs/pii/S0012825219307640?dgcid=rss_sd_all

Highlights
• A critical review is provided on how sea level rise (SLR) will influence estuarine hydrodynamics and knowledge gaps are identified.
• Current literature is inconclusive regarding the influences of SLR on estuarine hydrodynamics.
• Hydrodynamic modelling, rather than static approaches, is needed when assessing estuarine responses to SLR.
• Under SLR, the estuarine shape, bathymetry, friction, reflection and tidal resonance influence estuarine hydrodynamic parameters, including tidal range, tidal wave asymmetry, saltwater intrusion, and mixing.
• A conceptual framework is provided to highlight the likely responses of different types of estuaries to SLR.

Abstract
Sea level rise (SLR) poses a hazard to assets, ecosystems, and economies in coastal zones, including over 600 million people worldwide who currently reside near estuaries. SLR implications include more frequent oceanic inundation, shoreline erosion, and the failure of stormwater and drainage infrastructure. To predict and manage these potential impacts, a comprehensive understanding of SLR on estuarine hydrodynamics was assessed via a review of existing theory and available literature. The review highlighted that the most common method of assessing SLR impacts in estuaries has been via simplistic static approaches, such as elevation-based water level projections, that are of limited value as they do not include fundamental hydrodynamic responses to estuarine entrance restriction, geometry, bathymetry, friction, and floodplain connectivity. A much smaller number of studies have conducted hydrodynamic modelling of SLR in estuaries showing that estuarine shape, bathymetry, friction, reflection and resonance have a strong influence on estuarine hydrodynamic parameters such as tidal range and asymmetry, saltwater intrusion, and mixing. The majority of the existing SLR estuarine hydrodynamic literature has focused on the influence of estuarine tidal parameters providing conflicting results in terms of influence of SLR on estuarine tidal dynamics and patterns. For most studies, the saltwater intrusion length of the estuary was shown to increase under SLR, whereas very few studies examined the influence of SLR on estuary entrance condition, friction, reflection, resonance, and mixing. A significant knowledge gap identified was the lack of a generic framework to conceptualise how different estuary types respond to SLR based on shape, bathymetry, and entrance condition. To this aim, several conceptual models are introduced to highlight the role of tidal friction, resonance and tidal wave penetration in estuaries under SLR.

[AbruptSLR]

Many pundits ignore effective radiative forcing when discussing the likely impacts of reactive gases (like methane) and aerosols on GMSTA projections.  Nevertheless, these impacts are real and the linked reference helps to quantify such effective radiative forcings:

Thornhill, G. D., Collins, W. J., Kramer, R. J., Olivié, D., O'Connor, F., Abraham, N. L., Bauer, S. E., Deushi, M., Emmons, L., Forster, P., Horowitz, L., Johnson, B., Keeble, J., Lamarque, J.-F., Michou, M., Mills, M., Mulcahy, J., Myhre, G., Nabat, P., Naik, V., Oshima, N., Schulz, M., Smith, C., Takemura, T., Tilmes, S., Wu, T., Zeng, G., and Zhang, J.: Effective Radiative forcing from emissions of reactive gases and aerosols – a multimodel comparison, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2019-1205, in review, 2020.

https://www.atmos-chem-phys-discuss.net/acp-2019-1205/

Abstract. This paper quantifies the effective radiative forcing from CMIP6 models of the present-day anthropogenic emissions of NOx, CO, VOCs, SO2, NH3, black carbon and primary organic carbon. Effective radiative forcing from pre-industrial to present-day changes in the concentrations of methane, N2O and halocarbons are quantified and attributed to their anthropogenic emissions.

Emissions of reactive species can cause multiple changes in the composition of radiatively active species: tropospheric ozone, stratospheric ozone, secondary inorganic and organic aerosol and methane. We therefore break down the ERFs from each emitted species into the contributions from the composition changes.

The 1850 to 2014 mean ERFs are 1.1 ± 0.07 W m−2 for sulfate, −0.24 ± 0.01 W m−2 for organic carbon (OC), and 0.15 ± 0.04 W m−2 for black carbon (BC), and for the aerosols combined it is −0.95 ± 0.03 W m−2. The means for the reactive gases are 0.69 ± 0.04 W m−2 for methane (CH4), 0.06 ± 0.04 W m−2 for NOx, −0.09 ± 0.03 W m−2 for volatile organic carbons (VOC), 0.16 ± 0.03 W m−2 for ozone (O3), 0.27 W m−2 for nitrous oxide (N2O) and −0.02 ± 0.06 W m−2 for hydrocarbon (HC). Differences in ERFs calculated for the different models reflect differences in the complexity of their aerosol and chemistry schemes, especially in the case of methane where tropospheric chemistry captures increased forcing from ozone production.

[AbruptSLR]

Paul Ehrlich makes some good points in the linked article about our current, and likely future, global situation:

Title: "Paul R. Ehrlich: A pandemic, planetary reckoning, and a path forward"

https://www.dailyclimate.org/pandemic-population-covid-19-2645545497.html

Extract: "The COVID-19 pandemic is bringing environmental destruction and the deterioration of social and cultural systems into sharp focus. But we can learn from this.
…
But nothing is more impractical than civilization trying to continue business as usual as it circles the drain.

The current pandemic disaster may end up damping down consumerism and improving the environment – there are reports of the lethal smog usually blanketing some Chinese cities clearing during pandemic lockdowns.

Maybe there's some chance that people are learning lessons.

We can always hope."

[AbruptSLR]

People want wealth and wealthy people use more energy as discussed in the linked reference:

Oswald, Y., Owen, A. & Steinberger, J.K. Large inequality in international and intranational energy footprints between income groups and across consumption categories. Nat Energy 5, 231–239 (2020). https://doi.org/10.1038/s41560-020-0579-8

https://www.nature.com/articles/s41560-020-0579-8

Abstract: "Inequality in energy consumption, both direct and indirect, affects the distribution of benefits that result from energy use. Detailed measures of this inequality are required to ensure an equitable and just energy transition. Here we calculate final energy footprints; that is, the energy embodied in goods and services across income classes in 86 countries, both highly industrialized and developing. We analyse the energy intensity of goods and services used by different income groups, as well as their income elasticity of demand. We find that inequality in the distribution of energy footprints varies across different goods and services. Energy-intensive goods tend to be more elastic, leading to higher energy footprints of high-income individuals. Our results consequently expose large inequality in international energy footprints: the consumption share of the bottom half of the population is less than 20% of final energy footprints, which in turn is less than what the top 5% consume."

[nanning]

People want wealth and wealthy people use more energy as discussed in the linked reference

Best strategy but very difficult for wealthy people: Use less energy.

[gerontocrat]

People want wealth and wealthy people use more energy as discussed in the linked reference

Best strategy but very difficult for wealthy people: Use less energy.

The objective of Governments, Central Banks and the Private Sector Oligarchs is to get through the covid-19 ASAP, enter a solid V-shaped recovery and BAU by the end of the year.

This will no doubt include throwing a few squillions of dosh at the fossil fuel industries, legacy auto-makers and aviation etc.  And guess who in the end will have to pay? You, me, the kids,and  their kids.
_______________________________________________________-
There is something in the King James Bible about the sins of the fathers being visited on the children unto the 3rd and 4th generations? (A much misquoted and misused quote).

[AbruptSLR]

...
The objective of Governments, Central Banks and the Private Sector Oligarchs is to get through the covid-19 ASAP, enter a solid V-shaped recovery and BAU by the end of the year.

This will no doubt include throwing a few squillions of dosh at the fossil fuel industries, legacy auto-makers and aviation etc.  And guess who in the end will have to pay? You, me, the kids,and  their kids.
...

Maybe we should all feel lucky that the novel corona virus doesn't have the multi-billion dollar disinformation campaign budgets that the fossil fuel industry uses each year to delay effective climate action, otherwise, we wouldn't be entering a solid V-shaped recovery. 

[AbruptSLR]

GRACE and GRACE-FO satellites indicate that Greenland's ice mass loss in the summer of 2019 was twice that of the 2002-2019 average.  When combined with the observed high ice mass loss rates from West Antarctica, that is not good news:

Title: "GRACE, GRACE-FO Satellite Data Track Ice Loss at the Poles"

https://scitechdaily.com/nasa-satellites-track-how-quickly-the-poles-are-melting-greenland-lost-600-billion-tons-of-ice-in-2-months/

Extract: "During the exceptionally warm Arctic summer of 2019, Greenland lost 600 billion tons of ice — enough to raise global sea levels by nearly a tenth of an inch (2.2 millimeters) in just two months, a new study shows.

Led by scientists at NASA’s Jet Propulsion Laboratory and the University of California, Irvine, the study also concludes that Antarctica continues to lose mass, particularly in the Amundsen Sea Embayment and the Antarctic Peninsula on the western part of the continent; however, those losses have been partially offset by gains from increased snowfall in the northeast.
…
For context, last summer’s losses are more than double Greenland’s 2002-2019 yearly average.
“In Antarctica, the mass loss in the west proceeds unabated, which will lead to an even further increase in sea level rise,” Velicogna said. “But we also observe a mass gain in the Atlantic sector of East Antarctica caused by an uptick in snowfall, which helps mitigate the enormous increase in mass loss that we have seen in the last two decades on other parts of the continent.”"

[AbruptSLR]

The linked reference, and the associated linked article, indicates that the Denman Glacier in East Antarctica is currently retreating relatively rapidly, and that it could be destabilized if modified CDW keeps causing the grounding line to retreat:

V. Brancato et al. Grounding line retreat of Denman Glacier, East Antarctica, measured with COSMO-SkyMed radar interferometry data, Geophysical Research Letters (2020). DOI: 10.1029/2019GL086291

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL086291

Abstract
Denman Glacier, East Antarctica, holds an ice volume equivalent to a 1.5 m rise in global sea level. Using satellite radar interferometry from the COSMO‐SkyMed constellation, we detect a 5.4±0.3 km grounding line retreat between 1996 and 2017‐2018. A novel reconstruction of the glacier bed topography indicates that the retreat proceeds on the western flank along a previously unknown 5 km wide, 1,800 m deep trough, deepening to 3,400 m below sea level. On the eastern flank, the grounding line is stabilized by a 10 km wide ridge. At tidal frequencies, the grounding line extends over a several kilometer‐wide grounding zone, enabling warm ocean water to melt ice at critical locations for glacier stability. If warm, modified Circumpolar Deep Water reaches the sub‐ice‐shelf cavity and continues to melt ice at a rate exceeding balance conditions, the potential exists for Denman Glacier to retreat irreversibly into the deepest, marine‐based basin in Antarctica.

Plain Language Summary
Using satellite radar data from the Italian COSMO‐SkyMed constellation, we document the grounding line retreat of Denman Glacier, a major glacier in East Antarctica that holds an ice volume equivalent to a 1.5 m global sea level rise. The grounding line is retreating asymmetrically. On the eastern flank, the glacier is protected by a subglacial ridge. On the western flank, we find a deep and steep trough with a bed slope that makes the glacier conducive to rapid retreat. If warm water continues to induce high rates of ice melt near the glacier grounding zone, the potential exists for Denman Glacier to undergo a rapid and irreversible retreat, with major consequences for sea level rise.

Key Points
•   CSK interferometric SAR observations of Denman Glacier, East Antarctica, reveal a 5.4±0.3 km grounding line retreat in the last twenty years
•   Denman Glacier is retreating along a deep trough, with a retrograde bed slope, deepening to 3.4 km below sea level, one of the deepest basins in Antarctica
•   The retrograde glacier bed and likely presence of warm water in the sub‐ice‐shelf cavity makes this region likely prone to marine instability

See also:

Title: "East Antarctica's Denman Glacier has retreated almost 3 miles over last 22 years"

https://phys.org/news/2020-03-east-antarctica-denman-glacier-retreated.html

Extract: "East Antarctica's Denman Glacier has retreated 5 kilometers, nearly 3 miles, in the past 22 years, and researchers at the University of California, Irvine and NASA's Jet Propulsion Laboratory are concerned that the shape of the ground surface beneath the ice sheet could make it even more susceptible to climate-driven collapse.:

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The linked article discusses the possibility that as an economic stimulus measure associated with the novel corona virus outbreak, China's 14th five-year plan may (or may not) promote investments in coal-fire power plants.  All I can say is that I hope that other national leaders around the world do not possibly give in to similar temptations to simulate their economies by returning to their old habits of subsidizing/promoting the use of fossil fuels:

Title: "Analysis: Will China build hundreds of new coal plants in the 2020s?"

https://www.carbonbrief.org/analysis-will-china-build-hundreds-of-new-coal-plants-in-the-2020s

Extract: "China’s 14th five-year plan (FYP), setting out its national goals for 2021-2025, will arguably be one of the world’s most important documents for global efforts to tackle climate change.

The overarching plan for economic and social development in the world’s largest emitter is to be finalised and approved in early 2021, followed by more detailed sectoral targets over the next year. A power sector plan can be expected around winter 2021-22.

Ahead of the FYP’s publication, powerful stakeholders, such as the network operator State Grid and industry body the China Electricity Council, are lobbying for targets that would allow hundreds of new coal-fired power stations to be built. And a recent update to the “traffic light system” for new coal-power construction signaled further relaxation of permitting.
This is all despite significant overcapacity in the sector, with more than half of coal-power firms already loss-making and with typical plants running at less than 50% of their capacity.
…
As the country grapples with the coronavirus pandemic, however, controls on overcapacity may be vulnerable to the political priority of propping up economic growth. As a result, the restraints on another coal power boom are likely to be financial and economic, rather than regulatory.
…
Many experts and industry bodies argue for a move away from top-down targets and controls, to investment driven by market forces. However, the spending needed to fuel a new stimulus program can only be mobilized if investment is directed at the behest of the state, rather than the market – as a rule, China does not fund stimulus with on-budget spending, but by directing state-owned enterprises and commercial banks to spend more. In these circumstances, lack of controls on capacity additions runs a high risk of over-investment.

For example, efforts to control overcapacity might be vulnerable to the political priority of boosting investment spending to reach economic targets. An indication of this was the loosening of “traffic lights” for new coal-plant approvals, published by the National Energy Administration in February.
…
A new wave of coal power in China would pose clear risks for global efforts to limit climate change and could greatly complicate the country’s own energy transition. Yet even if the 14th five-year plan targets another coal boom, it could end up falling short due to economic and financial constraints.

There is a parallel in the 12th five-year plan. This created major overcapacity in the sector, but still fell far short of the target set for coal-power growth. Such an outcome would, however, create significant uncertainty, both for the domestic power industry and the international community."

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The linked reference (& associated article) estimates that previous estimates of methane emissions associated with coal mining are about half of what they actually are, and that abandoned mine methane (AMM) emissions will continue for long after the coal mines are shut-down.  This is not good news:

Kholod, N. et al. (2020) Global methane emissions from coal mining to continue growing even with declining coal production, Journal of Cleaner Production, doi:10.1016/j.jclepro.2020.120489

https://www.sciencedirect.com/science/article/pii/S0959652620305369

Highlights
• This study presents estimates of global coal mine methane emissions through 2100.
• Methane emissions related to coal extraction are higher than reported from previous estimates.
• Coal mines continue emitting methane even if coal production is ceased.
• Evidence-based emission factors are applied to account for increasing mining depth.
• A new methodology for calculating emissions from abandoned mines is proposed.

Abstract
This paper presents projections of global methane emissions from coal mining under different coal extraction scenarios and with increasing mining depth through 2100. The paper proposes an updated methodology for calculating fugitive emissions from coal mining, which accounts for coal extraction method, coal rank, and mining depth and uses evidence-based emissions factors. A detailed assessment shows that coal mining-related methane emissions in 2010 were higher than previous studies show. This study also uses a novel methodology for calculating methane emissions from abandoned coal mines and represents the first estimate of future global methane emissions from those mines. The results show that emissions from the growing population of abandoned mines increase faster than those from active ones. Using coal production data from six integrated assessment models, this study shows that by 2100 methane emissions from active underground mines increase by a factor of 4, while emissions from abandoned mines increase by a factor of 8. Abandoned mine methane emissions continue through the century even with aggressive mitigation actions.

See also:

Title: "Coal mines emit more methane than oil-and-gas sector, study finds"

https://www.carbonbrief.org/coal-mines-emit-more-methane-than-oil-and-gas-sector-study-finds

Extract: "Methane emissions from coal mines could be more than double previous estimates, according to a new study."
…
The authors also note that, for the first time, they developed a methodology for estimating global methane emissions from old mining sites, suggesting a considerable role for abandoned mine methane (AMM), which in the past has been largely ignored. When factoring this in, coal methane emissions in 2020 rise to 114Mt.
…
“When active mines are closed, it is important to preserve information on the mine and prepare the mine to extract AMM in the future…it is clear that methane from closed mines will be a problem for years to come.”

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The linked reference discusses state of the art work on modeling geothermal heat flow in Antarctica.  The attached summary image makes it clear that the findings are not good news for the stability of key portions of the WAIS:

Burton-Johnson, A., Dziadek, R., and Martin, C.: Geothermal heat flow in Antarctica: current and future directions, The Cryosphere Discuss., https://doi.org/10.5194/tc-2020-59, in review, 2020.

https://www.the-cryosphere-discuss.net/tc-2020-59/
https://www.the-cryosphere-discuss.net/tc-2020-59/tc-2020-59.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 extract GHF, 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 beneath the interior of the East Antarctic Ice Sheet (the region most sensitive to GHF variation) via long-wavelength microwave emissivity. 3) Estimate GHF from inverse glaciological modelling, constrained by evidence for basal melting. 4) Revise geophysically-derived GHF estimates using a combination of Curie depth, seismic, and thermal isostasy models. 5) 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. And 6) continue international interdisciplinary communication and data access.

Caption: "Fig. 16. Difference in heat flow values between the most recent magnetic (Martos et al., 2017) and seismic (An et al., 2015b) heat flow models."

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The linked reference finds 60% more subglacial lakes in the Ellsworth Subglacial Highlands than previously assumed and also finds that the water catchment area for the Thwaites Glacier is much larger than previously assumed (see attached image). Both of these findings imply that current consensus models for the WAIS underestimate the risks for increasing ice mass loss with continued global warming.

Napoleoni, F., Jamieson, S. S. R., Ross, N., Bentley, M. J., Rivera, A., Smith, A. M., Siegert, M. J., Paxman, G. J. G., Gacitúa, G., Uribe, J. A., Zamora, R., Brisbourne, A. M., and Vaughan, D. G.: Subglacial lakes and hydrology across the Ellsworth Subglacial Highlands, West Antarctica, The Cryosphere Discuss., https://doi.org/10.5194/tc-2020-68, in review, 2020.

https://www.the-cryosphere-discuss.net/tc-2020-68/
https://www.the-cryosphere-discuss.net/tc-2020-68/tc-2020-68.pdf

Abstract. Subglacial water plays an important role in ice sheet dynamics and stability. It is often located at the onset of ice streams and has the potential to enhance ice flow downstream by lubricating the ice-bed interface. The most recent subglacial lake inventory of Antarctica mapped nearly 400 lakes, of which ~ 14 % are found in West Antarctica. Despite the potential importance of subglacial water for ice dynamics, there is a lack of detailed subglacial water characterization in West Antarctica. Using radio-echo sounding data, we analyse the ice-bed interface to detect subglacial lakes. We report 37 previously uncharted subglacial lakes and present a systematic analysis of their physical properties. This represents a ~ 60 % increase in subglacial lakes in the region. Additionally, a new digital elevation model of basal topography was built and used to create a detailed hydropotential model of Ellsworth Subglacial Highlands to simulate the subglacial hydrological network. This approach allows us to characterize basal hydrology, subglacial water catchments and connections between them. Furthermore, the simulated subglacial hydrological catchments of Rutford Ice Stream, Pine Island Glacier and Thwaites Glacier do not match precisely with their ice surface catchments.

Extract: "We observe that most of the subglacial water draining towards ASE is routed through the Bentley Subglacial Trench in the upper part of the hydrological catchment and driven through the Byrd Subglacial Basin towards the trunk of Thwaites Glacier. The high topography in the mid PIG catchment (Vaughan et al., 2006) means that the hydrological drainage system does not link to the faster flowing trunk of PIG. Instead, the basal hydrological system is captured by Thwaites. This drainage pattern has two main implications. Firstly, the subglacial hydrological catchments of PIG and Thwaites do not correspond to the ice catchments; they do not coincide either in position or size. Secondly, the hydrological system of TG trunk (Schroeder et al., 2013) may be fed by water sourced in the upper glaciological catchment of PIG, within the ESH. Any change in the water catchment of the TG, at the head of PIG, could therefore have important glaciological consequences for the ice dynamics of Thwaites Glacier and the wider ASE. This is particularly critical since the subglacial water drainage area of TG is bigger than previously thought and recent investigations (e.g., Smith et al., 2017) have demonstrated the presence of active subglacial lakes, in a cascade system-type, beneath the trunk of TG. Any water accumulation/drainage (e.g., chain of active subglacial lakes) in this area may affect the basal friction of the ice and therefore the ice flow velocity."

Partial Caption: "The red line indicates the boundary of the water catchment. The blue lines show the subglacial water drainage and the arrows indicates the general flow direction."

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The linked reference indicates that the interaction of oceanic induced ice melting and the calving of tidewater glaciers is not linear.  This implies that most consensus climate models of this interaction err on the side of least drama at higher oceanic ice melting rates (such as for the PIG and the Thwaites Glacier):

R. Mercenier, M.P. Lüthi  and A. Vieli (22 March 2020), "How oceanic melt controls tidewater glacier evolution", Geophysical Research Letters, https://doi.org/10.1029/2019GL086769

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL086769

Abstract
The recent rapid retreat of many Arctic outlet glaciers has been attributed to increased oceanic melt, but the relationship between oceanic melt and iceberg calving remains poorly understood. Here, we employ a transient finite‐element model that simulates oceanic melt and ice break‐off at the terminus. The response of an idealized tidewater glacier to various submarine melt rates and seasonal variations is investigated. Our modeling shows that for zero to low oceanic melt, the rate of volume loss at the front is similar or higher than for intermediate oceanic melt rates. Only very high melt rates lead to increasing volume losses. These results highlight the complex interplay between oceanic melt and calving and question the general assumption that increased submarine melt leads to higher calving fluxes and enhanced retreat. Models for tidewater glacier evolution should therefore consider calving and oceanic melt as tightly coupled processes rather than as simple, additive parametrizations.

Key Points
•   The effect of oceanic melt on tidewater glacier evolution is investigated using a transient calving model based on damage evolution
•   Oceanic melt has a complex influence on tidewater glacier evolution and increased melt rates may not necessarily lead to more volume loss
•   The calving and oceanic melt processes are not additive which has implications on the forcing of models for tidewater glacier evolution

[kassy]

Shrinking Ozone Hole, Climate Change Are Causing Atmospheric “Tug of War”

The Southern Hemisphere jet stream is shifting, bringing more rain to some spots and less to others

The notorious Antarctic “ozone hole” sparked worldwide concern after its discovery in the 1980s, and for good reason — declining ozone allows harmful ultraviolet radiation to reach the Earth’s surface, a major threat to public health.

But the ozone hole had another effect on the planet: It caused major atmospheric changes in the Southern Hemisphere.

With less ozone trapping solar radiation higher in the atmosphere, the stratosphere began to cool. The jet stream shifted toward the South Pole. The warm, wet tropics expanded, and the dry zone below the tropics shifted southward, as well. Weather patterns in certain parts of the Southern Hemisphere began to change.

https://www.scientificamerican.com/article/shrinking-ozone-hole-climate-change-are-causing-atmospheric-tug-of-war/

A pause in Southern Hemisphere circulation trends due to the Montreal Protocol

Observations show robust near-surface trends in Southern Hemisphere tropospheric circulation towards the end of the twentieth century, including a poleward shift in the mid-latitude jet1,2, a positive trend in the Southern Annular Mode1,3–6 and an expansion of the Hadley cell7,8. It has been established that these trends were driven by ozone depletion in the Antarctic stratosphere due to emissions of ozone-depleting substances9–11. Here we show that these widely reported circulation trends paused, or slightly reversed, around the year 2000. Using a pattern-based detection and attribution analysis of atmospheric zonal wind, we show that the pause in circulation trends is forced by human activities, and has not occurred owing only to internal or natural variability of the climate system. Furthermore, we demonstrate that stratospheric ozone recovery, resulting from the Montreal Protocol, is the keydriver of the pause. Because pre-2000 circulation trends have affected precipitation12–14, and potentially ocean circulation and salinity15–17, we anticipate that a pause in these trends will have wider impacts on the Earth system. Signatures of the effects of the Montreal Protocol and the associated stratospheric ozone recovery might therefore manifest, or have already manifested, in other aspects of the Earth system

Link in the SA article above.

So rest of human crap overrides Montreal recoveries in the noughties. Permafrost flips ca 2015.

I don´t feel to fucking confident.

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Hopefully, lessons learn from the referenced study of tidal pressures near the grounding zone of the Ross Ice Shelf will be applied to models of the PIIS, and the TEIS, ocean interactions:

Carolyn Branecky Begeman, Slawek Tulaczyk, Laurie Padman, Matt King, Matthew R. Siegfried, Timothy O. Hodson and Helen A. Fricker1(6 March 2020), "Tidal pressurization of the ocean cavity near an Antarctic ice shelf grounding line", JGR Oceans, https://doi.org/10.1029/2019JC015562

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JC015562?af=R

Abstract
Mass loss from the Antarctic Ice Sheet is sensitive to conditions in ice‐shelf grounding zones, the transition between grounded and floating ice. To observe tidal dynamics in the grounding zone, we moored an ocean pressure sensor to Ross Ice Shelf, recording data for 54 days. In this region the ice shelf is brought out of hydrostatic equilibrium by the flexural rigidity of ice, yet we found that tidal pressure variations at a constant geopotential surface were similar within and outside of the grounding zone. This implies that the grounding zone ocean cavity was overpressurized at high tide and underpressurized at low tide by up to 10 kPa with respect to glaciostatic pressure at the ice shelf base. Phase lags between ocean pressure and vertical ice‐shelf motion were tens of minutes for diurnal and semidiurnal tides, an effect that has not been incorporated into ocean models of tidal currents below ice shelves. These tidal pressure variations may affect the production and export of meltwater in the subglacial environment and may increase basal crevasse heights in the grounding zone by several meters, according to linear elastic fracture mechanics. We find anomalously high tidal energy loss at the K1 constituent in the grounding zone and hypothesize that this could be explained by seawater injection into the subglacial environment at high tide or internal tide generation through interactions with topography. These observations lay the foundation for improved representation of the grounding zone and its tidal dynamics in ocean circulation models of sub‐ice‐shelf cavities.

Plain language summary
One of the challenges for sea level rise prediction is understanding how the Antarctic ice sheets and the Southern Ocean interact. Ocean tides are an important component of this interaction, influencing ice shelf melting and the flow rate of grounded ice toward the coast. We report new observations relevant to this interaction: tidally‐varying ocean pressures where the ice first goes afloat to become an ice shelf. These tidal ocean pressure variations influence tidal currents below the ice shelf, and we propose that they also push seawater beneath the ice inland of the ice shelf and extend fractures at the ice‐shelf base. This study identifies tidal processes that may affect melt and fracture near the inland edge of ice shelves, a highly sensitive zone for ice dynamics.

Key Points
•   We present the first concurrent observations of ocean pressure and ice flexure in the grounding zone of an Antarctic ice shelf
•   Peak ocean pressure in the grounding zone at high tide exceeded glaciostatic pressure and preceded the peak ice shelf tidal deflection
•   These pressure variations may enhance basal crevassing and influence subglacial hydrology near the grounding line

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The linked reference indicates that the MOC is subject to short-term disruptions that could abruptly cause it to slowdown in the future.

Eirik Vinje Galaasen, Ulysses S. Ninnemann, Augustin Kessler, Nil Irvalı, Yair Rosenthal, Jerry Tjiputra, Nathaëlle Bouttes, Didier M. Roche, Helga (kikki) F. Kleiven, David A. Hodell. Interglacial instability of North Atlantic Deep Water ventilation. Science, 2020 DOI: 10.1126/science.aay6381

https://science.sciencemag.org/content/367/6485/1485

Abstract
Disrupting North Atlantic Deep Water (NADW) ventilation is a key concern in climate projections. We use (sub)centennially resolved bottom water δ13C records that span the interglacials of the last 0.5 million years to assess the frequency of and the climatic backgrounds capable of triggering large NADW reductions. Episodes of reduced NADW in the deep Atlantic, similar in magnitude to glacial events, have been relatively common and occasionally long-lasting features of interglacials. NADW reductions were triggered across the range of recent interglacial climate backgrounds, which demonstrates that catastrophic freshwater outburst floods were not a prerequisite for large perturbations. Our results argue that large NADW disruptions are more easily achieved than previously appreciated and that they occurred in past climate conditions similar to those we may soon face.