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Messages - Juan C. García

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1
ASLR,
How would " increased freshwater inflow into the Arctic Ocean ... work to destabilize the halocline in that ocean"?  I've read elsewhere (other ASIF threads, and maybe this one, too) that rivers (dumping fresh water into the Arctic) support the reestablishment of the halocline where storms and currents have somewhat mixed the top 30 or 50 meters.

Tor,

While you are correct that increasing influx of fresh riverine water into the Arctic Ocean increases the thickness of the halocline layer; which reduces heat flux from the Atlantic layer to the Arctic atmosphere. 

Nevertheless, as the first linked reference cites, excess fresh surface water is frequently heated in the northern Chukchi Sea and then stored in the interior of the Beaufort Gyre.  So more freshwater discharge into the Arctic Ocean will increase the heat stored in the Beaufort Gyre; which when released (during a temporary reversal of the Beaufort Gyre) will melt large areas of Arctic sea ice; which, will destabilize the halocline releasing more heat from the Atlantic layer into the Arctic atmosphere thus accelerating Arctic Amplification.

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

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

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

&

Also, the second linked reference indicates that in addition to the freshwater accumulated in the Beaufort Gyre the entire Arctic Ocean surface layer has been accumulating atypically high volumes of freshwater that are only recently beginning to leak atypically high volumes of freshwater into the North Atlantic.  This implies that for many years now the full impacts of unusually high (anthropogenically driven) discharges of freshwater into the Arctic Ocean (and then on to the North Atlantic) have been masked.  As thick layers of freshwater in the Arctic Ocean reduce the rate of heat flux from the deeper/warming layers of ocean water into the Arctic atmosphere, this atypically high accumulation of freshwater in the Arctic Ocean surface layers implies that in recent years the Arctic has been cooler than it otherwise would have been (without this atypically high accumulation).  Thus if/when the Beaufort Gyre finally reverses it will likely not only release excessively high freshwater volumes accumulated in the Gyre into the North Atlantic, but it would likely also flush excess freshwater from the atypically high accumulations from the ocean surface layers in much of the Arctic Ocean and would likely melt large portions of the existing sea ice; which, would flush even more freshwater into the North Atlantic where this additional freshwater flux would serve to rapidly slow the AMOC:

Alexandra Jahn and Rory Laiho (27 July 2020), "Forced Changes in the Arctic Freshwater Budget Emerge in the Early 21st Century", Geophysical Research Letters, https://doi.org/10.1029/2020GL088854

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL088854?af=R

Abstract
Arctic liquid freshwater (FW) storage has shown a large increase over the past decades, posing the question: Is the Arctic FW budget already showing clear signs of anthropogenic climate change, or are the observed changes the result of multi‐decadal variability? We show that the observed change in liquid and solid Arctic FW storage is likely already driven by the changing climate, based on ensemble simulations from a state‐of‐the‐art climate model. Generally, the emergence of forced changes in Arctic FW fluxes occurs earlier for oceanic fluxes than for atmospheric or land fluxes. Nares Strait liquid FW flux is the first to show emergence outside the range of background variability, with this change potentially already occurring. Other FW fluxes have likely started to shift but have not yet emerged into a completely different regime. Future emissions reductions have the potential to avoid the emergence of some FW fluxes beyond the background variability.

Plain Language Summary
The surface waters of the Arctic Ocean are fresher than the rest of the world oceans, due to the input of large amounts of river runoff. The very fresh surface ocean affects the ocean circulation and climate not just in the Arctic Ocean, but also at lower latitudes, especially in the North Atlantic. The last two decades have seen a freshening of the surface Arctic Ocean, for reasons that are currently unknown. Here we demonstrate that this freshening is likely already driven by climate change. Furthermore, we find that due to man‐made climate change, Arctic freshwater fluxes to the North Atlantic are also likely to soon start showing signs of change beyond the range of the variability we have observed in the past. The information provided here about the expected timing of the emergence of climate change signals will allow us to monitor upcoming changes in real time, to better understand how changes in the Arctic Ocean can impact climate worldwide.

Key points
•   The observed increase in Arctic liquid freshwater (FW) storage is likely already driven by climate change
•   A forced change in liquid FW flux through Nares Strait is likely to emerge within the next decade
•   The already changing nature of many FW budget terms can delay detection of shift and emergence from observations

Best,
ASLR

2
Policy and solutions / Re: Carbon Capture and Storage (CCS)
« on: November 25, 2020, 06:57:51 PM »
Carbon sequestration investments may be included in a new US stimulus plan early next year.

https://www.technologyreview.com/2020/11/09/1011859/biden-calls-for-major-investments-into-carbon-removal-tech/

Quote
Biden calls for major investments into carbon removal tech

The president-elect’s transition plan also recommends research and development funding for batteries, renewable hydrogen and advanced nuclear.

James Temple
November 9, 2020

President-elect Joe Biden wasted little time setting a new tone on climate change.

On Sunday, one day after major outlets called the presidential election for the former vice president, the Biden-Harris transition team released documents laying out the incoming administration’s early priorities, including a blueprint for “tackling the climate crisis.”

Most of the details were drawn directly from Biden’s sweeping campaign climate plan, which would dedicate $1.7 trillion to overhaul energy, transportation, agriculture, and other sectors. But the list of areas in which Biden hopes to make “far-reaching investments” includes at least one new term: negative-emissions technologies.That phrase encompasses a number of approaches for drawing greenhouse gases out of the atmosphere. These can include carbon-sucking machines that companies like Climeworks and Carbon Engineering are developing; methods to speed up natural processes through which minerals capture and lock away carbon; and schemes that rely on plants to absorb carbon dioxide, then convert them into fuel sources and capture any resulting emissions (a process known as “bioenergy with carbon capture and sequestration”).

Scientists say that removing billions of tons of carbon dioxide per year by midcentury will be essential for preventing very dangerous levels of global warming.

Quote
Policy observers believe that there could be opportunities to incorporate significant research and development funding for clean energy in upcoming economic stimulus packages, noting that such measures have bipartisan support. Indeed, Congress largely beat back the Trump administration’s repeated efforts to slash federal investments in these areas during the last four years.

3
Policy and solutions / Re: Carbon Capture and Storage (CCS)
« on: November 25, 2020, 06:50:02 PM »
As companies seek to reach net zero or even sequester all of their historic emissions, "carbontech" firms are becoming economically viable.

https://www.greenbiz.com/article/carbontech-getting-ready-its-market-moment

Quote
Carbontech is getting ready for its market moment

By Heather Clancy
October 28, 2020

It may be a little early to start writing about trends for 2021, but I’m going to do it anyway. What’s on my mind? Carbontech, a category of climate tech I’d love to see break through next year. It's the exciting idea that we can take something that could be considered waste, draw it out of the atmosphere and turn it into a source of revenue or economic growth.

There are signs that give me optimism. This morning, digital payments company Stripe announced a plan to let its merchant customers divert a portion of their revenue to carbon removal projects. The move follows Stripe’s own pledge to put $1 million into four "high potential" projects earlier this year, and the two initiatives are related. The specific technologies that Stripe is funding are carbon-sequestering concrete (CarbonCure), geologic storage (Charm Industrial), direct air capture (Climeworks) and ocean mineralization (Project Vesta).

Quote
Lest I forget, another well-known commerce player, Shopify, last month picked carbon removal and carbontech as a focus for its Sustainability Fund, which commits $5 million annually to climate-tech solutions. Some companies it is supporting are the same as Stripe (CarbonCure, Charm Industrial and Climeworks). It is also including ocean sequestration in the mix through its support of Planetary Hydrogen. And it is also letting merchants add options for offsetting that buyers can select during transactions.

Quote
How ginormous could the carbontech market get? According to nonprofit Carbon180, the total addressable market for products that could be affected is $6 trillion — with the biggest opportunities for using "waste CO2" found in transportation fuels and building materials. Captured carbon also could be a resource for food, fertilizers, polymers and chemicals. (Before you ask, very few innovators that CCN is tracking are focused on enhanced oil recovery applications.)

4
Science / Re: Trends in atmospheric CH4
« on: November 25, 2020, 09:34:38 AM »
A bit of a different perspective. In June/July, the methane concentration usually dips below the value from the preceding winter. However, this year, this effect was very limited. The value is barely below the last local minimum from February. The last time something similar happened was in 2014, and back then what happened next was the biggest autumn jump we've seen since the 20th century, with the winter of 2015 being around 15-16 ppm higher than the winter of 2014. Will this happen this year too?

5
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: November 21, 2020, 10:03:49 PM »
New high quality Sentinel2 image, I take this opportunity to show the rapid changes at the SIS and at the SSM (the SdDZ Damage Zone)

> animation based on the two images of 11/11 and 21/11 (10 days apart, homogeneous orbits), centred on the marginal rifts of the SIS. One can see the rapid changes not only in WmR4, but also in the other rifts, which will soon lead to calvings in this sector.

> animation based on the two images of 17/11 and 21/11 (4 days apart, the orbits are not homogeneous, but they show the speed of change), centred on the SSM and the SdDZ

Large images, click to animate

update: blocks B1, B2 and B3 move relative to the SIS (slightly)

6
Permafrost / Re: Arctic Methane Release
« on: November 21, 2020, 03:05:09 AM »
Bubbling methane craters and super seeps - is this the worrying new face of the undersea Arctic?

http://siberiantimes.com/other/others/news/bubbling-methane-craters-and-super-seeps-is-this-the-worrying-new-face-of-the-undersea-arctic/

   
Bubbling methane craters and super seeps - is this the worrying new face of the undersea Arctic?
By Valeria Sukhova, Olga Gertcyk
19 November 2020

Video and pictures from latest research mission show gas release in the Laptev and the East Siberian seas.

A team of 69 scientists from ten countries documented bubble clouds rising from a depth of around 300 metres (985ft) along a 150km (93 mile) undersea slope in the Laptev Sea, and confirmed high methane concentrations by hundreds of onboard chemical analysis. Picture: TPU

Scientists have shared the first results of a trip to the world’s largest deposit of subsea permafrost and shallow methane hydrates.

Fields of methane discharge continue to grow all along the East Siberian Arctic Ocean Shelf, with concentration of atmospheric methane above the fields reaching 16-32ppm (parts per million).

This is up to 15 times above the planetary average of 1.85ppm.

The preliminary results are from this year’s only international scientific expedition to the eastern Arctic.

Methane bubbling in the Eastern Arctic, video from this autumn international expedition to the Laptev and to the East Siberian Sea 

A team of 69 scientists from ten countries documented bubble clouds rising from a depth of around 300 metres (985ft) along a 150km (93 mile) undersea slope in the Laptev Sea, and confirmed high methane concentrations by hundreds of onboard chemical analysis.

A second discovery is pockmarks and craters sunk deep in shelf sediments of both the Laptev and East Siberian seas, actively venting bubbles and strong methane signals.

‘All previously discovered fields of methane discharge showed an increase to various degrees, now we need to figure out exactly how much they grew,’ said the head of the expedition Professor Igor Semiletov.

‘One of the new discoveries was a field of sea bottom craters in the shallow part of the Laptev Sea, some of them 30 metres (98 ft) in diameter.

‘They look like holes in the permafrost and, as our studies showed, they were formed by massive methane discharge.

‘Also two more powerful seeps emitting methane through iceberg furrows were discovered in the East Siberian Sea

For the first time the scientists managed to take samples of bottom sediments in a methane seep near the delta of River Lena, one of Siberia’s giant waterways.

7
Arctic sea ice / Re: Latest PIOMAS update (November mid-monthly update)
« on: November 18, 2020, 09:41:20 AM »
Updated volume and volume-anomaly graphs.

8
Arctic sea ice / Re: Latest PIOMAS update (November mid-monthly update)
« on: November 18, 2020, 09:33:25 AM »
PIOMAS has updated the gridded thickness data to day 320 (16th or 15th of November). Calculated volume on day 320 was 8.07 [1000km3], second lowest, slightly over the 8.00[1000km3] in 2016 .

Here is the animation for November so far.

9
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: November 15, 2020, 06:19:27 AM »
I love you folks. Just wanted to say that. Thanks.

10
The rest / Re: Animation project on sea ice collapse
« on: November 07, 2020, 11:45:41 AM »

11
Science / Re: Where are we now in CO2e , which pathway are we on?
« on: November 06, 2020, 10:50:22 PM »
Yes, of course. See my posting Oct 10, where I state that the true value is higher than that I had just posted. I only take care of these four "NOAA gases" because their concentration is followed on a daily (CO2) or monthly basis (CH4, N2O, SF6) by NOAA.
In the end I think that the absolute value itself is not too interesting. So I focus on the increase which I think is concerning, and please do not forget the slightly exponential development of all of these four gases, where we all should have taken a U-turn decades ago...

12
Science / Re: Where are we now in CO2e , which pathway are we on?
« on: November 06, 2020, 07:42:33 PM »
To finalize my update on greenhouse gases here is the summary of the four postings in the individual gas concentration threads.

More radiative forcing of the "NOAA gases" (CO2, CH4, N2O, SF6) in July 2020 than in July 2019, but less than in June 2020, because CO2 and CH4 reach their seasonal maximum in May.

The values [W/m²], change to June 2020 and change to July 2019:
CO2 2.136    (- 0.025)    (+ 0.034)   
CH4 0.519    (- 0.000)    (+ 0.005)
N2O 0.206   (+ 0.001)    (+ 0.004)
SF6  0.0054 (+ 0.0001)  (+ 0.0002)
sum  2.865  (- 0.026)    (+ 0.043) (rounding differences)

The relative annual increase is 1.49 %, a little bit higher than June 2020.

This recalculates to a CO2eq of 474.8 ppm (annual increase of 3.7 ppm).

13
Consequences / Re: Weird Weather and anecdotal stories about climate change
« on: November 05, 2020, 04:35:39 PM »
And therefore "Climate Weirding" (popularized by Katharine Hayhoe)

14
Arctic sea ice / Re: Latest PIOMAS update (November)
« on: November 04, 2020, 05:12:10 PM »
2020 Andy Lee Robinson video.
Arctic sea ice minimum volumes (1979-2020).

It ends with 4,030 km3 instead of 4,161 km3.
4,030 km3 is minimum of the daily volume,
4,161 km3 is the September Monthly average volume.

15
Trump Administration Ends Gray Wolf's Endangered Species Protections
https://www.theguardian.com/environment/2020/oct/29/gray-wolf-endangered-species-trump-administration

The Trump administration has removed endangered species protections from the gray wolf, a species once persecuted to near-extinction in the US, in a move that has been condemned as premature by conservationists.

The wolves have been provided federal protection for more than 45 years but this is no longer needed according to David Bernhardt, the US interior secretary, who announced the decision in Minnesota on Thursday.

... With no federal safeguards, gray wolves will be subject to a patchwork of state and local laws, some of which will allow the trapping and killing of the animals. Many ranchers still view wolves as a threat to livestock, while hunters consider them unhelpful competition for deer and elk. William Perry Pendley, the acting director of the Bureau of Land Management, once wrote to Disney to complain that its movie White Fang was too kind to wolves.

Protections for wolves have already been lifted in Idaho, Wyoming and Montana, leading to the deaths of more than 500 wolves in Idaho just in the past year, according to analysis by environment groups.

---------------------------------------------

Trump Administration Strips Protection from US’s Largest Forest
https://www.aljazeera.com/news/2020/10/29/trump-administration-strips-protections-from-uss-largest-forest

The Trump administration has lifted environmental protection in Tongass National Forest, opening up more than three million hectares in the United States’s largest forest to logging despite opposition from environmental groups and Indigenous leaders.

In an official notice of the decision on Thursday, the US Department of Agriculture said Tongass would be exempt from a 2001 federal law known as the “Roadless Rule” that prohibits timber harvest and road construction in specific areas.

The Tongass – sometimes referred to as “America’s Amazon” – spans nearly seven million hectares (17 million acres) across southeast Alaska, including the capital, Juneau, and is home to diverse wildlife and trees. It is considered the largest contiguous temperate rainforest in the world.

Alaska’s Republican governor, Mike Dunleavy, welcomed the Trump administration’s decision, which opens up 55 percent of the forest (3.9 million hectares/9.6 million acres) to timber harvest activities and road-building.

In August, the Trump administration opened up part of another key ecological site in Alaska, the Arctic National Wildlife Refuge, to oil and gas exploration.

16
The rest / Animation project on sea ice collapse
« on: October 29, 2020, 05:27:30 PM »
I had just began learning to play "The sunken cathedral" by Debussy, when the idea for an animation appeared out of nowhere in my head.

The script is very simple: sea ice, sunken cathedral beneath the ice, ice melts, methane accumulates on the top of the cathedral, a whale breathes methane and dies, sea floor destabilizes, cathedral implodes, current sweeps the silt and reveals lots of human bones and life goes on.

On text it's not very pretty, but with the images and music it will be very poetic.

I will posting the work in progress here.





17
Permafrost / Re: Permafrost general science thread
« on: October 27, 2020, 04:57:15 PM »
But we have to wait for a peer-reviewd paper next year to find out how whoops! it really is.

https://www.theguardian.com/science/2020/oct/27/sleeping-giant-arctic-methane-deposits-starting-to-release-scientists-find
'Sleeping giant' Arctic methane deposits starting to release, scientists find
Exclusive: expedition discovers new source of greenhouse gas off East Siberian coast has been triggered

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

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

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

The international team onboard the Russian research ship R/V Akademik Keldysh said most of the bubbles currently are dissolving in the water but methane levels at the surface are four to eight times what would normally be expected and this is venting into the atmosphere.

At this moment, there is unlikely to be any major impact on global warming, but the point is that this process has now been triggered. This East Siberian slope methane hydrate system has been perturbed and the process will be ongoing,” said the Swedish scientist Örjan Gustafsson of Stockholm University in a satellite call from the vessel.

The scientists – who are part of a multi-year International Shelf Study Expedition – stressed their findings are preliminary. The scale of methane releases will not be confirmed until they return, analyse the data and have their studies published in a peer-reviewed journal.

But the discovery of potentially destabilised slope frozen methane raises concerns that a new tipping point has been reached that could increase the speed of global heating. The Arctic is considered ground zero in the debate about the vulnerability of frozen methane deposits in the ocean. With the Arctic temperature now rising more than twice as fast as the global average, the question of when – or even whether – they will be released into the atmosphere has been a matter of considerable uncertainty in climate computer models.

The 60-member team on the Akademik Keldysh believe they are the first to observationally confirm the methane release is already under way across a wide area of the slope about 600km offshore.


The latest discovery potentially marks the third source of methane emissions from the region. Semiletov, who has been studying this area for two decades, has previously reported the gas is being released from the shelf of the Arctic – the biggest of any sea.

For the second year in a row, his team have found crater-like pockmarks in the shallower parts of the Laptev Sea and East Siberian Sea that are discharging bubble jets of methane, which is reaching the sea surface at levels tens to hundreds of times higher than normal. This is similar to the craters and sinkholes reported from inland Siberian tundra earlier this autumn.

18
Consequences / Re: Hurricane Season 2020
« on: October 25, 2020, 04:57:40 PM »
Quote
Eric Holthaus (@EricHolthaus) 10/25/20, 10:45 AM
We now have Tropical Storm Zeta.
https://twitter.com/ericholthaus/status/1320375819827634176
⬇️ 8am map below.

Zeta is the 27th named storm of the 2020 Atlantic Hurricane season, 1 behind the record of 28 in 2005.
It's also the 4th storm to threaten the Yucatan peninsula this year, and the 7th storm to threaten Louisiana.

Hurricane Delta hit just two weeks ago:

Hurricane Delta at the human scale (with interviews from Cancun and Lake Charles)   - The Phoenix
https://thephoenix.substack.com/p/hurricane-delta-at-the-human-scale

19
Consequences / Re: Wildfires
« on: October 23, 2020, 08:59:05 AM »
Colorado wildfire smoke turns Minnesota's sky and snow orange
https://www.mprnews.org/story/2020/10/22/colorado-wildfire-smoke-turns-minnesotas-sky-and-snow-orange

Our surreal orange sky Thursday featured lightning, thunder and orange-tinted snow

20
Consequences / Re: Wildfires
« on: October 23, 2020, 03:26:24 AM »
Colorado Fire Grows By Over 100,000 Acres In 1 Day, Hits Rocky Mountain National Park
https://www.npr.org/2020/10/22/926838887/colorado-fire-grows-by-over-100-000-acres-in-1-day-hits-rocky-mountain-national-



Already battling the largest fire in state history, Colorado is now dealing with another blaze that grew by more than 100,000 acres in a day.

The flames traveled east, fueled by beetle-eaten pine trees and dry winds. Hundreds evacuated. The fire jumped the Continental Divide, which is 10,000 to 12,000 feet above sea level. Conditions forced the closing of Rocky Mountain National Park.

The fire, called East Troublesome after a nearby creek, has spread to more than 125,000 acres. Smoke plumes stretched 40,000 feet in the air. The nearby town of Grand Lake was forced to evacuate.



... "The growth that you see on this fire is unheard of," Grand County Sheriff Brett Schroetlin said during a Thursday press conference. "We plan for the worst. This is the worst of the worst of the worst. And no matter how we look at it, we can't control Mother Nature." ... "It was basically out of a movie. It was a firestorm in downtown Grand Lake. Smoke and embers flying around. It was just a chaotic scene,"

21
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 21, 2020, 03:28:25 PM »
The ice on the Eurasian side of the N pole is slightly greater than 1 meter thick according to Russian reports. They just sent a new icebreaker to the pole to test its performance but the ice was too thin to test it. They hoped to find some 3 m thick ice but icebreaker went to the pole unhindered by any thick ice. From the Barents Observer
 https://thebarentsobserver.com/en/arctic/2020/10/north-pole-ice-cap-too-thin-testing-russias-giant-icebreaker

“Ice tests are still ahead, probably this year, because now ice tests did not work out, the ice thickness was 1,1 to 1,2 meters. It was thin and loose, the icebreaker received no resistance at all,” Shchapin says.

He adds: “We tried to find a three-meters ice floe, but they did not find it.”

22
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: October 19, 2020, 01:28:03 PM »
Thank you Oren,
Here is the new version (NSM and SSM) with the suggested improvements

Click to animate

23
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: October 19, 2020, 12:21:21 PM »
As promised I am posting the history of the SSM in the new format. I will post the next update (NSSM and SSM) on 26/10 or the next day.

Fixed: My apologies, the order of the images was not good

Click to animate

24
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: October 18, 2020, 11:00:34 PM »
I was looking for a good compromise to present the history (size and readability) and I think I found it. This is the result for the NSM. This is the history from 17/02 to 14/10, one front line every 12 days (NB the Sentinel1 images from 29/02 and 03/08 are missing)

If the result suits you it could become a regular post (every 12 days and with the SSM).

Click to animate

25
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 17, 2020, 12:11:51 AM »
Quote
There's a reason scientists studying climate change use complex models not tea cups
Right. The discussion has not been at the level of the mid-1700's.

How many people here can expand the acronym SHEBA -- was there a need or could it all have been intuited from gedanken experiments?

Worst freeze season ever underway ... would never know it from the posts. How can 1 person on twitter (https://twitter.com/ZLabe) cover it better than 1777 persons?

1738 – Daniel Bernoulli publishes Hydrodynamica, initiating the kinetic theory
1749 – Émilie du Châtelet derives the conservation of energy from Newtonian mechanics.
1761 – Joseph Black shows ice absorbs heat without changing its temperature when melting
1772 – Dan Rutherford discovers nitrogen which he explains in terms of phlogiston theory
1776 – John Smeaton paper on power, work, momentum, and kinetic energy
1777 – Carl Scheele distinguishes heat transfer by thermal radiation from convection and conduction
1783 – Tony Lavoisier discovers oxygen and develops caloric explanation for combustion
1784 – Jan Ingenhousz describes Brownian motion of charcoal particles on water
1791 – Pierre Prévost shows that all bodies radiate heat, no matter how hot or cold they are

Here's what we are watching unfold (Oct 11):


26
Permafrost / Re: Permafrost general science thread
« on: October 16, 2020, 09:49:46 PM »
Arctic Ocean Sediments Reveal Permafrost Thawing During Past Climate Warming
https://phys.org/news/2020-10-arctic-ocean-sediments-reveal-permafrost.html

Sea floor sediments of the Arctic Ocean can help scientists understand how permafrost responds to climate warming. A multidisciplinary team from Stockholm University has found evidence of past permafrost thawing during climate warming events at the end of the last ice age. Their findings, published in Science Advances, caution about what could happen in the near future: That Arctic warming by only a few degrees Celsius may trigger massive permafrost thawing, coastal erosion, and the release of the greenhouse gases carbon dioxide (CO2) and methane (CH4) into the atmosphere.

... "Our new study shows for the first time the full history of how warming at the end of the last ice age triggered permafrost thawing in Siberia. This also suggests the release of large quantities of greenhouse gases," says Jannik Martens, Ph.D. student at Stockholm University and lead author of the study. "It appears likely that past permafrost thawing at times of climate warming, about 14,700 and 11,700 years ago, was in part also related to the increase in CO2 concentrations that is seen in Antarctic ice cores for these times. It seems that Arctic warming by only a few degrees Celsius is sufficient to disturb large areas covered by permafrost and potentially affect the climate system."

In the current study, the scientists used an eight meters long sediment core that was recovered from the sea floor more than 1 000 meters below the surface of the Arctic Ocean during the SWERUS-C3 expedition onboard the Swedish icebreaker Oden back in 2014. To reconstruct permafrost thawing on land, the scientists applied radiocarbon (14C) dating and molecular analysis to trace organic remains that once were released by thawing permafrost and then washed into the Arctic Ocean.

"From this core we also learned that erosion of permafrost coastlines was an important driving force for permafrost destruction at the end of the last ice age. Coastal erosion continues to the present day, though ten times slower than during these earlier rapid warming period. With the recent warming trends, however, we see again an acceleration of coastal erosion in some parts of the Arctic, which is expected to release greenhouse gases by degradation of the released organic matter," says Örjan Gustafsson, Professor at Stockholm University and leader of the research program. "Any release from thawing permafrost mean that there is even less room for anthropogenic greenhouse gas release in the earth-climate system budget before dangerous thresholds are reached.

Gustafsson, Martens and their colleagues are now again in the Arctic Ocean as part of the International Siberian Shelf Study (ISSS-2020) onboard the Russian research vessel Akademik Keldysh. The expedition left the port of Arkhangelsk on September 26 and is currently in the East Siberian Sea, seeking more answers to how changing climate may trigger release of carbon, including greenhouse gases, from Arctic permafrost systems, including coastal erosion and permafrost below the sea bottom preserved from the past ice age.



Remobilization of dormant carbon from Siberian-Arctic permafrost during three past warming events. Sci. Adv. 6, eabb6546 (2020)
https://advances.sciencemag.org/content/6/42/eabb6546



... This demonstrates that Arctic warming by only a few degrees may suffice to abruptly activate large-scale permafrost thawing, indicating a sensitive trigger for a threshold-like permafrost climate change feedback.

27
Antarctica / Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« on: October 15, 2020, 02:46:43 AM »
For those who missed this research last month [the first attached image illustrates how the deep seafloor channels converge at the base of the TEIS and the Thwaites Ice Tongue in the seafloor trough that leads directly to the Byrd Subglacial Basin (BSB); thus guiding relatively warm modified CDW to relatively quickly form a subglacial cavity in this trough area]:

Title: "Thwaites: 'Doomsday Glacier' vulnerability seen in new maps"

https://www.bbc.com/news/science-environment-54079587

Extract: "Now, a UK-US team has surveyed the deep seafloor channels in front of the glacier that almost certainly provide the access for warm water to infiltrate and attack Thwaites' underside.

It's information that will be used to try to predict the ice stream's future.

"These channels had not been mapped before in this kind of detail, and what we've discovered is that they're actually much bigger than anyone thought - up to 600m deep. Think of six football pitches back to back," said Dr Kelly Hogan from the British Antarctic Survey (BAS).

"And because they are so deep, and so wide - this allows a lot more water to get at, and melt, Thwaites' floating front as well as its ice that rests on the seabed," she told BBC News."

Edit: For ease of comparison I provide the last three images from earlier posts in this thread; where the second image shows how in 2012-13 the ice surface dropped abruptly when a portion of the subglacial cavity collapsed in this area.

Edit2: For those who forgot, or have not scrolled back through this thread, I note that the last two images show that the southside of what I have termed the 'Big Ear' subglacial cavity has an ice surface that is about 140m above sea level and that the ice over the 'Big Ear' subglacial cavity is essentially floating.  Thus, a surge of the Thwaites Ice Tongue (as occurred in the 2013-14 season, and which I believe may likely occur again well before 2040) could unpin the ice over the 'Big Ear' Subglacial cavity (thus allowing this ice to float away); which would likely expose a bare ice cliff face (potentially about 140m above the water surface); which according to Bassis' 2020 WAIS Workshop analysis, would be sufficient to trigger an MICI-type of collapse leading straight into the BSB.

28
Antarctica / Re: Ice Apocalypse - MULTIPLE METERS SEA LEVEL RISE
« on: October 14, 2020, 04:49:36 PM »
Despite the presences of the North Atlantic cold spot, the linked reference indicates that the North Atlantic SSTs are the warmest that they have been in the ~2,900 years:

Francois Lapointe et al. (October 12, 2020), "Annually resolved Atlantic sea surface temperature variability over the past 2,900 y", PNAS; https://doi.org/10.1073/pnas.2014166117

https://www.pnas.org/content/early/2020/10/06/2014166117

Significance
Atlantic multidecadal sea surface temperature variability (AMV) strongly influences the Northern Hemisphere’s climate, including the Arctic. Here using a well-dated annually laminated lake sediment core, we show that the AMV exerts a strong influence on High-Arctic climate during the instrumental period (past ∼150 y) through atmospheric teleconnection. This highly resolved climate archive is then used to produce the first AMV reconstruction spanning the last ∼3 millennia at unprecedented temporal resolution. Our terrestrial record is significantly correlated to several sea surface temperature proxies in the Atlantic, highlighting the reliability of this record as an annual tracer of the AMV. The results show that the current warmth in sea surface temperature is unseen in the context of the past ∼3 millennia.

Abstract
Global warming due to anthropogenic factors can be amplified or dampened by natural climate oscillations, especially those involving sea surface temperatures (SSTs) in the North Atlantic which vary on a multidecadal scale (Atlantic multidecadal variability, AMV). Because the instrumental record of AMV is short, long-term behavior of AMV is unknown, but climatic teleconnections to regions beyond the North Atlantic offer the prospect of reconstructing AMV from high-resolution records elsewhere. Annually resolved titanium from an annually laminated sedimentary record from Ellesmere Island, Canada, shows that the record is strongly influenced by AMV via atmospheric circulation anomalies. Significant correlations between this High-Arctic proxy and other highly resolved Atlantic SST proxies demonstrate that it shares the multidecadal variability seen in the Atlantic. Our record provides a reconstruction of AMV for the past ∼3 millennia at an unprecedented time resolution, indicating North Atlantic SSTs were coldest from ∼1400–1800 CE, while current SSTs are the warmest in the past ∼2,900

29
Permafrost / Re: Arctic Methane Release
« on: October 14, 2020, 04:15:35 PM »
https://www.commondreams.org/news/2019/10/09/truly-terrifying-scientists-studying-underwater-permafrost-thaw-find-area-arctic

Scientists studying the consequences of methane emissions from underwater permafrost in the Arctic Ocean announced this week that they found a 50-square-foot area of the East Siberian Sea "boiling with methane bubbles."

"This is the most powerful seep I have ever been able to observe," lead scientist Igor Semiletov said Monday, using a term for methane gas bubbling up from the seafloor to the surface. "No one has ever recorded anything similar."

30
Antarctica / Re: What's new in Antarctica ?
« on: October 13, 2020, 06:40:27 PM »
It goes without saying that the cited research does not consider MICI types of failures which could cause an armada of icebergs (as noted by James Hansen) from the WAIS; which would raise sea level as soon as the associate calving events (without melting).
Let's see if we can observe some failures of that type in the nearish future, or whether something stops those from taking place. Fingers crossed...

In my opinion, the first place that we are likely to MICI types of ice cliff failures in the WAIS will be near the base of the Thwaites Ice Tongue, and if so such ice cliff failure are likely to rapidly propagate upstream into the BSB within years of the initial ice cliff events in this area.

31
Arctic sea ice / Re: What's new in the Arctic ?
« on: October 12, 2020, 09:49:10 PM »
Maybe rather "New out of the Arctic" - Polarstern:-

https://www.bbc.co.uk/news/science-environment-54515518

32
Antarctica / Re: What's new in Antarctica ?
« on: October 12, 2020, 07:10:52 PM »
That's a function of future greenhouse gas emissions.  The article was specifically talking about 2 major glaciers.  With 'all' inputs (especially the expansion of warming sea water) there are projections that vary quite a bit.  (See ASLR postings for all the scientifically documented reasons he believes the following 'published' estimates are on the low side.)

For 300 million people, sea level 'problems' will occur during my children's life time.  11' (3.3 meters) sea level rise (over the year 2000 sea level) will be attained in 1-400 years, as best I can tell.  11 meters (36') will be attained in 400-1000 years, as best I can tell.

So there is definitely a cataclysmic problem for many, which might turn into a cataclysmic problem for the rest of us.  (For example, where will that 'first' 300 million go?)

Some quotes:
Forbes:
Quote
By 2050, sea-level rise will push average annual coastal floods higher than land now home to 300 million people, according to a study published in Nature Communications.
Skeptical Science:
Quote
the most likely sea level rise by 2100 is betweem 80cm and 1 metre.  Longer term, sea levels will continue to rise even after emissions have been reduced or eliminated.
Forbes:
Quote
The IPCC’s range for “multi-millennial” [400 years] commitment is 3 to 13 meters (10 to 36 feet) for warming of 2 degrees C.
Express:
Quote
“Our research reveals that ice melt in the last interglacial period caused global seas to rise about 10 metres above the present level. The ice melted first in Antarctica, then a few thousand years later in Greenland.

“Sea levels rose at up to 3 metres per century, far exceeding the roughly 0.3-metre rise observed over the past 150 years.
ASLR's latest post:
Quote
coming climate changes:
"… will continue throughout the decades and the millennia – some occurring abruptly and (others) being irreversible."

33
Consequences / Re: Hurricane Season 2020
« on: October 09, 2020, 02:23:39 AM »
Michael E. Mann: 
When we run out of Greek names, we’ll start naming storms after fossil fuel companies
https://twitter.com/michaelemann/status/1314323929369063424

34
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 09, 2020, 01:16:19 AM »
Quote
Would really like to see that math
It won't be forthcoming because in addition to imperative cloud considerations, it would also have to explain why the Barents no longer freezes over in winter despite reaching 80ºN where it's also rather cold. Ice may blow in from the Kara or across the FJL-SV line but apparently no longer forms significant sea ice on its own.

Like the Yermak, Barents too receives a branch of Atlantic Water inflows and has largely lost its stratification (previously maintained by fresh water from ice melt); in terms of wind mixing, over a third of the Arctic Ocean (mostly on the Siberian side) has shallower water than the ~300m deep Barents.

The Bering Sea too no longer freezes over in winter despite large water exchanges with the Chukchi -- which still has open water on Jan 1st in recent years. The Chukchi is well over a thousand km south of the Barents and only partly above the Arctic Circle.

There are no instances over the last 7 years of Jan 1st open water in the ESS or Laptev. This year bears watching however for open water persisting after mid-November because of the cumulative impact of double diffusion of Atlantic Waters over the years and the massive solar heat input this July to early low albedo open waters of the Laptev.

The AW brings in enough heat each year to melt all the ice, the question has always been how much of that heat it leaves behind -- more and more per Mercator Ocean and Laptev moorings (Polyakov 2019).

It should not be assumed that all the open water in the Arctic Basin will magically refreeze in winter. As time goes on, more and more open water will persist later and later into the depths of winter. A lot of blackbody radiation (Planck effect) comes right back down so it doesn't have the cooling effect that one might imagine.

It's all about clouds and moisture intrusions from mid-latitude:

Following moist intrusions into the Arctic using SHEBA observations in a Lagrangian perspective
S. Mubashshir Ali  Felix Pithan  19 June 2020
https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/qj.3859

"Warm and moist air masses are transported into the Arctic from lower latitudes throughout the year. Especially in winter, such moist intrusions (MIs) can trigger cloud formation and surface warming. While a typical cloudy state of the Arctic winter boundary layer has been linked to the advection of moist air masses, direct observations of the transformation from moist midlatitude to dry Arctic air are lacking.

"The Surface Heat Budget of the Arctic (SHEBA) and the Norwegian Young Sea Ice (N‐ICE2015) expeditions have shown that the wintertime Arctic boundary layer is characterized by a bi‐modal distribution between a radiatively clear and an opaquely cloudy state. This bi‐modality is also observed in the time series from the ARM site at Utqiaġvik for the boreal winter (F Pithan 2014, fig 10). The two states have different net surface long‐wave radiation (NetLW) as the clear state is characterised by strong long‐wave cooling (NetLW ∼ − 40 W·m−2) under clear skies or ice clouds and the cloudy state with little to no surface cooling (NetLW ∼ 0 W·m−2) under low‐level mixed‐phase clouds."

Cloud Radiative Forcing of the Arctic Surface: The Influence of Cloud Properties, Surface Albedo, and Solar Zenith Angle
Matthew D. Shupe; Janet M. Intrieri
J. Climate (2004) 17 (3): 616–628.  classic paper on subject from co-leader of Mosaic
https://journals.ametsoc.org/jcli/article/17/3/616/30440/Cloud-Radiative-Forcing-of-the-Arctic-Surface-The

"An annual cycle of cloud and radiation measurements made as part of the Surface Heat Budget of the Arctic (SHEBA) program are utilized to determine which properties of Arctic clouds control the surface radiation balance. Surface cloud radiative forcing (CF), defined as the difference between the all-sky and clear-sky net surface radiative fluxes, was calculated from ground-based measurements of broadband fluxes and results from a clear-sky model. Longwave cloud forcing (CFLW) is shown to be a function of cloud temperature, height, and emissivity (i.e., microphysics). Shortwave cloud forcing (CFSW) is a function of cloud transmittance, surface albedo, and the solar zenith angle. The annual cycle of Arctic CF reveals cloud-induced surface warming through most of the year and a short period of surface cooling in the middle of summer, when cloud shading effects overwhelm cloud greenhouse effects."

Arctic amplification is caused by sea-ice loss under increasing CO2
Aiguo Dai, Dehai Luo, Mirong Song & Jiping Liu   10 January 2019
https://www.nature.com/articles/s41467-018-07954-9

"Increased outgoing longwave radiation and heat fluxes from the newly opened waters cause Arctic Amplification, whereas all other processes can only indirectly contribute to it by melting sea-ice. Seasonal sea-ice melting from May to September opens a large portion of the Arctic Ocean, allowing it to absorb sunlight during the warm season. Most of this energy is released to the atmosphere through longwave (LW) radiation, and latent and sensible heat fluxes during the cold season from October to April when the Arctic Ocean becomes a heat source to the atmosphere10 (Supplementary Figure 1)"

35
Science / Re: Where are we now in CO2e , which pathway are we on?
« on: October 07, 2020, 02:46:28 PM »
Using ESRL AGGI you can extrapolate the annual CO2 equivalent down to a monthly value.
With the seasonal cycle in GHGs, I would only use year over year monthly changes.

A radiative forcing increase of 0.05 Watts/m2 is worth ~5 ppm of CO2 equivalent.
https://www.esrl.noaa.gov/gmd/aggi/aggi.html

36
Science / Re: Where are we now in CO2e , which pathway are we on?
« on: October 06, 2020, 08:41:14 PM »
To finalize my update on greenhouse gases here is the summary of the four postings in the individual gas concentration threads.

More radiative forcing of the "NOAA gases" (CO2, CH4, N2O, SF6) in June 2020 than in June 2019, but less than in May 2020, because CO2 and CH4 reach their seasonal maximum in May.

The values [W/m²], change to May 2020 and change to June 2019:
CO2 2.161    (- 0.009)    (+ 0.031)   
CH4 0.519    (- 0.001)    (+ 0.005)
N2O 0.205   (+ 0.000)    (+ 0.003)
SF6  0.0053 (+ 0.0000)  (+ 0.0001)
sum  2.891  (- 0.009)   (+ 0.040) (rounding differences)

The relative annual increase is 1.43 %, a little bit higher than May 2020.

37
Science / Re: Trends in atmospheric CH4
« on: October 06, 2020, 08:35:52 PM »
Here is the latest monthly average of Mauna Loa CH4 concentration:

June 2020:     1872.2 ppb
June 2019:     1858.8 ppb
Last updated: October 05, 2020

This is an annual increase of 13.4 ppb. This is the highest annual increase since February 2015!

I set an index = 100 for the 1980 average [1601.2 ppb]. June 2020 is at 116.9 compared to that index.

38
Science / Re: Trends in Atmospheric SF6
« on: October 06, 2020, 08:33:38 PM »
The latest monthly average for SF6 is available from NOAA:

June 2020:     10.26 ppt
June 2019:       9.92 ppt
Last updated: October 05, 2020

The annual increase is 0.34 ppt. It is about average of what has been observed in the last decade.

I set an index of 100 for the year 1980 [0.848 ppt]. June 2020 is at 1,210.

39
Science / Re: Trends in Atmospheric N2O
« on: October 06, 2020, 08:32:08 PM »
The latest NOAA monthly average for N2O is available.

June 2020:     332.9 ppb
June 2019:     331.7 ppb
Last updated: October 05, 2020

The annual increase is 1.2 ppb. This is higher than the annual increase of most of the last years.

I set an index = 100 to the average of 1980 [301.1 ppb]. June 2020 has a relative value of 110.6 compared to 1980.

40
Science / Re: 2020 Mauna Loa CO2 levels
« on: October 06, 2020, 08:23:58 PM »
And here comes the official value from NOAA:

September 2020:       411.29 ppm
September 2019:       408.54 ppm
Last updated: October 6, 2020

The annual increase is 2.75 ppm. Last year (Sep 2019 vs. Sep 2018) it was at 3.03 ppm.

41
Arctic sea ice / Re: Freeform season chatter and light commentary
« on: October 03, 2020, 12:05:09 PM »
Thanks for the SMOS post. As we suspected, all that MYI exported to the Beaufort tail has nearly melted out, and will give no resilience against next year's melting season.

https://www.forbes.com/sites/jeffmcmahon/2018/01/15/carbon-pollution-has-shoved-the-climate-backward-at-least-12-million-years-harvard-scientist-says/#13f60898963e

"The chance that there will be any permanent ice left in the Arctic after 2022 is essentially zero," Anderson said, with 75 to 80 percent of permanent ice having melted already in the last 35 years.

"Can we lose 75-80 percent of permanent ice and recover? The answer is no."

42
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: October 01, 2020, 04:55:55 PM »
Nice combo! Might think about cropping off lower Greenland, looks like there is room for 2x the inset resolution. That consistent spike at 50% suggests a round-off bias. Or, if you are taking pixel counts off the grayscale, that conversion could also do it if there is a palette collision on fairly uncommon concentration classes.

Found some more open water papers. The first distinguishes between 'ice albedo effect' (much discussed on forums) and 'ice-ocean albedo effect' (my current interest) which focuses on dominant lower albedo of open water and the non-radiation of sunlight back out to space.

Cumulative solar adsorption by a small patch of open water on May 20th in the Chukchi really starts to add up after fourteen weeks (September), as do ice-free Bering Kara and Barents seas which also affect the Arctic basin, compared to a big patch opening up in mid-August at 80ºN which barely gets a couple of weeks of post peak solstice insolation. (Multiply area under the surface insolation curve by sq km of open water to get 20:1 effect.)

Evidence for ice-ocean albedo feedback in the Arctic Ocean shifting to a seasonal ice zone
H Kashiwase, K Ohshima, S Nihashi & H Eicken
Scientific Reports v7 8170 (2017)
https://www.nature.com/articles/s41598-017-08467-z

"Ice-albedo feedback due to the albedo contrast between water and ice is a major factor in seasonal sea ice retreat, and has received increasing attention with the Arctic Ocean shifting to a seasonal ice cover. However, quantitative evaluation of such feedbacks is still insufficient.

"Here we provide quantitative evidence that heat input through the open water fraction is the primary driver of seasonal and inter-annual variations in Arctic sea ice retreat. Divergent ice motion in early melt season triggers large-scale feedback which subsequently amplifies summer sea ice anomalies; divergence has doubled since 2000 due to a more mobile ice cover.

"Until recently, the Arctic Ocean has been characterized by a thick multiyear ice cover that persisted throughout the summer, with melt confined to its upper surface. In the seasonal ice zone, presence of an open water fraction with a much lower albedo results in high solar radiation absorption by the upper ocean which in turn serves as the dominant heat source for sea ice lateral and bottom melt. Since the seasonal ice zone is dominated by thin and undeformed first-year ice, the melting of sea ice immediately increases the fraction of open water in the ice-covered area and thus ice-ocean albedo feedback drives up absorption of solar energy in the upper ocean.

"Here we show the dominance of heat input through the open water fraction on sea ice loss We selected the Pacific Arctic Sector (fan-shaped area in figure) as the main study area. This region experienced the largest reductions in summer ice extent and volume anywhere in the Arctic Ocean beginning in the 2000s. Inter-annual variation of ice retreat in this region explains about 86% of the variance over the entire Arctic Ocean (p < 0.001).

Dominance of heat input through the open water fraction: "For the ice-covered area defined by ice concentrations >15%, we have analyzed the daily heat budget separately for the water and ice surfaces from 1979 to 2014. During the summer season, net heat flux at the water surface is much larger than that at the ice surface because shortwave radiation is the dominant component of heat budget in the analysis area…

"The fraction of multiyear ice based on ice age data has decreased from 49 to 31%. This reduction affects sea ice dynamics, in particular through decreases in ice mechanical strength and internal ice interaction forces, and increases in ice deformation rates

"Other factors such as changes in atmospheric circulation patterns, influence of cloud cover, long wave radiative forcing due to anthropogenic CO2 emission, melt pond distribution in the early summer season, release of the solar heat stored in a near-surface layer of the ocean, and increases in the heat inflow through Bering Strait may also contribute to drastic ice reductions. However, we note that these factors are intrinsically linked to divergence in the ice pack, because increased heat input from any source may enhance sea ice mobility.

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015JD023712

Yet another reason not to use DMI 80: "The European ERA‐Interim reanalysis data and NCEP‐CFSv2 analysis data are used to investigate the surface energy budget and atmospheric conditions in 2012 and 2013. The ERA‐Interim reanalysis data are the latest global atmospheric reanalysis produced by the ECMWF is available from 1989 onward The ERA‐Interim reanalysis routines provide major improvements compared with ERA‐40 such as better vertical consistency of the air temperature in the Arctic region and an improved representation of the hydrological cycle.

"The open water fraction is typically small (often less than 10%), but the fact that open water absorbs 2 to 3 times as much broadband solar radiation as bare ice means that these small areas can contribute significantly to the overall uptake of solar radiation in the region. Changes that increase the amount of melt, such as an earlier melt onset, will lead to thinner ice that can more easily allow the dynamic formation of leads or be completely melted through.

"The conditions in 2012 exhibited a longer and more continuous period of ice and snowmelt, with earlier melt onset and later freeze‐up than in 2013, resulting in more ice melt in 2012 than in 2013 [see Perovich  2014a].

"The earlier melt onset in 2012 likely preconditioned the system to allow a longer melt season with lower albedo, resulting in much more solar heat input to the ice‐ocean system in 2012 than in 2013. This additional deposited solar energy would melt the surface, thin the ice, and warm the upper ocean, resulting in more melting and longer melt period. This enhances the positive ice‐albedo feedback."

43
Greenland and Arctic Circle / Re: What's new in Greenland?
« on: September 30, 2020, 06:39:53 PM »
Greenland Is On Track to Lose Ice Faster Than In Any Century Over 12,000 Years: Study
https://phys.org/news/2020-09-greenland-track-ice-faster-century.html



Greenland's rate of ice loss this century is likely to greatly outpace that of any century over the past 12,000 years, a new study concludes.

The research will be published on Sept. 30 in the journal Nature. The study employs ice sheet modeling to understand the past, present and future of the Greenland Ice Sheet. Scientists used new, detailed reconstructions of ancient climate to drive the model, and validated the model against real-world measurements of the ice sheet's contemporary and ancient size.

The findings place the ice sheet's modern decline in historical context, highlighting just how extreme and unusual projected losses for the 21st century could be, researchers say.

... "If the world goes on a massive energy diet, in line with a scenario that the Intergovernmental Panel on Climate Change calls RCP2.6, our model predicts that the Greenland Ice Sheet's rate of mass loss this century will be only slightly higher than anything experienced in the past 12,000 years," Briner adds. "But, more worrisome, is that under a high-emissions RCP8.5 scenario—the one the Greenland Ice Sheet is now following—the rate of mass loss could be about four times the highest values experienced under natural climate variability over the past 12,000 years."

Jason P. Briner, et.al, Rate of mass loss from the Greenland Ice Sheet will exceed Holocene values this century, Nature (2020)
https://www.nature.com/articles/s41586-020-2742-6

44
Science / Re: Where are we now in CO2e , which pathway are we on?
« on: September 29, 2020, 06:37:46 PM »

Hi sorry new to the forum. Long time lurker but had a question. The data presented in the 2.6 column it is as if we continued on the path of the current amount emissions of CO2 and Methane and then each sequential line to the right is if we were to increase in amounts being thrown into the atmosphere or is there some type of mitigation process in there i'm not seeing in 2.6 and 4.5? Clearly 8.5 is the most ambitious of them.

Thanks,
Tylor

Tylor,

The RCPs are "representative concentration pathways" and each present a series of inputs for running climate simulations in models.  They're meant to represent a pattern of climate forcings, not really a forecast of future emissions.  So we'll never be entirely on one path or another.

The number at the end of the RCP is the radiative forcing in the year 2100.  So RCP 2.6 would see 2.6 watts per meter of forcing while RCP would have 8.5 watts per meter in 2100.

The pattern of forcings over the years is broadly described in each of the scenario descriptions.  RCP 8.5 assumes continued growth in fossil fuel emissions, including burning coal at an increasing rate, for the rest of the century.  RCP 2.6 assumes we began reducing non-CO2 greenhouse gas emissions, especially methane, in 2011 (which we haven't), we reach a peak in CO2 emissions around 2040 and then decline and use Negative Emissions Technologies to reduce CO2 concentrations from 2050 through 2100.  RCPs 4.5 and 6.0 assume a peak of CO2 emissions in the second half of the century and then stabilization of concentrations toward the end of the century.

A good summary in easy to read format is available at skepticalscience.org at this link:

https://www.skepticalscience.com/rcp.php

That website has some very useful graphics that show the assumed emission trajectories in each of the scenarios:



The assumed atmospheric concentrations:



One of the interesting features of all of the RCPs, which were developed about 15 years ago, is that they assumed that renewable energy would be too expensive to deploy extensively.  This is shown in another image at the skeptical science article:



Of course, wind and solar are now cheaper than coal and competitive with natural gas, so these assumptions are way too pessimistic.  By 2030, almost all new energy investment will be wind and solar (about 67% is now, with coal seeing almost no new investment the past two years), so by 2050, almost no fossil fuel power plants will be operating. 


45
Arctic sea ice / Re: What's new in the Arctic ?
« on: September 25, 2020, 09:58:54 PM »
Journal article - The hysteresis of the Antarctic Ice Sheet
Julius Garbe, Torsten Albrecht, Anders Levermann, Jonathan F. Donges & Ricarda Winkelmann
Nature volume 585, pages538–544(2020)
https://www.nature.com/articles/s41586-020-2727-5
    New (to me) term - "Creep instability"   Good fit for the times.

"The Graduate" updated for 2020:
Mr. McGuire:  I want to say one two words to you. Just one two words.

Benjamin:  Yes, sir.

Mr. McGuire:  Are you listening?

Benjamin:  Yes, I am.

Mr. McGuire: Plastics.  Creep Instability.

46
Edited into the first post.

47
Arctic sea ice / Re: The 2020/2021 freezing season
« on: September 24, 2020, 10:22:36 PM »
From the looks of it, it appears the MYI in the Beaufort tail is still melting, moving around in southerly waters and with temps apparently not low enough. More of a graveyard than an ice preserve. This tail will not serve as the backbone of a resilient Beaufort next year.

ESRL/PSL agrees. They suggest agressive bottom melting of 2cm per day through the forecast period. Further west around the dateline, there is a bit of bottom growth for a time, before more forecast southerlies put a stop to the growth.

48
Arctic sea ice / Re: What's new in the Arctic ?
« on: September 24, 2020, 09:35:59 PM »
So if we manage to get CO2e past 750 ppm Antarctica melts to the bedrock and the seas rise 70 meters or more?
     70 meters will take a long while, but if 3.3 meters floats your boat that can happen at just  650ppm held steady long enough according to a study published yesterday.
 
      Study out yesterday found that eventually West Antarctic Ice Sheet is drinkable at 2.36C above preindustrial.  IPPC 2014 CO2 and Temp tables for RCP8.5 (closest analog to path we are currently on) put 2.36C at about 650 ppm CO2.  Quick skim of article did not find any timeline should that occur, and they take pain to say their report is NOT a projection or forecast.  Based on Deconto and Pollard 2016 simulation, my guess is that to reach that new equilibrium would take 100 years or more.  Then again, who's to say we would stop at 650ppm CO2 (even less likely for 650 ppm CO2e)?
   
     (Speaking of Dec and Poll 2016, the new paper does NOT account for their proposed ice cliff instability, which apparently is still being debated for validity.  If it does apply, then it seems the new study's melt rates would be underestimates by leaving it out.  On the other hand, the new paper mentions both negative and postive feedbacks that could affect this new disaster scenario.) 

     See animated simulation posted yesterday by Potsdam Institute: 
The Hysteresis of the Antarctic Ice Sheet
Sep 23, 2020


Journal article - The hysteresis of the Antarctic Ice Sheet
Julius Garbe, Torsten Albrecht, Anders Levermann, Jonathan F. Donges & Ricarda Winkelmann
Nature volume 585, pages538–544(2020)
https://www.nature.com/articles/s41586-020-2727-5
    New (to me) term - "Creep instability"   Good fit for the times.

49
Arctic sea ice / Re: The 2020/2021 freezing season
« on: September 22, 2020, 05:45:44 AM »
September 17-21.

2019.

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Arctic sea ice / Re: The 2020 melting season
« on: September 22, 2020, 02:25:35 AM »
Arctic Summer Sea Ice Second Lowest On Record: US Researchers
https://phys.org/news/2020-09-arctic-summer-sea-ice-lowest.html
https://nsidc.org/arcticseaicenews/2020/09/arctic-sea-ice-decline-stalls-out-at-second-lowest-minimum/

The year's minimum was reached on September 15, at 3.74 million square kilometers (1.44 million square miles), according to preliminary date from scientists at the National Snow and Ice Data Center (NSIDC) at the University of Colorado Boulder.



https://nsidc.org/arcticseaicenews/2020/09/arctic-sea-ice-decline-stalls-out-at-second-lowest-minimum/

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