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salbers

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Sea Level Rise Accelerating
« on: March 04, 2018, 07:40:20 PM »
A recent PNAS paper shows SLR is accelerating at .08mm/yr^2. One can look at the doubling time of each component and there we see Antarctic Ice Sheets have a relatively low contribution now, though the shortest doubling time, on the order of 6 years. The overall doubling rate of the rise is roughly 35 years.

http://www.pnas.org/content/early/2018/02/06/1717312115

Andre Koelewijn

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Re: Sea Level Rise Accelerating
« Reply #1 on: March 04, 2018, 08:02:08 PM »
Still, the rather conservative value of 65 cm rise by the year 2100.

salbers

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Re: Sea Level Rise Accelerating
« Reply #2 on: March 04, 2018, 08:06:49 PM »
Indeed the 65cm value is a reasonable estimate of a simple quadratic extrapolation. One might also calculate a quadratic estimate of each component. Then the sum of the total will no longer be quadratic. The Antarctic component doubling each 6 years would come to dominate and the total value by 2100 seems it could be more than 65cm.

vox_mundi

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Re: Sea Level Rise Accelerating
« Reply #3 on: November 12, 2018, 08:08:14 PM »
Modest Warming Risks 'Irreversible' Ice Sheet Loss

Quote
Scientists have known for decades that the ice sheets of Greenland and Antarctica are shrinking, but it had been assumed that they would survive a 1.5-2C temperature rise relatively intact.

However, according to a new analysis published in the journal Nature Climate Change, even modest global warming could cause irreversible damage to the polar ice, contributing to catastrophic sea level rises.

"We say that 1.5-2C is close to the limit for which more dramatic effects may be expected from the ice sheets," Frank Pattyn, head of the department of geosciences, Free University of Brussels and lead study author, told AFP.

 Many models of the 1.5-2C scenario allow for the threshold to be breached in the short term, potentially heating the planet several degrees higher, before using carbon capture and other technologies to bring temperatures back into line by 2100.

The study warned against this approach, however, saying that a feedback loop set off by higher temperatures would "lead to self-sustained melting of the entire ice sheet" even if those rises were later offset.

For Greenland, the team said with 95 percent certainty that major ice sheet decline would occur at 1.8C worth of warming.

"For both Greenland and Antarctica, tipping points are known to exist for warming levels that could be reached before the end of this century," said Pattyn.

The Greenland and Antarctic ice sheets under 1.5 °C global warming, Nature Climate Change (2018
« Last Edit: November 12, 2018, 08:28:59 PM by vox_mundi »
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wili

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Re: Sea Level Rise Accelerating
« Reply #4 on: November 29, 2018, 01:30:02 PM »
https://www.axios.com/sea-level-rise-will-be-costly-if-we-dont-take-action-8d63cf4a-db07-4512-a97b-5718920aaa38.html

Rising sea levels could cost the U.S. trillions

Andrew Freedman

Quote
...parts of Antarctica are far less stable than previously thought. That's why its sea level rise projections are higher than prior reports from the...IPCC...
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wolfpack513

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Re: Sea Level Rise Accelerating
« Reply #5 on: November 30, 2018, 05:52:53 AM »
It has been mention a lot but once the selling starts for coastal properties it’s going to get bad.  People will lose equity/savings and that of course will impact the greater economy.  You don’t want to be the last house on the block to put the “for sale” sign up.  This alone will be trillions before the water rises.

KiwiGriff

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Re: Sea Level Rise Accelerating
« Reply #6 on: August 06, 2019, 09:47:40 AM »
Global sea level rise began to accelerate in the 1960s, 30 years earlier than suggested by previous assessments, a new study finds.

Quote
Previous studies reconstructed twentieth-century global mean sea level (GMSL) from sparse tide-gauge records to understand whether the recent high rates obtained from satellite altimetry are part of a longer-term acceleration. However, these analyses used techniques that can only accurately capture either the trend or the variability in GMSL, but not both. Here we present an improved hybrid sea-level reconstruction during 1900–2015 that combines previous techniques at time scales where they perform best. We find a persistent acceleration in GMSL since the 1960s and demonstrate that this is largely (~76%) associated with sea-level changes in the Indo-Pacific and South Atlantic. We show that the initiation of the acceleration in the 1960s is tightly linked to an intensification and a basin-scale equatorward shift of Southern Hemispheric westerlies, leading to increased ocean heat uptake, and hence greater rates of GMSL rise, through changes in the circulation of the Southern Ocean.
https://www.nature.com/articles/s41558-019-0531-8


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Klondike Kat

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Re: Sea Level Rise Accelerating
« Reply #7 on: August 06, 2019, 03:01:34 PM »
According to his analysis, continued acceleration in SLR would reach ~10 mm/year by 2100, resulting in a total additional rise of about half a meter.

Juan C. García

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Re: Sea Level Rise Accelerating
« Reply #8 on: August 19, 2019, 09:08:54 PM »
This is an article about the gravitational pull of Greenland. I also included a NASA video that shows the lowering of sea levels around Greenland as the ice cap melts, and the gravitational pull weakens. This could also maybe explain why sea levels in Ireland are going up?

Gravitational Attraction of Ice Sheets on the Sea
http://sealevelstudy.org/sea-change-science/whats-in-a-number/attractive-ice-sheets
Great post of Freegrass.
I think that it should be also posted here.

Links to the video:
NASA: https://sealevel.nasa.gov/resources/78/monthly-changes-in-gravity-affect-sea-level
Youtube:
« Last Edit: August 20, 2019, 12:24:56 AM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Tom_Mazanec

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Re: Sea Level Rise Accelerating
« Reply #9 on: August 27, 2019, 09:21:11 PM »
Shoreline industry poses hazards as sea level, floods increase
https://www.bayjournal.com/article/shoreline_industry_poses_hazards_as_sea_level_floods_increase
Quote
But with the Earth warming and sea level rising, many riverside clusters of industry are ground zero for rising waters — posing a new risk for the environment and those living nearby.

In a report issued this spring, the Center for Progressive Reform finds that almost 1,100 industrial facilities in Virginia’s James River watershed that use state or federally regulated chemicals are exposed to both potential flooding and projected sea level rise. Worse, they are located in socially vulnerable communities where residents have the fewest resources to escape a disaster’s effects.

Tom_Mazanec

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Re: Sea Level Rise Accelerating
« Reply #10 on: September 15, 2019, 03:34:49 AM »
15 To 20 Foot Sea Level Rise Possible Sooner Rather Than Later
https://cleantechnica.com/2019/09/13/15-to-20-foot-sea-level-rise-possible-sooner-rather-than-later/
Quote
Why is Alley’s threat assessment greater than the people who are preparing reports for IPCC? Bureaucracy, mostly. They are written in collaboration with a large group of scientists and are often watered down by endless debate and consensus-building. In total there are 18 lead authors and 69 contributing authors on the chapter that considers sea-level rise. Also, by the time the final reports are written, the underlying data is often not the most current available.

sidd

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Re: Sea Level Rise Accelerating
« Reply #11 on: December 21, 2019, 06:17:23 AM »
AGU has the GRACE/GRACE-FO talk online now. I just watched Velicogna on land ice loss.

highlights:

GIS: ice loss of 600GT in 2019, like in 2012, steady decline 250 GT/yr
AIS; Amundsen, Wilkes land sustain decline since 2001, Queen Maud land sustained increase since 2009, Peninsula decline till 2016, then increase from snowfall in 2016, back to decline now. Pause in acceleration today, this has been seen before. Slodown in overall mass loss since 2016
Other glaciers,ice caps, Himalayas: 250GT/yr mass loss

Have to register at AGU fall meet website. Chekitout.

sidd

Hefaistos

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Re: Sea Level Rise Accelerating
« Reply #12 on: August 06, 2020, 01:18:46 PM »
Not so much SLR in the Pacific though, by considering the average of 29 tide gauges included in the Japan-5, Oceania-4 and West Coast of North America-20 data sets, both the relative rate of rise and the acceleration are negative, i.e this report shows deceleration.

"Conclusion
The Pacific Atolls are not drowning because the sea level is rising much less than what was once thought. By considering the average of the 29 long-term-trend (LTT) tide gauges of Japan, Oceania and West Coast of North America, both the relative rate of rise and acceleration are negative, −0.02139 mm yr−1 and −0.00007 mm yr−2, respectively. Since the start of the 1900s, the sea levels of the Pacific have been remarkably stable, rising or falling mostly because of subsidence. The evidence proposed by Duvat (2018) is supported by the long-term tide gauge indication."

https://content.sciendo.com/configurable/contentpage/journals$002fquageo$002f38$002f1$002farticle-p179.xml

/link above broken, must copy missing part manually/

See also "A global assessment of atoll island planform changes over the past decades" by
Virginie K. E. Duvat, 2018.
https://onlinelibrary.wiley.com/doi/abs/10.1002/wcc.557

Maybe we have SLR acceleration in some Seas, and deceleration in others?

gerontocrat

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Re: Sea Level Rise Accelerating
« Reply #13 on: August 23, 2020, 06:49:44 PM »
And so it goes on

28 Trillion tons of ice gone from 1994 to 2017.
If its all in the sea that's nearly 8 cms sea level rise.
EDIT: Whoops, But it isn't - 54% of ice loss issea ice and floating ice shelves.
So that's about 3.5 cms of actual sea level rise to 2017 & about 4cms by end 2020.

At 1.2 trillion tons per annum that's 31 trillion tons by end 2020 - nearly 9cms.

ADDENDUM
Every year global ocean heat content rises on average by just over 1 x 10^22 joules of energy.
That is enough to melt all those circa 30,000 cubic kilometers of ice melted from 1994 to the present - with a little bit of energy left over.


https://www.theguardian.com/environment/2020/aug/23/earth-lost-28-trillion-tonnes-ice-30-years-global-warming
Earth has lost 28 trillion tonnes of ice in less than 30 years
Quote
The scientists – based at Leeds and Edinburgh universities and University College London – describe the level of ice loss as “staggering” and warn that their analysis indicates that sea level rises, triggered by melting glaciers and ice sheets, could reach a metre by the end of the century.

“To put that in context, every centimetre of sea level rise means about a million people will be displaced from their low-lying homelands,” said Professor Andy Shepherd, director of Leeds University’s Centre for Polar Observation and Modelling.

The level of ice loss revealed by the group matches the worst-case-scenario predictions outlined by the Intergovernmental Panel on Climate Change (IPCC), he added.

https://tc.copernicus.org/preprints/tc-2020-232/
Review Article: Earth's ice imbalance
Quote

Abstract.
We combine satellite observations and numerical models to show that Earth lost 28 trillion tonnes of ice between 1994 and 2017. Arctic sea ice (7.6 trillion tonnes), Antarctic ice shelves (6.5 trillion tonnes), mountain glaciers (6.2 trillion tonnes), the Greenland ice sheet (3.8 trillion tonnes), the Antarctic ice sheet (2.5 trillion tonnes), and Southern Ocean sea ice (0.9 trillion tonnes) have all decreased in mass. Just over half (60 %) of the ice loss was from the northern hemisphere, and the remainder (40 %) was from the southern hemisphere.

The rate of ice loss has risen by 57 % since the 1990s – from 0.8 to 1.2 trillion tonnes per year – owing to increased losses from mountain glaciers, Antarctica, Greenland, and from Antarctic ice shelves. During the same period, the loss of grounded ice from the Antarctic and Greenland ice sheets and mountain glaciers raised the global sea level by 35.0 ± 3.2 mm.

The majority of all ice losses were driven by atmospheric melting (68 % from Arctic sea ice, mountain glaciers ice shelf calving and ice sheet surface mass balance), with the remaining losses (32 % from ice sheet discharge and ice shelf thinning) being driven by oceanic melting.

Altogether, the cryosphere has taken up 3.2 % of the global energy imbalance.
« Last Edit: August 23, 2020, 09:57:01 PM by gerontocrat »
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Tom_Mazanec

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Re: Sea Level Rise Accelerating
« Reply #14 on: August 23, 2020, 07:40:31 PM »
Quote
At 1.2 trillion tons per annum that's 31 trillion tons by end 2020 - nearly 9cms.
But it will almost certainly be much more than that later in the century.

KiwiGriff

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Re: Sea Level Rise Accelerating
« Reply #15 on: August 23, 2020, 08:32:03 PM »
The Paper Hefaistos just linked to is by a well known crank.
 Albert Parker/ Alberto Boretti
Being a member of  Principia Scientific International he is a fuckin gibbering loon class crank.
 https://www.desmogblog.com/albert-parker



« Last Edit: August 23, 2020, 08:37:43 PM by KiwiGriff »
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oren

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Re: Sea Level Rise Accelerating
« Reply #16 on: August 23, 2020, 11:45:43 PM »
I was wondering about that paper but did not have time to follow through.
I guess the quest to show AGW isn't as bad as feared takes one to dark places.

oren

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Re: Sea Level Rise Accelerating
« Reply #17 on: August 24, 2020, 04:36:14 AM »
Here is some non-cherry-picked data about sea level rise.






Hefaistos

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Re: Sea Level Rise Accelerating
« Reply #18 on: August 24, 2020, 09:53:44 AM »
The Paper Hefaistos just linked to is by a well known crank.
 Albert Parker/ Alberto Boretti
Being a member of  Principia Scientific International he is a fuckin gibbering loon class crank.
 https://www.desmogblog.com/albert-parker

Sorry for not checking their credentials!
I'm more focused on research and results, than on the people behind the research. Never heard of Parker or Boretti before.

However, their data seem to be correct. If you compare with the map with sampling stations that oren just posted it seems there is no conflict, as their data mainly came from Japan and the US.
Good to have the more complete picture.

Hefaistos

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Re: Sea Level Rise Accelerating
« Reply #19 on: August 24, 2020, 09:56:46 AM »
Here is some non-cherry-picked data about sea level rise.


Thanks oren!
The last two charts, is that global data, or for the Pacific?

ArcticMelt2

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Re: Sea Level Rise Accelerating
« Reply #20 on: August 24, 2020, 11:03:55 AM »
Indeed the 65cm value is a reasonable estimate of a simple quadratic extrapolation. One might also calculate a quadratic estimate of each component. Then the sum of the total will no longer be quadratic. The Antarctic component doubling each 6 years would come to dominate and the total value by 2100 seems it could be more than 65cm.

I agree. A doubling of the rate of ice melting can occur every 10-15 years.


« Last Edit: August 24, 2020, 11:23:12 AM by ArcticMelt2 »

oren

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Re: Sea Level Rise Accelerating
« Reply #21 on: August 24, 2020, 11:24:15 AM »
Here is some non-cherry-picked data about sea level rise.


Thanks oren!
The last two charts, is that global data, or for the Pacific?
Both global.
These are just taken from Wikipedia ("sea level" and "sea level rise") and did not need much searching at all. The research you posted did not pass the sniff test and should not have passed yours either. Sea level rise is an undeniable fact. I believe the denier source both cherry-picked the specific region, AND twisted the data, from the little I could understand of their methods from the poorly written and obfuscating paper. In addition most of the references point to articles by the same authors, and other references' conclusions are twisted to fit the central narrative. You would do well to stay away from such sources and perform better checks when the conclusions are suspicious.

ArcticMelt2

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Re: Sea Level Rise Accelerating
« Reply #22 on: August 24, 2020, 11:39:22 AM »
Still, the rather conservative value of 65 cm rise by the year 2100.

For the United States, say half a meter by 2050.

https://www.eurekalert.org/pub_releases/2020-02/viom-usr020320.php

In some places it will be even higher.

Quote
The three highest rates of sea-level rise in 2019 occurred along the Gulf Coast at Grand Isle, Louisiana (7.93 millimeters per year) and at Rockport (6.95 mm/yr) and Galveston (6.41 mm/yr) Texas. Rockport also topped all 32 stations in its rate of acceleration, at 0.26 mm per year per year. If this continues, sea level here will be 0.82 meters (2.69 feet) higher in 2050 compared to 1992.

S.Pansa

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Re: Sea Level Rise Accelerating
« Reply #23 on: August 24, 2020, 12:26:42 PM »
Talking about the methods of Parker/Boretti . Tamino has more insight on some of them here & here - (simply making stuff up, etc).

Apart from the scientific methods, Parker/Boretti are obviously one and the same person.
From Tamino" You see, Albert Parker also goes by the name Alberto Boretti."

Thankfully this kind of science gets no soil to flourish here.

Tom_Mazanec

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Re: Sea Level Rise Accelerating
« Reply #24 on: August 24, 2020, 12:52:14 PM »
Interesting post, oren.
The map seems to show near zero SLR for LA but quite a bit for Miami. Interesting.

Simon

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Re: Sea Level Rise Accelerating
« Reply #25 on: August 24, 2020, 01:07:09 PM »
For an overall view of sea level rise, the Americans have a good site here:

https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level


wili

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Re: Sea Level Rise Accelerating
« Reply #26 on: August 24, 2020, 03:08:41 PM »
As I recall, sea level rise is (counter-intuitively) faster on the US east coast than many other places because the 'Gulf Stream' is predicted to move closer to shore, bringing its (bernoulli effect?) bulge with it.

Some areas, of course, are also in the long-term process of sinking, including Florida, but at a much slower rate than the sea is rising.

https://www.theinvadingsea.com/2020/03/19/yes-the-land-is-slowly-sinking-in-parts-of-florida-but-the-sea-is-rising-much-faster-and-poses-a-far-greater-threat-of-flooding/
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sidd

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Re: Sea Level Rise Accelerating
« Reply #27 on: September 08, 2020, 12:38:27 AM »
von Schuckmann has a review out on earth energy imbalance and accumulation of heat in the oceans:

"The study obtains a consistent long-term Earth system heat gain over the period 1971–2018, with a total heat gain of 358±37 ZJ, which is equivalent to a global heating rate of 0.47±0.1 W m−2. Over the period 1971–2018 (2010–2018), the majority of heat gain is reported for the global ocean with 89 % (90 %), with 52 % for both periods in the upper 700 m depth, 28 % (30 %) for the 700–2000 m depth layer and 9 % (8 %) below 2000 m depth. Heat gain over land amounts to 6 % (5 %) over these periods, 4 % (3 %) is available for the melting of grounded and floating ice, and 1 % (2 %) is available for atmospheric warming. Our results also show that EEI is not only continuing, but also increasing: the EEI amounts to 0.87±0.12 W m−2during 2010–2018. Stabilization of climate, the goal of the universally agreed United Nations Framework Convention on Climate Change (UNFCCC) in 1992 and the Paris Agreement in 2015, requires that EEI be reduced to approximately zero to achieve Earth’s system quasi-equilibrium. The amount of CO2 in theatmosphere would need to be reduced from 410 to 353 ppm to increase heat radiation to space by 0.87 W m−2, bringing Earth back towards energy balance."

"Our results show that EEIis not only continuing, but also increasing. Over the period 1971–2018 average EEI amounts to 0.47±0.1 W m−2, but it amounts to 0.87±0.12 W m−2 during 2010–2018 (Fig. 8).Concurrently,  acceleration  of  sea-level  rise  (WCRP,  2018;Legelais et al., 2020), accelerated surface warming, record temperatures and sea ice loss in the Arctic (Richter-Mengeet al., 2019; WMO, 2020; Blunden and Arndt, 2020) and ice loss  from  the  Greenland  ice  sheet  (King  et  al.,  2020),  and intensification of atmospheric warming near the surface and in the troposphere (Steiner et al., 2020) have been – for example – recently reported. To what degree these changes are intrinsically linked needs further evaluations"

doi: 10.5194/essd-12-2013-2020

open access, read all about it. Worth it for the references alone. Earth energy imbalance and OHC continue increasing.

sidd

« Last Edit: September 09, 2020, 06:53:17 AM by sidd »

Richard Rathbone

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Re: Sea Level Rise Accelerating
« Reply #28 on: September 08, 2020, 08:04:50 PM »
I was wondering which thread this one should go in.

Its pretty much impossible for increasing EEI not to accelerate sea level rise.

Hansen has suggested a feedback where increased ice cap melt leads to increased EEI, I wonder if this is contributing to the higher EEI in the 2010s.

The 350ppm stablised climate seems to be getting hotter as well as requiring more CO2 removal to achieve it.

FishOutofWater

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Re: Sea Level Rise Accelerating
« Reply #29 on: September 09, 2020, 04:27:54 PM »
Gulf Stream slowdown contributes to SLR on the SE coast of the U.S. Compaction driven subsidence is a major factor in apparent SLR in coastal Louisiana.

Hansen's papers discussed melt driven slowdowns in deep water formation in both hemispheres contributing to ocean heat build up. That started years ago and certainly got going strong in 2010.

Arctic ice loss is affecting the whole NH climate. The polar vortex weakens when warm water moves into the Barents sea. This winter should be very weird very likely with a weak vortex.

kassy

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Re: Sea Level Rise Accelerating
« Reply #30 on: October 21, 2022, 01:02:34 PM »
Ocean Warming Rate Doubles, WIll Be Unstoppable Through 2100; What Happens Next?

According to Nature.com, the temperature of seas have been rising for decades. This trend is increasing and threatens to fuel more powerful storms, destroy marine ecosystems, and disrupt the lives and livelihoods of millions of people.

The study, which was published this week in the journal Nature Reviews, reveals that the planet's highest ocean layers, or around the top 2,000 meters, or just over a mile, have been warming since at least the 1950s, with the Atlantic and Southern seas showing the most pronounced changes.

Data published in the Washington Post suggests that the heating has accelerated over time and has gradually penetrated deeper and deeper depths, according to the review's authors, who include experts from China, France, the United States, and Australia. The experts predict that this warming, which is expected to be unstoppable through the year 2100, will continue and lead to the formation of additional hotspots across the world, particularly if greenhouse gas emissions are not drastically and quickly reduced by humans.

...

The effects of warmer waters are already evident in a variety of ways.

According to scientists, the effects of thermal expansion in ocean water are responsible for around 40% of the worldwide sea level increase. Rising sea levels result from faster ice sheet melting and warmer waters. They alter regular weather patterns and, in certain places, exacerbate drought. Additionally, they intensify hurricanes and set the stage for more devastating flooding and severe rain.

...

https://www.natureworldnews.com/articles/53788/20221021/ocean-warming-rate-doubles-will-unstoppable-through-2100-what-happens.htm

Past and future ocean warming

...

Observationally constrained projections suggest that historic ocean warming is irreversible this century, with net warming dependent on the emission scenario. By 2100, projected warming in the top 2,000 m is 2–6 times that observed so far, ranging from 1,030 [839–1,228] ZJ for a low-emission scenario to 1,874 [1,637–2,109] ZJ for a high-emission scenario. The Pacific is projected to be the largest heat reservoir owing to its size, but area-averaged warming remains strongest in the Atlantic and southern oceans.

...

https://www.nature.com/articles/s43017-022-00345-1#Abs1
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gerontocrat

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Re: Sea Level Rise Accelerating
« Reply #31 on: October 21, 2022, 04:15:49 PM »
I use NOAA data  https://www.ncei.noaa.gov/access/global-ocean-heat-content/ for global heat and temperature data. Unsurpringly, the annual change in ocean heat agrees with the data used in the science paper https://www.nature.com/articles/s43017-022-00345-1#Abs1

The NOAA temperature data says that over the period 2000 to 2021 0-700 metre sea temperatures have risen by 0.15 degrees celsius, and 0-100 metre sea temperatures have risen by 0.29 degrees celsius (0.42 in the Northern Hemisphere).

So if the study is correct, we are talking very significant rises in sea temperatures even on a low emissions scenario well before 2100, and extreme rises on a high emissions scenario (which imply annual global increase in global ocean heat content at least doubling by 2100). This of course accelerates sea level rise.
« Last Edit: October 21, 2022, 04:27:17 PM by gerontocrat »
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kassy

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Re: Sea Level Rise Accelerating
« Reply #32 on: October 21, 2022, 06:33:51 PM »
It is also one of these invisible things. You can measure it but it is still very abstract. Measures like Greenland melt having been locked in to cause at least 28 cm for the rest of the century are easier to understand. It was on Greenland and now it is in the water.

AFAIK there is no simple way to translate the amount of warming in the ocean to some average sea level rise.

So it is slowly creeping up. More SLR but warmer waters also hold less CO2.
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Re: Sea Level Rise Accelerating
« Reply #33 on: October 21, 2022, 06:59:46 PM »
Thanks for the Cheng reference.

Re:  translate the amount of warming in the ocean to some average sea level rise

Currently about 40% of SLR is due to warming of ocean.

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Re: Sea Level Rise Accelerating
« Reply #34 on: November 09, 2022, 06:40:30 PM »
Ice Loss From Northeastern Greenland Significantly Underestimated
https://phys.org/news/2022-11-ice-loss-northeastern-greenland-significantly.html

Ice is continuously streaming off Greenland's melting glaciers at an accelerating rate, dramatically increasing global sea levels. New results published today in Nature indicate that existing models have underestimated how much ice will be lost during the 21st century. Hence, its contribution to sea-level rise will be significantly higher.



By 2100, the Northeast Greenland Ice Stream will contribute six times as much to the rising sea level as previous models suggested, adding between 13,5 to 15,5 mm, according to the new study. This is equivalent to the entire Greenland ice sheet's contribution in the past 50 years. The research was carried out by researchers from Denmark, the United States, France, and Germany

Our previous projections of ice loss in Greenland until 2100 are vastly underestimated," said first author Shfaqat Abbas Khan, Professor at DTU Space.

"Models are mainly tuned to observations at the front of the ice sheet, which is easily accessible, and where, visibly, a lot is happening."

Ice loss occurs more than 200 km inland

The study is partly based on data collected from a network of precise GPS stations reaching as far as 200 km inland on the Northeast Greenland Ice Stream—located behind the Nioghalvfjerdsfjord Gletscher and Zachariae Isstrøm glaciers, one of Earth's most hostile and remote terrains. The GPS data were combined with surface-elevation data from the CryoSat-2 satellite mission and high-resolution numerical modeling.



"Our data show us that what we see happening at the front reaches far back into the heart of the ice sheet," said Khan.

"We can see that the entire basin is thinning, and the surface speed is accelerating. Every year the glaciers we've studied have retreated further inland, and we predict that this will continue over the coming decades and centuries. Under present day climate forcing, it is difficult to conceive how this retreat could stop."



"It is possible that what we find in northeast Greenland may be happening in other sectors of the ice sheet. Many glaciers have been accelerating and thinning near the margin in recent decades. GPS data helps us detect how far this acceleration propagates inland, potentially 200–300 km from the coast. If this is correct, the contribution from ice dynamics to the overall mass loss of Greenland will be larger than what current models suggest."

The Zachariae Isstrøm was stable until 2004, followed by steadily retreat of the ice front until 2012, when a large portion of the floating sections became disconnected. As more precise observations of change in ice velocity are included in models, it is likely that IPCC's estimates of 22–98 cm global sea level rise will need to be corrected upwards.



"We foresee profound changes in global sea levels, more than currently projected by existing models," said coauthor Eric Rignot, professor of Earth system science at the University of California, Irvine.

Shfaqat Abbas Khan, Extensive inland thinning and speed-up of North-East Greenland Ice Stream, Nature (2022).
https://www.nature.com/articles/s41586-022-05301-z
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Re: Sea Level Rise Accelerating
« Reply #35 on: November 09, 2022, 08:29:16 PM »
Thanks for the Khan paper.

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Re: Sea Level Rise Accelerating
« Reply #36 on: November 16, 2022, 06:55:46 PM »
Surprise; Surprise! ...

Rising Sea Level Could Exceed Estimates for US Coasts, NASA Study Finds
https://phys.org/news/2022-11-sea-exceed-coasts-nasa.html



New results show average sea level rise approaching the 1-foot mark for most coastlines of the contiguous U.S. by 2050. The Gulf Coast and Southeast will see the most change.

By 2050, sea level along contiguous U.S. coastlines could rise as much as 12 inches (30 centimeters) above today's waterline (which is already 8-12 inches above 1980 levels), according to researchers who analyzed nearly three decades of satellite observations. The results from the NASA Sea Level Change Team could help refine near-term projections for coastal communities that are bracing for increases in both catastrophic and nuisance flooding in coming years.

Global sea level has been rising for decades in response to a warming climate, and multiple lines of evidence indicate the rise is accelerating. The new findings support the higher-range scenarios outlined in an interagency report released in February 2022.

https://oceanservice.noaa.gov/hazards/sealevelrise/sealevelrise-tech-report.html

That report, developed by several federal agencies—including NASA, the National Oceanic and Atmospheric Administration (NOAA), and the U.S. Geological Survey—expect significant sea level rise over the next 30 years by region. They projected 10 to 14 inches (25 to 35 centimeters) of rise on average for the East Coast, 14 to 18 inches (35 to 45 centimeters) for the Gulf Coast, and 4 to 8 inches (10 to 20 centimeters) for the West Coast.

Building on the methods used in that earlier report, a team led by scientists at NASA's Jet Propulsion Laboratory in Southern California leveraged 28 years of satellite altimeter measurements of sea surface height and correlated them with NOAA tide gauge records dating as far back as 1920. By continuously measuring the height of the surrounding water level, tide gauges provide a consistent record to compare with satellite observations.

The researchers noted that the accelerating rate of sea level rise detected in satellite measurements from 1993 to 2020—and the direction of those trends—suggest future sea level rise will be in the higher range of estimates for all regions.

The hazards of rising sea level are amplified by natural variabilities on Earth.

For instance, by the mid-2030s, every U.S. coast will experience more intense high-tide floods due to a wobble in the Moon's orbit that occurs every 18.6 years. Hamlington said that this lunar cycle, in combination with rising sea level, is projected to worsen the impacts of high-tide flooding during the 2030s and 2040s.



Benjamin D. Hamlington et al, Observation-based trajectory of future sea level for the coastal United States tracks near high-end model projections, Communications Earth & Environment (2022).
https://www.nature.com/articles/s43247-022-00537-z
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