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JimD

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Re: Sea Level Rise Projections and Maps
« Reply #100 on: March 06, 2014, 04:58:13 PM »
Lennart

Thanks, good info.  Once again I note from the graphs showing expected slr with the various scenarios (and from other papers the equivalent regarding temperatures) that the longer we follow the various BAU approaches the harder it is going to be for those who pass through the bottleneck.  A limited number of people after the collapse can adapt to the world we are making in terms of slr and temperature rise, but the actual number is going to be very constrained if we run the table via BAU.  We desperately need an early collapse.
We do not err because truth is difficult to see. It is visible at a glance. We err because this is more comfortable. Alexander Solzhenitsyn

How is it conceivable that all our technological progress - our very civilization - is like the axe in the hand of the pathological criminal? Albert Einstein

sidd

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Re: Sea Level Rise Projections and Maps
« Reply #101 on: March 06, 2014, 08:30:13 PM »
I was wrong in my statement that the fingerprint effect is only a few centimeters. There is a relatively simple treatment in Clark(1977, Nature, v267, pp 206 et seq.) which shows that in the immediate vicinity of WAIS, the SLR would fall by 500% of the global average. I enclose Fig 2. from Clark here, Please note that more sohisticated treatments are avilable today, see eg (Mitrovica, 2014, http://dx.doi.org/10.1016/j.quascirev.2013.12.022)


JimD

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Re: Sea Level Rise Projections and Maps
« Reply #102 on: March 18, 2014, 02:09:51 PM »
Just another government policy gone awry.  Flood insurance.

Quote
Congress Just Undid The 1 Good Thing It's Done On Climate Change

Congress approved changes to the federal flood insurance program in June 2012 that lawmakers said then would fix the program's problems and make it more financially stable. The bipartisan reforms phased out subsidies for high-risk coastal properties, which onlookers concerned about climate change said was key to discouraging unsustainable coastal development. It was perhaps the only good thing on climate that Congress had done in a really long time.

Last week, Congress decided to undo it.

Quote
"Congress had a real opportunity here with Biggert-Waters to start to address some of the necessary reforms to the National Flood Insurance Program, both to deal with growing risk from sea level rise as well as development along our coasts," said Rachel Cleetus, a senior climate economist with the Union of Concerned Scientists. "But instead they've done what they seem to have perfected -- burying their heads in the sand. They're not dealing with the tough issues here."

I guess we could say they are burying their heads in the sand?

http://www.huffingtonpost.com/2014/03/17/congress-flood-insurance_n_4981226.html
We do not err because truth is difficult to see. It is visible at a glance. We err because this is more comfortable. Alexander Solzhenitsyn

How is it conceivable that all our technological progress - our very civilization - is like the axe in the hand of the pathological criminal? Albert Einstein

JimD

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Re: Sea Level Rise Projections and Maps
« Reply #103 on: March 18, 2014, 03:07:32 PM »
More stupid people.

While the seas rise in the Outer Banks and elsewhere in NC, science treads water

Quote
There’s not much dispute these days, up and down the coast, about whether the ocean is rising. The question is: How high will it go here, and how fast?

North Carolinians must wait until 2016 for an official answer. That’s the law.

After promoters of coastal development attacked a science panel’s prediction that the sea would rise 39 inches higher in North Carolina by the end of this century, the General Assembly passed a law in 2012 to put a four-year moratorium on any state rules, plans or policies based on expected changes in the sea level. The law sets guidelines under which the Coastal Resources Commission, a development policy board for the 20 coastal counties, will formulate a new sea-level prediction to serve as the official basis for state planners and regulators.

http://www.newsobserver.com/2014/03/15/3702235/while-the-seas-rise-science-waits.html#storylink=cpy
We do not err because truth is difficult to see. It is visible at a glance. We err because this is more comfortable. Alexander Solzhenitsyn

How is it conceivable that all our technological progress - our very civilization - is like the axe in the hand of the pathological criminal? Albert Einstein

RaenorShine

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Re: Sea Level Rise Projections and Maps
« Reply #104 on: April 29, 2014, 02:08:37 PM »
http://www.bbc.co.uk/news/science-environment-27202192

Quote
Megacities contend with sinking land

Subsiding land is a bigger immediate problem for the world's coastal cities than sea level rise, say scientists.

In some parts of the globe, the ground is going down 10 times faster than the water is rising, with the causes very often being driven by human activity.

sidd

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Re: Sea Level Rise Projections and Maps
« Reply #105 on: September 17, 2017, 05:59:17 AM »
This is strange. AVISO shows sea level stall for one and a half years. I attach image.  colorado sealevel concurs within spread.

https://www.aviso.altimetry.fr/en/data/products/ocean-indicators-products/mean-sea-level.html

http://sealevel.colorado.edu/

Has it been raining on land more for the last yearish ? mebbe good for aquifers.

I can believe we have exported enuf heat into deep ocean to account for this. Or slowed land/above flotation ice melt by that much, about 5mm global SLR over the period.

sidd

oren

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Re: Sea Level Rise Projections and Maps
« Reply #106 on: September 17, 2017, 07:49:39 AM »
I think it's basically reversion to mean following the El NiNo. But There's also been heavy snows on Greenland this past year.

Aluminium

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Re: Sea Level Rise Projections and Maps
« Reply #107 on: September 21, 2017, 12:50:48 AM »
Hello, ASIF. :)

Few months ago I attempted to estimate acceleration of SLR. I took data from AVISO before February 2017. Simple polynomial approximation was used: at2+bt+c.

Results for 2017.0
Velocity = 0.393 cm/y. 1 sigma = 0.005 cm/y.
Acceleration = 0.0055 cm/y2. 1 sigma = 0.0004 cm/y2.

bligh8

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Re: Sea Level Rise Projections and Maps
« Reply #108 on: September 26, 2017, 05:03:00 PM »
This is strange. AVISO shows sea level stall for one and a half years. I attach image.  colorado sealevel concurs within spread.



When Oceans Drop

Could La Niña or El Niño shrink the ocean?

“By looking at gravity measurements of oceans and land around the globe, the researchers could spot areas that weighed more in 2011. Boening said, “GRACE allowed us to actually track down the water to see where it went. And it turned out it was in northern South America, Southeast Asia, and Australia.” The strong La Niña had affected the oceans to an unusual extent, not by cooling the water so much as by moving the water on to land. Rainfall follows warm pools of water, and during El Niño, more rain tends to fall over the Pacific Ocean. But during La Niña, cooler oceans push that rainfall over continents.”

“The plot below shows ocean levels since 1993. The red line shows sea level rise and the blue line indicates the trend. The red circle shows the sudden dip in 2010 and 2011, and the arrow points to a map of where that missing water went: primarily to Australia and northern South America (indicated by blue arrows on the inset map). While the ocean lost water, the continents experienced a gain because of increased rainfall brought on by the 2010/2011 La Niña. By mid 2012, global mean sea level had recovered by more than the five millimeters it dropped.

 (Courtesy NASA JPL)”
https://earthdata.nasa.gov/user-resources/sensing-our-planet/when-oceans-drop



Rob Dekker

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Re: Sea Level Rise Projections and Maps
« Reply #109 on: September 27, 2017, 08:36:09 AM »
SLR was cruising a bit high over the past couple of years, so a bit of a stall was not unexpected.



Overall, we are still seeing an acceleration of SLR since the 20th century :

This is our planet. This is our time.
Let's not waste either.

AbruptSLR

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Re: Sea Level Rise Projections and Maps
« Reply #110 on: September 27, 2017, 11:05:33 AM »
This is strange. AVISO shows sea level stall for one and a half years. I attach image.  colorado sealevel concurs within spread.

Following a very strong El Nino event it is normal for the sea level rise to either stall or fall back a little, but when one uses the Jason 2 time series from July 2008 to Feb 2017 (see attached image), one still gets a relatively high rate of sea level rise of 4.41 mm/year:
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

bligh8

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Re: Sea Level Rise Projections and Maps
« Reply #111 on: September 27, 2017, 04:18:21 PM »
This is strange. AVISO shows sea level stall for one and a half years. I attach image.  colorado sealevel concurs within spread.

Following a very strong El Nino event it is normal for the sea level rise to either stall or fall back a little, but when one uses the Jason 2 time series from July 2008 to Feb 2017 (see attached image), one still gets a relatively high rate of sea level rise of 4.41 mm/year:

Although a relatively high rate the Jason 2 time series is down a bit. See attached image from July
2016


sidd

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Re: Sea Level Rise Projections and Maps
« Reply #112 on: October 19, 2017, 07:59:32 PM »
Sea level rise occurs in steps, new evidence from coral reefs in the last deglaciation:

https://www.nature.com/articles/s41467-017-00966-x

Open access (i checked ...) Read all about it.

sidd

AbruptSLR

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Re: Sea Level Rise Projections and Maps
« Reply #113 on: October 26, 2017, 07:26:16 PM »
The linked open access reference indicates that sea level rise projections using the new SSP forcing scenarios and emulating cliff failures and hydrofracturing leads to significantly higher estimates than were including in AR5:

Alexander Nauels , Joeri Rogelj, Carl-Friedrich Schleussner ,MalteMeinshausen and
MatthiasMengel (2017), "Linking sea level rise and socioeconomic indicators under the Shared Socioeconomic Pathways", Environ. Res. Lett. 12, 114002 https://doi.org/10.1088/1748-9326/aa92b6

http://iopscience.iop.org/article/10.1088/1748-9326/aa92b6

Abstract: "In order to assess future sea level rise and its societal impacts, we need to study climate change pathways combined with different scenarios of socioeconomic development. Here, we present sea level rise (SLR) projections for the Shared Socioeconomic Pathway (SSP) storylines and different year-2100 radiative forcing targets (FTs). Future SLR is estimated with a comprehensive SLR emulator that accounts for Antarctic rapid discharge from hydrofracturing and ice cliff instability. Across all baseline scenario realizations (no dedicated climate mitigation), we find 2100 median SLR relative to 1986–2005 of 89 cm (likely range: 57–130 cm) for SSP1, 105 cm (73–150 cm) for SSP2, 105 cm (75–147 cm) for SSP3, 93 cm (63–133 cm) for SSP4, and 132 cm (95–189 cm) for SSP5. The 2100 sea level responses for combined SSP-FT scenarios are dominated by the mitigation targets and yield median estimates of 52 cm (34–75 cm) for FT 2.6 Wm−2, 62 cm (40–96 cm) for FT 3.4 Wm−2, 75 cm (47–113 cm) for FT 4.5 Wm−2, and 91 cm (61–132 cm) for FT 6.0 Wm−2. Average 2081–2100 annual SLR rates are 5 mm yr−1 and 19 mm yr−1 for FT 2.6 Wm−2 and the baseline scenarios, respectively. Our model setup allows linking scenario-specific emission and socioeconomic indicators to projected SLR. We find that 2100 median SSP SLR projections could be limited to around 50 cm if 2050 cumulative CO2 emissions since pre-industrial stay below 850 GtC, with a global coal phase-out nearly completed by that time. For SSP mitigation scenarios, a 2050 carbon price of 100 US$2005 tCO2 −1 would correspond to a median 2100 SLR of around 65 cm. Our results confirm that rapid and early emission reductions are essential for limiting 2100 SLR."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Tor Bejnar

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Re: Sea Level Rise Projections and Maps
« Reply #114 on: May 08, 2019, 04:26:56 PM »
From the Arctic Methane Release thread:

From some information I posted elsewhere (here and here), it appears that sea level around Greenland is lowering at roughly the same rate as sea level is rising 'globally', at least as long as the continental ice sheet melt is dominated by West Antarctica and Greenland (and not East Antarctica).  On a rough scale, when global average sea level rises 2 meters (about 2080-2100?), sea level 'near' Greenland (within 2,000 km, but diminishing with distance) will lower about 2 meters.

How much 'less pressure' would this represent?
Tor, I think this is not the case. It should be a factor of about 5 between Greenland sea level drop and global SLR. I think the explanation is that part of the global SLR is due to other glaciers worldwide, changes in hydrology, and thermal expansion.
Oren,
Can you explain further?  I think you saying 2 meters of global sea level rise will show as 10 meters of Greenland sea level drop - is this accurate?  reference?  Any comment on consequences of East Antarctica melt?  I've not read anything.

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oren

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Re: Sea Level Rise Projections and Maps
« Reply #115 on: May 08, 2019, 06:21:05 PM »
It's certainly not accurate...
I've seen a couple of references that I will dig up later. IIRC, one of them said if West Antarctica melted, SLR would be 7 meters and sea level drop nearby could reach up to 90 meters. The other, posted on the forum recently, said if Greenland melted SLR would be 6 or 7 meters while sea level drop nearby would be 30-50 meters. Not sure why there is such a difference between the locations.
So a back of the envelope naive calculation says that for an SLR of 2m, 1m from GIS 1m from WAIS, should see a drop of 7m (40/6.5*1) near Greenland, and 13m (90/7*1) near West Antarctica. But because of the 1m coming fro the other location, it should be 6m and 12m respectively.
So my general factor should have been 3 for Greenland, and 6 for Antarctica. But it really depends on lots of variables.

oren

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Re: Sea Level Rise Projections and Maps
« Reply #116 on: May 08, 2019, 06:29:16 PM »
http://nautil.us/issue/33/attraction/why-our-intuition-about-sea_level-rise-is-wrong
Quote
So if the Greenland ice sheet were to catastrophically collapse tomorrow, the sea level in Iceland, Newfoundland, Sweden, Norway—all within this 2,000 kilometer radius of the Greenland ice sheet—would fall. It might have a 30 to 50 meter drop at the shore of Greenland. But the farther you get away from Greenland, the greater the price you pay. If the Greenland ice sheet melts, sea level in most of the Southern Hemisphere will increase about 30 percent more than the global average. So this is no small effect.

oren

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Re: Sea Level Rise Projections and Maps
« Reply #117 on: May 08, 2019, 06:35:30 PM »
https://news.harvard.edu/gazette/story/2010/12/ice-sheet-in-peril-gravity-to-rescue/
Quote
But physics teaches that a gravitational pull is exerted by every bit of matter on every other bit of matter. Other than the grounding effect of Earth’s gravity, though, that is negligible for most aspects of our day-to-day lives. But graduate student Natalya Gomez and her adviser, Professor of Geophysics Jerry Mitrovica, have been working hard in recent years to understand the gravitational effects of the enormous areas that make up the ice sheets.

Gomez’s research makes use of the fact that the sheets are so vast that they are exerting a significant gravitational pull on the ocean. When the ice sheets melt, the expected sea level rise from all that meltwater entering the oceans would be counterbalanced by the relaxation of the sea level near the ice sheet due to a decreased pull from the gravity of the remaining ice.

The effect would be not just noticeable, but massive. In that earlier work, Gomez showed that if all of the West Antarctic sheet melted, it could actually lower sea level near the ice by as much as 300 feet.

Rich

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Re: Sea Level Rise Projections and Maps
« Reply #118 on: May 08, 2019, 06:44:14 PM »
It's certainly not accurate...
I've seen a couple of references that I will dig up later. IIRC, one of them said if West Antarctica melted, SLR would be 7 meters and sea level drop nearby could reach up to 90 meters. The other, posted on the forum recently, said if Greenland melted SLR would be 6 or 7 meters while sea level drop nearby would be 30-50 meters. Not sure why there is such a difference between the locations.
So a back of the envelope naive calculation says that for an SLR of 2m, 1m from GIS 1m from WAIS, should see a drop of 7m (40/6.5*1) near Greenland, and 13m (90/7*1) near West Antarctica. But because of the 1m coming fro the other location, it should be 6m and 12m respectively.
So my general factor should have been 3 for Greenland, and 6 for Antarctica. But it really depends on lots of variables.

It seems like the difference between WA and Greenland would be due to the distribution of gravitational forces in the region. The proportion of land mass in the South Pole tied up in ice is greater than the proportion in the region around Greenland which has a lot more land in the vicinity (Canada for example).

I would not assume that is either a linear process or that it depends on a lot of variables. The effect should be back-weighted and dependent on a single variable....gravitational force and remaining land mass.

gerontocrat

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Re: Sea Level Rise Projections and Maps
« Reply #119 on: May 08, 2019, 07:16:52 PM »
Two questions.

A general increase in sea level from the melting of the ice sheets of Greenland and Antarctica causes a localised sea level drop due to reduced gravitational pull from the reduced mass of Greenland and Antarctica. That must result in a sea level rise above the average elsewhere.
How does one calculate that? How significant is that rise above the average ?

Various examples re quoted on local sea level drop arising from various events, e.g. if Greenland melted SLR would be 6 or 7 meters while sea level drop nearby would be 30-50 meters. Can one then say if Greenland melt causes a sea level rise of 6-7 cms local sea level drop would be 30-50 cms, and would the increase elsewhere also be linear? i.e. is the relationship linear? (My guess is no - gravitational pull is proportional to the square of the distance ?)

In other words, I want to know how much extra SLR Mar-el-Largo will get if / when Greenland melts.

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oren

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Re: Sea Level Rise Projections and Maps
« Reply #120 on: May 08, 2019, 07:48:11 PM »
The links I quoted said far-off places, like Miami, would see a 25% or 35% higher local SLR compared to global average SLR.

Are the processes linear? I would say yes at first approximation. Assume all mass is lost at the center of mass of the ice sheet, and the more is lost the more the local water level drops. The distances don't change, only the relative masses, hence linear. But it also depends on other SLR contributions, on the relative contribution of Greenland and the WAIS, on the local distribution of ice mass loss within the ice sheets, and on the speed of the process, as there are other processes such as isostatic uplift, and even slowdown of the planet's rotation due to more weight at the equator, thereby affecting SLR further. Without a full simulation it's impossible to account for everything. I am sure some of the papers by Mitrovica and Gomez have more detailed answers.

Re East Antarctica, I think the main assumption is that ice mass losses there will be negligible compared to the GIS and the WAIS. And I sure do hope this assumption holds.

Rich

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Re: Sea Level Rise Projections and Maps
« Reply #121 on: May 08, 2019, 09:06:34 PM »
If the gravitational mass is lost in a linear process, the gravitational force is lost is a exponentially accelerating manner.

If we assume an object weighs 100 lbs, the first 10 pounds of loss represent a 10% decrease. (10 / 100). The next 10 pounds represent an 11.1% decrease (10 / 90). The last 10 pounds represent a 100% decrease (10/10).

This is of course a simplification. Not all of the gravitational land mass in Antarctica and Greenland and Antarctica is ice. There is solid earth underneath which will continue to exert gravitational pull on the surrounding waters even after all the ice would be gone.

In the case of Greenland, there are clearly more concentrated and substantial land masses in the Arctic region such as North America and Russia which would still be pulling water toward the north pole in the absence of Greenland Ice.

Antarctica doesn't have the same concentration of land masses in the region, so Antarctic Ice represents a greater proportion of the gravitational mass in that region than Greenland does in it's own region. That's why Antarctic Ice loss would be accompanied by a larger local drop in sea level.

Tor Bejnar

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Re: Sea Level Rise Projections and Maps
« Reply #122 on: May 08, 2019, 09:33:30 PM »
The links in one of my posts had some information...
 
Quote
We lack robust forecasting models for future ice changes, which
diminishes our ability to use these fingerprints to accurately predict local sea-level (LSL)


Should coastal planners have concern over where land ice is melting?
Eric Larour,Erik R. Ivins and Surendra Adhikari
Science Advances  15 Nov 2017

Going to the abstract
Quote
We apply GFM to 293 major port cities to allow coastal planners to readily calculate LSL change as more reliable predictions of cryospheric mass changes become available.
The paper is available, but I don't have time to look at it now... (get there from the abstract link)
Arctic ice is healthy for children and other living things.