Historical records may underestimate global sea level rise

Historical records may underestimate global sea level rise
The pattern of sea level change or 'fingerprint' resulting from one millimeter per year of Greenland ice melt derived from NASA GRACE measurements. The black circles show locations of the best historical water level records, which mostly fall in the blue areas that are less than one millimeter per year. As a result, these records underestimate global average sea level rise due to Greenland melt by about 25 percent. Credit: Thompson, et al., 2016

New research published in Geophysical Research Letters shows that the longest and highest-quality records of historical ocean water levels may underestimate the amount of global average sea level rise that occurred during the 20th century. Dr. Philip Thompson, associate director of the University of Hawai'i Sea Level Center in the School of Ocean and Earth Science and Technology (SOEST), led the study.

"It's not that there's something wrong with the instruments or the data," said Thompson, "but for a variety of reasons, sea level does not change at the same pace everywhere at the same time. As it turns out, our best historical sea level records tend to be located where past sea level rise was most likely less than the true global average."

A team of earth scientists from the University of Hawai'i at Mānoa, Old Dominion University, and the NASA Jet Propulsion Laboratory worked together to evaluate how various processes that cause sea level to change differently in different places may have affected past measurements. One particularly important concept is the existence of "ice melt fingerprints", which are global patterns of caused by deviations in Earth's rotation and local gravity that occur when a large ice mass melts. Each glacier, ice cap, or ice sheet has a unique melt fingerprint that can be determined using NASA's GRACE satellite measurements of Earth's changing gravitational field.

Historical records may underestimate global sea level rise
The current site of the San Francisco tide gauge operated by NOAA, which is one of the longest and highest-quality records of ocean water level in the world. The tide gauge was initially installed in 1854. Credit: Image courtesy of NOAA Tides and Currents.

During the 20th century, the dominant sources of global ice melt were in the Northern Hemisphere. The results of this study showed that many of the highest-quality historical water level records are taken from places where the melt fingerprints of Northern Hemisphere sources result in reduced local sea level change compared to the global average. Furthermore, the scientists found that factors capable of enhancing sea level rise at these locations, such as wind or Southern Hemisphere melt, were not likely to have counteracted the impact of fingerprints from Northern Hemisphere .

"This is really important, because it is possible that certain melt fingerprints or the influence of wind on ocean circulation might cause us to overestimate past ," said Thompson, "but these results suggest that is not likely and allow us to establish the minimum amount of global sea level rose that could have occurred during the last century."

The investigation concludes that it is highly unlikely that global average sea level rose less than 14 centimeters during the 20th century, while the most likely amount was closer to 17 centimeters.

The full paper can be found here, and more information about sea level change can be found on the University of Hawai'i Sea Level Center website and the NASA change website.


Explore further

Study shows Indian Ocean sea level on the rise

More information: P. R. Thompson et al, Are long tide gauge records in the wrong place to measure global mean sea level rise?, Geophysical Research Letters (2016). DOI: 10.1002/2016GL070552
Journal information: Geophysical Research Letters

Citation: Historical records may underestimate global sea level rise (2016, October 3) retrieved 20 June 2019 from https://phys.org/news/2016-10-historical-underestimate-global-sea.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
313 shares

Feedback to editors

User comments

Oct 03, 2016
17cm. Even if true. Not a big deal.

Oct 03, 2016
17cm. Even if true. Not a big deal.


10cm doubles the risk of flooding in coastal areas. We're almost at 20cm. And you don't think that's a big deal?

Oct 03, 2016
Problem: Observed data not dangerous to man nor beast.

Solution: Make the data look worse than it really is.

Call me when the dairy farms on Greenland are, again, 400 years old.

Oct 04, 2016
In other words, it's risen more where we haven't measured it. So then...if it hasn't been measured, how do you know this? This is just supposition framed within such phrases as "most likely", "not likely", "possible", highly unlikely". Good grief.

Oct 04, 2016
...if it hasn't been measured, how do you know this?
@Omnishambles
if a murder occurs and the cops aren't there to see it, did it happen?
forensics can tell a lot about what actually did happen even though it isn't measured or observed...

this is the same, and can be demonstrated by taking something like, say, the Buffalo river water levels
when walking along the river it doesn't have scientific measurement stations but you can tell that, historically, it's levels got to at least a few certain points because of the debris and erosion plainly visible on the riverbanks

you can do that with oceans, lakes and other water sources as well

also note that you can see exactly how they determined the measurements and data by reading the entire study (whereas just the abstract is visible on the wiley page)

Oct 04, 2016
This comment has been removed by a moderator.

Oct 05, 2016
So science is a step wise process. Each piece of data builds on previous knowledge, and the puzzle takes shape one piece at a time.


Most of the time, this is true.. but sometimes we are using the wrong puzzle box picture as a basis for what the puzzle is supposed to look like.

I don't see that this changes that much - but still reinforces "Houston we have a problem."


When your assumption is change = problem, then yes, I suppose your statement is accurate but that's a very unscientific stance in that it assumes a relatively unchanging "Eden" prior to the Industrial Revolution.

Science/models have also likely UNDER-estimated past temperature changes (the reference to which we compare modern change). This doesn't mean everything is fine and we have nothing to worry about but it does suggest that language calling modern change "unprecedented" isn't accurate and is more based on ignorance due to the low resolution of our proxies. (cont'd)

Oct 05, 2016
"Our work indicates instead that geological episodes of climatic or evolutionary change likely fail to capture the true pace of changes on timescales of most relevance for understanding the impact of similar changes today. Implicitly, our findings also mean that caution must be exercised when describing recent temperature changes as unprecedented in the context of geological rates."

http://www.nature...omms9890

Oct 05, 2016
but that's a very unscientific stance in that it assumes a relatively unchanging "Eden" prior to the Industrial Revolution
@jeffe
sorry, but this is bullsh*t and you've not been able to justify it's validity WRT climate science at all

and nowhere does science ever claim or infer some unchanging eden, nor does it make a claim that change is bad - it does, however, note that the rate of change as well as the overwhelming evidence is demonstrating a potential serious problem for the future, and that the potential for it being on the level of an extinction event is far to high to ignore (which you're ignoring, BTW)


Oct 05, 2016
and nowhere does science ever claim or infer some unchanging eden, nor does it make a claim that change is bad - it does, however, note that the rate of change as well as the overwhelming evidence is demonstrating a potential serious problem for the future, and that the potential for it being on the level of an extinction event is far to high to ignore (which you're ignoring, BTW)

To equate change with extinction, especially the extinction of a species that lives in ALL parts of the planet (cold hot, dry, tropical) is a fear-based emotional reaction and not remotely rational/scientific. And I'm not ignoring anything... I just make an attempt to tone down the near-hysteria I see in people every time an article like this comes along. I also prefer the adaptation route to that of the futile attempt to control climate conditions. We continue to move in a direction of efficiency and stewardship but it will NEVER be fast enough for some people.

Oct 05, 2016
Also, that three people have already rated 1-star to a simple, direct quote from a peer-reviewed study speaks volumes. The fear narrative seems far more important than rational analysis to many here.

Oct 05, 2016
deniers are a sickening bunch of pukes.

Oct 05, 2016
Oh, you got to admire the AGW Cult they have learned well from that other infamous cult; the Church. If history defies your dogma, then rewrite history i.e. make shit up. They did it with the temperature record and the ignorant Chicken Littles swallowed it up, so why not sea levels. Eat up Chicken Littles.

Oct 06, 2016
Also, that three people have already rated 1-star to a simple, direct quote from a peer-reviewed study speaks volumes. The fear narrative seems far more important than rational analysis to many here.

It's because you mine a quote, and then place it without context as if it is a point being made.You deserve a one. In fact, your comment should be deleted.

Oct 06, 2016
To equate change with extinction, especially the extinction of a species that lives in ALL parts of the planet (cold hot, dry, tropical) is a fear-based emotional reaction and not remotely rational/scientific
@jeffe
idiot boy, i equated rate of change and it has a scientific basis - historically we can show links and evidence where the rate of change is directly involved with extinction events... you know, sh*t like:
https://en.wikipe...on_Event

of course, i can name more but you won't read any of it... mostly because you don't want to see the evidence that is refuting your delusion

Oct 06, 2016
I say B-cubed's points are well taken. The layers of denial are really incredible. You have ego driven idiots that have to deny AGW to please their peer reference group, and those that see the stupidity and danger of it...deny that it is best practices to ignore trolls. What part of denying the clear consensus reached after reviewing much data do they not get???

It's pure Donald Trump stupidity. His rhetoric is the best gift ISIS ever got. They couldn't have created a candidate that represents what they want more. But his followers, and he, are too stupid to see that. They think they can win in that mud wrestling match. No difference. Just like the "saviors" on here. They deny the obvious, that they are giving aid and comfort to environmental terrorists, and really believe they can win that fight.

Bottom line, you have people as stupid as Trump and people a lot more stupid than that posting. Wonderful.

Oct 06, 2016
BS, self defense isn't murder. A terrorist is a terrorist. Most have no real agenda, just a love of terrorizing. Rabid animals. We don't have a vaccine for that yet. You can let them savage you if you want, but I agree with the basic logic that you don't tolerate that lest you concede everything to them. The meek will inherit sweet fuck all.

Oct 06, 2016
Just for comparison, the sea level rise around 12 000 years ago was around 100 meters. They should make a graph for sea level rise for last 15 000 years and try to put the 17 centimeter rise in such way, that it is visible. Quite a challenge :)

Oct 06, 2016
The amusing thing is in their fabrication they have Japan with a 2mm/year rise. But, let's see what JMA has to say.
no clear long-term trend of rise is seen for the period from 1906 to 2015. Variations with 10- to 20-year periods (near-10-year variations) are seen for the period from 1906 to 2015, with the MAXIMUM sea level appearing around 1950.

http://www.data.j...pan.html

Oct 06, 2016
I do finally get to the point of putting worst offenders such as goracle on ignore. Perhaps it is part of my process - in terms of trying to understand the fucked up world I live in - and how to live in that world - and decide on a path for myself.
-- onion jackass brays again
Uh huh, bray to us again, how you boasted about your 1200 mile jaunt, in which you emitted more than a tenth of the US ANNUAL average CO2, in just 2 days. The world is only fucked up because of jackasses like you who IGNORE their own hypocrisy but believe they are saving the world by braying at the heretics. Your process is to be a parasite on society.

I disagree with you there. I have kids - who are in a far better position than me to make a difference in their world - due to upbringing where they learned to see the world - and think critically.
-- onion jackass brays again.
Thankfully, they took after their real father.

Oct 06, 2016
idiot boy, i equated rate of change and it has a scientific basis - historically we can show links and evidence where the rate of change is directly involved with extinction events... you know, sh*t like:
https://en.wikipe...on_Event

of course, i can name more but you won't read any of it... mostly because you don't want to see the evidence that is refuting your delusion


Welcome to my ignore list... happy our enlightening discussions went out with me scoring a point... as conceded by your third grade insult.

Oct 06, 2016
Just for comparison, the sea level rise around 12 000 years ago was around 100 meters. They should make a graph for sea level rise for last 15 000 years and try to put the 17 centimeter rise in such way, that it is visible. Quite a challenge :)


Shhh, this is not a place for pertinent facts, context, or rational discussion... this site is about falling into line and saying "OMG we're gonna die!!!" every time a climate change-related article is posted.... or facing the dire consequences of 1-star ratings ;)

Oct 06, 2016
arguing with these idiots. That is either insane or compulsive. Which is it?
@burnBabyBurn
if you allow the proliferation of false information without challenge then the information literally spreads like wildfire - it's dangerous, especially for the stupids
(as noted on a PO article here: http://phys.org/n...mes.html )

if no one posts valid science or a refute to the blatant stupidity of the pseudoscience idiots, then the misinformation spreads and the typical person (who is usually scientifically illiterate, like bschitt or benji) ends up falling for unsubstantiated BS like the eu, aether or similar conspiratorial crap

see also: https://www.youtu...EwjBXlZE

given that PO refuses to actually moderate or abide by it's own rules (now called guidelines)... then....

Oct 06, 2016
In a debate, you don't defend your point of view with a gun
@bschitthead
you don't give rides across a river to the poisonous snake because he promises not to bite...
Articles like this do not do anything except expose an agenda
to someone like you who is a conspiracist, then any article is proof of agenda, regardless of content
you can see an article on fairy farts and how they mess up Leprechaun hair and say it's proof of AGW agenda
Are you trying to put suicide bombers into the same category as people who state a verbal disagreement with a concept?
fanaticism always starts with a concept, usually a delusional one that ignores reality and then erupts from there (in your case, your "reality" is anti-science, like benji, zeph and the eu cult)...

it's just like any other religion and it's fanatics:
they just need someone like you to help them see that their stupidity isn't isolated to themselves

Oct 06, 2016
Welcome to my ignore list.
@jeffeTROLL
1- you already said this once... why did you take me off?

2- you have YET to produce any viable reputable evidence to support your claims, so i don't care if you want to score a thousand points in your delusional mind...
Pseudoscience is pseudoscience no matter how many time you claim to be an authority

the only thing you've produced is argument from emotional hatred of anyone posting pro-AGW comments
Shhh, this is not a place for pertinent facts, context, or rational discussion...
if you could actually produce some you wouldn't be treated like a toddler in need of a new nappy

all i ever asked you for was evidence for your claims...

that is also something you've yet to be able to produce

well, you did try, but you completely misunderstood them and got called on it by Thermo, myself and others...
by your third grade insult.
i tried to keep it to a level you could understand...too hard for ya?

Oct 07, 2016

bschott 1 / 5 (4) 17 hours ago
Somebody is confused as to his mission in life:


Translation: Don't Ignore me, PLEASE, oh, PLEEEASE, oh, PLEEEEEEASE!!!

Which really demonstrates the point.

Captain Stumpy 5 /5 (2) 7 hours ago
@burnBabyBurn
if you allow the proliferation of false information without challenge then the information literally spreads like wildfire - it's dangerous, especially for the stupids


No. Your arguing with them makes it spread like wildfire. Ignore idiots like the aforementioned and they go away. OK. Demonstrate. Show me how THOUSANDS of lines of posts about Thunderbutts has made ANY difference in their frequency here, or affected their discussions back on their own site.

It hasn't. That analogy with Trump is a good one. You really think you can win that war and don't see you are giving aid and comfort to the enemy.

Oct 07, 2016

AlbertPierrepointOBE 3 / 5 (2) 17 hours ago
BS, self defense isn't murder


So, which way is it all you good "support the vets" types? I think we can exempt the mentally ill, like BS, and the stupid, life Jeffey, but what of those that just want to make trouble, like anti? You say defensive action against an environmental terrorist is evil? But it was OK for our good vets to bomb children by the hundreds of thousands in WWII and since because they happen to have been born in the wrong place? You can't say one is murder and the other is valor. People like anti are FAR guiltier than those that your vaunted vets have killed at the behest of the empire, no questions asked.

I don't know which is more disgusting on here, the hypocrisy or the mental illness.

Oct 07, 2016
bschott 1 /5 (3) 17 hours ago

BS, self defense isn't murder


In a debate, you don't defend your point of view with a gun


I think the point, if you could bother to read it, was that it isn't a debate, it isn't science, it isn't a discussion, it's a threat. And you do deal with that with a gun.

Oct 07, 2016
Show me how THOUSANDS of lines of posts about Thunderbutts has made ANY difference in their frequency here, or affected their discussions back on their own site.

While it may not have changed their stance it certainly kept them out of the hair of scientists. Think about what damage they could do if they would rob real scientists their time of day by their inane postings in email form.

Ignoring them (while certainly an option for personal peace of mind) doesn't make them go away. They'll just go an troll elsewhere. Better they do it here where erudite people show them up for what they are: people who pit mere opinion against hard facts. Instead of having them somewhere else (e.g. in politics) where people think every opinion is worth an equal amount.

Oct 07, 2016
The physorg articles are full of facts, context, and rational discussion. Then along comes the pop a mole of the denier community - who are certainly not interested in those three factors.
-- onion jackass brays again
FACT - You boasted about your 1200 mile CO2 spewing jaunt, during which you emitted more than a tenth of the US annual average, in JUST 2 DAYS.
CONTEXT - You claim to know the science behind global warming and yet you burn fossil fuels like there is no tomorrow and then have the audacity to bray at the heretics.
RATIONAL DISCUSSION - Let's have one. It would be interesting to see how you could rationalize your behaviour.

Oct 07, 2016
They present model based proof, so why do you say there isn't any?
-- physTard
LOL
To this retard, a computer simulation is proof of what's really happening with sea levels, despite the fact that the ACTUAL data disagrees. This is the kind of retard who would walk out in pouring rain because the weather forecast said, sunshine.
The Retard of the Year is gunning for Retard of the Decade.

Oct 07, 2016
To bschott's defense, HE is correct. Most sea level rise estimations are based on calculations, which are subsequently based on estimations of meltwater from landlocked ice in Greenland since a recent NASA study has previously shown Antarctica gaining ice overall. It is notable however that since the best tidal gauges (aka actual sea level measurements) show a slower rate of rise than expected, they have to put a significant rise in areas where there is little to no data at all. Similar to the "missing" heat in the deep ocean. I wonder if their models account for precipitation rates, soil moisture, and overall atmospheric humidity, since that could account for the slower rise as well?

Oct 07, 2016
Australian sea levels have been falling for 7000 years
http://joannenova...0-years/

Oct 07, 2016
If yes - please provide support for your assertion - that the projections are only taking into consideration meltwater from landlocked ice in Greenland.


That's to simplify discussion since the vast majority of landlocked ice is either in Antarctica or Greenland and Antarctica is presently gaining mass. http://water.usgs...vel.html

And in answer to my own question... 3.2 trillion tons of water added to land is nothing to sneeze at.. and is quite necessary to support the amount of plant life needed to help regulate CO2 AND support crop production.

http://www.nasa.g...-on-land

Than who expected? Please provide support for this assertion.


I'm going to concede this one. It seemed in order for them to look in the direction they did, they would be operating from an assumption of a "missing" rise but since I can't find that language directly, I'm going to drop it.

Oct 07, 2016
That's to simplify discussion
In other words - I am not careful with the assertions that I make. This is about science - and you need to be accurate - or you will be called out.


I provided a link supporting the assertion... did you bother looking at it? Are you really going to attack me because I failed to list the names of all the glaciers that account for 0.5% of the land-locked ice? You need to know when to drop an issue as well.

Oct 07, 2016

It is notable however that since the best tidal gauges (aka actual sea level measurements) show a slower rate of rise than expected

Than who expected? Please provide support for this assertion.


Did you read the article we are commenting under? Why do you think they are trying to sell us on an additional 3 cm of rise no one can find unless they look at a "model"?

Sorry for answering that one Jeff.



No biggie. Since I couldn't find a direct quote, I let it go. But I agree with your thinking on this.

Oct 07, 2016
It is notable however that since the best tidal gauges (aka actual sea level measurements) show a slower rate of rise than expected
Than who expected? Please provide support for this assertion.
-- The onion jackass brays again.
This is the jackass, who brays that he knows the science, yet he boasts about his 1200 mile, CO2 spewing jaunt, during which he emitted over a tenth of the US annual average, in JUST 2 DAYS.
He cares so much for the environment and about global warming that he is here constantly braying at the heretics.
So jackass, please provide support for how much you care about global warming.

Oct 07, 2016
So it is you who does not give a shit about facts, and context, and reason.
-- onion jackass brays again.
This from the jackass who boasted about his 1200 mile, CO2 spewing jaunt, during which he emitted over a tenth of the US ANNUAL average, in JUST 2 DAYS.

Oct 08, 2016
About "antigoracle".
Vietvet who posted here that was going to die of cancer has not posted since april.
"antigoracle" explicitly expressed his satisfaction that he is no longer here.
This blog sometimes is like a toilet that is never flushed.

Well, that has definitely earned you Retard of the Decade, since it's a blatant lie.

As for Vietvet, he wasn't a poster, but a down voting troll, who was encouraged by the Chicken Littles, and that's not just my opinion.

Oct 08, 2016
My mistake, the vomit is cd85.
I take this particular insult back, antigoracle.
All other insults, quite a list, are still active.

You are nothing but an ignorant lying A-hole.
You still got the Retard of the Decade award.

This blog sometimes is like a toilet that is never flushed.

With the likes of you here, I would have to agree.

Oct 09, 2016
Ignoracle, words fail to express my contempt for you.
Only a declaration of your insanity from a certified psychiatrist could stem me milder.
The retard award is too great an honour, plus you offered it to Niels Bohr first.
Inadvertently.

The Retard of the Decade demonstrates why he so deserved the "award".
Keep braying jackass, I'm not the one deliberately posting blatant lies about others.
You are nothing, but a retard and lying A-hole.

Oct 09, 2016
By commonly accepted definition it was not a lie.
Let me spell that out to you so you have a chance to understand.
"A lie is a statement that the stating party believes to be false and that is made with the intention to deceive. "
https://en.wikipe...wiki/Lie

The Retard of the Decade is gunning for Retard of the Century.
Keep braying jackass. Look how quickly you found the actual person who made the comment. You knew very well that it wasn't me but still deliberately LIED.
So, tell us, by commonly accepted definition, which is you:
-- Liar
-- Retard
-- A-hole
-- All of the above.

Oct 11, 2016
Now here is a quote from the article you referenced -
sea level has been rising about 1 to 2 millimeters per year due to the reduction in volume of ice caps, ice fields, and mountain glaciers in addition to the thermal expansion of ocean water.
So it is you who does not give a shit about facts, and context, and reason.


No, apparently I care more than you since I was willing to look at the table I've now cited SEVERAL times and do the simple math.... 180,000 cubic kilometers attributed to "all other ice caps, ice fields, and valley glaciers" is 0.6% of the total 32,328,300 cubic kilometers of ice that can potentially contribute to sea rise. The other 99.6% being contained in Antarctica (which is presently gaining ice) and Greenland, thus supporting my assertion that the focus is on melt water from Greenland. Stop fighting a losing battle.

Oct 11, 2016
You knew very well that it wasn't me but still deliberately LIED.


Read this: http://apt.rcpsyc...12/6/404


Read this.
So, tell us, by commonly accepted definition, which is you:
-- Liar
-- Retard
-- A-hole
-- All of the above.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more