Sea-level change in Southeast Asia 6,000 years ago has implications for today

February 10, 2017, Rutgers University
Credit: Tiago Fioreze / Wikipedia

For the 100 million people who live within 3 feet of sea level in East and Southeast Asia, the news that sea level in their region fluctuated wildly more than 6,000 years ago is important, according to research published by a team of ocean scientists and statisticians, including Rutgers professors Benjamin Horton and Robert Kopp and Rutgers Ph.D. student Erica Ashe. That's because those fluctuations occurred without the assistance of human-influenced climate change.

In a paper published in Nature Communications, Horton, Kopp, Ashe, lead author Aron Meltzner and others report that the relative sea level around Belitung Island in Indonesia rose twice just under 2 feet in the period from 6,850 years ago to 6,500 years ago. That this oscillation took place without any human-assisted climate change suggests to Kopp, Horton and their co-authors that such a change in sea level could happen again now, on top of the rise in sea level that is already projected to result from . This could be catastrophic for people living so close to the sea.

"This research is a very important piece of work that illustrates the potential rates of that can happen from natural variability alone," says Horton, professor of marine and coastal sciences in the School of Environmental and Biological Sciences. "If a similar oscillation were to occur in East and Southeast Asia in the next two centuries, it could impact tens of millions of people and associated ecosystems."

Meltzner, a senior research fellow at the Earth Observatory of Singapore at Nanyang Technological University, along with Horton, Kopp and their co-authors, used coral microatolls to understand when, and by how much, the sea level had risen and fallen near the Indonesian island of Belitung, which lies between Sumatra and Borneo. A microatoll is a circular coral colony, typically no more than about 20 feet across, in which the topmost coral is dead and the bottom part living and growing. By taking samples from microatolls in different places, scientists can date rises and falls of sea level.

The microatolls are what scientists call a "proxy" - a natural process that provides a reliable record of past events. "In any region, you try to find the proxy controlled by sea level," Horton says. "In New Jersey, we have no corals, so we use salt marshes. In the tropics, corals are the go-to proxy."

The scientists studied microatolls at two sites on opposite sides of the island. Meltzner says they didn't expect the fluctuations they found because those changes in sea level contradicted what they knew about sea level in Southeast Asia. "Our conventional understanding of ocean circulation and ice-melting history told us that such fluctuations should not occur, so we were a bit mystified at the results from our first site," Meltzner says. "But after finding a similar pattern at a second site 80 kilometers to the southeast, and ruling out other plausible explanations, it was clear that the coral growth patterns must reflect regional changes in sea level. There would be way too many coincidences otherwise."

The paper comes out of a long-running research project aimed at understanding the physical processes involved in rise. Such understanding, Kopp says, is necessary to help scientists understand the present and likely future state of the ocean. "This is a basic science problem," Kopp says. "It's about understanding past changes. Understanding what drove those changes is what allows us to test the climate models we use to predict future changes."

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12 comments

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FactsReallyMatter
1.6 / 5 (13) Feb 10, 2017
So the sea level changed before without the assistance of man. Who would have guessed that??

"Understanding what drove those changes is what allows us to test the climate models we use to predict future changes."

Oh, the models need to be tested do they, I wonder -what are the error bars versus the predictions?
SamB
2 / 5 (12) Feb 10, 2017
I can not believe that the sea levels fluctuated in the past without mans influence. I have been led to understand that nothing ever changes unless man interferes with nature... I wonder if the antarctic ice sheet has ever had a crack before man came along?... mmmm
cjones1
1.6 / 5 (7) Feb 10, 2017
Speaking of Antartica, was the sea level rises due to a significant melting of Antarctica's ice. There are ancient maps of Antarctica's coastline that are accurate and compiled long before modern man was able to discern the coastline.
barakn
4 / 5 (8) Feb 10, 2017
No there aren't. There's just the Piri Reis map, in which the cartographer ran out of room while drawing the coastline of South America, forcing him to draw the southern part of it horizontally along the bottom of the page.
Solon
1 / 5 (7) Feb 11, 2017
The sea level did not rise, the land sunk. It will happen again.
humy
4.5 / 5 (8) Feb 11, 2017
FactsReallyMatter

and

SamB

Please stop your incredibly stupid straw man of pretending we scientists claim there exists only man made causes without any natural causes. OBVIOUSLY, NOBODY CLAIMS all causes of climate change are man made.
And obviously there is no logical contradiction in there sometimes being BOTH natural and man made causes.
humy
5 / 5 (5) Feb 12, 2017
misedit;

"...no logical contradiction in there sometimes being BOTH natural and man made causes..."

should be;

"...no logical contradiction in there sometimes HAVING BOTH natural and man made causes..."
highzone
5 / 5 (3) Feb 12, 2017
So the sea level changed before without the assistance of man. Blooblaablee....


No sh$$t loonbin, you look once again like the absolute moron you are, by saying "who would've guessed" No one Guessed we all KNOW this, except YOU. That's why manamade climate change is so bad because it adds unnatural warming towards an already natural warming state.

Get the facts that really matter to the table, don't fool yourself by lying, it only rubs some more insult into your stupidity.

Nik_2213
not rated yet Feb 12, 2017
Hmm. Have they adjusted for uplift / fall due mega-thrust quakes, such as drowned those 'ghost forests' along Pacific NW ??
FactsReallyMatter
1 / 5 (2) Feb 13, 2017

......pretending we scientists claim there exists only man made causes without any natural causes. OBVIOUSLY, NOBODY CLAIMS all causes of climate change are man made.
...


What's not true exactly? I repeatedly hear that 97% of "your scientists" agree that global warming is real and that the man-made part of it is the problem. Then I hear how the science is settled, then how the ice will all melt, then how the sea levels will rise, then how millions of people will die, etc, etc, etc...

I hear repeatedly that it IS the man-made part of it which is the problem. Now you tell me that I should stop worrying about the man-made part because there is also natural warming.

Really, I understand that it is hard to keep the fear mongering lies straight, but do make an effort. It makes it more entertaining...

humy
3 / 5 (2) Feb 13, 2017
I repeatedly hear that 97% of "your scientists" agree that global warming is real

FactsReallyMatter

Correct. So what?
and that the man-made part of it is the problem.

No, we say ALL of it is the problem. But its the man made part that we can do something about therefore it is the man made part that we should be concerned with.
Then I hear how the science is settled,

That's because it is settled. We are part of the cause of global warming.
then how the ice will all melt

Then there is something wrong with your hearing. The ice MIGHT only eventually all melt IF we stupidly did nothing; the big operative words there are MIGHT and IF.
then how the sea levels will rise,

It is already rising.
humy
3 / 5 (2) Feb 13, 2017
-continued-

then how millions of people will die,

FactsReallyMatter

Not necessarily and, even then, probably only IF we completely stupidly did nothing about it.
Now you tell me that I should stop worrying about the man-made part because there is also natural warming.

I never said any such thing. We should do something about the man made part because we can.
And it isn't about the need to "worry" but rather the need to do something about it. As long as we do what we can about it, we can then dispense with the superfluous "worry". In fact, unless that "worry" translates into "action", we can dispense with the superfluous "worry" to start with and just stick with the action without the worry. We only need to ACT, not 'worry'.

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