Why seas are rising ahead of predictions

Nov 01, 2012
This image shows past and possible future changes in sea level. Credit: Map by Emanuel Soeding, Christian-Albrechts University, using US National Oceanic & Atmospheric Administration Etopo2v1 elevation data.

Sea levels are rising faster than expected from global warming, and University of Colorado geologist Bill Hay has a good idea why. The last official IPCC report in 2007 projected a global sea level rise between 0.2 and 0.5 meters by the year 2100. But current sea-level rise measurements meet or exceed the high end of that range and suggest a rise of one meter or more by the end of the century.

"What's missing from the models used to forecast are critical feedbacks that speed everything up," says Hay. He will be presenting some of these feedbacks in a talk on Sunday, 4 Nov., at the meeting of The in Charlotte, North Carolina, USA.

One of those feedbacks involves , another the Greenland ice cap, and another and .

"There is an Arctic sea ice connection," says Hay, despite the fact that melting sea ice—which is already in the ocean—does not itself raise sea level. Instead, it plays a role in the overall warming of the Arctic, which leads to ice losses in nearby Greenland and northern Canada. When sea ice melts, Hay explains, there is an oceanographic effect of releasing more fresh water from the Arctic, which is then replaced by inflows of brinier, warmer water from the south.

"So it's a big heat pump that brings heat to the Arctic," says Hay. "That's not in any of the models." That warmer water pushes the Arctic toward more ice-free waters, which absorb sunlight rather than reflect it back into space like sea ice does. The more open water there is, the more heat is trapped in the , and the warmer things can get.

Then there are those gigantic stores of ice in Greenland and Antarctica. During the last , sea level rose 10 meters due to the melting of all that ice—without any help from humans. New data suggests that the sea-level rise in the oceans took place over a few centuries, according to Hay.

"You can lose most of the in a few hundred years, not thousands, just under natural conditions," says Hay. "There's no telling how fast it can go with this spike of carbon dioxide we are adding to the atmosphere."

This possibility was brought home this last summer as Greenland underwent a stunning, record-setting melt. The ice streams, lubricated by water at their base, are speeding up.

Hay notes, "Ten years ago we didn't know much about water under the Antarctic ice cap." But it is there, and it allows the ice to move—in some places even uphill due to the weight of the ice above it.

"It's being squeezed like toothpaste out of a tube," explains Hay. The one thing that's holding all that ice back from emptying into the sea is the grounded ice shelves acting like plugs on bottles at the ends of the coastal glaciers. "Nobody has any idea how fast that ice will flow into the oceans once the ice shelves are gone."

Another missing feedback is the groundwater being mined all over the world to mitigate droughts. That water is ultimately added to the oceans (a recent visualization of this effect in the U.S. was posted by NASA's Earth Observatory: http://earthobservatory.nasa.gov/IOTD/view.php?id=79228).

All of these are positive feedbacks speeding up the changes in climate and rise.

"You would expect negative feedbacks to creep in at some point," says Hay. "But in climate change, every feedback seems to go positive." The reason is that Earth's climate seems to have certain stable states. Between those states things are unstable and can change quickly. "Under human prodding, the system wants to go into a new climate state."

Explore further: Synchronization of North Atlantic, North Pacific preceded abrupt warming, end of ice age

More information: gsa.confex.com/gsa/2012AM/fina… /abstract_209198.htm

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User comments : 24

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Tangent2
1 / 5 (1) Nov 01, 2012
I am very happy to read that they are finally starting to account for the self-reinforcing feedback loops. How serious researchers can provide a model without accounting for these differences, I will never know.
Lurker2358
3.9 / 5 (7) Nov 01, 2012
"You can lose most of the Greenland ice cap in a few hundred years, not thousands, just under natural conditions," says Hay. "There's no telling how fast it can go with this spike of carbon dioxide we are adding to the atmosphere."


The present trend in Greenland turns out to be that the annual rate of net loss is itself accelerating by 20km^3 per year, therefore the math for total greenland meltdown without further positive feedbacks is:

2,850,000 = 20 * N * (N plus 1)/2

Solve for N;

n = 533 years.

But 33 of those years have already past, leaving 500.

However, this curve will be greatly accelerated in just a few years as the summer arctic sea ice minimum reaches zero, for every year thereafter. My initial guess is probably at least an immediate doubling of the rate of melting, if not more than that, and the rate of acceleration will probably also increase.

Because Greenland's ice is very thick it is buffered, but it is already doomed...see below..
Lurker2358
3.7 / 5 (6) Nov 01, 2012
If we somehow brought the Keeling Curve to a slope of zero, Greenland would still continue melting for centuries, and may melt completely anyway, because the "stable state," for summer minimums anyway, has been pushed so far that sea ice is totally melted even on much of the Northern end of the island. This means continental ice will continue melting.

At the present time, I do not understand the mechanism that will stop the trend, unless some sort of feedback from amplified continental snowfall in N. America and Europe somehow offsets this. I don't see how that would be possible at this time though, due to our roads, roofs, snow plows, and salting. It seems continental snows just won't stick around long enough nor keep a high enough albedo to offset this.

In fact, melting days have been increasing for several decades in almost all northern hemisphere regions, so if there is a negative feedback mechanism from increased snowfall, it has not grown large enough to matter at this time...
Lex Talonis
Nov 01, 2012
This comment has been removed by a moderator.
PhotonX
3.3 / 5 (4) Nov 01, 2012
Hey Lex Talonis: Why don't you take your profane, hateful bile over to Yahoo!Answers, where the other 14-year-olds might think you're clever?

If no one can later tell why I posted this, it's because this idiots post has been deleted by the moderators.
DarkWingDuck
1.5 / 5 (8) Nov 01, 2012
They haven't include the collapse of the thermosphere that dumped enough water from the atmosphere to account for 1/8 of the rise over the past 50 years.

Now that it's expanding since mid-2009, it should start picking some of that water up which I think we started seeing with the droughts.
DarkWingDuck
1.7 / 5 (6) Nov 01, 2012
Low ranking my post is like saying you don't like facts.

NASA reported the data. I trust their figures. It's not my fault climate "scientists" leave out key areas reaquired for a real predictive model.
joefarah
1.8 / 5 (5) Nov 02, 2012
Just curious if anyone knows why Greenland was so named?
VendicarD
3.9 / 5 (7) Nov 02, 2012
"Greenland was so named"

It was a ploy to get fools to go there thinking that it actually was something other than almost perpetually frozen rock.

Today fools are still falling for the old ploy that it was green, warm and lush when the name Greenland was chosen.
VendicarD
2.3 / 5 (3) Nov 02, 2012
I find it amusing that the ocean is rising at all after a decade of claims made by denialists that ocean levels were falling.

Lying is a way of life for them.

rubberman
3.7 / 5 (3) Nov 02, 2012
Low ranking my post is like saying you don't like facts.

NASA reported the data. I trust their figures. It's not my fault climate "scientists" leave out key areas reaquired for a real predictive model.


Can you link to the info. about the collapse adding water to the ocean? I have read the NASA article on the 08-09 collapse due to the solar minimum (this happens every solar minimum but not to the extent of this one), it mentioned nothing of water vapour in the thermosphere.

http://science.na...osphere/
ubavontuba
1.6 / 5 (5) Nov 04, 2012
Sea levels are rising faster than expected from global warming, and University of Colorado geologist Bill Hay has a good idea why. The last official IPCC report in 2007 projected a global sea level rise between 0.2 and 0.5 meters by the year 2100. But current sea-level rise measurements meet or exceed the high end of that range and suggest a rise of one meter or more by the end of the century.
What a load of crap. The official CU Sea Level Research Group's rate is 3.1mm per year (and this includes a .3 mm per year upward "adjustment"). And, it has been steady for many decades. Supposing it remains steady, as reflected in the past, puts the total for 2100 at just over a quarter of a meter.

And to raise a panic over this, when the sea levels have been steadily rising since before AGW could have possibly contributed, is both disingenuous and unconscionable.

Wolf358
not rated yet Nov 05, 2012
"You would expect negative feedbacks to creep in at some point," says Hay. "But in climate change, every feedback seems to go positive." The reason is that Earth's climate seems to have certain stable states. Between those states things are unstable and can change quickly. "Under human prodding, the system wants to go into a new climate state."

Under human prodding, the geologically recent stability is being pushed into the non-stable. A new state of dynamic stability will assert itself when the prodding stops. Until then, hang on tight; it's going to be a rough ride.
antialias_physorg
5 / 5 (4) Nov 05, 2012
"You would expect negative feedbacks to creep in at some point," says Hay. "But in climate change, every feedback seems to go positive."

There will be negative feedback eventually (no system can go on a runaway rampage forever* - and the Earth will go to a new stable state. But there is no assurance at all that that state will be able to support life. The stable state might look somthing like we see on Mars today.

*except, maybe, black holes
VendicarD
3 / 5 (3) Nov 05, 2012
As the following graphic shows, the rate of sea level increase is accelerating.

http://www.carbon...tty-good

"And, it has been steady for many decades." - UbVonTard

Since the heat capacity of water is many times greater than that of air, the rate of increase of ocean temperatures are in the short term heavily dampened with respect to air temperatures. So increases in ocean temperature will appear more or less linear over multi-decade time scales.

What the linearity does show however, is that there hasn't been a dramatic change in cloud cover over the earth as claimed by lying blog denialists like sunshinehours1 aka. ParkerTard.

FastEddy
1 / 5 (4) Nov 05, 2012
If anyone wants to sell their beach front properties real cheap, I'm listening ... and buying ... even in the storm ravaged New Jersey shore ...
FastEddy
1 / 5 (4) Nov 05, 2012
'... "What's missing from the models used to forecast sea-level rise are critical feedbacks that speed everything up," ...'

So, speeding up the [software] models' [virtual] feedback is what, speeding up the real sea level rises? Or just speeding up and skewing the "modeled" outcome? It would seem that the modeled/predicted outcome is more important than the actual, real indicators.

It is true that at one time more than 1000 years ago, Greenland was actually green [or at least a lot greener], but did the sea levels rise then? Every indication is Not!
rubberman
3.7 / 5 (3) Nov 05, 2012
I think you're misunderstanding what a "feedback" is Ed. And Greenland has never been green, see Vendicar post above.
ubavontuba
1 / 5 (4) Nov 05, 2012
I think you're misunderstanding what a "feedback" is Ed. And Greenland has never been green, see Vendicar post above.
AGW alarmists never learn...

Proof on Ice: Southern Greenland Was Once Green; Earth Warmer

SteveS
3 / 5 (2) Nov 06, 2012
AGW alarmists never learn...
http://www.scient...h-warmer

Willerslev used four measures ... to date the forest to at least 400,000—and possibly as much as 800,000—years ago, the team reports in Science. That means this area of southern Greenland has been continuously coated in ice for at least that long.

Greenland was named by Eric the Red 1200 years ago
VendicarD
3 / 5 (2) Nov 06, 2012
UbvonTard is incapable of learning.

His own reference - which he obviously did not read - states that the forests on Greenland existed a half million years ago.

Since Eric the Red did not live a half million years ago, is choice of name for Greenland couldn't have been due to forest cover as UbVonTard so ignorantly implies

"AGW alarmists never learn" - UbVonTard
ubavontuba
1 / 5 (2) Nov 06, 2012
AGW alarmists never learn...

Proof on Ice: Southern Greenland Was Once Green; Earth Warmer
Willerslev used four measures ... to date the forest to at least 400,000—and possibly as much as 800,000—years ago, the team reports in Science. That means this area of southern Greenland has been continuously coated in ice for at least that long.

Greenland was named by Eric the Red 1200 years ago
The claim was: "Greenland has never been green" Obviously, this statement is false.

ubavontuba
1 / 5 (2) Nov 06, 2012
Uba is incapable of learning.

His own reference - which he obviously did not read - states that the forests on Greenland existed a half million years ago.

Since Eric the Red did not live a half million years ago, is choice of name for Greenland couldn't have been due to forest cover as UbVonTard so ignorantly implies

"AGW alarmists never learn" - Uba
Vendibot never learns.

The claim was: "Greenland has never been green" Obviously, this statement is false.

rubberman
1 / 5 (1) Nov 07, 2012
Ub is correct, I have lied and mislead all of you by ommitting the words "In human history" before the rest of my statement. Apologies to all. However, since we are taking the words at total face value, since that island has been named greenland, it has never been green.
VendicarD
3 / 5 (2) Nov 07, 2012
Poor UbVonTard. He has no evidence that Greenland was Green a million years ago.

For all he knows, it might have been blue, or purple.

"The claim was: "Greenland has never been green" Obviously, this statement is false." - UbVonTard

UbVonTard. He is incapable of learning.