GSA Annual Meeting Presentation: Could Estimates of the Rate of Future Sea-Level Rise Be Too Low?
Boulder, Colorado, USA – 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 sea-level rise 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 Geological Society of America in Charlotte, North Carolina, USA.
One of those feedbacks involves Arctic sea ice, another the Greenland ice cap, and another soil moisture and groundwater mining.
“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 Arctic waters, and the warmer things can get.
Then there are those gigantic stores of ice in Greenland and Antarctica. During the last interglacial period, 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 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.”
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 sea-level 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.”
WHAT: Could Estimates of the Rate of Future Sea-Level Rise Be Too Low?
WHEN: Sunday, 4-November, 9:15–9:30 a.m.
WHERE: Charlotte Convention Center, Room 219AB
ABSTRACT: https://gsa.confex.com/gsa/2012AM/finalprogram/abstract_209198.htm
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Dr. Hay may find this upcoming NASA JPL project problematic with his claims:
Finally: JPL intends to get a GRASP on accurate sea level and ice measurements
But it’s been pointed out here that this model is wrong. Ice-free water in the high Arctic is about as reflective as ice, because of the low angle of incidence, and it is not an insulator like ice, so it emits heat on balance, rather than absorbing it.
November 1, 2012 at 7:41 pm | John Brookes says:
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John, you’re a much nicer bloke when you don’t talk through the back of your head.
Real measurements are 2 – 3mm per year in some locations and zero in others … the models are just wild guesses with loaded logarithms. We already know that all of the feedbacks are not positive so there goes Hay’s theory in a puff of smoke!
Stephen Rasey says:
November 1, 2012 at 8:50 pm
“Ok, a tide gage history from San Francisco is good, (thx Dave Burton).
Given the news, however this 150 year record from The Battery, New York City, (at 11 inches per century) seems more to the point.”
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Just on general earth science principles, especially isostacy,
http://www.britannica.com/EBchecked/topic/296537/isostasy
and density,
http://www.cmacn.org/energy/basics/mat_density.htm
. . . there can be made a case for the sinking of the entire “greater New York” region, thus bringing about the 0.91 feet in 150 years indicated.
Compare these:
http://www.globecorner.com/i/t/newy1850.GIF
http://www.absolutnuevayork.com/wp-content/uploads/2010/05/NEW-YORK.jpg
Of course, I actually don’t know but for $1.673 M a proposal can be submitted forthwith. Where should I send it?
Birdieshooter says:
November 1, 2012 at 6:06 pm
So can someone reconcile this forecast with the NOAA global mean sea level trend of 2.8mm per year in this link?
…http://ibis.grdl.noaa.gov/SAT/SeaLevelRise/LSA_SLR_timeseries_global.php
====================
Short answer: No
Longer answer: This is climate science. Everyone gets to have their own numbers. Some other numbers:
1.0mm/yr +-1.5 Morner based on changes in Earth rotation rate
1.1 +-.4 AR4 Thermal Expansion +Ice Melt 42 years (1961-2003)
1.9mm/yr Most usual value for Tidal Gauge Data (every estimate is different)
2.0 +-1.9 ERS1 Satellite
2.8 +-.6 AR4 Thermal Expansion +Ice Melt 11 years (1993-2003)
2.9-3.4 +.4/-.6 Topex/Poseidon Satellites
In general, sea level rise numbers are characterized by fairly small numbers, comparatively large uncertainties, difficulties with somewhat hazy (at the mm scale) reference frames and the problem that sea level rise apparently is not the same everywhere with differences taking many years to resolve themselves
If I HAD to pick a number for current sea level rise, I’d go with ERS1 — 2.0 mm/yr — despite the broad error limits. I am coming to have serious doubts about the objectivity of the folks at CU. I think that they are intentionally or unintentionally fudging their numbers high, quoting absurdly low error estimates, and in general not entirely credible.
I do agree with Hays the the results of future ground water pumping have probably been underestimated
For the current sea level rise and prediction for the year 2100 see the bottom of this page:
http://www.climate4you.com/SeaTemperatures.htm#Global%20sea%20level
“Estimated average global sea level change until year 2100, according to sea level change values provided by the Colorado Center for Astrodynamics Research at University of Colorado at Boulder ….. … Last diagram update: 18 September 2012, with a prognosis (red graph) of about 17 cm average global sea level rise until 2100.”
Roger Knights says:
November 1, 2012 at 10:10 pm
But it’s been pointed out here that this model is wrong. Ice-free water in the high Arctic is about as reflective as ice, because of the low angle of incidence, and it is not an insulator like ice, so it emits heat on balance, rather than absorbing it.
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I think that is correct. Water reflectance looks to be high below an incidence angle of about 45 degrees. The incidence angle in the polar zones is, I think, always below 45 degrees except close to the Arctic/Antarctic circles for a short period around their respective Summer Solstices.
William McClenney says:
November 1, 2012 at 9:45 pm
michaelwiseguy says:
November 1, 2012 at 9:25 pm
“After brief stillstands at +6 and perhaps +8.5 m, sea level fell with apparent speed to the MIS 5d lowstand and much cooler climatic conditions. It was during this regression from the MIS 5e highstand that the North Atlantic suffered an oceanographic ‘‘reorganization’’ about 11873 ka ago. During this same interval, massive dune-building greatly enlarged the Bahama Islands. Giant waves reshaped exposed lowlands into chevron-shaped beach ridges, ran up on older coastal ridges, and also broke off and threw megaboulders onto and over 20 m-high cliffs.”
WOW! That really does sound scientific, but it probably adds to the equation.
Mike Jonas says:
November 1, 2012 at 9:44 pm
“During the last interglacial period, sea level rose 10 meters due to the melting of all that ice“.
10m! Wow! Let’s see what the IPCC report says about this interglacial period.
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I think Hays means the Eemian – 125000 years ago Mike. The Eemian was apparently warmer and wetter than today. It’s not clear why. His number for Eemian sea level rise seems high. 5 meters would be closer to most estimates. See Wikipedia http://en.wikipedia.org/wiki/Eemian for an overview.
Why does climate science ignore the fact that everything else in nature is cyclical?
There was a huge sea level rise 10 thousand years ago. Where was the CO2?
John Brookes says:
November 1, 2012 at 7:41 pm
“… will not be predicted until after it happens.”
You’ve got to love “climate science”…
“””””…..Don K says:
November 1, 2012 at 10:51 pm
Roger Knights says:
November 1, 2012 at 10:10 pm
But it’s been pointed out here that this model is wrong. Ice-free water in the high Arctic is about as reflective as ice, because of the low angle of incidence, and it is not an insulator like ice, so it emits heat on balance, rather than absorbing it.
================
I think that is correct. Water reflectance looks to be high below an incidence angle of about 45 degrees. The incidence angle in the polar zones is, I think, always below 45 degrees except close to the Arctic/Antarctic circles for a short period around their respective Summer Solstices…….”””””
Well for starters, “Incidence angles” in Optics, are always measured from the local normal to the surface, not from the tangent to the surface. So Arctic sea incidence angles are always greater than 45 degrees; not less.
Also surface reflectance is almost constant from normal incidence up to the Brewster Angle (arctan (N/1) ) where N is the refractive index of the water (1.333). For water, B is about 53 degrees, so reflectance is less than 3$ up to that angle. Normal reflectance is ((N-1)/(N+1))^2 which is 0.02 (2%).
At the Brewster angle the reflectance of the polarisation with the electric vector in the plane of incidence, goes to zero, while the other component, polarised normal to the plane of incidence roughly doubles. The total reflectance is almost the same at the Brewster angle. For greater incidence angles both polarisation reflection coefficients climb rapidly to one.
But so what, at such oblique angles, the solar radiation passes through a greatly increased air mass, which reduces the higher energy shorter wavelength photons; and then the incidence area increases as 1/cos(incidence angle), so the surface irradiance is very low.
Yes when you consider wave action the surface can tip towards the incoming beam direction, but then on the other side of the wave, the incidence angle is increased, so moderate wave action doesn’t affect reflected energy much.
Arctic sea contribution to earth albedo is greatly overestimated.. snowy surfaces have substatial optical trapping by TIR, and melted surfaces have low reflectance just like water.
GSA Seminar? More Strippers and Champagne baths? Oh, wait, thats the other GSA…
Never Mind.
From the “water mining” link – “The maps above combine data from the twin satellites of the Gravity Recovery and Climate Experiment (GRACE) with other satellite and ground-based measurements to model the relative amount of water stored near the surface and underground as of September 17, 2012. The top map shows moisture content in the top 2 centimeters (0.8 inches) of surface soil; the middle map depicts moisture in the “root zone,” or the top meter (39 inches) of soil; and the third map shows groundwater in aquifers.”
GRACE seems to be aging well. (-:
otsar says:
November 1, 2012 at 6:24 pm
Correction:
grasping at straws?
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Nay, it’s gasping at thaws – except that there ain’t no thawing going on up there…
Sorry for me playing with words, I just couldn’t resist.
For those tired of climate alarmism, how about magnetic field reversal alarmism:
“While the effects are hard to predict, the consequences may be enormous. The loss of the magnetic field on Mars billions of years ago put paid to life on the planet if there ever was any, scientists say.”
http://www.reuters.com/article/2012/10/03/science-earth-magneticfield-idUSL6E8K7JJG20121003
This writer (whose name doesn’t deserve mention) tries really hard to link a magnetic field reversal to an apocalyptic end of life on Earth.
Of course, these field reversals have happened thousands of times during the lifetime of the Earth, and during the lifetime of life on Earth. Life is doing pretty good, don’t you think?
I’m surely mistaken but a vaguely recollect that most of the Greenland ice cap survived the very warm Eemian which lasted around 15,000 years.
Don K – Sea levels in the Eeemian rose to something like 5-10m above today’s level“. The total rise in the Eemian from the previous glacial was comparable to the current rise (120m).
http://upload.wikimedia.org/wikipedia/commons/c/c0/Sea_level_temp_140ky.gif
Hay appears to be referring to the total rise, not the relationship to today:-
“Then there are those gigantic stores of ice in Greenland and Antarctica. During the last interglacial period, 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 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.”“.
Typo
I’m surely mistaken but I vaguely….
Heh. When I started to read this article and I got to the bit about current sea-level rise exceeding the “high end” of 2 to 5 mm per year, I thought to myself, “What the hell is Anthony talking about? Even NOAA only says 2.8 mm per year.” Then there were all the usual suspects making an appearance: fresh water melt, open sea positive feedbacks, ground water mining. I kept thinking, “Is Anthony pulling some weird April Fool’s thing in November? Has someone hacked Watts Up With That? Did aliens replace our host with a bizarro version?”
Then I got to the end. Ah … Anthony didn’t write it. I don’t know about the rest of you, but in my browser that was totally non-obvious. (And then I noticed: Cool! It’s actually in Charlotte, where I live. I wonder if I can sneak in…)
“Stephen Rasey says:
November 1, 2012 at 8:50 pm
Ok, a tide gage history from San Francisco is good, (thx Dave Burton).
Given the news, however this 150 year record from The Battery, New York City, (at 11 inches per century) seems more to the point.”
Almost the whole East Coast of the US is sinking. It is in fact a classic example of a “ria” coast where the river mouths are at the end of long inlets that are really drowned river valleys (e. g. Chesapeake bay) and where sediment from the rivers form barrier islands off-shore. On stable coastlines rivers build deltas out into the sea instead.
Given this it is actually rather odd that it took almost 200 years to beat the 1821 high-water mark in New Yoork.
A brief summary of the more obvious howlers:
“During the last interglacial period, sea level rose 10 meters due to the melting of all that ice”
Very exaggerated. 5 meters is a more reasonable figure. The best data from the most stable coastline available (the Gawler craton in South Australia) actually suggests 2-3 meters.
“New data suggests that the sea-level rise in the oceans took place over a few centuries, according to Hay.”
It most certainly did not. The chronology of the last interglacial is well established, and the melting of the icecaps took on the order of 10,000 years. It was however faster than during the present interglacial since there was no Younger Dryas interruption of the melting.
“Ten years ago we didn’t know much about water under the Antarctic ice cap.”
A direct lie. It has been long-known that the Antarctic ice-cap is partly cold- and partly warm-based.
“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.”
In that case it is rather odd that most antarctic glaciers don’t have any ice-shelves. Ice shelves only exist in the Ross Sea and Weddell Sea sectors, around parts of the Antarctic peninsula and in Prydz bay.
And in any case ice-shelves are by definition not grounded. If they were they wouldn’t be shelves, since shelves are floating on ocean water. Also note that there are no ice shelves around Greenland, and hasn’t been in historical times.
Finally I do agree that ground water depletion will add to sea-level.
” Sea levels are rising faster than expected from global warming, and University of Colorado geologist Bill Hay has a good idea why.”
No Bill. Sea levels are not rising faster than expected , it is your highly error prone satellite altimetry that is rising faster than any physical record of water height or even exaggerated climate models.
NOW, STOP LYING AND MISLEADING EVERYONE AND FIX YOUR CALCULATIONS.[It is appreciated that sometimes emphasis is required in a statement but many of your colleagues here find shouting quite offensive . . mod]
Can you speed up the grant please Christmas is nearly here!
All of these are positive feedbacks speeding up the changes in climate and sea-level rise.
Groundwater isn’t a positive feedback.
“You would expect negative feedbacks to creep in at some point,” says Hay. “But in climate change, every feedback seems to go positive.”
I can think of several negative feedbacks.
More open Arctic water = increased evaporation and snow on Greenland = increased elevation and decreased melt.
Faster melt of older ‘dirty’ (less BC) ice = replacement with new cleaner ice = increased albedo cooling.
And the example you give, 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. Anything that increases heat transport to the Arctic cools the climate