Heat-driven expansion not a major source of sea level rise
With the power to drown low-lying nations, destroy infrastructure, and seriously affect sensitive coastal ecosystems, sea level rise may be one of the most readily apparent consequences of global warming that is already under way. However, the sources of the rising waters, and the dynamics driving them, are not so clear. Melting land-locked glaciers, shrinking ice sheets over Greenland and Antarctica, and the ocean’s thermal expansion will all play a part, but the expected contribution from each of these sources is still up for debate. Previous studies have suggested that thermal expansion driven by rising sea surface temperatures will account for up to 70 percent of sea level rise in the near future, but research by McKay et al. suggests this may be a drastic overestimate.
The authors draw on paleoclimate records and model simulations of the last interglacial period, when the sea level rose by more than 6 meters (19.7 feet), to isolate the contribution of thermal expansion to sea level rise during a previous period of global warming. The authors found that during the last interglacial period, between 130,000 and 120,000 years ago, the global average sea surface temperature changed between .4 and 1.3 degrees Celsius (-0.7 and 2.3 degrees Fahrenheit). On the basis of research into the temperature sensitivity of thermal expansion, the authors suggest that between .2 and 0.7 m (-0.66 and 2.29 ft) of ocean rise would have been attributable to thermal expansion. With thermal expansion playing such a small role in the pronounced sea level rise during the last interglacial, the authors suggest that the Greenland and, in particular, Antarctic ice sheets may be more sensitive to increasing temperatures than previously thought, with important implications for estimates of future sea level rise.
Source:
Geophysical Research Letters, doi:10.1029/2011GL048280, 2011
http://dx.doi.org/10.1029/2011GL048280
Title: The role of ocean thermal expansion in Last Interglacial sea level rise
Authors: Nicholas P. McKay: Department of Geosciences, University of Arizona, Tucson, Arizona, USA;
Jonathan T. Overpeck: Department of Geosciences, Institute of the Environment, and Department of Atmospheric Science, University of Arizona, Tucson, Arizona, USA;
Bette L. Otto-Bliesner: National Center for Atmospheric Research, Boulder, Colorado, USA.
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the authors suggest that the Greenland and, in particular, Antarctic ice sheets may be more sensitive to increasing temperatures than previously thought
who would have thought
Typo alert: Anoter sea level rise fallacy falls short should be “Another sea level rise fallacy falls short”
Typo in heading: “Anoter” should be “Another”.
Here we go again: “[might be] worse than we thought”, while continually reminding us that it is sea SURFACE temperatures that they discuss. In short, an insignificant volume of the total sea, yes? So what is the fuss about? Who, aside from themselves, are they trying to frighten?
Tell that to the people of Japan. LAND levels FELL at least 1m as a result of the quake movements this year, and are STILL shifting. So it appears only alarmists assume land levels are static and sea levels change.
And there is the money grab sound bite “model simulations”…it has to be true ‘coz it’s on a computer and in full 1080p HD colour.
I don’t see the message here. They are saying that thermal expansion was a small fraction of a 6m rise. Well, yes – if we are to have a 6m rise, the thermal component would also be a small percentage. Do you expect that?
Another paper to reinforce GRL’s post-rational reputation. More funds required to investigate the magical properties of polar ice.
Maybe the aliens will have the answers.
Mike Bromley the Kurd says: ” Here we go again: “[might be] worse than we thought”, ”
It always is, that is why I am 100% sure that they are lying through their teeth. It is not in the nature of the warmists to err on the side of caution with regard to their computer models. A sea level rise of 2 inches in 100 years does not get headlines a sea level rise of 30 feet does, especially if followed by the statement this is worse than the 20 feet our initial computer models predicted. There is no getting away from the fact that somewhere in all the data that has been collected there has to be results showing that global temperature increases/ sea level rises are less than predicted. This is in the very nature of statistics, but we the general public are not privy to it. Neither I suspect are the politicians. I would also say that all of this propaganda as well as it’s content cherry picked, so is it’s timing. There were very few press releases in the UK last winter, and any debate used the phrase “climate change” as opposed to “global warming”. Now that summer is here we are back to “global warming” ( not that that is very convincing in UK this summer!!). They might not be very clever with regards to what is actually happening to the climate, but they surely are when it comes to propaganda.
Josef Goebbels would be proud of them!!
Nick, I have trouble with evidence for past melting of land ice in the Antarctic. Nobody appears to have demonstrated an unconformity or disconformity in Antarctic ice layers indicative of past erosion of any large type or scale. It sems to be assumed that the annual record is preserved. If we use Vostok, with its admitted data imperfections, can we not comfortably assume that failure of the land ice sheet to melt in the last 700,000 years is comforting for the immediate future? To the contrary, the measurable several km of ice thickess would seem to indicate accumulative mechanisms that favour lowering ocean levels. Have you seen evidence of past melting on either Greenland or Antarctica, of a type that could change ocean levels substantially? Any references?
I’ve been telling anyone who would listen that when people talk about sea level rise due to thermal expansion of water, they’re forgetting about a little concept called thermoclines. You may warm the surface five degrees, but once you get a hundred meters down the temperature isn’t going to change a hell of a lot. The dynamics of a large fluid body with the unique properties of water – it starts getting less dense with decreasing temperature below 277 K – dictate that you can’t warm the whole thing from the surface and expect it to expand. You’re actually going to find that any water that is below 277 K (and there’s a whole lot of it in the deep oceans) will contract and drop sea levels if its temperature increases.
The fact that many people have devoted doctoral theses to deep ocean dynamics should be an indication that the problem is slightly more complicated than simply applying the thermal expansion coefficient of water at an arbitrary temperature to the entire ocean.
With thermal expansion playing such a small role in the pronounced sea level rise during the last interglacial, the authors suggest that the Greenland and, in particular, Antarctic ice sheets may be more sensitive to increasing temperatures than previously thought, with important implications for estimates of future sea level rise.
It might be worse than we thought! Send money so we can be sure!
Heh. Considering that we seem to be on the downslope of the current interglacial, catastrophic sea level rise isn’t much of a concern.
Since the discussion is about sea level, there ought to be a link to
http://sealevel.colorado.edu/
Admittedly 1 year is not significant, but it looks like sea levels took a dive in 2011
So, if the sea level rise hockey stick is correct(lol) and it’s not from thermal expansion then there must also be a hockey stick in land locked ice volume loss. Another Mann paper for sure.
If sea level rise is mainly due to melting land ice, then that melting ice has removed a lot of heat in the form of latent heat of fusion. Water at 0°C has a much greater heat content than does ice at 0°C. Adding cold water to the ocean must lower the average heat content., and therefore the temperature, or at least partially offset any warming.Since the added cold water is close to the land ice, it has a negative feedback effect on local air temperature. I seem to recall a paper published maybe last year on this effect around Greenland.
The Eemian basically only lasted about 11k years, but hung on in Europe for another 12k. The current interglacial is getting somewhat long in the tooth. Most of the melting action took place during the first hundred years. Sorry, warmies, but sea level rise is only going to continue at its current snails pace of roughly 4 to 6 inches per century. If anything, Antarctic ice is expanding, and Arctic ice melt has slowed to a crawl. The future for climate alarmism looks dim. I suggest they seek another line of work. Perhaps palm reading or tarot cards would be up their alley.
Here’s a copy, though maybe not the finished product.
The role of ocean thermal expansion in Last Interglacial sea level rise
http://www.leif.org/EOS/2011GL048280-pip.pdf
Whatever component of U Colorado’s adjustment was based on increased sea level rather than post glacial rebound, already assumed mass increase due to ice melt rather than rise due to deep thermal expansion, which has the effect of decreasing density and even decreasing bottom pressure, as the water mass is moved inland on mostly northern continental shelves (see http://wcrp.ipsl.jussieu.fr/Workshops/SeaLevel/Posters/7_7_Landerer.pdf).
According to Landerer’s model thermal expansion, depending on its depth, will have a negligible or slightly decreasing effect on LOD, whereas a melting Antarctic should increase LOD. Current decreasing LOD then suggests lots of new snow at the poles, and/or continued rebound probably more from the Little Ice Age than from the Last Glacial Maximum. But core/mantle coupling provides a convenient deus ex machina–up to a point. –AGF
“The authors draw on paleoclimate records and model simulations of the last interglacial period”
Sounds like rock solid, fact-generating, effin science. Just give ’em a trillion to start fixing this thing right away.
Anthony, should there be a clarification regarding this statement: “The authors draw on paleoclimate records and model simulations of the last interglacial period, when the sea level rose by more than 6 meters (19.7 feet).”?
Do you mean that the sea levels in the previous interglacial, at their peak, were 6 meters higher than today?
Sea levels rose in this interglacial by about 350 feet, from the depth of the last ice age to the present, and mostly likely did the same prior to and during the previous interglacial.
Antarctica and Greenland don’t melt much during the “interglacials”; it’s North America and Eurasia that fluctuate. Only if ALL the ice melted would you get a rise of 100 meters.
Question. Isn’t only the top few feet of the seas that gets warmed by the sun before plunging down to the cold depths? Hence the thermal component of the oceans must include the entire cold depths? Is there any indications that the deep oceans are warming/cooling?
Speaking of worse than we thought:
–snip–
For those who may not know of this, look up Glacier Girl. A P38 that was extracted from the icepack along Greenland’s east coast. A group of WWII planes was forced landed on the icepack. The planes were abandoned. Expaditions found them, and extracted one P38 from the ice. They had to go down some 200 FEET! So if all this ice is melting in Greenland in the last 60 years, how did 200 feet accumulate and bury these planes in that same 60 years? Me thinks these predictions of melting ice are a tad off.
Why is it that scientists are so certain that the understand AGW and the effects, when we continue to hear them say things are worse than they previously thought. Doesn’t that mean that what they though previously was wrong?
Also, if the science on climate change is settled, then why continue to pay money to fund research on the subject? We should halt the funding for research and move to engineering. De fund the scientists and politicians and start funding the engineers and put people back to work building things of value. Scientific studies and the taxes that drive them are not contributing to the national wealth.