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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I’m not sure why so many are becoming agitated about this. It seems to be a straight forward investigation of the cause(s) of sea level rise. Their conclusion is that melting icesheets contribute more than has been thought to be the case.
I can’t see any reason to find that objectionable. In fact I find it interesting.
jorgekafkazar said @ur momisugly August 19, 2011 at 12:39 pm
“Metal objects frozen into ice don’t remain at a constant level. The weight causes the ice beneath to melt very slowly, letting them sink. The 200′ doesn’t all represent accumulated ice.”
Granted. So is there an engineer who can calculate for us how much of the 200′ is due to the planes sinking?
Of course. It takes about sixty times more heat (thermal energy) to rise sea level via thermal expansion of water than by melting land based ice. That much is elementary physics, it does not require an overcomplicated computational model.
If heat is actually accumulating in the climate system and if it does, how much of it is focused on the polar regions is an entirely different question. Currently ~16 million square kilometers are covered by ice sheets, some 3% of the entire surface. The interior of these ice sheets is very cold, 20-50°C below freezing, that is, no projected warming would ever melt it. Ablation can only happen along the edges, which is a tiny fraction of the surface area. At the same time higher average SST (Sea Surface Temperature) implies more evaporation, therefore more snow accumulation where it is still damn cold, that is, over the ice sheets themselves.
Ice sheet mass balance is determined by the fine equilibrium of these opposing processes, which is not simple physics. Current ice sheets can’t be compared to the huge Laurentide, Fennoscandian or Tibetan ice sheets of the past, any of which extended to much lower latitudes than either the Antarctic of Greenland ice sheet does now, so they got much more insolation on average.
Any report based on Topex/Poseidon sea level measurements is principally flawed because a most critical part outside 66º N and S is left out. In these areas the sea level sinks dramatically. Around Antarctica down to -2 metres! This massive dip is caused by strong W to E winds driving equally strong currents. Due to strong Coriolis forces near the poles, the water is then pushed equator-ward where it heaps up (Ekman spiral). Topex/Poseidon looks only at the heap and not at the trough, as do moored buoys.
Wind strength, which can change by 25% on a decadal scale and 30% in a century, has a most determining effect on sea levels everywhere. Because of the seminal work of Dr Joseph fletcher, we can no longer ignore this.
Dr Fletcher’s lecture http://www.seafriends.org.nz/issues/global/fletcher.htm
What is normal climate change?: http://www.seafriends.org.nz/issues/global/climate7.htm
Are sea levels rising?: http://www.seafriends.org.nz/issues/global/climate4.htm#Are_sea_levels_rising?
JohnW –
Perhaps you can explain, but if there is widespread acceptance here at WUWT that GW is happening but it just isn’t A, why does Anthony loves him some posts about snowpack in the High Sierras, snowfall in NZ, seals unexpectedly turning up in Boston Harbor, etc?
And as someone who is interest in climate change but who believes that the Earth is warming (although not anthropogenically) – why exactly, doesn’t Anthony run posts that discuss notable trends of change in plant and animal migration that are consistent with significant global warming?
You see – I keep reading at this here site that folks accept GW but not AGW, but then I see post after post that implies a lack of belief in GW. And I also see comment after comment that doubt a Greenhouse Gas Effect, and that say that the Earth is cooling.
Curious, isn’t it? It makes it seem as if there’s a whole lot o’ inconsistent logic being bandied about, doesn’t it?
Kohl says:
August 19, 2011 at 3:01 pm
I’m not sure why so many are becoming agitated about this. It seems to be a straight forward investigation of the cause(s) of sea level rise. Their conclusion is that melting icesheets contribute more than has been thought to be the case.
I can’t see any reason to find that objectionable. In fact I find it interesting.
No one’s “upset”. It’s pretty much SOP warmscience. It has the trappings of science, but because the assumptions are so completely out of whack, so are the conclusions. The fact that sea level rise apparently has less to do with thermal expansion and more to do with actual melting than they thought might be interesting if somewhat useless information. It is the warmist spin they and others (like Gates) will no doubt put on it which is troublesome.
R. Gates is correct. The IPCC projections for sea level rise were based almost entirely on thermal expansion. Climatologicts knew that warming seas undermined greenland and antarctic ice resting on land below sea level, which would evewntually result in these shelves detaching, but did not know enough about the mechanism to calculate how much this would add. So these “alarmists” simply left this contribution to sea level rise out of calculations entirely.
Increasing knowledge of this mechanism has now allowed estimates to be made, which is why projections of sea level rises by 2100 have been increased. Loss of land based ice sheets will be a relatively sudden addition to sea levels, which is why you cannot extrapolate the current thermal expansion rates to the end of the century.
Floor Anthoni, thank you for the three references. I have read some of your papers before, but not these ones. The connection between “sea level” and wind is very interesting and persuasive.
IanM
Philip Shehan,
Observations are falsifying your conjecture: click
For Bruce Cobb
If you are going to quote what I said, please make sure that it is actually what I wrote. I didn’t say “upset” and didn’t imply it.
Otherwise, I have two problems with what you say –
1. “The fact that sea level rise apparently has less to do with thermal expansion and more to do with actual melting than they thought might be interesting if somewhat useless information.”
It seems to me that to-day’s “useless” information might turn out to be tomorrow’s essential foundation. A great deal of science used to be ‘blue sky’. That is to say, the results of research did not always have immediate or even expected practical impact or application. I would hate to see that change.
(As an aside and per contra, I rather think that it has already changed significantly as the influence of government and large private company funding tends to require ‘results’ for continued funding).
2. “It is the warmist spin they and others (like Gates) will no doubt put on it which is troublesome.”
Whatever ill use ‘they and others’ might make of this study is best dealt with when it occurs. Pre-emptive dismissal of ideas on the basis of what use ‘might’ be made of those ideas looks a lot like censorship to me.
jorgekafkazar says:
August 19, 2011 at 12:39 pm
Metal objects frozen into ice don’t remain at a constant level. The weight causes the ice beneath to melt very slowly, letting them sink. The 200′ doesn’t all represent accumulated ice.
——–
In this case it does. Objects, non metal, left on the ice surface when the crew was rescued was still with the aircraft 200 ft down. The planes were not deformed in any way, which would be the case if the planes sunk into the ice. So the planes did not sink into the ice, the ice accumulated around the planes as snow.
Joshua says:
August 19, 2011 at 5:28 pm
JohnW –
Perhaps you can explain, but if there is widespread acceptance here at WUWT that GW is happening but it just isn’t A, why does Anthony loves him some posts about snowpack in the High Sierras, snowfall in NZ, seals unexpectedly turning up in Boston Harbor, etc?
And as someone who is interest in climate change but who believes that the Earth is warming (although not anthropogenically) – why exactly, doesn’t Anthony run posts that discuss notable trends of change in plant and animal migration that are consistent with significant global warming?
You see – I keep reading at this here site that folks accept GW but not AGW, but then I see post after post that implies a lack of belief in GW. And I also see comment after comment that doubt a Greenhouse Gas Effect, and that say that the Earth is cooling.
Curious, isn’t it? It makes it seem as if there’s a whole lot o’ inconsistent logic being bandied about, doesn’t it?
—————
Not at all. The AGW claim is the planet is getting hotter. But it isn’t. Parts of the planet are getting less cold in the winters, such as the north. Summer temps are flat in the tropics, no change since records began, just fluctations. Canada, for example, has had FEWER heat waves today since the 1930’s. It’s all that together that is driving the average temperature up, and shows that a global planetary average temperature is completely meaningless. What we see posted here is a planet with a very complex climate system, with cycles within cycles, and different cycles at different locations. It’s the claim that the entire planet is “warming” evenly everywhere because of CO2 that is the curious concept indeed.
Pompous Git says:
August 19, 2011 at 3:35 pm
jorgekafkazar said @ur momisugly August 19, 2011 at 12:39 pm
“Metal objects frozen into ice don’t remain at a constant level. The weight causes the ice beneath to melt very slowly, letting them sink. The 200′ doesn’t all represent accumulated ice.”
Granted. So is there an engineer who can calculate for us how much of the 200′ is due to the planes sinking?
Several flaws in the “the aircraft sunk through the ice” theory:
These WWII aircraft were very, very light in terms of their wing area, tail planes, and fuselage body areas. They landed with their wheels down, and rolled to a stop. Available photo’s hundreds of feet under the ice show all with virtually no damage, and all at nearly the same depth and at stable, flat, attitudes. Hundreds of similar WWII fighters and bombers landed at sea and stayed floating for hours on water … proof again, that at low speeds and no crash impact to tear the structure apart immediately, a WWII aircraft’s wings WILL keep a similar aircraft suspended above a hard mass like snow indefinitely. That the larger, heavier bomber and smaller-winged but lighter fighters were all at just about the same depth means that none “sunk” but that all were buried under ice and snow after the event.
So any twisting, sinking or “ice-melting” can be eliminated. It simply didn’t happen. (Sure, the first 5 feet? The wheels and struts could have “sunk in” . but no further. After that 5 foot drop, they were stable, and stayed stable for 60-odd years.
Will a small, heavy metal plate sink in? Certainly. But that heavy “plate” is not a lightweight airplane wing!
All of the 200 foot of the ice and snow above them was deposited in place in the 60 years between their crash-landing and their removal.
jrwakefield –
Looks like you and JohnW need to have a sit-down.
Kohl says: August 19, 2011 at 7:28 pm “(As an aside and per contra, I rather think that it has already changed significantly as the influence of government and large private company funding tends to require ‘results’ for continued funding).”
Do tell, where else does substantial funding come from? The Green Party? The tooth Fairy? The WWF?
Patrick Davis says:
August 19, 2011 at 4:25 am
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.==============
huh? theres world of difference between a plate of crust moving some land- or supposed warm water or some C02 in their sinking islands, which..also..seems not to be happening anywahere.
tuvaalu eg.
This is ALL speculation, because THERE ARE NO actual witnessed records of ice age temperatures. We must ask British “Time Lord”, Doctor Who, to go back for us in his “TARDIS” and have a look, and preferably make some videos & etc. Then we can maybe know the truth.
Maybe it was the terrible “Skith” what done that seal level; thing ?
http://tardis.wikia.com/wiki/The_Age_of_Ice
it’s as likely as the yarns that these “scientists” spin in here about catastrophic sea level rises.
Joshua says:
August 19, 2011 at 5:28 pm >>>– why exactly, doesn’t Anthony run posts that discuss notable trends of change in plant and animal migration that are consistent with significant global warming?<
because evrything any animal bird bug does lately is immediately linked as "warming affected"
when the fact is until now they either didnt have (AGW)funding to go look. or any reason to tout it loudly and make unproven claims
so if AGW funds you, going against the grain with observations purely as observations of range habitat etc, is sort of UNlikely.
those that do dont get published as easily, if at all. and they sure dont get a new grant.
you will see people here like Willis actively asking for critiques and revision and sharing working out info, freely.
funny how "msm style researchers like a certain mann, refuse to allow that?
Smokey: It would have been helpful to see what the various plots on the graph actually describe but I will limit my comment to saying that apart from envisat, which apppears to be anomolous compared to the other lines, the current short term dip is similar to other short term variations in the record within the long term rise.
@ur momisugly Kohl; Perhaps I was unclear. The paper reeks of Alarmism, and that is what people object to. Their conclusion: “These results reemphasize the concern that both the Antarctic and Greenland Ice Sheets may be more sensitive to temperature than widely thought” is not science, but Alarmist spin. Why should there be “concern”?
Joshua says:
August 19, 2011 at 5:28 pm
And as someone who is interest in climate change but who believes that the Earth is warming (although not anthropogenically) – why exactly, doesn’t Anthony run posts that discuss notable trends of change in plant and animal migration that are consistent with significant global warming?
It is completely meaningless, and in fact disingenuous to say that “the Earth is warming”. All we can truthfully say is that is has warmed, or did warm since the end of the LIA, although the extent is greatly exaggerated, and purposely, by the Alarmists. The previous warming has in fact stalled, and we are likely going into a period of cooling. If there are any plants or animals currently in the process of migrating, it would more likely be in the warm direction, unless they are suicidal.
Bruce –
So, then, you disagree with what I am told is the majority opinion here at WUWT?
And I notice that still, no one can answer my questions.
Interesting.
The Earth can only do two things.
It can be warming, or it can be cooling.
Humans cannot alter that fact,
though some would like to do so.
Like fleas on an elephants back, arguing which way
that the elephant should next go, months into the future.
Humans have about as much idea or hope as those
fleas of getting ANY prediction right, except for the rather
obvious one. In the future, it will either get warmer or colder.
sea level rise due to thermal expansion of the top layer of the ocean is a localized effect. It does not affect coastal sea levels. Only thermal expansion in the lower layers of the ocean affects coastal sea level.
Thermal expansion of the top layer of the ocean does affect satellite-measured sea level, but for coastal planning purposes that doesn’t matter. (That’s one of the reasons it is Just Plain Wrong to create a graph which combines tide gauge-measured coastal seal levels through ~1995 with satellite-measured sea levels from 1995 on, as Hansen likes to do, to create the illusion of acceleration in rate of sea level rise.)
Quantifying the effect of deep ocean thermal expansion is problematic, at present. The Argo Buoys are attempting to measure deep ocean temperatures, but they aren’t finding much warming in the ocean depths. In fact, early reports (now disputed) were that the Argo Buoys were detecting a slight cooling, rather than warming.
If it isn’t clear to you why thermal expansion of the top layer of the ocean doesn’t affect coastal sea levels, recall that the top layer of the ocean basically floats on the lower layers. Consider what happens when there is a density change in the top layer of seawater in the open ocean (perhaps due to temperature change). If the density decreases (the water expands) then the sea level rises, in place, in the open ocean, without affecting coastal sea levels at all.
Mariners call this concept “displacement” – it is measured in units of mass, not volume.
Examples of this are icebergs and sea ice. When frozen, water has reduced density, so an iceberg (or Arctic icecap) rises above the surrounding liquid water. Its top surface is a locally elevated sea level. When the ice melts, that locally elevated sea level falls, but it has no effect at all on coastal sea level, because the iceberg’s water has the same mass (displacement) regardless of its varying density and solidity.
The same thing happens when surface water warms in the open ocean. Sea level goes up locally, in the open ocean, due to thermal expansion of the water, but it has no effect at all on coastal sea levels.
Density changes in seawater in lower layers of the ocean do affect coastal sea levels, but it takes hundreds of years for surface heat to find its way down to the lower layers of the ocean, so anthropogenic global warming cannot have much affected it yet.
daveburton,
Face it, sea level rise is decelerating. The reason for the previous rise was the natural warming since the LIA. And the 3,351 ARGO buoys are not wrong, even though some alarmist dispute the measurements. They argue about the readings because a cooling ocean debunks thier “carbon” globaloney. The models are wrong, not the observations.