Guest Post by Willis Eschenbach
It has been known for some time that the “Pacific Warm Pool”, the area just northeast of Australia, has a maximum temperature. It never gets much warmer than around 30 – 31°C. This has been borne out by the Argo floats. I discussed this in passing in “Jason and the Argo Notes“, and “Argo Notes Part 2“. I’d like to expand on this a bit. Let me be clear that I am by no means the originator of the claim that there is a thermostat regulating the maximum ocean temperature. See among many others the Central Equatorial Pacific Experiment. I am merely looking at the Argo data with this thermostat in mind.
First, Figure 1 shows the distribution of all of the ~ 700,000 surface temperature measurements taken by Argo floats to date.
Figure 1. A “histogram” shows how many data points fall in each of the 1°C intervals shown along the bottom axis. The maximum is in the interval 28°-29°C.
The number of temperature records peaks around 29°C, and drops quickly for temperatures above 30°C. This clearly establishes the existence of the mechanism limiting the oceanic temperatures.
What else can the Argo data tell us about this phenomenon? Quite a bit, as it turns out.
First, a look at the year by year evolution of the limit, and how it affects the temperatures at different latitudes.
Figure 2. Annual temperature variations measured by all northern hemisphere argo floats that exceeded 30°C. Temperature observations are colored by latitude. Click on image for full-sized graphic.
A couple points of interest. First, the cap clearly affects only the warm parts of the year. Close to the equator, that is most of the year. The further from the equator, the less of the annual cycle is affected.
Second, the majority of the breakthroughs through the ~30° ceiling that do occur are from areas further from the equator, and are short-lived. By and large, nobody exceeds the speed limit, especially those along the equator.
Figure 3 is a closeup of the years since 2005. I chose this starting point because prior to that the numbers are still changing due to limited coverage. To show how the mechanism is cropping the tops of the warmer parts of the year, I have added a Gaussian average (129 point width) in dark gray for each two-degree latitudinal band from 0°-2°N up to 10°-12°N.
Figure 3. Annual temperature variations measured by all northern hemisphere argo floats that exceeded 30°C. Dark lines have been added to highlight the average annual swings of the data by latitude band. Click on image for full-sized graphic.
As you can see, the warm parts of the yearly cycle have their high points cropped off flat, with the amount cropped increasing with increasing average temperatures.
Finally, here is the corresponding plot for the southern hemisphere:
Figure 4. Annual temperature variations measured by all southern hemisphere argo floats that exceeded 30°C. Click on image for full-sized graphic.
Note that there is less of the southern ocean that reaches 30°C, and it is restricted to areas closer to the equator.
Next, where are these areas that are affected by the temperature cap? I had always thought from the descriptions I’d read that the limitation on ocean temperature was only visible in the “Pacific Warm Pool” to the northeast of Australia. Figure 5 shows the areas which have at some point been over 30°C.
Figure 5. Locations in the ocean which are recorded at some time as having reached or exceeded 30°C.
Figure 5a. A commenter requested a Pacific-centered view of the data. We are nothing if not a full-service website.
Clearly this mechanism operates in a wider variety of oceans and seas than I had realized, not just in the Pacific Warm Pool.
Finally, here is another way to consider the effect of the temperature maximum. Here are the average annual temperature changes by latitude band. I have chosen to look at the northern hemisphere area from 160 to 180 East and from the Equator to 45°N (upper right of Figure 5, outlined in cyan), as it has areas that do and do not reach the ~ 30° maximum.
Figure 6. Average annual temperature swings by latitude band. Two years (the average year , shown twice) are shown for clarity.
Note that at say 40°N, we see the kind of peaked summer high temperatures that we would expect from a T^4 radiation loss plus a T^2 or more evaporative loss. It’s hard to get something warm, and when the heat is turned down it cools off fast. This is why the summer high temperature comes to a point, while the winter low is rounded.
But as the temperature starts to rise towards the ocean maximum, you can see how that sharp peak visible at 40°N starts first to round over, then to flatten out at the top. Curiously, the effect is visible even when the temperatures are well below the maximum ocean temperature.
Speculations on the mechanism
I want to highlight something very important that is often overlooked in discussions of this thermostatic mechanism. It is regulated by temperature, and not by forcing. It is insensitive to excess incoming radiation, whether from CO2 or from the sun. During the part of the year when the incoming radiation would be enough to increase the temperature over ~ 30°, the temperature simply stops rising at 30°. It is no longer a function of the forcing.
This is very important because of the oft-repeated AGW claim that surface temperature is a linear function of forcing, and that when forcing increases (say from CO2) the temperature also has to increase. The ocean proves that this is not true. There is a hard limit on ocean temperature that just doesn’t get exceeded no matter how much the sun shines.
As to the mechanism, to me that is a simple question of the crossing lines. As temperature rises, clouds and thunderstorms increase. This cuts down the incoming energy, as well as cooling the surface in a variety of ways. Next, this same process moves an increasing amount of excess energy polewards. In addition, as temperature rises, parasitic losses (latent and sensible energy transfers from the surface to the atmosphere) also go up.
So … as the amount of total radiation (solar + greenhouse) that is warming any location rises, more and more of the incoming solar radiation is reflected, there are more and more parasitic losses, more cold water and air move from aloft to the surface as cold wind and rain, and a greater and greater percentage of the incoming energy is simply exported out of the area. At some point, those curves have to cross. At some point, losses have to match gains.
When they do cross, all extra incoming energy above that point is simply transferred to the upper atmosphere and thence to the poles. About 30°C is where the curves cross, it is as hot as this particular natural system can get, given the physics of wind, water, and wave.
I make no overarching claims for this mechanism. It is just one more part of the many interlocking threshold-based thermostatic mechanisms that operate at all temporal and spatial scales, from minutes to millennia and kilometres to planet-wide. The mechanisms include things like the decadal oscillations (PDO, AMO, etc), the several-year Nino/Nina swings, the seasonally opposing effects of clouds (warming the winters and cooling the summers), and the hourly changes in clouds and thunderstorms.
All of these work together to maintain the earth within a fairly narrow temperature band, with a temperature drift on the order of ± 0.2% per century. It is the stability of the earth’s climate system which is impressive, not the slight rise over the last century. Until we understand the reasons for the amazing planetary temperature stability, we have no hope of understanding the slight variations in that stability.
My regards to you all,
w.
UPDATE (by Anthony):
Dr. Roger Pielke Sr. has some praise for this essay here:
If this really is a limit it would seem to throw a lot of cold water over the water vapor feedback theory. If the ocean cannot warm, then there would be no increase in evaporation. The “C” in CAGW would cease to exist.
The 30C maximum means that the whole air column conforms to the adiabatic temperature profile and any temperature increase at any point in the air column will immediately result in convection. Portions of the air column can be cooler than the adiabatic temperature profile and the air column will remain stable as long as the adiabatic lapse rate is not exceeded at any altitude. The flat-top on the equatorial sea-surface temperature is an excellent illustration of the fact that the adiabatic temperature profile determines the maximum surface temperature of the earth (as well as any other planet), as an absolute limit.
Willis, thank you for bringing these important diagrams to us. They make it crystal clear that these high-temperature hobgoblins raised by the alarmists are mere phantoms of their overheated minds.
There is a maximum temperature for land as well. There is a point where the temperature will not climb any higher.
Records are seldom broken and then it is usually a local phenomenom. New record new location!
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Jimmy Haigh says:
February 12, 2012 at 4:56 am
Water is at its densest at approx. 4 degrees centigrade which may explain why the temperature at the bottom of the oceans is 4C.
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That’s been explained here more times I can count. SALT water’s density isn’t the same as fresh — it increases down to its freezing point. The cold water is present due to cold, sinking water in the polar regions (which spread out on the bottom globally). The ocean is largely stratified below the mixing zone, so cold water is “preserved” until it upwells. Think of an ocean “thermos bottle” below the mixing zone, w/cold water leaking in and out.
Willis
One has to be careful not to fall into the trap to which those proffering the cAGW theory fall into, namely that merely because one can see some general pattern(s) in the data that that indicates causation. One must bear in mind that correlation is not necessarily causation.
First, it is necessary to put forward a physical hypothesis which can be tested against the data. Second, one has to explain exactly what the data set is measuring; in this regard what exactly is ARGO measuring when it provides data on SST? In other words, are we looking at the top millimetres, or top centimetre, the first 5 or 10 centimetre etc. It is very important to be clear on this since this may have a bearing on the extent to which the physical hypothesis can be tested against the data. Third, if there are examples in the data set, even if this is only one example, which contradicts the physical hypothesis then unless that one example (or examples) can be shown to be some anomaly, the physical hypothesis is wrong. When I say wrong, I do not mean that it is necessarily fundamentally flawed, but it does require revision.
No doubt the majority of those sceptical of the cAGW theory are of the view that there are (or probably are) negative feedbacks which tend to control temperature within a reasonably small band and which make tipping points unlikely.
I note your tentative mechanism. I am pleased to see that this is stated wider than the mechanism that you proffered a couple of days ago. I still consider that in that mechanism, one should probably include ocean overturning. I also consider that it is probable that the topography of the seabed especially in and around the continental shelf also plays a role.
Ocean currents are difficult to understand. Not only in their lateral location but also in their vertical profile. As a diver, you will know well how localised water temperature can be, and how matters of metres one way or another both laterally and/or vertically can make a significant difference to the prevailing local temperature. Until the physical mechanisms involved in creating the profiles of currents are well understood, inevitably it will be difficult to understand how ocean temperatures are fully controlled.
The air temperature above the ocean is (predominantly) governed by the ocean temperature, This can be seen by the small diurnal range over oceans. You may take it from me that it can also be seen in temperature profiles recorded in ship’s logs in circumstances where the ship is sailing in a warm current, air temperature usually closely correlates to the warm localised sea temperature.
Obviously, oceans at the same latitude in theory receive the same amount of solar irradiance. Given that air temperature is a response to ocean temperature, this begs the question why is the ocean at the same latitude not all at the same temperature?
DWLWIR has little penetrative effect and therefore it is difficult to envisage a mechanism whereby it directly heats the ocean. To the extent that it has any heating effect, it is likely that this goes to increase the evaporation on the first few microns which in turn is likely to result in a cooling, not a warming of the surface layer (by which I mean the layer at about 1mm and immediately below).
One cannot efficiently heat a body of liquid, merely by warm air above it. If you place a drink say at 2 degC in a well insulated cup (sides and bottom being well insulated and of material that is not a good conductor) in a room at 20degC, the drink will not tend to warm quickly and to the extent that it does, this is more influenced by short comings with the insulation. Nor will the rate of evaporation be greatly influenced by whether the ambient room temperature and hence the air immediately above the open surface of the drink is at 5 deg C or 20 deg C. That being the case, and not forgetting that the air temperature above the ocean is driven by the temperature of the ocean itself, it is not immediately apparent that evaporation rates are governed by air temperature as opposed to being a feedback to forcing, primarily solar since DWLWIR penetrates only to microns.
So where is this taking us, apart from the obvious that namely much more thought needs to go into what is driving ocean temperature, how it responds to those forcings and what processes are at play that will naturally place some restrictions on how warm the ocean can get?
At this moment, I have no great answers and need to give much further thought to this matter. But in the meantime, there needs to be a thorough explanation as to why, for example, the open Indian ocean off both the East and West coast of India and the East Coast of Africa can and does get up to 34 degC, and why the Atlantic ocean off the West coast of Africa around Ghana. Ivory Coast can and does get up to 35 degC..
This would be a great test of a model of sea surface temperatures. Does the model produce W. Eschenbach’s 30° C cap? …. and I don’t mean by fudging, for example:
100 IF T > 30 THEN LET T = 30 ( as it would be put in BASIC)
All this sort of begs the question of how the great oceanic transport currents are generated and how that heat transport mechanism fluctuates over time. I remember well getting lost one night when crossing the gulf stream from Florida to the Grand Banks near Bimini. I was sailing southbound evidenced by the North star trying to hold position until the night fog bank lifted yet I ended up 20 to 30 miles North of my expected position. That experience taught me to respect the power of the ocean currents.
“Richard M says:
February 12, 2012 at 5:54 am
It does appear that the limit only shows up in the open ocean. The coastal areas and seas have no problem going over 30°. It may be informative to look only at these areas and see if they have another limiting factor”
Salinity. As the evaporation rate increases, salinity increase, and then the rate of evaporation drops. With a fixed heat input the higher the salt content, the higher the temperature and the lower the rate of evaporation.
Thus, salinity should plot with Tmax.
here is another flat top graph-
http://upload.wikimedia.org/wikipedia/commons/thumb/c/c5/Orbital_path.jpg/800px-Orbital_path.jpg
Willis,
The facts that you have helpfully set out are not news.
It has been known for decades that the water at or near the equator never gets much warmer than 28 or 29C.
Your own thermostat proposals are based on that well established information.
However you still fail to join the dots.
It is atmospheric pressure which dictates the limit for the energy content of the air at the surface.Once that limit is reached the global air circulation simply reconfigures itself to maintain system stability.
All unknowingly you are producing evidence in support of Nikolov, Zeller, Jelbring. myself and various others and evidence against your earlier vigorous attempts at debunking the significance of atmospheric pressure.
Read this article of mine:
http://climaterealists.com/index.php?id=7798
“The Setting And Maintaining Of Earth’s Equilibrium Temperature”
The rate at which the oceans can release their previously acquired solar energy to the air is dependent on surface atmospheric pressure.
The rate at which the surface can release energy to space through the atmosphere is dependent on atmospheric surface pressure but is modulated by changes in the surface air pressure distribution when ANY factor tries to divert the atmospheric emperature profile from the dry adiabatic lapse rate set by surface pressure.
Every aspect of climate is simply the negative system response to destabilising influences and compared to the scale of natural variability our emissions come nowhere.
The key to it all is the energy budget balancing process provided by variable atmospheric heights in the vertical plane and shifting surface air pressure distribution in the horizontal plane.
It really is that simple.
And this article of yours helps to prove the point.
Geoff Sherrington says:
February 12, 2012 at 4:17 am
Reflect on the fact that life on earth would largely be eliminated except for that fact that ice floats. Were it to sink, the oceans would have filled up with ice long ago, never to turn liquid except for a thin veneer perhaps several tens of meters thick in equatorial regions during the summertime. As one huge block of ice, the “oceans” would have no circulating currents to help distribute massives amounts of thermal energy from equator to the poles. The resulting climate would be harsh, indeed; humans and many other animals would probably not be around.
Now extend this conceptual example to (near freezing) water, which does indeed sink, where it stays for some time, but it isn’t solid. And that cold water will stay down there until forced to the surface by some impediment like a continental mass, although circulation through mid-oceanic spreading centers does transfer significant amounts of heat, but sinking cold water at the polar regions far offsets this addition.
So it’s “worse that we thought.” The oceans can only absorb so much heat, therefore in the future air temperature warming will be at even faster rates.
What do the GCMs show when it comes to ocean temps?
Well in spite of my previous post where I had not noticed the graph depicted the Southern Hemisphere, not the Northern, those graphs still confuse me a tad. When I see color coding my mind keeps trying to tell me red means hotter and blue means colder. But in your graphs red means equatorial and blue means polar. Might it be worthwhile to plot the same data with the vertical axis representing latitude and the color coding representing water temperature?
This is very important because of the oft-repeated AGW claim that surface temperature is a linear function of forcing, and that when forcing increases (say from CO2) the temperature also has to increase. The ocean proves that this is not true. There is a hard limit on ocean temperature that just doesn’t get exceeded no matter how much the sun shines.
Willis, I can’t agree here. The hard limit on ocean temperature is not 30 degrees. It is the maximum heating from the sun (which just happens to be around 30). Increase the energy from the sun and the temperature goes up. Decrease it and the temperature will go down.
Also if you want to discuss CO2 forcing increases and its effect on temperature you just can’t look at the Argo data. The variation within the time series is too great to extract a small CO2 forcing signal. What I find interesting (thanks to the enormous effort you have invested Willis) is the year over year trends in the troughs of the data. It almost looks like a trend to lower mid-latitude temperatures with time. How does that fit with global warming when the mid-latitude oceans are cooling?
M.R.B. states you can’t heat water from above. How come my pond gets so hot in the summer? I must have an underground heat leak somewhere.
Reply to Stephan Richards, “The only mechanism available to start an ice age is the sun.” Not so… since the Pleistocene Era c. 2.6-million years-before-present (YBP), geophysical plate-tectonic distribution of landmasses has separated eastern from western hemispheres’ atmospheric/oceanic circulation patterns by interposing North and South American continents.
Since the Cretaceous/Tertiary (K/T) Boundary c. 65-million YBP, five major geophysical eras have lasted a median 12 – 14+ million years apiece. On this basis, cyclic Pleistocene glaciations should persist another 10-million years or so at minimum.
Only when plate-tectonic “continental drift” via sea-floor spreading re-disposes continental landmasses will Planet Earth revert to the more stable climatic equilibrium that prevailed –subject to extraterrestrial bombardment and super-volcanic episodes– throughout post-Cambrian times, now totaling near 550-million years.
Meantime, if not for Earth’s 1,500-year Younger Dryas “cold shock” that ended c. 9,300 YBP (BC 7300), chances are that our current Holocene Interglacial Epoch would have ended coincident with the Roman Warm that preceded a 500-year Dark Age cooling phase from c. AD 450.
@Willis
Did it not occur to you that 30C is the blackbody temperature for the equator? Calm water has a very low average albedo (i.e. it’s very close to black) and it also varies little between day and night. Thus what this should be telling you is that under optimal conditions of clear equatorial sky and calm water this is the highest average daily temperature that can be acheived. You can add greenhouse gases until the cows come home and it won’t get any higher because the bottom line is that greenhouse gases cannot raise the temperature above the blackbody temperature. Greenhouse gases can help to approach the blackbody temperature in a roundabout way of making the surface appear darker (i.e. absorbs a greater percentage of the incident energy) but in no way can it exceed the maximum which is limited by solar energy through a perfectly clear sky falling on a surface that absorbs 100% of it. Optimal conditions can approach that maximum but my not exceed it. Exceeding it requires a greater amount of energy reaching the surface than the sun provides so unless the sun gets hotter there’s nothing else that can do it.
As I recall from my sailing days, 28C is the ocean surface temperature at which you are at risk for cyclone formation. The ocean surface temperature will not go much above this, because the energy goes into storm formation.
If upper atmosphere winds are high, the energy is simply carried aloft and from there to other parts of the globe, without a cyclone forming. If upper atmosphere winds are low, then the rising energy gets a chance to organize and start things spinning.
For those who have not followed closely the “Jason and ARGO Notes” post, I consider that it would be beneficial to post a couple of comments I made in relation to that post .
I did not comment upon the statistical analysis performed by Willis since this is a work in progress. However, one assertion of a scientific nature caught my eye because of the potential consequences it could have on cAGW.
The scientific assertion was: “No matter how much incoming solar there is, the ocean doesn’t get any warmer than that [30 degC]. This provides a “cap” on how hot the ocean can get. Above that temperature, any extra incoming energy is converted to latent and sensible heat, rather than warming the surface..”
I considered that assertion incorrect for two reasons. First, open ocean temperatures can and do, in a number of places, exceed 30degC such that the 30degC figure is too low. Second, whilst not disputing that processes are at play which tend to limit ocean temperature, I considered the one mechanism cited by Willis as being not the only process at work. Since then Willis has widened the processes at play which tend to place a limit on ocean temperatures. I consider that to be an improvement but still it fails to take account of other processes which probably contribute in particular ocean overturning and topography.
There is of course a problem with this. Namely, we know for example the Atlantic ocean off the coast of Ghana and Ivory coast regularly gets to 34 degC if not 35 degC. Why is this and why does the immediately adjacent ocean at same latitude not also get to such temperatures? Is it possible that this area of the Atlantic ocean which gets up to 34 deg C (even 35 degC) to increase in area? If not why not? What are the limiting restrictions on the area involved? These are just some of the issues that arise that need to be considered and explained.
Ditto, we know that the Indian ocean off the West coast of India (and indeed in places off the East coast of Africa) regularly gets to 32 degC and at times and in places up to 34 degC. Why is this and why does other parts of the ocean at same latitude not get similarly warm? Is it possible that this area of the Indian ocean which gets up to 32 deg C (even 34 degC) to increase in area? If not why not? Again, what are the limiting restrictions on the area involved? These are just some of the issues that arise that need to be considered and explained.
The above examples are not exhaustive either of the areas of open ocean that regularly exceed 30degC nor of the issues that are involved. Further there are the issues raised in relation to enclosed, semi enclosed and shallower oceans.
If the reason lies in the hydrological process, why is this different in some parts of the ocean?
Further we need to consider the historical data. In particular, we need to consider the pre-historic tropical ocean which I understand (without endorsing consensus) is generally accepted to have been warmer than the tropical ocean is today. Why was that? Especially, as solar may well have been less powerful. This of course is difficult given that the then tropical ocean had different topography and we know nothing (or nearly nothing) about currents and heat transport then on going.
We also need to consider carefully what ARGO is measuring and also what it is not measuring. Putting things in context this is important since it may be that there is some cap of temperature placed on the very top of the ocean surface but the same cap is not necessarily imposed at say 10cm or 20cm or 50cm or 1m (or what have you) below the surface. If that is the case, it may be that whilst the temperature at the surface cannot exceed XdegC, the temperature beneath the surface can exceed X degC or WdegC and the ocean at that point may well nr significantly below WdegC and is presently warming towards WdegC.
Whilst I am sceptical of cAGW, if there is plenty of temperature headroom lying at a depth a little below the surface and if in that depth the ocean is undergoing warming, there is still the possibility for cAGW.
So what am I saying? Well really only this, before one offers Willis the Nobel prize (as one commentator suggested) and before we all get too carried away, let’s give some proper thought to this and not simply fire from the hip.
ps: by cyclone I mean hurricane, typhoon, etc. The names differ depending on where you live.
” Geoff Sherrington says:
February 12, 2012 at 4:17 am
I’m also interested in why deep ocean waters are close to freezing. How and when did they get so cold? It’s the other end of the cap. Were they always this way, or are deep ocean temperatures part of global energy dynamics as well? Remember that we have had small but omnipresent heat from radioactive decay for millions of years.
Presumably if ocean waters below the thermocline, that is, the major portion of ocean waters, were at 20 deg C, the surface cap of 30 deg C might be displaced to give rather different outcomes.”
The deep ocean has not always been cold. When you think about it is rather odd that it is, since it has warm water on top and hot rocks underneath. The reason it is cold is that it is always the densest water in the ocean that will sink to the bottom. In the present icehouse climate which has lasted for c. 35 million years this is either very cold and salty water which is “frozen out” when sea ice forms around Antarctica or very cold and salty water which is formed by evaporative cooling in subarctic parts of the North Atlantic. In both cases the water is also well oxygenated, consequently the deep ocean is also fairly well oxygenated.
During periods with hothouse climate (which is most of the time actually) the ocean is warm all the way to the bottom. There is no cold, briny arctic water around, so the heaviest water available is instead warm, briny water created by evaporation in the tropics. This water is much less oxygenated than present-day deep ocean water, both because of temperature and less vigorous mixing at the surface. Periods with hothouse climate therefore also leads to OAE:s (Ocean Anoxic Events), periods when the deep ocean, or at least parts of it becomes stagnant and anoxic. The last time this happened on a large scale was in the mid-Cretaceaous about 100 million years ago, but there have been many such episodes in the past (and each time life in the deep ocean must have been wiped out, and restarted by colonization from shallower areas when deep ocean circulation speeded up again).
Superbe analysis – again!
Interesting to see how the 31 C wall can hardly be overcome.
Around 30 C waters simply has to let go of the heat. This also seems to explain why ENSO patterns has such a significant impact on temperatures around the world.
And this also makes the relation between temperatures in Nino3,4 and global temperature make even more sence:
http://hidethedecline.eu/media/Pendulum/enso-temperature-Fig1.gif
From recent article: http://hidethedecline.eu/pages/posts/the-siberian-pacific-climate-pendulum-251.php
– because: These equatorial waters at 30 C release more heat to the atmosphere that anywhere else, and thus, differences here affects the whole world.
K.R. Frank
Steve from Rockwood says:
February 12, 2012 at 8:11 am
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Your pond is heated by solar, not by hot air. Ambient air temperature is important to how much heat is lost at night.
In Summer, my swimming pool ,regularly reaches 35 to 36 degC and yet the air temperature may be 30 to 33 degC. It is usually able to maintain a night time temperature of 31 to 33 deg C even though night time temperatures may be down to 24 to 25 deg C.
Tim says:
February 12, 2012 at 2:35 am
R.M.B. says:
“You can not heat water from above because of surface tension”
————-
I have seen this statement several times on these pages. Can someone explain to me why surface tension should totally inhibit heat transfer from gas to liquid?
Thanks.
______________
Tim,
Simply put, the main reason is that at very short distances from the surface [approx micrometres and less] the forces that produce bulk mixing in the ocean become much less important, and diffusion becomes dominant. This diffusion constraint affects how fast heat can be transferred DOWN from the surface [the “Einstein-Smoluchowski” limit is often how it is taught in Chemistry, where it has an important effect on reaction rates]. You cannot make it go faster by simply stirring with wind/wave/convection. So when the heat cannot be rapidly transferred downwards, then more water evaporates, effectively transferring the heat UPWARDS [as latent heat]. This heat now CAN be transported efficiently by wind and convection. It will later reappear when it condenses back to water somewhere else on the planet, higher in the atmosphere, closer to the poles, etc.
Now, Infra red radiation is so strongly absorbed by the top micrometres within this surface zone limited by diffusion rates, that a resulting temperature rise [from increased IR radiation] is more easily lost by evaporation than it is transferred to depths. Dave Springer has often posted about this on these blogs, and elsewhere. It has been used to argue than “Trenberth’s missing heat” in the oceans never did enter the oceans.
Visible light can penetrate much further down into the ocean, allowing it to warm the deeper water rather than evaporate it. This is why changes in the Sun’s spectrum are as important as well as the total amount of radiation received across the spectrum.
Personally, I find the phrase “penetrating surface tension” a bit misleading because surface tension is a force, not a physical object that can be penetrated [“penetrating gravity” would sound similarly non-physical to me]. Surface tension does, of course, operate at surfaces, but the phenomenum is essentially unrelated to the absorbtion of light or infrared radiation.
richard verney says:
February 12, 2012 at 8:34 am
If the reason lies in the hydrological process, why is this different in some parts of the ocean?
Cyclones (huricane/typhoon) are not distributed evenly around the globe. They tend to affect the east coast of continents more than the west coast. The ocean basins themselves tend to be steeply sloping on the west coasts of the continents and shallow sloping on the east coasts. What effect the rotation of the earth plays in this is an interesting discussion.
“All of these work together to maintain the earth within a fairly narrow temperature band, with a temperature drift on the order of no more than ± 0.2% per century.”
This may be the case for present conditions when things are relatively stable. However I’m not sure that this is true given the dramatic temperature changes that were seen during the Little Ice Age period; both up and down. Even more so at the beginning and end of the Younger Dryas. It was an interesting time in Nova Scotia where massive storms carried land detritus (spruce needles and cones) out to and deposited them at the edge of the continental shelf. It is a good example of where massive storms were not caused by warming, rather by rapid cooling.