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Unforced Variations: Mar 2021

Filed under: — group @ 1 March 2021

This month’s open thread. Northern Hemisphere Spring is on it’s way, along with peak Arctic/minimum Antarctic sea ice, undoubtedly more discussion about the polar vortex, and the sharpening up of the (currently very uncertain) ENSO forecast for the rest of this year.

115 Responses to “Unforced Variations: Mar 2021”

  1. 101
    MA Rodger says:

    Bob Loblaw @100,
    Thank you for your input. I wasn’t clear what was meant by “heat diffusion” and my spelling possibly didn’t help. The use of the term as meaning “thermal conduction” is not one I use and not one l’m familiar with in liquids which don’t diffuse as much as gases, while Piotr @95 presented questions about his use of the term rather than clarity (which took until #99 to eventually arrive).

    Piotr @99,
    We still face the pantomime of the obvious absence of the eons-worth of atmospheric IR boiling away the oceans (and I’m not sure if that is the “the ocean still boils – a 50m-deep mixed-layer boils in mere … 3 years “ assertion or whether this 50m-in-3-years assertion is still invoking solar radiation). You argue this obvious absence is the proof of something which you propose and which is at odds with something you say I propose, to which I try to respond more usefully than just “Oh no it’s not!!!”

    Water isn’t the best of thermal conductors which is why a puddle of surface water around the tropics can sit at +30°C for eons atop a puddle on the ocean floor at -1°C just a few thousand metres beneath and this without the need for super convection currents to recharge the frigid depths from the poles. Indeed, some of these abyssmal waters are down there for more than a millennium and show no significant warming. Because water is such a bad conductor, it is unable to create the temperature gradients required to pass energy down into the abyss.

    Similarly, the tiny temperature gradients within the surface skin of the ocean create a barrier between the goings-on in the mixed layer and the goings-on at the actual surface. Thus the surface and the mixed layer are “decoupled.” I do not mean by this that the micro-layer is a barrier impervious to all heat transport yet your “the ocean still boils” comments appear to show that to be your version of what I mean by “decoupled.”
    It seems our understanding of each other’s meaning of the term “decoupled” have likewise become “decoupled” (this in the meaning I mean and not the meaning you appear to mean).

  2. 102
    Bob Loblaw says:

    MA Rodger @ 101:

    Thermal conduction and thermal diffusion are not exactly the same thing, although they both come out of Fourier’s laws.

    Conduction relates to the energy transferred along a temperature gradient. This can happen even in a steady state: constant temperature gradient means constant heat flux.

    Diffusion phenomena are more akin to how a body responds to temperature changes. Take an object at steady state (e.g. uniform temperature) and add a pulse of heat at a point or face of the object. How does that pulse of heat spread through the object? How does the temperature of the object, at different points in the object, respond? That involves both conduction and heat capacity (by volume), and the two show up in the equations as a ratio. That ratio is the thermal diffusivity, and as log as it is known you can calculate the movement of the pulse without needing to know either thermal conductivity or heat capacity. The units of thermal diffusivity are m^2/s, just like the units for mass diffusivity.

    Thermal diffusion is mathematically equivalent to placing a drop of ink in a Petri dish of water and watching it spread slowly through the water. Drop a pulse of heat, and watch it spread.

    As for the discussions of skin layers, etc.

    * Still water is a better conductor than still air.
    * The atmosphere has a laminar boundary layer that requires diffusion to get heat or water vapour across it. Also extremely thin.
    * Nobody seems to talk about the atmosphere being unable to move heat away from the surface. It seems the atmosphere tends to rapidly get rather turbulent, which vastly increases its ability to move heat (or water vapour, or CO2…)
    * Last time I went sailing, the water didn’t seem to be all that smooth and still. I suspect it is also rather turbulent. (end sarcasm)

    Do these skin layer arguments actually seem to think that there is some magical cellophane-like layer on the water surface that creates a perfect seal that prevents the surface water from mixing with the water below?

  3. 103
    Piotr says:

    MA Rodger (101) “I’m not sure if that whether this 50m-in-3-years assertion is still invoking solar radiation

    Given the context of my argument… what ELSE could it have invoked?

    MAR(101) “I try to respond more usefully than just “Oh no it’s not!!!

    I appreciate the good intentions, but the result has been, well, a bit underwhelming – your explanations are irrelevant and/or don’t prove what they purportedly prove. A few examples:

    1. MAR(100): “ yes it is correct to say of the the ocean – “it has been absorbing heat from solar shortwave radiation for eons” but at these shorter wavelengths, the penetration is far greater with blue light penetrating perhaps 20m and red light 5m (on average).

    What does it add and how does it falsify my statement that shortwave radiation is absorbed in the mixed layer, when the typical mixed layer covers both 5m and 20m?

    Then we have this:
    2. MAR(100): “Water isn’t the best of thermal conductors which is why a puddle of surface water around the tropics can sit at +30°C for eons atop a puddle on the ocean floor at -1°C just a few thousand metres beneath and this without the need for super convection currents to recharge the frigid depths from the poles.”

    Huh?
    a) Paleoceanography problem: 45 mln yrs ago deep ocean was 15C. I.e. no “-1C puddles” left from the previous “rechargings” either 30 mln (from previous cold period) or 230mln (from previous major glaciation), MUCH LESS: “for eons“.

    b) Different processes: temperature profile from the surface to ocean bottom are controlled by advection and mixing of water masses coming from different geographic sources. Hence a WRONG analogy for the transfer of heat across a thin VISCOUS layer.

    c) Different scales: your “water isn’t the best of thermal conductors” while true for heat flow across several KILOMETERS, may not be do so for a heat flow across 1 MILIMETER (the shorter the distance, the steeper the gradient, the stronger the flow).

    Finally:
    3. MAR(101): I do not mean by this that the micro-layer is a barrier impervious to all heat transport

    You can’t have it BOTH ways:
    – either ALL of the 190 W/m2 of shortwave rad. that was absorbed by the mixed layer moves into the microlayer and, from there, into the air – and then my argument was correct

    – or it can’t move all 190 W/m2, and then the ocean’s mixed layer keeps getting warmer and warmer, and Minnett was wrong since in his JGR paper he didn’t use any other mechanism of moving heat between the mixed layer and microlayer than I did.

    So, which of the two?

  4. 104
    Piotr says:

    Bob Loblaw (102)“Do these skin layer arguments actually seem to think that there is some magical cellophane-like layer on the water surface that creates a perfect seal that prevents the surface water from mixing with the water below?”

    Well, I’d say pretty _close_ to that magic cellophane:

    MARodgers (90): ““The depth of the viscous layer means there is no ‘defusing downward’ but only conduction which greatly limits any downward flux”

    And as a result:

    MA(90) “viscous layer insulates the micro-layer preventing the strong thermal coupling [with the ocean-s mixed-layer below it] your reasoning relies on.”

    with my reasoning being:
    Piotr (89):”the top of the mixed layer will warm the bottom of the surface film, heat diffusion will move the heat from this bottom to the top of the film, from which it will move into the air in form of conduction, convection, latent heat of evaporation AND upward IR”.

    So the seal by the magic cellophane must have been pretty darn good to “insulate the micro-layer” tightly enough to make my above reasoning “inadequate“.

  5. 105
    Richard Caldwell says:

    Bob L: Do these skin layer arguments actually seem to think that there is some magical

    RC: Gravity is a big driver. Warmer surface waters stratify, thus requiring a 1000 or whatever year loop driven largely by salt and the temperature differential between the poles and the tropics.

    But the atmosphere is cooler than the surface, bringing convection into play. Plus, water has a huge thermal mass. So it makes sense that the oceans seem to act at least a bit like they incorporated magic cellophane, given that human experience is mostly with air.

  6. 106
    MA Rodger says:

    Piotr @103,
    I said @101 “It seems our understanding of each other’s meanings of the term “decoupled” have likewise become “decoupled” (this in the meaning I mean and not the meaning you appear to mean).” That is we can see a great deal of [wordage/energy]* passing between [us/the ocean’s surface layers]* but the [meaning behind that wordage/processes generating the energy fluxes]* are failing to register across the divide. [*Delete as applicable.]
    I could unpick the detail of the wordage provided @103 but the level of “Either I’m right or you’re wrong!! Which of the two is it?!!!” within the wordage rather swamps the more interesting content so it is perhaps better to leave it with you insisting that you are ever correct and I am flat wrong, and what you call the Minnett JGR paper (presumably Wong & Minnett (2018)) is also flat wrong, all this because you are eons cleverer than we could ever imagine.

  7. 107
    MA Rodger says:

    Bob Loblaw @102,
    Magic cellophane-like layers aside, there is an ocean surface layer through which any energy flux is in the hands of conduction and it is only the upper part of that layer which can radiate to the atmosphere. As you say, still air is even worse at conduction than still water but a lot more fluid and stretchy so any atmospheric boundary layer above the ocean surface would be much thinner to the point of insignificance for the radiative energy fluxes. As it is generally the net radiative fluxes that dictate the level of ocean surface warming/cooling, it will be the material integrity of the surface layer (which would surely be a statistical thing as the mixing of the mixed layer becomes the non-mixing of the micro-layer and I assume would not involve any magic) that will be the defining factor on ocean temperature.
    Mind, there are areas of ocean where there is an impressive cellophane layer but it is apparently not very magic.

  8. 108
    JCH says:

    Do these skin layer arguments actually seem to think that there is some magical cellophane-like layer on the water surface that creates a perfect seal that prevents the surface water from mixing with the water below?

    If a temperature gradient is magical, then yes.

    It’s not all, it’s progressively less and less as GHGs increase.

    What would the graphs for OHC look like if Minnett is wrong? The same?

    The curvature adjustment of the temperature in the TSL shows that the additional heat due to absorption of the increased LWin@zenith has modified the TSL profile to reduce the transfer of heat from the mixed layer to the atmosphere. This modification, therefore, provides an explanation for the immediate indirect heating of the ocean even though the increased LWin@zenith is not absorbed throughout the upper few meters of the water column. Thus the heat (which is a product of the absorption of solar radiation during the previousdays) within the uppermost few meters of the ocean is unable to escape into the atmosphere, resulting inthe retention of heat in the upper ocean.

  9. 109
    zebra says:

    JCH #108,

    That last quote seems to present a reasonable argument, although the misuse of the word “heat” is atrocious. Perhaps poor communication skills by the author contributed to all the confusion in the first place…until Bob Loblaw chimed in, the discussion was really hard to follow.

    So is it fair to say that what is proposed is analogous to the ‘GHG effect’, where the surface of the water is something like the layer before the layer where radiant energy escapes to space?

  10. 110
    Bob Loblaw says:

    Richard, MA, et al:

    …but the ocean density stratification, etc. applies primarily below the ocean mixed layer, which is in the order of 60-100m deep. Wind action keeps the mixed layer – well, er, mixed.

    You can argue that there is a very thin laminar layer of water at the surface, but there is also a very thin laminar air layer there, too. Yes, radiation easily makes it through atmospheric laminar layer, but it too is restricted to thermal and vapour diffusion to allow heat and water vapour to reach the mixed atmosphere above it, where turbulent transfer can take over. Fortunately, that laminar layer is very thin (in the order of a millimetre, thinner when it is windier), so the required large temperature or vapour pressure gradient can exist without a huge temperature or vapour pressure difference.

    On a sunny day, air temperature at the surface (and I mean the surface. where air is in contact with the land or ocean) is easily several degrees warmer than the air temperature at screen height (1-2m), even with lots of turbulent mixing (translation: wind). Those differences/gradients are a must to allow for energy or mass transfer by turbulent mixing. The laminar air layer at the surface fails to insulate the atmosphere from surface temperature – why would the ocean and its laminar water layer be any different?

  11. 111
    Bob Loblaw says:

    While I am at it, let’s put some numbers on how much heat we can get through a thin layer of water using only conduction.

    The thermal conductivity of still water is temperature-dependent, but works out to be about 0.6 W per metre-Kelvin at realistic surface temperatures. (Or units of W/m^2 per K/m if you want to keep the heat flux and temperature gradient terms isolated).

    For a layer 1mm thick, or 0.001m, with a temperature difference across the later of 1C (or 1K), the temperature gradient is 1000 K/m.

    Without using a calculator, my ball-park estimate is that we can get about 600 W/m^2 of thermal conduction across that thin layer under those conditions. This does not seem to be a physically-unlikely rate in nature.

    And that is only if you can get the water to not move at all. I have used water as a test material for measuring thermal conductivity. Not as easy as it sounds, because the d@#%ed stuff will not keep still, even in a small beaker. As soon as you apply a small temperature gradient to measure thermal conductivity, it’s starts mixing. You lose heat a lot faster, and overestimate the thermal conductivity. The only way to get it to stay still is to add a small % of gelatin, cook, and cool (i.e., make Jello without the sugar). Then it actually works pretty well as a reference material.

  12. 112
    Piotr says:

    Bob Loblaw (111) “For a layer 1mm thick, or 0.001m, with a temperature difference across the later of 1C (or 1K), the temperature gradient is 1000 K/m.[…] my ball-park estimate: about 600 W/m^2 of thermal conduction across. This does not seem to be a physically-unlikely rate in nature.

    Yes, it is not – assuming that the mixed layer gets on average 190 W/m2 “surplus” heat from solar shortwave – it means that in a steady state it has to get the 190W/m2 through the layer and from there into the air. So much for MARodgers:

    viscous layer insulates the micro-layer preventing the strong thermal coupling [with the mixed layer] your reasoning relies on”.

  13. 113
    Piotr says:

    MA Rodger (106) I said @101 “It seems our understanding of each other’s meanings of the term “decoupled” have likewise become “decoupled”

    Since I am not interested in the zebra-esque discussions on how many angels could dance on the tip of a needle without “not very strong” decoupling, I proposed
    that INSTEAD of discussing what exactly you meant by “not very strongly” –
    we simple TEST of our ideas on their outcomes:

    Since ~ 190 W/m2 enters the mixed layer in form of the short-wave radiation, the test was what happens to it:

    – I argued that most (under steady state: all) of 190 W/m2 moves from mixed layer across the 1mm viscous layer into the microlayer at the top of it, from where it is exported into the air.

    – you argued that “viscous layer insulates the micro-layer preventing the strong thermal coupling your reasoning relies on.”.But if it isolates strongly enough to falsify my explanation – then it means that most (all?) of this 190 W/m2 stays in the mixed layer. Which would make a 50-m mixed layer boil after several years (3 years if all 190 W/m2 stayed).

    Since we don’t see a boiling fish soup atop of the ocean, you: accused me of relying on …. imprecise wordage, presented my falsifiable test of our claims as me saying …. “Either I’m right or you’re wrong!!” and announced your exit because of
    MAR(106): “
    you insisting that you are ever correct and I am flat wrong, all this because you are eons cleverer than we could ever imagine
    Whau.

    P.S. MAR(106): “you insisting that you are ever correct and [Minnett is] flat wrong

    That’s symptomatic of our discussion:

    – I said: MARodgers is right then Minnett is wrong.
    – You portrayed it as me saying: “ since I am ever correct then Minnett is “all wrong”
    You see the difference, right?

  14. 114
    MA Rodger says:

    Piotr @113,

    Forgive me as I am a mere denizen of reality, but you appear to me to be first accusing me @106 of preposterous argumentation before then yourself embarking on you own preposterous argumentation. I hoped I had explained @106 that such a situation was exactly why I was not minded to “unpick the detail of the wordage provided @103” by such a clever one as yourself.

    As for the post script you append @113, of course we both “see the difference, right?” It is ‘righting the difference’ that is beyond us.
    Mind, concerning that ‘difference’, I am a little confused as @89 you say “the long and rather technical quantitative paper like the one by Minnett et al** is something you “didn’t go through the details of,” this said to explain why you were “not saying the paper is wrong or irrelevant,” thus as a minimum putting in doubt the validity of the paper.
    Now @113 you appear to be saying that this paper is correct and perhaps that you are actually in agreement with “Minnett”. Perhaps if you were to “go through the details of it,” which shouldn’t be too much to ask of one eons cleverer than I could ever imagine, we could then establish whether you agree or disagree with (presumably) Wong & Minnett (2018).

    [** I assume you refer here to Wong & Minnett (2018)‘The Response of the Ocean Thermal Skin Layer to Variations in Incident Infrared radiation’ as the alternative candidate referenced @81 you complained @83 was on a non-functioning URL [fixed now]

  15. 115
    sidd says:

    Convection does complicate measurement of thermal conductivity in fluids, but in my eexperience this is dealt with by using very short measurement times, and/or keeping the dimensions pf the apparatus smaller than the capillary length. See

    https://www.sciencedirect.com/science/article/abs/pii/0031891449901299

    https://ctherm.com/resources/newsroom/blog/avoid-convection-errors-in-measuring-the-thermal-conductivity-of-liquids/

    sidd