More on “Why Is The Ocean So Cold?”

I need some help here. In particular, I’m looking for people who have at least an undergraduate level of training in thermodynamics generally and energy flow specifically, or self taught equivalent. (I have studied energy transfer in a number of university courses, but that was many years ago now. I’m pretty confident in my ability to perform an energy balance, but I’m stumped by this one).

Here, in a nutshell, is my conundrum:

Why is the ocean so cold?

Our friends at BEST, CRU, GISS, etc. going all the way back to Fourier, all agree that the “surface temperature” of the earth is more than 10 celcius or 283 kelvin. Further, it is  hypothesized that the “surface temperature” of the earth has always been at least 10 celcius and often more.

So how is it that the temperature of the ocean, which is in direct contact with this “surface” is at least 6 degrees colder than the “surface temperature”? Not only is the ocean in direct contact with this “surface”, but the earth itself is constantly shedding thermal energy into the ocean from the crust.

If someone can show me a complete energy balance that allows the ocean to be at a steady state temperature that is lower than the “surface temperature”, I would be grateful. If there isn’t such a balance, one of two things must be true. The “surface temperature” is colder than estimated or the laws of thermodynamics don’t apply to the oceans.
Just to be clear, it is an absolute certainty that the laws of thermodynamics
apply to the oceans.

No hand waving allowed. I’ve seen a number of debating point style arguments. I would like to see some math on this. I’m working on my math on this. My first run approximation has the oceans boiling away a few billion years ago, so something is not right. If you are not sure how the oceans should have boiled away billions of years ago, add 0.1 W/m² of energy to a 4 km column of  water for 1 billion years and determine what the temperature that of the water should be. That is lower than the approximation of the rate of energy transfer from the crust to the bottom of the ocean.


I’ve had two exchanges with Dr. Gavin Schmidt at RealClimate. Thanks Dr. Schmidt. His short answer is there is no short answer. In order to understand the mechanisms for the heat transfer that occurs, I must first learn a GCM. This answer is exactly correct and exactly useless. So it seems the answer is: The ocean is so cold because of reasons that are too complicated to explain.

I am going back to my little explanation of the greenhouse effect using engineering methods for now. When that is done I’ll look at the ocean again.


About John Eggert

A minerals processing engineer in Canada. A cynic by nature, but open to being convinced!
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7 Responses to More on “Why Is The Ocean So Cold?”

  1. John West says:

    Saw your post @ WUWT. I’m afraid I’m not going to be much help, but I can at least explain why somewhat mathematically.

    ∆E = q(input) – W (out)
    [Change in Internal Energy of a system] = [Heat Input] – [Work Accomplished]

    [Heat input] = [Heat In] – [Heat Out] (Essentially, “Heat Input” means “net” heat input.)

    ∆E = q(in) – q(out) – W(out)
    q(in )= q(out) + W(out) + ∆E

    So for ∆E to be essentially zero on average over long time frames, which must be the case or the ocean wouldn’t be “so cold”, the net heat uptake must roughly balance the work being done by the ocean.

    And here’s where I’m at a loss too, quantifying the work of expansion, currents, etc; not to mention all the latent heat involved with evaporation and melting/freezing of water seems to be quite insurmountable from my perspective. As Willis on WUWT keeps trying to get across, the system has so many “thermostats” it’s crazy complicated. I do offer my moral support though!

  2. John Eggert says:

    The work in maintaining global currents may be the answer. I’ll have to think about that a bit. If the currents are not changing in velocity, is there net work being done? There is energy in to keep the current going and energy out as friction loss. These would be equal if the current velocity is constant, so there is no net work for currents. For expansion and the work required to lift the 4km column of water, that can be calculated. This is not a trivial sum, but once done, it too goes to 0. Thus with work gone to 0 and the system at steady state, that is no net change in energy, q(in)=q(out). If this is the case, we need only look at the ins and outs. And for that, we need only look at the second law of thermodynamics. If the ocean is cooler than the atmosphere, there will be a net flow of energy from the atmosphere to the ocean until they are at the same temperature. Similarly with the interface of the ocean and the crust. So we get back to the initial question, how can the ocean be at a lower temperature than the atmosphere, at steady state, at (for all intents and purposes) an infinite time.

  3. John Eggert says:

    I have received a responce from Gavin at RealClimate.

    Response: The answer can be found in any basic text book in oceanography and has been known since the days of Challenger expedition – the ocean is stratified by density. Colder water at a fixed salinity is more dense than warmer water. Therefore cooling of the surface (during winter, in high latitudes) is far more effective at producing denser water than warming the surface (at least at surface salinities experienced today). – Gavin

    He was a tad condescending and didn’t provide any math, but there is logic to it. That being said, if he is right, this would amount to a very interesting feedback mechanism. What happens when ice cover increases? Surface salinity is no longer constant. Water under multidecadal ice has a higher salinity due to freeze thaw action, hence will be denser. Thus as the ice cover increased, the transfer of heat out of the ocean to the atmosphere would decrease. As ice cover decreases, heat transfer increases. Thus a negative feedback. Mayhap this is sufficient to explain Trenberth’s “missing heat”.

  4. John, have a look at slide 26 of this presentation by the late Dr Noor Van Andel (a chemical engineer) to KNMI. Trenberth’s missing heat is a bit of a smoke screen for his nonsense gobal heat balance. If you look at the surface heat transfer by convection and evaporation and then add the radiation window (66W/m2) there is no extra radiation which could be absorbed by the so-called greenhouse gases and there is no missing heat. Dr Van Andel has/had patents for heat exchangers. As a chemical engineer he understood heat and mass transfer. This was another presentation to KMNI shortly before he died of cancer
    Gavin Schmidt has no chemical engineering qualifications and has demonstrated he does not fully understand heat & mass transfer and particularly evaporation & condensation.
    Evaporation cools the ocean surface particularly in the tropics. When the water vapor condenses in the upper atmosphere to form clouds heat is released. This reduces the lapse rate from 9.5K/1000m to 6.5K/1000m. The ice and water droplets in clouds are the main radiators to space (note the emissivities of ice and water at cloud temperatures is close to 1). The Miskolczi theory ( explained very well by Dr Van Andel (A note on the Miskolczi theory) which you can download with other papers here ) indicates that the optical density has remained constant for the last 60yrs that the CO2 does not affect climate.

  5. Lars P. says:

    I agree that the oceans are of great relevance for the climate and ignoring them was the main cause which allowed for wrong assumptions for the greenhouse warming in first step.

    First the way how the oceans warm, as we have the short infrared from the sun which penetrating maybe only the first meter and the visible light which is going up to 200 m. So the warmth is dissipated over the whole column of water. The oceans do not warm directly at the surface as solid rock which would heat to 70-80°C by day.

    Oceans radiate only at the surface. There is no IR inside the oceans as water is opaque to IR. Oceans act as a heat accumulator at the equator where the radiated heat is less then incoming heat.
    Downwelling radiation from the atmosphere does not penetrate the oceans it ends at the very surface (and is consumed for evaporation ?)
    The heat “trapped” by the oceans is slowly distributed to the north and south.
    At the very north and south areas the oceans are covered with ice and thus do not radiate heat. Ice is a very bad heat conductor so almost no heat from the oceans escapes.
    The heat capacity of the oceans is additional increased with the freezing/defreezing heat exchange and enthalpy – so a huge heat reservoir.
    I understand that through the ice sheets north and south there is one feedback mechanism of the oceans, if the oceans unfreeze in summer on a wider area it might result not in increasing heat intake but in an additional cooling of the ocean the longer the open area stays.

    The real greenhouse is in the oceans, what the atmosphere does is more to increase albedo through clouds and redistribute heat there where the oceans are absent – continents and north/south pole, so I would not see them as cooling agent for greenhouse but more as defining climate.
    These are my 2 cents, hope this is of any help. Let me know if this makes sense for you.

    • John Eggert says:


      First, sorry for the long wait to approve. I’ve been at a work site with limited internet (in the Yukon).

      Yes, this does make sense. The method of heat absorption into the ocean is not absolutely critical. What is critical is that the ocean is warm above, warm below, yet cold in between. Dr. Schmidt asserts that evaporative losses at higher latitudes is the reason. In the little spare time I have, I’m putting together an estimate of just how much water must be evaporated by the oceans to cause the excess cooling required to keep the 4 kilometer column of water cold. From this mass, one can then provide a change to absolute humidity that would result. Whatever the result, I’ll post it when I’m done.



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