Something to keep you up at night.

Deep Ocean heating and climate

The heat capacity of the atmosphere is insignificant compared to the heat capacity of the ocean.

Heating of the ocean by the atmosphere is also insignificant. Imagine trying to warm a bathtub full of 80 degree water by warming the room to 90 degrees. Evaporation from the water in the tub would cool it faster than the heat conduction could warm it. Yet we are told recent increases in ocean heat content are proof that CO2 is warming the planet.

The physics don’t work, but though the estimates of ocean heat content may be exaggerated, there has been an increase that warmer air cannot explain. So, where does the warming come from?

Measuring the temperature of the ocean is tricky. We can measure the surface temperature, but prior to the year 2000, our ability to measure the deeper water has been very limited.

If we had an ideal ocean, uniform salinity and no currents, then the water would be warmest at the surface, (except for where it is coldest) and get gradually colder as it got deeper, until it reached 39°F which would be the temperature all the way to the bottom. Water reaches its maximum density at 39°F so if it gets colder, it rises instead of sinking, and becomes floating ice at just under 32°F

But we don’t have an ideal ocean. The Southern hemisphere ocean is saltier and thus heavier. Thus there is a transport from North to South.

All of that is fascinating, but it doesn’t explain the apparent increases in heat content. It can’t be coming from the atmosphere. so? Well, most of Earth’s volcanoes are under the ocean, if they were uniformly heating the ocean, they would reach a steady state in which the warmed water would rise and the heat dissipated by evaporation and convection at the surface.

Water is not supposed to be compressible, but it has gases disolved in it that can be squeezed out at very high pressures and water around volcanic vents can be a lot saltier, so in the very deep oceans you can get temperature inversions where water can be up to 2.5°C above the water above it. That is unstable and various changes can result in a “burp” of relatively warm water rising to the surface.

We don’t know how large these pockets of trapped (relative) warm water are, if a big one “burped” it could result in rapid climate change, and it doesn’t make a bit of difference what kind of car you drive.

So much for the illusion of control.

3 thoughts on “Something to keep you up at night.

  1. RE: “Water is not supposed to be compressible,”

    I remember this from oceanography class in college (many years ago). Yes, water is not compressible under normal conditions, but in the deepest depths of the world’s oceans where pressures are intense, the viscosity of water changes. That is, the water molecule itself becomes compressed, changing the fluid properties of the medium.

    If the deep oceans are trapping volcanic heat beneath layers of thickened water, that indeed is worrying. But why worry about something that couldn’t be changed, anyway?

    I ask only because there are many such conditions in life.


    1. No, the ocean is not a bathtub.

      As I pointed out, the Southern hemisphere is saltier and cooler. That drives the thermohaline circulation.

      But the effect of warming from the surface is still much like that bathtub. Convective heat from the air is cancelled out by evaporative heat loss. The primary heating of the ocean is from sunlight, and that is regulated by cloud cover.

      Think of the Ocean as a surface layer and the deep ocean, separated by an abrupt change at the thermocline. Heating the surface layer does not warm the deep ocean, it just makes the surface layer thicker.

      But the heat capacity of the ocean is so much greater than the atmosphere, that the atmosphere could be on fire and it wouldn’t significantly warm the ocean. It would just drive the thermocline down a few feet on average.


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