The Photon Current - 7

Only One Way To Go

The way heat moves within the ocean (e.g. from surface to bottom) is the movement/transfer of 'heat energy', beginning with the absorption of solar radiation at sea level in the form of both visible light photons and invisible infrared photons.

It continues when those surface level absorbed photons are 're-radiated' as infrared photons into 'cooler atoms' near the atoms that first absorbed the Sun's light (cooler means containing less energy).

This re-radiation is governed by the Second Law of Thermodynamics, which is the 'direction' of hot to cold, warm to cool, which in the ocean generally means top to bottom (it can be up, down, or sideways so long as it is hot-to-cold).

After initial absorption the re-radiation of those photons in the form of invisible-to-the-human-eye infrared photons, 'heat transfer' becomes an ongoing dynamic:

"Infrared radiation is popularly known as 'heat radiation', but light and electromagnetic waves of any frequency will heat surfaces that absorb them. Infrared light from the Sun accounts for 49% of the heating of Earth, with the rest being caused by visible light that is absorbed then re-radiated at longer wavelengths [infrared photons have a longer wavelength than visible light photons have]."

(Wikipedia, Infrared). This infrared photon heat transfer phenomenon is universal, i.e. it is not limited to the oceans of the Earth:

"To astrophysicists studying the universe, infrared sources such as planets are relatively cool compared to the energy emitted from hot stars and other celestial objects. Earth scientists study infrared as the thermal emission (or heat) from our planet. As incident solar radiation hits Earth, some of this energy is absorbed by the atmosphere and the surface, thereby warming the planet. This heat is emitted from Earth in the form of infrared radiation. Instruments onboard Earth observing satellites can sense this emitted infrared radiation and use the resulting measurements to study changes in land and sea surface temperatures."

(NASA, Infrared, emphasis added). Oceanographers take it further in that they measure temperature changes (in situ measurements) all over the oceans of the Earth then report the measurement results to the World Ocean Database (WOD).

Using those in situ values in the WOD we can process them using the latest oceanographic/thermodynamic computer science and software to derive the heat content (potential enthalpy) at each location that has been measured (Wikipedia, TEOS-10). 

Those results tell us that those infrared photons have reached some of the deepest depths (The Photon Current, 2, 3, 4, 5, 6).

The next post in this series is here, the previous post in this series is here.

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