# Defining a superfluid ocean

I'm working on a world where water acts as a high-temperature superfluid. Specifically, H2O's lambda point is above its boiling point. Thus, all liquid water on the planet behaves as a superfluid. It still boils and freezes normally, at 100$$^{\circ}$$C and 0$$^{\circ}$$C, respectively. I haven't worked out the exact physics that permits this, so take this as given for the following question if possible.

I'm having trouble understanding how this superfluid would function on a global scale. Assuming an Earth-like planet, there's plenty of water to go around. If I understand superfluid physics correctly, the following phenomena will be observed:

• A thin film of water covers the entire planet, per the Rollin film
• All areas beneath sea level are submerged. Caves and tunnels are filled by the Onnes effect as soon as they form and are exposed to water. Similarly, all lakes and streams above sea level are empty
• Superfluid water is highly thermally conductive, indicating that all water on the planet is the same temperature, regardless of depth or latitude
• Following from this, the poles will not have sea ice - frozen water on the planet must be kept separate from any liquid water or the ice will be melted as the heat is redistributed
• Waves are present in the ocean and the water film, existing as first, second, and third sound
• Currents in the ocean are far more powerful, as superfluid water has no viscosity to slow it down. The currents therefore move at the speed of the air flowing above them, but they are also much shallower because the deeper water isn't dragged along
• Gyres in the ocean do not exist as we know them, but instead are large-scale collections of quantized vortices. There are multiple possibilities for the fine-scale structure of these vortices, as a function of temperature and pressure.
• The superfluid ocean still obeys density-dependent dynamics, but lacks an overturning circulation due to homogenous temperature.
• The definition of density in superfluids is apparently debated?

I've been unable to find any information about the effect of impurities in superfluids, so I have no idea whether this ocean would be salty. Depending on the response to this question and the answers I get, I may post a followup question asking for more help with the water cycle and mechanisms of erosion that would make this superfluid ocean salty, but for now assume it's pure water.

Is the logic above sound and in line with real-world physics, as best we understand it? Are there additional differences between an ocean on Earth and an ocean in an alternate universe where water acts as a room temperature superfluid?

• I'd be more interested in figuring out how any water-based life could form. My guess is that it couldn't – Carl Witthoft Jul 23 '19 at 19:06
• Does rain behave the same way? Maybe water in rain is more ordinary until it contacts the planet-wide body of water. Then, over some amount of time, it turns into the super fluid water. Maybe you can avoid the contact by using heat and boiling away a ring around water you want to keep ordinary. That way you can have swimming pools and such. When you want to drain your pool you could just drag some of the world-water over the edge of the pool. – puppetsock Jul 29 '19 at 19:44
• Wow, I wrote up a whole answer about your errors in discussing supercritical fluids before I realized you wrote "superfluid" which I didn't even know existed :( – kingledion Jul 31 '19 at 12:32
• I don't think humans could survive because any water they drink would immediately run back out of their mouth. – Bilbo Baggins Aug 2 '19 at 23:46

You've got a few errors:

Similarly, all lakes and streams above sea level are empty

You'll still have lakes and streams, they just won't stay wet for very long. "Zero viscosity" doesn't mean "infinitely fast flow", so any time you get rainfall, you'll get temporary ponds and lakes. The Rollin film ensures that even endorheic basins eventually drain into the ocean, but conventional streams are still the preferred way for water to flow.

Following from this, the poles will not have sea ice - frozen water on the planet must be kept separate from any liquid water or the ice will be melted as the heat is redistributed

It takes time to melt ice. The sea may have high thermal conductivity, but glaciers don't. You're not going to have ice shelves on the scale of Greenland or Antarctica, but you'll still have glaciers protruding into the water, and if the glaciers are thick enough, icebergs (though they won't last nearly as long as they do on Earth).

Waves are present in the ocean and the water film, existing as first, second, and third sound

The Rollin film doesn't have "first sound" waves (it's not thick enough).

Currents in the ocean are far more powerful, as superfluid water has no viscosity to slow it down. The currents therefore move at the speed of the air flowing above them, but they are also much shallower because the deeper water isn't dragged along

Fast, shallow currents aren't very powerful. The lack of dragging means there isn't much water moving -- the "currents" are basically just a surface film.

On the subject of impurities, superfluid helium can dissolve substances, with interesting results: see quantum solvent.

• Yes, one should keep in mind that superfliud still has mass and obeys Newton laws. There will be tidal waves. And it does not have infinitive thermal conductivity, wich means that water will have different temprature. And air is not a superfluid - there will be cyclons, but weather overall will be more constant. There will be areas of almost constant evaporization and areas almost constant rains (with lakes and rivers due to this) – ksbes Jul 29 '19 at 14:36