Temperature and climate "under" the gas giant in a tidally locked moon

I've begun the laborious (but fun!) process of putting another world together.

Known constraints include:

• Habitable, (super-)Earth-sized, tidally-locked moon to a gas giant; the giant, where visible, is reasonably large in the sky to be rather spectacular a sight;
• All land forms a single supercontinent, exact size to be determined;
• The "day length" on the moon (i.e. its orbital period w.r.t. the gas giant) is about 40 hours long; year length currently undefined;
• We may assume a moderate axial tilt for the gas giant (20-something degrees), and the moon may orbit around the giant's equatorial plane, or any similar plane that would generate "some tilt" with respect to the sun. The moon's own axial tilt is undefined at this point, but likely small; at any rate, the point is that some semblance of seasons should be in place;
• The moon's climate and precise geography is still up in the air, as I'd like to get the astronomy out of the way first;
• Low volcanic activity on the moon. After all, it needs to be a good place to live (and we can also ignore any radiation from the gas giant, save for spectacular auroras);
• Other "fixed", but presumably less relevant details: The star is a "blue straggler" by virtue of me wanting it to be blue (NB: This is likely completely nonsensical, ignore it); the giant may have other moons so that they may occasionally be seen by the inhabitants of our main moon.

I've not figured out how much illumination the moon will get from the sun yet, because I've got a more pressing question: What would the temperature "under" the gas giant side (the place where the giant would be seen 90° up in the sky) be, where the tidal bulge is, ignoring the moon's own climate? Will it tend towards being hot, or will it tend towards being cold? One can find contradictory information about this, as this answer suggests a large, freezing (or frozen) ocean at that spot; this answer, ignoring poles, suggests that the "under-giant" region may be hot instead, as the giant might be "hot". Does it depend on the giant? Does it even matter at all, or can one go with whatever he wants? I'd certainly appreciate some concrete information on this particular question, as I was unable to find a solid, logical line of reasoning to follow about this one.

I'm personally rather in favour of the side "towards" the giant (or "under", if you're on the moon) being hot rather than cold, but it'd bug me to simply assume this without clear understanding of how and why that would be (and whether it's even possible or likely).

Being "science-based" is important to me (no wizards allowed), but I'd always put the super-hard minutiae away in favour of a "plausible" solution that fits with the concept at hand. In other words, don't worry about maths, solar size and distance, or the time needed for the moon to form in comparison to the sun's lifespan.

NB: It's also highly likely that some of the assumptions I've made earlier in this post are wrong; after all, I've only been reading up on tidal locking since yesterday. If that is the case, corrections will be greatly appreciated.

posted about 5 years ago

Lumos‭

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