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I have an Earth-like planet that has no frozen poles. It is very similar to a Cretaceous Earth. Is there any sort of odd, yet reoccurring weather event, that could cause freezing air from the upper atmosphere to descend quickly to lower the temperature of several islands in a non-polar latitude down to freezing?

Edit: By freezing an Island, I mean allowing water to get cold enough to form ice on the island, resulting in a colder climate than surrounding areas.

Edit: My world has large oceans uninterrupted by any continents, with the world's only two terrestrial continents being at the poles and dominated by forests. This island is volcanic in nature, so having a higher elevation isn't unreasonable.

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  • $\begingroup$ Air in the upper atmosphere is at low pressure. Air near the surface is at normal pressure. When a gas is compressed it heats up; see adiabatic heating. Anyway, the heat capacity of air is very low; for a practical example, one can put their hand in a heated oven with no ill effects. I don't fully understand what you mean by "freezing an island" (islands are made of rock, which is already frozen at normal temperatures). $\endgroup$
    – AlexP
    Commented Dec 30, 2018 at 4:17
  • $\begingroup$ I'll clarify my question! $\endgroup$
    – Thalassan
    Commented Dec 30, 2018 at 4:19
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    $\begingroup$ You may want to look up katabatic winds, for example the bora in the Adriatic Sea. These occur when air atop an elevated plateau is cooled by radiative cooling and flows down a slope, cooling the land at the bottom. There are places in the Antarctic, such as the McMurdo Dry Valleys which experience frequent katabatic winds. But such winds don't come for "upper atmosphere". $\endgroup$
    – AlexP
    Commented Dec 30, 2018 at 4:29
  • $\begingroup$ Katabatic winds seem to be the result of higher elevation areas that are possibly covered in snow and ice. The area I plan on putting this does not have any sort of ice or snow. $\endgroup$
    – Thalassan
    Commented Dec 30, 2018 at 4:37
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    $\begingroup$ How long need the island be frozen? Minutes? Forever? Where is the island located? Do you have a map of your world? You can get cold air via tornados and cold air funnels. What makes sense will depend on where and how long you need ice. $\endgroup$
    – JBH
    Commented Dec 30, 2018 at 6:43

2 Answers 2

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Like the comments already state several times, your whole idea is a long-shot. But given that, perhaps your planet can have some set of conditions that provide the Mother of All El Niño - La Niña cycles.

Here on this Earth, said cycle takes the form of periodic variations in the winds, currents, and temperature of the surface of the southern Pacific Ocean, which in turn influences weather patterns throughout most of the planet. This cycle is about seven years long, and the temperature variations are only about half a °C water temp, but still cause noticeable changes in precipitation and air temp across entire continents.

Our scientists are just beginning to hypothesize about the exact cause and mechanisms, leaving you possibly even more freedom in a fictional work to handwave.

For some reason, the axial tilt, the positions of land-masses, the contour of the ocean bottom, the orbits of its natural satellites, and presence of maedupium in the atmosphere, all conspire upon Thalassan-World to make a hundred-year long cycle with sudden shifts of +/-30°C. Just as an example.

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This could happen regularly if the planet rotates around a variable star:

  • a pulsating star or
  • a star with a strong stellar cycle, i.e. it could last for 11 years (like the Sun) but at the minimum the star could dim significantly.

You should be careful what star you choose as some are so unstable they would have huge stellar flares or even blow up in a supernova. $:)$

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