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This relates to my previous question about a fictional planet: Length of seasons on a planet with eliptical orbit.

In short summary, it is an oceanic world with many islands and archipelagoes that have 45 degrees axial tilt to the orbital plane (and a very elliptical orbit, if it matters in this question).

The question is: how would be climatic zones - tropic, subtropic, temperate, polar - distributed on such a planet?

Adding details for which the need has transpired:

The planet has tectonic activity, the same as Earth. It causes quakes and volcanic eruptions, fractures the planet's crust into plates, and makes them drift around.

The largest island is similar in size and shape to Greenland, but it is located on the equator and with a long point towards the west; thus, it splits the equatorial circumnavigating stream in two. There are a few little bit smaller islands, but most of the land mass is small islands and archipelagoes similar to those of the Pacific Ocean and Mediterranean.

Islands that are large enough to have mountains or mountain ranges. In some archipelagoes, major islands form a line with close gaps of water between them, as if a mountain range submerged in water, leaving only peaks above, and are situated in a way that disrupts major oceanic streams.

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  • $\begingroup$ What is the geography of this world? We have perennial snow close to the Equator in our world, something one would not tell just by its axial tilt $\endgroup$
    – L.Dutch
    Feb 16, 2023 at 11:01
  • $\begingroup$ Also axial tilt is not enough in case of elliptical orbit to provide any simulation. You also need to set tilt vs ecliptics angle, whether the revolution axis is tilted alongside semimajor axis of the planet's orbit or not. With them aligned, the distant pole at the planet's aphelion would be liquefying atmosphere cold, and at perihelion it will be scorching hot. $\endgroup$
    – Vesper
    Feb 16, 2023 at 12:21
  • $\begingroup$ @Vesper, I linked my previous question where this planet is described in great detail. $\endgroup$ Feb 16, 2023 at 12:52
  • $\begingroup$ @L.Dutch, do you mean mountain glaciers? $\endgroup$ Feb 16, 2023 at 12:53
  • $\begingroup$ Aha read the data. I think this asks for a simulation, also given there are no large landmasses the climate zones should be belts of latitude. And you really depict the scenario of southerm hemisphere having huge problems. Not sure if the ocean would be deep enough to not freeze to the bottom in the south during long winter, this could go awry if it would freeze all the way down. $\endgroup$
    – Vesper
    Feb 16, 2023 at 12:59

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Mostly polar

The "very elliptic orbit" does really matter here. With your orbit parameters, your planet would spend a lot of time in a zone where insolation is smaller than required to keep the planet's average temperature above zero Celsius. So even if it's fully covered with water, it would just freeze over. Yet, when it'll be polar summer in the south, when the sun is constantly above the south pole and the planet is at 0.7AU from it, the insolation would produce a lot of water vapor, melting oceans at the south-polar area and causing major harsh winds over the equator into the polar night of the northern hemisphere. I'm not sure whether the depths of the ocean would remain frozen, after all the south pole won't receive any light for the majority of time so the ocean there is almost certain to freeze down to the bottom over the long sunless southern winter, and there won't be much energy transfer from the northern hemisphere in this period as the insolation would barely heat the north pole to about -20 Celsius. Since there will be major temperature difference between winter and summer, I doubt that there would be highly organized life (aka plants) in the far southern lands, rather something short-lived and able to hibernate would live in there, like moss. Thus a very harsh polar climate zone would be in the far south.

The interesting things should happen at the 0-45S latitudes, as there will be "winter" with high strong sun but low daytime and another winter with low weak sun when the planet is distant, but two "summers" with the sun in zenith while insolation is above average. I'd call this climate zone "subpolar" as it will be fully covered with snow in winter, but a rapid spring lasting some hundred days would allow liquid water on the surface, enough insolation would let plants bloom, the excess humidity from the far south would cause heavy rains allowing fertility of the soil, yet past the second summer everything should cover up as the long incoming winter would freeze things up.

The 0-45N latitudes would look grim, because the local summer would not bring in enough sunlight to make things warm, heavy snow coming in while the planet is heated the most would cover whatever would get thawed, if any, and the hottest period there would be spring, still I doubt there would be enough heat to uncover the ground. So, frozen over.

The 45-90N or far north would be even more grim, because the only time the lands there would see the sunlight is when the planet is too far from the sun to ever heat it above zero, and the polar day in the far north would be as freezing as one on Mars, and since the planet's albedo would be very high due to complete snow coverage, even those little bits of energy would be reflected into space. Again, frozen over and look like Antarctic on steroids. Not too cold to liquify the atmosphere, but pretty close, at least CO2 will start snowing at a constant rate.

What should you try with this planet to fix climate

First, lower eccentricity (and amplify the sun's power if you desire a really long year - the sun's mass determines not just its power but also the year's length) so that the insolation difference won't be as dramatic (a factor of 8 is waaay too much). Perhaps down to 0.1 or 0.15, so the difference would be about 2 times, that would make winters more bearable in either part of the planet. Next, if your orbital parameters would still make it too cold - add CO2 and amp ground level pressure, it doesn't look like atmospheric pressure has a strong dependence on planet's gravity, so your atmospheric pressure could be a lot higher than on Earth. This will introduce a greenhouse effect, with enough potential to allow better than subpolar weather (at least temperate) in at least one band on the planet, and allow plant proliferation to greater extent, together with soil fertility, microbiome activity and overall temperature under the snow during winter. This could in turn allow sentient life to appear, settling underground to be kept warm in cold seasons and eventually evolve. Allow travelling over the ocean while it's frozen over, if there would be global freezing, again check average temperature. Add a moon for tidal heating of the ocean depths, although constant tides would probably wash over your puny islands destroying life on them... Consider it anyway. Add tectonic activity, as any revolving planet with so much flat surface would have VERY high winds, I can't check if the winds would just be too strong to handle, limiting plant life to surface clinging forms and whatever animal life to crawling. Maybe there's more, but currently your planet is too harsh, although some positive temperatures do touch its surface allowing some life to be present.

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  • $\begingroup$ Thank you for the suggestions! The result I want to get is this planet having a 1020 days long year, half of it reasonably warm and wet summer in the northern hemisphere, which together with long spring and autumn makes a long and bountiful agricultural season with several harvests, while the southern hemisphere has half-year long very cold winter; on the opposite end is short and snowy winter with temperatures not higher than those of winters in Earth's temperate climate zones, but polar glaciers extending much farther, and short but extremely hot summer in the southern hemisphere. $\endgroup$ Feb 17, 2023 at 7:45
  • $\begingroup$ I'm going to add in my description about tectonic activity, islands and mountains. $\endgroup$ Feb 17, 2023 at 7:50
  • $\begingroup$ You should probably ask for required star size/distance over at astronomy SE, because an orbit of 1018 days around a sun-like star would place your planet beyond Mars' orbit, thus no goldilocks zone. And increasing insolation would also increase star size and mass, altering everything else. You would need star system parameters that would have your planet be in the star's habitable zone and have required orbit parameters. $\endgroup$
    – Vesper
    Feb 17, 2023 at 8:29
  • $\begingroup$ I can't accept the bit about ocean depths staying frozen when the top layers melt. As known from physics, ice is less dense than liquid water; thus, it floats. If ice is melting under the sun, it will lift up and get more water under it. $\endgroup$ Feb 17, 2023 at 8:33
  • $\begingroup$ Mars is in the Goldilocks zone. The problem is the lack of an atmosphere that would keep it warm and wet. The current theory is that Mars had it not so long ago, and it was habitable like Earth. This fictional planet also is within the Goldilocks zone; only its orbit takes it from one edge to another. $\endgroup$ Feb 17, 2023 at 8:40

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