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I think of a world of islands floating in the sky. The planet basically is (was) our Earth. For some reason all that is left is a small ball covered nearly completely with water. Pieces of the shattered continents are floating in the sky, maybe at a level of 4,000 m height. The rest of the Earth system still works as usual, e.g. the radius of the core shrunk only insignificantly, the rotation is the same, the moon is still there etc. Assume that the ocean is mostly the same depth everywhere, insignificantly small islands like current hotspot volcano islands exist.

The "islands" don't have the size of the old continents, they are a lot smaller but diverse in size.

How would the wind system of the world change in this scenario?

Wind system (Source: Wikimedia commons

Would there be special stack effects? Or would I get just a "boring" system of circular winds without much of seasonal and geographical changes?

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  • $\begingroup$ If your islands are floating only through their kinetic energy, they are either out of the atmosphere or falling down. Is there a magic force maintaining them up there? $\endgroup$ – PatJ Oct 18 '16 at 9:44
  • $\begingroup$ @PatJ Yes, assume magic on this part (it will be some unobtanium later). The islands will have a reasonable thickness to settle on them, some dozens to hundreds of meters. $\endgroup$ – his Oct 18 '16 at 10:00
  • $\begingroup$ Are they evenly distributed around Earth? Over the poles? Over the oceans? $\endgroup$ – PatJ Oct 18 '16 at 11:51
  • $\begingroup$ @PatJ They are not evenly distributed, they are distributed roughly above the positions of the old continents, but smaller; fixed at a location (through magic/unabtanium). So not "free floating" but "hovering". "Over the oceans?" No/Yes ;-). There is just one huge ocean left. $\endgroup$ – his Oct 18 '16 at 21:04
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I disagree with Kingledion's answer. Yes, the general atmosphere would work like he wrote, however I believe the floating islands will interfere with the development of high and low pressure systems which form the backbone of the hadley/ferrel cell circulation.

The floating islands, while not continent sized, will create shadows on the surface of the planet. This will create areas of cooling. The surface of the floating islands will warm up due to reflection of sunlight and the heat transpired by any plants and animals. This will affectively bring extra warmth to the middle - upper regions of the atmosphere (depending on how high they are floating).

On the surface this will create areas of low pressure in the island shadows, and areas of higher pressure in areas with direct sunlight warming the surface. On the floating island surface, there is also isolated areas of higher pressure and areas of cooler pressure in the open air.


So now you have three dimensions to take into account; (1) the 'horizontal' surface to surface dimension, (2) the 'vertical' atmosphere to surface dimension and (3) the 'horizontal' atmosphere to atmosphere dimension.

The surface generally warms more at the equator than at the poles. So localised shadow affects will change the way that the wind and atmosphere moves. If there are more islands concentrated in a certain latitude band at specific times (as suggested by Kingledion), this will result in more shadows on the ground, resulting in a cooler than expected ground temperature.

(1) This will result in surface low pressure systems in areas that would normally be experiencing high pressure systems. eg if a low pressure system forms around the equator because of the islands, air will end up flowing from the midlatitudes towards the equator, instead of away from the equator as it does now on Earth. So wherever you have a concentration of floating islands, the surface winds will change in accordance - wind blowing from the sunlight warm areas to the cooler shadow areas.

(2a) This will create a strong pressure differential between the cooler surface than the warmer floating island tops. Wind moves from areas of high pressure to low. So you will have stronger downward winds wherever there are large concentrations of islands. (note, even though 'heat rises', air temperature does cool with altitude. About 1 degree celsius for every 100m. I doubt you will get equator surface temperatures on your equator floating islands, but the temperature will be warmer than expected at that altitude in comparison to Earth).

(2b) Winds pulling cold mid to upper atmosphere air down to the surface is what normally happens at the poles. It is one of the reasons why it is so cold there. But if you have floating islands at the poles, they may break the airflow, as well as bring slightly warmer air (from transpiration and albedo reflection etc) to the mid to upper reaches of the polar region. This could result in slightly warmer sinking polar winds (only slightly, as the poles are still terribly cold due to lack of sunlight for 6 months of the year). This might actually result in more snow fall, as for snow to fall temperatures need to drop to below freezing and then rise again. So you can expect more winter snow storms in your polar regions. But also a slightly warmer summer, so you still have to worry about global warming as a whole.

(3a) Winds will also blow from the islands warmer center towards the outer ridges of the islands into empty space. So winds will be blowing off the islands and then be pulled down (might want to erect some fences along the edges for any toddlers).

(3b) Warm air doesn't mix well with cold air. It generally creates very big storms. Think hurricanes. A steady source of warm air in the typically cooler mid to upper atmosphere will feed upper atmosphere storm systems. Resulting in more rain falling to the surface or at least around the edges of the floating islands.


So you can see, if you have large 'concentrations' of floating islands, this can mess with the local atmospheric pressures. If this happens, I believe you will still have the Hadley/ferrel circulation cell system, but it will be weaker. Less warmth rising from the equator surface and slightly less cold sinking at the poles. This will impact the strength of the overall resultant atmospheric winds systems, the general atmospheric winds like the jet streams etc will be weaker, and prone to disruptions from the ever changing nature of the floating islands below them.

But never fear, if a large concentration of islands does develop, a once in a 100 or once in a 1000 year storm will come along and break them apart scattering them in all directions. And you can start all over again.

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  • $\begingroup$ If the islands are floating low, then they concentrate at the equator and the heat energy striking them (at 4000m, not higher than mountains on earth) is distributed to the lower part of the Hadley cell. If the islands float in the higher part of the Hadley cell, they concentrate at 30N/S and their shadow reinforces the already existing low pressure zone. Either way, the effects you describe (which I argue are not significant in the first place) reinforce the system I describe. $\endgroup$ – kingledion Oct 19 '16 at 1:48
  • $\begingroup$ @kingledion, the 4000m height is why I kept referring to the middle atmosphere. If the concentrated islands are 'floating' low at the equator, any surface heat that is rising will be trapped between the surface and the bottom of the islands. Then, at say, 2000-3000m, the top of the islands average temperature would be diminished by the altitude affects. So any heat rising, won't be reinforcing an Earth like Hadley cell, but rather starting from a lower temp, with less time to heat up before cooling it would be weaker area of rising air. $\endgroup$ – EveryBitHelps Oct 19 '16 at 6:35
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If your floating islands have some sort of magically assisted buoyancy, then they will pushed by prevailing winds into certain locations on earth. This depends on how high they are; in the upper or lower region of the Hadley cell.

The rising air masses from the equator will blow any high floating islands that started within ~3° of the equator outwards and concentrate them at 30° N or S. Low floating islands, on the other hand, will be concentrated at the equator. Outside the tropics, high floating islands will end up at ±30° and the poles, while low floating islands will end up at ±60°.

The oceanic surface being so large in comparison to the size of the islands will give the entire planet an oceanic climate. Seasonal and daily temperature variations will be low everywhere. Without any continents to disrupt weather patterns, a perfect ideal Hadley and Polar cell will develop. There will not be significant variations as seen on earth, like the Gulf air masses that make the Eastern US relatively wet, the cold currents that turn Baja California into a desert, or the monsoon rains of India.

The location that your islands end up will affect their weather. The islands will move as the seasonal progression pushes the high/low pressure zones north and south. Equatorial low islands would wander from the equator around 10 degrees north and south, into the hemisphere that is having summer. In any case, the islands will stay in the equatorial zone, giving them the perfect rainforest climate.

At ±30° the islands will be in a perfect warm desert, as the islands will drift away from the advancing sun in the summer, and towards the retreating sun in the winter. They would never get too hot or too cold, but would always be dry, like summer in California or Sicily.

A ±60°, the island would be stuck in permanent winter. 60 degrees off of the sun is New York in January or February…so not great for habitation. Again, these islands will drift north (or south) away from the advancing seasonal sun, so they won't really have a summer. I don't see much life here.

The Polar islands would basically be Antarctica.

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It depends just how much of the sky those islands cover, that's going to effect how much heat the ocean gets and thus whether the traditional wind model will apply. Also important is where the islands are, well mainly how much of the equator they cover since that's where most insolation occurs. Ultimately thermal input is the real driver behind the world's oceanic and atmospheric circulation.

There are going to be two other effects that you need to consider when looking at life on that world, one is that with no relief (in the topographic sense) to break the rush wind is going to travel uninterrupted around the world, Easter Island will give some clues to just how strong those winds are going to get. The second thing is that the world ocean is going to be pretty well dead due to lack of oxygen, there's nothing to drive currents on a basically flat ball of rock.

Life up on those islands is not going to be fun, half the sea level air pressure we're used to having is going to make it really hard to survive, human start to get altitude sickness from 1500m onwards and with the continents gone it'll be even worse.

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