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Having found a setting for my story, I am thinking of a country which encompasses a giant New Zealand, basically a partially surfaced Zealandia, and having studied a little science, I have noticed that sea levels and polar, and non-polar ice sheets are often intertwined.

When you think of it, ice actually is solid water, frozen away from the ocean, when it melts, it turns into water and rejoins the ocean, but is unlikely to evaporate since the climate has yet never reached beyond 30° beyond the Arctic and Antarctic circles.

If ice accumulates at the poles, then that means water turns into ice and is not water anymore, so sea levels get lower, if the ice melts, it turns into water, now there's more water than before, sea levels are now higher.

Now to the plan, I am thinking of throwing a satellite in space to shield the southern hemisphere, shielding everything at least 1 kilometer below New Guinea, so that the ice sheet in Antarctica get bigger and expand further.

My ideal would be to resurface parts of Zealandia and other parts of the South hemisphere still underwater, at least 1,500 meters of water turned into ice, that means a sea level 1,500 meters lower than now. The Earth is also not a perfect sphere, and sea levels are influenced principally by natural forces, such as continents moving, currents and temperatures.

My hypothetical and desired results would be that the Australian subtropical ridge gets pushed away over higher latitudes, the Australian ridge being the reason most of Australia gets so dry since it passes over in the middle, so Australia becomes more fertile.

The increase of the Antarctic ice sheets would lower sea levels, thus increasing the amount of land in the south hemisphere, that would resurface huge parts of Oceania, southern Africa as a whole and the southern cone.

My last desired effect would be a much cooler south hemisphere, Australia and southern Africa become more oceanic and Zealandia and Patagonia become either more continental or subpolar, although a form of agriculture would be worked on in my scenario.

I still don't know a lot about this kind of thing, so I couldn't provide all the infos, but I think I explained what was necessary. Lastly, this question ignores the effects on the Northern hemisphere, and the supposed or real climate change has been reversed.

My question is: How would the change (The south hemisphere 5 degrees colder), if successful, influence the climate, landscape and geography of the whole entire South hemisphere, more particularly the temperate regions?

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    $\begingroup$ "The increase of the Antarctic ice sheets would lower sea levels": thus cutting off Russia and China from the ocean. Russia preëmptively shoots down the satellite and shoots dead the daft promoters of the idea. The sea level does not change. (And lowering the sea level by 1500 meters would have dramatic effects on the climate worldwide. Lots of big deserts, for example.) $\endgroup$
    – AlexP
    May 18, 2023 at 17:38
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    $\begingroup$ @AlexP How would Russia and China be cut off from the ocean? Their territory is expanding and leaving their ports barren, that is a given. But they would rebuild the ports on the shore. 1500 meters is only 1.5 kilometers. A lot of cites are larger than 30 kilometers in diameter. Russia may have a problem for a few years because a large number of her ports are in the Black Sea. But they also have some up north on the Baltic Sea. $\endgroup$
    – Martamo
    May 18, 2023 at 17:55
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    $\begingroup$ @Martamo: Look at a map. In the case of Russia, ignore their Pacific coast; they have almost no infrastructure there, 99% of it is only accessible by air, and there is literally no permanent road linking Moscow and the Pacific coast. (There are two railways.) But all the Baltic will be dry land, cutting off St. Petersburg, and the Bosphorus is only 35 meters deep, cutting off the Black Sea. In the case of China, the only possible access to the ocean would be through the now dry East China Sea; too bad that the Ryukyu Islands which form the eastern boundary of the sea belong to Japan... $\endgroup$
    – AlexP
    May 18, 2023 at 18:10
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    $\begingroup$ @AlexP I did look a map. I just didn’t realize how much 1500 meters of water is. $\endgroup$
    – Martamo
    May 18, 2023 at 18:20
  • $\begingroup$ Is there a particular reason you need this satellite and such radically lower sea levels? Wouldn't it work to just bamf the continent into place? If you followed your plan, I'm pretty sure the climate of the entire planet would be considerably altered. $\endgroup$
    – elemtilas
    May 18, 2023 at 18:55

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Average ocean depth is 3688m. If you managed to freeze nearly half of Earth's ocean it would affect entire world in a million complex unpredictable ways. The global warming everyone so concerned about now raised Earth's average temperature by ~1 degree Celsius over 140 years, your project would top that multiple times over.

Forget the South hemisphere, think about the North one. Complete collapse of agriculture and transport, famine, energy problems. Nuclear winter is the only somewhat similar scenario and there is no really good estimates for it. Still, here is one of them (https://en.wikipedia.org/wiki/Nuclear_winter):

According to a peer-reviewed study published in the journal Nature Food in August 2022, a full-scale nuclear war between the United States and Russia ... would kill 360 million people directly and more than 5 billion indirectly by starvation during a nuclear winter.

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Thank you for this interesting thought

From what I understand… You are more interested in the effects of climate change in the southern hemisphere than the effects of increasing the number of glaciers in the world.

Before I start, I would like to make a few deductions that may or may not be true. You live in the southern hemisphere. You wrote this during the summer months. It was a hot day when writing this. You spend a lot of time in thought. You see yourself as a kind, well mannered individual. You have few friends, but close friends! You are young or an adult that does not feel fulfilled mentally with the external world. You are often misunderstood.

If their are any truths to what I have said than please reason on for details about climate change in the southern hemisphere.

Unfortunately after initial research there is not much conclusive data to go off of.

That being said I enjoy thinking so let’s break it down using the opposite scenario.

Sea temperatures around the world are drastically rising. Just in the last century they have increased more than in the last 11000 years! It is safe to eat from basic googling that this is wreaking havoc on the local flora and fauna because they cannot adapt fast enough.

All of this being said the ocean seems to be much more sensitive than the land. Mammals lose body heat 25 times faster in water so the numbers add up to why little changes can have big effects if there is no significant adaptation period.

Going back to land now… I believe a 5 degree drop in the southern hemisphere would create very lucrative new markets in the world of “fashion”. 5 degrees for the mammals may change migration habits or delay/increase speed of season changes.

The most exciting thought/question is if 5 degrees would create a new season in the southern hemisphere and how would that season effect EVERYTHING!? Sorry to answer your question with a question lol :)

Cold blooded reptiles will feel this change the most and iguanas may start falling from trees in the winter. They usually don’t die unless they hit a hard surface. Insects are resilient and highly adaptable. Organisms I do not know enough about :)

Thank you again for your thought. I only hope that I touched on what your main interest is and apologize if I went in the completely wrong direction. If that is the case, remember I am only human ;) -justhochie

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