What would the climate on a planet with 85% or more of the surface area covered in water be like?

Question

Around 85% of my world is covered in water. I know that water tends to make temperatures more stable and reduce the extremes, but I don't know the details which is why I'm here.

Would such a planet have more or less storms/hurricanes? Would they be more or less powerful?

How would the monsoons be affected?

It would probably rain more than here on earth right? Would it rain so much that crops would have trouble surviving?

How would the climate change in the individual climate zones (tropical, sub-tropical, temperate, arctic)?.

Some additional information:

• It's a fantasy world. Thus, should you wish to do so, I don't mind if you ignore stuff like the sea currents or mountain ranges. It doesn't need to be perfect, just good enough to fool me into thinking so.

• The landmasses, while different shaped, are placed in a manner somewhat similar to earth, though my equivalents for Greenland, Antarctica and Australia are missing and there are small gaps between the N.A / S.A and between Asia / Africa.

• The planet has a moon just like ours.

Answer 1

We already live on an ocean planet; minimal change

Earth is already 71% ocean on the surface. The Southern hemisphere is 80% water. The Western hemisphere (i.e. the Americas) is 83 % water.

All in all, your world is not much different from the Southern or Western hemisphere. Anything you see on Earth, you could see on your planet. You aren't likely to see weather and climate conditions that you don't see on Earth.

Incidentally, to answer your questions bullet by bullet:

• Hurricanes are less powerful in the Western Hemisphere and almost non-existent in the Southern.
• The Southern hemisphere's monsoon (Northern Australia) is weaker than the Asian, the Western Hemisphere's monsoon (Arizona to Mexico) is much weaker and incomplete.
• The Western Hemisphere (especially South America) is much wetter than Eurasia, but the Southern Hemisphere isn't, since Africa and Australia are pretty dry.

Answer 2

Climates are incredibly complex things to work out in even rough detail. You quite simply could not develop a model climate for a world with such a vague sketch as this.

First of all the amount of land isn't telling us anything much. The shape and distribution of the land is what matters most.

The shape (of land and hence oceans) defines, when combined with other factors, the trade winds, main ocean currents and the basic circulatory system that defines the climate.

In addition the distribution and locations of e.g. mountain ranges makes a significant difference.

The complexity of these interactions is such that we have only recently become able to model Earth's climate accurately, and we have as much data as we want about the layout of Earth.

You are, in effect, talking about removing half the Earth's land surface. But what half ? For example, if I removed the strip of land between North and South America so that the Pacific and Atlantic oceans were now open to each other, this would radically alter the ocean currents and with it the wind and the conditions (temperature, salinity, you name it) of every Northern land mass, expect perhaps (and only perhaps) the Arctic.

What if India vanished ? What if Japan did ? What if Alaska vanished leaving a large sea where the Bearing Strait was ? These would all have huge implications.

If you're looking at this for a fictional setting then I would advice first developing a map of land masses and significant coastal and mountainous features. Then find a friendly climatologist and try and enlist their help.

If you want to have a go yourself then first learn the basics of Earth's Global Circulation system ( the Thermohaline circulation ) and the Trade Winds.

Answer 3

Look at the Late Cretaceous..

Sea levels were perhaps 200m higher in the late Cretaceous, from a combination of no ice caps and thermal expansion. This gave us huge, shallow epicontinental seas in the central US and Europe. 82% of the planet was ocean.

The combination of warmer water and bigger oceans almost certainly meant more powerful hurricanes, and bigger waves due to the larger 'fetch' distances. It also meant that the habitats were often different - fewer coastal plains.

That's the reality, what about the fantasy?

Well, with that little land, ocean circulation will easily reach the poles, so the world thermal gradient will probably be lower - warmer poles, no ice caps, and significant forests/ecosystems all the way to the poles. Storms will be much worse when they hit land, having had more time to build up on the oceans. Plains will be rare - most land will be hills or mountains.

Deserts would be more restricted (although they are a feature of circulation as much as isolation from the sea). They would still exist in the same latitudes as on Earth (think the Sahara), but you would not get rain shadow deserts like the Gobi to the same extent, because you'd never be that far from the sea.

Another impact of smaller equator-pole temperature gradients is something we see with global warming - the weather getting 'stuck' in patterns, of either drought or extreme rainfall. This could be another feature of your world. It would make agriculture harder, obviously. I suspect they'd do a lot of fishing in your world - those shallow epicontinental seas would be very productive.

Answer 4

A Banded Planet

    In addition to what StephenG and kingledion said, you don't mention a moon, which is very important to the movement of our oceans and interaction with land. Frozen poles? Jury is out on that with either no ice or significantly more. Scholarly articles get tough to decipher but a friendly person on reddit has helped (link) and included links to studies. The jet stream bands may largely cut off heat transfer north and south resulting in larger ice poles. Other models say smoother deep water exchange would shrink the polar ice or eliminate it though it may be perpetually snowing.
  What aquaplanet modeling studies have in common is that the jet streams would be straighter without mountains in the way. This would follow for all winds and pretty much weather as well in that it would all be based on latitude. On our earth, warm ocean currents keep Europe warm while similar latitude Canada is colder. Not on your planet. So pictures of Jupiter might very well show a pattern you're more likely to see.
  Ocean currents might follow suit but they are a bit crazier, also dependent on ocean floor topology, here is a link to NASA animation of our currents, look right toward the end where it's just the Pacific looking like your aquaworld, overall get some bands but lots of gyres and swirls.
  Rainfall may depend on ocean depth and uniformity and which model you go with (polar ice or not). Overall my hunch is that it would be similar or less but once again intensity would be relegated to certain latitudes.

Answer 5

Nothing significant would happen is those are the only changes. the crops would most likely to survive.