What if the Earth had a giant equatorial ocean?

September 12, 2018 12:37 PM

Just as a thought experiment, what would the Earth be like if all the land was in the northern and southern poles, and the equator was a giant, uninterrupted ocean?

Would the central ocean be a zone of never-ending winds and storms without land to stop the winds and currents? What would the climates of northern and southern continents be like?

posted by fimbulvetr to Science & Nature (8 answers total)

A pretty good place to ask this would be the Worldbuilding StackExchange, or perhaps the Earth Science one (but I don't know their policy on speculative questions).
posted by InTheYear2017 at 1:05 PM on September 12, 2018 [2 favorites]

There would be a westward flowing current. I doubt if winds in the tropical zone would be much different than they are in the Pacific.

A lot depends on at what latitude the land starts. You are still going to have a seasonal cycle (assuming the same axial tilt, etc.) so you would probably get a large monsoon effect (very rainy in the warm season) like you do in India. This is from the rising air centered at the hot spot, which should be on the land during the summer (land being much more variable in temperature than ocean). Assuming the land doesn't start too far poleward.

If it is just solid land all the way around in the upper latitudes, you'd get a much drier (and more extreme in temperature) climate as there wouldn't be big sources of water (except during the monsoon season). I guess this could change somewhat if there are big mountain ranges that introduce turbulence to the global circulation.

You might have a lot less polar ice.
posted by tracer at 1:12 PM on September 12, 2018

Well, the Antarctic Circumpolar Current is held to keep that continent colder than it would be if land closed off the Southern Ocean, and this isolation seems to be a big part of what triggered major ice build-up there.

I'm guessing unrestricted ocean on such a scale would mean massive latitudinal currents, and much less of the longitudinal redistribution of ocean heat that happens with our current continent configuration.

So perhaps much stronger heat gradients between the equator and the poles... though this would create much more turbulent atmospheric conditions... how that would play out climate wise I don't know enough to speculate on. And perhaps seasonal changes in ocean temperature across such a large water mass would create bi-annual "tides" of north-south warm water movement.

Interesting question!
posted by protorp at 1:28 PM on September 12, 2018 [3 favorites]

On average, the planet would be warmer, since you would have more dark ocean at low latitudes to soak up the sun. To understand local climate, you would need to run a model. It's been a long time since I played with it, but there are educational climate models you can run at home:
posted by Maxwell's demon at 2:35 PM on September 12, 2018 [1 favorite]

IAMNAC but would suggest assuming the same general proportion of land mass to ocean not too much difference. The pacific's huge already and less happens at the mid latitudes than elsewhere. The weather is air movement from just north of the equator to the arctic. The sargasso sea might be slightly more migratory but slowly, the currents again move south to north (or north to south on the other side:-)
posted by sammyo at 5:36 PM on September 12, 2018

Response by poster: What about hurricanes in this scenario? Warmer water, less north-south movement of currents, strong circumequitorial winds, and no land to stop them... I was thinking such a planet might end up with strong and long lasting storms.
posted by fimbulvetr at 3:41 AM on September 13, 2018

That would be a neat question to submit to Randall Munroe's What if?

It has been a while since he posted a new one, but this might pique his interest.
posted by brianogilvie at 7:56 AM on September 13, 2018

sammyo's point is good: we're nearly there already. The Pacific is nearly half the planet wide.

Air in the Hadley cells (which go from the equator to 30° N/S) moves diagonally, poleward + westward. So it's not really that the wind wants to zoom straight west and is impeded by the continents.

What you'd get more of is monsoons. These form when the equator is ocean and there's a continent within about 30°-- India and SE Asia are perfect. So if you replaced equatorial Africa with a nice wide ocean zone (warning: do not do this), you'd get monsoons on the newly created coasts.
posted by zompist at 6:25 PM on September 13, 2018