A World of Lakes

So, here's an idea I have.

It's a planet without any oceans or seas. Instead, numerous lakes dot the surface of the planet. They are around the size of the Great Lakes in North America.

I imagine civilization being confined to the coast of the lakes until they achieve some manner of flight.

What affects would this have on the world, mainly concerning life and climate? Is such a world really habitable?

They can't walk around the lakes?

My first question is "how are these lakes being maintained?" If the feed-in from rivers or glacial run-off or whatever is too low they should evaporate away; too high and they stop being lakes and start being seas/oceans. They'd also be pretty darn salty since there's no way for any of the salt to leave.

Well, in many ways, we already have an example of this—the satellite Titan (methane instead of water, but the OP didn't specify).

Oceans are really just giant salt lakes ya know.

All it would really take is to have a greater percentage of land mass such that you don't have a load of interconnected oceans. A sea is often either a local ocean or a salty lake.

So if you have Earth but with reversed land and water, you'd already have what you want.

It would have very distinct effects on climate, since so much of the Earth's climate is affected by ocean currents. I'm not sure how—I think there would be less temperature exchange across the globe, so less extreme weather and reduced seasonal change?

More land = more extremes in climate. Water is the best thermal transfer/retention/resistance agent in the Universe. It moderates the entire planet a hell of a lot.

To put it in perspective, in the last supercontinent cycle of Pangaea the climate was a greenhouse Earth and a great amount of inland Pangaea was simply desert. Hot desert at that, ice caps on Earth didn't exist 200 million years ago.

If we inverted the land to water ratio on Earth, depending on orbit and a couple of other things the planet's landmasses would be mostly desert and depending on those other things they'd be either cold Antarctic style deserts built of ice sheets or hot Sahara type.

It's also possible with that setup the planet would experience a feedback effect to become either an entirely hot desert world or a snowball. (Both extremes of Single-Biome Planet have occurred on Earth.)

Edited by MajorTom on Jun 7th 2020 at 8:08:11 AM

I'm assuming that the "Lake Planet" is stable in that state, since the OP implies that. I presume that such a stable state is possible, that is, there exists some combination of an amount of total water on the planet and temperature that a series of large lakes would not evaporate. Given that presumption, we can conclude a few things.

Based on what I've been able to find (there isn't much online) and it appears that a mostly land Earth would experience greater temperature extremes pole to pole—much colder at the poles, much hotter at the equator. This would presumably lead to a larger number and greater severity of wind storms, esp. around the lakes. A series of "great lakes" sized lakes all around the planet would probably be enough to maintain the water cycle—so lots of rain with the storms. Plenty of cloud cover, though not constant overcast.

Lots of energy plus lots of shallow water (basically inland seas) and you have the conditions under which life evolved, so should be habitable. There might be less overall diversity since the ocean on Earth contains most of the biomass and species, but enough to maintain a viable ecosystem. If this had happened here on Earth, temperate grasslands would probably dominate.

Again, I would like to point out that if you switch "methane" for "water", we're basically describing Titan, except for the ecosystem (so far as we know). That's why so many people are interested in that place—it's surprisingly Earthlike, and one of the best candidates for extraterrestrial life.

What percentage of the planet is covered in water?

If we inverse earth, it would probably be 30%.

In terms of more temperature extremes, the oceans ensure a steady flow of heat from the equator to the poles. So in absence of connected oceans, the poles would indeed be much colder and the equator much hotter.

You would end up with two temperate bands, one in each hemisphere. Depending on how hot the equator gets, that could isolate them from each other, leading to two separate isolated evolutionary biomes. That leads to some interesting speculative implications for life on that planet. I could see two intelligent species evolving there.

Edited by DeMarquis on Jun 8th 2020 at 11:10:03 AM

In terms of wildlife I could see semi-aquatic animals being much more prominent and if the lakes are connected by rivers than boating could be the primary mode of travel.

To me, this looks like a planet that started off with much less water than Earth, say because it had a weaker gravity field. So much less that plate tectonics failed to get off the ground, leading to a stagnant lid regimen where there are no trenches, no mid-ocean ridges, no ocean basins and no continents. Only Hawaii-type volcanoes and mountains/valleys formed by the crust cracking up when pressured from below by ascending mantle plumes. Water would pool in such valleys, forming separate lakes, instead of accumulating in a World Ocean.

Actually, I think a planet without oceans would be much warmer than Earth. Lack/scarcity of water means a weak water cycle means a weak carbonate-silicate cycle means high concentrations of atmospheric greenhouse gases. But this is all not a given. Note that lakes could sustain a hydrological cycle even if they don't form a World Ocean.

Regarding climate, I suspect that the climate of such a system will primarily depend on the insolation, chemical composition (which governs the atmospheric greenhouse gases via the carbonate-silicate cycle) and rotation rate (a slowly spinning planet will have a powerful Hadley cell that reaches the poles and balances temperatures planet-wide) and not so much on the size and presence of oceans.

Finally, going by this publication on Earth the bulk of poleward heat transport actually occurs in the atmosphere. So a planet without an ocean won't have a much steeper pole-equator temperature gradient than Earth.

I thought of a scenario that actually makes this work. A psuedo-Snowball Planet. Most of the planet's "oceans" are iced over alongside a large portion of the land. What land isn't ice caps or ice sheets or glaciers would be ice-fed rivers and lakes with only very small "salt lakes" (actually the ocean) at the terminus of some hydrological systems.

Such a planetary setup has one major caveat. Owing to feedback effect of albedo from all that ice, such a planet would be either collapsing into a Snowball Planet meaning the ice-free regions are but a momentary form of refugia. Or alternatively, it is just emerging from a Snowball Planet scenario through increased volcanism or other mechanisms that cause a warming of the planet. In the latter scenario, any residents that are there are going to have to think of a language term for ultra large lakes aka "ocean" in the very long term.

Perhaps in the latter scenario the inhabitants are actually space colonists who are transplants regressed to a Neolithic lifestyle, that the forests, grasslands, swamps, marshes and life otherwise there are terraforming efforts? Maybe a major plot twist is some of the characters come across the remains of the ship that brought their people there?

Your "snowball planet that doesn't get any worse" could be the result of a highly irregular orbit around the star.