What if the oceans were lakes?

What would the world be like if the oceans were not connected, i.e. assuming surface areas (land:water ratio) remain the same but the configuration is such that all land is connected and all water is held in ‘inland lakes’? Either a smallish number of huge lakes, a huge number of smaller lakes or, an extreme example, what if all land was a wide belt round the equator separating a north and south ocean?

Is there a reason this scenario couldn’t happen? What with the constant drifting of the continents could they join up, not in a super continent way, but in a way that cuts off the oceans from each other?

That’s pretty much what happened when Panama was formed. I am just guessing, but I expect the main impact would be on ocean currents, which would in turn have a major impact on climates. We would might see more evolutionary specialization among fish, cetaceans, etc., if they are trapped in separate oceans.

I don’t know whether there is a reason it couldn’t happen, other than that the cntinents currently take up so much less surface area than do the oceans now.

Once upon a time there existed Pangea (sp?), which was just one supercontinent. But AFAIK it was surrounded by water, not the other way around.

I’m wondering what the currents would look like at the poles. Maybe there wouldn’t be a current?

WAG[sup]2[/sup] In case of the belt of land around the equater I wonder if there would be any polar ice caps. It occurs to me that the water near the poles would be heavy and sink bringing warmer water directly to the poles from the warm latitudes.

You’d still have oceans. Lakes are freshwater bodies that empty into saltwater oceans. The salts come from the runoffs having no further place to go.

The land/water ration probably couldn’t stay constant. There’s more than twice as much water as land, so having gigantically huge bodies of water surrounded by thin strips of high ground would imply that somebody has been tinkering artificially with the system.

The consequences would depend greatly on the configuration. The belt of land scenario would be wildly different from the oceans surrounded by mountains scenario because of the reasons stated: ocean currents drive all weather and much of the current climate on the planet.

Now would any of these be stable, since tectonics would bust them open in the blink of an eye, geologically speaking.

Maybe if you picked one configuration people could make some wild stabs at guesses, but there’s no good answer for such a general question.

Ok, how about what’s nearly the case: Have the Arctic ocean closed off , have South America and Africa reach down to Antarctica and close off the Atlantic from the Pacific and Indian oceans, and finally turn Indonesia/ Australia/ New Zealand and Tasmania into a long isthmus that reaches to Antarctica as well, closing off the Indian ocean. In this case, you still have the gigantic Pacific ocean taking up almost a hemisphere of the Earth by itself, so that’s maybe not the best example from the OP premise. The most extreme changes would probably be related to the closing off of the Arctic and the blocking of the southern circumpolar current.

An interesting case would be if all the world’s land mass was broken up into fragments no bigger than say, Britain, separated by relatively small seas. You’d expect smaller extremes of temperature and I don’t know what else- more inland rainfall?

I’d imagine that you’d get the same sorts of convection-cell patterns that we currently get with the atmosphere. The net effect would be that you’d get bands of easterly and westerly currents circulating around the poles. This might get shut down, though, at the latitude where the average temperature is 4 Celsius (at which point water is at its maximum density).

How far back are we going?
If the oceans weren’t all connected when life first formed, it would have a difficult time spreading from the ocean in which it first started to other bodies of water. This could lead to wide differences in types of life in different oceans, much like Madagascar and Australia on land. One ocean might not even have fish, only decendants of former land dwellers.

They would be like lakes with no outlet except evaporations, such as Great Salt Lake, Mono Lake, the Aral Sea, etc. In fact, that’s what they are now.

They would still be oceans. It’s the size that mostly matters. Shrink them down and we may need to call them seas.

Probably the biggest effect would be that there would be no thermohaline circulation, AKA the ocean conveyor belt. The current plays a big role in regulating global climate by moving heat toward the polar regions. For speculation on what a shutdown of the thermohaline circulation would entail, see here.

Sorry for the rather loosely defined OP, allow me to try to explain a little more what i was thinking.

First off, regarding when, i was really thinking of a ‘what if the world had formed that way’ scenario, i.e. it was never in it’s current config.

Part of my question was about trying to understand why we have the current scenario - It’s almost like half a dozen or so huge islands ‘floating’ (figuratively speaking) about in one huge ocean. Why is that? I guess i don’t quite understand the formation process - did water vapour cool and gradually flood a dry surface? If so, is it just chance that the terrain allowed all the water to join up? Or is it more a case of once the water bodies have joined up (through the movement of plates) it’s more likely they’ll stay that way?

I guess i’m imagining a scenario where the tectonic plates are almost like bowls, so as they migrate they still keep huge lakes* (wholly within that plate) seperated from each other (or even lots of smaller lakes) and leaving a continuous land area around. Note - I don’t really think water:land area is an issue as such, the ratio that’s there would hardly require a fishnet look to achieve the scenario described, there could still be fairly large land masses.

Regardless of whether this is possible or not the other part of my question was how would things be different if this *had * happened. I’m thinking there would be quite a few things to consider, obviously there would be evolutionary impacts due to isolation of water species (and the opposite for land species), but what would these impacts be? And what else would be different? Ocean currents and the effect on climate is a good one to ponder.
*It’s not overly nitpicky i guess, but the terminolgy isn’t really the question here. Using the term lakes is the easiest way to convey the mental image, regardless of how incorrect that term may be.

ETA: **Lumpy ** - your scenario is kinda where i was thinking. Like it really wouldn’t take *that * much for them to be isolated from each other.

There are two big scenarios on how the earth got its water. One is that it was part of the original rocks and emerged as the earth warmed to molten state in the earliest days and precipitated back down. The other is that a deluge of big icy comets hit the earth and brought the water to it. Of course, there’s also the “little of both” scenario. In any case, the earth was covered in water very early on, well before any life emerged and pretty much as soon as the rocks cooled down enough so that it didn’t vaporize the water at a touch. There probably never was a dry surface of the earth for the water to cover.

The tectonic plates are better thought of as conveyor belts bumping into one another. Mountains form where one plate smashes into and pushes up another. However, the return side of the belt dives back into the crust and creates bowls. These are oceans. Even in the oceans volcanic activity constantly creates new land; either underwater mountain chains like at the center of the Atlantic or individual islands. (All extremely oversimplified, to be sure.)

There’s no real chance that enough land can emerge to wall off the oceans. I don’t believe that has ever happened in earth’s history. It takes a lot of pushing to get any land up over sea level. Erosion, subduction, and climate keep the land from growing. Even at the height of the ice ages, with sea level down hundreds of feet from today, not that much additional land was exposed. The edges of the continents pushed farther out but oceans are thousands of feet deep and a couple of hundred feet makes little difference. You could never under any realistic model have lots of lakes surrounded by large land masses instead of a world ocean with a little bit of land peeking out.

Over earth’s history, the exact composition of land has changed a zillion times, and even over the evolutionary history of land animals the changes have been significant. I don’t see any way to say what changes would happen without a detailed representation of hundreds of millions of years of alternate history.

I may be mistaken but I thought I’d read that billions of years ago the Earth’s crust was almost completely balsitic (ocean floor), and that geological processes have over time increased the amount of continental crust, which is lighter and “floats” on top of the denser ocean crust. Is this correct, and if so is it still going on?

What if there simply wasn’t as much water on a planet just like Earth in most other respects? That is, an Earth-like planet only with more land area than sea area.

Then everything would change.

The problem is you can’t say what that means unless you define everything rigorously. That means defining how the planet is shaped, where the land and water is, how the planetary plates are moving, how warm or cool the planet is, what the output of the sun is and how it’s varying and so forth.

You’re building an entire world and unless you have detailed specs you can’t describe the outcome at all. Not even loosely. It’s like saying, imagine taking your identical twin and placing him on an alternate world. What would he be like when he grew up? How could anybody know without a zillion details? The earth example is even less well defined than that.