Hypothetical A: Let’s say the Earth’s oceans contained only one-tenth its current quantity of water - a much shallower ocean. Would there be any meaningful impact on the rest of the planet’s ecosystem? Only difference that comes to mind is that there might not be as much of the deep-sea anglerfish type of species, and the Earth’s marine biology might overall be of a more photosynthetic nature. And as for global warming, the absorption of carbon dioxide by the ocean isn’t really affected by whether it’s 1,000 feet or 10,000 feet deep, right?
Hypothetical B: Now, let’s say the Earth’s oceans contained 10 times more than its current quantity of water - a much deeper ocean. Would there be any meaningful impact on the rest of the planet’s ecosystem? And would it possible for there to be a super-deep ocean trench of, say, 200,000 feet deep, dwarfing the current Mariana Trench, or is that not physically possible because of seismic or geothermal activity?
Oceanic conditions have major effects on atmospheric conditions and on land temperatures.
The oceans tend to form large-scale clockwise (in the northern hemisphere) flows called gyres. The Gulf Stream is a well-known example. This effects the on-shore weather patterns and ecosystems. You also have things like El Niño that happen, and so on.
These would be very different in an ocean with one tenth the water, or ten times as much water.
Also, major changes in the depth of the oceans would have a great effect on the temperatures of those oceans. If more sunlight managed to get into a greater % of the oceans’ waters (because of having much less water there), I would expect the oceans to be much warmer. There would be a lot more evaporation, which would obviously have a great effect on atmospheric weather fronts and precipitation patterns. If the oceans were deeper, I would expect the oceans to be much colder, with other effects.
IANAMeterologist. The above speculations are just pulled from my ass, but they seem to make some sense.
Al Gore gave an example in his movie An Inconvenient Truth.
He cited evidence of a glacier that once covered much of North America. On top of the glacier was a large lake of very cold water. One fine day, the glacier broke on the east coast, and a massive amount of cold glacier water spilled out into the Atlantic Ocean. This mass infusion of cold water into the warm Gulf Stream essentially shut down the North Atlantic Gyre. Within a few years, Europe fell into an ice age because of that.
If there were 10x more water, there wouldn’t be any land, based on the present distribution of continental crust. The average depth of the ocean is 3.5 km, while the average height of the continents is only 800 m. If there was 10x more water, the entire surface of the continents would be several km below the surface.
But perhaps you mean that the current continents would still be present, but the oceans would be 10x deeper than they are now. However, that wouldn’t be possible without completely changing the basic geology of the Earth. The continents are made out of lighter rock than the ocean floor, and basically “float” on the lithosphere. For them to float higher you would have to entirely change the composition of the continents or the lithosphere.
With 10 x less water, the ocean basins would only be partially full; each of the continents would be much larger, extending to the edge of the continental shelf and beyond. Down the centre of the major oceans, a new mountain chain would appear, and much of the Pacific would be empty; see this drawing from XKCD, a marvellous depiction of a low-water Earth.
With such large continents the interior spaces would be very dry, just as the continent of Pangaea was dry in the distant past; but there might still be some regions of relatively wet land to support life. Note that the albedo of this planet would be much higher than our planet, since land is more reflective than sea - but there would be fewer clouds due to the lower water content, an effect which would lower the albedo/ I think that overall the effect would be sufficient to cool the planet slightly- but then snow and ice would form on the extensive land surface, making the albedo higher still. Result - a cool dry planet, something like Percival Lowell’s imagined Victorian Mars.
With 10 x more water the continents would be submerged. Submerged continents exist on our world - only small ones, but they are there. Here is the Kerguelen Plateau in the Southern Ocean.
Plate tectonics would continue at the bottom of the ocean, so you’d get black smokers and underwater volcanoes - but the eruptions wouldn’t reach the surface except as chaotic regions of gaseous turbulence. Overhead, in the atmosphere, the weather would be much simpler than it is on Earth, forming regular Hadley Cells with no mountains or inland seas to disrupt the patterns.
I don’t think that complex life would emerge on a water planet, but you might get thermophiles round the black smokers and photosynthetic scum on the free-flowing ocean.
The OP is grossly underestimating - or ignoring - the immense role the oceans play in their interactions with the planet as a whole. Either scenario would render the planet unrecognizable, and not merely due to the amount of water.
This graphic, from USGS is stunning. The amount of water on earth (salt, fresh and available surface water). Shown in a way we can understand, relative to the overall size of the earth.
It does not directly address the OP’s question, but, I think is appropriate for this thread.
Good cite. I was going to post a link to that article. The whole article is Drain the Oceans and is worth reading for the incremental treatment of ocean levels with declining water supply.
If there was 10x less ocean water, sea level would be miles lower than it is now. Consequently either atmospheric pressure would be much higher at sea level or much lower in the middle of the continents. It might resemble C.S. Lewis’s fictional Malacandra where only deep trenches and former ocean bottoms had enough atmosphere and the continents were too high to support life.
In the 1/10th scenario (or similar), what would our coastlines look like? I’ve scuba dived off the edge of some islands that have a nice gentle slope, with a sudden drop off into a really impressive wall. Would our coasts be cliffs, or would there still be gentle beaches and places that would make sense for ports?
(Not that they’d necessarily be used for that…land travel being so much more predominant, and people possibly not existing…)
As Lumpy has noted, the atmospheric pressure would be affected, too; the tips of many mountain ranges would be at extremely low pressure, assuming that the atmospheric mass is the same; we could never climb Everest without a pressure suit, for example. Mexico City would be uninhabitable, and so on.
I’m not so sure you can use averages like that. Remember: the volume of a cone scales as the depth ^3. Wouldn’t the summit of Mount Everest (Heck, perhaps even Ararat ( survive a tenfold volume expansion?
Let’s look at it another way. If the oceans have an average depth of 3.5km, and cover 70% of the globe, then they would be only 2.45km deep if they covered the entire surface of an Earth with no continents. Ten times this depth would be 24.5 km; easily enough to cover the continents and mountains of our planet. In fact the oceans would be a little deeper than that, since the bulk of the continents would displace a little water; 800 metres (average height of the continents) x 30% (fraction of Earth covered in continents) = 240 metres; a total depth of 24.74 km.
Not deep enough to form high pressure ice at the bottom, but enough to compress anything but the largest volcanic eruption into a stream of turbulent bubbles.
We’re talking about a sphere here. Increasing the volume of water by 10x would not increase the depth by 10x. I can’t do the math right now, but the depth would be much less.
It’s a sphere 6400 Km in radius. Adding a layer of water about 20Km thick will make the sphere have radius 6420. That’s an increase of 0.3%, so not a real big change in radius and hence in surface area. So the crude calculation that the oceans would be 10x deeper is close to correct within a couple decimal places.
:dubious:…well, OK. If I did the math correctly, multiplying the volume of water by 10 increases the depth from 20km to 188km, which is close enough for jazz.
10x deeper or 10x shallower is very different from 10x more or 10x less. In the latter, we’re talking about volume, not depth.
I just did this on Excel, assuming the Earth to be a uniform sphere of radius 6400 km and the oceans to be uniformly 3.5km deep over the whole surface. The result, surprisingly, was that 10x more water made the depth LOWER by a few metres…
Clearly this is wrong, but the error is in Excel’s rounding. Since it handles figures with up to 20 decimal places fairly well, we can be sure that the actual difference would be relatively insignificant. I’m suggesting plus or minus no more than 20 metres.
survive a tenfold volume expansion?