Wow. The Baffin/Hudson/Labrador/Arctic ocean will be awesome. :-D But you're in for some serious long-term Arctic glaciation there, especially considering that you're busting up the thermohaline circulation pretty seriously. I assume you worked all this out though.
Surely the Antarctic will even out? It's really lacy there, which I suspect is an effect of using current sea level values; maybe once you apply glaciation it'll look more reasonable.
Have you looked into "inertial interchange true polar wander" as a mechanism? It didn't really happen, probably, but it could! Not sure why it might wipe anyone out though, but I'm sure you could come up with something...
Cool! :D I had never before heard of this IITPW-theory. That could be just the gravitational anomaly I was looking for. Thanks!
About such a mechanism causing a mass extinction, I fear I got more than I bargained for. Shifting the climate bands like that, would kill of lots of plant life (for instance the Russian pinewoods and Congo basin both lying smack in the middle of desert bands,) release lots of carbon, basically resulting in a kind of "clathrate gun," similar to the PT-extinction. Flooding the atmosphere with such massive amounts of carbon, uses up the oxygen, killing even more life, making it possible for free methane to flood the atmosphere, resulting in a run-away greenhouse effect, killing of more life, releasing even more carbon.
Though I may have a safety net: Some of the tropical rainforests, especially the Amazon, are left in place. The carbon left by the clathrate gun actually stimulates plant growth, while the lack of oxygen takes away large herbivores and the danger of wild fires. So the jungles have a field day! Similarly the algeal blooms in the subpolar regions may regenerate quite quickly. So after an initial global suffocation follows a global oxygen injection, reducing the methane and returning everything back to normal.
Just two things:
1: I have no idea how long this mechanism would take to unfold.
2: I have no idea how severe it would be and how it would effect the human species and its domesticates.
(Scary thought: Isn't this clathrate gun exactly what is going on right now in the real world?)
By the way, you're saying this geography will bust up the thermohaline circulation. Could you elaborate that further?
I have a gut feeling you are right, you see, but I'm still unable to rationalize it.
I think I may be able to finish the continental shelves today, so I'll pbb post a new map this evening.
I was thinking that a gravitational effect sufficient to wander the axis of rotation by 30 degrees would also set off ticking time bombs like Yellowstone ... which would help in the mass-extinction department.
Absolutely! Globally intensified tectonics, bunch of volcanos going off all at once, earthquakes, land slides and tsunamis all over the place, that would really mess the planet up!
It would also fill the sky with aerosols, blocking sunlight, causing an initial iceage and killing off even more plant life, including algae, in turn causing an anoxic event in the seas as well.
However now we have an iceage followed by a clathrate gun and no forests left to restore the system. That's what I was afraid of.
Climactic cataclysm on this scale would kill about everything. Permo-triassic extinction all over. Only now with chemical toxins, heavy metals and radioactive material left behind unchecked.
I'm not sure I'll have any macroorganisms left to work with, let alone humans. After the original PT-extinction it took trees about 6 million years to reevolve, during which the entire planet was pretty much a giant desert.
If I don't find some way to lighten the burden, I think I'll have a very dead and boring planet.
My bet is still on human domestication and agriculture. Think about it, if we can't even terraform are own planet, we won't stand a chance on other planets.
But changing Earth into a second Mars may just be a bit too much of a challenge.
Alternatively, the early triassic did spawn some interesting clades, like dinosaurs, pterasaurs and ichtiosaurs. At the same time some older clades were still walking, especially the dicynodonts and cynodonts (that would later give rise to modern mammals.)
I could take the time scale to entirely different level and have the humans left behind as the next cynodonts while having all kind a weird new species evolve around them...
This is starting to look more and more like "Nausicaa of the Valley of the Wind"
Well, a clathrate release only hangs around in the atmosphere for a hundred years or so, since methane's got an atmospheric residence time of something like 15 years IIRC. So that'd be a brief heat boom -- this is the supposed PETM trigger, and that was an incredibly brief blip, less than 100,000 years.
The volcanic release would be more significant, but I'm still not sure it'd be on a Siberian Traps scale. The last few times the Yellowstone hotspot has gone off, it's been well below 5000 cubic km -- enough to cause a volcanic winter and make some large herbivores briefly unhappy, but not enough to register as a blip on the extinction scale. Furthermore it's rhyolitic IIRC so you'd just get a ton of ash, though well enough to make it locally uninhabitable for a while. The Siberian Traps were something on the order of a million cubic km, and basaltic so they all stayed local.
The "nuclear winter" effects of the Chicxulub impact didn't make the angiosperms go extinct -- they did just fine, as did most of the bugs living in them, in fact. The part of North America that got the ashfall would be hosed as far as forests go, that is, but the forests of SE Asia and the Amazon should be alright, and the tropical Australian forests should spread. You've drastically reduced the amount of land in the 30° desert zone, and increased that in the tropical-forest zone. Plus there's a ton of new drowned shelf in the Baffin-Hudson-Arctic ocean area, which should stimulate the ocean ecosystems.
If you're putting yourself 100,000 years after the cataclysm, I think you should be past the clathrate warming, acidification, and volcanic-winter nastiness -- at least if we take the PETM as an example. Or PETM + Long Valley Caldera eruption, for that matter. You'd have to figure out what went extinct, though, and what's taking its place. But I doubt you'd be getting into P-Tr, "everything but the stromatolites is gone" type territory.
Regarding my comment about the thermohaline circulation (I love that image), you're nuking the very cold meltwater that sinks in the North Atlantic with this as well as breaking the circum-Antarctic current loop...
Hmmm... your analysis is actually quite a relief :)
Honestly I had no idea the clathrate gun would only work for such a short amount of time. So I guess it wouldn't stop a volcanic winter.
Of course globally increased volcanic activity would be a little more of a problem than just Yellow Stone going boom, though I agree with you that it still wouldn't be Siberian Traps scale. Still, the ash being emitted world wide instead of locally, could result in more impact-like winter, maybe making the Chixculub event a better model to work from, albeit in a less severe fashion.
I'll lose most wild large animals, as most are few in number. But as cows, horses, sheep, goats, dogs etc. are just as widely spread as humans, and probably cared after by at least some survivors, I'll have quite some large animals left.
Indeed bugs and other small animals will be doing just fine, as well as many species of birds and of course former pets and pests.
So in this light I guess the early postapocalyptic age will be a lot more like the Fallout universe. But then the planet will be up and running modern style within a mere thousand years or so.
As I learned as a young kid playing SimEarth, the slightest tweaks to a planet can turn it in either a freezer or an oven. Now I'm running into the balance between a brief discomfort and global extermination.
I'm trying to get the human population down to a few million world wide or even less. Then I want to challenge them enough to diversify into new species. Incomplete speciation and stuff like ring species will probably be the norm, as 100 000 years is a bit on the short side for evolution, but who doesn't like hybrids in fantasy :P
Octopod? Do you have any pointers on how to work out a fictional thermohaline system? Because eventhough I've read about the thermohaline circulation several times, the mechanics behind it still baffle me when it comes to a fictional world.
Do polar waters always attract surface waters? And is there a logical way to plot the course of deep sea waters from the poles to upwellings? And most importantly, how can you tell if the system is balanced, whether it stimulates or frustrates heat conduction from the tropics to the poles?
Plus, you have to keep in mind that, IIRC, the Chixulub impact's really deadly part was the raining of fire everywhere (a lot of stuff got thrown into sub-orbital space and fell back down as I understand it); I don't think a global winter would be nearly as devastating. You'd lose a lot of the cold-blooded stuff, for the most part. The bigger mammals would actually probably be ok; they have lots of keep-warm mechanisms already.
So no fern spike then. More like a couple of years of darkness and cold, and a bit of volcanic glass splinters tearing open lungs and digestive systems and a bit of acid rain.
Biggest problem for most life is the acute shift of climate zones. And also the complete collapse of human economy/society.
I'll have a better understanding of the scale of destruction when I have my climate zones ready.
I...actually don't have any general way to work out the circulation, honestly.
The formation of deep water is governed by density, which is a balance between salinity and temperature, both of which are governed by wind-driven surface evaporation. So...
1) Fast wind and freezing temperatures both cause water to become colder and saltier, and therefore to sink; hot rainy climates make it warmer and fresher and therefore less dense. (Hot dry weather and cold rain both have less effect, obviously)
2) The water that sinks to the bottom flows downhill, and flows away from the points where it sinks from the surface; water is "produced" at the rainy tropical latitudes and flows toward the points where it sinks.
I don't know what you can do with this -- I have to go do other science but I'll be back later. :-P