[WIP] Building a world from tectonics onward

[MrBragg]

Perhaps there's something obvious I'm missing here, but to my eyes the results produced manually using the Azelor/Charerg/AzureWings method seem more plausible to me.

Yep, that's the exact same boat I'm in here. The results from the Azelor/Charerg/AzureWings tutorial feel more right, but I also know nothing about climate forcings and so am entirely unqualified to be making these judgements. That the July results match up so well while January is so different is confusing, so I'm playing around with changing parameters somewhat systematically to see if I can't figure out why this is. If I stumble onto anything interesting I'll definitely let you know

[worldbuilding pasta]

Thanks for posting this! I have always wondered about the practical differences between the Azelor tutorial and the Nikolai's much-more-involved version. The latter honestly struck me as a great deal of additional work and processing power for what seems like a less-exact result. I was also skeptical of his results that seemed too warm at the poles for my liking (the final result for Teacup Ae had no south polar tundra despite having a large continent at something like 85º south). My initial guess is that the Clima-sim methods understate the cooling effects of having a great deal of land directly next to the poles, which is likely to result in extensive ice-caps and thus cooler temperatures even in summer than what an agnostic model predicts. Clima-sim even allows for inputting ice caps into the land cover map, but it seems this doesn't matter much.

Of course, the Clima-sim algorithm is much more advanced than the Cartographer's guild model that much more strictly uses Earth as a base, and I'm not a climatologist and haven't fiddled around with Clima-sim at all. Perhaps there's something obvious I'm missing here, but to my eyes the results produced manually using the Azelor/Charerg/AzureWings method seem more plausible to me.

The warm south pole in that model is due to Teacup Ae's eccentricity, which causes stronger seasons in the southern hemisphere; the significantly warmer summers (and generally flat terrain of the southern continent) evidently prevent permanent glaciers from forming, and without that ice-albedo feedback the south pole stays remarkably temperate. Later runs with a formal climate model have largely confirmed this result (though that also helped highlight some of the shortfalls to my approach to determining precipitation).

There may be something similar going on here: If there isn't sufficient landmass at the south pole to maintain a large glacier, the overall albedo of the poles will be far lower and so they will be warmer compared to Earth's (you can play around with the ice cover in clima-sim to see if you can get different results, though; there's a certain inertia to global climates wherein the presence of a reflective ice cap can help keep itself cool in a situation where an initially ice-free pole might not form an ice cap).

[MrBragg]

First of all I wanted to say thanks for putting together your tutorials; they're super informative and I always enjoy reading your material

There may be something similar going on here: If there isn't sufficient landmass at the south pole to maintain a large glacier, the overall albedo of the poles will be far lower and so they will be warmer compared to Earth's (you can play around with the ice cover in clima-sim to see if you can get different results, though; there's a certain inertia to global climates wherein the presence of a reflective ice cap can help keep itself cool in a situation where an initially ice-free pole might not form an ice cap).

This is what I'm currently playing around with. If I give the north pole partial ice coverage it dramatically lowers the northernmost temperatures and pushes the 0 C isotherm somewhat farther south than without the ice. I don't really have an intuition for 1) whether it's appropriate to add this type of sea ice cover since there is no land up there (as you say, feedback is potentially quite important), and 2) whether the ice-free version accurately reflects the temperature distribution or whether that is "too mixed" and thus too warm in the winter. As a baseline initial test, I'd be curious to see what ExoPlaSim predicts for a water world so I could compare that to a Cilma-sim water world output, I just need to find the time to run that test...

[MrBragg]

Ok, so another interesting tidbit is the comparison between calculations on Earth in January with 1) a starting ice cap on Antarctica, and 2) without a starting ice cap. When the model starts with ice, things look reasonable enough, but when it doesn't... the south pole gets hotter than the outback in the summer. This seems like a spurious result and, even if it isn't, does go to show the massive (50 degrees C!) dependence on the starting conditions.

With Ice (Left), Without Ice (Right)

[Peter Toth]

This is unfortunate as I'm come to rely on Clima-Sim for its supposed accuracy and its ability to automate climate modeling with a consumer PC. Are you changing the CO2 levels or any other parameter between the two simulations? Did you repeat the simulation to verify it wasn't some random error by the processor (if that's at all possible)?

I'm intending to move on to ExoPlasim and I'm wondering if this program is more accurate. I remember morne's experimentation lately that resulted in a desert that extends much too far north, so I'm very skeptical.

By the way, MrBragg, I'm highly impressed by your Wilbur results from a couple weeks ago. I'm experimenting with Wilbur as well to generate some realistic terrain, but I'm not easily satisfied by my results so far.

Looking forward to the completion of your conworld!

Peter

[worldbuilding pasta]

1) whether it's appropriate to add this type of sea ice cover since there is no land up there (as you say, feedback is potentially quite important), and 2) whether the ice-free version accurately reflects the temperature distribution or whether that is "too mixed" and thus too warm in the winter. As a baseline initial test, I'd be curious to see what ExoPlaSim predicts for a water world so I could compare that to a Cilma-sim water world output, I just need to find the time to run that test...

1, Clima-Sim should determine sea ice cover on its own.

2, Not too sure what you mean by "too mixed". The general approach I'd advise if you're aiming to have ice caps is to begin by over-estimating the extent of ice, running the model, and then remove ice from areas that get over 0 C in summer (be sure you're looking at temperatures at the surface, not sea level), and iterate until you find an equilibrium.

Regarding the test you ran with Antarctica, there should indeed be a significant difference there--and you'd be surprised how warm polar regions can get without ice thanks to constant sunlight in summer. This might be overstating it a bit though; Clima-sim doesn't seem to do a good job of allowing heat to flow from the poles to lower latitudes when the former gets warmer than the latter, which is why it essentially breaks at higher axial tilts.

re: Peter, I took a look at morne's world and that high-latitude desert is a reasonable outcome of a large mountain range casting a large rainshadow. ExoPlaSim has its weaknesses (most notably the low resolution, static glaciers, and lack of deep ocean currents) but it's in a whole other league compared to Clima-sim in terms of the complexity and accuracy of the underlying simulation and its flexibility in handling a range of climate parameters.

[Tiluchi]

The warm south pole in that model is due to Teacup Ae's eccentricity, which causes stronger seasons in the southern hemisphere; the significantly warmer summers (and generally flat terrain of the southern continent) evidently prevent permanent glaciers from forming, and without that ice-albedo feedback the south pole stays remarkably temperate. Later runs with a formal climate model have largely confirmed this result (though that also helped highlight some of the shortfalls to my approach to determining precipitation).

Thanks for that explanation! And thanks for the great posts on your blog, I recently completed your GPlates tutorial and I'm a Patreon subscriber. I'd missed the bit about Teacup's eccentricity, but that makes sense. A question however about the elevation: it seems that at the poles, elevation and the presence of ice sheets are somewhat endogenous to each other. For instance, most of Greenland would be below 1000 meters above sea level if it weren't for the presence of the Greenland Ice Sheet, which is 2-3 kilometers thick. The high elevation brings temperatures down, which allows for a continuing ice sheet- a feedback loop basically. I'm assuming that Clima-sim or ExoPlasim would give us ice cap climates near the poles if we were to include 2000-meter-thick ice caps in our elevation map inputs. So barring a detailed history of atmospheric CO2 for the world, maybe the presence of an ice sheet is a decision we have to make ahead of time as we're building the planet, rather than assuming from our geology that doesn't take into account the potential presence of thick ice sheets at some of the poles.

What do you think? As I said earlier I'm not really a climatologist, and I don't have either of the simulation programs as I'm using Mac OS, so these are just my educated guesses.

[MrBragg]

Regarding the test you ran with Antarctica, there should indeed be a significant difference there--and you'd be surprised how warm polar regions can get without ice thanks to constant sunlight in summer.

That it was warmer made sense, but the magnitude seemed off. As a followup here I removed the ice from Greenland and saw qualitatively similar but somewhat less crazy warming of Greenland / Siberia / northern Canada. My guess is that's due to the moderating effect of water near the pole, though removing half the land from an ice-free Antarctica still gives temperatures nearing 30 C in the summer.

Ice-free Greenland


As a point of comparison, I'd actually be really curious to know what ExoPlaSim predicts for the temperature of your southern continent in the summer to see how that compares to the >40 C predicted by Clima-sim. Even with its systematic issues, I'd be much more inclined to trust the output from ExoPlaSim given how much more explicitly it treats things.

[worldbuilding pasta]

As a point of comparison, I'd actually be really curious to know what ExoPlaSim predicts for the temperature of your southern continent in the summer to see how that compares to the >40 C predicted by Clima-sim. Even with its systematic issues, I'd be much more inclined to trust the output from ExoPlaSim given how much more explicitly it treats things.

I checked and it reached about 20-25 C in summer, but that's with years about 1/3 the length of Earth's (and various other tweaked parameters) so it's not a direct comparison to clima-sim's model. I've also recently been running a range of models of Earth at different temperatures (there will be a post up about it soon) and for Earth 10 C hotter than today on average, with fully melted ice caps (though topography not adjusted to account for that because it'd be a ton of effort) Antarctica reached around 30-40 C in summer. So all in all, yes, there's probably something funky going on with clima-sim here, likely because it's just not really designed to handle heat flowing away from the poles.

A question however about the elevation: it seems that at the poles, elevation and the presence of ice sheets are somewhat endogenous to each other. For instance, most of Greenland would be below 1000 meters above sea level if it weren't for the presence of the Greenland Ice Sheet, which is 2-3 kilometers thick. The high elevation brings temperatures down, which allows for a continuing ice sheet- a feedback loop basically. I'm assuming that Clima-sim or ExoPlasim would give us ice cap climates near the poles if we were to include 2000-meter-thick ice caps in our elevation map inputs. So barring a detailed history of atmospheric CO2 for the world, maybe the presence of an ice sheet is a decision we have to make ahead of time as we're building the planet, rather than assuming from our geology that doesn't take into account the potential presence of thick ice sheets at some of the poles.

There is a valid point there, but if your ultimate concern is the extent of the ice sheets, then it doesn't really matter. The extent of a glacier is determined by its edges, where it's fairly thin; if those edges melt away, the interior will melt down towards the land surface, and if the edges are stable, the interior will be as well regardless of whether it's 10 meters or 4 kilometers thick.

Of course in reality, flow of ice from the glacier interior to the edges has a cooling effect that helps the glacier expand, and that will depend on the internal structure of the glacier, but glacial flow isn't modeled in ExoPlaSim (or clima-sim for that matter, but it's a bit easier to adjust glacial extent on the fly there) so it's a moot point. You kind of just have to accept that the model will underestimate the extent of glaciers in most cases. However, if your intent is to have an Earth-like world emerging from a recent ice age, it does help to run the model to balance first at something like 5-10 C colder than your intended temperature, and then warm it up from there. (Also ExoPlaSim does have the capacity to model the presence of deep glaciers on top of the topography, but doing so would require messing around with the running files and probably be more effort than it's worth).

Also, ExoPlaSim can run on mac, though it takes a bit more fiddling around; there's some notes on it in the readme on its github

[Ottehcnor]

Wow! This is an amazing amount of work with great results. It definitely has me wanting to re-do a map I'm currently working on to create a more realistic world.

The process is actually nothing particularly special and is mostly a collection of various techniques I've learned on here. If you're interested though I could detail it.

If you're serious about going into detail on your process, I for one would love to have that tutorial.