As a result of the Auto-Evo algorithm, I’m starting to reach a point where I need to implement environmental compounds like oxygen, carbon dioxide, ammonia, etc. Meanwhile, TJ is making great progress in building the first version of a Planet Generator for the upcoming update. So as a way of hitting two birds with one stone, I think it would be good to create simple theoretical models of how compounds cycle through the environment. We’ll specifically be modelling how we implement this in Thrive.
This field is referred to as Biogeochemistry, and includes the famous nutrient cycles you may have heard of (the carbon cycle, the nitrogen cycle, the phosphorous cycle, etc). On this thread we’ll focus just on tackling the Carbon Cycle. Hopefully by creating a model for the carbon cycle we can come up with a way of knowing how much carbon dioxide can be found in each patch at any moment in time.
I think the best way to think of these cycles is to draw out a diagram of Bins and Flows. A bin is something that holds carbon, and a flow is a process that causes carbon to move from one bin to another. A bin could be something like the ocean, and a flow could be something like acid rain (moving carbon from the atmosphere into the oceans).
Here is the diagram I’ve made so far of how to model the carbon cycle. It purely looks at abiotic flows of carbon throughout the planet (flows that are not related to living organisms).
Black arrows represent one-way flows. Red arrows represent two-way arrows, meaning the carbon will reach an equilibrium between the two bins.
I’ll explain the different bins and flows:
- This represents the entire atmosphere of the planet.
- This represents the first few hundred meters at the top of the ocean.
- This represents the remaining ocean underneath the ocean surface. The deep ocean typically contains huge reserves of dissolved carbon dioxide.
- This represents the top 5-50km of the rock layer of the planet. These rocks comprise the tectonic plates that move around (via tectonic drift) and form continents.
- This represents the next layer of molten rock beneath the crust. Volcanoes draw their magma from this layer. The layers below this (including the Planetary Core) are assumed to be irrelevant to the carbon cycle
Air-Sea Gas Exchange
- The exposure of the surface ocean waters to the atmosphere causes a constant exchange back and forth between carbon dioxide in the atmosphere and carbon dioxide in the ocean surface. The ocean surface and atmosphere reach equilibrium within days to years.
- This refers to the cycling of hot and cold water containing different levels of dissolved carbon dioxide throughout the ocean. Warm upwelling water rises to the ocean surface from the deep ocean and delivers carbon dioxide, while cold sinking water takes carbon dioxide from the ocean surface and stores it in the deep ocean. This process of equilibrium is MUCH slower and takes centuries.
- When carbon dioxide dissolves in the ocean, a small fraction of it turns into carbonate. Over time, this carbonate binds to calcium and small particles (like sand) and turns into carbonate rock that deposits at the bottom of the ocean (such as limestone). These rocks become a part of the planetary crust. As the carbonate turns into rocks, this reduces the carbonate remaining in the ocean and more of the dissolved carbon dioxide turns into carbonate. Overall this slowly reduces the dissolved carbon dioxide in the ocean.
Tectonic Plate Subduction
- Tectonic plates are pieces of the planetary crust. Over time, some plates will eventually get pushed under by other plates. When they get pushed under, they will be pushed into the mantle where the heat and pressure melts the rocks into basically magma.
- When volcanoes erupt, carbon dioxide is typically the second most common gas they release. Depending on where the volcano forms, it can release this carbon dioxide into the atmosphere or into the oceans. Around 70% of volcanic eruptions on Earth are underwater.
- When volcanoes erupt, they also often release lava as well. This lava is drawn from the planetary mantle and can contain many of the carbonate containing rocks that were earlier subducted. This releases them back into the crust.
What do you guys think of such a model? Any changes? How can this apply to patches (I have an idea on this but want to hear what you guys think)