Carbon cycle

Short cycle

Carbon cycle : Short cycle part 1

SHORT CYCLE
Hydrosphere - atmosphere exchanges

Dissolution of atmospheric CO2 in the ocean and degassing of CO2 from the ocean to the atmosphere

  • Exchange of 300 GT of CO2 per year ;

  • Residence time = quantity of the element in the reservoir / sum of the flows of contribution in the reservoir.

Video to watch :

Henry's Law and Gas Solubility Explained https://www.youtube.com/watch?v=9JtTpPEesOk

At constant temperature and saturation, the partial pressure in the vapor phase of a volatile solute is proportional to the mole fraction of that body in the liquid solution.

So the higher the temperature, the less CO2 is soluble, and the more carbon is redistributed to the atmosphere.

For a given amount of carbon in the ocean+atmosphere, the amount of CO2 in the atmosphere increases if the temperature increases.

CO2 control : CO2 balance in the hydrosphere

DIC = [CO2(aq)] + [H2CO3] + [HCO3−]+ [CO32−]

Carbon cycle : Short cycle part 2

Diversion and leakage in the hydrosphere-atmosphere physical exchanges

There is a diversion of carbon flux from the atmosphere to the ocean through the weathering of rocks.

To know more about weathering of rocks : https://www.youtube.com/watch?v=sk B_A2sfBcY

There is a leakage of carbon from the hydrosphere to the lithosphere : the formation of carbonates.

Calcium carbonate solubility

Ω > 1 Precipitation

Ω = 1 Equilibrium

Ω < 1 Dissolution

Modern Sea Surface Ω ≈ 2-5

Sea surface is supersaturated with respect to CaCO3, but calcium carbonates are not constantly precipitating.

To precipitate calcium carbonate :

(http://www.luckysci.com)

Woosley, Ryan J. 2018. « Carbonate Compensation Depth ». In Encyclopedia of Geochemistry, édit  par William M. White, 204‑5. Encyclopedia of Earth Sciences Series. Cham: Springer International Publishing. https://doi.org/10.1007/978-3-319-39312-4_85.

Carbon cycle : Short cycle part 3

Photosynthesis and respiration

From atmosphere to biomasse continental and oceanic

Photosynthesis

440 Gt of CO2 per year, shared equally between the oceans and the continents.

From biomass to atmosphere

  • Breathing 90º

  • Natural combustion 10º

Aerobic respiration chemical reaction :

Carbon cycle : Short cycle part 4

Organic carbon leakage to lithosphere :kerogen formation

Figure : Organic carbon cycle with the flow of kerogen (black solid lines) and the flow of biospheric carbon (green solid lines) showing both the fixation of atmospheric CO2 by terrestrial and marine primary productivity. The combined flux of reworked kerogen and biospheric carbon into ocean sediments constitutes total organic carbon burial entering the endogenous kerogen pool (Galy et al., 2015; Hedges and Oades, 1997).

Conclusion of the short cycle

Long cycle

Long carbon cycle

  1. CO2 + CaSiO3 <-> CaCO3 + SiO2

  2. CO2 + H2O <-> CH2O + O2

Berner, Robert A. 2003. « The Long-Term Carbon Cycle, Fossil Fuels and Atmospheric Composition ». Nature 426 (6964): 323‐26. https://doi.org/10.1038/nature02131.

CO2 + CaSiO3 <->CaCO3 + SiO2

Contact Metamorphism Vs. Regional Metamorphism https://www.geologypage.com/

Trap rock forming a characteristic pavement, Giant's Causeway, Northern Ireland (left)

Three Devil's Grade in mid-Moses Coulee , USA (right)