Simulation of the Ocean Carbon Uptake

Name: Simulation of the Ocean Carbon Uptake
Author: Aiyyna Tatarinova Method: System dynamic
Tool: Vensim

Introduction and Problem definition

Carbon dioxide (CO2) is a crucial greenhouse gas responsible for trapping heat. It originates from the extraction and combustion of fossil fuels (such as coal, oil, and natural gas), wildfires, and natural phenomena like volcanic eruptions. The initial chart displays the levels of atmospheric carbon dioxide (CO2) recorded by NOAA at the Mauna Loa Observatory in Hawaii since 1958.

Athmospheric CO2

Since the advent of industrialization in the 18th century, human activities have elevated atmospheric CO2 levels by 50%, resulting in the current amount being 150% of its value in 1750. This anthropogenic increase surpasses the naturally occurring rise observed at the conclusion of the last ice age 20,000 years ago. Carbon is in carbon dioxide, which is a greenhouse gas that traps heat close to Earth. It helps Earth hold some of the heat it receives from the Sun so it doesn't all escape back into space. But CO2 is only good up to a point – beyond that point, Earth's temperature warms up too much. NASA research satellites such as OCO-2 and OCO-3 are studying how carbon moves around the planet.

This graph shows how atmospheric CO2 has increased since the Industrial Revolution

The ocean holds approximately sixty times more carbon in the form of dissolved inorganic carbon than the pre-anthropogenic atmosphere (~600 Pg C). Over time scales <105 years, the ocean serves as the largest reservoir of inorganic carbon (~38,000 Pg C), engaging in exchanges with atmospheric carbon dioxide (CO2) and thus exerting significant control over atmospheric CO2 levels. The average concentration of inorganic carbon in the ocean is approximately ~2.3 mmol kg−1, with a residence time of about ~200 thousand years.

Dissolved carbon dioxide in the ocean primarily exists in three inorganic forms: free aqueous carbon dioxide (CO2(aq)), bicarbonate (HCO3−), and carbonate ion (CO32−). A minor presence is true carbonic acid (H2CO3), accounting for less than 0.3% of [CO2(aq)]. The combined concentrations of [CO2(aq)] and [H2CO3] are represented as [CO2].The predominant form of dissolved inorganic carbon in the contemporary ocean is bicarbonate (HCO3−), comprising over 85% of the total.

Carbon dioxide undergoes exchange between the atmosphere and the ocean through molecular diffusion. A disparity in CO2 pressure between the atmosphere and the ocean drives the exchange of CO2. Specifically, CO2 transfers from the air to the water when the atmospheric CO2 pressure is higher. The ocean dissolves CO2 due to its solubility.

The solubility of carbon dioxide is influenced by the water's salinity and temperature, with a limited capacity for absorption by the water. Colder water has a higher capacity to dissolve CO2, contributing to variations in solubility.

Variables

The model setup: • Units for Time = Year

• INITIAL TIME = 0

• FINAL TIME = 250

• TIME STEP = 1

The model variables are set as follows:

• Dissociation constant = 6.352

• Bicarbonate = Dissolved carbon dioxide in the ocean/100*98 = Dissolved carbon dioxide in the ocean / 100 * 98

• Bicarbonate HCO3 concentration = Bicarbonate*0.001/Molar mass HCO3

• Bicarbonate HCO3 concentration in mol/l = Bicarbonate HCO3 concentration*1000

• Carbon dioxide = Dissolved carbon dioxide in the ocean/100*2

• Carbon dioxide concentration = Carbon dioxide*0.001/Molar mass CO2

• Carbon dioxide concentration in mol/l = Carbon dioxide concentration*1000

• pH value = Dissociation constant+LOG("Bicarbonate HCO3 concentration in mol/l"/"Carbon dioxide concentration in mol/l", 10)

• Molar mass HCO3 = 61

• Molar mass CO2 = 44

• Dissolved carbon dioxide in the ocean = Atmosphere/100*30

• Atmosphere = INTEG (CO2 emissions+CO2 release+decomposition+respiration-CO2 absorption-photosynthesis,898.86)

• ocean mixing = 100*(Deep Ocean/38100)

• Ocean surface = INTEG ( CO2 absorption+ocean mixing-remains-CO2 release, 1020)

• Deep Ocean = INTEG ( remains-ocean mixing, 38100)

• photosynthesis = 121.8*(Atmosphere/750)

• Forest = INTEG ( photosynthesis-death-respiration, 610)

• death = 60 * (Forest/610)

• CO2 emissions = 5.5

• Fuel = INTEG ( -CO2 emissions, 10000)

• remains = 91.6 * (Ocean surface/1020)

• CO2 absorption = 92 * (Atmosphere/750)

• CO2 release = 90* (Ocean surface/1020)

• decomposition = 60 * (Soils/1580)

• respiration = 61.6 * (Forest/610)

• Soils = INTEG ( death-decomposition, 1580)

Model

The diagram of carbon dioxide shows exchange in the atmosphere and its impact on ocean water acidity in the context of climate change. The diagram begins by indicating the primary sources of carbon dioxide in the atmosphere, including industrial processes, fuel combustion. The diagram illustrates how carbon dioxide is partially absorbed by the ocean. Remains and carbon dioxide sink into the depths of the ocean. Additionally, the model allows for the measurement of water pH depending on the amount of dissolved carbon dioxide.

Stock and flow diagram