The Carbon Cycle Flashcards
What are Earth’s 3 rapidly exchanging carbon reservoirs?
Ocean: contains the most carbon (40.000 Pg), most of it in the form of Dissolved Inorganic Carbon (DIC) in middle to deep layers of the ocean. Marine biota transfer carbon from surface to deep water (biological pump). Ocean-atmosphere carbon exchange depends on the difference between surface ocean and atmospheric partial pressures.
Land: second biggest carbon reservoir (4.000 Pg). On land carbon is stored in living vegetation, in soils and permafrost. Over 100 Pg of carbon are removed from the atmosphere by plants through photosynthesis and turned into organic matter. This organic carbon is then respired by bacteria and turned back into inorganic CO2.
Atmosphere: relatively small reservoir (ocean is 40 times bigger, land is 10 times bigger). However it is crucial in linking together ocean and land in carbon exchanges.
What is the difference between the natural carbon cycle and the anthropogenic one?
The natural carbon cycle consists in the natural exchanges of carbon between atmosphere, ocean, and land.
The anthropogenic carbon cycle is man-induced and consists of the human effects on the carbon cycle.
What is the main cause of human-made carbon emissions?
Currently humans emit about 10 billion tons of carbon into the atmosphere per year mostly from fossil fuel burning (~90 %). However, deforestation continues to be a significant contribution (~10%). Anthropogenic carbon emissions from fossil fuel burning have increased rapidly after World War Two.
What is roughly the distribution of anthropogenic carbon emission between atmosphere, ocean and land?
The ocean has taken up about 40% (155/395) of all anthropogenic carbon emissions. 60 % (240/395) have stayed in the atmosphere, whereas the land comes out in a wash because of loss due to deforestation and gain due to recent regrowth.
Which country emits more carbon?
Among the 4 top emitters, the US has one of the largest emissions per person. The average American emits more than 4 metric tons of carbon into the air each year.
The US is responsible of 25% of all carbon emitted in the past, Europe is responsible for 22%.
What are cumulative emissions?
All carbon put into the atmosphere by humans since the industrial revolution.
What evidence do we have of human-induced increased carbon emissions in the atmosphere?
The first evidence comes from economic data: fossil fuels are traded international, therefore we know how much oil, coal and gas a country imports and uses.
Second evidence is based on carbon isotope measurements. carbon exists as 3 isotopes: carbon 12 with 6 protons and 6 neutrons, the most common one; carbon-13 with one additional neutron, and carbon-14 with two additional neutrons (radioactive). Fractioning during photosynthesis leads to plants and algae having very depleted carbon 13 values. Since fossil fuels are derived from ancient plants they are depleted in carbon 13 isotopes as well. Thus, the addition of carbon with a very depleatd carbon 13 signature to the atmosphere leads to a decrease in carbon 13 values of atmosphere CO2.
Another evidence is based on oxygen measurements in air. Burning fossil fuels has a similar chemical reaction to that of respiration - carbohydrates react with oxygen to form CO2 and water, releasing energy. This burning carbohydrates consumes oxygen. By measuring oxygen to nitrogen ratio in the air the changes in atmospheric oxygen concentration can be detected even though they are small compared to absolute oxygen concentrations.
What is ocean acidification?
It’s a significant and harmful consequence of excess carbon dioxide in the atmosphere that happens underwater. At least one-quarter of the carbon dioxide (CO2) released by burning coal, oil and gas doesn’t stay in the air, but instead dissolves into the ocean. Since the beginning of the industrial era, the ocean has absorbed some 525 billion tons of CO2 from the atmosphere, presently around 22 million tons per day.
When carbon dioxide dissolves in seawater, the water becomes more acidic and the ocean’s pH (a measure of how acidic or basic the ocean is) drops. Even though the ocean is immense, enough carbon dioxide can have a major impact. In the past 200 years alone, ocean water has become 30 percent more acidic—faster than any known change in ocean chemistry in the last 50 million years.
At its core, the issue of ocean acidification is simple chemistry. There are two important things to remember about what happens when carbon dioxide dissolves in seawater. First, the pH of seawater water gets lower as it becomes more acidic. Second, this process binds up carbonate ions and makes them less abundant—ions that corals, oysters, mussels, and many other shelled organisms need to build shells and skeletons.
How exactly does the atmosphere exchange carbon with the ocean?
CO2 enters the ocean from the atmosphere through gas exchange if the partial pressure in the atmosphere is larger than the partial pressure in the ocean. More gas can be dissolved in colder water.
