The Global Carbon Cycle- part 1 (Types of flux: (Photosynthesis- plants…
The Global Carbon Cycle- part 1
:question: What is carbon?
The best element for joining with others elements to form compounds necessary for life, such as sugars, starches, fats, and proteins
Accounts for half of the total dry mass of all living things.
"The building block of life"
Organic Carbon refers to biologically derived compounds (complex substances produced only by the growth of living organisms).
Inorganic Carbon refers to mineral compounds that can be formed in the absence of biological activity (sometimes with the assistance of living things, e.g. sea shells).
Where is it found?
The crust stores the largest amount of carbon in sedimentary rock, 100,000,000 PgC. Another 4,000 PgC is stored in the Earth’s crust as hydrocarbons.
The oceans contain 38,000 PgC, mostly in the form of dissolved inorganic carbon stored at great depths. A much smaller amount of carbon, approximately 1,000 Pg, is located near the ocean surface.
The atmosphere contains 750 PgC, mostly in the form of CO2, with much smaller amounts of methane (CH4) and various other compounds. 560 PgC is believed to be the normal upper limit for the Earth under natural conditions.
Terrestrial ecosystems contain carbon in the form of plants (560 PgC), soils (1500 PgC), animals, and micro-organisms. Of these, plants and soils are by far the largest and smaller pools are often ignored.
Movement of carbon between these reservoirs is called a flux, and is expressed as a rate with units of the substance being transferred over a period of time (e.g. g cm-2 s-1 or kg km2 yr-1)
A single carbon pool can have fluxes both adding and removing carbon simultaneously. E.g. the atmosphere has inflows from decomposition, forest fires and fossil fuel combustion and outflows from plant growth and uptake by the oceans
Shortest- seconds to minutes- plants take carbon out of the atmosphere through photosynthesis and release it back into the atmosphere via respiration.
Longer- years to centuries- carbon from dead plant material can be incorporated into soils, where it resides before being broken down by microbes and released back into the atmosphere.
Longer still- millenia- organic material buried in deep sediments and protected from decay slowly transforms into coal, oil and natural gas. When we burn these fossil fuels, carbon that has been stored for millions of years is released once again in the form of carbon dioxide.
How does it affect earth?
Key role in regulating climate
This is natural, but humans are having an impact.
CO2 has risen to approximately 30% above natural background levels, as a result of human activity over the last 150 years
Rise in global temperatures
Maintaining the Equilibrium:
Earth’s carbon reservoirs naturally act as both sources, adding carbon to the atmosphere, and sinks, removing carbon from the atmosphere. If all sources are equal to all sinks, the carbon cycle can be said to be in equilibrium
A Petagram is equal to a trillion kilograms or a billion tonnes
:question: What is the Carbon cycle?
The actual global carbon cycle is immensely complex. , scientists often describe the carbon cycle by lumping similiar objects or environments into simpler groups (forest, grassland, atmosphere, ocean) and focusing only on the processes that are most important at the global scale
Types of flux:
Photosynthesis- plants use energy from sunlight to combine CO2 with water to create carbohydrates. Carbon is stored for relatively long periods, with 610 PgC stored in plants at any given time. The process removes 120 PgC/year from the atmosphere.
Respiration- cells use carbohydrates from photosynthesis for energy. This represents half (60 PgC/year) of the CO2 that is returned in the terrestrial portion of the carbon cycle.
Soil respiration: organic matter is decomposed by bacteria and fungi, CO2 is released into the atmosphere at an average rate of about 60 PgC/year globally
Ocean-atmosphere interchange: Inorganic carbon is absorbed and released at the interface of the oceans’ surface and surrounding air, through diffusion.
Litterfall: decomposition of shed leaves, roots and branches
Fossil fuels & land cover change: important; stem from human activities. Fossil fuel combustion represents approximately 6-8 PgC/year, and forest clearing a net flux of about 1.5 PgC/year. Regrowth can act as a carbon sink.
Geological processes: the formation of sedimentary rocks and their recycling via plate tectonics, weathering, and volcanic eruptions.