Carbon Cycle Flashcards
(19 cards)
Carbon on Earth
The carbon cycle involves the flow of carbon between these spheres. It is stored in carbonate rocks such as limestone, sea floor sediments, ocean water (as dissolved CO₂), the atmosphere (as CO₂ gas), and in the biosphere.
Lithosphere
Atmosphere
Hydrosphere
Biosphere
Importance of carbon
Carbon is an economic resource as it is contained in fossil fuels
Life is carbon-based; built on large molecules of carbon atoms
Agricultural crops and trees also store carbon
The carbon cycle also helps regulate temperatures on Earth; the greenhouse effect makes Earth habitable.
Measuring Carbon Stores
To measure carbon, we use Petagrams & Gigatons.
Petagram (Pg), also known as a Gigaton (Gt), is equal to:
One quadrillion (1,000,000,000,000,000 or 1015) grams.
or one trillion (1,000,000,000,000 or 1012) kg.
Residency time
used to calculate the time carbon stays in each store
residency time = amount in reservoir/ flows in or out
Carbon store variation
The growing season for vegetation in higher latitudes would therefore be far shorter and less carbon would be stored as biomass in the biosphere in these regions. Furthermore, due to low precipitation throughout the year in high latitudes this would restrict vegetation growth further and result in very sparse vegetation and low amounts of carbon stored in this form as a result. The opposite is true for tropical regions.
Carbon sequestration
Carbon sequestration is a natural or artificial process of capturing carbon dioxide from the atmosphere and storing it, in solid or liquid form, in other stores such as forests, soil, oceans, geological formations.
Biological carbon pump
is driven by phytoplankton and autotrophs which absorb carbon dioxide through photosynthesis, converting it into organic matter.
This moves up the food chain through predation/consumption. When plants and animals die their remains sink into deeper water as detritus and decompose, releasing carbon dioxide and nutrients back into the water.
In addition, carbon is stored in hard body parts like the shells of molluscs and crustaceans in the form of calcium carbonate
Physical carbon pump
refers to carbon dissolving into the ocean surface and then being driven deep down into the lower ocean currents by downwelling due to the thermohaline circulation or by wind-driven upwelling & downwelling.
downwelling.
Ocean temperatures are lower at the poles, here ocean waters sink because they are colder and denser
upwelling
Towards the equator, ocean temperatures are higher, thus ocean waters rise as they are warmer and less dense
Wind-driven upwelling
Upwelling currents bring nutrients and carbon up to the surface.This can occur when winds push surface water currents away from a coastline, leading to carbon-rich deeper ocean currents rising to replace the water, increasing surface water dissolved carbon dioxide content and the transfer of carbon to the atmosphere
Wind-driven downwelling
The downwelling process leads to carbon dioxide dissolved in surface waters being carried down into and stored in the deep ocean. This can occur when winds push water toward the coastline, where it is forced downwards and cools as it sinks, transporting the dissolved CO2 in surface waters to the deep ocean currents and sequestering it and where it stays for hundreds of years
El Niño & the carbon cycle
Due to the weakened trade winds, less of the cold, carbon-rich water makes it to the ocean surface, suppressing the amount of CO2 the ocean would normally release to the atmosphere.
On the other hand, during El Niño, Southeast Asia experiences unusually dry conditions, warmer temperature conditions typically follow drier periods. These conditions cause fires through large swaths of forests and peat bogs that release an immense amount of carbon dioxide into the atmosphere, dwarfing whatever reduction in oceanic release of CO2 occurs during this time.
CHANGES TO THE CARBON CYCLE
Volcanic activity
Carbon can be transferred from the lithosphere to the atmosphere through volcanoes. The Earth’s land and ocean surfaces sit on several moving crustal plates. When the plates collide, one sinks beneath the other, and the rock it carries melts under the extreme heat and pressure. The heated rock recombines into silicate minerals, releasing CO2
In addition, volcanoes can ironically cause COOLING of temperatures despite emitting carbon. This is because during volcanic eruptions Sulphur Dioxide and huge quantities of dust are also emitted. The SO2 combines with water in the atmosphere to create sulphuric acid. This acid, together with the dust, act to reflect radiation from the sun back to space
Wildfires
These wildfires release carbon into the atmosphere and clear a lot of vegetation. However, over time plants will grow back and the ecosystem will re-establish itself as a secondary succession.
Diurnal changes
NPP would be highest during the day due to higher temperatures and more sunlight resulting in higher rates of photosynthesis.
Photosynthesis would be dominant during the day whereas respiration would be more dominant during the night due to less sunlight resulting in lower rates of photosynthesis.
Atmospheric carbon levels would reduce during the day due to CO2 being absorbed through photosynthesis, whereas the atmospheric carbon store would increase during the night due to vegetation releasing CO2 through respiration
Monitoring short term changes
We use Moderate Resolution Imaging Spectroradiometer (MODIS) instruments, flying on NASA’s Aqua and Terra satellites, to measure changes in the carbon cycle.
NASA measures atmospheric CO2 using the Orbiting Carbon Observatory-2 (OCO-2) and ground-based measurements at Mauna Loa in Hawaii.
Using a satellite enables measurements around the globe rather than at fixed locations; providing data that is more representative on a wider spatial scale.
