Carbon Cycle and Climate Change Notes Flashcards
Carbon Sources
processes that add carbon to the environment
Carbon Sinks
places where carbon is stored (oceans/ bodies of water = largest sinks on Earth; other sinks = organisms, rocks, atmosphere)
Carbon Fluxes
processes that move/ transfer carbon (photosynthesis = largest flux on Earth); negative flux = remove carbon; positive = add carbon
Photosynthesis and Carbon
Carbon dioxide in the atmosphere or hydrosphere diffuses into autotrophs and is “fixed” as organic compounds (e.g. sugars, and even proteins and lipids) – Remember the Calvin Cycle (the light independent reactions?!?)
Note: Photosynthesis has the LARGEST role in transferring carbon/ transfers the LARGEST mass of carbon in the carbon cycle!
Feeding and Carbon
Organic carbon moves from autotrophs to heterotrophs, from one trophic level to the next in food chains/ webs
Respiration and Carbon
All organisms (including plants) metabolize (break down) organic compounds for energy, (ATP) and release carbon dioxide (diffuses into air/ water)
Decomposition and Carbon
releases carbon (as CO2 or CH4) into soil/ water/ atmosphere
Decomposers/ saprotrophs release CO2 during decay (aerobic process)
Methanogens (archaeans) release methane (CH4) as they break down organic matter in ANAEROBIC conditions (methane diffuses into atmosphere or accumulates underground)
In atmosphere, CH4 is oxidized to CO2 and water
In soils/ sea beds, deposits of CH4 (in anoxic conditions) form natural gas
In waterlogged soils, anaerobic conditions produce acidic conditions that inhibit saprotrophs, so organic matter only partially decomposed = forms PEAT
Lithification and Carbon
compaction of carbon-containing compounds in sediments/ rocks/ fossils
Fossilization and Carbon
Carbon from partially decomposed/ dead organisms becomes trapped in
sediment/ porous rock and forms coal, oil, and natural gas over millions of years
PEAT becomes compressed under sediments, heat and pressure remove moisture and force out impurities = COAL forms
Marine organisms die/ partially decay on ocean floor, buried/ compressed/ heated under sediments in anoxic conditions and hydrocarbons form OIL and NATURAL GAS (which move into surrounding porous rock)
Combustion and Carbon
During the burning of fossil fuels and biomass (forests etc.), carbon dioxide is released
Carbon Cycling in Oceans/ Bodies of Water
-Carbon dioxide dissolves in bodies of water (from the atmosphere) - used for aquatic food chains (photosynthesis, feeding, and respiration)
-As CO2 dissolves in water, some of it combines with water to form carbonic acid: 1. CO2 + H2O ⇄ H2CO3
-Carbonic acid dissociates to form hydrogen carbonate ions and hydrogen ions (release of H+ ions due dissociation causes water pH to become more acidic - this is why pH drops as CO2 dissolves in water)
2. H2CO3 ⇄ HCO3– + H+
3a. Carbonate ions combine with sediments/ calcium on the ocean floor to form calcium carbonate; compacts over time (lithification) to form limestone
3b. Aquatic organisms (molluscs and corals) absorb carbonate ions and combine them with calcium ions to form calcium carbonate to create exoskeletons and shells
Methane in the Carbon Cycle
-Methanogens produce methane as a metabolic byproduct in ANAEROBIC conditions (wetlands - swamps/ marshes, marine sediments - muds in lake beds etc., digestive tracts of ruminants - cows, sheep, goats)
-Methane diffuses into atmosphere or accumulates underground (when organic matter is buried in anoxic conditions, methane deposits form natural gas)
-Methane in the atmosphere is oxidized to form carbon dioxide and water:
CH4 + 2 O2 → CO2 + 2 H2O
Formation of PEAT
In most soils, saprotrophs (bacteria/ fungi) break down dead organisms/ leaves etc. and return their nutrients to the soil (nutrient cycling). This decomposition is an AEROBIC process (it requires oxygen).
Waterlogged soils create anaerobic conditions. Anaerobic respiration in these soils creates organic acids.
Saprotrophs are inhibited by acidic conditions, so organic matter is not fully decomposed and carbon-rich molecules remain in the soil forming PEAT
Formation of Oil/ Natural Gas/ Coal
Over time, sediments are deposited over the peat, compacting it.
As the peat is buried deeper and deeper in the Earth, heat and pressure remove moisture, force out impurities, and cause a chemical transformation of the carbon compounds into coal
In oceans, sediments form on top of decaying organic matter, creating anoxic conditions (organic matter is only partially decomposed)
As more sediments form on top of this matter, heat and pressure create hydrocarbons, which form oil and gas
Oil and gas move out of the source rock and form deposits in the surrounding porous rocks
Short/ Long Wavelength Radiation and the Greenhouse Effect
ncoming radiation from the sun is short-wave ultraviolet radiation (passes through greenhouse gases)
Short-wave radiation is absorbed or converted to long-wave radiation on Earth’s surface
Long-wave radiation (infrared radiation/ IR/ heat) cannot pass back through greenhouse gases and is reflected back toward Earth/ absorbed by greenhouse gases (warms!)
Some of the radiation is reflected by the Earth’s surface back into space
Relationship between Greenhouse Effect and Rising Global Temperatures
-CO2 is a greenhouse gas that absorbs infrared radiation (IR/ heat), “trapping” heat and keeping the Earth warm (greenhouse effect)
-Over time, CO2 concentrations and Earth’s temperature have fluctuated naturally
-Anthropogenic (human-caused) activities (such as burning fossil fuels - combustion, and deforestation - removal of carbon sink) have led to increased CO2 in the atmosphere (more CO2 = more heat trapped = increased global temperatures)
-More heat causes polar ice caps to melt (reducing reflectivity of light from Earth’s surface too = even more heat re-radiated from Earth’s surface = more warming)
Deforestation, Industrialization, Increased Farming
increase greenhouse gas emissions (CO2, methane, water vapor, oxides of nitrogen) into the atmosphere - note that CO2 is increasing the most rapidly and this is due to anthropogenic combustion
Ocean warming and acidification threatening coral reefs/ marine organisms
More CO2 in atmosphere = more CO2 diffuses into oceans = more H+ ions and decreased pH (more acidic) - because CO2 combines with water to form carbonic acid which dissociates into bicarbonate and H+ ions
Decreased pH (acidic) dissolves calcium carbonate structures (shells/ exoskeletons of molluscs/ corals)
H+ ions combine with carbonate ions in water, reducing availability of carbonate ions to molluscs/ corals to build shells/ exoskeletons so thinner/ deformed/ populations reduced
Warmer temps cause corals to expel
zooxanthellae (symbiotic algae) which causes bleaching
Arctic ecosystems threatened
Warming temperatures melting permafrost which has
traditionally trapped methane; Faster decomposition at
higher temps, so more decomposition of detritus;
Decreased availability of ice to polar bears for hunting;
Migration patterns disrupted/ more species moving
north and temps not as cold, so more competition for
resources/ reduction in resources
Data to Support Global Warming
-Experimental data (Charles Keeling) from Mauna Loa, Hawaii
CO2 concentrations measured since 1958: “Keeling curve” shows a clear pattern of carbon flux
-Researchers measure CO2 in air bubbles trapped in ice and can determine year based on depth of the ice core (Note: CO2 levels appear higher now than any time in past 400,000 years! Yikes! – graph on right)
Anthropogenic Factors that Affect Carbon Fluxes
-Deforestation (less photosynthesis = more CO2 in atmosphere)
-Burning of fossil fuels
-Farming/ livestock (more methane into atmosphere)
Climate Conditions that Effect Carbon Fluxes
-Photosynthesis (fluctuates seasonally as more direct sunlight during summer seasons)
-Climate events (El nino etc.)
-Ocean temperatures (determine solubility of CO2 = inverse relationship; higher temps = less solubility)
-Polar ice caps melting (less reflectivity of light/ more decomposition of detritus)
Natural (ish) Factors that Effect Carbon Fluxes
-Forest fires (more CO2 into atmosphere/ less photosynthesis)
-Volcanic eruptions (CO2 into atmosphere)
