Transcript Formation of the Earth Age of the Earth Structure of the Earth

A Historical Perspective
•People have been aware of climate
variability and incorporating in into their
local histories and folklore for thousands
of years.
– Levels of yearly Nile flood levels recorded
as early as 3000 B.C.
– Egyptian tombs have written records and
pictures of years of drought and famine
– Climatic catastrophes such as floods occur
in numerous accounts.
Early Scientific Writings
• Aristotle (384-322 B.C.) was
first to write on climate change
in a critical manner:
" The same parts of the Earth are
not always moist or dry, but
they change according as rivers
come into existence or dry up.
And so the relation of land to
sea changes too, and a place
does not always remain land or
sea throughout all time.... But
we must suppose these changes
to follow some order and
cycle."
Supplemental reading for March 25 – April 2
http://www.geog.ouc.bc.ca/physgeog/contents/9r.html
And
http://www.geog.ouc.bc.ca/physgeog/contents/9s.html
Last Class
Relationship between
CO2 and Climate
Sources and Sinks for
CO2
Human Influence on
Atmospheric CO2
Absorption Spectra of Atmospheric
Gases
WAVELENGTH (micrometers)
Anthes, p. 55
CO2 Variation
Sharp Changes
• But from ice core
records we know
that CO2 changes
naturally, and
sometimes very
quickly
• Temperature
matches CO2
change closely
• Positive or
Negative
Feedback?
• Change in
greenhouse effect
CO2 from atm.
Biological Pump
• What if we change
how efficient this is?
• Turn it off - CO2 will
rise in atmosphere to
720 ppm
• 100% efficient (i.e.
use all nutrients
• CO2 to 165 ppm
Global CO2 Variations
• Increasing
trend with time
• Seasonal effect
• Larger in the
N. Hemisphere
• Increase
greater in N.
Hemisphere
CO2 - The Human Influence
• Burning Fossil Fuels
– 60% of total
Europe
N.A.
• Changes in land use
– “Pioneer Effect”
– Deforestation
– Loss of organic
matter in soil
– 40% of total
Fossil Fuels
• Always increasing…
• Presently around
6 Gtons
• Europe, N.America
and China account for
almost all of this
Fossil Fuels and Atmospheric CO2
• Burning fossil fuels release CO2 to
atmosphere
• But CO2 in
atmosphere is
increasing slower than
the rate at which we
are burning fossil fuels
Atmospheric CO2 Budget
What we know
– Rate of fossil fuel
consumption (~10%)
– Atm. Increase (~4%)
What we don’t know
very well –
The controls on the
carbon cycle
Where is the missing CO2
• CO2 is being transferred to another
reservoir….
• Rate is very fast…
• What carbon reservoirs are connected to
atmospheric CO2 with large fluxes?
CO2 Sinks
• The Ocean
– Dissolution of CO2 -> carbonic acid ->
bicarbonate-> carbonate
• Reforestation - Northern Hemisphere
– Northeast US 1850’s ~20% forest - today ~80%
– 0.5 Gtons C/yr in northern hemisphere
• Fertilize Existing Forest
– The “Greening” of the earth
The Carbon Cycle
Pools (reservoirs) and fluxes
Controls on rates
Anthropogenic Impacts
Carbon Cycle
• Probably the most active area of
research in both geological and
ecological sciences
• Regulation of climate - paleo records
• Global Warming / Fossil Fuels
• What are the reservoirs of carbon?
The Major Components of the Carbon Cycle
The carbon cycle – system analysis.
What are the major pools of carbon?
What are the major fluxes of carbon?
Rocks
65,000,000
Pools
Amount (x1015 gigatons C)
Rocks
65,000,000
Oceans
36,000
Soils
1,500
Atmosphere*
760
Land plants
560
Carbon Reservoirs
• Organic vs. Inorganic
• Biologic vs Geologic
• Short term vs Long term
The carbon cycle – System analysis.
What are the major pools of carbon?
What are the major fluxes of carbon?
Atmospheric CO2 Budget
What we know
– Rate of fossil fuel
consumption (10%)
– Atm. Increase (1%)
• What we don’t
know very well
– Deforestation
– Greening
– Ocean uptake
Annual Fluxes w/r/t Atmosphere
• Photosynthesis – 100 gigatons C
• Respiration – 100 gigatons C
– Aerobic
– Anaerobic - fermentation
• Ocean Dissolution – 1.6 gigatons C
• Fossil Fuel use – 5.0 gigatons C
• Biomass burning – 1.8 gigatons C
Reservoirs affected - atmosphere, biomass, organic
carbon in soils/sediments, ocean, vegetation
•Sources of CO2
–Everything living – natural sources
–Land use change (e.g. deforestation)
–Fossil Fuel Use
Sinks for CO2
- The ocean (both physical and biological)
- Growing vegetation – (eventually into soil)
Annual atmospheric mass balance for CO2
Major fluxes in to atmosphere
Respiration = 100 (x 1015 g C / yr)
Fossil fuels = 5.0 (x 1015 g C / yr)
Biomass burning = 1.8 (x 1015 g C / yr)
106.8
Major fluxes out of atmosphere
Ocean uptake = 1.6 (x 1015 g C / yr)
Photosynthesis = 100 (x 1015 g C / yr)
Calculated rate of increase
- 101.6
= 5.2
Annual atmospheric mass balance for CO2
Major fluxes in to atmosphere
106.8
Major fluxes out of atmosphere
- 101.6
Calculated rate of increase
= 5.2
BUT!
Measured Rate of Increase equals
3.0!
We are missing 2.2 gigatons of carbon each year!
Residence Times
• CO2 - ~8 years
• Organic carbon in soil/sediments - 50 years
• Short term “life cycle” of carbon
– Photosynthesis - respiration
• Will repeat 500 times before a “leak”
– What is this leak to the system?
Hint – know how to calculate residence time
Natural Processes Cycling carbon
Biotic – autotrophs and heterotrophs
Abiotic – chemical reactions
Anthropogenic Impacts
Fossil Fuel Use
Land use
CO2 Feedback
•
•
•
•
CO2 Fertilization
Increase CO2 in atmosphere
Photosynthesis goes faster
But many other things limit biomass production
Photosynthesis
• Primary Productivity - the amount of organic
matter produced by photosynthesis per unit time
over a unit area
• CO2 + H2O + Sun Energy--> CH2O + O2
• Converts inorganic carbon to organic carbon
• Removes carbon from atmosphere to organic
carbon in biomass and soil organic carbon residence time about 10 years
• Producers or Autotrophs are the majority of
biomass
Respiration
• CH2O + O2 --> CO2 + H2O + Energy
• Reverse of photosynthesis
• Converts organic carbon to inorganic
carbon --> releases energy
• Consumers or Heterotrophs - organisms
that utilize this energy - small part of
biomass (1%)
• Aerobic respiration - with oxygen
Respiration, cont.
• Processes is accelerated by enzymes
• Half of gross primary productivity is
respired by plants themselves
• Other half is added to organic layer in soils
--> microbes - bacteria and fungi break
down this organic matter
• Below the surface - Anaerobic respiration
without oxygen
Marine vs. Terrestrial Carbon
Cycling
• Primary Productivity takes place both
in oceans and on land
• On lands - green plants
• In oceans - phytoplankton - free
floating photosynthetic organisms
• What controls marine photosynthesis?
Biological Pump
• Photosynthesis occurs
in shallow ocean but
decomposition is in
deep ocean biological pump
moving nutrients and
carbon
• Where is
photosynthesis
greatest?
• Link this idea with
deep ocean circulation
Carbon Reservoirs in Ocean
• Carbon in
the oceans is in these
four forms + Biomass
- But Biomass is difficult
to measure
•What are the controls
on the size and residence
time of carbon in these
pools?
Relative Abundance of Organic Carbon in the Ocean
Dissolved Organic Matter
95%
Particulate Organic Matter
5%
Phytoplankton (algae)
0.1%
Zooplankton
0.01%
Fishes
0.0001%
• What controls marine photosynthesis?
–Sunlight/ Energy
–Nutrients
–CO2
Ocean Productivity
High in high latitudes
• Where is
photosynthesis
greatest?
•Where there is upwelling
leading to high nutrient
supplies
•Not where there is lots of
sun
Map of Chlorophyll content in ocean
Map of Ocean productivity
- nutrients are the key
Proposed "Fixes“ for removing atmospheric CO2
The "Geritol Fix"
- algal growth in the southern oceans is limited by Fe. If you add
Fe you stimulate growth and the uptake of CO2 from the
atmosphere by algae.
- reduce our atmospheric CO2 concentrations by 10%.
Fertilizer Effect
- CO2 stimulates the growth of land plants - we could solve the
whole greenhouse gas problem by planting more trees.
- problem finding enough nutrients and water!
Inorganic Carbon
• Cycling of carbon that does not involve
biology or organic carbon… (but is closely
linked!)
• Important Reservoirs
– Limestone - CaCO3
– Dissolved CO2 in water esp. the oceans
– Atmospheric CO2
Dissolved CO2
• Carbon Dioxide
– Exchanges with atmosphere
– Dissolves in water
– Carbonic Acid
• CO2 + H2O <----> H2CO3
Carbonic Acid
• Equilibrium Process - goes backwards and
forwards - wants to maintain a balance
Dissolved CO2
Carbonic Acid
• Dissolved CO2 in water
• CO2 + H2O <----> H2CO3
• Carbonic Acid Dissociates - splits in to cations
and anions
• H2CO3 <----> HCO3- + H+
Bicarbonate
• HCO3- <----> CO32- + H+
• pH determines how much inorganic CO2 the
ocean can hold
• Ocean has a high pH - ~8
• Cold Water dissolves CO2 more readily
Dissolved CO2
• What happens to anthropogenic CO2?
• CO2 + H2O <----> H2CO3
Increase CO2 - dissolve more in oceans
And form more carbonic acid
• H2CO3 + CO32- <----> 2HCO3But this reacts with carbonate
present in ocean
• Enhanced ability to absorb atmospheric CO2
Carbonate Precipitation
• In the Oceans…
• Reverse of carbonate weathering on land….
Precipitate
carbonate
• Ca2+ + 2HCO3- --> CaCO3 + H2CO
3
minerals
• Most formed biotically - that is through organisms
such as forams and cocco. As the structural part of
their skeletons
• Can also form abiotically
• Shift carbonate equilibrium - dissolve more CO2
Ocean a Source or Sink
• Sinks vs.
Sources
• Why this
pattern?
• = Nutrients
and CO2
Limiting Factors for Biological Productivity
- Plants never seem to be able to “fix”, or assimilate all
- The carbon available to them – something is limiting production
- This is true both on land and in the ocean
Examples:
We’ve seen that light can limit productivity,
So can water, and
Certain nutrients too
Liebig's Law of the Minimum 1840 - ~1985
In 1840, J. Liebig suggested that organisms are generally limited by
only one single physical factor that is in shortest supply relative to
demand.
Now thought to be inadequate – too simple!
- complex interactions between several physical factors
are responsible for distribution patterns, but one can
often order the priority of factors
Temperature is a strong
Limiting factor.
Although plants in colder
areas are optimized for
Colder conditions
Water also is a strong
Limiting factor.
Much steeper curve =
A much stronger positive
Reaction
i.e. a little water goes a long way!
As we’ve seen, nutrients are often limiting.
Why nutrients?
Needed for enzymes, cellular structures, etc.
Pretty much analogous to vitamins for humans
Soon as you meet the requirements for one, another
ends up being limiting
Nutrient elements needed for all life
C HOPKINS Mg CaFe run by CuZn Mo
Carbon
Molybdinum
Hydrogen
Zinc
Oxygen
Copper
Phosphorus
Potassium
Iron
Iodine
Nitrogen
Calcium
Sulfur
Magnesium
Order of Importance of Nutrient Elements in Different Environments
On Land
In Freshwater
In the Ocean
1) Nitrogen
1) Phosphorus
1) Iron
2) Phosphorus
2) Nitrogen
2) Phosphorus
3) Potassium
3) Silica
3) Silica
Tuesday
Carbon Pools,
Photosynthesis,
& Respiration
Today
- Exam Grades
-Links to Ocean
-Links Geologic Cycle
-Per Capita Emissions
-In-Class Activity
There is no doubt CO2
Concentrations are increasing
Concurrently with increase
human use
Ocean a Source or Sink
• Sinks vs.
Sources
• Why this
pattern?
• What affect
will
increased
CO2 have?