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 ( 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 And

Last Class Relationship between CO 2 and Climate Sources and Sinks for CO 2 Human Influence on Atmospheric CO2

Absorption Spectra of Atmospheric Gases Anthes, p. 55 WAVELENGTH (micrometers)

CO 2 Variation But from ice core records we know that CO 2 changes naturally, and sometimes very quickly Temperature matches CO 2 change closely Positive or Negative Feedback? Change in greenhouse effect Sharp Changes

Biological Pump What if we change how efficient this is? Turn it off - CO 2 will rise in atmosphere to 720 ppm 100% efficient (i.e. use all nutrients CO 2 to 165 ppm CO 2 from atm.

Global CO 2 Variations Increasing trend with time Seasonal effect Larger in the N. Hemisphere Increase greater in N. Hemisphere

CO 2 - The Human Influence Burning Fossil Fuels –60% of total Changes in land use –“Pioneer Effect” –Deforestation –Loss of organic matter in soil –40% of total EuropeN.A.

Fossil Fuels Always increasing… Presently around 6 Gtons Europe, N.America and China account for almost all of this

Fossil Fuels and Atmospheric CO 2 Burning fossil fuels - release CO 2 to atmosphere But CO 2 in atmosphere is increasing slower than the rate at which we are burning fossil fuels

Atmospheric CO 2 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 CO 2 CO 2 is being transferred to another reservoir…. Rate is very fast… What carbon reservoirs are connected to atmospheric CO 2 with large fluxes?

CO 2 Sinks The Ocean –Dissolution of CO 2 -> 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

PoolsAmount (x10 15 gigatons C) Rocks 65,000,000 Oceans 36,000 Soils 1,500 Atmosphere* 760 Land plants560

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 CO 2 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 CO 2 –Everything living – natural sources –Land use change (e.g. deforestation) –Fossil Fuel Use Sinks for CO 2 - The ocean (both physical and biological) - Growing vegetation – (eventually into soil)

Annual atmospheric mass balance for CO 2 Major fluxes in to atmosphere Respiration = 100 (x g C / yr) Fossil fuels = 5.0 (x g C / yr) Biomass burning = 1.8 (x g C / yr) Major fluxes out of atmosphere Ocean uptake = 1.6 (x g C / yr) Photosynthesis = 100 (x g C / yr) Calculated rate of increase = 5.2

Annual atmospheric mass balance for CO 2 Major fluxes in to atmosphere Major fluxes out of atmosphere 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 CO 2 - ~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

CO 2 Feedback CO 2 Fertilization Increase CO 2 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 CO 2 + H 2 O + Sun Energy--> CH 2 O + O 2 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 CH 2 O + O 2 --> CO 2 + H 2 O + 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 Fishes % Zooplankton 0.01% Phytoplankton (algae) 0.1% Particulate Organic Matter 5% Dissolved Organic Matter95%

What controls marine photosynthesis? –Sunlight/ Energy –Nutrients –CO 2

Ocean Productivity Where is photosynthesis greatest? Map of Chlorophyll content in ocean High in high latitudes Where there is upwelling leading to high nutrient supplies Not where there is lots of sun

Map of Ocean productivity - nutrients are the key

Proposed "Fixes“ for removing atmospheric CO 2 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 - CaCO 3 –Dissolved CO 2 in water esp. the oceans –Atmospheric CO 2

Dissolved CO 2 Carbon Dioxide –Exchanges with atmosphere –Dissolves in water –Carbonic Acid CO 2 + H 2 O H 2 CO 3 Equilibrium Process - goes backwards and forwards - wants to maintain a balance Carbonic Acid

Dissolved CO 2 Dissolved CO 2 in water CO 2 + H 2 O H 2 CO 3 Carbonic Acid Dissociates - splits in to cations and anions H 2 CO 3 HCO H + HCO 3 - CO H + pH determines how much inorganic CO 2 the ocean can hold Ocean has a high pH - ~8 Cold Water dissolves CO 2 more readily Carbonic Acid Bicarbonate

Dissolved CO 2 What happens to anthropogenic CO 2 ? CO 2 + H 2 O H 2 CO 3 H 2 CO 3 + CO HCO 3 - Enhanced ability to absorb atmospheric CO 2 Increase CO 2 - dissolve more in oceans And form more carbonic acid But this reacts with carbonate present in ocean

Carbonate Precipitation In the Oceans… Reverse of carbonate weathering on land…. Ca HCO > CaCO 3 + H 2 CO 3 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 CO 2 Precipitate carbonate minerals

Ocean a Source or Sink Sinks vs. Sources Why this pattern? = Nutrients and CO 2

Examples: We’ve seen that light can limit productivity, So can water, and Certain nutrients too 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

In 1840, J. Liebig suggested that organisms are generally limited by only one single physical factor that is in shortest supply relative to demand. Liebig's Law of the Minimum ~1985 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 Hydrogen Carbon Zinc Molybdinum Oxygen Copper Calcium Phosphorus Magnesium Iron Iodine Potassium Nitrogen Sulfur

Order of Importance of Nutrient Elements in Different Environments On LandIn FreshwaterIn the Ocean 1) Nitrogen1) Phosphorus 1) Iron 2) Phosphorus2) Nitrogen 2) Phosphorus 3) Potassium3) 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 CO 2 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?