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$$$1.00$$$ to Alex - p.37, exercise 1.6 (a) “globally averaged surface pressure is 16 hPa lower than globally averaged sea-level pressure of 1013 hPa” p. 11, exercise 1.1 states, Globally averaged surface pressure is 985 hPa

Renee Alex Patrick Mehmet Andrew

Ocean structure definitions

The Carbon Cycle: Water cycle -> phase changes Carbon cycle -> chemical changes Why do we care ? Regulates 2 important greenhouse gases: Carbon dioxide CO 2, and methane CH 4

12 years 6,500 yrs 200,000 yrs Units in kg m -2

Increased evidence of human impact: Greenhouse Warming Monthly-mean C02 concentrations, Carbon Dioxide

Monthly-mean C02 concentrations, Carbon Dioxide increase only 1/2 of that predicted From fossil fuel consumption and forest burning

Where is the missing carbon ? Oceans appear to uptake more than they expend. Units in gigatons of carbon or Gt C

Carbon Exchange: CO 2 + H 2 O -> CH 2 O + O 2 photosynthesis CH 2 O + O 2 -> CO 2 + H 2 O respiration Rxn uses visible Light wavelengths Of 0.43 (blue) and 0.66 (orange) Micron. Plants Reflective in Near-IR

Euphotic zone takes up carbon dioxide, decaying matter Sinks it deeper.

Carbon in the Oceans: 1.CO 2 + H 2 O -> H 2 CO 3 carbonic acid 2.H 2 CO 3 -> H + + HCO 3 bicarbonate ion 3. HCO 3 -> H + + CO 3 2- Net: CO 2 + CO H 2 O -> 2HCO 3 This is connected to Calcium from the Earth’s mantle: Ca + 2HCO 3 -> CaCO 3 + H 2 CO 3 coral Where the Ca derived from the weathering of Rocks containing Ca-Si.

Sedimentation,Weathering,Metamorphosis Weathering increases with temperature

Oxygen: Unique component of Earth’s atmosphere Increasing with time: Photosynthesis creates oxygen - and - Reduction of water (H 2 O -> H 2 + O) via mineralization, with hydrogen escaping to space.

Oxygen in carbonates estimated from carbon mass.

Early Earth’s History, in brief: 1.~ 4.5 billion years ago (bya): accretion from planetesimals, evidence is lack of noble gases relative to cosmos. 2. 1st ~750 millions years, named Hadean Epoch: more bombardment, early atmosphere, moon 3. 1st production of O 2, bya. Low atmos. conc., but ozone layer 4. Increased O 2, 2 bya. -> 1st glaciation

Sudbury Shatter cones K-T extinction -> nuclear winter

Sun’s luminosity increases w/ time as core contracts. Why wasn’t Earth’s surface frozen ?

Initial high methane conc. gives way to oxygen -> 3 major glaciations. First is ~ 2.3 bya

2nd glaciation: ~ 2.5 million years ago. Reduced plate tectonics -> reduced volcanic emission of CO 2. + Increased sink of CO 2 in oceans through increased Atmospheric carbon Movement of Antarctica to SP -> increased albedo Drake Passage opens, Panama Isthmus closes -> Changing thermohaline circulation -> less poleward heat transport ->colder Arctic

3rd glaciation, within last million years Temperature, CO 2, CH 4 vary coherently. Antarctica ice core Decrease is quick, rise less rapid

Last glacial maximum 20,000 years ago Global sea level ~ 125 m lower CO 2 levels ~ 180 ppm Snow/ice extent preceeds CO2 changes

Venus Mars Jupiter Hot: No oceans: No hydrogen or water Atmosphere all carbon “runaway greenhouse Effect” Cold & small: No (liquid) water No vulcanism No atmosphere

WHY LIFE ON EARTH ? ROLE OF OCEANS: ROLE OF CHEMICAL PHYSICS: ROLE OF TECTONICS ROLE OF OTHER PLANETS: