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Reminders

Reminders. Midterm Exam 10/19 – in class. Material through 10/14 . Review Sessions: Fri. 14th, 4-5 pm, Angell C Mon. 17th, 4-5pm, 1040 Dana No lab meeting next week, instead…there is a TAKE HOME ASSIGNMENT: “The Science Behind Media Reports”

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Reminders

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  1. Reminders • Midterm Exam 10/19 – in class. Material through 10/14 . Review Sessions: Fri. 14th, 4-5 pm, Angell C Mon. 17th, 4-5pm, 1040 Dana • No lab meeting next week, instead…there is a TAKE HOME ASSIGNMENT: “The Science Behind Media Reports” • Remember that your project proposal is due the week of Oct. 25th before your lab section

  2. General Lab Comments • Questions about last week’s lab • Lecture questions • Read over your writing

  3. Goal of Today’s Lab • Using Excel, analyze data from the Vostok Ice Core • Perform paleoclimate calculations using isotope ratios and greenhouse gas concentrations • Understand mechanisms behind climate change and the magnitude of past changes

  4. Some background on… • Vostok and Glacial Ice • Isotope Hydrology • Milankovitch Theory

  5. Vostok, Antarctica A “two-mile time machine” Source: LDEO, Columbia University

  6. Subglacial Lake Vostok • Sealed from atmosphere for 15 My • Evolutionary implications? • Possible location for X-Files alien mothership

  7. Ice accumulates in annual layers Source: Earth’s Climate, Ruddiman

  8. Snow Sintering Source: Raynaud, 1992

  9. Bubbles in the Ice Small bubbles appear as round inclusions – see the orange crystal in center Fossil air! http://domefuji.at.infoseek.co.jp/gif/core150.jpg http://academic.emporia.edu/aberjame/ice/lec11/lec11.htm

  10. Hydrogen Isotopes • Hydrogen has two stable isotopes • 1H and 2H

  11. Oxygen Isotopes Three stable isotopes: 16O, 17O, 18O

  12. Hydrogen & Oxygen Isotopes D = 8*18O + 10

  13. What happens to the ratios?

  14. Oxygen Isotopes and Climate Interglacial Glacial 16O 16O 16O, 18O 18O (Stanley, Earth System History)

  15. Milankovitch Cycles • Past changes in climate have often been triggered by changes in orbital characteristics. • Variations in earth’s eccentricity, obliquity, and precession alter the seasonality of solar radiation. • It is the seasonality and location of insolation that impact the contrast between the seasons (not total solar energy). Serbian mathematician Milutin Milankovitch

  16. Eccentricity Deviation of the shape of the Earth’s orbit around the Sun from a perfect circle. Varies between: -0.03 and +0.02 Cyclicity: 100ka & 413ka Source: Earth’s Climate, Ruddiman

  17. Obliquity (a.k.a, Axial Tilt) • Inclination of the Earth’s axis in relation to its plane of orbit around the Sun Source: Earth’s Climate, Ruddiman Varies between 22.5° and 24.5° Cyclicity: 41ka

  18. How is the distribution of insolation affected in each case? Source: Earth’s Climate, Ruddiman

  19. Precession Earth’s slow wobble as it spins on axis Varies between 22.5° and 24.5° Cyclicity: 23ka Source: Earth’s Climate, Ruddiman

  20. Milankovitch theory of climate change Glacial Ice Growth Configuration: • Low eccentricity • Low Tilt • Large Earth-Sun Distance in NH Summer Net Effect: Less seasonal contrast

  21. Milankovitch theory of climate change Inter-Glacial Ice Growth Configuration: • High eccentricity • High obliquity (tilt) • Small Earth-Sun Distance in NH Summer Net Effect: More seasonal contrast

  22. Eccentricity Obliquity Precession Adding cycles creates new cycles! Cyclicities Source: Earth’s Climate, Ruddiman

  23. CO2, CH4, and Temperature T CH4 CO2

  24. CO2, CH4, and Temperature Both CO2 and CH4 are greenhouse gases. Warmer temperatures are associated with higher levels of greenhouses gases and vice versa. What could affect the levels of CO2 in the atmosphere? • Burning of fossil fuels (Anthropogenic effects) • Uptake of CO2 from the oceans via the “biological pump” – feedback loop • Weathering reactions (break down of granites consumes CO2)

  25. Dust and Temperature Change vs. Age During glacial times, sea level was lower, exposing the continental shelves. What consequences does this have for dust concentrations?

  26. Now it’s your turn!

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