Factor Influencing Climate Change • Tectonics • Ocean Circulation Patterns and the Thermohaline Cycle • Orbital Forcing Mechanisms • Atmospheric Variations
Climate Reconstruction Using Proxy Records • Ice Cores • Marine Sediments • Banded Corals • Pollen • Tree Rings • Loess • Speleothems • Varved Lake Sediments • Peat • Geomorphological Evidence • Historical Evidence
Thermohaline Cycle • Driven by TEMPERATURE and SALINITY • Shutdown of the system causes periods of cold -Shutdowns caused by: Freshwater pulses and changes in temperature which causes changes in density • The “bipolar seesaw” theory -Shutdown of the thermohaline cycle causes cold in the Northern Hemisphere and warming in the Southern Hemisphere and vice versa.
Orbital Forcing Mechanisms • Obliquity - tilt of the Earth • Precession – Shape of the Earth Orbit about the Axis (think top) • Eccentricity – Shape of the Earth’s Orbit about the Sun
Orbital Forcing Mechanisms cont. • All factors influence insolation -How much of the radiation from the sun is being trapped within the Earth’s Atmosphere • Insolation decrease promotes cooling and ice sheet growth • Insolation increase promotes warmth and ice sheet melting
Atmospheric Variations • Rising concentrations of Greenhouse gases • Methane, CO2, water vapor, SO4 • Rises caused by: • Anthropogenic effects • Shutdown of Thermohaline Cycle • Orbital Forcing • Increased plant life (burial vs. growth)
Atmospheric Variations cont. • Volcanic Eruptions • Albedo (positive feedback) • Reflection of radiative heat
Final Thoughts • Dating is the most crucial aspect of climate reconstruction, but is the most difficult to perfect, • No one record, or person, has all of the answers. You need to put together all of the information, and ask questions, in order to understand picture being painted.