Quaternary Environments Climate and Climatic Variation Geologic Time

Quaternary Environments Climate and Climatic Variation

Geologic Time Scale

Glacial Time Scales in the Northern Hemisphere

Blytt-Sernander Scheme of European Peat Stratigraphy

Scale of Variation

The Climate System T End-product of T Atmosphere T Oceans T Biosphere T Land surface T Cryosphere

Major Components of the Climate System

Atmosphere T Clouds T Atmospheric circulation T Greenhouse gasses (Water, Carbon Dioxide, Methane, Nitrous Oxides) T Temperature T Incoming solar radiation (INSOLATION)

Insolation (W/m 2)

Oceans T Thermohaline Circulation T Thermal Inertia T Source of Moisture T Sea Level Rise T Melting of ice sheets T Thermal expansion

Thermohaline Circulation (Schmitz 1995)

Cross Section of Thermohaline Circulation (Brown et al. 1989)

Biosphere T Vegetation Effects on Climate T Albedo T Roughness T Evapotranspiration T Atmospheric T Vegetation composition Response to Climate T Faunal Response to Climate

CO 2 Sequestration

Land Surface T Effects of Land Surface on the Climate System T Aspect T Elevation T Albedo T Response T River to the Climate System systems T Sea level change T Glacial evidence

Cryosphere T Ice Extent T Albedo T Feedback Effects T Temperature Control

Energy Balance in the Atmosphere T Sensitive heat flux (H) T Latent heat flux (LE) T Bowen Ratio (H/LE)

Energy Balance

Time Scales of Climatic Variation T Climate Varies on All Time Scales T Driving Processes

Climate Variation Over Multiple Scales

Variations of the Earth’s Orbital Parameters T James Croll; Scottish natural historian 1867 T Milankovitch; Elaborated on Croll’s original hypothesis in 1941 T Berger; Advances Milankovitch’s work in the late 1970 s

Milankovitch Cycles T T T Eccentricity – 95, 800 year period. Changes in the orbital path of the Earth around the Sun. Affects the relative intensities of the seasons. Obliquity – 41, 000 year period. Changes in axial tilt of the Earth. Precession – 21, 700 year period. Wobble of the axis causing a precession of the equinoxes. Perihelion during Northern Hemisphere summer occurred 11, 000 years ago.

Orbital Factors

Wobble on the Earth’s Axis

Precession

Insolation and 18 O

Long Term Solar Radiation

http: //www-istp. gsfc. nasa. gov/Education/Intro. html; Illustration by Steele Hill