GEOLOGICAL - GEOGRAPHICAL Causes of Climate Change

CHRONOLOGICAL SCALE
109 106 103 102 10 YR
    GEOLOGIC 1. 2. 3. 4. 5. 6. 7. 4.
GEOGRAPHICAL SCALE
  Local  Regional  Global 
    GEOLOGIC 4. 6. 5. 7. 1. 2. 3.

EFFECTS OF GEOLOGICAL EVOLUTION OF THE EARTH'S SURFACE


PRECAMBRIAN TEMPERATURE: heat capacity of water vs. land

1. THE LACK OF CONTINENTS prior to 2.5 Gy allowed more efficient poleward heat transport and prevented growth of polar ice caps
(Endal and Schattaen, 1982)

Seasonality would be less pronounced in continent-less world


2. GLOBAL PALEOGEOGRAPHY of the late Precambrian, Permian, and Pleistocene, were similar
- large land masses covered the polar areas.
Pre-Pleistocene Glacial Epochs: Permian, Silurian/Devonian, Precambrian
    Pleistocene:
      Greenland, Antarctica at poles
      Arctic Basin Closed, permanently frozen
    Permian:
      Gondwana: Antarctica, South Africa, India at South Pole

A. Polar landmasses serv as a platforms for ice sheet e.g., S. Greenland @ 60o N
  • no summer melting (SUMMER TEMPERATURE CRITICAL)
  • high albedo of snow, ice further reduces temperature
  • glaciers create their own climate
  • lower sea level produces exposed continental shelf: high albedo, dust in atm.

B. Lower specific heat of land vs. water
  • land, at poles, cools faster than water at poles, freeze every night
  • air above water = 0
  • air above sea ice << 0

C. Closed basins promote accumulation of sea ice


 D. Continental Geography effected oceanic circulation:
  • Tertiary - blocking of equatorial circulation forced pole-ward movement of warm water which provides a moisture source for glacier growth: glaciers may "starve" in cold climate
  • Paleocene (50 - 60 My) - opening of Norwegian and Labrador seas allowed cold water to enter the North Atlantic
  • Oligocene (30-37 My) - circumpolar circulation after opening of Drake Passage separation of Australia 37 my permitted glacier buildup on Antarctica
  • Pliocene (3-4 My)
    • closure of Bolivar Trench (Panama) ca. 3 my preceded global cooling, similar to Permian - Pangea at Equator forces N-S oceanic circulation
    • closure of Indonesian seaway preceeded African drying (Cain & Molnar, 2001)
http://www.scotese.com/
3. SEA FLOOR SPREADING CONTROLS ATMOSPHERIC CO2: (Berner et al., 1983)
Effects of atmospheric CO2 and Ca, Mg and HCO3 in the ocean
  • sea-floor spreading: subduction at plate margin results in metamorphism of carbonates, volcanism injects subducted C, as CO2, into atmosphere
  • negative feedback: increased atm. CO2 increases temperature and accelerates weathering; i.e., production and burial of calcite and dolomite

    Worsley et al., (1986) suggest that 0.5 by cycle of climatic change results from cycles of tectonism, seafloor spreading, atmospheric change.





4. LGM ICE MOUNTAIN EFFECT

(regional)

Glacial Anti-Cyclone
(COHMAP, 1988)
  • moist air from Pacific Ocean to the polar ice
  • cold air from glaciers westward into continents

5. TECTONISM AND THE PLEISTOCENE COOLING

(regional)
  • last 2 my uplift Tibetan Plateau and American Intermountain Region
  • deflects zonal circulation
    • stronger zonal westerlies
    • northward deflection of westerlies brings moist air to polar ice

6. TECTONISM AND THE PLEISTOCENE RAINSHADOWS

(local)
  • last 2 my uplift Sierra Nevada and Colorado Plateau
    • Sierra Nevada Rainshadow creates deserts
    • Higher Colorado Pleateau is colder and wetter

7. TECTONISM AND MONSOON ACTIVITY

(regional)

(Parrish & Petersen, 1988) - Permian
primary factors


Geological Climate Readings


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