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Why did Gondwana’s movement over the South Pole matter to Ordovician climate?
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Ordovician Period
The distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the Ordovician Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.
The movement of Gondwana over the South Pole was a critical factor in triggering the terminal Ordovician glaciation, despite the period's generally high atmospheric carbon dioxide levels.1
This geographic placement facilitated cooling through several key mechanisms:
- Albedo Effect: Once snow began to accumulate on the landmass of Gondwana, the increased albedo (surface reflectance) of the snow cover fostered lower temperatures, which in turn encouraged further snow accumulation and the development of a glacial period.1
- Carbon Cycle Feedback: The presence of the ice sheet eventually hindered the removal of carbon dioxide from the atmosphere. As thick layers of glacial ice covered the continent, silicate rocks were shielded from the atmosphere, reducing the rate of chemical weathering—a primary natural process for sequestering carbon.1
- Oceanic Circulation: The resulting glaciation chilled surface waters, causing them to descend and displace warmer deep-ocean water. This accelerated ocean circulation and increased the upwelling of nutrient-rich waters, which boosted the productivity of photosynthetic organisms and further influenced atmospheric carbon levels.12