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How did changes in snow cover amplify cooling during Pleistocene ice ages?

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Map showing the extent of the Laurentide, Cordilleran, and Greenland ice sheets during the Wisconsin glaciation, roughly 100,000 to 11,000 years ago. The Laurentide Ice Sheet covers most of present-day Canada and parts of the northern United States in light blue, the Cordilleran Ice Sheet covers the Pacific Northwest in teal, and the Greenland Ice Sheet is marked in purple. Modern international and state or provincial boundaries are outlined for reference. — Pleistocene Epoch Ice sheets during the Wisconsin glacial episode penetrated deep into North America.

During the Pleistocene Epoch, changes in snow cover acted as a critical feedback mechanism that amplified the cooling initiated by orbital variations. The primary driver of this amplification is albedo, which refers to the reflectivity of the Earth's surface.12

As snow cover increases in high-latitude areas, the surface becomes more reflective, causing a larger proportion of incoming solar radiation to be reflected back into the atmosphere rather than being absorbed by the ground. This reduction in surface absorption leads to further cooling, which in turn encourages the persistence and expansion of snow and ice. This process creates a positive feedback loop: as the surface remains cooler due to high albedo, more snow can accumulate and survive through the summer, which maintains or increases the high-albedo surface area, thereby reinforcing the cooling trend.132

This mechanism is essential for explaining why relatively small changes in solar radiation caused by orbital cycles resulted in the significant climatic shifts observed during the Pleistocene.2