Explain the positive feedback mechanism involving snow and albedo.

• A. Snow melts, decreasing albedo (reflectivity), which increases temperature and leads to further melting
• B. Snow increases albedo, cooling the surface and stopping melt
• C. Snow has no effect on albedo
• D. Snow cover reduces solar absorption leading to warming

Answer: (A)

Snow has a high albedo, meaning it reflects a large portion of incoming sunlight back to space, which helps keep the surface cooler. When snow starts to melt, the surface becomes darker as the white cover recedes or becomes dirty, and the albedo drops. Darker surfaces absorb more solar energy, so the surface warms up. That extra heat speeds up further melting, which reduces albedo even more, leading to even more warming and more melting in a self-reinforcing cycle. This positive feedback is especially strong in regions where snow cover dominates the surface energy balance, such as high latitudes and alpine areas. The key idea is that melting decreases reflectivity, which increases absorption of sunlight and drives additional melting.