When sea ice melts, the darker ocean surface that is revealed absorbs more solar radiation, which in turn causes warming and melts more ice, which in turn creates a greater area of darker ocean surface. What is this process called?

This process is called polar ampliication.

Explanation:

As intuitive as it sounds, it really is akin to an amplification process. Small changes in ice sheet cover cause net larger changes as a consequence. This is because when the ice sheet reduces, the albedo effect –the tendency of earth surface to reflect sunlight back to space- also reduces. Remember ice sheets are white hence high albedo. Reduced albedo effect means the oceans get warmer which melts more ice sheets reducing albedo even farther and causing even more warming.

the answer is 12 as i may remember

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3. dark matter

empty space could also be a simple vacuum