Explanation:

so that it can cool the whole interior by setting up convection currents 

-In a refrigerator, the freezer at the top of the unit contains the evaporator, which cools the air. Cold air is more dense than warmer air, so it sinks to the bottom of the freezer. There the cold air flows through vents (usually inside the meat keeper) into the refrigerator cabinet where it sinks to the bottom of the fridge (the crisper). Air warmed by the contents of the fridge rises as the cold air displaces it, and the 'warm' (only a few degrees difference) air enters into the freezer compartment where the cycle begins again.