Both the polar regions are cold because they get very less solar radiation than mid latitudes and the tropics.
Explanation:
South Pole is very cold than the North Pole because as it is situated on the top of thick ice sheet. The surface of the sheet of ice at the South Pole is higher than 9000 feet altitude than mile half above the sea level.
Antarctica is the highest continent present in the Earth, Comparing to that in the middle portion of the Arctic Ocean the North Pole resides , where the floating ice surface moves only a foot or it is above the sea that is surrounded.
The Arctic Ocean acts as a heat reservoir that warms the cold atmosphere during winter and draws heat from atmosphere during summer.