Dense ice is a type of ice that has a high concentration of water molecules packed closely together. This structure makes it heavier and more compact than regular ice, which is less dense due to air pockets trapped within. Dense ice is commonly found in glaciers and polar regions, where the pressure from overlying layers compresses the ice. The formation of dense ice occurs through processes like recrystallization, where existing ice crystals change shape and size under pressure. This type of ice plays a crucial role in the Earth's climate system, influencing sea levels and ocean currents, particularly in areas like the Arctic and Antarctic.