Pack ice refers to a large area of sea ice that forms when ocean water freezes, creating a floating layer of ice. This ice can vary in thickness and is typically found in polar regions, such as the Arctic and Antarctic. Pack ice is made up of many individual ice floes that can drift and shift due to wind and ocean currents. Pack ice plays a crucial role in the Earth's climate system by reflecting sunlight and helping to regulate temperatures. It also serves as a habitat for various marine species, including seals and polar bears, which rely on the ice for breeding and hunting.