Pack ice refers to a type of sea ice that forms when ocean water freezes and the ice drifts together in large, floating masses. This ice can vary in thickness and is typically found in polar regions, such as the Arctic and Antarctic. Pack ice plays a crucial role in regulating the Earth's climate by reflecting sunlight and insulating the ocean. Pack ice is important for various marine ecosystems, providing habitat for species like seals, polar bears, and penguins. It also affects shipping routes and weather patterns. As climate change progresses, the extent and thickness of pack ice are changing, impacting both wildlife and human activities.