First-year ice refers to sea ice that has formed and survived for a single winter season and can grow to 2 metres thick. It is typically thinner and more vulnerable than multi-year ice. The new ice in the Arctic and Antarctic is significant. It has an impact on the amount of ice present, its growth, and animal habitats. Monitoring and studying first-year ice is important in understanding the dynamics of polar ice cover and its response to climate change.

Multi-year ice is ice that has survived at least two melting seasons, making it at least two years old. It remains stable in a steady climate, enduring through the summer after the winter. However, warmer summers pose a threat, causing more of it to melt. When perennial ice melts below a thickness of 2 metres, it becomes detached. Multi-year ice forms when ice floes settle on older ice or land. It serves as a nucleus for the freezing season, maintaining thickness and snow cover. Bright and reflective, it cools the Arctic during sunny summers. Less multi-year ice means darker ocean surfaces, faster heating, more heat stored in summer, and increased ice melting.

Marginal Ice Zones (MIZ)are defined as the transitional zone between open sea and dense drift ice. It is usually not a sharply demarcated edge but a belt comprising ice floes with patches of open water in between them. The MIZ consist of first-year and multi-year ice. When seawater freezes, the salt is expelled, causing the ice to float on the sea surface. The channels and small spaces created by salt rejection and ice melting provide habitats for tiny animals and algae.