Cryosphere is the collective component of the Earth system where water exists in a frozen state, including snow cover, sea ice, lake and river ice, glaciers, ice sheets, and permafrost. As a research field, it investigates the distribution, properties, processes, and dynamics of these frozen elements and their profound interactions with the atmosphere, hydrosphere, lithosphere, and biosphere, recognizing their critical role in regulating global climate, sea level, and ecosystem functioning.