Cryosphere
The cryosphere is the frozen part of Earth: snow, sea ice, glaciers, ice sheets, ice shelves, frozen lakes and rivers, permafrost, and seasonally frozen ground. It stores freshwater, reflects sunlight, shapes ecosystems, influences sea level, and responds quickly to climate change.
What the cryosphere is
The cryosphere is the part of Earth where water exists in solid form. It includes seasonal snow, mountain glaciers, the Greenland and Antarctic ice sheets, floating sea ice, ice shelves, icebergs, frozen lakes and rivers, permafrost, and frozen ground. Some parts last only through winter; others preserve ice for thousands of years.
Snow and seasonal ice
Snow cover changes quickly with weather and seasons. It stores water in mountains, insulates soil, affects plant growth, and controls how much sunlight a landscape reflects. Frozen lakes and rivers can shape transportation, ecosystems, and flood risk. Because seasonal snow and ice respond rapidly to temperature, they are sensitive indicators of climate variability.
Glaciers and ice sheets
Glaciers form where snow survives long enough to compact into ice and flow under its own weight. Ice sheets are much larger bodies of land ice, mainly in Greenland and Antarctica. When land ice loses more mass than it gains, it contributes to sea-level rise. Glacier retreat can also alter river flow, hazards, sediment, and water supplies downstream.
Sea ice and ocean connections
Sea ice forms when seawater freezes, so it floats on the ocean and does not raise sea level when it melts. Its importance is still large: it reflects sunlight, insulates the ocean from the atmosphere, affects winds and currents, and provides habitat for polar ecosystems. Sea ice grows, drifts, fractures, ridges, and melts as winds, currents, and temperature change.
Permafrost and frozen ground
Permafrost is ground that stays at or below freezing for at least two consecutive years. It may contain soil, sediment, rock, ice, and ancient organic matter. When ice-rich permafrost thaws, the ground can slump, drainage can change, and infrastructure can be damaged. Thaw can also expose stored carbon to microbial decomposition.
Albedo and feedbacks
Snow and ice usually have high albedo, meaning they reflect a large share of incoming sunlight. When they melt, darker ocean water, soil, rock, or vegetation can absorb more energy. This can reinforce warming in a feedback loop, especially in polar and high-mountain regions. The cryosphere is therefore both a climate indicator and an active part of the climate system.
How scientists observe it
Researchers monitor the cryosphere with satellites, aircraft, field stations, ice cores, ocean buoys, radar, laser altimeters, GPS, weather records, and local observations. Satellites are essential because many frozen regions are remote, dangerous, dark for part of the year, or too large to measure only from the ground.
Why it matters
The cryosphere matters because frozen water connects climate, oceans, mountains, ecosystems, and human infrastructure. Its changes affect sea level, Arctic and mountain communities, freshwater timing, shipping, wildlife habitat, hazards, and global energy balance. Watching the cryosphere is one way to see climate change in motion.