Snow, Ice, and Permafrost

How does Climate Change Affect Snow and Ice? 

Frozen landscapes profoundly shape their natural and human communities. Plants, animals, and humans have evolved to deal with the challenges that characterize the cold – navigating slippery ice and deep snow, finding and storing food through long winters, staying warm, etc. Yet a warming Earth is shifting seasonal temperatures and precipitation patterns, affecting rain, snow, and ice across the globe. This has a particularly dramatic impact on the parts of the Earth dominated by snow, ice, and frozen ground, called the cryosphere.  

Snow and ice are critical elements of the Earth’s water supply. While rainwater gets absorbed into watersheds almost immediately, frozen water is effectively inaccessible until it melts. Thus, snow and ice can “store” water over cold periods (such as winter months or ice ages) and release it during warmer periods. Winter snowpack is a seasonal “savings account,” releasing meltwater slowly over warm summer months. Sea ice and glaciers are more like long-term water “savings bonds.” Sea ice freezes for months or years, capping oceans at the poles with bright white reflective surfaces. Glaciers can store water for millennia at a time, trapping so much water on land that it affects global sea levels. However, warming temperatures are melting these resources at rates never seen before, threatening wildlife, water supplies, and coastal communities facing sea level rise. 

Sources/Usage: Public Domain. View Media Details

Snow

When snow falls on higher elevations, it accumulates as snowpack. As the snowpack melts, it waters lower elevation landscapes over spring and summer months. In some areas of the Rocky Mountains, snowmelt provides almost 70% of the water local communities depend on for municipal water, irrigation, and hydroelectric dams. The timing of snowmelt affects not only when water is available for communities and ecosystems, but also the risk of hazards like avalanches, floods, and wildfires. 

Warmer temperatures from climate change often translate into less snowy winters, or winters where it rains instead of snows. This means less snowpack, and less water “saved up” for later in the year. Many communities are also experiencing earlier and faster snowmelt, leading to repercussions on water supply, risk management, tourism, and ecosystem health in Western watersheds. Less snow also impacts plants and animals of the region. Some species benefit from earlier spring green-ups or from not having to navigate icy hazards. Yet this is bad news for snow-dependent species, like snowshoe hares that need white snow for camouflage or small animals that hibernate underneath insulating snowbanks.  

Sources/Usage: Public Domain. View Media Details

Sea Ice 

For at least part of the year, sea ice covers approximately 15 percent of the global ocean, mainly in polar regions. All this sea ice influences global climate and major weather patterns. In winter, it acts as a thermal blanket, trapping heat in the oceans. Sea ice also reflects solar radiation, keeping polar temperatures much cooler than those at the equator. Sea ice is crucial to wildlife and human communities in the Arctic. Walruses, seals, polar bears, Arctic foxes, many bird species, and even microorganisms such as phytoplankton rely on sea ice as habitat. People in the Arctic also depend on stable sea ice for winter transportation and hunting. 

Warming temperatures delay the formation of sea ice and hasten its melting. This results in larger areas of open water—which absorb more solar radiation—for longer periods each year. This raises ocean temperatures and sets off a feedback cycle of warming and melting. This is especially pronounced in the Arctic, where ice forms over open water. Changes in sea ice cover also disrupt how ocean currents behave, affecting nutrient flows and marine communities.  As the ice-free season lengthens, the Arctic coast is more susceptible to erosion from waves and storm surge, threatening Arctic communities, infrastructure, and ecosystems.  

Sources/Usage: Public Domain. View Media Details

Glaciers 

Glaciers play an important role in both local and global water cycles. Glaciers typically gain ice through snow accumulation each winter (accumulation season) and lose ice through melting each summer (melt season). Glacier meltwater released during summer months dumps cold freshwater into lakes, streams, and oceans. These freshwater influxes feed unique local ecosystems, for example creating ideal habitat for coldwater salmon in Alaska. Glaciers are also important for human communities, contributing to agriculture, hydropower, recreation, and tourism. On a global scale, glaciers act as “long term savings” for much of the world’s freshwater (almost 70%, to be exact). If all the glaciers were to melt at once, the ocean would rise 230 feet, creating a very different world! 

Glaciers are tightly linked to climate. Climatic warming in the last century has resulted in substantial glacier ice loss around the world. As climate change has intensified over the several decades, glacial melting has become noticeable even within a human lifespan. Loss of glaciers contributes to sea-level rise and can alter both freshwater and marine habitats. Retreating glaciers leave behind scarred and destabilized landscapes, increasing the risks of hazards such as ice avalanches and glacial lake outburst floods. Over time, these landscapes will transform into new ecosystems, altering the biological communities of the region. 

Permafrost 

Water is not the only frozen resource in cold climates. Soil can also freeze, locking nutrients and organic matter into an underground material called permafrost. The top layer of soil above permafrost thaws and re-freezes every year, providing a seasonal foothold for hardy plants and releasing water and nutrients into the ecosystem. 

Climate change is causing permafrost across the world to melt. This dramatically alters the specialized ecosystems that have evolved around them – softening the soil, shifting nutrient flows, even releasing different minerals into both surface water and groundwater. Thawed permafrost also releases previously locked-away carbon dioxide, transforming permafrost landscapes from an important carbon sink into a major carbon source. Thawing permafrost coastlines are also more susceptible to erosion from waves and storms, transforming coastlines across the Arctic. 

USGS Science helps Understand the Impacts to Cryosphere

Reduced high elevation snowpack and declining sea ice, glaciers, and lake ice is not something that is easily reversed.  However, we can work to understand how these losses will affect people and the Earth’s ecosystems. USGS scientists provide critical information and tools to mitigate climate impacts to snow, ice, and permafrost.   

USGS research helps to: 

• Understand current and predict future changes to the cryosphere, including seasonal snowpack, sea ice, glacier, and permafrost dynamics

• Understand impacts of snow and ice loss on plants, animals, and human communities 

• Identify climate refugia that may retain cold conditions and shelter cold-dependent species 

• Quantify climate change repercussions of greenhouse gas emissions from melting ice and permafrost 

• Help communities understand, predict, and prepare for hazards such as landslides, avalanches, and glacial lake outburst floods 

• Understand relationships between snow/ice loss and droughts, floods, and fires 

• Understand, monitor, and predict coastal erosion in the Arctic 

Sources/Usage: Public Domain. View Media Details