While most of Earth’s water is saline, a crucial portion exists as freshwater. This freshwater is distributed across various reservoirs, including lakes, rivers, groundwater, and significant amounts locked away in frozen forms.
The Global Picture of Frozen Water
Approximately 2.5% to 3% of all water on Earth is freshwater. Of this, a significant majority, ranging from nearly 69% to 90%, is locked within ice and snow. This makes frozen water the planet’s largest reservoir of available freshwater.
Where Earth’s Frozen Water Resides
The planet’s frozen water primarily resides in massive ice sheets and glaciers. The Antarctic Ice Sheet, covering about 14 million square kilometers, holds the largest volume of ice on Earth, containing around 26.5 million cubic kilometers of ice. This single ice sheet accounts for approximately 61% of all freshwater on Earth. The Greenland Ice Sheet is the second largest, encompassing about 1.7 million square kilometers and containing roughly 2.9 million cubic kilometers of ice.
Beyond these immense ice sheets, mountain glaciers and ice caps contribute to the global frozen water inventory, with over 200,000 distinct glaciers worldwide. Permafrost, ground that remains frozen for two or more consecutive years, also contains significant ice, particularly in Arctic and high-latitude regions. Sea ice, formed from frozen ocean water, is another component of Earth’s cryosphere; its melting does not directly contribute to global sea level rise, unlike land-based ice.
The Vital Role of Frozen Water
Frozen water maintains Earth’s systems and supports life. Ice sheets and glaciers serve as the planet’s largest freshwater reservoirs, supplying water to rivers and streams that sustain billions of people, particularly in mountainous regions. This stored water is crucial for irrigation, hydropower generation, and potable water supplies.
These expansive ice covers also influence global climate through the albedo effect. Their bright, reflective surfaces bounce a large portion of incoming solar radiation back into space, helping to regulate Earth’s temperature. Sea ice acts as an insulating layer between the ocean and atmosphere, influencing heat exchange and contributing to global ocean circulation patterns. Unique ecosystems, including polar bears, seals, and various marine species, depend on sea ice and glacial environments for survival.
Understanding Changes in Frozen Water
Earth’s frozen water bodies are undergoing significant transformations. Global temperatures are causing ice sheets and glaciers to melt at an accelerated pace. For instance, the Greenland Ice Sheet experienced a seven-fold increase in ice loss between 1992-2001 and 2012-2016. This melting land ice contributes directly to global sea level rise, which accelerated from 1.4 millimeters per year throughout much of the 20th century to 3.6 millimeters per year from 2006–2015.
Permafrost thaw also represents a notable change, altering hydrological processes in Arctic regions and potentially impacting coastal areas. Scientists monitor these changes using satellite observations and other techniques to understand the extent and implications of ice loss. The ongoing reduction in frozen water affects freshwater availability, coastal communities, and the planet’s climate regulation mechanisms.