The question of “how deep is the snow” in Antarctica refers to the depth of the Antarctic Ice Sheet, a vast accumulation of ancient, compacted ice that has built up over millions of years. This continental-scale glacier covers approximately 98% of the landmass and represents the largest volume of ice on the planet. This immense reservoir of frozen freshwater holds the potential to dramatically reshape global coastlines. Understanding the sheer scale and underlying topography of this ice mass is fundamental to assessing its stability.
The Scale of the Antarctic Ice Sheet
The Antarctic Ice Sheet has an average thickness of about 2.16 kilometers across its 14 million square kilometer area. This measurement is only an average, however, as the depth varies drastically across the continent’s major divisions.
The East Antarctic Ice Sheet (EAIS) is significantly thicker, reaching a maximum known depth of 4,897 meters in a region near Adélie Land. The EAIS is the largest and most stable section, with an average thickness of approximately 2.2 kilometers. In contrast, the West Antarctic Ice Sheet (WAIS) is much smaller and generally thinner, with ice depths reaching up to 1.3 kilometers. The EAIS holds over ten times the volume of ice compared to the WAIS.
This volume of ice is estimated to be around 27 million cubic kilometers. If the entire Antarctic Ice Sheet were to melt, the resulting influx of water would raise the global sea level by nearly 58 meters. This enormous frozen mass contains roughly 90% of the world’s ice and about 61% of all the fresh water on Earth.
Determining the Depth
Scientists cannot simply drill boreholes across the entire continent to measure the ice depth, so they rely on remote sensing technology to map the ice sheet’s base. The primary tool used to measure the thickness is ice-penetrating radar, also known as Radio Echo Sounding (RES).
This technique involves flying aircraft over the ice surface and transmitting low-frequency radio waves downward. The radio waves travel through the ice until they encounter a boundary, such as the interface with the underlying rock or water, which reflects back to the surface. By precisely measuring the time it takes for the echo to return, researchers calculate the distance to the bedrock, determining the ice thickness.
Other methods complement the radar data, including deep ice core drilling, which provides localized measurements that help calibrate the remote sensing data. Satellite altimetry is used to track the elevation of the ice surface over time, which can reveal changes in ice mass and movement. By combining data from these sources, scientists piece together a detailed picture of the ice sheet’s dimensions and dynamics.
The Bedrock Below
The variation in ice depth is directly related to the complex and rugged topography of the land hidden beneath the ice sheet. Antarctica’s bedrock is not a flat plain; it features massive mountain ranges, like the buried Gamburtsev Mountains, alongside deep subglacial basins. The greatest known depression in the bedrock is the Byrd Subglacial Basin, which lies more than 2,500 meters below sea level.
The pressure-melting effect of the thick ice, combined with geothermal heat, allows for liquid water at the ice-bed interface, forming hundreds of subglacial lakes. The largest of these is Lake Vostok, which is covered by nearly 4 kilometers of ice. These bodies of water can influence ice flow, as the water acts as a lubricant, allowing ice streams to move more rapidly toward the ocean.
The West Antarctic Ice Sheet rests on bedrock that is well below sea level, making it a marine-based ice sheet. This configuration makes the WAIS susceptible to warm ocean currents, which can melt the ice from beneath and destabilize the structure. The sheer weight of the ice sheet has depressed the underlying land by as much as 500 meters, a process known as isostatic depression.