Antarctica, a land synonymous with vast expanses of ice and extreme cold, harbors a dynamic network of lakes. These aren’t merely fleeting puddles but complex hydrological systems, some of which are immense and have existed for millions of years. Scientists continue to uncover new insights into these hidden bodies of water, challenging previous understandings of the continent’s frozen landscape. The presence of liquid water in such an icy environment offers unique opportunities for discovery and plays a role in the continent’s dynamics.
Types of Antarctic Lakes
Antarctic lakes generally fall into two main categories: subglacial and supraglacial. Subglacial lakes are found deep beneath the colossal ice sheets, often kilometers below the surface. Lake Vostok, the largest known subglacial lake, stretches approximately 250 kilometers long and 50 kilometers wide, covering an area of around 12,500 square kilometers under roughly 4,000 meters of ice. Over 400 subglacial lakes have been identified across the continent.
Supraglacial lakes form on the surface of the ice. These are typically seasonal, appearing during warmer summer months from November to February when meltwater accumulates in depressions on the ice surface. While most refreeze, some supraglacial lakes can drain into the ice sheet. Thousands of these surface lakes have been mapped, particularly along the coastal margins of the East Antarctic Ice Sheet and on floating ice shelves, and they can vary significantly in size, with some reaching over 70 square kilometers.
How They Form and Endure
The persistence of liquid water beneath thousands of meters of ice in subglacial lakes is due to two phenomena. Geothermal heat emanating from the Earth’s interior warms the bedrock beneath the ice sheet, causing the basal ice to melt at a rate of a few millimeters per year. This process is augmented by pressure melting, where the immense weight of the overlying ice lowers the freezing point of water, allowing it to remain liquid even at temperatures below 0°C. Water flows from areas of higher hydraulic pressure to lower pressure, accumulating in topographic depressions to form these lakes.
Supraglacial lakes form directly from surface meltwater. During periods of warmer temperatures, typically in the austral summer, snow and ice on the surface melt. This meltwater collects in natural depressions or hollows on the ice surface, creating temporary or seasonal lakes. Factors such as local wind patterns, ice surface topography, and albedo (the reflectivity of the ice) influence where these lakes form and how large they become.
Life and Exploration
Subglacial lakes are isolated ecosystems, often cut off from the Earth’s atmosphere for millions of years. These environments, characterized by extreme cold, high pressure, darkness, and limited nutrients, are home to extremophiles. These microorganisms, including bacteria and archaea, thrive under harsh conditions, often relying on chemical reactions for energy. Studies of accretion ice from Lake Vostok have revealed unique DNA sequences, suggesting potential hydrothermal activity.
Accessing these remote environments presents technical challenges, requiring specialized drilling to prevent contamination. Clean access hot-water drills have been developed for this purpose. The successful sampling of subglacial Lake Whillans in 2013 by a U.S. team confirmed the existence of active microbial life and biogeochemical cycling beneath the ice sheet. Studying these unique ecosystems has implications for astrobiology, serving as earthly analogs for potential ice-covered oceans on extraterrestrial bodies like Jupiter’s moon Europa or Saturn’s moon Enceladus, informing the search for life beyond Earth.
Their Impact on Antarctica’s Future
Antarctic lakes play a role in the dynamics of the continent’s ice sheets and have implications for global sea levels. Subglacial lakes influence ice flow by acting as a lubricant at the ice-bed interface, speeding up ice movement toward the ocean. Meltwater and saturated subglacial sediments reduce friction, enabling basal sliding and accelerating glacier velocities.
Supraglacial lakes also contribute to ice sheet instability. When these surface lakes drain through the ice, the meltwater can reach the ice sheet’s bed, enhancing basal sliding and faster ice flow. Supraglacial lakes have been linked to ice shelf collapse. The removal of ice shelves, which are floating extensions of land ice, increases inland ice flow into the ocean, directly contributing to sea level rise. The sediments and water within these lakes also hold ancient climate records, offering insights into past climate changes over the last 20,000 years and potentially much longer, with some ice cores providing continuous records spanning over 1.5 million years.