Climate Fact: Antarctica’s Subglacial Lakes
Beneath the Antarctic ice sheet lie some of Earth’s final frontiers – networks of subglacial lakes, many of which have been isolated from the atmosphere for as long as 15 million years. Outlet channels allow these lakes to periodically drain into the ocean, refill and drain again. The largest of these lakes, Lake Vostok, lies about 2.5 miles below the surface of the East Antarctic ice sheet and is about the size of Lake Ontario. Recently, subglacial lakes have attracted the attention and imagination of much of the scientific community for two primary reasons:
- Ice Stream Stability: Ice streams are areas of continental ice sheets where inland ice flows rapidly into the ocean – they can be characterized as “rivers of ice.” Subglacial lakes are an important component of ice stream dynamics. A series of large lakes sit at the onset of the Recovery ice stream, which comprises eight percent of the East Antarctic ice sheet, providing the initial “lubricant” for ice destabilization and movement (which occurs at a rate of about 320 feet per year). The periodic drainage of these lakes can lead to periodic accelerations in ice flow as well. Better understanding the relationship between subglacial lakes and the ice that covers them is crucial to predicting future rates of continental ice loss and sea level rise.
- Unique Ecosystems: Because subglacial lakes have been essentially untouched by sunlight, oxygen and other ecosystems for millions of years, the life that does exist in these lakes is unique and potentially analogous to early life on Earth, particularly life that survived in extensive glacial periods of Earth’s distant past (500-1,000 million years ago). Samples taken from outlet water flowing from a subglacial lake 500 yards below Taylor Glacier in West Antarctica reveal that the microorganisms living there use a series of reactions with sulfate and ferric iron to “breathe” and metabolize the limited organic matter in this virtually oxygen-free environment. Similar reactions have been performed in laboratories, but no where else on Earth have such ecosystems been found. The scouring of the iron rich rocks by the massive ice sheets is thought to be the source of the nutrients that feed this life.
To see depictions of Antarctica’s subglacial lake networks and Lake Vostok, visit http://www.earthgauge.net/climate-facts-image-library#4. These images come from the National Science Foundation and are in the public domain.
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Sources: Grom, Jack. “Ancient Ecosystem Discovered Beneath Antarctic Glacier.” ScienceNOW Daily News 16 April 2009. Accessed Online 14 January 2010 and Bell, RE et al. “Large subglacial lakes in East Antarctica at the onset of fast-flowing ice streams.” Nature 445 (2007): 904-907 and Mikucki, JA et al. “A Contemporary Microbially Maintained Subglacial Ferrous ‘Ocean.’” Science 324 (2009): 397-400 and Christner, BC et al. “Limnological conditions in Subglacial Lake Vostok, Antarctica.” Limnology and Oceanography 51 (2006): 2485-2501.
