Exploration of Antarctic Subglacial Aquatic Environments

摘要

Antarctica is renowned for its extreme cold; yet liquid water occurs at the base of the Antarctic ice sheet, several kilometers beneath the surface. This discovery was first made in the 1970s by researchers using airborne radio-echo sounding measurements. Using both airborne and surface radar, researchers have now identified more than 145 subglacial lakes, the largest of which is Lake Vostok with a surface area of 14,000 km2, similar to that of Lake Ontario. In addition, radio-echo sounding data indicate that shallow, swamplike features the size of several city blocks, as well as water-saturated layers of soils or broken rocks, may exist beneath the ice sheet, giving rise to a wide range of subglacial aquatic environments beyond just the large lakes. All of these subglacial aquatic environments form from meltwater that develops as a result of steady geothermal heat flux from the Earth, the melting point lowering caused by the weight of the overlying ice, and the insulation of the ice sheet. Recent evidence shows that many of the subglacial aquatic environments comprise vast watersheds connected by rivers and streams that flow beneath the ice sheet. The presence of subglacial lakes on the frozen continent has captured the interest of people, both scientists and nonscientists alike. These lakes and their connected aquatic systems are among the last unexplored places on Earth. Moreover, they have been sealed from free exchange with the atmosphere for millions of years, making it possible for unique microbial communities to exist in these environments.