It was almost as if subglacial lakes were destined to remain hidden. Early seismic data was misinterpreted. Records were destroyed in fires. Equipment failed just as teams driving hundreds of miles reached the edge of the lakes. Some tantalizing hints suggested there might be water under the ice sheet, but it was not until we had the perspective of looking at the ice sheet from space that the large lakes became evident. Detailed measurements of the height of the ice surface provided the first real opportunity to "see the lakes". The surface of most of the ice on the sheet is rough as it flows over the hills and mountains below. Just as in winter a woodland lake will be an expanse of horizontal floating ice continuing to the horizon, the ice above a subglacial lake floats and the ice surface is very flat.
These lakes exist because the thick ice acts as an insulating blanket, capturing the heat emerging from the Earth's interior. The temperature at the top of an ice sheet is minus 50 degrees Fahrenheit (–45.5 degrees Celsius), while at the bottom it is a positively warm at 28.4 degrees F (–2 degrees C)—very close to the melting point of ice. The pressure of the overlying ice lowers the melting temperature of ice a bit, but the main reason for the warm temperatures is primarily the natural geothermal gradient.
Twenty-five years ago, no one would have believed that there could be lakes under the . Ten years ago, scientists thought these lakes were stagnant and isolated from one another. Today, we know that subglacial lakes are connected under the ice through a maze of plumbing, and that this connectivity can subject them to rapid drainage akin to pulling the plug from a bathtub, allowing water to drain from one lake into another. Draining water from subglacial lakes may contribute to the onset of ice streams, accelerating their movement toward the continental edges, where they rest against the surrounding ocean water.
In East Antarctica, the largest subglacial lakes are found in the foothills of the Gamburtsev Mountains. Lake Vostok, the size of Lake Ontario, and two other large deep lakes mark the eastern edge of the mountainous province. On the western edge, four large lakes are linked to the onset of the rapid flow of the ice sheet. Using airborne imaging technologies, we will collect the first data that may tell us why these large lakes are found in the Gamburtsev Foothills. We are trying to understand how the subglacial lake system may influence the flow of polar ice toward the global oceans. This International Polar Year program (AGAP) to study the Gamburtsev Mountain Province will allow us to gather critical information on these lakes and help connect the dots on their role in Antarctic glacial plumbing.
Exploring Hidden Terrains
If the East Antarctic Ice Sheet were dropped on top of the lower 48 U.S. states, every single town would be covered. Only a few mountain peaks would be exposed. Satellites cannot see through the ice sheets. Studying mountains and lakes covered by a thick blanket of ice is a challenge.
Fifty years ago, scientists had no good estimate of the thickness of the Antarctic ice sheet. At the beginning of the last IPY, using oil industry technology, convoys of tracked snow vehicles from many nations set out across Antarctica. The convoys, or traverses, stopped every 50 miles (80 kilometers) to lay sensitive recording devices (geophones), drill a 150-foot (45-meter) hole, and set off small explosive charges. The explosions would send a fountain of snow into the air and energy deep into the ice sheet. The downward propagating wave would bounce off the hills and valleys at the bottom. The return echo would be recorded by the geophone. Each explosion produced one measurement of ice thickness.