Antarctic: Lakes under the ice affect climate
Meltwater accelerates outflow of ice into the seaRead out
Under the ice of the Antarctic are concealed several lakes and waterways. As scientists now report in "Nature", the water from this extended system accelerates the removal of ice from the interior to the coast. The lakes also play an important role in climate change as a whole.
Ice streams are large, fast-flowing structures within the ice cover that transport meltwater and ice from land to sea. One of these streams, the Recovery Glacier Ice Stream, has a catchment area of eight percent of the total Antarctic ice cover - an area larger than the United States. Every year, more than 35 billion tons of ice flow into the Weddell Sea.
A team of researchers headed by geophysicist Robin Bell and Michael Studinger of Columbia University, New York City, has now studied this ice current more closely using advanced satellite technology. With images taken from the NASA satellites Terra and Aqua, they also mapped minute changes in the surface structure of the ice flow, while the RADARSAT instrument of the Canadian Space Agency provided a view under the ice cover.
Seawater as a lubricant
And there were a few surprises in store: the researchers not only discovered four previously unknown Lower Lake lakes, they also found that these lakes play a crucial role in the flow rate of the Recovery Glacier ice stream. While the ice upstream of the lakes moves barely a meter per year, the flow speed increases downstream to almost 500 meters per year. According to the scientists, the liquid water of the lakes serves as a kind of lubricant that keeps the electricity moving. The water prevents the base of the ice stream from freezing on the bedrock.Lake Vostok lies in the interior of the Antarctic continent under a kilometer thick ice sheet. It is considered one of the largest freshwater lakes in the world. © Columbia University, Lamont-Doherty Earth Observatory
"It's as if the lakes are storing the geothermal energy of the entire basin and then releasing it into the ice, " explains Bell. "They drive the engine, which regulates the runoff of the ice cover." The water in the lakes remains liquid despite the great cold and thus acts as l or lubricant between the ground and ice, Bell: "The more we learn about these lakes, the more we realize how important they are to the stability of the ice sheets." Display
Climate influence also global
However, the results of the research team also suggest that the Lower Lake Lakes could play an important role in sea-level rise and in the regional as well as global climate. "We have found that the meltwater at the base of the ice sheet accelerates the flow of recovery ice into the sea, " Bell said. This, in turn, contributes to higher sea levels worldwide. We know that in the past several flash floods have occurred from inside the ice sheets, probably mainly from these Lower Ice lakes. These sudden outbreaks of seepage could disturb the nearby ocean currents and thus also affect the transport of heat across the oceans and thus the global climate system,
(NASA, 07.03.2007 - NPO)