Posted on February 17 2016
Image: Shaun Merritt
Every time we think all the amazing landforms on Earth have been found and documented, something totally unexpected shows up. A lot of what comes to light is under the sea, discovered with the use of advanced sonar. With satellites scanning all of Earth’s land surface, there isn’t much we can’t zero in on and study, even if it exists deep in hard-to-access wilderness. But there’s another place for geomorphology to hide.
NASA has a program called Operation IceBridge, which is dedicated to observation of the polar regions in good old airplanes during a period between the flights of two polar scanning satellites, ICESat, and ICESat-2. The satellites are charged with, “providing multi-year elevation data needed to determine ice sheet mass balance” as well as compiling other surface topography data. The second of these satellites is scheduled to launch sometime in the next couple of years. In the meantime, as a “bridge,” the airplane overflights of Operation IceBridge are using radar to assess surface and subsurface characteristics of the ice. This has been done in conjunction with British and German air surveys. All this data is crucial to understanding the rate at which the glaciers and ice sheets of the polar regions are shrinking. Radar signals also detect layers of ice by their differences in density, and when compared to information gleaned from ice cores, detailed maps of the ages and thicknesses of layers can be produced. But beyond their usefulness at modeling the ice surface and its interior structure, radio waves, at particular frequencies, can penetrate ice all the way down to the bedrock. The signals that bounce back from rock bottom provide a view of the underlying landscape.
A couple of years ago, scientists studying the data from flights concentrating on Greenland could see that the radar revealed a huge canyon in the bedrock buried under a mile-thick layer of ice. Starting from the middle of the landmass, the canyon follows a twisted course similar to a river-cut gorge, winding northward to the coast where Petermann Glacier empties into the Arctic Ocean. Running more than 460 miles in length, it beats the course of the Grand Canyon by nearly 200 miles. Reaching a half a mile in depth, it’s not as deep, but still quite a gouge on the land. Researchers say it was cut before the coming of the ice that has covered at least parts of Greenland for three million years. It may still play a role in transporting water–the scientists believe it is a key mover of subsurface glacial meltwater enroute to the ocean. While no doubt a stunning sight, no one is in a hurry to see this impressive canyon with their own eyes. To reveal it would necessitate the melting of the entire Greenland ice sheet, causing massive sea level rise. The way things are going, it may come to light sooner than anybody wants.