Washington: A new laser-based technology from the National Aeronautics and Space Administration (NASA) holds promise to tell how the melting of earth’s frozen regions may affect our climate.
This opens a new vista for researchers to better track the melting or growth of ice sheets, glaciers and sea ice. A high-altitude aircraft from NASA flew over the icy Arctic ocean and the snow-covered terrain of Greenland recently. Aboard that aircraft flew the Multiple Altimeter Beam Experimental Lidar, or MABEL, which is an airborne test-bed instrument for NASA's ICESat-2 satellite mission - slated to launch in 2017. Armed with a new photon-counting technique, MABEL flew over southwest Greenland's glaciers and sea ice to test a new method of measuring the height of earth from space.
The MABEL sent out pulses of green laser light and measured how long it took individual light photons to bounce off earth's surface and return. “Using the individual photons to measure surface elevation is a really new thing,” said Ron Kwok, a senior research scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. ICESat-2 is tasked with measuring elevation across earth's entire surface but with a focus on change in the frozen areas of the planet, where scientists have observed dramatic impacts from climate change, said a NASA press release.
The two types of ice - ice sheets and sea ice - reflect light photons in different patterns. Ice sheets and glaciers are found on land, like Greenland and Antarctica, and are formed as frozen snow and rain accumulates. Sea ice, on the other hand, is frozen seawater, found floating in the Arctic ocean and offshore of Antarctica. “MABEL's Greenland campaign was designed to observe a range of interesting icy features,” said Bill Cook, MABEL's lead scientist at NASA's Goddard Space Flight Centre in Greenbelt, Maryland. With the photon counts from different surfaces, other scientists could start analysing the data to determine which methods allow them to best measure the elevation of earth's surface.
The flights over the ocean near Greenland allowed researchers to demonstrate that they can measure the height difference between open water and sea ice, which is key to determining the ice thickness. MABEL can detect enough of the laser light photons that bounce off earth's surface and return to the instrument, and programmes can then make necessary elevation calculations, Cook added. “We were pretty happy with the precision. The flat areas are flat to centimetre level and the rough areas are rough,” he said. The density of photons detection could also tell researchers what type of ice the instrument was flying over. The instrument team is planning a 2014 summer campaign to fly over glaciers and ice sheets in warmer weather.
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