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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