The skies were clear, the winds were low, and the lasers aligned. In April, instruments aboard NASA's Operation IceBridge airborne campaign and the Ice, Cloud and Land Elevation Satellite-2 succeeded in measuring the same Arctic sea ice at the same time, a tricky feat given the shifting sea ice. Scientists have now analyzed airborne and spaceborne height measurements, and found that the two datasets match almost exactly, demonstrating how precisely ICESat-2 can measure the heights of the sea ice's bumpy, cracked surface.
"If you look at the height profiles from ICESat-2 and IceBridge, you can tell that they're almost the same," said Ron Kwok, a sea ice scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, and lead author of the new study. "It's a good pitch for the quality of the ICESat-2 data."
ICESat-2 uses its laser instrument to measure the heights of Earth's surface, focusing on the glaciers, ice sheets and sea ice in the planet's polar regions. When it launched on Sept. 15, 2018, scientists were poised to take measurements from planes and on the ground to check against the satellite's data, helping to and ensure the accuracy of the measurements from orbit.
The Operation IceBridge team has been flying campaigns over Greenland and Antarctica for a decade, and once ICESat-2 was in orbit they adjusted several missions to fly along the same path as the satellite. When they flew over ice sheets it was relatively straightforward, since the masses of ice don't gain or lose much height over a day or two, or even a week or two.
Sea ice, however, is pushed around by winds and ocean currents. If IceBridge flew along an ICESat-2 orbit track an hour after the satellite passed, it could be measuring completely different ice. So IceBridge mission scientist John Sonntag had to calculate where and when ICESat-2 was going to be over a specific spot in the Arctic ocean, and how to navigate the plane to be there at the exact same time - preferably with low winds, and definitely with no clouds to block ICESat-2's view.
"He was able to nail it," Kwok said. "He was able to get to that part of the Arctic so there's almost zero time lag between ICESat-2 and the airplane."
When Kwok and his colleagues used computer programs to line up the two datasets, they saw the same ridges, bumpy surface, and open water in both elevation profiles. With four flights worth of data comparisons, over more than 600 miles (1,000 kilometers), the two sets of height measurements closely match each other: Researchers would call an exact match 1.0, and these were correlated to more than 0.95.
Sea ice height profiles from ICESat-2 can tell scientists whether the ice is a newly formed, smooth surface or an older, rougher section. The key measurement from ICESat-2, however, is how high the ice surface is above the open water, called freeboard. If scientists know that number, they can calculate the thickness - which isn't directly measured from satellite data. When Kwok and his colleagues compared freeboard measurements from ICESat-2 and Operation IceBridge's Airborne Topographic Mapper instrument for the April flights, they were within 0.8 to 1.6 inches (2 to 4 centimeters) of each other.
With additional flights over land and sea ice in both Greenland and Antarctica this fall, Operation IceBridge is continuing to help assess ICESat-2 data, along with other efforts including the third year of an Antarctic ground traverse along a section of the 88 degree South line of latitude.
Kate Ramsayer | EurekAlert!
First research results on the "spectacular meteorite fall" of Flensburg
18.02.2020 | Westfälische Wilhelms-Universität Münster
The Antarctica Factor: model uncertainties reveal upcoming sea-level risk
14.02.2020 | Potsdam-Institut für Klimafolgenforschung
Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.
Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...
Investigation of the temperature dependence of the skyrmion Hall effect reveals further insights into possible new data storage devices
The joint research project of Johannes Gutenberg University Mainz (JGU) and the Massachusetts Institute of Technology (MIT) that had previously demonstrated...
Researchers at Chalmers University of Technology, Sweden, recently completed a 5-year research project looking at how to make fibre optic communications systems more energy efficient. Among their proposals are smart, error-correcting data chip circuits, which they refined to be 10 times less energy consumptive. The project has yielded several scientific articles, in publications including Nature Communications.
Streaming films and music, scrolling through social media, and using cloud-based storage services are everyday activities now.
After helping develop a new approach for organic synthesis -- carbon-hydrogen functionalization -- scientists at Emory University are now showing how this approach may apply to drug discovery. Nature Catalysis published their most recent work -- a streamlined process for making a three-dimensional scaffold of keen interest to the pharmaceutical industry.
"Our tools open up whole new chemical space for potential drug targets," says Huw Davies, Emory professor of organic chemistry and senior author of the paper.
Superconductivity approaching room temperature may be possible in hydrogen-rich compounds at much lower pressures than previously expected
Reaching room-temperature superconductivity is one of the biggest dreams in physics. Its discovery would bring a technological revolution by providing...
12.02.2020 | Event News
16.01.2020 | Event News
15.01.2020 | Event News
18.02.2020 | Power and Electrical Engineering
18.02.2020 | Information Technology
18.02.2020 | Physics and Astronomy