In 2012, UCI Earth System Science professor Eric Rignot has been awarded $2.2 million by the Gordon and Betty Moore Foundation to deploy high resolution airborne gravity developed for mining and oil companies to survey ice thickness in the Patagonia ice fields and in challenging parts of Greenland. The results have been a game changer for the mapping of ice thickness in the most challenging parts of the Earth where traditional radar sounding techniques have repeatedly failed to systematically detect bed echoes.
“We are very excited to have received this vital funding from the prestigious Gordon and Betty Moore Foundation,” said Rignot, adding that the advanced helicopter survey work “will provide critical data to improve our understanding of how glacial ice contributes to sea level rise in a warming climate.” Partners in the three-year project will be Centro de Estudios Cientificos in Chile (CECS) and Sander Geophysics in Canada. “We’re thrilled that one of our outstanding professors will be able to continue his global work, thanks to the Foundation’s generosity,” said physical sciences Dean Kenneth Janda. Jacob Levin, assistant vice chancellor for research development, said private funding for the South American work was indispensable because no U.S. science agency covers the area. “Research is extremely important on the glaciers of Patagonia, the largest in the Southern Hemisphere outside Antarctica,” he said.
The first missions took place in May 2012 and November 2012 in Patagonia in collaboration with CECS and Sumaair and in Greenland in August 2012 in association with HeliGreenland. The Sanders Geophysics Ltd. (SGL)’s AIRGrav instrument was flown on helicopter platforms at low speed (50 knots) and low ground clearance (80m) for the first time. In Patagonia, we also deployed a new MHz radar in collaboration with the Federal Institute for Geosciences and Mineral Resources (BGR), Hanover, Germany. The Greenland survey was a major success with 100% of lines, while the Patagonia missions faced severe weather and strikes in the region which limited the survey to about 50% of the initial, ambitious objectives. Several additional campaigns took place over the years, notably in 2014 (WISE radar sounder, NASA funding) and in the winter of 2016 (AIRGrav, GBMF extension) where we focused on the plateau of NPI and SPI.
As the results piled up, we started to measure fjord bathymetry in Greenland for the first time with multi beam echo sounding from ship. Inland, we worked with Prof. Morlighem to develop a mass conservation method that could combine the existing radar-derived thickness, with surface mass balance records and flow vectors derived from satellite interferometry to obtain a reconstruction of high-resolution bed topography that was not available previously. We progressively moved from 2D inversions to 3D inversions constrained by multi beam echo sounding and MC inversions in Greenland to focus our attention on the transition region between grounded and floating ice. In Patagonia, we deployed the JPL/UCI Warm Ice Sounding Experiment (WISE) 2.5 MHz radar in November 2014 funded by NASA to provide additional ground control in areas where we could pick bed echoes.
Additional MBES campaigns were organized in Greenland in the ensuing years. In Patagonia, we flew a final campaign in July 2016 using a Cessna 206 owned by Servicios Aereos Transportes, from Villa O’Higgins, at the foothills of the Southern Icefield and were fortunate to complete 110% of our objectives using a low-flying, low speed fixed-wing aircraft based on the known performance of the system on helicopters.
The project has had major impacts on glaciology. NASA Operation IceBridge funded a high-resolution gravity survey of Southeast Greenland which was flown in July 2016 and has provided completely new view at bed mapping in this region (Millan et al., 2018). In 2015, NASA funded an Earth Venture Suborbital Mission (E. Rignot, Deputy PI) which included a complete gravity and MBES surveys of all major fjords in Greenland based on the legacy of the GBMF project. These advances have enabled the BedMachine mapping of Greenland glaciers and fjords, Version 3 (Morlighem et al., 2017) and an upcoming Version 4. In Patagonia, following our initial success (Gourlet et al., 2016), we have now produced a complete map of ice thickness on the Northern and Southern Icefields high plateaux for the first time in history. This work has in essence demonstrated the practicality of using modern, high-resolution, high-precision gravity data to map ice thickness with a precision of about 30-40 m in places where other techniques, including MBES and radar sounding, fail to obtain results.
The gravity data obtained through this project is readily available at NSIDC as part of Operation IceBridge.
In the coming years, we plan to go back to Patagonia for more work on the glaciers, most likely collecting fjord bathymetry to study ice-ocean and ice-lake interactions.