[Source: Proceedings of the National Academy of Sciences of the United States of America, full page: (LINK). Abstract, edited.]
Multidecadal observations of the Antarctic ice sheet from restored analog radar records
Dustin M. Schroeder, Julian A. Dowdeswell, Martin J. Siegert, Robert G. Bingham, Winnie Chu, Emma J. MacKie, Matthew R. Siegfried, Katherine I. Vega, John R. Emmons, and Keith Winstein
PNAS first published September 3, 2019 / DOI: https://doi.org/10.1073/pnas.1821646116
Edited by Eric Rignot, University of California, Irvine, CA, and approved August 8, 2019 (received for review December 19, 2018)
One of the greatest challenges in projecting the sea-level contributions of ice sheets over the next century is the lack of observations of conditions within and underneath the ice sheet that span more than a decade or two. By digitizing archival ice-penetrating radar data recorded in the 1970s on 35-mm optical film, we can compare modern and archival radar-sounding data at their full resolution in order to observe changes in the Antarctic ice sheet over more than 40 y. This makes it possible to investigate and model subsurface processes over both large scales and several decades for the first time.
Airborne radar sounding can measure conditions within and beneath polar ice sheets. In Antarctica, most digital radar-sounding data have been collected in the last 2 decades, limiting our ability to understand processes that govern longer-term ice-sheet behavior. Here, we demonstrate how analog radar data collected over 40 y ago in Antarctica can be combined with modern records to quantify multidecadal changes. Specifically, we digitize over 400,000 line kilometers of exploratory Antarctic radar data originally recorded on 35-mm optical film between 1971 and 1979. We leverage the increased geometric and radiometric resolution of our digitization process to show how these data can be used to identify and investigate hydrologic, geologic, and topographic features beneath and within the ice sheet. To highlight their scientific potential, we compare the digitized data with contemporary radar measurements to reveal that the remnant eastern ice shelf of Thwaites Glacier in West Antarctica had thinned between 10 and 33% between 1978 and 2009. We also release the collection of scanned radargrams in their entirety in a persistent public archive along with updated geolocation data for a subset of the data that reduces the mean positioning error from 5 to 2.5 km. Together, these data represent a unique and renewed extensive, multidecadal historical baseline, critical for observing and modeling ice-sheet change on societally relevant timescales.
Antarctica – radio echo sounding – glaciology – remote sensing – archival data
Keywords: Antarctica; Climate change; Global warming.