Schroeder, and 10 co-authors, report that 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, the authors demonstrate how analog radar data collected over 40 years ago in Antarctica can be combined with modern records to quantify multidecadal changes. Specifically, the authors digitized over 400,000 line kilometers of exploratory Antarctic radar data originally recorded on 35-mm optical film between 1971 and 1979.
The authors leveraged the increased geometric and radiometric resolution of their 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, the authors compared 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.
The authors also released 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.
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, The authors can compare modern and archival radarsounding data at their full resolution in order to observe changes in the Antarctic ice sheet over more than 40 years. This makes it possible to investigate and model subsurface processes over both large scales and several decades for the first time.
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