Multidecadal observations of the Antarctic ice sheet from restored analog radar records

Abstract

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.

Five decades of radioglaciology

“…However, several regions remained free of data (Pritchard, 2014). Other compilations are now due that will incorporate new data that have been acquired to fill many of Bedmap2's gaps, including, for example, across Marie Byrd Land, West Antarctica, the Recovery Basin/South Pole, the Dome F region and Princess Elisabeth Land, as well as newly remastered TUD-NSF-SPRI film data and updated thickness measurements for the Ross Ice Shelf (Tang and others, 2016; Young and others, 2016; Popov, 2017; Humbert and others, 2018; Jordan and others, 2018a; Karlsson and others, 2018; Morlighem and others, 2019; Paxman and others, 2019; Schroeder and others, 2019; Tinto and others, 2019). Compared to Antarctica, surveys of Greenland starting in the 1990s by the University of Kansas as part of NASA's Program for Arctic Regional Climate Assessment (PARCA) and later OIB have led to relatively abundant and mutually interpretable observations of the ice-sheet bed and englacial properties (Bamber and others, 2013; Gogineni and others, 2014; MacGregor and others, 2015a; Morlighem and others, 2017).…”

Antarctic palaeotopography

“…The progressive mapping of Antarctica's subglacial topography has been driven by a substantial community effort since the 1970s (Drewry, 1983;Fretwell et al, 2013;Lythe et al, 2001;Morlighem et al, 2019;Schroeder et al, 2019). Ground-based and airborne radio-echo sounding (RES) surveys are widely used to measure ice thickness in Antarctica.…”

Statistical emulation of a perturbed basal melt ensemble of an ice sheet model to better quantify Antarctic sea level rise uncertainties

“…Despite its potential to contribute to sea level rise (SLR) vastly more than any other single source (∼ 5 m West Antarctica, ∼ 60 m all Antarctica), and documented ice shelf thinning (e.g. Schroeder et al, 2019;Reese et al, 2018), Antarctica's contribution to future sea level remains highly uncertain (Heal and Millner, 2014).…”