Totten Ice Shelf history over the past century interpreted from satellite imagery

Abstract. Totten Glacier is currently the largest source of mass loss in the East Antarctic Ice Sheet. The glacier has been losing mass for decades and inland thinning was detected in the earliest satellite-altimetry observations in the early 1990s, but for how long the glacier has been losing mass remains unknown. We calculate decadal ice-speed anomalies to confirm that Totten Glacier has not undergone sustained acceleration since at least 1973. Together with observations of grounding-line retreat from 1973–1989, we confirm that the glacier was losing mass in the 1970s. Surface undulations form on Totten Ice Shelf close to a bathymetric high point near the grounding line in response to time-varying melt rates and are preserved downstream for several decades. Using the full Landsat archive, we produce a century-long record of surface-undulation formation that we interpret as a qualitative record of basal-melt-rate variability. An anomalous ∼ 20-year absence of undulations associated with the mid-20th century manifests a period when ice passing close to a bathymetric high point near the grounding line was pervasively thinner, and may represent an anomalous warm period that triggered the onset of modern-day mass loss at Totten Glacier. We also observe the collapse of a nearby small ice shelf between 1963 and 1973, that is consistent with a regionalised mid-20th century warm period. Our results highlight that the currently available ∼ 30-year satellite-altimetry records are not long enough to capture the full scale of decadal variability in basal-melt rates and mass-loss patterns.