Abstract

Dotson Ice Shelf has resisted acceleration and ice-front retreat despite high basal-melt rates and rapid disaggregation of the neighboring Crosson Ice Shelf. Because of this lack of acceleration, previous studies have assumed that Dotson is durable. Here we show clear evidence of Dotson's vulnerability as it decelerates, contrary to the common assumption that ice-flow deceleration is synonymous with increased ice-shelf buttressing. Ungrounding of a series of pinning points initiated acceleration in the Upper Dotson in the early 2000s, which subsequently plugged ice flow in the Lower Dotson. Discharge from the tributary Kohler Glacier into Crosson increased, but non-proportionally. Given current surface-lowering rates, we estimate that several remaining pinning points in the Upper Dotson could unground within one to three decades.