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Ice shelves play a vital role in regulating loss of grounded ice and in supplying freshwater to coastal seas. However, melt variability within ice shelves is poorly constrained and may be instrumental in driving ice shelf imbalance and collapse. High-resolution altimetry measurements from 2010 to 2016 show that Dotson Ice Shelf (DIS), West Antarctica, thins in response to basal melting focused along a single 5km-wide and 60km-long channel extending from the ice shelf's grounding zone to its calving front. If focused thinning continues at present rates, the channel will melt through, and the ice shelf collapse, within 40-50years, almost two centuries before collapse is projected from the average thinning rate. Our findings provide evidence of basal melt-driven sub-ice shelf channel formation and its potential for accelerating the weakening of ice shelves.

Plain Language Summary Ice shelves act as safety bands around the Antarctic ice sheet. Many ice shelves are currently thinning, leading to acceleration of the grounded ice behind. Here we show that ice shelves' thinning is stronger along a channel structure formed by the ocean circulation under the ice shelf. The thinning is 3 times higher than the ice shelf's average, hence leading to a more rapid weakening of the ice shelf. This study provides evidence of basal melt-driven sub-ice shelf channel formation and its potential for accelerating the weakening of ice shelves.