Retreat, lowering and persistent supraglacial streams at the Barnes Ice Cap, Baffin Island, Canada.

Significant and widespread surface melt is prevalent across glaciers and ice caps, and such surface melt is transmitted through complex supraglacial pathways. The efficiency with which this water transits across glaciers and ice caps is important since it is by these networks that water is removed from the system, constituting mass loss. Here, we use remote sensing to explore mass loss of the Barnes Ice Cap in Arctic Canada since the 1980s alongside a detailed investigation of supraglacial drainage evolution, focussing on the central-southern outlet which is the fastest moving part of the ice-cap. The Barnes Ice Cap is almost entirely covered in a network of supraglacial channels from the highest to lowest elevations. These channels exhibit extraordinary stability over many years and are re-used annually. We also observe significant and widespread surface lowering across most of the Barnes Ice Cap, yet erosion by flowing water in these channels is of sufficient magnitude to ensure they persist rather than re-establishing anew each year. As a result, efficient routing of water across and off the ice cap is likely re-initiated quickly each year, removing large volumes of water from the glacier system.