Surface meltwater drains across ice sheets, forming melt ponds that can trigger ice-shelf collapse1, 2, acceleration of grounded ice flow and increased sea-level rise3, 4, 5. Numerical models of the Antarctic Ice Sheet that incorporate meltwater’s impact on ice shelves, but ignore the movement of water across the ice surface, predict a metre of global sea-level rise this century5 in response to atmospheric warming6. To understand the impact of water moving across the ice surface a broad quantification of surface meltwater and its drainage is needed. Yet, despite extensive research in Greenland7, 8, 9, 10 and observations of individual drainage systems in Antarctica10, 11, 12, 13, 14, 15, 16, 17, we have little understanding of Antarctic-wide surface hydrology or how it will evolve. Here we show widespread drainage of meltwater across the surface of the ice sheet through surface streams and ponds (hereafter ‘surface drainage’) as far south as 85° S and as high as 1,300 metres above sea level. Our findings are based on satellite imagery from 1973 onwards and aerial photography from 1947 onwards. Surface drainage has persisted for decades, transporting water up to 120 kilometres from grounded ice onto and across ice shelves, feeding vast melt ponds up to 80 kilometres long. Large-scale surface drainage could deliver water to areas of ice shelves vulnerable to collapse, as melt rates increase this century. While Antarctic surface melt ponds are relatively well documented on some ice shelves, we have discovered that ponds often form part of widespread, large-scale surface drainage systems. In a warming climate, enhanced surface drainage could accelerate future ice-mass loss from Antarctic, potentially via positive feedbacks between the extent of exposed rock, melting and thinning of the ice sheet.
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Extended data figures and tables
Extended Data Figures
- Extended Data Figure 1: Drainage on Shackleton Glacier. (2,377 KB)
a, WorldView 1 image showing a surface stream flowing from Shackleton Glacier, across the grounding line28 (black), onto the Ross Ice Shelf, from 11 February 2010. See also Fig. 2j. b, Shackleton Glacier surface profile extracted from Bedmap2 (ref. 30). c–f, Aerial reconnaissance photography over Shackleton Glacier from 12 January 2010. Photo credit J. Stone, University of Washington, 2010. c, A large pond, P1, at the head of Swithinbank Moraine, SM. d, Meltwater ponds on SM. e, Further surface ponding on SM. f, A meltwater channel, S5 running parallel to ice flow. Source data for this figure is available in the HTML version of the paper.
- Extended Data Figure 2: Drainage onto and across Amery Ice Shelf. (2,976 KB)
Landsat imagery from 2015 (a), 1988 (b) and 1974 (c). The black boxes show the extent of Fig. 3b. Drainage basins computed from Bedmap2 (ref. 30) are shown in red in a. The drainage network that feeds the large pond in Fig. 3b is shown in green and other major drainage systems are shown in blue. See inset in Fig. 3b for location in East Antarctica. The grounding line28 is in black.
- Extended Data Figure 3: Drainage across Pine Island Ice Shelf. (1,788 KB)
a, MODIS Mosaic of Antarctica (MOA)35 image showing the ice shelf and surroundings, including Pine Island Glacier (PIG). Inset shows location in West Antarctica. White box shows the extent of the images in the other panels. b–h, Satellite imagery showing the growth of a melt pond during the 2013/14 melt season. The grounding line28 is in black.
- Extended Data Figure 4: Persistence of nine surface drainage systems. (104 KB)
Squares show the year of observations of surface drainage in each system. This figure represents a lower bound on the occurrence of drainage in each location. Colours indicate whether the observation is from Landsat imagery, WorldView imagery, Aster imagery or aerial photography. The vertical line at 1972 marks the launch of the first Landsat satellite. See Extended Data Table 2 for details.
- Extended Data Figure 5: Pre-satellite era aerial photography of persistent surface drainage systems. (315 KB)
a–c, Oblique aerial photography of melt ponds on Roi Baudouin Ice Shelf, fed by surface streams. Inset shows location in West Antarctica. Look direction is approximately northwards from the grounding line. The pond that appears on the right in a can also be seen in b and c. d, Aerial photograph of Shackleton Glacier, 9 December 1960, showing meltwater features P1, P2 and S1, that are visible in more recent satellite imagery and aerial photographs (Fig. 2).
- Extended Data Figure 6: Surface drainage across the Riiser–Larsen Ice Shelf. (996 KB)
a, White box shows the location of the images shown in the other panels. Background image is from MOA. The inset shows the location in East Antarctica. b–e, Landsat images from 1974, 1984, 1988 and 2014. f, Enlarged view of melt ponds in e. In all panels the grounding line28 is in black.
- Extended Data Figure 7: Drainage on Ross Ice Shelf, downstream of Darwin Glacier. (974 KB)
a, The location of the other panels is shown in white, background image is from MOA. Inset shows location in Antarctica. b–f, Landsat satellite images showing meltwater ponding and drainage crossing the grounding line28 shown in black, over a 40-year period.
- Extended Data Figure 8: Ice-flow speed and proximity to rock and blue ice at surface streams. (203 KB)
Proximity of upper ends of streams to exposed rock (black) and blue-ice areas (blue) and ice-flow speed at the surface at the upper end of the streams, across the entire continent (solid curves) and further south than 75° S (dashed curves) (n = 696). Source data for this figure is available in the HTML version of the paper.