Abstract
Abstract. Surface meltwater on ice shelves can exist as slush, it can pond in lakes or crevasses, or it can flow in surface streams and rivers. The collapse of the Larsen B Ice Shelf in 2002 has been attributed to the sudden drainage of ∼3000 surface lakes and has highlighted the potential for surface water to cause ice-shelf instability. Surface meltwater systems have been identified across numerous Antarctic ice shelves, although the extent to which these systems impact ice-shelf instability is poorly constrained. To better understand the role of surface meltwater systems on ice shelves, it is important to track their seasonal development, monitoring the fluctuations in surface water volume and the transfer of water across ice-shelf surfaces. Here, we use Landsat 8 and Sentinel-2 imagery to track surface meltwater across the Nivlisen Ice Shelf in the 2016–2017 melt season. We develop the Fully Automated Supraglacial-Water Tracking algorithm for Ice Shelves (FASTISh) and use it to identify and track the development of 1598 water bodies, which we classify as either circular or linear. The total volume of surface meltwater peaks on 26 January 2017 at 5.5×107 m3. At this time, 63 % of the total volume is held within two linear surface meltwater systems, which are up to 27 km long, are orientated along the ice shelf's north–south axis, and follow the surface slope. Over the course of the melt season, they appear to migrate away from the grounding line, while growing in size and enveloping smaller water bodies. This suggests there is large-scale lateral water transfer through the surface meltwater system and the firn pack towards the ice-shelf front during the summer.
Highlights
The total mass loss from Antarctica has increased from 40 ± 9 Gt yr−1 in 1979–1990 to 252 ± 26 Gt yr−1 in 2009– 2017, providing a cumulative contribution to sea-level rise of 14.0 ± 2.0 mm since 1979 (Rignot et al, 2019)
The surface meltwater system transitions from a series of small isolated water bodies clustered towards the grounding line (Fig. 5a) to a connected system dominated by two linear water bodies with a length of (a) ∼ 20.5 km and (b) ∼ 16.9 km that propagate towards the ice-shelf front (Fig. 5d)
By 17 December (Fig. 5b), there has been a marked increase in the total volume (3.2 × 107 m3) and area (4.7 × 107 m2) of surface meltwater, held in both circular and linear surface water bodies (Table 1)
Summary
The total mass loss from Antarctica has increased from 40 ± 9 Gt yr−1 in 1979–1990 to 252 ± 26 Gt yr−1 in 2009– 2017, providing a cumulative contribution to sea-level rise of 14.0 ± 2.0 mm since 1979 (Rignot et al, 2019). One of the most notable events was the February–March 2002 collapse of Larsen B, leading to both an instantaneous and a longer-term speedup of the glaciers previously buttressed by the ice shelf (Scambos et al, 2004; Wuite et al, 2015; De Rydt et al, 2015) and resulting in their increased contribution to sea-level rise (Rignot et al, 2004). Hubbard et al, 2016; Bevan et al, 2017; Banwell et al, 2019).
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