Lateral meltwater transfer across an Antarctic ice shelf

Abstract

Abstract. Surface meltwater on ice shelves can be stored as slush, in melt ponds, in surface streams and rivers, and may also fill crevasses. 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, however, 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 the ice shelf. Here, we use Landsat 8 and Sentinel-2 imagery to track surface meltwater across the Nivlisen Ice Shelf in the 2016–2017 melt season. Using the Fully Automated Supraglacial-Water Tracking algorithm for Ice Shelves (FASTISh), we identify and track the development of 1598 water bodies. The total volume of surface meltwater peaks on 26th January 2017 at 5.5 × 107 m3. 63 % of this total volume is held within two large linear surface meltwater systems, which are orientated along the ice shelves north-south axis and appear to migrate away from the grounding line during the melt season, facilitating large scale lateral water transfer towards the ice shelf front. This transfer is facilitated by two large surface streams, which encompass smaller water bodies and follow the surface slope of the ice shelf.

Rapid fragmentation of Thwaites Eastern Ice Shelf, West Antarctica

“…By offsetting the effects of lithostatic pressure, water in surface crevasses can shift an ice shelf into a tensile stress regime, leading to deep penetration of the crevasses and runaway failure (Scambos et al, 2003;Robel and Banwell, 2019;Lai et al, 2020). Supraglacial stream networks can transport water off ice shelves or focus it in vulnerable areas, and hence play either a stabilising or destabilising role in the hydrofracture process (Kingslake et al, 2017;Bell et al, 2017;Dell et al, 2020). Alternatively, unpinning from ice shelf margins or grounding points impacts ice shelf stability by removing sources of resistive stress.…”

Observations of Buried Lake Drainage on the Antarctic Ice Sheet

“…Recent work indicates that meltwater production and ponding on the AIS are more extensive than previously thought (Bell et al., 2018; Kingslake et al., 2017). Large‐scale drainage networks transport meltwater across ice shelves, feeding surface melt ponds (Dell et al., 2020; Kingslake et al., 2017; Phillips, 1998) and, in some cases, exporting water to the ocean via large waterfalls (Bell et al., 2018). Additionally, a portion of meltwater is stored in buried lakes, which are located within the firn and can be buried up to a few meters below the ice surface (Lenaerts et al., 2017; MacAyeal et al., 2019; Miles et al., 2017).…”

The triggers of the disaggregation of Voyeykov Ice Shelf (2007), Wilkes Land, East Antarctica, and its subsequent evolution

“…We note that total lake area is considerably less than on other Antarctic ice shelves (Fig. 7; Stokes and others, 2019; Arthur and others, 2020; Dell and others, 2020), and has not exceeded 9 km 2 since 2000 (<1% of the ice shelf area), though this partly reflects both the small total ice shelf area and its heavily rifted surface through which meltwater can drain before it can accumulate as lakes. In summary, during the 2006–2007 melt season preceding disaggregation, VIS experienced short-lived intense surface melting and above-average supraglacial lake coverage, though surface meltwater does not accumulate extensively on VIS.…”

“…The Normalized Difference Water Index (NDWI ice ) adapted for ice was used to extract pixels containing liquid water, which uses the red and blue bands (Yang and Smith, 2013). A threshold value of 0.25 was applied, meaning pixels with NDWI >0.25 were assumed to be water-covered, following previous studies (Bell and others, 2017; Banwell and others, 2019; Arthur and others, 2020; Dell and others, 2020; Moussavi and others, 2020). No exposed rock nunataks or outcrops are present in this region and we isolated clouds, cloud shadow, seawater, shaded snow and dark areas (such as crevasses), following Moussavi and others (2020) (Table 2).…”