Evolution of supraglacial lakes on the Larsen B ice shelf in the decades before it collapsed

Abstract

<p class="Abstract"><span lang="EN-US">The Larsen B ice shelf collapsed in 2002 losing an area twice the size of Greater London to the sea (3000 km<sup>2</sup>), in an event associated with widespread supraglacial lake drainage. Here, we use optical and radar satellite imagery to investigate the evolution of the ice shelf’s lakes in the decades preceding collapse. We find 1) that lakes spread southwards in the preceding decades at a rate commensurate with meltwater saturation of the shelf surface, 2) no trend in lake size, suggesting an active supraglacial drainage network which evacuated excess water off the shelf and 3) lakes mostly re-freeze in winter but the few lakes that do drain are associated with ice break up 2-4 years later. Given the relative scale of lake drainage and shelf break up, however, it is not clear from our data whether lake drainage is more likely a cause, or an effect, of ice shelf collapse.</span></p>

Observations of Buried Lake Drainage on the Antarctic Ice Sheet

“…Although Antarctic surface lake drainage events have been observed remotely (Langley et al., 2016; Leeson et al., 2020; Scambos et al., 2000, 2009), and lake drainage via stream overflow has been documented with field measurements on the McMurdo Ice Shelf (Banwell et al., 2019), until this study, there have been no field observations of vertical lake drainage on the AIS via the rapid hydrofracture mechanism.…”

Recent understanding of Antarctic supraglacial lakes using satellite remote sensing

“…meltwater in a lake) (Figure 9) (Labarbera and MacAyeal, 2011;Sergienko, 2013) and is successfully able to replicate the near-synchronous lake drainage and widespread fracture network that fragmented Larsen B Ice Shelf into unstable blocks capable of capsizing (Banwell et al, 2013). More recently, Leeson et al (2020) showed that SGLs spread southwards on the ice shelf in the two decades preceding its collapse at a rate commensurate with meltwater saturation of its surface. However, lake deepening across the ice shelf over this period suggests this could be the result of enhanced lake bed ablation rather than the result of successive lake filling and draining (Leeson et al, 2020).…”

“…More recently, Leeson et al (2020) showed that SGLs spread southwards on the ice shelf in the two decades preceding its collapse at a rate commensurate with meltwater saturation of its surface. However, lake deepening across the ice shelf over this period suggests this could be the result of enhanced lake bed ablation rather than the result of successive lake filling and draining (Leeson et al, 2020).…”