Damage accelerates ice shelf instability and mass loss in Amundsen Sea Embayment

Abstract

Pine Island Glacier and Thwaites Glacier in the Amundsen Sea Embayment are among the fastest changing outlet glaciers in West Antarctica with large consequences for global sea level. Yet, assessing how much and how fast both glaciers will weaken if these changes continue remains a major uncertainty as many of the processes that control their ice shelf weakening and grounding line retreat are not well understood. Here, we combine multisource satellite imagery with modeling to uncover the rapid development of damage areas in the shear zones of Pine Island and Thwaites ice shelves. These damage areas consist of highly crevassed areas and open fractures and are first signs that the shear zones of both ice shelves have structurally weakened over the past decade. Idealized model results reveal moreover that the damage initiates a feedback process where initial ice shelf weakening triggers the development of damage in their shear zones, which results in further speedup, shearing, and weakening, hence promoting additional damage development. This damage feedback potentially preconditions these ice shelves for disintegration and enhances grounding line retreat. The results of this study suggest that damage feedback processes are key to future ice shelf stability, grounding line retreat, and sea level contributions from Antarctica. Moreover, they underline the need for incorporating these feedback processes, which are currently not accounted for in most ice sheet models, to improve sea level rise projections.

The 32-year record-high surface melt in 2019/2020 on the northern George VI Ice Shelf, Antarctic Peninsula

“…For the northern GVIIS, we also derive smaller-scale melt information from an enhanced resolution C-band (5.225 GHz) VV polarization radar backscatter image time series collected by EUMETSAT's Advanced SCATterometer (AS-CAT), aboard the tandem polar-orbiting satellites MetOp-A and MetOp-B. The 4.45 km enhanced product is obtained by applying the Scatterometer Image Reconstruction (SIR) algorithm with filtering (Lindsley and Long, 2016), which is used to improve the spatial resolution of irregularly and oversampled data (Early and Long, 2001). The effective spatial resolution was estimated at ∼ 12-15 km, three-fold finer than the effective resolution of the SMMR/SSMI-based product (∼ 50 km).…”

Drivers of Pine Island Glacier speed-up between 1996 and 2016

“…The open source ice flow model Úa (Gudmundsson, 2020) uses the finite-element method to solve the shallow ice stream equations, commonly referred to as SSA or SSTREAM (Hutter, 1983;MacAyeal, 1989), on an irregular triangular mesh. The diagnostic velocity solver is based on an iterative Newton-Raphson method.…”

32-year record-high surface melt in 2019/2020 on north George VI Ice Shelf, Antarctic Peninsula

“…Extensive surface ponding (Arthur et al 2020;Dell et al, 2020;Kingslake et al, 2017) may threaten ice-shelf stability due to stress variations associated with meltwater movement, ponding and drainage (Scambos et al, 2000(Scambos et al, , 2003MacAyeal et al, 2003;Banwell and MacAyeal, 2015;Banwell et al 2019). These processes may initiate meltwater-induced vertical fracturing ('hydrofracturing') (Van der Veen, 2007;Dunmire et al, 2020;Lai et al 2020), especially if the ice shelf is already damaged with a high density of crevasses (Lhermitte et al, 2020). The collapse of the Larsen B ice shelf in 2002 is arguably the most famous break-up event due to its rapidity and extent (e.g.…”