Abstract
Speedup of Pine Island Glacier over the past several decades has made it Antarctica's largest contributor to sea-level rise. The past speedup is largely due to grounding-line retreat in response to ocean-induced thinning that reduced ice-shelf buttressing. While speeds remained fairly steady from 2009 to late 2017, our Copernicus Sentinel 1A/B-derived velocity data show a >12% speedup over the past 3 years, coincident with a 19-km retreat of the ice shelf. We use an ice-flow model to simulate this loss, finding that accelerated calving can explain the recent speedup, independent of the grounding-line, melt-driven processes responsible for past speedups. If the ice shelf's rapid retreat continues, it could further destabilize the glacier far sooner than would be expected due to surface- or ocean-melting processes.
Highlights
In the decades since it and neighboring Thwaites Glacier were called “the weak underbelly of the West Antarctic Ice Sheet,” [1] Pine Island Glacier (PIG; Fig. 1) has sped up in fits and starts [2,3,4,5,6] as its grounding line retreated [7]
Several modeling studies have shown that past speedups were due to melt-driven thinning concentrated near the grounding line and the resulting loss of basal traction as the grounding line retreated [8,9,10,11], with ice shelf calving only having a minor influence on ice discharge across the grounding line [12]
To investigate the cause of the recent speedup, we modeled the 2017– 2020 loss as a single, instantaneous calving event using a shallow-shelf, ice-flow model of the entire PIG catchment and ice shelf
Summary
In the decades since it and neighboring Thwaites Glacier were called “the weak underbelly of the West Antarctic Ice Sheet,” [1] Pine Island Glacier (PIG; Fig. 1) has sped up in fits and starts [2,3,4,5,6] as its grounding line retreated [7]. Several modeling studies have shown that past speedups were due to melt-driven thinning concentrated near the grounding line and the resulting loss of basal traction as the grounding line retreated [8,9,10,11], with ice shelf calving only having a minor influence on ice discharge across the grounding line [12]. Beginning in 2015, the Copernicus Sentinel 1A/B synthetic aperture radar (SAR) satellites began collecting data every 12 (before fall 2016) and 6 days (fall 2016 to present) over PIG and much of its catchment. We use these data to investigate changes in PIG’s flow speed as its ice shelf retreated by nearly 20 km since late 2017. We analyze changes in flow speed and geometry using an iceflow model to investigate the cause of the recent speedup
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