Abstract
AbstractA decrease in the mass and volume of Western Palmer Land has raised the prospect that ice speed has increased in this marine‐based sector of Antarctica. To assess this possibility, we measure ice velocity over 25 years using satellite imagery and an optimized modeling approach. More than 30 unnamed outlet glaciers drain the 800 km coastline of Western Palmer Land at speeds ranging from 0.5 to 2.5 m/d, interspersed with near‐stagnant ice. Between 1992 and 2015, most of the outlet glaciers sped up by 0.2 to 0.3 m/d, leading to a 13% increase in ice flow and a 15 km3/yr increase in ice discharge across the sector as a whole. Speedup is greatest where glaciers are grounded more than 300 m below sea level, consistent with a loss of buttressing caused by ice shelf thinning in a region of shoaling warm circumpolar water.
Highlights
Over the past three decades, Antarctica’s contribution to global sea level rise has been dominated by ice loss from some of its marine-based sectors [Rignot et al, 2008; Mouginot et al, 2014; Shepherd et al, 2012]
Observed changes in ice flow at the Antarctic Peninsula have been largely restricted to its northern sectors, there is evidence of recent ice shelf [Shepherd et al, 2010; Pritchard et al, 2012; Paolo et al, 2015] and grounded ice [McMillan et al, 2014; Helm et al, 2014; Wouters et al, 2015] thinning within its southerly glacier catchments, which could impact on future sea level rise
The Western Palmer Land coastline is characterized by a 300 km wide central region of ice flowing with indistinct margins between the Horne Nunataks (À71.7°S, À66.7°W) and Eklund Island (À73.2°S, À71.8°W), and by discrete glaciers separated by areas of stagnant flow elsewhere (Figure 1)
Summary
Over the past three decades, Antarctica’s contribution to global sea level rise has been dominated by ice loss from some of its marine-based sectors [Rignot et al, 2008; Mouginot et al, 2014; Shepherd et al, 2012]. Glaciers draining the Amundsen Sea sector of West Antarctica and the Antarctic Peninsula have undergone widespread retreat, acceleration, and thinning [Shepherd et al, 2002; Rignot, 2008; Shuman et al, 2011; Park et al, 2013; McMillan et al, 2014; Mouginot et al, 2014; Rignot et al, 2014; Rott et al, 2014] These changes have been attributed to the effects of oceanic [Shepherd et al, 2003; Thomas et al, 2008; Jacobs et al, 2011; Cook et al, 2016] and atmospheric [Vaughan and Doake, 1996; Scambos et al, 2000] warming, which has eroded grounded ice and floating ice shelves at the terminus of key marine-based glaciers [Shepherd et al, 2003; Shepherd and Wingham, 2007; Pritchard et al, 2012], triggering widespread dynamical imbalance upstream [Payne et al, 2004; Joughin et al, 2012, 2014a]. Changes in ice flow can, further, be an indicator of dynamic instability, where mass loss leads to a positive
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