West Antarctic Ice Sheet collapse – the fall and rise of a paradigm

Abstract

It is now almost 30 years since John Mercer (1978) first presented the idea that climate change could eventually cause a rapid deglaciation, or "collapse", of a large part of the West Antarctic ice sheet (WAIS), raising world sea levels by 5 metres and causing untold economic and social impacts. This idea, apparently simple and scientifically plausible, created a vision of the future, sufficiently alarming that it became a paradigm for a generation of researchers and provided an icon for the green movement. Through the 1990s, however, a lack of observational evidence for ongoing retreat in WAIS and improved understanding of the complex dynamics of ice streams meant that estimates of likelihood of collapse seemed to be diminishing. In the last few years, however, satellite studies over the apparently inaccessible Amundsen Sea sector of West Antarctica have shown clear evidence of ice sheet retreat showing all the features that might have been predicted for emergent collapse. These studies are re-invigorating the paradigm, albeit in a modified form, and debate about the future stability of WAIS. Since much of WAIS appears to be stable, it may, no longer be reasonable to suggest there is an imminent threat of a 5-m rise in sea level resulting from complete collapse of the West Antarctic ice sheet, but there is strong evidence that the Amundsen Sea embayment is changing rapidly. This area alone, contains the potential to raise sea level by around ~1.5 m, but more importantly it seems likely that it could, alter rapidly enough, to make a significant addition to the rate of sea-level rise over coming two centuries. Furthermore, a plausible connection between contemporary climate change and the fate of the ice sheet appears to be developing. The return of the paradigm presents a dilemma for policy-makers, and establishes a renewed set of priorities for the glaciological community. In particular, we must establish whether the hypothesized instability in WAIS is real, or simply an oversimplification resulting from inadequate understanding of the feedbacks that allow ice sheets to achieve equilibrium: and whether there is any likelihood that contemporary climate change could initiate collapse.

The sedimentary legacy of a palaeo-ice stream on the shelf of the southern Bellingshausen Sea: Clues to West Antarctic glacial history during the Late Quaternary

“…Both the WAIS and the APIS have shown dramatic signs of ice loss over the last few decades (e.g. Rignot et al, 2004Rignot et al, , 2008Scambos et al, 2004;Thomas et al, 2004;Vaughan, 2008;Pritchard et al, 2009;Wingham et al, 2009). The WAIS is largely grounded below sea level and therefore considered to be the most vulnerable part of the Antarctic Ice Sheet (e.g.…”

“…The WAIS is largely grounded below sea level and therefore considered to be the most vulnerable part of the Antarctic Ice Sheet (e.g. Oppenheimer, 1998;Vaughan, 2008). A complete WAIS collapse would raise global sea level by w3.3e5 m (e.g.…”

“…A complete WAIS collapse would raise global sea level by w3.3e5 m (e.g. Vaughan, 2008;Bamber et al, 2009). If recent WAIS drawdown observed in the Amundsen Sea sector continues, this melting alone will cause global sea level to rise by w1.5 m (Vaughan, 2008).…”

“…Vaughan, 2008;Bamber et al, 2009). If recent WAIS drawdown observed in the Amundsen Sea sector continues, this melting alone will cause global sea level to rise by w1.5 m (Vaughan, 2008). A collapse of the land-based APIS would raise global sea level by w0.24 m (Pritchard and Vaughan, 2007), but the significance of its contribution to sea-level rise in the near future is under debate (cf.…”

“…Similarly, it is unclear if Antarctic deglaciation since the last glacial period has contributed to prominent global meltwater pulses (Clark et al, 2002;Licht, 2004;Peltier, 2005;Bassett et al, 2007). Therefore, knowledge of the history of the WAIS and the APIS since the last ice age is crucial not only for a better understanding of fundamental ice-sheet dynamics, but also for a reliable prediction of future WAIS and APIS behaviour in response to modern global warming (Alley et al, 2005;Vaughan, 2008).…”