Background
The West Antarctic Ice Sheet [WAIS] is often described as the world's most unstable large ice sheet.  As the authors of this paper report, "it was speculated, from observed fast grounding-line retreat and thinning of a glacier in Pine Island Bay (Rignot, 1998; Shepherd et al., 2001), from the timing of late Pleistocene-Holocene deglaciation in the Ross Sea (Bindschadler, 1998; Conway et al., 1999), and from predicted activity of ice-stream drainage in response to presumed future global warming (Oppenheimer, 1998), that the WAIS may disappear in the future, causing the sea-level to rise at a rate of 1 to 10 mm/year (Bindschadler, 1998; Oppenheimer, 1998)."

What was done
The authors studied the nature and history of glaciomarine deposits contained in sediment cores recovered from the West Antarctic continental margin in the Amundsen Sea to "test hypotheses of past disintegration of the WAIS."

What was learned
All proxies regarded as sensitive to a WAIS collapse, according to the authors, changed markedly during the global climatic cycles of the past 1.8 million years, "but do not confirm a complete disintegration of the WAIS during the Pleistocene" at a place where "dramatic environmental changes linked to such an event should be documented."  In fact, they say their results "suggest relative stability rather than instability of the WAIS during the Pleistocene climatic cycles."

What it means
In light of the findings of this study, it seems reasonable to conclude we are nowhere near having to worry about a disintegration of the WAIS.  This seems also to be the feeling of the authors, who - although careful to state their results "do not exclude the possibility of a WAIS melting in response to future global warming" - emphasize that their primary conclusion is "consistent with only a minor reduction of the WAIS during the last interglacial period (Huybrechts, 1990; Cuffey and Marshall, 2000; Huybrechts, 2002), which was slightly warmer than the Holocene."

Along these same lines, we note that all four of the interglacials that preceded the current interglacial were warmer than the Holocene, by an average of more than 2°C (see our Editorial of 9 August 2000), yet the WAIS still didn't disintegrate.

So, don't hold your breath waiting for the Big Meltdown to occur; it's just not in the cards.

References
Bindschadler, R.  1998.  Future of the West Antarctic Ice Sheet.  Science 282: 428-429.

Conway, H., Hall, B.L., Denton, G.H., Gades, A.M. and Waddington, E.D.  1999.  Past and future grounding-line retreat of the West Antarctic Ice Sheet.  Science 286: 280-283.

Cuffey, K.M. and Marshall, S.J.  2000.  Substantial contribution to sea-level rise during the last interglacial from the Greenland ice sheet.  Nature 404: 591-594.

Huybrechts, P.  1990.  The Antarctic Ice Sheet during the last glacial-interglacial cycle: a three-dimensional experiment.  Annals of Glaciology 14: 115-119.

Huybrechts, P.  2002.  Sea-level changes at the LGM from ice-dynamic reconstructions of the Greenland and Antarctic ice sheets during the glacial cycles.  Quaternary Science Reviews 21: 203-231.

Oppenheimer, M.  1998.  Global warming and the stability of the West Antarctic Ice Sheet.  Nature 393: 325-332.

Rignot, E.J.  1998.  Fast recession of a West Antarctic glacier.  Science 281: 549-551.

Shepherd, A., Wingham, D.J., Mansley, J.A.D. and Corr, H.F.J.  2001.  Inland thinning of Pine Island Glacier, West Antarctica.  Science 291: 862-864.