Stone, J.O., Balco, G.A., Sugden, D.E., Caffee, M.W., Sass III, L.C., Cowdery, S.G. and Siddoway, C. 2003. Holocene deglaciation of Marie Byrd Land, West Antarctica. Science 299: 99-102.
"The fate of humankind is linked to that of the remote West Antarctic Ice Sheet (WAIS) through global sea levels." So writes Ackert (2003) in his Science glaciology perspective on the report of Stone et al. (2003), who describe trends of deglaciation over parts of this crucially important polar ice sheet throughout the Holocene. Does their work reveal, as Ackert asks, "the early stages of rapid ice sheet collapse, with potential near-term impacts on the world's coastlines?"
If one pays any attention at all to the harangues of climate alarmists, one might assume this question has already been answered - and answered in the affirmative - especially in light of their oft-repeated claim that the increase in mean global air temperature of the past hundred years is "unprecedented over the past millennium." One might also assume the same in light of the fact that climate alarmists typically do suggest we are witnessing the early stages of West Antarctic Ice Sheet disintegration, especially when a large chunk of ice goes "crack in the night," escapes from its frigid homeland, and sets sail upon the Southern Ocean. The research of Stone and his colleagues, however, goes a long way towards putting these baseless claims to a well-deserved rest.
What was done
Working on western Marie Byrd Land, Stone et al. collected and determined cosmogenic 10Be exposure dates of glacially-transported cobbles in elevation transects on seven peaks of the Ford Ranges that are located between the ice sheet's present grounding line and the Clark Mountains some 80 km inland. Based on these ages and the elevations at which the cobbles were found, they determined a history of ice-sheet thinning over the past 10,000-plus years.
What was learned
The scientists say their data show that "the exposed rock in the Ford Ranges, up to 700 m above the present ice surface, was deglaciated within the past 11,000 years" and that "several lines of evidence suggest that the maximum ice sheet stood considerably higher than this." They also report that the consistency of the exposure age versus elevation trends of their data "indicates steady deglaciation since the first of these peaks emerged from the ice sheet some time before 10,400 years ago" and that the mass balance of the region "has been negative throughout the Holocene."
Continuing, Stone et al. say their results "add to the evidence that West Antarctic deglaciation continued long after the disappearance of the Northern Hemisphere ice sheets and may still be under way," and they report that the ice sheet in Marie Byrd Land "shows the same pattern of steady Holocene deglaciation as the marine ice sheet in the Ross Sea," where ice "has thinned and retreated since 7000 years ago," noting further that "there is strong evidence that the limit of grounded ice in both regions - and in Pine Island Bay - is still receding."
What it means
As long contended by scientists who disagree with climate-alarmist claims that we are witnessing CO2-induced "early stages of rapid ice sheet collapse," the work of Stone et al. convincingly demonstrates that the current thinning and retreat of the West Antarctic Ice Sheet are merely manifestations of a slow but steady deglaciation that has been going on and on and on, ever since the beginning-of-the-end of the last great ice age. Although this phenomenon is unabashedly used by climate alarmists to scare people into believing anthropogenic CO2 emissions are rapidly leading to the demise of the WAIS, Stone et al. say something quite different, i.e., that "the pattern of recent change is consistent with the idea that thinning of the WAIS over the past few thousand years is continuing." Ackert makes the point even plainer, when he says "recent ice sheet dynamics appear to be dominated by the ongoing response to deglacial forcing thousands of years ago, rather than by a recent anthropogenic warming or sea level rise."
So what's new with the West Antarctic Ice Sheet? Nothing. Nothing at all.
Ackert Jr., R.P. 2003. An ice sheet remembers. Science 299: 57-58.
Reviewed 29 January 2003