Volume 8, Number 24: 15 June 2005
In an important new paper, Davis et al. (2005) analyze the elevation change (dH) of over 8.5 million km2 of the grounded Antarctic ice sheet interior (~70% of the total ice-sheet area) using ~347 million dH measurements derived from ERS-1 and ERS-2 ice-mode satellite radar altimeter data (with coverage extending to 81.6°S) for the period 1992 to 2003, after which they compare the observed elevation changes of ~1500 1° x 2° (latitude x longitude) regions, 22 major drainage basins, Berkner Island, West and East Antarctica, and the entire region of coverage (ROC) to estimates of concomitant snowfall derived from meteorological models.
The primary result of this exercise revealed, in the words of the five scientists who conducted the work, that "the vast majority of regions in East Antarctica are thickening, especially in the interior, while regions in West Antarctica exhibit both strong thickening and thinning trends." At the basin scale, as they continue, "dH/dt values range from 0 to +6 cm/year for East Antarctica, while there is substantial spatial variability in West Antarctica with dH/dt values ranging from -10 to +19 cm/year." Overall, they report that the East Antarctic ice sheet interior within the ROC is thickening at a rate of 1.8 ± 0.3 cm/year, while that of the West Antarctic ice sheet interior is thinning at a rate of 0.9 ± 0.3 cm/year. For the entire ROC, the 5:1 ratio of East to West Antarctic area coverage "causes slight thickening overall at the rate of 1.4 ± 0.3 cm/year."
The second important finding of the team was that elevation-change rates estimated from model-derived snowfall trends were significantly smaller than measured dH/dt values. "Comparisons at regional to continental scales," as they describe it, "show that mean snow accumulation from meteorological models is very low over most of the interior of the Antarctic continent." Spatial patterns, however, were similar throughout the studied part of East Antarctica, although much poorer results were obtained for West Antartica. Nevertheless, the scientists conclude that the increasing thickness of the entire ROC "is probably the result of increased snowfall," because there is really no other explanation for it. This being the case, they also conclude that most of the difference between observed and modeled results is likely attributable to "underestimation of the magnitude of annual to decadal changes in snowfall by the meteorological models."
In describing the significance of their findings, Davis et al. note that "the vast size of the East Antarctic ice sheet means that even a small imbalance has a large effect on sea-level change." Specifically, they say their measurements suggest that "the East Antarctic ice sheet interior north of 81.6°S increased in mass by 45 ± 7 billion tons per year from 1992 to 2003," and that "a gain of this magnitude is enough to slow sea-level rise by 0.12 ± 0.02 millimeters per year," which they describe as "a conservative estimate." In addition, they note that "the spatially uniform and positive dH/dt values for the East Antarctic interior suggest that much of the area south of the East Antarctic ROC may also [be] thickening." Assuming it is doing so at the same mean rate as the rest of the ice sheet produces a conservative sea level reduction that is approximately equivalent to 10% of Church et al.'s (2004) "best estimate" of the mean global rate of sea level rise over the last half of the 20th century, which they computed to be 1.8 ± 0.3 mm/year.
There are many implications of these various observations that remain to be determined. At this point in time, however, we can safely conclude that the climate-alarmist claim of dramatic global flooding of earth's coastal areas in response to the melting of polar ice due to global warming has been thoroughly discredited, for during the period of time that they claim the planet experienced the warmest temperatures of the past two millennia, Antarctica experienced a net buildup of ice that actually removed water from earth's seas.
Sherwood, Keith and Craig Idso
Church, J.A., White, N.J., Coleman, R., Lambeck, K. and Mitrovica, J.X. 2004. Estimates of the regional distribution of sea level rise over the 1950-2000 period. Journal of Climate 17: 2609-2625.
Davis, C.H., Li, Y., McConnell, J.R., Frey, M.M. and Hanna, E. 2005. Snowfall-driven growth in East Antarctic Ice Sheet mitigates recent sea-level rise. Sciencexpress/www.sciencexpress.org/science.1110662.