A Fifty-Year Reconstruction of Antarctic Snowfall��

A Fifty-Year Reconstruction of Antarctic Snowfall

HYPERLINK "http://www.co2science.org/scripts/CO2ScienceB2C/articles/V9/N34/C1.jsp" http://www.co2science.org/scripts/CO2ScienceB2C/articles/V9/N34/C1.jsp

Reference
Monaghan, A.J., Bromwich, D.H., Fogt, R.L., Wang, S.-H., Mayewski, P.A., Dixon, D.A., Ekaykin, A., Frezzotti, M., Goodwin, I., Isaksson, E., Kaspari, S.D., Morgan, V.I., Oerter, H., Van Ommen, T.D., Van der Veen, C.J. and Wen, J. 2006. Insignificant change in Antarctic snowfall since the International Geophysical Year. Science 313: 827-831.

What was done
The authors derived a fifty-year time series of snowfall accumulation over Antarctica by combining climate model simulations and snowfall observations derived from "scores of new ice core records" plus snow pit and snow stake data.

What was learned
Monaghan et al. report that over both the East and West Antarctic Ice Sheets and the grounded ice sheet, "there are no statistically significant trends in snowfall accumulation over the past 5 decades, including recent years for which global mean temperatures have been warmest," although plots of their data show what must be non-significant downward trends over the past decade or so.

What it means
The results of this study have the potential to be quite significant, for if they are correct they imply, as the sixteen researchers gingerly suggest, that "Antarctic snowfall is not currently compensating for the oceanic-induced melting at the ice sheet periphery." However, they acknowledge that their findings are "somewhat inconsistent" with those of HYPERLINK "http://www.co2science.org/scripts/CO2ScienceB2C/articles/V8/N24/EDIT.jsp" Davis et al. (2005), who found from satellite radar altimetry data that the East Antarctic Ice Sheet (EAIS) had thickened over the past decade. Acknowledging the similar finding of HYPERLINK "http://www.co2science.org/scripts/CO2ScienceB2C/articles/V9/N10/C2.jsp" Zwalley et al. (2005), Monaghan et al. thus state that they "do not dispute that altimetry indicates a clear thickening signal over EAIS that mitigates sea level rise," which, of course, is just the opposite of what they find from their data and analysis. As with all good mysteries, therefore, this story is to be continued. For the time being, however, we feel forced to accept (tentatively, at least) the implication of the more directly measured results of Davis et al. and Zwally et al., i.e., that the East Antarctic Ice Sheet is indeed still gaining mass.

References
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. Science 308: 1898-1901.

Zwally, H.J., Giovinetto, M.B., Li, J., Cornejo, H.G., Beckley, M.A., Brenner, A.C., Saba, J.L. and Yi, D. 2005. Mass changes of the Greenland and Antarctic ice sheets and shelves and contributions to sea-level rise: 1992-2002. Journal of Glaciology 51: 509-527.

Reviewed 23 August 2006