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Changes in the Southern Greenland Ice Sheet
Krabill, W., Frederick, E., Manizade, S., Martin, C., Sonntag, J., Swift, R., Thomas, R., Wright, W. and Yungel, J. 1999. Rapid thinning of parts of the southern Greenland ice sheet. Science 283: 1522-1524.

What was done
Aircraft laser-altimeter measurements were conducted over southern Greenland in 1993 and 1998 in an effort to determine any changes that may have occurred in the mass of the ice sheet located south of 72 N latitude over this 5-year time interval.

What was learned
Results indicate an average thickening of the ice sheet of 0.5 0.7 cm per year for elevations above 2000 meters, where the data are considered "most reliable." Lower elevations, on the other hand, were reportedly thinning. On the whole, the authors believe that "the surveyed region is in negative balance." As for the cause of this possible glacial wasting, the authors note that it is "extremely unlikely" that the observed thinning could be explained by a "reduction in snowfall or by an increase in summer melting."

What it means
The data obtained in this study are still too uncertain to yield a firm assessment of the overall mass balance of the southern portion of the Greenland ice sheet; and of course, they say nothing about the northern portion. Hence, we still do not know the true status of the mass balance of the entire Greenland ice sheet. Consequently, as the authors suggest, further studies will be required to answer this important question.

Reviewed 15 April 1999