# The Mass Balance of the Greenland Ice Sheet



## Minho (28 Mar 2007 às 22:48)

Só realce ao último paragrafo...



> Every few weeks a new study of the mass balance of the Greenland Ice Sheet seems to appear in the scientific literature. In the 21 Oct 2005 issue of Science, it was the review of Alley et al. (2005), who claimed "the Greenland Ice Sheet may melt entirely from future global warming," which contention they buttressed with the statement that "recently detected rapid ice-marginal changes contributing to sea-level rise may indicate greater ice-sheet sensitivity to warming than previously considered." Between 1993-94 and 1998-99, for example, they said "the ice sheet was losing 54 ± 14 gigatons per year (Gt/year) of ice, equivalent to a sea-level rise of ~0.15 mm/year," adding that despite excess snowfall in the southeast in 2002 and 2003, "net mass loss over the 1997-to-2003 interval was higher than the loss between 1993 and 1999, averaging 74 ± 11 Gt/year or ~0.21 mm/year sea-level rise."
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> Just one day before Alley et al.'s paper appeared in print, however, Johannessen et al. (2005), working with satellite-altimeter data from Greenland, reported in a Sciencexpress paper posted online that although below 1500 meters the mean change of the ice sheet height with time was a decline of 2.0 ± 0.9 cm/year over the 11-year period 1992-2003, above 1500 meters there was a positive growth rate of fully 6.4 ± 0.2 cm/year due to snow accumulation; and they determined that averaged over the entire ice sheet the mean result was also positive, at a mean growth rate of 5.4 ± 0.2 cm/year, which when adjusted for an isostatic uplift of about 0.5 cm/year yielded a mean growth rate of approximately 5 cm/year, for a total increase in the mean thickness of the Greenland Ice Sheet of about 55 cm over the 11-year period, a result that was just the opposite of that reported by Alley et al.
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http://www.co2science.org/scripts/CO2ScienceB2C/articles/V10/N2/EDIT.jsp*


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