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Greenland melt ‘speeding up’
The meltdown of Greenland’s ice sheet is speeding up, satellite measurements show.
Data
from a US space agency (Nasa) satellite show that the melting rate has
accelerated since 2004.If the ice cap were to completely disappear,
global sea levels would rise by 6.5m (21 feet).Most of the ice is being
lost from eastern Greenland, a US team writes in Science journal.Jianli
Chen of the University of Texas at Austin and colleagues studied
monthly changes in the Earth’s gravity between April 2002 and November
2005.These measurements came from the US space agency’s Grace (Gravity
Recovery and Climate Experiment) satellite, launched in 2002.From these
data, they were able to estimate changes in the mass of Greenland’s ice
sheet.A number of factors contribute to fluctuations in the Earth’s
gravity field.But once the influence of the atmosphere and the oceans
is removed, the variations mostly reflect changes in the mass of ice
sheets and of water stored in the ground.Estimated monthly changes in
the mass of Greenland’s ice sheet suggest it is melting at a rate of
about 239 cubic kilometres (57.3 cubic miles) per year.This figure is
about three times higher than an earlier estimate of the mass loss from
Greenland made using the first two years of Grace measurements.Satellite data
Dr
Chen and colleagues partly attribute this to increased melting in the
past one-and-a-half years and partly to better processing of the
data.”Acceleration of mass loss over Greenland, if confirmed, would be
consistent with proposed increased global warming in recent years,” the
authors wrote in Science.This would amount to a contribution to global
sea level rise from Greenland of about half a millimetre (0.02 inches)
each year.The group’s findings agree remarkably well with a study
released earlier this year that used data from other satellites to
estimate mass changes in the Greenland ice.Grace also appears to have
detected a loss of ice from Arctic glaciers that were omitted from this
study and are separate from the main Greenland ice sheet.
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