WASHINGTON (AP) — Fueled by global warming, polar ice sheets in Greenland
and Antarctica are now melting three times faster than they did in the
1990s, a new scientific study says.
So far, that’s only added about half an inch to rising sea levels, not as
bad as some earlier worst case scenarios. But the melting’s quicker pace,
especially in Greenland, has ice scientists worried.
The new research concludes that Antarctica is melting, but points to the
smaller ice sheet in Greenland, which covers most of the island, as the
bigger and more pressing issue. Its melt rate has grown from about 55
billion tons a year in the 1990s to almost 290 billion tons a year recently,
according to the study.
“Greenland is really taking off,” said National Snow and Ice Data Center
scientist Ted Scambos, a co-author of the paper released Thursday by the
Study lead author Andrew Shepherd of the University of Leeds in England,
said their results provide a message for negotiators in Doha, Qatar, who are
working on an international agreement to fight global warming: “It’s very
clear now that Greenland is a problem.”
Scientists blame man-made global warming for the melting. Burning fossil
fuels, such as coal and oil, emits carbon dioxide and other greenhouse gases
that trap heat, warming the atmosphere and oceans. Bit-by-bit, that erodes
the ice sheets from above and below. Snowfall replenishes the ice sheets,
but hasn’t kept pace with the rate of melting.
Because the world’s oceans are so big, it takes a lot of ice melting — about
10 trillion tons — to raise sea levels 1 inch. Since 1992, ice sheets at the
poles have lost nearly 5 trillion tons of ice, the study says, raising sea
levels by about a half inch.
That seemingly tiny extra bit probably worsened the flooding from an already
devastating Superstorm Sandy last month, said NASA ice scientist Erik Ivins,
another co-author of the study. He said the extra weight gives each wave a
little more energy.
Globally, the world’s oceans rose about half a foot on average in the 20th
Century. Melting ice sheets accounts for about one-fifth of sea level rise.
Warmer water expands, contributing to the rise along with water from melting
glaciers outside the polar regions.
If all the polar ice sheets somehow melted — something that would take
centuries — global sea levels would jump by more than 200 feet, said
Pennsylvania State University ice scientist Richard Alley, who wasn’t part
of the research.
Some past studies showed melting on the polar ice sheets, while others said
that the Antarctic ice sheet was growing and offsetting melting in
Greenland. The new work by 47 scientists around the world combines three
methods and measurements from 10 satellites to come to a scientific
consensus on what’s happening to the polar ice sheets.
In the 1990s, the two ice sheets combined on average lost 110 billion tons
of ice each year to melting, the researchers reported. That increased and by
2005 to 2010, they were losing three times as much — 379 billion tons
yearly. The numbers don’t include the summer of 2012 when Greenland
experienced a melt that hadn’t been seen in more than a century, researchers