Thaw in Greenland threatens new ice age

Mark Jones markjones011 at tiscali.co.uk
Fri Jan 10 22:08:30 MST 2003



This week's big chill could prove a taster of winters to come

Paul Brown, environment correspondent
Saturday January 11, 2003
The Guardian

The snowfalls of the past week may be just a taster of what is to come, if
the latest predictions from scientists are correct. The amount of ice
melting from the surface of the Greenland ice sheet broke all known records
last year, threatening a rapid rise in sea levels and a return of very cold
winters to Britain because of a slowing down in the Gulf Stream.
Already the Gulf Stream, which bathes the west coast of Britain in warm
water from the Gulf of Mexico and keeps the country much milder than normal
for such northern latitudes, is slowing down. Even greater melting of the
Greenland ice could shut off the currents altogether, allowing depressions
to dump snow rather than instead of rain in Britain and leading to a much
colder continental climate, as has been experienced in the past week.

As happens on the eastern seaboard of Canada, which on the same latitude,
the sea could freeze and snow lie for weeks or months instead of a day of
two.

Last year large areas of the Greenland ice shelf, previously too high and
too cold to melt, began pouring billions of gallons of fresh water into the
northern Atlantic. Melted water trapped between the ice and the rock beneath
is causing an acceleration of glaciers breaking off in huge chunks and
increasing the number of icebergs.

According to scientists at the University of Colorado a very dramatic
melting trend has been in progress since 1979. Extreme melt years were 1991,
1995 and 2002.

The Greenland ice sheet's maximum melt area increased on average by 16% from
1979 to 2002. This year's maximum melt extent of 264,400 square miles
exceeds by 2.6 times the melt area measured in 1992. In particular, the
northern and north-eastern part of the ice sheet experienced melting
reaching up to an elevation of 2,000 metres (6,560ft).

This is the first time this area of the giant island, closest to the north
pole, has suffered this kind of melting. The Colorado-based Cooperative
Institute for Research in Environmental Sciences also found that
temperatures during the summer of 2002 were unusually warm over much of the
Arctic ocean.

"Since the season also was characterised by very stormy conditions, we
believe these two factors contributed to extensive melt and break-up of the
icepack," said research associate Mark Serreze, the lead author of the
study, which was presented at a meeting of the American Geophysical Union.

Sea ice in the Arctic last year was at the lowest since satellite
measurements began.

Mr Serreze said accelerated melting of sea ice, along with runoff from the
Greenland ice sheet, was bad news for British weather moderated by the Gulf
Stream. The warm water from the tropics now travels north past British
shores and warms the western coastlines of Europe as far north as Norway
before sinking to the bottom of the ocean and returning south.

This deep water convection in the north Atlantic has already been noted to
be slowing down by British scientists, and US scientists say the trend could
profoundly impact global ocean circulation and climate. "In other studies,
changes in the north Atlantic circulation have been implicated in starting
and stopping northern hemisphere ice ages," Mr Serreze said.

Climatologist Konrad Steffen, a professor of geography at Colorado, said a
change in the Greenland climate towards warmer conditions would lead to an
increase in the rate of sea level rise, mainly due to the dynamic response
of the large ice sheet rather than just the surface melting.

"For every degree increase in the mean annual temperature near Greenland,
the rate of sea level rise increases by about 10%," Professor Steffen said.
Oceans are now rising by a little more than half an inch every 10 years.

Both sea ice and glacier ice cool the earth, reflecting back into space
about 80% of springtime sunshine and 40% -50% during the summer melt. But
winter sea ice cover slows heat loss from the relatively warm ocean to the
cold atmosphere. Without large sea ice masses at the poles to moderate the
energy balance, warming escalates.


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