Paul Brown, environment
Saturday January 11, 2003
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
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
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
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,