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Tuesday, January 25, 2005

Arctic rivers 'flowing faster'

Arctic rivers 'flowing faster'
By Alex Kirby
BBC News website environment correspondent

Stepping softly: The Arctic warms up
The amount of fresh water entering the Arctic Ocean from the rivers
that feed it is increasing, UK scientists report.
Writing in the journal Geophysical Research Letters, they say the
increase is caused in part by human activities and is an early sign
of climate change.

The rise in fresh water entering the Arctic Ocean could change the
global distribution of water, the team says.

It could also affect the balance of the climate system itself and
even possibly alter the behaviour of the Gulf Stream.

The team is from the Hadley Centre for Climate Prediction and
Research, part of the UK Met Office.

Knock-on effects

The global hydrological cycle is the exchange of water between the
land, the oceans and the atmosphere. The rate of the exchange is
expected to increase as the Earth warms.

Part of the process is likely to mean more precipitation (hail, rain,
sleet and snow) at higher latitudes, and so more water flowing down
the rivers.

A wetting for Lenin as Siberia floods
If the global water distribution changes, this could have important
social and economic consequences. An altered hydrological cycle might
conceivably have a profound cooling effect on north-west Europe as

The American Geophysical Union, publisher of the journal, says: "It
could also alter the balance of the climate system itself, such as
the Atlantic thermohaline circulation, a kind of conveyor belt.

"Cold water flows southward in the Atlantic at great depths to the
tropics, where it warms, rises, and returns northward near the

"This flow helps keep northern Europe at a temperate climate, whereas
the same latitudes in North America are sparsely settled tundra or

The Hadley researchers compared data published in 2002 from
observations of Siberian river flows with model simulations, to see
whether they could identify a human influence on the increase in
fresh water.

Making allowances

They point out that higher emissions of greenhouse gases, caused by
human activities, are expected to intensify the hydrological cycle in
the Arctic, with higher precipitation there balanced by a reduction
in the tropics.

More fresh water could cool Europe
They tested the model with four simulations which took into account
both human inputs and natural factors, including solar variability
and volcanic eruptions.

The results showed a steady increase in river discharges, especially
since the 1960s, with the annual rate of increase since 1965 8.73
cubic kilometers, far greater than the long-term trend.

The simulations excluded human impacts in one instance and natural
impacts in another, and included all factors in a third.

Dominant part

The team concluded that if there had been no human inputs, the
hydrological cycle would have shown no trend at all in the 20th

Over the past four decades, they say, human activity played the major
role in the increased flows, and it is likely that the upward trend
is part of the early stages of an intensified hydrological cycle.

Dr Peili Wu, a team member, told the BBC: "It looks clear to us that
this is an early signal of human-induced climate change. If only
natural factors were involved, you wouldn't get these results.

"It is possible the increase in fresh water entering the Arctic Ocean
could contribute to an alteration in the thermohaline circulation,
because it is diluting the saltiness of the seawater and reducing its
From:  "mirakulu2003" <mirakulu2003@y...>
Date:  Sun Jan 23, 2005  1:55 pm


Stay in your heart. Regardless of what happens, stay in your heart.


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