Global Warming
Of Atlantic
Could Hit Fish
By Jeremy Lovell
31 March, 2005
Planet
Ark
The
potential shutdown due to climate warming of the key Atlantic Conveyor
current that warms northern Europe could have a major impact on fish
stocks in the region, a scientist said on Wednesday.
Oceanographers have predicted that the current that drags warm water
from the south to the north could weaken or even come to a halt as global
warming melts the Arctic polar icecap and dilutes the ocean's salinity.
"A disruption
of the Atlantic meridional overturning (AMO) circulation leads to a
collapse of the North Atlantic plankton stocks to less than half their
initial biomass," said Andreas Schmittner of Oregon State University.
Writing in the science
journal Nature, Schmittner said the steep drop in the plankton population
was due to it becoming separated from deep water nutrient layers as
the ocean current failed.
To date much work
has been done on the potential disruption of the Atlantic Conveyor as
the climate warms by an estimated two degrees centigrade this century
due to man-made greenhouse gases such as carbon dioxide.
However, relatively
little research has been published on the possible effect on the seaborne
food chain which provides sustenance for millions of people.
"A massive
decline of plankton stocks could have catastrophic effects on fisheries
and human food supply in the affected regions," Schmittner wrote.
"Hence, emission
pathways that lead to fast and large increases of future CO2 including
the risk of a collapse or substantial reduction of the AMO should be
avoided through early measures for emission reductions," he added.
He said there was
evidence that the current had switched on and off during the ice ages,
and his modelling work indicated that ocean productivity could drop
by 20 percent as plankton vanished.
"These model
results ... suggest that global ocean productivity is sensitive to changes
in the Atlantic meridional overturning circulation," he said.
It is not confined
to the northern Atlantic but has implications across the Indian, Pacific,
Arabian and southern Atlantic Oceans, he added.
Although the effect
was most noticeable in the north Atlantic where even a partial weakening
in the life-giving current caused a substantial drop in productivity,
it also registered globally.
"The results
... have important implications for the assessment of future greenhouse
gas emission scenarios," Schmittner said.