Global warming of Atlantic could hit fish -study
30 Mar 2005 18:00:01 GMT
By Jeremy Lovell
LONDON, March 30 (Reuters) - 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
"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
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,"
"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
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.