From: Reuters
Published December 29, 2008 09:24 AM
Seawater science can help climate change forecasts
By David Fogarty, Climate Change Correspondent, Asia
SINGAPORE (Reuters) - A team of scientists has come up with a new definition
of seawater which is set to boost the accuracy of projections for oceans and
climate.
Oceans help regulate the planet's weather by shifting heat from the equator
to the poles. Changes in salinity and temperature are major forces driving
global currents as well as circulation patterns from the surface to the
seabed.
Understanding exactly how much heat the ocean can absorb and accounting for
tiny differences in salinity are crucial for scientists to figure how oceans
affect climate and how that interaction could change because of global
warming.
"Getting these circulations right is central to the task of quantifying
the ocean's role in climate change," said Trevor McDougall of Australia's
state-backed research body the CSIRO, who is part of the international team
that updated the methods to define sea water.
He said the new definition allows for the first time to accurately calculate
ocean heat content and take into account small differences in salinity.
Previous methods assumed the composition of seawater was the same around the
globe.
Seawater is a mixture of 96.5 percent pure water with the remainder
comprising salts, dissolved gases and other matter. McDougall said data from
about 1,000 seawater samples showed global variations.
There were small but significant differences in the composition of seawater
between the North Pacific and North Atlantic, for example.
"We've got along quite well for 30 years without delving deeper into what
the sea salt is composed of," said McDougall, of the CSIRO's Wealth from
Oceans Flagship in Hobart in the southern Australian state of Tasmania.
But ever more complex computer models and greater demands to project how
oceans and climate will behave in a warmer world mean an increasing need for
more precise data.
McDougall said salinity affects ocean density, and changes in density help
drive huge vertical ocean circulation patterns.
"Water sinks to the bottom and rises to the top in a very slow circulation
that accounts for about half of the heat that the globe needs to transport
from the equator to the poles."
The constant circulation of heat by the oceans and atmosphere keeps the
planet livable.
"What we're doing is providing a more accurate way of estimating that
circulation," McDougall said.
McDougall chairs the Scientific Committee on Oceans Research, an
international guiding body, and said he expected the new methods to be
formally backed by the Intergovernmental Oceanographic Commission at a
meeting in June next year.
(Editing by Jerry Norton)
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