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Science Forum Index » Environment Forum » Scientists say that tropical oceans are more salty
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| Ilena |
 Posted: Tue Dec 23, 2003 7:36 am |
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Scientists say that tropical oceans are more salty
Special to A.M. Costa Rica
Tropical ocean waters have become dramatically saltier over the past
40 years while oceans closer to Earth's poles have become fresher.
These are relatively rapid oceanic changes that scientists say may
reflect transformations in the fundamental planetary system that
cycles fresh water around the globe.
An international team of scientists funded in part by the National
Science Foundation analyzed salinity measurements collected over
recent decades along a key region of the Atlantic Ocean, from the tip
of Greenland to the tip of South America.
The researchers, whose report was published in the Dec. 18 issue of
the journal Nature, observed that surface waters in tropical and
subtropical Atlantic Ocean regions have become markedly saltier over
the past 40 years. Simultaneously, much of the water column in the
high latitudes of the North and South Atlantic has become fresher.
The scientists take these changes in salinity as an indication that
net evaporation rates over the tropical Atlantic have increased by 5
to 10 percent over the past four decades. The trend appears to have
accelerated since 1990, when 10 of the
warmest years since record-keeping began in 1861 have occurred.
The fresh water lost from the low latitudes under this scenario falls
back to the oceans at high latitudes, explaining the fresher water in
those regions. Considering other recent studies revealing parallel
salinity changes in the Mediterranean, Pacific and Indian Oceans, a
growing body of evidence suggests that the global hydrologic cycle has
revved up in recent decades.
According to the study, an acceleration of Earth's global water cycle
can potentially affect worldwide precipitation patterns that govern
the distribution, severity and frequency of droughts, floods and
storms. Water cycle acceleration would also contribute to global
warming by rapidly adding more water vapor, itself a potent,
heat-trapping greenhouse gas, to the atmosphere. Further, it could
continue to freshen North Atlantic Ocean waters to a point that could
disrupt ocean circulation and trigger further climate changes.
The study was conducted by Ruth Curry of the Woods Hole Oceanographic
Institution; Bob Dickson of the Centre for Environment, Fisheries, and
Aquaculture Science in Lowestoft, U.K.; and Igor Yashayaev of the
Bedford Institute of Oceanography in Dartmouth, Canada. |
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