The Salinity Fingerprint
From: Andy Soos, ENN
Published December 19, 2012 04:25 PM
Salinity is the saltiness or dissolved salt content (such as sodium
chloride, magnesium and calcium sulfates, and bicarbonates) of a body of
water. Salinity is an ecological factor of considerable importance,
influencing the types of organisms that live in a body of water. As
well, salinity influences the kinds of plants that will grow either in a
water body, or on land fed by a water (or by a groundwater). For ages
salinity was mostly affected by slow geologic type processes. The
ocean's salinity field is driven primarily by evaporation,
precipitation, and river discharge, all key elements of the Earth's
hydrological cycle. Observations show the salinity field has been
changing in recent decades but more rapidly than expected and by mad
made effects.
The saltiness, or salinity, of the oceans is controlled by how much
water is entering the oceans from rivers and rain versus how much is
evaporating. This is the water cycle or the continuous movement of
water on, above and below the surface of the Earth. The water moves
from one reservoir to another, such as from river to ocean, or from the
ocean to the atmosphere, by the physical processes of evaporation,
condensation, precipitation, infiltration, runoff, and subsurface flow.
The more sunshine and heat there is, the more water can evaporate,
leaving the salts behind in higher concentrations in some places. Over
time, those changes spread out as water moves, changing the salinity
profiles of the oceans.
Oceanographers from Scripps Institution of Oceanography and Lawrence
Livermore National Laboratory fingerprinted salinity changes from 1955
to 2004 from 60 degrees south latitude to 60 degrees north latitude and
down to the depth of 700 meters in the Atlantic, Pacific and Indian
oceans.
The ocean data was compared to 11,000 years of ocean data generated by
simulations from 20 of the latest global climate models. When they did
that they found that the changes seen in the oceans matched those that
would be expected from human forcing of the climate. When they combined
temperature changes with the salinity, the human imprint is even
clearer.
"These results add to the evidence that human forcing of the climate is
already taking place, and already changing the climate in ways that will
have a profound impact on people throughout the world in coming
decades," the oceanographers conclude.
The key points from their report are:
1. Climate change has altered the salinity field of the world's oceans.
2. Changes match model predictions over the top 125 meters.
3. The human effect signal is even stronger when salinity is taken
jointly with temperature.
For further information see
Fingerprint.
Salinity image via Wikipedia.
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