SEA WATER COMPOSITION
I. Salinity: The amount of solid material dissolved in water
A.
1. Seawater is composed of Cl, Na, Ca, Mg, S, K.
These elements make up 99% of the dissolved materials in
the ocean.
Why is the ocean salty?
Clip on: why tell me why?
http://videos.howstuffworks.com/discovery/31006-why-tell-me-whyexplaining-saltwater-video.htm
Areas of Diverse Salinity
C. Variations:
1. Open ocean is between 33-38parts per
thousand
2. Brackish water has been diluted with
fresh water (estuaries and bays)
3. Hyper saline water is typical of inland
bodies of water where evaporation is high
and circulation low.
(Great Salt Lake 28.0%, Dead Sea 33.0%)
Salty lakes hid deep in the
Mediterranean
Geoscientists have discovered three lakes of extremely salty brine
lying in pockets on the floor of the Mediterranean Sea, south
west of the island of Crete. Such Lakes could help explain why
the Mediterranean is saltier than typical ocean water. The three
brine lakes situated more than 3300 meters below the sea surface
were discovered in 1993 and 1994 by a team of European
scientists conducting the Mediterranean Ridge Fluid Flow
project. MEDRIFF Researchers found the lakes using echo sonar
which sends down pulses of sound to probe the seafloor. The
boundary between the dense brine fluids and normal seawater
above creates a flat lake surface that stands out amid rougher
surrounding seafloor. The density contrast prevents the brine
from mixing easily with the seawater.
Salty lakes hid deep in the
Mediterranean
The scientists focused attention on a horseshoe-shpaed
lake, called Urania which had an average depth of 80
meters. The chloride content in the Urania brine
measured about 5X’s that of Mediterranean seawater.
The lakes formed when seawater dissolved deposits of
salt-rich rocks along the seafloor. These lakes may
explain the Mediterranean’s high salinity. Current
theories explain the high salinity to high evaporation
rates.
How does salinity affect the
density of water
Complete the Inquiry Activity from pg. 421
We tried this in class but this was not as accurate as the
hydrometer lab on 4.28.11 so ignore the inquiry activity
on pg. 421.
Effects of Salinity
D. Effects of Salinity
1. Salinity increases density
But is not a significant factor
in determining density at
depth (temperature is more
important)
2. Average ocean water has a salinity of
35g/1000ml.
The Range is 33-37 ppt
3. Salinity increases
temperature
at which water boils
4. Temperature is inversely proportional to density
Decrease in temp=increase in density
Increase in temp=decrease in density
5. Buoyancy changes with
changes in salinity
(higher=more buoyant,
lower=less buoyant)
due to density
Salinity and Humans
Lack of salt in a diet can produce goiters and
associated health issues