Water and Ocean Structure
WORLDS WATER SOURCES:
Learning Objectives
1. Understand the nature of the water molecule and its unique
properties (polarity, density and thermal properties) and how
these are altered by the presence of salt in solution.
2. Know the types of materials that are dissolved in sea water,
their importance and how they vary with time.
3. Explain variations in salinity, temperature, and pressure
within the sea and how they alter the chemical and physical
properties of the ocean.
States of Matter (e.g. water)
States of Matter (e.g. water)
Atomic Structure
http://www.dayah.com/periodic/Other/Periodic%20Table.pdf
Hydrogen bonds –
cohesion - surface tension!
http://www-math.mit.edu/~dhu/Climberweb/climberweb.html
The formation of ice in freshwater:
Density of freshwater:
Seawater density depends on temperature,
salinity and pressure! Therefore, it increases
with > salt content at const. temp;
high density in cold, salty waters –why is this
important?
Why does ice float on water?
Water is a powerful solvent:
(“the universal solvent”)
Sodium Chloride
Rock SALT
NaCl
Na

Cation
Cl
Ions

Anion
Cycling of dissolved
components in seawater:
Did oceans’ salinity increase over time?
Major dissolved components in seawater:
35 g of salt in 1000 g of seawater
Residence Time
How long do the various dissolved ions stay in the
ocean? Depends on how “reactive” they are.
Residence Time: The average time spent by a
substance in the Ocean =
Amount in Sea
Rate entering or exiting
The layer of rapidly
changing salinity
with depth; 3001000 meters;
Same as
pycnocline
(density) and
thermocline;
Salinity map showing areas of high salinity (36 o/oo) in green,
medium salinity in blue (35 o/oo), and low salinity (34 o/oo) in
purple. Salinity is rather stable but areas in the North Atlantic,
South Atlantic, South Pacific, Indian Ocean, Arabian Sea, Red Sea,
and Mediterranean Sea tend to be a little high (green). Areas near
Antarctica, the Arctic Ocean, Southeast Asia, and the West Coast
of North and Central America tend to be a little low (purple).
http://www.biosbcc.net/ocean/marinesci/02ocean/swcomposition.htm
Why is surface Atlantic
more salty than Pacific?
http://eesc.columbia.edu/courses/ees/climate/lectures/saltyatlantic.html
Summary:
Water is a polar molecule -- unique
properties (melting pt, heat capacity,
dissolving power, water denser than ice)
Salinity is the total dissolved solids
Salinity in the surface ocean varies by
Evaporation - Precipitation
Principle of Constant Proportions
Residence Time in the Oceans
pH = potential/power of
hydrogen
Carbonate buffering system keeps
the pH of seawater constant = 8.1
Carbonate Buffering System
What is temperature?
using  Kinetic temperature definition
What is temperature?
It is a direct measure of the average kinetic energy of
atoms and molecules that make up substance. Temp.
changes when heat energy is added to or removed
from a substance.
It is measured in (Celsius, Kelvin, and Fahrenheit).
HEAT
(the energy of moving molecules =
kinetic energy)
1) Represents the transfer of energy from
high to low temperature. Therefore, heat
has units of Energy (1 calorie, calor = heat;
the amount of heat required to raise the
temp. of 1 gram of water by 1 C°);
2) An object does not possess "heat"; the
appropriate term for the microscopic energy
in an object is internal energy.
Temperature vs Heat
Temperature is a measure of how fast
the molecules in a substance are moving
Heat is a measure of how much energy
has to be put into (or gotten out of) a
substance to change its temperature, or
“state” (solid, liquid, gas)
First Law of Thermodynamics
Heat Capacity – the amount of heat required
to raise the temp. of 1 g of any substance by
1 °C;
– Water has one of the highest heat
capacities known, which makes water
excellent heat transfer material; and
– therefore, allows ocean currents to
moderate global climate!
Evaporation from lakes, oceans,
rivers, etc. occurs for
temperatures lower than 100 oC
But it
requires
more energy
to do so
Atmospheric transport of surplus heat from low latitudes
into heat deficient high latitudes areas: