WATER & OCEAN STRUCTURE

UNUSUAL CHARACTERISTICS OF WATER

• The molecules polarity and bonds that hold it together.
• Large amount of heat needed to change its temperature.
• The amount of heat needed to change is physical state.

Waters influence on global temperature ..

Liquid waters thermal characteristics prevent broad savings of temperature during day and night and through a longer span during winter and summer. A much greater amount of heat is stored through the summer and given off in the winter. Liquid water has an important thermostatic balancing effect ( an ocean less Earth would be much colder in winter and much hotter in summer than the moderate temperatures we experience). Sea ice in the polar regions contributes to Earths moderate surface temperatures in a different way.

Density on Ocean Structure

Density is the mass per unit of volume.

The density of pure water is 1 gram per cubic centimeter (1g/cm to the 3rd power).

Oceans structure and large scale movement depend on changes in the density of seawater, with density dependent on temperature and salt content.

Molecules of Water

Pure water is a compound. A compound is a substance that contains 2 or more different elements Hydrogen (H) and Oxygen (O) in a fixed proportion of 2 to 1.

An element is a substance composed of identical particles called atoms. Atoms cannot be broken into similar substances by chemical means.

Water is a molecule (a group of atoms held together by chemical bonds). A chemical bond is the energy relationships between
atoms that hold them together which are formed when electrons, tiny negatively charged particles found toward the outside of an atom,
are shared between atoms or moved from one atom to another.
A water molecule forms when electrons are shared between two
hydrogen and one oxygen atom. The bonds formed by shared pairs of electrons are covalent.

When one hydrogen ends attracts the oxygen end of another molecule it is called a hydrogen bond.
This attraction leads to cohesion.

Cohesion gives water a high surface tension (measure of how difficult it is to stretch or break surface). ** water has the highest surface tension **
Adhesion is the tendency water to stick to other materials.
Both cohesion and adhesion are the properties that allow tater to soak through fabrics.

Temperature and Heat
Temperature measures how fast molecules move, while heat is the measure of how much energy has to be put into a substance to change its temperature or "state".
Many substance have different capacities. Heat capacity measures the amount of heat needed to raise temperature.

Water has the ability to absorb/release large amounts of heat while changing little in temperature due to the hydrogen bonds in it.

Water has the highest heat capacity of most known substances.

Unlike most substances as water gets cooler it becomes more dense & as it freezes it becomes less dense.

The density curve shows that as water losses heat its density increases. As water begins to freeze the hydrogen bonds expands decreasing he density. This is why ice floats.

There are 2 main types of heat.
Sensible heat is what we sense from different temperatures.

Latent heat is the energy needed to change the state of a substance.
There are two different types of latent heat. Fusion which is when hydrogen bonds break when freezing occurs & vaporization which is when hydrogen bonds break during vaporization which requires more heat.

Seawater
Seawater is about 96.5% pure. The added dissolved particles and gasses change the properties.

Seawater is more dense than pure water.

The density of seawater increases with salinity and pressure and decreases with temperature.

Global Effects
Thermostatic properties are those that act to moderate changes in temperature.

Thermal inertia is the tendency to resist a change in temperature with the gain/loss of heat energy.

Currents in the ocean and atmosphere, between the poles and the equator equalize the heat imbalance.

Masses of moving air accounts for 2/3 of poleward heat transfer with ocean currents moving the other 1/3.

THE OCEAN CAN BE DIVIDED INTO 3 ZONES

• Surface zone (mixed layer)
• Pycnocline
• Deep ocean

In the surface zone the temperature and salinity are relatively constant due to waves and currents.

It contains the least dense water and only accounts for about 2% of all ocean

In the pycnocline zone density increases as depth increases.

This zone keeps the surface layer and the deep ocean layer from mixing.

The deep ocean zone occurs in the mid-latitudes below 1,000 m with little change in density throughout the zone.


Accounts for 80% of all ocean water.

As the temperature of water decreases. Its density increases.

There are 3 main layers based on temperature: surface, thermocline and deep.

Not all zones are the same due to exposure to the sun.

Based on salinity the ocean can be layer by 3 layers: surface, halocline, deep.

The halocline and the thermocline often coincide creating a more pronounced pycnocline.

When light enters the water, it bends at an angle because the wave travel at different speeds in different mediums.

The speed of light is about ¾ slower in water than in air.

When sunlight does reach the water, it is scattered and absorbed.

The thin area of lighted water in the surface zone is called the photic zone.


All of the production of food occurs in the photic zone, this heated by the sun.

It is very important to the balance of life in the ocean.


The area below this is called the aphotic zone, without light, due to its darkness.

Sound waves are created from changes in pressure.

The intensity of sound waves decreases in water due to scattering, spreading, and absorption.

The speed of sound is dependent on temperature and pressure.

Sound travels faster in warm water since it has more vibrating molecules than in cooler water.