Chemical Oceanography Water and Seawater Chemistry

Water molecule Water= H2O or H-O-H Hydrogen bond allows water to have properties of cohesion and adhesion Adhesion –water sticks to other things Cohesion –water sticks to itself

Water temperature and Density Density is amount of mass per unit of volume g/l Lower temperature = more dense substance. WATER IS DIFFERENT Densest at 39* F--Freezes at 32* F Even though it is colder, ICE FLOATS!!!

High Specific Heat Water heats up slowly and cools down slowly! Moderates the climate of the Earth

Make-Up of Seawater All of the elements in the periodic table are in seawater 96.5% pure water 3.5% dissolved salts Salinity – measure of amount of salt dissolved in H2O Measured as grams of salt in 1000g of seawater Units are ppt (parts per thousand)

Temperature, salinity, and density Seawater is heaver and denser than fresh water(easier to float in the ocean) The combination of salt and temperature determines the density

Density layers of the ocean Surface zone/ mixed layer - temperature and salinity are constant Pynocline - density increases with depth Thermocline - depth where water temperature changes Halocline -zone of rapid salinity increase with depth Deep zone -80% of sea water- density and temperature constant

Thermal Structure of the Ocean at 3 Latitudes

Influences of Salts Lowers the freezing point of water, salts act as an antifreeze Evaporates more slowly, salts are more attracted to water and therefore “hold on” stronger Increases the density of the water: more salt = more mass per unit volume

Factors that affect salinity Salinity is effected by the size of the body of water, the amount of freshwater added to it, and the rate of evaporation. Average ocean salinity = 35 ppt

Ocean surface conditions Evaporation in the tropics exceeds rainfall – makes water saltier Evaporation in temperate and polar regions is LESS than rainfall – makes water more fresh Water in the deep ocean is the same temperature, salinity, and density all over the world.

Surface Salinity of the Oceans and Worldwide Patterns of Evaporation Evaporation – Precipitation cm/yr Salinity ppt Latitude South to North

Refraction and light in the ocean The speed of light in water is ¾ its speed in air. This bends the light waves causing light to bend (refraction)

Transparency How much sunlight can penetrate seawater Transparency is dependent upon what and how much is suspended in water How transparent the water is called turbidity. Cloudy = high turbidity. EX: mud, plant life, anything that can block the light Excessive river runoff can reduce transparency

Why are the oceans blue? All colors of light (ROY G BIV) can penetrate seawater Blue light is reflected the most Therefore, the oceans appear blue If the transparency is low, the oceans appear different colors

Sound in the ocean Sound waves can travel farther in water than light waves Many marine animals use sound to “see” under water rather than light. The speed of sound increases as temperature and pressure increase.

Sonar Shadow Zone Like light, sound refracts or bends as density of the water changes. At about 80 meters an area forms, called a shadow zone, that is undetectable to sonar.

SOFAR Channel Sound in the sea can often be “trapped” between ocean density layers and effectively carried very long distances. The SOFAR channel is found within the thermocline layer of the ocean.

Make a highway billboard to advertise the unique properties of water. You are a marketing director for a major advertising firm. You have been hired to sell the highly unusual substance, water. Make a highway billboard to advertise the unique properties of water. Must illustrate and describe at least 3 of water’s properties. Illustrations must fill the entire poster Must be colorful and attractive