Composition and Movement of Ocean Water

Salinity

•Seawater is a solution containing a variety of salts dissolved in water

•Expressed in grams of salt per kilogram of water

Physical Properties of Sea Water

•Density(1.02g/ml – 1.03 g/ml)– What would increasing the amount of

salt in the water do to the density?– Increasing the amount of salts,

increases the density– What would happen to the density of the

water if the temperature of the water increases?

– Increasing the temperature decreases the density

Movement of Ocean Water

•Constant movement of ocean water is caused by wind and density differences

•Surface Currents•Density Currents

What causes Surface Currents?

•Global wind systems•Affect the upper 100 to 150 meters of water across the globe

Can you notice any pattern to the direction of the winds above and below the equator in each ocean basin?

•Warm ocean currents such as the Gulf Stream Current in the North Atlantic, are important to global climate

•Warm ocean currents generally flow away from the Equator

• Beginning in the Caribbean and ending in the northern North Atlantic, the Gulf Stream Current is one of the world's most intensely studied current systems.

• This extensive western boundary current plays an important role in the pole-ward transfer of heat and salt and serves to warm the European coastal regions.

Gulf Stream Current

Gulf Stream Current

Gulf Stream at Present Time

Patterns to Surface Currents

•Cold ocean currents generally originate in polar regions and flow towards the Equator

Density Currents

Aim: How does water not affected by surface winds circulate throughout the ocean basins?

•An underwater current circles the globe with a force 16 times as strong as all the world's rivers combined •This deep-water current is known as the global conveyor belt and is driven by density differences in the water. •Water movements driven by differences in density are also known as thermohaline circulation

Density Currents

• Deep water circulation caused by differences in the densities of ocean water

• What might cause density differences in the ocean waters?– Temperature– Salinity

• As a result of temperature:

• Dense cold water from Polar regions sinks and slides along the ocean floor toward Equatorial regions.

• The less dense water in the warmer regions are displaced

As a result of salinity changes: The Gibraltar Current

• Mediterranean Sea– Evaporation of sea water near the surface

causes the surface water to have a higher salinity and therefore it becomes more dense

– This water sinks and flows out of the sea and into the Atlantic Ocean

– It is then replaced by water from the ocean.

Strait of Gibraltar

Lab Activity

• You will create and observe a model of a density current

• Do you think ocean currents ever stop moving?

• What might cause ocean water to mix?

• What would happen to a stream of warm water that flows out into a colder body of water?