GL 107 Earth Systems Science

K. Hannula

Discussion questions for 11/7/07

1.  Describe the chemical composition of seawater.  Where does each component come from?

Dissolved components include:

Na (sodium), Ca (calcium), Mg (magnesium), K (potassium): from chemical weathering of rocks; carried to ocean in dissolved load of rivers.

SO₄ (sulfate) and Cl (chlorine): primarily added to water by hydrothermal circulation at mid-ocean ridges.

2.  Describe the temperature and density layering of ocean water.

Temperature: surface waters are warmer than deep waters, because surface water is warmed by sunlight.

Density: deep water is denser than surface water.  The deepest water in the oceans is both very cold and very salty.

Deep ocean water forms near the poles, where freezing of sea ice concentrates salt and creates cold, salty, dense water, which sinks to the ocean floor.

3.  Describe the circulation of ocean currents in the Atlantic and Pacific Oceans.

Warm surface ocean currents flow north on the western side of the ocean basins, cross the northern part of each ocean, and then cold surface currents flow south along the eastern side of each ocean.

4.  What effect does the Gulf Stream have on the climate of northern Europe?

The Gulf Stream (a warm current) carries warm water across the Atlantic Ocean to northern Europe.  It creates a warmer, wetter, milder climate than at similar latitudes in eastern North America.

5.  What is the effect of the California Current on the climate of the western US?

The California Current is a cold surface current that flows south along the western coast of the US.  Because cold water is more difficult to evaporate than warm air, it creates low humidity along the coast of California, resulting in dry summer weather in California.

6.  What is upwelling?

Upwelling is a process that brings deep ocean water to the surface.  It generally occurs in places where winds blow away from the coast, pushing the surface water away and forcing deep water to flow up to replace it.  Because deep water (besides being cold and dense) also is very rich in nutrients (because of all the floating organisms that decay in deep water), areas where upwelling occur tend to be very rich in marine life.