The Atmosphere, The Oceans, and Weather

Unit 9 – Part C

Oceanic Circulation• Major movement of seawater results

from:– Wind-driven surface currents.– Density-driven deep-water currents.

– Density is controlled by two things:• Temperature• Salinity

Oceanic Circulation• Salinity:

– The amount of dissolved salts in seawater.

– Measured as the mass of salts dissolved in 1000 grams of seawater.

– Overall balance is maintained when:• Evaporation is offset by precipitation.• Runoff and Ice formation is offset by ice

melting.

Oceanic Circulation• Surface Currents:

– Frictional forces set surface waters into motion with wind

– Gyre: surface waters to spiral in a circular whirl pattern.• Clockwise in Northern Hemisphere and

Counter Clockwise in Southern Hemisphere.

Oceanic Circulation• Deep-Water Currents:

– Deep water flows because dense water sinks.

• Density increases with the increase of salt.– Colder and saltier water is the most

dense and sinks.