Oceans

Why do oceans matter?

• Provides half of world’s oxygen

• Holds 50x more carbon dioxide than the atmosphere

• largest ecosystem (coral reefs)

• economic value

Origins of ocean

• Ice comes to Earth from beyond Frost Line

• Earth is volcanic planet - ice sublimes

• Magma dissolves gasses including water vapor

• As pressure released, volcanoes outgassed forming Earth's early atmosphere

• The atmosphere shielded Earth from some solar radiation, allowing gradual cooling.

• Water vapor condensed in the atmosphere and fell as precipitation — The Great Rains

Why are oceans salty?

• Volatile chemicals from volcanic outgassing

• Dissolved minerals from volcanic hydrothermal vents

• Weathering and transport of rock minerals

Ocean circulation

• Water molecules in the ocean are not fixed in place

• continuous movement of ocean water driven by wind, temperature differences, salinity, and Earth's rotation.

Temperature & Density Relationship + Stratification & Thermocline

• Warmer water is less dense, so it stays near the surface.

• Colder water is more dense, causing it to sink.

• This creates stratification in the ocean, with warm water on top and cold water below.

• The thermocline is the layer where temperature drops rapidly with depth, influencing circulation.

Salinity and Density + Halocline

• high salinity = denser water = water sinking

• low salinity = less dense water = water floating.

• The halocline is the layer where salinity changes rapidly with depth

Temperature and Salinity Impact on Ocean Circulation

• Low Temperature + High Salinity = Density:

• Warm, less salty water stays on top

• Cold, salty water sinks

• = layers in the ocean, or stratification.

• This global system, called the "ocean conveyor belt," moves heat and nutrients around the world.

Thermohaline Circulation (Ocean Conveyor Belt)

Ocean circulation driven by temperature and salinity, which affect water density.

• circulation moves warm, less dense surface waters toward the poles, where they cool, become saltier, and sink, creating a continuous flow of ocean water

• regulate Earth's climate and distributes heat and nutrients across the globe.

Waves

The movement of energy caused by something disturbing the water.

Disturbances causing waves

• air density (winds) —> surface

• tidal (lunar) —> gravity

Breaking waves

• Waves approach the shore because the water becomes shallower

• wave gets closer to the bottom, friction slows it down.

• The top of the wave moves faster than bottom = to get steeper and crash.

Tides

• type of wave with very long wavelength

• gravitational disturbance

• Gravity between Earth and Moon pulls water

Equilibrium Theory of Tides

• tides caused by the gravitational pull of the Moon and Sun

• In a perfect world with no land, the ocean would form two bulges—one facing the Moon and one opposite it.

• As Earth rotates, these bulges cause high tides and low tides.

Currents

• movements of seawater across Earth's surface

• driven by prevailing winds and atmospheric circulation

• move in patterns that transport warm water toward the poles and cold water back toward the equator

Coriolis Effect

Earth's rotation makes moving air and water turn in a curved path, instead of straight.

• In the Northern Hemisphere, they curve to the right, and

• In the Southern Hemisphere, they curve to the left.

• latitudes influence temperature and how air and water move around the planet.

Gyres

large, circular ocean currents that flow in a pattern around each ocean basin. They are caused by wind, Earth's rotation (Coriolis effect), and the shape of the continents

Upwelling and downwelling

• Winds push surface water, which can cause deep, cold water rises to the surface

• surface water sinks down into deeper layers. It occurs when surface waters move toward a particular area and the water gets pushed down into the ocean

How surface water moves around the ocean

• Winds push the surface water in the direction they blow.

• Earth’s rotation (Coriolis effect) makes the water move in a curved path.

• Ocean currents, like gyres, are large circular flows of water that move the surface water around the ocean in big loops.