oceans

oceans science of water

saline water

Cannot be utilized for drinking, sanitation, irrigation, power plant cooling etc. because it contains a high concentration of dissolved water.

why does the ocean matter ?

Provides half of the world's oxygen

It is our greatest carbon sink

It is the largest ecosystem on Earth

Economic value e.g Tourism

origin of oceans

When the pressure is released

volcanoes outgas

• Lighter gases (hydrogen and helium)

dissipate into space

• Heavier gases are ejected but gravity

keeps them from escaping

These gases form the early atmosphere shields Earth from some insolation

Water condenses in the atmosphere, and begins to

fall as rain (The Great Rains)

Salinity

The amount of salt dissolved in water

Why are oceans saline?

Volatile chemicals from volcanic outgassing

Dissolved minerals from volcanic hydrothermal vents

Weathering and transport of rock minerals

Ocean Depth

Deepest point is Challenger Deep in the Marianas Trench at 10,920 meters

Pelagic Zone is the water column

Benthic Zone is the seafloor

ocean depth zones

Photic Zone = Light penetrates here supporting photosynthesis

Twilight Zone= Some light but no photosynthesis

Aphotic Zone = Open ocean with no light

Abyssal Zone= The deep ocean seafloor

Hadal Zone= Water in deep trenches

Ocean Basins

5 oceans

Pacific

Atlantic

Indian

Southern

Arctic

Ocean Circulation

Water molecules in the ocean are not fixed

Affected by 3 factors

temperature

Salinity

Density

Density

lowest when temperature is highest

In oceans the warmest water at the surface is the least dense

As depth increases and temperature decreases,

density increases

As depth increases and temperature decreases,

density increases

Thermocline

Temperature rapidly drops below the photic zone

Pycnocline

There is a matching rapid increase in density

Temperature and density

When surface temperatures are higher, density

differences are higher

stratification of the water column

Warm, low density layer on top of cold, dense layer

The formation of stable water layers with different temperatures, salinity, and densities, preventing vertical mixing.

Salinity and and circulation

Ocean water salinity between 33-37 g/kg

High salinity makes water high density e.g people floating in the Dead Sea

Processes affecting salinity only affect surface

waters

halocline

All deep ocean water has similar salinity

A layer in a body of water where salinity changes rapidly with depth, creating a distinct boundary between water masses.

Thermohaline Circulation

Surface currents controlled largely by wind

Temperature and salinity drive, global thermohaline

circulation, This global pattern is also known as Ocean Conveyor Belt

Thermohaline Circulation process

• The sun’s energy warms the Earth unevenly, with the most heat at the equator and the least at the poles.

• Evaporation increases salinity in tropical Atlantic waters.

• The Gulf Stream carries warm, salty water from the tropics to the North Atlantic.

• As the water moves north, it cools.

• Sea ice forms, leaving behind salt and making the water even denser.

• The dense water eventually sinks.

Sea Level

measures from the center of the earth

Eustatic Sea Level

Eustatic sea level can change by:

o The addition or removal of water to or from oceans

o Changing the size of ocean basins (plate tectonics)

Drivers of eustatic sea level change

Thermohaline changes (T↑, sea level ?)

Glacial ice volume (ice↑, sea level ?)

Seafloor spreading (SS ↑, sea level ?)