The Ocean

15.1 The Composition of Seawater

Make-up

Salinity

The Composition of Seawater

Salinity is the total amount of solid material

dissolved in water.

Because the proportion of dissolved

substances in seawater is such a small

number, oceanographers typically express

salinity in parts per thousands.

Most of the salt in seawater is sodium

chloride, common table salt.

The rain that falls on the land contains some dissolved carbon dioxide from the surrounding air. This causes the

rainwater to be slightly acidic.

The rain physically breaks down the rock and the acids chemically break down the rocks. Rain then carries the

dissolved salts and minerals along as it flows. The salts in the runoff are carried to the streams and rivers and then to the

ocean. http://www.classzone.com/books/earth_science/terc/content/visualizat

ions/es1303/es1303page01.cfm?chapter_no=visualization

Many of the dissolved salts are used by organisms in the ocean and are removed from the water. Others are not used

up and are left for long periods of time where their concentrations increase over time.

Hydrothermal vents are recently-discovered features on the ocean seafloor that

contribute dissolved minerals to the oceans.

These vents are the “exit points” on the ocean floor from which sea water that has seeped into the rocks of the oceanic crust has become hotter, has dissolved some of

the minerals from the crust, and then flows back into the ocean.

http://www.youtube.com/watch?v=D69hGv

CsWgA&list=PL88CB33C02CCF3D39&index=1

Similar to the previous process, during an

underwater volcano eruption, seawater

reacts with hot rock and some minerals are

dissolved into the sea water.

http://www.youtube.com/watch?v=U5

1cY6iod3U&index=5&list=PL88CB33C02

CCF3D39

Salinity

15.1 The Composition of Seawater

Sources of Sea Salt

• Chemical weathering of rocks on the continents

is one source of elements found in seawater.

• The second major source of elements found in

seawater is from Earth’s interior.

Salts in Seawater

Natural Processes Affecting Salinity

Salinity Processes Affecting Salinity

The Composition of Seawater

• Processes that decrease salinity:

• Processes that increase salinity:

- Precipitation

- Runoff from land

- Icebergs melting

- Sea ice melting

- Evaporation

- Formation of sea ice

Ocean Temperature Variation The ocean’s surface water temperature

varies with the amount of solar radiation

received, which is primarily a function of

latitude.

The Composition of Seawater

• The thermocline is the layer of ocean water

between about 300 meters and 1000 meters where

there is a rapid change of temperature with depth.

Temperature Variation with Depth

• The thermocline is a very important structure

because it creates a barrier to marine life.

Ocean Density Variation

Density is defined as mass per unit volume.

It can be thought of as a measure of how

heavy something is for its size.

The Composition of Seawater

• Seawater density is influenced by two main

factors: salinity and temperature.

Factors Affecting Seawater Density

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The 5 Oceans on Earth

Atlantic

Southern

Artic

Indian

Pacific

The 5 Oceans on Earth

Fun Fact about the 5 Oceans

Atlantic

Southern

Artic

Pacific

Indian

Create a mnemonic sequencing the oceans from largest to smallest

Variations in Ocean

Surface Temperature