1. Ocean Composition

2. Salinity
Salinity – a measure of the amount of dissolved solids in a given amount of liquid
Measured as grams of dissolved solids per kilogram of water
1 kg of ocean water contains 35 g of dissolved solids

3. Where does all that salt come from?
Runoff (Erosion)
Acid rain breaks down rocks  dissolved salts and minerals are carried away (runoff)  rain and dissolved salts and minerals are deposited in the ocean

4. Underwater Volcanoes Hydrothermal Vents
Result of seawater filtering down in the ocean crust where it meets the magma
Minerals in the crust begin to dissolve, adding to the salt content of the ocean
Underwater Volcanoes
Similar to the process with hydrothermal vents, during an underwater eruption, seawater reacts with hot rock and some minerals are dissolved into the ocean water

5. What affects salinity? Climate
Coastal water in places with hotter, drier climates has a higher salinity
Coastal water in cooler, more humid places has a lower salinity
More fresh water from streams and rivers run into the ocean in these areas
Glaciers melting add freshwater to the oceans
Heat INCREASES the evaporation rate. Evaporation removes water but leaves salts and other dissolved solids behind.

6. Water Movement Slower moving areas of water develop higher salinity
Example: bays, gulfs, seas, open ocean without currents running through them
Dead Sea = Very Salty – 337 PPT (33.7%)
Baltic Sea = Not Very Salty – 10 PPT (1%)

7. Changes in Temperature
Tropical Regions – As depth increases, water cools rapidly. That is because there is less sunlight to warm water as depth increases.
Polar Regions – The temperature remains fairly constant. This is because sunlight intensity at Earth’s poles is weaker than it is in other regions.

8. Changes in Salinity
The top 500 meters of warm water in tropical regions is saltier than polar regions.
Warm water evaporates more rapidly than cold water.
In polar regions, freshwater from melting glaciers decreases the salinity at the surface.
When ice forms, salt is left behind in the water.
cold, salty water is denser and sinks to a deeper layer

9. Changes in Density Ocean water is layered due to different densities.
Cold water is denser than warm water.
Salt water is denser than freshwater.