Chapter 24-1

OCEANSEDU 653- Keri Adams

Why isn’t Ocean Water Pure?

Two main dissolved gases = N2 and O2.

CO2 (in large amounts)

Other atmospheric gases (in small amounts)

How do Gases Enter the Ocean?

The atmosphere (most O2 enters this way)

Underwater volcanoes

Marine organisms

Streams and rivers

Temperature and Dissolved Gases

Gases dissolve more readily in COLD water.

Water at the surface of the ocean in COLD regions dissolve larger amounts of gases than water in WARM tropical regions.

Gases can return to atmosphere from ocean (evaporation).

Carbon Sink

Ocean = 60X as much Carbon as atmosphere

CO2 trapped in ocean for years and years

Ocean is a carbon sink….b/c ability to dissolve and contain a lot of CO2

CO2 traps thermal energy, so ocean is important in climate regulation

Dissolved Solids

Ocean water = 96.5% pure water and 3.5% dissolved solids called sea salts

Dissolved solids made of 75 elements.

Ocean water mostly: Cl, Na, Mg, S, Ca, K

85% of solids is HALITE

Trace elements(in small amounts) Au, Zn, P

Sources of Dissolved Solids

Volcanic eruptions

Chemical weathering of rock on land

Chemical reactions b/t sea water and newly formed sea floor rocks

Salinity of Ocean H2O

Salinity – measure of the amount of dissolved salts and other solids in a given liquid

Measured by # grams of dissolved solids in 1,000 grams ocean water (parts per thousand or ‰)

Higher salinity = better conductivity

Factors that Affect Salinity

Precipitation = fresh water

Ocean water evaporates or freezes…only H2O molecules removed

Rate of evaporation higher than precipitation = salinity of surface water increases

Equatorial water = salinity lower

Salinity ranges 33‰ to 36 ‰, average 34.7 ‰

Temperature of Ocean Water

Varies with depth and location on the surface

Temperature range is affected by amount of solar energy and movement of water in the ocean

Surface Water

Heat is distributed downwards to 100-300 m (this zone is relatively constant and decreases slightly as depth increases).

Temperature of surface water decreases as latitude increases

Ocean water freezes at -1.9°C.

Pack ice – floating layer of sea ice completely covers an area of an ocean surface; ≤5 m thick; insulates water below it

Thermocline

Thermocline – layer in a body of water in which water temperature drops with increased depth faster than it does in other layers

Changing temperatures or shifting currents alter the depth of the thermocline or cause it to disappear

Deep Water

Density of cold, deep water controls slow movement of deep ocean currents

Cold, deep ocean water holds more dissolved gases than warm, shallow ocean water

Density of Ocean Water Density = mass/volume

Density of pure water = 1 g/cm3

Salinity and temperature affect density!

Density of ocean water = 1.020 – 1.029 g/cm3

Ocean water becomes denser as it gets colder and saltier

Densest ocean water = polar regions

Ocean Water Color

Determined by the way it absorbs or reflects sunlight

White light from sun has all visible wavelengths of EMS

All colors are absorbed by the water except, blue, it is reflected allowing the color blue to be seen

Why is Ocean Color Important?

Phytoplankton – microscopic plants in the ocean that provide food to many of the ocean’s organisms; absorb red and blue light; reflect green light

Presence of phytoplankton affect shade of blue of the ocean

Phytoplankton require nutrients; presence or absence of them indicate health of ocean

Citations Allison, M. A., & DeGaetano, A. T. (2010). Oceans. Holt McDougal Earth

Science (Student ed., ). Austin, TX: Holt McDougal, a division of Houghton Mifflin Harcourt Publishing Co..