Marine Hydrology

Topics:

1) Oceanography

a) Main oceans

2) Properties of seawater

1) Composition a) Salinity b) Sources of sea salt 2) Density 1) Factors that impact density 2) Temperature a) Cold water vs. warm water b) Layers of temperature

14.1

The Vast World Ocean

Oceanography

 Nearly 71 percent of Earth’s surface is covered by the global ocean.



Oceanography

is a science that draws on the methods and knowledge of geology, chemistry, physics, and biology to study all aspects of world oceans.

14.1

The Vast World Ocean

Geography of the Oceans

 The world ocean can be divided into four main ocean basins: • The

Pacific Ocean

is the largest and deepest • The

Atlantic Ocean

is about half the size of the Pacific and not quite as deep. • The

Indian Ocean

, largely a southern hemisphere body, is slightly smaller than the Atlantic. • The

Arctic Ocean

is the smallest and about 7% of the size of the Pacific.

15.1

The Composition of Seawater Salinity



Salinity

is the total amount of dissolved solid material in water.

 Because the proportion of dissolved substances in seawater is so small, oceanographers express salinity as:

parts per thousand (ppt) Ex: 35g of salt per 1000 grams of water= 35 o / oo

Percentage of dissolved salts

 Most of the salt in seawater is

sodium chloride

, NaCl

Average seawater salinity = 35 o / oo 30.6 % Sodium (Na) 55.0 % Chloride (Cl) 14.4% Other

15.1 The Composition of Seawater Salinity

 Sources of Sea Salt

• 1) Chemical weathering and erosion

of rocks on the continents

• 2) Earth’s interior-

volcanic activity

15.1 The Composition of Seawater Salinity

 Processes Affecting Salinity

• Processes that decrease salinity:

- Precipitation - Sea ice melting - Icebergs melting - Runoff from land

• Processes that increase salinity:

- Evaporation - Formation of sea ice

Processes that impact salinity

15.1 The Composition of Seawater



Ocean Temperature Variation

The ocean’s surface water temperature depends on the amount of solar radiation received, which is primarily a function of latitude.



Temperature Variation with Depth •

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.

Variations in Ocean Surface Temperature

Variations in Ocean Water Temperature

15.1

The Composition of Seawater 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.

 Factors Affecting Seawater Density

•

Seawater density is influenced by two main factors: salinity and temperature.

15.1 The Composition of Seawater Ocean Density Variation

 Density Variation with Depth

•

The

pycnocline

is the layer of ocean water between about 300 meters and 1000 meters where there is a rapid change of density with depth.

Variations in Ocean Water Density

Ocean Layering

 Oceanographers generally recognize a three-layered structure in most parts of the open ocean: a shallow surface mixed zone, a transition zone, and a deep zone.

 Surface Zone • Shallow (300 to 450 meters) • Zone of mixing • Sun-warmed zone

15.1

The Composition of Seawater Ocean Layering

 Transition Zone • Between surface layer and deep zone • Thermocline and pycnocline  Deep Zone • Sunlight never reaches this zone.

• Temperatures are just a few degrees above freezing. • Constant high-density water

Ocean Zones