OceansOceans

Why study the ocean?Why study the ocean?

• One of the last frontiers• Biological & mineral resources• Food & oil shortages on land• Influences weather & climate• Travel & communication

OceanographyOceanography the science of our oceans that mixes biology, geology, chemistry, and physics (among other sciences) to unravel the mysteries of our seas.

Divisions of OceanographyDivisions of Oceanography• Chemical Oceanography – study

of chemical reactions• Biological Oceanography – study

of living things in their environment

Divisions of Oceanography (cont.)Divisions of Oceanography (cont.)

• Physical Oceanography – study of changes in motion of sea water• Geological Oceanography –

study of sediments & topography

The Global OceanThe Global Ocean

• Covers 71% of the Earth’s surface• Salt Water• 97% of all water on Earth–Where is the “other” water?

The Hemispheres of the EarthThe Hemispheres of the Earth

Northern Hemisphere

39% land

“Land Hemisphere”

Southern Hemisphere

19% land

“Water Hemisphere”

Divisions of the Global Ocean Divisions of the Global Ocean

• Pacific Ocean• Atlantic Ocean• Indian Ocean• Arctic Ocean• Southern Ocean

Distinguishing Characteristics Distinguishing Characteristics of Oceansof Oceans

• Size• Currents• Water Masses• Submarine Ridges• Some definable Land

Boundaries

PacificPacific

Pacific OceanPacific Ocean

• Largest and Deepest• Holds 52% of Earth’s ocean water• Covers 33% of Earth’s surface• Average depth = 4.3 kilometers (2.7 miles)• Mountain building along margins• Abundant islands (mostly volcanic)• Marianas Trench 6.8 miles deep

AtlanticAtlantic

Atlantic Atlantic OceanOcean

• 2nd largest ocean• 26% of Earth’s ocean water• Avg. depth = 3.9 km (2.4 miles)• Mid-Atlantic Ridge• Few islands• Large sediment deposits from rivers

(Amazon & Congo – 25% of world’s river discharge)

IndianIndian

Indian OceanIndian Ocean• 3rd largest ocean• Avg. depth = 3.9 km (2.4 miles) • 20% of Earth’s ocean water• Mostly in the S.Hemis.• Abundant fresh water due to river

discharge (Ganges, Brahmaputra, Indus)

ArcticArctic

Arctic OceanArctic Ocean• 4.2% of ocean water• Smallest & Shallowest• Surrounds the North Pole• Almost completely surrounded by

land• Covered with sea ice most of the year• Extension of the Atlantic

Southern (Antarctic)Southern (Antarctic)

• “Defined” in 2000• Starts at 60o S latitude• Surrounds Antarctica• 6.1% of ocean water

Earth’s Oceans and Seas

What is Ocean Water Composed of?

Composition of SeawaterComposition of Seawater

SalinitySalinity – amount of dissolved salt in water; usually expressed as parts per thousand (ppt)

Average salinity = 33 – 38 ppt 33 – 38 ppt (3.3-3.8%)(3.3-3.8%)Main salts/minerals present in oceans (ppt):

1. NaCl (halite) 23.48 (about 2.35%)2. MgCl 2 4.98 (about 0.50%)3. Na2SO4 3.924. CaCl2 1.105. KCl 0.666. NaHCO3 (Sodium bicarbonate) 0.1927. KBr 0.0968. H3BO3 (Hydrogen borate) 0.026

Where do the salts come from?Where do the salts come from?

1. Weathering of rocks and minerals2. Outgassing from Earth's interior 3. Hard parts of marine organisms (i.e., shell

material)

What affects salinity?What affects salinity?

What affects salinity?What affects salinity?

• Increase salinity (remove water) – – Evaporation– Formation of sea ice

• Decrease salinity (add water) – –Precipitation– Sea ice melting

Ocean TemperatureOcean Temperature• Surface water temperature varies with amount of

solar radiation received• Variation with depth – – Low latitudes = rapid decrease in temp. w/depth

(thermocline)– High latitudes = no rapid change in temp. w/depth

Ocean DensityOcean Density

• Density = mass/volume• Depends on: temperature and salinity• Determines water’s vertical position in the

ocean• Pure water = 1 g/cm3

• Remember – densest water is COLD & SALTY

Ocean LayersOcean LayersDetermined based on density:

1. Surface mixed zone (Epipelagic): 2%, warmest from solar energy, mixed by waves, 300 m, most saline

2. Transition zone (Mesopelagic): 18%, “Twilight Zone”, 200 – 1000 m, includes thermocline

3. Deep zone (Bathypelagic): 80%, “Midnight Zone”, just slightly above or below freezing, not very saline

LightLight in the Ocean in the OceanPhotic Zone - Sunlit layer of

water• Deepest in tropics• Typical value: 100 meters• Photosynthesis occurs here• Most ocean life found hereAphotic Zone – Complete

darkness

CirculationCirculation

• Atmospheric Circulation– Depends on density

• Surface Ocean Circulation– Depends on the wind

• Deep Ocean Circulation– Depends on density

Why is Ocean Circulation Important?Why is Ocean Circulation Important?

• Transports heat from equator to poles

• Transport nutrients and organisms

• Influences weather and climate

Ocean Circulation

Surface CurrentsSurface Currents

*Coriolis Effect - ocean currents are directed to the right (clockwise) in the northern hemisphere and to the left (counterclockwise) in the southern hemisphere

*Upwelling is the force that vertically moves cooler, nutrient rich water from approximately 1000 feet below the surface to the near surface.

Where winds blow towards the equator and parallel to the coastline (ex: west coast of California), surface water movement is deflected away from the coast and deeper water is thrust upward to the surface.

This creates a vertical component that causes temperatures drops in surface waters to nearly 10-15 degrees.

Thus, extensive nutrients like nitrates and phosphates are "upwelled" to the surface and plankton and other fish populations flourish.

UpwellingUpwelling

Equatorial to polar heat transport and water flow

Deep Ocean Currents (Thermohaline)Deep Ocean Currents (Thermohaline)Two factors are important in creating a dense mass of moving

water: 1. Temperature 2. Salinity

*Colder and salty water is denser than warmer, less salty water.

Thermohaline Circulation - The Ocean Conveyor