Oceanography

Understanding our Earth's Oceans

There are many branches in the field of oceanography. This two-hour course presents basic and intermediate information on the physical components and interactions of our oceans and estuaries. We cover the varied parameters of ocean water and how it is affected by changing climatic conditions. Underwater topography, earthquakes, tsunamis, tides and currents, seas, swells and storms are discussed. Hands-on activities demonstrating some of the discussion areas are also presented.

The information presented in this class fulfills the following State of Oregon education goals and benchmarks in SCIENCE:

CIM/Grade 10 Benchmarks

• Analyze the relationship between global energy transfer and climate.
• Analyze how physical, biological or geological systems can maintain equilibrium.
• Use conceptual and/or mathematical models to explain natural systems

OCEANOGRAPHY - a broad field in which many sciences are focused on the common goal of understanding the oceans

• GEOLOGICAL OCEANOGRAPHY - the study of the earth below the sea and the history of the processes that formed the ocean basins.
• PHYSICAL OCEANOGRAPHY - how and why the oceans move.
• MARINE METEOROLOGY - study of heat transfer, water cycles, and air-sea interactions.
• CHEMICAL OCEANOGRAPHY - study of the composition and history of the water
• BIOLOGICAL OCEANOGRAPHY - study of marine organisms and the relationship between these organisms and the ocean environment.
• OCEAN ENGINEERING - the designing and planning of equipment and installations for use at sea.

The ocean is a dynamic, living environment made up of many components, each playing an important part within the entire ecosystem.

• MAJOR CONSTITUENTS
  Chloride Cl- 55.07%
  Sodium Na+ 30.62%
  Sulfate SO4 2- 7.72%
  Magnesium Mg2+ 3.68%
  Calcium Ca2+ 1.17%
  Potassium K+ 1.10%
  These combine into various molecules to form salts, which make up 99.36% of all particulate in seawater.
• TRACE ELEMENTS
  All other elements dissolved in seawater in concentrations less than one part per million are considered trace elements. These elements are essential to the survival of organisms that live in the oceans.
• GASES
  Nitrogen N2 11% (48% surface)
  Oxygen O2 6% (36% surface)
  Carbon Dioxide CO2 83% (15% surface)
• NUTRIENTS
  Nitrogen (nitrate, NO3-) 500 ppb.
  Phosphorus (phosphate, PO43-) 70 ppb.
  Silicon (silicate, SiO4-) 3000 ppb.

Oceanographers study salinity, temperature and density to determine and monitor the water quality and overall health of our oceans.

• SALINITY - a measure of the quantity of dissolved salts in seawater, measured in parts per thousand (average seawater is 35 ppt.).
• SALINOMETER - an instrument for determining the salinity of water by measuring the electrical conductivity of a water sample of a known temperature.
• TEMPERATURE - a heat value of a water sample which changes with depth.
• DENSITY - the mass per unit volume of a substance measured in grams per cubic centimeter. Measured with a HYDROMETER, density is affected by salinity and temperature (average seawater is 1.028 g/cm3).

Geological oceanographers study the ocean floor. They identify the varied topographic features and search for mineral resources and hydrothermal activity.

• CONTINENTAL SHELF - the zone bordering a continent, extending from the line of permanent immersion to the depth at which there is a marked descent to the great depths.
• CONTINENTAL SLOPE - a relatively steep downward slope from the continental shelf break to depths.
• ABYSSAL PLAINS - the flat ocean-basin floor extending seaward from the base of the continental slope and continental rise.
• SEAMOUNT - an isolated volcanic peak that rises at least 1000 meters from the sea floor.
• GUYOT - a submerged flat-topped seamount that was formed by exposure to wind, rain and surface-sea erosion.
• RIFT VALLEY - a trough formed from faulting along a zone in which plates move apart and new crust is created, such as along the crest of a ridge system.
• SUBMARINE CANYON - a steep-sided and v-shaped underwater canyon extending up, into and across the continental shelf.
• TRENCH - a long, deep, narrow depression of the sea floor with relatively steep sides, associated with a subduction zone.
• OCEANIC RIDGE - a long, narrow elevation of the seafloor, with steep sides and irregular topography.

Compare the depths in the oceans with the heights of the mountains.

Mount Everest is 26,000 feet above sea level.

Deepest ocean trenches are 36, 080 feet below sea level. Pressure at this depth is 1100 atm. (16,170 lb/in2).

Peru-Chili Trench is 26, 240 feet below sea level.

Midocean ridges average 600 miles wide, 3500 to 7000 feet high and extends for 40,00 miles around earth.

Marine meteorologists study the way storms form and their effect on the ocean. They produce waves that can ultimately cause great damage to the coast.

• STORM SURGE - along the coast, the exceptionally high water accompanying a storm, owing to wind stress and low atmospheric pressure, made even higher when associated with a high tide and shallow depths.
• TSUNAMI - long-period sea wave produced by a submarine earthquake or volcanic eruption. It may travel across the ocean for thousands of miles unnoticed from its point of origin and build up to great heights over shallow water at the shore.
• TIDAL WAVE - long-period gravity wave that has its origin in the tide-producing force and is observed as the rise and fall of the tide.
• TIDAL BORE - high tide crest that advances rapidly up an estuary or river as a breaking wave.
• SEA - surface waves generated or sustained by the wind blowing in a relatively consistent direction over a continuous area of water.
• SWELL - long and relatively uniform wind-generated ocean waves that have traveled out of their generating area.
• SURF - wave activity in the area between the shoreline and the outermost limit of the breakers.
• BREAKER - sea surface-water wave that has become too steep to be stable and collapses.

Physical oceanographers study how wind and water interact with the spinning earth to form ocean currents.

Ocean currents are formed as prevailing winds push and drag the surface waters of the open ocean. As the Earth spins, a Coriolis effect is generated. This bends the currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. The currents generated are at a 45-degree angle to the prevailing winds. In the North Pacific the four major, clockwise currents are the North Pacific current flowing west to east, the California current flowing south, down the west coast of North America, the North Equatorial current flowing east to west and the Kuroshio current flowing north, up the east coast of Japan. This clockwise, circular flow is called the North Pacific gyre. The Alaska current is fed by water from the North Pacific current and is moving in a counterclockwise gyre in the Gulf of Alaska. These currents affect weather and climate by moving warm southern waters north, generating warm rains and thunderstorms and cold northern waters south, producing snowstorms and blizzards.

Since water currents are generated and directly affected by air currents there are many similarities between the two.

• Air and water currents are alike in that warm air and water rise while cool air and water sink. In the oceans, density is controlled by temperature and salinity. In fall and winter, cooler temperatures cause the water to become dense and sink. This creates a convection cycle, which in turn creates an upwelling current. This upwelling brings nutrient rich waters to the surface.
• Both air and water currents are affected and diverted by obstructions and landforms.
• Both air currents and the Coriolis effect deflects water currents, however water is affected to a greater degree.
• Water currents move much slower than air currents, water travels at 1/100th of the driving wind speed.
• Water and air currents increase speed when constricted through a narrow opening, the Florida current travels at 3 knots (3.45 mph).

As a post visit activity students should speculate on and discuss the many ways that people are becoming more dependent upon knowing about the oceans.

• FOOD PRODUCTION - aquaculture as a worldwide food source.
• MINING AND OIL PRODUCTION - supply growing energy needs.
• OXYGEN PRODUCTION - the majority of the Earth's oxygen comes from phytoplankton, which also consume carbon dioxide.
• CLIMATIC CHANGES - affect crops and causes natural disasters such as hurricanes and floods.
• OCEAN FISHING - production is dramatically affected by ocean conditions.
• INDICATOR SPECIES - information on environmental quality is gathered through study of marine organisms that are sensitive to changes in their environment.
• UNKNOWN BENEFITS - things we will only know through research.

Bibliography

• Parmenter, T and R. Bailey. 1985. The Oregon Oceanbook. Oregon Department of Land Conservation and Development. Salem, Oregon
• Pinet, P. 1998. Invitation to Oceanography. Jones and Bartlett Publishers. Sudbury, Mass.
• Thurman, H. 1983. Essentials of Oceanography. Charles E. Merrill Publishing Company. Columbus, Ohio
• Duxbury, A. and A. Duxbury. 1989. An Introduction to the World's Oceans. William C. Brown Publishers, Dubuque, Iowa
• Garrison, T. 1999. Oceanography, An Invitation to Marine Science. Wadsworth Publishing Company. Belmont, California

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Last Update: February 4, 2004

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