Oceanography Dr. R. B. Schultz

Oceanography and Our Oceans *71% of Earth's surface is covered with water, so it is important we know something about the water surrounding us.   Oceanography is the science of our oceans that mixes biology, geology, chemistry, and physics (among other sciences) to unravel the mysteries of our seas.    In the Northern Hemisphere, 61% is water and 39% is land, thus it is called the "Land Hemisphere". In the Southern Hemisphere, 81% is water and 19% is land, thus it is called the "Water Hemisphere".

The Hemispheres of the Earth Northern Hemisphere is approximately 39% land. The Southern Hemisphere is approximately 19% land.

Hydrologic Cycle

The 5 Oceans Pacific Ocean Atlantic Ocean Indian Ocean Arctic Ocean Largest and deepest ocean Mariana Trench: 11 km., 36,000 ft. (Mt. Everest 29,000 ft.) Atlantic Ocean About ½ the size of the Pacific Indian Ocean Southern hemisphere Arctic Ocean ¼ as deep, much smaller, sea ice Southern Ocean South of 50 deg. South latitude

“Just the Facts…” Mauna Kea on the Big Island of Hawaii, measures ~10,600 m from the ocean floor, making it the tallest mountain on the planet (surpassing even Mt. Everest). If the Earth’s contours were leveled to a smooth ball, the ocean would cover it to a depth of 2686 m.

Earth’s Oceans and Seas

Composition and Chemistry of Seawater: *Seawater is a complex mixture of water and salts (dissolved minerals) making up about 3.5% of seawater.   Salinity is the proportion of dissolved salts to pure water. It is usually expressed in terms of pph, parts per hundred, or percent. But because salts in seawater are small, we usually express it as ppt, or parts per thousand. What is the ppt of seawater?

Composition and Chemistry of Seawater: *Seawater is a complex mixture of water and salts (dissolved minerals) making up about 3.5% of seawater.   Salinity is the proportion of dissolved salts to pure water. It is usually expressed in terms of pph, parts per hundred, or percent. But because salts in seawater are small, we usually express it as ppt, or parts per thousand. Seawater is about 35 ppt

 *Salinity varies in oceans based on: the amount of freshwater added to the system or the amount of evaporation that takes place. If much evaporation occurs, the water is more saline because water is evaporating faster than freshwater is added. Thus, more salts are left over.   *Conversely, the more freshwater added to the system, the less the salinity is.

Where do the salts come from? 1. Weathering of rocks/minerals and salts introduced into streams that feed into the oceans. The total quantity of this is on the order of 2.5 billion tons annually. 2. Minerals and salts are also derived from volcanic eruptions, known as outgassing from Earth's interior. We know this is true because certain elements (Cl, Br, S, B) are more abundant in oceans than in Earth's crust. Many speculate that outgassing is responsible for our oceans' formation. 3. Hard parts of marine organisms. (i.e., shell material)

*Surprisingly, the salinity of the oceans is relatively constant. Although many billion tons of salts are added annually, salts are used in: making hard parts for ocean creatures (shells), absorbed by marine plants as nutrients, and much salts are precipitated out as sediment. Overall, the oceans naturally tend to chemically mass balance themselves.   *Humans also desalinate seawater to get fresh water. This process is time-consuming, expensive and in most places it is not economically feasible. Exceptions are Kuwait (100%), Saudia Arabia, and a few plants in California.

Our Layered Oceans Surface mixing zone is warmest; saltiest near bottom of zone. Transitional zone contains thermocline and halocline. Deep zone is 2 tons per square inch and coldest in temperature.

1. The continental margin includes: Ocean Topography: *Oceanographers studying the oceans and ocean floor have found (3) major parts: 1. Continental margin 2. Ocean basin floor 3. Mid-oceanic ridges 1. The continental margin includes: a.     Continental shelf -- very gentle slope (submerged land) b.     Continental slope -- steep slope on edge of continental shelf. c.     Continental rise -- gentle slope where trenches do not exist Surprisingly, we know very little about the mapping of our ocean floor. We probably have accurately mapped only 10% of the ocean floor. It is time-consuming, expensive, and our current technology only allows us to map a few miles at a stretch.     

Ocean Topography Seamount

What else is at the bottom of the ocean? Answer: Hydrothermal vents …a.k.a… Black smokers!

Echo Sounding Used for Mapping Ocean Floor

Side Scan Sonar

Ocean Current Surface Currents: *An important "river" of the ocean is the "Gulf Stream". It flows in response to atmospheric conditions and has a direct relationship with climatic conditions.   *Strangely, ocean currents are directed to the right (clockwise) in the northern hemisphere and to the left (counterclockwise) in the southern hemisphere. This has a direct relationship with the Coriolis Effect, which is a deflective force resulting from the Earth's rotation that causes currents to oftentimes move against the winds. *Upwelling is the force that vertically moves cooler water from approximately 1000 feet below the surface to the near surface.

Surface Ocean Currents

Oceans, Waves, Currents, and Tides Ocean circulation: *Involves surface currents and deep-water masses *Some are short-lived: seasonal and local *Others are permanent and extend over large portions of the globe  

Deep Ocean Currents: *In general, deep ocean currents are driven by: gravity and density differences.   *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. Thus, deep ocean circulation is referred to as thermohaline circulation.

Deep Ocean Currents