31 terms

Ch 15 Oceanography

STUDY
PLAY
Oceanography
The study of Earth's oceans, physical properties and organisms that live in them
Sonar
Technique that directs sound waves to the seafloor at an angle so that underwater hills and other topographic features can be mapped. Calculation:

Ocean depth =
(Time(seconds) x 1500m/s) divided by 2
Volcanism
One of the two main theories on the origin of water on Earth:
Volcanism says volcanoes gave off water vapor. As earth cooled, the vapor condensed into water forming the oceans.
(The other theory says comets brought water to earth. Comets are made of rock and ice. When they hit the earth, the ice melted forming the oceans.)
Sea Level
The average level of the surface of the ocean measured along a shoreline. The level is currently rising 1-2mm per year due to melting glaciers.
Sea
Salt water like oceans, but smaller and more land-locked.
Salinity
Measure of the amount of salts dissolved in seawater. Ocean water has an average salinity of 3.5% or 35ppt. PPT stands for "parts per thousand".
Temperature Profile
Is a plot of how water temperature changes with depth in the ocean. Includes the temperature and the latitudes where the following 3 layers are found: Surface Layer, Thermocline, Bottom Layer.
Thermocline
A transition layer that has rapidly decreasing temperature with depth. It is located between the warm sunlit Surface Layer and the cold dense Bottom Layer. See Fig 15-15 p.397.
Wave
Rhythmic movement that carries energy through space or matter. In oceans waves are created by wind moving over the surface of the water.
Crest
Highest point of a wave.
Trough
Lowest point of a wave.
Fetch
Distance that the wind blows over water. The bigger the fetch, the bigger the waves become.
Breaker
Collapsing ocean wave that forms when a wave reaches shallow water and is slowed by friction with the ocean bottom.
Tide
Periodic rise and fall of the sea level caused by the gravitational pull of the Earth, Moon & Sun. NOTE: The MOON's gravity has the biggest impact on tides.
Density Current
Current that forms when a mass of more dense seawater sinks beneath less dense seawater. It is too deep to be caused by wind. Instead the current is caused by differences in temperature and salinity which leads to differences in density.
Surface Current
Ocean current caused by wind that occurs at or near the ocean's surface.
Spring Tide
When the tidal range is greatest, meaning high tides are higher than usual and low tides are lower. Occur during full moon and new moon, when the Earth,Moon & Sun are all in a line. See Fig 15-22 p.403.
Neap Tide
Tide when the tidal range is the smallest, when the smallest difference between the levels of low and high tides occurs. Occurs during 1st quarter & 3rd quarter moons, when the sun and moon pull at right angles to each other. See Fig 15-22 p.403.
Gyre
Closed circular currents caused by the deflection (bouncing) of ocean currents when they hit continents. See Fig 15-23 p.404.
Upwelling
Movement of deep, cold, and nutrient-rich water to the surface. It is caused by winds pushing the surfacewater away so cold water can rise.
El Nino
Unusually warm ocean current off the west coast of South America. Current caused by equatorial winds that blow from west to east, opposite of the usual direction. It causes drought in Australia, warm/rainy weather in NW South America, warm winters in United States.
Origins of Earth's Water - 2 main theories
Two main theories:
1. Volcanoes gave off water vapor. As earth cooled, the vapor condensed into water forming the oceans.
2. Comets brought water to earth. Comets are made of rock and ice. When they hit the earth, the ice melted forming the oceans.
Ocean Size (3 largest)
Largest: Pacific
2nd largest: Atlantic
3rd largest: Indian
Salt Removal & Addition
See Figure 15-13 p. 395. Salt (salinity) levels remain constant in the ocean because salt is added & removed at the same rate through the following methods:

Addition: Volcanic gases dissolved in rain, & weathering of rock through ground water.

Removal: Evaporation of water around edges and from spray splashed on banks leaves salt on ground that doesn't come back down in the water cycle. Salts are also removed when they are used by animals for bones which end up on bottom of ocean after death rather dissolved in the water.
Ocean Layers
See Fig 15-16 p397. Surface layer, thermocline, bottom layer. Surface layer is sunlit and warm. Thermocline rapidly decreases in temperature and light with depth. Bottom layer is cold, dense and dark. All 3 layers are present at the equator. At the poles, because of the cold temperatures, only the bottom layer is present.
Deep Water Masses
3 of them: Antarctic Bottom Water, Antarctic Intermediate Water, Atlantic Bottom Water. Can you use Fig 15-17 p.398 on p.398 to determine where the masses come from, how they vary in temperature and density?
Wave Height
Vertical distance between crest & trough
Wave Length
Horizontal distance from crest to crest
Tidal Range
Difference of water level between high & low tides
Solar Tide
Effect of the sun's gravity on Earth's tides. The solar tide is much smaller than the lunar tide. The sun's gravity has a smaller effect because the sun is so far away.
Lunar Tide
Effect of the moon's gravity on Earth's tides. The lunar tide is much bigger than the solar tide. Even though the moon has much less gravity, it's gravity has a bigger effect because the moon is much closer.