Subsurface Topography & Waves, currents, and tides… ROLL TIDE! Chapter 13.1-13.4 Chapter 20.3 p. 705-706

Salinity The measure of the amount of dissolved salt contained in water. The range of salinity for most of the ocean's water is from 34.60 to 34.80 parts per thousand. Different bodies of water have different amounts of salt mixed in, or different salinities. Salinity is expressed by the amount of salt found in 1,000 grams of water. Therefore, if we have 1 gram of salt and 1,000 grams of water, the salinity is 1 part per thousand, or 1 ppt.

Salinity continued…. Did you ever wonder why the oceans are filled with salt water instead of fresh? Just where did the salt come from? And is it the same salt you find on a dining room table? Most of the salt in the oceans came from land. Over millions of years, rain, rivers, and streams have washed over rocks containing the compound sodium chloride (NaCl), and carried it into the sea. You may know sodium chloride by its common name: table salt! Some of the salt in the oceans comes from undersea volcanoes and hydrothermal vents. When water evaporates from the surface of the ocean, the salt is left behind. After millions of years, the oceans have developed a noticeably salty taste.

Density Is the measure of the amount of matter packed into a given volume. more dense less dense sink float rock cork

Continental Shelf Is the flat or gently sloping land that lies submerged around the edge of a continent and extends from the coast to the continental slope..

Different views of Continental Shelf

Continental Shelf

Sonar A system that uses sound waves to measure distances and to locate objects.

Other sonar examples

Ocean Current A mass of moving water. There are two types of ocean currents. There are two type of Ocean Currents: 1. Surface Currents--Surface Circulation These waters make up about 10% of all the water in the ocean. These waters are the upper 400 meters of the ocean.   2. Deep Water Currents--Thermohaline Circulation These waters make up the other 90% of the ocean These waters move around the ocean basins by density driven forces and gravity. The density difference is a function of different temperatures and salinity These deep waters sink into the deep ocean basins where the temperatures are cold enough to cause the density to increase.

Ocean Current continued…..

Ocean Currents continued ……

Downwelling Is the movement of water from the surface to greater depths.

Upwelling Is the movement of water up to the surface,

El Niño El Niño is a climate pattern that describes the unusual warming of surface waters along the tropical west coast of South America. El Nino has an impact on ocean temperatures, the speed and strength of ocean currents, the health of coastal fisheries, and local weather from Australia to South America.

El Niño

Ocean Waves

Longshore Current Moves water parallel to the shore. longshore current Longshore currents are currents of water flowing parallel to the shore. Longshore currents are formed by waves striking the shore at an oblique angle. Barrier spits are formed by longshore currents.  

Rip Current Rip currents are narrow streams of water that break through sandbars and drain rapidly back to sea.

Rip current

Tide The periodic rising and falling of the water level of the ocean.

Tidal Range The tidal range is the difference in height between high tide and the next low tide.

The exceptionally high and low tides that occur at the time of the new moon or the full moon when the sun, moon, and earth are approximately aligned. Spring Tide

Neap Tide A tide that occurs when the difference between high and low tide is least; the lowest level of high tide. Neap tide comes twice a month, in the first and third quarters of the moon.

Moon’s Gravity and Tides The moon, is also responsible for the changing ocean tides that we experience daily here on Earth. Basically, the moon has gravitational power, just like Earth does, and the moon's gravitational force exerts a powerful pull on the oceans on both sides of our planet. This causes the oceans to bulge away from the Earth. The ocean facing the moon bulges toward the moon, while the ocean on the other side of the Earth bulges in the opposite direction -- this is caused by the Earth actually pulling away from the ocean and toward the moon. The rotation of the Earth, along with the moon's gravitational pull, causes ocean tides to change.

Moon’s gravity affects Earth

High Tides vs. Low Tides

Salinity Salinity describes the amount of dissolved salts in the oceans water. Salinity is expressed in parts per thousand. The salinity level of the ocean is expressed in parts per thousand. The average salinity of ocean is 35 parts per thousand.