The Oceans Chapter 2 – Ocean

Chapter Words to Know Salinity wave current plankton Sonar wavelength Coriolis effect nekton Seamount frequency climate benthos Trench wave height El Nino food web Continental slope tsunami La Nina Continental shelf longshore drift Intertidal zone Abyssal plain rip current neritic zone Mid-ocean ridge groin open0ocean zone

Lesson 1 – Exploring the Ocean Salinity is the total amount of dissolved salts in a sample of water. In most parts of the ocean, the salinity is between 34-37 parts per thousand. The substance you know as table salt is sodium chloride. This salt is present in the greatest amount in ocean water. Near the ocean’s surface, rain, snow and melting ice add fresh water, lowering the salinity. Evaporation, on the other hand, increases salinity. Salt can also be higher near the poles, as the surface water freezes into ice, the salt is left behind in the water.

Effects of Salinity Salinity affects ocean water in different ways. Fresh water freezes at 0 degree Celsius, but ocean water doesn’t freeze until it reaches about -1.9 degree Celsius. Because its density is greater, seawater lifts, or buoys up, less dense objects floating in it.

Temperature The broad surface of the ocean absorbs energy from the sun. Like temperature on land, temperatures at the surface of the ocean vary with location and the seasons. Near the equator, ocean temperatures often reach 25 degree Celsius, about room temperature. Warm water is less dense than cold water, so it doesn’t sink.

Depth As you descend through the ocean, the water temperature decreases. There are three temperature zones in the water column. The surface zone is the warmest. The transition zone, temperatures can drop quickly as you extend down. In the ocean, pressure increases by 1 bar, the air pressure at sea level, with each 10 meters of depth.

What are some features of the Ocean Floor Major ocean floor features include trenches, the continental shelf, the continental slope, the abyssal plain and the mid ocean ridge. The features have all been formed by the interaction of Earth’s plates

Ocean Floor Features

Let’s Review What are the four features of the ocean floor? Why has investigations of the ocean been difficult? What are some characteristics of Earth’s oceans?

Lesson 2 – Wave Action Most waves form when winds blowing across the water’s surface transmit their energy to the water. The size of the wave depends on the strength of the wind and on the length of time it blows. Stronger winds therefore create larger waves. The size of the wave also depends on the distance over which the wind blows.

Wave Characteristics Scientists have a vocabulary to describe the characteristics of waves. The higher part of the wave is known as the crest. Long rolling waves with lots of space between crests have long wavelengths. Short, choppy waves have shorter wavelengths. The lowest part of the wave is known as the trough. During storms, waves can grow much higher and more powerful

Wave Energy and Motion Waves may appear to carry water towards shore, but water doesn’t actually move forward in deep water. The energy of the wave moves toward the shore, but the water itself remains in place. As waves pass, particles move in a circular path. They swing forward and down with the energy of the wave, then back up to their original position.

Breakers The white-capped waves that crash onto shore are often called “breakers.” In deep water, these waves usually travel as long, low waves called swells. As the waves approach the shore, the water becomes shallower. The bottom of the waves begin to touch the sloping ocean floor. Friction between the ocean floor and the water cause the wave to slow down. As the speed of the wave decreases, their shape changes. Near shore, wave height increases and wavelength decreses.

Tsunami Despite the huge amount of energy a tsunami carries, people on a ship at sea may not even realize a tsunami is passing. A tsunami in deep water may have a wavelength of 200 kilometers or more, but a wave height of less than a meter. When the tsunami reaches shallow water near the coast, friction with the ocean floor causes the long wavelength to decrease suddenly. The wave height increases as the water “piles up.” Tsunamis are most common in the Pacific Ocean, often striking Alaska, Hawaii and Japan.

How do waves affect the shore? As waves approach and crash onto the shore, the beach can change. Wave direction at sea is determined by the wind. Waves usually roll toward shore at an angle.

As the waves slow down, they deposit the sand they are carrying on the shallow, underwater slope, forming a long ridge called a sandbar. Waves shape a beach by eroding the shore in some places and building it up in others. Barrier beaches Sand dunes Groins

Lesson 3 – Currents and Climate Surface currents affect water to a depth of several hundred meters. They are driven mainly by winds. Unlike waves, currents carry water from one place to another. Some currents move water at the surface of the ocean; while some move water deep in the ocean. Most of the currents flow East or West.

Coriolis Effect If Earth were standing still, winds and currents would flow in more direct paths between the poles and the equator. But, as Earth rotates, the paths of the winds and currents curve. This effect Earth’s rotation on the direction of winds and currents is called the Coriolis effect.

Gulf Stream The largest and most powerful surface current in the North Atlantic Ocean which is caused by wind currents from the West. The Gulf Stream moves warm water from the Gulf of Mexico to the Caribbean Sea. When the Gulf Stream crosses the Atlantic it becomes the North Atlantic Drift.

The Gulf Stream

Effects on Climate A surface current warms or cools the air above it. This affects the climate of land near the coast. The Gulf Steam has a warming effect on the climate nearby land areas. Currents generally move warm water from the tropics toward the poles and bring cold water back toward the equator. Cold air holds less moisture than warm air, so cold currents tend to bring cool, dry weather to land areas in their path.

El Nino and El Nina Changes in wind patterns and currents have a major impact on the oceans and nearby land. El Nino begins when an unusual pattern of winds form over the western Pacific. El Nino conditions can last for one to two years before the usual wind and currents return. This can lead to severe weather changes: Warm Winters in the northeastern Unites States which can lead to heavy rains, flooding in other areas. El Nina is complete opposite, they bring colder than normal winters.

What Causes Deep Currents? Deep currents are caused by differences in the density of ocean water. Deep currents move and mix water around the world. They carry cold water from the poles toward the equator. When a warm surface current moves from the equator toward one of the poles, it gradually cools. As ice forms near the poles, the salinity of the water increases.

Let’s Review What causes deep currents? How does temperature of ocean water affect its density? What is a current? What causes surface currents?

Lesson 4 – Ocean Habitats Ocean zones include the intertidal zone, the neritic zone, and the open-ocean zone. Lesson 4 – Ocean Habitats

Ocean Zones The intertidal zone begins at the highest high-tide line on land and stretches out to the point on the continental shelf exposed by the lowest low tide. The neritic zone extends from the low-tide line out to the edge of the continental shelf. Beyond the continental shelf is the open-ocean zone.

Grouping Organisms Scientists group marine organisms according to where they live and how they move. Plankton are tiny algae and animals that float in the water and are carried by waves and currents. Nekton are free-swimming animals that can move throughout the water column. Benthos are organisms that inhabit the ocean floor.

Relationships among organisms Plankton, nekton and benthos are all found in most marine habitats. Photosynthetic plankton are called producers. Other plankton and benthos are called consumers. Some organisms that breakdown wastes and eat the remains of other organisms are known as decomposers. All the feeding relationships that exist in a habitat make up a food web.

Let’s Review Put the ocean zones in order from deepest to shallowest. What characteristics do scientists use to group living organisms? Sea cucumbers are small animals that crawl along the ocean floor. How would you group them and why?