Ocean Currents Study Guide

Ocean Currents / Study Guide

A current is the stream-like movement of water through the Earth's oceans. Some currents occur on the water's surface, while others occur deep in the ocean. No matter their location, currents are unique in that they move water, unlike waves which do not.

Surface currents affect water to a depth of 100 meters but can extend to hundreds of meters deep. Surface currents originate in different areas of Earth and move in circular patterns, following the patterns of major winds. They flow east to west then back again.

The Gulf Stream is an example of a surface current. It is the largest and most powerful surface current. It is more than 30 km wide and 300m deep. It moves more water than all the rivers in the world. It is caused by strong winds from the west and moves warm water from the Gulf of Mexico and the Carribean to the East Coast of the United States.

Multiple Choice

Surface currents do not move water. They move energy.

Multiple Choice

Surface currents are caused by ________.

• wind

• gravity

Multiple Choice

Surface currents move in the _____ direction as the wind.

• same

• opposite

Multiple Select

Which of the following characterize the Gulf Stream? Select all that apply.

• It is the largest, most powerful surface current.

• It is one of many similarly size surface currents caused by winds from the west.

• It moves warm water from the Gulf of Mexico to the East Coast of the United States.

• It moves more water than all the rivers of the in the world.

Surface currents are affected by three main factors: continental deflections, the Coriolois Effect, and global winds. Because Earth is scattered with continents, surface currents do not move in only one direction. Instead, the continents disrupt or deflect the winds and currents and send them in another direction. This is called continental deflection.

The effect of Earth's rotation on the direction of winds and surface currents is the Coriolis Effect. The Coriolis Effect causes Earth's winds and currents to curve instead of moving in a straight line. In the Northern Hemisphere, winds and currents move clockwise. Meanwhile, in the Southern Hemisphere, winds and currents move counterclockwise. These movements are a result of the Coriolis Effect.

Recall that wind is the cause of surface currents. The global winds that blow across Earth's surface can also affect the direction of surface currents. Different types of winds move in different ways and directions, affecting the movement of surface currents. For example the Westerlies and the Trade winds blow in opposite directions, creating a circular movement of wind and ocean currents, as observed with the Gulf Stream.

Multiple Select

Which of these are factors that affect surface currents? Select all that apply.

• Coriolis Effect

• continental deflection

• global winds

• continental drift

Multiple Choice

The Coriolis Effect is powered by Earth's ________.

• rotation on its axis

• revolution around the sun

Multiple Choice

The Coriolis Effect causes winds and currents to _________.

• stay straight

• stop

• curve

Multiple Choice

Due to the Coriolis Effect, currents in the Northern Hemisphere move ________, while currents in the ________ move counterclockwise.

• clockwise; Southern Hemisphere

• counterclockwise; Southern Hemisphere

• clockwise; deep ocean

• counterclockwise; near the equator

The Gulf Stream is the most powerful surface current and is responsible for moving warm water to areas of the East Coast of the United States. This, in turn, warms the climate of those areas. Climate is the pattern of temperature and precipitation typical of an area over a long period of time. Surface currents have a direct effect on climate. They affect the climate of an area by moving warm or cold water around the globe, which warms or cools the air above it.

For example, warm water currents warm the air above them. Winds pick up the moisture held in the warm air and move it, spreading mild, rainy weather. Cold water currents cool the air above them. Since cool air holds less moisture than warm air, the climate that comes with cold currents is typically cool and dry.

It's important to understand the difference between weather and climate. Weather is the short-term state of the atmosphere and can change within minutes or hours.

Climate is the pattern of temperature and precipitation typical of an area over a long period of time.

The Gulf Stream is the most powerful surface current and is responsible for moving warm water to areas of the East Coast of the United States. This, in turn, warms the climate of those areas. Surface currents have a direct effect on climate. They affect the climate of an area by moving warm or cold water around the globe, which warms or cools the air above it.

Warm water currents warm the air above them. Winds pick up the moisture held in the warm air and move it, spreading mild, rainy weather. Cold water currents cool the air above them. Since cool air holds less moisture than warm air, the climate that comes with cold currents is typically cool and dry.

Multiple Choice

______ is the (daily) pattern of temperature.

• Climate

• Weather

• Precipitation

• Temperature

Multiple Choice

_______ is typical of an area over a long period of time.

• Climate

• Weather

• Precipitation

• Temperature

Multiple Select

Which of these are effects that warm water currents have on climate? Select all that apply.

• rainy

• dry

• cold temperatures

• mild temperatures

Multiple Select

Which of these are effects that cold water currents have on climate? Select all that apply.

• rainy

• dry

• cold temperatures

• mild temperatures

Surface currents are currents that move water at the ocean's surface. Deep currents are currents that move water deep below the ocean's surface. They are caused by changes in water density, not by wind. Recall that density is affected by salinity and temperature: an increase in salinity results in an increase in density, just as a decrease in temperature results in an increase in density.

When a warm surface current moves from the Equator toward one of the poles, it eventually cools and freezes, resulting in an increase in salinity and ultimately, density. This colder, denser water sinks below the warmer, less dense water. The movement of the water from the surface to the deep ocean causes deep currents.

Multiple Choice

Surface currents and deep currents differ in their location in the ocean water, but not in their cause.

Multiple Choice

What causes the change in density that results in water sinking and becoming a deep current? Select all that apply.

• decrease in temperature

• decrease in gravity

• increase in friction

• increase in salinity

Surface currents and deep currents are linked together to move energy and matter throughout the world's oceans. Deep currents and surface currents work together to form a conveyor belt-like system of movement called convection currents. Convection currents move energy and matter throughout Earth's oceans. Convection currents can move in a cyclical or circular pattern. They result from differences in water density.

Multiple Choice

_________ are currents that result from the combination of surface currents and deep currents that move energy and matter throughout Earth's oceans.

• Deep currents

• Surface currents

• Offshore currents

• Convection Currents

Multiple Choice

The _____ is the energy source that begins the process of convection currents.

• ocean

• Sun

• gravity

Multiple Choice

An increase in _____ causes warm surface water to sink and become a deep current.

• friction

• density

• gravity

Multiple Choice

Deep currents rise to the surface water to sink and become a deep current.

• less dense

• denser

Ocean Current Transports

Currents transport dissolved solids, gases, water and energy throughout the global ocean. Convection currents move 40% of the energy moving around Earth's surface. Due to the increased amount of solar energy at the Equator, a large amount of solar and atmospheric energy is absorbed there. Warm water surface currents bring this energy to the cooler areas of the ocean. In the cooler areas of the ocean, the warm surface water cools and releases energy back into the atmosphere. This process affects Earth's climate by transporting energy in the form of heat throughout the ocean.

Ocean Current Transports (continued)

Ocean currents also transport dissolved solids, nutrients, and gases. Salt is one example of a dissolved solid that is transported by ocean currents. Nutrients such as nitrogen and phosphorus, which are critical to the life of marine animals, are also transported by ocean currents. The ocean also absorbs some of the gases that are present in the atmosphere. For example, oxygen and carbon dioxide are both present in the atmosphere as well as in the ocean. These gases are two of the gases that marine organisms need for survival.

Multiple Choice

A current is ______.

• a stream-like movement of water through Earth's oceans.

• a naturally occuring stream of water that prevents beach erosion.

• movement caused by wind.

• energy that moves through the Earth's oceans.

Multiple Choice

What is a surface current?

• A current that occurs at or near the surface of the ocean and is caused by the wind.

• A current caused by excessive precipitation.

• A current that is caused by underwater events such as earthquakes or volcanoes.

• A current resulting from a rapid decrease in wave speed.

Multiple Choice

What is the Coriolois Effect?

• The effect of the phase of the Moon on winds and currents.

• The effect of Earth's revolution around the Sun on winds and currents.

• The effect of Earth's rotation on the direction of wind and currents.

• The effect of latitude on the movement of winds and currents.

Multiple Choice

What is the definition of climate?

• The ratio of evaporation and precipitation over a long period of time.

• The pattern of temperature and precipitation typical of an area over a long period of time.

• The atmospheric changes that occur over a long period of time.

• A pattern of surface and deep currents over a long period of time.

Multiple Choice

Deep currents are ________.

• currents that are caused by an increase in friction between cold water and the ocean floor and move water below the ocean's surface

• currents that are caused by wind and move water deep below the ocean's surface.

• currents that are caused by gravity pulling cold water to the ocean floor and move water below the ocean's surface.

• currents that move water deep below the oceans surface and are caused by changes in water density.

Multiple Choice

Convection currents are _______.

• currents that are powered by gravity to move matter and energy throughout the Earth's oceans.

• currents that result from a rapid increase in friction between surface and deep currents and move energy and matter throughout Earth's oceans.

• currents that result from the energy of the Sun and move energy and matter throughout Earth's oceans.

• the combination of surface currents and deep currents that move energy and matter throughout Earth's oceans.