Ocean Currents Chapter 25 section 1

Think about it What is a current? Are all ocean currents the same?

Ocean Currents A movement of ocean water that follows a regular pattern. But what does that really mean? What do currents do for us?

Different Types There are Two (2) main types of currents. Surface Currents* Deep Currents*

Surface Currents Surface currents are horizontal (side to side) movements of ocean water caused by wind that occur at or near the ocean’s surface. Pretty simple for us to remember, since they occur at the SURFACE of the ocean. Surface currents are controlled by three factors: global winds, the Coriolis effect, and continental deflections.

Global Winds Have you ever blown gently on a cup of hot chocolate? These small ripples are just like surface currents, just on a very small scale. In nature, your breath is represented by wind.

Different Winds Different winds cause currents to flow in different directions. Near the equator, the trade winds blow ocean water east to west . Westerlies blow ocean water west to east.

Using Science Ships that transport consumer goods (toys, computers, cars) use surface currents to deliver their goods faster.

Continental Deflections Basically, the currents are constantly being pushed by winds. Well, as their being pushed, they sometimes run into a continent. When it runs into a continent (like South America) the surface current gets deflected, and then continues.

Worth a Thousand Words

Coriolis Effect So we all know that the Earth is constantly rotating. We also know this rotation causes something we call the Coriolis Effect*. Basically because the Earth is rotating, it causes Surface currents to moved in a curved path, instead of a straight path.

GYRES- huge circles of water caused by the Coriolis Effect

5 major ocean gyres

Deep Currents These occur deep within the ocean. They are not controlled by winds. Deep currents* are controlled by Water Temperature and Water Density (Salinity)

Density The colder the water gets, the denser (heavier) it is. Since heavy items sink, the colder water goes deeper into the ocean.

Deep and Surface Interactions Surface currents carry the warmer, less-dense water from other ocean regions to polar regions. Warm water from surface currents replaces colder, denser water that sinks to the ocean floor. Deep currents carry colder, denser water along the ocean floor from polar regions to other ocean regions. Water from deep currents rises to replace water leaving surface currents.

The Global Ocean The world has several oceans, and while we have different names for them, they are not really separate. There are no walls between the “oceans” Water is able to move freely between them They are all one GLOBAL OCEAN

Thermohaline circulation What does thermo mean? What does haline mean? (as in halite) What is thermohaline circulation?

GLOBAL CONVEYOR BELT There is a large-scale pattern to the way that seawater moves around the global ocean. This pattern is driven by changes in water temperature and salinity that change the density of water. It is known as the Global Ocean Conveyor Belt or thermohaline circulation. It affects water at the ocean surface and all the way to the deep ocean. It moves water around the world.

Currents Concluded Surface currents are stream like movements of water at or near the surface of the ocean. Surface currents are controlled by three factors: global winds, the Coriolis effect, and continental deflections. Deep currents are stream like movements of ocean water located far below the surface. Deep currents form where the density of ocean water increases. Water density depends on temperature and salinity. Thermohaline circulation is the pattern of the water movement in the global ocean due to temperature and salinity changes in the water

CLIMATE

How does the atmosphere affect solar radiation? 20 % is absorbed by clouds, dust and gases Solar radiation enters the atmosphere 50% absorbed by Earth’s surface 30% reflected by clouds, dust, air and Earth’s surface back into space

Factors Temperature Precipitation Latitude Heat absorption and release

There is a slight delay between the absorption of energy and an The temperature of the atmosphere in any region on Earth’s surface depends on several factors, including latitude, surface features, and the time of year and day. There is a slight delay between the absorption of energy and an Increase in the temperature

Temperature Climate described using average temps Average daily temp (add high and low for day and divide by 2) Use average daily temp to find the average monthly temp/ use average monthly to find yearly average Scientists use a yearly temperature range (differences between the highest and lowest monthly averages) to describe climate

Precipitation Also described using monthly and yearly averages. Months that have largest amount of precipitation are very important. Latitude, heat absorption and release and topography have the greatest influence on temperature and precipitation

Latitude is the primary factor that affects the amount of solar energy that reaches any point on Earth’s surface. The rays of the sun strike the equator at a 90 degree angle so the energy is more intense. At a smaller angle the energy is spread out and less intense

Global wind patterns Belts of cool, dense air form at polar latitudes Belts of warm, less dense air form near the equator Cool air = high pressure regions Warm air= low pressure regions Differences in pressure creates WIND

As seasons change, global wind belts shift in a north or south direction

Heat Absorption and Release Land heats faster than water…can reach a higher temperature in the same amount of time Why? Land is opaque and doesn’t move. Surface ocean water is transparent and moves continuously. The temperature of the land or ocean influences the amount of heat the air above the land or ocean absorbs or releases (affecting the temp of the air, affecting the climate of the area) Water releases heat more slowly than land does.

Ocean currents The temperature of the ocean currents that come in contact with the air influences the amount of heat absorbed or released by the air. EXAMPLE: The combination of warm Atlantic current and steady westerly winds give NW Europe a high avg. temp for its latitude. On the other hand, the Gulf Stream has little effect on the Eastern U.S. because westerly winds blow the Gulf Stream and its warm tropical air away from the coast.

Topography: mountains control the flow of air through a region Temperatures generally decrease as elevation increases.