New Notes: Ocean Currents

New Notes: Ocean Currents

• Warm-up: • 1. Look at your buoy map – If you dropped a buoy at

Latititude 100 and Longitude 1800, which direction will it drift?

• 2. Which direction do you think it would drift if you dropped it at Latitude -100 and Longitude 1800?

• Essential Question(s): What causes the patterns of ocean currents, and how do they affect the climate of the earth?

Continue Notes: Ocean Currents

• Mini-Quiz! (Answer on a separate piece of paper – I will pick it up)

• 1. Generally, what direction do the ocean currents of the Northern Hemisphere move in?

• 2. Generally, what direction do the ocean currents of the Southern Hemisphere move in?

• 3. Tell me one other thing you learned yesterday.

Ocean Water Movements Ocean currents are masses of

water that flow from one place to another.

Surface currents develop from friction between the ocean and the wind that blows across the

surface.Surface circulation of the oceans

are cause by many interacting “gyres”, which are large systems

of rotating ocean currents, particularly those involved with

large wind movements.

Ocean Water Movements Earth’s oceanic surface circulation is made up of five main gyres.

North Pacific Gyre

The gyres are related to atmospheric circulation.

South Pacific Gyre

North Atlantic Gyre

South Atlantic GyreIndian Ocean Gyre

Idealized surface circulation

pattern for the Atlantic Ocean. The prevailing winds create

circular-moving loops of water (gyres) at the

surface in both parts of the

Atlantic Ocean basin.

Figure 15.2

Average ocean surface currents from February to March. The oceans circulation is organized into five major current gyres (large, circular-moving loops of water), which exist

in the North Pacific, South Pacific, North Atlantic, South Atlantic, and Indian Oceans.

Large ships crossing the ocean have lost entire containers overboard. if the containers release floating items, inadvertent float meters are launched that help oceanographers track ocean surface currents. The map shows the path of drifting

shoes and recovery locations from a spill in 1990.

Four Main Currents Exist Within Each Gyre

Surface CirculationGyres are caused by the Coriolis Effect,

an apparent deflection of moving objects caused by the rotation of the earth and the inertia of the mass experiencing the

effect.The Coriolis force is quite small, and its

effects generally become noticeable only for motions occurring over large

distances and long periods of time, such as large-scale movement of air in the atmosphere or water in the ocean.

This force causes moving objects on the surface of the Earth to appear to veer to

the right in the northern hemisphere, and to the left in the southern.

Surface currents are extremely important to Earth’s climate, as they transfer

warmer water from low latitudes into higher latitudes, and thereby move heat

from warmer to cooler areas.

This false-color satellite image

shows sea-surface

temperatures of the Gulf Stream.Warmer waters

are shown in red and orange,

colder waters in green, blue, and

purple.As the Gulf

Stream meanders northward, some

of its branches pinch off to form

large, circular eddies.

The Gulf Stream

Importance of Surface CurrentsOcean currents have a significant

influence on climate.When currents from low-latitude

regions move to higher latitudes, they transfer heat from warmer to cooler

areas on Earth.This is how the Gulf Stream keeps

Great Britain and northwestern Europe warmer during the winter than should

be expected for their latitudes.On the other hand, as cold currents

originating in cold, high-latitude regions travel toward the equator, they

tend to moderate the warm temperatures of adjacent land areas.

For example, the cool Benguela current off the western coast of southern

Africa moderates the heat along this coast.

Figure 15.5

Importance of Surface CurrentsWinds can also cause vertical water

movements.Upwelling is the rising of cold waters

from deeper layers to replace warmer surface water.

Upwelling is most characteristic along the western coasts of continents

where winds blow toward the equator and parallel to the coast.These winds combined with the

Coriolis effect cause surface waters to move away from the shore, being

replaced by cooler water “upwelling” from below.

This process brings greater concentrations of dissolved nutrients

to the ocean surface.

Deep Ocean CirculationCirculation in the deeper ocean is a response to density differences of water at varying

depths.Recall that two factors create a dense mass of water: cold water and increased salinity.

Deep-ocean circulation is referred to as thermohaline circulation.

Most water involved in deep-ocean

currents begins in high latitudes at the

surface A simplified model of ocean circulation is

similar to a conveyor belt that travels from the Atlantic Ocean, through the Indian and Pacific Oceans,

and back again