Chapter 18: Ocean
Motion
Section 18-2 Ocean Currents
Notes Guide
Surface Currents





Ocean currents are a mass movement, or flow, of ocean
water. Currents are like rivers within the ocean.
Surface currents move water horizontally-parallel to the
Earth’s surface.
These currents are powered by wind, which forces the
ocean to move in huger circular patterns.
The currents on the ocean’s surface are related to the
circulation of the winds on Earth.
Surface currents move only the upper layer of seawater.
Ocean Surface Currents
How surface currents move

Surface ocean currents and winds are affected by the
Coriolis Effect.
-the Coriolis Effect is the shifting of winds and surface
currents from their expected paths that is caused by
Earth’s rotation.
-Because the Earth rotates toward the east, winds
appear to curve toward the right in the northern
hemisphere and to the left in the southern hemisphere.
-the winds cause the water to pile up in parts of the
ocean. When gravity pulls the water off the pile, the
Coriolis effects turns the water.
-Surface water in north of the equator turns to the right,
and currents south of the equator turn to the left.
Coriolis Effect
How surface currents move
continued…

The Gulf Stream is a very strong current that
brings warm water up from the equator, up the
east coast of the U.S., and towards England.
-Sailors used the Gulf Stream to travel quickly
from North America to England.
 Surface currents are tracked by drift bottles.
 These bottles are released in various locations.
People record information about where and
when the bottle was found, and scientists use
that information to learn about surface currents.
Gulf Stream
Warm and Cold Surface Currents

Currents formed on the east coast of continents
move warm water from the equator towards the
poles.
-The Gulf Stream is an east coast current.
 Currents formed on the west coast bring cold
water down from the poles toward the equator.
- The California Current is a west coast current.
 Currents play a key role in distributing heat
across the globe, and this transfer of heat
influences climate.
Upwelling





Upwelling is a vertical circulation in the ocean that brings
deep, cold water from the ocean bottom to the ocean
surface.
Wind blowing parallel to coasts carries the water away
from land. That warm surface water is then replaced by
cold, deep ocean water.
Water from the deep ocean is rich in nutrients that come
from dead and decayed organisms.
This nutrient rich water encourages plankton growth,
which in turn attracts fish.
Areas of upwelling are important fishing grounds.
Upwelling
Density Currents

Deep in the ocean, water circulated because of
density differences, not because of wind.
 A density current forms when a mass of
seawater becomes more dense than the
surrounding water.
 More dense water will sink below less dense
water.
-Saltier water is more dense than fresh water.
- Cold water is more dense than warm water..
 Density currents circulate ocean water slowly.
Oceanic Conveyer Belt