Ocean Currents and Climate:
Surface Currents
 A current is a large stream of moving water
that flows through the oceans.
Surface currents, which affect water to a depth of several hundred meters, are
driven mainly by winds.
 Climate is the pattern of temperature and
precipitation typical of an area over a long
period of time.
 Currents affect climate by moving cold and
warm water around the globe.
 In general, currents carry warm water from
the tropics toward the poles and bring cold
water back toward the equator.
 A surface current warms or cools the air
above it, influencing the climate of the
land near the coast.
Deep Currents*
 Deep currents are caused by differences
in the density of ocean water.
 Currents move water from the equator to the
poles. As water temperatures begin to
decrease and salinity increase, the water
becomes denser and sinks.
 Then, the cold water flows back along the
ocean floor as a deep current.
 Deep currents move and mix water
around the world. They carry cold water
from the poles toward the equator.
*Upwelling
 Upwelling is the movement of cold water
upward from the deep ocean
 Upwelling brings up tiny ocean
organisms, minerals, and other nutrients
from the deeper layers of the water.
Without this motion, the surface waters of
the open ocean would be very scarce in
nutrients.
Review Questions:
1. What is a current?
- A large stream of water moving through the
ocean.
2. Explain how deep currents form and move in
the ocean.
- Deep currents form when dense ocean water that
is near the poles is cold and sinks and slowly,
flowing along the ocean floor towards the
equator.
3. What causes upwelling?
- Upwelling occurs when wind blows surface water
away from a coast and cold water rises from the
ocean depths.