Earth Science Rocks!
Warm up Jan. 27
Question:
What is the primary driving force for surface
ocean currents?
A. Density layering
B. Global winds
C. Water temperature differences
D. Salt concentration
Earth Science Rocks!
MYP Unit Question: How do we use
water?
Area of Interaction: Health and Social
Education
Learner Profile: Thinker and Balanced
Earth Science Rocks!
Standard: Recognize the significant role of
water in the Earth’s processes.
Essential Question: How currents move
water?
CURRENTS
What is an Ocean Current?
What's
Up
Little
Dude
What are ocean currents?
Currents are a “river” of water within the
ocean
There are two types of currents:
1. Surface Currents
2. Deep Currents
SURFACE CURRENTS
Horizontal movement
Powered by the wind
Change directions when they meet a continent
Influenced by the Coriolis Effect
– Caused by Earth’s rotation
– Clockwise: northern hemisphere
– Counter clockwise: southern hemisphere
Affects the climate of coastal areas - warming or
cooling the air above it.
Example: Gulfstream carries water from the tropics
to the North Atlantic Ocean
SURFACE CURRENTS
Gulf Stream
Some of the Aleutian Islands of Alaska are
at the same latitude as England. Why would
England’s climate be much warmer?
What if…
What if you
made a raft
out of balsa
wood and
tried to sail it
from Peru to
Indonesia?
DEEP CURRENTS
Caused by water of different densities
Warm water rises: Cooler water sinks
Salty water sinks, less salty water rises
Water sinks
Water Cools
Water Warms
Or
Or
Salinity Increases
Salinity Decreases
Water rises
DEEP CURRENTS MOVE VERTICALLY
DEEP CURRENT EXAMPLES
Antarctica Current
Surface freezes  salt remains in water
= increase salinity/density  Water sinks
Bottom of the Earth (South Pole)
Up to 500 yrs just to move
along ocean bottom to
the Equator
DEEP CURRENT EXAMPLES
Mediterranean Sea
– Nearly closed sea
– Water evaporates  salt remains
– Increases salinity/density
– Water sinks to bottom
– Water flows
into Atlantic
Ocean
Upwelling
The process in which cold nutrient-rich
water from the deep ocean rises to replace
warm surface water
Very important to tiny organisms like
plankton. Fish and birds feed on these
organisms.
Upwelling
El Nino
Occurs every 2-7
years
Begins when an
unusual pattern of
winds forms over
the western Pacific.
Warm water moves
east.