OCEAN
CURRENTS AND
GYRES
The “rivers” of the sea.
TYPES OF CURRENTS
Surface Currents
Parallel to surface of ocean (horizontal)
Deep Currents
Perpendicular to surface (vertical)
What causes them?
1) Wind –the constant blowing of global winds causes surface currents.
***Primarily for surface currents.
2) Changes in sea level – underwater mounds and landforms actually push water up or let
it fall deeper down. This causes pressure differences that make water move.
3) Density variations – density differences cause water
to want to move from one area to another.
(vertically)
***primarily for deep currents.
GYRE – A CIRCULAR FLOW OF OCEAN
CURRENTS AS THEY CONTACT LAND AND
TURN.
In the northern hemisphere, gyres turn
right (clockwise)
In the southern hemisphere, gyres turn
left (counter-clockwise)
THE CORIOLIS EFFECT
THE EARTH’S ROTATION IS WHAT CAUSES THEM TO
CURVE IN A SPECIFIC DIRECTION.
Curves to the right of original
direction.
Curves to the left of original
direction.
-Density changes due to salinity and temperature changes will cause water to
sink
-When water sinks, the area that it left now needs to be replaced.
-This water is replaced by deep ocean water, causing deep ocean currents.
HOW DO WE KNOW ABOUT THESE CURRENTS?
OR
We can literally float
around in them and make
observations.
We can float a buoy in one
spot and measure the waters
movement as it passes.
WHY STUDY OCEAN CURRENTS? WHO
CARES? WHAT/WHO DO THEY AFFECT?
Redistributes heat
Redistributes pollution
Global
weather/climate (heat)
Affects shipping
and vessels
Carries plankton/food
Upwelling (mixing)