Ocean Currents: Causes and Effects

Ocean Currents

Ocean Currents

The Reality of Sending a

The Reality of Sending a

Message in a Bottle

Message in a Bottle

Ocean Current Layers

Ocean Current Layers



Surface Currents

Surface Currents

– top 10% of the

– top 10% of the

ocean; upper 400 m

ocean; upper 400 m



Deep Currents 

Deep Currents 

– lower 90% of the

– lower 90% of the

ocean

ocean

Properties

Properties

of

of

Ocean Water 

Ocean Water 



How they impact ocean currents

How they impact ocean currents

•

Temperature

Temperature

– remember heat

– remember heat

rises!

rises!

•

Salinity

Salinity

 – 

 – 

remember salty water

remember salty water

sinks!

sinks!

•

Density

Density

– a function of

– a function of

temperature and salinity

temperature and salinity

World Map

Surfers (Why)

Florida

California

Ocean Surface Temperatures

Ocean Surface Temperatures

http://www.bigelow.org/shipmates/sstemp_lg.gif

Temperature vs. Currents

Temperature vs. Currents

http://earth.usc.edu/~stott/Catalina/Oceans.html

Notes



Water by the equator is the hottest.



Water by the Poles is the coolest.



Ocean currents are caused by

Uneven Heating.



Ocean Currents are Convection

Currents.

CAUSES  OF  CURRENTS

CAUSES  OF  CURRENTS

1. shape of the continents

1. shape of the continents

2. temperature differences

2. temperature differences

(colder water is denser)

(colder water is denser)

3. spinning of the Earth

3. spinning of the Earth

        (deflecting currents to right in Northern

        (deflecting currents to right in Northern

hemisphere)

hemisphere)

4. winds

4. winds

Credits:  CNMOC, U. S. Navy; CNMOC, U. S. Navy; NASA; U. S. Geological Survey

Currents are

affected by:

1 continents

 2 temperature

3 Coriolis spin

4 Gulf Stream

4

3

2

1

Current Forces Explained

Current Forces Explained



Sun/solar heating

Sun/solar heating

- causes water to

- causes water to

expand and move

expand and move



Winds

Winds

 - 

 - 

push the water; winds blowing for

push the water; winds blowing for

10 hrs across ocean will cause the surface

10 hrs across ocean will cause the surface

water to flow @ ~2% wind speed; wind

water to flow @ ~2% wind speed; wind

has the greatest effect on surface currents

has the greatest effect on surface currents



Gravity

Gravity

 - 

 - 

pull water downhill or pile

pull water downhill or pile

against the pressure gradient (high/low);

against the pressure gradient (high/low);

influences tides

influences tides

Winds

Winds



Winds driven by

Winds driven by

uneven solar

uneven solar

heating & Earth’s

heating & Earth’s

spin, drive the

spin, drive the

movement of the

movement of the

ocean’s surface

ocean’s surface

currents.  The

currents.  The

prime movers are

prime movers are

the powerful

the powerful

westerlies

westerlies

and

and

the persistent

the persistent

trade winds

trade winds

(easterlies).

(easterlies).

Wind Driven Ocean Currents

Wind Driven Ocean Currents

http://www.bigel

http://www.bigel

ow.org/shipmates/hc_currents_lg.gif

ow.org/shipmates/hc_currents_lg.gif

Current Forces (cont’d)

Current Forces (cont’d)



Coriolis effect/force

Coriolis effect/force

- Force due to

- Force due to

the Earth's rotation, capable of

the Earth's rotation, capable of

generating currents. It causes

generating currents. It causes

moving bodies to be deflected to the

moving bodies to be deflected to the

right in the Northern Hemisphere

right in the Northern Hemisphere

and to the left in the Southern

and to the left in the Southern

Hemisphere. The "force" is

Hemisphere. The "force" is

proportional to the speed and

proportional to the speed and

latitude of the moving object. It is

latitude of the moving object. It is

zero at the equator and maximum at

zero at the equator and maximum at

the poles

the poles

http://www.csc.noaa.gov/text/glossary.html

http://www.csc.noaa.gov/text/glossary.html



causes the water to move around the

causes the water to move around the

mound of water

mound of water

Surface Currents

Surface Currents



Surface current – with surface currents

circulation is less dense and influenced

by winds

1.

Warm surface currents: wind and Earth’s

rotation

2.

Cold surface currents: flow towards the

equator

3.

Upwelling current: cold, nutrient rich; result

of wind

4.

Western Boundary currents: warm & fast

5.

Eastern Boundary currents: broad, slow, cool

& shallow, associated with upwelling



Ex: 

Gulf Stream

 = surface current that is

the upper 20% of the ocean, western

boundary current

Properties

Properties

 of

 of

 Deep Ocean Currents

 Deep Ocean Currents



Deep ocean water characteristics:

Deep ocean water characteristics:



Cold

Cold



Dense

Dense



Salty

Salty



Move by density forces and gravity

Move by density forces and gravity



Move slower than layers above

Move slower than layers above



Thermohaline Circulation

Thermohaline Circulation

:

:

is global ocean circulation.

is global ocean circulation.

It is driven by differences in the density of the sea

It is driven by differences in the density of the sea

water which is controlled by temperature (thermal)

water which is controlled by temperature (thermal)

and salinity (haline).

and salinity (haline).

http://www.climate.unibe.ch/~christof/div/fact4thc.html

http://www.climate.unibe.ch/~christof/div/fact4thc.html

Global Conveyer Belt

Global Conveyer Belt



Thermohaline circulation links the Earth's oceans. Cold, dense, salty water

Thermohaline circulation links the Earth's oceans. Cold, dense, salty water

from the North Atlantic sinks into the deep and drives the circulation like a

from the North Atlantic sinks into the deep and drives the circulation like a

giant plunger.

giant plunger.

http://www.columbia.edu/cu/record/23/11/13.html

http://www.columbia.edu/cu/record/23/11/13.html

Graphic - 

Graphic - 

http://www.grida.no/climate/vital/32.htm

http://www.grida.no/climate/vital/32.htm

Ocean Currents

Ocean Currents

&

&

Living Things

Living Things



Currents are important to

marine life as they help move

food and nutrients making them

available for photosynthesis,

metabolic requirements and or

consumption.