Ocean Currents

Friday, February 8th

• Winds/Coriolis Worksheet: Due Today

• Lab Worksheet: Finish Questions

Convection

cell model

Non-rotating Earth

Add rotation and add landmasses

unequal heating and cooling of the Earth

Whiteboarding

What direction does the wind blow in the

United States?

Whiteboarding

What flight would you expect to take longer:

flying from Las Vegas to New York, or New

York to Las Vegas?

Physical properties of the

atmosphere: Density

• Warm, low density

air rises

• Cool, high density

air sinks

• Creates circular-

moving loop of air

(convection cell)

Physical properties of the

atmosphere: Pressure

Whiteboarding

What type of air pressure exists between the

Hadley and Ferrel Cells?

ITCZ intertropical

convergence

zone= doldrums

Low pressure,

wet climate

High pressure, dry climate

Low pressure, wet climate

30o

30o

60o

60o

90o

90o

0o

High pressure, dry climate

The Coriolis effect

• The Coriolis effect

– Is a result of Earth’s rotation

– Causes moving objects to follow

curved paths:

• In Northern Hemisphere, curvature

is to right

• In Southern Hemisphere, curvature

is to left

– Changes with latitude:

• No Coriolis effect at Equator

• Maximum Coriolis effect at poles

The Coriolis effect on Earth

• As Earth rotates, different latitudes travel at different speeds

• The change in speed with latitude causes the Coriolis effect

Whiteboarding

What direction will a plane traveling from Las

Vegas to Canada be deflected due to the

Coriolis Effect?

Whiteboarding

What direction will the same plane be

deflected on the return flight from Canada to

Las Vegas?

Whiteboarding

Which of the following accurately shows the

deflection of a flight due South in the

Southern Hemisphere?

Monday, February 11th

• Grab the Ocean Currents Notes (if you

don’t have them already) from the front lab

table.

• Copy the objective and work on the warm-

up.

• Objective: We will diagram and explain the

causes of Surface Currents and Deep Water

Currents.

b

Surface Currents

The upper 400 meters of the ocean

(10%).

Deep Water Currents

Thermal currents (90%)

Ocean Currents

Surface Currents

Forces

1. Solar Heating (temp, density)

2. Winds

3. Coriolis

Wind-Driven and Density-Driven

Currents

• Wind-driven currents occur in the

uppermost 100 m or less

• Density differences causes by

salinity and temperature produce

very slow flows in deeper waters.

Wind-driven surface currents

http://www.classzone.com/book

s/earth_science/terc/content/vis

ualizations/es2401/es2401page

01.cfm?chapter_no=visualizatio

n

Sailors have know about ocean

currents for centuries

Sailors have know that “rivers” flow in the

seas since ancient times. They used

them to shorten voyages, or were

delayed by trying to stem them.

If navigators do not correct to deflection

by currents, they may be far away from

where they think they are and meet

disaster.

Ben Franklin and the Gulf Stream

Matthew Fontaine Maury

The first systematic study

of currents was done

by Maury based on

logbooks in the US

Navy’s Depot of Charts

and Instruments.

His charts and “Physical

Geography of the Sea”

assisted navigators

worldwide.

http://www.npg.si.edu/exh/brady/gallery/97gal.html

Winds and surface water

• Wind blowing over the ocean can move it due to frictional drag.

• Waves create necessary roughness for wind to couple with water.

• One “rule of thumb” holds that wind blowing for 12 hrs at 100 cm per sec will produce a 2 cm per sec current (about 2% of the wind speed)

Gyres

• Water moved by winds is then deflected by

the Coriolis Effect, forming Gyres.

Gyres are large circular-moving loops of water

Five main gyres (one in each ocean

basin):

• North Pacific

• South Pacific

• North Atlantic

• South Atlantic

• Indian

• Generally 4 currents in each gyre

• Centered about 30o north or south

latitude

Current Gyres

What do Nike shoes,

rubber ducks, and

hockey gloves have to

do with currents?

• “Great Pacific Garbage Patch”

• Estimate: 46,000 pieces of floating garbage/mi2.

North Pacific Subtropical Gyre

North Pacific Subtropical Gyre

135° to 155°W and 35° to 42°N

North Pacific Subtropical Gyre

http://marinedebris.noaa.gov/info/patch.html#6

Great Pacific Garbage Patch- Good Morning America 2010

http://www.youtube.com/watch?v=uLrVCI4N67M&feature=player_embedded

Surface and Deep-Sea Current

Interactions

Giant convection cell circulating around the Earth’s

oceans. Known as the “Global Ocean Conveyor

Belt”

http://seis.natsci.csulb.edu/rbehl/ConvBelt.htm

Global ocean circulation that is driven by differences in

the density of the sea water which is controlled by

temperature and salinity.

Deep Water Currents

• Water freezes at the poles, leaving cold,

salty water that has greater density and thus

sinks.

Deep Water Currents

• Water at the equator warms up from the sun

and thus has a lower density and rises.

• Warm surface currents flow towards the

poles.

Deep Water Currents

• Results in huge, slow moving, ocean current

• Just like demonstration in class.

White sections represent warm surface currents.

Purple sections represent deep cold currents

Venn Diagram

• Complete sentences: “One force causing surface currents

is…” or, “Both surface currents and deep water currents

are affected by…”

• Include:

– Forces that cause them

– Definitions of each

– Keywords associated with each (i.e. gyre and thermohaline

circulation)

– Direction of movement

Quick Questions

1. What is the primary force causing surface

currents?

Quick Questions

2. Surface Currents in the Southern

Hemisphere rotate ______________.

Quick Questions 3. Which of the following comparisons

between winds and ocean currents is NOT a

good comparison?

a. With the exception of the Ferrel Cell, warm air

and warm currents flow toward the poles.

b. Both are caused by the uneven heating of the

Earth’s surface.

c. Both are affected by the Coriolis Effect.

d. Both winds and currents can be caused by

differences in salinity.

Quick Questions 4. Based on the following picture, garbage dumped

off the East Coast in the United states would most

likely be found some time later on which of the

following continents?

a. Australia

b. Asia

c. Africa

d. Antartica

El Niño-Southern Oscillation

(ENSO) • El Niño = warm surface current in

equatorial eastern Pacific that occurs periodically around Christmastime

• Southern Oscillation = change in atmospheric pressure over Pacific Ocean accompanying El Niño

• ENSO describes a combined oceanic-atmospheric disturbance

El Niño

• Oceanic and atmospheric

phenomenon in the Pacific Ocean

• Occurs during December

• 2 to 7 year cycle

Sea Surface Temperature

Atmospheric Winds

Upwelling

Normal conditions in the

Pacific Ocean

El Niño conditions (ENSO

warm phase)

La Niña conditions (ENSO

cool phase; opposite of El

Niño)

El Niño Non El Niño

1997

Non El Niño

El Niño

thermocline

upwelling

El Niño events over the last 55 years

El Niño warmings (red) and La Niña coolings (blue) since

1950. Source: NOAA Climate Diagnostics Center

http://esminfo.prenhall.com/science/geoanimations/ani

mations/26_NinoNina.html

El Nino Animation

World Wide Effects of El Niño

• Weather patterns

• Marine Life

• Economic resources

Effects of severe El Niños