THE INSIDE STORY:

OCEANCIRCULATION

by Robert Perry

DISCLAIMER:

The images, maps and diagrams inthis presentation were taken from the public domain on the world

wide web. Any privately owned images not available for this non-

commercial, educationalproject will gladly be removed.

E-mail: zalophus@ucla.edu

The ocean waterscirculate in

specific patterns…

they don’t justsit there!

Currents in the ocean may be

horizontal

vertical

or

SURFACE

DEEP

UP

DOWN

1- HorizontalSurface Currents.

Surface currentsare powered bythe prevailing

winds.

Consider these average wind patterns.

Compare the wind patterns to the currents.

The surfacecurrents

rotate in circlescalled gyres

due to the Coriolis“Force” (or “effect”)

Atlanticgyres

Remember this slide:

we’ll see itagain later !

Clockwise rotationin northern hemisphere

Counter-clockwiserotation

in southern hemisphere

N

S

Pacificgyres

How aresurface currents

studied ?

Drifting buoyssend theirsignals to

satellites and are used to studyocean currents.

60,000 Nike shoes spilled from a storm-tossed cargo ship in the northeastern Pacific in May, 1990

1 shoe spill, May 27, 19902 250 recovered, March 26, 19913 200 recovered, May 18, 19914 100 recovered, January-February 19915 200 recovered, November-December 1990

6 200 recovered, February-March 1991

7 150 recovered, April 4, 19918 200 recovered, May 9-10, 19919 several recovered,

January-March 199310 predicted, January-July 1994

The Gulf Stream:

The shuttleEndeavorphotographedthe Gulf Streamoff Newfoundlandin 1992.

Ben Franklin’s map of

the Gulf Stream.

Gulf Stream

GULF STREAM

Warm water species:

“This satellite sea-surface temperature image of the Gulf Stream illustrates the two types of eddies, or rings, as they are now called: these are the warm core rings and the cold core rings. As the Gulf Stream flows north, it encounters the Labrador flowing south along the banks of Cape Hatteras. As these two currents meet, they begin to meander (they wind back and forth like a snake). Eventually, these meanders "pinch off"from the main flow and become independently rotating structures, known as rings”.

(From oceansonline.com)

Process ofring formation

from Gulf Streammeanders.

From:http://blitzen.sprl.umich.edu/PHAYS/Contents.html

“One set of rings, which contains the cold water of the Labrador Current, are known as cold core rings. These cold core rings spin off from the Gulf Stream and are propelled eastward into the North Atlantic Ocean. Their movements may take them quitefar from the Gulf Stream and, depending on their size, they may retain their characteristics for months. As they spin off

from the Gulf Stream, they have a certain rotational velocity, a net direction, and a characteristic temperature structure. Because their centers contain cold nutrient-rich water, a plankton bloom develops in the middle of these rings. The development of the plankton bloom, the development of organisms that feed on the plankton, and the eventual "death" of the ring as it mixes with the surrounding water is a fascinating study in the ecological succession of plankton communities. In recent years, entire oceanographic studies have been devoted to understanding the nature of the formation and evolution of these rings, and the biological communities that develop as a result of these rings”. (From oceansonline.com)

“On the other side of the Gulf Stream, warm water pinches off into structures called warm core rings. These rings typically spin off west and north of the Gulf Stream, and travel against the flow of the Labrador Current. Because their centers are composed of warm, nutrient-poor water, conditions are not ripe for plankton blooms. As such, these rings typically don't develop the kinds of biological communities we observe in cold-core rings”. (From oceansonline.com)

“The satellite image of sea surface temperature reveals quite nicely the differences between cold-core and warm-core rings. In the image shown, reds, oranges, and yellows are warm water, and greens and blues are cold water. Take a look at the center of the picture. You should be able to make out swirling masses of water associated with the northernmost part of the Gulf Stream.

Can you see two dots of green in the middle of the red and yellow water? These are cold core rings. Just above them, on the other side of the Gulf Stream, is a large swirl of yellow water floating in the middle of green water. This is a warm-core ring. Note also the meanders of the Gulf Stream as it bends towards the east. It is these meanders that give rise to these rings”.

(From oceansonline.com)

Horizontal watermovement:

2. DeepCirculation.

Basic ideas:WARM or LESS SALTY WATER RISES

COLD or MORE SALTY WATER SINKS

UP

!

DOWN !

THE SURFACE AND DEEPWATERS OF ALL MAJOR

OCEANS ARE CONNECTEDTOGETHER.

Deep ocean circulation (Stommel, 1958; Deep-Sea Res., 5, 80-82). Dots (o) are locations of deep water formation.

o

o

Vertical watermovement:

Upwelling.

2 things maycause upwelling:

2. WATER MOVINGAWAY FROM LAND.

1. WATER MASSESMOVING APART.

DUE TO CORIOLIS, EQUATORIAL CURRENTSTEND TO DIVERGE OR MOVE APART

CAUSING UPWELLING IN THE OPEN OCEAN.

CAUSES WATERTO MOVE AWAYFROM LAND IN

EACH HEMISPHERE

In the southern hemisphere, wind and surface currentsmove from south to north causing coastal upwelling.

California

In the northern hemisphere, wind and surface currentsmove from north to south causing coastal upwelling.

THE BIOLOGICAL IMPORTANCEOF UPWELLING IN THE SEA.

PHOTIC ZONE

SUNLIGHT

FERTILIZING NUTRIENTS FOR PHOTOSYNTHESIS ARE LOST TO

THE BOTTOM, BELOW THE PHOTIC ZONE

PHOTIC ZONE

SUNLIGHT

ONLY UPWELLING CANRETURN THE FERTILIZING

NUTRIENTS TO THE PHOTICZONE

PHOTIC ZONE

SUNLIGHT

COASTAL UPWELLINGALONG THE WEST COAST.

NOTICE THE COLDER WATERNEAR THE LAND, COMPARED

TO THE WARMER WATEROFFSHORE.

COASTAL UPWELLINGALONG THE WEST COAST.

THE LIGHT COLORSREPRESENT COLD

TONGUES OF WATERMOVING OFFSHOREDUE TO UPWELLINGALONG THE COAST.

U P

W E

L L

I N

G !

Horizontal watermovement:

3. Currents alongthe shoreline.

Incoming wavesbreak and washashore. Waterpiles up duringa set of waves

and travelsalong the shore.

This is the “Longshore

Current.”

The longshore current empties back out to sea. This is called

a “Rip Current.”

Caught in a rip?Swim parallel to the shore !

(Don’t try to swim in against it).

swim

out

swim

out

T H E E N D