Download Ocean Circulation Notes

Ocean Currents Notes Unit 3B
Ocean Circulation Powerpoint
Current Notes
Key Points
•Warming and expansion of the atmosphere causes winds which drag the water along
•The effects of temperature and the rotation of the earth on its’ axis and the positions of the
continents lead to the complex patterns found on the sea surface.
•Currents have considerable effect on human activities. From transportation to moderation
of local climates, humans depend on ocean currents.
Surface Circulation
•Surface currents are a response to the uneven heating of the earth by the sun.
•Temperature differences cause warmer water near the equator to swell and move toward the
poles.
•Wind energy is converted to water movements called "currents" by friction between the
wind and the water surface. The surface currents resemble the surface winds. Once these
surface currents are set in motion they are influenced by three other factors: Coriolis effect,
presence of coasts, and horizontal pressure gradients.
The Coriolis Effect
Objects, or ocean currents, moving through the Northern hemisphere are deflected to the
right because of changes in angular momentum that occur with the changes in latitude.
Because of the earth's rotation, any freely moving object or fluid will appear to:
o Turn to the right of its direction of motion in the Northern Hemisphere and
o Turn to the left of its direction of motion in the Southern Hemisphere.
This causes currents to travel clockwise around high pressure systems in the Northern
Hemisphere, and counter-clockwise in the Southern Hemisphere.
Wind Patterns
Surface currents are driven by winds.
The wind is again influenced by the Earth's rotation and in the latitudinal band of 30-60
degrees north and south, the Westerlies move currents towards the northeast (in the
Northern Hemisphere) and southeast in the Southern Hemisphere.
Between the equator and 30 degrees north and south, the trade winds blow toward the
southwest in the Northern Hemisphere and the northwest in the Southern Hemisphere.
The air currents moving along the surface of the Earth from the poles (90 degrees) to 60
degrees north and south of the equator, flow from east to west and are referred to as the
polar easterlies
Ocean Currents Notes Unit 3B
Surface Wind Patterns
Gyres
•Winds
together with the direct action of the Coriolis force move tremendous volumes of surface
water in a large circular patterns known as gyres which are centered around 30 degrees latitude both
north and south. These gyres move clockwise in the Northern Hemisphere and counter-clockwise in
the Southern Hemisphere.
The Ekman Current
•In 1905, Eckmann determined a theoretical value for this phenomenon known as the
Eckmann spiral. It contributes to the creation of the gyres.
•Ekman currents always carry water to the right of the wind in the northern hemisphere. The
Ekman currents push warm water to the center of the ocean. This surface convergence
creates a mound of surface water that is elevated up to one meter above the equilibrium sea
level.
The Effect of Currents
The currents regulate earth’s climate by transporting heat from tropical to polar regions and
greatly affect the geographic distribution of organisms.
Thermohaline Circulation
And the Great Ocean Conveyor
The Three Layer Ocean
•Surface layer
•Intermediate Layer (\cline)
•Deep or Bottom Layer
Ocean Currents Notes Unit 3B
Mixing (Overturn)
Downwelling
o Surface water sinks and displaces/mixes with deep water
o Temp and Density profile is consistent and straight down.
Upwelling
o Where offshore surface water movements transport water away from an area, this
area is compensated by the upward movement of deeper waters. The process of
upwelling brings nutrient rich waters to the surface allowing large phytoplankton
blooms to develop and feed which in turn support major fisheries.
o This is a common process near coastlines of continents when the water carried out to
the open ocean is replaced with water coming from depths between 100 and 200m.
The Great Ocean Conveyor
•Global Thermohaline circulation
•Critical in regulating the earth’s climate
•Brings dissolved oxygen to the deep ocean.
Tests – Monday, 10/30/06
Chemical and Physical Properties of Sea Water
Ocean Currents
What To Study????

Chemical Notes and Relationships
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Textbook – Pages 44-61
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Labs/WS
o How Salty is the Water
o The Effects of Salinity on Living Tissue – Potato Lab
o Salinity – Paper Lab
o Ocean Current Maps
o Ocean Current WS
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Current Notes
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Website practice Chapter 3 (remember we have not covered the entire chapter)
o Quizzes
o Do-it-yourself review
o Key Term Flash Cards