Transcript Currents and Climate

Water on Earth
 All living things need water in order to carry out their body
processes and maintain their habitats
Where is water found?
 Oceans- 97% of Earths water is salt water
 Rivers and Lakes- 3% of Earth’s water is fresh water
 Ice- 2/3 of fresh
water is ice
 Ground water1/3 of fresh water is
underground
You should be able to
describe the steps of
the water cycle
 Evaporation
 Transpiration
 Condensation
 Sublimation
 Precipitation
 Infiltration
Exploring the Ocean
Conditions in the ocean
Salinity- total amount of dissolved salts in a sample of water.
 Near surface of ocean, precipitation, melting snow and ice decrease
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salinity
Evaporation increases salinity
Ocean water near poles has higher salinity because when water
freezes, it leaves salt behind.
Salinity causes ocean water to freeze at -1.9oC instead of 0oC like fresh
water
Salt water has higher density than fresh water
Temperature
 Temperatures vary with location and season
 As depth increases, temperaure decreases.
Pressure
 As depth increases pressure increases
Currents and Climate
Surface Currents
Current- Large stream of moving water, like a river with in the ocean
 Surface currents affect water to a depth of several hundred meters. They are caused mainly by
wind.
 Most move in a circular pattern, moving east to west then the opposite way to complete the circle
 Why do currents
move in a circular
fashion?
 THE CORIOLIS
EFFECT-due to the
Earth’s rotation, winds
and currents take a curved
path, clockwise in the
Northern Hemisphere and
counterclockwise in the
Southern Hemisphere.
 The Gulf Stream
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Largest and most powerful
surface current in North
Atlantic Ocean
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30 km wide and 300 m deep
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Moves warm water from the Gulf of Mexico to Caribbean sea
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Curves eastward at coast of NC due to the coriolis effect
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Has a warming effect on the climate nearby land areas
Currents and Climate
Climate- pattern of temperature and precipitation typical of
an area over a long period of time.
 Currents affect climate by moving cold and warm water
around the globe
 Warm water from tropics toward poles, cold water from poles
toward tropics
 Mid Atlantic (VA, NC)= moderate climate (mild winter, humid
summer) due to Gulf Stream.
 A surface current warms or cools the air above it
affecting climate of land near the coast
 Warm currents pick up moisture = brings mild rainy weather
 Cold currents can hold less moisture and cool the air=brings
cool dry weather
Currents and Climate
El Nino-An abnormal climate event that occurs every two to seven
years in the Pacific Ocean, causing changes in wind, currents and
weather patterns for 1-2 years
 Occurs every 2-7 years in Pacific Ocean
 Unusual pattern of winds in western Pacific
 Last one occurred 1997-1998
 Warm water moves east toward S. America preventing cold water
from reaching the surface
 This causes shifts in weather patterns
 1997-1998 caused warm winter in northeastern US, heavy rains, flooding and
mudslides in CA, and deadly tornadoes in FL
La Nina-A climate event in the eastern Pacific Ocean in which
surface waters are colder than normal
 Opposite of El Nino-colder than normal winters, greater
precipitation to Pacific Northwest and the north central US.
Currents and Climate
Deep Currents
 Deep currents are caused by differences in the density of the ocean water
 Move and mix water around the world
 Carry cold water from the poles toward the equator
 Move very slowly
 Cold water is more dense than warm water
 Increase salinity = increase density
How they form:
 Warm water from equator
moves to the poles and cools
density increases)
 Ice forms causing the salinity
of the water to increase
(density increases)
 Water then sinks, flows along
ocean floor as a deep water current
 Deep water currents are also
affected by the Coriolis effect.
 Deep currents are like a conveyor belt moving water between the oceans
 Bring needed oxygen to marine life living at the bottom of the ocean