June 2011 Ocean Currents Ocean water circulates in __________ caused by _____ and by _________ differences Currents are the _____ of __________between areas of different surface _________or different _______________ Ocean Currents

Ocean Currents Ocean water moves constantly sideways, up, down because it is: Blown by __________ Moved by differences in __________ below the surface zone __________ unevenly

Ocean Currents Ocean water moves constantly sideways, up, down because it is: Affected by Earth’s __________ (Coriolis) Pulled by sun & moon (_______)

Currents Important because they Moderate ____________________ Mix ____________ & ________________ Transport ____________ & ____________

Coriolis Effect Causes currents to move _____________ in Northern Hemisphere _____________ in the Southern Hemisphere

Surface currents affect the uppermost ________ of the ocean Some surface currents are rapid and __________, with well-defined boundaries

Others are slow and _______ Largest currents organized into huge circuits called __________

Gyres - ________________________________________________

_________________ boundary currents are located on the __________________ side of the OCEAN - not the continent. _________________ boundary currents are located on the _________________ side of oceans.

Comparison of Boundary Currents Western Eastern currents bring __________ water from the equator 1. currents bring ____________ water from the poles 2. __________salinity; __________oxygen content 2. __________ salinity; __________high oxygen content 3. nutrient __________, __________ upwelling 3. nutrient _____________due to ____________ 4. __________ biomass 4. __________ biomass

Effect of Surface Currents on Climate Surface currents ________ heat worldwide Warm water flows to _______ ________ ____________ heat to the air and cools Moves back to __________ latitudes Absorbs __________ Repeats

Upwelling/Downwelling Upwelling and downwelling describe the ____________ movement of water

Upwelling __________ movement of water ____________ ___________ - due to divergence of surface currents ____________ ____________ - caused by wind blowing parallel to shore or offshore Brings ______________

Downwelling __________ movement of water Caused by ___________ in surface water density Wind blowing parallel to shore or onshore (__________ __________) Brings dissolved ________ & _________ to deeper water

NORMAL Normally, trade winds blow warm surface water toward the _________Pacific. When the ________ _________falter, ___________water piles up in the western Pacific about 1 & ½ feet higher than the average ocean surface.

NORMAL This causes the ______________ to rise near the surface in the eastern Pacific. __________, nutrient-rich water wells up from the thermocline to the ______ waters off the coast of Peru - good for fishing.

EL NIÑO El Niño describes _____________ oceanic and atmospheric conditions. First noticed off the coast of Peru around Christmas time, the condition was called El Niño referring to the Christ child.

El Niño’s ____________trade winds blow warm water ____________, across the equatorial region of the Pacific. This __________the thermocline across the Pacific, and stops ________________. Because warm water evaporates __________, the air fills with more water vapor and it produces more _________. NOAA El Niño occurs primarily in the __________ Pacific Ocean but it affects __________ __________.

La Niña When too much westerly wind blows surface water near the _______________, it has an effect on the weather that is often _____________to El Niño, called La Niña. NOAA

Comparison of El Niño and La Niña ____________ocean temperatures ____________ ocean temperatures occurs every ________ years frequency __________ __________ than normal summers __________ than normal summers __________ trade winds __________ trade winds ___________________ hurricanes forming in N. Atlantic

DENSITY DRIVEN CURRENTS AKA THERMOHALINE CURRENTS ____________ refers to temperature and ____________ refers to salinity Cold water sinks at the __________ and crawls toward the rising warmer water at the ____________________

Density Structure of the Ocean _______________ weighs 2-3% more than pure water Cold, salty water is more _____ than warm, less salty water Much of the ocean can be divided into ______ __________ zones: surface, pycnocline & deep

Density Zones __________ or Mixed Zone Temperature, salinity & density ____________________ due to currents and waves In contact with _____________ Exposed to _____________ Least __________ water 2% all of ocean water ~150 meters deep

Density Zones _____________ aka Thermocline aka Halocline Density ____________ with depth, temperature ____________, salinity ______________ Isolates __________ water from denser layer below 18% of all ocean water

Density Zones _____________ Zone Below pycnocline Depth below 1000 m Little __________ with depth Very cold (1-3C) and _______ 80% of all ocean water

Density stratificaiton in the ocean

Density Stratification & Water Movement Water mass – body of water with same temperature and salinity Even deepest water originates at ______________

Density Stratification & Water Movement Dense water masses form: near _________ (as water freezes) in __________ areas (where water evaporates)

Density Stratification & Water Movement Water masses below pycnocline do not mix – ________________ – too cold

Thermohaline Circulation Circulation of 90% of ocean water below surface zone is ________ driven Dense water _____, less dense _____ Movement called – __________ __________ Can take 100’s of years to circulate

Water masses almost always form at ocean __________ Densest and deepest form by surface conditions that caused the water to become very cold and salty at the ____________

The Global Heat Connection Because they transfer large quantities of heat, ocean currents affect world ________ and __________ The transport of _______ water to the _______ regions is part of the global conveyor belt for heat ________

Ocean Flow The slow, steady flow of water distributes dissolved ________ and ________ mixes __________ transports __________ marine organisms among ocean basins