Chapter 5 Flashcards
Describe the Eckman Spiral.
Earths rotation and friction:
Current moves to right of the wind Northern Hemisphere: Because of friction, current deflects more to the right with increasing depth.
What direction is the net water movement in the Northern Hemisphere? (angle, and direction) In the Southern Hemisphere? See Figure 5.5.
90 degrees to the right
90 degrees to the left
What is the controlling force behind surface currents?
Wind
Equatorial Currents
North Equatorial Current–Flows West (traced in red)–Located North of Equator–Normally Strong current•
South Equatorial Current–Flows West (traced in red)–Located South of Equator–Normally Strong
Equatorial Counter Currents
Located between North and South Equatorial Currents–Flows East (traced in red)–Normally weak–Strengthens during El Nino event
West Boundary Currents
Located on West side of Oceans•Carry warm water from the equator to the Poles (traced in red)•Flows North in the Northern Hemisphere and South in the Southern Hemisphere•Strong Currents
Eastern Boundary Currents
Located on East side of Oceans•Carry cold water from the poles to Equator (traced in red)•Flows South in Northern Hemisphere and North in Southern Hemisphere
What is up-welling?
•Cold, Nutrient-rich water rises to surface•Occurs when current moves away from coastline or when currents diverge•High bioproductivity-lots of life
What is downwelling?
•Warm, Nutrient-poor water sinks to depths•Occurs when current moves toward coastline or when currents converge•Low Bioproductivity-little life
Which (upwelling or downwelling) reduces biological productivity?
Downwelling
What is Pycnocline
Pycnocline-density increases rapidly with depth
What is thermocline
temperature decreases rapidly
Halocline
Salinity increases rapidly
What is thermohaline circulation?
•Deep water currents•Below the pycnocline•Result of density differences in the water•Much slower than surface currents
What is the driving force in thermohaline circulation?
Density differences in the water
What is the relationship between the pycnocline and the thermocline?
Both the pycnocline and thermocline have the same depth of 500 to 1000 m deep
What is the relationship between the pycnocline and the halocline?
Both the pycnocline and halocline have the same depth of 500 to 1000 m deep.
Why is there not a pycnocline near the poles? Hint: Think about temperature.
The water at the poles is nearly the same temperature regardless of depth. Therefore the density does not change with depth.
Describe the vertical structure of the ocean in middle latitudes based on the variation in temperature with increasing depth.
At middle latitudes-there is a mixed layer at the surface where temperature varies seasonally. This is where the surface currents are located. Then there is a pycnocline that develops because of a thermocline (temperature decreases with depth to 4°C). Below the pycnocline is a mixed layer where density and temperature are relatively constant. This deep layer is where the thermohaline currents are located.
Why is the thermocline different in summer versus winter?
In summer, the higher sun angles allow sunlight to penetrate deeper into seawater. This warms the water to a greater depth, thus a seasonal thermocline develops above the deep thermocline.In winter, the lower sun angles and higher albedo allow for less sunlight to penetrate seawater, thus the surface is colder. There is only a mixed layer and a deep thermocline (no seasonal thermocline)
Water sinks at high latitudes
cold water results in high density
So-what keeps the Equator from becoming hotter and hotter year after year and the poles colder and colder?
Global winds, Ocean Currents, and storm systems all contribute to mixing and spread the heat around
