Earth Systems Test Review
Why is it warmer in most of Europe than in northern California even though both are on the east side of an ocean and Europe is at higher latitude than California?
California is affected by a cold offshore current, whereas Europe has the warm north Atlantic current, the continuation of the Gulf Stream.
Palm trees associated with the subtropics can be found at the northern tip of the British Isles in Scotland. This is due to the transfer of heat from the
North Atlantic Current
When prevailing winds blow from onshore to offshore, what generally happens?
The winds cause offshore surface water to flow away from shore, forcing deeper water to rise to the surface.
El Niño is a well known-weather phenomenon. In Ecuador and Peru, fisherman knew about the phenomenon long before it was well known because their fishing would be very poor during El Niño conditions. Normally Peru and Ecuador have a remarkable fishery because there is a prominent upwelling along the coast which produces plantonic blooms that feed the entire ecosystem. This upwelling is driven by surface wind conditions. From your knowledge of currents and wind conditions, which of the following happens during El Niño conditions in this area?
The winds change from east to west (offshore flow) to onshore flow or weak winds during El Niño conditions.
When Europeans first came to the new world they would typically sail south and west to Canary Islands, then west to get to the West Indies. On their return they would go north past the Leeward Islands and Canadian Maritime provinces before turning east towards Europe? Why did they choose this circular route?
This route followed both the prevailing winds and ocean currents, speeding the trip despite longer distances.
The Bermuda high is a large, persistent high pressure system centered roughly on the island of Bermuda in the mid-Atlantic, hence the name. Air circulates clockwise around high pressure systems because of the Coriolis effect. Is there any connection between Atlantic Ocean currents and this weather feature?
Yes, North Atlantic circulation is approximately the same as the long term average circulation of the Bermuda high.
Equatorial currents that are part of the subtropical gyres flow ___. Equatorial counter currents between the gyres flow ___ .
east to west; west to east
As the tide falls, water flows out to sea as the ________ tide.
ebb
Cool ocean currents ___.
generally flow from high latitudes towards the equator
Large circular-moving currents of water within an ocean basin are called ________.
gyres
Which of the following statements is true for ocean gyres?
gyres are circular-moving currents
Upwelling zones are frequently ________.
high in nutrients
Deep ocean currents ______.
result from changes in water density (due to temperature and salt content)
Because of the Coriolis effect, surface ocean currents are deflected to the ________ of their path of motion in the Northern Hemisphere.
right
Which way would an airplane deflect if flying from the East Coast of the United States to the West Coast of the United States?
to the north
Which way would an airplane deflect if flying from the west coast of South Africa to the east coast of South Africa?
to the north
How would an object in Earth's atmosphere be deflected as a result of Earth's rotation?
to the right in the Northern Hemisphere, and to the left in the Southern Hemisphere
Which way would an airplane deflect if flying from the West Coast of the United States to the East Coast of the United States?
to the south
Which way would an airplane deflect if flying from the east coast of South Africa to the west coast of South Africa?
to the south
Which way would an airplane deflect if flying from the North Pole toward the equator?
to the west
Which ocean current is the only one to completely circle Earth?
The West Wind Drift
Density-driven ocean circulation is also called ________ circulation.
Thermohaline
The energy that creates surface ocean currents comes from ________.
prevailing winds
The energy that drives surface ocean currents such as the Gulf Stream comes from ________.
prevailing winds
Recall that global winds impact the direction of surface ocean currents. Examine the following map showing the Atlantic Ocean off the west coast of Africa. The direction of the surface current and the prevailing wind do not coincide. What can explain this discrepancy?
The Coriolis effect deflects ocean currents in the Southern Hemisphere to the left due to Earth's rotation. Because the current is located in the Southern Hemisphere, the subtropical gyre pulls the current in a counterclockwise direction.
What is the location and flow of the Gulf Stream?
The Gulf Stream flows northward along the east coast of North America
In the Cretaceous period of earth history there is clear evidence that the climate was much warmer than today. It was so warm that areas near the pole had tropical vegetation like palm trees, and there was almost certainly no sea ice and glaciers probably only existed at very high altitude. This produced widespread anoxia (stagnant, no-oxygen condition) on the floor of the oceans. From your knowledge of ocean circulation, which of the following explanations could account for the anoxia?
The lack of polar sea ice stopped any thermohaline deep circulation in the oceans, stratifying the water column to produce anoxia in the deep sea.
Coastal California is famous for fog and smog (fog mixed with smoke). Why is the California coast foggy/smoggy, whereas Houston, Texas, which is at a similar latitude, might get occasional smog from too many cars, but fog is relatively rare?
The ocean is warm off the Texas coast, but a cold current running offshore California generates fog when the cold, moist air is drawn ashore by a sea breeze.
_______________ ___________ is caused by density changes near the poles and equator.
Thermohaline circulation
Surface ocean currents ___.
are driven by winds are influenced by Coriolis effect form large rotating gyres in the major ocean basin
Warm ocean currents ___.
are warmer than the surrounding water
As a fluid (air or water) moves toward an area of lower pressure in the Northern Hemisphere, the Coriolis effect results in ________ circulation.
clockwise
Waters along the California coast are colder than those along the mid-Atlantic shore of the U.S. because ____________ ________________ occurs as surface waters move away from the coast.
coastal upwelling
Thermohaline circulation is ________.
deep circulation of water driven by a combination of cold temperature and high density related to high salinity from formation of sea ice, producing descending high density waters that flow southward to equatorial regions
Why is deep-ocean circulation referred to as thermohaline circulation?
deep-ocean circulation is caused by differences in both temperature and salinity
Why is deep-ocean circulation referred to as thermohaline?
differences in temperature or salinity cause oceanic deep circulation.
Prevailing winds toward a shoreline typically produce __________.
downwelling
Freezing seawater at ________ ____________ leads to increases in salinity and density.
high latitudes
When sea ice forms in high latitudes, the sea ice has ________.
lower salinity than the ocean waters it forms from
A warm current is one that is ________.
moving towards one of the poles
The subtropical gyres ___.
play a large role in climate
What is the Coriolis effect?
the deflection of objects to the right in the Northern Hemisphere, and to the left in the Southern Hemisphere
The Coriolis effect causes ocean currents in the Southern Hemisphere to be deflected ________ of their path of motion.
to the left
Which way would an airplane deflect if flying from the South Pole toward the equator?
to the left
Which way would an airplane deflect if flying from the North Pole toward the equator?
to the right
A poleward-moving ocean current is ________.
warm
The east and west coasts of the North America are dominated by ________ and ________ currents, respectively.
warm; cold
What is the primary driving force of surface-ocean currents?
wind
