CH 7 - Ocean Circulation

In relation to ocean circulation, a gyre is __________. A) a large, circular-moving loop of surface water B) a type of Greek sandwich C) a drift current meter D) found only in the "Roaring Forties" of the Southern Hemisphere E) a method of modeling El Niño

A) a large, circular-moving loop of surface water Correct. Ocean current gyres are circular, nearly closed surface current systems that are found throughout the oceans. See Figure 7.5.

Western intensification is ________. A) caused by the rotational center of a gyre being located to the west of the ocean basin's geographic center, thus causing more water to flow within a narrower "channel" B) found only in the northern Pacific Ocean C) another term for Ekman transport D) another name for the process of thermohaline flow E) demonstrated by El Niño

A) caused by the rotational center of a gyre being located to the west of the ocean basin's geographic center, thus causing more water to flow within a narrower "channel" Correct. Western intensification describes the narrow, strong flow of western boundary currents in all subtropical gyres. This is caused by Earth's rotation, which pushes the "hill," or apex, of a gyre to the west of the basin's center and produces a steeper elevational gradient on the west than on the east.

The Peru Current is a _______ current that flows _______. A) cold; north B) warm; east C) cold; south D) warm; north E) cold; east F) warm; south

A) cold; north Correct. The Peru Current is a cold-water current that flows along the west coast of South America from south to north.

Ekman transport is an average path of motion that, under ideal conditions, is at ________ to the wind's direction. A) 13.5 degrees B) 90 degrees C) 135 degrees D) 180 degrees E) 195 degrees

B) 90 degrees Correct. Ekman transport is the net movement of surface water, resolved into a direction perpendicular (90 degrees) to the wind.

The atmospheric circulation cell located in the equatorial South Pacific and created by the movement of air between high- and low-pressure regions is called the __________. A) gyros cell B) Walker cell C) Ferrel cell D) Hadley cell E) thermohaline cell

B) Walker cell Correct. This effect was first described in the 1920s by British meteorologist G. T. Walker and was named after him.

Thermohaline flow is a term that describes ________. A) hurricane-force winds B) deep-ocean current movement C) the Ekman spiral D) water sublimating E) El Niño-Southern Oscillation (ENSO) events

B) deep-ocean current movement Correct. The two factors that influence seawater density are temperature (thermo) and salinity (haline). Thus,thermohalineflow describes changes in seawater density, which creates deep-ocean current movement.

A geostrophic current is one that (ideally) flows _______. A) parallel to the coastline B) in a circular path around the central "hill" of a gyre C) downhill away from the center of a gyre D) always toward the North Pole, even in the Southern Hemisphere E) straight down vertically, deep into the ocean, until it touches the sea floor; at that point, it spreads out

B) in a circular path around the central "hill" of a gyre Correct. Geostrophic currents move in a circular path around the central "hill" of a gyre.

Surface ocean currents are caused by ___________, whereas deep currents are the result of __________. A) the Coriolis effect; the Ekman spiral B) surface wind belts; density differences C) the Ekman spiral; the Coriolis effect D) the pycnocline; the thermocline E) the Ekman spiral; the pycnocline

B) surface wind belts; density differences Correct. The surface wind belts of the world initiate surface currents, whereas density differences are the cause of deep-ocean currents.

The ocean's deep water is initially formed at the _________ and in _________ regions. A) ocean floor; subpolar B) surface; subpolar C) ocean floor; subtropical E) surface; subtropical

B) surface; subpolar Correct. Deep water forms at the surface in subpolar regions (North Atlantic or near Antarctica), where the water gets cold, increases in density, and sinks below the surface.

What is one of the first indications that an El Niño event may be occurring? A) The intensity of the prevailing westerlies increases as they flow over South America. B) Thermohaline flow becomes unusually strong. C) Warm water originating near Australia migrates toward South America. D) Upwelling increases along the coast of Peru. E) Ekman flow phenomena occur, causing the movement of surface currents.

C) Warm water originating near Australia migrates toward South America. Correct. During an El Niño event, water from the Pacific Warm Pool migrates across the equatorial South Pacific Ocean, from near Australia toward South America.

In subtropical gyres, western boundary currents have all of the following characteristics except being __________. A) relatively fast B) relatively deep C) relatively wide D) relatively warm

C) relatively wide Correct. This is the false statement; western boundary currents are relatively narrow.

Which of the following currents does not belong with the others as part of the same gyre? A) the South Equatorial Current B) the Benguela Current C) the Agulhas Current D) the West Wind Drift E) the Brazil Current

C) the Agulhas Current Correct. The Agulhas Current is actually part of the Indian Ocean Subtropical Gyre.

Which of the following statements about El Niño events is false? A) Upwelling slows or halts offshore of South America. B) A low-pressure zone migrates eastward toward Peru. C) The trade winds stop or even reverse. D) Fishing along Peru and Ecuador is much better. E) There is a deeper wedge of warm water off South America.

D) Fishing along Peru and Ecuador is much better. Correct. During an El Niño event, upwelling is diminished along the coast of Peru and Ecuador, so the entire marine food web is negatively impacted; fishing is much worse.

The Gulf Stream is a ________ current that flows ________. A) warm; west B) cold; north C) cold; west D) warm; north E) warm; south F) cold; south

D) warm; north Correct. The Gulf Stream is a warm-water current that flows along the east coast of North America from south to north.

The California Current is a ________ current that flows ________. A) cold; east B) cold; north C) warm; west D) warm; south E) cold; south F) warm; north

E) cold; south Correct. The California Current is a cold-water current that flows along the west coast of North America from north to south.

Which of the following is an example of a western boundary current of a subtropical gyre? A) the Canary Current B) the West Australian Current C) the Labrador Current D) the California Current E) the Kuroshio Current

E) the Kuroshio Current Correct. The Kuroshio Current is the western boundary current of the North Pacific Subtropical Gyre.

The East Australian Current is a ________ current that flows ________. A) cold; east B) cold; south C) warm; north D) cold; north E) warm; east F) warm; south

F) warm; south Correct. The East Australian Current is a warm-water current that flows along the east coast of Australia from north to south.

Subtropical gyres flow counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. True False

False Correct. See Figures 7.4 and 7.5.

Vertical mixing of surface and deep seawater takes place in the low latitudes. True False

False Correct. The sharp boundaries of the thermocline and pycnocline separating warm surface water and deeper cold water in low latitudes prevent vertical mixing.

The East Australian Current is the western boundary current of the South Pacific subtropical gyre. True False

True Correct. As odd as it sounds, the East Australian Current is the western boundary current of the South Pacific Subtropical Gyre.