14b review questions
1. what two main factors control the speed and direction of the major ocean surface currents?
2. what do oceanographers call the great circling ocean currents?
3. why does the ekman spiral happen? which way does it twist in the north atlantic?
4. how do ocean currents affect global weather patterns?
5. what is upwelling, and why is it important?
6. why are downwelling currents important to marine life in the abyssal zone of ocean basins?
7. describe the differences between a surface current and a subsurface current.
8. what do oceanographers call global deep - water circulation?
9. name three conditions that allow gravity to produce subsurface currents.
10. what kind of density current is caused by a muddy, rapidly flowing mixture of sediment and water? what events on land are similar to this?
11. (true or false) water enters the mediterranean sea as a surface current and leaves that basin as a bottom density current.

Question

Accepted Answer

### Question 1
# Brief Explanations:
The two main factors controlling ocean surface current speed and direction are wind (which provides the driving force) and the Coriolis effect (due to Earth's rotation, it deflects currents—right in the Northern Hemisphere, left in the Southern Hemisphere).
# Answer:
The two main factors are wind (the primary driving force) and the Coriolis effect (due to Earth’s rotation, which deflects the direction of the currents).

### Question 2
# Brief Explanations:
Oceanographers refer to the large, circular ocean currents (typically gyres, like the North Atlantic Gyre) as "gyres." These gyres form due to wind patterns and the Coriolis effect, circulating water in large loops in each ocean basin.
# Answer:
Oceanographers call the great circling ocean currents "gyres" (e.g., subtropical gyres, subpolar gyres).

### Question 3
# Brief Explanations:
The Ekman spiral occurs because wind transfers energy to surface water, and each successive layer of water (below the surface) moves slower and is deflected slightly by the Coriolis effect (and friction with the layer above). In the North Atlantic (Northern Hemisphere), the Coriolis effect deflects right, so the Ekman spiral twists clockwise (each deeper layer is deflected right from the layer above, creating a spiral pattern with depth).
# Answer:
The Ekman spiral happens because wind - driven surface water moves, and each deeper water layer is deflected by the Coriolis effect (and experiences friction with the layer above), causing a spiral of decreasing speed and deflected direction with depth. In the North Atlantic (Northern Hemisphere), it twists clockwise.

### Question 4
# Brief Explanations:
Ocean currents affect global weather by transporting heat: warm currents (e.g., Gulf Stream) carry heat from the equator toward higher latitudes, warming regions (like Western Europe), while cold currents (e.g., California Current) cool coastal areas. They also influence precipitation (e.g., warm currents increase moisture, leading to more rain; cold currents can create arid conditions) and storm patterns (by modifying temperature and moisture gradients in the atmosphere).
# Answer:
Ocean currents affect global weather patterns by transporting heat (warm currents warm regions, cold currents cool them), influencing precipitation (warm currents increase moisture for rain, cold currents can cause aridity), and modifying storm tracks and intensity (by altering atmospheric temperature/moisture gradients).

### Question 5
# Brief Explanations:
Upwelling is the process where deep, cold, nutrient - rich water rises to the ocean surface (typically caused by wind - driven divergence of surface water, or coastal winds pushing surface water away from the shore). It is important because the nutrient - rich deep water fuels phytoplankton growth, which is the base of the marine food web, supporting large fish populations and productive ecosystems.
# Answer:
Upwelling is the rise of deep, cold, nutrient - rich ocean water to the surface (often driven by wind - related water movement, like coastal winds pushing surface water away from shore). It is important because the nutrients in the upwelled water stimulate phytoplankton growth, which supports the entire marine food web (e.g., fish, seabirds, marine mammals) and enhances fisheries productivity.

### Question 6
# Brief Explanations:
Downwelling currents are important to abyssal zone marine life because they transport oxygen - rich surface water (and nutrients, though less directly for the abyssal zone) down to the deep ocean. The abyssal zone is dark and has low oxygen replenishment otherwise, so downwelling brings oxygen that supports deep - sea organisms (like benthic species, deep - water fish) and also helps in the global carbon cycle by transporting carbon - rich surface water (with organic matter) to the deep for storage.
# Answer:
Downwelling currents are important to abyssal zone marine life because they carry oxygen - rich surface water (and carbon - rich water with organic matter) down to the deep, oxygen - poor abyssal zone. This oxygen supports deep - sea organisms (e.g., benthic creatures, deep - water fish), and the carbon transport helps in the global carbon cycle (storing carbon in the deep ocean).

### Question 7
# Brief Explanations:
- **Surface Current**: Forms in the upper ~400m of the ocean, driven mainly by wind (and influenced by the Coriolis effect/gyre systems). It has a relatively high speed, and its direction is strongly affected by wind and Earth’s rotation.
- **Subsurface Current**: Occurs below the surface (deeper than ~400m, down to the deep ocean), driven by density differences (due to temperature/salinity variations, creating density currents) or other non - wind - related forces (e.g., gravity - driven from water mass differences). It is slower than surface currents, and its direction is more influenced by density gradients and ocean basin topography.
# Answer:
- **Surface Current**: Exists in the upper ~400 m of the ocean, is wind - driven (with Coriolis/gyre influences), has relatively high speed, and direction is strongly affected by wind and Earth’s rotation.
- **Subsurface Current**: Occurs below ~400 m (into deep ocean), is driven by density differences (temperature/salinity - based) or gravity - related forces, is slower, and direction is influenced by density gradients and ocean basin topography.

### Question 8
# Brief Explanations:
Oceanographers call global deep - water circulation the "thermohaline circulation" (or "global conveyor belt"). This circulation is driven by density differences in seawater, which are caused by variations in temperature ("thermo") and salinity ("haline"). Cold, salty water is dense and sinks, initiating a slow - moving global current that transports heat, nutrients, and carbon over long timescales.
# Answer:
Oceanographers call global deep - water circulation the "thermohaline circulation" (or the "global conveyor belt").

### Question 9
# Brief Explanations:
Three conditions allowing gravity to produce subsurface currents (density currents) are: 1) Differences in water density (e.g., due to temperature—colder water is denser; or salinity—saltier water is denser). 2) A sloped seafloor (so dense water can flow downhill under gravity, like in a submarine canyon or along a continental slope). 3) A source of dense water (e.g., coastal upwelling of cold water, or formation of sea ice which increases salinity of remaining water, making it denser).
# Answer:
Three conditions are: 1) Density differences in water (due to temperature/salinity variations, creating a denser water mass). 2) A sloped seafloor (so dense water can flow downhill under gravity). 3) A source of dense water (e.g., sea ice formation increasing salinity, or cold, nutrient - rich upwelled water).

### Question 10
# Brief Explanations:
A muddy, rapidly flowing mixture of sediment and water forms a "turbidity current" (a type of density current, as the sediment - laden water is denser than clear water). On land, events similar to this are landslides (or debris flows) —where a mixture of soil, rock, and water flows downhill, driven by gravity (like a turbidity current but on land, with sediment and water moving rapidly down slopes).
# Answer:
The density current is a "turbidity current". Similar land events are landslides (or debris flows), where a sediment - water mixture flows downhill rapidly under gravity.

### Question 11
# Brief Explanations:
Water enters the Mediterranean Sea as a surface current (from the Atlantic Ocean, through the Strait of Gibraltar—Atlantic water is less dense than Mediterranean water, so it flows in at the surface). As water in the Mediterranean evaporates, it becomes saltier and denser, so it leaves the basin as a bottom density current (flowing out into the Atlantic at depth, as dense water sinks and flows downhill). Thus, the statement is true.
# Answer:
True.

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