Ocean Circulation Overview
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Questions and Answers

What is the effect of Ekman transport in the Northern Hemisphere?

  • It moves water to the left
  • It deflects water to the right (correct)
  • It causes water to pile up at the edges
  • It creates a counterclockwise motion

What forms at the center of a subtropical gyre due to water piling up?

  • Water bowl
  • Water hill (correct)
  • Water dome
  • Water mound

How does the Coriolis effect influence geostrophic currents?

  • It causes them to flow downhill
  • It has no effect on the currents
  • It creates vertical movement in the water
  • It opposes gravity and curves the flow rightward (correct)

Which current is significantly faster than the California current?

<p>Kuroshio current (D)</p> Signup and view all the answers

What is western intensification?

<p>The acceleration of western boundary currents (D)</p> Signup and view all the answers

What effect does the Coriolis effect have on water flowing towards the equator?

<p>It strengthens and curves the water flow (C)</p> Signup and view all the answers

What happens to the velocity of water around the apex of the hill in a gyre?

<p>It is greater along the western margin than the eastern side (D)</p> Signup and view all the answers

What is the term used to describe the slower flow of water across the subtropical gyre?

<p>Bottleneck effect (C)</p> Signup and view all the answers

What causes equatorial upwelling?

<p>Divergence of surface waters (A)</p> Signup and view all the answers

What effect does downwelling have on deep sea conditions?

<p>It introduces oxygen-rich water to deeper depths (B)</p> Signup and view all the answers

Why is the equator considered a prolific fishing ground?

<p>Because of equatorial upwelling creating high productivity (D)</p> Signup and view all the answers

Which of the following describes the path of water during downwelling?

<p>Water sinks downward due to piling from convergence (A)</p> Signup and view all the answers

What role do coastal winds play in upwelling and downwelling?

<p>They facilitate Ekman transport (A)</p> Signup and view all the answers

What occurs when surface waters converge?

<p>The water must sink due to piling (A)</p> Signup and view all the answers

What is a characteristic of downwelling regions?

<p>Generally poor in productivity (D)</p> Signup and view all the answers

How does Ekman transport influence surface water movement in the Northern Hemisphere?

<p>It influences surface water to veer to the right (B)</p> Signup and view all the answers

What is the effect of Ekman transport when it brings water away from the shoreline?

<p>It results in upwelling. (C)</p> Signup and view all the answers

Which of the following factors can cause other water pathways besides Ekman transport?

<p>Offshore winds. (D)</p> Signup and view all the answers

What occurs during the warm phase of the El Nino Southern Oscillation (ENSO)?

<p>Air pressure decreases in the east. (B)</p> Signup and view all the answers

What happens to water levels in the western Pacific during the ENSO warm phase?

<p>Water levels increase due to thermal expansion. (B)</p> Signup and view all the answers

What is the main cause of extreme weather conditions during ENSO events?

<p>Weakening of Pacific winds. (A)</p> Signup and view all the answers

During the cool phase of ENSO, what is true about the air pressure in the western Pacific?

<p>It is lower than normal. (D)</p> Signup and view all the answers

What is a characteristic effect of the ENSO cool phase on trade winds?

<p>Trade winds are strengthened. (D)</p> Signup and view all the answers

How frequently do El Nino and La Nina events occur?

<p>Every 2 to 10 years. (A)</p> Signup and view all the answers

What effect does upwelling have on water sources according to the provided information?

<p>It occurs as a response to water loss. (A)</p> Signup and view all the answers

What happens in terms of water dynamics when coastal winds blow offshore?

<p>Upwelling occurs due to water being drawn away. (B)</p> Signup and view all the answers

Flashcards

Water Hills

A mound of water formed in the center of a subtropical gyre due to the convergence of water caused by Ekman transport.

Geostrophic Current

A current that flows parallel to the contours of a water hill, resulting from a balance between gravity pulling the water downhill and the Coriolis effect deflecting it rightward.

Western Intensification

A phenomenon where western boundary currents in subtropical gyres are faster, narrower, and deeper compared to their eastern counterparts.

Why are Western Boundary Currents Faster?

The apex of the water hill is closer to the western boundary current, forcing a greater volume of water through a smaller space.

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What drives Western Intensification (1)?

The Coriolis effect is stronger at higher latitudes, causing eastward flowing water from high latitudes to turn more strongly toward the equator.

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What drives Western Intensification (2)?

The Coriolis effect has a weaker influence on westward flowing water toward high latitudes, leading to a wider and slower flow across most of the subtropical gyre.

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Bottleneck Effect

The narrower space for poleward flow along the western margin of the ocean basin due to the wider eastward flow across the subtropical gyre.

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Kuroshio vs. California Current

The Kuroshio Current, a western boundary current, is 15 times faster, 20 times narrower, and 5 times deeper than the California Current, an eastern boundary current due to Western Intensification.

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Upwelling and Downwelling

The vertical movement of water in the ocean, either upward (upwelling) or downward (downwelling). This occurs due to water divergence or convergence, often influenced by coastal winds and the Ekman spiral.

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Divergence in Upwelling

When surface waters move away from each other, creating a gap that is filled by cold, nutrient-rich water rising from below.

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Equatorial Upwelling

A specific type of upwelling that occurs at the equator due to the divergence of surface water caused by the Ekman transport.

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Ekman Transport

The net movement of water 90 degrees to the right of the wind direction in the Northern Hemisphere and 90 degrees to the left in the Southern Hemisphere.

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Convergence in Downwelling

When surface waters move towards each other, piling up and causing water to sink downward to equalize the excess mass.

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Coastal Wind Upwelling/Downwelling

Winds blowing parallel to the coast can cause upwelling or downwelling due to the Ekman transport effect.

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Downwelling's Impact on Productivity

Downwelling areas are generally low in productivity because they bring oxygen-rich but nutrient-poor water to deeper depths.

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Gulf Stream and Labrador Current Convergence

The meeting point of the warm Gulf Stream and cold Labrador Current creates a convergence zone for downwelling, delivering oxygen-rich water to the deep sea.

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Upwelling

The process where cold, nutrient-rich water from the depths rises to the surface, often caused by Ekman Transport pushing surface water away from the shoreline.

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Downwelling

The process where warm surface water is pushed down to the ocean depths, often caused by Ekman Transport pushing surface water towards the shoreline.

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El Niño Southern Oscillation (ENSO)

A naturally occurring climate pattern that involves shifts in air pressure and ocean temperature in the Pacific Ocean, leading to extreme weather conditions like droughts and heavy rainfall.

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ENSO Warm Phase (El Niño)

A phase of ENSO characterized by warmer than average waters in the central and eastern Pacific Ocean, caused by weaker trade winds and a weakened pressure gradient.

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ENSO Cool Phase (La Niña)

A phase of ENSO characterized by cooler than average waters in the central and eastern Pacific Ocean, caused by stronger trade winds and a stronger pressure gradient.

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Trade Winds

Winds that blow from east to west near the equator, driven by the difference in pressure between the tropics and higher latitudes.

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Thermocline

The boundary between the warm surface water and the colder deep water. It plays a key role in upwelling and downwelling.

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Equatorial Countercurrent

A westward flowing current that runs along the equator, counteracting the eastward flow of the trade winds.

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Pacific Warm Pool

An area of warm surface waters in the western Pacific Ocean, a key part of the ENSO system.

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Study Notes

Ocean Circulation

  • Ekman transport moves water to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This is due to the Coriolis effect.
  • Ekman transport contributes to the clockwise rotation of northern subtropical gyres.
  • Subtropical convergence creates water hills in the center of gyres. These "water hills" can be up to 2 meters higher than the surrounding water.
  • Geostrophic currents are a result of the balance between gravity and the Coriolis effect. Gravity pulls water downhill, while the Coriolis effect curves the flow.
  • The net effect of these forces results in a circular current around the water hill.
  • Geostrophic currents move in a circular path around the water hill.
  • The apex of the water hill is closest to the western boundary current.
  • Western boundary currents are faster, narrower, and deeper than eastern boundary currents. An example is the Kuroshio current.
  • Western intensification is the phenomenon where currents near the western edges of ocean basins are stronger than those near the eastern edges. This is due to the Coriolis effect in combination with the shape of the water hills.
  • Western intensification impacts the flow of water toward the equator.
  • Upwelling occurs due to the divergence of surface waters or from coastal winds.
  • Downwelling occurs due to the convergence of surface waters.
  • Upwelling and downwelling are driven by the need to fill gaps in volume. Water lost equals upwelling, water gained equals downwelling.
  • Coastal winds can cause upwelling/downwelling due to Ekman transport. This depends on whether winds are blowing parallel to the coast in a way that pushes water away from the coast.
  • Other factors that may cause upwelling (or downwelling) include offshore winds, seafloor obstructions, coastal geometry bends

El Niño Southern Oscillation (ENSO)

  • ENSO leads to extreme conditions like droughts and extreme rainfall.
  • ENSO is caused by the weakening of Pacific winds and belts. This weakens the trade winds and results in the changing pressure between the west and east of the Pacific.
  • During an El Niño event, pressure decreases in the east and central Pacific, and it increases in the west. The opposite is true for La Niña.
  • ENSO events are caused by changes in winds and pressure patterns.
  • El Niño and La Niña occur every 2 to 10 years.
  • El Niño events are characterized by warming of waters in the equatorial Pacific and weakening trade winds.
  • During El Niño, the Pacific Warm Pool can flow back eastward, enhancing upwelling and mixing reducing the thermocline.
  • La Niña is an event opposite from El Niño.
  • In La Niña, air pressure is higher than normal in the west.

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Ocean Circulation: Module 7 Part 2 PDF

Description

This quiz explores key concepts of ocean circulation, including Ekman transport, geostrophic currents, and the dynamics of subtropical gyres. Understand how the Coriolis effect influences water movement and the differences between western and eastern boundary currents. Test your knowledge on how these processes shape our oceanic systems.

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