Oceanography Ch. 7

Discuss and compare the forces that are responsible for creating surface and thermohaline circulation in the oceans. Include in your answer the ultimate source of energy that drives both circulation system

??

What is a Doppler flow meter?

A doppler flow meter is a device that transmits low-frequency sound signals throughout the water. It measures the shift in frequency between the sound waves emitted and those backscattered by particles in the water to determine current movement.

What two major forces drive the Ekman spiral?

Frictional effects in the ocean (wind) and the Coriolis effect.

Which type of current flow moves in a circular path around a subtropical convergence, reflecting Ekman transport, gravity, and the Coriolis effect?

Geostrophic current.

Under what conditions does strong upwelling occur?

Strong upwelling can occur by diverging surface water (surface water that moves away from an area on the ocean's surface), converging surface water (surface waters that move towards each other), or coastal upwelling and downwelling (water flows away from shoreline and is replaced by water from below). Strong upwelling provides high productivity and rich marine life.

How Are Ocean Surface Currents Organized?

Surface currents are organized by distribution of continents, gravity, friction, and the Coriolis Effect.

How do Surface or wind-driven currents move water? In what direction?

Surface currents move water horizontally and occur on the ocean's surface.

What is the latitude of the West Wind Drift? What ocean does it occur in and what are the characteristics of this current?

The latitude of the West Wind Drift is 50 degrees south. It occurs in the Antarctic Ocean. It encircles Antarctica and moves more water than any other current. Only current to circumscribe earth.

What is the main current in Antarctic waters? What other name is it known as?

The main current is the Antarctic Circumpolar Current, also called the West Wind Drift.

Deep ocean currents are driven primarily by ___________ and modified by differences in _______________.

density differences; salinity and temperature

The circular movement of surface water currents driven by the major wind belts are called ______

gyres

Thermohaline circulation is driven by differences in __________________

temperature and salinity

Ekman Spiral is caused by ______ & ________ ?

wind; coriolis effect

Surface ocean currents are driven primarily by ______ and modified by the ________.

winds; Coriolis Effect

Does Deep ocean water travel across the equator?

No

What percentage of the earth's currents are Surface currents?

10%

What is a gyre? How does it form?

A gyre is a large, circular-moving loop of water that forms from the major wind belts.

Do Deep ocean currents move cold, dense water away from the poles or towards the poles? Discuss the origin and characteristics of deep-ocean currents

Deep ocean currents move cold, dense water away from the poles. Deep ocean currents are created by density differences that cause denser waters to sink. They move large volumes of water and are much slower.

How does deep ocean water become enriched in oxygen?

Deep ocean water becomes enriched because cold water can dissolve more oxygen than warm water.

What are the characteristics of Deep ocean water masses in terms of temperatures and salinities?

Deep ocean water has a lower temperature and an increased salinity. Most deep ocean current water originates at the surface, where the water cools and its salinity increases. When it becomes dense enough, the water sinks.

Describe the El Niño Southern Oscillation. What global environmental effects characterize an El Niño event? What global environmental effects characterize a La Niña event?

El Nino weakens high pressure in the Eastern Pacific. Trade winds are weaker. Warm pools migrate eastward. Thermocline is deeper in the Eastern Pacific. Downwelling occurs, and there is lower biological productivity. Walker cell circulation is disrupted.

Which pattern of oscillation is created by the relationship between sea surface temperature and changing atmospheric pressure.....El Nino or La Nina?

El Nino.

What conditions are caused by Western intensification?

Equatorial countercurrents, a steeper slope of surface water in the western section of the gyre, fast western boundary currents, and the center of the gyre to be shifted to the west. These currents are also narrower and deeper

What two forces drive Geostrophic circulation within a gyre?

Gravity and the Coriolis Effect.

Deep-water circulation brings dense, cold, oxygen-rich water from the surface to the deep ocean because of:

Greater dissolution of oxygen in colder water than warmer water

Where is the densest ocean water found?

In the Antarctic Bottom Water.

What are seasonal pressure systems that develop at lower latitudes over continents, which cause changes in seasonal winds and precipitation patterns?

Monsoons

Describe the circulation of deep ocean water.

Most deep ocean water originates at the surface. Surface water becomes cold and salinity increases as sea ice forms. When the water becomes dense enough, it sinks. As this water is sinking, deep water masses are also upwelling.

Briefly describe the different ways that ocean currents are measured.

Surface currents can be measured by a floating device tracked through time, a propeller flow meter (determines the currents true flow rate), indirect methods, such as determining the internal distribution of density, radar altimeters (determine lumps and bulges at the ocean surface), or doppler flow meter (transmits low-frequency sound signals). Deep water currents can be measured using the Argo. Argo is a global array of free-drifting profiling devices that move vertically and measure the temperature and salinity of water in the ocean.

Compare and contrast the direction of the northern and southern hemisphere flows of Ekman transport.

The Ekman Transport movement is 90 degrees to the right in the Northern Hemisphere and 90 degrees to the left in the southern hemisphere.

In the southern hemisphere, the direction of Ekman transport is always (to the left or the right of the wind pattern?) Explain why!

The Ekman Transport moves to the left of the wind in the southern hemisphere because of the Coriolis Effect.

Why is the Gulf Stream so important to our planet?

The Gulf Stream is so important to our planet because it provides unique biology and abundant marine life. It is responsible for transferring tropical heat to northern latitudes.

Do Western boundary currents such as the Gulf Stream transport warm or cold water from the tropics towards higher latitudes? Explain your answer.

The Gulf Stream transports warm water up towards high latitudes. It flows north bringing warmer water from the south up to the north.

Which of the surface water patterns of circulations produce two circumpolar currents dominating, and one current that moves water to the east and one current that moves water to the west?

The North and South Atlantic Subtropical Gyres

What is the West Wind Drift and what impact does it have on our oceans?

The West Wind Drift is a current that circumnavigates around Antarctica. It moves more water than any other current. It strongly influences global climate and marine diversity.

Describe the monsoon wind patterns during winter months

There is little precipitation, high pressure, air over Asia rapidly cools. Wind blows from Southeast Asia off the continent and over the ocean.

What force drives Thermohaline circulation?

Thermohaline circulation is caused by density variations that cause deep ocean circulation. The deep ocean circulation is caused by changes in temperature and salinity, affecting the density.

The five subtropical gyres exhibit geostrophic flow, related to pressure gradients, friction, and the Coriolis effect. Explain that statement.

This statement means that in each of the five subtropical gyres, there is geostrophic flow, a current that moves in a circular path around the center of the hill. Geostrophic flow is related to gravity because the water in the subtropical convergence tends to flow downhill in response to gravity. However, the Coriolis Effect opposes gravity and deflects the water to the right in a curved path into the hill again. Friction between water molecules causes the water to move gradually down the slope of the hill as it flows around it.

What force drives Equatorial currents?

Trade winds

Upwelling and Downwelling

Upwelling is caused by wind that blows parallel to the coastline. The wind causes the water to move perpendicular to it, away from the coast. When the water near the coastline moves away, deeper ocean water must replace it. The water moves vertically up towards the surface. Upwelling moves cold, nutrient rich water to the surface and provides abundant biological life. Downwelling is caused by surface water becoming denser and sinks below the surface.

Discuss the biological impact of upwelling and downwelling on marine ecosystems. Provide examples of marine systems that are impacted by these processes in your answer.

Upwelling provides high productivity and rich marine life. It supports incredible numbers of fish and whales. Downwelling provides low productivity and a lack of marine life.

Describe the location of the western boundary and eastern boundary current within a gyre. How is the direction of these currents related to heat distribution of the Earth's oceans?

Western Boundary Currents carry warm water to high latitudes and Eastern Boundary Currents carry cold water to lower latitudes.

Compare an eastern boundary current in a gyre to a western boundary current.

Western Boundary Currents reach the western portion of an ocean basin, where they turn. The coriolis effect deflects these currents away from the equator. They carry warm water to higher latitudes (north). Eastern boundary currents are caused by currents that flow back across the ocean basin. The coriolis effect and continental barriers turn them towards the equator. They carry cold water from high latitudes to lower latitudes.

Compare and contrast the depth, speed, and width of the eastern and western boundary currents.

Western boundary currents are deep, fast, warm, and narrow. Eastern boundary currents are shallow, slow, cold, and wide.

Describe the worldwide effects of El Niño

Worldwide effects include marine life impacted, floods, coastal erosion, drought, coral reef damage, bird life impacted, forest fires, and tropical storms.