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05.02 Ocean Currents

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lauren briley

on 7 January 2014

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Transcript of 05.02 Ocean Currents

05.02 Ocean Currents
What is upwelling and why is it important to the marine ecosystem?
Upwellings play an important role in the global energy balance of the ocean and of the Earth. In tropical regions, they allow an accumulation of heat that is later transferred to higher latitudes by major currents. They also strongly mediate interactions between the ocean and the atmosphere by inducing meteo-oceanic oscillations that affect climate across the entire tropical belt, such as the phenomenon known for centuries as (Neso).

Wherever they occur, upwellings boost biological productivity as well. The high nutrient concentrations generally found in deeper waters are adverted upward into the photic layer where photosynthesis is promoted. This increase in primary productivity benefits the entire food chain.
Describe four factors that influence ocean currents.

1. Wind
Wind is the single biggest factor in the creation of surface currents. Strong winds moving across an expanse of water move the surface of the water. These strong winds are not random breezes; the major winds that most often effect the creation of ocean currents are the Westerlies, which blow west to east, and the Trade Winds, which blow east to west.

2. Water Density
Another major factor in the creation of currents is water density, caused by the amount of salt in a body of water, and its temperature. Water with a higher salinity, or colder water, is more dense and likely to sink. Sinking water pushes the water below it up. The combination of sinking and rising in the same area causes a current.


Explain how the Coriolis Effect impacts ocean currents.
Let's say you're a water parcel traveling poleward.
Although your motion relative to the sea floor is ONLY poleward,
you have a certain eastward speed inherited from the earth's rotation.
As you move poleward, you keep this eastward speed,
because you are not rigidly attached to the sea floor.
But you are moving into a region where the eastward speed of the
sea floor itself is SMALLER, because the latitude circles are smaller.
So your eastward speed is now greater than that of the sea floor,
and you start drifting towards the east, relative to the sea floor.
So you started by moving poleward, but you are now moving
both poleward and eastward.
If you were in the N hemisphere going north, you are now going NE.
If you were in the S hemisphere going south, you are now going SE.

Similarly, if you start off by moving equatorward,
your eastward speed soon becomes too SMALL
for your new latitude,
so you start drifting west.
If you were in N hemisphere going south, you are now going SW
If you were in S hemisphere going north, you are now going NW

The arguments about how eastward motion turns into NE or SE motion
or how westward motion turns into NW or SW motion
are a bit harder to grasp,
but the two arguments above give you a basic understanding
of why ocean current motion in the N hemisphere is clockwise
and in the S hemisphere is counterclockwise.
What is the relationship between ocean currents and climate?
Oceans and air currents transfer heat to one another. Ocean currents depend on the temperatures of the air, gravity, tides, the salt-content (density) of the water itself, and as always, carbon dioxide levels (in both the water and air). One interruption to the ocean currents could have an enormous impact on the climate. Such things triggered many ice ages in the past.

An example: the way Atlantic currents travel north from tropical latitudes warms European countries at the same latitudes as very, very cold places in North America.

3. Ocean Bottom Topography
Water contours to the topography of the ocean floor or bed. If the ocean bottom "drops out," like in a valley or trench, the moving water will move downward. If there is a rise in the ocean bottom, like a ridge or mountain, the water moving along it will be forced upward. The sudden upward or downward change of direction causes water displacement, creating a current.

4. Coriolis Effect
When a rotating object collides with another moving or stationery force, it creates a new motion. The Earth's rotation creates two currents: one, a clockwise movement of water in the Northern Hemisphere; the other, a counter-clockwise movement of water in the Southern hemisphere. When these currents are deflected by land masses, they create huge ocean currents called gyres.

Explain the relationship density has on wind currents and ocean currents.
Pretty simple. A denser material will always "fall" through a less-dense material, or alternatively look at it as the less dense material being more buoyant and thus rising through the denser material. Actually... look at it as both! High pressure areas are normally caused by a phenomenon called subsidence, meaning that as the air in the high cools it becomes denser and moves toward the ground. Pressure increases here because more air fills the space left from the low. Subsidence also evaporates most of the atmosphere's water vapor so high pressure systems are usually associated with clear skies and calm weather. Since everything in nature flows form high to low, you'll have winds blowing out of a high pressure area and toward a low pressure zone. The high pressure zone will generally be colder, but drier.

Alternatively... low pressure zones are where air rises. As the rising air cools, clouds will begin to form. The instability of the air will produce quite large vertical development of cumuliform clouds with associated rain showers (such as cumulonimbus cloud). Now, hook this together and you get circulating currents with hot/less dense air rising in one place, cool/more dense air falling in another place, and thus creating surface winds from high to low, and upper atmosphere the other direction as it cools. In the ocean, density-driven currents act the same way. The Global Ocean Conveyor Belt is created when very cold, dense ocean water in the North Atlantic descends through the water column. It starts the cycle of pushing the whole thing around the globe. In the warm waters of the equatorial Pacific, waters rise to the surface. Just a version of high pressure to low pressure; the water behaves in essentially the same manner as the atmosphere (not surprising, because technically they're both fluids).
Which factor in creating currents has the greatest influence on weather patterns?

Heat capacity is the factor that has the greatest influence on weather patterns and the oceans influence the world's climate by storing vast amounts of solar energy and distributing that energy around the planet through currents and accompanying atmospheric winds.
Part 1 :
Part 2 :
On the Pacific Ocean.
The major current is the California Current
which flows southward from British Columbia.
Its temperature is usually around 60F,
keeping the central coast of California
cool year-round.
1. Location: Name and location of geographic area. Include continent, country, and which coast the area is located on.
Morro Bay, California.
North America, United States, Pacific coast.
2. Climate: Daytime high and nighttime low average temperatures in January.
Daytime high and nighttime low average temperatures in July.
Describe the climate of this region.
Jan temperatures 62 F and 42 F
July temperatures 65 F and 52 F
Climate type = Mediterranean ...
dry summers, almost all rain occurs in winter.
3. Ocean Currents:
What ocean is the area on?
What are the major currents that pass by this coastline?
What is the temperature(s) of the passing currents?
How do these currents influence the local climate?
Choose a coastal location on the Earth. Answer the following information regarding your chosen area.
By: Lauren Briley
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