Patterns of Circulation

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  • Created by: Megan
  • Created on: 23-04-14 10:38

Atmospheric Pressure

...exerted by the weight of air in the atmosphere at the surface of the Earth

The layers of the atmosphere closest to the ground have the greatest weight acting on them, so pressure is greatest here - this decreases with Altitude

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Surface Winds

Pressure differences occur spatially because of global temperature variation - Temperature increases so air rises adn expands, reducing pressure. Temperature decrease means air is denser so sinks, increasing pressure.

Wind is the horizontal movement of air on the Earth's surface and result frrom differences in air pressure, blowing down the pressure gradient.

Wind also affects temperature - temperature of winds is influenced by it sarea of origin and the surface it travels over

Winds blowing on land from the sea are relatively warm in winter and raise air temperatures. In summer, they depress air temperatures as the sea over which they travel, is cooler than the land surface.

THe pattern of winds changes seasonally, land and sea influence wind direction on a local level

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Ocean Conveyor Belt

...the transfer of cold water at depth frrom polar regions to the equator...

Water cool at the poles and ice formation leaves the remaining water saltier and denser. THis water sinks througgh the water column, and sweeps the Antarctic continent at 4km and then flows into the major ocean basins. These motions are reciprocated by the movement of the less salty, less dense surface currents which move north towards the North Atlantic for example.

These warmer waters have a signifcant effect on the temperature as they give up about a 1/3 of the energy they had previously stored from the sun.

The North Atlantic is warmer than the North Pacific, which gives rise to higher evaporation rates and salinity. THe sinking of the saltier, denser water in the North Atlantic drives the conveyor belt and, over time, the cold currents feed into the Pacific where is mixes with the warmer, less dense water fouund there, reducing water density overall.

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Ocean Currents

...large scale movements of water caused by differences in water density - dependent on temperature and salinity.

They are affected by surface winds, land mass position and other currents. Currents transfer heat energy from warm to cold regions. Warm currents warm air and cold currents cools air temperatures.

Warm currents migrate polewards and cold currents replace them moving towards the equator. THe trade winds push water west along the equator. This means that these circular motion's rotate colckwise in the Northern hemisphere and anticlockwise in the Southern. They are called Gyres.

THe directions of water movement is deflected by the Coriolis effect. THe world's major ocean currents are particularly dominant along the western sides of the ocean basins and those that are less well defined and relatievly weak are on the east.

The piling up of the west is counteracted by currents like the Gulf Stream.

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