The Sun's energy is distributed unevenly across Earth's surface. Areas near our planet's equator absorb far more heat energy than areas near the poles. This uneven distribution of heat creates instability in Earth's atmosphere and oceans, and instability leads to movement of air and water.
Air in the atmosphere is warmed by heat radiating from Earth's surface. The warmer the surface is, the warmer the air above it becomes. Because warm air is less dense than cold air, it tends to expand and rise, which lowers air pressure near the surface. Thus, regions of low air pressure generally form over warm water and land, while high-pressure regions form over cool surfaces. Such pressure differences create circular patterns of air called convection currents. In a convection current, warmer, low-pressure air rises and cooler, high-pressure air rushes in to fill the void. As the warm air rises, it loses heat in the upper atmosphere, cools, and sinks back toward Earth's surface, completing the circuit.
The movement of air from high to low pressure in convection currents is responsible for most winds that blow across Earth's surface. The northern and southern hemispheres each have three zones in which winds blow predictably from east to west or west to east. On either side of the equator are zones dominated by the northeast and southeast trade winds, which blow strongly from east to west, and drive ocean currents in the same direction. The constant blowing of these strong winds pushes the warm surface water westward and causes a swell of warm water to build up in the western Pacific. In most years, the height of the sea surface near Indonesia is about 0.5 meters (1.6 feet) higher than off the coast of Ecuador, and the water temperature is warmer by about 8 degrees Celsius (14 degrees Fahrenheit). On the east side of the ocean, cold water rises up from great depths to replace the water that was pushed westward.
The interaction between global surface winds and ocean currents creates predictable climate patterns. For example, the heat carried westward by the warm ocean current causes powerful thunderstorms in northeastern Australia and eastern Indonesia. In contrast, the cold ocean surface on the east side of the Pacific gives rise to high pressure areas and low precipitation for much of the west coast of South America.
About every three to four years, climate patterns in and around the Pacific Ocean change dramatically. The trade winds slacken and warm water that had been pushed to the west side of the Pacific is allowed to return eastward. This pattern, known as El Niño, typically causes droughts in Australia and Indonesia and damaging thunderstorms and floods in parts of South America and southern North America.
Climate Change, how ocean currents affect climate?
Ever wondered how ocean currents affect climate? Ocean currents are a continuous and directed movement of the ocean water. This happens through forces acting on the water, such as difference in salinity, the waves breaking, temperature, the wind or even the Coriolis effect. The direction of the current is determined by the depth of the contours, other currents acting on the ocean and the nature of the shoreline.
How Oceans currents affect climate
The currents will travel thousands of kilometers, in the process establishing a conveyer belt globally that brings about different climatic conditions across the world. The currents will either act above the surface of the ocean, or deep below the surface of the ocean (at least 300 meters). Depending on the cause, ocean currents will move vertically or horizontally, and they can also be influenced by the land masses that border the ocean, the topography or the shape of the ocean basin.
How climate is determined by ocean currents
As the horizontal currents are moving south or northwards, they carry with them cool or warm water over an extended distance. It is the displaced water that affects the air, by warming or cooling it, thereby transferring the same effect to the land surface over which it blows. This is how ocean currents affect climate.
Warm and cool ocean currents
Cold ocean currents are large masses of cold water that move towards the equator, from a level of high altitude to lower levels. They absorb the heat they receive in the tropics, thereby cooling the air above them. The cold currents often form when the air on the subtropical high blows over a cold mass of water, then the cold air is dragged to the equator.
Warm currents, on the other hand, are large masses of warm water moving further away from the equator, at higher temperatures. They form when salty cold water becomes heavy and sinks, in the process forcing warm and lighter water to move in the opposite direction.
The influence of the flow of currents usually depends on the level of saltiness of the water, the rotation of the earth, the topography of the land and the orientation of the wind. It is these that bring cold water to the surface of the earth from the depths, and in the process forcing away the original surface water. It is because of this reason that you will always notice that the ocean is often cooler to the eastern coastal side than the western coastal side.
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