SLO2

Reconstruct the major circulation patterns of the dominant ocean circulation systems, atmospheric circulation systems, and analyze their interrelationships.

Atmospheric Circulation

Have you ever wondered, what unseen forces drives the incredible weather on Planet Earth and where all that Atmospheric energy comes from? Atmospheric circulation is a complex topic which drives a large portion of the weather we experience in our day-to-day lives. It begins as the Earth absorbs and re-radiates the sun's solar radiation as greenhouse gases. Due to the slight tilt of the Earth, the solar radiation is not evenly distributed nor absorbed. It's no coincidence that the tropics in the middle absorb much more heat than the more distant North and South Pole.

This particular imbalance of heat causes the warmer air to expand, which in turn makes it less dense than its cooler counterpart, resulting in a greenhouse effect. The air warmed by the surface rises, while the cooler air sinks and moves across the surface to replace the rising air. This transfer of heat is referred to as convection, and it is the primary driver of atmosphere circulation around the tropics. This tropics circulation patter is one of the three major air masses and is commonly referred to as the Hadley Cell and can be located at the latitudes of 30°N to 30°S. The second major air mass, located at 60°N and 60°S, is known as the Ferrel cell, where air flows westward and equatorward at higher elevations and eastward/poleward near the surface. The third and final cell is located at 90°N and 90°S and is known as the Polar cell, in which the warm air rises and travels towards the poles. Once it reaches the poles the air cools and begins to sink which in turn forms polar highs.

Ocean Circulation

Ocean circulation is relatively similar to atmospheric circulation in that they are mostly determined by factors such as current atmospheric conditions, the water cycle, and the amount of solar radiation absorbed. The surface level currents are primarily driven by wind pushing against the surface of the water, and their direction and range of movement is determined by the distribution of continents. These surface currents can also be referred to as horizontal currents and similar to the wind that drives them, they rarely move in straight lines due to the rotation of the Earth also known as the Coriolis effect. The second type of current which drives Ocean circulation is known as vertical currents, which similarly to atmospheric currents are driven by differences in temperature and salinity of water. The warmer the water, the less dense it is, and the saltier the water, the denser it becomes. The surface winds will move the warmer water towards the poles, where it will become cooler and denser, sinking to the bottom. This particular form of Ocean circulation is referred to as thermohaline circulation (therme=heat, halos=salt).

Works Cited:

“Atmospheric Circulation.” Understanding Global Change, 8 Mar. 2022, https://ugc.berkeley.edu/background-content/atmospheric-circulation/.
“Ocean Circulation.” Understanding Global Change, 8 Mar. 2022, https://ugc.berkeley.edu/background-content/ocean-circulation/.
US Department of Commerce, NOAA. “Global Circulations.” NWS JetStream, NOAA's National Weather Service, 9 Aug. 2019, https://www.weather.gov/jetstream/circ.

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