Ocean currents and circulation

Oceanic circulation, encompassing ocean and sea currents, is driven by two main factors: wind and thermohaline circulation. The latter, driven by density differences from temperature and salinity, will be discussed first.

Thermohaline circulation is initiated by density variations in water, where 'thermo' refers to temperature and 'halien' to salinity. Cold and salty water is denser and sinks. Seawater warms at the equator, flows towards the poles, cools, and evaporates, increasing its salinity. This denser water then sinks, forming deep water and driving the 'ocean conveyor belt'.

The second driver of ocean currents is wind. Westerly winds north of 30 degrees latitude push surface water, and the Coriolis effect deflects it. Combined with easterly trade winds, this creates circular ocean currents called gyres. The Northern Hemisphere has clockwise-rotating gyres in the Atlantic and Pacific, while the Southern Hemisphere has counter-clockwise gyres in the Atlantic, Pacific, and Indian Oceans. These gyres also accumulate plastic waste.

Warm ocean currents from the equator flow along eastern coasts, bringing heat and increasing precipitation, as seen with the Gulf Stream warming Western Europe. Conversely, cold currents on western coasts lead to less precipitation. Ocean currents play a crucial role in redistributing heat globally; without them, the equator would be hotter and the poles colder. The Antarctic Circumpolar Current prevents warm water from reaching Antarctica, contributing to its extreme cold.

In summary, oceanic circulation is driven by differences in temperature, salinity, and wind, and it significantly influences temperature and precipitation patterns in coastal regions worldwide.