Currents: the conveyor belts of the ocean
What are currents made of and how do they form?
An ocean current is a portion of ocean water moving in one direction. Currents are driven by two main factors: the coriolis effect and differential heating.
The coriolis effect is a phenomena that occurs when differences in speed at which the equator and the poles of the Earth rotate cause objects not attached to the ground to travel in a non- straight line. An example of this would be ocean currents: currents in the northern hemisphere veer towards the right, and currents in the southern hemisphere to veer towards the left. Besides currents, the coriolis effect is also responsible for many wind patterns.
Differential heating (differences in water temperature) also amount to currents. Warm water is less dense than cold water, and the variation in density results in a cycle of warm water rising to the surface of the ocean, cooling, and sinking to the bottom of the ocean before pushing warmer water higher up.
How do currents impact our daily lives?
Ocean currents are extremely important because they influence the Earth’s weather system and bring nutrients to sea organisms. They help regulate the heat around the globe, so that temperatures at the poles and at the equator are not too extreme by sending cool water to the equator and warm water to the poles. In addition, they are also like conveyor belts, transporting precipitation and nutrients all across the planet.
What are the types of currents?
There are two types of currents: surface currents and deep ocean currents.
Surface currents are fueled by wind, and transfer heat from warmer places to the poles of the Earth. An example of a surface current is one from the Gulf Stream, which keeps places in Northern Europe much warmer than places that have equal latitude.
There are also deep ocean currents, which are currents that are formed by differences in temperature and salinity. Deep ocean currents are known as thermohaline circulation. The sinking and transport of masses of water with different densities is what generates deep ocean currents.
Many circular ocean currents join together form a gyre, and movements of gyres are what causes water to circulate around the entire planet. There are five main systems of gyres in the world. One of them is the North Atlantic Gyre, which is responsible for Northern Europe having a warmer climate than places with equal latitude. Warm water from the Caribbean Sea travels along the East Coast of the U.S., crosses the Atlantic and travels down Europe, before cooling down when traveling along the west coast of Africa, and then crossing the Atlantic again to the Caribbean Sea. As shown from the picture below, gyres in the Northern Hemisphere rotate clockwise, and gyres in the southern hemisphere rotate counter clockwise; this is due to the Coriolis effect.
Does global warming impact currents?
Global warming can have a tremendous impact on currents because they distort densities of water. As a consequence of the melting of the Greenland ice sheet, more water is in the ocean, and the surplus amount can reduce salinity.
Differences in density may amount to stratification, the separation of different levels of water. It means it is harder for nutrient, oxygen, and carbon dioxide transfer between various levels of water, and that waters with varying temperatures might not mix. When too much warm water stays at the surface, it can amount to storms such as hurricanes.
Warmer waters also means that waters at the pole are less cold, and when the differences of the temperatures of currents are not substantial, the circulation is weaker.