An ocean current is the movement of ocean water from area A to area B. In this new lesson of the Windy.app Meteorological Textbook (WMT) for better weather forecasting you will learn the different types of ocean currents and their main features.
An ocean current or surface current is the movement of ocean water from area A to area B. What causes that movement? First of all, the wind. When the wind blows above the surface of the ocean, it moves the upper layers of water. The movement is transmitted to deeper layers and from them to even deeper waters. This is how the wind determines the movement of a fairly thick layer of seawater — mostly up to 400 meters deep.
Surface currents are originally created by the wind. The movement of air drives the water, i.e. the blowing wind draws the water away with it. But wind can only drive the upper layers of water. At great depths, water movement is often caused by another force — created by the difference in water density. What is it exactly?
Rip currents are powerful narrow channels of fast-moving water. The water moves away from the shore, so that a person caught in the stream is quickly carried away into the sea. Lifeguards say these are the ones that cause most accidents on the water. To survive, you either have to spot the current in advance and not get into it, or know how to get out of it. Read carefully — we will now learn both.
Thermohaline circulation is what allows water from the surface of the ocean to mix with deeper waters. The name contains parameters that affect the cause of mixing: “thermo”, i.e. temperature and “haline”, i.e. salinity. In short, circulation occurs because different parts of the ocean have different temperatures and salinity. So the thermohaline circulation in the ocean is also called the global ocean conveyor.
The Gulf Stream is one of the largest, longest and most powerful ocean currents on Earth. The Gulf Stream carries more water than all the rivers on our planet combined! It brings tropical heat to Europe and the North Atlantic. Its speed is also worth mentioning: in some places it reaches 2.5 m/s. Usually surface currents move at a speed of less than 1 m/s. The average width of the Gulf Stream is 70–100 km.
Once in a few years in the Pacific Ocean, the surface layer of water warms up considerably and for a long time. Until the 20th century, sailors believed that there is a warm current, calling it El Niño — ’a boy’ in Spanish. In the same region, sometimes the water gets noticeably cold on the contrary, and this phenomenon was called La Niña, ’a girl’. Later it turned out that El Niño and La Niña are two phases of the same process called Southern Oscillation.
You have probably heard of stalactites, icicle-shaped formations hanging from the ceiling of caves. A similar phenomenon can be found under water, in the oceans. Downward growing icicles which are formed beneath developing sea ice are called brinicles. They can be seen in any sea covered with ice. Sea ice, in turn, is formed in many seas and oceans of the northern and southern hemispheres in winter. In the Arctic Ocean and off the Antarctic coast, it is present all year round.
Explore the different types of all the main weather phenomena:
Text: Windy.app team
Cover photo: Todd Quackenbush / Unsplash