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Nature & Outdoors

A Guide to Ocean Currents: What You Should Know

A dip in the ocean is the perfect escape from the summer heat. As you wade into the water, you feel the waves crashing over you and the mix of the cool water and the sun on your skin. Floating on your back, you are carried along by the ocean, only to find that soon after you are further down the beach than you were when you started. This is due to the ocean’s current—the continuous movement of seawater caused by a number of different forces.

Ocean currents flow over long distances, and the direction and intensity of these currents can have drastic effects on the world’s climate. The ocean covers 71% of the earth’s surface and holds 97% of its water. The ocean plays a key role in the storage and transfer of heat across the world. Ocean currents affect local weather conditions, cycling of gases, and the stabilization of global climate patterns. 1

The relaxing feeling you get from breathing in this unique mix of essential oils mimics the relaxing feeling of an evening spent at the shore. The complexity and importance of the ocean are often taken for granted. Remember: the health of the ocean affects the health of all living beings on earth.


Causes of Ocean Currents

Ocean currents are caused by a number of different factors. They are affected by the rise and fall of the tides, wind, thermohaline circulation, the sun, and the rotation of the earth.


Tides are the result of the gravitational pull between the moon and the sun. They create strong currents near bays, estuaries, and coasts. These tidal currents follow regular patterns and changes are easily predictable.


The wind creates currents that are on or near the ocean’s surface. Closer to the coast, winds operate on a localized scale and can sometimes lead to coastal upwelling—a process in which deep, cold water rises to the surface. Further out in the open ocean, winds affect currents which can circulate water for thousands of miles. Although the wind has a great effect on currents, it doesn’t affect currents below 100 meters.

Thermohaline Circulation

Thermo, meaning temperature, and haline, referring to salinity, both affect the density of water in the ocean. If water is cooled or becomes saltier due to evaporation, its density increases. Currents caused by thermohaline circulation can occur at both shallow and deep levels. They tend to move much slower than surface or tidal currents. 2


The sun is the root cause of both wind and thermohaline circulation. As the sun heats the atmosphere, it creates winds that cause surface currents. The sun also affects the temperature and salinity of the ocean, which causes thermohaline circulation.

Rotation of the Earth

The rotation of the earth affects ocean currents due to something known as the Coriolis effect. This causes the water in the Northern Hemisphere to move to the right, and water in the Southern Hemisphere to move to the left. The Coriolis effect increases the further you get away from the equator. 3

 width= Types of Ocean Currents

There are two main types of ocean currents: surface currents and deep currents.

Surface Currents

Surface currents occur both locally and globally and are mostly affected by wind. This results in water movement both horizontally and vertically. Local, short-term horizontal currents include rip currents, tidal currents, and longshore currents. Upwelling currents cause water to move vertically, bringing cool water to the surface and pushing less-dense, warmer water deeper into the ocean.

Deep Currents

Deep currents are usually caused by the density of the water and have a different scale, speed, and energy than surface currents. When the water is cooler and saltier, it is denser. When it is warmer and less salty, it is less dense. A large difference in the density of water between different layers of the ocean causes more extreme circulation.

The differences in the density of global water play a great role in the global conveyor belt. This includes both surface and deep ocean currents that circulate the earth over 1,000 years. This conveyor belt distributes heat throughout the globe, helping to regulate climate, cycle gases, and distribute vital nutrients.

Importance of Ocean Currents

Ocean currents play a large role in the life cycles of marine organisms and ecosystems. Currents help transport nutrients, allowing many species of plants and animals to thrive. Many of these species have limited mobility, relying fully on ocean currents to bring them the nutrients they need. Currents also help distribute larvae and reproductive cells.

Upwelling currents help bring nutrient-rich water from the deep ocean up to the surface. This helps support fish and other marine animals that live in shallow waters. These currents also help support the growth of seaweed and phytoplankton, which helps provide energy for larger marine mammals, fish, and humans. 4

One of the most important roles of ocean currents is the effect they have on the earth’s climate. Currents such as the Gulf Stream help carry heat from tropical waters further north. This helps regulate air temperature and precipitation, especially in places such as Northern Europe.

Without the Gulf Stream bringing so much warm water to these areas, many European countries would be much colder and less habitable. Without the global conveyor belt, much of the earth would be either too hot or too cold for human habitation. Countries near the equator would be unbearably hot, while those far from the equator would be unbearably cold.

 width= The Effects of Climate Change on Ocean Currents

Some research has suggested that the global conveyor belt may be affected by climate change. Increased rainfall and the continued melting of glaciers may cause an influx of warm freshwater into the ocean. This can disrupt the sinking of cold, salty water, which could slow or even stop the global conveyor belt altogether. Without this conveyor belt regulating earth’s temperatures, much of the world could experience drastic temperature changes. 5

Final Thoughts

The dynamics of the ocean are intricate and astonishing to consider. Because of this delicate process, it's especially important for humans to play their part in bringing about positive environmental changes that can keep the oceans clean and begin to offset some of the effects of climate change.

Photo credits: Diak/, Raland/, IvanKurmyshov/, FloridaStock/

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