A Detailed Discussion on Ocean Currents
Among the various extraordinary incidences that the earth hosts, ocean current is one. It is the seawater movement directionally and continuously influenced by gravity, the Coriolis Effect of the wind, and the density of water. Now the ocean current can show two directional movements- horizontal and vertical. The former is termed as “current” while the latter is termed as “upwelling” or “downwelling.” Ocean currents, a part of the abiotic system of the environment, contribute to the transfer of heat, bringing in biodiversity variations and also develop the global climate system.
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What are the Types of Ocean Currents?
Broadly, as ocean currents UPSC syllabus determines, the ocean currents are of two types- warm and cold. Equator regions carry the warm ocean currents while cold currents originate from the Polar Regions. Based on the strength of the flow, the currents can be of two more types. Western boundary currents are the ones with strong and fast currents, whereas Eastern boundary currents are the ones with comparatively shallow and moderate strength of the currents.
What is Thermohaline Circulation?
Thermohaline circulation, or THC, is a part of the ocean circulation where the density gradient of the ocean water plays a pivotal role. The difference in density is caused by the flow of freshwater and the surface heat. It is the temperature and the salt content of the water that gives rise to the different density of the seawater leading to the name “thermohaline,” where thermo refers to temperature and haline refers to the salt content.
What is Agulhas Current?
Agulhas current, a warm current, is formed by the merging of Mozambique and Madagascar current. This current continues southwards till it meets the Northwesterly wind. It increases temperature along the east coast of South Africa.
What is Kuroshio Current?
Yet another warm ocean current, the Kuroshio Current, flows from Taiwan to the Bering Strait. It is also known as the Japan current or the Black current, or the Black stream. It is generally found on the west side of the North Pacific Ocean. Being a western boundary current, this type of wind is quite powerful.
What is Gulf Stream Current?
One of the strong ocean currents, the Gulf Stream, is responsible for bringing warm water into the Atlantic Ocean from the Gulf of Mexico. The eastern coasts of Canada and the United States is the region where this current extends. Oceanic gyre is the main reason behind its formation. Gyres are a system consisting of powerful winds and a series of circular currents. One such gyre is the North Atlantic Subtropical Gyre, of which the Gulf Stream Current is a part. As the Gulf Stream brings in the warm water, the cold water already existing in the Atlantic Ocean is forced to move south as it is denser. Ultimately the cold water flows to Antarctica.
What is Oyashio Current?
It is one of the cold ocean currents. The Kamchatka current flows along the Kamchatka peninsula from Bering Strait in SW direction. This later form Oyashio Current and some of its parts join the North Pacific Current. The water that Oyashio Current carries comes from the Arctic Ocean and continues to flow along south through the Bering Sea. Along the way, it comes across the Kuroshio Current around the Eastern Japan shore and together forms one of the Pacific Ocean currents, namely North Pacific Current. The current brings cold water from the Arctic sea into the Pacific Ocean.
What are Equatorial Currents?
There are two types of Equatorial currents- north and south. The brief details of these currents are as follows:
1. North Equatorial Currents:
This current originates from the western coast of Mexico and flows in a westerly direction. California current and NE monsoon is responsible for the formation of this current. It carries warm water towards Alaska.
2. South Equatorial Currents:
This originates due to the influence of SE trade winds and flows from East to West. Then it gets bifurcated near New Guinea into the Northern and Southern Branch. The first one turns eastward and flows as a counter equatorial current, and the latter moves into the north direction along the NE coast of Australia.
What is Humboldt Current?
This current is the continuation of west Wind drift from the Antarctic that flows northwards along the western coast of South America. It is associated with the El-Nino effect in South America. It also affects the timely arrival of the Indian monsoon.
What are Labrador and Benguela Currents?
Labrador current originates in the Baffin Bay and the Davis Strait and moves eastward, merging with Gulf Stream near Newfoundland. Its confluence with Gulf Stream produces heavy fog along the coast of Newfoundland, a vital fishing ground globally, such as as- Grand Bank, Dogger Bank, George Bank.
Benguela Current flows from south to north along the western coast of South Africa and merges with the South Equatorial current. It leads to foggy conditions along the coast of Namibia. This particular current helped in the development of the Namibian and Kalahari Desert.
Did you know?
Rotation of the earth creates oceanic water to bulge out.
Currents move clockwise in the northern hemisphere, whereas in the southern hemisphere, left deflection currents lead the counterclockwise movements.
Western Boundary Currents lack nutrients and thus contain sterile water.
Eastern boundary currents do not have well-defined boundaries.
FAQs on Ocean Current
1. What is an ocean current?
An ocean current is the continuous, predictable, and directional movement of seawater. This movement is driven by several forces, including gravity, wind, and differences in water density. Ocean water moves both horizontally and vertically. The horizontal movements are what we typically call currents, while the vertical movements are known as upwellings or downwellings.
2. How are ocean currents classified?
Ocean currents are primarily classified in two ways:
- Based on Temperature: Currents are categorised as either warm or cold. Warm currents flow from low latitudes (near the equator) towards high latitudes (near the poles), bringing warmer water to colder regions. Cold currents flow from high latitudes towards the equator, bringing cooler water to warmer regions.
- Based on Depth: Currents are classified as surface or deep water currents. Surface currents make up about 10% of all ocean water and are mainly driven by wind. Deep water currents are driven by differences in water density (caused by temperature and salinity) and move water in the deep ocean basins.
3. What are the primary forces that drive ocean currents?
The formation and movement of ocean currents are driven by a combination of factors, which can be grouped as follows:
- Planetary Winds: The friction between wind and the ocean's surface creates drag, setting the surface water in motion and forming surface currents like the trade winds and westerlies.
- Temperature Differences: Water near the equator is warmer and lighter, while water near the poles is colder and denser. This difference causes water to move as it seeks equilibrium.
- Salinity Differences: Higher salinity makes water denser, causing it to sink. Variations in salinity, caused by factors like evaporation and freshwater influx from rivers, create density gradients that drive currents.
- Earth's Rotation: The Coriolis effect, caused by the Earth's rotation, deflects the path of moving water to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, influencing the circular pattern of currents.
4. What is the difference between an ocean current and a wave?
The primary difference lies in the movement of water. An ocean current involves the actual, continuous flow of a mass of water from one location to another, much like a river in the ocean. In contrast, a wave is primarily a transfer of energy through the water. While the energy travels across the ocean, the water particles themselves move in a circular or orbital motion and do not experience significant horizontal displacement.
5. How do ocean currents influence global climate and marine life?
Ocean currents act as a global heat distribution system. They transport warm water from the tropics towards the poles and cold water from the poles back towards the tropics. This process helps regulate global temperatures, making many regions more habitable. For instance, the warm Gulf Stream keeps Western Europe's climate much milder than other areas at the same latitude. For marine life, currents transport nutrients and plankton, which form the base of the marine food web, thus determining the location of major fishing grounds.
6. Why are areas where warm and cold currents meet often foggy and rich in fish?
When a warm, moist air mass moves over a cold current, the air cools to its dew point, causing the water vapour to condense and form dense fog. This is common in areas like Newfoundland, where the warm Gulf Stream meets the cold Labrador Current. These meeting zones are also extremely productive fishing grounds because the mixing of warm and cold water encourages upwelling, which brings deep, nutrient-rich water to the surface. This fuels the growth of plankton, attracting a large and diverse fish population.
7. What would happen to global temperatures if ocean currents stopped circulating?
If ocean currents were to stop, the Earth's climate would become much more extreme. Without the currents redistributing heat, the equatorial regions would become intensely hot, while the polar regions would become frigidly cold. This disruption of the global heat conveyor belt would drastically alter weather patterns, lead to severe temperature imbalances, and make large portions of the planet uninhabitable for humans and many other species.
8. What are some examples of major warm and cold ocean currents?
Here are some well-known examples of ocean currents:
- Major Warm Currents: The Gulf Stream (Atlantic), the North Atlantic Drift (Atlantic), the Kuroshio Current (Pacific), and the Agulhas Current (Indian).
- Major Cold Currents: The Labrador Current (Atlantic), the Canary Current (Atlantic), the California Current (Pacific), and the Benguela Current (Atlantic).
