Mains Practice Question


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What are ocean currents? Discuss the ways it influences human behaviour.


A Simple Introduction about Ocean Currents

The ocean is not a stagnant body of water. Instead, it's constantly on the move, with currents transporting water from place to place. These currents are measured in meters per second or knots (one knot is roughly equal to 1.85 kilometres per hour).

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Three key factors influence the movement of ocean currents: wind, water density variations, and tides.

  • Tides and Tidal Currents: The rise and fall of tides create currents, especially strong near coastlines, bays, and estuaries. These predictable "tidal currents" follow a regular pattern and can be forecast for future dates.

  • Wind-Driven Currents: Winds have a powerful influence on currents flowing near the ocean's surface. Coastal winds can generate localized currents, such as coastal upwelling where nutrient-rich deep water rises to the surface.

  • Thermohaline Circulation: This large-scale circulation system is driven by density differences in the ocean. Temperature (thermal) and salinity (haline) variations cause water density to change across different regions. This density contrast creates a slow-moving conveyor belt of deep and shallow currents that are much slower than tidal or surface currents.

Impact of Ocean Currents on Climate and Human Activities

Ocean currents exert a profound influence on climate and human activities, shaping the environmental conditions along coastlines and impacting various socio-economic sectors. Here's an overview of their effects:

Temperature Regulation:

Cool ocean currents along the west coasts of continents in tropical and subtropical latitudes moderate temperatures, resulting in relatively modest average temperatures with limited diurnal and yearly fluctuations. Despite arid landscapes, fog is common in these regions.

Conversely, warm ocean currents bordering the west coastlines of continents at the middle and higher latitudes create distinct marine climates characterized by pleasant summers, generally warm winters, and narrow yearly temperature ranges.

Climate Patterns:

Warm currents moving parallel to the east coasts of continents in tropical and subtropical latitudes contribute to warm and rainy climates, particularly on the western borders of subtropical anticyclones.

Ecological Impact:

Mixing of warm and cold ocean currents facilitates oxygen replenishment and promotes the growth of plankton, the primary food source for fish populations. These mixing zones, often found at the convergence of warm and cold currents, serve as some of the world's best fishing grounds.

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A recent study has raised concerns about the stability of the Atlantic Meridional Overturning Circulation (AMOC). This critical system of ocean currents plays a vital role in regulating global climate patterns. The AMOC is the Atlantic branch of a much larger circulation system called the Thermohaline Circulation (THC), often referred to as the ocean's conveyor belt. It acts as a massive conveyor, distributing heat and nutrients throughout the world's oceans. The AMOC operates like a giant loop. It carries warm surface waters northward from the tropics in the Atlantic Ocean. As these warm waters travel towards the North Atlantic, they cool down and become denser. This denser water then sinks towards the ocean floor, eventually returning southward as a deep current. 


Other Points to Consider 


What happens if AMOC collapses?

Difference between warm currents and cold currents

Location of important water currents


Previous Year Questions

1. What are the forces that influence ocean currents? Describe their role in the fishing industry of the world. (2022)

2. Explain the factors responsible for the origin of ocean currents? How do they influence regional climates, fishing and navigation? (2015)


22-May 2024