UPSC Mains 2022 GS1 Q14: What Forces Shape Ocean Currents, and Their Role in Fishing

Steady surface winds, like the trade winds and westerlies, drag the ocean’s surface layer along with them, setting the primary direction of major surface currents.

Earth’s rotation deflects moving water, curving currents clockwise in the Northern Hemisphere and counter-clockwise in the Southern Hemisphere, rather than letting them flow in a straight line.

Differences in temperature and salinity change water density. Colder, saltier water sinks and flows along the deep ocean floor, driving the slow global thermohaline circulation.

The shape of ocean basins and the position of continents redirect currents, forcing them into large rotating loops called gyres in each major ocean basin.

Wind-driven surface currents and density-driven deep currents together form a connected global ‘conveyor belt,’ moving heat and nutrients around the planet over long timescales.

Where deep, cold, nutrient-rich water rises to the surface, called upwelling, it fertilizes surface waters and supports dense concentrations of plankton, the base of the marine food chain.

The Peru Current off South America drives strong coastal upwelling, sustaining one of the largest single fisheries on Earth, historically dominated by anchoveta catches.

Where warm and cold currents meet, nutrient mixing again boosts productivity. The Grand Banks off Newfoundland, where the Labrador Current meets the Gulf Stream, became one of the world’s richest historical fishing grounds this way.

Because major fisheries depend on specific current and upwelling patterns, disruptions like an El Niño event weakening the Peru Current can sharply cut fish catches and hit coastal economies dependent on them.

Currents affect where fish migrate and concentrate seasonally, directly shaping where fishing fleets operate and how fishing communities plan their seasons.

List the four physical forces (wind, Coriolis, density, basin shape) that shape ocean currents, then connect currents to the fishing industry through upwelling and convergence zones, using the Peru Current and Grand Banks as concrete examples.