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

Ocean currents are large-scale seawater movements caused by unequal heating, prevailing winds, Earth’s rotation, and density differences.

• Origin: Uneven solar heating creates pressure and sea-level differences; winds drive surface flow; Coriolis force deflects it into gyres; temperature–salinity contrasts generate deep currents; coastlines and ocean-floor relief modify their course.
• Influence: Warm currents raise coastal temperatures, humidity and rainfall, while cold currents cool coasts, reduce rainfall and may cause coastal deserts. Mixing of warm and cold currents and upwelling enrich nutrients, creating major fishing grounds. Currents aid or hinder navigation by affecting speed, fuel use and safety, but also cause fog, drift ice and coastal hazards.

Thus, ocean currents strongly shape regional climate, fisheries and maritime transport.