Q20 · UPPSC PCS Mains 2018 · GS I · 12 marks · ~200 words in the hall · 2 min read

← Q19

Mention the factors responsible for the origins of ocean currents and name the currents of the Atlantic Ocean.

Topic: Physical geography. Syllabus: Salient features of Physical Geography — Earthquake, Tsunami, Volcanic activity, Cyclone, Ocean Currents, winds and glaciers. Same official PYQ from year-wise 2018 and Physical geography.

Revision summary

Winds start surface currents; Coriolis and basin shape turn them into gyres. Density from heat and salt drives the deep conveyor, including North Atlantic sinking. North Atlantic names include North Equatorial, Gulf Stream, North Atlantic Drift, Canary, and Labrador. South Atlantic names include South Equatorial, Brazil, Benguela, and Falkland. The Equatorial Counter Current and Guinea Current complete the tropical belt. Pacific names such as Kuroshio do not belong on this Atlantic list.

Model answer

Introduction

Ocean currents are large, fairly persistent horizontal movements of seawater. They originate where wind, density, the Earth’s rotation, and the shape of ocean basins act together, and the Atlantic displays the clearest textbook gyres of that engine.

Body

Factors responsible for origin

  • Prevailing winds are the primary generator of surface currents: trade winds drive the equatorial currents; westerlies drive the eastward drift of mid-latitudes.
  • Planetary vorticity and the Coriolis force turn moving water to the right in the north and to the left in the south, building subtropical gyres rather than straight wind drift.
  • Temperature and salinity differences create density (thermohaline) contrasts; sinking of cold, salty water in the North Atlantic is the deep limb of the conveyor, not only a surface curiosity.
  • Evaporation, precipitation, ice melt, and river inflow modify salinity and therefore density-driven motion, especially in high latitudes and enclosed seas.
  • Continental configuration, submarine ridges, and the narrowness of passages (Florida Strait, Drake Passage analogues on other oceans) steer and intensify western boundary currents.
  • Gravity, pressure-gradient force, and friction with the seafloor and adjacent layers close the force budget; tides matter more for local tidal streams than for the great gyres.

Currents of the Atlantic Ocean

  • North Atlantic subtropical gyre: North Equatorial Current, Antilles and Caribbean flow into the Gulf Stream, then the North Atlantic Drift (North Atlantic Current), the Canary Current, and the southward close of the gyre.
  • South Atlantic subtropical gyre: South Equatorial Current, Brazil Current, South Atlantic (westerly) Current, and the cold Benguela Current along south-west Africa.
  • Cold equatorward or polar limbs and branches: Labrador Current, East Greenland Current, Falkland (Malvinas) Current, and the Canary and Benguela already named.
  • Equatorial and connecting flows: Atlantic Equatorial Counter Current between the two equatorial currents; Guinea Current along the north Gulf of Guinea; the warm Gulf StreamNorth Atlantic Drift is the famous heat pump toward north-west Europe.
  • Deep Atlantic: North Atlantic Deep Water as the sinking, southward deep current of the thermohaline circulation, distinct from the surface names but part of origin physics.

Naming without mixing oceans

  • Humboldt, Kuroshio, and Agulhas are Pacific or Indian; the Atlantic list above is the one the question asks to name.
  • A fair answer therefore pairs wind-Coriolis-density-basin factors with the North and South Atlantic gyre names plus Labrador, Falkland, Guinea, and the deep NADW limb.

Flow diagram

flowchart TD
  W[Wind density Coriolis] --> G[Atlantic gyres]
  G --> N[Gulf Stream NAD Canary Labrador]
  G --> S[Brazil Benguela Falkland]

Conclusion

Ocean currents originate from wind drag, Coriolis turning, thermohaline density, water-budget salinity, and basin shape. The Atlantic’s named surface set is the two subtropical gyres—Gulf Stream, North Atlantic Drift, Canary, North and South Equatorial, Brazil, Benguela—plus Labrador, Falkland, Guinea, and the counter-current.

Quick related

Students also ask

  • Is the Gulf Stream only a wind current?

    Wind and western-boundary intensification start it. Heat and salt it carries also feed the thermohaline sinking farther north, so origin factors mix.

  • Why name both Brazil and Benguela?

    They are the warm western and cold eastern limbs of the same South Atlantic gyre; naming one gyre current and omitting the other would be incomplete.

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