Oceanography: UPSC Previous Year Questions (Geography)

Explanation

The Equatorial Counter Current (CEC) is an eastward-flowing current located between the North Equatorial Current (NEC) and the South Equatorial Current (SEC) in the oceans near the equator. It is most prominent in the Pacific and Indian Oceans and helps redistribute heat across the equator, contributing to global climate regulation.

Option (a) is incorrect: While the Earth’s rotation influences large-scale oceanic circulation through the Coriolis force, it does not directly explain the eastward flow of the Equatorial Counter Current. The Coriolis effect is minimal near the equator.

Option (b) is correct: The North Equatorial Current (NEC) and the South Equatorial Current (SEC) flow westward due to trade winds. As these currents converge in the western parts of the oceans, water piles up. Under the influence of gravity, this piled-up water flows eastward, forming the Equatorial Counter Current.

Option (c) is incorrect: While salinity influences vertical water movement, its impact on large-scale horizontal currents like the Equatorial Counter Current is negligible.

Option (d) is incorrect: The Doldrums (regions of calm winds near the equator) do not actively cause the eastward flow. Instead, they create areas of weak wind, which are more relevant for localized weather conditions than large-scale currents. Fig.: Equatorial counter current in Pacific Ocean

Explanation

Tides are the periodic rise and fall of sea levels, driven by various forces acting upon Earth’s water bodies. These forces include:

The Sun’s gravitational pull plays a secondary role in creating tides, as it is much farther away from Earth compared to the Moon. However, its gravitational influence still contributes significantly to spring tides (higher-than-normal tides) when the Sun, Moon, and Earth are aligned (new moon and full moon phases). The Moon’s gravitational force is the primary driver of tides. Due to its proximity to Earth, the Moon exerts a stronger pull on Earth’s oceans, causing the bulge of water that forms high tides. The gravitational pull of the Moon is nearly 2.5 times more effective than that of the Sun in causing tides due to its closer proximity. The Earth-Moon system rotates around a common center of mass, creating a centrifugal force that acts opposite to the Moon’s gravitational pull. This force also contributes to the formation of tides on the side of Earth opposite the Moon, leading to high tides there. It helps explain the formation of high tides on the side of Earth opposite the Moon.