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Oceans of World Notes with PDF

By October 4, 2025 Educational Resources 0 Comments

These notes are your ultimate revision weapon to revise Oceans of World. We’ve distilled years of previous exam questions (PYQs) into one powerful, concise resource. Everything you need to know, nothing you don’t.

  • PYQs, Decoded: All key concepts from past exams, organized and simplified.
  • Revise in Record Time: Short, precise, and designed for last-minute review.
  • Focus on What Matters: Master high-probability topics and boost your confidence.
  • Free PDF to download.

Oceanography Fact Sheet

Ocean Currents

Factors Influencing Ocean Currents

  • Primary Influencing Factors:
    • Earth’s rotation
    • Winds (prevailing winds)
    • Air pressure
    • Density of ocean water (affected by temperature and salinity)
  • Non-Influencing Factor:
    • The Earth’s revolution around the Sun does not affect ocean currents.

Characteristics & Effects

  • Definition: The slow surface movement of water in the ocean.
  • Heat Balance: They maintain the Earth’s heat balance by transferring warmth from equatorial regions to polar regions and coolness in the opposite direction.
  • Geographical Influence: The shape and configuration of the ocean basin affect the direction and nature of currents.

Classification of Currents (Warm vs. Cold)

  • Warm Currents: Flow from warmer to cooler regions.
    • Examples: Gulf Stream, Brazil Current, Kuroshio, Agulhas Current.
  • Cold Currents: Flow from cooler to warmer regions.
    • Examples: Canary Current, Labrador Current, Benguela Current, Peruvian (Humboldt) Current, Oyashio, Falkland Current.

Major Ocean Currents by Ocean

  • Atlantic Ocean
    • North Atlantic: Gulf Stream (warm), North Atlantic Drift (warm, moderates Europe’s climate), Canary Current (cold).
    • South Atlantic: Brazil Current (warm), Benguela Current (cold).
    • Circulation Pattern: Forms a complete, anticlockwise circle: South Equatorial -> Brazil -> West Wind Drift -> Benguela -> South Equatorial.
  • Indian Ocean
    • Unique Characteristic: Heavily influenced by Monsoon winds, causing seasonal reversal of currents in its northern part (Monsoon Drift).
    • Major Currents: Agulhas Current (warm), Mozambique Current (warm), West Australian Current (cold).
  • Pacific Ocean
    • North Pacific: Kuroshio Current (warm), California Current (cold), Oyashio Current (cold).
    • South Pacific: Peruvian (Humboldt) Current (cold).

Specific Current Phenomena

  • Equatorial Counter-Current: An eastward-flowing current located between the westward-flowing North and South Equatorial Currents, caused by the piling up of water due to the Earth’s rotation.

Ocean Salinity

Definition & Measurement

  • Halocline: The zone in the ocean where salinity changes rapidly with depth.
  • Average Salinity: Approximately 35 parts per thousand (ppt).

Sources & Composition

  • Primary Source: The land, with rivers being the main delivery mechanism.
  • Other Factors: Evaporation, wind, rain, ocean currents, and volcanic ash.
  • Most Abundant Salt: Sodium Chloride (common salt), which constitutes about 77.8% of the dissolved salts in seawater.

Global Distribution & Extremes

  • High Salinity Bodies of Water:
    • Lake Van, Turkey: 330 ppt
    • Dead Sea: 238 ppt
    • Great Salt Lake, USA: 220 ppt
  • Open Seas:
    • Red Sea: 36 to 41 ppt (very high for an open sea)
    • Arabian Sea: ~36 ppt (higher due to more evaporation and less river inflow)
    • Bay of Bengal: ~30 ppt (lower due to high river inflow)

Salinity and Density

  • An increase in seawater density is associated with an increase in salinity.

Ocean Tides

Causes of Tides

  • Primary Cause: The gravitational pull of the Moon (has 2.17 times more tide-generating power than the Sun).
  • Other Factors: The gravitational force of the Sun and the centrifugal force of the Earth’s rotation.
  • High Tides: Caused by the Moon’s gravitational pull and the Earth’s centrifugal force (causing indirect high tides).

Types of Tides

  • Spring Tides: Occur when the Sun, Earth, and Moon are in a straight line (during New Moon and Full Moon). These are the highest tides.
  • Neap Tides: Occur when the Sun and Moon are at right angles to the Earth (first and last quarter moons). High tide is lower than normal and low tide is higher than normal.

Frequency

  • Most places experience two high tides and two low tides every day.

Oceanic Trenches

Deepest Points by Ocean

  • Pacific Ocean: Mariana Trench (deepest point: Challenger Deep) – the deepest known trench in the world.
  • Atlantic Ocean: Puerto Rico Trench.
  • Indian Ocean: Java Trench (Sunda Trench). The Diamantina Trench (fracture zone) is also located here.
  • Arctic Ocean: Eurasian Basin.

Specific Trenches and Locations

  • Aleutian Trench: North Pacific Ocean.
  • Kermadec Trench: South Pacific Ocean.
  • South Sandwich Trench: South Atlantic Ocean.

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