Currents and shi

Concise Notes on Seasons, Coriolis Effect, Global Wind Belts, and Surface Ocean Currents

Ocean Formation

  1. How Oceans Formed:

    • Volcanic Outgassing: Released water vapor, which condensed and rained for millions of years.

    • Comets: Melted ice contributed additional water.

  2. Salinity Origin:

    • Rain dissolved halite (NaCl) on Earth's surface; runoff carried dissolved salts into the ocean.

Seasons

  1. Earth’s Tilt:

    • 23.5° tilt causes direct rays of the sun to shift between Tropic of Cancer (23.5°N) and Tropic of Capricorn (23.5°S).

  2. Solstices:

    • Summer Solstice (June 21): Sun directly overhead at 23.5°N.

    • Winter Solstice (December 21): Sun directly overhead at 23.5°S.

  3. Equinoxes:

    • Spring Equinox (March 21) and Autumnal Equinox (September 21): Sun directly overhead at the equator (0°).

    • Angle of Insolation:

      • Direct sunlight delivers more concentrated energy than angled sunlight

Atmospheric Density and Pressure

  1. Factors Affecting Density:

    • Temperature: Warm air is less dense and rises; cold air is denser and sinks.

    • Moisture: Moist air is less dense than dry air. - water vapor replaces other air molecules that are heavier

  2. Behavior:

    • Rising air leads to cooling, cloud formation, and rain.

    • Sinking air creates high-pressure zones, often clear skies.

    • High Pressure Belts: These occur in regions where cool, dense air sinks, such as at 30° latitude in both hemispheres and at the poles. The sinking air leads to clear skies and dry conditions because it inhibits cloud formation.

    • Low Pressure Belts: These are found where warm air rises, such as at the equator (0°) and around 60° latitude. The rising air expands and cools, leading to condensation and cloud formation, resulting in wet conditions and increased precipitation.

Global Wind Belts

  1. 3-Celled Model:

    • Hadley Cell (0°-30°): Warm air rises at the equator and sinks at 30°.

    • Ferrel Cell (30°-60°): Air sinks at 30°, moves towards 60°, and rises again.

    • Polar Cell (60°-90°): Cold air sinks at the poles and flows towards 60°.

  2. Wind Patterns:

    • Trade Winds (0°-30°): Blow east to west.

    • Westerlies (30°-60°): Blow west to east.

    • Polar Easterlies (60°-90°): Blow east to west.

Coriolis Effect

  1. Definition:

    • Earth’s rotation causes moving air and water to deflect:

      • Right in the Northern Hemisphere.

      • Left in the Southern Hemisphere.

  2. Impact on Wind and Currents:

    • Northern Hemisphere currents rotate clockwise.

    • Southern Hemisphere currents rotate counterclockwise.

    • Drives the rotation of gyres.

Surface Ocean Currents

  1. Drivers:

    • Global winds, Coriolis effect, and continental deflections.

  2. Gyres:

    • 5 major gyres: North Atlantic, South Atlantic, North Pacific, South Pacific, and Indian Ocean.

    • Warm currents flow poleward (western side of gyres).

    • Cold currents flow equatorward (eastern side of gyres).

  3. Examples:

    • Gulf Stream: Warm, western boundary current. Atlantic

    • California Current: Cold, eastern boundary current. Pacific

    • Canary Current: Cold, eastern Atlantic boundary current. Atlantic

  4. Global Wind Belts and Ocean Interaction

    1. Winds:

      • Trade Winds (0°-30°): Drive equatorial currents westward.

      • Westerlies (30°-60°): Drive mid-latitude currents eastward.

    2. Climate Influence:

      • Warm currents moderate coastal climates (e.g., Gulf Stream warms Northern Europe).

      • Cold currents cool coastal regions.

Questions and Insights

  1. Temperature and Current Flow:

    • Warm currents flow away from the equator.

    • Cold currents flow away from the poles.

  2. Climate Impact:

    • Currents regulate global temperatures.

    • Example: Gulf Stream warms Europe but veers off before affecting New England winters.

  3. Regional Examples:

    • Warm ocean currents: Found on the western sides of ocean basins.

    • Cold ocean currents: Found on the eastern sides of ocean basins.

Key Takeaways

  1. Global Wind Interaction:

    • Trade winds push equatorial currents westward.

    • Westerlies drive mid-latitude eastward currents.

  2. Climate Influence:

    • Ocean currents distribute heat globally, affecting coastal climates.

    • Areas near warm currents experience milder winters.