physical oceanography

Study Guide on Physical Oceanography

Introduction to Physical Oceanography

  • Definition: The study of physical conditions and processes within the ocean, including the motions and physical properties of ocean waters.

  • Sub-domains of Oceanography:

    • Biological Oceanography

    • Chemical Oceanography

    • Geological Oceanography

Types of Physical Oceanography

  1. Descriptive Physical Oceanography

    • Focuses on observations and complex numerical models that describe fluid motions.

    • Uses measurements to provide data about ocean properties like temperature, salinity, and currents.

  2. Dynamical Physical Oceanography

    • Centers on processes governing the motion of fluids.

    • Emphasizes theoretical research and models, linking to Geophysical Fluid Dynamics (GFD).

    • The Coriolis force plays a significant role in fluid motions.

Physical Setting of Oceans

  • The oceans make up about 97% of the Earth's water and are vital for the water cycle, climate moderation, and geological processes.

  • Average ocean depth: 3,800 meters, compared to average land elevation of 840 meters.

  • Areas, Volumes, and Depths of Major Oceans:

    • Pacific Ocean: Area: 165.2 million km², Depth: 4282 m.

    • Atlantic Ocean: Area: 82.4 million km², Depth: 3926 m.

    • Indian Ocean: Area: 73.4 million km², Depth: 3963 m.

    • Southern Ocean: Area: 20.3 million km².

    • Arctic Ocean: Area: 14.1 million km².

Temperature, Salinity, and Density

Temperature

  • Mean temperature of seawater is low (0° – 5 °C) in deep ocean waters.

  • Surface mixed layer, thermocline, and abyssal zone exhibit distinct thermal stratification.

    • Surface Mixed Layer: Thickness varies from 50 to 200 meters.

    • Thermocline: Rapid temperature decrease with depth, pronounced in tropics.

    • Abyssal Zone: Cold and stable temperature around 0°-3°C.

Salinity

  • Salinity levels typically between 34 and 35 ppt; varies due to localized factors.

  • Halocline: Rapid salinity change at certain depths.

  • Polar Regions: Generally have lower surface salinity due to freshwater input from melting ice.

Density

  • Density variation is affected by temperature and salinity (pycnocline).

  • Thermohaline Circulation: Global conveyor belt driven by density differences in water.

Ocean Circulation

  • Ocean currents driven by various forces including wind and thermohaline circulation.

  • Coriolis Effect: Deflection of ocean flows; significant in shaping ocean currents.

  • Ekman Transport: Net water movement at 90 degrees to wind direction, changing with depth due to Coriolis.

  • Langmuir Circulation: Creates visible surface patterns called windrows.

Ocean-Atmosphere Interactions

Heat Exchange

  • Oceans gain heat from solar radiation, with variations between tropical and polar regions.

  • Heat moderates coastal climates, illustrated by the North Atlantic Drift's impact on Western Europe.

Moisture Exchange

  • Associated with evaporation and precipitation, impacting ocean salinity and potentially altering currents.

Climate Variability

  • Interaction of ocean currents and climate measures results in oscillations (e.g., Pacific decadal oscillation).

  • El Niño and La Niña events shift climate patterns globally.

Major Ocean Currents

  • Important currents include:

    • Antarctic Circumpolar Current

    • Gulf Stream

    • Kuroshio Current

    • Labrador Current

  • Currents are influenced by wind, water density, and earth’s rotation.

Sea Level Change & Tides

  • Sea level has been rising globally (1.5–3 mm/year).

  • Influences of tides on coastal regions, including tidal bores and resonance effects (e.g., Bay of Fundy).

  • Tsunamis caused by large-scale water displacement from seismic activity.

This study guide encompasses an overview of key topics within physical oceanography, emphasizing major concepts required for a deeper understanding of oceanic processes.