1. Introduction to Oceanography

Rules of Thumb & Things to Remember

  • Seawater temperature: 0 – 30 °C
  • Seawater density: 1024 kg/L
  • Thickness of wind-driven surface-currents: 100-150 m
  • Average rate of sea level rising: 2.28 mm/year (Jason-1 satellite)
  • Accuracy of satellite altimetry: 3 cm

1.1. What is Oceanography?

Oceanography is the science that studies the ocean environment. It includes the study of:
(1) Currents, waves and the dynamics of ocean flows (Physical Oceanography).
(2) Ocean-level flow of chemical substances and their properties.
(3) Marine organisms and ecosystems.
(4) Geology of the oceanic floor (Marine Geology).

1.2. What is Physical Oceanography?

Physical Oceanography studies the physical properties of oceans and the relevant phenomena such as currents, waves, ocean circulation. Next, we will focus on the main topics of physical oceanography that are important for Offshore Engineering. Those are:
(1) Seawater properties, Stromatographty.
(2) Coriolis Effect
(3) Surface currents (Wind-driven)
(4) Surface currents (Geostrophic currents)
(5) Surface currents (Thermal Wind)
(6) Deep water currents
(7) Tides

1.3. Seawater Temperature

Sea surface temperature varies from 0°C to 30°C

Seawater temperature extreme degrees

The figure below shows the seawater temperature in relation to water depth. At low latitudes (tropics) the seawater temperature profile is pretty constant. At mid-latitude the surface temperature varies between winter and summer and this is reflected on the temperature profile.

Sea water temperature decrease depth profile

1.4. Seawater density

The average seawater density is 1024 kg/m3

Seawater density world map ocean variation

1.5. Seawater density

Seawater salinity world map ocean variation

1.6. Q & A

Q: Explain the terms Thermocline, Halocline, Pycnocline

Thermocline: is the range of sea water depths where the seawater temperature reduces rapidly with the increase of water depth. This region is located below the well-mixed, surface layer of the sea and above the calm deep water. Thermocline range is roughly 100-1000 m

Halocline: is the range of sea water depths where the seawater salinity reduces rapidly with the increase of water depth.

Pycnocline: is the range of sea water depths where the seawater density reduces rapidly with the increase of water depth.

sea water temperature, salinity, density vs depth
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