Introduction to Oceanography: Water, Salinity, Sediments, and Climate

What is the dipolar structure of a water molecule?

The water molecule (H2O) has two hydrogen atoms bonded to one oxygen atom at an angle of 105°, resulting in a slight positive charge on the hydrogen end and a slight negative charge on the oxygen end.

What are hydrogen bonds?

Weak electrostatic forces between oppositely charged ends of adjacent water molecules.

What are the three states of water under Earth's surface conditions?

Solid (Ice), Liquid (Water), and Gas (Vapor).

Why does ice float on water?

Ice is less dense than liquid water due to its rigid crystalline structure formed by hydrogen bonds.

What is the universal solvent property of water?

Water's dipolar structure allows it to weaken electrostatic attractions between ions, enabling it to dissolve many substances, such as NaCl.

Define sensible heat.

Heat energy that causes a measurable change in temperature, representing the vibrational energy of water molecules.

Define latent heat.

Heat energy required for a phase change without a change in temperature.

What is the latent heat of fusion?

80 cal/g, the heat energy absorbed or released during the melting or freezing of water.

What is the latent heat of vaporization?

540 cal/g, the heat energy absorbed or released during the evaporation or condensation of water.

What is the hydrologic cycle?

The cycle that transports heat from low-latitude ocean areas toward higher latitudes through evaporation, condensation, and precipitation.

What is salinity?

The measure of total dissolved inorganic solids (salts) in seawater, typically expressed in parts per thousand (‰).

What is the average salinity of seawater?

Approximately 35‰ (3.5% dissolved solids).

What are the six major ions that account for 99.4% of dissolved solids in seawater?

Chloride (Cl−), Sodium (Na+), Sulfate (SO4²−), Magnesium (Mg²+), Calcium (Ca²+), and Potassium (K+).

How is salinity measured using electrical conductivity?

A salinometer measures the conductivity of seawater, as dissolved ions conduct electric currents.

What causes lower salinity at the equator?

Heavy precipitation (P>E) in the Intertropical Convergence Zone (ITCZ) dilutes seawater.

What are terrigenous sediments?

Sediments derived from the weathering and erosion of continental rocks, such as sand, silt, and mud.

What are biogenic sediments?

Sediments primarily derived from the hard parts of microscopic plankton, such as calcareous ooze.

What is the significance of the Calcite Compensation Depth (CCD)?

It is the depth below which calcareous sediments dissolve, affecting the distribution of calcareous ooze on the ocean floor.

What role do biological activities play in the geochemical balance of seawater?

Marine organisms extract ions to build shells and skeletons, which eventually settle to the seafloor, affecting the chemical composition of seawater.

What is the process of sublimation in the context of phase changes?

The direct phase change from solid (ice) to vapor, requiring significant energy input.

What is deposition in the context of phase changes?

The direct phase change from vapor to solid, such as frost formation.

What is the steady-state assumption in the context of seawater composition?

The chemical composition of seawater remains relatively constant over long periods because total inputs equal total outputs.

What is the impact of volcanic activity on seawater composition?

Volcanic gases emit elements directly into the atmosphere and ocean, contributing to dissolved salts.

What is hydrothermal activity?

The circulation of seawater through hot volcanic rock at seafloor spreading centers, adding dissolved metals and ions to seawater.

What is the significance of subduction zones in the geochemical balance of seawater?

They recycle sediment and oceanic crust back into Earth's mantle, affecting the overall composition of seawater.

What is the primary distribution of calcareous ooze?

Covers ~40% of the ocean floor on bathymetric highs above the Calcite Compensation Depth (CCD).

Which organisms are primarily responsible for siliceous ooze?

Diatoms (siliceous phytoplankton) and Radiolarians (siliceous zooplankton).

Where does siliceous ooze typically accumulate?

In areas of high biological surface productivity/upwelling, such as the Equatorial Pacific and Southern Ocean around Antarctica.

What are authigenic sediments?

Chemical deposits that precipitate directly from seawater under specific conditions.

Give an example of authigenic sediments.

Polymetallic Iron-Manganese (Fe-Mn) Nodules on abyssal plains.

What are volcanogenic/hydrothermal sediments?

Metalliferous precipitates formed around hydrothermal vents ('black smokers') along spreading centers.

What is the thermocline?

A depth interval (100-1000 m) where water temperature decreases rapidly with depth.

What is the pycnocline?

A depth interval (100-1000 m) where water density increases rapidly with depth.

What characterizes the mixed layer of the ocean?

The warm upper surface layer (10-100 m) homogenized by wind, waves, and surface currents.

How does temperature affect water density?

Warmer water is less dense, while colder water is denser.

What is the significance of Earth's axial tilt?

It causes the seasons as Earth revolves around the Sun.

What is the greenhouse effect?

The trapping of heat in the atmosphere by absorbing outgoing infrared radiation.

What are the three major atmospheric circulation cells in each hemisphere?

Hadley Cell, Ferrel Cell, and Polar Cell.

What is the Coriolis Effect?

The apparent deflection of moving objects caused by Earth's rotation.

How do cyclones rotate in the Northern Hemisphere?

Counter-Clockwise (CCW).

What is the primary cause of interannual climate variability?

Patterns such as ENSO (El Niño Southern Oscillation) that affect long-term climate.

What are trade winds?

Prevailing winds blowing from East to West toward the Equator between 0° and 30° latitude.

What is the role of the polar jet stream?

It separates cold polar air from warm temperate air along the Polar Front (60° N/S).

What happens during the summer solstice in the Northern Hemisphere?

The Northern Hemisphere is tilted toward the Sun, receiving direct sunlight.

What is the significance of the equinoxes?

The Sun is directly over the Equator, resulting in equal hours of daylight and darkness.

What is the formula for calculating the noon sun angle?

Noon Sun Angle = 90° − |Observer Latitude ± Declination Latitude|.

What is the effect of higher salinity on water density?

Higher salinity increases water density.

What defines deep waters in the ocean?

Cold, dense water masses below 1000 m.

What is the typical temperature of deep ocean waters?

Less than 3.5 °C.

What is the relationship between latitude and thermocline presence?

Low latitudes have a strong permanent thermocline; high latitudes have none.

What is the significance of the Hadley Cell?

It describes warm air rising at the Equator and sinking at 30° N/S, creating wet and dry zones.

What type of weather is associated with the Ferrel Cell?

Rainy and stormy conditions at 60° N/S.