Marine Science: Physics and Chemistry of Seawater

Vocabulary flashcards covering key terms and concepts from the lecture on the physics and chemistry of seawater.

Chemical Nature of Water

One of the five major factors that determine seawater behavior, referring to water’s molecular structure and polarity.

Temperature (of seawater)

A measure of the speed of molecules in a mass; higher speed equals higher temperature.

Salinity

Total amount of salt dissolved in seawater, expressed in parts per thousand (ppt).

Clarity (Transparency)

How much light can pass through water; affected by dissolved and suspended matter.

Pressure (in seawater)

Force exerted per unit area, increasing 1 atmosphere every 10 m (33 ft) of depth.

Water Molecule (H₂O)

Two hydrogen atoms and one oxygen atom joined by polar covalent bonds.

Polar Covalent Bond

A bond resulting in unequal charge distribution within the water molecule.

State (Phase) of Matter

Solid, liquid, or gas; water exists in all three naturally on Earth.

Polar Compound

A molecule with oppositely charged ends; water’s hydrogen side is + and oxygen side –.

Adhesion

Water’s tendency to stick to other substances.

Cohesion

Water molecules’ tendency to stick to each other.

Capillarity

Water’s ability to climb narrow tubes against gravity due to adhesion and cohesion.

Surface Tension

Membrane-like skin on water’s surface caused by cohesion, supporting light objects.

Specific Heat (of water)

Amount of heat needed to raise water’s temperature slightly; water’s is very high.

Heat of Vaporization

Large heat required to convert water to vapor, helping keep lakes from drying.

Heat of Fusion

Large heat that must be removed to freeze water, protecting aquatic life.

Density (of seawater)

Mass per unit volume; increases as temperature decreases or salinity increases.

Anomalous Expansion of Water

Below 3.8 °C water expands, making ice less dense so it floats.

Universal Solvent

Water’s ability to dissolve more substances than any other natural liquid.

Ion

Electrically charged particle that bonds to oppositely charged ions in salts.

Dissociation (of salts)

Process where ionic compounds fall apart in water as ions become surrounded by water molecules.

Rule of Constant Proportions

Relative amounts of major ions in seawater remain the same regardless of salinity.

Precipitation

Addition of pure water to the ocean, lowering salinity.

Evaporation

Removal of pure water as vapor, increasing salinity.

Reversing Thermometer

Traditional device used to measure temperature at depth.

Niskin Bottle

Sampling bottle formerly used to collect water at specific depths.

Electronic Probe/Sensor

Modern instrument that measures temperature, salinity, and other parameters electronically.

Gas Exchange

Process by which O₂, CO₂, and N₂ move between seawater and the atmosphere.

Turbidity

Amount of suspended and dissolved matter in water; inverse of clarity.

Secchi Disk

Circular plate lowered to measure water transparency.

Atmospheric Pressure

14.7 lb in⁻² at sea level; baseline of one atmosphere.

Water Column

Imaginary vertical shaft of water from surface to bottom used for measurements.

Coriolis Effect

Deflection of large-scale motions due to Earth’s rotation—right in Northern, left in Southern Hemisphere.

Trade Winds

Steady winds blowing toward the equator in the tropics.

Horse Latitudes

Unsteady winds at ~30° N & S where descending air creates calm zones.

Polar Easterlies

Cold winds that blow from the poles toward lower latitudes.

Ekman Spiral

Progressive deflection of water layers, causing surface currents to move ~45° from the wind.

Fetch

Distance over which wind blows uninterrupted, influencing wave height.

Wavelength

Horizontal distance between successive wave crests.

Wave Height

Vertical distance from trough to crest.

Trough

Lowest point of a wave.

Crest

Highest point of a wave.

Seas

Waves under direct influence of the wind; chaotic in shape.

Swells

Waves that have traveled away from the wind area; smooth and regular.

Surf

Waves that steepen and topple as they interact with the seafloor.

Tsunami

Seismic sea wave generated by underwater disturbances.

Tide

Regular rising and falling of sea level driven mainly by the Moon and Sun.

Tidal Range

Vertical difference between successive high and low tides.

Spring Tide

Greatest tidal range occurring when Earth, Moon, and Sun align.

Neap Tide

Lowest tidal range occurring when Moon and Sun are at right angles.

Semidiurnal Tide

Pattern with two equal high and two equal low tides daily.

Mixed Semidiurnal Tide

Two daily high tides of different heights.

Diurnal Tide

One high and one low tide each day.

Profile (Oceanographic)

Graph showing how a characteristic (e.g., temperature) varies with depth.

Thermocline

Layer where temperature changes rapidly with depth.

Halocline

Layer where salinity changes rapidly with depth.

Pycnocline

Layer where density changes rapidly with depth.

Surface Layer (Mixed Layer)

Upper ocean layer (~100–200 m) churned by wind.

Intermediate Layer

Zone below mixed layer to ~1500 m that contains the main thermocline.

Deep & Bottom Layers

Water masses from ~1500 m to the seafloor, cold and dense.

Heat Distributors

Atmospheric circulation and ocean currents that move heat globally.