48 terms

Chapter 3

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hydrogen bond
weak bonds between water molecules that result from an attraction between the hydrogen atoms of one molecule and the oxygen atoms of adjacent molecules
evaporation
The escape of molecules from the liquid phase into the gaseous phase, or vapor.
crystal
A solid that consists of a regular pat- tern of molecules.
latent heat of melting
The amount of heat energy needed to melt a substance, that is, to change it from a solid to a liquid.
heat capacity
The amount of heat that must be added to a substance to raise its temperature by a given amount, which reflects the sub- stance's ability to store heat.
latent heat of evaporation
The amount of heat energy needed to melt a substance, that is, to change it from a solid to a liquid.
evaporative cooling
The lower speed and hence lower temperature of molecules remain- ing in the liquid phase after evaporation of the fastest molecules.
salt
A substance that consists of ions that have opposite electrical charges.
ions
An atom or a group of atoms that is electrically charged.
dissociation
The breaking up of a salt molecule into ions when placed in water or other solvents.
weathering
The physical and chemical breakdown of rocks.
hydrothermal vent
A deep-sea hot spring where heated seawater forces its way up through the crust.
salinity
The total amount of salts dissolved in seawater. It is generally expressed in parts per thousand (‰).
practical salinity units (psu)
A measure- ment of seawater salinity based on electrical conductivity, numerically equivalent to parts per thousand.
profile
A graph that shows changes in temperature, salinity, or any other parameter with depth.
water column
The vertical column of seawater that extends from the surface to the bottom.
gas exchange
The movement of oxygen and other gases between the atmosphere and the ocean, or between the water or atmosphere and living organisms, in which case it is often called respiratory exchange.
Pressure
The weight exerted over a unit area of surface. This is equal to 1 atmosphere (14.7 lb per square inch) at the sea surface and 1 atmosphere plus the pressure exerted by the water column, which is 1 atmosphere per 10 m (33 ft) of depth.
Coriolis effect
The tendency of objects moving large distances on the earth's surface to bend to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
Trade winds
Steady winds that blow from east to west toward the Equator, replacing the hot air that rises at the Equator.
Westerlies
The winds that blow from west to east at middle latitudes.
Polar easterlies
Variable winds that blow at high latitudes.
Ekman spiral
The spiral change in the movement of water in the water column when the water is pushed by wind. The Ekman layer is that part of the water column affected by wind; Ekman transport is the net water movement 90 from the wind direction.
Equatorial currents
Major ocean currents that move parallel to the Equator.
Gyre
A large, nearly circular system of wind-driven surface currents that center around latitude 30 in both hemispheres.
Surface layer
The upper layer of water that is mixed by wind, waves, and currents.
Mixed layer
See surface layer.
Thermocline
A zone in the water column that shows a sudden change in temperature with depth. The main thermocline is the zone where the temperature change marks the transition between the warm surface water and the cold deep water.
Intermediate layer
Of the three main layers of the ocean, the one below the surface, or mixed, layer. It includes the main thermocline.
Main thermocline
A zone in the water column that shows a sudden change in temperature with depth. The main thermocline is the zone where the temperature change marks the transition between the warm surface water and the cold deep water.
Deep and Bottom layers
The deepest and coldest of the three layers of the ocean.
Downwelling
The sinking of surface water that is denser than underlying water layers.
Overturn
The sinking of surface water that is denser than underlying water layers.
Water mass
A body of water that can be identified by its temperature and salinity.
Thermohaline circulation
Ocean circulation that is driven by differences in water density, due to variations in water temperature and salinity, rather than by the wind or tides.
The Great Ocean Conveyor
A global circulation pattern in which water cycles throughout the ocean basins.
Wave
The undulation that forms as a disturbance moves along the surface of the water. Waves can be described by their height (the vertical distance between wave crest and trough), wavelength (the horizontal distance between adjacent crests), and period (the time the wave takes to move past a given point).
Fetch
The span of the sea surface over which the wind blows to form wind-driven waves.
Sea
A wave that has a sharp peak and a relatively flat wave trough. Seas are found in areas where waves are generated by the wind.
Swell
A wave with a flatter, rounded wave crest and trough. Swells are found away from the area where waves are generated by the wind.
Surf
A wave that becomes so high and steep as it approaches the shoreline that it breaks.
Tidal range
The difference in water level
between successive high and low tides.
tide The periodic, rhythmic rise and fall of the
sea surface.
Spring tides
The tides with a large tidal range; they occur around the times of full or new moon. Compare neap tides.
Neap tides
The tides with a small tidal range.
They occur around the times when the moon is in quarter. Compare spring tides.
Semidiurnal tide
A tidal pattern with two high and two low tides each day.
septa The thin tissue partitions in the polyp of anthozoans.
Mixed semidiurnal tide
A tidal pattern with two successive high tides of different heights each day.
Diurnal tide
A tidal pattern with a high and a low tide each day.
Tide table
A table that gives the predicted time and height of tides for particular points along a coast.