marine biology vocab for exam 1

Convergent tectonic boundaries

plates collide/move towards each other

Divergent tectonic boundaries

plates move apart from each other = creates new oceanic crust (eg: Mid-Atlantic Ridge) 

CTD

instrument used by oceanographers in which measures conductivity, temperature, and depth (pressure) of seawater

Ekman Spiral

 the consequence rotation pattern in the upper layers of the ocean

Ekman Layer

total depth of the frictional influence of the wind

Ekman Drift

• mean current across the Ekman layer

• strongly influenced by the thickness of the mixed layer

• largely dependent on the time of year and wind speed

Ekman Transport

the volume of water transported by the Ekman drift

Bathymetry

The study of underwater depth of lake or ocean floors.

Continental shelf

The part of the ocean floor bordering the continents at a depth of 200 m or less below the sea surface.

Continental slope

The part of the ocean floor extending from the edge of the continental shelf to the start of the continental rise. The continental slope has an average gradient of around 4deg.

Abyssal plane

The flat part of the ocean floor that lies between about 4 and 6 km below the sea surface.

Hydrothermal vent

Fissures on the seafloor out of which flows water that has been heated by underlying magma.

Constancy of composition

The principle for seawater that, although the concentration of dissolved salts can vary from place to place, the relative proportions of the ions remains virtually constant.

Stratification

Where water masses with different properties of salinity, oxygenation, density and temperature form layers that act as barriers to water mixing.

 Albedo

The reflection coefficient of a surface - the fraction of the amount of incoming radiation that is reflected from a surface. (measure of how much incoming radiation a surface reflects → eg: low albedo (dark surfaces, like the ocean) most of solar radiation is absorbed to heat surface)

 Isohalines

Contour line joining points of equal salinity either on maps or in vertical sections.

Wind-mixed layer

Surface water that has been mixed by the wind to create a layer with uniform physical properties. (locations where winds are stronger the mixed layer can be up to 200m thick // after the mixed layer both temp. and salinity decrease = permanent thermocline)

 Eddy viscosity

 Internal friction between the molecules of a liquid that transfers momentum.

Permanent thermocline

The region beneath the mixed layer where temperature decreases with depth.

 Isotherms

Contours of constant temperature.

 Gyre

 A large-scale circulatory feature of the ocean circulation, usually extending across many thousands of kilometers.

Water mass

A very large volume of water with uniform temperature, salinity and, therefore, density.

Salt rejection

A process that occurs during sea ice formation where salt is pushed from forming ice into the surrounding seawater, increasing the salt concentration there.

Mid-Atlantic Ridge

underwater mountain ranges formed by tectonic plates pulling apart, a peak rising from abyssal planes & North-South suboceanic ridge in the Atlantic Ocean from Iceland to Antarctica