GLOSSARY - Introduction to the Physical and Biological Oceanography of Shelf Seas - page 378

functional type because of their role in
cycling silicate; cyanobacteria are a
single type because of their role in
regenerated production and their lower
importance to the export of carbon.
Other functional types include the nitrogen
fixers (e.g. Trichodesmium), the
calcifiers (e.g. coccolithophores) and the
flagellates (which might include the
dinoflagellates).
potential energy anomaly A measure of the
stability of the water column defined as the
difference between the potential energy
(per unit volume) of the water column
after, and before, complete vertical mixing.
practical salinity scale

regenerated production Primary production
that utilises inorganic carbon and nutrients
which have been recycled by bacteria
within the surface layer. Regenerated
production tends to be carried out by small
phytoplankton, particularly the
cyanobacteria. It does not result in any net
drawdown of CO 2 from the atmosphere.
Region Of Freshwater Influence (ROFI)
Coastal region where the input of
buoyancy through freshwater discharge
from rivers is comparable to buoyancy
changes due to surface heating and cooling
in the seasonal cycle.
residual circulation The net movement of
water as a result of the combined effects of
different forces (e.g. wind, tides, density
gradients). Residual circulation is generally
seen as a long-term averaged flow, filtering
out the often much stronger oscillatory
tidal flows and episodic wind-driven
currents.
resonance Enhanced response of a
mechanical system which occurs when the
system experiences forcing at one of its
natural frequencies of oscillation. Tidal
resonance can occur, for example, in a gulf
whose natural period is close to that of tide
in the adjacent ocean.
Reynolds number Re Ratio of inertial forces
(mass x accelerations) to viscous forces in
fluid flow. Re is a key parameter in
determining whether a fluid flow will be
laminar or turbulent.
Rossby radius of deformation Ro Scale of
movement involved as a homogeneous
fluid, initially at rest, comes into
geostrophic balance with, for example, an
applied surface slope. Ro is the lengthscale
which controls the seaward extent of a
Kelvin wave travelling along a coastal
boundary.
spring bloom The often dramatic, first flush
of phytoplankton growth after the low
productivity of the winter. The spring
bloom is generally most clearly defined in
shelf areas, away from coastal sources of

Standard scale for
the measurement of salinity based on
simultaneous measurements of the
conductivity, temperature and pressure of
seawater. Salinity is derived from a series of
polynomials using the ratio of the observed
conductivity to an accurate laboratory
standard.
practical salinity unit (psu) Widely used, but
strictly inappropriate, unit, since salinity,
which is derived from a conductivity ratio,
is dimensionless and therefore does not
require units.
progressive wave Wave which moves
through a medium transferring energy as it
travels (as opposed to a standing wave
which does not move and does not involve
energy transfer).
prokaryotes Organisms, usually single-
celled, that lack a cell nucleus. All bacteria
are prokaryotes.
Redfield ratio Named after the

oceanographer Alfred Redfield, this is the
set of molecular ratios between carbon,
nitrogen and phosphorus typically found in
marine organic matter C:N:P ¼ 106:16:1.

reduced gravity Effective value of the

gravitational acceleration in a stratified
fluid when buoyancy effects are taken into
account. For two layers, differing in
density by D r , the value of the reduced
gravity is g 0 ¼ g( D r/r 0 ).