- Pacific-Antarctic Basin
- One of three major basins in the
Southern Ocean. It extends from
its western border with
the Australian-Antarctic Basin
at the longitude of Tasmania (about 145 E) to
its eastern border with the
at the Scotia Ridge and Drake Passage
(about 70 W).
It consists of the
Abyssal Plains and is
separated from the basins further north in the Pacific
by the Pacific-Antarctic Ridge and the East Pacific Rise in the
east and by the Chile rise in the east.
- Pacific Basin Extended Climate Study (PBECS)
- A proposed CLIVAR program to put in place in the
Pacific Ocean a long-term process experiment to test and improve
dynamical models of the ocean processes that participate in climate
Specific program objectives are:
- to obtain a quantitative description of the low-frequency,
three-dimensional circulation and associated thermohaline structure
of the upper Pacific Ocean with sufficient accuracy to measure
advective fluxes and their divergences;
- to test models of this circulation and its intrinsic modes of
variability as well as those due to coupling with the atmosphere; and
- to understand the processes that couple the tropical and
subtropical Pacific oceanic gyres on climatic time scales and to test
hypotheses about the role of the ocean in basin-scale variability on
a broad range of climate time scales.
- Pacific Decadal Oscillation (PDO)
- A long-lived El Niño-like pattern of Pacific climate
variability. The PDO is distinguished from El Niño by two
Two full PDO cycles have been identified for the 20th century.
Cool regimes prevailed from 1890-1924 and again from 1947-1976, while
warm regimes domained from 1925-1946 and from 1977 through at least the
PDO fluctuations are most energetic in the 15-25 year and
50-70 year bands.
The PDO Index is defined as the leading principal component of
North Pacific monthly sea surface temperature variability (poleward
of 20N for the 1900-1993 period).
- 20th century PDO events have persisted for 20 to 30 years, while
typical ENSO events persist for 6 to 19 months; and
- the fingerprints of the PDO are most visible in the North Pacific and
North American sector, with secondary signatures in the tropics, while
the opposite is true for ENSO events.
Large changes in Northeast Pacific ecosystems have been correlated
with PDO phase changes. Warm eras are characterized by increased
coastal ocean productivity in Alaska and inhibited productivity off
the coast of the contiguous U.S., while cold eras show the opposite
See Zhang et al. (1996) and
Mantua et al. (1997).
- Pacific Deep Water (PDW)
- In physical oceanography, a water mass
found in the Pacific Ocean in the depth range
from 1000-3000 m. It does not participate much in the overall
circulation and as such its properties are determined mostly by
slow mixing processes. It is composed of a mixture of
AABW, NADW and
AAIW, and has a characteristic salinity
from 34.60-34.65 and a temperature around 2 C.
It is also has an oxygen minimum and a silica maximum, with the
latter's lateral origin in the northeastern Pacific.
This is separated from the bottom
AABW by a benthic front in the southern and
western North Pacific.
See Tomczak and Godfrey (1994), p. 159.
- Pacific Equatorial Water
- In physical oceanography, the water mass that
occupies the largest volume of the Pacific thermocline waters.
The NPEW and the SPEW are
two varieties of this separated, as one might guess, by the Equator.
They differ in T-S properties above 8 C but merge into a single
curve below this, which reaches T-S combinations showing high salinities
indicative of mixing with deep water.
See Tomczak and Godfrey (1994).
- Pacific High
- A center of action centered off the
coast of Baja, California at about 30 N and 140 W in winter.
It moves northwestward to about 40 N and 150 W and intensifies
in the summer and effectively fills in the Aleutian Low.
See Angell and Korshover (1974).
- Pacific Marine Environmental Laboratory (PMEL)
- A part of the NOAA ERL
network the carries out interdisciplinary scientific investigations
in oceanography, marine meteorology, and related subjects.
See the PMEL Web site.
- Pacific Ocean
- The largest and probably least understood of the world oceans.
Early attempts at synthesizing and charting the currents of the
Pacific are summarized in Peterson et al. (1996).
Wüst published the first modern
(i.e. using his core layer method)
treatise on the deep circulation
of the Pacific in 1929. This treatise, published four years before
his better known work on the Atlantic, outlined the basics of the
deep circulation reasonably well given the poor database with which
he worked. More recent summaries by
Reid (1986), and
Talley (1995) have provided a much more detailed look at
the circulation at all depths, the variability, and the water
masses of the Pacific Ocean.
The surface current structure of the Pacific consists of
(from north to south)
a cyclonic subpolar gyre,
an anticyclonic North Pacific
a cyclonic and very narrow northern tropical
cell including the
North Equatorial Countercurrent (NECC),
the westward flowing
South Equatorial Current (SEC) at and to
the south of the equator,
an anticyclonic subtropical gyre in the South Pacific, and
the Antarctic Circumpolar Current (ACC).
The subropical gyre circulations shrink poleward with increasing
depth in the North and South Pacific.
The western parts of these gyres are C-shaped wherein the
western boundary current has a westward and equatorward recirculation
just equatorward of and east of the boundary current and its
eastward flowing separated extension. This recirculation reconnects
to the eastward flow of the gyre at a lower latitude.
The dominant water masses consist of
(proceeding from the surface downward):
an upper ocean with alternating bands of fresh and saline water directly
influenced by surface exchanges,
relatively fresh intermediate layers in the Antarctic and North Pacific,
Pacific Deep Water (PDW) formed in
the north via upwelling and diffusion which intrudes southward,
Circumpolar Water (CW) intruding
Antarctic Bottom Water (AABW) intruding
The northward spreading CW and AABW are separated from the overlying
PDW by a jump in temperature around 1-2 C associated with
a vertical stability maximum.
- Acronym for PanAmerican Climate Studies, a proposed program in the
1995-2004 time frame directed toward the goal of improving the skill
of operational seasonal-to-interannual climate prediction (with
emphasis on precipitation) over the Americas. It is a sequel to
the NOAA EPOCS program.
PACS includes the process studies
- Acronym for Past Global Changes, an
IGBP Core Project charged with providing
a quantitative understanding of the Earth's past environment
and defining the envelope of natural climate variability within
which we can assess anthropogenic impact on the Earth's biosphere,
geosphere, and atmosphere. PAGES seeks the integration and
intercomparison of ice, ocean, and terrestrial paleorecords and
encourages the creation of consistent analytical and database
methodologies within the paleosciences.
- Acronym for Profiling ALACE float, a float with all of the capabilities
of an ALACE float as well as a longer lifetime
and a CTD profiler to obtain vertical temperature and salinity profiles.
See Davis et al. (2001).
- Acronym for Paleoclimate of Arctic Lakes and Estuaries, an
NSF/ARCSS and PAGES initiative to study the
paleoclimate of arctic lakes and estuaries. The goal is to reconstruct
Arctic climate variations over the past 150,000, 20,000 and 2,000 years
and understand its interation with the global climate. PALE
ended circa 2001 and was expanded to become
- The study of the spatial distribution of ancient organisms, including
analysis of the ecological and historical factors governing this
distribution. In contrast to paleoecology,
most paleobiogeographical studies have dealt with distributions of
individual taxa or with questions of global or
regional provincialism. See Briggs and Crowther (1990), pp. 452-460.
- The science dealing with the fields of evolution, ecology and
the subsequent taphonomy of extinct
animals and plants. See Briggs and Crowther (1990).
- paleocalibration method
- A method for calculating the relationship between paleoclimates and
the future climate. For a given time interval, one obtains both
the difference from present-day globally averaged surface temperature
(DT) and the difference from the present-day globally averaged radiative
forcing (DQ). DT is obtained from whatever geologic proxies
are available. DQ is obtained by calculating or estimating the
total effect of the heat trapped by greenhouse gases and the changes
in absorption of solar radiation due to changes in solar luminosity,
surface albedo and atmospheric aerosol content. Finally, the ratio
DT/DQ is defined as the climate sensitivity, i.e. the global
temperature response to the radiative forcing.
See Covey et al. (1996).
- The branch of limnology that
studies of past fresh water, saline and brackish environments.
This is done in large part by taking cores from a limnological
sediment system and examining the geological, biological and
chemical components preserved in the core.
- The use of various paleoclimate proxy data
to attempt to gauge paleotemperatures.
- The theories of the tidal evolution of the Earth-Moon system show
that the effects of tidal friction
are such that the Moon's motion and the Earth's rotation can
drastically change on geologic time scales.
The theories gained empirical support from the
paleontological studies of skeletal growth increments in fossil
marine invertebrates by
Wells (1963) showing an increasing
number of days per year, days per lunar month, and lunar months
per year going back through the
Models of the evolution of the Earth-Moon system show the Earth
and Moon to have been much closer together in the distant past
with the separation increasing with time.
The first models of the Earth as a phase lagged
ellipsoid with a constant phase lag angle showed the
Earth and Moon to have been close enough together at some point in
the past 2.5 billion years (b.y.) to result in tides 1 km high with
tidal energy sufficient to not only boil off the oceans but also to
melt a part of the Earth and the lunar mantle. It would also have
increased the surface air temperature to 1700 K (via an increased
greenhouse effect due to increased water vapor in the atmosphere)
and eliminated life on Earth.
The complete absence of physical evidence for such an event
led to relaxing the assumption
of a constant phase lag via the incorporation of the effects of continental
drift, i.e. a change in continental configuration will change
the resonance properties of the ocean and the tides and tidal
dissipation therein and therefore the evolution of the Earth-Moon system.
Numerical modeling studies have shown the consolidation of
continents to attenuate/amplify semidiurnal/diurnal oscillations
and the dispersal of continents to have the opposite effect.
The inclusion of this effect leads to a more reasonable scenario
for the Earth-Moon tidal evolution history.
See Kagan and Sündermann (1996).
- A wind of the geological past. The practical geological indicators
of paleowind are several scalar properties (bed thickness, grain size
and sorting, mineral proportions) and directional structures
(dune forms, yardangs
and wind furrows, dune cross-bedding,
windblown trees, wind ripples, adhesion ripples, flues and grooves).
Such an indicator can be an effective paleoclimatic tool only if
it is reasonably common, of high geological preservation potential,
easily recognized and measured, and capable of unique or at least
statistical interpretation. See ().
- Acronym for Peroxyacetyl Nitrate.
- Acronym for Paleoclimates of the Northern and Southern Hemispheres
program, a proposed project of PAGES.
- The Early Mesozoic world ocean.
It was a single ocean reaching from pole to pole, probably
consisting of single southern and northern gyres, deep water
formation at both poles, and slothlike deep-water circulation.
See Bowen (1991).
- Abbreviation for Photosynthetically Available Radiation,
a quantity used in studies of photosynthesis as a measure of
total available light. It is defined as a flux of quanta
rather than energy and is usually considered to be the
total photon flux between 400 and 700 nm (with the lower
limit sometimes moved to 350 nm). This is around
38% of the total extraterrestrial solar irradiance.
PAR is defined, as a function of depth, by
where is Avagadro's constant, is Planck's
constant, the speed of light, the wavelength,
and the irradiance. The units
of PAR are einsteins
per square meter per second, and it is
measured underwater using a device called
a quantum meter.
- parabolic approximation
- See Mei (1990).
- paradox of the plankton
- The long-term coexistence of plankton species that might be expected
to compete. This is due to the degree to which chance encounters
dictate the degree to which intra- or interspecific competition occurs.
This, in turn, is due to plankton be unusually dependent on their
physical environment for support, transport and food.
See Rigby and Milsom (2000).
- Parallel Community Climate Model (PCCM)
- A parallel version of the NCAR
Community Climate Model (CCM2) implemented for MIMD massively
parallel computers using the message passing programming
paradigm. It can be implemented on a massively parallel machine
supporting message passing or across a network of machines with
the PVM software package.
PCCM Web site.
- In numerical modeling, the method of incorporating a process by
representation as a simplified function of some other fully resolved
variables without explicitly considering the details of the
process. The classic example is the representation of
sub-grid scale turbulence as the product of a function of the
velocities at the local grid points and an empirically derived
coefficient (in analogy to the molecular viscosity
coefficient). This analogy has been known to fail. See, for
example, the classic (and wonderfully titled)
monograph of Starr (1968).
The processes that must be parameterized in ocean circulation models,
as summarized by James McWilliams at the
APROPOS meeting in 1998, include:
- effects of surface gravity waves on currents (vortex forces and mean
- turbulent transports within the planetary boundary layers and
entrainment/detrainment at their interior edges (convective plumes,
shear vortices, Langmuir cells);
- interior diapycnal mixing processes (gravity waves, Kelvin-Helmholtz
vortices, double diffusion);
- topographic roughness effects (form stress, gravity wave generation,
local secondary circulations);
- mesocale eddy transports of momentum and tracers, including potential
vorticity (isentropic mixing and mean Lagrangian transport);
- topographic barriers (sills and straits);
- effects of deep convection and its preconditioning (in shallow seas,
over topographic features, in interior regions); and
- transports by gravity currents over sills and off of continental
- Acronym for Paleoenvironmental ARCtic Science, a part of ARCSS program.
The theme is to explore the importance of land-ocean interactions
and the variation in freshwater and chemical fluxes within the total
- Particle and Optics Profiling System (POPS)
- An assembly of instruments designed to count and measure
particles and to determine optical and environmental properties
of water as a function of depth.
The main part of the POPS system is the
Large Aggregate Profiling System (LAPS) package used to
measure particles ranging from 250 microns to several millimeters
It also usually carries an
LISST which measures smaller particles
ranging from one to 250 microns in diameter.
Other instruments found on POPS include
a transmissometer (for measuring particles
less than 20 microns in diameter),
a fluorometer and an
a-c meter (for measuring
LSS (for measuring particle abundance).
- particulate matter
- The suspended particle load that controls the chemistry of
the oceans. The physical and chemical properties of the
particles control how rapidly a chemical species is removed
from solution and incorporated in sediment.
The four main sources of this in the
oceans are: (1) fluvial input of terrigenic material;
(2) aeolian input from wind erosion of continental masses,
volcanism and anthropogenic sources; (3) resuspension of
sedimentary material by current erosion, earthquakes and
slumping; and (4) authigenic production
by biota, submarine volcanism and the precipitation
of inorganic minerals.
See Simpson (1982).
- Acronym for the Patches Experiment, which took place off the California
coast in October 1986.
See Brainerd and Gregg (1993).
- Acronym for Pacific Transport of Heat and Salt, a joint program
among Canada, Japan and the U.S.
See WMO (1983).
- Acronym for
Pacific Basin Extended Climate Study.
- Abbreviation for
planetary boundary layer.
- This is a collection of programs that deal with data pertaining to
the PBL. See the
PBL-LIB Web site.
- Abbreviation for principal component analysis, usually used
synonymously with EOF.
- Abbreviation for Parallel Community Climate Model.
- Abbreviation for Pacific Climate Information System, a comprehensive
information system containing statistical information on rainfall
clmiatology and variation with the ENSO cycle for almost 300 Pacific
- Abbreviation for the Program for Climate Model Diagnosis and
Intercomparison, whose mission is to develop improved methods
and tools for the diagnosis, validation and intercomparison of
global climate models.
- The equilibrium partial pressure of CO2.
- Abbreviation for Polar Continental Shelf Project, a
- Abbreviation for
Pacific Decadal Oscillation.
- Abbreviation for Precision Depth Recorder.
- See Pacific Deep Water.
- Abbreviation for primitive equations.
- Acronym for Pacific ENSO Applications Center,
a NOAA project established to conduct
research and produce information products on climate variability
related to the ENSO climate cycle in the U.S.-affiliated
PEAC Web site.
- Acronym for Paleo Environment and Climate History of the
Russian Arctic, a project whose main purpose is to increase the understanding
of climate changes and the impact these changes have on the environment
in arctic Russian during the last interglacial-glacial cycle.
The goals are:
- reconstruction of the Barents and Kara Ice Sheets through time;
- reconstruction of fauna, vegetation and climate history; and
- reconstruction of the history of human settlement.
- An acoustically tracked velocity profiler.
See Spain et al. (1981).
- Acronym for the Pacific Equatorial Dynamics Experiment.
See Eriksen (1987).
- Peclet number
- A dimensionless number
expressing the ratio of
advection to thermal diffusion.
It is expressed by
where is a velocity scale, a horizontal length scale,
Molecular diffusion of heat is negligible when
In practice, the Peclet number is almost always large except for
extremely small-scale phenomena with low velocities.
This is similar to the Reynolds number
except that the kinematic viscosity
has been replaced by the
thermal diffusivity .
See Kraus and Businger (1994), p. 32.
- Descriptive of organisms that inhabit open water, as opposed
This is sometimes divided into five separate ecological zones
which are, proceeding from the surface to the bottom, the
See Bruun (1957).
- Pelagic Fisheries Research Program (PFRP)
- A research program established in 1992 to provide scientific
information on pelagic fisheries to the Western Pacific Regional
Fishery Management Council (WPRFMC) after the Magnuson Fishery
Conservation and Management Act of 1976 was amended to include
highly migratory fish. It is located at JIMAR
at the University of Hawaii.
- Greek acronym for 'Hydrodynamics and Biogeochemical Fluxes in the Straits
of the Cretan Arc', a project designed to research the hydrodynamics of
the South Aegean Sea and the southeastern
Ionian and northwestern
Levantine Seas, with the aim of investigating
biogeochemical fluxes through the Straits of the Cretan Arc.
The project was launched within the framework of the Mediterranean
Targeted Project (MTP) of the Marine Science and Technology Programme
(MAST) of the European Union (EU), and included scientists from Greek,
British and French institutions.
The National Centre for Marine Research (NCMR) in Athens coordinated the
program during its contracted duration from September 1993 to March 1996.
The study area originally covered the Straits of the Cretan Arc
(Eastern Mediterranean Basin), but was eventually extended further, first
into the South Aegean Sea, and then to the
southeastern Ionian Sea and the
northwestern Levantine Sea.
The field programme of PELAGOS lasted from March 1994 to June 1995, during
which time four major synoptic surveys were
undertaken in the Cretan Sea, the Straits of the Cretan Arc and
adjacent seas (northwestern Levantine and southeastern Ionian). In
addition, four seasonal surveys (for the investigation of specific
variables) were undertaken along a west-east section of the Cretan
Sea. Finally, several short cruises were undertaken in connection
with current meter and sediment trap deployments, recoveries, and
re-deployments. The synoptic cruises were carried out on board R/V
Aegaio for hydrographic, chemical (nutrients, dissolved oxygen)
and biological (phytoplankton, chlorophyll-a, zooplankton)
sampling. The other surveys were directed mainly towards biological and
geochemical sampling, undertaking ADCP measurements, and
the deployment/recovery of current meters and sediment trap moorings.
The primary tasks were the measurement of various physical, chemical,
biological and geochemical parameters; together with the water
circulation controlling their basin-wide distribution and disposition.
Particular emphasis was placed upon the processes across the
Straits of the Cretan Arc and their seasonal time-scales. Hence, expanded
horizontal coverage and dense vertical
sampling/measurement of temperature and salinity was established.
Concurrently, data on nutrients, dissolved oxygen, trace elements
dissolved in seawater and the geochemical characteristics of suspended
particulate matter (SPM) were collected at selected depths, to
enable their subsequent vertical and horizontal integration with the
various water exchanges. The chemical analyses of dissolved trace
elements, together with SPM trace and major elements, were related
mainly to the Straits of the Cretan Arc and along an east-west
section of the Cretan Sea. Self-recording current meters were
deployed within the Straits of the Cretan Arc for a year. These
deployments improved the understanding of the prevailing flow patterns
and controlling mechanisms, together with their variability;
similarly, they permitted the estimation of fluxes of water and
associated (dissolved or suspended) material through the various Straits.
At the same time, moored sediment traps provided independent
(time-series) assessments of the vertical flux of settling particles and
the nature of material deposited in the western Straits
(Antikithira Strait). Size-fractionated chlorophyll-a and primary
determinations were undertaken, to estimate productivity. In
addition, phytoplankton and zooplankton sampling was performed, to obtain
qualitative and quantitative estimations of the aforementioned
parameters and their variability.
See Balopoulos and Collins (2000) and the other papers in Volume 44
of "Progress in Oceanography" for further details.
Project data and results are archived at the
- Acronym for Pole-Equator-Pole, a PAGES
sponsored inter-American paleoenvironmental research program focuses
on the dynamics of transequatorial atmospheric and ocean linkages.
- peristaltic pumping velocity
- See eddy-induced transport velocity.
- permanent thermocline
- A relatively sharp change in temperature (and therefore density)
beneath the seasonal thermocline
maintained by a balance between downward diffusion of heat and
the gradual upwelling of deep, cool water.
- Persey Current
- See Pfirman et al. (1994).
- Persian Gulf
- A marginal sea of the
Indian Ocean centered at
approximately 52 E and 27 N.
It is surrounded by Iran to the north, Kuwait, Saudi Arabia,
Qatar, and the United Arab Emirates to the east and south,
and connects with the
Gulf of Oman (and on into the
Strait of Hormuz
to the east.
It has a length of 990 km, ranges in width from 56 to 338 km,
covers an area of 241,000 km, occupies a volume of
10,000 km, has a mean depth of 40 m, and a maximum
depth of about 170 m.
The circulation features have been well summarized in
RSMAS (2000) as:
The basic features of the Arabian (or Persian) Gulf can be
divided into a northern and southern
or eastern regime. The northern regime is
dominated by wind forcing to the south along
the axis of the Gulf and the riverine input at the Gulf's
head. The wind-driven response of the
Gulf appears to be the typical adjustment of the pressure
field such as to produce a down-wind
flow, i.e. there is downwelling on the western coast
and upwelling on the coast of Iran, and
evidence for a southeastward flowing coastal current
along both the northern and southern
coasts (Reynolds (1993)). The flow along the Kuwait
and Saudi coast is augmented by the
freshwater input from the north which forms a
riverine plume. The river inflows are
approximately split between the flow out of the
Shalat Ariabi (Tigris and Euphrates) and rivers
flowing out of the highland of Iran (the Hendijan,
Hilleh, and Mand). In current times the flow of
the Shalat Ariabi is much smaller than it once was
because of massive dam projects in Turkey.
It is not clear what changes this decline in freshwater
input has made. The center of the
northern Gulf appears to be fairly stagnant (Reynolds (1993)).
end of this regime corresponds roughly to the longitude of
Qatar and Bahrain, although the termination of the
northern circulation is poorly understood.
The flow along the Iran coast seems to
continue into the southeastern basin as a tightly trapped
coastal current extending perhaps as far as the Strait of Hormuz. This flow
becomes very complex in proximity to the island of Jazareh in
the northern portion of the Strait.
The northern Gulf is separated from the southern regime by a
front that typically is found off Qatar. This front is most intense
in summer and weakest, at least in sea surface temperature,
in the late winter and spring. The location of this front appears in both
climatological hydrographic data and remotely sensed SST to
be tied to the penetration of fresh inflow into the Gulf from the Strait of
Hormuz. The available data suggests that much of this inflow may
terminate in a counter-clockwise, cyclonic flow to the east of the
mid-Gulf front. This cyclone appears in circulation climatologies
and appears as a coherent SST anomaly in satellite imagery.
East of this front the available data suggest a flow out of
the Gulf around the tip of the Musandem peninsula and into the northern Gulf
of Oman. The large evaporation over the Gulf leads to an inverse
estuarine circulation with the highly saline waters leaving the Gulf
through the deep part of the Strait of Hormuz and being replaced by
a fresh surface inflow from the Gulf of Aden. The saline bottom
waters that flow out through the Strait may originate from several
locations in the Gulf. Historical salinity data and SST data implicate a
broad region of high salinity waters extending from Qatar eastward
along the Emirate coast. Waters in this
shallow region can reach very high salinities (42 psu) and
appear to form a warm and salty endpoint of the Gulf outflow. The
temperature salinity relationships of the observed outflowing
waters imply a fairly complicated set of water mass modifications in the
Gulf. Colder and somewhat fresher waters are also found in the
deep outflow from the Gulf and suggest another source, probably from
the northern Gulf. Modeling results suggest that some of the
outflow arises from sinking in the shallow high
salinity area off the Emirates, but that further sinking occurs in the vicinity of the variable mid-Gulf front.
The deep water arising from these sources exits the Gulf on the
southern (deepest) side of the Strait of Hormuz at a maximum depth of
100 m. Unlike the Mediterranean or Red Sea the Gulf is
shallow (100 m) and there is no prominent sill to constrain the outflow. The
annual mean outflow of the deep waters and compensating fresh
surface inflow is estimated from the Knudsen relations to be
approximately 0.2 Sv, assuming a mean evaporation rate of
approximately 1.5 m/yr and net
freshwater input from rivers of 0.2 m/yr. Estimates
of the exchange rate from available models span a range from 0.1
Sv to nearly 0.4 Sv.
Seasonal variability of the deep outflow and surface inflow is not clearly
established, although recent measurements
suggest that the deep outflow may be fairly steady throughout the
See Elliot and Savidge (1990),
Flagg and Kim (1998),
Bower et al. (2000) and
- Peru-Chile Countercurrent (PCCC)
- One of two branches into which the Pacific
Equatorial Undercurrent (EUC)
splits when it encounters the Galapagos Islands.
The Poleward Undercurrent (PUC)
is one branch, while the other branch flows to the southeast of the
Islands and approaches the coast at about 6-7S to form the
Tongues of minimum phosphate distributions and surface drifters have
been used to identify this current.
According to Strub et al. (1998):
Evidence for the location and variability of the Peru-Chile Countercurrent
is less conclusive, especially off Chile.
It is better documented off Peru, where it appears 200 m offshore in
mean sections at 10S.
South of 15S is was originally thought to flow straight south
along approximately 75-77W.
More recently, three years of satellite altimetry data show a continuous
band of poleward currents 100-300 km from the coast that extend from
approximately 8-35S, following the coastline.
The poleward currents in the altimeter data are maximum in austral
spring and minimum in fall.
See Strub et al. (1998).
- Peru-Chile Undercurrent
- Another name for the
Poleward Undercurrent (PUC).
- Peru Coastal Current (PCC)
- According to Strub et al. (1998) ...
... water mass properties suggest that the equatorward surface flow
[of the current] is strongest in austral winter, when equatorward
winds are maximum. It carries colder and saltier upwelled water
to the north in the equatorial cold tongue, characteristic of
the South Equatorial Current (SEC).
Its confluence with the warm and fresh water moving southward out of
the Panama Bight creates the strong Equatorial Front (EF). Low
temperatures in the cold tongue are maintained by upwelling along
the equator and the extent of the cold tongue is maximum at the
end of austral winter (September-October). In austral spring and
summer, the cold tongue collapses back toward the coast as the
trade winds weaken in the eastern equatorial Pacific. At this
time the Equatorial Front is unpredictable, weak or absent and
a warm tongue extends southwest along an offshore region from the
equator to northern and central Chile, which may be related to the
Peru-Chile Countercurrent (PCCC).
This and the
Chile Coastal Current (CCC) are
together sometimes referred to as the
Inshore Peru Current.
See Strub et al. (1998).
- Peru Current
- A component of the eastern limb of the
counterclockwise-flowing southern subtropical
gyre in the Pacific Ocean. The flow rate has been estimated
at around 15 Sv, although variations from this can be
considerable. This current is part of the most impressive
upwelling system in the oceans,
with the upwelling driven by prevailing winds from the east
that push the surface water westward, allowing the cold, nutrient-rich
water beneath to well to the surface. Without the upwelling, this
current lowers the temperatures along South America several
degrees belows the zonal average, and the upwelling serves to
lower the temperatures without about 100 km of the coast another
2 to 4 C. The nutrient content of the upwelled water makes
this region the most productive upwelling region in the world
ocean, although a combination of overfishing and the effects of
the El Nino phenomenon put an end to
what was the largest fishery in the world before 1973.
The southern part of the Peru Current is sometimes called the
Other names used for the entire current have been
Humboldt Current and
Oceanic Peru Current.
See Tomczak and Godfrey (1994).
- Peterson grab
- A type of bottom sampler used in biological oceanography to
for the quantitative investigation of
benthic organisms in relatively
shallow waters. It comprises a set of heavy hinged jaws
that are held open during descent but are released when
the device hits bottom. The jaws close on an area of
benthic material (usually around 0.1 m2) when the cable
is drawn tight and the device returned to the surface.
The organisms thus caught are screened from the bottom
sediments, classifed and counted to develop statistics for
organisms per square meter in the study area.
See Sverdrup et al. (1942).
- Pettersson, Hans
- Head of the
Swedish Deep Sea Expedition
and son of Otto Pettersson.
See Guberlet (1964).
- Pettersson, Otto
- A Swedish chemist and physical oceanographer who organized many
of the earliest cooperative cruises in Scandanavian waters and
promoted the idea of what would become the ICES.
See Schlee (1973) and
- Acronym for Baltic Sea Patchiness Experiment, an
ICES investigation which took place
in the Gotland Basin during April through May in 1986 under
the leadership of B. Dybern. The basic objective of the
experiment was to study the heterogeneous and patchiness
in the distribution of physical, chemical and biological
properties in the region. Almost all of the Baltic Sea
countries contributed to a total of 15 research vessels
used in this experiment.
- Abbreviation for Polar Front.
- Abbreviation for
Pelagic Fisheries Research Program.
- Abbreviation for
Polar Frontal Zone.
- Descriptive of a heterotrophic
phytoplankton species that feeds
on phytoplankton or detritus.
- Philippine Sea
- See Qu et al. (1998).
- Phleger Bottom Sampler
- A bottom sampler used for quantitative studies of foraminifera,
designed to take a short core of the upper sediment layers
without disturbing the surface layer.
This sampler, first used in 1951, is a short weighted tube with
a removable lining tube and a replaceable cutting edge. The
liner is a clear plastic tube with a diameter of 3.5 cm.
It can be operated with a light winch in depths up to
500 m when weighted with 35-40 pounds of molded lead, and
to depths of 4600 m in more cohesive sediments.
See Hedgpeth (1957b).
- Phosphorus is an essential nutrient
used by all organisms for energy transport and growth.
One of the most important aspects of the phosphorous cycle is its
role in governing productivity, thereby acting with the exogenic
part of the carbon cycle.
Known P oceanic sources are:
The known P sinks are:
- rivers, the predominant source, with a total estimated flux of
mol P yr;
- aeolian deposition, with an estimated flux of
mol P yr; and
- volcanic emissions, a more local and intermittent source.
- biological uptake and incorporation into sinking particulate
organic matter, the predominant sink, is estimated to have a total
flux of 2.8-3.1
mol P yr;
- absorption onto the surface of shells via iron oxyhydroxide
coatings, estimated to be 4.0-5.3
mol P yr;
- the burial of phosphorites, estimated to be
mol P yr; and
- hydrothermal processes, estimated at
mol P yr.
The global marine inventory of dissolved P is about 3.2
mol P, with the residence time relative to the known P sources estimated
to be 20,000 to 80,000 years. The residence time relative to the known
sinks is thought to be less than 10,000 years, down from previous estimates
as high as 80,000 years as the role of coastal regimes and phosphorite
deposits as sinks have become better understood.
See Föllmi (1996) and
- photic zone
- See euphotic zone.
- The process in plants by which carbon dioxide
is converted into organic compounds using the energy of light
absorbed by chlorophyll, which in all plants except some bacteria
involves the production of oxygen from water.
- Descriptive of
a phytoplankton species that lives
primarily by photosynthesis.
- The study of algae, especially
seaweeds. This is also called
algology. Professional organizations for phycologists are the
Phycological Society of America and the
British Phycological Society.
- Physical Oceanographic Real-Time System (PORTS)
- An information acquisition and dissemination technology developed
by the NOS that supports safe adn cost-efficient
navigation by providing ship masters and pilots with accurate real-time
information required to avoid groundings and collisions.
PORTS provides real-time water levels, currents, and other
oceanographic and meteorological data from bays and harbors to the
maritime user community in a variety of formats.
It also provides nowcasts and predictions of these parameters
via the use of numerical circulation models.
- physical oceanography
- The study of physical conditions and physical processes within the
ocean, especially the motions and physical properties of the ocean.
This is usually further divided into the activities of
descriptive and theoretical oceanography, the former being
concerned with observing the oceans to prepare
maps of the spatial and temporal variations of its properties,
and the latter with constructing theoretical models to attempt
to explain the observations. As in most natural sciences, most
significant advances are the result of the interaction between
theory and observation.
Physical oceanography is not a pure but an applied science in which
the knowledge of many disciplines is relevant,
e.g. fluid mechanics,
optics (optical oceanography),
acoustics (acoustical oceanography),
thermodynamics and, especially in the age of satellites,
This is one of four sub-fields into which the general field
has been divided, the others
- That part of the benthos
consisting of plant life.
- One of two groups into which plankton
are divided, the other being
Phytoplankton comprise all the freely floating photosynthetic
forms in the oceans, i.e. they are
free-floating microscopic plants which, having little mobility,
are distributed by ocean currents.
Most marine phytoplankton
are found in one of five Phyla:
See Johnson (1957) and Riley and Chester (1971).
- Abbreviation for particulate inorganic carbon.
- Abbreviation for North Pacific Marine Science Organization, whose
purpose is to promote and coordinate marine scientific research in
order to advance scientific knowledge of the living resources in
the North Pacific. It was founded in 1992 and the members now
include Canada, Japan, the People's Republic of China, the USA,
the Russian Federation and the Republic of Korea. This is sort
of a version of the ICES but for the
North Pacific rather than the North Atlantic.
- Acronym for Production Induite en Zone de Convergence par les
Ondes Longues, a program to attempt to understand how a heavy
catch of tun occurs in a region considered biologically poor
although prone to tropical instability waves.
- Acronym for Pilot Study for Intensive Data Collection and Analysis
of Precipitation, a component study of
The objectives are:
- to collection and analyze measured and estimated precipitation from
different data sources;
- to compare different precipitation data sets against each other to
identify and establish reliable standards for model validation;
- to validate the output of BALTEX Regional Models against such
data sets; and
- to deveop, test and establish necessary data management and analysis
- Pierson, Willard
- More later.
- Pierson-Moskowitz spectrum
- A wave spectrum devised for fully
developed wind waves in an open sea.
This method assumes that both duration and fetch are large enough
to permit an equilibrium state between the mean wind, turbulence and
waves. If this is true, then all other variables are determined
by the wind speed.
It can be expressed as
is the frequency of the spectral peak, is gravitational
acceleration, the wind speed, and the wave frequency
considered. That is, if the spectral peak is known, then the spectrum and
the energy content of the wave field are determined.
See Pierson and Moskowitz (1964).
- Abbreviation for Particulate Inorganic Matter.
- Abbreviation for principal interaction patterns, a method of
reducing the complexity of a full covariance matrix by combining
an EOF-type pattern expansion in the spatial domain with an
ARMA-type dynamical modeling approach in the time domain.
This technique is useful for constructing simple dynamical
models for forecasting or diagnostic purposes and as an
approximate multivariate spectral compression technique.
See Hasselmann (1988) and Hasselmann (1993).
- Acronym for Program for International Polar Oceans Research.
- Acronym for Polar Ice Prediction System.
- Acronym for Pilot Research Moored Array in the Tropical Atlantic,
a plan for an observing system to support tropical Atlantic climate
studies from 1997-2001. PIRATA will install and maintain an array
of 12 moored ATLAS buoys as part of a multinational effort involving
Brazil, France and the U.S.
It consists of 12 ATLAS moorings spanning along the equator and
two meridional lines. This configuration was chosen to provide
coverage along the region of regions of strong wind forcing in the
western basin and significant seasonal to interannual variability
in SST in the central and eastern basin.
The meridional arrays cover the regions of high SST variability
associated with the SST dipole mode.
The purpose of PIRATA is to remedy the crucial lack of oceanic
and atmospheric data in the tropical Atlantic. The scientific
A pilot phase
is proposed for 1997-2000 to be followed, if successful, by a
long-term operational system to monitor the area maintained by
GOOS and GCOS.
- to provide an improved description of the
seasonal-to-interannual variability in the upper ocean and at
the air-sea interface,
- to improve understanding of the relative
contributions of the different components of the surface heat flux
and ocean dynamics to the seasonal and interannual variability of
SST within the tropical Atlantic basin,
- to provide a data set
that can be used to develop and improve predictive models of the
coupled Atlantic climate system,
- to design, deploy, operate and maintain a pilot array of moored
buoys similar to those used during the TOGA
program in the tropical Pacific; and
- to collect and transmit via satellite in real-time a set of oceanic
and atmospheric data to monitor and study the upper ocean and atmosphere
of the tropical Atlantic.
- piston velocity
- The velocity with which gas diffuses across the air-sea interface
stagnant film model.
It is proportional to the molecular diffusivity of the gas in
sea water and inversely proportional to the thickness of the
stagnant film across which it travels.
The piston velocity has been found to be a function of the
Schmidt number, with different
dependencies at high and low wind speeds. The velocity
is also a function of wind speed, increasing
nonlinearly with wind speed and having a greater sensitivity to wind
changes at higher wind speeds, with the change in sensivity occurring
fairly abruptly at around 10 m/s. Due to the variability of real
winds and this variable sensitivity, the piston velocity at the
average wind speed will be lower than the average piston velocity.
The general functional form of the piston velocity is usually taken
where is the Schmidt number and the wind speed.
This is also occasionally known as the transfer velocity.
See Najjar (1991).
- Abbreviation for
Polar Intermediate Water.
- planetary boundary layer
- A generic term for either
oceanic boundary layer (OBL) or
atmospheric boundary layer
These layers are fundamentally turbulent and extend from near the
surface to the boundary layer depth or height, defined as the
limit to which boundary layer eddies can penetrate in the vertical.
- planetary geostrophic equations
- A set of filtered equations in which the advection of momentum is
neglected in the momentum equations, i.e. the inertia-gravity wave modes
have been filtered out.
Their use in inappropriate for anything but large-scale, i.e.
Unlike the quasi-geostrophic equations, these do allow large
variations in both the Coriolis parameter
and layer depth.
These were first developed by
Robinson and Stommel (1959) and Welander (1959).
They can be expressed in spherical coordinates
(following Muller (1995)) as
where is the mean radius of the Earth,
are polar coordinates where is longitude,
latitude and radial distance,
is specific volume,
are the velocity components,
is the variation of the density from a reference state,
is the reference density,
is the variation of the pressure from a reference state,
is the vertical component of the
planetary vorticity vector, and
is the beta parameter, i.e.
The first equation is the density equation, a prognostic equation governing
the dynamical evolution of the flow. The other equations are diagnostic
relations. Another prognostic equation can be found by first
decomposing the pressure
where the first part is the barotropic component due to the
displacement of the surface, and the second the baroclinic
component due to density fluctuations.
The evolution of the baroclinic part is governed by the density equation,
and the barotropic part by the kinematic surface boundary condition, i.e.
at in the planetary geostrophic limit.
This is usually converted to an equation for the mass transport stream
function since lateral boundary conditions are simpler for the
stream function than for surface displacement.
The planetary geostrophic equations are usually used in their
steady-state form to study the
See Hasselmann (1982) and Muller (1995) for further
details of the equations and their derivation.
- planetary vorticity
- See vorticity.
- One of three major ecological groups into which marine
organisms are divided, the other two being the
nekton and the
benthos. Plankton are
small aquatic organisms (animals and plants) that, generally having no
locomotive organs, drift with the currents.
The animals in this category include
small crustaceans, and the larval stages of larger
organisms while plant forms are mainly diatoms.
- Marine organisms associated with the water surface or the
uppermost water layer that possess special adaptations allowing
them to passively float there.
This term was originally used in freshwater biology to refer
to microscopic plants and animals associated with the surface
film and supported by surface tension, but it is now also
used by marine biologists to describe organisms found in the
upper 100 meters of the ocean.
Pleuston was historically used especially by Soviet scientists,
with their western counterparts more likely to group the
pleuston in with the neuston.
See Cheng (1975).
- Convective elements that carry fluid particles vertically over
distances comparable to the depth of the ocean.
The horizontal scale is about 1 km, and they are driven by intense
cooling at the sea surface that reaches 1000 W m.
They are ascending and descending currents that can reach speeds
in excess of 10 cm s.
Plumes penetrate most of the water column and efficiently homogenize
its properties, forming deep, cold mixed layers called
The chimneys are maintained close to neutrality, geostrophically
adjust, and break up into fragments called
cones on a time scale of a few days.
The cones have a spatial scale of several kilometers.
See Jones and Marshall (1993).
- Plum Island Sound
- See Vallino and Hopkinson Jr. (1998).
- Abbreviation for
Pacific Marine Environmental Laboratory.