Oceanographic profile data are data collected at one location - one geographic coordinate - in the vertical, typically from the sea surface to some subsurface depth, in some cases to just above the ocean bottom.
Profiles are often collected from a ship which stopped at that location to collect the profile. Those stops are called stations, and so the word station is sometimes used instead of profile, although it is not necessary to make a station stop to obtain a profile: for example eXpendable BathyThermograph - 'XBT' - temperature vs. depth profiles are often collected from moving ships, or even from airplanes and submarines.
Two principal types of profile data from oceanographic stations are bottle data and CTD data.
Many seawater characteristics cannot be sampled, or sampled at high enough quality, by electronic sensors.
Bottle data originate from water sample bottles attached to a lowered wire or group-mounted on a frame (called a “rosette” water sampler) attached to a lowered wire, which are closed at chosen levels, isolating water samples then subsampled shipboard for various parameters such as salinity, dissolved oxygen (or other dissolved gasses), dissolved inorganic nutrients, or many other substances.
From one water bottle brought up from the deep, subsamples can be drawn for many different seawater characteristics.
Physical oceanographers have found that it is useful to obtain water samples for determination of dissolved oxygen concentration and the concentrations of the inorganic 'nutrients' nitrate (NO3), phosphate (PO4), and silicate (SiO3). Beginning primarily in the 1970s global measurements of other natural and anthropogenic dissolved substances began to be feasible and useful, for example components of the CO2 system, radiocarbon, helium, tritium, and, beginning in the 1980s, CFCs.
CTD data originate from semi-continuous sampling electronic profilers, which are lowered into the ocean, recording output typically from pressure, conductivity, temperature sensors, and sometimes other sensors as well.
The sensors in a CTD provide measurements of conductivity, temperature, and pressure. The salinity profile from a CTD is calculated from C, T, and P by a computer. A non-ocean-experienced engineer might call the instrument a 'CTP' for what it measures, or an 'STP' for the parameters in its processed data stream, but oceanographers use the traditional designation 'CTD'.
For convenience, oceanographers sometimes (in informal non-research publications) interchange the words 'depth' and 'pressure' due to the similarity of depth expressed in meters and pressure expressed in decibars.
Oceanographers rarely use conductivity data themselves in ocean water mass and circulation studies because the vertical variation of conductivity is a strong function of temperature and pressure. By using the calculated property 'salinity' the oceanographer has a valuable parameter whose values are essentially independent of pressure and temperature.
Most modern bottle data include data parameters from the CTD sensors recorded at the time the bottle was closed. An oceanographic section is composed of a series of profiles/stations across an oceanographic region or feature. Oceanographers most often use sections from single ship transects, called quasi-synoptic sections, but useful sections may also be pieced together from various data.