Salinity is the saltiness or amount of salt dissolved in a body of water, called saline water. It is usually measured in g/L or g/kg.
Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5%. This means that every kilogram of seawater has approximately 35 grams (1.2 oz) of dissolved salts. Average density at the surface is 1.025 kg/l. Seawater is denser than both fresh water and pure water because the dissolved salts increase the mass by a larger proportion than the volume. In comparison, most human physiological saline levels are approximately one quarter of this, for example blood is 9g/l. The freezing point of seawater decreases as salt concentration increases. At typical salinity, it freezes at about −2 °C (28 °F). The coldest seawater still in the liquid state ever recorded was found in 2010, in a stream under an Antarctic glacier: the measured temperature was −2.6 °C (27.3 °F). Seawater pH is typically limited to a range between 7.5 and 8.4. However, there is no universally accepted reference pH-scale for seawater and the difference between measurements based on different reference scales may be up to 0.14 units.
Thermohaline circulation (THC) is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, factors which together determine the density of sea water. Wind-driven surface currents travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes. This dense water then flows into the ocean basins. While the bulk of it upwells in the Southern Ocean, the oldest waters upwell in the North Pacific. Extensive mixing therefore takes place between the ocean basins, reducing differences between them and making the Earth's oceans a global system. The water in these circuits transport both energy and mass around the globe. As such, the state of the circulation has a large impact on the climate of the Earth.
Argo is an international program that uses profiling floats to observe temperature, salinity, currents, and, recently, bio-optical properties in the Earth's oceans; it has been operational since the early 2000s. The real-time data it provides is used in climate and oceanographic research. A special research interest is to quantify the ocean heat content (OHC).
In oceanography, a halocline is a cline, a subtype of chemocline caused by a strong, vertical salinity gradient within a body of water. Because salinity affects the density of seawater, it can play a role in its vertical stratification. Increasing salinity by one kg/m3 results in an increase of seawater density of around 0.7 kg/m3.
An acoustic Doppler current profiler (ADCP) is a hydroacoustic current meter similar to a sonar, used to measure water current velocities over a depth range using the Doppler effect of sound waves scattered back from particles within the water column. The term ADCP is a generic term for all acoustic current profilers, although the abbreviation originates from an instrument series introduced by RD Instruments in the 1980s. The working frequencies range of ADCPs range from 38 kHz to several Megahertz. The device used in the air for wind speed profiling using sound is known as SODAR and works with the same underlying principles.
The oceanic or limnological mixed layer is a layer in which active turbulence has homogenized some range of depths. The surface mixed layer is a layer where this turbulence is generated by winds, surface heat fluxes, or processes such as evaporation or sea ice formation which result in an increase in salinity. The atmospheric mixed layer is a zone having nearly constant potential temperature and specific humidity with height. The depth of the atmospheric mixed layer is known as the mixing height. Turbulence typically plays a role in the formation of fluid mixed layers.
The World Ocean Circulation Experiment (WOCE) was a component of the international World Climate Research Program, and aimed to establish the role of the World Ocean in the Earth's climate system. WOCE's field phase ran between 1990 and 1998, and was followed by an analysis and modeling phase that ran until 2002. When the WOCE was conceived, there were three main motivations for its creation. The first of these is the inadequate coverage of the World Ocean, specifically in the Southern Hemisphere. Data was also much more sparse during the winter months than the summer months, and there was—and still to some extent—a critical need for data covering all seasons. Secondly, the data that did exist was not initially collected for studying ocean circulation and was not well suited for model comparison. Lastly, there were concerns involving the accuracy and reliability of some measurements. The WOCE was meant to address these problems by providing new data collected in ways designed to "meet the needs of global circulation models for climate prediction."
Aquarius was a NASA instrument aboard the Argentine SAC-D spacecraft. Its mission was to measure global sea surface salinity to better predict future climate conditions.
A drifter is an oceanographic device floating on the surface to investigate ocean currents and other parameters like temperature or salinity. Modern drifters are typically tracked by satellite, often GPS. They are sometimes called Lagrangian drifters since the location of the measurements they make moves with the flow. A major user of drifters is the Global Drifter Program.
The following are considered essential ocean climate variables by the Ocean Observations Panel for Climate (OOPC) that are currently feasible with current observational systems.
Note: This page refers to the device used to measure the speed of sound in water for use in hydrography
The Barrier layer in the ocean is a layer of water separating the well-mixed surface layer from the thermocline.
CORA is a global oceanographic temperature and salinity dataset produced and maintained by the French institute IFREMER. Most of those data are real-time data coming from different types of platforms such as research vessels, profilers, underwater gliders, drifting buoys, moored buoys, sea mammals and ships of opportunity.
The Tropical Atmosphere Ocean (TAO) project is a major international effort that instrumented the entire tropical Pacific Ocean with approximately 70 deep ocean moorings. The development of the TAO array in 1985 was motivated by the 1982-1983 El Niño event and ultimately designed for the study of year-to-year climate variations related to El Niño and the Southern Oscillation (ENSO). Led by the TAO Project Office of the Pacific Marine Environmental Laboratory (PMEL), the full array of 70 moorings was completed in 1994.
The Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) is a system of moored observation buoys in the Indian Ocean that collects meteorological and oceanographic data. The data collected by RAMA will greatly enhance the ability of scientists to understand climatic events and predict monsoon events. Climatic and oceanic events in the Indian Ocean affect weather and climate throughout the rest of the world, so RAMA will support weather forecasting and climate research worldwide. Although widely supported internationally, the system has only been partially implemented due to pirate activity off the coast of Somalia.
A float is an oceanographic instrument platform used for making subsurface measurements in the ocean without the need for a ship, propeller, or a person operating it. Floats measure the physical and chemical aspects of the ocean in detail, such as measuring the direction and speed of water or the temperature and salinity. A float will descend to a predetermined depth where it will be neutrally buoyant. Once a certain amount of time has passed, most floats will rise back to the surface by increasing its buoyancy so it can transmit the data it collected to a satellite. A float can collect data while it is neutrally buoyant or moving through the water column. Often, floats are treated as disposable, as the expense of recovering them from remote areas of the ocean is prohibitive; when the batteries fail, a float ceases to function, and drifts at depth until it runs aground or floods and sinks. In other cases, floats are deployed for a short time and recovered.
Regional Ocean Modeling System (ROMS) is a free-surface, terrain-following, primitive equations ocean model widely used by the scientific community for a diverse range of applications. The model is developed and supported by researchers at the Rutgers University, University of California Los Angeles and contributors worldwide.
The Global Drifter Program (GDP), was conceived by Prof. Peter Niiler, with the objective of collecting measurements of surface ocean currents, sea surface temperature and sea-level atmospheric pressure using drifters. It is the principal component of the Global Surface Drifting Buoy Array, a branch of NOAA's Global Ocean Observations and a scientific project of the Data Buoy Cooperation Panel (DBCP). The project originated in February 1979 as part of the TOGA/Equatorial Pacific Ocean Circulation Experiment (EPOCS) and the first large-scale deployment of drifters was in 1988 with the goal of mapping the tropical Pacific Ocean's surface circulation. The current goal of the project is to use 1250 satellite-tracked surface drifting buoys to make accurate and globally dense in-situ observations of mixed layer currents, sea surface temperature, atmospheric pressure, winds and salinity, and to create a system to process the data. Horizontal transports in the oceanic mixed layer measured by the GDP are relevant to biological and chemical processes as well as physical ones.
The Haline contraction coefficient i.e., β, is a coefficient that describes the change in density in the ocean due to the salinity change, while the potential temperature and the pressure are kept constant. It is a parameter in the Equation Of State (EOS) of the ocean. In literature, β is also described as the saline contraction coefficient and is measured in [kg]/[g] in the equation of seawater (EOS) that describes the ocean. An example is the TEOS-10. This is the Thermodynamic equation of state.
