Relationship between salinity and density of seawater

The Ocean and Temperature -

relationship between salinity and density of seawater

The new density–salinity relation may be used to verify the constant .. coefficients of empirical correlations between salinity and (relative). Brought to you by the National Earth Science Teachers Association · Sun This is a simple density-depth ocean water profile. Increasing salinity also increases the density of sea water. There are not walls between more. The content and activity in this topic will work towards building an understanding of how salinity and temperature differences affect the density and buoyancy of.

Direct microscopic counts and cultures were used, the direct counts in some cases showing up to 10 times that obtained from cultures. These differences were attributed to the occurrence of bacteria in aggregates, selective effects of the culture media, and the presence of inactive cells.

Seawater - Wikipedia

A marked reduction in bacterial culture numbers was noted below the thermoclinebut not by direct microscopic observation. Large numbers of spirilli -like forms were seen by microscope but not under cultivation. The disparity in numbers obtained by the two methods is well known in this and other fields.

This revealed a far greater diversity than previously suspected, so that a litre of seawater may hold more than 20, species. Mitchell Sogin from the Marine Biological Laboratory feels that "the number of different kinds of bacteria in the oceans could eclipse five to 10 million. Density One principle of physics is that material that is less dense will rise, while material that is more dense will sink. This principle applies to water.

Water that is more dense will sink to the ocean floor. As this happens, less dense water has to move out of the way. The less dense water rises.

This process creates a circular pattern known as a convection current.

The Ocean and Temperature

Temperature Temperature really is a measure of energy. The greater the energy, the higher the temperature. When temperatures are high, the atoms in matter become "excited" from the energy and start to expand.

relationship between salinity and density of seawater

Molecules, which are made up of atoms, also expand in this way. As density increases, the amount of salts in the water—also known as salinity, increases. Various events can contribute to change in the density of seawater. Salinity can decrease from the melting of polar ice or increase from the freezing of polar ice. Evaporation increases salinity and density while the addition of freshwater decreases salinity and density.

The Mississippi delta The ocean water is constantly churning underneath, bringing nutrients up to the top.

Exploring Our Fluid Earth

The difference in density of cold water versus density of warmer water is responsible for ocean currents and upwelling. This slightly heavier density is another contributing factor to upwelling as it causes the water molecules to roll over each other. Salinity is usually 35 ppt parts per thousandbut can range from ppt and is highest in the northern Red Sea.

The Red Sea When the temperature, density or salinity of a layer changes rapidly, this region is referred to as a cline. Thermoclines, or areas of rapid change in temperature, familiar to most people who enjoy swimming in the ocean, are the most important due to their effect on planktonic ecosystems and primary producers.

Areas of rapid change in density are pycnoclines and areas of rapid change in salinity are haloclines. Thermoclines occur a short distance offshore when the shallow surface water is heated by the sun, resulting in warm, less dense, water staying at the surface and the sinking of cold, dense water. A seasonal thermocline is formed when surface water is cooled, and sinks to the bottom resulting in a mixing of the layers.

relationship between salinity and density of seawater

The approaching cool weather impacts primary production in the euphotic zone by cooling the surface water and bringing phytoplankton with nutrients to the creatures below. Shorter days and lower angles of sunlight limit the growth rate of the phytoplankton, which in turn limits the primary production and growth rate of organisms higher on the food chain. The waters turn from blue to green as the increase in the number of phytoplankton dissolving inorganic nutrients causes an increase in chlorophyll biomass.

Herbivorous zooplankton biomass also begins to increase, providing food for an entire food web above that depend on the energy they provide. During the summer, the phytoplankton absorb most of the dissolved inorganic nutrients from the surface waters and are consumed by the zooplankton, decreasing the rate of photosynthesis. Vertical mixing ceases and phytoplankton, which remain in the upper layers, become nutrient-limited.

The cycle starts all over in the fall when the surface water cools, churning the deeper, nutrient-rich waters into the depleted surface waters.