|Photographer:||K. Watson [View profile]||Title:||SIGMA T||Added:||Jun 10, 2009|
|Research vessel SIGMA T underway in the Narrows,Halifax,Nova Scotia.Sigma T is attached to the Bedford Institute of Oceanography and is used primarally for seawater sampling and measurement/analysis in coastal waters.
The vessels name is derived from the following:
The density of a material is given in units of mass per unit volume and expressed in kilograms per cubic metre in the SI system of units. In oceanography the density of seawater has been expressed historically in grams per cubic centimetre. The density of seawater is a function of temperature, salinity, and pressure. Because oceanographers require density measurements to be accurate to the fifth decimal place, manipulation of the data requires writing many numbers to record each measurement. Also, the pressure effect can be neglected in many instances by using potential temperature. These two factors led oceanographers to adopt a density unit called sigma-t (σt). This value is obtained by subtracting 1.0 from the density and multiplying the remainder by 1,000. The σt has no units and is an abbreviated density of seawater controlled by salinity and temperature only.
Photographed at Halifax on June 4th 2009.
© Capnken 2009.