About Density, Temperature, Salinity, Mixed Layer, and Dissolved Oxygen in the Ocean

Density of a sea is distributed along with horizontal pressure gradients and ocean currents, while it is influenced by temperature and salinity. Temperature and salinity of a sea are influenced by evaporation, precipitation, melting of sea ice, and heat fluxes which can also calculate the density of the ocean. They can be interpreted by a graph of temperature based on depth of a sea, it shows there is an extreme change of temperature on the area of the surface of sea. This happens because of the radiation of the sun and could also lead to severe changes in salinity and density of the sea.

            Salinity is the total amount of dissolved material in grams in one kilogram of sea water. Salinity extend from 34.6 to 34.8 ppt and the unit has no dimension. Salinity is allocated into surface salinity which varies from 33 to 37 ppt, upper layer salinity which influenced by temperature than density, and deep water salinity which has an average from 34.6 to 34.9 ppt. In an open ocean, the salinity varies at 0.5 ppt annualy. Measuring salinity is calculated on chlorinity or conductivity of the sea.

            Temperature is allocated into three different layers such as surface temperature which has low temperature in coastal area as a cause of upwelling, upper layer and thermocline which has severe decreasing temperature on the thermocline, and deep water layer which is increasing in temperature because of the pressure. In the upper layer, temperature varies about 1-2 K in the equator and 5-10K in 40° lattitude.

            Ocean mixed layer is a 10-200m thick layer which take place on tropical and mid-lattitude where temperature and salinity must be constant. Ocean mixed layer created as wind blows the ocean and stirs the upper layer at the surface of the sea. In a mixed layer, depth and temperature varies in response to heat fluxes and turbulences. When evaporation exceeds precipitation, mixed layer is becoming saltier than the thermocline as it happens in 10° to 40° lattitude, but it is fresher in high lattitude because of rain and ice melting.

Review on Dissolved Oxygen

            Dissolved oxygen is an amount of oxygen dissolved in a body of water such as a lake, river, or stream. Dissolved oxygen is the most important indicator of the health of a water body and its capacity to support a balanced aquatic ecosystem of plants and animals. Wastewater containing organic pollutants depletes the dissolved oxygen and may lead to the death of marine organisms. Dissolved oxygen comes from the air through the plant and slowly diffuse across the water’s surface so it is mixed through aeration caused by wind or a man-made air pump.