Oceanography (2+1)

Temperature and Thermal properties of sea water

The mean temperature of seawater is low, roughly 75% of the ocean's volume has a temperature from 0° – 5°C (Pinet 1996). The same percentage falls in a salinity range between 34–35 ppt (3.4–3.5%) (Pinet 1996). There is still quite a bit of variation, however. Surface temperatures can range from below freezing near the poles to 35°C in tropical seas .The vertical structure of the temperature can be divided into three basic layers, a surface mixed layer , where gradients are low, a thermocline where gradients are high, and a poorly stratified abyssal layer which are poorely statified.

Temperature,in the ocean's layers are highly latitude dependent. The thermocline is pronounced in the tropics and the, but nonexistent in polar waters (Marshak 2001). The Thermocline usually lies near the surface, where evaporation raises salinity in the tropics, or meltwater dilutes it in polar regions. These variations of salinity and temperature with respect to  depth change the density of the seawater, creating the pycnocline .

Surface water temperature of the ocean as a whole ranges from -2⁰C to 35⁰c.  Temperature is highest along the equator because of the warming of the earth in the tropics and the sea generally becomes cooler along the poles. At the sea surface the temperature changes with latitude.

 Potential temperature θ is calculated by correlating the adiabatic compression at a given depth and is more important than in situation temperature. The temperature of deep sample when brought to surface reduces to range at about 0.1 to 0.2⁰C and this called potential temperature and it will be slightly cooler than the temperature at depth called the in situation temperature.

 The distribution of temperature in the ocean controls the distribution of marine organisms and density of seawater. Because of the greater heat capacity of water the surface temperature of the sea varies far less than land temperature. Consequently the sea provides a better stable environment for marine life and a moderating influence on the coastal climate.

Thermal properties of seawater

Ocean can absorb great amount of solar heat during the day without undergoing drastic change in temperature. Oceans can supply enormous quantity of thermal energy to the atmosphere in the form of vapour and rain is formed due to condensation of water vapour on coaling.

Seawater never freeze due to high latent energy of fusion. The Ocean acts as a reservoir of heat energy that becomes neither hot in the summer nor cold in winter. A thermal gradient exists between the ocean and atmosphere. The ocean exchange heat energy with the atmosphere rapidly,and as a result heat in the ocean and the air temperature are thermostatiscally controlled.