Heat and salt budgets, Ocean deposits | Oceanography | Principle Of Geography

 

Oceanography

Principle Of Geography

Geography Complete Study Material

(Paper - I)

Heat and Salt budgets, Ocean deposits

Heat budgets

         This section deals with the spatial and vertical variations of temperature in various oceans. Ocean waters get heated up by the solar energy just as land. The process of heating and cooling of the oceanic water is slower than land.

Factors Affecting Heat Distribution 

           The factors which affect the distribution of Heat of ocean water are :

(i) Latitude : the Heat of surface water decreases from the equator towards the poles because the amount of insolation decreases poleward. 

(ii) Unequal distribution of land and water : the oceans in the northern hemisphere receive more heat due to their contact with larger extent of land than the oceans in the southern hemisphere. 

(iii) Prevailing wind : the winds blowing from the land towards the oceans drive warm surface water away form the coast resulting in the upwelling of cold water from below. It results into the longitudinal variation in the temperature. Contrary to this, the onshore winds pile up warm water near the coast and this raises the Heat.

(iv) Ocean currents : warm ocean currents raise the temperature in cold areas while the cold currents decrease the temperature in warm ocean areas. Gulf stream (warm current) raises the temperature near the eastern coast of North America and the West Coast of Europe while the Labrador current (cold current) lowers the temperature near the north-east coast of North America.

        All these factors influence the Heat of the ocean currents locally. The enclosed seas in the low latitudes record relatively higher temperature than the open seas; whereas the enclosed seas in the high latitudes have lower temperature than the open seas.

Salt budgets

          Total salt in the ocean water remains the same over a larger duration is called the Salt Budget of the ocean. Rainwater is generally acidic in nature and erodes the rocks. Salt from rocks came out and get dissolved in the surface water. Through surface runoff, they reach to ocean. Ocean ridges are also sources of salt for the ocean. Submarine volcanos eruptions. Ocean gets salts from the atmosphere in the form of Dust Salt. Phytoplankton and Zooplankton do contain salt in their body after decomposition they dissolved in the ocean. 

Distribution of Salt

             Surface seawater salinities largely reflect the local balance between evaporation and precipitation. Low salinities occur near the equator due to rain from rising atmospheric circulation. High salinities are typical of the hot dry gyres flanking the equator (20-30 degrees latitude) where atmospheric circulation cells descend. Salinity can also be affected by sea ice formation/melting (e.g. around Antarctica). The surface N. Atlantic is saltier than the surface N. Pacific, making surface water denser in the N. Atlantic at the same temperature and leading to down-welling of water in this region this difference is because on average N. Atlantic is warmer (10.0 C) than N. Pacific (6.7 C). This is mostly because of the greater local heating effect of the Gulf Stream, as compared to the Kuroshio Current. Warmer water evaporates more rapidly, creating a higher residual salt content The influence of surface fluctuations in salinity due to changes in evaporation and precipitation is generally small below 1000 m, where salinities are mostly between about 34.5 and 35.0 at all latitudes. Zones where salinity decreases with depth are typically found occur at low latitudes and mid latitudes, between the mixed surface layer and the deep ocean. These zones are known as haloclines. The spatial distribution of salinity across oceans, is studied in two ways:

• Horizontal Distribution of Salinity
• Vertical Distribution of Salinity

Ocean Deposits

       Ocean deposits are sediments that come from different sources by different means and it settles down on the ocean floor. The following are the sources of Ocean deposits:

• Terrestrial sediments
• Volcanos sediments
• Marine Organism
• Extraterrestrial

Terrestrial sediments:Both biotic and abiotic sediments from continents get accumulated on the continental shelf and slope via river, winds, and wave erosion.

Volcanos sediments:Some oceanic sediments are of volcanic origin that deposit in the ocean directly or indirectly from the air.

Marine Organism:The main sources of Ooze deposits in the deep ocean are dead marine organism that derives from Zooplankton and Phytoplankton.

Extraterrestrial: Sediments from meteorites.

Classification Of  Ocean deposits

           Ocean deposits are sediments that come from different sources by different means and it settles down on the ocean floor.  John Murray has classified ocean deposits into two broad categories based on the settlement locations.

• Terrigenous deposits
• Pelagic Deposits

Terrigenous Deposits:The Deposits which are mainly found on the Continental shelf are called Terrigenous deposits. The main sources of Terrigenous deposits are terrestrial sediments. 

• Boulders, sand, gravel, rocks, and mud are major components of these deposits.
• Marine Fossil fuel is also present in the ocean deposit on the continental shelf

Pelagic Deposits:Pelagic deposits are comprised of both organic and inorganic sediments and are generally found in the deep oceans in the continental slope, continental rise, trenches, and abyssal plains. Pelagic Deposits are generally two types:

• Mud
• Ooze