Oceans

Oceans

1. Salinity

   • The amount of dissolved salt in the ocean
   • Salinity levels: In warm ocean areas (such as near the equator) where there is little rainfall and much evaporation, the amount of dissolved salts is much greater. In polar regions, the salinity levels are high because temperatures are cold enough for ocean water to freeze. Pure water is removed and salts are left behind.

2. Gases

   • The most abundant gases in ocean water are nitrogen, carbon dioxide and oxygen. The amounts of these elements vary with depth. They are more abundant at the ocean’s surface where sunlight causes more plant life.

3. Temperature

   • Warm water holds less dissolved gas than cold water. When ocean water is cold, like in polar regions, it sinks and carries oxygen rich water to the ocean depths. As a result, fish and other animals can live in deep parts of the ocean.
   • Sun is the major source of heat for the ocean. Motions of the ocean, such as waves and currents, mix the surface water and transfer the heat downward.

4. Zones

   • Surface Zone
     • extends 100 to 400m downwards
     • water is mixed by waves and surface currents
     • temperature changes due to seasons and locations
   • Thermocline
     • the zone of rapid temperature change
     • the depth o f the thermocline is altered by the season and flow of ocean currents
     • exists because warm surface water does not mix easily with colder, denser water - transition zone
   • Deep Zone
     • extremely cold water
     • extends from the bottom of the thermocline to depths of 400m or more
     • The three ocean zones are not found in the polar (Arctic and Antarctica) regions since the surface waters are always cold.
     • Thermohaline Circulation
       • heat and salt. determine the density of water
         • warm water less dense - rises
         • cold water more dense sinks
         • water density also increases with a higher salt content
       • The conveyor that is the Thermohaline circulation system is driven by changes in the density of water as a result of changes in both temperature and salinity. Here’s how this circulation pattern works: Warm water in a shallow current near the surface moves toward the North Pole near Iceland. As this water reaches the colder polar region, some of it freezes or evaporates, leaving behind the salt that was dissolved in it. The resulting water is colder and has more salt per volume than it did before (and thus is more dense).
         • The cold, dense, salty water sinks deeper into the ocean and moves to the south, as far as Antarctica. After it makes its way near Antarctica, the cold, deep current splits, one branch moving up toward India into the Indian Ocean and the other continuing along Antarctica into the Pacific Ocean. The warm, shallow, less dense surface current moves to the west, across the Pacific Ocean, and into the Indian Ocean, where it re-joins the Indian Ocean branch. Both branches then continue into the Atlantic Ocean and head back toward the North Pole.
           • Each branch of the cold, deep current is eventually warmed in the Indian Ocean or the northern part of the Pacific Ocean. Although the water still contains the same amount of salt, it’s a little less dense because it’s warmer than the cold water surrounding it; as a result, it moves upward, becoming a surface current.

5. Gulf Stream

   • south-east trade winds drive warm surface water to the north-west into the gulf of mexico where it heats up to 30dc.
     • the turning of the earth and the west winds direct the gulf stream towards europe and split it up.
       • one part flows south, one part east to the canary current and a third part to the north where it releases a lot of heat into the atmosphere as the north alantic current.
         • the water becomes colder there. its salt and density content rise on account of the evaporation there and it drops down between greenland, iceland and norway

6. mixing and upwelling in the ocean, transport nutrient rich waters to the ocean's surface

7. El Nino and La Nina

8. Eddy - circular moving body of water that spins off a main current.

9. coriolis effect

   • The observed effect of the Coriolis force, especially the deflection of an object moving above the earth, rightward in the northern hemisphere and leftward in the southern hemisphere.
     • Many of the ocean's largest currents circulate around warm, high pressure areas called gyres. Though the circulation is not as significant as that in the air, the deflection caused by the Coriolis effect is what creates the spiraling pattern in these gyres.
       • These major spirals of ocean-circling currents are called “gyres” and occur north and south of the equator. They do not occur at the equator, where the Coriolis effect is not present.

10. Pycnocline is a layer within the water column where water density changes rapidly with depth.

11. Carbon cycle

    • Living things in the ocean move carbon from the atmosphere into surface waters then down into the deeper ocean and eventually into sediment and rocks. This action of organisms moving carbon in one direction is often called a biological pump.
      • Carbon gets incorporated into marine organisms as organic matter or structural calcium carbonate. When organisms die, their dead cells, shells and other parts sink into deep water. Decay releases carbon dioxide into this deep water.
        • The solute CO2 is pulled into the ocean depths along with the sinking surface water, and stays “sunk” until the deeper water naturally returns to the surface in the future (upwellings).
    • The physical carbon pump is most efficient in colder sea water. This is because the colder water can absorb more CO2 and because it is denser than warmer water. The physical pump is dragging CO2 down with the sinking water to the deep ocean layer
      • The solute CO2 is pulled into the ocean depths along with the sinking surface water, and stays “sunk” until the deeper water naturally returns to the surface in the future (upwellings).