The constant and dynamic movement of the ocean is more intense and visible on the surface. Waves, tides and surface currents promote the mixing of ocean waters, which has effects on life in the seas. The currents and the waves are influenced by the winds. The winds in turn are influenced by the heat generated by the sun. Marine currents carry large amounts of water and energy in the form of heat, so they influence the distribution of salinity and temperature. As a result, the climate and water productivity are affected.
Physical Properties of Saltwater
- Saltwater has unique properties that distinguish it from other fluids. Within the most important physical properties are its specific high heat, its slight conduction of heat and the great capacity of dissolution. To a large extent these properties depend on temperature, salinity and pressure.
- The average temperature of the ocean is approximately 17.5 ° C. The maximum temperature is 36 ° C in the Red Sea and the minimum temperature is – 2 ° C in the Weddell Sea in Antarctica. The temperature distribution of the waters depends on the solar radiation and the mixing of the bodies of water in the ocean.
- The warm surface waters transmit heat to the nearby waters below them forming a productivity zone, approximately 200-400 m. At 1000-1800 m the temperature decreases gradually and under 1800 m the water remains cold.
- The salinity of the water surface depends largely on evaporation and precipitation. In tropical areas where evaporation is greater than precipitation we are higher salinity water (> 35 0 / 00 ). In coastal regions, freshwater flows near the mouths of rivers and salinity generally does not exceed 15-20 0 / 00 .. In areas of the poles, the process of freezing and melting ice exerts greater influence On the salinity of surface waters. In the Arctic summer, we find the lowest salinity (~ 29 0 / 00 ).
- The average ocean salinity is 35 0 / 00 but may vary depending on the season, latitude and depth. Overall, temperature and salinity affect water density. In turn, density affects many other parameters such as mixing processes of different masses of water and sound transmission. Stratified water prevents the mixing of surface water with water from the depth, while low stratified water favors mixing.
Formation of Marine Currents
They are water movements that occur inside the sea. They can be deep currents due to changes in temperature, salinity and density, or surface currents due to the action of the wind.
In the drawing you can see the different temperatures of the oceans. The blue and green colors are cold waters, while the yellow and red colors correspond to the warmer waters.
They are movements of masses of water within the ocean. The origin of these is in the solar radiation and in the redistribution of the heat that yields to the Earth.
The movement of the currents depends on the wind and the density of the water, conditioned by the ocean topography, the distribution of continents and the rotational rotation of the Earth.
Two types of currents can be distinguished:
They are produced by the wind and influenced by the distribution of the continents and the terrestrial rotation.
In the Northern Hemisphere they move round in a clockwise direction. In the southern hemisphere they move in a circular fashion in an anti-clockwise direction.
Winds that blow westward move these currents in that direction, allowing cold, deep waters with a great amount of nutrients to ascend. These zones constitute Outcrops . They are very rich in fishing, the most important being on the coasts of Peru and California, in America and on the coasts of the Sahara, Kalahari and Namibia, in Africa.
They are produced by density differences generated by differences in temperature or salinity. That is why these currents are known as thermohalines . They are affected by the topography of the ocean floor and the rotation of the Earth.
In the North Atlantic a stream of cold and very saline water, the arctic current, is generated. It sinks deep moving south.
After the equator at 60 ° south latitude, the current rises to be pushed by another still cooler current, the Antarctic current. This current flows northward through the Atlantic, Indian and Pacific Ocean.
The movement of these currents is very slow of 2 to 40 cm / s being able to have a direction opposite to the surface currents.
As the deep currents increases, outcrops occur.
Effect of active water movement on energy
and nutrient in Xeniids
Xeniids (ZEE need ids) do a certain exercise nearly 24 hours a day, a voluntary movement unlike any other oceanic creature in existence. What they do is they wave their arms in the air, slowly yet gently connecting their fingertips together until it forms almost a clasp, like a person wringing their hands together. Then they go back and back in again, doing this over and over in less than ten seconds per up and down motion. Over in Jerusalem, Israel these creatures are affectionately called “Amazing Pulsating Carpets” by Maya Kremian at Hebrew University who has discovered a reason the corals won’t stop moving. Why? In one word:
Every time they move they mix with the water bringing in water filled with rich nutrients while at the same time ridding itself of too much oxygen. In a sense it is similar us to how us humans breathe in and out. Over in Townsville, Australia at the Institute of Marine Science, Katherina Fabricius believes it’s “great to see the mystery solved” because she and her staff “have wondered why it has pulsated for decades” and like other scientists who couldn’t be more thrilled she is ecstatic as to why coral exercise the way they do since Xeniids are the only ones who do this particular kind of exercise, especially for the ocean.
As every scientist knows, photosynthesis is when water and carbon dioxide are transformed by light into food, which is key to coral survival. However, it is the algae within them that does this and in thanks they give a share of the production to their hosts, whether they realize it or not. Single-celled algae that are found in corals, namely Xeniids, photosynthesize like we see in our land bound green plants, but according to Kremien’s team these pulsating corals seem to receive all their sustenance from Zeniids.
Because Xeniidsrequire oxygen for even photosynthesis to work these scientists at both the Hebrew University and at the Institute of Marine Science discovered that if you have too much of a good thing, oxygen, it can destroy the photosynthesis process. Algae have to photosynthesize to allow the coral to survive, but if there is too much oxygen then the amount of carbon dioxide it can use is limited. But Kremian and her people say that to bring carbon-dioxide rich water the Xeniid corals need to get rid of the unused oxygen via their pulsing swishes. That solely relies, however, only if there was too much oxygen, and unfortunately that is unpredictable.
The scientists were dubious, to say the least, and the only way they were able to be sure of this was if they tested the Xeniids themselves, so they put them into water tanks, and sure enough the swishing of water not only allowed an excess of high levels oxygen to be removed by the Xeniids. Unlike corals exposed to average oxygen levels photosynthesis in these Xeniid corals slowed down to a crawl. The conclusion? Swishing actually brings in more food for the corals