Oceanography Mid-Term
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- Continental shelf. This the edge of the continent, which is always flooded or swampy, and it is still shallow. Geologically, the continental shelf is the continental crust which is overlaid with the sediments of the marine.The continental shelf is also defined by scientists and geologists as part of the margin of the continent, which is found between the shore and the point where the shelf breaks. It is also known as the slope of the continent, which is not noticeable, and it is between the shore of the sea to the depth of say,100-200 meters.
Continental slope, it is the steeper margin of the continental crust that proceeds from the seafloor to the deeper part of the ocean. Continental slopes are areas of sharply sloping seafloor that is between the continent shelf and the ocean basin; it also shows the equilibrium between the sediments deposited or eroded. The steep slopes encourage sediment gravity processes.
Continental rise.at the end of the steep, the crust of the ocean joins the continental crust. The point at which the two meets is the continental rise. This layer of rise is made of sediments from the continent.
- The following are the two ways used by the oceanographers to map the bathymetry of the ocean;
a). Satellite altimetry. In this mapping method, satellites are employed in measuring the accurate distances, or the heights of various surfaces of the sea, and the differences in height are noted for mapping.
To calculate the terrain of the sea floor to an accuracy of 0.03 meters, two very accurate distance dimensions must be made. First, the distance of the target above the ellipsoid is measured by tracking the satellite from a geographically dispersed beam and Doppler system. Using dynamic orbit equations, the path and altitude of satellites are also optimized. Second, this satellite’s position above the nearest sea surface is determined by a microwave sensor functioning inside a pulse-limited area.
b). Multi-beam sonar. This method uses the technic of multiple echoes sounds to map the narrow parts of the ocean floor. Scientific ocean vessels with high accuracy are used in this method.
- The rule of constant proportionsstates that ”although the salinity of various seawater samples may vary, the ratio of major salts is constant.’’
The rule of constant has helped scientists appreciate that the difference in seawater’s salinity is due to the amount of freshwater added or removed and no difference in salt; it is also necessary to estimate salinity and tracing the mixing of water masses in the ocean.
- a) Carbon dioxide depth profile.
- b) oxygen gas depth profile.
- c) phosphate gas (nutrient) depth profile.
- Ocean acidificationis triggered by the dissolution of atmospheric carbon dioxide gas into the ocean water.
Ocean acidification lowers the Ph of the ocean water, making it more acidic.
Ocean acidification diminishes carbonate in the ocean water resulting in difficulty developing shells and skeletons in sea organisms.
- Ekman transportis the resultant motion of water due to the balance between Coriolis and turbulent strain forces. It is the movement of floating particles on the sea due to the dragging force that it contains. It has structures filled with air that also tends to aid it in floating.
Sargassum is a large brown seaweed that floats on water; it looks like an island when floating. Sargassum is found in abundance in the ocean; if you carefully observe the sea, you are likely to see a sizeable leafy attachment with branches and structures that looks like berries.in most cases, these berry-like parts which seen are gas-filled, particularly with oxygen gas. These gas-filled structures of the plant make it buoyant hence it floats on the surface of the sea. These floating heaps of the sea Sargassum can always spread over a wide area on the sea.
Sargassum is critical in the sea ecosystem because, as it floats, it provides a living place for some sea animals such as fishes and others.
When sargassum becomes old, it loses its ability to float; hence, it sinks to the sea’s bottom where it decomposes.
- The physical characteristics used in defining water masses are pressure, temperature, and salinity. In contrast, the chemical properties used in identifying water mass are; dissolved magnesium, sulfate, calcium, potassium, and gases such as nitrogen, oxygen, and carbon dioxide.
From the diagram of the major currents drawn, the following are the currents represented;
1). Norwegian current
2). East Greenland current
3). Labrador current
4). North Atlantic drift
5). canaries’ current
6). Gulf stream
7). Florida current
8). Antilles current
The following factors influence the direction of flow of currents in an ocean;
a). Global winds wind causes waves typically on the water’s surface, making water currents move in the wind flow direction. Due to the blowing of winds, the force always tends to pull superficial water in its order; this phenomenon ends up creating water currents. As the currents drift to the west, the Coriolis effect deflects them, making the currents bend towards the right, hence heading northwards. Winds can either be global or local winds. The difference between the two is that the global wind always moves in the same direction making it one of the factors influencing how the sun causes heating in various parts of the earth.
b). The Coriolis effect. It affects the ocean’s current by causing a colossal wind that eventually moves in a circular pattern. Therefore, the Coriolis effect results in the bending of the direction of sea currents towards the right in the polar hemisphere and then finally southwards. The Coriolis effect, thus, results in the circular movement of winds and currents in the sea.
Coriolis effect is validated by using a ball and a spinning plate. when the ball is spinning, it will move in a circular path just like the water particles in the current will move when the earth is rotating
c). The shape of the ocean basins. The shape of the ocean affects the currents of the sea. When the current from the sea strikes the land, the collision will change the current direction.
- The primary Physical properties of seawater, such as temperature and salinity, affects its density; similarly, the density is also affected by chemical properties like the dissolved chemicals such as magnesium and sulfur.
The two sites of deep water formation are;
a). North Atlantic deep water (NADW), deep water is formed in this site due to the mixing of water from the gulf stream and that from the Norwegian sea.
b). Antarctic bottom water (AABW), here the deep water is formed due to the sinking of icy water.
- The major requirements for the primary production to take place in the ocean are; the levels of carbon dioxide in the water, the temperature of the water, the availability of nutrients, the amount of solar energy, and levels of moisture.
These requirements are necessary for biological processes such as the process of photosynthesis to take place to produce primary nutrients for the organisms living in the water.
From the given requirements of primary production, it is clear that the production is higher in areas receiving optimum levels of these requirements. But it is lower in areas with a deficiency of the requirements. For example, the sea area that receives direct sunlight and experiences other nutrients’ availability will have the highest rate of primary production compared with other regions.
References
Clams, G. (2017). Oceanography and Marine Biology. Oceanography and marine biology: an annual review, 55, 2-303.
Gibson, R. N., Atkinson, R. J. A., & Gordon, J. D. (Eds.). (2017). Oceanography and marine biology: an annual review (Vol. 45). CRC press.
Hughes, R. N., Hughes, D. J., & Smith, I. P. (Eds.). (2013). Oceanography and marine biology: an annual review (Vol. 51). CRC Press.
Thurman, H. V., & Burton, E. A. (1997). Introductory oceanography. New York: Prentice-Hall.