SLOs: ocean layers, composition, and properties, tides, waves and islands.
The oceans are divided up into layers according to the variable characteristics of depth. The predominant layers identified by oceanographers (scientists who study the ocean) are the mixing zone at the surface layer, the transition zone at the thermocline layer, and the deep cold zone at the bottom layer. The mixing zone takes up the smallest volume of world-wide ocean water and is generally warmer and more mobile than the other layers. The transition zone is a an area between the surface and bottom layers that is both cooler and less mobile than the surface layer; the temperature gradient changes rapidly with depth in this column of water. The deep cold zone makes up the majority of the ocean's water volume and, as the name indicates, is generally much colder than the above layers. The reasons for the presence of these layers are better explained by the chemical composition of ocean water. Ocean water is made up of chlorine, sodium, magnesium, sulfur, calcium, potassium, bromine, as well as dissolved gases (nitrogen, carbon dioxide, and oxygen), organic matter, and other trace elements. However, the major driving force behind ocean water differences is determined by salinity (the dissolved solids in the ocean by volume) and accompanying density based on salinity and temperature levels. The relationship between these are explained as follows: water that is more saline is more dense, while water that is less saline is less dense; water that is colder is more dense, while water that is warmer is less dense. However, salinity (along with density and temperature) change with latitude because water at the equator is always more saline than water at higher latitudes because of evaporation rates. Thus, the salinity, density, and temperature levels within multiple layers of ocean water and between latitudinal zones influence the characteristics, especially the movements, of ocean water. This is especially important in terms of the oceanic conveyor belt, which moves ocean water on a global scale. This conveyor belt influences climate by bringing warm and cold water to different parts of the world (influencing atmospheric conditions), so its functionality is necessary for moderation of our climate systems everywhere. These global ocean and atmospheric characteristics account for our local oceanic conditions.
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|(physical structure of the ocean)|
All oceans on Earth contain salt. Given the information about ocean water salinity, density, and temperature above, answer the following question. If a column of ocean water in the Pacific Ocean at 34 degrees latitude (a latitude ranging through Ventura County) has 34 parts per thousand of salinity at 60 degrees Fahrenheit, then how dense (more or less) would you expect a column of ocean water in the Pacific Ocean at 0 degrees latitude with 36 parts per thousand of salinity and a temperature of 75 degrees Fahrenheit to be?
Coasts are the borders between lands and oceans. The inputs to coastal systems include energy from the sun, winds, climates, bedrocks, and human influences. Tidal fluctuations are also significant features of coastlines. Tides are created by the gravitational pulls of the Moon and the Sun, respectively. The positions of the Earth, the Moon, and the Sun determine what types of tides occur on our planet; whether flood tide (rising tide) or ebb tide (falling tide), spring tide (Moon/Sun gravitational pulls aligned to form major tidal changes) or neap tides (Moon/Sun gravitational pulls misaligned to form minor tidal changes). The mean sea level is the average level of all tides combined. Also, there are both high and low tides everyday depending on location and gravity. Daily on the coasts of Ventura County, there are diurnal (1 low, 1 high tide), semi-diurnal (2 low, 2 high equal tides), or mixed semi-diurnal (2 low, 2 high unequal tides) cycles.
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|(tides based on the Earth, Moon, and Sun)||(high tide, mixed semi-diurnal, at Ventura Point Beach)||(low tide, mixed semi-diurnal, at Channel Islands Harbor)|
Use a tide book for the current year to get today's high and low tides for a coastal range in Ventura County. What are the highs and lows? Based on these tides, do you think we are experiencing a spring tide or a neap tide? [Note: you can search on-line for a free reading or go to a local surf shop to get a free/low cost tide book.]
Waves are created by the friction between the ocean surface and atmospheric winds. In the open ocean, these waves have distinctive crests (high heights) and troughs (low heights). As the waves get closer to shore, the depth of water decreases and the waves break. Wave convergence and divergence is a function of coastal physical features. Wave energy converges, or concentrates, at points (headlands) where erosion occurs. Wave energy diverges, or diffuses, in bays (coves) where deposition occurs. The littoral flow, or general flow of ocean water in a single direction parallel to the coast, coincides with the predominant wave direction as well as the flow of sediments. In California, the littoral flow is basically north to south. However, Ventura County coasts experience wave directions anywhere from northwest to south. Some swells, or groupings of waves, actually come from the southern hemisphere. Tsunamis (formed by movements on the sea floor) can also reach nearby coastlines. However, the northern Santa Barbara Channel Islands (specifically San Miguel, Santa Rosa, Santa Cruz, Anacapa, and Santa Barbara) block much of the wave energy and even tsunamis from reaching our coasts. Coastal wetlands also influence the dynamics of our coastlines. Some examples of these features are shown below.
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|(Rincon Point)||(Port Hueneme Bay)||(Ormond Beach wetland)||(Anacapa Island)|
Using Google Earth or another coastal map of Ventura County, locate three headlands and three coves along the shoreline. What are their names and what kind of wave energy would you expect at each type? Also, locate the Santa Barbara Channel Islands and find Anacapa (the single northern S.B. Channel Island within Ventura County boundaries).
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© 2006 Jessica Douglas