1. Dissolved Solids
1.1. Composition
1.1.1. Ocean water is 96.5% pure water. Dissolved solids make up about 3.5%..
1.1.1.1. The dissolved solids are comprised of 75 different elements, the most common of which are, in order from greatest to least:
1.1.1.1.1. Chlorine (55.0%)
1.1.1.1.2. Sodium (30.6%)
1.1.1.1.3. Magnesium (7.7%)
1.1.1.1.4. Sulfur (3.7%)
1.1.1.1.5. Calcium (1.2%)
1.1.1.1.6. Potassium (1.1%)
1.1.1.2. The salt "halite" makes up 85% of all ocean salts, and is made of sodium and chloride ions.
1.1.1.3. Trace elements (those found in minute amounts) make up 0.7% of dissolved solids.
1.1.2. The dissolved solids, commonly called "sea salts", give the ocean its salty taste.
1.2. Sources of dissolved solids
1.2.1. Note! The net amount of ocean salts in the ocean is always increasing, because there are very few means by which dissolved solids leave ocean water, all of which are very ineffective (such as the water cycle).
1.2.2. Volcanic Eruptions
1.2.3. Chemical weathering remains of of rock that is eroded into the sea (esp. via rivers)
1.2.4. Chemical reactions between sea water and newly-formed rock on the sea floor (such as igneous rock that forms are mid-ocean ridges)
1.3. Salinity
1.3.1. A measure of the amount of dissolved solids in a given body of liquid (in this case, ocean water).
1.3.1.1. It is given in grams of dissolved solids per 1000g of ocean water (i.e., parts per thousand, or %%).
1.3.1.1.1. Ocean water is typically 35%%, or 3.5% salts, whereas fresh water is usually just 1%%, or 0.1% salts.
1.3.2. Factors that affect salinity
1.3.2.1. Evaporation vs precipitation
1.3.2.1.1. Precipitation, such as rain and snow, is pure water.
1.3.2.1.2. When ocean water evaporates, only the pure water part of the ocean water actually evaporates. The dissolved material is left behind. The same happens when ocean water freezes.
1.3.2.1.3. So, when the precipitation into an area of the ocean exceeds the evaporation & freezing rates of that area, the salinity decreases (or is kept low). The reverse is also true.
1.3.2.2. Rate at which dissolved solids are being added into the ocean vs rate at which they are being removed.
1.3.3. The average salinity of ocean water is about 34.7%%, but the salinity varies from as low as 33%% (Arctic Ocean waters) to as high as 40%% (Red Sea).
2. Dissolved gases
2.1. Composition
2.1.1. Primary gases are nitrogen, N2, and oxygen, O2, which also are the primary gases in the atmosphere.
2.1.2. While CO2 is not a major component of the atmosphere, a lot of CO2 is dissolved in water.
2.1.3. There are several trace gases that dissolve in ocean water.
2.2. Ways gases get dissolved in ocean water
2.2.1. Streams and rivers carrying dissolved gases emptying into the ocean..
2.2.2. Underwater volcanic eruptions
2.2.3. Organisms directly releasing gas into the ocean, such as O2 from plant photosynthesis.
2.2.4. Directly from the atmosphere, which is the primary source of dissolved gases.
2.3. Temperature
2.3.1. Gases dissolve much more readily in colder waters than in warmer ones.
2.3.1.1. Hence, the higher latitude waters (because they tend to be much colder than lower latitudes) dissolve a lot more gases than lower latitudes.
2.3.2. Variations in temperature of the water cause variations in dissolved gas composition.
2.3.2.1. Rises in ocean water temperature release dissolved gases into the atmosphere, which then get re-absorbed in colder waters. This also happens when ocean currents carry colder waters to warmer areas. All this forms a continuous cycle of gas exchange in the system.
2.4. Oceans as carbon sinks
2.4.1. The ocean contains 60 times more CO2 than the atmosphere does, and that CO2 can remain dissolved in the water for thousands of years, especially in temperature- and pressure-stable waters.
2.4.2. Because CO2 affects the atmosphere's ability to absorb thermal energy from the sun, oceans as carbon sinks play an important role in the temperature of the planet, and by extension, the climate of the planet.
3. Ocean water, unlike pure water, is a mixture of many solids, liquids, and gases, as well as micro-organisms, and possesses many properties, all of which are key to sustaining plant and animal life within its body.
4. Temperature
4.1. Ocean temperatures, like salinity, vary depending on depth and location on the surface of the ocean (latitude).
4.1.1. Surface Water
4.1.1.1. The mixing of surface water distributes heat pretty evenly for a depth of up to 100-300m, and so the temperature is relatively constant and changes only a little with increasing depth (depth is less of a factor here).
4.1.1.2. Temperature, however, does decrease with increasing latitude, due to the amount of solar energy sent to a given latitude (less the higher the latitude).
4.1.1.2.1. Tropical waters (low latitudes) typically see temperatures near 30 degrees Celsius, whereas the poles (high latitudes) see temperatures as low as -2 degrees Celsius, and vast expanses of ice are observed.
4.1.1.2.2. In middle latitudes, the temperatures fluctuate depending on the season, with some areas seeing as much as 10-20 degrees Celsius variation between summer and winter.
4.1.2. Thermocline
4.1.2.1. Past 100-300m, the water temperature does depend on depth, and at the region of the thermocline, the water temperature decreases more drastically with depth than in other regions of the ocean water.
4.1.2.1.1. It exists because the warmer surface water is less dense than the colder deep water, and they don't mix very well. Hence, at their border, we find the thermocline.
4.1.2.2. Changing temperatures or shifting currents may alter the depth of the thermocline or cause it to disappear. Nevertheless, a thermocline is usually present beneath most of the ocean surface.
4.1.3. Deep water
4.1.3.1. The temperature of this zone is usually 2 degrees Celsius.
4.1.3.2. The high density of this ocean water controls the deep ocean currents, which come about when the cold, dense water at the poles sink down below the warm surface waters of regions near the equator.
4.2. The range of ocean temperatures is affected by the amount of solar energy an area receives (which is affected by several factors) and by the movement of ocean water.
5. Density
5.1. Density is mass per unit volume of a given substance.
5.2. Pure water has a density of 1g/cm^3.
5.3. Two factors affect the density of ocean water:
5.3.1. Salinity
5.3.1.1. Dissolved solids add mass to ocean water without changing the volume by much. Hence, they increase the density of ocean water.
5.3.1.1.1. Ocean water is thus more dense than pure water, and ranges from 1.026g/cm^3 to 1.028g/cm^3.
5.3.2. Temperature
5.3.2.1. As temperature decreases, density increases, so the density of water at the poles is much higher than the density of equatorial waters.
6. Color
6.1. The color of the ocean, as with all things, is determined by the way white light is reflected of of it. Sunlight is white light, and possesses all the wavelengths of the electromagnetic spectrum. When sunlight is absorbed by the ocean, all of its wavelengths are absorbed except for blue, which is reflected back and is what we see.
6.2. Substances or organisms in the ocean water can affect the shade of blue of that area of the ocean.
6.2.1. One such organism - phytoplankton - affects the shade of green of the ocean water, as they absorb blue and red wavelengths but reflect green.
6.2.1.1. By studying variations in the color of the ocean, scientists can determine the presence of phytoplankton, which can in turn reflect the health of that area of the ocean, because not only do phytoplankton provide food for most of the ocean's organisms but also require nutrients to survive. Lack of phytoplankton indicates lack of nutrients or hostile environments.