Ahhhhhh…. SEAWATER
Seawater Seawater Seawater is a solution of about 96.5 percent water and 3.5 percent dissolved salts. The most abundant salt in seawater is sodium chloride (NaCl).
Seawater Seawater
Salinity is a measure of the amount of dissolved salts in seawater Parts Per Thousand (ppt). The total salt content of seawater is, on average, 35 ppt, or 3.5 %
Variations in Salinity 37 ppt in subtropical region Salinities are lower in equatorial regions where precipitation is abundant. Salinities of 32 or 33 ppt occur in polar regions The lowest salinities often occur where large rivers empty into the oceans.
Chemical Properties of Seawater
Sources of Sea Salt Minerals flushed in by Rivers Seawater Minerals flushed in by Rivers Weathering of crustal rocks Chlorine and sulfur dioxide dissolve in water from Volcano Eruptions
Removal of Sea Salts Salts are removed and added at the same rate. Seawater Salts are removed and added at the same rate. Some sea salts precipitate from seawater near arid, coastal regions. Salty spray droplets from breaking waves are picked up by winds and deposited inland. Marine organisms remove ions from seawater to build their shells, bones, and teeth.
Chemical Properties of Seawater
_ Cold water (sinks) is more dense than warm water (rises) Seawater Freshwater has a maximum density of 1.00 g/cm3 - density of seawater 1.02 g/cm3 -1.03 g/cm3 _ Cold water (sinks) is more dense than warm water (rises) Freezing point: Sea= -2 C Fresh = 0 C
Absorption of Light Seawater Water absorbs light, which gives rise to another physical property of oceans—they are dark. In general, light penetrates only the upper 100 m of seawater.
Ocean Layering Ocean surface temperatures range from –2°C in polar Seawater Ocean Layering Ocean surface temperatures range from –2°C in polar 30°C in equatorial average surface temperature being 15°C. Ocean water temperatures decrease significantly with depth.
Seawater Ocean Layering A typical ocean temperature profile plots changing water temperatures with depth.
3. The bottom layer is cold and dark with temperatures near freezing. 1. The first layer is a relatively warm, sunlit, surface layer some 100 m thick. 2. The thermocline is a transitional layer which is characterized by rapidly decreasing temperatures with depth. Seawater 3. The bottom layer is cold and dark with temperatures near freezing.
Seawater Ocean Layering Both the thermocline and the warm surface layer are absent in polar seas, where water temperatures are cold from top to bottom. In general, ocean layering is caused by density differences of warm and cold water. Cold water migrates toward the equator as a cold, deep water mass along the ocean floor.
Seawater Water Masses Three water masses account for most of the deep water in the Atlantic Ocean. 1. Antarctic Bottom Water forms when antarctic seas freeze during the winter and water temperature drops below 0°C. 2. North Atlantic Deep Water forms in a similar manner offshore from Greenland. 3. Antarctic Intermediate Water forms when the relatively salty waters of the Antarctic Ocean decrease in temperature during winter and sink.
Seawater Water Masses The Indian and Pacific Oceans contain only the two deep antarctic water masses.
Seawater Section Assessment 1. By what processes are salts removed from seawater? Salts are removed from seawater through the formation of evaporites, sea spray that is carried inland by wind, and biological processes.
Section Assessment 2. What is a thermocline? Seawater Section Assessment 2. What is a thermocline? A thermocline is a transitional layer between warm surface waters and cold bottom waters in a body of water that is characterized by rapidly declining temperatures with depth.
Seawater Section Assessment 3. Identify whether the following statements are true or false. true false ______ North Atlantic Deep Water overrides Antarctic Bottom Water. ______ Photosynthesis can occur to a depth of 200 m. ______ Sodium is the most prevalent ion in seawater. ______ Salt water is always denser than freshwater, regardless of temperature.