15.1 Composition of Seawater

 The total amount of solid material dissolved in water  Mass of dissolved substances : Mass of the water sample  Shown in %  Most of the salt in seawater is Sodium Chloride (NaCl), common table salt Salinity

 Chemical weathering of rocks on the continents is a source of elements found in seawater  Reach oceans through runoff from rivers and streams  Another source is of elements found in seawater is from Earth’s interior  Through volcanic eruptions, large amounts of water vapor & other gases have been emitted into the atmosphere Sources of Sea Salts

 Surface salinity varies in the ocean normally from 33% - 38%  Variations in salinity result from changes in the water content of the solution Processes Affecting Salinity

 Add freshwater to saltwater  Precipitation  Runoff from land  Icebergs melting  Sea ice melting  Remove freshwater from saltwater  Evaporation  Formation of sea ice Continued…

 Ocean’s surface water temperature varies with the amount of solar radiation it gets. (Fxn. of latitude)  Surface waters = higher temperatures (in LL)  Deeper waters = lower temperatures (in LL)  Thermocline is the layer of ocean water btw 300 m – 1000 m where rapid change of temperature is seen with depth  Vertical barrier to many types of animals Ocean Temperature Variation

 In HL (high latitude)…  Surface water = cooler than in LL  Deeper water = similar to the surface temperature  Curve is vertical CONTINUED…

 Density – mass per unit volume  Pycnocline – layer of ocean water btw 300 m – 1000 m where there is a rapid change of density with depth  Saltwater density is influenced by two factors…  Salinity  Temperature  Most important factor affecting saltwater density  Inversely proportional to density Ocean Density Variation

 Layered according to denisty  Low density is near the surface  Higher density is near the bottom  3 layered structure  Shallow surface mixed zone  Transition zone  Deep zone Ocean Layering

 Surface Zone  Warmest water temperature  Transition Zone  Temperature falls quickly  Distinctive layer between warm surface layer & the deep cold layer  Deep Zone  Sunlight never reaches this zone  Right above freezing Continued…

 What is salinity?  Explain how latitude and sea surface temperature relate.  What are the 3 main zones of the ocean?  Where would more dense water be found? Less dense water? Review Questions