SALINITY SALINITY OCEAN OCEAN by Robert Perry Welcome to our powerpoint slide presentation on the subject of salt in the sea. by Robert Perry

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SALINITY The amount of salts dissolved in the ocean water. What is meant by the term “salinity?”

Why is the ocean salty ? …that is the question…

Why is the ocean salty? The ocean is salty because of the weathering of rocks in the early stages of the formation of the oceans and continents. The ocean probably is continuing to become saltier very slowly (on geologic time scales) as rivers bring dissolved material to the sea. Even though the concentrations of dissolved salts in "fresh" river water is tiny, evaporation from the ocean surface (which is how water gets back to the rivers) removes only pure water so whatever salt enters from rivers remains in the sea and slowly builds up. Sea water is 35o/oo or 3.5% salt by weight, which means the total quantity of dissolved salt, if dried, would form a layer 45m thick over the entire earth, or 153m thick over the present land area. Where did the salt in the ocean come from? How much salt is there in the ocean?

The salt in sea water is composed of a variety of components, primarily sodium chloride (table salt), magnesium chloride, magnesium sulfate and calcium carbonate, along with many trace elements. One of the remarkable aspects of ocean salinity is how constant the relative ratios of these constituents are in sea water, no matter where in the oceans one looks. This suggests that the oceans are "well-mixed" on the time scale of salt input. Total salinity, however, varies from about 3.3% to 3.8% in open-ocean surface waters, depending on the rainfall, evaporation, and river runoff in different regions. Salinity in bays or near the mouths of rivers is less, for example the salinity of Puget Sound near Seattle is about 2.9-3.2%. Deep-ocean salinity is much less variable. What kind of “salts” make up the salts in the ocean?

Can you list the major and minor constituents of seawater?

The origin of ocean salts. Here’s a graphic look at the origin of salts in the sea. The origin of ocean salts.

Na = sodium Cl = chlorine NaCl ..a more artistic look… Na = sodium Cl = chlorine Modified “Chemistry NaCl,”courtesy of the artist Craig A. Finseth, http://www.finseth.com/~fin

The polarity of the water molecule and its relationship How are the molecules of salt and water arranged? The polarity of the water molecule and its relationship with the sodium and chlorine ions.

Sea salts being extracted by evaporation. Name one source of salt production. Sea salts being extracted by evaporation.

SALINITY MEASUREMENTS: Oceanographers report salinity (total salt content) and the concentrations of individual chemical constituents in sea water -- chloride, sodium, or magnesium for example -- in parts per thousand, for which the symbol o/oo (or ppt) is used. That is, a salinity of 35 o/oo means 35 pounds of salt per 1,000 pounds of sea water. Similarly, a sodium concentration of 10 o/oo means 10 pounds of sodium per 1,000 pounds of water. What units are used to measure salinity? What do they mean?

Here’s an easy way to measure the salinity of a water sample… THERMOMETER Name 2 common instruments that can be used to determine the salinity of a seawater sample. HYDROMETER

SST and DENSITY determine the SALINITY John Jones 6 Sept. 21, 2000 9:10 am 22.3 0.0 310 green 2 90 % 20.0 2 4 5 7 SST and DENSITY determine the SALINITY Name 2 different bits of data that can be used to determine the salinity of a seawater sample.

What are two kinds of data one must already have in order to use the salinity conversion chart?

LET’S FIND SALINITY: If our SST was 20.0OC and our density was 1.0245 g/cm3. Let’s do a practice problem using the salinity conversion chart.

Here’s where the lines intersect. The salinity is: 34.5 o/oo Find the density curve and the temperature line. Where they cross will give you the salinity. The salinity is: 34.5 o/oo

The amount of dissolved salts in the ocean is controlled by temp- John Jones 6 Sept. 21, 2000 9:10 am 22.3 0.0 310 green 2 90 % 20.0 2 4 5 34.5 7 The amount of dissolved salts in the ocean is controlled by temp- erature, which increases evaporation and causes the salinity to increase. Also, during the winter rainy season, large volumes of fresh water (especially from the Pacific Northwest region) can dilute the salt content and lower salinity values. SALINITY What factors influence the salinity of our coastal ocean waters?

A rosette or cluster of water sampling bottles is ready to be lowered into the sea. This is one way ocean salinities are determined at different depths below the surface. How do oceanographers on the big research vessels determine salinity?

Surface salinity of the western Pacific. What is the range of salinity in the Pacific? Where are regions of low salinity and high salinity located/

Most ocean salinities are between 34.6 and 34.7 ppt. Can you explain the global distribution of salinity?

d What is the relationship between latitude and salinity? If you were taking a vacation in the Caribbean, what can you predict about the saliniy there?

The red line shows surface salinity vs. latitude. The dashed line Regions of higher precipitation Regions of higher precipitation Regions of higher precipitation Regions of higher evaporation Regions of higher evaporation Ocean salinity is a consequence of two opposing forces….can you name them? The red line shows surface salinity vs. latitude. The dashed line shows evaporation minus precipitation. (Areas above zero are dry and those below zero are wet). Note the similarity in the lines.

Antarctic Bottom Water North Atlantic Deep Water Higher evaporation than precipitation Higher evaporation than precipitation Antarctic Bottom Water North Atlantic Deep Water From the surface to the bottom, what happens to the salinity of the ocean water? Atlantic Ocean Salinity Cross Section

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