Salinity of water

Slide 1: 

There are more water molecules in a single droplet of water than there are grains of sand on Wrightsville Beach You are 65% water Determines the distribution of plants and animals that live in the ocean. Affects other properties of seawater, such as its density and the amount of dissolved oxygen. Why Study Salinity… Salinity is the total amount of dissolved salts in water; grams of salts per kilogram of water (g/kg) or as parts per thousand (ppt).

Slide 2: 

About 70% of the Earth is covered with water. Over 97% of that water is found in the oceans. Everyone who has taken in a mouthful of ocean water while swimming knows that the ocean is really salty! Dissolved salts in ocean water make it taste salty. Fresh water has dissolved salts in it too, but not nearly as many as ocean water!

Slide 3: 

The most abundant mineral in seawater is of course sodium chloride, or common salt. If all the salt in the ocean were dried, it would form a mass of solid salt the size of Africa! Or we can build a 180-mile-tall, one- mile-thick wall around the equator! Why are oceans salty? Most of the salt in the sea comes from minerals that were part of the solid Earth (land!). When rivers flow over rocks on land, minerals get dissolved by the river water. These minerals are deposited into the oceans as the rivers flow into the oceans.

Slide 4: 

The technical term for saltiness in the ocean is halinity, from the fact that halides - chloride specifically – are the most abundant anions in the mix of dissolved elements. In oceanography, it has been traditional to express salinity not as percent, but as parts per thousand (ppt or ‰), which is approximately grams of salt per liter of solution.

Slide 5: 

Sea Surface Salinity All over the globe and from the top of the ocean all the way to the bottom of the ocean, salinity is between ~33-37 ppt or psu (average salinity of the ocean is 35 ppt).

Slide 6: 

Life in the oceans has adapted to this salty environment. But, most creatures that live in the ocean could not live in fresh water. In 1978, oceanographers redefined salinity in the Practical Salinity Scale (PSS) as the conductivity ratio of a sea water sample to a standard KCl solution.

Slide 7: 

When the salty waters of the ocean meet fresh water, an estuary is formed. This is a special environment where some creatures have learned to adapt to a mixture of fresh and salt water. Humans have the responsibility to make sure their actions are not causing damage to these special environments where life thrives.

Slide 8: 

View of the high salinity, open water area of the White Oak River estuary.

Slide 9: 

Salinity variations Open ocean salinity 33 to 38% Coastal areas salinity varies more widely Influx of freshwater lowers salinity or creates brackish conditions Greater rate of evaporation raises salinity or creates hypersaline conditions Salinity may vary with seasons (dry/rain)

Slide 10: 

CTD recorder to measure salinity, temperature and depth of the water.

Slide 11: 

How does the surface and subsurface ocean vary in salinity Polar regions: salinity lower, lots of rain/snow and runoff Mid-latitudes: salinity higher, high Rate of evaporation Equator: salinity lower, lots of rain Thus, salinity at surface varies primarily with latitude Halocline, rapid change of salinity with depth Deep ocean variation of salinity Surface ocean salinity is variable Deeper ocean salinity is nearly the same (polar source regions for deeper ocean water)