Sea Salt

Test your knowledge of ocean salinity and its relationship to climate change and ocean circulation.

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1. LOOKING DEEP

Salinity is a measurement of which property of seawater?

Salinity is the concentration of dissolved salts in water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium, calcium, potassium and sulfate.
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2. SALT OF THE SEA

On average, how much salt is there in 1,000 pounds of seawater?

On average, there is about 35 pounds of salt dissolved in 1,000 pounds of seawater. Oceanographers use the term "parts per thousand" when referring to salinity.
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3. OCEAN PLANET

Which ocean is the saltiest?

Surface waters in the Atlantic have the highest salinity, higher than 37 parts per thousand in some areas. This is because, on average, there is more evaporation than combined rainfall and river runoff into the Atlantic Ocean, maintaining higher salinity than in the other basins.
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4. JUST A PINCH

The variation in saltiness throughout the ocean is very small.

Although ocean salinity does vary from place to place, the variability of dissolved salt is very small: from about 32 parts per thousand to about 37 parts per thousand. Nonetheless, this small variation can have a massive influence on ocean circulation.
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5. IT'S ELEMENTAL

Other than the water, what are the two most abundant elements in seawater?

Over 30 elements, ions and compounds are present in seawater. Chloride and sodium are the most abundant. Other salts include sulfates, magnesium, calcium and potassium.
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6. DEEP QUESTION

Water near the seafloor is saltier than water at the sea surface.

For example, very cold and very salty water forms in polar regions every winter. This cold and salty water is denser, so it sinks toward the seafloor.
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7. WATERED DOWN

What causes sea water to become less salty?

Each of these processes can bring freshwater into an ocean basin and dilute the concentration of salt.
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8. GO WITH THE FLOW

Changes in ocean salinity patterns may indicate changes in:

Salinity is tied to many processes that occur in the ocean. Density-driven currents are affected by changes in salinity and temperature. Rain adds freshwater to the ocean, while evaporation "subtracts" freshwater from the ocean. The melting of glaciers and icebergs with climate warming adds freshwater to our salty seas.
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9. GRAIN BY GRAIN

Climate change is adding salt to the ocean.

Over the last 200 million years, the amount of salt in the ocean has been relatively constant. What makes seawater more or less salty is the addition (precipitation) or removal (evaporation) of the water.
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10. AGE OF AQUARIUS

Over the next 100 years, ocean salinity will likely:

NASA's Aquarius instrument will measure the salt's concentration at the ocean surface — and how it changes over the globe — to improve our understanding of Earth's ocean and climate.