Throughout most of history, global understanding of ocean surface salinity was difficult because sampling by ships, buoys, drifters, and moorings was extremely limited. Between and AD, awareness of changes in salinity, temperature, and smell helped Polynesians explore the southern Pacific Ocean. In the s, scientists aboard H. Challenger systematically measured salinity, temperature, and water density in the world's oceans. Over the years, techniques for measuring such ocean water properties have changed drastically in method and accuracy.
Salinity variations, one of the main drivers of ocean circulation, are closely connected with the cycling of freshwater around the planet and provide scientists with valuable information on how the changing global climate is altering global rainfall patterns. The salinity sensor detects the microwave emissivity of the top 1 to 2 centimeters about an inch of ocean water — a physical property that varies depending on temperature and saltiness.
The instrument collects data in kilometer-wide mile swaths in an orbit designed to obtain a complete survey of global salinity of ice-free oceans every seven days. Data from Aquarius has unveiled a world of varying salinity patterns. The Arabian Sea, nestled up against the dry Middle East, appears much saltier than the neighboring Bay of Bengal, which gets showered by intense monsoon rains and receives freshwater discharges from the Ganges and other large rivers.
Another mighty river, the Amazon, releases a large freshwater plume that heads east toward Africa or bends up north to the Caribbean, depending on the prevailing seasonal currents. One of the features that stand out most clearly is a large patch of highly saline water across the North Atlantic. This area, the saltiest anywhere in the open ocean, is analogous to deserts on land, where little rainfall and a lot of evaporation occur. In future years, one of the main goals is to fine-tune the readings and retrieve data closer to the coasts and the poles.
Land and ice emit very bright microwave emissions that swamp the signal read by the satellite. Another factor that affects salinity readings is intense rainfall. Well, the rain that falls from the sky is not just pure water — it actually contains small amounts of chemicals called carbon dioxide and sulphur dioxide, which are absorbed by the water while it is still in the air. This means that rain is actually very slightly acidic but not enough to do you any harm. When the rain falls on the ground, this weak acid can dissolve small amounts of mineral salts from the rocks, including sodium and chloride, which then enter the water.
Sodium chloride is the main salt in seawater, and the same one you might have on your table at home. The rain water flows off the land and into the rivers and streams that lead all the way to the sea — carrying the dissolved salts along with it.
The salts in the seas have built up over billions of years, and seawater contains about times more dissolved salts than average river water. To put it another way, every one litre of seawater has 35 grams of salts dissolved in it, while a litre of freshwater would only have 0. Some salts can also enter the seas from hot vents on the deep ocean floor and from volcanoes on the land and in the sea. This is mainly due to the huge amount of freshwater added from hundreds of rivers.
Even slightly denser seawater sinks below less dense water. However, the effect is greater if the salty water gets cold, as temperature has a greater effect on density than salinity does. A combination of high salinity and low temperature makes seawater so dense that it sinks to the bottom of the ocean and flows across ocean basins as deep, slow currents.
Add to collection. Go to full glossary Add 0 items to collection. Download 0 items. Twitter Pinterest Facebook Instagram. But, most of Earth's water, and almost all of the water that people can access, is saline, or salty water.
Do you wear contact lenses? If so, you most likely use a saline water solution to clean them. But what else do we use saline water for and do we really use that much? Read on to learn all about the use of saline water.
Skip to main content. Search Search. Water Science School. Why is the Ocean Salty? Water Basics Information by Topic Topics. Science Center Objects Overview Related Science Multimedia FAQ The oceans cover about 70 percent of the Earth's surface, and that about 97 percent of all water on and in the Earth is saline—there's a lot of salty water on our planet.
Credit: NASA. More science topics about saline water:. Date published: September 11, Filter Total Items: 2. Year Select Year Apply Filter. Date published: June 11,
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