This evaporation removes water — when water vapour rises into the atmosphere, it leaves the salt behind, so the salinity of the seawater increases. This causes the seawater to become denser. You can see on the map that the north and south Atlantic have high salinity — these are areas where there are strong winds and not much rain.
The Mediterranean Sea in Europe has very high salinity — 38 ppt or more. It is almost closed from the main ocean, and there is more evaporation than there is rain or extra freshwater added from rivers. Some parts of the ocean have lots of rain.
The freshwater added at the surface dilutes the seawater, reduces the salinity and so makes the seawater less dense. Seawater can also be less saline near land, where rivers add freshwater.
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. Heavy rain can affect salinity readings by attenuating the microwave signal Aquarius reads off the ocean surface as it travels through the soaked atmosphere.
Rainfall can also create roughness and shallow pools of fresh water on the ocean surface. An ultimate goal is combining the Aquarius measurements to those of its European counterpart, the Soil Moisture and Ocean Salinity satellite SMOS to produce more accurate and finer maps of ocean salinity. In addition, the Aquarius team, in collaboration with researchers at the U. Learn More About This Image.
Salinity Although everyone knows that seawater is salty, few know that even small variations in ocean surface salinity i. The ions in the runoff are carried to the streams and rivers and then to the ocean. Many of the dissolved ions are used by organisms in the ocean and are removed from the water. Others are not used up and are left for long periods of time where their concentrations increase over time.
The two ions that are present most often in seawater are chloride and sodium. By the way, the concentration of salt in seawater salinity is about 35 parts per thousand. In other words, about 35 of 1, 3. And, just so you don't think seawater is worthless, a cubic mile of it also can contain up to 25 pounds of gold at a concentration of 0.
Before you go out and try alchemy on seawater, though, just think about how big a cubic mile is 1 cubic mile contains 1,,,, gallons! In , scientists exploring the NW Eifuku volcano near the Mariana Islands reported seeing small white chimneys emitting a cloudy white fluid near the volcano's summit, as well as masses of bubbles rising from the sediment around the chimneys. In this picture you can see masses of minerals and carbon dioxide escaping from the earth's crust into the ocean.
These vents contribute dissolved minerals to the oceans, which is one reason the oceans are salty. Credit: NOAA. Rivers and surface runoff are not the only source of dissolved salts. Hydrothermal vents are recently-discovered features on the crest of oceanic ridges that contribute dissolved minerals to the oceans. These vents are the exit point on the ocean floor from which sea water that has seeped into the rocks of the oceanic crust has become hotter, has dissolved some of the minerals from the crust, and then flows back into the ocean.
With the hot water comes large amounts of dissolved minerals. Estimates of the amount of hydrothermal fluids now flowing from these vents indicate that the entire volume of the oceans could seep through the oceanic crust in about 10 million years. Thus, this process has a very important effect on salinity.
The concentration of salt in seawater salinity varies with temperature, evaporation, and precipitation. Salinity is generally low at the equator and at the poles, and high at mid-latitudes. The average salinity is about 35 parts per thousand. Stated in another way, about 3. What is a hydrothermal vent? NASA: Measuring salinity via satellite.
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