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. This movie shows salinity patterns as measured by Aquarius from December through December Red colors represent areas of high salinity, while blue shades represent areas of low salinity. It is important to understand salinity, the amount of dissolved salts in water, because it will lead us to better understanding of the water cycle and can lead to improved climate models.
High concentrations over 37 practical salinity units are usually in the center of the ocean basins away from the mouths of rivers, which input fresh water. High concentrations are also in sub-tropical regions due to high rates of evaporation clear skies, little rain, and prevailing winds and in landlocked seas in arid regions.
At high latitudes, salinity is low. This can be attributed to lower evaporation rates and the melting of ice that dilutes seawater. To sum up, salinity is low where precipitation is greater than evaporation, mainly in coastal or equatorial regions. In this region, surface waters can becomes dense enough to sink to the ocean depths. This pumping of surface water into the deep ocean forces the deep water to move horizontally until it can find areas where it can rise back to the surface.
This very large, slow current -- estimated to be on the order of years to complete a full circuit -- is called the thermohaline circulation because it is caused by temperature thermo and salinity haline variations.
NASA's Aquarius instrument has been orbiting earth since June , measuring changes in salinity, or salt concentration, in the surface of the oceans. In fall , the Aquarius team released this first global map of ocean saltiness, a composite of the first two and a half weeks of data since the instrument became operational on August 25, Click on image to see full size version.
But when the wind is stronger, vertical mixing is more rapid and the convection currents increase, potentially affecting weather patterns. A recent study indicates that this could very well be the case. Image created with PO. I think with the information we're obtaining from Aquarius, we're learning to go back and re-assess - re-evaluate - the role of vertical mixing and horizontal advection in ocean dynamics. So, even for a region we think is dominated by evaporation, or for some reason, dominated by precipitation, now the general picture is we can only grasp these as hypotheses.
Horizontal advection, vertical mixing, evaporation, precipitation, all these play an important role at different times, at different scales and resolutions. For example, another very interesting science phenomena discovered by Aquarius is what we call a tropical instability wave in the Atlantic and Pacific Oceans. Tropical instability waves are north-south deflections of the "tongue" of upwelled cold water that extends westward from African and South American continental margins and along the Equator.
These waves propagate with an average period of about 30 days, and a wavelength of about kilometers. This is a new discovery by Aquarius. While it has been seen in ocean surface temperature images from locations a few degrees north of the equator, Aquarius now shows us that these kinds of waves also exist near the equator - but can only be seen in the salinity dataset.
The other example is the river outflow. Standard thinking has been that fresh river outflow from the Mississippi River would only affect coastal regions near Texas, Mississippi and Louisiana. The Aquarius data now shows that the fresh water on the surface can reach all the way to the southern end of the Gulf of Mexico. In the winter, when there's not much precipitation in the region, then in the summer when there is precipitation, we can see that salinity cycle in the upper ocean through the Aquarius data.
Another example I'd like to tell you is pretty interesting, it's something that we've just started to understand. It's a combination of how useful it is to combine the whole motion image salinity together. One of the interesting regions for the oceanographer or the climate scientist is the ocean surrounding the Indian Subcontinent. Why is that region so important? They have a monsoon season, right? In September, they get a lot of rain. Then, in the Indian sub-continent, around Tibet, they also get lots of snow.
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