Water mission reveals insight into Amazon plume

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How sea-surface salinity varies in the Tropical Atlantic Ocean as a result of the influx of fresh water from the Amazon River, as seen by ESA's Soil Moisture and Ocean Salinity (SMOS) mission. This influx is known as the Amazon Plume. The animation includes observations from mid-July to mid-August 2010 and highlights some interesting aspects of this region of ocean. A decrease in sea-surface salinity due to influx from the Orinoco River is also visible. These observations from SMOS are leading to new insights into how local currents affect these two major freshwater influxes. Tracking the variability in surface salinity and how fresh and salty water interact is important for a better understanding, not only of ocean circulation, but also of water ecology, biogeochemistry and bio-optics (the study of how living organisms affect the light in the sea). Credits: N. Reul, Ifremer & J. Tenerelli, CLS

The Soil Moisture and Ocean Salinity (SMOS) mission has been delivering observations of 'brightness temperature' to the science community since mid-July. As a measure of radiation emitted from Earth's surface, this information can be used to derive global maps of soil moisture every three days and maps of ocean salinity at least every 30 days.

By consistently mapping soil moisture and ocean salinity, SMOS will advance our understanding of the exchange processes between Earth's surface and atmosphere - the water cycle - and help improve weather and climate models. In addition, these data will be of practical use for agriculture and water resource management.

Soil moisture and ocean salinity data products will be released later this month, but scientists are very encouraged by what they are already seeing.

Talking about observations that relate to ocean salinity, Nicolas Reul from Ifremer said, "One of the dramatic steps forward achieved with SMOS is that we now have the ability to track the movement of low-salinity surface waters, particularly those resulting from large 'plumes' such as the Amazon.

"Observations between mid-July and mid-August clearly show how the North Brazilian Current transports fresh water from the Amazon River as the current flows across the mouth of the river. These observations confirm the excellence of the data we are already getting from SMOS."

Soil moisture and ocean salinity data products will be released later this month, but scientists are very encouraged by what they are already seeing.

Talking about observations that relate to ocean salinity, Nicolas Reul from Ifremer said, "One of the dramatic steps forward achieved with SMOS is that we now have the ability to track the movement of low-salinity surface waters, particularly those resulting from large 'plumes' such as the Amazon.

"Observations between mid-July and mid-August clearly show how the North Brazilian Current transports fresh water from the Amazon River as the current flows across the mouth of the river. These observations confirm the excellence of the data we are already getting from SMOS."

"Over the last weeks we have been able to track how the Amazon freshwater plume curves back on itself at this time of year as large North Brazilian Current eddies form northwest of the river mouth," said Dr Reul.

"At the same time, the Orinoco plume has also been clearly visible as a tongue of fresh water entering the Tropical Atlantic along the windward side of the Caribbean islands.

"These observations are a good example of how well SMOS is performing and they show us that the mission can provide data on temporal sea-surface variability at scales of less than a week."

Along with temperature, variations in ocean salinity drive global three-dimensional ocean-circulation patterns. This conveyor-like circulation is an important component of Earth's heat engine and crucial in regulating weather and climate. Ocean salinity data from SMOS are therefore expected to greatly improve our knowledge of the conditions that influence these circulation patterns and thus climate.

Provided by European Space Agency (news : web)