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Environmental Monitoring


November 2011 Issue

Aquarius Yields NASA's First Global Map of Ocean Salinity
NASA's new Aquarius instrument produced in September its first global map of the salinity of the ocean surface, demonstrating its ability to detect large-scale salinity distribution features clearly and with sharp contrast, NASA scientists said.

Launched in June from Vandenberg Air Force Base in California, Aquarius has been operational and collecting data since late August. To produce the map, Aquarius scientists compared the early data with ocean surface salinity reference data. Although the early data contain some uncertainties and months of additional calibration and validation work remain, scientists said they were impressed by the initial data's quality.

"Aquarius has exposed a pattern of ocean surface salinity that is rich in variability across a wide range of scales," said Arnold Gordon, Aquarius science team member and professor of oceanography at Columbia University. "This is a great moment in the history of oceanography. The first image raises many questions that oceanographers will be challenged to explain."

Using data collected between August 25 and September 11, the satellite found the average salinity on the map was 35 grams of salt per kilogram of seawater.

The map also shows well-known ocean salinity features such as higher salinity in the subtropics; higher average salinity in the Atlantic Ocean compared to the Pacific and Indian oceans; and lower salinity in rainy belts near the equator, in the northernmost Pacific Ocean and elsewhere. These features are related to large-scale patterns of rainfall and evaporation over the ocean, river outflow and ocean circulation. For more information, visit http://aquarius.nasa.gov.

Scripps to Link Wave Gliders With Seafloor Seismometers
Scientists from Scripps Institution of Oceanography received a $1.02 million grant from the National Science Foundation (NSF) to develop a deep-ocean seismic system in which Liquid Robotics Inc.'s (Sunnyvale, California) Wave Glider platform will link with ocean-bottom sensors to relay live seismic data from the ocean surface to shore via satellite, Scripps announced in October.

The resulting system will have applications in areas such as earthquake monitoring, deep Earth structure and dynamics studies, and tsunami warning systems, Scripps said.

Seafloor seismometers will be deployed and relay their data in real time via an acoustic link to a Wave Glider, an AUV that is powered solely by wave energy and solar power. The Wave Glider will navigate to a specific location, keep on station with its own power, link with a Scripps ocean-bottom seismometer and serve as a communications gateway to relay live seismic data from the ocean surface to shore via satellite.

Traditionally, ocean-bottom seismometers are deployed by ships, record data for a specific period of time and are retrieved when a ship returns to the location.

"We haven't made progress in getting long-term seismic stations established in the oceans because of the expense, so this project will help us fill in lots of holes in the coverage of the global network," team leader and geophysicist Jonathan Berger said.

The data will be integrated into the global seismographic network Project IDA and utilize software for sensor integration and platform control developed by the NSF's Ocean Observatories Initiative.

The total project is valued at $1.46 million, with contributions from Scripps, the Cecil H. and Ida M. Green Foundation for Earth Sciences and Liquid Robotics Inc. For more information, visit http://scrippsnews.ucsd.edu.

Researchers Find Arctic Sea Ice Is Getting Thinner, Younger
Thinner. Younger. These are results most of us could only dream of, but scientists will not be celebrating the results anytime soon.

That's because in the central Arctic, the proportion of old, thick sea ice has declined significantly, and the ice cover now largely consists of thin, one-year-old floes, report scientists who returned in October from a 16-week Arctic expedition on the RV Polarstern.

To create an ice thickness profile of the central Arctic, sea ice physicists from the Alfred Wegener Institute for Polar and Marine Research deployed an EM Bird, a nearly four-meter-long, torpedo-shaped probe that is flown over the ice with a helicopter, measuring ice thickness through electromagnetic induction. The probe operated over a total distance of more than 2,500 flown kilometers.

The scientists found that at sites where the sea ice had been mainly composed of old, thicker ice floes in the past decades, there was now primarily one-year-old ice with an average thickness of 90 centimeters. Only in the Canadian Basin and near the Severnaya Zemlya island group in northern Siberia did the scientists encounter significant amounts of several-year-old ice. Typically, this old ice is between two and five meters thick.

The scientists compared this recent data with measurements from 2007, when the extent of the sea ice diminished to a record minimum of 4.3 million square kilometers. The researchers have not yet found any differences, which they said indicates the ice has not recovered and it appears to have melted to the same degree as in 2007. For more information, visit www.awi.de.

New Method Gives More Precise Measurements of Arctic Albedo
The Finnish Meteorological Institute has developed a new method for estimating the amounts of solar radiation reflected from the Arctic sea area, or solar albedo, that is based on microwave data collected from satellites, the institute announced in October.

Unlike conventional optical methods, neither clouds nor the low Sun angle in the Arctic region interfere with measurements taken with the microwave-based method, the institute said. For instance, it is possible to detect whether spring is coming unusually early, which optical instruments do not necessarily reveal at that time of year.

Estimates of albedo affect the accuracy of model calculations pertaining to climate change, but they are also a good indicator of the change that has already taken place. The surface albedo of Arctic regions, which is relatively poorly understood, is particularly important with respect to climate change because changes in the extent of the ice cover in polar regions are crucial for albedo values. For more information, visit http://en.ilmatieteenlaitos.fi.


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