Seawater Saltiness Seen from Space
The ocean, by some estimates, holds enough salt to cover the entire surface of the Earth, layered to the height of a 40-story office building. Ocean salt comes from rock eroded by slightly-acidic rainwater. Carbon dioxide in the rainwater chemically breaks down the rocks, sending dissolved salts -- lots of them -- into riverbeds, streams and eventually the ocean. A cubic mile of seawater contains about 120 million tons of salt, according to USGS.
In June 2011, NASA launched its first satellite designed to measure ocean saltiness. From more than 400 miles above Earth, the Aquarius mission scans and maps salt in the Earth's oceans with unprecedented precision. The equipment on the satellite is sensitive enough to detect the equivalent of a pinch of salt in a one-gallon bucket of water.
Last week, the Aquarius team released dazzling new maps that chronicle changes in sea surface saltiness. It showed sharply different conditions in different ocean regions. In the North Pacific, for example, heavy rainfall causes reduced salinity. And in Africa, a wonderful plume of freshwater pulses from the Amazon River and into the sea. The saltiest patch of water stretches across the North Atlantic Ocean, where little rainfall and lots of evaporation occurs.
Freshwater is constantly getting sucked out of the ocean by evaporation and rising as water vapor into the atmosphere, where it condenses and then gets dumped back into the ocean as rainfall. And as changes in climate cause the rates of evaporation and rainfall to change and intensify, so do variations in ocean saltiness.
Measuring how salt is distributed throughout the ocean can tell us a great deal about climate: By tracking salinity, scientists can measure changes in the freezing and melting of sea ice, rainfall, evaporation, ocean temperature and circulation -- all crucial factors for understanding the planet's water cycle.
"When we think about circulation, most people think about currents that move horizontally," said Gene Carl Feldman, an oceanographer and project manager for the Aquarius mission. "But the oceans are over seven miles deep. So there's a three-dimensional circulation of ocean water, which is very critical for regulating many many things on the planet -- most importantly temperature."
Indeed, ocean temperature is a critical factor in global temperatures. In fact, the upper three meters of ocean holds as much heat as the entire atmosphere, Feldman points out.
"The ocean is a beautiful heat sink -- it stores heat," Feldman said. "That's why Sioux Falls, South Dakota is a hell of a lot colder than Seattle, Washington. It has to do with surrounding waters."
One other thing: Carbon dioxide levels in the Earth's atmosphere link directly to salinity and the water cycle. High salinity water is more dense, and high density water has a sinking component. In other words, it causes elements like carbon dioxide and chlorofluorocarbons to sink into the ocean, sometimes staying underwater and out of the atmosphere for thousands, even tens of thousands of years, William Large, director of the climate and global dynamics division of the National Center for Atmospheric Research, told us in an interview shortly before the launch. If the ocean had not been taking up as much carbon dioxide, carbon dioxide levels in the atmosphere would be much higher, he said.
QUICK BITES
Schizophrenia, bipolar disorder, autism, major depression and attention deficit hyperactivity disorder, though different, share several "genetic glitches that can nudge the brain along a path to mental illness," researchers -- and Gina Kolata -- report in the New York Times.
Don't miss our report on what changes in winter climate and a lack of steady snowfall has meant for the ski industry. Watch the video report here:
With the number of antibiotic resistant infections on the rise and fewer medicines in development, drug makers are looking down -- 1,600 feet down -- for clues about resistance, Bloomberg reports.
"The brains of two rats on different continents have been made to act in tandem," Nature's Ed Yong reports. "When the first, in Brazil, uses its whiskers to choose between two stimuli, an implant records its brain activity and signals to a similar device in the brain of a rat in the United States." It's fascinating. And you can watch how it works here:
For the National Science Foundation's latest Science Nation, Miles O'Brien looks at the social structure and of invasive fire ants.
Photographs of internal ocean waves -- seen here from the north coast of Trinidad -- have been captured by the International Space Station.
Thursday was Introduce a Girl to Engineering Day. Here are 25 of the world's most powerful female engineers, according to Business Insider.
NOT SAFE FOR LUNCH
Scientists subject King Richard I's heart to a battery of tests. "Scanning electron microscopy identified pollen grains from myrtle, mint and other known embalming plants, as well as poplar and bellflower, which were in bloom when the king died." From Nature.
Rebecca Jacobson, Patti Parson and David Pelcyger contributed to this report.
