15 June 2011

Measuring Sea Salt From Orbit and A Fun Quiz!

Posted by Dan Satterfield

NASA Image of the launch of Aquarius

I still remember clearly my first trip to the ocean at age 7 in the mid 1960’s. It was beautiful Galveston, Texas and you could drive right out onto the beach in those days. Erosion and sea level rise, has taken much of that beach away now, but the greatest surprise to me was that the ocean was salty! As a little 7-year-old from land locked Oklahoma, I had no idea! Fast forward to 2011 and we may be about to find out a lot more about just where it is saltiest, and how that sea salt affect our climate.

NASA has launched the Aquarius satellite into orbit and it promises to send back some real eye-opening data. If you are wondering  just how it is possible to measure how much salt is in ocean water from 300km in space, you aren’t alone. It turns out that saltier water emits radiation slightly differently than fresher water and scientists have designed an instrument that cam measure the difference and thus indirectly deduce the salinity content of the oceans. Doing it from space means we can get data over much of the globe.

NASA has a great quiz on the Aquarius website about ocean salinity. I made an 80% but I don’t feel too bad since NASA’s climate expert Gavin Schmidt said he made a 70%! You can take the quiz by clicking on the image below.

This research is of vital interest to climate scientists because it will help explain the workings of the thermohaline circulation. The Gulf Stream for instance, is just one part of this great movement of water from the surface to the ocean depths. It is estimated that it takes a blob of ocean water about a thousand years to make a complete circuit and the saltiness of sea water is part of what drives it. One of the most difficult things about tracking sea water, is that how heavy it is depends not only on its temperature, but also on how salty it is!

Salty and cold means dense and heavy and sea water east of Greenland in the North Atlantic becomes heavy enough to sink to the bottom of the ocean. That water may not see the  light of day for a thousand years and be in the Pacific when it does so! How this circulation will change as we make the oceans fresher (by melting sea ice) is a big question that researchers need answered. The NASA website (linked above) has a great explanation and is well worth reading. I think some bright students could come up with a pretty neat science fair project out of it as well!