Thursday, September 22, 2011
First Aquarius Map
The first map of ocean salinity as measured by the Aquarius satellite was released today. (NASA link.) I like that I can look at this and know what I'm seeing. Usually oceanographers specify salinity as a ratio to a standard KCL solution (potassium chloride.) This is called the Practical Salinity Scale. It is used for any measurement based on conductivity and has no units. I think they are making the assumption here that grams per kilogram is the same as PSU, for practical salinity units, which is of course a silly name, because it's unit-less. g/kg is a compromise I'm willing to accept.
Anyway, 35 is what oceanographers consider nominal for PSU. Green is normal sea water. That blue band across the Pacific? That's an equatorial counter current moving towards South America. When it's blue like that it's called La Niña. You can equate lower salinity with lower temperature in this case. If it was an El Niño year there would be a red band across the Pacific indicating hotter, saltier water from increased evaporation. The side effect of that low evaporation in the Pacific is Texas is very dry. Dry earth heats up more than wet earth, and I am here to testify to it. The lowest high temperature in September in Austin so far is 90°F. There might be two more of those days and this is not one of them. It's going to be 101°F this weekend.
I'm not sure what the Gulf of Mexico salinity looks like in a normal summer (No La Niña or El Niño.) Looks to me like the lack of fresh water from Texas and Mexico is making it pretty salty on the West. I'm glad my Georgia home is producing lots of water. That blue and purple area in the aptly named Florida Big Bend is from fresh water input from the Appalachicola and Mississippi Rivers. That's what makes it oyster friendly.
The other big purple and blue blotch off the Venezuela part of South America is the Orinoco and the Amazon comes out of that notch farther south. You can see it runs north and heads across towards Africa in the Equatorial Counter Current. I love that I can see features in an up-to-date salinity map that I had to memorize off lines and arrows on maps.
I'm not sure what to make of all that detail of differences down around Antartica. That's kind of fascinating.
And you can tell a lot of sea ice is melting up in the Arctic adding all that fresh water to the surface.
Thanks Aquarius! Fun times!