Wednesday, February 17, 2010

CTD #3

Now that you know how to run a CTD and how it works, what about the data it collects? This figure is more or less what I see on my screen while the CTD is in the water.

There's a lot going on. The y-axis shows pressure (in a unit called the decibar), which is almost the same as depth in meters. So you can think of the vertical scale as depth.

There are four x-axes: fluorometer (remember, that records the microscopic plants), salinity, temperature, and oxygen. Having all four on one graph means that I can keep track of lots of different variables at once.

What do you notice about this graph? I notice that below 40m, temperature and oxygen vary inversely - when one gets bigger, the other gets smaller. I also notice that at around 140m, it gets warmer very suddenly. I can also see that the maximum fluorescence is at 15m, so I bet the biologists will want a sample of the water there.

This graph only shows the top 200m, but the CTD actually went down to 600 m at this location. It's in a place called Hughes Bay on the western side of the Antarctic Peninsula. And there's something special about this cast, something that makes it different from all the other casts. Can you guess what it is?

1 comment:

  1. Hi Ms T,
    Well I am not a scientist, so I am hazarding a guess here...
    The temp vs Oxygen : Are they not proportional (I am not too sure about the units that are used for the graph?), it looks like they both tend to follow the same general line (barring the 2 "blips" at around 40m and 130m).
    The salinity seems to increase as you descend, does this have anything to do with the changes in pressure, or is it something to do with ice melting at the surface of the water, diluting the saline content at the surface?
    I guess what makes this graph so special for me is that you are lucky enough to be doing these measurements!!!! Wish I was there....