Two transects down and so far so good. I made some preliminary plots of the Scanfish hydrographic data. The instrument actually saves data 32 times every second, so for each of these transects we have more than 30,000 data points. However to make sense of it and get rid of small errors we do a bit of averaging. Again, this is preliminary data and our QA/QC folks will pour through most of the data points in the coming months to make sure there are no instrumental or other problems. Bad things can happen to electronics that are dragged through saltwater, as you might imagine, so we have to check through the data carefully to make sure it’s all copacetic.
But even without the exacting QA/QC process, we can learn a bit about what is going on out there by looking at the minimally processed data. There are six plots on the figure below. The upper left is a map with the transect lines plotted on it. The next five plots are 3-dimensional, colored “curtain maps” for each of five different variables: from left to right, top to bottom:
- Dissolved Oxygen (DO)
- Temperature (T)
- Salinity (S)
- Chlorophyll a fluorescence (CHL)
- Colored Dissolved Organic Matter (CDOM)
For each of these 5 panels, the bottom axes are Latitude and Longitude, and the vertical axis is depth in meters. Colors are scaled to each variable, and the scales are shown at the left. Each panel shows two “curtains”. The transect names are Q and W for the western and eastern ones, but I’m just going to call them western and eastern for the rest of this discussion. When we get more data in, we’ll give them their letter names but for now they’re west and east.
If we look at these plots there are a few simple patterns that stand out, and a few distinct missing patterns. Starting with oxygen, there isn’t much structure at all. Hypoxia, or low oxygen, is often defined as values below 2 mg per litre, and here we have no values below 4 and those are very rare. There are some very high values of oxygen in the nearshore section of the eastern transect – see the bluer section in the upper right corner of the DO plot – which are likely the result of “super saturation” from photosynthesis. In that area we ran through an algal bloom of some sort (for the taxonomy buffs: further from shore it was mostly dinoflagellates, closer to sure it was all centric diatoms). Other than that there isn’t too much to write home about in the oxygen plot.
Temperature and salinity are about what we might expect – cooler, less salty water nearer to the coast. One interesting feature is the “temperature inversion” ofshore on the eastern transect. You can see the reddish colors in the lower right of the temperature plot, with cooler greens and yellows above it. That same region on the salinity plot shows a region of elevated salinity. Where did that warm salty water come from? I have some ideas but I have no idea. Maybe we’ll have a physical oceanographer weigh in tomorrow…
The last two plots show chlorophyll a fluorescence and colored dissolved organic matter – CHL and CDOM. What to make of them? Well both variable are low off shore and have peaks near shore. If you look back and forth quickly between DO and CHL there seems to be some correlation between them. CDOM was higher on the eastern transect nearshore than on the western transect. Why? Perhaps it had to do with material coming out of Sabine Pass, which is right at the inshore end of the transect, as you can see from the map in the upper left.
Well that’s about it for now. I’m off to bed, so I can rise for my 4-8 watch. More data is coming, and some more pictures too.