I had every intention of putting up a plot of our hydrographic data within a day of collecting it with the Scanfish, but alas, here we are, four days after collecting it and I’m just getting around to it. The good news is that I’ve honed the routine so it should go faster last time. The bad news is that I’ll never keep up with the style and speed of the RU COOL blog, one of my favorite science sites. Once you’re done here I suggest you go check out their page about the Scarlett Knight, a glider that made it across the Atlantic unmanned.
On the right you will see the data plot of our Scanfish survey, along with a map of the actual track line, with our stations shown in red and green. If you compare it with data from our May cruise, you’ll see that by now we’ve got lots more low oxygen now. That is what we expected; as the summer progresses the biological activity in the water uses up the oxygen. On the LiDZ cruise in July they found low and no oxygen along their transects, and we’re seeing something similar. There is some evidence that wind conditions can factor into the persistence and maintenance of hypoxia in the Bay, but that’s a story for a physical oceanographer. The temperature plot shows that conditions are fairly consistent along the transect, and our stations have pretty similar temperature profiles. Another thing to notice in this new data set is that the salinity is pretty high (comparatively) at the southern end of the transect, just south of where our station was. For the first 24 hours at that southern station, we were collecting data every hour on the physical conditions – temperature, salinity, fluorescence, turbidity, and oxygen – but I haven’t plotted that data up yet. Finally if you look at the last plot you’ll see the fluorescence data. This is uncalibrated, but the important point to take away from it is that it’s pretty patchy and that many of the high values are in the deeper water. The lowest values seem to track the low oxygen pretty well, as we might expect, but the highest values seem to occur right near the interface between oxygenated surface water and hypoxic bottom water. There is a density difference in these two water masses too, driven by the salinity and temperature differences, and we call the transition between them the pycnocline (pycno- for density, -cline for gradient).
These are preliminary data, but I wanted to show an example of they type of data we collect. It’s important to note that the equipment that we use to gather this data, the Scanfish, is complicated, expensive, and requires lots of maintenance. We are dragging a large piece of electronic equipment through saltwater at 6 knots, and that means that a lot can go wrong. You might notice that our Scanfish survey on this cruise is a bit shorter than on the previous one, and that is because we had some problems with it early on. In fact almost the minute we tried to use it. The technicians aboard the RV Hugh R Sharp worked tirelessly to get it running, and even called for back up help from Delaware. We stopped in Solomons, MD to pick up some of our collaborators around 3 pm on the first day of the cruise, and the tech from Delaware drove over to meet the boat there, and together the tech team were able to get us back up and running. Huge thanks go to them and the ship’s crew, who have been invaluable to our success as always. Oceanography, more than most sciences I think, relies heavily on collaboration not only between scientists but also between the scientists and the professionals that allow us to gather our data in often difficult and inhospitable conditions.
Well, the rest of the team is catching jellies, and it’s almost time to get some more zooplankton so I’d best don my work vest and boots and head out on deck. Tomorrow I’ll write about some very tiny critters, and try to get some good pictures up. I have a nice photo of the blueberry & cherry topped cheesecake that I’ll put up, but I don’t want to gloat about our food too much. I will say we have a fantastic cook and that we’re eating well out here. ‘Til next time.