3 September 2018

The first deployments

A scouting WaveGlider and a test of the MMP

We did science today!

En route to deploy Tom Peacock’s PIES in the morning, the University of Washington team deployed a WaveGlider on the shelf. It will follow a small rectangular pattern while we head to the shelf break to deploy the PIES and do a ~24 hour survey of the area to find a good place to use our full arsenal of oceanographic equipment. In the meantime, it will send updates every 30 minutes about what it’s seeing. It measures waves, the temperature and salinity of the water, air temperature, and wind speed, which will all be useful for picking out a good spot.

Our group also did a quick test of the MMP on the fast CTD winch. We found that there’s a lot of noise in the signal that’s really drowning out the data, so the engineers immediately got to work diagnosing the problem. The leading theory is that one of the cables that runs from the lab and out along the deck to the winch is interfering with the other cables and messing with what should be a clean signal. A simple fix would be to separate the cables. Hopefully that does the trick!

If you go on a research cruise and don’t filter water, did you even really go on a research cruise?

I spent a lot of time during grad school filtering water to measure phytoplankton biomass and primary productivity. The auditory memory of that steady vibrating hum of a vacuum pump is forever locked in my mind. A ship is a loud place with the engine, ventilation systems, computers, and freezers constantly running, not to mention the unpredictable slaps of large waves against the hull, but there’s something about that vacuum pump that, to me, sounds like science.

This cruise is all about physical oceanography, but we have one graduate student among us, Ben Barton, who has been tasked to bring home some samples of particulate organic matter, a task which requires….filtering! Today I spent about 3 hours filtering 3 liters of seawater from the underway throughflow system onto a small round filter. This volume is required to collect a nice mass of organic matter. Ben and I will continue filtering water samples from the surface as we transit through the Beaufort Sea. We’ll also do a few casts with the CTD rosette to collect water from different depths at a few key locations. This effort is part of the PEANUTS project (Primary production driven by escalating Arctic nutrient fluxes?) led by Yueng-Djern Lenn at Bangor University.

The project intersects physical and biological oceanography. As seasonal sea ice in the Arctic has declined, the net primary productivity has increased. This is somewhat expected since more open water means more area over which phytoplankton can grow, but the rate of increase far exceeds what we would predict just from the retreat of sea ice. The Arctic Ocean is typically nitrate limited, so how are there sufficient nutrients for phytoplankton to grow? The hypothesis is that increased mixing is bringing deep nutrients to the surface. The organic matter samples we’re filtering will be used alongside measurements of nitrate from waters samples we’ll collect at the same locations, and measurements of turbulence to try to determine if this theory holds.