Tuesday, June 28, 2011

What are the smallest things in the ocean?

- Phil Bresnahan [Scripps Institution of Oceanography]

When many people think of oceanography, they picture the whales, sharks, waves, coral reefs, and submarines. Most think of the large things, whether they're organisms, phenomena, or machines associated with the water. Many of us learn about the microscopic plankton that live in the ocean in our early school years, but those things are, at least for most of us, the smallest that are out there.

We're on this trip, however, to study things even smaller: the chemicals in the ocean and those in the air just above the ocean as well as the forces that cause them to move back and forth between the two. My own research involves inorganic carbon--basically carbon dioxide gas that has dissolved into ocean water. There are two main things that we can learn from studying dissolved inorganic carbon: 1) there was always a certain amount of inorganic carbon in the water but a very large quantity of the carbon dioxide that humans have emitted has dissolved (and is dissolving) in the oceans; we can use dissolved inorganic carbon measurements to help determine where and how quickly the CO2 is entering the ocean (it doesn't occur at equal rates at different places across the globe). 2) Just as humans & other land heterotrophs (things that eat stuff, quite simply--like a hippopotamus, for example) respire by intaking oxygen and releasing carbon dioxide and plants & other land photoautotrophs (things that make energy from sunlight--like dandelions) produce oxygen and capture carbon dioxide, so to do ocean creatures capture carbon dioxide (phytoplankton) or release it (zooplankton, fish, etc.); we can estimate rates of respiration and production with our measurements.

My type of oceanography is unique. I don't watch or listen for whales or collect samples of water from the ship. Instead, I let the water come to me. Oceanographic ships (as well as many other ships, named volunteer observing ships) have small intake pumps on the hull at the bow of the ship which deliver water directly to instruments inside the ships' labs. In this picture, you can see that there is quite a bit of sophisticated equipment; all of it is inside the Knorr's lab and will never need to leave its location since the ocean water is coming directly to it.

If you look closely, you might notice that every piece of equipment is meticulously tied down. While the conditions we've seen so far have been quite mild, the ocean is a powerful (and potentially destructive force). It's better for us to be prepared well in advance of any bad weather that could suddenly arise. We aren't searching for storms out here but it would certainly be interesting to see the changing chemistry during violent weather patterns!

Air-sea CO2 Exchange (SUNY Albany)

- Scott Miller [SUNY Albany]

The oceans currently take up a considerable fraction (roughly 25%) of the carbon dioxide emitted by human activities. Thus, at the global scale there is a net transport (or 'flux') of CO2 across the air-sea interface from the atmosphere to the ocean. One of our main goals is to directly measure CO2 flux using a technique called eddy covariance (http://en.wikipedia.org/wiki/Eddy_covariance). While the net global CO2 flux is large, the per-unit-area flux that we measure is actually very small; i.e., the global flux is large because the oceans are very big. The smallness of the local flux we are trying to measure provides many challenges at sea.
R/V Knorr mast

Our setup involves mounting sensors on the ship's bow mast to measure the turbulent wind and CO2 concentrations. We want to be at the most forward location of the ship to minimize flow disturbance and contamination of air samples due to the ship's exhaust. The bow mast was heavily instrumented in port, with the mast lowered to a horizontal position above the main deck. Before leaving port, the mast was raised to the vertical position and secured.
mast lowered to install equipment

Ideally, we would not need to access the sensors after leaving port; however, at sea instruments rarely behave ideally, and at times we need to service the instruments when the ship is on station (not underway) and the environmental conditions permit.

Accessing sensors on station.

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