Tuesday, June 28, 2011

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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