The fourth unit is to rotate between Cape Grim and Barrow in order to test the intercomparability of data collected at these two sites. We are building four additional instruments with independent funding for shipboard sampling in the Atlantic and Pacific Oceans. The instruments are being constructed at Bowdoin College, Brunswick, Me., by Professor Mark Battle, who developed the technology in the P. I. s lab at the University of Rhode Island and Princeton. Our goal is to construct four automatic air samplers and deploy them as described above. The samplers are built to a design modified from samplers that we have periodically used for nearly 5 years.
Air is drawn from the bow of the ship using a diaphragm pump.
When sample collection is to begin, valves in the air stream open, directing the flow to the sampling flasks, and valves to two liter sampling bottles are opened mechanically using a stepper motor with optical encoder. After the flasks are flushed with ten volumes of air, the airflow is redirected to the waste line, and the valves are closed, completing the actual sampling. The entire operation is controlled by a laptop computer running LabView. The first sampler has been constructed and is being installed on the Ka imimoana for sampling in the equatorial Pacific. This will be used to collect data for testing models of ocean circulation and the carbon cycle, which predict an equatorial maximum that remains to be identified in the sum of the O2 and CO2 concentrations of air.