Award: OCE-1154001

Recent observations of oxygen in the ocean suggest that there has been a measurable decrease in concentration over the past several decades. Understanding how the oxygen concentration is changing with time is one of the key indicators of man?s impact on the ocean environment. Our knowledge of the distribution of oxygen in the ocean suffers from the fact that the ocean is dramatically undersampled and will always be if oceanographers have to rely only on shipboard operations as the means for collecting data. To overcome this problem it is necessary to make oxygen measurements remotely on platforms like surface moorings, gliders and floats. The research in this NSF grant helps to make it possible to obtain accurate oxygen measurements from in situ observations. The limiting factor with this approach is that the accuracy of commercially-available oxygen sensors drift with time in the ocean. The goals of this project were to construct and test an in situ calibration device for oxygen sensors that are deployed on ocean moorings so that it is possible to obtain accurate in situ estimates of oxygen concentration and air-water oxygen flux. The device we developed calibrates the oxygen sensors deployed on surface moorings by periodically pumping air to the sensor and recording the air pressure and oxygen partial pressure response. Two versions of the in situ calibration system were constructed and deployed for six months on a surface mooring on the continental shelf off of Washington State. Both instruments recorded accurate atmospheric pressure and pO2 for the entire period of deployment and are thus proven to work in the ocean environment. This work represents the addition of a new physical resource to help scientists in oceanography and all environmental sciences measure accurate oxygen concentrations remotely on moorings. The research done on this grant was the Masters Thesis of graduate student Seth Bushinsky in the School of Oceanography at the University of Washington, and resulted in a publication in the oceanography journal Marine Chemistry. (Bushinsky, S and S. Emerson (2013). A method for in situ calibration of Aanderaa oxygen sensors on surface moorings. Marine Chemistry, 155, 22) Last Modified: 08/31/2016 Submitted by: Steven R Emerson