Underway measurements of net community production in the Amudsen Sea

The coastal polynyas in the Amundsen Sea are known for high primary production in austral summer (Arrigo et al., 2012). Rapid environmental changes in the Amundsen Sea poses questions such as how the biological and chemical systems respond to the environmental changes. During the cruise, we measured net community production (NCP), defined as the difference between autotrophic photosynthesis and (autotrophic and heterotrophic) respira-tion, as a measure of biological pump. By measuring chemically and biologically inert Ar to-gether with O2, it is possible to remove O2 variation by physical processes (e.g., air tempera-ture and pressure change and mixing of water masses) and deduce O2 variation by biological processes (Craig and Hayward, 1987).
In order to investigate the spatial and temporal variations of NCP in the surface wa-ters of the polynyas and the proposed correlation between them, we observed the horizontal and vertical (upper 100 m) distributions of ΔO2/Ar, a proxy of NCP, in the Amundsen Sea using a membrane inlet mass spectrometer (MIMS) (Tortell, 2005).