Spatial variability of ΔO2/Ar and net community production in the surface waters of the Northwest Pacific: from Incheon, Korea to Nome, Alaska

Abstract

Saturation anomaly of dissolved oxygen (O2) in surface waters of the ocean is, in general, associated with physical and biological processes. Given that argon (Ar) have similar solubility and diffusivity in seawater to those of O2, Ar measurement can be used to isolate the O2 saturation anomaly related to physical processes such as the changes of seawater temperature and atmospheric pressure, and bubble injections among the various processes. Remaining biological O2 anomaly, ΔO2/Ar (=[O2/Ar]sample/[O2/Ar]saturation−1), reflects the difference between photosynthetic production and respirational consumption of O2, corresponding to net community production (NCP). To investigate the variability of biological productivity and its possible connection to atmospheric chemistry, we surveyed ΔO2/Ar in the surface waters along Araon cruise track from Incheon to Nome, Alaska (July 13 − 29, 2012), using an equilibrator inlet mass spectrometer. We divided the cruise track into four regions: Yellow Sea and South Sea of Korea (YS), East Sea (ES), Northwest Pacific (NP), and Bering Sea (BS). Each of the region showed distinctive oceanographic parameters including ΔO2/Ar. YS had ΔO2/Ar in the range of 0 — 8% and largest average of 4.3%. To the contrary, ES is the least productivity region, with average Δ O2/Ar of 1.5%. NP showd modest spatial variability of ΔO2/Ar with average of 2.8%easurement can be used to isolate the O2 saturation anomaly related to physical processes such as the changes of seawater temperature and atmospheric pressure, and bubble injections among the various processes. Remaining biological O2 anomaly, ΔO2/Ar (=[O2/Ar]sample/[O2/Ar]saturation−1), reflects the difference between photosynthetic production and respirational consumption of O2, corresponding to net community production (NCP). To investigate the variability of biological productivity and its possible connection to atmospheric chemist