Abstract
Abstract. We have been carrying out in-situ monitoring of atmospheric O2/N2 ratio at Cape Ochi-ishi (COI; 43°10' N, 145°30' E) in the northern part of Japan since March 2005 by using a modified gas chromatography/thermal conductivity detector (GC/TCD). The standard deviation of the O2/N2 ratio is estimated to be about ±14 per meg (≈3 ppm) with intervals of 10 minutes. Thus, the in-situ measurement system has a 1σ precision of ± 6 per meg (≈1.2 ppm) for one-hour mean O2/N2 ratio. Atmospheric potential oxygen (APO≈O2+1.1 CO2), which is conserved with respect to terrestrial photosynthesis and respiration but reflects changes in air-sea O2 and CO2 fluxes, shows large variabilities from April to early July 2005. Distribution of satellite-derived marine primary production indicates occurrences of strong bloom in the Japan Sea and the latitudinal band between 30° and 40° N in the western North Pacific in April and in the Okhotsk Sea and northeastern region near Hokkaido Island in the North Pacific in June. Back trajectory analysis of air masses indicates that high values of APO, which last for several hours or several days, can be attributed to the oxygen emission associated with the spring bloom of active primary production.
Highlights
Observation of atmospheric oxygen has been conducted for decades since the development of methods for measuring atmospheric O2/N2 ratios (e.g. Keeling, 1988; Bender et al, 1994)
We have been carrying out in-situ measurements of the atmospheric O2/N2 ratio at Cape Ochi-ishi (COI; 43◦10 N, 145◦30 E) in the northern part of Japan since March 2005 using the gas chromatography/thermal conductivity detector (GC/TCD) analyzer
The standard deviation of the O2/N2 ratio is estimated to be about ±14 per meg (≈3 ppm) for the in-situ measurement system, resulting in a standard error of ±6 per meg (≈1.2 ppm) for the 1-h mean O2/N2 ratio
Summary
Observation of atmospheric oxygen has been conducted for decades since the development of methods for measuring atmospheric O2/N2 ratios (e.g. Keeling, 1988; Bender et al, 1994). Spatial and temporal distributions of APO have been revealed through flask sample measurements (Battle et al, 2006; Manning and Keeling, 2006; Tohjima et al, 2005b), there are short-term APO variations that can not be detected from flask sampling. At stations such as Cold Bay, Alaska (CBA: 55◦ N, 162◦ E) (Battle et al, 2006) and Cape Ochi-ishi, Hokkaido (COI; 43◦10 N, 145◦30 E) (Tohjima et al, 2003), plots of APO are scattered, which may be related to variation of O2 flux from the oceans caused by active marine primary production near the stations
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